Search PubMed⌕ Search

Biomedical subjects

R Booth

Publications and source records attributed to R Booth.

At least 55 records · Page 3Linked to original sources
PubMed1980

The preparation and purification of isolated rat corpus-luteum cells and their use in studying the relationship between cholesterol biosynthesis and the lutropin-stimulated formation of progesterone.

Isolated luteal cells, prepared from superovulated rat ovaries by digestion with collagenase, were subjected to density-gradient centrifugation on Percoll to give a more highly purified preparation of luteal cells than has been reported previously. The cells formed progesterone when incubated in vitro; lutropin stimulated this steroidogenesis. Progesterone formation was linear for at least 2 h; a minimal lutropin concentration of 1.0 ng/ml was needed for stimulation and concentrations of 3.0 and 100 ng/ml gave half-maximal and maximal responses respectively. The cells were unresponsive towards hormones other than lutropin. Exposure to lutropin raised the cellular cyclic AMP concentration, and dibutyryl cyclic AMP, but not dibutyryl cyclic GMP, was as effective in stimulating steroidogenesis as was lutropin. Aminoglutethimide, an inhibitor of cholesterol side-chain cleavage, completely blocked progesterone formation by the cells, showing cholesterol side-chain cleavage to be an obligatory step in steroidogenesis by these cells. Neither the activity of 3-hydroxy-3-methylglutaryl-CoA reductase nor the incorporation of radioactively labelled acetate or mevalonate into cholesterol by cells incubated in vitro were detectable unless the rats had been treated previously with 4-aminopyrazolo[3,4-d]pyrimidine. In cells from rats so treated, compactin was found to block almost completely the incorporation of radioactively labelled acetate, but not of mevalonate, into cholesterol, indicating that this inhibitor acts in corpus luteum in the same way as it does in other tissues. In cells from rats not treated with 4-aminopyrazolo[3,4-d]pyrimidine compactin had no effect on progesterone formation in vitro, showing cholesterol biosynthesis to be unnecessary for the rapid steroidogenic response by luteal cells to lutropin.

Animals↗
PubMed1979

Detection of deep venous thrombosis by scanning of 99mtechnetium-labelled red-cell venous pool.

A comparative study of 32 patients with suspected deep venous thrombosis was carried out using blood-pool radionuclide scanning and conventional x-ray phlebography. Results of the two methods showed close agreement, the sensitivity (positive correlation) of the scan being 100% and its specificity 89%. We conclude that a patient's red cells labelled with 99mtechnetium (99mTc) provide an excellent medium for this type of scanning. The technique has particular advantages in visualising the whole venous system, giving a persisting image, and obviating the need to inject into a vein of the affected limb. In view of the inherent disadvantages of contrast phlebography, 99mTc-red-cell scanning is clearly an acceptable alternative.

Erythrocytes↗
PubMed1978

The early diagnosis of acute occlusive mesenteric ischaemia: experimental results and clinical applications.

The diagnosis of acute superior mesenteric artery occlusion in the dog has been achieved in every case by isotope scanning of the abdomen using technetium-labelled red cells or technetium-labelled human serum albumin. The white cell count is also significantly elevated, but the changes in the levels of the enzymes CPK, LDH, AST and serum amylase are not specific for actue mesenteric ischaemia. In the human the presence of a normal gut circulation can be demonstrated by isotope scanning provided that the patient is not severely shocked. The presence of a normal gut circulation as shown on the scintigram conclusively eliminates the possibility of acute main trunk occlusion of the superior mesenteric artery. This should be of help in differentiating acute occulusive mesenteric ischaemia from other causes of the acute abdomen. Abdominal scintiscanning is complementary to angiography, which still remains the most precise means of diagnosing acute mesenteric ischaemia. Although the abdominal scintigram is more limited in its application and is not as accurate as angiography, it is quicker to perform, non-invasive, and entirely safe. Abdominal scintiscanning is an excellent screening test to be used in patients suspected of suffering from acute occlusive mesenteric ischaemia.

Acute Disease↗
PubMed1977

A new method for assaying rat liver microsomal 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity and its application in a study of the effect of dietary cholesterol on this effect of dietary cholesterol on this enzyme.

A new method suitable for measuring rat liver 3-hydroxy-3-methylglutaryl-CoA reductase activity is described and its advantages over methods previously available are discussed. An accurate time course was measured for the inhibition of liver microsomal 3-hydroxy-3-methylglutaryl-CoA reductase activity by dietary cholesterol; this enzyme was affected 1 1/4 h after the rats began to consume a cholesterol-rich diet. In this experiment there was no correlation between concentrations of microsomal cholesterol ester and the activity of 3-hydroxy-3-methylglutary-CoA reductase.

Alcohol Oxidoreductases↗
PubMed1975

Specificity of the effect of dietary cholesterol on rat liver microsomal 3-hydroxy-3-methylglutaryl-coenzyme a reductase activity.

Dietary cholesterol lowers the activity of rat liver microsomal 3-hydroxy-3-methylglutaryl-CoA reductase without affecting various other liver microsomal enzymes. This is consistent with a specific regulatory mechanism and distinguishes the action of cholesterol on 3-hydroxy-3-methylglutaryl-CoA reductase from that of at least one other stimulus known to affect this enzyme.

Administration, Oral↗