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Biomedical subjects

J Hernandez

Publications and source records attributed to J Hernandez.

At least 145 records · Page 8Linked to original sources
PubMed1990

Genotypic variation in 'Campylobacter upsaliensis' from blood and faeces of patients in different countries.

Chromosomal DNA from 62 strains of 'Campylobacter upsaliensis' from blood and faecal specimens of patients in Australia, Belgium, South Africa and England, and seven dog isolates from England and Sweden were examined. DNA base compositions of 21 strains were 35 +/- 1 mol% G + C. Electrophoresis of HaeIII DNA digests gave patterns comprising about 20 well resolved bands of 2 to 10 kb, and visual comparisons revealed considerable genomic variation with 26 different digest patterns identifiable. Differences were evident between genomic DNA patterns of strains from different geographical locations, and between human and dog strains. Each set of human strains from the four geographical locations was comprised of 5 to 8 DNA pattern types. The HaeIII DNA digest patterns were generally more discriminatory than the HindIII, PvuII, CfoI, SmaI and XhoI patterns although some DNAs (12%) were not cut with HaeIII. We conclude the method provides an excellent basis for typing most strains of 'C. upsaliensis'.

Base Composition↗
PubMed1990

DNA restriction digest and ribosomal RNA gene patterns of Campylobacter jejuni: a comparison with bio-, sero-, and bacteriophage-types of United Kingdom outbreak strains.

DNA restriction endonuclease (Hae III and Hind III) total digest and 16S and 23S ribosomal (r)RNA gene patterns (ribopatterns) were determined for 18 isolates of Campylobacter jejuni from three separate outbreaks of diarrhoea in the north of England. Strains were also characterized by biotyping, serotyping and phage typing. Comparisons of the DNA patterns by visual and numerical methods revealed five distinct strain groupings with clear differences between isolates from different outbreaks as well as some heterogeneity between strains within the community outbreak and one of the school outbreaks. An excellent correlation was observed between the genomic DNA fingerprints data and the Preston bacteriophage group, both of which gave better discrimination than biotyping and serotyping alone or in combination. Only one phage group (PG 37) was not confirmed by the DNA data. DNA fingerprints therefore provide additional information of value in studying the epidemiology of outbreaks of C. jejuni.

Animals↗
PubMed1990

Halothane, isoflurane and enflurane potentiate the effect of noradrenaline on ventricular automaticity in the rat heart: evidence of the involvement of both alpha- and beta-adrenoceptors.

Direct evidence has been sought as to what extent the sensitization of heart to the arrhythmogenic action of sympathomimetic drugs in the presence of the inhalatory anaesthetics, halothane, isoflurane and enflurane, is mediated by either alpha- or beta-adrenoceptors. For this purpose, the effects of isoprenaline, noradrenaline and phenylephrine on ventricular automaticity induced by local injury have been studied in the isolated right ventricle of the rat. Isoprenaline was more potent in increasing ventricular automaticity than either phenylephrine or noradrenaline. The anaesthetic potentiated the effects of noradrenaline, as well as that of higher concentrations of phenylephrine, but not those of isoprenaline. These results support the contention that increases in ventricular automaticity induced by sympathomimetic drugs are mainly mediated by adrenoceptors of the beta-type. However, the simultaneous activation of both alpha- and beta-adrenoceptors seems to be necessary for the effect of the anaesthetics in sensitizing the heart to sympathomimetic drugs.

Anesthetics↗
PubMed1990

Prognostic significance of age and tonsillectomy in uvulopalatopharyngoplasty.

The objective of this study was to analyze the results of uvulopalatopharyngoplasty on 133 adult patients with sleep apnea. This group of patients was subjected to computer analysis by a statistician. Two previously unreported observations were revealed: There was a straight line decline in measurable improvement with advancing age so, by age 60, there were no patients with improvement; and patients who had tonsillectomy as a part of the uvulopalatopharyngoplasty had a markedly increased success rate compared to those who did not have tonsils. These two previously unreported observations might have significance and value in establishing guidelines for preoperative prognostic predictions of success.

Adult↗
PubMed1989

Kinetic model of the effects of electrogenic enzymes on the membrane potential.

Electrogenic enzymes contribute to the electrical field existing across biological membranes by using a source of free energy to generate an ionic current. The model introduced here permits one to evaluate this contribution. Since the model incorporates the electrogenic enzyme in the form of a sequential kinetic diagram, it permits one to study the kinetic effects of the concentration of the enzyme, the substrates and the different ligands on the membrane potential. Ionic electrodiffusion is expressed in terms of a chemical reaction; ionic permeabilities are thus treated as voltage-dependent rate constants. We use the condition of global electroneutrality to obtain an expression for the electrical potential difference across the membrane; such expression constitutes an extension of the Goldman-Hodgkin-Katz equation. The enzyme-related terms appear in the equation as functions of the rate constants and the diverse concentrations. The model is used to analyze the case of a cell membrane traversed by Na+ and K+ by simple diffusion, and by electrogenic transport mediated by a Na+-K+ ATPase. The enzyme reaction is represented by the six-step scheme proposed by Chapman et al. (1983, J. membr. Biol. 74, 139-153). The main results of the numerical calculations are that, within a certain interval, the membrane potential difference depends linearly on the enzyme density and hyperbolically on the ATP concentration. A similar behavior has been experimentally observed for the electrogenic proton pump of Neurospora crassa. Thus, the model here can be useful in the explanation and prediction of effects of electrogenic enzymes on the membrane potential.

Animals↗
PubMed1989

B-cell chronic lymphocytic leukaemia: prognostic value of the immunophenotype and the clinico-haematological features.

Sixty-two previously untreated patients with B-cell chronic lymphocytic leukaemia were analysed to study the prognostic value of both the immunologic phenotype and the clinicobiologic characteristics. Univariate studies showed that none of the immunological markers analysed, sheep-rosette, mouse-rosette, slg, and HLA/DR, CD20, FMC7, CD5, and CD9 antigens, had a significant influence on survival. On the other hand, several clinical and haematological characteristics were identified as being associated with survival: 1) clinical features--presence of lymphadenopathies (P less than .05) and hepatomegaly and/or splenomegaly (P less than .04); 2) haematologic parameters--presence of anaemia and/or thrombopenia (P less than .05), the absolute peripheral blood lymphocyte count (P less than .03), and the presence of hypogammaglobulinemia (P less than .08); 3) biochemical parameters--serum uric acid (P less than .03); and 4) bone marrow histopathological features--biopsy pattern (P less than .04) and the percentage of lymphocytes in bone marrow aspirate (P less than .03). Both the Rai staging and the International Workshop on CLL staging systems were effective in identifying groups of patients with significantly different prognoses (P less than .05). Multivariate regression analysis demonstrated that the combination of three clinicopathologic characteristics (bone marrow histopathologic pattern, absolute peripheral blood lymphocyte count, and the presence or not of hypogammaglobulinaemia) had the strongest predictive relationship with survival time. In summary, our findings show that the clinicobiological and anatomopathologic parameters have much more prognostic relevance than the immunological markers analysed in the present study.

Antigens, Differentiation↗
PubMed1989

Social and economic indicators of well-being among hemophiliacs over a 5-year period.

The psychosocial characteristics of a 1983 population of hemophiliacs were described and compared to the 1978 patient population from the same hemophilia center to document any improvements that newer medical treatment and social programming were expected to bring and to compare the 1983 population of hemophiliacs to the general population. Findings included a reduction in the use of pain medication, an increase in the number of 18-35 year olds in school, and a decrease in the proportion of unemployed to employed workers. This updated profile will be helpful for professionals who are planning comprehensive programs for hemophiliacs, including those who have tested seropositive for AIDS.

Adolescent↗
PubMed1989

Ischemic stroke due to fibromuscular dysplasia.

Fibromuscular dysplasia is a segmental, nonatheromatous angiopathy. A 13-year-old patient is reported with stroke. Left-sided carotid angiogram revealed typical findings of fibromuscular dysplasia in the left carotid artery.

Adolescent↗
PubMed1989

Interactions between diltiazem and inhalation anaesthetics in the isolated heart.

It has been postulated that inhalation anaesthetics may interfere with calcium movement across cell membranes. We have evaluated the interaction between diltiazem and the inhalation anaesthetics halothane and isoflurane on sinus automaticity in the isolated right atrium (SAIRA). Isoflurane significantly reduced atrial rate at all concentrations tested. However, halothane produced only a small but significant decrease at the higher concentrations used (1-2 v/v%). Diltiazem modified the maximal negative chronotropic response to inhalation anaesthetics. Maximum depression of SAIRA was significantly greater in the presence of two different doses of diltiazem compared with exposure to halothane and isoflurane alone. These results suggest that inhalation anaesthetics may block the influx of extracellular calcium through voltage-dependent calcium channels inhibited by diltiazem.

Animals↗
PubMed1989

Effects of halothane, isoflurane and enflurane on isolated rat heart muscle.

Since the effects in the intact organism are complicated by central as well as peripheral effects, we compared the direct cardiac effects of three commonly used inhalational anaesthetics--halothane, isoflurane and enflurane--on isolated heart muscle. Concentration-response curves for inotropic, chronotropic and ventricular automaticity effects of halothane, isoflurane and enflurane (0.1-2% v/v) on electrically stimulated left atria, right atria and right ventricles of the rat were obtained. All three inhalational anaesthetics significantly decreased contractile force; the inhibitory concentration 50 (IC50) of enflurane was 0.55 +/- 0.06% v/v, significantly lower than halothane (0.96 +/- 0.08% v/v) and isoflurane (0.67 +/- 0.05% v/v). Similar results were obtained on atrial nomotopic rate. Halothane, isoflurane and enflurane produced negative chronotropic effects in this preparation. On the other hand, halothane and isoflurane significantly reduced the ventricular ectopic automaticity. However enflurane (0.3, 0.5, 1% v/v) increased ventricular rate. There were statistically significant differences between the IC50 values of atrial and ventricular rate for halothane and isoflurane. These results indicate: (a) direct negative inotropic and chronotropic effects for the three inhalational anaesthetics tested; (b) anti-dysrhythmic actions for halothane and isoflurane; and (c) dysrhythmogenic effects of enflurane.

Animals↗
PubMed1988

Postnatal development of 5-HT1 receptors: [3H]5-HT binding sites and 5-HT induced adenylate cyclase activations in rat brain cortex.

The postnatal development of the 5-HT1 receptor system was studied in young rat brain cortex from birth to adulthood (14 successive ages). The high-affinity binding of [3H]5-HT was low at birth but developed markedly between the 8th and the 15th day postnatally. The basal adenylate cyclase activity produced 50 pmoles cAMP/mg protein/min at birth and increased from the 8th to the 15th day. 5-HT could stimulate the adenylate cyclase activity in adult rat brain cortex with two different affinity constants: Km = 1 nM and Km = 0.5 microM; these low- and high-affinity constants presumably correspond to 5-HT1A and 5-HT1non-A.non-B.non-C (5-HT1D) respectively. These two activities developed parallelly from the 14-15th to the 28th day. The 8-hydroxy-2-(di-n-propylamino-tetralin) (8-OH-DPAT)-induced activity described a curve similar to the one that corresponded to 10 microM 5-HT. These results establish that 5-HT1A and 5-HT1non-A.non-B.non-C receptors mainly develop during the synaptogenesis.

Adenylyl Cyclases↗
PubMed1988

Tulobuterol: a full beta-adrenoceptor agonist or a partial beta-agonist with membrane stabilizing activity?

1. The effects of tulobuterol on the atrial rate was compared with those of isoproterenol, pindolol and propranolol in spontaneously beating isolated right atria of the rat. 2. Isoproterenol markedly increased atrial rate. To the contrary, propranolol, pindolol and tulobuterol decreased atrial frequency. The chronotropic effect of tulobuterol was similar to that of pindolol but lower than that of propranolol. 3. Interactions between tulobuterol and isoproterenol showed that tulobuterol potentiated the chronotropic effect of low concentrations of isoproterenol but reduced the positive chronotropic response to higher concentrations of isoproterenol. 4. These results suggest that tulobuterol is a partial agonist on atrial beta-receptor but also seems to have another action (possibly a membrane stabilizing activity) which reduced the originally induced effect on beta-receptors as a non-competitive antagonist.

Adrenergic beta-Agonists↗