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Biomedical subjects

J Chamberlain

Publications and source records attributed to J Chamberlain.

At least 181 records · Page 10Linked to original sources
PubMed1978

Determination of molsidomine in plasma by high-performance liquid column chromatography.

A high-performance liquid chromatographic method is described for the analysis of the anti-anginal compound 5-ethoxycarbonyl-3-morpholinosydnonimine (Molsidomine) in human and dog plasma. The drug was extracted from plasma into chloroform and the analysis was carried out on a reversed-phase column, the column effluent being monitored by UV absorption at 312 nm. The method is sensitive (2 +/- 0.3 ng/ml) and specific. The method was applied to a study in which human volunteers received an aqueous solution of the drug and then, on a separate occasion, a tablet formulation. Peak plasma levels of 20--30 ng/ml (tablet) and 10--19 ng/ml (aqueous solution) were obtained following a 2-mg oral dose.

Animals↗
PubMed1978

Determination of oral anti-diabetic agents in human body fluids using high-performance liquid chromatography.

Two widely prescribed anti-diabetic agents for which no simple assay method was previously available can now be determined by high-performance liquid chromatography using a UV detection system. The two drugs investigated were tolbutamide (a sulphonylurea) and phenformin (a biguanide). Tolbutamide can be assayed directly, after a single extraction step, on a reversed-phase system, illustrating the simplicity of the technique for carrying out analyses on underivatised drug compared with gas chromatography. Phenformin was not so easily chromatographhed using straightforward partition systems; however, by the choice of a suitable ion-pair agent it was possible to chromatograph the underivatised drug in a relatively simple reversed-phase system.

Administration, Oral↗
PubMed1978

Choice of screening tests.

In this paper, we consider one of the decisions that have to be made about a screening programme: which type of test to use. Our study shows that knowledge of the sensitivities, specificities, and costs of alternative tests is an inadequate basis for the choice of test. The monetary values of the different possible results of the test must also be estimated, or judgements made about the likely magnitude of these values. If judgements have to be made, they should be explicit, because different individuals are likely to judge differently, and their opinions will critically affect the choice of test.

Breast Neoplasms↗
PubMed1977

The effects of splenectomy and glucocorticoids on survival and hepatic uptake of damaged red cells in the mouse.

We have studied the effects of splenectomy and glucocorticoids on the survival and sequestration of Heinz body-containing red blood cells (RBC-HZB). Mice were injected with phenylhydrazine damaged 51Cr labeled isologous red blood cells (RBCs). The spleen removed 36% and the liver 19% of the injected dose after 120 hrs. Red cell survival (T 1/2) fell from 180 hrs for undamaged red cells to 16 hrs for RBC-HZB. Splenectomy resulted in an increase in hepatic uptake of damaged RBCs (36% of the injected dose) and a modest improvement in red cell survival (T 1/2 54 hrs). Treatment of non-splenectomized mice with glucocorticoids reduced the splenic uptake to 16% and the hepatic uptake to 14% of the injected dose. The reduction of splenic upatke was associated with a decrease in splenic mass rather than a decrease in uptake per unit weight of splenic tissue, while reduction in hepatic uptake was associated with both a decrease in hepatic mass and uptake per unit weight. A marked decrease was observed in hepatic uptake and in phagocytosis by Kupffer cells in glucocorticoid-treated splenectomized mice. These data suggest that increased hepatic uptake may decrease the effectiveness of splenectomy in RBC-HZB hemolytic anemia and that glucocorticoids may decrease the hepatic uptake by reducing phagocytosis by Kupffer cells.

Animals↗
PubMed1977

Pulse wave from transit ratios in the assessment of peripheral vascular disease.

This paper presents a ratio of the pulse wave form transit times in the proximal and distal arterial tree, produced by a simple, non-invasive, repeatable and reproducible technique. It has been shown to be highly significant in separating normal from disease states and the proximal from the distal lesion. It has been shown to be independent of the effects of age. In the clinical situation the ratio is of value in the initial assessment of the patient (by separating ischaemic from now-ischaemic limb pain); in elucidation of significant occult proximal lesions in the presence of distal disease; in indicating the type of angiography required (femoral arteriography rather than translumbar aortography in suitable subjects); in following the progress of patients in operative and conservative management régimes; and in the long term follow-up of the natural history of obliterative vascular disease.

Adult↗
PubMed1977

The significance of aortoiliac atherosclerosis as assessed by Doppler ultrasound.

A simple, noninvasive method of assessing atherosclerotic aortoiliac obstruction is described using Doppler ultrasound with a concurrent electrocardiogram. The method is significantly more accurate than clinical examination. The pulse wave velocity profile at the common femoral artery is recorded with a nondirectional Doppler probe. The time delay from the R wave of the concurrent electrocardiogram to the ultrasound waveform peak and to a point half-way up the waveform upslope is measured. By evaluating the mean of ten such measurements at each point and then by taking the ratio of the former to the latter, a Proximal Damping Quotient (PDQ) may be derived. If the PDQ is greater than 1.4, significant proximal obstruction is probable. Conversely, a PDQ of less than 1.4 suggests a functionally clear aortoiliac segment. Any patient with a PDQ of less than 1.3 in whom reconstructive surgery is being correlated may thus be spared an aortogram and the affected limb may be investigated by femoral angiography alone. A low PDQ is supporting evidence of an adequate "run-in" to the distal segment when a distal arterial reconstruction is proposed. Similarly, if a femoro-femoral crossover graft is to be used, then significant aortoiliac atherosclerosis proximal to the donor femoral artery may be excluded without recourse to aortography.

Adult↗
PubMed1977

A simple gas chromatographic method for the determination of nomifensine in plasma and a comparison of the method with other available techniques.

1. A rapid simple gas chromatographic technique for determining nomifensine in plasma is described. 2. Nomifensine is rapidly absorbed after oral administration to man. 3. Following a 100-mg dose, peak levels of an acid-labile conjugate of 2--3 microgram/ml are reached about 1.5 h after administration. 4. The conjugate is cleared with a half-life of between 1 and 2 hours.

Chromatography, Gas↗
PubMed1976

A comparison of the dissolution and bioavailability characteristics of three spironolactone tablet formulations, including preliminary data on two spironolactone metabolites.

The bioavailabilities of three spironolactone tablet formulations specially selected for major differences in in vitro dissolution tests were compared in normal male volunteers by measuring plasma and urinary levels of the pharmacologically active spironolactone metabolite canrenone. It was possible to demonstrate small but statistically significant differences in plasma canrenone concentration-time curves derived from the three formulations together with significant differences in the time course of urinary canrenone excretion. The bioavailabilities of the three formulations did not differ significantly although the tablet with the poorest in vitro dissolution produced a significant delayed peak canrenone concentration. The dissolution rate methodology and results are described and an approach to the development of improved in vitro dissolution tests for spironolactone is suggested. The use of a new method for canrenone estimation resulted in the incidental detection of two other quantitatively significant spironolactone metabolites and preliminary information is given on these.

Adolescent↗