PubMed Health⌕ Search

Biomedical subjects

R Marín

Publications and source records attributed to R Marín.

At least 19 recordsLinked to original sources
PubMed1998

Preeclampsia, lipid peroxidation, and calcium adenosine triphosphatase activity of red blood cell ghosts.

OBJECTIVE: We evaluated the effect of lipid peroxidation on the calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive pregnant women and compared it with the adenosine triphosphatase activity and lipid peroxidation in preeclampsia. STUDY DESIGN: Ten nulliparous normotensive and 10 nulliparous preeclamptic pregnant women (38 to 39 weeks of gestation) were used as blood donors. Preeclampsia was diagnosed on the basis of blood pressure (>140/90 mm Hg) and proteinuria (>0.5 gm of urinary protein per day). Red blood cell ghosts were prepared for both groups and used for calcium adenosine triphosphatase activity and lipid peroxidation determinations. Control ghosts (normotensive) were irradiated with ultraviolet light for different lengths of time. RESULTS: Calcium adenosine triphosphatase activity of red blood cell ghosts from normotensive women is sensitive to lipid peroxidation. The lipid peroxidation of red blood cell ghosts from preeclamptic women is higher than that from normotensive women. CONCLUSION: The diminution of the calcium adenosine triphosphatase activity with preeclampsia could be explained by the sensitivity of this adenosine triphosphatase to lipid peroxidation.

Adult↗
PubMed1998

Ouabain-insensitive Na(+)-ATPase activity of Malpighian tubules from Rhodnius prolixus.

In the present paper, we show the existence of a furosemide-sensitive Na(+)-stimulated, Mg(2+)-dependent ATPase activity in cell lysates of Malpighian tubular cells from Rhodnius prolixus, which could be the biochemical expression of the Na(+)-pump. The main characteristics of this activity are: (1) K0.5 for Na+ = 1.49 +/- 0.18 mM, (2) Vmax = 2.8 +/- 0.1 nmol inorganic orthophosphate (Pi).mg prot-1.min-1, (3) it is fully abolished by 2 mM furosemide, (4)it is insensitive to ouabain concentrations up to 10(-2) M, (5) it is sensitive to the presence of vanadate in the incubation medium indicating it to be a P-type ATPase, and (6) it is stimulated by nanomolar concentrations of Ca2+ in the incubation medium.

Adenosine Triphosphatases↗
PubMed1998

[Hepatocellular carcinoma associated to porphyria cutanea tarda and hepatitis C virus infection without cirrhosis].

The molecular basis of porphyria cutanea tarda is defective activity of hepatic uroporphyrinogen decarboxylase. A common characteristic is liver dysfunction than goes from cirrhosis to hepatocellular carcinoma. A high prevalence of hepatitis C virus markers has been demonstrated. We study a patient with PCT and hepatitis C virus markers that finally develops to hepatocellular carcinoma without previous cirrhosis. Previous studies with association of PCT and hepatitis C virus markers, have found liver diseases ranging from cirrhosis to hepatocellular carcinoma. The importance of this study is the absence of cirrhosis.

Carcinoma, Hepatocellular↗
PubMed1998

[Clock drawing test: qualitative and quantitative evaluation methods].

INTRODUCTION: The interest about the Clock Drawing Test (CDT) is justified because the importance of praxic disorders and especially the constructive apraxias in demented patients. Generally, this kind of deficits or intellectual losses has been less studied than aphasisas and agnosias. Nevertheless, praxias are usually affected in demential processes, even in initial stages. OBJECTIVE: We try to determine if the CDT can be useful as an assessment tool for dementia. We have used two assessment systems of the clock drawing in order to select an useful and reliable method of correction. PATIENTS AND METHODS: The sample is made up of 35 subjects older than 60 years, they were administered the Mini Cognitive Examination (MCE) and the CDT. Patients with previous diagnosis of dementia, others with physical pathology without neurological affectation and, finally, subjects without any kind of pathology were included in order to get a wide rank of punctuations. We carried out a reliability analysis between two raters and the discriminant validity of the CDT compared to the Spanish adaptation of the Mini Mental Examination. RESULTS: We achieve a high reliability inter examiner rates. Quantitative criteria of both scales are more objective than qualitative ones, therefore, these last should be more operativized. CONCLUSIONS: The results obtained in this work suggest that the clock drawing allow a rapid evaluation of cognitive function as the presence of cognitive impairment.

Aged↗
PubMed1997

A family with a milder form of adult dominant polycystic kidney disease not linked to the PKD1 (16p) or PKD2 (4q) genes.

Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disease. Most families show positive linkage to polymorphic markers around the PKD1 (16p13.3) or PKD2 (4q21-23) loci. The PKD1 and PKD2 genes have been cloned and mutations defined in a number of patients. Several clinical studies have described a milder phenotype for PKD2 patients. More recently, evidence for a third genetic locus has been found in one Portuguese, one French-Canadian, and one Italian family. We identified a Spanish family with negative linkage to the PKD1 and the PKD2 loci. This family showed a very mild clinical phenotype compared to the other forms of ADPKD, including the non-PKD1/non-PKD2 families previously described.

Adult↗
PubMed1996

[Shunt surgery versus disconnection in portal hypertension. A comparative study].

Controversy remains about the best treatment for patients with esophagogastric variceal bleeding. In spite of different therapeutic alternatives and recent progress, such as liver transplantation of TIPS, many patients will finally be treated by standard surgery. With the aim to know the results of surgery in shunting vs non-shunting procedures, we have analyzed a recent and consecutive series of 68 cirrhotics patients operated on for variceal hemorrhage. According to the surgical technique there were three groups: I) 30 patients underwent a total portacaval shunt; II) 18 cases with an azygosportal disconnection; III) 20 patients with a partial portacaval shunt (8-10 mm H-portacaval PTFE graft). All groups were homogeneous considering age, sex etiology, Child-Pugh grade and timing of surgery (elective vs urgent). The complications and mortality rates were similar for the three groups. The overall operative mortality was 10%, and 5% in selected cases (Child-Pugh A-B, non urgent cases). With a follow-up for I, II and III group of 47, 44 and 27 months respectively, chronic encephalopathy have been seen in 61%, 15% and 15% respectively (p < .05). No patient in group I has rebled, and only one case in the II and III groups had a recurrence of hemorrhage. The actuarial three years survival was 76%, 86% and 85% (p NS), and the five year survival was 41% vs 86% for the groups I and II respectively (p < .05). In conclusion, in selected cases, surgery gives excellent immediate and long term results. In patients with variceal bleeding and failure of first line treatments, such as sclerosis or pharmacology, the partial H-portacaval shunt and non-shunting procedures are good alternatives, with low incidence of rebleeding and chronic encephalopathy.

Adult↗
PubMed1995

Na,K-ATPase activity in red blood cells from patients with Chediak-Higashi syndrome.

Na,K-ATPase activity of red blood cells from Chediak-Higashi syndrome (CHS) patients and relatives (gene heterozygous) was determined and compared to that of control, healthy, individuals. The enzyme activity was found to be strongly diminished in the CHS patients and slightly lower in their relatives. This reduced activity was due to a lower turnover number of the Na, K-ATPase as well as a decreased number of pumps. The reduced enzyme activity observed in these patients could be the result of an abnormal cell membrane fluidity, and the lowered number of Na, K-pumps could be explained as a consequence of an altered or deficient cell machinery caused by the CHS gene.

Adolescent↗
PubMed1995

Ouabain-sensitive Na+,K(+)-ATPase in the plasma membrane of Leishmania mexicana.

The mechanism responsible for the regulation of intracellular Na+ and K+ concentrations in trypanosomatids is unknown. In higher eukaryotes a ouabain-sensitive Na+,K(+)-ATPase located in the plasma membrane is the main mechanism for the regulation of the intracellular concentrations of Na+ and K+, while in trypanosomatids there are conflicting evidences about the existence of this type of ATPase. By the use of a highly enriched plasma membrane fraction, we showed that an ouabain-sensitive Na+,K(+)-ATPase is present in L. mexicana. The affinity of the enzyme for Na+ and K+ is similar to that reported for the mammalian Na+,K(+)-ATPase, showing also the same kinetic parameters regarding the relative concentration of those cations that give the optimal activity. Vanadate (10 microM) fully inhibits the ATPase activity, suggesting that the enzyme belongs to the P-type family of ionic pumps. The enzyme is sensitive to ouabain and other cardiac glycosides. These cardiac glycosides do not show any appreciable effect on the higher Mg(2+)-ATPase activity present in the same preparation. By the use of [3H]ouabain, we also show in this report that the binding of the inhibitor to the enzyme was specific. Taken together, these results demonstrate that an ouabain-sensitive Na+,K(+)-ATPase is present in the plasma membrane of Leishmania mexicana. Therefore, this Na+,K(+)-ATPase should participate in the intracellular regulation of these cations in Leishmania.

Animals↗
PubMed1994

Comparative aspects of Na+/K+ pump-mediated uncoupled Na+ efflux in red blood cells and kidney proteoliposomes.

Ouabain-sensitive uncoupled Na+ efflux has been studied in human, pig, and rat red cells and in vesicles containing reconstituted kidney Na+/K+ pumps obtained from these same species. The red cells from the different species gave qualitatively similar results; the uncoupled Na+ efflux was 15-30% of the Na+/K+ exchange rate, and this flux was inhibited at 5 mM extracellular Na+ (Na+o). At higher levels of Na+o there was a monotonic increase in the Na+ efflux. As has previously been observed in human red cells, the uncoupled efflux from pig red cells consists of Na+ and anion cotransport, suggesting that anion cotransport may be a general characteristic of uncoupled Na+ efflux in red cells. The uncoupled Na+ efflux carried out by pig and rat kidney Na+/K+ pumps differs from the red cell activity in that it represents no more than 2-4% of the Na+/K+ exchange rate and that 5 mM Na+o does not inhibit this efflux. Furthermore, the efflux does not appear to be dependent on anion cotransport. Vesicles containing human kidney Na+/K+ pumps differ from vesicles derived from pig or rat kidneys in that the Na+ efflux is not inhibited or stimulated by Na+ present on the opposite side; it thus appears that the Na+,K(+)-ATPase in these vesicles may be incapable of Na+/Na+ exchange. These results indicate that the ligand and kinetic properties of the uncoupled Na+ efflux mode of red cells are markedly different from kidney-derived Na+/K+ pumps reconstituted into proteoliposomes. The basis for these differences may be inherent in the Na+/K+ pumps themselves or represent differences between the two types of preparations studied.

Animals↗
PubMed1994

Preeclampsia and calcium adenosine triphosphatase activity of red blood cell ghosts.

OBJECTIVE: The current work was undertaken to study the calcium adenosine triphosphatase activity of red blood cell membranes from pregnant women with preeclampsia. STUDY DESIGN: Six normotensive and six preeclamptic pregnant women at 38 to 39 weeks of gestation were studied. The diagnosis of preeclampsia was made on the basis of blood pressure (> 140/90 mm Hg), proteinuria (> 0.5 gm of urinary protein per day), or edema. Hemoglobin-free red blood cell ghosts were prepared from the heparinized blood samples and were used to determine the calcium adenosine triphosphatase activity. RESULTS: It was found that the calcium adenosine triphosphatase activity of preeclamptic women is diminished by about 50% compared with that of normotensive pregnant women. CONCLUSION: A diminution of the calcium adenosine triphosphatase activity of erythrocytes in preeclampsia might be an indication that the in vivo activity of the calcium pump of these cells is diminished, which could, in turn, drive the cells to increase their cytoplasmic free calcium concentration.

Adult↗
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↗