1
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Vendeville JB, Kyriakides MJ, Takebayashi Y, Rama S, Preece J, Samphire J, Ramos-Soriano J, Amieva AM, Holbrow-Wilshaw ME, Gordon Newman HR, Kou SL, Medina-Villar S, Dorh N, Dorh JN, Spencer J, Galan MC. Fast Identification and Quantification of Uropathogenic E. coli through Cluster Analysis. ACS Biomater Sci Eng 2021; 8:242-252. [PMID: 34894660 DOI: 10.1021/acsbiomaterials.1c00732] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rapid diagnostic tools to detect, identify, and enumerate bacteria are key to maintaining effective antibiotic stewardship and avoiding the unnecessary prescription of broad-spectrum agents. In this study, a 15 min agglutination assay is developed that relies on the use of mannose-functionalized polymeric microspheres in combination with cluster analysis. This allows for the identification and enumeration of laboratory (BW25113), clinical isolate (NCTC 12241), and uropathogenic Escherichia coli strains (NCTC 9001, NCTC 13958, J96, and CFT073) at clinically relevant concentrations in tryptic soy broth (103-108 CFU/mL) and in urine (105-108 CFU/mL). This fast, simple, and efficient assay offers a step forward toward efficient point-of-care diagnostics for common urinary tract infections.
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Affiliation(s)
| | | | - Yuiko Takebayashi
- School of Cellular and Molecular Medicine, University of Bristol, University Walk, BS8 1TD Bristol, United Kingdom
| | - Sylvain Rama
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - James Preece
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - Jenny Samphire
- School of Chemistry, University of Bristol, Cantock''s Close, BS8 1TS Bristol, United Kingdom
| | - Javier Ramos-Soriano
- School of Chemistry, University of Bristol, Cantock''s Close, BS8 1TS Bristol, United Kingdom
| | | | | | | | - Sio Lou Kou
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - Sandra Medina-Villar
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - Neciah Dorh
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - Josephine Ndoa Dorh
- FluoretiQ, Unit DX, St Philips Central, Albert Road, BS2 0XJ Bristol, United Kingdom
| | - James Spencer
- School of Cellular and Molecular Medicine, University of Bristol, University Walk, BS8 1TD Bristol, United Kingdom
| | - M Carmen Galan
- School of Chemistry, University of Bristol, Cantock''s Close, BS8 1TS Bristol, United Kingdom
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2
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Zbili M, Rama S, Benitez MJ, Fronzaroli-Molinieres L, Bialowas A, Boumedine-Guignon N, Garrido JJ, Debanne D. Homeostatic regulation of axonal Kv1.1 channels accounts for both synaptic and intrinsic modifications in the hippocampal CA3 circuit. Proc Natl Acad Sci U S A 2021; 118:e2110601118. [PMID: 34799447 PMCID: PMC8617510 DOI: 10.1073/pnas.2110601118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2021] [Indexed: 11/18/2022] Open
Abstract
Homeostatic plasticity of intrinsic excitability goes hand in hand with homeostatic plasticity of synaptic transmission. However, the mechanisms linking the two forms of homeostatic regulation have not been identified so far. Using electrophysiological, imaging, and immunohistochemical techniques, we show here that blockade of excitatory synaptic receptors for 2 to 3 d induces an up-regulation of both synaptic transmission at CA3-CA3 connections and intrinsic excitability of CA3 pyramidal neurons. Intrinsic plasticity was found to be mediated by a reduction of Kv1.1 channel density at the axon initial segment. In activity-deprived circuits, CA3-CA3 synapses were found to express a high release probability, an insensitivity to dendrotoxin, and a lack of depolarization-induced presynaptic facilitation, indicating a reduction in presynaptic Kv1.1 function. Further support for the down-regulation of axonal Kv1.1 channels in activity-deprived neurons was the broadening of action potentials measured in the axon. We conclude that regulation of the axonal Kv1.1 channel constitutes a major mechanism linking intrinsic excitability and synaptic strength that accounts for the functional synergy existing between homeostatic regulation of intrinsic excitability and synaptic transmission.
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Affiliation(s)
- Mickaël Zbili
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France
| | - Sylvain Rama
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France
| | - Maria-José Benitez
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), Madrid 28002, Spain
- Departamento de Química Física Aplicada, Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Laure Fronzaroli-Molinieres
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France
| | - Andrzej Bialowas
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France
| | - Norah Boumedine-Guignon
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France
| | - Juan José Garrido
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), Madrid 28002, Spain
| | - Dominique Debanne
- Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS), UMR_S 1072, INSERM, Aix-Marseille Université, Marseille 13015, France;
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3
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Abstract
Calculations of entropy of a signal or mutual information between two variables are valuable analytical tools in the field of neuroscience. They can be applied to all types of data, capture non-linear interactions and are model independent. Yet the limited size and number of recordings one can collect in a series of experiments makes their calculation highly prone to sampling bias. Mathematical methods to overcome this so-called "sampling disaster" exist, but require significant expertise, great time and computational costs. As such, there is a need for a simple, unbiased and computationally efficient tool for estimating the level of entropy and mutual information. In this article, we propose that application of entropy-encoding compression algorithms widely used in text and image compression fulfill these requirements. By simply saving the signal in PNG picture format and measuring the size of the file on the hard drive, we can estimate entropy changes through different conditions. Furthermore, with some simple modifications of the PNG file, we can also estimate the evolution of mutual information between a stimulus and the observed responses through different conditions. We first demonstrate the applicability of this method using white-noise-like signals. Then, while this method can be used in all kind of experimental conditions, we provide examples of its application in patch-clamp recordings, detection of place cells and histological data. Although this method does not give an absolute value of entropy or mutual information, it is mathematically correct, and its simplicity and broad use make it a powerful tool for their estimation through experiments.
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Affiliation(s)
- Mickael Zbili
- Lyon Neuroscience Research Center (CRNL), Inserm U1028, CNRS UMR 5292, Université Claude Bernard Lyon1, Bron, France
| | - Sylvain Rama
- Laboratory of Synaptic Imaging, Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
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4
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Henneberger C, Bard L, Panatier A, Reynolds JP, Kopach O, Medvedev NI, Minge D, Herde MK, Anders S, Kraev I, Heller JP, Rama S, Zheng K, Jensen TP, Sanchez-Romero I, Jackson CJ, Janovjak H, Ottersen OP, Nagelhus EA, Oliet SHR, Stewart MG, Nägerl UV, Rusakov DA. LTP Induction Boosts Glutamate Spillover by Driving Withdrawal of Perisynaptic Astroglia. Neuron 2020; 108:919-936.e11. [PMID: 32976770 PMCID: PMC7736499 DOI: 10.1016/j.neuron.2020.08.030] [Citation(s) in RCA: 123] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 06/14/2020] [Accepted: 08/28/2020] [Indexed: 02/07/2023]
Abstract
Extrasynaptic actions of glutamate are limited by high-affinity transporters expressed by perisynaptic astroglial processes (PAPs): this helps maintain point-to-point transmission in excitatory circuits. Memory formation in the brain is associated with synaptic remodeling, but how this affects PAPs and therefore extrasynaptic glutamate actions is poorly understood. Here, we used advanced imaging methods, in situ and in vivo, to find that a classical synaptic memory mechanism, long-term potentiation (LTP), triggers withdrawal of PAPs from potentiated synapses. Optical glutamate sensors combined with patch-clamp and 3D molecular localization reveal that LTP induction thus prompts spatial retreat of astroglial glutamate transporters, boosting glutamate spillover and NMDA-receptor-mediated inter-synaptic cross-talk. The LTP-triggered PAP withdrawal involves NKCC1 transporters and the actin-controlling protein cofilin but does not depend on major Ca2+-dependent cascades in astrocytes. We have therefore uncovered a mechanism by which a memory trace at one synapse could alter signal handling by multiple neighboring connections.
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Affiliation(s)
- Christian Henneberger
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK; Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany; German Center for Neurodegenerative Diseases (DZNE), 53175 Bonn, Germany.
| | - Lucie Bard
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Aude Panatier
- INSERM U1215, Neurocentre Magendie, 33000 Bordeaux, France; Université de Bordeaux, 33000 Bordeaux, France; Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, 33000 Bordeaux, France
| | - James P Reynolds
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Olga Kopach
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | | | - Daniel Minge
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Michel K Herde
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Stefanie Anders
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Igor Kraev
- Life Sciences, The Open University, Milton Keynes MK7 6AA, UK
| | - Janosch P Heller
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Sylvain Rama
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Kaiyu Zheng
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Thomas P Jensen
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | | | - Colin J Jackson
- Research School of Chemistry, Australian National University, Acton, ACT 2601, Australia
| | - Harald Janovjak
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria; EMBL Australia, Australian Regenerative Medicine Institute, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, VIC 3800, Australia
| | - Ole Petter Ottersen
- Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; Karolinska Institutet, 171 77 Stockholm, Sweden
| | | | - Stephane H R Oliet
- INSERM U1215, Neurocentre Magendie, 33000 Bordeaux, France; Université de Bordeaux, 33000 Bordeaux, France
| | | | - U Valentin Nägerl
- Université de Bordeaux, 33000 Bordeaux, France; Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, 33000 Bordeaux, France.
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK.
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5
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Zhu S, Atisha D, Evangelistia M, Barry R, Rama S, Ghosh S, Cannella C, Chen Y, Bensenhaver J, Levin K, Walker E. Factors Associated with Chronic Breast Lymphedema After Adjuvant Radiation in Women Undergoing Breast Conservation Therapy. Int J Radiat Oncol Biol Phys 2020. [DOI: 10.1016/j.ijrobp.2020.07.1059] [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] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Rama S, Atisha D, Evangelista M, Cannella C, Barry R, Ghosh S, Luker J, Chen Y, Zhu S, Bensenhaver J, Levin K, Walker E. The Effect of Oncoplastic Reduction on The Incidence of Post-Operative Lymphedema in Breast Cancer Patients Undergoing Lumpectomy. Int J Radiat Oncol Biol Phys 2020. [DOI: 10.1016/j.ijrobp.2020.07.1085] [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] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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Zbili M, Rama S, Yger P, Inglebert Y, Boumedine-Guignon N, Fronzaroli-Moliniere L, Brette R, Russier M, Debanne D. Axonal Na + channels detect and transmit levels of input synchrony in local brain circuits. Sci Adv 2020; 6:eaay4313. [PMID: 32494697 PMCID: PMC7202877 DOI: 10.1126/sciadv.aay4313] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 02/19/2020] [Indexed: 06/11/2023]
Abstract
Sensory processing requires mechanisms of fast coincidence detection to discriminate synchronous from asynchronous inputs. Spike threshold adaptation enables such a discrimination but is ineffective in transmitting this information to the network. We show here that presynaptic axonal sodium channels read and transmit precise levels of input synchrony to the postsynaptic cell by modulating the presynaptic action potential (AP) amplitude. As a consequence, synaptic transmission is facilitated at cortical synapses when the presynaptic spike is produced by synchronous inputs. Using dual soma-axon recordings, imaging, and modeling, we show that this facilitation results from enhanced AP amplitude in the axon due to minimized inactivation of axonal sodium channels. Quantifying local circuit activity and using network modeling, we found that spikes induced by synchronous inputs produced a larger effect on network activity than spikes induced by asynchronous inputs. Therefore, this input synchrony-dependent facilitation may constitute a powerful mechanism, regulating synaptic transmission at proximal synapses.
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Affiliation(s)
- Mickaël Zbili
- UNIS, INSERM, UMR 1072, Aix-Marseille Université, 13015, Marseille, France
| | - Sylvain Rama
- UNIS, INSERM, UMR 1072, Aix-Marseille Université, 13015, Marseille, France
| | - Pierre Yger
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Yanis Inglebert
- UNIS, INSERM, UMR 1072, Aix-Marseille Université, 13015, Marseille, France
| | | | | | - Romain Brette
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Michaël Russier
- UNIS, INSERM, UMR 1072, Aix-Marseille Université, 13015, Marseille, France
| | - Dominique Debanne
- UNIS, INSERM, UMR 1072, Aix-Marseille Université, 13015, Marseille, France
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8
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Rama S, Jensen TP, Rusakov DA. Glutamate Imaging Reveals Multiple Sites of Stochastic Release in the CA3 Giant Mossy Fiber Boutons. Front Cell Neurosci 2019; 13:243. [PMID: 31213985 PMCID: PMC6558140 DOI: 10.3389/fncel.2019.00243] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [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: 02/26/2019] [Accepted: 05/16/2019] [Indexed: 11/17/2022] Open
Abstract
One of the most studied central synapses which have provided fundamental insights into cellular mechanisms of neural connectivity is the “giant” excitatory connection between hippocampal mossy fibers (MFs) and CA3 pyramidal cells. Its large presynaptic bouton features multiple release sites and is densely packed with thousands of synaptic vesicles, to sustain a highly facilitating “detonator” transmission. However, whether glutamate release sites at this synapse act independently, in a stochastic manner, or rather synchronously, remains poorly understood. This knowledge is critical for a better understanding of mechanisms underpinning presynaptic plasticity and postsynaptic signal integration rules. Here, we use the optical glutamate sensor SF-iGluSnFR and the intracellular Ca2+ indicator Cal-590 to monitor spike-evoked glutamate release and presynaptic calcium entry in MF boutons. Multiplexed imaging reveals that distinct sites in individual MF giant boutons release glutamate in a probabilistic fashion, also showing use-dependent short-term facilitation. The present approach provides novel insights into the basic mechanisms of neurotransmitter release at excitatory synapses.
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Affiliation(s)
- Sylvain Rama
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Thomas P Jensen
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
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9
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Abstract
Axons link distant brain regions and are usually considered as simple transmission cables in which reliable propagation occurs once an action potential has been generated. Safe propagation of action potentials relies on specific ion channel expression at strategic points of the axon such as nodes of Ranvier or axonal branch points. However, while action potentials are generally considered as the quantum of neuronal information, their signaling is not entirely digital. In fact, both their shape and their conduction speed have been shown to be modulated by activity, leading to regulations of synaptic latency and synaptic strength. We report here newly identified mechanisms of (1) safe spike propagation along the axon, (2) compartmentalization of action potential shape in the axon, (3) analog modulation of spike-evoked synaptic transmission and (4) alteration in conduction time after persistent regulation of axon morphology in central neurons. We discuss the contribution of these regulations in information processing.
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Affiliation(s)
- Sylvain Rama
- UNIS, UMR_S 1072, INSERM, Aix-Marseille Université, 13015 Marseille, France; Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Mickaël Zbili
- UNIS, UMR_S 1072, INSERM, Aix-Marseille Université, 13015 Marseille, France
| | - Dominique Debanne
- UNIS, UMR_S 1072, INSERM, Aix-Marseille Université, 13015 Marseille, France.
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10
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Abstract
Action potentials (APs) in the mammalian brain are thought to represent the smallest unit of information transmitted by neurons to their postsynaptic targets. According to this view, neuronal signaling is all-or-none or digital. Increasing evidence suggests, however, that subthreshold changes in presynaptic membrane potential before triggering the spike also determines spike-evoked release of neurotransmitter. We discuss here how analog changes in presynaptic voltage may regulate spike-evoked release of neurotransmitter through the modulation of biophysical state of voltage-gated potassium, calcium and sodium channels in the presynaptic compartment. The contribution of this regulation has been greatly underestimated and we discuss the impact for information processing in neuronal circuits.
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Affiliation(s)
- Mickael Zbili
- UNIS, UMR_S 1072, Institut National de la Santé et de la Recherche Médicale (INSERM), Aix-Marseille Université Marseille, France
| | - Sylvain Rama
- UNIS, UMR_S 1072, Institut National de la Santé et de la Recherche Médicale (INSERM), Aix-Marseille Université Marseille, France
| | - Dominique Debanne
- UNIS, UMR_S 1072, Institut National de la Santé et de la Recherche Médicale (INSERM), Aix-Marseille Université Marseille, France
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11
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Abstract
Understanding neuronal physiology requires to record electrical activity in many small and remote compartments such as dendrites, axon or dendritic spines. To do so, electrophysiology has long been the tool of choice, as it allows recording very subtle and fast changes in electrical activity. However, electrophysiological measurements are mostly limited to large neuronal compartments such as the neuronal soma. To overcome these limitations, optical methods have been developed, allowing the monitoring of changes in fluorescence of fluorescent reporter dyes inserted into the neuron, with a spatial resolution theoretically only limited by the dye wavelength and optical devices. However, the temporal and spatial resolutive power of functional fluorescence imaging of live neurons is often limited by a necessary trade-off between image resolution, signal to noise ratio (SNR) and speed of acquisition. Here, I propose to use a Super-Resolution Shift and Mean (S&M) algorithm previously used in image computing to improve the SNR, time sampling and spatial resolution of acquired fluorescent signals. I demonstrate the benefits of this methodology using two examples: voltage imaging of action potentials (APs) in soma and dendrites of CA3 pyramidal cells and calcium imaging in the dendritic shaft and spines of CA3 pyramidal cells. I show that this algorithm allows the recording of a broad area at low speed in order to achieve a high SNR, and then pick the signal in any small compartment and resample it at high speed. This method allows preserving both the SNR and the temporal resolution of the signal, while acquiring the original images at high spatial resolution.
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Affiliation(s)
- Sylvain Rama
- INSERM, UMR_S 1072 Marseille, France ; Unité de Neurobiologie des canaux Ioniques et de la Synapse (UNIS) Marseille, France ; Department is UNIS, Unité de Neurobiologie des canaux Ioniques et de la Synapse, Aix-Marseille University Marseille, France
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12
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Bialowas A, Rama S, Zbili M, Marra V, Fronzaroli-Molinieres L, Ankri N, Carlier E, Debanne D. Analog modulation of spike-evoked transmission in CA3 circuits is determined by axonal Kv1.1 channels in a time-dependent manner. Eur J Neurosci 2014; 41:293-304. [PMID: 25394682 DOI: 10.1111/ejn.12787] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/01/2014] [Accepted: 10/16/2014] [Indexed: 11/28/2022]
Abstract
Synaptic transmission usually depends on action potentials (APs) in an all-or-none (digital) fashion. Recent studies indicate, however, that subthreshold presynaptic depolarization may facilitate spike-evoked transmission, thus creating an analog modulation of spike-evoked synaptic transmission, also called analog-digital (AD) synaptic facilitation. Yet, the underlying mechanisms behind this facilitation remain unclear. We show here that AD facilitation at rat CA3-CA3 synapses is time-dependent and requires long presynaptic depolarization (5-10 s) for its induction. This depolarization-induced AD facilitation (d-ADF) is blocked by the specific Kv1.1 channel blocker dendrotoxin-K. Using fast voltage-imaging of the axon, we show that somatic depolarization used for induction of d-ADF broadened the AP in the axon through inactivation of Kv1.1 channels. Somatic depolarization enhanced spike-evoked calcium signals in presynaptic terminals, but not basal calcium. In conclusion, axonal Kv1.1 channels determine glutamate release in CA3 neurons in a time-dependent manner through the control of the presynaptic spike waveform.
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Affiliation(s)
- Andrzej Bialowas
- INSERM, UMR_S 1072, Marseille, France; Aix-Marseille Université, UNIS, Marseille, France
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13
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Campanac E, Gasselin C, Baude A, Rama S, Ankri N, Debanne D. Enhanced Intrinsic Excitability in Basket Cells Maintains Excitatory-Inhibitory Balance in Hippocampal Circuits. Neuron 2013; 77:712-22. [DOI: 10.1016/j.neuron.2012.12.020] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2012] [Indexed: 12/24/2022]
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14
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Abstract
Synaptic transmission in the brain generally depends on action potentials. However, recent studies indicate that subthreshold variation in the presynaptic membrane potential also determines spike-evoked transmission. The informational content of each presynaptic action potential is therefore greater than initially expected. The contribution of this synaptic property, which is a fast (from 0.01 to 10 s) and state-dependent modulation of functional coupling, has been largely underestimated and could have important consequences for our understanding of information processing in neural networks. We discuss here how the membrane voltage of the presynaptic terminal might modulate neurotransmitter release by mechanisms that do not involve a change in presynaptic Ca(2+) influx.
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Affiliation(s)
- Dominique Debanne
- INSERM, UMR_S 1072, and Aix-Marseille Université, UNIS, 13015, Marseille, France.
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15
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Affiliation(s)
- Dominique Debanne
- INSERM, U641, Marseille, 13344 France
- Université de la Méditerranée, Faculté de Médecine secteur nord, IFR 11, Marseille, 13344 France
| | - Sylvain Rama
- INSERM, U641, Marseille, 13344 France
- Université de la Méditerranée, Faculté de Médecine secteur nord, IFR 11, Marseille, 13344 France
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16
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Rama S, Vetrivel L, Semyanov A. Second-harmonic generation voltage imaging at subcellular resolution in rat hippocampal slices. J Biophotonics 2010; 3:784-790. [PMID: 20815024 DOI: 10.1002/jbio.201000073] [Citation(s) in RCA: 7] [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] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Action potential (AP) is a major signaling mechanism in the neuronal networks. Dendritic AP propagation is important for information processing within the individual neurons. Due to limitations of electrode-based techniques most research on subcellular AP propagation has been restricted to soma and proximal parts of the primary dendrites. Development of voltage-sensitive dyes (VSD) has opened up a possibility to measure voltage changes in the oblique dendrites and the spines. Membrane-bound organic VSD can be used both for fluorescent imaging and imaging of second-harmonic generation (SHG). Both phenomena are voltage dependent and can be used for measuring membrane potential changes. However, changes in SHG are linear to the change in the local membrane potential and its slope is constant across different compartments of cells. Although SHG demonstrates reasonable change with membrane voltage (over 10% per 100 mV), the signal-to-noise (S/N) ratio is currently lower in SHG measurement than in fluorescent methods.
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Affiliation(s)
- Sylvain Rama
- RIKEN Brain Science Institute BSI, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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17
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Neelima PS, Rao Rekha M, Rama S, Rao AJ. Effect of human telomerase reverse transcriptase transfection on differentiation in BeWo choriocarcinoma cells. Reprod Biomed Online 2009; 18:838-49. [PMID: 19490790 DOI: 10.1016/s1472-6483(10)60035-1] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Arrest of proliferation is one of the prerequisites for differentiation of cytotrophoblasts into syncytiotrophoblasts, and thus during differentiation telomerase activity, as well as human telomerase reverse transcriptase (hTERT) expression, is down-regulated. Considering this, it is of interest to investigate whether syncytium formation can be delayed by prolonging the expression of telomerase in cytotrophoblasts. BeWo cells were transfected with pLPC-hTERT retroviral vector and the reverse transcription-polymerase chain reaction analysis for hTERT mRNA concentrations in the transfected cells revealed a several-fold increase in hTERT mRNA compared with the cells transfected with empty vector, and this confirmed that the transfection was successful. An increase in the proliferation, as assessed by bromodeoxyuridine incorporation assay, as well as an increase in mRNA and protein concentration of various cyclins and proliferating cell nuclear antigen, was noticed. The effect of hTERT transfection was also assessed after the addition of forskolin to induce differentiation and it was observed that cell-cell fusion was delayed and differentiation did not occur in hTERT-transfected cells. However, the effects seen were only transient as stable transfection was not possible and the cells were undergoing apoptosis after 72 h, which suggested that apart from hTERT other factors might be important for immortalization of BeWo cells.
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Affiliation(s)
- P S Neelima
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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18
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Sánchez-Brunete JA, Dea MA, Rama S, Bolás F, Alunda JM, Torrado-Santiago S, Torrado JJ. Influence of the vehicle on the properties and efficacy of microparticles containing amphotericin B. J Drug Target 2008; 13:225-33. [PMID: 16051534 DOI: 10.1080/10611860500097107] [Citation(s) in RCA: 15] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
New microparticles containing amphotericin B (AMB) have been developed and manufactured by spray drying. To this end albumin, polylactic-co-glycolic acids (PLGA) and poly(sebacic anhydride) have been employed as drug carriers. The selection of the solvent used to disperse the drug and the vehicle before spray drying was critical on production yields and physical properties of the microparticles. Once particle size, morphology and dispersability in some aqueous media were shown to be acceptable for an intravenous administration, in vivo efficacy was evaluated and compared with the reference medicine Fungizone. Microparticles prepared with albumin, albumin heated at a high temperature, some kinds of PLGA or polyanhydride, as well as Fungizone, were tested in an experimental hamster model of infection with Leishmania infantum, by evaluating the evolution of parasitic burdens in spleen, liver and antibody responses. After the injection of three doses corresponding to 2 mg of AMB per kilogram each, diverse reactions were reported depending on the vehicle. The best dispersability, reduction of parasites and antibody response were achieved when the treatment was performed with AMB in albumin microspheres.
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Affiliation(s)
- J A Sánchez-Brunete
- Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Complutense University, Madrid, 28040, Spain
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Rama S, Krapivinsky G, Clapham DE, Medina I. The MUPP1-SynGAPalpha protein complex does not mediate activity-induced LTP. Mol Cell Neurosci 2008; 38:183-8. [PMID: 18417361 PMCID: PMC4057800 DOI: 10.1016/j.mcn.2008.02.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2007] [Revised: 01/23/2008] [Accepted: 02/13/2008] [Indexed: 11/24/2022] Open
Abstract
At excitatory synapses of hippocampal neurons, the multi-PDZ domain scaffolding protein, MUPP1, assembles the NR2B subunit of the NMDA receptor (NMDAR), Ca2+-calmodulin kinase (CamKII), and the alpha1 isoform of the postsynaptic density GTPase activating protein, SynGAP (SynGAPalpha). In order to evaluate the role of this complex in excitatory synaptic neurotransmission we specifically disrupted MUPP1-SynGAPalpha interactions in CA1 neurons of acute hippocampal slices using intracellular perfusion with peptides derived from SynGAPalpha-MUPP1 binding domains. Disruption of the interaction between MUPP1 and SynGAPalpha with two complementary peptides derived from SynGAP and MUPP1 mutual binding sites resulted in enhancement of excitatory postsynaptic currents (EPSCs). This potentiation did not occlude pairing-induced long-term potentiation (LTP); indeed the amplitude of postsynaptic responses of activity-potentiated synapses was further increased. Pre-potentiation of excitatory synapses with theta burst stimulations did not modify the MUPP1-SynGAPalpha-dependent enhancement of EPSCs. Our data suggest that MUPP1-SynGAPalpha complex dissociation triggers a mechanism for AMPAR enhancement that is distinct from activity-induced LTP.
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Affiliation(s)
- Sylvain Rama
- INMED/INSERM Unite 901, 163 Route de Luminy, 13009 Marseille, France; Mediterranean University, 163 Route de Luminy, 13009 Marseille, France
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20
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Ivanov A, Pellegrino C, Rama S, Dumalska I, Salyha Y, Ben-Ari Y, Medina I. Opposing role of synaptic and extrasynaptic NMDA receptors in regulation of the extracellular signal-regulated kinases (ERK) activity in cultured rat hippocampal neurons. J Physiol 2006; 572:789-98. [PMID: 16513670 PMCID: PMC1779993 DOI: 10.1113/jphysiol.2006.105510] [Citation(s) in RCA: 246] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The extracellular signal-regulated kinases (ERK) signalling cascade is a key pathway that mediates the NMDA receptor (NMDAR)-dependent neuronal plasticity and survival. However, it is not clear yet how NMDARs regulate ERK activity. Stimulation of the NMDARs induces a complex modification of ERK that includes both ERK activation and inactivation and depends on particular experimental conditions. Here we show that there exists a differential restriction in the regulation of ERK activity that depends on the pool of NMDAR that was activated. The synaptic pool of NMDARs activates ERK whereas the extrasynaptic pool does not; on the contrary, it triggers a signalling pathway that results in the inactivation of ERK. As a result, simultaneous activation of both extrasynaptic and synaptic NMDAR using bath application of NMDA or glutamate (a typical protocol explored in the majority of studies) produced ERK activation that depended on the concentration of agonists and was always significantly weaker than those mediated by synaptic NMDARs. Since the activation of the extrasynaptic NMDA is attributed mainly to global release of glutamate occurring at pathological conditions including hypoxic/ischaemic insults, traumas and epileptic brain damage, the reported differential regulation of ERK cascade by NMDARs provides a unique mechanism for an early identification of the physiological and/or pathophysiological consequences of NMDAR activation. The negative regulation of the ERK activity might be one of the first signalling events determining brain injury and constitutes a putative target of new pharmacological applications.
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Affiliation(s)
- Anton Ivanov
- INMED/INSERM Unite 29, 163 Route de Luminy, 13009 Marseille, France
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21
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Abstract
Estrogen classically is recognized as a growth-promoting hormone. Recent evidence suggests that estrogens are also involved in a wide variety of cellular and physiological functions involving the central nervous system, immune system, cardiovascular system and bone homeostasis. Our studies in cytotrophoblasts and BeWo cells, demonstrated that 17beta-estradiol induces terminal differentiation of placental trophoblasts directly and this differentiation is coupled with an increased production of TGFbeta1, which, in turn, affects telomerase activity and telomerase associated components at the level of hTERT. Furthermore, using rats treated in vivo with either EDS or estradiol and in vitro Leydig cell cultures, we proposed that 17beta-estradiol mediated down-regulation of collagen IV alpha4 expression could be one of the possible mechanisms for the inhibition of progenitor Leydig cell proliferation. In this review, we summarize the results from both the model systems, the human placental cytotrophoblast and rat Leydig cells to conclude that 17beta-estradiol has a unique stage-specific role in differentiation.
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Affiliation(s)
- R Yashwanth
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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Chudotvorova I, Ivanov A, Rama S, Hübner CA, Pellegrino C, Ben-Ari Y, Medina I. Early expression of KCC2 in rat hippocampal cultures augments expression of functional GABA synapses. J Physiol 2005; 566:671-9. [PMID: 15961425 PMCID: PMC1464776 DOI: 10.1113/jphysiol.2005.089821] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 06/10/2005] [Indexed: 12/18/2022] Open
Abstract
The development of GABAergic synapses is associated with an excitatory to inhibitory shift of the actions of GABA because of a reduction of [Cl-]i. This is due to a delayed postnatal expression of the K+ -Cl- cotransporter KCC2, which has low levels at birth and peaks during the first few postnatal weeks. Whether the expression of the cotransporter and the excitatory to inhibitory shift have other consequences on the operation of GABA(A) receptors and synapses is not yet known. We have now expressed KCC2 in immature neurones at an early developmental stage and determined the consequences on the formation of GABA and glutamate synapses. We report that early expression of the cotransporter selectively enhances GABAergic synapses: there is a significant increase of the density of GABA(A) receptors and synapses and an increase of the frequency of GABAergic miniature postsynaptic currents. The density of glutamate synapses and frequency of AMPA miniature postsynaptic currents are not affected. We conclude that the expression of KCC2 and the reduction of [Cl-]i play a critical role in the construction of GABAergic networks that extends beyond the excitatory to inhibitory shift of the actions of GABA.
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Sánchez-Brunete JA, Dea MA, Rama S, Bolás F, Alunda JM, Torrado-Santiago S, Torrado JJ. Amphotericin B molecular organization as an essential factor to improve activity/toxicity ratio in the treatment of visceral leishmaniasis. J Drug Target 2005; 12:453-60. [PMID: 15621670 DOI: 10.1080/10611860400006596] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [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: 10/26/2022]
Abstract
An in vivo study has been performed in order to determine the influence of amphotericin B (AMB) molecular organization on the toxicity and activity of this drug in the treatment of experimental visceral leishmaniasis. Three formulations with similar composition but different drug molecular self-association in aqueous media were prepared. Acute toxicity was evaluated by injecting them in healthy hamsters. Sub-acute toxicity and efficacy were studied administering them to animals previously infected with Leishmania infantum. The preparation with drug molecules completely dissolved into monomers (formulation "C") and produced the highest acute toxicity. The formulation whose AMB molecules were disposed as non-water-soluble multi-aggregates (formulation "B") proved to provide the lowest acute toxicity. This formula also showed an improved activity, mainly in the liver, if compared with the third tested formulation containing AMB molecules disposed as smaller dimerical "water-soluble" aggregates (formulation "A"). As a conclusion, molecular aggregation in biological media should be an important factor to consider when researching or optimizing medicines containing AMB. The liberation of molecules as large dispersed non-water-soluble multi-aggregates seems to improve the narrow therapeutic margin attached to the use of this drug.
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Affiliation(s)
- J A Sánchez-Brunete
- Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, Complutense University, 28040 Madrid, Spain
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24
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Abstract
The human placenta is a tumor-like tissue in which highly proliferative, migratory, and invasive extra-villous trophoblast cells, migrate and invade the uterus and its vasculature, to provide a vital link between the mother and the developing fetus. In the present article, we review our studies on a series of experiments, designed to identify molecular events responsible for the phenotypic changes during placental growth. Our observations illustrate that the human placenta is endowed with the biochemical machinery to proliferate indefinitely throughout gestation, yet, there are intrinsic mechanisms that effectively circumscribe the extent and duration of trophoblast proliferation. The placenta combines in itself the unique ability to produce a wide variety of protein, peptide and steroid hormones, but intricately interwoven in this process, is also the remarkable capacity to simultaneously regulate their synthesis and secretion. The placenta therefore represents an autonomous or a self-sufficient unit capable of modulating its own growth and function, while assisting the developing fetus until it is capable of independent existence.
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Affiliation(s)
- S Rama
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
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25
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Sánchez-Brunete JA, Dea MA, Rama S, Bolás F, Alunda JM, Raposo R, Méndez MT, Torrado-Santiago S, Torrado JJ. Treatment of experimental visceral leishmaniasis with amphotericin B in stable albumin microspheres. Antimicrob Agents Chemother 2004; 48:3246-52. [PMID: 15328080 PMCID: PMC514726 DOI: 10.1128/aac.48.9.3246-3252.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [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: 01/12/2004] [Revised: 04/26/2004] [Accepted: 05/24/2004] [Indexed: 11/20/2022] Open
Abstract
Hydrophilic albumin microspheres are proposed as a new delivery system for amphotericin B (AMB; AMB microspheres). The acute toxicity of AMB microspheres was lower than that of the AMB-deoxycholate (AMB-Doc) reference formulation in hamsters. Lethal doses in healthy and infected animals were improved at least eight times. Intravenous bolus administration of doses of AMB microspheres up to 40 mg/kg of body weight did not produce acute symptoms of toxicity. The efficacy of this new formulation was tested against Leishmania infantum-infected hamsters at doses of 2, 10, 20, and 40 mg/kg. With the 2-mg/kg dose, the activity of AMB, as assessed through the parasite load reductions in the liver and spleen and the evolution of antibody levels, was also improved (P < 0.05) by use of the AMB microsphere system. At the higher doses of 10, 20, and 40 mg/kg, reductions in parasite levels of more than 99% were achieved in the liver and spleen after the administration of AMB microspheres. A pharmacokinetic study was performed to study the serum, liver, and spleen AMB concentrations after administration of AMB microspheres and the reference formulation. Interestingly, a significant accumulation of AMB in the spleen and liver was observed after AMB microsphere administration. Our results suggest that this new formulation is a promising alternative to the conventional AMB-Doc formulation for the treatment of visceral leishmaniasis.
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Affiliation(s)
- J A Sánchez-Brunete
- Department of Pharmacy and Pharmaceutical Technology, Universidad Complutense, Plaza Ramón y Cajal s/n, 28040 Madrid, Spain
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26
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Abstract
During the first trimester of pregnancy, the human placenta is an actively dividing and highly invasive tumour-like tissue, while near term, it represents a fully developed, non-invasive unit. In order to understand the molecular basis of this marked difference in the placental phenotypes, an approach based on a differential display-reverse transcription-polymerase chain reaction (DD-RT-PCR) was adopted to analyse changes in gene expression, using total RNA isolated from first-trimester and term placental villi. Using this approach, T-plastin was initially identified as being differentially expressed in the human first-trimester placenta. T-plastin is an actin-bundling protein and is known to be highly expressed in actively dividing cells and up-regulated in several carcinomas. Using a homogenous population of cytotrophoblasts and syncytiotrophoblasts isolated from human placentae, the present authors demonstrate the differential expression of T-plastin in cytotrophoblasts compared with the terminally differentiated syncytiotrophoblasts. The down-regulation of T-plastin expression is further demonstrated in human trophoblastic BeWo cells induced to differentiate using transforming growth factor (TGF)beta1, a growth factor known for its anti-proliferative and anti-invasive response in placental cells. These studies suggest that expression of T-plastin in the placental context may indeed be associated with the enhanced replicative potential of placental trophoblasts.
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Affiliation(s)
- Rekha M Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Rama S, Petrusz P, Rao AJ. Hormonal regulation of human trophoblast differentiation: a possible role for 17beta-estradiol and GnRH. Mol Cell Endocrinol 2004; 218:79-94. [PMID: 15130513 DOI: 10.1016/j.mce.2003.12.016] [Citation(s) in RCA: 36] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Revised: 11/10/2003] [Accepted: 12/17/2003] [Indexed: 10/26/2022]
Abstract
We have examined the role of 17beta-estradiol and gonadotropin releasing hormone (GnRH) in the regulation of functional differentiation in human trophoblasts. In contrast to its recognized functions as a proliferation-promoting hormone in a variety of cell types, we found that 17beta-estradiol induced terminal differentiation in human trophoblastic cells, and that this event was estrogen-receptor-mediated. This process involved a loss in expression of Cyclins A2 and E, and a coincident increase in p27(Kip1). The anti-proliferative effects of 17beta-estradiol were annulled by specific transforming growth factor-beta 1 (TGFbeta1)-neutralizing antibody, suggesting that 17beta-estradiol may mediate its growth-inhibitory actions, through TGFbeta1 activity. Following exposure to Buserelin, cultured human trophoblastic cells stopped proliferating and formed functionally mature syncytiotrophoblasts. This differentiation event, that involved a drastic loss in expression of proliferating-cell-nuclear-antigen, could be blocked by Cetrorelix, suggesting the involvement of functional GnRH receptors. Preliminary studies on the characterization of the human placental GnRH receptor, indicate the presence of multiple receptor isoforms across human gestation.
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Affiliation(s)
- S Rama
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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28
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Khader V, Rama S. Effect of maturity on macromineral content of selected leafy vegetables. Asia Pac J Clin Nutr 2003; 12:45-9. [PMID: 12737010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
Macro mineral contents were estimated in commonly consumed green leafy vegetables in India, namely; Koyyathotakura and Peddathotakura (varieties of Amaranthus species); Erragogu and Tellagogu (variety of Hibiscus species); Gangabayalakura (Portulaca olereceo) and Palak (Spineces olerecea) at three different stages of maturity. Varietal differences were also observed. The results of the study showed that as the plant matured from stage I (15 days) to stage II (30 days) calcium and magnesium content increased. In contrast, phosphorus content decreased as the plant matured. Varietal differences were also observed at different stages of maturity. The results also indicated that the consumption of green leafy vegetables at stage I (15 days) and stage II (30 days) potentially provide the greatest amount of minerals.
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Affiliation(s)
- Vijaya Khader
- Post Graduate & Research Centre, College of Home Science (Achrya N.G. Ranga Agril University (ANGRAU), Rajendranagar, Hyderabad, India.
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29
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Abstract
Transforming growth factor-beta 1 (TGF beta1) plays a crucial role in controlling trophoblast growth and invasion. Loss of this key regulatory function provides the pathophysiological basis for several tumors, which are characterized by uncontrolled telomerase activity. We have shown earlier that telomerase activity is negatively regulated during terminal differentiation of human trophoblasts, and that TGF beta1 may be an important factor governing the transcription of human telomerase reverse transcriptase (hTERT) (the catalytic subunit of the telomerase complex) during this process. In the present study, we extend these observations to identify possible functional effectors of TGF beta1-induced loss in telomerase activity during human trophoblastic differentiation. We show that this regulation may involve the suppression of c-Myc and an increased production of Mad1. We also observed a simultaneous increase in the expression of cyclin-dependent-kinase inhibitors, p21, p27, p15 and p16, associated with a loss in expression of Cyclin-A2 and Cyclin-E. Thus, TGF beta1 may induce multiple independent signals to check the proliferative potential of human trophoblastic cells and allow their functional differentiation.
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Affiliation(s)
- S Rama
- Department of Biochemistry and Department of Molecular Reproduction, Development & Genetics, Indian Institute of Science, Bangalore 560 012, Kamataka, India
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30
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Abstract
The transient tumor-like attributes of the first-trimester placenta anchor the developing embryo to the uterine wall thus establishing a vital link between the mother and the fetus. Dysregulation of this invasive behavior and/or controlled proliferation of the placenta is associated with abnormal pregnancies. Several of these diseased states also exhibit aberrant telomerase activity, among other pathophysiological manifestations. Considering the strong correlation between telomerase activity and tumorigenesis, it was of interest to see whether the crucial processes of trophoblast proliferation and differentiation were brought about through the modulation of telomerase. Using two in vitro model systems of trophoblast differentiation, we demonstrate here that telomerase activity is negatively regulated during placental differentiation. We further show that this modulation is at the level of transcription of hTERT. We also propose a role for TGF beta1 in regulating telomerase activity in differentiating trophoblasts by down-regulating the expression of hTERT at the transcriptional level.
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Affiliation(s)
- S Rama
- Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India
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Abstract
Hypothalamic gonadotrophin-releasing hormone (GnRH) plays a major role in the endocrine control of reproduction. Acting through its high affinity receptors on pituitary gonadotrophs, it regulates the secretion of gonadotrophins. In addition, GnRH also functions as a local regulator in a number of other cell lines and tissues, including the placenta. In a manner analogous to hypothalamic GnRH stimulation of LH and FSH from the anterior pituitary, GnRH was found to cause a dose-dependent release of human chorionic gonadotrophin (HCG) from the placenta. So began the search for a putative GnRH receptor in the human placenta. Although early radio-receptor studies reported specific binding, the properties of these 'putative' GnRH binding sites were found to differ significantly from those of their pituitary counterparts in several important respects. This was followed by a series of contradictory reports that led to more questions and opened up avenues for further investigations. Even after nearly two decades of research, the human placental GnRH receptor has not been characterized beyond all reasonable doubt. This review recalls the discovery, the controversies and unanswered questions concerning the human placental GnRH receptor.
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Affiliation(s)
- S Rama
- Department of Biochemistry, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
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32
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Abstract
Micromineral contents were estimated in commonly consumed green leafy vegetables: Koyyathotakura and Peddathotakura (varieties of Amaranthus species); Erragogu and Tellagogu (variety of Hibiscus species) Gangabayalakura and palak at three different stages of maturity. Varietal differences were also observed. The results of the study showed that as the plant matured from stage 1 (15 days) to stage II (30 days), iron and manganese contents increased whereas zinc and copper contents decreased as the plant matured. Varietal differences were also observed at different stages of maturity. The results also indicated that the consumption of green leafy vegetables at stage I and stage II potentially provides the greatest amount of a mineral.
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Affiliation(s)
- V Khader
- Center for Advanced Studies in Foods and Nutrition, ANGR Agricultural University, Rajendranagar, Hyderabad, India
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Giraldi C, Paterni F, Cecchini S, Rama S, Mazzoni M. [Paralysis of the parasympathetic ocular nerve after influenza syndrome]. Riv Neurol 1991; 61:180-2. [PMID: 1808676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A 41 year-old-man developed diplopia, bilateral ptosis, paralysis of conjugate eye movement upwards and horizontal, with dilated and fixed pupils, after an influenza syndrome. Radiological, cerebrospinal fluid and electrophysiological data were normal, except BAEPs. The different aetiologies and pathogenesis are discussed.
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Abstract
It is known that cartilage collagen in higher vertebrates conforms to Type II collagen but very little is known of the nature of shark cartilage. This study was undertaken to determine the differences, if any, between shark cartilage collagen and that of higher vertebrates. Collagen was obtained from shark cartilage by pepsin solubilization and characterized by amino acid analysis and determination of chain composition by SDS-polyacrylamide gel electrophoresis and CM-cellulose chromatography. Results indicated the presence not only of Type II collagen but also of Type I collagen. Type I collagen accounted for about one third of the total collagen content of shark cartilage.
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Rama S, Chandrakasan G. Physico-chemical characterisation and molecular organisation of the collagen from the skin of an air-breathing fish (Ophiocephalus striatus). J Biosci 1983. [DOI: 10.1007/bf02716853] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Rama S, Chandrakasan G. Role of aliphatic alcohols & alkyl ureas on the stability & aggregation of skin collagen of Ophiocephalus striatus. Indian J Biochem Biophys 1981; 18:375-6. [PMID: 7341417] [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: 01/24/2023]
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37
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Ardito R, Cecchini S, Rama S. [Duration of antidepressive treatment. Recurrences and their prevention]. Minerva Med 1977; 68:1667-74. [PMID: 865708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The basic strategy for the pharmacological treatment of depression, with special regard to its continuance following the start of remission, is outlined. The problem of the prevention of recurrences of dysthymic symptomatology is discussed and emphasis laid on the importance of lithium about whose use a fair literature is already available. The results obtained to date demonstrate the undoubted advantages of lithium salts (particularly of carbonate) in the maintenance of good affective balance, above all in the case of those subjects in whom the frequency or gravity of dysthymia seriously handicaps working or social life.
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38
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Rama S. [On the oxidation at ordinary temperatures of particles of graphitic carbon of very small diameter and their possible pathological effects]. Riv Ital Ig 1968; 28:753-6. [PMID: 5743270] [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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