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Biomedical subjects

I T Ivanov

Publications and source records attributed to I T Ivanov.

At least 19 recordsLinked to original sources
PubMed2000

Influence of some DNA-alkylating drugs on thermal stability, acid and osmotic resistance of the membrane of whole human erythrocytes and their ghosts.

Human erythrocytes and their resealed ghosts were alkylated under identical conditions using three groups of alkylating antitumor agents: mustards, triazenes and chloroethyl nitrosoureas. Osmotic fragility, acid resistance and thermal stability of membranes were changed only in alkylated ghosts in proportion to the concentration of the alkylating agent. All the alkylating agents decreased acid resistance in ghosts. The clinically used drugs sarcolysine, dacarbazine and lomustine all decreased osmotic fragility and thermal stability of ghost membranes depending on their lipophilicity. DM-COOH did not decrease osmotic fragility and thermal stability of ghost membranes, while NEM increased thermal stability of membranes. The preliminary but not subsequent treatment of ghosts with DM-COOH fully abolished the alkylation-induced thermal labilization of ghost membrane proteins while NEM had a partial effect only. The present study gives direct evidence that alkylating agents, having a high therapeutic activity against malignant growth, bind covalently to proteins of cellular membranes.

Alkylating Agents↗
PubMed1999

Low pH-induced hemolysis of erythrocytes is related to the entry of the acid into cytosole and oxidative stress on cellular membranes.

HCl-induced lysis of mammalian erythrocytes, pretreated with DIDS, which is a specific inhibitor of the anion transport in their membranes, was markedly delayed. After acidification of a suspension of DIDS-inhibited cells, hemolysis was initiated by addition of a protonophore (Na-salicylate) at any moment chosen by will. These findings revealed that low-pH hemolysis depended on the rate of the transfer of acid equivalents into cytosole. Erythrocyte acid resistance was studied in a group of mammals and found to be inversely related to the rate of monovalent anion exchange in membranes which supported the above observations. In human erythrocytes, the critical level of cytosole acidification was found to be about pH 5.7 by measuring the acid equivalent absorbed by cells prior to hemolysis. HCl-induced hemolysis was also studied in human erythrocyte ghosts resealed with one-sixth of the initial hemoglobin content of cells. During the prelytic interval the ghosts suspended in isotonic NaCl/sucrose media shrunk, indicating an increase in ion permeability. The increase in prelytic permeability and hemolysis were strongly delayed in ghosts prepared from DIDS-treated cells, suggesting a uniform mechanism of lysing in cells and their ghosts. The prelytic increase in ion permeability was measured by the corresponding rate of ghost shrinkage and was found to be pH-dependent, with a high value below pH 3.4 and a very low one above pH 4.0. Compared to cells, the prelytic barrier impairment in ghosts had more mild character although it required greater concentration of cytosolic H+. While finally complete, hemolysis of cells was strongly delayed in the presence of catalase (500-1500 U/ml) and superoxide dismutase (200-600 U/ml) in hemolytic media. In conclusion, the acid-induced hemolysis could be associated with an oxidative injury of membranes, mainly triggered by the entry of acid equivalents into the cytosole.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1999

Changes in passive electric parameters of human erythrocyte membrane during hyperthermia: role of spectrin phosphorylation.

In prefixed by 1 mmol/l OsO4 human erythrocytes, the discocyte shape was preserved upon heating to temperatures which include the denaturation temperature of the main peripheral protein spectrin. Nevertheless, the suspension of fixed cells displayed threshold decrease in its capacitance and resistance at the temperature range where spectrin denaturates. The same changes were established using intact cells and their resealed ghosts. For packed cells (ghosts), the capacitance and resistance decreased about 17% (31%) and 30% (19%). These data indicate a decrease in the beta dispersion of erythrocyte membrane associated, according to a previous study (Ivanov 1997), with the heat denaturation of spectrin at 49.5 degrees C. The amplitude of the 49.5 degrees C decrease in beta dispersion was reversibly reduced in intact erythrocytes and white ghosts following reversible decrease in the phosphorylation of their membrane proteins. It was fully eliminated in ghosts following their resealing with alkaline phosphatase (0.1 mg/ml) which dephosphorylated membrane proteins. These findings are discussed in relation to similar changes found in normal and tumour tissues and cells during hyperthermia.

Adenosine Triphosphate↗
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

Spectrofluorometric and microcalorimetric study of the thermal poration relevant to the mechanism of thermohaemolysis.

This study sheds light on the structural changes in erythrocyte membrane during thermally induced poration, an event involved in thermohaemolysis. Two major membrane disturbing events can be induced during transient heating, the denaturation of spectrin and thermoporation. The first one precedes the latter but is not involved in it. Ethanol linearly reduces the onset temperature of both events but with different efficiencies. Thermoporation efficiency exceeds by 3.5 fold that of spectrin denaturation. Thus, at a specific concentration of ethanol (18% v/v), the poration occurs at 39.5 degrees C, which precedes the denaturation of spectrin by 6 degrees C. To induce and study the poration avoiding spectrin denaturation, cells were put in contact with preheated (39 degrees C) isotonic (60mM) NaCl) media containing 18% v/v ethanol and sucrose as an osmotic protectant. After 3 min heating, the porated cells were washed, their membranes isolated and studied. The control cells were processed similarly except that they were incubated at 23 degrees C, thus avoiding thermoporation. Using scanning microcalorimetry, the enthalpy and the temperature of denaturation of spectrin were found to be the same in control as well as in porated membranes which indicates similar spectrin structure in both membranes. While the enthalpy of denaturation of the anion channel was preserved, its denaturation temperature was lowered by 2.5 degrees C after poration. These results confirmed that the heat denaturation of the main membrane proteins was not needed and not involved in thermoporation and, hence, in thermohaemolysis. Analysis of the fluorescence of membrane bound ANS gave an apparent increase in the number of binding sites for ANS in membranes after poration. In relation to the control, the eximerization of pyrene in porated membranes changed, depending on the location of the probe: in the domain of free lipids it decreased by 18% but it increased by 60% in the lipid milieu proximal to membrane proteins. Likewise, the eximerization of N-(3-Pyrene) maleimide bound to membrane proteins increased by 67% after poration, which proves increased intramolecular mobility of proteins following poration. The maximal efficiency for transferring energy from tryptophans to neighbouring pyrene was determined to be 0.93 in control, which is almost the same as in intact membranes, and 0.70 in porated membranes, indicating a strong decrease in the lipid/protein contact zone. This data suggests a mild conformational change, possibly an irreversible perturbance of the transbilayer distribution of membrane proteins in porated membranes in comparison to the control and intact ones.

Calorimetry↗
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↗