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Biomedical subjects

N L Baenziger

Publications and source records attributed to N L Baenziger.

30 records · Page 2Linked to original sources
PubMed1978

Sensitivity of fatty acid cyclooxygenase from human aorta to acetylation by aspirin.

The rate of acetylation of fatty acid cyclooxygenase (prostaglandin synthase, EC 1.14.99.1) by [acetyl-3H]-aspirin was measured in microsomes from human aortas and coronary arteries and intact and disrupted human platelets. We also measured the inhibition by aspirin of prostacyclin generation from exogenous arachidonic acid in shredded human aorta. Cyclooxygenase in human aorta and coronary artery microsomes is approximately 1/250th as sensitive to aspirin as enzyme in intact platelets, and 1/60th as sensitive to aspirin as enzyme measured in a platelet microsomal preparation. On the basis of the in vitro data presented, we predict that small oral doses of aspirin are sufficient to inhibit platelet prostaglandin production but are not sufficient to substantially affect aorta or coronary artery prostaglandin production.

Acylation↗
PubMed1978

Platelet release reaction and intracellular cGMP.

Enchanced cAMP concentrations inhibit the aggregation and release reaction of isolated human platelets and platelet-rich plasma to all known inducing agents. An opposing role for cGMP in this phenomenon has been proposed by some but not by others, and the function of cGMP in this secretory process is unclear. To further elucidate the role of cGMP in the release reaction, the effect of increased concentrations of this cyclic nucleotide on 14C-serotonin release was evaluated utilizing isolated human platelets and highly purified human thrombin or commercially available bovine thrombin. Several recently described stimulators of guanylate cyclase, including sodium nitroprusside, sodium azide, nitrosoquanidines, and ascorbic acid, were found to markedly augment platelet cGMP levels. Enhanced platelet cGMP concentrations produced by these drugs or by the exogenous addition of cGMP and its analogues neither caused these cells to secrete nor modulated the thrombin-induced serotonin release reaction. The inhibition of serotonin release by increased cAMP concentrations was not counteracted by increased cGMP levels. Platelet cGMP concentrations were unaltered by thrombin. These data indicate that cGMP is not an obligatory signal or a modulator of the thrombin-induced platelet release reaction.

Ascorbic Acid↗
PubMed1975

Reverse transcriptase associated with A-type particles from murine myeloma cells.

Our findings may be summarized as follows: (a) a DNA polymerase is associated with murine type A particles, which is very similar to the reverse transcriptases found in true RNA tumor viruses; (b) the majority of the RNA isolated from A particles is of low molecular weight (probably due to degradation), byt appears to contain an amount of unique sequence information comparable to that found in other oncornavirus particles. These results suggest that A-type particles may be very similar, and perhaps related, to the two other classes (B and C) of oncornaviruses.

Base Sequence↗
PubMed1975

Characterization of DNA polymerase and RNA associated with A-type particles from murine myeloma cells.

The RNA-dependent DNA polymerase present in intracisternal A-type particles from mouse myeloma tumor cells has been studied. This polymerase can use either endogenous A particle RNA or an exogenous synthetic polynucleotide [poly (rA)] as a template. The DNA reaction product is small (4S-10S) and over 90% of it hybridizes to A particle RNA, whereas up to 50% of it hybridizes to murine sarcoma-leukemia virus RNAs. The RNA isolated from purified A particles is generally of low molecular weight (5S-15S) but contains small amount of 70S and 35S components. These results suggest that A-type particles may be related to C-type oncornaviruses.

Animals↗
PubMed1972

The effects of thrombin on adenyl cyclase activity and a membrane protein from human platelets.

Washed human platelets were incubated with 0.1-1.0 U/ml human thrombin and the effects on adenyl cyclase activity and on a platelet membrane protein (designated thrombin-sensitive protein) were studied. Adenyl cyclase activity was decreased 70-90% when intact platelets were incubated with thrombin. The T(1/2) for loss of adenyl cyclase activity was less than 15 sec at 1 U/ml thrombin. There was no decrease of adenyl cyclase activity when sonicated platelets or isolated membranes were incubated with these concentrations of thrombin. Loss of adenyl cyclase activity was relatively specific since the activities of other platelet membrane enzymes were unaffected by thrombin. Prior incubation of platelets with dibutyryl cyclic adenosine monophosphate (AMP), prostaglandin E(1), or theophylline protected adenyl cyclase from inhibition by thrombin. Incubation of intact but not disrupted platelets with thrombin resulted in the release of thrombin-sensitive protein from the platelet membrane. The rapid release of this protein (T(1/2) < 15 sec) at low concentrations of thrombin suggested that removal of thrombin-sensitive protein from the platelet membrane is an integral part of the platelet release reaction. This hypothesis is supported by the parallel effects of thrombin on adenyl cyclase activity and thrombin-sensitive protein release in the presence of dibutyryl cyclic AMP, prostaglandin E(1), and theophylline at varying concentrations of thrombin.

Adenylyl Cyclases↗
PubMed1971

A thrombin-sensitive protein of human platelet membranes.

The action of thrombin on intact human platelets has been studied with the aid of polyacrylamide gel electrophoresis in sodium dodecylsulfate. A single major membrane protein band with a molecular weight of 190,000 disappears after thrombin treatment, while a new membrane protein with a molecular weight of 107,000 appears. This may represent hydrolysis of the thrombin-sensitive protein. When platelets are disrupted or when the thrombin-sensitive protein is solubilized from membranes prior to thrombin treatment, no hydrolysis occurs. The effect of thrombin on the platelet membrane protein is complete within 2 min which suggests that hydrolysis of this membrane protein may trigger the physiological effects of thrombin on platelets.

Blood Platelets↗