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Biomedical subjects

J Soler

Publications and source records attributed to J Soler.

At least 163 records · Page 9Linked to original sources
PubMed1990

ATP inhibition of Phycomyces pyruvate kinase: a kinetic study of the inhibitory effects on the allosteric kinetics shown by the enzyme.

Studies on ATP effects on the allosteric kinetics shown by pyruvate kinase from Phycomyces blakesleeanus NRRL 1555 (-) are reported. Phosphoenolpyruvate showed an allosteric ATP-dependent substrate inhibition. The results supported the existence of spatially distinct catalytic binding sites and the inhibitory binding sites for phosphoenolpyruvate, and ATP showed opposite heterotropic effects with respect to these two types of binding site. With respect to Mg2+ ions, ATP caused a negative heterotropic effect. The global inhibitory effect of ATP was in agreement with the predictions postulated by the two-state concerted-symmetry model of Monod, Wyman and Changeux.

Adenosine Triphosphate↗
PubMed1989

A kinetic study of the pH effect on the allosteric properties of pyruvate kinase from Phycomyces blakesleeanus.

This paper reports the pH-dependence of the allosteric kinetics of Phycomyces blakeseeanus pyruvate kinase with phosphoenol pyruvate and Mg2+ ions in the presence and in the absence of fructose 1,6-bisphosphate (allosteric activator) and L-alanine (allosteric inhibitor). Hydrogen ions increase the affinity of the inhibitory binding sites for phosphoenol pyruvate and Mg2+ ions. Assuming partial conformational states of high and low affinity for inhibitory binding sites, the data presented are in good agreement with the predictions postulated by the two-state concerted-symmetry model of Monod, Wyman, and Changeux. Fructose-1,6-bisphosphate and L-alanine show opposite effects on the interactions of phosphoenol pyruvate and Mg2+ ions with their respective catalytic and inhibitory binding sites. At pH 6.0, the regulation of the Phycomyces pyruvate kinase activity by the concentrations of phosphoenol pyruvate and Mg2+ ions is controlled mainly by L-alanine.

Alanine↗
PubMed1989

[Study of thyroid function parameters and thyrotropin in general non-thyroid diseases].

The changes in the parameters of thyroid function and thyrotropin (TSH) have been evaluated in 5 groups of patients with general non-thyroid disease (GNTD): acute severe bacterial infection (16 patients), acute myocardial infarction (22 patients), diabetic ketoacidosis (24 patients), non-ketotic hyperosmolar decompensation (8 patients), protein-calorie undernutrition (12 patients), without associated conditions or drug therapies that might have modified the thyroid hormones. These patients were evaluated at the beginning of their GNTD and after recovery. Thyroxine (T4), triiodothyronine (T3) and reverse T3 (rT3) were measured by radioimmunoassay (RIA), the TBC index by competitive analysis, the free T4 by a labeled T4 analogue and T4 by immunoradiometric analysis (IRMA). In all patients similar changes in thyroid hormones and in IRMA were found, and they returned to normal after recovery; the changes were most marked in diabetic ketoacidosis, followed by hyperosmolar decompensation and by undernutrition. When the 5 groups were evaluated together, T3 was the most commonly low value (57.3%), followed by T4 and TBC index (26.8%), free T4 (20.7%) and the free T4 index (10.9%). The level of rT3 was increased in 39% of cases. Baseline TSH was, initially, 1.05 +/- 1.05 microU/ml, and 1.36 +/- 0.85 microU/ml after recovery (p less than 0.001). It was only found to be suppressed in one patient (a female with diabetes mellitus and Graves disease); in 17 cases it had borderline values between 0.1 and 0.4 microU/ml, and in the remaining patients it was normal. GNTD induces profound changes in the thyroid functional parameters, with reductions below their normal range, including the analogue measured T4 and low TSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Cross-cultural differences in driver risk-perception.

This study investigated differences in risk-perception among U.S., Spanish, West German, and Brazilian drivers. Subjects estimated the risk involved in slide-projected traffic scenes. The scenes, photographed in the United States and Spain, were rated for the amount of risk by using a seven-point scale. The subject groups in each country included younger, middle-aged, and older nonprofessional drivers, as well as middle-aged professional (bus, taxi, or truck) drivers. In the data analyses, the independent variables were subjects' country, age, professional driving experience, and sex, and 23 dichotomously coded characteristics of the traffic scenes. The following are the main findings: (1) Spanish drivers reported the highest risk, while U.S. drivers reported the lowest risk; (2) younger drivers tended to report lower risk than middle-aged and older drivers; (3) nineteen of the 23 analysed characteristics of traffic scenes contributed significantly to risk ratings, even after simultaneously controlling for the effects of all other scene characteristics; (4) ten scene characteristics had a differential effect on the risk ratings in the four tested countries; (5) two scene characteristics had a differential effect on the risk ratings in the four tested subject groups; (6) none of the variables affected differentially the risk ratings of professional vs. nonprofessional drivers and males vs. females. These findings provide information concerning the desirable country- and age-specific emphasis in driver education, driver licensing, and public information campaigns.

Accidents, Traffic↗
PubMed1989

Cross-cultural differences in driver risk-taking.

This study investigated differences in simulated driver risk-taking behavior among U.S., Spanish, and West German subjects. The task consisted of performing a simulated intersection crossing on a video display. Subjects were shown an intersection with moving traffic on a horizontal road, and they were asked to attempt (under time pressure) a fixed number of crossings with a car moving vertically. The subjects in all three countries included younger, middle-aged, and older persons of both sexes. The following are the main findings: (1) The performance of West German subjects tended to differ from those of U.S. and Spanish subjects. Specifically, West German subjects attempted fewer crossings, had a higher probability of success, and had greater safety margins. (2) Target risk-level of performance, measured by probability of successful crossings, was not affected by age or sex. (3) Probability of attempted crossings was greater for males and younger subjects than for females and older subjects. (4) Similarly, safety margins during attempted crossings were smaller for males and younger subjects than for females and older subjects. These results suggest that there are differences among countries in the target risk-level of performance. However, the present findings imply that within each country all subjects (regardless of age and sex) tended to have the same target risk-level. To attain this risk-level of performance, males and younger subjects (because of their presumed superior psychomotor skills and/or greater experience with video tasks) attempted to cross more gaps (and, consequently, smaller gaps), with resulting smaller safety margins.

Adult↗
PubMed1989

Cross-cultural differences in driver self-assessment.

This study investigated differences in driver self-assessment among U.S., Spanish, and West German drivers. Subjects responded to 14 questions that used five-point semantic scales dealing with driver performance and abilities. Pairs of questions, concerning the same driving-related aspects, differed by requesting a self-assessment on an absolute basis and in relation to the average driver. The subjects in all three countries included younger, middle-aged, and older drivers of both sexes. The following are the main findings: (1) a majority of drivers in each country rated themselves positively on all driving-related scales studied; (2) significant effects of country, age group, and sex of the subjects were present for several of the scales; (3) some of these effects remained significant even after controlling for the differential driving experience. For example, U.S. drivers assessed themselves as safer than did West German and Spanish subjects, younger subjects less wise than middle-aged and older subjects, and males more relaxed than females.

Adult↗
PubMed1989

Effect of glucose on isocitrate lyase in Phycomyces blakesleeanus.

Repression of the synthesis of isocitrate lyase by glucose and/or induction of the synthesis of isocitrate lyase by acetate in Phycomyces blakesleeanus were demonstrated. Both glycerol and ethanol failed to induce isocitrate lyase activity. Furthermore, glucose appeared to cause an in vivo catabolite inactivation of the derepressed enzyme. Isocitrate lyase was inactivated both reversibly and irreversibly by glucose.

Acetates↗
PubMed1989

Use of monoclonal anti-actin as a megakaryocyte marker in paraffin wax embedded bone marrow biopsy specimens.

Monoclonal anti-actin was used as a marker of megakaryocytes in Zenker's fixed, paraffin wax embedded bone marrow tissue, using an immunoperoxidase staining method. Twenty bone marrow samples were studied, including controls, and different myeloproliferative and myelodysplastic syndromes. The results were compared with those obtained using factor VIII related antigen (F VIII RAg) immunolabelling. Anti-actin is as good a marker for megakaryocytes as anti-FVIIIRAg and is potentially clinically useful when morphological identification is difficult, when bone marrow aspiration is unsuccessful, or when quantitative evaluation of tissue sections is required.

Actins↗
PubMed1989

Acute erythroblastic leukemia. Cytological, cytogenetic and phenotypic studies in one case.

We report the clinical, cytological, immunophenotypic, and cytogenetic findings in one patient with acute erythroblastic leukemia. Blast cells were identified by their reactivity with the early erythroid antibodies FA6-152 and carbonic anhydrase I. The leukemic blasts had no specific differentiating features identifying them as erythroblasts even at an ultrastructural level. Cytogenetic studies revealed multiple chromosome aberrations: 45,XX,i(11q),-16,-17,-21,+der(21)t(21;?)(q22;?),+mar 1.

Aged↗
PubMed1989

Transient hypothyroidism after iodine-131 treatment of Graves' disease.

One hundred twenty six patients with Graves' disease, 26 with toxic multinodular goiter, and 18 with toxic adenoma were treated with 131I (3-15 mCi), and followed at monthly intervals for six months. Transient hypothyroidism occurred at two months in 22 patients with Graves' disease. In this state TSH levels became elevated in seven patients, but were normal or suppressed in seven. In 17 patients T4 and T3 levels returned to normal without T4 replacement. Five patients developed recurrent thyrotoxicosis, and required repeated doses of 131I. The possibility of transient hypothyroidism in the early months after 131I therapy in Graves' disease should be borne in mind.

Adult↗
PubMed1989

Islet-cell antibodies: markers of a more severe insulin-dependent diabetes mellitus?

The aim of the present study was to analyze if an association exists between metabolic condition, C-peptide secretion and islet-cell antibody (ICA) presence in insulin-dependent diabetes mellitus (IDDM) at the clinical onset of the disease. Two hundred and nine IDDM patients were studied at diagnosis. 89% of the subjects showed residual C-peptide secretion that correlated inversely with blood glucose and glycosylated hemoglobin at diagnosis and with insulin requirement at discharge. Islet-cell antibodies were detected in 68.6% of the patients, complement-fixing ICA in 30% and insulin autoantibodies in 17.3%. Islet-cell antibody positive patients had a lower glucagon stimulated C-peptide than ICA negative subjects (0.41 +/- 0.22 versus 0.54 +/- 0.25 nmol/l, p = 0.005). However patients with high titers of ICA expressed in JDF units (JDF greater than 20) showed similar C-peptide secretion than ICA positive patients with a low level of JDF (JDF less than 20). When acid-base condition was analyzed patients on ketoacidosis at diagnosis had significant higher insulin requirement, lower C-peptide secretion and higher prevalence of ICA compared to patients that were not ketotic at diagnosis. Our findings suggest that residual beta-cell secretion plays a role on metabolic condition at diagnosis of IDDM and that ICA may be the markers of a more severe form of IDDM.

Adolescent↗
PubMed1989

Induction of intracellular and extracellular beta-galactosidase activity in Phycomyces blakesleeanus.

The inductive effect of different sugars on beta-galactosidase synthesis in Phycomyces blakesleeanus has been studied. The enzyme was inducible by galactose and fructose. When grown on these sugars the enzyme level was 10-20 times greater than when grown on glucose. We have detected both intra- and extracellular beta-galactosidase activity when Phycomyces blakesleeanus was grown on galactose, but only extracellular beta-galactosidase activity when grown on fructose plus lactose.

Cell Membrane↗
PubMed1988

Carbamoyl-phosphate synthase in Phycomyces blakesleeanus.

A carbamoyl-phosphate synthase has been purified from mycelia of Phycomyces blakesleeanus NRRL 1555 (-). The molecular weight of the enzyme was estimated to be 188,000 by gel filtration. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed that the enzyme consists of two unequal subunits with molecular weights of 130,000 and 55,000. The purified enzyme has been shown to be highly unstable. The carbamoyl-phosphate synthase from Phycomyces uses ammonia and not L-glutamine as a primary N donor and does not require activation by N-acetyl-L-glutamate, but it does require free Mg2+ for maximal activity. Kinetic studies showed a hyperbolic behavior with respect to ammonia (Km 6.34 mM), bicarbonate (Km 10.5 mM) and ATP.2 Mg2+ (Km 0.93 mM). The optimum pH of the enzyme activity was 7.4-7.8. The Phycomyces carbamoyl-phosphate synthase showed a transition temperature at 38.5 degrees C. It was completely indifferent to ornithine, cysteine, glycine, IMP, dithiothreitol, glycerol, UMP, UDP and UTP. The enzyme was inhibited by reaction with 5 mM N-ethylmaleimide.

Carbamoyl-Phosphate Synthase (Ammonia)↗