Dipeptidyl aminopeptidase yspI mutants of Schizosaccharomyces pombe: Genetic mapping of dpa1+ on chromosome III

Abstract A mutant strain of Schizosaccharomyces pombe lacking dipeptidyl aminopeptidase yspI was isolated from a strain already defective in aminopeptidase activity by means of a staining technique with the chromogenic substrate ala-pro-4-methoxy-β-naphthylamide to screen colonies for the absence of the enzyme. The defect segregated 2⁺ :2⁻ in meiotic tetrads, indicating a single chromosomal gene mutation, which was shown to be recessive. Gene dosage experiments indicated that the mutation resides in the structural gene of dipeptidyl aminopeptidase yspI, dpa 1⁺. The dpa 1⁺ gene was located on chromosome III by using l m- fluorophen-ylalanine-induced haploidization and mitotic analysis. dpa1 mutants did not show any obvious phenotype under a variety of conditions tested.     

Evaluation of DNA damage induced by norfloxacin in liver and kidney of adult rats and in fetal tissues after transplacental exposure

Norfloxacin, a recently developed antimicrobial fluoroquinolone, was investigated for DNA-damaging activity in rat liver and kidney. After oral administration of single doses ranging from 1 to 8 mmole/kg, DNA fragmentation was absent in liver and kidney both 2 and 6 h after treatment. However, when administered to pregnant rats, the highest doses produced a detectable amount of DNA damage in fetal tissues. This damage appears to be an aspecific consequence of maternal and fetal toxicity rather than a specific genotoxic effect.     

Comparison of an antimetabolic assay and an antiproliferative assay, both using 3H-thymidine incorporation, to test drug sensitivity of human tumors

Two assays based on the inhibition of 3H-thymidine incorporation into DNA were used to measure either the antimetabolic or the antiproliferative effects of anticancer drugs. A direct comparison of the two assays was made with cell suspensions obtained from 11 ovarian cancers and 22 malignant melanomas. Drugs with different effects on cell cycle phases were tested by both assays, for a total of 53 drug comparisons. When the sensitivity indices specific for each system was used, a significant association (p less than 0.01) was noted between the two assays. The agreement of both assays in defining in vitro sensitivity or resistance was 100% for ovarian cancer. For melanoma, 97% of samples resistant to the antimetabolic assay were also resistant to the antiproliferative assay; whereas, only 45% of samples sensitive to the antimetabolic assay were sensitive to the antiproliferative assay.     

Effect of different physico-chemical conditions on malolactic fermentation of fourLactobacillus plantarum wild strains isolated from wines of northwestern Spain

Summary Four strains ofLactobacillus plantarum, were tested for malolactic fermentation under conditions of variations in temperature, pH and SO2, L-malate and ethanol levels. When the pH value was below 3.5, malolactic fermentation was lower and was more sensitive to temperature changes. Malolactic fermentation decreased when the SO2 and ethanol levels were increased. The effects of L-malate levels were not significant.     

Intracellular Ca2+ stores in neurons. Identification and functional aspects.

Various aspects of the rapidly exchanging intracellular Ca2+ stores of neurons and nerve cells are reviewed: their multiplicity, with separate sensitivity to either the second messenger, inositol 1,4,5-trisphosphate, or ryanodine-caffeine (the latter stores are probably activated via Ca(2+)-induced Ca2+ release); their control of the plasma membrane Ca2+ permeability, via the activation of a peculiar type of cation channels; their ability to sustain localized heterogeneities of the [Ca2+]i that could be of physiological key-importance. Finally, the molecular composition of these stores is discussed. They are shown (by high resolution immunocytochemistry and subcellular fractionation) to express: i) a Ca2+ ATPase responsible for the accumulation of the cation; ii) Ca2+ binding protein(s) of low affinity and high capacity to keep Ca2+ stored; and iii) a Ca2+ channel, activated by either one of the mechanisms mentioned above, to release Ca2+ to the cytosol. Results obtained in Purkinje neurons document the heterogeneity of the stores and the strategical distribution of the corresponding organelles (calciosomes; specialized portions of the ER) within the cell body, dendrites and dendritic spines.     

Influence of the curing of the killer phenotype inSaccharomyces cerevisiae wine strains on their fermentative behaviour

Fermentative behaviour and cell growth have been studied in grape juice inoculated either with two killerSaccharomyces cerevisiae wild strains or with their Acridine Orange-cured isogenic counterparts. The number of viable cells/ml at the beginning of the fermentation, as well as during exponential growth, were higher in grape juices inoculated with the cured strains. The CO₂ production, fermentative rate and ethanol and acetic acid production were also higher in the cured strains, particularly during the stage of active fermentation. These differences, however, were minimal at the end of the fermentations.     

Kinetic study of nitrite inhibition during alcoholic fermentation of beet molasses

Summary Alcoholic fermentation cycle with Saccharomyces cerevisiae has been studied on beet molasses exempt from nitrite ions and containing added amounts of these ions from 200 to 400 ppm. Experimental results indicate that fermentation duration increases with increasing nitrite concentration in the molasses. A detailed kinetic study reveals that this increase occurs only during the latency period. Moreover, the biomass and the ethanol production curves drawn after this period appear to be quite linear, their slope being independent of initial nitrite concentration. It has also been shown that nitrite ions turn completely into nitrate ions during the latency period. We have proved that this oxidation must be ascribed to yeast action and not to any chemical reactions between nitrite ions and molasses components.     

Age-related effect induced by oxidative stress on the cerebral glutathione system

In the forebrain from male Wistar rats aged 5, 15 and 25 months, age-related putative alterations in the glutathione system (reduced and oxidized glutathione; redox index) were chronically induced by the administration in drinking water of free radical generators (hydrogen peroxide, ferrous chloride) or of inhibitors of endogenous free radical defenses (diethyl-dithio-carbamate, an inhibitor of superoxide dismutase activity). In hydrogen peroxide administered rats, both reduced glutathione and the cerebral glutathione redox index markedly declined as a function of aging, whereas oxidized glutathione consistently increased. In contrast, chronic iron intake failed to modify the reduced glutathione in forebrain from the rats of the different ages tested, whereas the oxidized glutathione was increased in the older brains. The chronic intake of diethyl-dithio-carbamate enhanced the concentrations of reduced glutathione in the forebrains from the rats of the different ages tested, the oxidized glutathione being unchanged. In 15-month-old rats submitted to chronic oxidative stress, ergot alkaloids (and particularly dihydroergocriptine) interfered with cerebral glutathione system, while papaverine was always ineffective. The comprehensive analysis of the data indicates that: (a) both the type of oxidative stress and the age of the animals modulate the cerebral responsiveness to the putative modifiers in the level of tissue free radicals; (b) aging magnifies the cerebral alterations induced by oxidative stress; the (c) cerebral glutathione system may be modified by metabolic rather than by circulatory interferences; (d) a balance between the various cerebral antioxidant defenses is present, the perturbation of an antioxidant system resulting in the compensatory modified activity of component(s) of another system.     

Developmental and Regional Expression of NMDA Receptor Subtypes Containing the NR2D Subunit in Rat Brain

Abstract: The regional and developmental expression of NMDA receptors containing the NR2D subunit was analyzed on the level of the subunit mRNA and protein in rat brain. RNase protection experiments indicated that among two proposed splice variants of the NR2D subunit, only the NR2D-2 subunit is expressed. The regional distribution of the NR2D subunit protein was visualized with a newly developed NR2D-2 subunit-specific antiserum on brain sections using the histoblot technique. In adult brain, NR2D immunoreactivity was mainly restricted to diencephalic, mesencephalic, and brainstem structures. During postnatal development, the NR2D subunit was detected transiently in certain regions, such as the ventro-basal complex of the thalamus, hippocampus, inferior colliculus, and brainstem reticular formation, suggesting that NR2D subunit-containing receptors play a role in these brain areas only during development. The level of NR2D subunit mRNA and protein decreased during late postnatal development. However, significant levels of NR2D subunit mRNA and protein were present in adulthood, in particular, in the globus pallidus, thalamus, subthalamic nuclei, and superior colliculus. These results indicate a functional relevance for NMDA receptors containing the NR2D subunit in the developing and adult brain, although its expression in the adult brain is less prominent and restricted to a few brain areas.