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Biomedical subjects

V A Nikitin

Publications and source records attributed to V A Nikitin.

At least 19 recordsLinked to original sources
PubMed2000

[The reaction of endoplasmic reticulum of Mauthner cells of Xenopus laevis tadpoles in response to the partial denervation].

The structure of the Mauthner cells in Xenopus laevis tadpole was investigated by light- and electron microscopy in norm and after early unilateral enucleation. It was found that enucleation at early stages caused a delay in morphological development of the contralateral neurons during embryogenesis. We observed a decrease in size of the soma and nucleus and in the number of dendrites, a marked structural underdevelopment of the majority of cell organoids, as well as proliferation and hypertrophy of transversal cisternae in the contralateral Mauthner cells. The ipsilateral neurostructure remained normal in embryogenesis. The data obtained suggest the availability of some unknown powerful afferent contralateral input to Mauthner cells from the optical analyzer.

Animals↗
PubMed1999

Receptor-mediated transport of foreign DNA into preimplantation mammalian embryos.

Mouse and rabbit preimplantation embryos with intact zona pellucida were incubated for 3 hr with DNA-carrying constructs containing insulin as an internalizable ligand: (insulin-polylysine)-DNA and (insulin-polylysine)-DNA-(streptavidin-polylysine)-(biotinylated adenovirus). Video-intensified microscopy demonstrated that the constructs penetrated the zona pellucida and accumulated in the blastomere perinuclear space. The percentage of blastocysts formed was about 70% after incubation of zygotes and two-cell embryos with the constructs. Foreign DNA was detected after 51 hr in 80% of rabbit embryos and after 96 hr in 73% of mouse embryos. Inclusion of various adenoviruses into the construct improved foreign DNA preservation in early embryos. Blot hybridization revealed genome-integrated foreign DNA in 12- and 15-day mouse embryos and in a newborn. Thus, the ligand-mediated mechanism can be employed for introducing foreign genetic material into early mammalian embryos; insulin provides for delivery inside the cell and to the nucleus, while adenoviruses ensure release from endosomes.

Adenoviridae↗
PubMed1999

[Morphogenesis of Mauthner neurons of Xenopus laevis tadpoles following early unilateral eye enucleation].

The connection between Mauthner neuron (CMN) and visual analyzer in Xenopus laevis tadpoles was studied using these neurons capacity to change their morphogenesis during the development in case of interruption of their connections with afferent fibres. In phase 31 of development tadpoles were subjected to unilateral enucleation of eye. Morphogenesis of contralateral (experimental) and ipsilateral (control) MN with respect to the operated eye was followed up. Comparison with intact Mauthner neuron of the tadpole of the same age who were not exposed to operation was conducted. Contralateral MN were found to be delayed in development phases 47 and 50. This was associated with 1.5-3.3 fold difference in neuron body central section area and 2-3 fold differences in nuclear section area. Three-dimensional reconstruction revealed lower number of cell processes in contralateral MN as well as decline in their length and diameter. Control and intact MN showed no difference similar to experimental and control ones in phase 41. The data obtained indicate that MN of Xenopus laevis tadpole possess powerful ipsilateral connections originating from the side of visual analyzer and contralateral ones from the side of the eye. This affects MN development and in contrast to octavolateral system (including vestibular apparatus and organs of lateral line) controls the contralateral neuron.

Animals↗
PubMed1998

Receptor-mediated transfection of murine and ovine mammary glands in vivo.

Transfection of HC-11 murine epithelial mammary cells as well as murine and sheep mammary glands were carried out using insulin-containing constructs that deliver DNA by receptor-mediated endocytosis to receptor-expressing cells. In vivo transfection of mammary gland tissue with the luciferase gene was carried out by introducing the DNA constructs into the mammary ducts of both mice and sheep. The successful transfection of ewe mammary glands was demonstrated by the detection of luciferase activity in mammary gland biopsy material up to a month after a single administration of the construct. To test whether products of expression of transfected genes could be secreted into the milk in this system, the N-terminal secretory signal sequences of bovine beta-lactoglobulin or the entire coding sequence of human alpha-lactalbumin were fused to the N terminus of the luciferase gene. After transfection with the modified luciferases, both murine and sheep milk could be shown to contain luciferase activity, whereas mice, which had been transfected with the nonmodified luciferase gene, did not secrete any activity in the milk. This approach demonstrates for the first time the possibility of gene transfer in vivo into mammary gland epithelial cells using constructs delivering DNA via receptor-mediated endocytosis.

Animals↗
PubMed1989

[Effect of the oxidation-reduction potential of the medium on the production of gentamycin].

The medium redox potential had an effect on gentamicin production by Micromonospora purpurea v. violacea, strain VNIIA 7R. The Eh influence was shown to be statistically reliable when the results were expressed in relative units against the control. In the laboratory experiments with low volumes of the medium the Eh increase by more than 170 per cent induced inhibition of gentamicin biosynthesis while the Eh increase by 108 to 168 per cent induced stimulation of the activity.

Culture Media↗
PubMed1989

[Therapeutic endoscopy in combined therapy of gastroduodenal ulcers].

The method of therapeutic endoscopy is a very important component in the complex treatment of chronic gastroduodenal ulcers. In 115 of 116 patients with gastric or duodenal ulcers who were treated by the authors the ulcer epithelialized and a cicatrix formed. When therapeutic endoscopy with the application of hippophae oil was added to the basic therapy, the period of the inpatient treatment reduced 1.5-2 times. The late results of the management of chronic gastroduodenal ulcers by this method were studied and confirmed its sufficiently high therapeutic efficacy (the results were positive in 93.7% of cases).

Adult↗
PubMedDate not supplied

[Autoselection in Candida utilis yeasts in a chemostat culture].

Long-term continuous cultivation of Candida utilis in the conditions of chemostat, with the growth rate being limited with phosphates, was accompanied by autoselection. The culture obtained had a higher growth rate and differed by some physiological characteristics from the parent culture. The content of intracellular phosphates varied from 1.9 to 0.55% per dry weight, depending on the concentration of phosphates in the growth medium. At the threshold concentration (0.007 g/litre), phosphates were not virtually utilized by the culture. Specific time of transitional processes depends on the value of interfering effect.

Bacteriological Techniques↗
PubMedDate not supplied

[NMR spin-echo study of the lyophilized biomass of Candida utilis yeasts at different growth stages].

Characteristics of the mobile water fraction isolated from some intracellular structures of freeze-dried cells of Candida utilis were studied as a function of the growth phase by the NMR spin-echo method. Part of the mobile water fraction in the log phase decreases down to ten percent of the biomass weight as compared with 2,5-4% in the stationary phase and in the beginning of the lag phases. Mobility of this water is invariable. A considerable decrease of the mobile water fraction is observed in the post-stationary phase too. A decrease of the mobile water fraction correlates with a decrease of the durability of C. utilis cells and is connected probably with some defects in the membrane structure of the cells and their incomplete development in the log phase of the growth.

Candida↗
PubMedDate not supplied

[Fluorescent analysis of cryopreserved totipotent cells of amphibian embryos].

The cryotolerance of totipotent cells from dissociated embryos of amphibian (grass frog Rana temporaria and grey toad Bufo bufo) was studied. Cell integrity and preservation of the cell barrier function were evaluated by fluorescent analysis. It was shown that the best cryopreservation of the cells was achieved by using the cryoprotective agent 10% dimethyl sulfoxide and 10% saccharose. These cells were successfully used for the homotransplantation of nuclei into enucleated eggs. The development of reconstructed eggs to the blastula stage was noted.

Animals↗
PubMedDate not supplied

[Study of the relationship between the free water fraction in dried Candida utilis and the phosphorus content of cells].

The relationship between the free water fraction and the phosphate content in lyophilized yeast cells of Candida utilis was studied. The yeast were cultivated continuously and periodically, their growth rate being limited by phosphates. The decrease in the phosphate pool from 2% to 0.56% was followed by an increase in the fraction of free water by 6.3 times.

Candida↗
PubMedDate not supplied

[Correlation between the cellular content of mobile water and the viability of lyophilized yeast cells].

Spin-echo NMR studies showed that lyophilized yeast cells contain isolated mobile water (IMW), whose content varied from 0.25% (of the dry weight of cells) in the lyophilized exponential-phase yeast cells to 3.8% in the lyophilized lag-phase and stationary-phase yeast cells. The viability rate of yeast cells varied from 20% in the lyophilized preparation of exponential-phase cells to 86% in the lyophilized preparation of early-stationary-phase cells. In the lyophilized preparation of yeast cells grown in a chemostat mode at a constant specific rate, the content of IMW depended on the growth-limiting factor, being minimal in the case of growth limitation by carbon source. In the latter case, the viability rate of cells was also minimal. The data obtained show that there is a correlation between the IMW content and the viability rate of yeast cells in lyophilized preparations.

Candida↗