TPC Functions in the Immune System

Two-pore channels (TPCs) are novel intracellular cation channels, which play a key role in numerous (patho-)physiological and immunological processes. In this chapter, we focus on their function in immune cells and immune reactions. Therefore, we first give an overview of the cellular immune response and the partaking immune cells. Second, we concentrate on ion channels which in the past have been shown to play an important role in the regulation of immune cells. The main focus is then directed to TPCs, which are primarily located in the membranes of acidic organelles, such as lysosomes or endolysosomes but also certain other vesicles. They regulate Ca²⁺ homeostasis and thus Ca²⁺ signaling in immune cells. Due to this important functional role, TPCs are enjoying increasing attention within the field of immunology in the last few decades but are also becoming more pertinent as pharmacological targets for the treatment of pro-inflammatory diseases such as allergic hypersensitivity. However, to uncover the precise molecular mechanism of TPCs in immune cell responses, further molecular, genetic, and ultrastructural investigations on TPCs are necessary, which then may pave the way to develop novel therapeutic strategies to treat diseases such as anaphylaxis more specifically.

Two-Pore Channels Regulate Inter-Organellar Ca2+ Homeostasis in Immune Cells

Two-pore channels (TPCs) are ligand-gated cation-selective ion channels that are preserved in plant and animal cells. In the latter, TPCs are located in membranes of acidic organelles, such as endosomes, lysosomes, and endolysosomes. Here, we focus on the function of these unique ion channels in mast cells, which are leukocytes that mature from myeloid hematopoietic stem cells. The cytoplasm of these innate immune cells contains a large number of granules that comprise messenger substances, such as histamine and heparin. Mast cells, along with basophil granulocytes, play an essential role in anaphylaxis and allergic reactions by releasing inflammatory mediators. Signaling in mast cells is mainly regulated via the release of Ca2+ from the endoplasmic reticulum as well as from acidic compartments, such as endolysosomes. For the crosstalk of these organelles TPCs seem essential. Allergic reactions and anaphylaxis were previously shown to be associated with the endolysosomal two-pore channel TPC1. The release of histamine, controlled by intracellular Ca2+ signals, was increased upon genetic or pharmacologic TPC1 inhibition. Conversely, stimulation of TPC channel activity by one of its endogenous ligands, namely nicotinic adenine dinucleotide phosphate (NAADP) or phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), were found to trigger the release of Ca2+ from the endolysosomes; thereby improving the effect of TPC1 on regulated mast cell degranulation. In this review we discuss the importance of TPC1 for regulating Ca2+ homeostasis in mast cells and the overall potential of TPC1 as a pharmacological target in anti-inflammatory therapy.

A simple liquid state 1H NMR measurement to directly determine the surface hydroxyl density of porous silica

Silica is widely used in industrial applications and its performance is partially decided by its surface hydroxyl density α_OH. Here we report a quick, simple liquid ¹H NMR method to determine α_OH using a benchtop ¹H NMR spectrometer. The results show excellent agreement with the literature with an α_OH range from 4.16 to 6.56 OH per nm².

Winter survival of the unicellular green alga Micrasterias denticulata: insights from field monitoring and simulation experiments

Peat bog pools around Tamsweg (Lungau, Austria) are typical habitats of the unicellular green alga Micrasterias denticulata. By measurement of water temperature and irradiation throughout a 1-year period (2018/2019), it was intended to assess the natural environmental strain in winter. Freezing resistance of Micrasterias cells and their ability to frost harden and become tolerant to ice encasement were determined after natural hardening and exposure to a cold acclimation treatment that simulated the natural temperature decrease in autumn. Transmission electron microscopy (TEM) was performed in laboratory-cultivated cells, after artificial cold acclimation treatment and in cells collected from field. Throughout winter, the peat bog pools inhabited by Micrasterias remained unfrozen. Despite air temperature minima down to -17.3 °C, the water temperature was mostly close to +0.8 °C. The alga was unable to frost harden, and upon ice encasement, the cells showed successive frost damage. Despite an unchanged freezing stress tolerance, significant ultrastructural changes were observed in field-sampled cells and in response to the artificial cold acclimation treatment: organelles such as the endoplasmic reticulum and thylakoids of the chloroplast showed distinct membrane bloating. Still, in the field samples, the Golgi apparatus appeared in an impeccable condition, and multivesicular bodies were less frequently observed suggesting a lower overall stress strain. The observed ultrastructural changes in winter and after cold acclimation are interpreted as cytological adjustments to winter or a resting state but are not related to frost hardening as Micrasterias cells were unable to improve their freezing stress tolerance.

Gold nanoparticles (AuNPs) impair LPS-driven immune responses by promoting a tolerogenic-like dendritic cell phenotype with altered endosomal structures

Dendritic cells (DCs) shape immune responses by influencing T-cell activation. Thus, they are considered both an interesting model for studying nano-immune interactions and a promising target for nano-based biomedical applications. However, the accentuated ability of nanoparticles (NPs) to interact with biomolecules may have an impact on DC function that poses an unexpected risk of unbalanced immune reactions. Here, we investigated the potential effects of gold nanoparticles (AuNPs) on DC function and the consequences for effector and memory T-cell responses in the presence of the microbial inflammatory stimulus lipopolysaccharide (LPS). Overall, we found that, in the absence of LPS, none of the tested NPs induced a DC response. However, whereas 4-, 8-, and 11 nm AuNPs did not modulate LPS-dependent immune responses, 26 nm AuNPs shifted the phenotype of LPS-activated DCs toward a tolerogenic state, characterized by downregulation of CD86, IL-12 and IL-27, upregulation of ILT3, and induction of class E compartments. Moreover, this DC phenotype was less proficient in promoting Th1 activation and central memory T-cell proliferation. Taken together, these findings support the perception that AuNPs are safe under homeostatic conditions; however, particular care should be taken in patients experiencing a current infection or disorders of the immune system.

A new technical approach for preparing frozen biological samples for electron microscopy

BACKGROUND

Many methodological approaches have focused so far on physiological and molecular responses of plant tissues to freezing but only little knowledge is available on the consequences of extracellular ice-formation on cellular ultrastructure that underlies physiological reactions. In this context, the preservation of a defined frozen state during the entire fixation procedure is an essential prerequisite. However, current techniques are not able to fix frozen plant tissues for transmission electron microscopy (TEM) without interrupting the cold chain. Chemical fixation by glutaraldehyde and osmium tetroxide is not possible at sub-zero temperatures. Cryo-fixation methods, such as high pressure freeze fixation (HPF) representing the state-of-the-art technique for best structural preservation, are not equipped for freezing frozen samples. In order to overcome this obstacle, a novel technical approach for maintaining the cold chain of already frozen plant samples prior and during HPF is presented.

RESULTS

Different algae (Micrasterias denticulata, Klebsormidium crenulatum) and higher plant tissues (Lemna sp., Ranunculus glacialis, Pinus mugo) were successfully frozen and prepared for HPF at freezing temperatures (- 2 °C, - 5 °C, - 6 °C) within a newly developed automatic freezing unit (AFU), that we manufactured from a standard laboratory freezer. Preceding tests on photosynthetic electron transport and ability to plasmolyse show that the temperatures applied did not impair electron transport in PSII nor cell vitality. The transfer of the frozen specimen from the AFU into the HPF-device and subsequently cryo-fixation were performed without intermediate thawing. After cryo-substitution and further processing, the resulting TEM-micrographs showed excellent ultrastructure preservation of the different organisms when compared to specimens fixed at ambient temperature.

CONCLUSIONS

The method presented allows preserving the ultrastructure of plant cells in the frozen state during cryo-fixation. The resulting high quality TEM-images represent an important step towards a better understanding of the consequences of extracellular ice formation on cellular ultrastructure. It has the potential to provide new insights into changes of organelle structure, identification of intracellular injuries during ice formation and may help to understand freezing and thawing processes in plant tissues. It may be combined with analytical TEM such as electron energy loss spectroscopy (EELS), X-ray analyses (EDX) and various other electron microscopic techniques.

Cell Wall Reinforcements Accompany Chilling and Freezing Stress in the Streptophyte Green Alga Klebsormidium crenulatum

Adaptation strategies in freezing resistance were investigated in Klebsormidium crenulatum, an early branching streptophyte green alga related to higher plants. Klebsormidium grows naturally in unfavorable environments like alpine biological soil crusts, exposed to desiccation, high irradiation and cold stress. Here, chilling and freezing induced alterations of the ultrastructure were investigated. Control samples (kept at 20°C) were compared to chilled (4°C) as well as extracellularly frozen algae (-2 and -4°C). A software-controlled laboratory freezer (AFU, automatic freezing unit) was used for algal exposure to various temperatures and freezing was manually induced. Samples were then high pressure frozen and cryo-substituted for electron microscopy. Control cells had a similar appearance in size and ultrastructure as previously reported. While chilling stressed algae only showed minor ultrastructural alterations, such as small inward facing cell wall plugs and minor alterations of organelles, drastic changes of the cell wall and in organelle distribution were found in extracellularly frozen samples (-2°C and -4°C). In frozen samples, the cytoplasm was not retracted from the cell wall, but extensive three-dimensional cell wall layers were formed, most prominently in the corners of the cells, as determined by FIB-SEM and TEM tomography. Similar alterations/adaptations of the cell wall were not reported or visualized in Klebsormidium before, neither in controls, nor during other stress scenarios. This indicates that the cell wall is reinforced by these additional wall layers during freezing stress. Cells allowed to recover from freezing stress (-2°C) for 5 h at 20°C lost these additional cell wall layers, suggesting their dynamic formation. The composition of these cell wall reinforcement areas was investigated by immuno-TEM. In addition, alterations of structure and distribution of mitochondria, dictyosomes and a drastically increased endoplasmic reticulum were observed in frozen cells by TEM and TEM tomography. Measurements of the photosynthetic oxygen production showed an acclimation of Klebsormidium to chilling stress, which correlates with our findings on ultrastructural alterations of morphology and distribution of organelles. The cell wall reinforcement areas, together with the observed changes in organelle structure and distribution, are likely to contribute to maintenance of an undisturbed cell physiology and to adaptation to chilling and freezing stress.

DNA from microdissected tissues may be extracted and stored on microscopic slides

With regard to complex structure of tissues, laser capture microdissection represents an important step in analytical workflow streaming to proper molecular characterization of different cell types in examined samples. Therefore the simple method for simultaneous processing of higher numbers of microdissected tissues leading not only to rapid and efficient DNA isolation but allowing also the repeated sampling and easy storage may be useful in the practice of histopathological laboratories. We elaborated such a methodology applicable downstream after the microdissection from formalin-fixed paraffin embedded tissues.The tissues for examination are microdissected directly into the circular areas having the diameter 2 mm and marked on the microscopic slide. In this way, one slide is able to accommodate multiple samples. The DNA extraction is performed in low volume of buffer with Proteinase K in a droplet covered by mineral oil just on the slide. Mineral oil in the quality for molecular biology not only avoids evaporation during DNA extraction, but it helps to position the microdisssected tissue, to control the level of cell lysis microscopically and to protect the DNA sample during subsequent manipulations. We provided the evidence that DNA isolated by our methodology remains in the positions on microscopic slide for months without any changes in the lengths of available fragments and that it may be removed from each position repetitively for different kinds of analysis. The new methodological approach presented by us can be practically applied in broad spectrum of laboratories performing routinely genetic analysis on microdissected tissues.

Genome-wide methylation analysis of tubulocystic and papillary renal cell carcinomas

Tubulocystic renal cell carcinoma (TRCC) represents a rare tumor with incidence lower than 1 % of all renal carcinomas. This study was undertaken to contribute to characterization of molecular signatures associated with TRCC and to compare them with the features of papillary renal cell carcinoma (PRCC) at the level of genome wide methylation analysis.We performed methylated DNA immunoprecipitation (MeDIP) coupled with microarray analysis (Roche NimbleGen). Using the CHARM package, we compared the levels of gene methylation between paired samples of tumors and control renal tissues of each examined individual. We found significant global demethylation in all tumor samples in comparison with adjacent kidney tissues of normal histological appearance but no significant differences in gene methylation between the both compared tumor entities. Therefore we focused on characterization of differentially methylated regions between both tumors and control tissues. We found 42 differentially methylated genes.Hypermethylated genes for protocadherins (PCDHG) and genes coding for products associated with functions of plasma membrane were evaluated as significantly overrepresented among hypermethylated genes detected in both types of renal cell carcinomas.In our pilot study, we provide the first evidence that identical features in the process of carcinogenesis leading to TRCC and/or to PRCC may be found at the gene methylation level.

Perforated Diverticulitis with Generalized Peritonitis: Low Stoma Rate Using a "Damage Control Strategy"

PURPOSE

Optimal surgical management of perforated diverticulitis of the sigmoid colon has yet to be clearly defined. The purpose of this study was to evaluate efficacy of a "Damage Control Strategy" (DCS).

MATERIALS AND METHODS

Patients with perforated diverticulitis of the sigmoid colon complicated by generalized peritonitis (Hinchey III and IV) surgically treated according to a damage control strategy between May 2011 and February 2017 were enrolled in the present multicenter retrospective cohort study. Data were collected at three surgical centers. DCS comprises a two-stage concept: [1] limited resection of the perforated colon segment with oral and aboral blind closure during the emergency procedure and [2] definitive reconstruction at scheduled second laparotomy (anastomosis ∓ loop ileostomy or a Hartmann's procedure) after 24-48 h.

RESULTS

Fifty-eight patients were included into the analysis [W:M 28:30, median age 70.1 years (30-92)]. Eleven patients (19%) initially presented with fecal peritonitis (Hinchey IV) and 47 patients with purulent peritonitis (Hinchey III). An anastomosis could be created during the second procedure in 48 patients (83%), 14 of those received an additional loop ileostomy. In the remaining ten patients (n = 17%), an end colostomy was created at second laparotomy. A fecal diversion was performed in five patients to treat anastomotic complications. Thus, altogether, 29 patients (50%) had stoma at the end of the hospital stay. The postoperative mortality was 9% (n = 5), and median postoperative hospital stay was 18.5 days (3-66). At the end of the follow-up, 44 of 53 surviving patients were stoma free (83%).

CONCLUSION

The use of the Damage Control strategy leads to a comparatively low stoma rate in patients suffering from perforated diverticulitis with generalized peritonitis.

Ionic stress induces fusion of mitochondria to 3-D networks: An electron tomography study

Mitochondria are central organelles for energy supply of cells and play an important role in maintenance of ionic balance. Consequently mitochondria are highly sensitive to any kind of stress to which they mainly response by disturbance of respiration, ROS production and release of cytochrome c into the cytoplasm. Many of the physiological and molecular stress reactions of mitochondria are well known, yet there is a lack of information on corresponding stress induced structural changes. 3-D visualization of high-pressure frozen cells by FIB-SEM tomography and TEM tomography as used for the present investigation provide an excellent tool for studying structure related mitochondrial stress reactions. In the present study it is shown that mitochondria in the unicellular fresh-water algal model system Micrasterias as well as in the closely related aquatic higher plant Lemna fuse to local networks as a consequence of exposure to ionic stress induced by addition of KCl, NaCl and CoCl₂. In dependence on concentration and duration of the treatment, fusion of mitochondria occurs either by formation of protuberances arising from the outer mitochondrial membrane, or by direct contact of the surface of elongated mitochondria. As our results show that respiration is maintained in both model systems during ionic stress and mitochondrial fusion, as well as formation of protuberances are reversible, we assume that mitochondrial fusion is a ubiquitous process that may help the cells to cope with stress. This may occur by interconnecting the respiratory chains of the individual mitochondria and by enhancing the buffer capacity against stress induced ionic imbalance.

A bioimpedance analysis of head-and-neck cancer patients undergoing radiotherapy

Malnutrition is a frequent manifestation in patients with head-and-neck cancer undergoing radiation therapy and a major contributor to morbidity and mortality. Thus, body composition is an important component of an overall evaluation of nutrition in cancer patients. Malnutrition is characterized by weight loss, loss of muscle mass, changes in cell membrane integrity, and alterations in fluid balance. Bioelectrical impedance analysis is a method to analyze body composition and includes parameters such as intracellular water content, extracellular water content, and cell membrane integrity in the form of a phase angle (Φ). Bioelectrical impedance analysis has consistently been shown to have prognostic value with respect to mortality and morbidity in patients undergoing chemotherapy. The goal of the present study was to evaluate the relationship between Φ, time, intracellular water content, and weight for head-and-neck cancer patients undergoing radiotherapy. The results demonstrate that Φ decreases with time and increases with intracellular water content and weight.

Prospective multicentre clinical study on inter- and intrapatient genetic variability for antimicrobial resistance of Helicobacter pylori

OBJECTIVES

We report on a large prospective, multicentre clinical investigation on inter- and intrapatient genetic variability for antimicrobial resistance of Helicobacter pylori.

METHODS

Therapy-naive patients (n = 2004) who had undergone routine diagnostic gastroscopy were prospectively included from all geographic regions of Austria. Gastric biopsy samples were collected separately from antrum and corpus. Samples were analysed by histopathology and real-time PCR for genotypic resistance to clarithromycin and quinolones. Clinical and demographic information was analysed in relation to resistance patterns.

RESULTS

H. pylori infection was detected in 514 (26%) of 2004 patients by histopathology and confirmed in 465 (90%) of 514 patients by real-time PCR. PCR results were discordant for antrum and corpus in 27 (5%) of 514 patients, indicating inhomogeneous infections. Clarithromycin resistance rates were 17% (77/448) and 19% (84/455), and quinolone resistance rates were 12% (37/310) and 10% (32/334) in antrum and corpus samples, respectively. Combination of test results per patient yielded resistance rates of 21% (98/465) and 13% (50/383) for clarithromycin and quinolones, respectively. Overall, infection with both sensitive and resistant H. pylori was detected in 65 (14%) of 465 patients.

CONCLUSIONS

Anatomically inhomogeneous infection with different, multiple H. pylori strains is common. Prospective clinical study design, collection of samples from multiple sites and microbiologic methods that allow the detection of coinfections are mandatory for collection of reliable data on antimicrobial resistance patterns in representative patient populations. (ClinicalTrials.gov identifier: NCT02925091).

[Improvement of emergency physician education through simulator training. Consideration on the basis of the model project "NASimSaar25"]

BACKGROUND

Prehospital emergency medicine is a challenge for trainee emergency physicians. Rare injuries and diseases as well as patients in extreme age groups can unexpectedly face emergency physicians. In the regulations on medical education the German Medical Association requires participation in 50 emergency missions under the supervision of an experienced emergency physician. This needs to be improved because on-the-job training does not generally represent the whole spectrum of emergency medicine and a good and structured training under on call conditions is nearly impossible.

AIM

The subject of the model project described was whether practical training for emergency physicians can be achieved by participation in simulation training instead of real emergency situations.

MATERIAL AND METHODS

After modification of the Saarland regulations on medical education it was possible to replace up to 25 participations in emergency missions by simulation training. The concept of the course NASimSaar25 requires participants to complete 25 simulator cases in 3 days in small training groups. Emergency situations from all medical disciplines need to be treated. A special focus is on the treatment of life-threatening and rare diseases and injuries. Modern simulators and actors are used. The debriefings are conducted by experienced tutors based on approved principles. Medical contents, learning targets from the field of crew resource management (CRM) and soft skills are discussed in these debriefings.

RESULTS

Education in the field of emergency medicine can be improved by simulator-based learning and training. However, practical work under a tutor in real and clinical experience cannot be completely replaced by simulation. Simulator training can only be successful if theoretical knowledge has already been acquired.

CONCLUSION

A simulator-based course concept can result in an improvement of emergency medical education. The model project NASimSaar25 was well received by the target audience and mostly very well evaluated in terms of learning and reality. If this project becomes established the demand on simulation-based training will increase. The training should achieve a consistent standard of quality.

Servo-integrated patterned media by hybrid directed self-assembly

A hybrid directed self-assembly approach is developed to fabricate unprecedented servo-integrated bit-patterned media templates, by combining sphere-forming block copolymers with 5 teradot/in.(2) resolution capability, nanoimprint and optical lithography with overlay control. Nanoimprint generates prepatterns with different dimensions in the data field and servo field, respectively, and optical lithography controls the selective self-assembly process in either field. Two distinct directed self-assembly techniques, low-topography graphoepitaxy and high-topography graphoepitaxy, are elegantly integrated to create bit-patterned templates with flexible embedded servo information. Spinstand magnetic test at 1 teradot/in.(2) shows a low bit error rate of 10(-2.43), indicating fully functioning bit-patterned media and great potential of this approach for fabricating future ultra-high-density magnetic storage media.

[Colorectal cancer: screening and surveillance in inflammatory bowel diseases - consensus of the working group for inflammatory bowel diseases of the Austrian Society of Gastroenterology and Hepatology]

Patients with ulcerative colitis and Crohn's colitis are at increased risk of colorectal cancer (CRC). This risk is dependent on the duration and extent of disease, inflammatory activity and possible additional risk factors. Thus, the aim is to reduce this risk and to detect dysplastic and malignant lesions at an early stage. The working group for Inflammatory Bowel Diseases (IBD) of the Austrian Society of Gastroenterology and Hepatology (ÖGGH) has developed consensus statements on the following topics: risk of colorectal cancer, screening and surveillance, procedure of surveillance colonoscopy, dysplasia and its management, and chemoprevention. This consensus is intended to increase awareness of the increased risk of CRC in IBD and to support a standardised approach in cancer prevention.

Abstract P4-07-05: MEDI3379, an antibody against HER3, is active in HER2-driven human breast tumor models

HER3 (ERBB3) is a member of the EGFR/HER family of receptor tyrosine kinases (RTK), consisting of EGFR, HER2, HER3 and HER4. Unlike the other HER family members, HER3 lacks intrinsic tyrosine kinase activity and therefore needs to form heterodimers with EGFR, HER2 or other kinase-proficient RTKs to be functionally active. Dimerization is induced by overexpression of EGFR or HER2 in a ligand-independent (LI) manner. In this process HER3 acts as a driver in divergent cancer types including HER2-positive breast cancer (BC) via induction of the PI3K-AKT pathway. Alternatively, heregulin (NRG1/HRG), the major HER3 ligand, induces a conformational shift in HER3 which leads to dimer formation with a partner RTK in a ligand-dependent (LD) manner.

We have developed an antagonistic human monoclonal antibody against HER3, termed MEDI3379, and tested it in multiple breast cancer cell lines. We observed effective suppression of constitutive pHER3 and pAKT with MEDI3379, leading to anti-proliferation effects in cell culture models. Preclinical evaluation of MEDI3379 demonstrated antitumor activity in several orthotopic BC xenografts in nude mice which did not express HRG. For example, the BC xenograft model BT474 with amplified HER2 responded to MEDI3379 (65% dTGI). In conclusion, our findings with targeting of HER3 in mouse models support continued development of MEDI3379 for cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-07-05.

Poster - Thur Eve - 57: Craniospinal irradiation with jagged-junction IMRT approach without beam edge matching for field junctions

PURPOSE

Craniospinal irradiation were traditionally treated the central nervous system using two or three adjacent field sets. A intensity-modulated radiotherapy (IMRT) plan (Jagged-Junction IMRT) which overcomes problems associated with field junctions and beam edge matching, improves planning and treatment setup efficiencies with homogenous target dose distribution was developed.

METHODS AND MATERIALS

Jagged-Junction IMRT was retrospectively planned on three patients with prescription of 36 Gy in 20 fractions and compared to conventional treatment plans. Planning target volume (PTV) included the whole brain and spinal canal to the S3 vertebral level. The plan employed three field sets, each with a unique isocentre. One field set with seven fields treated the cranium. Two field sets treated the spine, each set using three fields. Fields from adjacent sets were overlapped and the optimization process smoothly integrated the dose inside the overlapped junction.

RESULTS

For the Jagged-Junction IMRT plans vs conventional technique, average homogeneity index equaled 0.08±0.01 vs 0.12±0.02, and conformity number equaled 0.79±0.01 vs 0.47±0.12. The 95% isodose surface covered (99.5±0.3)% of the PTV vs (98.1±2.0)%. Both Jagged-Junction IMRT plans and the conventional plans had good sparing of the organs at risk.

CONCLUSIONS

Jagged-Junction IMRT planning provided good dose homogeneity and conformity to the target while maintaining a low dose to the organs at risk. Jagged-Junction IMRT optimization smoothly distributed dose in the junction between field sets. Since there was no beam matching, this treatment technique is less likely to produce hot or cold spots at the junction in contrast to conventional techniques.

Depositing Metals into Porous Silicon - the Impact on Luminescence

Indium, tin, antimony and aluminum are deposited by an electrochemical process into the pores of n-type porous silicon which is anodized with ultraviolet light applied during formation. The presence of these metal atoms in the porous layer is checked by electron microprobe measurement. As reported previously, UV-light etched material shows red photoluminescence (630 nm) and blue electroluminescence (470 nm) without the metal treatment. After metal deposition the photoluminescence intensity decreases slightly (factor 0.5 - 0.8), whereas the spectral position remains constant. The electroluminescence efficiency is significantly enhanced by indium, aluminum and tin in the pores (factor 5 - 90). The tin and antimony treatment causes a red shift to 580 nm and 740 nm, respectively. The conductivity is slightly increased by all kinds of metals by a factor 2-5.

Stabilization of electroluminescence and photoluminescence of porous n-silicon by chemical oxidation in H2O2

We have oxidized porous (n-)silicon samples in solutions of H202 and have found that PL can be stabilized at a high level. The PL intensity of as prepared samples (PL quantum efficiencies in the range of 5 %) degrades to about 1/3 of the initial value in some ten minutes (the exact value depends on the experimental conditions). After having treated the samples for about 30 - 45 minutes in hydrogen peroxide it can be observed that bright PL remains stable for hours. These results confirm similar experiments performed with porous silicon made from p-substrates1. While red electroluminescing samples have shown long time stability for about 100 hours2, samples with blue-green electroluminescence have a lifetime of about 20 - 40 minutes. Oxidizing electroluminescent samples as described above results in a stabilization of electroluminescence for more than 7 hours.

Austrian experiences with redo antireflux surgery

BACKGROUND

From 1996, the entire number of fundoplications performed in Austria increased dramatically, favoring the laparoscopic technique. Despite good results, some patients experience failure of antireflux surgery and therefore require redo surgery if medical therapy fails to control symptoms. The aim of the study was to describe the refundoplication policy in Austria with evaluation of the postoperative results.

METHODS

A questionnaire was sent to all Austrian surgical departments at the beginning of 2003 with questions about redo fundoplications (number, techniques, intraoperative complications, history, migration of patients, preoperative workup, mortality, and postoperative long-term complaints). It also included questions about primary fundoplications (number, technique, postoperative symptoms).

RESULTS

Out of 4,504 primary fundoplications performed in Austria since 1990, 3,952 have been carried out laparoscopically. In a median of 31 months after the primary operation, 225 refundoplications have been performed, laparoscopically in the majority of patients. The Nissen and the partial posterior fundoplication were the preferred techniques. The conversion rate in these was 10.8%, mainly because of adhesions and lacerations of the spleen, the stomach, and the esophagus. The mortality rate after primary fundoplications was 0.04%, whereas the rate after refundoplications was 0.4%, all resulting from an open approach.

CONCLUSION

Laparoscopic refundoplications are widely accepted as a treatment option after failed primary antireflux surgery in Austria. However, the conversion rate is 6 times higher and the mortality rate is 10 times higher than for primary antireflux surgery. Therefore, redo fundoplications should be performed only in departments with large experience.

Pharmacokinetics of ethambutol in children and adults with tuberculosis

SETTING

Five hospitals in the United States.

OBJECTIVE

To describe ethambutol pharmacokinetics in children and adults with active tuberculosis (TB).

DESIGN

Prospective, open-labeled study in 56 adults and 14 children with active tuberculosis who received ethambutol as part of their multidrug TB regimens.

RESULTS

Most serum samples were collected up to 10 h post dose and assayed using a validated gas chromatography assay with mass selective detection (GC/MS). Concentration data were analyzed using non-compartmental and population pharmacokinetic methods. Drug exposure increased with dose, but less than proportionally at doses >3000 mg. Lower than expected maximum serum concentrations (Cmax <2 microg/ml) were common in adults. Very low Cmax (<1 microg/ml) were common in children, as was delayed absorption (time to Cmax >3 h). Many Cmax were at or below typical TB minimal inhibitory concentrations. Cmax values for HIV-positive patients were 20% lower than HIV-negative patients with daily doses, but were similar with larger twice-weekly doses.

CONCLUSIONS

Adult TB patients often had lower than expected ethambutol serum concentrations, and most pediatric TB patients had very low ethambutol serum concentrations. Higher doses and therapeutic drug monitoring may be indicated for many of these patients.

Design and validation of a tool for neurite tracing and analysis in fluorescence microscopy images

BACKGROUND

For the investigation of the molecular mechanisms involved in neurite outgrowth and differentiation, accurate and reproducible segmentation and quantification of neuronal processes are a prerequisite. To facilitate this task, we developed a semiautomatic neurite tracing technique. This article describes the design and validation of the technique.

METHODS

The technique was compared to fully manual delineation. Four observers repeatedly traced selected neurites in 20 fluorescence microscopy images of cells in culture, using both methods. Accuracy and reproducibility were determined by comparing the tracings to high-resolution reference tracings, using two error measures. Labor intensiveness was measured in numbers of mouse clicks required. The significance of the results was determined by a Student t-test and by analysis of variance.

RESULTS

Both methods slightly underestimated the true neurite length, but the differences were not unanimously significant. The average deviation from the true neurite centerline was a factor 2.6 smaller with the developed technique compared to fully manual tracing. Intraobserver variability in the respective measures was reduced by a factor 6.0 and 23.2. Interobserver variability was reduced by a factor 2.4 and 8.8, respectively, and labor intensiveness by a factor 3.3.

CONCLUSIONS

Providing similar accuracy in measuring neurite length, significantly improved accuracy in neurite centerline extraction, and significantly improved reproducibility and reduced labor intensiveness, the developed technique may replace fully manual tracing methods.

Overexpression of the ATP-dependent helicase RecG improves resistance to weak organic acids in Escherichia coli

Increased resistance to several weak organic acids was conferred on Escherichia coli by overexpression of the ATP-dependent helicase RecG and, to a lesser extent, by overexpressing the helicase RuvAB. This property of helicases was identified by reproducible selection of recG-bearing clones from genomic libraries of the acetate-resistant species Acetobacter aceti and Staphylococcus capitis. We show that overexpression of RecG from both species, but also from E. coli, increased the maximum biomass concentration attained by E. coli cultures that were grown in the presence of various weak organic acids and uncouplers. Furthermore, overexpression of RecG from A. aceti significantly improved the maximum growth rates of E. coli under weak organic acid challenge. Based on the known role of RecG in DNA replication/repair, our data provide a first indication that weak organic acids negatively affect DNA replication and/or repair, and that these negative effects may be counteracted by helicase activity.

Detektion von Leberläsionen mit der Gadolinium-verstärkten VIBE-Sequenz im Vergleich zur SPIO-verstärkten MRT

PURPOSE

Detection of malignant liver lesions with gadolinium-enhanced volumetric interpolated breath-hold examination (VIBE) in comparison with SPIO-enhanced MRT (four different SPIO-enhanced T2w sequences) and histological and imaging follow-up in non-cirrhotic livers at 1.5 T.

PATIENTS AND METHODS

Twenty-two patients with suspected focal liver lesions prospectively underwent a gadolinium-enhanced 3D VIBE. Four T2w sequences (HASTE sequence, fast spin-echo-sequence with and without fat-saturation, FLASH 2D gradient echo-sequence) after administration of superparamagnetic iron oxide (SPIO) served as gold standard combined with histological work-up in 17 patients and histological and imaging follow-up in five patients. The image quality was evaluated and the detectability of intrahepatic lesions was rated by the alternative free-response receiver operating characteristic (AFROC) analysis. In addition, the contrast-to-noise ratio was compared.

RESULTS

Altogether 49 malignant and 35 benign liver lesions were found. Concerning the image quality, VIBE turned out to be of slightly poorer image quality than the SPIO-enhanced examination with HASTE sequence (4.95 vs. 5.0). The fast spin-echo-sequence without fat-saturation demonstrated the highest contrast-to-noise ratio. All sequences showed a comparable certainty in detecting lesion (area under the curve 0.68-0.73) and identifying malignant liver lesions.

CONCLUSION

Despite the small number of patients, VIBE seems to be a comparable, inexpensive and fast method in diagnosing malignant liver lesions.

Heparanase-1 gene expression in normal, hyperplastic and neoplastic prostatic tissue

Heparanase-1 (Hpa-1) has been implicated in tumour invasion and metastasis. In the present study, we evaluated the clinicopathological significance of Hpa-1 mRNA expression in prostate cancer and non-cancerous prostatic tissue by one-step polymerase chain reaction (PCR) of laser microdissected prostatic gland cells. In addition, cell type-specific expression of Hpa-1 mRNA in prostatic tissue was analysed by in situ hybridisation. Hpa-1 mRNA expression was found in 50% of normal and 40% of hyperplastic prostatic tissue. In situ hybridisation showed that Hpa-1 mRNA was strongly expressed in prostate gland cells. Of the 26 prostate carcinomas tested, 42% were positive for Hpa-1 mRNA. However, in non-cancerous prostatic tissue, Hpa-1 mRNA was significantly more often expressed than in less differentiated or more invasive prostate cancers (P<0.05). In situ hybridisation revealed only focal Hpa-1 mRNA expression in the neoplastic gland cells. Hpa-1 mRNA expression in the tumours significantly correlated with tumour differentiation and tumour stage (P<0.05). Our data indicate that Hpa-1 gene expression may be lost during dedifferentiation of prostatic gland cells.

Interactions between synaptic vesicle fusion proteins explored by atomic force microscopy

Measuring the biophysical properties of macromolecular complexes at work is a major challenge of modern biology. The protein complex composed of vesicle-associated membrane protein 2, synaptosomal-associated protein of 25 kDa, and syntaxin 1 [soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) complex] is essential for docking and fusion of neurotransmitter-filled synaptic vesicles with the presynaptic membrane. To better understand the fusion mechanisms, we reconstituted the synaptic SNARE complex in the imaging chamber of an atomic force microscope and measured the interaction forces between its components. Each protein was tested against the two others, taken either individually or as binary complexes. This approach allowed us to determine specific interaction forces and dissociation kinetics of the SNAREs and led us to propose a sequence of interactions. A theoretical model based on our measurements suggests that a minimum of four complexes is probably necessary for fusion to occur. We also showed that the regulatory protein neuronal Sec1 injected into the atomic force microscope chamber prevented the complex formation. Finally, we measured the effect of tetanus toxin protease on the SNARE complex and its activity by on-line registration during tetanus toxin injection. These experiments provide a basis for the functional study of protein microdomains and also suggest opportunities for sensitive screening of drugs that can modulate protein-protein interactions.

Technique of mobilization and mesh fixation in laparoscopic hernia repair by transabdominal preperitoneal mesh prosthesis

In laparoscopic inguinal hernia repair the preparation technique is very important to avoid recurrences. A standardized dissection, mesh placement and fixation with staplers provides safe closure of every inguinal and femoral hernia.

[Comparison of an edema-sensitive HASTE-TIRM sequence with delayed contrast enhancement in acute myocardial infarcts]

GOAL

Comparison between a fluid-sensitive (HASTE-TIRM)-sequence and delayed contrast-enhancement in patients with acute myocardial infarct (AMI) in MRI.

MATERIAL AND METHODS

32 patients with AMI were imaged 7 +/- 4 days after the time of infarction with a 1.5 T unit using a T2 HASTE-TIRM and a contrast-enhanced (CE) T1 turbo FLASH sequence. A threshold method (>2 SD in comparison with normal myocardium) was used to quantify the hyperintense zones in both sequences. The transmurality of the hyperintense regions was measured on a segmental basis.

RESULTS

The hyperintense areas were larger on the HASTE-TIRM sequence with 29.6 +/- 13.2 % of the left ventricular (LV) area as compared to the CE-MRI with 19.2 +/- 10 % of the LV area (p < 0.0001). The measured transmurality was higher with the HASTE-TIRM sequence than with the CE-MRI (p < 0.0001). While the correlation between CE-MRI and peak creatine kinase (CK max) was good (r = 0.59, p < 0.001), no correlation was found between the HASTE-TIRM sequence and CK max (r = 0.29, p = ns).

CONCLUSIONS

The peri-infarct edema can be depicted with a HASTE-TIRM sequence in addition to the non-viable infarct zone. The HASTE-TIRM sequence shows a higher transmurality of the hyperintense regions than the CE-MRI. The additional area depicted by the HASTE-TIRM sequence could represent functionally impaired but viable myocardium).

[Establishing a quality management system according to DIN EN ISO 9001:2000 in an academic radiological department]

PURPOSE

Establishing a quality management (QM) system according the guidelines of DIN EN ISO 9001:2000 in an academic radiological department.

MATERIALS AND METHODS

To fulfill the requirements of an academic radiological department a quality management system according the guidelines of DIN EN ISO 9001 : 2000 has been established within one year. All important educational, research and patient care issues have been discussed in plenary sessions of all employees of the department twice a week. All core processes of the department have been documented as process instructions and standard operation procedures.

RESULTS

Supported by the staff unit "quality assurance" of the university hospital, the QM system has been established during one year. Assisted by all parties of the department, obliging regulations have been established which are well accepted in the daily routine clinical work but also in research and education. The implementation of the QM system caused an additional work load. However, spreading the work load by a consequent responsibility assignment, it could be reduced effectively.

CONCLUSION

The implementation of a QM system within the daily routine work of an academic radiological department is feasible. It allows the installation of generally accepted rules which regulate the principal tasks of research and education, and patient care.

Overexpression of neuronal Sec1 enhances axonal branching in hippocampal neurons

The soluble N-ethylmaleimide-sensitive factor-attached protein receptor (SNARE) proteins syntaxin 1 and synaptosomal-associated protein-25 have been implicated in axonal outgrowth. Neuronal Sec1 (nSec1), also called murine unc18a (Munc18a), is a syntaxin 1-binding protein involved in the regulation of SNARE complex formation in synaptic vesicle membrane fusion. Here we analysed whether nSec1/Munc18a is involved in neurite formation. nSec1/Munc18a expressed under the control of an inducible promoter in differentiated PC12 cells as well as in hippocampal neurons appears first in the cell body, and at later times after induction along neurites and in growth cones. It is localised to distinct tubular and punctated structures. In addition, exogenous nSec1/Munc18a inhibited regulated secretion in PC12 cells. Overexpression in PC12 cells of nSec1/Munc18a or its homologue Munc18b, reduced the total length of neurites. This effect was enhanced with nSec1-T574A, a mutant that lacks a cyclin-dependent kinase 5 phosphorylation site and displays an increased binding to syntaxin 1. In contrast, in hippocampal neurons the total length of all primary neurites and branches was increased upon transfection of nSec1/Munc18a. Detailed morphometric analysis revealed that this was a consequence of an increased number of axonal side branches, while the average lengths in primary neurites and of side branches were not affected. From these results we suggest that nSec1/Munc18a is involved in the regulation of SNARE complex-dependent membrane fusion events implicated in the ramification of axonal processes in neurons.

Proteins induced during adaptation of Acetobacter aceti to high acetate concentrations

As a typical product of microbial metabolism, the weak acid acetate is well known for its cytotoxic effects. In contrast to most other microbes, the so-called acetic acid bacteria can acquire significant resistance to high acetate concentrations when properly adapted to such hostile conditions. To characterize the molecular events that are associated with this adaptation, we analyzed global protein expression levels during adaptation of Acetobacter aceti by two-dimensional gel electrophoresis. Adaptation was achieved by using serial batch and continuous cultivations with increasing acetate supplementation. Computer-aided analysis revealed a complex proteome response with at least 50 proteins that are specifically induced by adaptation to acetate but not by other stress conditions, such as heat or oxidative or osmotic stress. Of these proteins, 19 were significantly induced in serial batch and continuous cultures and were thus noted as acetate adaptation proteins (Aaps). Here we present first microsequence information on such Aaps from A. aceti. Membrane-associated processes appear to be of major importance for adaptation, because some of the Aap bear N-terminal sequence homology to membrane proteins and 11 of about 40 resolved proteins from membrane protein-enriched fractions are significantly induced.

[MRI first-pass myocardial perfusion in patients undergoing percutaneous myocardial laser revascularization]

PURPOSE

Evaluation of MRI first-pass myocardial perfusion pre- and post-percutaneous myocardial laser revascularisation (PMR).

PATIENTS AND METHODS

MRI was performed in 10 patients with coronary heart disease grade III-IV, 1-4 days prior to PMR, as well as 1-5 days and 6 months after PMR. Contrast enhanced (0.1 ml/kgBw; 4 ml/s) "first-pass" MRI imaging was obtained by breath-hold, ECG-triggered, multislice Turbo-FLASH GRE. For quantitative analysis the absolute and percentual signal-to-noise (S/N)-measurements were calculated. Positron emission tomography (PET) was regarded as the gold standard for myocardial perfusion.

RESULTS

The mean values of absolute and % S/N increase revealed no statistical difference between pre- and immediately post-PMR imaging. 6 months following PMR both values were significantly elevated (14.1 vs. 24.4 and 127 vs. 176; p = 0.03 and p = 0.01). However, the non-treated myocardial segments revealed a similar S/N pattern. Intraindividual analysis showed a significant S/N increase post PMR in one patient, and in additional 4 patients 6 months later. PET revealed increased myocardial perfusion in only two patients. Following PMR 5/10 patients experienced a significant reduction of chest pain equivalent to two CCS grades. Two of these had significant S/N elevations but no evidence of increased perfusion by PET.

CONCLUSION

S/N first-pass calculations following PMR do not correlate well with the true situation of myocardial perfusion. They seem to be more closely associated with other histological phenomena and possible explanations for the improved clinical symptomatology.

MRT in der präoperativen Diagnostik der chronischen Sinusitis im Vergleich mit der CT

PURPOSE

To determine the value of MRI in the preoperative evaluation of chronic paranasal sinusitis and to compare the results with CT and intraoperative findings.

METHOD/MATERIALS

42 patients with clinical signs of chronic paranasal sinusitis underwent MRI after CT evaluation on one day, with subsequent functional endoscopic sinus surgery on the next day. Coronary CT was obtained with 5-mm slices and table-feed in the prone position, while MRI was performed in the supine position with coronary T2-TSE + pd and coronary and transverse HASTE, each with 5-mm slice thickness. Aquisition time in MRI was less than 8 minutes. Two radiologists reviewed the CT and MRI scans for signs of sinusitis and detection of anatomical landmarks. The results were correlated with the intraoperative findings.

RESULTS

MRI offered no artifacts of dental work and showed more often high quality pictures than CT. CT and MRI demonstrated a good correlation in the detection of mucosal pathologies (kappa = 0.46-0.87) and anatomic variants (kappa = 0.55-0.86). All important anatomical structures could be evaluated sufficiently with MRI for preoperative management. Both diagnostic tools showed an unsatisfactory correlation with intraoperative findings in the ethmoidal complex and maxillary sinus (tau = -0.08-0.3).

CONCLUSIONS

MRI is a fast and reliable alternative to preoperative CT in examining paranasal sinuses and offers a good visualization of mucosal changes. CT and MRI both give an unreliable representation of the ethmoidal complex.

Temperature quantification using the proton frequency shift technique: In vitro and in vivo validation in an open 0.5 tesla interventional MR scanner during RF ablation

Open magnetic resonance (MR) scanners allow MR-guided targeting of tumors, as well as temperature monitoring of radio frequency (RF) ablation. The proton frequency shift (PFS) technique, an accurate and fast imaging method for temperature quantification, was used to synthesize thermal maps after RF ablation in an open 0.5 T MR system under ex vivo and in vivo conditions. Calibration experiments with 1.5% agarose gel yielded a chemical shift factor of 0.011 +/- 0.001 ppm/ degrees C (r2 = 0.96). Three gradient echo (GRE) pulse sequences were tested for thermal mapping by comparison with fiberoptic thermometer (Luxtron Model 760) readings. Temperature uncertainty decreased from high to low bandwidths (BW): +/-5.9 degrees C at BW = 15.6 kHz, +/-1.4 degrees C at BW = 3.9 kHz, and +/-0.8 degrees C at BW = 2.5 kHz. In vitro experiments (N = 9) in the paraspinal muscle yielded a chemical shift factor of 0.008 +/- 0.001 ppm/ degrees C. Temperature uncertainty was determined as +/-2.7 degrees C (BW = 3.9 kHz, TE = 19.3 msec). The same experiments carried out in the paraspinal muscle (N = 9) of a fully anesthetized pig resulted in a temperature uncertainty of +/-4.3 degrees C (BW = 3.9 kHz, TE = 19.3 msec), which is higher than it is in vitro conditions (P < 0.15). Quantitative temperature monitoring of RF ablation is feasible in a 0.5 T open-configured MR scanner under ex vivo and in vivo conditions using the PFS technique.

Long-term excessive magnesium supplementation is deleterious whereas suboptimal supply is beneficial for bones in rats

The long-term effects of a suboptimal magnesium supply inducing a marginal or moderate deficiency or of an excessive magnesium supplementation corresponding to a basal diet with a high pharmacological intake were investigated in 36 growing Sprague-Dawley female rats. The rats were randomly divided in three groups and received a purified diet with 7 g calcium, 5 g phosphorus and either 0.2, 0.5 or 2 g magnesium per kg diet for 7 months. At the end of the trial, plasma and erythrocyte total magnesium concentrations were significantly lower in the magnesium-deficient group than in the respective control group. Serum concentrations of 1,25-dihydroxyvitamin D, PTH and IGF-I and the length of the right humeri were not affected by the dietary treatment. The volumes corrected for body weight, the medio-lateral diameters and the ratios dry weight/length of the right humeri, and the dry weight corrected for body weight of the left tibiae and of the right humeri were significantly smaller in the magnesium-supplemented group than in the two other groups. The magnesium contents of the left tibiae and of the first lumbar vertebrae were significantly lower in the magnesium-deficient group than in the two other groups. In the right femora, dual energy X-ray absorptiometry revealed significantly smaller areas in the proximal part and significantly smaller mineral contents in the second proximal quarter in the magnesium-supplemented group compared with the two other groups. Peripheral quantitative computer tomography of the right humeri revealed in the cortex significantly larger values for the relative area, mineral content, mineral density and thickness in the magnesium-deficient group compared with the control group. The maximum point of the load-deformation curve was significantly reduced in the fifth lumbar vertebrae and in the proximal femoral metaphyses of the magnesium-supplemented group. These results indicate that the long-term suboptimal magnesium supply improved some of the parameters indicators of bone health whereas the long-term supplementation was deleterious.