The neurochemical basis of recurrent inhibition in the reflex arch of the defensive reaction]

Mechanisms of habituation in the network of identified neurones were investigated in isolated preparation of central nervous system in the snail Helix. It has been found that intracellularly induced spike discharge in premotor command neurones decreases synaptic responses to repeated nerve stimulation in all recorded command neurones. Application of the neuropeptide FMRFamide elicits similar changes in the network. Taking into account that the investigated command neurones contain FMRFamide, as was shown immunochemically, it is possible to assume the existence of recurrent inhibition in the network underlying avoidance reactions. This recurrent inhibition causes habituation of the network output in the cases when the repeated stimuli do not evoke sensitization via activation of serotonergic cells.     

Action of genotypical surrounding of host Drosophila melanogaster on biological effects of endosymbiont Wolbachia (strain wMelPop)

In this work, a comparative study of the structure of symbiotic bacteria Wolbachia (strain wMelPop decreasing the fly lifespan) in genotypically different Drosophila melanogaster, as well as the effect of the bacteria on the host cell ultrastructure was investigated out. As a result of special crossings, the Drosophila melanogaster [w]Trl ³⁶² and [w]Trl ^en82 lines, which are carried of mutations for the gene Trithorax-like, are synthesized (lines infected with Wolbachia are designated as [w]). The Drosophila melanogaster line free of Wolbachia was obtained by treatment with antibiotics of the initially infected [w]w ¹¹¹⁸ line. The complex of the used methods and approaches has allowed us to perform a comparative study of the morphology of cell structures for the first time before and after the infestation of insects with bacteria and to evaluate effect of the bacteria on viability and fertility of flies of these lines. Electron microscopy analysis has shown that the embryos of the analyzed lines contain typical Wolbachia in contact with various host cell compartments; the ultrastructural organization of the bacteria indicates the preservation of their functional activity. In the cytoplasm of embryos that are mutant for the gene Trithorax-like, morphologically atypical mitochondria were revealed, as well as Wolbachia (wMelPop) of unusual morphology with a modified form of membtane envelopes. The presence of Wolbachia in ovarian cells of the female mutant fly lines has been found to produce no effect on the amount of the female-ovipositioned eggs. It has been established for the first time that lifespans of the infected and Wolbachia-free Drosophila melanogaster mutant lines TM3 containing chromosome 3 as a balancer are equal. However, it is significantly shorter in the imago of the [w]w ¹¹¹⁸ line than in flies of the mutant lines. This has allowed us to suggest that either the chromosome-balancer TM3 or mutation of the gene Trl play an important role in the host-symbiont interactions. On checking this suggestion, it was found that the lifespan of homozygotes [w]Trl ³⁶² and [w]Trl ^en82 after the infection of flies with bacteria decreased markedly and was close to the lifespan of [w]w ¹¹¹⁸ line. The obtained data indicate that the chromosome-balancer TM3 can have a significant effect on the symbiont-host interaction.     

Ser1928 is a common site for Cav1.2 phosphorylation by protein kinase C isoforms

Voltage-dependent Ca(2+) channel (Ca(v)1.2, L-type Ca(2+) channel) function is highly regulated by hormones and neurotransmitters in large part through the activation of kinases and phosphatases. Regulation of Ca(v)1.2 by protein kinase C (PKC) is of significant physiologic importance, mediating, in part, the cardiac response to hormonal regulation. Although PKC has been reported to mediate activation and/or inhibition of Ca(v)1.2 function, the molecular mechanisms mediating the response have not been definitively elucidated. We show that PKC forms a macromolecular complex with the alpha(1c) subunit of Ca(v)1.2 through direct interaction with the C terminus. This interaction leads to phosphorylation of the channel in response to activators of PKC. We identify Ser(1928) as the residue that is phosphorylated by PKC in vitro and in vivo. Ser(1928) has been identified previously as the site mediating, in part, the protein kinase A up-regulation of channel activity. Thus, the protein kinase A and PKC signaling pathways converge on the Ca(v)1.2 complex at Ser(1928) to increase channel activity. Our results identify two mechanisms leading to regulation of Ca(v)1.2 activity by PKC: pre-association of the channel with PKC isoforms and phosphorylation of specific sites within the alpha(1c) subunit.     

Structure and diversity of the mitochondrial gene pool of the aboriginal population of Tuva and Buriatia from restriction polymorphism data

The populations of Tuvinians (N = 36) and Buryats (N = 105) were characterized by using the data on mitochondrial DNA (mtDNA) polymorphism. The gene pools of both ethnic groups possessed the mtDNA types belonging to the four main haplogroups, A, B, C, and D, found only in the indigenous populations of Asia and America. The total frequencies of the A, B, C, and D haplogroups in Tuvinians and Buryats were 72.3% and 52.4%, respectively. These values, along with the frequency for Altai populations (57.2%), were highest in the Asian populations studied, indicating that the populations Southern and Eastern Siberia can be considered as ancestral relatives to the ethnic groups of the New World. Analysis of the mtDNA region V polymorphism showed the presence of 9-bp deletion and 4-bp insertion in both populations with frequencies respectively of 13.9 and 5.56% in Tuvinians and 4.8 and 1.9% in Buryats. The frequency of the +AvaII/8249 variant was 11.1% in Tuvinians and 3.81% in Buryats. Analysis of the association between the region V deletion-insertion polymorphism and certain restriction haplogroups pointed to repeated and independent emergence of the 4-bp insertion in Siberia.     

Polymorphism and differentiation of multilocus DNA markers in natural populations of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Using multilocus (RAPD) markers, variation and divergence of genomic DNA was examined in two Drosophila melanogaster populations from Russia and three populations from Ukraine. The populations were found to exhibit high polymorphism at RAPD markers. Estimation of genetic distances between the populations showed low differentiation of geographically distant populations of D. melanogaster. Significant gene flow between the D. melanogaster populations was found, which depended on the geographical distance between them.     

The Stockholm populations of Adalia bipunctata (L) (Coleoptera: Coccinellidae)--a case of extreme female-biased population sex ratio

The genetic composition and sex ratio in the Stockholm populations of Adalia bipunctata have been studied. The overall frequency of melanics is 3.2%, which is significantly lower than in the populations of St. Petersburg and other large cities along the Baltic Sea. The secondary sex ratio in the Stockholm populations is female-biased 82:18. More than half of A. bipunctata females are infected with the male-killing Spiroplasma bacterium. Beetles of the co-existing species Adalia decempunctata are infected with a different bacterium belonging to the genus Rickettsia.     

Homogeneous assay for biotin based on Aequorea victoria bioluminescence resonance energy transfer system

Here we describe a homogeneous assay for biotin based on bioluminescence resonance energy transfer (BRET) between aequorin and enhanced green fluorescent protein (EGFP). The fusions of aequorin with streptavidin (SAV) and EGFP with biotin carboxyl carrier protein (BCCP) were purified after expression of the corresponding genes in Escherichia coli cells. Association of SAV-aequorin and BCCP-EGFP fusions was followed by BRET between aequorin (donor) and EGFP (acceptor), resulting in significantly increasing 510 nm and decreasing 470 nm bioluminescence intensity. It was shown that free biotin inhibited BRET due to its competition with BCCP-EGFP for binding to SAV-aequorin. These properties were exploited to demonstrate competitive homogeneous BRET assay for biotin.     

Localization of cohesin complexes of polytene chromosomes of Drosophila melanogaster located on interbands

The distribution of cohesin complex in polytene chromosomes of Drosophila melanogaster was studied. Cohesin is a complicated protein complex which is regulated by the DRAD21 subunit. Using immunostaining for DRAD21p, the cohesins were shown to be preferentially located in the interband regions. This specificity was not characteristic for puffs, where uniform staining was observed. The presence of a few brightly fluorescent regions (five to ten per chromosome arm) enriched with cohesin complexes was shown. Some of these regions had permanent location, and the others, variable location. No antibody binding was detected in the chromocenter. Immunostaining of interphase nuclei of neuroblasts revealed large cohesin formations. On the polytene chromosomes of D. melanogaster, the Drad21 gene was mapped to the chromocentric region (81) of the L arm of chromosome 3.