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Biomedical subjects

B Popov

Publications and source records attributed to B Popov.

At least 19 recordsLinked to original sources
PubMed2003

Schematic illustration of some of the mechanisms for maintenance of homeostasis in organism.

The aim of the present paper is to illustrate schematically by a non-equal arm lever system the mechanisms that maintain the homeostasis of reactive oxygen species, glucose, mean arterial pressure and electrolytes. All regulating factors that increase the values of each physiological parameter are placed on the same arm of the lever system. The regulating factors that decrease this value are placed on the other arm of the lever. In this way the two types of factors interact with one another and maintain the lever system in a dynamic equilibrium, i.e., contribute to keeping the homeostasis. Illustrating the maintenance of homeostasis by a non-equal arm lever system gives the opportunity to express the quickness, flexibility, stability and effectiveness of physiological regulations.

Animals↗
PubMed2003

Lipid peroxidation, superoxide dismutase and catalase activities in brain tumor tissues.

Free radical-mediated damages may play an important role in cancerogenesis. To investigate their relevance in the cancer process, malonyl dialdehyde (MDA) level, superoxide dismutase (SOD), and catalase (CAT) activities were determined in the normal brain tissue and brain tumor tissue. When compared with the normal brain tissue, we have detected: (i) significantly lower MDA concentration in brain tumor tissue (1.63 nmol/mg Pr vs 2.04 nmol/mg Pr; p = 0.03); (ii) SOD activity in brain tumor tissue was significantly lower (3.15 U/mg Pr vs 4.97 U/mg Pr; p = 0.0002); and (iii) CAT activity in brain tumor tissue was 106.3% higher than that in controls.

Adult↗
PubMed2000

Disruption of the actin cytoskeleton leads to inhibition of mitogen-induced cyclin E expression, Cdk2 phosphorylation, and nuclear accumulation of the retinoblastoma protein-related p107 protein.

The actin cytoskeleton has been found to be required for mitogen-stimulated cells to passage through the cell cycle checkpoint. Here we show that selective disruption of the actin cytoskeleton by dihydrocytochalasin B (H(2)CB) blocked the mitogenic effect in normal Swiss 3T3 cells, leading to cell cycle arrest at mid to late G(1) phase. Cells treated with H(2)CB remain tightly attached to the substratum and respond to mitogen-induced MAP kinase activation. Upon cytoskeleton disruption, however, growth factors fail to induce hyperphosphorylation of the retinoblastoma protein (pRb) and the pRb-related p107. While cyclin D1 induction and cdk4-associated kinase activity are not affected, induction of cyclin E expression and activation of cyclin E-cdk2 complexes are greatly inhibited in growth-stimulated cells treated with H(2)CB. The inhibition of cyclin E expression appears to be mediated at least in part at the RNA level and the inhibition of cdk2 kinase activity is also attributed to the decrease in cdk2 phosphorylation and proper subcellular localization. The expression patterns of cdk inhibitors p21 and p27 are similar in both untreated and H(2)CB-treated cells upon serum stimulation. In addition, the changes in subcellular localization of pRb and p107 appear to be linked to their phosphorylation states and disruption of normal actin structure affects nuclear migration of p107 during G(1)-to-S progression. Taken together, our results suggest that the actin cytoskeleton-dependent G(1) arrest is linked to the cyclin-cdk pathway. We hypothesize that normal actin structure may be important for proper localization of certain G(1) regulators, consequently modulating specific cyclin and kinase expression.

3T3 Cells↗
PubMed1999

Experimental data proving the presence of inhibitors of amylase activity in biliary and pancreatic juice.

Two parallel studies on albino male rats are performed. In the first study, there is a group which underwent resection of the proximal third of the small intestine. While the other group despite resection of the same segment also has a ligated common biliary and pancreatic duct. In the second study, one group of the experimental animals is only with ligated pancreatic duct and in the other group the same duct is implanted in the initial part of the ileum. On the 15th day after the surgical interventions the amylase activity and the absorption of glucose in the small intestine are studied by the method of turned sacs "in vitro". It is established that the glucose transport does not change after the four surgical interventions. However, the amylase activity increases about twice times after resection of the upper third of the small intestine and more than 4 times after resection of the same segment with simultaneous ligature of the common biliary and pancreas duct. Only at ligating the duct, the amylase activity is decreased in the jejunum and is significantly increased in the ileum, while its implantation in the initial part of the ileum does not change its activity in both studied segments of the small intestine. It is concluded that there are unknown inhibitors for the amylase activity in the biliary and pancreatic juice. The discussed issue is why they inhibit only the enzymatic compensatory processes without influencing the transport systems of the small intestine.

Amylases↗
PubMed1998

A study on the influence of basic nutrients on glucose and glycine transport in the small intestine.

INTRODUCTION: The present study addresses the questions of the onset of adaptation of the small intestine transport functions to different nutritional effects and of the extent to which the detected changes could be interpreted as adaptive. MATERIAL AND METHODS: Two independent experiments with male white rats as experimental animals were carried out. In the first experiment three groups of animals were subjected to a single administration of respectively unadulterated protein, carbohydrates and fatty food and were examined 4 hours after end of feeding. In the second experiment the same diets were applied in the course of 10 days. In both experiments the glucose and glycine absorption was studied by means of the method of accumulating preparation from the mucosa of small intestine "in vitro". RESULTS: We found that rapid readjustment responses to the nutritional effects of basic nutrients could be detected as early as 4 hours after the food intake only in the carbohydrate transport systems. In the case of amino acids adequate changes in their transport systems were registered as late as 10 days after their reception. CONCLUSIONS: The mechanisms of the rapid adaptive responses are probably not associated with any quantitative changes in the enzyme and transport capacity of the small intestine but amount to its efficient readjustment in accordance with the specific nutritional effect.

Adaptation, Physiological↗
PubMed1995

On the possibilities of existence of enzymatic hydrolysis in the membranes themselves of the intestinal epithelial cells.

On the basis of literary data is made a profound survey of the place of the final stages of the sugars and peptides hydrolysis in the small intestine. It is pointed out that whereas it has been proved for the oligosaccharides to be situated on the surface of the enterocyte membranes the discussion on the cytoplasmic and membrane localization of the most dipeptidases has not ended up yet. In our own experimental investigation it has been established that the repeated washing of the small intestine with Ringer solution reduces the maltase activity whereas the glycyl-glycin dipeptidase activity does not change. This confirms the surface membrane localization of the disaccharidase while the dipeptidase is evidently not there. Due to the low pH in the cytoplasm the glycyl-glycin-dipeptidase is considered hardly likely to be localized intracellularly. A hypothesis is advanced according to which this enzyme is structurally related to the enterocyte membranes, his catalytic centre being in the membranes themselves. In this way hydrolysis is realized in the membrane pores as well, which allows the supposition that there exists intramembrane digestion.

Animals↗
PubMed1994

Antibody raised to the short sequence from the zinc-finger domain of the EGR-1 recognizes 102 KD protein in mouse fibroblasts.

EGR (early growth response) genes represent a family of the proteins whose structure includes a zinc finger domain(s) interacting with the specific site in regulatory sequences of different genes. Using as an antigen the short sequence RSNHLTTHIR from the middle of the zinc finger domain of EGR-1 we have generated a clone of the hybridoma cells producing the monoclonal antibody (mAb) that binds to 102 kD and 58 kD proteins, but apparently does not bind EGR-1 protein. The 102 kD protein is probably made of the 58 kD subunit and another one of 44 kD. Expression of these proteins is strongly induced in serum stimulated mouse fibroblasts.

3T3 Cells↗
PubMed1991

Binding specificity of human nuclear protein interacting with the Alu-family DNA repeats.

We have demonstrated earlier that human cells contain nuclear protein interacting with conserved GC-rich sequence motifs of human Alu-family DNA repeats. One of these sequences is located in the region between elements A and B of bipartite RNA polymerase III promoter of Alu (AB-region). In this study we have used a DNase I footprinting assay with an Alu restriction subfragment covering AB-region, as well as a gel mobility shift assay with appropriate synthetic oligonucleotides to analyse in more detail the interaction of the protein with AB-region. We have also used antibodies raised against a zinc-finger peptide to examine the presence of a zinc-finger in the Alu-binding protein. The results indicate that AGG triplets may be important for high-affinity binding of the protein to DNA, and that the Alu-binding protein is a zinc-finger protein.

Amino Acid Sequence↗
PubMed1983

[Scintigraphy with 67Ga-citrate and 169Yb-citrate in the diagnosis of lung cancer].

A scintigraphic study was made of 44 lung cancer patients. At first the diagnosis was made on the basis of an x-ray finding, then it was specified with the help of radioisotope scintigraphy and fibrobronchoscopy with histological examination. 67Ga-citrate and 169Yb-citrate with the activity of 74 MBk were used i. v. for scintigraphy. The scanning was done 72 hrs. after the application of a radionuclide using the magnascanner Picker-500 (USA). In 88.3% of the cases positive scintigraphic results were confirmed histologically as a malignant lung process. A conclusion has been made that both radionuclides are suitable for tumorotropic lung scintigraphy. Owing to its potentialities they can substitute in certain cases for more traumatic roentgenobronchography that also gives radiation exposure.

Adult↗
PubMed1980

Cell wall regeneration of Canadida spec. protoplasts.

A yeast of the genus Candida which is able to grow on n-alkanes was characterized by biochemical investigations: Crabtree effect, inhibition of ammonium utilization by asparagine, changes in the concentration of polysaccharides mainly concentrated in the cell wall. The yeast was compared biochemically and electron-microscopically with its pure protoplast population, and the regeneration of the cell wall was studied. In correspondence with the asynchronously developing accumulation of glucan and manna, electron microscopical studies have first only revealed glucan fibrils. Matrix formation (mannan) occurs only in the second stage of regeneration. After a regeneration period of 9 hours, the polysaccharides in the former protoplast population reached the concentration of the period before enzymatic removal of the cell wall. A tube-like structure observed by light microscopy during the early stages of regeneration is shown electron-microscopically to consist of a fibrillar network without matrix. Between newly formed cell wall and plasma membrane, in some cells groups of large flat vesicles were found, whose fracture faces are free of particles. After protoplast formation the invaginations of the plasma membrane arrange themselves in rows one behind the other. These findings are supported by further evidence suggesting that the invaginations are structures on the basis of lipid domains.

Candida↗
PubMed1980

[Morphological studies of the small intestine in experimental operations to isolate segments from the digestive tract].

Changes in the small intestine of white rats, developing within fifteen days of experimental operation for the isolation of a segment outside the digestive tract, are investigated using light and fluorescent microscopy. The isolated segment with intact nerve and humoral connections resides in the abdominal cavity. Findings in the distal (functioning) segment reveal hypertrophy of the muscular layers of the small intestine, more intensive development of the loose connective tissue, whereas the villi are shortened and thickened and display a reduced resorptive surface. This occurs at the expense of the considerably augmented number of mucous (calicine) cells, and of the dystrophic and desquamative changes taking place in the resorptive epithelium. In the isolated (lacking function) segment normal blood supply to the submucosa, slight atrophy of the muscle layers, and decreased number of glands of Lieberkühn is observed. In the same time the small intestinal villi are elongated, having larger resorptive surface, and containing reduced number of mucous (calicine) cells, whereas their epithelium is made up of cells with profuse and succulent cytoplasm free of desquamations. The inference is reached that the changes recorded in case of retaining the isolated segment within the abdominal cavity are attributable to the reciprocal action between the two small-intestinal areas by route of the existing neurohumoral linkage. Moreover the processes tend to preserve the isolated segment at the expense of developing structural-functional derangements in the functioning area.

Animals↗
PubMed1977

[Primary idiopathic myocardiopathies].

Forty eight cases with primary idiopathic myocardiopathies were diagnosed in clinical conditions for a period of 2 years. Among the patients, being mainly young, at the age of 17-20--hypertrophic myocardiopathies predominated (44 cases), 27 of them were obstructive forms. Modern investigation methods were used in making the diagnosis of the cases, including cardiac probe with angio--and ventriculography, isotope gamma cardiographic, echocard ographic investigations as well as pharmacodynamic follow up of murmur findings with alfa beta blockers. Pseudoinfarction ECG images in young people, presence of systolic murmur of expulsion with p.m. at B. Erb and X-ray data for symmetric or asymmetric hypertrophy of the heart were the indicating sings for the diagnosis. The presence and recording of expulsion murmurs is stressed upon in making the diagnosis of those diseases which after alfa and beta blockers alter their intensity and character, the infarction-like ECG and especially the significance of echocardiography.

Adolescent↗
PubMed1977

[Effect of alcohol on glucose resorption in the small intestine of white rats].

Using the method of inverted bags according to Wiseman and Wilson, the effect of alcohol on glucose transport in the small intestine of white rats is studied. A noteworthy increase in glucose absorption is established in the group of animals receiving 2ml 50 degrees ethyl alcohol before meal over a period of one month, and in the group treated a single time in fasting conditions at analogical alcohol dose. No statistically significant difference is established between the control group of animals, and those treated with the indicated above alcohol dose under conditions of ordinary diet. The obtained results are interpreted in the light of updated concepts about the active transport of substances in the small intestine, with due consideration being given to the eventual effect exerted by ethyl alcohol on its mechanisms.

Animals↗