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Biomedical subjects

R Marín

Publications and source records attributed to R Marín.

At least 55 records · Page 3Linked to original sources
PubMed1994

Phosphate from the phosphointermediate (EP) of the human red blood cell Na/K pump is coeffluxed with Na, in the absence of external K.

This study is concerned with Na/K pump-mediated phosphate efflux that occurs during uncoupled Na efflux in human red blood cells. Uncoupled Na efflux is known to be a ouabain-sensitive mode of the Na/K pump that occurs in the absence of external Nao and Ko. Because this efflux (measured with 22Na) is also inhibited by 5 mM Nao, the efflux can be separated into a Nao-sensitive and a Nao-insensitive component. Previous work established that the Nao-sensitive efflux is actually comprised of an electroneutral coefflux of Na with cellular anions, such as SO4 (as 35SO4). The present work focuses on the Nao-insensitive component in which the principal finding is that orthophosphate (P(i)) is coeffluxed with Na in a ouabain-sensitive manner. This P(i) efflux can be seen to occur, in the absence of Ko, in both DIDS-treated intact cells and resealed red cell ghosts. This efflux of P(i) was shown to be derived directly from the pump's substrate, ATP, by the use of resealed ghosts made to contain both ATP and P(i) in which either the ATP or the P(i) were labeled with, respectively, [gamma-32P]ATP or [32P]H3PO4. (These resealed ghosts also contained Na, Mg, P(i), SO4, Ap5A, as well as an arginine kinase/creatine kinase nucleotide regenerating system for the control of ATP and ADP concentrations, and were suspended usually in (NMG)2SO4 at pH 7.4.) It was found that 32P was only coeffluxed with Na when the 32P was contained in [gamma-32P]ATP and not in [32P]H3PO4. This result implies that the 32P that is released comes from ATP via the pump's phosphointermediate (EP) without commingling with the cellular pool of P(i). Ko (as K2SO4) inhibits this 32P efflux as well as the Nao-sensitive 35SO4 efflux, with a K0.5 of 0.3-0.4 mM. The K0.5 for inhibition of P(i) efflux by Ko is not influenced by Nao, nor can Nao act as a congenor for Ko in any of the flux reactions involving Ko. The stoichiometry of Na to SO4 and Na to P(i) efflux is approximately 2:1 under circumstances where the stoichiometry of Na effluxed to ATP utilized is 3:1. From these and other results reported, it is suggested that there are two types of uncoupled Na efflux that differ from each other on the basis of their sensitivity to Nao, the source (cellular vs substrate) and kind of anion (SO4 vs P(i)) transported.(ABSTRACT TRUNCATED AT 400 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

ADP+orthophosphate (P(i)) stimulates an Na/K pump-mediated coefflux of P(i) and Na in human red blood cell ghosts.

The Na/K pump in human red blood cells that normally exchanges 3 Nai for 2 Ko is known to continue to transport Na in a ouabain-sensitive and ATP-dependent manner when the medium is made free of both Nao and Ko. Although this Na efflux is called "uncoupled" because of removal of ions to exchange with, the efflux has been shown to be comprised of a coefflux with cellular anions. The work described in this paper presents a new mode of operation of uncoupled Na efflux. This new mode not only depends upon the combined presence of ADP and intracellular orthophosphate (P(i))i but the Na efflux that is stimulated to occur is coeffluxed with (P(i))i. These studies were carried out with DIDS-treated resealed red cell ghosts, suspended in buffered (NMG)2SO4, that were made to contain, in addition to other constituents, varying concentrations of ADP and P(i) together with Na2 SO4, MgSO4 and hexokinase. While neither ADP nor P(i) was effective alone, ouabain-sensitive uncoupled Na efflux, (measured with 22Na) could be activated by [ADP+P(i)] where the K0.5 for ADP in the presence of 10 mmol (P(i))i/liter ghosts was 100-200 mumol/liter ghosts and the K0.5 for (P(i))i, in the presence of 500 mumol ADP/liter ghosts was 3-4 mmol/liter ghosts. [ADP+P(i)] activation of this Na efflux could be inhibited by as little as 2 mumol ATP/liter ghosts but the inhibition could be relieved by the addition of 50 mM glucose, given entrapped hexokinase. While ouabain-sensitive Na efflux was found to be coeffluxed with P(i) (measured with entrapped [32P]H3PO4), this was not so for SO4 (measured with 35SO4). The stoichiometry of Na to P(i) efflux was found to be approximately 2 to 1. Na efflux as well as (P(i))i efflux were both inhibited by 10 mM Nao (K0.5 approximately equal to 4 mM). But, whereas 20 mM Ko (K0.5 approximately equal to 6 mM) inhibited the efflux of (P(i))i, as would be expected from previous work, Na efflux was actually increased. When Ko influx was measured in this situation there was a 1 for 1 exchange of Nai for Ko, that is, of course, downhill with respect to the gradient of each ion. Surprisingly AsO4 was unable to replace P(i) for activation of Na efflux but Na efflux could be inhibited by vanadate and oligomycin. In terms of mechanism, it is likely that ADP acts to promote the formation of the phosphoenzyme (EP) by (P(i))i that would otherwise be inhibited by Nai.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate↗
PubMed1993

[Modulation of Na pump in proximal kidney tubules cells of the rat].

The present paper shows evidence indicating that one of the active mechanisms of sodium extrusion shown to be present in basolateral plasma membranes of the proximal tubular cells of mammalian kidney, the Na-pump (which extrudes sodium from the cells accompanied by chloride and water), is modulated in its activity by the cell volume. An increase of the cell volume, produces a concomitant increase of the activity of the Na-pump. On the other hand, the activity of the Na, K-pump, which extrudes sodium from the cells in exchange for potassium, is totally independent of the cell volume. The modulating effect of the cell volume on the activity of the Na-pump, can be either demonstrated under "in vitro" or "in vivo" conditions.

Animals↗
PubMed1993

[Lipid peroxidation and ATPase activities].

In the present paper we summarize the theoretical aspects of the process of lipid peroxidation of the plasma membranes from cells of animal tissues. Also, we review the activity of plasma membrane ATPases, i.e., The Na,K-, Na- and Ca-ATPases, and how this modulation could play a role in some diseases.

Adenosine Triphosphatases↗
PubMed1993

[Cardiovascular risk factors in peripheral arterial disease. A study of 403 cases].

We studied the prevalence of risk factors and related cardiovascular complications in 403 patients with periferal arterial disease (PAD) arising from atherosclerosis. The control group was made up of 126 patients of the same age and sex and without PAD. The average age was 66.9 +/- 12 years, and the percentage of men was 80%. Among the male subjects, smoking, the presence of diabetes, total cholesterol count, and age were the prevalent risk factors, even after logistic regression analysis. Among women, only smoking and diabetes showed significant differences. Among both sexes, the prevalence of arterial hypertension was similar to that of the controls. Greater prevalence of related cardiovascular complications was found only in men. We conclude that for PAD, smoking and diabetes are the most important cardiovascular risk factors, with total cholesterol level being an important additional factor in men.

Adult↗
PubMed1993

A modular knowledge base for the follow-up of clinical protocols.

From the knowledge engineering point of view, the observation of patients subjected to clinical protocols of therapy constitutes a domain characterized by the existence of strongly structured knowledge. We have approached the problem from the perspective of a homogeneous and modular knowledge representation theory, based on the concept of Generalized Magnitude. This concept arises from identifying and collecting all possible facts of a domain established a priori, and being inspired by the concept of physical magnitudes. The Generalized Magnitudes scheme includes temporal extensions necessary to solve a medical problem for which exists a therapy and a follow-up plan with temporal specifications, and also facilitates the creation of advisory expert systems.

Drug Therapy, Computer-Assisted↗
PubMed1992

Partial characterization of the inhibitory effect of lipid peroxidation on the ouabain-insensitive Na-ATPase of rat kidney cortex plasma membranes.

The present work evaluates the effect of lipid peroxidation on the ouabain-insensitive Na-ATPase of basolateral plasma membranes from rat kidney proximal tubular cells as an indirect way to study the lipid dependence of this enzyme. An inverse relationship between lipid peroxidation and Na-ATPase activity was found. This effect was due neither to a change in the optimal Km of the system for Na+ nor for the substrate Mg:ATP, nor the optimal pH value of the medium. The optimal temperature value, however, was shifted toward a higher value. There was also an increase of the apparent energy of activation in the region of temperatures above the transition point (20 degrees C) with increase in lipid peroxidation. Peroxidized membranes incubated with phosphatidylcholine from soybean restored their Na-ATPase activity. On the other hand, the Na-ATPase activity was sensitive to oleoly lysophosphatidylcholine. These results suggest that lipid peroxidation might be affecting the Na-ATPase activity through either an increase of peroxidized phospholipids, which might change the membrane fluidity of the lipid microenvironment of the ATPase molecules, or through a direct effect of lysophospholipids released during the lipid peroxidation.

Adenosine Triphosphatases↗
PubMed1991

Ouabain-insensitive Na-ATPase activity in homogenates from different animal tissues.

1. Two Na(+)-stimulated ATPase activities were determined in gill homogenates from squid, shrimp and teleost fish; in kidney slice homogenates from teleost fish, bullfrog, toad, iguana, chicken, duck, rat, pig and cow, as well as in homogenates from rat small intestinal cells, brain cortex and liver slices. The two Na(+)-stimulated ATPase activities, the Na- and the Na,K-ATPase, showed a different behavior toward K+ and ouabain. 2. The ouabain-insensitive, K(+)-independent, Na-ATPase activity for all the studied homogenates was completely inhibited by 2 mM furosemide. 3. An increase in cell volume of the kidney, brain cortex and liver slice preparations, as well as of the rat small intestinal cells, produced a concomitant increase of the ouabain-insensitive Na-ATPase.

Adenosine Triphosphatases↗
PubMed1991

Na(+)-ATPase activity, cell ion and water contents of kidney cortex slices from rats on a high Na+ diet.

Rats chronically fed for 15 months with an isotonic NaCl solution show a volume increase of their kidney proximal tubular cells as well as of the ouabain-insensitive, Na-stimulated ATPase activity of basolateral plasma membranes from these cells. If the experimental rats are changed to tap water after 15 months of the high sodium diet, the results are partially reversed. Thus, the cell volume and the Na-ATPase activity of their basolateral plasma membranes decrease, reaching values closer to those of control rats. There is more Na+ and Cl- in the cells from rats under the high Na(+)-diet than in the cells from control rats. On the other hand, when the rats on the high sodium diet are changed to control conditions (drinking tap water), their Na+ and Cl- contents decrease, approaching control values. It is proposed that the Na-ATPase activity is modulated "in vivo" by the cell volume.

Animals↗
PubMed1990

Effect of a high Na+ diet on cell volume and Na(+)-stimulated ATPase activities of rat kidney membranes.

Proximal tubular cells from kidneys of male rats chronically fed with an isotonic NaCl solution, show a volume increase which is dependent on the length of the treatment with NaCl, when compared with control rats. Parallel to the cell volume increase, there is an increase of the ouabain-insensitive Na-ATPase activity, whereas the ouabain-sensitive Na,K-ATPase activity remains unchanged. These results establish a clear relationship between a chronic Na-diet, kidney cell volume and Na-ATPase activity.

Adenosine Triphosphatases↗
PubMed1990

Ouabain-insensitive, Na-ATPase activity in pure suspensions of rat kidney proximal tubules.

The present work was undertaken to evaluate the distribution of the Na-ATPase activity in the different components of the rat kidney cortex. Suspensions of glomeruli, proximal and distal tubules were prepared following a collagenase digestion of outermost kidney cortex slices and a separation on a Percoll gradient. It was found that the Na-ATPase activity is higher in the fraction enriched in proximal tubules. The fraction enriched in glomeruli and in distal tubules show also a Na-ATPase activity, but it is lower.

Alkaline Phosphatase↗
PubMed1990

Increase of sulfadiazine effect against Toxoplasma gondii by using watermelon or cantaloupe seeds.

In an experimental model the anti--Toxoplasma effect of watermelon and cantaloupe seeds, together with sulfadiazine (Sd7.5 and Sd15) given by oral route, were studied. Combination of any of these seeds with the drug was able to increase the survival time and cure some tachyzoite infected mice. The effect was produced either by peeled or complete seeds and more significant results were obtained when Sd7.5 and 10(3) tachyzoite inoculum was used in the model. Some Toxoplasma oocyst infected mice were cured with the seeds alone (75% for watermelon, 37,5 or 50% for cantaloupe. Body weight variations are independent of the treatment with Sd alone or in combination with watermelon or cantaloupe seeds.

Animals↗
PubMed1989

Acute mercury vapour intoxication: report of six cases.

In a group of six workers acutely exposed to metallic mercury vapour in a confined space, one patient had acute renal and respiratory failure which required daily haemodialysis and mechanical ventilation, another had acute bilateral pneumonitis with respiratory insufficiency, and the other four had corrosive oropharyngeal mucositis with a 'flu-like syndrome. Serum and urinary mercury showed an obvious correlation with the clinical picture. After removal from the source of exposure and the institution support measures (including chelant therapy in the first two patients), all recovered without evidence of residual damage.

Acute Disease↗