Phase advance of the light-dark cycle perturbs diurnal rhythms of brain-derived neurotrophic factor and neurotrophin-3 protein levels, which reduces synaptophysin-positive presynaptic terminals in the cortex of juvenile rats.

In adult rat brains, brain-derived neurotrophic factor (BDNF) rhythmically oscillates according to the light-dark cycle and exhibits unique functions in particular brain regions. However, little is known of this subject in juvenile rats. Here, we examined diurnal variation in BDNF and neurotrophin-3 (NT-3) levels in 14-day-old rats. BDNF levels were high in the dark phase and low in the light phase in a majority of brain regions. In contrast, NT-3 levels demonstrated an inverse phase relationship that was limited to the cerebral neocortex, including the visual cortex, and was most prominent on postnatal day 14. An 8-h phase advance of the light-dark cycle and sleep deprivation induced an increase in BDNF levels and a decrease in NT-3 levels in the neocortex, and the former treatment reduced synaptophysin expression and the numbers of synaptophysin-positive presynaptic terminals in cortical layer IV and caused abnormal BDNF and NT-3 rhythms 1 week after treatment. A similar reduction of synaptophysin expression was observed in the cortices of Bdnf gene-deficient mice and Ca(2+)-dependent activator protein for secretion 2 gene-deficient mice with abnormal free-running rhythm and autistic-like phenotypes. In the latter mice, no diurnal variation in BDNF levels was observed. These results indicate that regular rhythms of BDNF and NT-3 are essential for correct cortical network formation in juvenile rodents.

A phase advance of the light-dark cycle stimulates production of BDNF, but not of other neurotrophins, in the adult rat cerebral cortex: association with the activation of CREB.

Circadian variation in the expression of brain-derived neurotrophic factor (BDNF) indicates that BDNF is involved in the regulation of diurnal rhythms in a variety of biological processes. However, it is still unclear which brain regions alter their BDNF levels in response to external light input. Therefore, in selected brain regions of adult male rats, we investigated diurnal variation, as well as the effects of a single eight-hour phase advance of the light-dark cycle, on the levels of BDNF and of other neurotrophins. The cerebellum, hippocampus and cerebral cortex containing visual cortex (VCX) showed diurnal variation in BDNF protein levels and the VCX also in NT-3 levels. In the VCX and the region containing the entorhinal cortex and amygdala (ECX), BDNF protein levels were increased 12 h after the phase advance, while BDNF mRNA levels were increased significantly in the VCX and slightly in the ECX after 4 h. After one week, however, BDNF protein levels were reduced in eight brain regions out of 13 examined. BDNF levels in the ECX and VCX were significantly different between light rearing and dark rearing, while a hypothyroid status did not produce an effect. Cyclic AMP responsive element-binding protein (CREB), a transcription factor for BDNF, was greatly activated by the phase advance in the ECX and VCX, suggesting the existence of CREB-mediated pathways of BDNF synthesis that are responsive to external light input.

Distribution and immunohistochemical localization of GDNF protein in selected neural and non-neural tissues of rats during development and changes in unilateral 6-hydroxydopamine lesions.

The tissue distribution of glial cell line-derived neurotrophic factor (GDNF) during development and changes in GDNF levels by unilateral 6-hydroxydopamine lesions were investigated in rats using a newly established enzyme immunoassay system and by immunohistochemistry. The detection limit of the assay was 0.3 pg/0.2 ml and the system recognized glycosylated mature GDNF. Concentrations of GDNF were relatively high in the kidney and testis during the embryonic and neonatal periods, respectively, and decreased with age. In the striatum, hippocampus and brain stem, GDNF reached a maximal level at around postnatal day 14. However, brain levels were generally lower than those in non-neural tissues. In the CNS, GDNF immunoreactivity was observed in striatal neurons, pyramidal neurons in the hippocampus and the Vth layer of the cortex, large neurons in the diagonal band and brain stem, and spinal motor neurons. It was also evident in several non-neural, tissue-specific cells, such as cells in the renal collecting ducts and distal tubules, and testicular Sertoli cells. Destruction of nigral dopaminergic neurons by 6-hydroxydopamine enhanced the levels of striatal GDNF protein, with apparent involvement of astrocytes. These results suggest that GDNF is normally synthesized in neurons, but may also be produced by astroglial cells in damaged brains.

Parental origin and cell stage of non-disjunction of double trisomy in spontaneous abortion.

Using polymorphic analysis of microsatellites, we investigated the parental origin and mechanism of double trisomies seen in cases of spontaneous abortion. We obtained chorionic villi from spontaneous abortions, and peripheral blood from females who experienced abortion and their spouses. Chromosomal analysis of 170 cases revealed four cases with double trisomy. The karyotypes of these cases are 48,XX,+16,+22, 48,XXY,+18, 48,XX,+15,+21 and 48,XX,+2,+5. In the present study, the incidence of double trisomy was 2.4% of spontaneous abortions. Polymorphic analysis of microsatellites indicated that extra chromosomes were all of maternal origin in the four cases of double trisomy. The predominance of maternal origin in cases of double trisomy is similar to cases of single trisomy. The result also indicated that both extra chromosomes in two cases occurred by non-disjunction at the first meiotic division, and extra chromosomes in the other two cases occurred by non-disjunction at the first mitotic division. The mean maternal age in cases of double trisomy was significantly higher than that in cases of single trisomy. These findings suggest the possibility that abnormal separation of two or more chromosomes may occur simultaneously in oogonia, and that this phenomenon may increase in relation to the increase in age of women.

Pro-oxidant action of phloxine B on fission yeast Schizosaccharomyces pombe.

A Schizosaccharomyces pombe mutant deficient in Cu,Zn-superoxide dismutase (sod1 mutant) was hypersensitive to phloxine B, which is used as a food-colouring agent and also to distinguish diploid strains of Sz. pombe from haploid strains, under illumination with light. The pro-oxidant nature of phloxine B was confirmed biochemically. The carbonyl content of proteins (which represents protein oxidation) increased, and the reduced form of glutathione was transiently decreased by phloxine B treatment under illumination with light. When cells were treated with phloxine B under light, carbonyl content of proteins in the sod1 mutant was greater than that in the wild-type and amount of glutathione was much decreased in the sod1 mutant compared with the wild-type. Genes induced by oxidative stress were induced by phloxine B under illumination with light and some were induced by phloxine B without light.

Characterization of Cu, Zn-superoxide dismutase-deficient mutant of fission yeast Schizosaccharomyces pombe.

A Cu, Zn-superoxide dismutase gene ( sod1+) deletion mutant of fission yeast Schizosaccharomyces pombe was constructed and its properties were investigated. Superoxide dismutase activity was not detected in the mutant on activity staining of polyacrylamide gels. The mutant showed cysteine or methionine and lysine auxotrophy, slow growth and sensitivity to menadione. While expression of the apt1+ gene, induction of which depends on the Pap1 transcription factor, was induced at the same concentration of menadione in both the wild-type cell and the sod1 mutant, expression of the gpx1+ gene, induction of which depends on the Atf1 transcription factor, was induced at a lower concentration of menadione in the mutant compared with the wild-type control. Expression of the sod1+ gene was induced by oxidative stress and no induction was observed in pap1, prr1 and spc1 mutants.