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Biomedical subjects

N Popov

Publications and source records attributed to N Popov.

At least 19 recordsLinked to original sources
PubMed2005

Cytotoxicity and apoptotic effects of microcystin-LR and anatoxin-a in mouse lymphocytes.

There is an increasing amount of knowledge on the cytotoxic properties of cyanotoxins, but relatively little is known regarding their fine specificity and mechanisms of action. In this study, we investigated the influence of microcystin-LR and AnTx-a on mouse B- and T-lymphocyte subpopulations in vitro. Cyanotoxins significantly decreased the cell viability after 4 and 24 h, compared to the untreated control. After 24 h exposure to microcystin-LR and anatoxin-a, the viability of splenocytes dropped to 23% and 57%, respectively. Our data demonstrate that microcystin-LR induced apoptosis specifically in mouse B cells, probably via the B-cell antigen receptor and mitochondrial pathway, while the T cells were not affected. AnTx-a showed cytotoxic effects on both lymphocyte subpopulations, but the effects were driven by mechanisms different from apoptosis. These findings demonstrate that the cyanotoxins could cause cytotoxic alterations in a variety of cell types different from the major targets, operating via distinct mechanisms.

Animals↗
PubMed2003

Morphological, genetic and functional variability of a T-cell hybridoma line.

The variability in the morphology, modal number of chromosomes, TCR expression and functional reactivity of a CII-specific T-cell hybridoma at continuous subcultivation have been investigated. As the number of passages increased, besides the oval semiadherent cells (normal phenotype), fibroblast-like cells (transformed phenotype) were also observed. The two cell subpopulations differed in their karyotype characteristic, as well as in their functional reactivity. The cell population with a normal phenotype was characterized by a tetramodal number of chromosomes (30, 40, 48 and 70) and trisomies of chromosomes 6 and 14, while the cell population with a transformed phenotype was characterized by a trimodal number of chromosomes (11, 68 and 74) and trisomy of chromosome 12. A nullisomy of sex chromosomes was established in both types of cells. In the initial passages of subcultivation, 73.04% of the cells with a normal morphological phenotype expressed TCR-CD3 complexes on their surface and possessed high functional reactivity. After a two-week subcultivation, the values of these indices went down considerably: 46.11% of the cells expressed functional TCR-CD3 complexes, as a result of which their functional reactivity decreased. Only 2.71% of the cells with a transformed morphological phenotype expressed functional TCR-CD3 complexes on their surface. In these cells, a total loss of reactivity towards the specific antigens was established. The achieved results show that at continuous subcultivation the T-cell hybridomas are unstable, and with the increase in the number of passages there appear chromosome rearrangements, leading to loss of their functional reactivity.

Animals↗
PubMed2001

Switch from Myc/Max to Mad1/Max binding and decrease in histone acetylation at the telomerase reverse transcriptase promoter during differentiation of HL60 cells.

Recent evidence suggests that the Myc and Mad1 proteins are implicated in the regulation of the gene encoding the human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. We have analyzed the in vivo interaction between endogenous c-Myc and Mad1 proteins and the hTERT promoter in HL60 cells with the use of the chromatin immunoprecipitation assay. The E-boxes at the hTERT proximal promoter were occupied in vivo by c-Myc in exponentially proliferating HL60 cells but not in cells induced to differentiate by DMSO. In contrast, Mad1 protein was induced and bound to the hTERT promoter in differentiated HL60 cells. Concomitantly, the acetylation of the histones at the promoter was significantly reduced. These data suggest that the reciprocal E-box occupancy by c-Myc and Mad1 is responsible for activation and repression of the hTERT gene in proliferating and differentiated HL60 cells, respectively. Furthermore, the histone deacetylase inhibitor trichostatin A inhibited deacetylation of histones at the hTERT promoter and attenuated the repression of hTERT transcription during HL60 cell differentiation. In addition, trichostatin A treatment activated hTERT transcription in resting human lymphocytes and fibroblasts. Taken together, these results indicate that acetylation/deacetylation of histones is operative in the regulation of hTERT expression.

Acetylation↗
PubMed1999

Assessment of left ventricular systolic function and diastolic time intervals by the bioimpedance polyrheocardiographic system.

In order to detect left ventricular systolic function and diastolic time intervals using a new improved bioimpedance polyrheocardiographic system (BPCS), 110 healthy subjects and 128 patients with myocardial infarction were examined. Twenty-four simultaneous measurements of cardiac output by thermodilution and BPCS were performed in 11 patients with complicated acute left ventricular failure. Studies demonstrated a high degree of correlation (r = 0.91, p < 0.001). The correlation between the methods of using signals of the second derivative and the subtracted first derivative waveform of BPCS and continuous-wave Doppler echocardiography of systolic and diastolic time intervals was studies in 51 patients. The methods were closely correlated, especially with respect to left ventricular ejection time (r = 0.95), isovolumic relaxation time (r = 0.85), time to peak filling (r = 0.90), and deceleration of rapid filling time (r = 0.91). New bioimpedance hemodynamic parameters such as peak volume acceleration of ejection (PVAE) and peak power ejection (PPE) in patients with heart failure (NYHA Class I-III) were studied. Significant reductions of PVAE and PPE in groups of patients with marked progression of heart failure were noted. These results have demonstrated that BPCS is a noninvasive, simple accurate method of assessment of left ventricular systolic function and diastolic time intervals.

Adult↗
PubMed1990

Metabolization of a retention-improving dosage of methylglucamine orotate in rat brain.

The present study was carried out to investigate the time course of metabolization in brain and the influence on RNA synthesis of a retention-improving dosage of methylglucamine orotate after intracerebroventricular application. As determined by the HPLC technique, 73% of acid-soluble radioactivity were recovered in unmetabolized orotic acid 30 min after injection of 1 mumole methylglucamine [6-14C]orotate. Two hours later the amount of radioactivity found in this compound was negligible. Analysis of the sequence of labelling of uridine compounds revealed uridine to be the metabolite exhibiting the highest radioactivity at 30 min, whereas UMP- and UDP-sugars attained their maximum 90 min after injection of the precursor. Incorporation of [3H] guanosine into brain RNA was not altered by intraventricular application of 1 mumole methylglucamine orotate as compared to methylglucamine chloride-treated controls. The results are interpreted in the light of behavioural findings in which the pyrimidine nucleotide precursor at the dosage used improved the retention performance of an acquired behaviour in the rat.

Animals↗
PubMed1990

[A dental concept in gerontology].

The necessity of gerontal dental care programme will be caused by statistical datas. The mainpoints of this prophylactically orientated care programme are described.

Aged↗
PubMed1990

Effects of intraventricularly applied methylglucamine orotate on [3H] acetylglucosamine incorporation into rat brain tissue during a learning experiment.

The present work was undertaken to study the influence of intraventricularly applied methylglucamine orotate (MGO) at a memory-facilitating dose of 1 mumole vs. 1 mumole methylglucamine chloride (MGCl) as a control substance on the incorporation of intraventricularly injected [3H]acetylglucosamine into rat hippocampus and striatum plus thalamus. MGO or MGCl were applied 50 min prior to application of labelled aminosugar, the incorporation times being 1, 4 and 24 h. In non-trained animals, MGO produced an increased labelling of hippocampal proteins (20%) after 24 h, whereas labelling of the lipid fraction was virtually not altered. In trained animals (brightness discrimination model), the increase in labelling caused by MGO in hippocampal proteins was more marked (49%), and an even higher increase in labelling was noted for the hippocampal proteins was more marked (49%), and an even higher increase in labelling was noted for the hippocampal lipids (63%). The second brain region under investigation, striatum plus thalamus, showed no MGO-induced alterations in labelling. The findings are discussed in the light of the working hypothesis of the functional role of macromolecular changes occurring mainly in the hippocampus during memory formation.

Acetylglucosamine↗
PubMed1989

Influence of dopamine receptor agonists and antagonists on calmodulin translocation in different brain regions.

Acute and chronic experiments were performed to study the effects of intraperitoneally administered dopamine receptor agonists and antagonists on the translocation of cytosolic and membrane-bound calmodulin in the striatum and hippocampus of the rat brain. Single doses of apomorphine and a low-dose amphetamine (1.25 mg/kg) resulted in a translocation of calmodulin, as measured by a decrease in membrane-bound and increase in cytosolic calmodulin in the striatum, whereas bromocryptine was ineffective. Amphetamine exerted a similar effect in the hippocampus and striatum. However, a high-dose amphetamine (5 mg/kg) had an opposite effect on translocation, in that there was an increase in membrane-bound calmodulin. Chronically applied amphetamine (5 mg/kg) and haloperidol (1 mg/kg), i.e. under conditions of dopamine receptor supersensitivity, tended to decrease cytosolic calmodulin in the striatum and hippocampus, and to increase membrane-bound calmodulin. The findings and, especially, the chronic effects of haloperidol and the high dose of amphetamine are interpreted in the light of the current concept which suggests that transmitters and intraneuronal signalling systems converge, thereby influencing the more complex processes of neuronal plasticity, rather than receptor sensitivity only.

Amphetamine↗
PubMed1989

[In vitro cytotoxicity of melanoidins isolated from cooked meat and fish samples].

A study has been undertaken to investigate the biological activity of melanoidins isolated from meat samples baked according to Kuntscheva (electro-baking oven, 200-300 degrees C, 60-210 min) and from semi-finished meat products baked in swimming fat (200 degrees C, 3 X 50 min, repeated use of the oil) as well as from semi-finished fish products (190 degrees C, 60 min). A weak toxicity of the melanoidins formed within a longer thermal treatment, but no mutagenic effect was stated. The cytotoxic alterations showed no specific character.

Animals↗
PubMed1989

Effects of intraventricularly applied gangliosides and N-acetylneuraminic acid on acquisition and retention performance of a brightness discrimination task in rats.

The effects of intraventricularly applied gangliosides (about 90 to 120 nmoles/10 microliters) and N-acetylneuraminic acid (800 nmoles/10 microliters) on acquisition and retention of a brightness discrimination task were studied in rats. Single injection of GT1b and N-acetylneuraminic acid improved the retention performance. GM1 showed an enhancing effect on both acquisition and retention, while GD1a and GD1b exerted no influence on the behavioral parameters tested. The findings presented show how memory may be improved by exogenous application of substances commonly occurring in the mammalian body.

Animals↗
PubMed1989

Effects of intraperitoneally applied D-galactosamine on uridine and cytidine plasma content and brain activity of uridine kinase in the rat.

As determined by the HPLC technique, injection of 1.85 mmoles/kg D-galactosamine caused strong alterations in the plasma level of cytidime. Thus, 2 h and 4 h after application of the amino sugar only 54% and 61%, respectively, of the normal values were measured, while an increase to 135% of controls was observed 24 h later. In contrast, intraperitoneal application of D-galactosamine had no influence on the plasma level of uridine. The activity of the enzyme, uridine kinase, in the hippocampal area of the rat brain was increased 2 h and 4 h after D-galactosamine treatment. The results are discussed in the light of behavioural findings in which intraperitoneally applied D-galactosamine at this dosage improves the retention performance of an acquired behaviour in the rat.

Animals↗
PubMed1989

[Exchangeable system synthetics-rider at the bridge-joint prosthetics].

In order to improve the prosthetic supply, a clam-on system for bar-joint-mandibular dentures has been developed. When replacing clamp No. 1 by clamp No. 2 both the vertical translation and the frontal rotation of the prosthesis are ensured over a longer time of function. Placing at disposal ready-made plastic bar-joint elements facilitates the clinic and the laboratory technology for making the bar-joint-mandibular denture.

Denture Design↗
PubMed1988

Alterations in calmodulin and S-100 protein content of hippocampal slices during long-term potentiation.

The content of calmodulin and S-100 protein in fractions of rat hippocampal slices was assayed by solid phase radioimmunology and radial immunodiffusion, respectively. One hour after tetanization (electrical stimulation of area dentata granular cells and recording from CA3 pyramids) an inverse translocation of these Ca++-binding proteins was observed: an increase in the calmodulin content in the water-soluble and a decrease in the Lubrol-soluble fractions, while an increase in S-100 protein in the Triton-soluble and a decrease in the water-soluble fractions occurred. The results are suggestive of a regulatory function of these proteins in events during repetitive stimulation of a synaptic input. The calmodulin increase in the cytosolic compartment may reflect the involvement of Ca++-calmodulin dependent intraneuronal metabolic processes underlying the induction and/or temporary maintenance of neuronal functional changes occurring after repeated or intense synaptic activity. The elevated S-100 protein level in the membrane compartment might be interpreted in terms of functionally induced redistribution in that neuronal cells are provided with additional amounts of S-100 protein originating from the surrounding glial cells which store large amounts of soluble S-100 protein.

Animals↗