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Biomedical subjects

M Huber

Publications and source records attributed to M Huber.

At least 235 records · Page 13Linked to original sources
PubMed1990

Metabolism of cysteinyl leukotrienes in monkey and man.

The proinflammatory cysteinyl leukotrienes are inactivated in primates by (a) intravascular degradation, (b) hepatic and renal uptake from the blood circulation, (c) intracellular metabolism of leukotriene E4 (LTE4), and (d) biliary and renal excretion of LTC4 degradation products. We have analyzed cysteinyl leukotriene metabolites excreted into bile and urine of the monkey Macaca fascicularis and of man. In both species, hepatobiliary leukotriene elimination predominated over renal excretion. In a representative healthy human subject at least 25% of the administered radioactivity were recovered from bile and 20% from urine within 24 h. In monkey and man intravenous administration of 14,15-3H2-labeled LTC4 resulted in the biliary and urinary excretion of labeled LTE4, omega-hydroxy-LTE4, omega-carboxy-LTE4, omega-carboxy-dinor-LTE4, and omega-carboxy-tetranor-dihydro-LTE4. Small amounts of N-acetyl-LTE4 were detected in human urine only. Oxidative metabolism of LTE4 proceeded more rapidly in the monkey resulting in the formation of higher relative amounts of omega-oxidized leukotrienes in this species as compared to man. [3H]H2O amounted to less than 2% of the administered dose in monkey and human bile and urine samples. Incubation of isolated human hepatocytes with [3H2]LTC4, [3H2]LTD4, and [3H2]LTE4 showed that only [3H2]LTE4 underwent intracellular oxidative metabolism resulting in the formation of omega- and beta-oxidation products. N-Acetylated LTE4 derivatives were not detected as products formed by human hepatocytes. By a combination of reversed-phase high-performance liquid chromatography and radioimmunoassay, endogenous LTE4 and N-acetyl-LTE4 were detected in human urine in concentrations of 220 +/- 40 and 24 +/- 3 pM, corresponding to 12 +/- 1 and 1.5 +/- 0.2 nmol/mol creatinine, respectively (mean +/- SEM; n = 10). Endogenous LTD4 and LTE4 were detected in human bile (n = 3) in concentrations between 0.2-0.9 nM. Our results demonstrate that LTD4 and LTE4 are major LTC4 metabolites in human bile and/or urine and may serve as index metabolites for the measurement of endogenously generated cysteinyl leukotrienes. Moreover, omega-oxidation and subsequent beta-oxidation from the omega-end contribute to the metabolic degradation of LTE4 not only in monkey but also in man.

Acetylation↗
PubMed1990

Inhibition of leukotriene omega-oxidation by omega-trifluoro analogs of leukotrienes.

omega-Oxidation with subsequent beta-oxidation from the omega-end is the major pathway for inactivation and degradation of leukotrienes. Oxidative degradation of leukotriene E4 (LTE4), N-acetyl-LTE4, and LTB4 was inhibited by the omega-trifluoro analogs of LTE4, omega-trifluoro-LTE4 (omega-F3-LTE4), and (1S,2R)-5-(3-[1-hydroxy-15,15,15-trifluoro-2-(2-1H- tetrazol-5-ylethyl-thio)pentadeca-3(E),5(Z)-dienyl+ ++]phenyl)-1H-tetrazole (LY 245769). The latter substance inhibited the oxidative degradation of LTE4 and N-acetyl-LTE4 in the rat in vivo by 50% at a dose of 7 mumol/kg body weight. In rat hepatocyte cultures both omega-trifluoro analogs interfered with the omega-oxidation of N-acetyl-LTE4 and LTB4 with IC50 values of about 4 microM. Both analogs inhibited the omega-hydroxylation in isolated rat liver microsomes with IC50 values between 16 and 37 microM. This inhibition is apparently competitive. In addition, in liver cytosol, the conversion of the omega-hydroxylated leukotrienes to omega-carboxy-LTE4 and omega-carboxy-LTB4 was inhibited by both compounds. omega-Trifluoro analogs of leukotrienes provide a new tool for interfering with the inactivation of leukotrienes in the omega-oxidation pathway.

Animals↗
PubMed1990

Demonstration of herpes simplex virus DNA in CSF cells by in situ hybridization for early diagnosis of herpes encephalitis.

Herpes simplex virus (HSV) was studied by in situ DNA hybridization with a biotinylated cDNA probe in 56 air-dried methanol-fixed cerebrospinal fluid (CSF) cell preparations which had been collected from 12 patients with herpes simplex encephalitis (HSE) during the previous 5 years. In three additional HSE cases, freshly prepared acetone-fixed CSF cell preparations were available. In all cases, CSF cell preparations were obtained by cytocentrifugation. Herpes simplex virus DNA could be demonstrated in 8 of the 12 HSE cases with methanol-fixed cells (66%) and in all 3 cases with fresh acetone-fixed CSF cells. The earliest CSF sample was available at the onset of symptoms and showed positive DNA hybridization. In three cases hybridization was positive after a clinical course of more than 5 weeks but was usually found in the 1st week of illness before the beginning of specific inthrathecal IgG synthesis. In 54 control cases with other acute inflammatory diseases of the CNS, including 14 cases of varicella-zoster meningitis, no positive hybridization was detected. These findings strongly suggest that in situ hybridization in CSF cells is a reliable tool for the early and rapid diagnosis of HSE, especially at the onset of the disease, when no antibodies can be detected.

Adult↗
PubMed1990

A method for delivery of precise doses of smoked cocaine-base to humans.

Despite increasing smoked cocaine-base use, there have been relatively few parametric studies in this area. The major reason for the limited number of studies is the lack of a simple procedure for the administration of precise doses of smoked cocaine-base to human volunteers. This paper describes a new method that allows for the delivery of precise doses of smoked cocaine-base. A complete description of the method and the precision of the administration procedure are presented. Furthermore, a study is described which was undertaken to determine: 1) the reproducibility of peak blood cocaine levels when the same dose of cocaine was given on two separate occasions; and 2) the dose-related effects on smoking topography, biochemical, physiological and subjective measures. Subjects (N = 5) were administered three doses of cocaine-base (10, 20 and 40 mg). Four subjects were given repeated doses of cocaine-base. Subjects were blind to the dose and in most cases randomly assigned to different doses. The results showed: 1) a significant correlation of peak whole blood cocaine concentrations among similar doses within subjects (r = .99); 2) no significant effects of dose on smoking topography; and 3) significant dose effects for whole blood cocaine concentrations, heart rate and systolic blood pressure.

Adult↗
PubMed1990

Cloning and characterization of mepA, the structural gene of the penicillin-insensitive murein endopeptidase from Escherichia coli.

The putative structural gene mepA of the penicillin-insensitive murein endopeptidase from Escherichia coli was cloned and sequenced. N-terminal sequence determination with the isolated endopeptidase protein showed that this enzyme is coded by the mepA gene and that it is synthesized initially with an N-terminal signal peptide. No significant sequence homology with the other (penicillin-sensitive) murein endopeptidase (dacB) or any other protein was found. The precise chromosomal mapping position of mepA relative to two other genes, aroC and fabB, was shown to be 50.4 min. E. coli strains carrying multicopy plasmids with the mepA gene produced 5-6-fold more endopeptidase and secreted it into the periplasm, where it appeared to function normally in vivo since the release of cell wall peptides into the medium increased in parallel. The transformed cells were, however, not unusually sensitive to penicillin and their murein had a normal degree of cross-bridges.

Amino Acid Sequence↗
PubMed1990

[Fractures due to primary tumors and tumor-like changes].

The incidence of pathological fractures resulting from primary bone tumors and tumor-like lesions and various treatment options for such fractures are discussed. In addition to the benign/malignant nature, site, and extent of the tumorous lesion, the patient's age and activity level have to be considered if optimal treatment is to be selected. The treatment is completely different for a pathological fracture resulting from a benign tumor or a tumor-like lesion than for a fracture resulting from a primary malignant bone tumor. As a rule, benign tumors and tumor-like lesions require wide curettage when a fracture occurs, until macroscopically normal bone is reached. The residual cavity is then filled with autogenous cancellous bone grafts. Other fractures, e.g. those resulting from solitary bone cysts, may be treated as if normal bone were concerned. On the other hand, the treatment of a pathological fracture resulting from a primary malignant bone tumor is subordinate to the management of the primary disease, which may be life-threatening. A pathological fracture means a poorer prognosis because of contamination of the surrounding tissues. The risk of local recurrence is high, so that in most cases wide or radical resection or amputation is required.

Adult↗
PubMed1990

[Clinical and pathologic-anatomic findings in acute basilar thromboses. A study of 30 autopsy verified cases].

In a retrospective study of 30 cases with fatal basilar artery thrombosis we compared clinical and autopsy findings for clinicopathological correlation. There are only few clinical symptoms which point to a definite localisation and extent of thrombosis or cerebral infarction. In most cases loss of consciousness and hemi- or tetraparesis are due to pontine or mesencephalic infarction. Palsy of the facial nerve suggests infarction of the pons. The incidence of cranial nerve involvement is too low to allow localisation of infarction. There was no case showing infarction of the diencephalon or the medulla oblongata when pontine or mesencephalic structures were intact. Moreover, these infarctions remained clinically silent. No clinical predictors of outcome could be defined. Even in patients without detectable impairment of consciousness or stenosis of the vertebral arteries, the disease may prove fatal.

Adult↗
PubMed1989

Direct photoaffinity labeling of leukotriene binding sites.

Due to their conjugated double bonds the leukotrienes themselves are photolabile compounds and may therefore be used directly for photoaffinity labeling of leukotriene binding sites. Cryofixation eliminates unspecific labeling taking place in solution by photoisomers and photodegradation products of leukotrienes. After fixation of receptor ligand interactions by shock-freezing of the samples, irradiation-induced highly reactive excited states and/or intermediates can form covalent bonds with the respective binding site in the frozen state. After cryofixation of a solution of albumin incubated with [3H8]leukotriene E4, irradiation at 300 nm resulted in time-dependent incorporation of radioactivity into the protein. Photoaffinity labeling of rat as well as of human blood serum with [3H8]leukotriene E4 after cryofixation revealed that only one polypeptide with an Mr of 67,000 was labeled. This polypeptide was identified as albumin. Photoaffinity labeling of rat liver membrane subfractions enriched with sinusoidal membranes resulted in the labeling of a polypeptide with an apparent Mr of 48,000, whereas no polypeptide was predominantly labeled in the subfraction enriched with canalicular membranes. Photoaffinity labeling of isolated hepatocytes disclosed different leukotriene E4 binding polypeptides. In the particulate fraction of hepatocytes a polypeptide with an apparent Mr of 48,000 was labeled predominantly, whereas in the soluble fraction several polypeptides were labeled to a similar extent. One of these, with an apparent Mr of 25,000, was identified as subunit 1 of glutathione transferases by immunoprecipitation. The method of direct photoaffinity labeling in the frozen state after cryofixation using leukotrienes as photoactivatable compounds, as exemplified by leukotriene E4, may be most useful for the identification and characterization of various leukotriene binding sites, including receptors, leukotriene-metabolizing enzymes, and transport systems.

Animals↗
PubMed1989

Ethanol-induced inhibition of leukotriene degradation by omega-oxidation.

omega-Oxidation of leukotrienes is a major pathway in the degradation and inactivation of these proinflammatory mediators. Ethanol inhibited this process in vivo and in vitro. In rat liver in vivo the catabolism of LTE4 to omega-carboxylated leukotrienes was inhibited by 57% by an ethanol dose of 25 mmol/kg body mass administered intragastrically. The site of inhibition was the oxidation of omega-hydroxy-N-acetyl-LTE4 to omega-carboxy-N-acetyl-LTE4 resulting in an accumulation of omega-hydroxy-N-acetyl-LTE4 and of N-acetyl-LTE4. Analogous results were obtained for the oxidative degradation of LTB4 and omega-hydroxy-LTB4 in rat hepatocyte suspensions. Ethanol, at a concentration of 12.5 mmol/l (0.07%; by vol.), caused 68% inhibition of the oxidation of omega-hydroxy-LTB4 by 50% in hepatocyte suspensions. The conversion of omega-hydroxy-LTB4 to omega-carboxy-LTB4 by rat and human liver cytosol was inhibited by ethanol with half maximal concentrations of 100 mumols/l and 300 mumols/l, respectively. Our measurements indicate that direct interference by ethanol of the omega-oxidation of leukotrienes as well as an increased NADH/NAD+ ratio induced by ethanol led to the inhibition of leukotriene degradation. The impairment of leukotriene inactivation in the liver by ethanol may contribute to the development of the inflammatory reaction in acute alcoholic liver disease.

Animals↗
PubMed1989

[Follow-up and prognosis of herpes simplex encephalitis. Observations on 57 patients between 1960 and 1987].

A retrospective study of outcome in 57 herpes simplex encephalitis (HSE) patients treated between 1960 and 1987 is reported. HSE was confirmed by virus isolation or detection of intrathecal anti HSV synthesis. 24 patients did not receive antiviral therapy, 19 were vidarabine recipients and 14 were treated with acyclovir. Mortality was not correlated with sex or age but with the level of consciousness at onset of therapy. Acyclovir therapy was by far superior to vidarabine with respect both to mortality and neurologic sequelae after a mean follow-up period of 170 days.

Acyclovir↗
PubMed1989

Entamoeba histolytica ribosomal RNA genes are carried on palindromic circular DNA molecules.

Highly abundant DNA fragments obtained after restriction enzyme digests of nuclear DNA of Entamoeba histolytica strain HM-1:IMSS have been cloned and characterized. Northern blot hybridization to E. histolytica rRNA and sequence analysis identified the abundant DNAs as ribosomal DNA containing species. Several overlapping clones containing these abundant DNAs were isolated from 4 different genomic libraries of E. histolytica. Alignment of the restriction maps was consistent with a circular molecule, about 24.6 kilobase pairs (kb) in size. Nuclease BA131 digestion provided additional evidence for the circular nature of this DNA. The ribosomal DNA molecule contains two large inverted repeat-regions, each at least 5.2 kb in length. Sequence analysis of clone R715 revealed homology to the large rRNA units of various eukaryotic organisms. This clone was located in both inverted repeats, suggesting two rRNA cistrons per molecule. The inverted repeats are flanked by stretches of DNA which contain tandemly reiterated sequences. Southern blot analysis of E. histolytica nuclear DNA revealed the presence of two populations of molecules. These molecules have identical arrangements of restriction sites, but differ in size (0.7 kb) in a fragment containing tandemly reiterated sequences. Analysis of E. histolytica nuclear DNA by electron microscopy also revealed circular molecules. These molecules are about 26.6 kb +/- 0.5 kb in size and contain structural features predicted by the restriction map of the extrachromosomal ribosomal DNA of E. histolytica.

Animals↗