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Biomedical subjects

M Lucas

Publications and source records attributed to M Lucas.

At least 181 records · Page 10Linked to original sources
PubMed1988

[Review of clindamycin].

Clindamycin use in dental infections is reviewed in this article. A broad spectrum against most strains associated to odontostomatological pathology (caries, pulp and periodontal infections) is emphasized, as soon as the high levels in gingival fluid, bone and saliva with clindamycin obtained.

Adult↗
PubMed1987

Impaired calcium sequestration activity in liver microsomes from fasted rats.

Calcium uptake activity was assayed in liver microsomal vesicles from fed and fasted rats. This activity required ATP and was stimulated by the calcium trapping agent oxalate. The most striking feature was the low rate of calcium accumulation in liver microsomes from fasted rats. Maximal rate was inhibited up to 66 and 82% after 1 and 3 days starvation, respectively. This defective microsomal calcium handling suggests its possible involvement in the massive glycogen breakdown during starvation.

Animals↗
PubMed1987

Ionic and substrate requirements of the high affinity calcium pumping ATPase in endoplasmic reticulum of pancreas.

1. Calcium transport and ATPase activities were determined in microsomal vesicles from pancreatic tissue enriched in endoplasmic reticulum membranes. 2. Calcium transport and ATPase share the following properties: (i) magnesium was required with a K0.5 of 0.7 mM and maximal pumping ATPase activity at 5 mM Mg-ATP; (ii) at saturating magnesium concentrations, calcium increased ATP splitting activity up to three times with an apparent K0.5 close to 0.3 microM calcium; (iii) potassium stimulated the high calcium affinity Mg2+-dependent ATPase and calcium transport. 3. The properties of the calcium pumping system fulfil the cationic and substrate requirements from a physiological point of view.

Animals↗
PubMed1987

Amniotic fluid testosterone and testosterone glucuronide levels in the determination of foetal sex.

Unconjugated testosterone levels were assayed in 351 amniotic fluid samples obtained at 15-19 weeks gestation. The median values for unconjugated testosterone in the 166 female foetuses and 185 male foetuses were 137 and 712 pmol/l respectively. Sixteen amniotic fluid samples from male foetuses had unconjugated testosterone levels lower than the highest female unconjugated testosterone value (361 pmol/l). Testosterone glucuronide was measured in amniotic fluid from 48 female and 55 male foetuses. There was a significant sex difference in the median values of testosterone glucuronide between female (median 160 pmol/l, range 64-465 pmol/l) and male (median 817 pmol/l, range 68-3707 pmol/l) amniotic fluid specimens (P less than 0.001). Of the sixteen male foetuses with amniotic fluid unconjugated testosterone levels in the female range, 12 had amniotic fluid testosterone glucuronide levels within the male testosterone glucuronide range of values. Hence used in conjunction with unconjugated testosterone, testosterone glucuronide increased the predictive accuracy of foetal sexing from 95.4 to 98.9%. Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no significant difference between female (median 2591 pmol/l) and male (median 2964 pmol/l) testosterone sulphate levels.

Amniocentesis↗
PubMed1987

Ionophoric properties of the proteolipid apoprotein from bovine brain myelin.

Ionophoric properties of the Proteolipid Apoprotein have been assayed. This is a highly purified and delipidated intrinsic myelin membrane protein, isolated from bovine brain white matter. The preparation of myelin membrane vesicles or the incorporation of purified protein into Dimiristoylphosphatidylcholine liposomes have been carried out. According to our results, the myelin Proteolipid protein may act as a Na+ and Rb+ (K+) unidirectional ionophoretic channel, which main physiological role could be related to the maintenance of ionic equilibrium of myelin sheath around the axons.

Animals↗
PubMed1987

Effect of pH and ionophores on the calcium-pumping ATPase of endoplasmic reticulum microsomes from guinea pig pancreas.

The effects of the proton-ionophore FCCP, the electroneutral calcium-proton ionophore A23187, pH and oxalate on calcium uptake and (Ca-Mg)ATPase activity were assayed in microsomal vesicles prepared from guinea pig pancreas. The results can be summarized as follows: 1) The optimum pH for ATP-dependent calcium uptake was 7, whereas the (Ca-Mg)ATPase activity was maximal at pH 7.5-8; 2) after a time lag of oxalate-insensitivity, oxalate stimulated strongly the ATP-dependent calcium uptake; 3) FCCP uncoupled the process of calcium uptake and ATP hydrolysis; 4) the effects of FCCP on calcium transport and ATPase activity were quite similar to those induced by the calcium ionophore A23187. These results can be explained by the formation of a proton gradient through membrane vesicles during the calcium pumping process.

Animals↗
PubMed1987

Stimulation by calcium of glucose uptake and lactate production in pigeon erythrocytes.

The rate of glucose conversion into phosphorylated or charged intermediates was determined and related to lactate output and ATP levels. The calcium ionophore A23187 stimulated strongly the production of lactate in pigeon erythrocytes. It required the presence of calcium and simultaneously ATP levels fell down in red cells. The rate of glucose uptake by pigeon erythrocytes was measured as the conversion of [U-14C]glucose into phosphorylated or charged intermediates. A23187 increased the rate of glucose uptake and required the presence of micromolar calcium concentrations. Neither glucose uptake nor lactate production could be related to the decrease of cellular ATP. The results suggest that changes in intracellular calcium alone can stimulate glucose uptake and lactate production.

Adenosine Triphosphate↗
PubMed1986

Isolation of murine neuron-specific and non-neuronal enolase cDNA clones.

cDNA clones corresponding to subunits of neuron-specific (gamma gamma and alpha gamma) and non-neuronal (alpha alpha) enolase isozymes were characterized from two mouse brain cDNA libraries. Our hybridization data revealed a partial homology of the coding sequences of mouse alpha, mouse gamma and rat gamma mRNAs. The noncoding sequences, however, appear to be specific for each mouse mRNA. Although coding for two polypeptides of the same molecular weight, the mRNA for the gamma subunit (2600 bases) is larger than that for the alpha subunit (1900 bases). The noncoding sequences for neuron-specific gamma mRNA (about 1300 bases) are therefore longer than those of the non-nervous tissue specific alpha mRNA (about 600 bases).

Animals↗
PubMed1986

Correlation of the presence of seminal white blood cells and the prevalence of separated spermatozoal heads with subclinical Brucella ovis infection in rams.

A breeding soundness evaluation was conducted on 824 Colorado range rams. These rams were determined to be free from epididymitis via testicular palpation. Semen evaluation included microscopic observation for the presence of WBC. Of the 824 rams, 15.5% failed the breeding soundness evaluation on the basis of the semen evaluation: 10.6% had WBC in the semen and 4.9% had poor sperm morphology. The prevalence of Brucella ovis isolation varied from 0% to 16.2% within flocks. The prevalence of subclinical B ovis infection was 10% in the control flocks. Brucella ovis was isolated from 71.9% of the rams that had WBC in their semen. From this study, it appeared that palpation and vaccination may be inadequate for control of ram epididymitis.

Animals↗
PubMed1986

Intracellular calcium distribution in pigeon erythrocytes.

Subcellular compartmentation of calcium has been studied in digitonin-treated pigeon erythrocytes. The following calcium pools could be detected: A non-vesicular and tightly bound pool of calcium able to reach values equivalent to 5 mumol calcium/ml cells that required millimolar calcium concentrations. A vesicular calcium pool with high calcium affinity that had properties similar to mitochondrial calcium transport. Extracellularly added ATP was strongly hydrolyzed by intact pigeon erythrocytes in the presence of either magnesium or calcium. The hydrolysis of ATP was not coupled to fluxes of either 45Ca2+ or 86Rb+ and most probably took place inside the cells.

Adenosine Triphosphate↗
PubMed1986

Peripheral T-cell phenotypes in chronic active hepatitis B. Correlation with serum hepatitis B virus (HBV) markers and clinical features.

We have studied peripheral blood T-cell phenotypes using monoclonal antibodies in untreated heterosexual patients with chronic active hepatitis B (CAH-B) to investigate its relationship to HBV serological markers and clinical features. Compared to the controls, CAH-B patients formed three subgroups: one with low, one with normal and a third with high OKT4/OKT8 ratios. The CAH-B patients with an elevated OKT4/OKT8 ratio tended to be symptomatic, have a past history of acute hepatitis, a shorter disease duration and a more severe histological liver disease than patients with a low OKT4/OKT8 ratio. All cases with high OKT4/OKT8 ratio were HBeAg-positive and 88% HBV-DNA-positive by molecular hybridization. In contrast only 10% of the cases with low OKT4/OKT8 ratio were HBeAg-positive and 40% HBV-DNA-positive. Delta-positive cases were only found in the subgroups with low (40%) and normal (25%) ratios. Sequential studies were performed in the 12 HBeAg-positive cases: seroconversion of HBeAg to anti-HBe was observed in 3, all with high OKT4/OKT8 ratios. This study delineates two major subgroups in CAH-B using peripheral T-cell phenotypes. This classification may prove to be useful in the follow-up of patients with CAH-B and in predicting their responsiveness to anti-viral therapy.

Adult↗