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Results for “Cell Membrane Permeability”

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PubMed1980

Osmotic properties of differentiating bone marrow precursor cells: membrane permeability to non-electrolytes.

Membrane permeability to the non-electrolyte probes urea and thiourea was measured in a population of differentiating bone marrow precursor cells (Cicoria and Hempling, '80). The phenomenologic equations of Kedem and Katchalsky ('58) were applied. The population of cells, which can be separated by velocity sedimentation, was examined over the maturation range of 400 to 1,000 cubic micra. Several membrane properties were observed: 1) Solute permeability (omega RT) increased linearly as the cell volume increased, while the reflection coefficients (sigma) remained constant. 2) Membrane permeability to urea was significantly greater than to thiourea; however, their respective sigmas did not differ significantly. Solute permeability was independent of sigma at 22 degrees C. 3) In the two maturation phases observed, omega RT varied directly with the volume of osmotically active water. 4) The permeability to urea and to thiourea has provided information on the characteristics of the pathways used for water and non-electrolytes, as well as a description of the phenomenologic membrane events accompanying cellular maturation.

Animals↗
PubMed1983

Pregnancy induced hypertension: evidence for increased cell membrane permeability to sodium.

In a cross sectional study of 137 women of childbearing age (16-40) the effects of normal pregnancy, hypertensive pregnancy, and oral contraceptives on red cell electrolyte content and sodium efflux rates were examined and the results compared with values in a control group of normotensive, non-pregnant women. Efflux rate constants were significantly increased in normotensive pregnancy and in women taking oral contraceptives. This was associated with a significant increase in sodium permeability in the contraceptive group. A much larger increase in sodium permeability and efflux rate constant was seen in the hypertensive group. The results permit a hypothesis that the hormonal changes induced by pregnancy and oral contraceptives increase membrane permeability to sodium and stimulate sodium efflux. The rise in blood pressure associated with use of oral contraceptives may have a similar aetiology to that occurring in pregnancy induced hypertension.

Adolescent↗
PubMed1974

Probability density function of the red cell membrane permeability coefficient.

The distribution of a random variable is determined by the probability density functions (PDF) of all other random variables with which the variable in question is jointly distributed. If the PDF of the random variable of interest is normal, or skewed normal, then the distributions with which it is jointly distributed determine its mean and standard deviation. In the case described here (where hemolysis time of the red blood cell is a function of the permeability coefficient and geometric variables of the cell) the mean and standard deviation of the permeability coefficient and the known distributions of the geometric variables on which the hemolysis time depends determine a predicted distribution of hemolysis time. An observed distribution of the hemolysis time is obtained spectrophotometrically. By choosing the mean and standard deviation of the permeability coefficient so that the predicted PDF of the hemolysis time matches the observed PDF best by least-squares criterion, the complete distribution of the permeability coefficient is determined.

Cell Membrane↗
PubMedDate not supplied

Research on red cell membrane permeability in arterial hypertension.

Arterial hypertension, including the elucidation of hypertension pathogenic mechanisms involving elements in the composition of the blood, continues to represent a topical research area. Recent work, such as nuclear magnetic resonance studies looking into red cell permeability, illustrates the presence of modifications of red cell permeability to water (RCPW) related to the stage of arterial hypertension. The identification of a significant increase of RCPW compared to that present in the population with normal arterial pressure values can be useful both in early diagnosis and in warning about a possible predisposition for this condition. At the same time, the dynamic investigation of protonic relaxation time of both intra- and extra-erythrocytic water, the assessment of proton exchange time across the red cell and the calculation of permeability to water enable one not only to diagnose arterial hypertension but also to ascertain the evolution of the disease, its complications and the effectiveness of anti-hypertensive medication. Our studies have also proven the existence of a correlation between the values of systolic arterial pressure and red cell permeability to water. The curve describing the interdependence of the two values has the shape of a bell, in the case of males. The peak of the curve is reached for a systolic pressure of 160 mmHg and gets below the values of the control group in the case of systolic pressures above 200 mmHg. The RCPW test can also be considered a valuable indicator in evaluating the risk of stroke in hypertensive patients. In the chronic therapy of arterial hypertension with various types of anti-hypertensive drugs, one can note differences in the RCPW values related to the effectiveness of the respective medication, to the clinical form and stage of the disease, the sex of the patient as well as to the existence of cerebro-vascular complications.

Adrenergic alpha-Agonists↗
PubMed2003

[Laser therapy of duodenal ulcers: effect on indices of microcirculation, cell membrane permeability and homeostasis of trace elements].

AIM: To study the efficiency of including laser therapy (LT) in the duodenal ulcer (DU) treatment complex. MATERIALS, METHODS: 123 patients with duodenal ulcer were examined. LT was included in the therapy complex for 89 of them. 34 patients underwent only traditional drug therapy and formed a control group. LT was carried out by 2 ways: intracavitary--by ulcer defect irradiation with the light guide through the gastroscope biopsy canal and helium-neon laser (HNL), and noninvasive--through the front abdominal wall in the corresponding areas, which was made by infrared laser (IRL). RESULTS: The comparison of two groups established that by including LT in the therapy complex for DU patients the dynamics of clinical and laboratorial data is essential better than during traditional drug treatment (TMT). CONCLUSION: It was established that the inclusion of LT in the duodenal ulcer treatment complex has a positive impact on the course of the disease. This impact was displayed as faster reverse development of clinical symptoms, positive laboratory and instrumental data dynamics, blood serum microelements content normalization, membrane permeability increase by indicators of Na-Li counter-transport in the erythrocytes membrane and microcirculation improvement, mainly in the intravascular section.

Adolescent↗
PubMed1990

Lanthanum probing of cell membrane permeability in the rat heart: pathological versus artefactual alterations.

The influence of fixation on membrane permeability has been examined in the isolated rat heart using lanthanum as a permeability probe. Normal and ischaemic hearts were probed at various stages during a conventional fixation programme with either ionic or colloidal lanthanum and compared with lanthanum saline administered prior to fixation. Fixation of the myocardium coincident with or followed by lanthanum probing resulted in an influx of the probe into most myocytes in normal tissue. Alterations in permeability after ischaemic episodes could not be distinguished from the artefact. However, lanthanum saline prior to fixation showed exclusion of the probe from normal tissue, while the increased permeability demonstrated after ischaemia was associated with declining myocardial performance during subsequent reperfusion. These results illustrate the need for caution in the application and evaluation of methods determining permeability in fixed tissue. Probes of differing size and charge permeated fixed tissue to varying degrees thereby implicating the formation of specific lesions during chemical fixation.

Animals↗
PubMed1980

Characterization of the concanavalin A-induced increase in lymphocyte cell membrane permeability by furosemide.

The effect of ConA on passive 42K+ fluxes in human lymphocytes was analysed by treatment with furosemide and ouabain. Furosemide has no effect on net K+ transport and pump flux. The component of passive efflux of 42K+ which depends on K+-K+ exchange is inhibited by furosemide; its mechanism is discussed in detail. The 42K+ uptake in lymphocytes consists of 1. an ouabain-sensitive pump influx, 2. an ouabain-insensitive leak influx and 3. a furosemide-sensitive K+-K+-exchange. Only the first two components of 42K+ uptake are stimulated by ConA.

Biological Transport↗