Various forms of potentials recorded from caudate nucleus neurons

Spontaneous and evoked activity of caudate nucleus neurons was recorded extracellularly in acute experiments on cats. Different forms of potentials were found by analysis of the results. The potentials recorded belong to three types: ordinary action potentials; prepotentials or incomplete spikes differing from ordinary action potentials in their lower amplitude and slower decline, and complex discharges in which a spike of somewhat reduced amplitude is followed by a slow positive-negative wave. In the spontaneous activity prepotentials were observed both in complete action potentials and in isolation. The frequency of the complex discharges was 0.5–1 per second. The slow wave of these discharges blocked prepotential and action potential formation. The origin of these forms of potentials in neurons of the caudate nucleus is discussed and they are compared with analogous forms of potentials described for the Purkinje cells of the cerebellum.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukranian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 149–156, March–April, 1977.     

Evidence for the uninemy of eukaryotic chromatids

Polytene chromosomes of Chironomus thummi were stretched to their rupture in a pronase solution. A 176±26-fold elongation was achieved. The DNA compaction ratio, defined as the ratio of DNA length in a haploid set (85±5 mm) to the length of a polytene chromosome set (520±40 m), was 164±22. Closeness of these two values demonstrates the uninemy of the chromatids of Chironomus chromosomes. The effect of ethidium bromide on the elastic properties of chromosomes prestretched in a pronase solution and the lengthening of these chromosomes after ethidium staining suggest that DNA molecules are double-stranded and supercoiled to the moment of the chromosome rupture. It is concluded that a Chironomus chromatid consists of a single DNA molecule (or of a single chain of linked DNA molecules) both ends of which are located in the telomeres.To the memory of Prof. Vera V. Khvostova     

Unitary responses of the caudate nucleus to direct stimulation

Unitary responses of the caudate nucleus to stimulation of various parts of it were investigated by extracellular recording. Latent periods of response discharges varied from 3.5 to 40 msec. Most neurons were excited by stimulation of the most rostral part of the head of the caudate nucleus. Irrespective of the site of stimulation, in most cases responses consisted of initial excitation in the form of one or, less frequently, two discharges followed by a period of depression of spontaneous activity. Recovery of activity took place gradually, without postinhibitory facilitation. No afterdischarges or periodic repetitions of spikes were observed after the initial response. Repetitive stimulation of the caudate nucleus showed that the neurons of this nucleus reproduce frequencies of stimulation badly above 30/sec, and under these circumstances in many cases they continued to discharge on average at a frequency of 5–15/sec. The results are examined from the standpoint of participation of the caudate nucleus in the formation of spindle activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 497–506, September–October, 1976.     

The Excitotoxin Quinolinic Acid Induces Tau Phosphorylation in Human Neurons

Some of the tryptophan catabolites produced through the kynurenine pathway (KP), and more particularly the excitotoxin quinolinic acid (QA), are likely to play a role in the pathogenesis of Alzheimer''s disease (AD). We have previously shown that the KP is over activated in AD brain and that QA accumulates in amyloid plaques and within dystrophic neurons. We hypothesized that QA in pathophysiological concentrations affects tau phosphorylation. Using immunohistochemistry, we found that QA is co-localized with hyperphosphorylated tau (HPT) within cortical neurons in AD brain. We then investigated in vitro the effects of QA at various pathophysiological concentrations on tau phosphorylation in primary cultures of human neurons. Using western blot, we found that QA treatment increased the phosphorylation of tau at serine 199/202, threonine 231 and serine 396/404 in a dose dependent manner. Increased accumulation of phosphorylated tau was also confirmed by immunocytochemistry. This increase in tau phosphorylation was paralleled by a substantial decrease in the total protein phosphatase activity. A substantial decrease in PP2A expression and modest decrease in PP1 expression were observed in neuronal cultures treated with QA. These data clearly demonstrate that QA can induce tau phosphorylation at residues present in the PHF in the AD brain. To induce tau phosphorylation, QA appears to act through NMDA receptor activation similar to other agonists, glutamate and NMDA. The QA effect was abrogated by the NMDA receptor antagonist memantine. Using PCR arrays, we found that QA significantly induces 10 genes in human neurons all known to be associated with AD pathology. Of these 10 genes, 6 belong to pathways involved in tau phosphorylation and 4 of them in neuroprotection. Altogether these results indicate a likely role of QA in the AD pathology through promotion of tau phosphorylation. Understanding the mechanism of the neurotoxic effects of QA is essential in developing novel therapeutic strategies for AD.     

The Microbial Community of Poultry Farm Waste and Its Role in Hydrogen Sulfide Production

Microbiology - The microbiota of chicken litter remains largely unexplored, despite its leading role in the formation of volatile odorants and unpleasant odors. One of the main components of the...     

Prokaryotic Communities in Saline Soils of the Lake Elton Area in a Soil Catena along the Khara River

Microbiology - Analysis of the taxonomic structure of prokaryotic microbial complexes of the saline soils in the Lake Elton area and their comparative characteristics were carried out for a soil...     

Spatial,temporal and interindividual epigenetic variation of functionally important DNA methylation patterns

DNA methylation is an epigenetic modification that plays an important role in gene regulation. It can be influenced by stochastic events, environmental factors and developmental programs. However, little is known about the natural variation of gene-specific methylation patterns. In this study, we performed quantitative methylation analyses of six differentially methylated imprinted genes (H19, MEG3, LIT1, NESP55, PEG3 and SNRPN), one hypermethylated pluripotency gene (OCT4) and one hypomethylated tumor suppressor gene (APC) in chorionic villus, fetal and adult cortex, and adult blood samples. Both average methylation level and range of methylation variation depended on the gene locus, tissue type and/or developmental stage. We found considerable variability of functionally important methylation patterns among unrelated healthy individuals and a trend toward more similar methylation levels in monozygotic twins than in dizygotic twins. Imprinted genes showed relatively little methylation changes associated with aging in individuals who are >25 years. The relative differences in methylation among neighboring CpGs in the generally hypomethylated APC promoter may not only reflect stochastic fluctuations but also depend on the tissue type. Our results are consistent with the view that most methylation variation may arise after fertilization, leading to epigenetic mosaicism.