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Biomedical subjects

J R Murphy

Publications and source records attributed to J R Murphy.

At least 271 records · Page 15Linked to original sources
PubMed1976

Rheological studies of Hb SS blood: influence of hematocrit, hypertonicity, separation of cells, deoxygenation, and mixture with normal cells.

Studies of the rheological properties of Hb SS blood indicate that the marked increase in viscosity with deoxygenation is primarily due to cell-cell interaction of cells which were not permanently deformed. The permanently deformed cells, the bottom fraction of cells separated by centrifugation, show only a fraction of the increase in viscosity compared to top cells, when each was deoxygenated. Top cells showed a greater degree of morphologic change with deoxygenation compared to bottom cells. The viscosity of deoxygenated Hb SS blood was disproportionately reduced by the addition of compatible deoxygenated Hb AA cells. A mixture of 1/4 Hb AA cells and 3/4 Hb SS cells reduced the viscosity of deoxygenated Hb SS blood 50 per cent. Studies of Hb SS cells in hypertonic media indicate that hypertonicity per se does not cause sickling. Normal and Hb SS erythrocytes both show identical changes in rheological properties when suspended in hypertonic serum. However, changes in oxygen saturation due to a decrease in intracellular pH with certain hypertonic media may lead to sickling when Hb SS blood is at intermediate PO2 levels. The addition of x-ray contrast material to blood results in the changes due to hypertonicity but does not cause sickling of Hb SS cells. The contrast material lowers the pH of the media and raises intracellular pH.

Anemia, Sickle Cell↗
PubMed1976

Stimulation of megakaryocytopoiesis by acute thrombocytopenia in rats.

Rats were made acutely thrombocytopenic by injection of antiplatelet serum. Marrow sections and squash preparations were made at intervals during 120 hr. Determinations were made of mitotic index, stage of maturation, ploidy level, and cell size of megakaryocytes; number and size of platelets were measured. Increased endomitosis among megakaryocytes was followed by an increase in the proportion of immature megakaryocytes, a greater average ploidy level of recognized megakaryocytes, and larger megakaryocytes. Maximum changes in these several parameters occurred between 32 and 72 hr after induction of thrombocytopenia. By 120 hr all megakarocyte parameters were near normal. For about 3 days, beginning at about 36 hr, platelet numbers increased rapidly. Average platelet size rose and returned to normal within about 60 hr. Changes in ploidy and size of megakaryocytes were measured in the immature and mature maturation stages. The results suggest that the initial stimulus in response to acute thrombocytopenia acts primarily on diploid precursors, programming them to mature into a population of megakaryocytes with an average ploidy approximately one level greater than in normal rats and a proportionate increase in cell size. The larger megakaryocytes presumably produce more platelets, accounting for a major part of the increased rate of platelet production. Since the changes in megakaryocytes begin to reverse before circulating platelet numbers have reached the normal level, reversal of the stimulus appears to be initiated by some change other than platelet mass.

Acute Disease↗
PubMed1976

Efficacy of oxibendazole against gastrointestinal nematodes of cattle.

In 3 separate studies, oxibendazole in drench and premix formulation was shown efficacious against larvae and adults of the genera Haemonchus, Ostertagia, Trichostrongylus, Strongyloides, Nematodirus, Cooperia, Bunostomum, Capillaria, Oesophagostomum, and Trichuris. In the first study, artificially infected calves were cleared of virtually all histotrophic larvae and adult parasites after medication with oxibendazole drench at a dose level of 10 mg/kg of body weight. Smaller doses (7.5 and 5.0 mg/kg) expelled 84 to 100% of the parasites. Oxibendazole at a dose level of 15 mg/kg in premix form was given to artificially infected calves 3, 7, or 42 days after infection in a 2nd study. Third stage and 4th stage Cooperia oncophora larvae were, respectively, 92 and 98% susceptible to the drug at day 3 and day 7 after infection; neither larval stages of Ostertagia ostertagi and of Oesophagostomum radiatum were susceptible. Premix given on day 42 after infection removed 83 to 100% of adult O ostertagi, Nematodirus spp, C oncophora, O radiatum, and Trichuris spp. In a 3rd study, calves harboring a mixture of parasitic stages from artificial and pasture-acquired infections were medicated with oxibendazole at a dose of 15 mg/kg in premix form. The burdens of larvae from the abomasum and small intestines were reduced 93 to 95%, respectively; the burdens of adults of 11 species of worms were reduced 87 to 100%.

Animals↗
PubMed1975

Platelet recovery after induction of acute thrombocytopenia.

After mild thrombocytopenia (about 50-100% of control platelet level), induced by injection of antiplatelet serum (APS), platelets increased at a fairly constant and moderate rate for about 4 days and reached a maximum count, greater than pretreatment levels, on the fifth day. After moderate to severe thrombocytopenia, an early moderate rate of platelet increase was succeeded within 2 days by a second more rapid rate that persisted for about 3 days. The maximum overshoot of the platelet count was usually less than twice the pretreatment level. After the largest doses of APS, the platelet count remained depressed for several days. Platelet response after acute thrombocytopenia induced with antiserum is therefore variable, depending on the level and duration of thrombocytopenia.

Acute Disease↗
PubMed1974

Synthesis of diphtheria tox-gene products in Escherichia coli extracts.

In a protein-synthesizing system extracted from E. coli, purified DNA from corynephages betac(tox+) and beta45c was used to direct the in vitro synthesis of diphtheria toxin and of the related nontoxic protein, CRM45, as well as of other beta-phage proteins. When betac(tox+)-DNA or betac-DNA was added to a similar system extracted from the nonlysogenic Corynebacterium diphtheriae strain, C7(s)(-)(tox-), neither toxin nor the CRM45 protein was produced, although other beta-phage proteins were synthesized in amounts equivalent to those produced in the E. coli system from the same amount of beta-phage DNA. Preliminary experiments suggest that both toxinogenic and nontoxinogenic strains of the diphtheria bacillus contain a factor that specificially blocks expression of the tox gene. Synthesis of toxin and the CRM45 protein in the E. coli system could not be inhibited by relatively high concentrations of inorganic iron, but could be inhibited by extracts from the C7(s)(-)(tox-) strain of C. diphtheriae.

Amino Acids↗
PubMed1972

Demonstration of rhodanese activity in polyacrylamide gels.

Rhodanese activity from crude extracts of Thiobacillus sp. strain IV-85 was demonstrated in polyacrylamide gels after incubation in the reaction mixture by staining with dichloroindophenol in the presence of methylphenazonium methosulfate. The sensitivity of the staining system was found to be 8 x 10 moles of sulfite.

Journal Article↗