Neurogenesis in subclasses of vomeronasal sensory neurons in adult mice

The vomeronasal sensory epithelium contains two distinct populations of vomeronasal sensory neurons. Apical neurons express G_i2α‐linked V1R vomeronasal receptors and project to the anterior portion of the accessory olfactory bulb, while basal neurons express G_oα‐linked V2R receptors and project to the posterior portion. Sensory neurons expressing V1R and V2R vomeronasal receptors are sensitive to different stimuli. Neurons in the vomeronasal system undergo continuous cell turnover during adulthood. To analyze over time neurogenesis of the different sensory cell populations, adult mice were injected with bromodeoxyuridine (BrdU) and sacrificed at postinjection days 1, 3, 5, 7, and 11. Newborn vomeronasal neurons were revealed by antibodies against BrdU while subclasses of vomeronasal neurons were identified using antibodies against G_oα or G_i2α proteins. To ascertain whether G proteins are early expressed during neurogenesis, multiple labeling experiments using PSA‐NCAM and doublecortin were performed. Distribution of BrdU‐labeled cells was analyzed in angular segments from the margin of the sensory epithelium. No sexual differences were found. Within survival groups, BrdU‐G_oα labeled cells were found more marginally when compared with BrdU‐G_i2α labeled cells. The number of BrdU‐positive cells decreased from day 1 to day 3 to remain constant afterwards. The relative proportions of BrdU‐G_i2α and BrdU‐G_oα labeled cells remained similar and constant from postinjection day 1 onwards. This rate was also comparable with BrdU‐positive cells starting day 3. These results indicate an early, constant, and similar rate of neurogenesis in the two major subclasses of vomeronasal neurons, which suggests that both cell populations maturate independently. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 961–970, 2010     

Symmetry Breaking by Spontaneous Crystallization – Is it the Most Plausible Source of Terrestrial Handedness we have Long Been Looking for? – A Reappraisal

In the light of recent and controversial findings on spontaneous resolution of racemates and their implications in the origin of homochirality on earth, we present here a detailed review of this important topic. Although spontaneous resolution cannot at this moment be reliably predicted, there has also been considerable progress in crystal structure prediction and, not only thermodynamic factors, but also kinetic ones, play important roles in the efficiency of packing and crystallization. In addition, self-association and supramolecular control phenomena may be identified in cases where spontaneous resolution of enantiomers is actually occurring. While this contribution summarizes our current understanding of this intriguing phenomena, it is hoped that future work on crystalline conglomerates (or homochiral crystals) of prebiotic importance will be of further help to understand the general problem of terrestrial chirogenesis.     

Pyridoxal-5'-phosphate as a cofactor for rat brain histidine decarboxylase.

The cofactor requirements of brain histidine decarboxylase activity have been studied. Preincubation with carbonyl reagents caused inhibition of the activity ranging from 90% for 10^?2m -semicarbazide, 10^?3m -phenylhydrazide and 10^?3m -hydroxylamine to 50% for isonicotinic acid hydrazide. Sodium borohydride, a reducing agent, also caused complete inhibition of activity. The histidine decarboxylase activity was maximal at 10^?4m -pyridoxal-P concentration and was inhibited at higher concentrations of the cofactor. The cofactor-apoenzyme mode of binding was studied by dialysing brain homogenates against several media. Neither the dialysis against buffers alone nor against buffers containing semicarbazide nor cysteine plus EDTA caused a total loss of activity. A 50% of the activity dialysed easily while the other 50% remained ‘tightly’ bound to the apoenzyme. The dialysable and non dialysable activity is evenly distributed between the soluble and particulate activity.     

Identification of the High-Virulence Clone of Group B Streptococci in Mexican Isolates by Growth Characteristics at 40°C

Group B streptococci (GBS) colonizing the vagina and rectum of pregnant women cause invasive disease of the offspring in a small number of cases. The immune status of the host and differences in virulence among strains appear to be the main determinants for neonatal infection. A high-virulence clone (HVC) was proposed to cause much of the morbidity and mortality when a collection of GBS isolates was examined by multilocus enzyme electrophoresis. HVC isolates could be further distinguished by their inability to grow at 40°C. This characteristic was used in the present study to examine a collection of 57 GBS isolates from Mexico City for the HVC. Three serotype III invasive strains were classified in the HVC. The other eleven invasive strains and all carrier isolates had growth curves unaffected at 40°C. These results demonstrate the presence of the HVC in Mexico. Such a low prevalence could explain in part the low rate of GBS invasive neonatal disease in Mexico. Received: 21 May 1998 / Accepted: 14 September 1998