Bumetanide induces post-traumatic microglia-interneuron contact to promote neurogenesis and recovery

Although the Na-K-Cl cotransporter (NKCC1) inhibitor bumetanide has prominent positive effects on the pathophysiology of many neurological disorders, the mechanism of action is obscure. Attention paid to elucidating the role of Nkcc1 has mainly been focused on neurons, but recent single cell mRNA sequencing analysis has demonstrated that the major cellular populations expressing NKCC1 in the cortex are non-neuronal. We used a combination of conditional transgenic animals, in vivo electrophysiology, two-photon imaging, cognitive behavioural tests and flow cytometry to investigate the role of Nkcc1 inhibition by bumetanide in a mouse model of controlled cortical impact (CCI). Here, we found that bumetanide rescues parvalbumin-positive interneurons by increasing interneuron-microglia contacts shortly after injury. The longitudinal phenotypic changes in microglia were significantly modified by bumetanide, including an increase in the expression of microglial-derived BDNF. These effects were accompanied by the prevention of CCI-induced decrease in hippocampal neurogenesis. Treatment with bumetanide during the first week post-CCI resulted in significant recovery of working and episodic memory as well as changes in theta band oscillations 1 month later. These results disclose a novel mechanism for the neuroprotective action of bumetanide mediated by an acceleration of microglial activation dynamics that leads to an increase in parvalbumin interneuron survival following CCI, possibly resulting from increased microglial BDNF expression and contact with interneurons. Salvage of interneurons may normalize ambient GABA, resulting in the preservation of adult neurogenesis processes as well as contributing to bumetanide-mediated improvement of cognitive performance.

Adherence to Psychological First Aid after Exposure to a Traumatic Event at Work among EMS Workers: A Qualitative Study

Managing post-traumatic stress reactions in the first few days after exposure to a potentially traumatic event in the course of one's work remains a challenge for first responder organizations such as Emergency Medical Services (EMS). Psychological First Aid (PFA) is an evidence-informed approach to reducing initial distress and promoting short- and long-term coping strategies among staff in the aftermath of exposure. PFA provided by peer helpers is considered a promising solution for first responder organizations. Unfortunately, first responders may encounter stigma and barriers to mental health care. Therefore, a deeper investigation is needed regarding adherence over time to implemented PFA intervention. The purpose of this study is to qualitatively explore factors that influence adherence to PFA intervention of recipients and peer helpers. EMS workers (n = 11), working as PFA peer helpers for one year, participated in semi-structured interviews. Data were analyzed using thematic analysis; intercoder reliability (κ = 0.91) was also used. Researchers identified four themes and 11 subthemes influencing adherence to PFA intervention: (1) individual perceptions and attitudes of peer helpers and recipients about pfa intervention; (2) perceived impacts on peer helpers and recipients; (3) organizational support to pfa intervention; and (4) congruence with the occupational culture. Study findings herein suggest that it is conceivable to act on various factors to improve adherence to PFA intervention among peer helpers and recipients within EMS organization. This could lead to enhanced understanding of the challenges involved in sustaining a peer led PFA program for first responders.

Protective Role of Low Ethanol Administration Following Ischemic Stroke via Recovery of KCC2 and p75NTR Expression

A striking result from epidemiological studies show a correlation between low alcohol intake and lower incidence for ischemic stroke and severity of derived brain injury. Although reduced apoptosis and inflammation has been suggested to be involved, little is known about the mechanism mediating this effect in vivo. Increase in intracellular chloride concentration and derived depolarizing GABAAR-mediated transmission are common consequences following various brain injuries and are caused by the abnormal expression levels of the chloride cotransporters NKCC1 and KCC2. Downstream pro-apoptotic signaling through p75NTR may link GABAA depolarization with post-injury neuronal apoptosis. Here, we show that changes in GABAergic signaling, Cl- homeostasis, and expression of chloride cotransporters in the post-traumatic mouse brain can be significantly reduced by administration of 3% ethanol to the drinking water. Ethanol-induced upregulation of KCC2 has a positive impact on neuronal survival, preserving a large part of the cortical peri-infarct zone, as well as preventing the massive post-ischemic upregulation of the pro-apoptotic protein p75NTR. Importantly, intracortical multisite in vivo recordings showed that ethanol treatment could significantly ameliorate stroke-induced reduction in cortical activity. This surprising finding discloses a pathway triggered by low concentration of ethanol as a novel therapeutically relevant target.

Efficacy and follow-up of anti-VEGF injections in diabetic macular edema in real-life practice at the Dijon university medical centre through the Save Sight Registries

PURPOSE

To evaluate the efficacy of intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections (IVT) in diabetic macular edema (DME) in real-life practice using the Save Sight Registries (SSR).

MATERIAL AND METHODS

We conducted an observational, single-centre, retrospective study in the department of ophthalmology of the Dijon University Hospital. We included treatment-naive patients who presented with DME between January 2016 and December 2017. Demographic and clinical data, follow-up visits, and treatments administered were entered into the SSR, an international online ophthalmic registry. Primary endpoints were the change in best-corrected visual acuity (BCVA) and central subfield thickness (CST) from baseline to 12 and 24 months.

RESULTS

Fifty-eight eyes of 43 patients with a mean [standard deviation (SD)] age of 67.1 [9.5] years were included. Forty-one eyes completed 12 months of follow-up, and 17 eyes completed 24 months of follow up. Median [SD] baseline BCVA was 56.1 [22.9] ETDRS letters and the median [95% confidence interval (95% CI)] baseline CST was 447.9 [161.0] micrometers (μm). Median [95% CI] improvement in BCVA from baseline to months 12 and 24 were respectively, +5.6 [+0.5; +10.7] ETDRS letters and +7.7 [-2.8; +18.2] ETDRS letters. The median [95% CI] decrease in CST from baseline to months 12 and 24 were respectively, -110.9 [-154.5; -67.3] μm and -125.5 [-198.0; -53.0] μm.

CONCLUSION

Our clinical practice can be evaluated easily with the SSR system. In real life, anti-VEGF IVT are an effective treatment for DME, which result in improved BCVA and decreased CST.

A proliferation-inducing ligand-mediated anti-inflammatory response of astrocytes in multiple sclerosis

OBJECTIVE

The two related tumor necrosis factor members a proliferation-inducing ligand (APRIL) and B-cell activation factor (BAFF) are currently targeted in autoimmune diseases as B-cell regulators. In multiple sclerosis (MS), combined APRIL/BAFF blockade led to unexpected exacerbated inflammation in the central nervous system (CNS) of patients. Here, we investigate the role of the APRIL/BAFF axis in the CNS.

METHODS

APRIL expression was analyzed in MS lesions by immunohistochemistry. The in vivo role of APRIL was assessed in the murine MS model, experimental autoimmune encephalitis (EAE). Functional in vitro studies were performed with human and mouse astrocytes.

RESULTS

APRIL was expressed in lesions from EAE. In its absence, the disease was worst. Lesions from MS patients also showed APRIL expression upon infiltration of macrophages. Notably, all the APRIL secreted by these macrophages specifically targeted astrocytes. The upregulation of chondroitin sulfate proteoglycan, sometimes bearing chondroitin sulfate of type E sugar moieties, binding APRIL, in reactive astrocytes explained the latter selectivity. Astrocytes responded to APRIL by producing a sufficient amount of IL-10 to dampen antigen-specific T-cell proliferation and pathogenic cytokine secretion. Finally, an intraspinal delivery of recombinant APRIL before disease onset, shortly reduced EAE symptoms. Repeated intravenous injections of recombinant APRIL before and even at disease onset also had an effect.

INTERPRETATION

Our data show that APRIL mediates an anti-inflammatory response from astrocytes in MS lesions. This protective activity is not shared with BAFF. ANN NEUROL 2019;85:406-420.

A new polymer-based approach for in vivo transfection in postnatal brain

BACKGROUND

Gene delivery within the central nervous system at postnatal age is one of the most challenging tasks in neuroscience and currently only a few effective methods are available.

COMPARISON WITH EXISTING METHODS

For postnatal central nervous system cells, viral approaches are commonly used for genetic engineering but they face several biosafety requirements for production and use making them less accessible to the community. Conversely, lipid-based methods are widely used in cell culture but face limitation in vivo mainly due to the inflammatory responses they induce. To this aspect, the use of a transgenic mouse line can represent a credible answer to the community working on rat models still requires an effective and successful solution to circumvent these difficulties.

NEW METHOD

We describe a new polymer-based gene delivery system allowing persistent and robust in vivo transfection with low DNA amount, reduced inflammation and high diffusion. The expression profile along the brain, the stability, the diffusion of the DNA together with the quantity of cells transfected were evaluated through in vivo approaches.

RESULTS

With a single low-volume injection, we targeted different cell types within the rat brain. We measured the diffusion rate ranging from 1 to 5 mm based on the injected volume, in the three-dimensions axis. Finally, we modified brain susceptibility to epileptic seizures using a specific knock-down of the neuronal specific potassium-chloride transporter 2.

CONCLUSIONS

This safe and easy system opens perspectives for non viral gene delivery in the rat brain with perspectives to study brain function in vivo.

Morphology-induced phonon spectra of CdSe/CdS nanoplatelets: core/shell vs. core-crown

Recently developed two-dimensional colloidal semiconductor nanocrystals, or nanoplatelets (NPLs), extend the palette of solution-processable free-standing 2D nanomaterials of high performance. Growing CdSe and CdS parts subsequently in either side-by-side or stacked manner results in core-crown or core/shell structures, respectively. Both kinds of heterogeneous NPLs find efficient applications and represent interesting materials to study the electronic and lattice excitations and interaction between them under strong one-directional confinement. Here, we investigated by Raman and infrared spectroscopy the phonon spectra and electron-phonon coupling in CdSe/CdS core/shell and core-crown NPLs. A number of distinct spectral features of the two NPL morphologies are observed, which are further modified by tuning the laser excitation energy E_exc between in- and off-resonant conditions. The general difference is the larger number of phonon modes in core/shell NPLs and their spectral shifts with increasing shell thickness, as well as with E_exc. This behaviour is explained by strong mutual influence of the core and shell and formation of combined phonon modes. In the core-crown structure, the CdSe and CdS modes preserve more independent behaviour with only interface modes forming the phonon overtones with phonons of the core.

EFS Centre-Atlantique donor's biobank: Ten years of samples usage

INTRODUCTION

The French Establishment of Blood Centre Atlantique (EFSCA) is one of the French regional blood transfusion centers. Donor's biobank is a mandatory activity leading to the storage of biological samples taken from the blood donor. Samples of each blood donation are preserved for a 5-year period at Châteauroux in the form of two straws of 500microliters stored in liquid nitrogen. The aim of this study was to analyze the samples usage by studying quantitative, qualitative and economic criteria.

MATERIAL AND METHOD

We analyzed all the requests of stored blood samples from 2005 to 2014. They were coming either from the blood donor qualification laboratory (BDQL), in order to perform complementary tests, or from hemovigilance inquiry.

RESULTS

Among the blood donation samples, 2,144,636 (whole blood, plasma or platelets apheresis) were preserved during these ten years. During this period, 548 (0.025%) requests for samples were received; 78% were in relation with a request of the BDQL and 22% in relation with a request of hemovigilance. For the straws, the mean exit delay with regard to the blood donation date was 11.5 months (2-55). The cost of samples exit includes only working hours of a laboratory technician. On average, the annual working time dedicated to this activity was 23h. Also, the average price for one-year issuing activity was 620.31 euros.

CONCLUSION

In our study, the donor's biobank was little used. The part of hemovigilance was weak but essential for the blood safety.

Abdominal skin temperature variation in healthy broiler chickens as determined by thermography

Abdominal skin temperature of healthy broiler chickens was determined by thermography to estimate the normal range of between- and within-bird temperature variation. Effects of potential confounding factors, such as bird's contention duration, abdominal side, age, and time of day, were also estimated. Mean skin temperature was estimated from thermogram pictures by computer image analysis of a predetermined abdominal area. Results demonstrated that skin temperature was not significantly affected by contention duration. However, skin temperature was higher on the right abdominal side in younger birds and at 1200 h. Between- and within-bird variation in healthy birds was small (< 0.5 degrees C) when age, abdominal side, and time of day were taken into account. This work suggests that skin temperature measurement using thermography can be adapted for the study of skin temperature in broiler chickens.

Structure-based chimeric enzymes as an alternative to directed enzyme evolution: phytase as a test case

Thermostability is a key feature for commercially attractive variants of the fungal enzyme phytase. In an initial set of experiments, we restored ionic interactions and hydrogen bonds on the surface of Aspergillus terreus phytase, which are present in the homologous but more thermostable enzyme from A. niger. Since these mutations turned out to be neutral, we replaced-in the same region and based on the crystal structure of A. niger phytase-entire secondary structure elements. The replacement of one alpha-helix on the surface of A. terreus phytase by the corresponding stretch of A. niger phytase resulted in an enzyme with improved thermostability and unaltered enzymatic activity. Surprisingly, the thermostability of this hybrid protein was very similar to that of A. niger phytase, although the fusion protein contained only a 31 amino acid stretch of the more stable parent enzyme. This report provides evidence that structure-based chimeric enzymes can be used to exploit the evolutionary information within a sequence alignment. We propose this method as an alternative to directed enzyme evolution if due to expression constraints the screening of large mutant populations is not feasible.

Cellulitis in broiler chickens: a one-year retrospective study in four Québec abattoirs

A 1-yr retrospective study was undertaken to verify whether the prevalence of cellulitis in broiler chicken flocks was associated 1) with sex and average body weight controlling for the time of year and 2) with some other condemnation causes such as air-sacculitis, ascites, cyanosis, emaciation, valgus varus deformity, peritonitis, and total condemnation rate controlling for sex, average body weight, and time of year. Data were collected from four Québec abattoirs between October 1992 and September 1993. Data from 2452 unisex male and female broiler flocks were compiled and analyzed with univariate and multivariate models. The prevalence of cellulitis among flocks was 42.2 per 10,000 birds slaughtered. Cellulitis was associated with sex and increased with time of year (P < 0.0001). The prevalence was higher in male (mean +/- SD, 50.7+/-24.3; median, 31.8) than in female flocks (mean +/- SD, 34.2+/-15.6; median, 20.0) but showed no relationship with average body weight. Associations between condemnation causes and cellulitis were relatively weak; increases in the prevalence of cellulitis correlated with increases in total condemnation rate (r2 = 0.19), ascites (r2 = 0.09), airsacculitis (r2 = 0.0), cyanosis (r2 = 0.04), peritonitis (r2 = 0.03), emaciation (r2 = 0.02), and valgus varus deformity (r2 = 0.02). These results suggest that flock sex is a potential correlate of cellulitis prevalence in broiler chickens. Associations between the prevalence of cellulitis and other diseases observed at the abattoir were not very strong. However, it appears here that general disease status of Québec broiler flocks is a better indicator of cellulitis occurrence than the main diseases considered individually.

[Influence of biotic and abiotic factors on the morphology and reproduction of Suaeda maritima on a salt marsh]

The aim of this study was to estimate the influence of biotic and abiotic factors on Suaeda maritima reproduction on a salt marsh. Individuals of Suaeda maritima were submitted in natural conditions to four series of densities (100, 1,000, 4,000 and 8,000 plants/m2). When density increases, individuals tend to be less or non-branched, while individual biomass decreases. Consequently, individual seed production decreases as density increases. Despite morphological modifications, Suaeda maritima present density-dependent mortality. For a unit area, total biomass and seed production are higher at intermediate density (1,000 plants/m2). Environmental factors could interfere with self-thinning. They seem to limit the effect of competition on mortality and to have an influence on individual and total seed production. This experiment stressed the importance of a biotic factor such as intra-specific competition, which occurs at the same time as abiotic factors, in Suaeda maritima dynamics in the field.

Optimization of the catalytic properties of Aspergillus fumigatus phytase based on the three-dimensional structure

Previously, we determined the DNA and amino acid sequences as well as biochemical and biophysical properties of a series of fungal phytases. The amino acid sequences displayed 49-68% identity between species, and the catalytic properties differed widely in terms of specific activity, substrate specificity, and pH optima. With the ultimate goal to combine the most favorable properties of all phytases in a single protein, we attempted, in the present investigation, to increase the specific activity of Aspergillus fumigatus phytase. The crystal structure of Aspergillus niger NRRL 3135 phytase known at 2.5 A resolution served to specify all active site residues. A multiple amino acid sequence alignment was then used to identify nonconserved active site residues that might correlate with a given favorable property of interest. Using this approach, Gln27 of A. fumigatus phytase (amino acid numbering according to A. niger phytase) was identified as likely to be involved in substrate binding and/or release and, possibly, to be responsible for the considerably lower specific activity (26.5 vs. 196 U x [mg protein](-1) at pH 5.0) of A. fumigatus phytase when compared to Aspergillus terreus phytase, which has a Leu at the equivalent position. Site-directed mutagenesis of Gln27 of A. fumigatus phytase to Leu in fact increased the specific activity to 92.1 U x (mg protein)(-1), and this and other mutations at position 27 yielded an interesting array of pH activity profiles and substrate specificities. Analysis of computer models of enzyme-substrate complexes suggested that Gln27 of wild-type A. fumigatus phytase forms a hydrogen bond with the 6-phosphate group of myo-inositol hexakisphosphate, which is weakened or lost with the amino acid substitutions tested. If this hydrogen bond were indeed responsible for the differences in specific activity, this would suggest product release as the rate-limiting step of the A. fumigatus wild-type phytase reaction.

Parallel gene expression monitoring using oligonucleotide probe arrays of multiple transcripts with an animal model of focal ischemia

High density oligonucleotide arrays offer tremendous potential to study gene changes occurring in disease states. The authors described the first case of using a custom designed high density oligonucleotide probe array containing 750 genes to monitor the changes in mRNA transcript levels occurring after focal ischemia for a period of 3 hours. Permanent middle cerebral artery occlusion in the rat resulted in neuronal degeneration in the dorsolateral cortex and striatum over a time course of 24 hours. Comparing the changes in hybridization levels in the frontal and parietal cortices and the striatum, between the ipsilateral and contralateral sides of the brain using the probe arrays resulted in the up-regulation of 24 genes, which showed greater than a twofold change. Very few genes were found to be downregulated after the ischemic insult. Many of the immediate early genes (IEGs) such as c-fos, NGFI-A, NGFI-C, and Krox-20 were found to be robustly upregulated in the three different regions studied. Other genes that were up-regulated in perifocal regions included Arc, Inhibin-beta-A, and the phosphatases MKP-1 and MKP-3. The hybridization signal intensity from the probe arrays enabled quantification of many genes relative to one another, and robust changes in expression were obtained with very little interanimal variability. Furthermore, the authors were able to validate the increased expression of NGFI-C and Arc using in situ hybridization. This represented the first example of using high density oligonucleotide probe arrays in studying the expression of many genes in parallel and in discrete brain regions after focal ischemia.

Active site residue 297 of Aspergillus niger phytase critically affects the catalytic properties

The wild-type phytases from the Aspergillus niger strains NRRL 3135 and T213 display a three-fold difference in specific activity (103 versus 32 U/mg protein), despite only 12 amino acid differences that are distributed all over the sequence of the protein. Of the 12 divergent positions, three are located in or close to the substrate binding site. Site-directed mutagenesis of these residues in A. niger T213 phytase showed that the R297Q mutation (R in T213, Q in NRRL 3135) fully accounts for the differences in catalytic properties observed. Molecular modelling revealed that R297 may directly interact with a phosphate group of phytic acid. The fact that this presumed ionic interaction - causing stronger binding of substrates and products - correlates with a lower specific activity indicates that product (myo-inositol pentakisphosphate) release is the rate-limiting step of the reaction.

Sauna-induced myocardial ischemia in patients with coronary artery disease

PURPOSE

Sauna bathing is a popular recreational activity that is generally considered to be safe. However, there have been case reports of adverse cardiac events. We sought to determine whether sauna use caused myocardial ischemia in patients with coronary artery disease.

METHODS

Sixteen patients with proven coronary artery disease were submitted to three conditions (rest, exercise, and sauna bathing) with continuous electrocardiographic (ECG) monitoring and regular blood pressure measurements. During each condition, patients were injected with Tc-99 sestamibi followed by nuclear scintigraphic imaging. Perfusion defect scores were calculated in 15 patients.

RESULTS

Sauna bathing was well tolerated. There was a mean (+/- SD) increase in heart rate of 32% +/- 20% in the sauna (resting mean heart rate = 60 +/- 9 beats per minute vs sauna mean heart rate = 79 +/- 11 beats per minute, P <0.001) and a 13% +/- 6% drop in systolic blood pressure (resting mean systolic blood pressure = 142 +/- 14 mm Hg vs sauna mean systolic blood pressure = 123 +/- 15 mm Hg, P <0.001). There were no arrhythmias or ECG changes in the sauna. Compared with rest, there was significant ischemia during sauna bathing (average perfusion defect score at rest = -0.44 vs average sauna score = -0.93, P <0.001). The perfusion defect score in the sauna was worse than the resting score in 14 of the 15 patients. Sauna-associated perfusion defect scores were highly correlated with exercise-induced scores (R2 = 0.65, P <0.001).

CONCLUSION

In patients with stable coronary artery disease, sauna use is clinically well tolerated but is associated with scintigraphically demonstrated myocardial ischemia.

Biophysical characterization of fungal phytases (myo-inositol hexakisphosphate phosphohydrolases): molecular size, glycosylation pattern, and engineering of proteolytic resistance

Phytases (myo-inositol hexakisphosphate phosphohydrolases) are found naturally in plants and microorganisms, particularly fungi. Interest in these enzymes has been stimulated by the fact that phytase supplements increase the availability of phosphorus in pig and poultry feed and thereby reduce environmental pollution due to excess phosphate excretion in areas where there is intensive livestock production. The wild-type phytases from six different fungi, Aspergillus niger, Aspergillus terreus, Aspergillus fumigatus, Emericella nidulans, Myceliophthora thermophila, and Talaromyces thermophilus, were overexpressed in either filamentous fungi or yeasts and purified, and their biophysical properties were compared with those of a phytase from Escherichia coli. All of the phytases examined are monomeric proteins. While E. coli phytase is a nonglycosylated enzyme, the glycosylation patterns of the fungal phytases proved to be highly variable, differing for individual phytases, for a given phytase produced in different expression systems, and for individual batches of a given phytase produced in a particular expression system. Whereas the extents of glycosylation were moderate when the fungal phytases were expressed in filamentous fungi, they were excessive when the phytases were expressed in yeasts. However, the different extents of glycosylation had no effect on the specific activity, the thermostability, or the refolding properties of individual phytases. When expressed in A. niger, several fungal phytases were susceptible to limited proteolysis by proteases present in the culture supernatant. N-terminal sequencing of the fragments revealed that cleavage invariably occurred at exposed loops on the surface of the molecule. Site-directed mutagenesis of A. fumigatus and E. nidulans phytases at the cleavage sites yielded mutants that were considerably more resistant to proteolytic attack. Therefore, engineering of exposed surface loops may be a strategy for improving phytase stability during feed processing and in the digestive tract.

Gene cloning, purification, and characterization of a heat-stable phytase from the fungus Aspergillus fumigatus

The finding of heat-stable enzymes or the engineering of moderately thermostable enzymes into more stable ones by random or site-directed mutagenesis has become a main priority of modern biotechnology. We report here for the first time a heat-stable phytase able to withstand temperatures up to 100 degrees C over a period of 20 min, with a loss of only 10% of the initial enzymatic activity. The gene (phyA) encoding this heat-stable enzyme has been cloned from Aspergillus fumigatus and overexpressed in Aspergillus niger. The enzyme showed high activity with 4-nitrophenyl phosphate at a pH range of 3 to 5 and with phytic acid at a pH range of 2.5 to 7.5.

Isolation and characterization of the carotenoid biosynthesis genes of Flavobacterium sp. strain R1534

The Gram-negative bacterium Flavobacterium sp. strain R1534 is a natural producer of zeaxanthin. A 14 kb genomic DNA fragment of this organism has been cloned and a 5.1 kb piece containing the carotenoid biosynthesis genes sequenced. The carotenoid biosynthesis cluster consists of five genes arranged in at least two operons. The five genes are necessary and sufficient for the synthesis of zeaxanthin. The encoded proteins have significant homology to the crtE, crtB, crtY, crtI and crtZ gene products of other carotenogenic organisms. Biochemical assignment of the individual gene products was done by HPLC analysis of the carotenoid accumulation in Escherichia coli host strains transformed with plasmids carrying deletions of the Flavobacterium sp. strain R1534 carotenoid biosynthesis cluster.

The limited photochemical activity of solid aggregated forms of bovine rhodopsin

The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin.

[Adolescence and sexuality : the stakes in prevention.]

Studies of adolescent girls underline the limits of clinical services in the prevention of undesired pregnancies. This article concerns a study carried out at the St-Denis Youth Clinic with the aim of collecting data to permit the development of adequate preventive measures in work with the adolescent population. The author deals with factors linked to the development of the adolescent personality and presents two theories explaining preventive behaviour. She gives an account of evaluations of current practices in Quebec in relation to sexuality and contraception, and suggests avenues to pursue at different levels of prevention.

[The St-Denis youth clinic.]

The Clinique des Jeunes St-Denis was founded in 1977 to provide complete medical and psychosocial services to young clients in matters of sexuality. The work assumed by a multi-disciplinary team has provided its members with an opportunity for growth and allowed them to investigate the different aspects of their work load. The actual clinical needs and the effective treatment are discussed : abortion, incest, sexually transmitted diseases, etc. Groups are formed in order to perceive the adolescent as a whole and not only its sexual dimension ; and a concern for preventive action is always present. A research on these matters has been initiated.

Amino-acids condensations in the preparation of N alpha-9-fluorenylmethyloxycarbonylamino-acids with 9-fluorenylmethylchloroformate

Synthesis of N alpha-9-fluorenylmethyloxycarbonyl (Fmoc) amino-acids by reaction of free amino-acids (glycine and alanine) with 9-fluorenylmethylchloroformate leads to formation of small amounts of Fmoc-dipeptide which are difficult to eliminate by crystallization. The alternative way to prepare Fmoc-amino-acids by reacting the Fmoc-chloride first with sodium azide and then with the free amino-acid eliminates this side reaction, at least for glycine and alanine.

Are interactions with phospholipids responsible for pharmacological activities of cardiotoxins?

Cardiotoxins are small basic proteins (7 000 daltons) that are found in the venoms of Elapidae snakes. Although they are structurally close to alpha-neurotoxins present in the same secretions, their activity is related to their ability to interact with every cell membrane inducing, near micromolar concentration, the modification of its biological properties and/or physical structure. The mode of action of cardiotoxins, on a molecular level, is still under investigation. However, lipid-protein interactions are more and more involved in their binding to membrane and in their activities. Using new experimental data a better definition of phospholipid-cardiotoxin interaction is arrived at and a tentative molecular explanation of the pharmacological activities of these proteins is presented and discussed.

Structure-function relationships for cardiotoxins interacting with phospholipids

Four cardiotoxins (CTX I-IV) from Naja mossambica mossambica were compared for their ability to interact with phospholipid vesicles and their capacity to bind erythrocytes. It is concluded that the affinity of the toxins always increases in the order: I approximately equal to II less than III less than IV. The binding is specific for charged lipids even in lipid mixtures. Proteolytic attack of the free and lipid-bound cardiotoxin indicates that at least the first loop Leu1-Thr13 is at the lipid contact. Tryptic and synthetic peptides constitutive of this loop are shown to interact with lipids. Arg5 residue increases the affinity toward the bilayer. The Raman spectra of lipid-bound cardiotoxin indicate a secondary and tertiary structure mainly similar to that of the free toxin. On charged lipids cardiotoxins induce a decrease of the enthalpy and an increase of disorder without change in the transition temperature; at saturating amounts of toxin the transition is abolished. In binary mixtures of phosphatidylcholine and charged lipids the observed effects can be accounted by a phase separation induced by the toxin.