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Biomedical subjects

I T Ivanov

Publications and source records attributed to I T Ivanov.

17 recordsLinked to original sources
PubMed1997

Involvement of erythrocyte membrane proteins in temperature-induced disturbances of the permeability barrier.

The ion permeability of human erythrocyte membrane displays two maxima at 48-52 degrees C and 62-67 degrees C [6, 8]. Both these independent maxima were investigated in modified membranes in order to elucidate the participation of the main types of membrane proteins. The modification protocols included the bilateral proteolytic digestion of membranes with 2-20 micrograms/ml trypsin, denaturation of the peripheral protein spectrin by exposing the membranes to 50 degrees C for 4 min or 1.5 M urea for 20 h, and preparation of the inside-out vesicles depleted of main peripheral proteins. Only the second maximum was registered in these membranes. Also, both maxima were absent in the unilamellar liposomes prepared from lipids extracted from intact membranes. The results indicate that different types of proteins were involved in the two disturbances: peripheral proteins (mainly spectrin)--in the first one and part of integral proteins-in the second. The different sensitivities of the disturbances to local anesthetics, protein thermostabilizers, n-alcohols, and detergents correlated with this conclusion. A correlation between the peak temperature of the second disturbance and the sphingomyelin content in the membrane of mammalian erythrocytes was also shown.

Alcohols↗
PubMed1993

Do changes in cell shape affect suspension conductivity?

The conductivity of a suspension containing uniformly oriented asymmetric cells depends on the shape of the cells. Whether the shape of cells with random spatial orientation also affects the conductivity of a suspension is not clear. A highly sensitive apparatus was used to register the dynamic changes in conductivity of erythrocyte suspension, upon induced morphological transformation discocytes<-->spherocytes). The results obtained with a sensitivity of up to 0.06% show that the drastic change of cell shape itself did not affect the suspension conductivity.

Electric Conductivity↗
PubMed1986

[Natural resistance and immunological reactivity in pigs weaned at various ages].

Studies were carried out on the changes in some indices of the natural resistance and immunologic response (total protein, monoamino-oxidase, and lysozyme, antibacterial, and phagocytic activity, and erythrocyte-rosette forming cells and antibody activity) of the blood of pigs that were weaned and vaccinated at 42, 28, and 18 days. The dynamic of these indices in the process of weaning and vaccination as well as in a 3-week period pointed to certain advantages with pigs weaned at more advanced age.

Aging↗
PubMed1986

[Viral and bacterial shedding in calves raised under commercial conditions].

Etiological, clinical, and epizootiological studies were carried out with newborn calves on two cow complexes of 500 animals each, raised under industrial conditions. Virologic and bacteriologic investigations of a total of 300 fecal samples taken from both calves and dams on the day of calving up to the 10th day as well as on the 20th and 30th day revealed that in 90 per cent of the cases there were rotaviruses. With calves that remained with the cows up to the 72nd hour 30 to 50 per cent of the rotaviruses were found from the second to the tenth day, and with calves that were separated from their dams immediately after calving rotaviruses were found at more advanced age too. Bacteriologically, as many as 92 strains of Escherichia coli were established as isolated from the fecal samples studied. Antigen K99 was demonstrated with 3.26 per cent of the strains. It was concluded that both with regard to the numbers of the E. coli strains isolated and to the period during which these were found the bacterium prevailed in calves that did not suck directly from their dams in the first days following calving.

Animals↗
PubMed1984

[Virological and bacteriological research on the etiology of gastroenteritis in newborn calves].

Virologic and bacteriologic studies were carried out of samples taken from calves with clinical gastroenteritis and from calves that died at the age of 2 to 10 days. A total of 199 samples were investigated of calves on 48 cattle-breeding farms. In 69 of the cases (34.2 per cent) strains of Escherichia coli were isolated, prevailing being those of the O8, O9, O15, O21, O26, O55, and O78 serogroups. Three of the strains isolated from fecal samples of clinically affected calves possessed the K99 antigen. The indirect immunosorbent method was employed, with 113 samples (56.8 per cent) identifying rotaviruses, and via the indirect immunofluorescence method in 26.6 per cent of the post mortem samples the virus of the mucosal disease was identified. On individual farms with records of the disease most often mixed infections of E. coli and rotaviruses were found. In order to organize effective prophylaxis and control complex bacteriologic and virologic investigations should be carried out with higher number of clinical and post mortem samples.

Animals↗
PubMed1983

[Prevention of colibacillosis in pigs with CA-80 polyvalent vaccine].

A live polyvalent Escherichia coli vaccine, CA-80, has been produced and adopted into practice in this country. It contains a definite amount of immunogenic agents, such as the K 88 antigen, the LT and ST toxins, the K 99 antigen, and an enteroinvasive strain. Laboratory and field experiments have shown that the immunization of sows with newborn sucking pigs leads to the drop of mortality rate from 8.48 to 1.84 per cent as well as to the rise of the average liveweight by 400 to 600 g on the 30th day following birth. Besides, the live vaccine has been shown to act protectively both against the homologous and heterologous enterotoxigenic strains of Escherichia coli and against E. coli strains with a K 99 antigen.

Animals↗
PubMed1983

[Cerebrocortical necrosis in calves, sheep and goats].

Cerebrocortical necrosis was induced through the oral application of amprolium to calves (0.250 g/kg to 1.00 g/kg) and weaned lambs and goats (1.25 g/kg) in the course of 25 to 35 days. In order to shed light on the etiology of the disease an experiment was carried out with a ration rich in carbohydrates for calves and sheep. Clinically, the disease was manifested with nervous symptoms. Biochemically, a drop of the amount of B1 in the blood serum, liver, and brain was established, along with a rise of pyruvic acid in the blood serum. Morphologically, most characteristic were the laminar necroses, the domination colliquative processes that led to deformation, and the atrophy of the folds of the brain cortex. Analogous changes were found also in the investigation of the spontaneously affected calves and lambs originating from different farms.

Animals↗
PubMed1983

[Linear discriminant analysis in the diagnosis of metabolic diseases in cows].

Studied were a total of 480 high-producing cows to determine the signs of highest information value by which the animals could be divided into groups of normal ones and such of animals presenting various metabolic disturbances: osteomalacia, ketosis, and liver dystrophia. Used were as many as 25 qualitative signs as established through the anamnesis and the clinical and paraclinical investigations. It was found that by means of 8 of these signs only (age, erythrocytes, blood sugar, vitamin A, carotene, total protein, total bilirubin in the blood serum, and pH of the urine), employing a linear discriminant function formed with them one could properly diagnose the disease condition of 83 per cent of all investigated animals. It was also established that the increase on the number of signs to form the linear discriminant function did not lead to an essential change in the preciseness of diagnosis.

Animals↗
PubMedDate not supplied

Correlation between the n-alkanols-induced sensitization of erythrocytes to hyperthermia and the fluidization of their membrane.

It was reported recently that the thermohaemolysis of mammalian erythrocytes is related to a thermo-induced membrane event of permeability barrier impairment in which the inactivation of membrane proteins is implicated. Here, the influence of different n-alkanols, methanol to octanol, on the onset temperature Tm of this barrier impairment event was compared with the changes in the dynamic properties of the membrane lipid region for human erythrocytes. The potencies of these n-alkanols to decrease Tm, to fluidize and disorder the lipid region were strongly related to their lipid solubilities. With respect to their membrane concentration, all the applied n-alkanols were roughly equipotent in decreasing Tm and in fluidizing and disordering the membrane lipids. Since Tm corresponds to the stability of erythrocytes against hyperthermia, this result indicates that the heat sensitization of these cells, induced by the n-alkanols employed, strongly correlated the fluidization (disordering) of the lipid region of their membranes.

Alcohols↗
PubMedDate not supplied

[The effect of chaotropic anions on the course of acid hemolysis in an isotonic sugar medium].

The influence of CNS-, ClO4-, NO3-, and SO4(2-) on the kinetics of acid hemolysis of erythrocytes of man, lamb, rat and rabbit was investigated. These chaotropic anions exercised strong and specific effects on the extent and time course of acid hemolysis under such conditions. In accordance with the intensity of the exercised antihemolytic effect, these anions formed a row coinciding with the Hoffmeister's row of their chaotropic action. The results demonstrate the impact of intermolecular interactions disturbance applied mainly on the cell membrane on the mechanism of acid hemolysis.

Animals↗
PubMedDate not supplied

[Aggregation of denatured membrane proteins--the initial stage of acid hemolysis].

Influence of some sulfhydryl reagents on kinetics of acid hemolysis has been investigated. The results obtained indicate that the mechanism of acid hemolysis includes aggregation of some denatured membrane integral proteins, following the intermolecular disulfide bond formation. A suggestion is made that in this hemolysis-inducing aggregation free SH-groups containing proteins only take place.

Hemolysis↗
PubMedDate not supplied

[Kinetics of acid hemolysis in an isotonic sugar medium].

The kinetics of acid hemolysis of human erythrocytes suspended in isotonic sucrose media was investigated. Three successive changes on the curve of the suspension extinction derivative were discriminated and characterized as changes due to morphological transformation, swelling and lysis of the cells. The change due to the reversible morphological transformation could develop in two opposite directions depending on some conditions. The cell swelling was apparently induced by the protonization of hemoglobin with protons entering through the cell membrane. The phases of cell swelling and lysis partly covered each other by isotonicity, but at higher tonicities they were completely separated. These results demonstrate the increased informability of the method applied under such conditions.

Culture Media↗
PubMedDate not supplied

[Use of methods of derivative conductometry and photometry for assessing the structure of a cellular suspension].

Experimental proofs for the possibility of studying the dynamical structure of rotatory moving erythrocyte suspension with the methods of derivative conductometry and photometry are presented. The amplitude of the recorded impulses was proportional to the cell concentration and the angle velocity, and strongly depended on the shape of the suspended cells.

Cell Movement↗