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Biomedical subjects

O Popescu

Publications and source records attributed to O Popescu.

At least 55 records · Page 3Linked to original sources
PubMed1983

Effect of chlorpromazine on proteins in human erythrocyte membranes as inferred from spin labeling and biochemical analyses.

ESR spectra of erythrocyte membranes labeled with a maleimide spin label (MSL) show two types of label environment: a weakly immobilized component and a strongly immobilized component. Chlorpromazine (CPZ) markedly altered the spectra: at pH 8.0, 3 mM CPZ reduced the amplitude of the spectrum by 40%, and the weakly immobilized component was almost completely removed. In order to clarify the mechanisms of these spectral changes the protein release from erythrocyte membranes induced by CPZ has been followed. CPZ had a weak solubilizing effect on erythrocyte membranes: less than 1% of the membrane protein was released, mainly Band 6. By comparison with the protein release induced by low-salt treatment it was found that the "detergent-like" property of CPZ cannot explain the alterations in the ESR spectra. The nature of the spectral changes induced by CPZ was different from that of changes induced by lowering the pH to 4.5; correlated with other data this shows that changes in organization or conformation of membrane protein cannot explain the CPZ-induced alterations in the ESR spectra. These spectral changes appeared to be due to the reduction by CPZ of the nitroxide free radical. This was documented by the marked reduction of spin concentration of the labeled ghosts in the presence of CPZ resulting in a decrease in amplitude of the ESR spectrum of MSL-labeled erythrocyte ghosts induced by CPZ. The reduction by CPZ of the nitroxide free radical was compared with that induced by ascorbate. It was found that CPZ preferentially reduces the mobile component of the ESR spectrum of MSL-labeled ghosts. The action of CPZ in reducing free radicals may have consequences for patients receiving long-term treatment with phenothiazine derivatives.

Blood Proteins↗
PubMed1981

Effects of temperature and pH on the water exchange through erythrocyte membranes: nuclear magnetic resonance studies.

The temperature and pH dependence of water exchange has been studied on isolated erythrocytes suspended in isotonic buffered solutions. At pH 7.4 a break in the Arrhenius plot of water exchange time at around 26 degrees C was found. The mean value of the apparent activation energy of the water exchange time at temperatures higher than that of the discontinuity was 5.7 kcal/mole (+/- 0.4); at lower temperatures the values of the apparent activation energy were below 1.4 kcal/mole. The pH dependence of water exchange time of isolated erythrocytes revealed a marked increase of the water exchange time values in the acid range of pH; a much smaller variation of the same parameter occurs between pH 7.0 and 8.0. These finding could be correlated with other processes involving erythrocyte membranes that showed similar pH and temperature dependence and were considered to indicate state transitions in the membranes. It is suggested that the temperature and pH effects on water diffusion indicate that conformational changes and cooperative effects are implicated in the mechanism of this transport process.

Adult↗
PubMed1976

Effect of intravenous L-isoleucine infusion upon concentration of free isoleucine in milk.

The growth of Streptococcus agalactiae in milk is inhibited by elevated free isoleucine. Free amino acid concentrations in both plasma and milk from three lactating dairy cows were studied after intravenous infusions of L-isoleucine at 62, 300, 380, and 840 mumol/kg of body weight. Free isoleucine was lower in milk than in plasma. The concentration of free isoleucine in plasma increased after infusions of isoleucine at the three higher amounts. The highest concentration of free isoleucine in milk measured was 1.5 mumol/100 ml of skin milk. This was observed after infusion of isoleucine for 12 h at 380 mumol/kg of body weight. Free isoleucine in both plasma and milk dropped to the preinfusion concentrations a short time after the isoleucine infusions were stopped. When relatively large quantities of isoleucine were infused into the blood of cows, free isoleucine in blood increased as much as twofold. The source of free isoleucine in milk appeared to be free isoleucine in plasma, but isoleucine in milk only reached concentrations that would give about 50% of the growth inhibition of S. agalactiae obtainable with isoleucine in vitro. It would be difficult to elevate free isoleucine in milk by dietary manipulation sufficiently to inhibit S. agalactiae.

Amino Acids↗
PubMedDate not supplied

A novel class of embryonic cell adhesion glycan epitopes is expressed in human colon carcinomas.

A new class of acidic glycans isolated from marine sponges and sea urchin embryos was shown to mediate cell adhesion via carbohydrate-carbohydrate interactions. Cell aggregation blocking monoclonal antibodies (Block 1 and Block 2 mAbs) directed against these polysaccharides localized functional epitopes in embryonic sea urchin gut. Immunofluorescence light microscopy of human colon carcinomas and healthy colon samples with Block 1 and Block 2 mAbs established that the carbohydrate structures similar to the invertebrate acidic glycan adhesion molecules are also expressed in humans. The Block 1 mAb labeled basal and apical lamina of tumor cells, whereas the Block 2 bound exclusively to the apical part of the epithelium. In normal tissue whole goblet cell membrane was stained with both antibodies indicating that transformation leads to spatial rearrangement of glycan antigens. Acidic glycans from human colon carcinomas and normal colon were isolated after delipidation, and complete pronase and DNase digestion, by gel filtration and adsorption to anion exchange membranes. Immunodot assay with Block 1 and Block 2 mAbs revealed that tumor cells have elevated expression of both carbohydrate structures. These results suggest that the acidic glycan adhesion molecules, originally found in sponges and sea urchin embryos, may represent a new class of carbohydrate carcino-embryonal antigens involved in cellular interactions associated with morphogenesis, metastasis and renewal of adult tissue.

Animals↗
PubMedDate not supplied

Decreased water permeability of erythrocyte membranes in patients with Duchenne muscular dystrophy.

The water proton relaxation times of erythrocytes (T'2a) from 15 Duchenne muscular dystrophy (DMD) patients and age-matched controls have been determined by a pulse nuclear magnetic resonance technique. Statistically significant higher values of T'2a were noted for the DMD erythrocytes, both in the presence or absence of p-chloromercuribenzene sulfonate, a potent inhibitor of water diffusion through erythrocyte membrane. As the values of T'2a are inversely related to the water permeability, the results indicate a decreased permeability of erythrocyte membrane in DMD. The findings are discussed in relation to the molecular mechanisms of water diffusion across erythrocyte membrane and in regard to the general problem of membrane abnormalities in DMD.

Adolescent↗
PubMedDate not supplied

On measuring the diffusional water permeability of human red blood cells and ghosts by nuclear magnetic resonance.

The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes and ghosts by a doping nuclear magnetic resonance technique. In contrast to all previous investigations, systematic measurements were performed on blood samples obtained from a large group of donors. The mean values of P ranged from 2.2 X 10(-3) cm.s-1 at 5 degrees C to 8.1 X 10(-3) cm.s-1 at 42 degrees C. The reasons for some of the discrepancies in the permeability coefficients reported by various authors were found. In order to estimate the basal permeability, the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzenesulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 1.3 X 10(-3) cm.s-1 at 20 degrees C, 1.6 X 10(-3) cm.s-1 at 25 degrees C, 1.9 X 10(-3) cm.s-1 at 30 degrees C and 3.2 X 10(-3) cm.s-1 at 37 degrees C. The results reported here represent the largest series of determinations of water diffusional permeability of human red blood cells (without or with exposure to mercurials) available in the literature, and consequently the best estimates of the characteristics of this transport process. The values of P can be taken as references for the studies of water permeability in various cells or in pathological conditions.

4-Chloromercuribenzenesulfonate↗
PubMedDate not supplied

Quantitative and qualitative approach of glycan-glycan interactions in marine sponges.

Cell recognition and adhesion involving many kinds of cell surface molecules operate via homotypic and/or heterotypic protein-protein and protein-carbohydrate binding. Our investigations in marine sponges have provided direct evidence for a novel molecular mechanism of multivalent glycan-glycan binding related to cellular interactions. Biochemical characterization of purified proteoglycans revealed the presence of specific acidic glycans, different from classical glycosaminoglycans. Such acidic glycans of high molecular weight, containing fucose, glucuronic or galacturonic acids, and pyruvate and sulfate groups may represent a new class of primordial proteoglycans, named by us glyconectins. The thermodynamic and kinetic approaches of biological macromolecule interactions do not provide a direct measurement of the intermolecular binding forces that are fundamental for the function of the ligand-receptor association. Using the atomic force microscopy (AFM), we provided the first quantitative evaluation of the binding strength between cell adhesion proteoglycans. Measurement of binding forces intrinsic to cell adhesion glyconectin proteoglycans (AGPs) is necessary to assess their contribution to the maintenance of the anatomical integrity of multicellular organisms. (i) As a model, we selected the cell AGP isolated from the marine sponge Microciona prolifera; it mediates in vivo cell recognition and aggregation via homotypic, species-specific, multivalent, and calcium ion-dependent glycan-glycan interactions. (ii) Under physiological conditions, a large cohesive force theoretically able to hold the weight of approximately 1600 cells was measured. (iii) The C-2 autocomplementarity model for AGP-AGP interactions; and (iv) the requirement of the calcium ionic bridges suggest also that the self-recognition and multivalency of glycan-glycan interactions are essential for cell adhesion. (v) The evolution of glyconectin-like proteoglycan molecules may have been a fundamental prerequisite for the emergence of the first multicellular organisms. Glycan-glycan interactions may thus provide a new paradigm for molecular self-recognition.

Animals↗
PubMedDate not supplied

Serum lipid picture of rabbits fed on silicate-supplemented atherogenic diet.

Silicon is recognised as a protective trace element in atherosclerosis by epidemiologic and biochemical studies. The goal of the present work was the evaluation of the antiatheromatous effect of the natrium silicate in an experimental trial on 30 rabbits given a standard diet (control), an atherogenic diet (L1 lot) and a natrium silicate-supplemented atherogenic diet (L2 lot), by comparing the variation of the lipid pictures between each of the experimental lots and control. Levels of total lipids, cholesterol, triglycerides (TG), free fatty acids (FFA) and phospholipids indicated that the natrium silicate supplemented to the atherogenic diet minimised the lipid metabolism unbalance by keeping constant the level of FFA and TG in rabbits.

Animals↗
PubMedDate not supplied

A dynamic study of vanilmandelic acid elimination in the urine of divers in a dive at 21 ATA in saturation with a helium-oxygen respiratory mixture.

The purpose of this paper is a first assessment of the effect of stress agents specific for hyperbarism in professional divers. We selected the elimination of vanilmandelic acid (VMA) in the urine as an indicator. We studied four professional divers in a dive at 21 ATA. In order to assess the strain-induced by every distinct moment of the saturation profile we took samples of urine and determined VMA at four-hour intervals, before and after the distinct moment of saturation. The values found in the same four divers at the surface were used as "controls". VMA dosing in the urine proves to be a sensitive indicator for the assessment of stress and adaptive reactions during saturation.

Administration, Inhalation↗
PubMedDate not supplied

Clinical management of bronchial asthma with inhaled high-dose beclomethasone dipropionate (Beclomet 250--Orion).

The efficacy of inhaled high-dose beclomethasone dipropionate (BDP) in intrinsic and cortico-dependent asthma was studied in 12 asthmatics (3 males and 9 females), average age 39 years (range 17-62 years), with a mean duration of the disease of 9 years (range 2-20 years). The patients were instructed to use one actuation (250 micrograms), three times daily or two actuations three times daily in severe cases in which dyspnoea persisted during the intake of oral corticosteroids. The results during the 6 month follow-up period were: Clinical: dyspnoea, wheeze and cough disappeared or diminished, oral administration of corticosteroids stopped or the daily dose was reduced, the intake of beta-agonists decreased; Functional: after 2-4 weeks, in almost all cases, the base line values of FEV 1.0 and Raw were normal and hyperinflation significantly diminished after the first month of BDP therapy. Clinical and functional improvement were maintained during the follow-up period; no side-effects were revealed.

Administration, Inhalation↗
PubMedDate not supplied

The role of the cerebrospinal fluid during embryonic development. A biochemical study.

The total protein content and the protein fractions were determined in the blood serum and the cerebrospinal fluid (CSF) of chick embryos and foetuses between the 4th and 20th day of incubation and of 2-day-old chickens (by Lowry's method and by polyacrylamide gel electrophoresis respectively). The main results were the following: The total protein content of the CSF increased from 1.8 mg/ml on day 4 to 3.1 mg/ml on day 10. After a slight decrease to 2.6 mg/ml on day 12 no further changes were detected. In the blood serum the total protein content was 4.3 mg/ml on day 4 and 4.7 mg/ml on day 9. Beginning with day 10 it increased constantly to 23.2 mg/ml on day 2 after hatching (daily rate 1-1.2 mg/ml). It results that the "protein barrier" between blood and CSF begins to function after 10-12 days of incubation. Of the protein fractions determined, the light fraction I in the CSF represents 50 per cent of the similar blood serum fraction (on day 10). As to the heavy fractions XI-XIV, their concentration in the CSF represents, beginning with day 10, 51 per cent of the similar blood serum fraction (until the end of the period investigated). It results that the "protein barrier" has an active, selective character. Some comparative aspects with literature data are discussed.

Animals↗