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Biomedical subjects

M O'Brien

Publications and source records attributed to M O'Brien.

At least 289 records · Page 16Linked to original sources
PubMed1982

Utilization of chondroitin sulfate by Bacteroides thetaiotaomicron growing in carbohydrate-limited continuous culture.

When Bacteroides thetaiotaomicron, an obligate anaerobe from the human colonic flora, was grown in continuous culture with the mucopolysaccharide chondroitin sulfate as the limiting source of carbohydrate, growth yields ranged from 48 g of cell dry weight per mol of equivalent monosaccharide at a growth rate of 3.5 h per generation to 32 g per mol at a growth rate of 24 h per generation. The theoretical maximum growth yield (61 g of cell dry weight per mol of equivalent monosaccharide) was comparable to that of 54 g per mol, which was obtained previously when glucuronic acid, a component of chondroitin sulfate, was the limiting carbohydrate (S. F. Kotarski and A. A. Salyers, J. Bacteriol. 146:853-860, 1981). However, the maintenance coefficient was three times higher when chondroitin sulfate was the substrate than when glucuronic acid was the substrate. The specific activity of chondroitin lyase (EC 4.2.2.4), an enzyme which cleaves chondroitin sulfate into disaccharides, declined by nearly 50% as growth rates decreased from 3.5 to 24 h per generation. By contrast, the specific activities of several glycolytic enzymes and disaccharidases remained constant over this range of growth rates. Although chondroitin sulfate was growth limiting, some carbohydrate was detectable in the extracellular fluid at all growth rates. At rapid growth rates (1 to 2 h per generation), this residual carbohydrate included fragments of chondroitin sulfate having a wide range of molecular weights. At slower growth rates (2 to 24 h per generation), the residual carbohydrate consisted mainly of a small fragment which migrated on paper chromatograms more slowly than the disaccharides produced by chondroitin lyase but faster than a tetrasaccharide. This small fragment may represent the reducing end of the chondroitin sulfate molecule.

Bacteroides↗
PubMed1982

Enzymatic profile of Pseudomonas maltophilia.

An enzymatic profile of 20 strains of Pseudomonas maltophilia was undertaken with conventional plate tests, API ZYM, and 4-methylumbelliferyl-conjugated substrates. All strains produced DNase, RNase, arbutinase, esterases and lipases, mucinase, acid and alkaline phosphatases, alkaline pyrophosphate diesterase, phosphoamidase, beta-glucosidase, leucine arylamidase, and acetatase and were hemolytic for horse, sheep, and rabbit blood. The majority of strains produced chitinase, hyaluronidase, albuminase, valine arylamidase, trypsin, alpha- and beta-glucosidases, and N-acetyl-beta-glucosaminidase. API ZYM and 4-methylumbelliferyl-conjugated substrate assays are rapid, simple, specific, and sensitive and may be useful as diagnostic aids in the identification of P. maltophilia and other pseudomonads.

Deoxyribonucleases↗
PubMed1981

Potential and problems with growth of breast cancer in a human tumor cloning system.

A human tumor cloning system has been utilized to culture 431 patients' breast cancer specimens. Overall, 288 or 67% of the specimens formed colonies in soft agar. Of the primary lesions 188/260 (72%) formed colonies and 100/171 (58%) of the metastatic lesions formed colonies. The median number of colonies per 500,000 nucleated cells plated was 47 for the primary lesions and 30 for the metastatic lesions. Growth from a variety of metastatic sites ranged from 22% for intradermal lesions to 77% for solid visceral metastases. Methods to increase the number of colonies from a specimen are reported including increasing the number of nucleated cells plated and making a variety of changes in the growth media. None of these methods has had a major impact on colony growth. The antitumor activity of standard anticancer agents such as adriamycin and medroxyprogesterone in the assay is presented. In addition, in vitro results with two new anthracene derivatives demonstrate good antitumor activity for the derivatives. The cloning assay represents a new model for both the basic and clinical studies of human breast cancer.

Anthracenes↗
PubMed1981

Hypolipidemic effects of clofibrate and selected chroman analogs in fasted rats: I. Chow-fed animals.

The hypolipidemic properties of ethyl 6-chlorochroman-2-carboxylate (II), ethyl 6-phenylchroman-2-carboxylate (III) and ethyl 6-cyclohexylchroman-2-carboxylate (IV) were compared to clofibrate (I) in fasted normolipidemic rats. The chroman analog II, like its parent compound, clofibrate, reduced serum and alpha-lipoprotein cholesterol concentrations. Although analog III had no effect on serum cholesterol, it caused a slight elevation of alpha-lipoprotein cholesterol concentration. Serum free cholesterol was increased and LCAT activity was reduced in clofibrate-treated rats. The hypolipidemic agents had no consistent effect on liver lipid concentrations and liver microsomal HMG-CoA reductase activity. In addition, we have shown that drug efficacies varied directly with seasonal variations in serum lipid concentrations.

Animals↗
PubMed1981

Mechanisms of PCA-induced hypothermia, ejaculation, salivation and irritability in rats.

Injections of p-chloramphetamine (PCA, 5 mg/kg) induced hypothermia, ejaculation, salivation and irritability in male rats kept at an ambient temperature of 20 +/- 1 degree C. PCA-induced hypothermia was attenuated by pretreatment with the 5-hydroxytryptamine (5-HT) uptake blockers Lundbeck 10-171 (Lu 10-171, 10 mg/kg) and chlorimipramine (CMI, 20 mg/kg) and the 5-HT synthesis inhibitor parachlorophenylalanine (PCPA, 150 mg/kg daily for 3 days); it was potentiated by pretreatment with the noradrenaline uptake blocker Lundbeck 5-003 (Lu 5-003, 10 mg/kg) and the catecholamine synthesis inhibitor alpha-methyl-p-tyrosine (AMPT, 50 mg/kg every 3 hr for 9 hr). PCA- induced ejaculation was attenuated by pretreatment with Lu 10-171 and CMI. PCA-induced salivation was attenuated by pretreatment with Lu 10-171 and CMI and potentiated by pretreatment with Lu 5-003. PCA-induced irritability was potentiated by pretreatment with PCPA. These results suggest that both 5-HT and the catecholamines play a role in PCA-induced hypothermia, ejaculation, and salivation.

Aggression↗
PubMed1981

Cytoplasmic inclusions in a case of prolymphocytic leukemia.

A case of B-prolymphocytic leukemia (B-PLL) is reported in which intracytoplasmic inclusions were seen at transmission electron microscopy (TEM). The inclusions were electron dense, often membrane bound, and a proportion showed acid phosphatase reactivity.

Acid Phosphatase↗
PubMed1981

Simultaneous or spontaneous occurrence of lympho- and myeloproliferative disorders: a report of four cases.

We describe four patients with mixed lympho- and myeloproliferative disorders. One patient had hairy cell leukaemia and acute myelomonocytic leukaemia, another lymphocytic lymphoma in leukaemic phase and chronic myelomonocytic leukaemia and the third patient had chronic lymphocytic leukaemia and polycythaemia rubra vera; none of these patients had received any prior therapy, and in two the diagnosis of the two malignancies was simultaneous. The fourth patient developed acute monocytic leukaemia 4 years after the diagnosis of chronic lymphocytic leukaemia after only 2 weeks of therapy with chlorambucil. The nuber of cases with concurrent or sequential but spontaneous occurrence of lympho- and myeloproliferative disorders reported so far is now 38. The questions relating to the pathogenesis of the two malignancies are discussed.

Aged↗
PubMed1981

Megakaryoblastic leukemia presenting as acute myelofibrosis -- a study of four cases with the platelet-peroxidase reaction.

Acute myelofibrosis (AM) or malignant myelosclerosis is a myeloprofilerative syndrome in which bone marrow fibrosis is associated with a proliferation of immature myeloid cells. In four patients with typical AM, investigated by the platelet-peroxidase reaction at ultrastructural level, the blast cells were found to be megakaryoblasts. One patient, treated with the drug combination DAT, achieved a complete remission of 5 mo duration. This study supports the view that megakaryoblastic leukemia is the most frequent underlying cause of AM and proposes that it should be classified as a form of acute myeloid leukemia.

Acute Disease↗
PubMed1981

Hairy cell leukemia and myelomatosis: chance association or clinical manifestations of the same B-cell disease spectrum.

We describe three patients who had typical features of hairy cell leukemia (HCL) and multiple myeloma (MM) at the same time. In two, both diagnoses were made within a short period of time, and in the third, HCL had been present for 2 yr before the appearance of a paraprotein, bone lesions, and plasma-cell infiltrates established the diagnosis of MM. Although this association has not been previously reported, cases of HCL with osteolytic lesions or a paraprotein band have been described. The cases described may represent clinical manifestations of closely related disorders arising from divergent differentiation from a common B-cell precursor rather than a chance association.

Aged↗