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Biomedical subjects

H Sands

Publications and source records attributed to H Sands.

53 records · Page 3Linked to original sources
PubMed1978

Phosphoprotein phosphatase in bovine tracheal smooth muscle. Multiple fractions and multiple substrates.

Phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) from bovine tracheal smooth muscle extracts was isolated and its activity determined using two [32P]phosphorylated proteins as substrates, i.e. phosphorylated histone (H-P) and a phosphorylated muscle specific substrate protein (MS-P) for the tracheal smooth muscle protein kinase. The enzyme was purified by the use of DEAE-cellulose followed by a two stage chromatography on a histone-Sepharose affinity column. Elution from the affinity column resolved the phosphoprotein phosphatase into four activity fractions. While fractions expressed phosphatase activity against both tested substrates the relative amounts of either activity varied. The ratio of activity towards H-P to activity towards MS-P changed from 11.5 to 0.12. The characterization of four phosphoprotein phosphatase fractions was based on the differences found in the following parameters: substrate specificity; sensitivity to NaF; influences of nucleotides (ATP, 5'-AMP, cyclic AMP, cyclic GMP) and the requirement of Mn2+ for maximal activity. Mg2+, Ba2+ or Ca2+ could not substitute for Mn2+.

Animals↗
PubMed1978

Effects of cyclic AMP and of protein kinase on the calcium uptake by various tracheal smooth muscle organelles.

The role of cyclic AMP, if any, in the regulation of smooth muscle tone is not understood. In the present study the effects of cyclic AMP and of protein kinase on the uptake of calcium by "microsomal", "plasma" and "mitochondrial" preparations obtained from bovine tracheal smooth muscle were examined. Cyclic AMP and protein kinase had only a slight and variable effect on the uptake of calcium by microsomes, and no effect on the uptake of calcium by the plasma membrane or the mitochondria. These findings are not compatible with a role of cyclic AMP and protein kinase in the control of the uptake of calcium by the subcellular organelles of tracheal smooth muscle.

Animals↗
PubMed1977

Determination of calcium transport and phosphoprotein phosphatase activity in microsomes from respiratory and vascular smooth muscle.

1. Calcium transport into microsomal vesicles of respiratory (tracheal) smooth muscle was characterized. This calcium transport was ATP dependent and stimulated by the presence of the oxalate ion. The magnitude of transport was similar to that reported for microsomes from other types of smooth muscle. 2. Bovine and rabbit, heavy and light microsomes were isolated from respiratory (tracheal) and vascular (aortic) smooth muscle. Preincubation of these vesicles with cyclic AMP and protein kinase did not alter the transport of calcium into the vesicles. There uas no evidence of phosphate incorporation into microsomal membrane proteins. Similar results were obtained if phosphorylase b kinase replaced the combination of cyclic AMP and protein kinase during the preincubation. 3. The phosphoprotein phosphatase activity of cardiac sarcoplasmic reticulum and smooth muscle microsomes was determined. The activity of this enzyme was found to be several-fold less in the cardiac sarcoplasmic reticulum than in various smooth muscle microsome preparations.

Animals↗
PubMed1976

Cyclic AMP-stimulated phosphorylation of bovine tracheal smooth muscle contractile and non-contractile proteins.

1. Various proteins isolated from bovine tracheal smooth muscle were examined as phosphate acceptor substrates for a cyclic AMP-dependent protein kinase isolated from the same tissue. A fraction prepared in a manner similar to that of skeletal muscle troponin was the best substrate of the presumptive contractile proteins isolate. Actomyosin and tropomyosin were relatively poor substrates. 2. An assay was developed for the rapid detection in a large number of samples of the muscle specific substrate for the protein kinase on which we reported previously. 3. Using this assay, the muscle specific substrate found in bovine tracheal smooth muscle was partially purified resulting in a preparation which when resolved by polyacrylamide gel electrophoresis showed a single peak of 32P incorporated, and which could be further characterized. 4. Our findings suggest that the substrate contains a protein subunit of molecular weight 19 000, which can be phosphorylated at serine and threonine residues, in the presence of cyclic AMP and protein kinase. The phosphate is in a covalent ester linkage with these residues. 5. A phosphoprotein phosphatase was isolated from the bovine tracheal smooth muscle. 6. Bovine tracheal smooth muscle contains cyclic AMP dependent protein kinase and phosphoprotein phospahatase activity as well as the muscle specific substrate, suggesting that these elements may be part of a mechanism which regulates smooth muscle tone.

Animals↗
PubMed1976

Cyclic AMP and protein kinase in the spontaneously hypertensive rat aorta and tissue-cultured aortic smooth muscle cells.

Cyclic AMP levels and protein kinase activity were determined in the aortas of rats with normotension, moderate and severe spontaneous hypertension. While the cyclic AMP levels were reduced in the aortas from rats with moderate and sever hypertension the protein kinase levels were found to be elevated only in the aortas from rats with severe hypertension. We have grown in tissue culture, aortic smooth muscle cells from the normotensive and severely hypertensive rat. Cultured cells from both strains have similar growth patterns and morphology. The differences seen in cyclic AMP and protein kinase levels in the intact aortas are also seen in the aortic smooth muscle cells in cluture.

Animals↗
PubMed1975

Actomyosin isolated from bovine tracheal smooth muscle.

A contractile protein (actomyosin) was isolated from bovine tracheal smooth muscle by the use of "classical" procedures. The protein was considered to be actomyosin because it demonstrated: ATPase activity; superprecipitation upon the addition of ATP, and the solubility and extraction characteristics of actomyosin. The ATPase and superprecipitation reactions were not inhibited by EGTA, and did not require calcium. Lack of an effect of either calcium or EGTA could not be reversed by the addition of active bovine skeletal muscle troponin and tropomyosin. No troponin-tropomyosin like activities could be demonstrated in various tracheal muscle fractions.

Actomyosin↗
PubMedDate not supplied

9-Nitrocamptothecin is an effective drug for the treatment of human lung tumors: comparison of in vitro and in vivo studies.

9-Nitrocamptothecin (9NC) results in complete regression of small-cell lung carcinoma (SCLC) and non-SCLC (NSCLC) growing as xenografts in immunodeficient mice. In this study, we have monitored histological changes in the tumors during 9NC-induced regression, and perturbations in the cell cycle of cells derived from these tumors using flow cytometry. In vivo, 9NC treatment induces dramatic changes in the tumor cells, which die by apoptosis and are ultimately eliminated from the normal tissue. In vitro, 9NC treatment resulted in apoptosis and cytostasis of the NSCLC and SCLC cells, respectively. Further, 9NC induced cytostasis in control, normal human lung fibroblasts. Therefore, the studies in vivo have indicated that 9NC acquires a remarkable antitumor activity against both the SCLC and NSCLC types tested, and that results of studies in vitro may not reflect the results observed in vivo.

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