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Biomedical subjects

D Exley

Publications and source records attributed to D Exley.

36 records · Page 2Linked to original sources
PubMed1968

Ultramicro determination of plasma testosterone by electron-capture detection of testosterone diheptafluorobutyrate.

1. A new highly sensitive and accurate ultramicro method for the estimation of testosterone in human peripheral plasma is described. The method uses paper-and thin-layer-chromatographic separation of plasma testosterone, which is determined as testosterone diheptafluorobutyrate by electron-capture detection after gas-liquid chromatography. 2. The average difference between duplicates is +/-2% (range 1-5%) with as little as 2.5ml. of human male peripheral plasma. With 10ml. of plasma the method is sensitive enough for the accurate determination of testosterone in human female plasma. The high order of accuracy is achieved by the use of a radioactive label and an internal standard for gas chromatography, and by obtaining several gas chromatograms from the same plasma sample. 3. As little as 40mumug. of peripheral plasma testosterone can be detected. The method is 20 times as sensitive as electron-capture techniques with the monochloroacetate derivative. 4. The method is simpler and quicker than double-isotope-derivative methods, and slightly more sensitive. The advantages of the method, which is specific for testosterone, are its high sensitivity and accuracy, which are achieved with relative convenience.

Chemical Phenomena↗
PubMed1968

The site of action of 'chlormadinone acetate' (6-chloro-delta 6-dehydro-17 alpha-acetoxyprogesterone) in blocking ovulation in the mated rabbit.

1. In a study of the site of action of a steroid in current use for contraceptive purposes (6-chloro-Delta(6)-dehydro-17alpha-acetoxyprogesterone; ;chlormadinone acetate'), the ovarian responses [secretion rate of 20alpha-hydroxypregn-4-en-3-one (20 alpha-OH), and the occurrence of ovulation] were observed in control oestrous rabbits and in rabbits following mating, injection of luteinizing hormone, and after electrical stimulation of the median eminence.2. Chlormadinone acetate pretreatment (0.5 mg I.V.) did not lower significantly the secretion of 20 alpha-OH in otherwise untreated oestrous rabbits.3. Chlormadinone acetate, given 24 hr before mating, prevented the rise in 20alpha-OH that would otherwise have occurred, and also blocked the ovulation response following mating.4. Chlormadinone acetate pretreatment did not prevent the ovarian responses to administration of luteinizing hormone.5. Chlormadinone acetate pretreatment did not prevent the ovarian responses to electrical stimulation of the median eminence of the tuber cinereum of the hypothalamus.6. The conclusion is drawn that the chlormadinone acetate block of the ovarian responses following mating is at a site in the central nervous system located above the median eminence.

Anesthesia↗
PubMed1965

A specific method for the determination of millimicrogram amounts of urinary oestrone.

1. A new combined radioactivity-fluorescence method is described for urinary oestrone, which involves acid hydrolysis, extraction and purification of the phenolic fraction, saponification, a Girard T separation and alumina chromatography of acetylated oestrone. 2. Sulphuric acid fluorescence is used for quantitation and specificity is achieved by the addition of tritiated oestrone to the urine hydrolysate. This radioactive tracer functions both as an internal corrector for purification losses and enables the demonstration of constant specific activity through the oestrone peaks to act as an index of specificity in each determination. 3. By using one-fifth of a 24hr. urine sample, 1mug. of urinary oestrone/24hr. can be determined with an accuracy of +/-4%. Fluorescence emission spectra from processed urine samples are identical with that of authentic oestrone acetate. 4. The advantages of the method are its high sensitivity and specificity, which is achieved with relative convenience.

Chemistry, Clinical↗