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Biomedical subjects

M C García

Publications and source records attributed to M C García.

At least 55 records · Page 3Linked to original sources
PubMed1998

Are plasma 1,25-dihydroxyvitamin D3 concentrations appropriate after successful kidney transplantation?

We studied 28 patients with parathyroid hormone (PTH) concentrations >65 pg/ml immediately prior to kidney transplant and who had stable allograft function with serum creatinine <2 mg/dl. After 12-18 months of transplantation, biochemical parameters (including 25-hydroxy- and 1,25-dihydroxy-vitamin D3) were studied. Patients were divided into three groups according to their PTH concentrations. Patients with renal transplant were compared with 50 healthy subjects and 20 patients with primary hyperparathyroidism. The mean 1,25-dihydroxy-vitamin D3 concentration of the transplant patients did not differ from the controls, but was lower than in patients with primary hyperparathyroidism. Using univariate linear regression analysis, 1,25-dihydroxy vitamin D3 correlated positively with PTH (P=0.008) and serum calcium (P=0.0015), and inversely with creatinine clearance (P=0.01). However, it did not correlate significantly with serum phosphorus. Our data suggest that renal transplant recipients may have an inappropriate production of 1,25-dihydroxy vitamin D3; suboptimal allograft function may be a major limiting factor.

Adult↗
PubMed1997

Simultaneous separation of soya bean and animal whey proteins by reversed-phase high-performance liquid chromatography. Quantitative analysis in edible samples.

A reversed-phase high-performance liquid chromatography method was developed successfully for the simultaneous and rapid separation of the main soya bean proteins (globulins) and animal whey proteins (alpha-lactalbumin and beta-lactoglobulin). This method consisted of a linear gradient of two mobile phases (0.1% trifluoroacetic acid in water and 0.1% trifluoroacetic acid in acetonitrile). For the first time, soya bean globulins were separated from animal whey proteins. The analysis time for this separation was 20 min, eluting soya bean globulins in the first 10 min. The method was applied to quantify soya bean proteins in soya bean commercial milks with the possibility of detecting the presence of animal whey proteins. Adulteration of a powdered soya bean milk by animal whey proteins was detected. The possibility of detecting the presence of soya bean proteins in animal milks was also studied.

Acetonitriles↗
PubMed1997

Rapid separation of soybean globulins by reversed-phase high-performance liquid chromatography.

A rapid separation of the main soybean proteins (7S and 11S globulins) was carried out by reversed-phase high-performance liquid chromatography. For this purpose, a linear binary gradient acetonitrile--water--0.1% trifluoroacetic acid, at a flow-rate of 1 ml/min and 50 degrees C temperature was designed. Under the experimental conditions of this work, it was possible to separate five peaks corresponding to the globulins from a soybean protein isolate in 9 min. The characterization of soybean proteins was accomplished by analyzing the 7S and 11S purified fractions obtained from a soybean protein isolate. The method was applied to the separation of soybean proteins from commercial foodstuffs: soybean flour, textured soybean and soybean milks.

Chromatography, High Pressure Liquid↗
PubMed1997

Composition and characterization of soyabean and related products.

Soyabean contains about 48 to 50% proteins. Among these, storage proteins are predominant. 7S and 11S globulins are two storage proteins that constitute 80% of the total protein content in soyabean. Moreover, there are other less abundant storage proteins such as 2S, 9S, and 15S globulins. In addition to globulins, enzymes, protease inhibitors (Kunitz and Bowman-Birk), lectin, and other complete the soya protein content. Different methods exist to characterize soya proteins. These methods involve (1) an isolation of proteins from soya commercial products and (2) the use of analytical techniques for protein determination. Soya proteins may interact with other soya components such as minerals, phytic acid, ascorbic acid, and fiber. These interactions, which depend on soya processing and treatment, can decrease the bioavailability of minerals and proteins. Swelling, solubility, viscosity, and capacity to form a gel, an emulsion, or a foam are the main functional properties of soyabean. They are responsible for the wide use of soya in industrial processes.

Amino Acids↗
PubMed1997

[Serum erythropoietin levels in newborn infants at term].

INTRODUCTION: There are many differences between fetal and adult erythropoiesis, but in both cases erythropoietin (EPO) is the critical controlling haemopoiesis. EPO can be measured in fetal blood by the 16th gestational week, and its levels show a gradual rise to term in parallel with the rise in haemoglobin levels. The aim of this study was to determine EPO levels in normal newborns and correlate them with the delivery, maternal EPO and pregnancy complications. PATIENTS AND METHODS: Serum levels of EPO were measured in 71 postpartum women and their respective newborns. There were no prematures. We also determine mother and child haemoglobin. Three groups of term pregnancies were compared: those delivered vaginally with and without vacuum and those delivered by cesarean section. We also investigate the presence of pregnancy complications. RESULTS: The mean serum EPO in the mother group was 20.7 +/- 18.3 mU/mL (2-80) with no differences from that observed in the newborn group, 19.3 +/- 17.5 mU/mL (2.5-80). There were no differences between the form of delivery. Mothers show higher levels of EPO than the normal population (p < 0.001). CONCLUSIONS: We obtained normal EPO levels for mothers and newborns for our area, similarly to the previously described ones.

Adolescent↗
PubMed1996

Modulation of Ca2+ channels, charge movement and Ca2+ transients by heparin in frog skeletal muscle fibres.

This study is an investigation into the modulatory effects of heparin, a component of the extracellular matrix that binds to dihydropyridine receptors, on contraction and Ca2+ channels in frog skeletal muscle. Using tension and Ca2+ signal measurements in single intact skeletal muscle cells we have found that heparin (100-200 micrograms ml-1) substantially potentiates twitch and tetanic tension (55% and 28%, respectively). In contrast, heparin reduces the amplitude of K+ contractures. Heparin most likely potentiates twitch tension by prolonging action potentials. The ionic basis of this effect was investigated in voltage-clamp experiments. Membrane currents were monitored in voltage-clamped segments of single fibres using the triple Vaseline gap technique. We found that heparin partially blocks delayed rectifier potassium channels. The depressive effects of heparin on K+ contractures prompted us to investigate the effects of heparin on charge movement and Ca2+ currents (ICa) under voltage-clamp. Charge movement was measured using a subtraction procedure that employed a -20 mV control pulse from a holding potential of -100 mV. Heparin depresses the total charge by 25%. We propose that the reduction in the amplitude of potassium contractures is related to a partial blockade of charge movement. Extracellular heparin shifts the ICa-V relation toward more negative voltages and delays the deactivation of tail currents. Double pulse experiments revealed that conditioning depolarizations speed the activation of ICa during test depolarizations. Heparin does not affect this process. The primary action of heparin is to accelerate the activation of ICa during pulses not preceded by conditioning depolarizations. Overall, the kinetic effects of heparin on ICa would increase the Ca2+ influx associated with action potentials. However, mechanical and optical experiments performed in Ca(2+) -free solutions and in the presence of Ca2+ channel blockers revealed that twitch and tetanic potentiation occur even in the absence of Ca(2+) -influx.

Action Potentials↗
PubMed1996

[The fibrinolytic system in patients with dilated myocardiopathy].

OBJECTIVES: To study the fibrinolytic system in dilated cardiomyopathy (DCM) patients, and the relationship between the degree of severity (NYHA degree), and the presence of complications (atrial fibrillation, intracavity thrombus, and peripheral embolism). We also analyzed the influence of the antithrombotic therapy on the fibrinolysis's proteins. PATIENTS AND METHODS: We included 18 patients, stratified in two etiologic groups: 9 with idiopathic and 9 with ethyl DCM. The fibrinolytic system was investigated through the plasma levels of antigenic and functional t-PA and PAI-1. We also carried out a venous occlusion test to investigate the fibrinolytic the fibrinolytic activity in t-PA secretion. The clinical aspects were recorded. We included 30 healthy individuals matched for age and sex, as controls. RESULTS: The antigenic levels of t-PA and PAI-1, were significantly higher in the DCM group than in the control group (p < 0.01). The venous occlusion test responses were normal. No relationship between the fibrinolytic parameters and clinical data were observed. DISCUSSION: The high levels of antigenic t-PA found in DCM patients were considered as a vascular injury marker, and a atherothrombotic risk factor. Furthermore, there is a hypofibrinolytic condition shown by a PAI-1 augmentation. In conclusion, we are prone to consider long term oral anticoagulation in the management of DCM patients.

Adult↗
PubMed1995

Numerical taxonomy of an 'atypical' population of gram-positive cocci isolated from freshly dressed lamb carcasses.

One hundred Gram-positive, catalase-positive strains were isolated from freshly dressed lamb carcasses. They were randomly selected from a non-selective medium and tested for 75 characters. Only nine cultures could be identified by conventional methods. A numerical taxonomic study was conducted on the whole population and 25 reference strains. At the 80% similarity level (Ssm), ten clusters were formed. Five of them were entirely composed of reference strains. Phena V and VIII contained seven isolates and two reference strains of Micrococcus. Phena VI (six unidentified isolates), VII (nine staphylococci) and IX (69 unidentified isolates) were more related to M. kristinae than to the remaining reference strains. Properties with possible implications in meat spoilage were: strong lipolytic activity (76%), anaerobic growth (85%), tolerance to 15% (w/v) NaCl (95%) and ability to grow at 15 degrees C (95%) and 4 degrees C (26%).

Animals↗
PubMed1995

[Appendiceal Crohn's disease].

Crohn's disease of the appendix is an uncommon process that is more frequent in young people. The most common preoperative diagnosis is acute appendicitis. At exploratory laparotomy the appendix is enlarged and malignancy may be suspected. The differential diagnosis may be difficult. Serologic tests and cultures should be performed to exclude Yersinia infections. Appendicectomy is a safe procedure when the disease is limited to the appendix. The postoperative course is usually uncomplicated with a low rate of complications and recurrence. Although it may be a different process than Crohn's disease and the recurrence rate is low, it is suggested that all the patients should be followed-up so that recurrences may be recognized and treated as early as possible. A new case is presented after two years of follow-up without recurrence.

Abscess↗
PubMed1995

[Antiphospholipid antibodies in women with habitual abortions. Treatment with prednisone and acetylsalicylic acid during pregnancy].

PURPOSE: To discover the prevalence of antiphospholipid antibodies in women with a history of repeated miscarriages. Therapy evaluation of aspirin and prednisone to achieve living term foetus from women in whom antiphospholipid antibodies had been detected and who had become pregnant again. PATIENTS AND METHODS: 82 consecutive women with history of at least of two miscarriages, with no live foetus in either case. 14 women positive for antiphospholipid antibodies who had become pregnant again (group of therapy evaluation), were treated with aspirin (125 mg/d) and prednisone (20 mg/d). 60 normal pregnant women (control group). Lupus anticoagulant evaluation: APTT tests caolin clotting time and APTT system neutralized with platelet phospholipids. Antiphospholipid antibodies: ELISA test. RESULTS: 13.4% were positive to antiphospholipid antibodies (ELISA), and 2.4% were positive in both positive in both test. Therapy evaluation: 75.5% (11 cases) of pregnancies were successful (normal foetus), 14% (2 cases) of fetal losses, and 7% (1 case) of foetal malformations (acranius). CONCLUSIONS: In our study the antiphospholipid antibodies represent one of the main causes of repeated foetal losses. We recommended in cases of infertile women to test for antiphospholipid antibodies regularly. We confirm the effectiveness of the therapy (aspirin and prednisone) in achieving successful pregnancies in patients with a history of infertility.

Abortion, Habitual↗
PubMed1994

Antiplatelet therapy and development of hypertension induced by recombinant human erythropoietin in uremic patients.

The pathogenesis of hypertension induced by recombinant human erythropoietin (rHuEPO) remains a subject of intense interest. The observation that patients treated with antiplatelet drugs never developed hypertension following rHuEPO therapy prompted us to study retrospectively the incidence and risk factors associated with the development of hypertension in 91 patients on renal replacement therapy who had commenced rHuEPO therapy in the last three years. Logistic regression analysis was used to determine the risk factors associated with the development or aggravation of hypertension during the first six months on rHuEPO therapy. The predictors were: age, gender, number of months on dialysis, antecedent of hypertension, use of antiplatelet drugs, and those parameters related with dose, route and magnitude of the hematological response to rHuEPO. Of the 91 patients studied, 34 developed hypertension (37%). Of the 34 patients who were on antiplatelet treatment, 2 (5.8%) developed hypertension, whereas among 57 who did not receive antiplatelet drugs, 32 (56%) developed it. By multiple logistic regression analysis, the best predictive variables over the development of hypertension were: age (odds ratio: 0.959, P = 0.02), antecedent of hypertension (odds ratio: 6.52, P = 0.002), and use of antiplatelet therapy (odds ratio: 0.030, P < 0.0001). The rest of the studied variables failed to explain the development of hypertension. Antiplatelet therapy may prevent the development of hypertension in patients treated with rHuEPO. Since the antiplatelet drugs used in this study did not have a significant hemodynamic effect, we infer that changes in platelet aggregability induced by rHuEPO may be involved in the pathogenesis of hypertension induced by this hormone.

Adolescent↗
PubMed1994

Positive inotropic effect of adrenaline on potassium contractures in tonic skeletal muscle fibres of the frog.

K+ contractures were elicited in small bundles of tonic skeletal muscle fibres of the frog. Adrenaline (1 microM) increased the amplitude of K+ contractures in a [K+]o-dependent manner: maximal effects were produced between 20 and 60 mM [K+]o. In contrast, we found no effect of adrenaline on K+ contractures of twitch fibres. The potentiating effect of adrenaline depended on [Ca2+]o. Increasing [Ca2+]o from 1.8 to 10 mM doubled the positive inotropic effect of adrenaline. In a nominally Ca2+ free saline, adrenaline had no potentiating effect. The Ca2+ channel blockers nifedipine (20 microM) and Ni2+ (1.8 mM) reversibly reduced the amplitude of the tonic phase of K+ contractures and blocked the potentiation by adrenaline. The mechanical effects of adrenaline cannot be explained by changes in the membrane potential, as revealed by intracellular recordings at several [K+]o. It was concluded that the potentiating effect of adrenaline in tonic muscle fibres of the frog may be mediated through Ca2+ channels.

Animals↗
PubMed1993

[Resistance in Haemophilus influenzae in Spain. 2d study (1990)].

AIM: To study the resistance to strains of H. influenzae simultaneously isolated during 1990 in 10 Spanish cities with this being the second multicentric study carried out in Spain. METHODS: Three hundred eight strains of H. influenzae were consecutively isolated with less than 50% being from the respiratory tract. The sensitivity by microdilution in supplement Isosensitest was studied. RESULTS: Thirty-five percent of the strains were producers of beta-lactamase which predominate among those isolated in systemic infections and specially among those from Madrid (58.78%) and Barcelona (61.8%). The strains producing beta-lactamase were more resistant to all the antimicrobials than the non producers. Five point two percent of the strains were resistant to ampicillin by non enzymatic mechanisms. Resistance to chloramphenicol is frequent (28.6%) especially among strains producing beta-lactamase, strains of ocular origin and ORL (46%) and systemic infections (74.3%). The distribution is irregular, being more frequent in Seville (66.7%) and not detectable in Barcelona. Resistance to tetracycline is also usually linked to the production of beta-lactamase and not necessarily to that of chloramphenicol. Resistance to cotrimoxazole is the most frequent (67.5%) specially in Valladolid (87.5%). Resistance to cefaclor is of 60.7% being the most frequent among those isolated from ocular processes and ORL. Only 28 strains (9.1%) were sensitive to all the antimicrobials tested. Thirty-nine percent were multiresistant. CONCLUSIONS: The authors found a slight increase in the high resistance detected in 1986. This increase was not uniform in all of Spain being significant in Madrid with producers of beta-lactamase, in Seville to chloramphenicol, to tetracycline in Bilbao and cotrimoxazole in Valencia.

Bacterial Proteins↗
PubMed1992

Ultrastructural and mechanical properties of electrically inexcitable skeletal muscle fibers of the crustacean Atya lanipes.

Examination of the ultrastructure and mechanical activation of the ventro-abdominal flexor muscle of the freshwater crustacean Atya lanipes shows that the fibers are of the long sarcomere, tonic type. The fibers possess an ample and well-organized internal membrane system, with extensive regions of T/SR dyad contacts near the ends of the A bands. An orbit of 10-12 thin filaments surrounds each thick filament. The lanthanum tracer method reveals a highly regular organization of the T-system, Z-tubules, and multiple internal clefts. Tension generation responds to extracellular potassium in a concentration dependent manner and is very slow. Mechanical activation is strictly dependent on extracellular Ca2+, even though these muscle fibers do not generate Ca2+ currents when depolarized. Tension development responds to caffeine and is also dependent on extracellular Na+, suggesting that Ca2+ release from the SR and Ca2+ influx via the Na/Ca exchanger intervene in mechanical activation.

Animals↗
PubMed1992

Muscarinic acetylcholine receptor enhances phosphatidylcholine hydrolysis via phospholipase D in bovine chromaffin cells in culture.

Although it is well-established that inositol-containing lipids serve as precursors of intracellular second messenger molecules in chromaffin cells, we describe some findings that show the formation of diacylglycerol from phosphatidylcholine in response to agonist-mediated stimulation. Stimulation of chromaffin cells by acetylcholine produced a high turnover of phosphatidylcholine, as suggested by the release of [3H]choline derived from [3H]-phosphatidylcholine in experiments performed with [3H]choline chloride-prelabeled cells. An enhanced breakdown of phosphatidylcholine was also inferred from the finding of an increased formation of [3H]diacylglycerol in chromaffin cells prelabeled with [3H]glycerol. The diacylglycerol mass that accumulated after stimulation showed a distinct temporal course and seemed to exceed the mass that has been reported to be derived from phosphatidylinositol. In keeping with the purported origin from phosphatidylcholine, diacylglycerol showed a high content in [3H]oleate molecular species. Phospholipase D activity measurements and experiments performed in the presence of propranolol (an inhibitor of phosphatidic acid:phosphohydrolase) suggested that phosphatidylcholine is hydrolyzed by a phospholipase D activity, producing phosphatidic acid, which is subsequently degraded to diacylglycerol, rather than by a phospholipase C. Incubation of chromaffin cells in the presence of atropine before addition of acetylcholine showed complete inhibition of the increased formation of [3H]-diacylglycerol, whereas d-tubocurarine failed to do so. Taken together, these results suggest that acetylcholine activates phosphatidylcholine breakdown and diacylglycerol formation in chromaffin cells via a muscarinic-type receptor.

Acetylcholine↗