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Biomedical subjects

L W Powell

Publications and source records attributed to L W Powell.

At least 253 records · Page 14Linked to original sources
PubMed1972

Corticosteroids in liver disease: studies on the biological conversion of prednisone to prednisolone and plasma protein binding.

The conversion of prednisone to the biologically active corticosteroid prednisolone and the degree of plasma protein binding of prednisolone were studied in 22 patients with acute or chronic liver disease and in eight control subjects. In patients whose disease was active at the time of study, as judged by elevated serum levels of bilirubin and transaminase, significantly higher levels of plasma prednisolone were obtained after prednisolone administration than after equivalent doses of prednisone. In addition, the amount of unbound drug in the plasma was higher in patients with active disease. There was a significant correlation between the extent of plasma protein binding of prednisolone and the serum albumin concentration. Azathioprine did not affect the plasma binding of prednisolone in vitro. The plasma half-life of prednisolone was prolonged in two of three patients with chronic liver disease studied. These results suggest that in patients with acute hepatitis or active chronic liver disease there is impairment of reduction of the 11-oxo group of prednisone, and also impaired ring A reduction of prednisolone. Thus, incomplete conversion of prednisone to prednisolone occurs, which is a necessary step for biological activity; on the other hand there is also impairment of prednisolone degradation. These, together with low serum albumin concentrations which are associated with higher levels of circulating unbound prednisolone, result in quite different levels of biologically active corticosteroids compared with equivalent doses of prednisone or prednisolone in subjects without liver disease. The findings have important practical implications for the use of corticosteroids in patients with active liver disease.

Adolescent↗
PubMed1970

Failure of a pure progestogen contraceptive to affect serum levels of iron, transferrin, protein-bound iodine, and transaminase.

Medroxyprogesterone acetate, a pure progestational agent which is not metabolized to oestrogen, was given to 30 women and shown to have no effect on the serum levels of iron, total iron-binding capacity, transferrin, and protein-bound iodine. Eighteen of these women had previously taken oral contraceptives of the combined oestrogen-progestogen "sequential" type, and during that time these serum levels were raised. Nevertheless, the levels all fell significantly after medroxyprogesterone acetate was given and the "sequential" oral contraceptive was stopped. In a further 12 postpartum women the serum levels did not change significantly after medroxyprogesterone acetate.These observations strongly suggest that raised plasma protein levels resulting from the administration of oral contraceptives are due to the oestrogen component.

Adolescent↗
PubMed1970

Intestinal mucosal uptake of iron and iron retention in idiopathic haemochromatosis as evidence for a mucosal abnormality.

The process of iron absorption has been studied in 23 patients with idiopathic haemochromatosis, in eight with iron-deficiency anaemia, and in 20 control subjects. The initial uptake of iron by the intestinal mucosa was estimated by administering (59)Fe-ferric citrate during a standard meal together with a non-absorbable marker, (51)Cr-chromic chloride. Body iron absorption (iron retained at 14 days) was measured by whole body counting with discriminant analysis to separate the two isotopes. Thus, the fraction of the initial mucosal uptake finally retained in the body was calculated (the mucosal transport index of iron). In control subjects the mean values for mucosal uptake of iron and body iron absorption were 12.0 - SD 4.9% and 3.6 - SD 2.4%, with a mean mucosal transport index of 0.31 - SD 0.21. Mucosal iron uptake and body absorption were both considerably increased in the patients with iron-deficiency anaemia (33.5 - 15.6 and 29.8 - 17.0% respectively) and in the eight patients with idiopathic haemochromatosis treated by venesection therapy until the excess iron stores were removed (27.2 - 12.0 and 26.6 - 14.6% respectively). The mucosal transport index in all these subjects approached 1.0. Eight patients with haemochromatosis were studied before venesection therapy. The mucosal uptake of iron was within the normal range in all (mean 14.0 - 2.8%) but body iron absorption was increased in five (mean 9.1 - 4.8%). The mean mucosal transport index of iron was significantly increased in this group (0.62 - 0.28; p < 0.01). The findings suggest that the increased iron absorption in subjects with idiopathic haemochromatosis results from an abnormality of the intestinal mucosa and not from altered intraluminal factors. However, whether the aberrant mucosal cell function is a primary defect in the cell or an acquired change, dependent on humoral or corporeal factors, is unknown.

Adult↗
PubMed1970

Use of Triton X-100 scintillant in a simple method for the simultaneous assay of 55Fe and 59Fe by liquid scintillation counting.

A method is described using Triton X-100 scintillant to simplify liquid scintillation counting of (55)Fe alone or in combination with (59)Fe. The Triton acts as an efficient solubilizing agent allowing small volumes of aqueous solutions of iron compounds in hydrochloric acid to be counted. The efficiencies achieved are comparable with those of previously described methods whilst the technique is less time-consuming and the scintillant-aqueous mixture is stable at low temperatures. Reproducible quantitative recovery of radioactivity has been obtained.

Ascorbic Acid↗