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Abstract
Problem: The ability to document a patient encounter is integral for any physician. Previous studies indicate that medical students' note writing skills are poor due to a lack of formal clinical documentation instruction. Barriers to formally teaching students how to write patient notes include the significant time burden and variability in faculty feedback. Implementing a near-peer teaching program to teach students how to write a patient note can overcome these barriers and fill this curricular gap. Intervention: Fourth year medical students who completed a Teaching in Medicine elective course were trained to provide individual feedback to 1st and 2nd year students on note writing as a part of their Introduction to Clinical Medicine course. In order to determine the effect of this two year, near-peer feedback program on note writing skills, we analyzed students' scores on the note writing portion of two Objective Structured Clinical Exams that took place at the end of the 2nd and 3rd years of medical school. Context: The near-peer feedback sessions were implemented in the Fall of 2013 during the preclinical years of the medical school curriculum. Data from students who received near-peer feedback (N = 112) were compared to a historical control group who did not receive near-peer feedback on their note writing (N = 110). Objective Structured Clinical Exam scores that were specific to note writing skills, including the history, physical exam, and differential diagnosis subscales were examined. Impact: The near-peer feedback had a positive impact on the quality of patient notes. On the end of the 2nd year Objective Structured Clinical Exam, the near-peer feedback intervention group outperformed the no feedback group on the history and physical exam subscale scores but not on the differential diagnosis subscale score. One year later, the near-peer feedback intervention group continued to outperform the no feedback group on the physical exam subscale score, but not the history or the differential diagnosis subscale scores. Lessons Learned: Near-peer teaching improves student documentation of the history and physical exam, however only the effects on the physical exam portion persist into the clinical years of training. Writing up a differential diagnosis is a skill that develops through the clerkship experience regardless of exposure to feedback in the preclinical years. Implementing near-peer teaching in the medical school setting is feasible and can provide students with valuable learning experiences without relying on clinical faculty.
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Affiliation(s)
- Doreen M Olvet
- Department of Science Education, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
| | - Andrew Wackett
- Office of Academic and Faculty Affairs, Renaissance School of Medicine, Stony Brook, New York, USA
- Department of Emergency Medicine, Renaissance School of Medicine, Stony Brook, New York, USA
| | - Shakita Crichlow
- Department of Emergency Medicine, Renaissance School of Medicine, Stony Brook, New York, USA
| | - Perrilynn Baldelli
- Clinical Skills Center, Renaissance School of Medicine, Stony Brook, New York, USA
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Lu WH, Baldelli P, Migdal P, Iuli R, Strano-Paul L, Zacharoff KL. Early Refill of an Opioid Medication: Recognizing Personal Biases Through Clinical Vignettes and OSCEs. MedEdPORTAL 2022; 18:11234. [PMID: 35497675 PMCID: PMC8986891 DOI: 10.15766/mep_2374-8265.11234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Introduction Efforts to improve pain education and knowledge about prescription opioid misuse and opioid/substance use disorder in undergraduate medical education continue to be inadequate. To advance educational practices and address training needs to counter the opioid epidemic, we created a longitudinal pain and addiction curriculum that includes three patient vignettes in which the patient requests an early refill of opioid medication. The goal was to introduce students to the potential impact of personal biases on health care delivery and medical decision-making with patients who have pain and/or substance use disorders. Methods Three clinical vignettes were presented to early matriculating medical students (MS 1s) using a progressive case disclosure approach in the format of a PowerPoint presentation with embedded audio interactions and follow-up audience response system questions. The same vignettes were converted into OSCEs for early clinical clerkship students (MS 3s). Results A total of 180 MS 1s participated in the case presentations, and 124 MS 3s participated in the OSCE session. There was a significant difference between students' level of comfort and individual patient requests for early prescription refills in both student cohorts. MS 1s were significantly more likely to provide the early refill to the elderly female patient compared to the two middle-age male patients, whereas a majority of MS 3s wanted more information. Discussion This module can be presented to medical students who have little clinical exposure and to health care trainees at other levels of clinical exposure.
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Affiliation(s)
- Wei-Hsin Lu
- Director of Assessment and Evaluation and Research Assistant Professor of Preventive Medicine, Renaissance School of Medicine at Stony Brook University
| | - Perrilynn Baldelli
- Director, Clinical Simulation Center, Renaissance School of Medicine at Stony Brook University
| | - Phyllis Migdal
- Clinical Assistant Professor, Department of Family, Population, and Preventive Medicine, Renaissance School of Medicine at Stony Brook University
| | - Richard Iuli
- Director, Pathways to Success, Office of Academic Affairs, Renaissance School of Medicine at Stony Brook University
| | - Lisa Strano-Paul
- Clinical Professor of Medicine and Assistant Dean for Clinical Education, Renaissance School of Medicine at Stony Brook University
| | - Kevin L. Zacharoff
- Clinical Instructor and Distinguished Visiting Scholar in Medical Humanities, Compassionate Care, and Preventive Medicine, Department of Family, Population, and Preventive Medicine, Renaissance School of Medicine at Stony Brook University
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Caldwell D, Baldelli P, Phelan N, Kenny P. A statistical alternative to current measures of image quality in digital mammography. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac4c2d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 01/17/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. Mammogram image quality in European breast screening systems is defined by threshold gold thickness (T) assessment of the CDMAM contrast-detail phantom. Previous studies have outlined several limitations of the phantom including expense, number of images required and inter-phantom manufacturing variability. Two alternative approaches to image quality assessment for routine quality control are examined and compared to the CDMAM technique: (i) A detectability index (d′) based on a non-prewhitened model observer with an eye filter (NPWE) and (ii) A statistical estimate of contrast based on image noise levels (CSTAT
). Approach. The d′ calculation follows a previously published methodology based on the NNPS and contrast, both measured from an image of 5 cm of PMMA containing a 0.2 mm Al target, as well as the MTF measured under standard conditions. For the proposed statistical method, pixels in the centre of the same NNPS image were re-binned into a range of equivalent CDMAM target areas. For any area, the minimum contrast necessary to distinguish a signal from the background, CSTAT
, is 3.29σ at a 95% level of confidence, where σ is the standard deviation of the background pixels. Theoretical analysis predicts a simple relationships between CSTAT
, T and d′. Measured values of CSTAT
were compared to T and d′ as a function of air kerma at the detector for ten digital mammography systems from three different manufacturers. Main Results. Theoretical relationships between CSTAT
,
d′ and T were demonstrated. Minimum acceptable image quality performance for 0.10 and 0.25 mm diameter discs, defined by the European Guidelines in terms of T, are equivalent to d′ values of 0.85 and 5.36 and threshold CSTAT
values of 0.055 and 0.022. Significance. Strong correlations between log(T), log(d′) and log(CSTAT
) suggest that either alternative approach produces information corresponding to that obtained using the CDMAM. CSTAT
should be considered as a simple, objective and cost-effective alternative to routine image quality assessment in mammography.
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Caldwell D, Baldelli P, Phelan N, Kenny P. Verification of threshold NPWE detectability indices, with a novel statistical alternative for image quality assessment in digital mammography. Phys Med 2021. [DOI: 10.1016/s1120-1797(22)00068-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Baldelli P, Cardarelli P, Flanagan F, Maguire S, Phelan N, Tomasi S, Taibi A. Evaluation of microcalcification contrast in clinical images for digital mammography and synthetic mammography. Eur J Radiol 2021; 140:109751. [PMID: 34000600 DOI: 10.1016/j.ejrad.2021.109751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/17/2021] [Accepted: 04/30/2021] [Indexed: 12/27/2022]
Abstract
PURPOSE The aim of this work was to compare, in a clinical study, digital mammography and synthetic mammography imaging by evaluating the contrast in microcalcifications of different sizes. METHODS A retrospective review of microcalcifications from 46 patients was undertaken. A Hologic 3-Dimensions mammography system and a HD Combo protocol was used for simultaneous acquisition of the digital and synthetic images. Microcalcifications were classified in accordance with their size, and patient breast images were classified in accordance with their density as adipose, moderately dense and dense. The contrast of the microcalcifications was measured and the contrast ratio between synthetic and digital images was compared. An additional qualitative assessment of the images was presented to correlate the conspicuity of the microcalcifications with the suppression of the structure noise. RESULTS Microcalcifications in adipose background always exhibit a comparable or better contrast on synthetic images, regardless their size. For moderately dense background, synthetic images show a better contrast in 91.2 % of cases for small microcalcifications and in 90.9 % of cases for large microcalcifications. For a dense background, better contrast is seen in 89.5 % of cases for small microcalcifications, and in 85.7 % of cases for large microcalcifications. The contrast ratio increases with increasing breast glandularity. The suppression of structure noise also contributes to the enhancement of microcalcifications in the synthetic images. CONCLUSIONS Synthetic mammography imaging is superior to digital mammography imaging in terms of microcalcification contrast, regardless their size and breast density.
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Affiliation(s)
- P Baldelli
- Breastcheck, National Breast Screening Program, 36 Eccles Street, Dublin 7, Ireland
| | - P Cardarelli
- National Institute for Nuclear Physics - Ferrara Division, via Saragat 1, 44122 Ferrara, Italy.
| | - F Flanagan
- Breastcheck, National Breast Screening Program, 36 Eccles Street, Dublin 7, Ireland; Mater Private Hospital, Eccles Street, Dublin 7, Ireland
| | - S Maguire
- Mater Private Hospital, Eccles Street, Dublin 7, Ireland
| | - N Phelan
- Breastcheck, National Breast Screening Program, 36 Eccles Street, Dublin 7, Ireland
| | - S Tomasi
- Dept of Physics and Earth Sciences, University of Ferrara, via Saragat 1, 44122 Ferrara, Italy
| | - A Taibi
- Dept of Physics and Earth Sciences, University of Ferrara, via Saragat 1, 44122 Ferrara, Italy
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Forte N, Binda F, Contestabile A, Benfenati F, Baldelli P. Synapsin I Synchronizes GABA Release in Distinct Interneuron Subpopulations. Cereb Cortex 2019; 30:1393-1406. [DOI: 10.1093/cercor/bhz174] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 01/28/2023] Open
Abstract
Abstract
Neurotransmitters can be released either synchronously or asynchronously with respect to action potential timing. Synapsins (Syns) are a family of synaptic vesicle (SV) phosphoproteins that assist gamma-aminobutyric acid (GABA) release and allow a physiological excitation/inhibition balance. Consistently, deletion of either or both Syn1 and Syn2 genes is epileptogenic. In this work, we have characterized the effect of SynI knockout (KO) in the regulation of GABA release dynamics. Using patch-clamp recordings in hippocampal slices, we demonstrate that the lack of SynI impairs synchronous GABA release via a reduction of the readily releasable SVs and, in parallel, increases asynchronous GABA release. The effects of SynI deletion on synchronous GABA release were occluded by ω-AgatoxinIVA, indicating the involvement of P/Q-type Ca2+channel-expressing neurons. Using in situ hybridization, we show that SynI is more expressed in parvalbumin (PV) interneurons, characterized by synchronous release, than in cholecystokinin or SOM interneurons, characterized by a more asynchronous release. Optogenetic activation of PV and SOM interneurons revealed a specific reduction of synchronous release in PV/SynIKO interneurons associated with an increased asynchronous release in SOM/SynIKO interneurons. The results demonstrate that SynI is differentially expressed in interneuron subpopulations, where it boosts synchronous and limits asynchronous GABA release.
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Affiliation(s)
- N Forte
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - F Binda
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - A Contestabile
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - F Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - P Baldelli
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
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Boykan R, Blair R, Baldelli P, Owens S. Using Motivational Interviewing to Address Tobacco Cessation: Two Standardized Patient Cases for Pediatric Residents. MedEdPORTAL 2019; 15:10807. [PMID: 30931386 PMCID: PMC6415006 DOI: 10.15766/mep_2374-8265.10807] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 01/25/2019] [Indexed: 05/21/2023]
Abstract
INTRODUCTION Motivational interviewing (MI) is a well-established evidence-based method of working with patients to promote health behavior change. Standardized patient (SP) simulation allows trainees to practice and receive feedback on clinical and communication skills and may be useful in applying MI techniques to address tobacco use and exposure. METHODS We developed two SP cases for pediatric residents to practice addressing tobacco use with parents of their patients. RESULTS Thirty-six residents participated, 26 of whom had prior MI training. Resident postencounter self-reflection identified MI-specific skills, including eliciting the SP's view on positive/negative aspects of smoking, identifying stressors/triggers associated with smoking, eliciting reasons for smoking, asking about motivation/willingness to quit, eliciting benefits of quitting smoking, letting the SP do the talking, and guiding the SP in making a quit plan. On paired-samples t tests, resident self-evaluation checklist scores averaged 6.79 out of 8.00 (SD = 1.018, SEM = 0.165), compared with SP checklist scores, which averaged 7.08 out of 8.00 (SD = 1.217, SEM = 0.197). DISCUSSION These two SP cases were useful in many ways, allowing residents with prior MI training the opportunity for practice/feedback on skills learned and introducing residents with no prior MI training to MI concepts through experience/feedback. Residents consistently identified using MI concepts on postencounter self-reflection; resident self-evaluation and SP evaluation of residents showed agreement. These sessions could be utilized within a communication/MI curriculum or as stand-alone sessions to introduce MI concepts/techniques for addressing tobacco cessation in the pediatric setting.
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Affiliation(s)
- Rachel Boykan
- Associate Program Director, Residency Training Program, Department of Pediatrics, Stony Brook University School of Medicine
- Corresponding author:
| | - Robyn Blair
- Clinical Associate Professor, Department of Pediatrics, Stony Brook University School of Medicine
- Program Director, Residency Training Program, Department of Pediatrics, Stony Brook University School of Medicine
| | - Perrilynn Baldelli
- Director, Clinical Simulation Center, Stony Brook University School of Medicine
| | - Susan Owens
- Simulation Education Coordinator, Clinical Simulation Center, Stony Brook University School of Medicine
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Lu WH, Mylona E, Lane S, Wertheim WA, Baldelli P, Williams PC. Faculty development on professionalism and medical ethics: the design, development and implementation of Objective Structured Teaching Exercises (OSTEs). Med Teach 2014; 36:876-882. [PMID: 25072644 DOI: 10.3109/0142159x.2014.916780] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
BACKGROUND As students are expected to develop competency in professionalism and medical ethics, faculty are also expected to facilitate medical students' learning and understanding of these areas. One of the main challenges to success in this domain has been uncertainty of whether or not faculty know the content and the methods to teach and assess these competencies. AIM We used the Objective Structured Teaching Exercise (OSTE) format as a faculty development tool to train and evaluate faculty on how to teach professionalism and medical ethics to students in clinical settings. METHODS The process for the design, development and implementation of OSTEs consisted of five phases: (1) performing a literature review and student needs assessment, (2) developing the OSTE cases and performance checklists, (3) recruiting and training of standardized students, (4) conducting a mock training session and (5) organizing faculty development workshops using OSTEs. RESULTS Twenty clinical faculty members participated in one of three half-day OSTE workshops offered. Faculty confidence and attitudes about teaching professionalism increased significantly (p < 0.05) from before participating in the workshop to afterwards. CONCLUSIONS Faculty feedback were positive stating that the OSTE scenarios were reflective of issues they generally encounter while teaching medical students, the information and skills they learned from the workshop are important to them as clinical educators, and that the information and skills will likely have an impact on the way they teach professionalism and ethics in the future.
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Affiliation(s)
- Wei-Hsin Lu
- Stony Brook University School of Medicine , USA and
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Gonzalez JC, Lignani G, Maroto M, Baldelli P, Hernandez-Guijo JM. Presynaptic Muscarinic Receptors Reduce Synaptic Depression and Facilitate its Recovery at Hippocampal GABAergic Synapses. Cereb Cortex 2013; 24:1818-31. [DOI: 10.1093/cercor/bht032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Malone J, Baldelli P, Balter S, Bischof N, Bosmans H, Dowling A, Edyvean S, Gallagher A, Faulkner K, Horner K, Malone L, Mclean ID, O'Connor U, Schreiner A, Vassileva J, Vano E, Zoetelief J. Criteria and suspension levels in diagnostic radiology. Radiat Prot Dosimetry 2013; 153:185-189. [PMID: 23173220 DOI: 10.1093/rpd/ncs295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The EC (European Council) Directive on radiation protection of patients requires that criteria for acceptability of equipment in diagnostic radiology, nuclear medicine and radiotherapy be established throughout the member states. This study reviews the background to this requirement and to its implementation in practice. It notes and considers parallel requirements in the EC medical devices directive and International Electrotechnical Commission standards that it is also important to consider and that both sets of requirements should ideally be harmonised due to the global nature of the equipment industry. The study further reviews the types of criteria that can be well applied for the above purposes, and defines qualitative criteria and suspension levels suitable for application. Both are defined and relationships with other acceptance processes are considered (including acceptance testing at the time of purchase, commissioning and the issue of second-hand equipment). Suspension levels are divided into four types, A, B, C and D, depending on the quality of evidence and consensus they are based on. Exceptional situations involving, for example, new or rapidly evolving technology are also considered. The publication and paper focuses on the role of the holder of the equipment and related staff, particularly the medical physics expert and the practitioner. Advice on how the criteria should be created and implemented is provided for these groups and how this might be coordinated with the supplier. Additional advice on the role of the regulator is provided.
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Affiliation(s)
- J Malone
- Trinity College Centre for Health Sciences, Dublin 8, Ireland.
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Ferrea E, Maccione A, Medrihan L, Nieus T, Ghezzi D, Baldelli P, Benfenati F, Berdondini L. Large-scale, high-resolution electrophysiological imaging of field potentials in brain slices with microelectronic multielectrode arrays. Front Neural Circuits 2012; 6:80. [PMID: 23162432 PMCID: PMC3496908 DOI: 10.3389/fncir.2012.00080] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 10/17/2012] [Indexed: 11/13/2022] Open
Abstract
Multielectrode arrays (MEAs) are extensively used for electrophysiological studies on brain slices, but the spatial resolution and field of recording of conventional arrays are limited by the low number of electrodes available. Here, we present a large-scale array recording simultaneously from 4096 electrodes used to study propagating spontaneous and evoked network activity in acute murine cortico-hippocampal brain slices at unprecedented spatial and temporal resolution. We demonstrate that multiple chemically induced epileptiform episodes in the mouse cortex and hippocampus can be classified according to their spatio-temporal dynamics. Additionally, the large-scale and high-density features of our recording system enable the topological localization and quantification of the effects of antiepileptic drugs in local neuronal microcircuits, based on the distinct field potential propagation patterns. This novel high-resolution approach paves the way to detailed electrophysiological studies in brain circuits spanning spatial scales from single neurons up to the entire slice network.
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Affiliation(s)
- E Ferrea
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genoa, Italy
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Cesca F, Yabe A, Spencer-Dene B, Scholz-Starke J, Medrihan L, Maden CH, Gerhardt H, Orriss IR, Baldelli P, Al-Qatari M, Koltzenburg M, Adams RH, Benfenati F, Schiavo G. Kidins220/ARMS mediates the integration of the neurotrophin and VEGF pathways in the vascular and nervous systems. Cell Death Differ 2011; 19:194-208. [PMID: 22048155 DOI: 10.1038/cdd.2011.141] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Signaling downstream of receptor tyrosine kinases controls cell differentiation and survival. How signals from different receptors are integrated is, however, still poorly understood. In this work, we have identified Kidins220 (Kinase D interacting substrate of 220 kDa)/ARMS (Ankyrin repeat-rich membrane spanning) as a main player in the modulation of neurotrophin and vascular endothelial growth factor (VEGF) signaling in vivo, and a primary determinant for neuronal and cardiovascular development. Kidins220(-/-) embryos die at late stages of gestation, and show extensive cell death in the central and peripheral nervous systems. Primary neurons from Kidins220(-/-) mice exhibit reduced responsiveness to brain-derived neurotrophic factor, in terms of activation of mitogen-activated protein kinase signaling, neurite outgrowth and potentiation of excitatory postsynaptic currents. In addition, mice lacking Kidins220 display striking cardiovascular abnormalities, possibly due to impaired VEGF signaling. In support of this hypothesis, we demonstrate that Kidins220 constitutively interacts with VEGFR2. These findings, together with the data presented in the accompanying paper, indicate that Kidins220 mediates the integration of several growth factor receptor pathways during development, and mediates the activation of distinct downstream cascades according to the location and timing of stimulation.
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Affiliation(s)
- F Cesca
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, via Morego 30, 16163 Genoa, Italy.
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McCullagh JB, Baldelli P, Phelan N. Clinical dose performance of full field digital mammography in a breast screening programme. Br J Radiol 2011; 84:1027-33. [PMID: 21586506 PMCID: PMC3473710 DOI: 10.1259/bjr/83821596] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 06/03/2010] [Accepted: 07/06/2010] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE BreastCheck, the Irish Breast Screening Programme, has employed three different models of a full field digital mammography (FFDM) system since its transition to a digital service in 2007. The three models from GE Healthcare, Hologic and Sectra exhibit differences in their design and function, the most significant of which include anode target/filter choice, detector technology and the type of exposure automation. METHODS The aim of this study was to use the results from a clinical breast dose survey to examine the differences between three different FFDM models in terms of exposure selection, breast mean glandular dose (MGD) and automatic exposure control (AEC) dose contribution. RESULTS The accuracy of the dose estimation was improved by inclusion of the AEC pre-exposure dose contribution. The photon-counting system demonstrated the lowest average MGD. The GE Healthcare and Hologic flat-panel detector systems demonstrated a small but statistically significant dose difference. The pre-exposure dose contribution did not exceed 13% of the total exposure dose for any system in the survey. A comparison of the system calculated organ dose estimate from each machine with the corresponding MGD calculated from medical physics measurements indicated reasonably accurate organ dose estimates for most systems in the survey. CONCLUSION The results of this study provide a comprehensive assessment of the breast dose performance of current digital mammography systems in a clinical screening setting.
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Affiliation(s)
- J B McCullagh
- BreastCheck, The National Cancer Screening Service, Infirmary Road, Cork, Ireland.
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Cesca F, Baldelli P, Valtorta F, Benfenati F. Corrigendum to “The synapsins: Key actors of synapse function and plasticity” [Prog. Neurobiol. 91 (4) (2010) 313–348]. Prog Neurobiol 2011. [DOI: 10.1016/j.pneurobio.2011.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
The primary purpose of this study was to evaluate the impact of digital mammography screening on breast dose by analysing the results of a patient dose survey of the Irish breast screening programme. Results from the survey were used to determine a dose reference level for the screening programme. Approximately, 100 examinations were acquired for each of the digital mammography systems operational in the screening programme. Each examination consisted of two standard views of each breast. The mean glandular dose for each acquired image was calculated. The dose reference level was established by calculating the 95th percentile of the average mean glandular dose for the average compressed breast thickness of the mediolateral oblique views. The overall average mean glandular dose per examination was 2.72 ± 0.04 mGy. The average compressed breast thickness was 61.4 ± 0.03 mm. The average compression force was 109 ± 7 N. A dose reference level value of 1.75 mGy was established for the screening programme. The results of this clinical dose survey provide a valuable indication of the dose performance of modern full field digital mammographic imaging systems. The results demonstrate clearly the dose benefits of digital mammography. The dose benefit of digital screening was further demonstrated by the establishment of a comparatively lower diagnostic reference level for the screening programme. The comparison of the dose performance of individual X-ray systems with the diagnostic reference level highlights the need for more optimisation within the service.
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Affiliation(s)
- P Baldelli
- BreastCheck, The National Cancer Screening Service, 36 Eccles Street, Dublin 7, Ireland.
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González JC, Albiñana E, Baldelli P, García AG, Hernández-Guijo JM. Presynaptic muscarinic receptor subtypes involved in the enhancement of spontaneous GABAergic postsynaptic currents in hippocampal neurons. Eur J Neurosci 2010; 33:69-81. [PMID: 21091801 DOI: 10.1111/j.1460-9568.2010.07475.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the effects of muscarinic acetylcholine receptor (mAChR) activation on GABAergic synaptic transmission in rat hippocampal neurons. Current-clamp recordings revealed that methacholine produced membrane depolarization and action potential firing. Methacholine augmented the bicuculline-sensitive and GABA(A) -mediated frequency of spontaneous inhibitory postsynaptic currents (sIPSCs); the action of methacholine had a slow onset and longer duration. The increase in methacholine-evoked sIPSCs was completely inhibited by atropine and was insensitive to glutamatergic receptor blockers. Interestingly, methacholine action was not inhibited by intracellular perfusion with GDP-β-S, suggesting that muscarinic effects on membrane excitability and sIPSC frequency are mainly presynaptic. McN-A-343 and pirenzepine, selective agonist and antagonist of the m1 mAChR subtype, respectively, neither enhanced sIPSCs nor inhibited the methacholine effect. However, the m3-m5 mAChR antagonist 4-DAMP, and the m2-m4 mAChR antagonist himbacine inhibited the methacholine effect. U73122, an IP(3) production inhibitor, and 2APB, an IP(3) receptor blocker, drastically decreased the methacholine effect. Recording of miniature events revealed that besides the effect exerted by methacholine on membrane firing properties and sIPSC frequency, muscarinic receptors also enhanced the frequency of mIPSCs with no effect on their amplitude, possibly modulating the molecular machinery subserving vesicle docking and fusion and suggesting a tight colocalization at the active zone of the presynaptic terminals. These data strongly suggest that by activating presynaptic m2, m3, m4 and m5 mAChRs, methacholine can increase membrane excitability and enhance efficiency in the GABA release machinery, perhaps through a mechanism involving the release of calcium from the endoplasmic reticulum.
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Affiliation(s)
- J C González
- Instituto Teófilo Hernando, IIS Hospital Universitario de la Princesa, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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17
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Boido D, Farisello P, Cesca F, Ferrea E, Valtorta F, Benfenati F, Baldelli P. Cortico-hippocampal hyperexcitability in synapsin I/II/III knockout mice: age-dependency and response to the antiepileptic drug levetiracetam. Neuroscience 2010; 171:268-83. [PMID: 20804820 DOI: 10.1016/j.neuroscience.2010.08.046] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 08/03/2010] [Accepted: 08/20/2010] [Indexed: 10/19/2022]
Abstract
Synapsins (SynI, SynII, SynIII) are a multigene family of synaptic vesicle (SV) phosphoproteins implicated in the regulation of synaptic transmission and plasticity. Synapsin I, II, I/II and I/II/III knockout mice are epileptic and SYN1/2 genes have been identified as major epilepsy susceptibility genes in humans. We analyzed cortico-hippocampal epileptiform activity induced by 4-aminopyridine (4AP) in acute slices from presymptomatic (3-weeks-old) and symptomatic (1-year-old) Syn I/II/III triple knockout (TKO) mice and aged-matched triple wild type (TWT) controls and assessed the effect of the SV-targeted antiepileptic drug (AED) levetiracetam (LEV) in reverting the epileptic phenotype. Both fast and slow interictal (I-IC) and ictal (IC) events were observed in both genotypes. The incidence of fast I-IC events was higher in presymptomatic TKO slices, while frequency and latency of I-IC events were similar in both genotypes. The major age and genotype effects were observed in IC activity, that was much more pronounced in 3-weeks-old TKO and persisted with age, while it disappeared from 1-year-old TWT slices. LEV virtually suppressed fast I-IC and IC discharges from 3-weeks-old TWT slices, while it only increased the latency of fast I-IC and IC activity in TKO slices. Analysis of I-IC events in patch-clamped CA1 pyramidal neurons revealed that LEV increased the inhibitory/excitatory ratio of I-IC activity in both genotypes. The lower LEV potency in TKO slices of both ages was associated with a decreased expression of SV2A, a SV protein acting as LEV receptor, in cortex and hippocampus. The results demonstrate that deletion of Syn genes is associated with a higher propensity to 4AP-induced epileptic paroxysms that precedes the onset of epilepsy and consolidates with age. LEV ameliorates such hyper excitability by enhancing the inhibition/excitation ratio, although the effect is hindered in TKO slices which exhibit a concomitant decrease in the levels of the LEV receptor SV2A.
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Affiliation(s)
- D Boido
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
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18
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Cesca F, Baldelli P, Valtorta F, Benfenati F. The synapsins: key actors of synapse function and plasticity. Prog Neurobiol 2010; 91:313-48. [PMID: 20438797 DOI: 10.1016/j.pneurobio.2010.04.006] [Citation(s) in RCA: 440] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 04/19/2010] [Accepted: 04/27/2010] [Indexed: 02/09/2023]
Abstract
The synapsins are a family of neuronal phosphoproteins evolutionarily conserved in invertebrate and vertebrate organisms. Their best-characterised function is to modulate neurotransmitter release at the pre-synaptic terminal, by reversibly tethering synaptic vesicles (SVs) to the actin cytoskeleton. However, many recent data have suggested novel functions for synapsins in other aspects of the pre-synaptic physiology, such as SV docking, fusion and recycling. Synapsin activity is tightly regulated by several protein kinases and phosphatases, which modulate the association of synapsins to SVs as well as their interaction with actin filaments and other synaptic proteins. In this context, synapsins act as a link between extracellular stimuli and the intracellular signalling events activated upon neuronal stimulation. Genetic manipulation of synapsins in various in vivo models has revealed that, although not essential for the basic development and functioning of neuronal networks, these proteins are extremely important in the fine-tuning of neuronal plasticity, as shown by the epileptic phenotype and behavioural abnormalities characterising mouse lines lacking one or more synapsin isoforms. In this review, we summarise the current knowledge about how the various members of the synapsin family are involved in the modulation of the pre-synaptic physiology. We give a comprehensive description of the molecular basis of synapsin function, as well as an overview of the more recent evidence linking mutations in the synapsin proteins to the onset of severe central nervous system diseases such as epilepsy and schizophrenia.
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Affiliation(s)
- F Cesca
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, via Morego 30, 16163 Genova, Italy
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19
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Baldelli P, Phelan N, Egan G. Investigation of the effect of anode/filter materials on the dose and image quality of a digital mammography system based on an amorphous selenium flat panel detector. Br J Radiol 2009; 83:290-5. [PMID: 20019173 DOI: 10.1259/bjr/60404532] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
A comparison, in terms of image quality and glandular breast dose, was carried out between two similar digital mammography systems using amorphous selenium flat panel detectors. The two digital mammography systems currently available from Lorad-Hologic were compared. The original system utilises Mo/Mo and Mo/Rh as target/filter combinations, while the new system uses W/Rh and W/Ag. Images of multiple mammography phantoms with simulated compressed breast thicknesses of 4 cm, 5 cm and 6 cm and various glandular tissue equivalency were acquired under different spectral conditions. The contrast of five details, corresponding to five glandular compositions, was calculated and the ratio of the square of the contrast-to-noise ratio to the average glandular dose was used as a figure-of-merit (FOM) to compare results. For each phantom thickness and target/filter combination, there is an optimum voltage that maximises the FOM. Results show that the W/Rh combination is the best choice for all the detection tasks studied, but for thicknesses greater than 6 cm the W/Ag combination would probably be the best choice. In addition, the new system with W filter presents a better optimisation of the automatic exposure control in comparison with the original system with Mo filter.
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Affiliation(s)
- P Baldelli
- Breastcheck, The National Cancer Screening Service, 36 Eccles Street, Dublin, Ireland.
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20
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Abstract
BACKGROUND Increased pressure ulcer prevalence and incidence rates led to the development of a pressure ulcer prevention program. OBJECTIVES To decrease pressure ulcer rates below national levels by implementing strategies to improve patient outcomes. METHODS Patients admitted to the Stony Brook University Medical Center (SBUMC) are assessed for placement in the pressure ulcer prevention program. The central element of the program is an evidence-based Pressure Ulcer Prevention Bundle using the "Bundle" concept from the Institute for Healthcare Improvement. RESULTS The March 2006 Prevalence and Incidence Benchmarking Study demonstrates not only a decrease in institutional prevalence and incidence rates but also places SBUMC rates below last year's national benchmark rates. CONCLUSION The implementation of a pressure ulcer prevention program has decreased prevalence and incidence rates at SBUMC and improved the quality of patient care.
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Affiliation(s)
- Perrilynn Baldelli
- Stony Brook University Medical Center Hospital, Stony Brook, New York 11733-9156, USA
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Arnaiz-Cot JJ, González JC, Sobrado M, Baldelli P, Carbone E, Gandía L, García AG, Hernández-Guijo JM. Allosteric modulation of alpha 7 nicotinic receptors selectively depolarizes hippocampal interneurons, enhancing spontaneous GABAergic transmission. Eur J Neurosci 2008; 27:1097-110. [PMID: 18312591 DOI: 10.1111/j.1460-9568.2008.06077.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of postsynaptic nicotinic receptors for acetylcholine (nAChRs) in mediating fast neurotransmission processes in the CNS is controversial. Here we have studied the modulation of synaptic transmission by an agonist (choline) and an allosteric modulator (5-OH-indole) of alpha7 nAChRs in rat hippocampal neuronal cultures. Choline evoked a fast inactivating inward current, causing neuron depolarization and action potential discharge, thereby enhancing the spontaneous postsynaptic current activity (sPSCs). This effect was markedly enhanced when both choline and 5-OH-indole were applied together and was blocked by the selective alpha7 nAChR antagonist methyllycaconitine. This choline action was suppressed by the GABA(A) receptor antagonist bicuculline, while the glutamatergic receptor antagonist kynurenic acid had no effect. Frequency, but not amplitude or area, of both excitatory and inhibitory miniature postsynaptic currents (mEPSCs and mIPSCs) were drastically reduced when Ca(2+) influx was blocked by Cd(2+). Additionally, nAChR activation did not modify the mIPSCs. These data suggest that Ca(2+) influx through the highly Ca(2+)-permeablealpha7 nAChRs was insufficient to directly activate neurotransmitter release, suggesting that a tight colocalization of this receptor with secretory hot spots is unlikely. In a few cases, the activation of alpha7 AChRs led to a suppression of spontaneous synaptic transmission. This effect may be related to the potentiation of GABAergic interneurons that inhibit the spontaneous activity of neurons making synapses with the cell under study. We suggest that GABA release is modulated by alpha7 nAChRs. Thus, selective allosteric modulators of alpha7 nAChRs could have potential therapeutic applications in brain disorders such as epilepsy and schizophrenia and in alterations of cognition and sensory processing.
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Affiliation(s)
- J J Arnaiz-Cot
- Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, Avenida Arzobispo Morcillo 4, 28029 Madrid, Spain
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22
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Marcantoni A, Baldelli P, Hernandez-Guijo JM, Comunanza V, Carabelli V, Carbone E. L-type calcium channels in adrenal chromaffin cells: Role in pace-making and secretion. Cell Calcium 2007; 42:397-408. [PMID: 17561252 DOI: 10.1016/j.ceca.2007.04.015] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2007] [Accepted: 04/29/2007] [Indexed: 11/16/2022]
Abstract
Voltage-gated L-type (Cav1.2 and Cav1.3) channels are widely expressed in cardiovascular tissues and represent the critical drug-target for the treatment of several cardiovascular diseases. The two isoforms are also abundantly expressed in neuronal and neuroendocrine tissues. In the brain, Cav1.2 and Cav1.3 channels control synaptic plasticity, somatic activity, neuronal differentiation and brain aging. In neuroendocrine cells, they are involved in the genesis of action potential generation, bursting activity and hormone secretion. Recent studies have shown that Cav1.2 and Cav1.3 are also expressed in chromaffin cells but their functional role has not yet been identified despite that L-type channels possess interesting characteristics, which confer them an important role in the control of catecholamine secretion during action potentials stimulation. In intact rat adrenal glands L-type channels are responsible for adrenaline and noradrenaline release following splanchnic nerve stimulation or nicotinic receptor activation. L-type channels can be either up- or down-modulated by membrane autoreceptors following distinct second messenger pathways. L-type channels are tightly coupled to BK channels and activate at relatively low-voltages. In this way they contribute to the action potential hyperpolarization and to the pace-maker current controlling action potential firings. L-type channels are shown also to regulate the fast secretion of the immediate readily releasable pool of vesicles with the same Ca(2+)-efficiency of other voltage-gated Ca(2+) channels. In mouse adrenal slices, repeated action potential-like stimulations drive L-type channels to a state of enhanced stimulus-secretion efficiency regulated by beta-adrenergic receptors. Here we will review all these novel findings and discuss the possible implication for a specific role of L-type channels in the control of chromaffin cells activity.
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Affiliation(s)
- A Marcantoni
- Department of Neuroscience, NIS Center of Excellence, CNISM Research Unit, Corso Raffaello 30, 10125 Torino, Italy
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23
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Sarnelli A, Taibi A, Baldelli P, Gambaccini M, Bravin A. Quantitative analysis of the effect of energy separation in k-edge digital subtraction imaging. Phys Med Biol 2007; 52:3015-26. [PMID: 17505086 DOI: 10.1088/0031-9155/52/11/006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The aim of the work is to quantitatively compare the effect of the energy separation in the k-edge digital subtraction imaging technique. Images of a custom-made, iodine filled (k-edge = 33.17 keV) test object have been acquired with monochromatic x-ray beams (energy spread <0.1 keV) at the ID17 biomedical beamline of the ESRF. Image acquisition has been performed using two energy separations, namely 0.65 keV (32.85 keV and 33.5 keV, respectively) and 4.4 keV (31.2 keV and 35.6 keV, respectively), using beams of energies on either side of the iodine k-edge. Signal and signal-to-noise ratio (SNR) analysis has been performed as a function of DeltaE and the contrast medium concentrations. The results show that the SNR values measured for DeltaE < 1 keV are only slightly higher than those measured for DeltaE = 4.4 keV. This preliminary study shows that monochromaticity and the energy separation obtained with quasi monochromatic beams from conventional x-ray sources might be suitable for this imaging technique.
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Affiliation(s)
- A Sarnelli
- Policlinico S. Orsola Malpighi, Via Massarenti 9, 40138 Bologna, Italy.
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24
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Bonanomi D, Menegon A, Baldelli P, Benfenati F, Valtorta F. [P60]: Protein kinase a‐mediated synapsin I phosphorylation is a developmentally conserved mechanism for the control of synaptic vesicle dynamics. Int J Dev Neurosci 2006. [DOI: 10.1016/j.ijdevneu.2006.09.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- D. Bonanomi
- San Raffaele Scientific Institute and “Vita‐Salute” UniversityItaly
| | - A. Menegon
- San Raffaele Scientific Institute and “Vita‐Salute” UniversityItaly
| | | | | | - F. Valtorta
- San Raffaele Scientific Institute and “Vita‐Salute” UniversityItaly
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25
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Baldelli P, Bravin A, Di Maggio C, Gennaro G, Sarnelli A, Taibi A, Gambaccini M. Evaluation of the minimum iodine concentration for contrast-enhanced subtraction mammography. Phys Med Biol 2006; 51:4233-51. [PMID: 16912379 DOI: 10.1088/0031-9155/51/17/008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Early manifestation of breast cancer is often very subtle and is displayed in a complex and variable pattern of normal anatomy that may obscure the disease. The use of dual-energy techniques, that can remove the structural noise, and contrast media, that enhance the region surrounding the tumour, could help us to improve the detectability of the lesions. The aim of this work is to investigate the use of an iodine-based contrast medium in mammography with two different double exposure techniques: K-edge subtraction mammography and temporal subtraction mammography. Both techniques have been investigated by using an ideal source, like monochromatic beams produced at a synchrotron radiation facility and a clinical digital mammography system. A dedicated three-component phantom containing cavities filled with different iodine concentrations has been developed and used for measurements. For each technique, information about the minimum iodine concentration, which provides a significant enhancement of the detectability of the pathology by minimizing the risk due to high dose and high concentration of contrast medium, has been obtained. In particular, for cavities of 5 and 8 mm in diameter filled with iodine solutions, the minimum concentration needed to obtain a contrast-to-noise ratio of 5 with a mean glandular dose of 2 mGy has been calculated. The minimum concentrations estimated with monochromatic beams and K-edge subtraction mammography are 0.9 mg ml(-1) and 1.34 mg ml(-1) for the biggest and smallest details, respectively, while for temporal subtraction mammography they are 0.84 mg ml(-1) and 1.31 mg ml(-1). With the conventional clinical system the minimum concentrations for the K-edge subtraction mammography are 4.13 mg ml(-1) (8 mm diameter) and 5.75 mg ml(-1) (5 mm diameter), while for the temporal subtraction mammography they are 1.01 mg ml(-1) (8 mm diameter) and 1.57 mg ml(-1) (5 mm diameter).
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Affiliation(s)
- P Baldelli
- Department of Physics, University of Ferrara, Via Saragat 1, 44100 Ferrara, Italy.
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26
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Giancippoli A, Novara M, de Luca A, Baldelli P, Marcantoni A, Carbone E, Carabelli V. Low-threshold exocytosis induced by cAMP-recruited CaV3.2 (alpha1H) channels in rat chromaffin cells. Biophys J 2006; 90:1830-41. [PMID: 16361341 PMCID: PMC1367332 DOI: 10.1529/biophysj.105.071647] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Accepted: 11/29/2005] [Indexed: 11/18/2022] Open
Abstract
We have studied the functional role of CaV3 channels in triggering fast exocytosis in rat chromaffin cells (RCCs). CaV3 T-type channels were selectively recruited by chronic exposures to cAMP (3 days) via an exchange protein directly activated by cAMP (Epac)-mediated pathway. Here we show that cAMP-treated cells had increased secretory responses, which could be evoked even at very low depolarizations (-50, -40 mV). Potentiation of exocytosis in cAMP-treated cells did not occur in the presence of 50 microM Ni2+, which selectively blocks T-type currents in RCCs. This suggests that the "low-threshold exocytosis" induced by cAMP is due to increased Ca2+ influx through cAMP-recruited T-type channels, rather than to an enhanced secretion downstream of Ca2+ entry, as previously reported for short-term cAMP treatments (20 min). Newly recruited T-type channels increase the fast secretory response at low voltages without altering the size of the immediately releasable pool. They also preserve the Ca2+ dependence of exocytosis, the initial speed of vesicle depletion, and the mean quantal size of single secretory events. All this indicates that cAMP-recruited CaV3 channels enhance the secretory activity of RCCs at low voltages by coupling to the secretory apparatus with a Ca2+ efficacy similar to that of already existing high-threshold Ca2+ channels. Finally, using RT-PCRs we found that the fast inactivating low-threshold Ca2+ current component recruited by cAMP is selectively associated to the alpha1H (CaV3.2) channel isoform.
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Affiliation(s)
- A Giancippoli
- Department of Neuroscience, NIS Centre of Excellence, CNISM Research Unit, 10125 Turin, Italy
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27
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Baldelli P, Fassio A, Corradi A, Cremona O, Valtorta F, Benfenati F. Synapsins and neuroexocytosis: recent views from functional studies on synapsin null mutant mice. Arch Ital Biol 2005; 143:113-26. [PMID: 16106992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- P Baldelli
- Neurolab, Departmnent of Experimental Medicine, Section of Human Physiology, University of Genova, Viale Benedetto XV 3, 16132 Genova, Italy.
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Abstract
Improvement in image contrast and dose reduction, in mammographic x-ray imaging, can be achieved using narrow energy band x-ray beams in the 16-24 keV range. As part of an Italian Government funded project, a quasi-monochromatic system for mammography applications has been developed. The system is based on a tunable narrow energy band x-ray source operating in the 16-24 keV energy range. The bremsstrahlung beam is monochromatized via Bragg diffraction by a highly oriented pyrolytic graphite mosaic crystal (HOPG). The scanning system provides a large field (18 x 24 cm2) of quasi-monochromatic x-rays with energy resolution ranging from 10% at 18 keV to 17.2% at 24 keV. The system has been characterized in terms of fluence rate and energy resolution. An x-ray tube developed ad hoc allows us to acquire images in a reasonable time to minimize the motion blur. A qualitative analysis has been performed in order to know if the prototype system performances are far from a clinical application, by evaluating the spatial resolution, the field uniformity and the image quality as a function of the quasi-monochromatic beam energy. Dose evaluation has been performed as a function of the energy and compared to a conventional system for mammography. The quasi-monochromatic prototype system can produce comparable image quality at half the dose.
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Affiliation(s)
- P Baldelli
- Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy.
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29
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Abstract
Several techniques have been introduced in the last year to reduce the dose to the patient by minimizing the risk of tumour induced by radiation. In this work the radiological potential of dose reduction in quasi-monochromatic spectra produced via mosaic crystal Bragg diffraction has been evaluated, and a comparison with conventional spectra has been performed for four standard examinations: head, chest, abdomen and lumbar sacral spine. We have simulated quasi-monochromatic x-rays with the Shadow code, and conventional spectra with the Spectrum Processor. By means of the PCXMC software, we have simulated four examinations according to parameters established by the European Guidelines, and calculated absorbed dose for principal organs and the effective dose. Simulations of quasi-monochromatic laminar beams have been performed without anti-scatter grid, because of their inherent scatter geometry, and compared with simulations with conventional beams with anti-scatter grids. Results have shown that the dose reduction due to the introduction of quasi-monochromatic x-rays depends on different parameters related to the quality of the beam, the organ composition and the anti-scatter grid. With parameters chosen in this study a significant dose reduction can be achieved for two out of four kinds of examination.
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Affiliation(s)
- P Baldelli
- Dipartimento di Fisca, Università di Ferrara and INFN, Sezione di Ferrara, via Paradiso 12, 44100 Ferrara, Italy.
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30
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Novara M, Baldelli P, Cavallari D, Carabelli V, Giancippoli A, Carbone E. Exposure to cAMP and beta-adrenergic stimulation recruits Ca(V)3 T-type channels in rat chromaffin cells through Epac cAMP-receptor proteins. J Physiol 2004; 558:433-49. [PMID: 15133061 PMCID: PMC1664977 DOI: 10.1113/jphysiol.2004.061184] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
T-type channels are expressed weakly or not at all in adult rat chromaffin cells (RCCs) and there is contrasting evidence as to whether they play a functional role in catecholamine secretion. Here we show that 3-5 days after application of pCPT-cAMP, most RCCs grown in serum-free medium expressed a high density of low-voltage-activated T-type channels without altering the expression and characteristics of high-voltage-activated channels. The density of cAMP-recruited T-type channels increased with time and displayed the typical biophysical and pharmacological properties of low-voltage-activated Ca(2+) channels: (1) steep voltage-dependent activation from -50 mV in 10 mm Ca(2+), (2) slow deactivation but fast and complete inactivation, (3) full inactivation following short conditioning prepulses to -30 mV, (4) effective block of Ca(2+) influx with 50 microM Ni(2+), (5) comparable permeability to Ca(2+) and Ba(2+), and (6) insensitivity to common Ca(2+) channel antagonists. The action of exogenous pCPT-cAMP (200 microM) was prevented by the protein synthesis inhibitor anisomycin and mimicked in most cells by exposure to forskolin and 1-methyl-3-isobutylxanthine (IBMX) or isoprenaline. The protein kinase A (PKA) inhibitor H89 (0.3 microM) and the competitive antagonist of cAMP binding to PKA, Rp-cAMPS, had weak or no effect on the action of pCPT-cAMP. In line with this, the selective Epac agonist 8CPT-2Me-cAMP nicely mimicked the action of pCPT-cAMP and isoprenaline, suggesting the existence of a dominant Epac-dependent recruitment of T-type channels in RCCs that may originate from the activation of beta-adrenoceptors. Stimulation of beta-adrenoceptors occurs autocrinally in RCCs and thus, the neosynthesis of low-voltage-activated channels may represent a new form of 'chromaffin cell plasticity', which contributes, by lowering the threshold of action potential firing, to increasing cell excitability and secretory activity during sustained sympathetic stimulation and/or increased catecholamine circulation.
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Affiliation(s)
- M Novara
- Department of Neuroscience, INFM Research Unit, 10125 Torino, Italy
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31
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Abstract
Monochromatic x-ray beams are desirable in various fields of diagnostic radiology; in fact a reduction of the dose and an enhancement of the contrast could be achieved. In this work two different methods to monochromatize x-ray beams produced by conventional tubes have been compared. In the first one the beam is obtained via Bragg diffraction on mosaic crystal and in the second one by attenuating the polychromatic beam with aluminium filters. We have simulated quasi-monochromatic x-ray spectra by setting suitable values of Bragg's angle to obtain beams tuned to 20, 30, 40 and 50 keV with the SHADOW code, an x-ray tracing program designed to study the propagation and the interaction of a photon beam through an optical system. We have validated such a program by comparing some calculated data with measurements carried out on an experimental apparatus. Attenuated polychromatic x-ray spectra have been simulated by setting appropriate values of aluminium filters and potential with the SPECTRUM PROCESSOR, the software version of the Catalogue of Spectral Data for Diagnostic X-Rays, which provides radiographic x-ray spectra that can be attenuated with several material filters. The relation between the energy resolution and the flux as a function of the mean energy has been investigated and results have been compared. Results show that quasi-monochromatic x-ray beams produced via Bragg diffraction exhibit, for a given mean energy and energy resolution, a higher total flux compared to attenuated spectra.
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Affiliation(s)
- P Baldelli
- Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy.
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32
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Abstract
We have investigated the potentiating action of cAMP on L-currents of rat chromaffin cells and the corresponding increase of Ca(2+)-evoked secretory responses with the aim of separating the action of cAMP on Ca(2+) entry through L-channels and the downstream effects of cAMP/protein kinase A (PKA) on exocytosis. In omega-toxin-treated rat chromaffin cells, exposure to the permeable cAMP analog 8-(4-chlorophenylthio)-adenosine 3',5'-monophosphate (pCPT-cAMP; 1 mM, 30 min) caused a moderate increase of Ca(2+) charge carried through L-channels (19% in 10 mM Ca(2+) at +10 mV) and a drastic potentiation of secretion ( approximately 100%), measured as membrane capacitance increments (deltaC). The apparent Ca(2+) dependency of exocytosis increased with pCPT-cAMP and was accompanied by 83% enhancement of the readily releasable pool of vesicles with no significant change of the probability of release, as evaluated with paired-pulse stimulation protocols. pCPT-cAMP effects could be mimicked by stimulation of beta(1)-adrenoreceptors and reversed by the PKA inhibitor H89, suggesting strict PKA dependence. For short pulses to +10 mV (100 ms), potentiation of exocytosis by pCPT-cAMP was proportional to the quantity of charge entering the cell and occurred independently of whether L, N, or P/Q channels were blocked, suggesting that cAMP acts as a constant amplification factor for secretion regardless of the channel type carrying Ca(2+). Analysis of statistical variations among depolarization-induced capacitance increments indicates that pCPT-cAMP acts downstream of Ca(2+) entry by almost doubling the mean size of unitary exocytic events, most likely as a consequence of an increased granule-to-granule rather than a granule-to-membrane fusion.
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Affiliation(s)
- V Carabelli
- Dipartimento di Neuroscienze, Unità di Ricerca, Instituto Nazionale Fisica della Materia, 10125 Turin, Italy.
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Taibi A, Fabbri S, Baldelli P, di Maggio C, Gennaro G, Marziani M, Tuffanelli A, Gambaccini M. Dual-energy imaging in full-field digital mammography: a phantom study. Phys Med Biol 2003; 48:1945-56. [PMID: 12884927 DOI: 10.1088/0031-9155/48/13/307] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A dual-energy technique which employs the basis decomposition method is being investigated for application to digital mammography. A three-component phantom, made up of plexiglas, polyethylene, and water, was doubly exposed with the full-field digital mammography system manufactured by General Electric. The 'low' and 'high' energy images were recorded with a Mo/Mo anode-filter combination and a Rh/Rh combination, respectively. The total dose was kept within the acceptable levels of conventional mammography. The first hybrid images obtained with the dual-energy algorithm are presented in comparison with a conventional radiograph of the phantom. Image-quality characteristics at contrast cancellation angles between plexiglas and water are discussed. Preliminary results show that a combination of a standard Mo-anode 28 kV radiograph with a Rh-anode 49 kV radiograph provides the best compromise between image-quality and dose in the hybrid image.
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Affiliation(s)
- A Taibi
- Dipartimento di Fisica, Università di Ferrara and INFN, Sezione di Ferrara, via Paradiso 12, 44100 Ferrara, Italy.
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Cesetti T, Hernández-Guijo JM, Baldelli P, Carabelli V, Carbone E. Opposite action of beta1- and beta2-adrenergic receptors on Ca(V)1 L-channel current in rat adrenal chromaffin cells. J Neurosci 2003; 23:73-83. [PMID: 12514203 PMCID: PMC6742137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
Voltage-gated Ca(2+) channels of chromaffin cells are modulated by locally released neurotransmitters through autoreceptor-activated G-proteins. Clear evidence exists in favor of a Ca(2+) channel gating inhibition mediated by purinergic, opioidergic, and alpha-adrenergic autoreceptors. Few and contradictory data suggest also a role of beta-adrenergic autoreceptors (beta-ARs), the action of which, however, remains obscure. Here, using patch-perforated recordings, we show that rat chromaffin cells respond to the beta-AR agonist isoprenaline (ISO) by either upmodulating or downmodulating the amplitude of Ca(2+) currents through two distinct modulatory pathways. ISO (1 microm) could cause either fast inhibition (approximately 25%) or slow potentiation (approximately 25%), or a combination of the two actions. Both effects were completely prevented by propranolol. Slow potentiation was more evident in cells pretreated with pertussis toxin (PTX) or when beta(1)-ARs were selectively stimulated with ISO + ICI118,551. Potentiation was absent when the beta(2)-AR-selective agonist zinterol (1 microm), the protein kinase A (PKA) inhibitor H89, or nifedipine was applied, suggesting that potentiation is associated with a PKA-mediated phosphorylation of L-channels (approximately 40% L-current increase) through beta(1)-ARs. The ISO-induced inhibition was fast and reversible, preserved in cell treated with H89, and mimicked by zinterol. The action of zinterol was mostly on L-channels (38% inhibition). Zinterol action preserved the channel activation kinetics, the voltage-dependence of the I-V characteristic, and was removed by PTX, suggesting that beta(2)AR-mediated channel inhibition was mainly voltage independent and coupled to G(i)/G(o)-proteins. Sequential application of zinterol and ISO mimicked the dual action (inhibition/potentiation) of ISO alone. The two kinetically and pharmacologically distinct beta-ARs signaling uncover alternative pathways, which may serve the autocrine control of Ca(2+)-dependent exocytosis and other related functions of rat chromaffin cells.
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Affiliation(s)
- T Cesetti
- Department of Neuroscience, INFM Research Unit, 10125 Turin, Italy
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35
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Baldelli P, Novara M, Carabelli V, Hernández-Guijo JM, Carbone E. BDNF up-regulates evoked GABAergic transmission in developing hippocampus by potentiating presynaptic N- and P/Q-type Ca2+ channels signalling. Eur J Neurosci 2002; 16:2297-310. [PMID: 12492424 DOI: 10.1046/j.1460-9568.2002.02313.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Chronic application of brain-derived neurotrophic factor (BDNF) induces new selective synthesis of non-L-type Ca2+ channels (N, P/Q, R) at the soma of cultured hippocampal neurons. As N- and P/Q-channels support neurotransmitter release in the hippocampus, this suggests that BDNF-treatment may enhance synaptic transmission by increasing the expression of presynaptic Ca2+ channels as well. To address this issue we studied the long-term effects of BDNF on miniature and stimulus-evoked GABAergic transmission in rat embryo hippocampal neurons. We found that BDNF increased the frequency of miniature currents (mIPSCs) by approximately 40%, with little effects on their amplitude. BDNF nearly doubled the size of evoked postsynaptic currents (eIPSCs) with a marked increase of paired-pulse depression, which is indicative of a major increase in presynaptic activity. The potentiation of eIPSCs was more relevant during the first two weeks in culture, when GABAergic transmission is depolarizing. BDNF action was mediated by TrkB-receptors and had no effects on: (i) the amplitude and dose-response of GABA-evoked IPSCs and (ii) the number of GABA(A) receptor clusters and the total functioning synapses, suggesting that the neurotrophin unlikely acted postsynaptically. In line with this, BDNF affected the contribution of voltage-gated Ca2+ channels mediating evoked GABAergic transmission. BDNF drastically increased the fraction of evoked IPSCs supported by N- and P/Q-channels while it decreased the contribution associated with R- and L-types. This selective action resembles the previously observed up-regulatory effects of BDNF on somatic Ca2+ currents in developing hippocampus, suggesting that potentiation of presynaptic N- and P/Q-channel signalling belongs to a manifold mechanism by which BDNF increases the efficiency of stimulus-evoked GABAergic transmission.
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MESH Headings
- Animals
- Brain-Derived Neurotrophic Factor/metabolism
- Brain-Derived Neurotrophic Factor/pharmacology
- Calcium Channel Blockers/pharmacology
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Channels, N-Type/drug effects
- Calcium Channels, N-Type/metabolism
- Calcium Channels, P-Type/drug effects
- Calcium Channels, P-Type/metabolism
- Calcium Channels, Q-Type/drug effects
- Calcium Channels, Q-Type/metabolism
- Cell Differentiation/drug effects
- Cell Differentiation/physiology
- Cells, Cultured
- Female
- Fetus
- GABA Antagonists/pharmacology
- Hippocampus/drug effects
- Hippocampus/embryology
- Hippocampus/metabolism
- Neural Inhibition/drug effects
- Neural Inhibition/physiology
- Potassium Chloride/pharmacology
- Pregnancy
- Presynaptic Terminals/drug effects
- Presynaptic Terminals/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, trkB/drug effects
- Receptor, trkB/metabolism
- Receptors, GABA-A/drug effects
- Receptors, GABA-A/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Up-Regulation/drug effects
- Up-Regulation/physiology
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- P Baldelli
- INFM Research Unit, University of Turin, I-10125 Turin, Italy
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Carbone E, Carabelli V, Cesetti T, Baldelli P, Hernández-Guijo JM, Giusta L. G-protein- and cAMP-dependent L-channel gating modulation: a manyfold system to control calcium entry in neurosecretory cells. Pflugers Arch 2001; 442:801-13. [PMID: 11680611 DOI: 10.1007/s004240100607] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Voltage-gated Ca2+ channels are crucial to the control of Ca2+ entry in neurosecretory cells. In the chromaffin cells of adrenal medulla, paracrinally or autocrinally released neurotransmitters induce profound changes in Ca2+ channel gating and Ca2+-dependent events controlling catecholamine secretion and cell activity. The generally held view of these processes is that neurotransmitter-induced modulation of the most widely expressed Ca2+ channels in these cells (N-, P/Q- and L-type) follows two distinct pathways: a direct membrane-delimited Gi/o-protein-induced inhibition of N- and P/Q-type and a remote cAMP-mediated facilitation of L-channels. Both actions depend on voltage, although with remarkably different molecular and kinetic aspects. Recent findings, however, challenge this simple scheme and suggest that L-channels do not require strong pre-pulses to be recruited or facilitated. They are available during normal depolarizations and may be tonically inhibited by Gi/o proteins activated by the released neurotransmitters. Like the N- and P/Q-channels, this autocrine modulation is localized to membrane microareas. Unlike N- and P/Q-channels, however, the inhibition of L-channels is largely independent of voltage and develops in parallel with cAMP-mediated potentiation of channel gating. As L-channels play a crucial role in the control of catecholamine release in chromaffin cells, the two opposite modulations mediated by Gi/o proteins and cAMP may represent an effective way to broaden the dynamic range of Ca2+ signals controlling exocytosis. Here, we review the basic features of this novel L-type channel inhibition comparing it to the well-established forms of L-channel potentiation and voltage-dependent facilitation.
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Affiliation(s)
- E Carbone
- Dipartimento di Neuroscienze, Unità di Ricerca INFM, Torino, Italy.
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37
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Carabelli V, Hernández-Guijo JM, Baldelli P, Carbone E. Direct autocrine inhibition and cAMP-dependent potentiation of single L-type Ca2+ channels in bovine chromaffin cells. J Physiol 2001; 532:73-90. [PMID: 11283226 PMCID: PMC2278521 DOI: 10.1111/j.1469-7793.2001.0073g.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2000] [Accepted: 11/23/2000] [Indexed: 11/29/2022] Open
Abstract
Using the cell-attached recording configuration, we found that in adult bovine chromaffin cells there exists a direct membrane-delimited inhibition of single Bay K-modified L-channels mediated by opioids and ATP locally released in the recording pipette. This autocrine modulation is mediated by pertussis toxin (PTX)-sensitive G-proteins and causes a 50 % decrease of the open channel probability (Po) and an equivalent percentage increase of null sweeps at +10 mV with no changes to the activation kinetics, single channel conductance and mean open time. The decrease in Po is mainly due to an increase in the occurrence and duration of slow closed times (> 40 ms). Addition of purinergic and opioidergic antagonists (suramin and naloxone) or cell pre-treatment with PTX removes the inhibition while addition of ATP and opioids inside the pipette, but not outside, mimics the effect. Strong pre-pulses (+150 mV, 280 ms) followed by short repolarizations are unable to remove the inhibition at test potential (+10 mV). Increasing the level of cAMP by either direct application of 8-(4-chlorophenylthio)-cAMP (8-CPT-cAMP) or mixtures of forskolin and 1-methyl-3-isobutylxanthine (IBMX) potentiates the activity of L-channels by increasing the mean open time and decreasing the mean closed time and percentage of null sweeps. The cAMP-induced potentiation occurs regardless of whether the G-protein-mediated inhibition is activated by ATP and opioids or inactivated by PTX. Protein kinase inhibitors (H7 and H89) prevent the effects of cAMP without altering the basal autocrine modulation associated with PTX-sensitive G-proteins. Our results provide new evidence for the coexistence of two distinct modulations that may converge on the same neuroendocrine L-channel: a direct G-protein-dependent inhibition and a cAMP-mediated potentiation, which may work in combination to regulate Ca2+ entry during neurosecretion.
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Affiliation(s)
- V Carabelli
- Department of Neuroscience, INFM Research Unit, Corso Raffaello 30, I-10125 Turin, Italy
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38
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Abstract
Neurotrophins exert short- and long-term effects on synaptic transmission. The mechanism underlying these forms of synaptic plasticity is unknown although it is likely that intracellular Ca2+ and presynaptic Ca2+ channels play a critical role. Here we show that BDNF, NGF and NT-3 (10-100 ng/mL) exhibit a selective long-term up-regulation of voltage-gated Ca2+ current densities in developing hippocampal neurons of 6-20 days in culture. NGF and NT-3 appear more effective in up-regulating L-currents, while BDNF predominantly acts on non-L-currents (N, P/Q and R). The effects of the three neurotrophins were time- and dose-dependent. The EC50 was comparable for BDNF, NGF and NT-3 (10-16 ng/mL) while the time of half-maximal activation was significantly longer for NGF compared to BDNF (58 vs. 25 h). Despite the increased Ca2+ current density, the neurotrophins did not alter the voltage-dependence of channel activation, the kinetics parameters or the elementary properties of Ca2+ channels (single-channel conductance, probability of opening and mean open time). Neurotrophin effects were completely abolished by coincubation with the nonspecific Trk-receptor inhibitor K252a, the protein synthesis blocker anisomycin and the MAP-kinase inhibitor PD98059, while cotreatment with the PLC-gamma blocker, U73122, was without effect. Immunocytochemistry and Western blotting revealed that neurotrophins induced an increased MAP-kinase phosphorylation and its translocation to the nucleus. The present findings suggest that on a long time scale different neurotrophins can selectively up-regulate different Ca2+ channels. The action is mediated by Trk-receptors/MAP-kinase pathways and induces an increased density of newly available Ca2+ channels with unaltered gating activity.
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Affiliation(s)
- P Baldelli
- INFM Research Unit and Department of Neuroscience, I-University of Turin, Corso Raffaello 30, I-10125 Turin, Italy
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39
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De Jaco A, Ajmone-Cat MA, Baldelli P, Carbone E, Augusti-Tocco G, Biagioni S. Modulation of acetylcholinesterase and voltage-gated Na(+) channels in choline acetyltransferase- transfected neuroblastoma clones. J Neurochem 2000; 75:1123-31. [PMID: 10936194 DOI: 10.1046/j.1471-4159.2000.0751123.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neurotransmitters appear early in the developing embryo and may play a role in the regulation of neuronal differentiation. To study potential effects of acetylcholine production in neuronal differentiation, we used the FB5 subclone of N18TG2 murine neuroblastoma cells stably transfected with cDNA for choline acetyltransferase. We tested whether the forced acetylcholine production can modify the expression or the cellular localization of different neuronal markers. We studied the activity, localization, and secretion of acetylcholinesterase in view of its possible role in the modulation of the morphogenetic action of acetylcholine and of its proposed role of a regulator of neurite outgrowth. FB5 cells are characterized by a high level of acetylcholinesterase, predominantly released into the culture medium. Acetylcholinesterase secretion into the medium was lower in choline acetyltransferase-transfected clones than in nontransfected and antisense-transfected controls. Moreover, sequential extraction of acetylcholinesterase revealed that detergent-extracted, i.e., membrane-associated, activity was higher in the transfected clones expressing choline acetyltransferase activity than in both control groups. These observations suggest that a shift occurs in the utilization of acetylcholinesterase in choline acetyltransferase-transfected clones from a secretion pathway to a pathway leading to membrane localization. In addition, the choline acetyltransferase-positive clones showed higher densities of voltage-gated Na(+) channels and enhanced high-affinity choline uptake, suggesting the accomplishment of a more advanced differentiated neuronal phenotype. Finally, binding experiments demonstrated the presence of muscarinic acetylcholine receptors in all examined clones. This observation is consistent with the proposed existence of an autocrine loop, which may be important for the enhancement in the expression of neurospecific traits.
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Affiliation(s)
- A De Jaco
- Dipartimento di Biologia Cellulare e dello Sviluppo, Università "La Sapienza," Roma, Italy
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40
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Abstract
Cultured spinal cord motoneurons from day 15 rat embryos (E15) represent a useful model to study Ca2+ channel diversities and their regulation by neurotrophins. Besides the previously identified L-, N- and P-type channels, E15 rat motoneurons also express high densities of R-type channels. We have previously shown that the P-type channel is nearly absent in 60% of these cells, while the R-type contributes to approximately 35% of the total current. Here, we show that chronic preincubation of cultured rat motoneurons with high concentrations (20-100 ng/mL) of brain-derived neurotrophic factor (BDNF) caused a selective up-regulation of the P- and R-type current density available after blocking N- and L-type channels, with no changes to cell membrane capacitance. N- and L-type channels were either not affected or slightly down-modulated by the neurotrophin. The onset of BDNF up-regulation of P/R-type currents had a half-time of 12 h and reached maximal values of approximately 80%. High concentrations of nerve growth factor (NGF; 50-100 ng/mL) had no effect on P/R currents, while BDNF action was prevented by the kinase inhibitor K252a and by the protein synthesis inhibitor anisomycin. These results suggest that chronic applications of BDNF selectively up-regulates the Ca2+ channel types which are most likely to be involved in the control of neurotransmitter release in mammalian neuromuscular junctions. The signal transduction mechanism is probably mediated by TrkB receptors and involves the synthesis of newly functionally active P- and R-type channels. Our data furnish a rationale for a number of recent observations in other laboratories, in which prolonged applications of neurotrophins were shown to potentiate the presynaptic response in developing synapses.
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Affiliation(s)
- P Baldelli
- Department of Neuroscience, INFM, Research Unit, Turin, Italy
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41
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Abstract
Ca2+ channels diversity of cultured rat embryo motoneurons was investigated with whole-cell current recordings. In 5-20 mM Ba2+, the whole-cell currents were separated in low- (LVA) and high-voltage-activated (HVA) current. The LVA current was evident since the first day in culture, while the HVA component was small and increased with time. Recordings after 4 days revealed approximately 20% L-, approximately 45% N- and approximately 35% P- and R-type currents. P-type currents were revealed only in 40% of motoneurons, in which 20-200 nM omega-Aga-IVA caused 20% irreversible block of total current. The remaining 60% of cells were insensitive even to higher doses of the toxin (500 nM in 5 mM Ba2+), suggesting weak expression and heterogeneous distribution of P-type channels compensated by high densities of HVA Ca2+ channels resistant to all the antagonists (R-type). A significant residual current could also be resolved after prolonged applications of 5 microM omega-CTx-MVIIC, which allowed separation of N- and P-type currents by the distinct onset of toxin block. The antagonists-resistant current reveals biophysical characteristics typical of HVA channels, but distinct from the alphaE channel. The current activates around -20 mV in 20 mM Ba2+; inactivates slowly and independently of Ca2+; is blocked by low [Cd2+] and high [Ni2+]; and is larger with Ba2+ than Ca2+. The uncovered R-type calcium current can account for part of the presynaptic Ca2+ current controlling neurotransmitter release at the mammalian neuromuscular junction whose activity is resistant to DHP-and omega-CTx-GVIA, and displays anomalous sensitivity to omega-Aga-IVA and omega-CTx-MVIIC.
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Affiliation(s)
- V Magnelli
- Department of Neuroscience, University of Turin, Italy
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42
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Abstract
In voltage-dependent ion channels, the gating of the channels is determined by the movement of the voltage sensor. This movement reflects the rearrangement of the protein in response to a voltage stimulus, and it can be thought of as a net displacement of elementary charges (e0) through the membrane (z: effective number of elementary charges). In this paper, we measured z in Shaker IR (inactivation removed) K+ channels, neuronal alpha 1E and alpha 1A, and cardiac alpha 1C Ca2+ channels using two methods: (a) limiting slope analysis of the conductance-voltage relationship and (b) variance analysis, to evaluate the number of active channels in a patch, combined with the measurement of charge movement in the same patch. We found that in Shaker IR K+ channels the two methods agreed with a z congruent to 13. This suggests that all the channels that gate can open and that all the measured charge is coupled to pore opening in a strictly sequential kinetic model. For all Ca2+ channels the limiting slope method gave consistent results regardless of the presence or type of beta subunit tested (z = 8.6). However, as seen with alpha 1E, the variance analysis gave different results depending on the beta subunit used. alpha 1E and alpha 1E beta 1a gave higher z values (z = 14.77 and z = 15.13 respectively) than alpha 1E beta 2a (z = 9.50, which is similar to the limiting slope results). Both the beta 1a and beta 2a subunits, coexpressed with alpha 1E Ca2+ channels facilitated channel opening by shifting the activation curve to more negative potentials, but only the beta 2a subunit increased the maximum open probability. The higher z using variance analysis in alpha 1E and alpha 1E beta 1a can be explained by a set of charges not coupled to pore opening. This set of charges moves in transitions leading to nulls thus not contributing to the ionic current fluctuations but eliciting gating currents. Coexpression of the beta 2a subunit would minimize the fraction of nulls leading to the correct estimation of the number of channels and z.
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Affiliation(s)
- F Noceti
- Department of Anesthesiology, School of Medicine, University of California, Los Angeles 90095-1778, USA
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43
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Neely A, Olcese R, Baldelli P, Wei X, Birnbaumer L, Stefani E. Dual activation of the cardiac Ca2+ channel alpha 1C-subunit and its modulation by the beta-subunit. Am J Physiol 1995; 268:C732-40. [PMID: 7900777 DOI: 10.1152/ajpcell.1995.268.3.c732] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Ca2+ channels are heteromultimeric proteins in which the alpha 1-subunit forms the voltage-dependent Ca(2+)-selective ionic channel. We reported recently that coexpression of the beta-subunit with the cardiac alpha 1-subunit (alpha 1C) facilitates channel opening without affecting either the amplitude or the time course of the gating currents (13). Here we present evidence for the existence of two modes of channel opening. Xenopus oocytes expressing the alpha 1C-subunit alone display two modes of activation as indicated by the double-exponential time course of macroscopic ionic currents and the two open-time distributions of single channels. Coexpression of the beta-subunit potentiates Ca2+ currents by a relative increase of the fast-activating component, an acceleration of the slow component, and a larger proportion of long openings. We propose that multiple modes of gating are encoded in the alpha 1-subunit and that the beta-subunit increases Ca2+ channel opening by favoring a willing mode of gating in which the final transitions leading to channel opening are facilitated. In addition, we show that the carboxy terminus of alpha 1C also modulates the channel-gating behavior.
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Affiliation(s)
- A Neely
- Department of Molecular Physiology, Baylor College of Medicine, Houston, Texas 77030
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44
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Mosier DR, Baldelli P, Delbono O, Smith RG, Alexianu ME, Appel SH, Stefani E. Amyotrophic lateral sclerosis immunoglobulins increase Ca2+ currents in a motoneuron cell line. Ann Neurol 1995; 37:102-9. [PMID: 7818241 DOI: 10.1002/ana.410370119] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The sporadic form of amyotrophic lateral sclerosis (ALS) is an idiopathic and eventually lethal disorder causing progressive degeneration of cortical and spinal motoneurons. Recent studies have shown that the majority of patients with sporadic ALS have serum antibodies that bind to purified L-type voltage-gated calcium channels and that antibody titer correlates with the rate of disease progression. Furthermore, antibodies purified from ALS patient sera have been found to alter the physiologic function of voltage-gated calcium channels in nonmotoneuron cell types. Using whole-cell patch-clamp techniques, immunoglobulins purified from sera of 5 of 6 patients with sporadic ALS are now shown to increase calcium currents in a hybrid motoneuron cell line, VSC4.1. These calcium currents are blocked by the polyamine funnel-web spider toxin FTX, which has previously been shown to block Ca2+ currents and evoked transmitter release at mammalian motoneuron terminals. These data provide additional evidence linking ALS to an autoimmune process and suggest that antibody-induced increases in calcium entry through voltage-gated calcium channels may occur in motoneurons in this disease, with possible deleterious effects in susceptible neurons.
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Affiliation(s)
- D R Mosier
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030
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45
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Abstract
The Cl- currents activated by GABA via GABAA receptors in rat cerebellum granule cells in culture were studied by whole-cell patch-clamp. These currents were measured at various extracellular pH. The currents activated by 100 microM GABA, both the peak and the steady-state component, increase at acidic pH's and decrease at basic pH's. The transition point being at around 7.7. Interestingly, passing from pH 7.4 to 6.4 the GABA dose-response curve indicates that the increases in the peak current are related to an augmented maximal current. The increases in the steady-state component are mainly due to a higher affinity of the receptors for the neurotransmitter and disappear at saturating [GABA]. The study of the I-V curves for the GABA activated peak Cl- currents at pH 6.4, 7.4 and 8.4 reveals linearity in the latter instance. However, an outward rectification is present at the two more acidic pH's. This fact suggests that the protonation of basic amino acids at the acid pH does involve rectification of Cl- channel conductance. Overall, the data indicate that slight changes in in situ extracellular pH may have profound influences on GABAA receptor function.
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Affiliation(s)
- M Robello
- Dipartimento di Fisica, Università di Genova, Italy
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46
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Affiliation(s)
- A Cupello
- Centro di Neurofisiologia Cerebrale, CNR, Genoa, Italy
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47
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48
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Malfanti PL, Salvatore L, Santini L, Massi A, Baldelli P, De Dominici O. [Left heart catheterization with the trans-septal method. Technics, indications and case statistics]. Cardiol Prat 1968; 19:545-7. [PMID: 5718164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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