Evaluation of CHROMagar™ StrepB agar, an aerobic chromogenic medium for prepartum vaginal/rectal Group B Streptococcus screening

An aerobic chromogenic medium, CHROMagar™ StrepB agar, designed for isolation of group B Streptococci, was evaluated on 285 prepartum vaginal/rectal swabs from pregnant women. After overnight enrichment in Todd-Hewitt broth containing 15 μg/ml nalidixic acid and 10 μg/ml colistin, sensitivities were respectively 79% on day 1 and 92% on day 2, and significantly higher than those achieved by blood agar (40% and 58%) and colimycin-nalidixic-acid agar (82% on day 2).     

Effects of the nonsteroidal inhibitor R76713 on testosterone-induced sexual behavior in the Japanese quail (Coturnix coturnix japonica)

A new triazole derivative, R76713 (6-[4-chlorophenyl)(1H-1,2,4-triazol-1-yl)methyl]-1-methyl-1H- benzotriazole), was recently shown to inhibit aromatase selectively without affecting other steroid-metabolizing enzymes and without interacting with estrogen, progestin, or androgen receptors. This compound was tested for its capacity to intefere with the induction of copulatory behavior by testosterone (T) in castrated Japanese quail (Coturnix coturnix japonica). In a first experiment, R76713 inhibited (range 0.01 to 1 mg/kg) the activation of sexual behavior by T silastic implants and hypothalamic aromatase activity in castrated male quail in a dose-dependent manner. The 5 alpha- and 5 beta- reductases of T were not systematically affected. Stereotaxic implantation of R76713 in the medial preoptic area similarly blocked the behavior activated by systemic treatment with T, demonstrating that central aromatization of androgen is implicated in the activation of behavior. These inhibiting effects of R76713 on behavior were observed when implants were placed in the medial part of the nucleus preopticus medialis, confirming the implication of this brain area in the control of male copulatory behavior. Finally, the behavioral inhibition produced by R76713 could be reversed by simultaneous treatment with a dose of estradiol, which was not behaviorally effective by itself. This suggests that the behavioral deficit induced by the inhibitor was specifically due to the suppression of estrogen production. This also shows that the activation of copulatory behavior probably results from the interaction of androgens and estrogens at the brain level, as the two treatments separately providing these hormonal stimuli (T with the aromatase inhibitor on one hand and a low dose of estradiol on the other hand) had almost no behavioral effects but they synergized to activate copulation when given concurrently. These data confirm the critical role of preoptic aromatase in the activation of reproductive behavior and demonstrate that R76713 is a useful tool for the in vivo study of estrogen-dependent processes.     

Gas-liquid chromatographic determination of human fecal bile acids

A method for the determination of total bile acids in human feces that is suitable for routine application is described and discussed. Bile acids are extracted from freeze-dried feces with acetic acid and toluene, in the presence of the internal standard 23-nordeoxycholic acid. After saponification of the extract, bile acids and the internal standard are methylated and converted by mild chromic acid oxidation into their ketonic derivatives. The resultant mixture of a few stable compounds can be separated and measured quantitatively by gas-liquid chromatography on a methylsiloxane polymer. A reference bile acid mixture including the internal standard is also taken through the entire procedure with each series of samples. It has been demonstrated that, in spite of the omission of the usual purification steps, the method is specific for bile acids.     

Coexpression of two thermosensitive defects in a Chinese hamster cell line : Manifestation of a G1 block associated with a mitosis defect

Asynchronous cultures of ts12, an anchorage-dependent derivative of the thermosensitive Chinese hamster cell line ts111, show a rapid drop in [3H]thymidine incorporation with accumulation of the cells in the G1 and in the G2 phases of the cycle, when shifted from 34.5 to 39.4 degrees C. Shift-up experiments carried out after either isoleucine deprivation or synchronization at 39.4 degrees C, locate the execution point of a ts function in late G1 (2.5-3 h before S). However, stimulation of proliferation of a high density-arrested population allows a fraction of the cells to enter S. In addition to the G1 ts defect, ts12 expresses a slight cytokinesis defect at 39.4 degrees C (8-15% binucleate cells). The results suggest that altered processes are taking place at a post-metaphasic stage during the first hours after the shift-up. When populations are synchronized by a thymidine block and released at 39.4 degrees C, multinucleate cells in addition to binucleate cells are observed. Part of these multinucleate cells result from abnormal karyokinesis without inhibition of cytokinesis. Evidence is presented suggesting that excess thymidine allows the re-expression of the multinucleation phenotype of ts111.     

Hierarchical control of dopamine neuron-firing patterns by nicotinic receptors

Nicotine elicits dopamine release by stimulating nicotinic acetylcholine receptors (nAChRs) on dopaminergic neurons. However, a modulation of these neurons by endogenous acetylcholine has not been described. We recorded, in vivo, the spontaneous activity of dopaminergic neurons in the VTA of anaesthetized wt and nAChR knockout mice and their response to nicotine injections. Deleting alpha7 or beta2 subunits modified the spontaneous firing patterns, demonstrating their direct stimulation by endogenous acetylcholine. Quantitative analysis further revealed four principal modes of firing, each depending on the expression of particular nAChR subunits and presenting unique responses to nicotine. The prominent role of the beta2 subunit was further confirmed by its selective lentiviral reexpression in the VTA. These data suggest a hierarchical control of dopaminergic neuron firing patterns by nAChRs: activation of beta2*-nAChR switches cells from a resting to an excited state, whereas activation of alpha7*-nAChRs finely tunes the latter state but only once beta2*-nAChRs have been activated.     

Salmonella enterica Flagellin Is Recognized via FLS2 and Activates PAMP-Triggered Immunity in Arabidopsis thaliana

Infections with Salmonella enterica belong to the most prominent causes of food poisoning and infected fruits and vegetables represent important vectors for salmonellosis. Recent evidence indicates that plants recognize S. enterica and raise defense responses. Nonetheless, the molecular mechanisms controlling the interaction of S. enterica with plants are still largely unclear. Here, we show that flagellin from S. enterica represents a prominent pathogenassociated molecular pattern （PAMP） in Arabidopsis thaliana, which induces PAMP-triggered immunity （PTI） via the recognition of the fig22 domain by the receptor kinase FLS2. The Arabidopsis fls2 mutant shows reduced though not abolished PTI activation, indicating that plants rely also on recognition of other S. enterica PAMPs. Interestingly, the S. enterica type III secretion system （T3SS） mutant prgH- induced stronger defense gene expression than wild-type bacteria in Arabidopsis, suggesting that T3SS effectors are involved in defense suppression. Furthermore, we observe that S. enterica strains show variation in the fig22 epitope, which results in proteins with reduced PTI-inducing activity. Altogether, these results show that S. enterica activates PTI in Arabidopsis and suggest that, in order to accomplish plant colonization, S. enterica evolved strategies to avoid or suppress PTI.     

Gamma-tubulin is essential for microtubule organization and development in Arabidopsis

The process of microtubule nucleation in plant cells is still a major question in plant cell biology. gamma-Tubulin is known as one of the key molecular players for microtubule nucleation in animal and fungal cells. Here, we provide genetic evidence that in Arabidopsis thaliana, gamma-tubulin is required for the formation of spindle, phragmoplast, and cortical microtubule arrays. We used a reverse genetics approach to investigate the role of the two Arabidopsis gamma-tubulin genes in plant development and in the formation of microtubule arrays. Isolation of mutants in each gene and analysis of two combinations of gamma-tubulin double mutants showed that the two genes have redundant functions. The first combination is lethal at the gametophytic stage. Disruption of both gamma-tubulin genes causes aberrant spindle and phragmoplast structures and alters nuclear division in gametophytes. The second combination of gamma-tubulin alleles affects late seedling development, ultimately leading to lethality 3 weeks after germination. This partially viable mutant combination enabled us to follow dynamically the effects of gamma-tubulin depletion on microtubule arrays in dividing cells using a green fluorescent protein marker. These results establish the central role of gamma-tubulin in the formation and organization of microtubule arrays in Arabidopsis.     

Effects of irradiation on facial development in mouse embryos

The purpose of this study was to observe the effects of irradiation on the craniofacial development of NMRI mouse embryos. Two populations of pregnant mice were irradiated with a single dose of 2 Gray on day 8 of gestation for the first population (Po. 1) and on day 9 of gestation for the second population (Po. 2). On gestational days 9 to 17, embryos were submitted to histological and scanning electron microscope examinations. The two populations of embryos presented a high percentage of centro-facial hypoplasia (74.7% for Po. 1 and 75% for Po. 2) which was more pronounced in the latter one. Ocular anomalies were present in 16% of the first population. Cases of anencephaly, cleft palate and anomalies of the central nervous system were found in both populations.