Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction

A prominent feature of synaptic maturation at the neuromuscular junction (NMJ) is the topological transformation of the acetylcholine receptor (AChR)-rich postsynaptic membrane from an ovoid plaque into a complex array of branches. We show here that laminins play an autocrine role in promoting this transformation. Laminins containing the α4, α5, and β2 subunits are synthesized by muscle fibers and concentrated in the small portion of the basal lamina that passes through the synaptic cleft at the NMJ. Topological maturation of AChR clusters was delayed in targeted mutant mice lacking laminin α5 and arrested in mutants lacking both α4 and α5. Analysis of chimeric laminins in vivo and of mutant myotubes cultured aneurally demonstrated that the laminins act directly on muscle cells to promote postsynaptic maturation. Immunohistochemical studies in vivo and in vitro along with analysis of targeted mutants provide evidence that laminin-dependent aggregation of dystroglycan in the postsynaptic membrane is a key step in synaptic maturation. Another synaptically concentrated laminin receptor, Bcam, is dispensable. Together with previous studies implicating laminins as organizers of presynaptic differentiation, these results show that laminins coordinate post- with presynaptic maturation.     

Iodination of salicylic acid improves its binding to transthyretin

Transthyretin (TTR) is a plasma homotetrameric protein associated with senile systemic amyloidosis and familial amyloidotic polyneuropathy. In theses cases, TTR dissociation and misfolding induces the formation of amyloidogenic intermediates that assemble into toxic oligomeric species and lead to the formation of fibrils present in amyloid deposits. The four TTR monomers associate around a central hydrophobic channel where two thyroxine molecules can bind simultaneously. In each thyroxine binding site there are three pairs of symmetry related halogen binding pockets which can accommodate the four iodine substituents of thyroxine. A number of structurally diverse small molecules that bind to the TTR channel increasing the protein stability and thereafter inhibiting amyloid fibrillogenesis have been tested. In order to take advantage of the high propensity to interactions between iodine substituents and the TTR channel we have identified two iodinated derivatives of salicylic acid, 5-iodosalicylic acid and 3,5-diiodosalicylic acid, available commercially. We report in this paper the relative binding affinities of salicylic acid and the two iodinated derivatives and the crystal structure of TTR complexed with 3,5-diiodosalicylic acid, to elucidate the higher binding affinity of this compound towards TTR.     

A New Protozoan of the Genus Cothurnia (Ciliophora, Peritrichia), Epibiont on the Marine Tanaid Halmyrapseudes spaansi (Crustacea Peracarida) from the French Guiana (SE America)

Specimens of the marine tanaid crustacea Halmyrapseudes spaansi, sampled in temporary littoral muddy patches near the mouth of the Kaw river (French Guiana, SE America), showed protozoan epibionts herein described as a new species: Cothurnia guyanensis sp. n. (Ciliophora, Peritrichia). These ciliates were covered by a cylindrical or bell-shaped lorica containing an oval elongated zooid with a rounded contractile vacuole located anteriorly in lateral position. The macronucleus was “S” shaped. The peristomial disk was anterior and included a polikinety and a haplokinety. The external stalk was short and broad, with 8–18 longitudinal conspicuous striations. Between the external stalk and the zooid, there were an endostyle and an mesostyle both short and broad. The striations of the external stalk were prolonged in the mesostyle. Telotroch stages were observed and described, as well as specimens with two zooids per lorica. Epibionts located on the ventral area, pereopods and antennae of the basibiont.     

Hydrozoan and protozoan epibionts on two decapod species, Liocarcinus depurator (Linnaeus, 1758) and Pilumnus hirtellus (Linnaeus, 1761), from Scotland

Crabs of the species Liocarcinus depurator and Pilumnus hirtellus, collected on the west coast of Scotland, showed hydrozoan and protozoan epibionts. The epibionts of Liocarcinus depurator were the protozoan Ephelota plana and the hydrozoans Clytia gracilis and Leuckartiara sp. The epibionts of Pilumnus hirtellus were the protozoans E. plana and Zoothamnium sp. For Liocarcinus depurator the number of Ephelota per crab fluctuated between 0 and 47 and the greatest number of suctorians were located on the chelipeds, carapace and anterior pereiopods. The hydrozoans, for Liocarcinus depurator, showed densities of 0-20 (Clytia gracilis on the second pereiopod) and 0-507 individuals per crab (Leuckartiara sp., principally on chelipeds, carapace and the fourth right pereiopod). For Pilumnus hirtellus, Ephelota plana showed densities between 3 and 56 individuals per crab, the greatest number of suctorians being located on the same areas as on Liocarcinus depurator. There was a density of 10-69 individuals per crab of Zoothamnium sp. on Pilumnus hirtellus (located on the carapace). Ephelota plana has not been observed previously as an epibiont on crustacea, nor had Zoothamnium sp. as an epibiont on Pilumnus hirtellus. Both hydrozoans, Leukartiara and Clytia, have not been previously described as epibionts on Liocarcinus depurator. Data about the morphological characteristics and distribution of these epibionts are included.     

Cytogenetic monitoring of hospital workers exposed to low-level ionizing radiation

In the present study the cytogenetic effects in hospital workers exposed to low-level radiation were evaluated. Samples of peripheral blood were collected from 63 subjects working in radiodiagnostics and from 30 subjects, working in the same hospitals, who were used as controls. A higher number of cells with chromosome-type aberrations (CA) was observed in the exposed workers vs. the controls and the difference was statistically significant (p less than 0.05). No correlation was, on the contrary, found between CA and years of exposure. A significant difference was observed in the incidence of cells with CA between smokers and non-smokers, but in the control group only. In contrast, in the workers exposed to ionizing radiation, the frequency of cells with CA was very similar in smokers and non-smokers.     

Sequential Therapy to Achieve Anovulatory Cycles

Sequential oral contraceptive therapy was devised to inhibit ovulation by a potent estrogen alone. A progestational agent was added at the end of the course of therapy to prepare the endometrium for adequate withdrawal bleeding. The program consisted of giving 80 μg. of metranol daily for 15 days and then a combination of 80 μg. of mestranol and 2 mg. of chlormadinone acetate for five additional days. Such a regimen proved to be effective in 6070 patients carefully observed for 82,085 cycles of therapy at 25 medical centres.Increased cycle regularity was noted: 98.1% of the cycles were 25 to 31 days long. In 80.1% of cycles, the withdrawal interval was two to five days in length. Duration of flow was four to six days in 85.3% of the therapeutic cycles. The amount of flow decreased as compared with pretreatment values. The incidence and severity of dysmenorrhea during sequential therapy were significantly lower than before treatment. Side effects, usually infrequent, diminished as therapy was continued; the average incidence of breakthrough bleeding was 1.9% and nausea was 2.9%. Extensive laboratory studies showed no consistent abnormalities. For oral contraception, sequential therapy has proved to be virtually 100% effective when taken as directed.     

Phylogenetic and Genome-Wide Deep-Sequencing Analyses of Canine Parvovirus Reveal Co-Infection with Field Variants and Emergence of a Recent Recombinant Strain

Canine parvovirus (CPV), a fast-evolving single-stranded DNA virus, comprises three antigenic variants (2a, 2b, and 2c) with different frequencies and genetic variability among countries. The contribution of co-infection and recombination to the genetic variability of CPV is far from being fully elucidated. Here we took advantage of a natural CPV population, recently formed by the convergence of divergent CPV-2c and CPV-2a strains, to study co-infection and recombination. Complete sequences of the viral coding region of CPV-2a and CPV-2c strains from 40 samples were generated and analyzed using phylogenetic tools. Two samples showed co-infection and were further analyzed by deep sequencing. The sequence profile of one of the samples revealed the presence of CPV-2c and CPV-2a strains that differed at 29 nucleotides. The other sample included a minor CPV-2a strain (13.3% of the viral population) and a major recombinant strain (86.7%). The recombinant strain arose from inter-genotypic recombination between CPV-2c and CPV-2a strains within the VP1/VP2 gene boundary. Our findings highlight the importance of deep-sequencing analysis to provide a better understanding of CPV molecular diversity.     

Action of aminoglycosides on platelet aggregation in vitro

The authors tested the influence of gentamicin, spectinomycin dihydrostreptomycin on the ADP and epinephrine in vitro induced platelet aggregation. Our aim was to demonstrate if platelet aggregation in vitro had some influences by antibiotics. A reduction in platelet aggregability, strictly dependent from the used antibiotic dose was observed. We have studied platelet function thanks to Born's method, adding to PRP gradual therapeutics doses of antibiotics. The results showed a reduction of platelet function which was dose-depended, and, particularly, gentamicin seemed to be the most effective among aminoglycosides. An interference between these drugs and the ADP and epinephrine binding to specific platelet receptor sites is proposed.