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J K Findlay

Publications and source records attributed to J K Findlay.

At least 217 records · Page 12Linked to original sources
PubMed1976

The influence of prostaglandin F-2alpha on pregnenolone metabolism by the autotransplanted ovary of the ewe.

Eight ewes each with an autotransplanted ovary received infusions of tritium-labelled pregnenolone (41 muCi/hr) for 8 hr into the artery supplying the ovary, together with prostaglandin (PG) F-2alpha (30 mug/hr) for 3 hr beginning 2 hr after the start of the pregnenolone infusion. All animals exhibited oestrus 2-3 days after the start of the experiment. During the PGF-2alpha infusion blood flow through the ovaries was increased by 13%, but subsequently returned to pre-infusion levels. Secretion rates of endogenous progesterone and 20alpha-hydroxypregn-4-en-3-one dropped rapidly 5 hr after the PGF-2alpha infusion had started from values of 250 mug/hr and 25 mug/hr to values below 60 mug/hr and 8 mug/hr, respectively. At this time the conversion of radioactive pregnenolone to progesterone was reduced by 50% of its initial value, but the secretion of endogenous pregnenolone and the formation of radioactive metabolites other than progesterone were not diminished. In 4 control animals, which received pregnenolone only, no changes in ovarian blood flow, steroid secretion rates, or in the conversion of labelled pregnenolone were observed. These results suggest a possible involvement of PGF-2alpha in the regulation of progesterone biosynthesis by an action on the 3beta-hydroxysteroid oxidoreductase-delta5(-4) isomerase enzyme system.

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PubMed1975

Radioimmunoassay for luteinizing hormone-releasing hormone (LHRH): its application to the measurement of LHRH in ovine and human plasma.

A radioimmunoassay for LHRH, MODIFIED FROM THe assay of Nett et al. (J Clin Endocrinol Metab 36: 880, 1973) and characterized in more detail, was applied to the measurement of endogenous plasma LHRH in the peripheral circulation of ewes and women around the time of gonadotropin release. Sensitivity was 1.2 pg/tube. Within- and between-assay coefficients of variation were 10% and 25%, respectively, over the range 10-100 pg/tube. Minimal cross reaction (less than 0.1%) was observed with LHRH analogues tested, except those which had undergone single amino acid alterations in the 4 or 8 positions (62-93%) and in the 1 position (1-3%). Inhibition curves parallel to synthetic LHRH were obtained with these immunoreactive analogs, and with crude hypothalamic and pituitary extracts from 16 cycling ewes and 3 pooled hypothalamic extracts from male rats. LHRH contents of ovine hypothalami and pituitaries ranged from 1.9-10.2 (4.5 plus or minus 2.1, mean plus or minus SD) and 0-27.5 (4.2 plus or minus 7.3, mean plus or minus SD) ng LHRH, respectively, with no obvious correlation between the contents of either tissue. LHRH contents of pooled hypothalami from normal, castrated-hypophysectomized male rats were 4.5, 2.9 and 1. 3 ng/hypothalamus. Recovery of synthetic LHRH added to plasma was quantitative, provided the storage time at 4 and 20 C was minimal. Synthetic LHRH administered to ewes by intravenous infusion or subcutaneous injection was readily detectable in peripheral plasma. The metabolic clearance rates of synthetic LHRH' in 3 sheep were 14, 11 and 14-1/day/kg, respectively. Endogenous immunoreactive material in single, unextracted plasma samples from sheep in various physiological states ranged from 0-400 pg/ml. However, the endogenous plasma immunoreactivity in these samples bone no resemblance to synthetic LHRH added to ovine plasma in that it was stable to gentle heat, and was undetectable after methanol extraction. No endogenous LHRH could be detected in methanol extracts of peripheral plasma obtained from estrous ewes or oophorectomized ewes injected iv with estradiol-17beta (40mug) and bled at 15 min intervals prior to gonadotropin release. Single daily plasma samples obtained from three normal women over their entire menstrual cycles contained no significant levels of endogenous LHRH.

Animals↗
PubMed1974

Chemical and biochemical studies on 18-hydroxyoestrone.

1. 18-Hydroxyoestrone was reduced by NaBH(4) in methanol, giving 18-hydroxyoestradiol-17alpha and 18-hydroxyoestradiol-17beta in the ratio 3:7. 2. Treatment of 18-hydroxyoestrone with a strong alkali yielded 18-noroestrone; however, the 18-hydroxyoestradiols did not undergo transformation to their respective 18-nor derivatives. 3. All the 18-hydroxylated oestrogens were stable under acid conditions. They formed Kober chromogens: the chromogenicity of 18-hydroxyoestrone was only one-third that of the 18-hydroxyoestradiols and oestriol. 4. Paper-, thin-layer- and gas-liquid-chromatographic systems for the characterization of these compounds are described. 5. An examination of the mass spectra revealed peaks characteristic of the substituted carbon atoms. Definite assignment of the 17alpha- and 17beta-hydroxyl groups of the epimeric 18-hydroxyoestrogens was possible by characteristic fragmentation of the free steroids. Further, the configuration of 18-hydroxyoestradiol-17beta was confirmed by the formation of the dimethylsildioxy derivative of the 3-methylether of the steroid. 6. Both rat and rabbit liver slices reduced 18-hydroxyoestrone to 18-hydroxyoestradiol-17beta and some other labile, polar metabolites with properties similar to 2-hydroxylated oestrogens. No formation of 18-hydroxyoestradiol-17alpha in vitro was observed. 7. The results are discussed with respect to the possible influence of the 18-hydroxyl group on reactions at C-17, as well as the reactions of 18-hydroxylated oestrogens with strong acid (Kober reactions) and alkali.

Animals↗
PubMed1974

Influence of an 18-hydroxyl group on the interaction of oestrogens and hydroxysteroid oxidoreductases.

1. Partially purified 17beta-hydroxy steroid-NAD(+) oxidoreductases, prepared from Pseudomonas testosteroni (EC 1.1.1.51), human term placenta (EC 1.1.1.62) and the cytoplasmic fraction of rat liver (EC 1.1.1.-) were tested for their ability to catalyse the oxidoreduction of 18-hydroxyoestradiol-17beta and 18-hydroxyoestrone. The products of incubation were identified by chromatographic procedures and by mass spectrometry. 2. The Pseudomonas enzyme catalysed both the oxidation of 18-hydroxyoestradiol-17beta and the reduction of 18-hydroxyoestrone; in contrast, the placental and rat liver enzymes only catalysed the reduction of 18-hydroxyoestrone. 3. These results were confirmed, by using a spectrophotometric assay; equimolar quantities of oestradiol-17beta and 18-hydroxyoestradiol-17beta were oxidized at approximately the same rate by the microbial enzyme. 4. These findings suggest that 18-hydroxyoestradiol-17beta may be a normal oestrogen metabolite. 5. The differences in ability of the mammalian and microbial enzymes to metabolize 18-hydroxylated oestrogens is explained on the basis of recognition sites with different geometrical dimensions, characteristic of the placental (Descomps & Crastes de Paulet, 1969) and the microbial steroid enzymes (Fosset & Crastes de Paulet, 1967).

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