Impact of elevated H(2)S on metabolite levels, activity of enzymes and expression of genes involved in cysteine metabolism.

The effects of elevated atmospheric hydrogen sulfide (H(2)S) levels (0.25, 0.5, and 0.75 microl l(-1)) have been investigated in a short-term exposure experiment (3-48 h) on the model plant Arabidopsis thaliana (L.) Heynh. in comparison to untreated control plants. The most pronounced effects of H(2)S fumigation could be observed on the metabolite level: the contents of the thiols cysteine and glutathione were increased up to 20- and fourfold, respectively. A direct positive correlation of the thiol contents with the H(2)S concentrations applied was observed. To elucidate the molecular basis for the increased thiol levels, enzyme activities, messenger RNA and protein steady-state levels of cysteine-synthesizing and degrading pathways have been determined. The enzyme activities of O-acetyl-l-serine(thiol)lyase (OAS-TL) (EC 4.2.99.8) and l-cysteine desulfhydrase (EC 4.4.1.-) proteins were not significantly higher at elevated H(2)S levels in comparison to untreated control plants. 3-Mercaptopyruvate sulfurtransferase (EC 2.8.1.2) activity was slightly higher after the longest H(2)S exposure times. Elevated H(2)S levels of 0.25 and 0.5 microl l(-1) had promoting effects on both mRNA and protein levels of cysteine-synthesizing and degrading enzymes whereas the highest H(2)S concentrations caused lower levels of expression combined with mild symptoms of oxidative stress, as the consequence of its phytotoxicity. The differences in the expression of the three different OAS-TL isoforms (cytoplasmic, plastidic and mitochondrial) by H(2)S were very small. Increasing concentrations of H(2)S and longer exposure times to H(2)S let to a reduction in the pool of O-acetyl-l-serine, the second precursor of cysteine, and N-acetyl-l-serine in the leaves and shoots, indicating a substrate depletion in agreement with the increased thiol levels.     

Cell type specificity of a neural cell surface antigen recognized by the monoclonal antibody A2B5

Summary The monoclonal antibody A2B5 reacts with the surface membrane of most neurons in monolayer cultures of cerebellum, retina, spinal cord, and dorsal root ganglion of embryonic and early postnatal C57BL/6J mice maintained in vitro for culture periods of 2 to 10 days. A small percentage of astroglial cells also expresses A2B5 antigen in murine, chicken and rabbit cerebellum, in chicken retina, and in murine spinal cord and dorsal root ganglion. Less mature astroglial cells are stained for A2B5 antigen to a greater extent than the more mature astrocytes. Astrocytes from rat cerebellum and mouse retina were not found to express A2B5 antigen under the present culture conditions. Some of the less mature oligodendrocytes recognized by 04 antibodies express A2B5 antigen, while the more mature 01 antigen and galactocerebroside-positive oligodendrocytes were not found to be A2B5 antigen-positive. Fibroblasts or fibroblast-like cells do not express detectable levels of A2B5 antigen. After fixation of the cells with paraformaldehyde and ethanol, all cell types present in culture are labeled by the A2B5 antibody intracellularly.     

Effects of Temporal Sampling Patterns of All-occurrence Recording in Behavioural Studies: Many Short Sampling Periods Are Better than a Few Long Ones

All-occurrence recording is generally thought to yield unbiased results. However, its accuracy and power to detect real effects may depend on the temporal patterning of the observation periods. Although several studies evaluated the suitability of time-sampling methods (one-zero and instantaneous sampling), there has not been an evaluation of various temporal patterns of the ‘all-occurrence’ method to date. Here we present an empirical comparison of time-sampling and all-occurrence recording methods, based on a large data set, with special reference to various temporal patterns of all-occurrence recording. The three different sampling methods were imposed on raw data protocols. The scores, obtained by the use of each method and temporal pattern, were compared with true values from the corresponding continuous video recordings. The accuracy and power of each method was estimated by comparison of medians and magnitudes of effect (r_m), respectively. We were able to confirm results of earlier studies on the suitability of time-sampling methods (one-zero and instantaneous sampling), but we found that different temporal patterns of all-occurrence sampling yielded magnitudes of effect that differed from true value magnitudes. We conclude that behavioural studies may reveal different results, even when all conditions are the same, only because of power differences of different temporal pattern of the observation periods, for example 1 × 15 min versus 15 × 1 min. Recommendations are made about appropriate application of methods.     

Dominance style in female guerezas (Colobus guereza Rüppell 1835)

Socioecological models assume that quality and distribution of food ultimately determine female social relationships: a high quality diet and clumped food distribution should result in the establishment of a hierarchy with stable rank relations which is supported by empirical studies on frugivorous cercopithecines. By contrast, folivorous species with their low quality diet and dispersed food distribution should have egalitarian social relationships but empirical data are very rare. This study on female guerezas of a zoo group aimed to test the models in a colobine species and the results largely agreed with the predictions of the models: facial expressions, vocalizations, and gestures were not used for signalling dominance or subordination. Unritualized aggressions occurred frequently but were of low intensity, and interventions by third parties were never observed. Aggressions were exchanged bidirectionally and this was true also for food stealing and retreats. All this indicated the lack of established rank relations. Allogrooming was distributed rather equally and showed no kin bias. All these features characterize egalitarian social relationships and, hence, support the socioecological models.     

Folate Receptor Alpha Defect Causes Cerebral Folate Transport Deficiency: A Treatable Neurodegenerative Disorder Associated with Disturbed Myelin Metabolism

Sufficient folate supplementation is essential for a multitude of biological processes and diverse organ systems. At least five distinct inherited disorders of folate transport and metabolism are presently known, all of which cause systemic folate deficiency. We identified an inherited brain-specific folate transport defect that is caused by mutations in the folate receptor 1 (FOLR1) gene coding for folate receptor alpha (FRα). Three patients carrying FOLR1 mutations developed progressive movement disturbance, psychomotor decline, and epilepsy and showed severely reduced folate concentrations in the cerebrospinal fluid (CSF). Brain magnetic resonance imaging (MRI) demonstrated profound hypomyelination, and MR-based in vivo metabolite analysis indicated a combined depletion of white-matter choline and inositol. Retroviral transfection of patient cells with either FRα or FRβ could rescue folate binding. Furthermore, CSF folate concentrations, as well as glial choline and inositol depletion, were restored by folinic acid therapy and preceded clinical improvements. Our studies not only characterize a previously unknown and treatable disorder of early childhood, but also provide new insights into the folate metabolic pathways involved in postnatal myelination and brain development.