Search Results

You are looking at 1 - 7 of 7 items for

  • Author: S. R. Stitch x
  • All content x
Clear All Modify Search
Restricted access

R. E. Oakey and S. R. Stitch

ABSTRACT

[4-14C] Testosterone was converted to [14C] oestrone and [14C]17β-oestradiol on incubation with slices of bovine follicles. These metabolites were identified by sequential chromatography, derivative formation and recrystallization to constant 14C/3H ratio. Both Graafian and atretic follicles were able to synthesize these oestrogens from testosterone.

The yield of [14C] oestrone plus [14C] 17β-oestradiol, measured by reverse isotope dilution analysis, varied from 4 μμmoles to 4459 μμmoles in the 19 follicles tested. Differences, much greater than the measured experimental error, were also found in the yields from the two halves of individual follicles. The difficulties imposed by these findings in demonstrating an effect of gonadotrophins are discussed.

On incubation of segments of two follicles, identified histologically as Graafian follicles, in the presence of ovine follicle stimulating hormone, the yield of radioactive oestrone and 17β-oestradiol from [4-14C] testosterone was markedly reduced. In eight other follicles, the majority of which were atretic, the conversion of [4-14C] testosterone was not influenced by gonadotrophin in vitro.

These results would suggest that, in some follicles, follicle stimulating hormone in vitro may modify steroid biosynthesis. In these cases the major locus of action of gonadotrophin on steroid biosynthesis appears to be before the synthesis of testosterone.

Restricted access

F. K. Habib, S. Q. Maddy, and S. R. Stitch

Abstract.

The binding of progesterone to plasma and endometrial cytosol is markedly influenced by Zn++, the degree and magnitude of this influence being dependent on the concentration of the metal ion. There is a critical protein concentration (approximately 10 mg/ml) beyond which the zinc exerts either a stimulatory or inhibitory effect.

Maximum increases in binding of over 60% were attained in solutions of plasma containing 30 mg of protein whereas increases of 10% were measured in cytosol specimens with 10 mg protein/ml. This metal mediated effect was however progressively diminished with increasing zinc concentration resulting finally in the return of the binding to the levels observed in the absence of added Zn++.

The zinc induced inhibition was most evident in plasma and cytosol with a protein concentration less than 10 mg/ml. The magnitude of this effect was inversely proportional to the levels of protein in solution.

Scatchard analysis of the the data revealed that the number of progesterone bindings sites in the receptor are affected by the presence of the metal while the association constants remained unchanged. The study also suggests that the zinc induced changes are partially reversed by dithiothreitol and EDTA. We believe that the metal interferes directly with the SH groups at the receptor binding sites.

Restricted access

M. M. Shahwan, R. E. Oakey, and S. R. Stitch

Restricted access

M. M. Shahwan, R. E. Oakey, and S. R. Stitch

ABSTRACT

Incubation of [14C] pregnenolone with sliced adrenal tissue from a newborn anencephalic infant yielded [14C] 16α-hydroxy-dehydroepiandrosterone (16α-OH-D). When [3H]dehydroepiandrosterone (D) was incubated with this tissue, [3H] 16α-OH-D could not be detected. Incubation of [3H] pregnenolone and [14C]D together in equimolar quantities yielded 16α-OH-D containing 3H but not 14C. This evidence suggests that 16α-OH-D can be formed in vitro by the adrenal of the newborn anencephalic infant from a C21 steroid by a pathway which avoids D.

16α-OH-D is an efficient precursor of oestriol in late pregnancy. The pathway demonstrated in vitro could therefore provide another source of oestriol precursor from foetal tissues, similar to that which Kirschner et al. (1966) suggested may operate in maternal tissues.

Restricted access

M. J. Levell, S. R. Stitch, and M. J. Noronha

ABSTRACT

Pituitary-adrenal function was tested in a group of 33 patients with multiple sclerosis who had been treated with corticotrophin for at least 1 year. Assessment was made by measuring the change in the plasma 11-hydroxycorticosteroid concentration following lysine vasopressin (LVP) administration. Ten patients showed abnormally small increases after LVP. Two of the 5 patients with the smallest increases still showed impairment 8 months later. The patients with no withdrawal symptoms had normal or nearly normal increases following LVP. There was an association between the concentration of 11-hydroxycorticosteroids immediately after withdrawal of ACTH and the subsequent response to LVP.

Restricted access

M. J. Levell, S. R. Stitch, M. Noronha, and C. Vas

ABSTRACT

Plasma cortisol and urinary 17-hydroxycorticosteroids and cortisol secretion rates have been measured on patients with multiple sclerosis taking part in a therapeutic trial of corticotrophin. Patients who had not received corticotrophin showed no evidence of abnormal adrenal function, although the combination of normal levels of plasma cortisol with somewhat low concentrations of urinary cortisol metabolites suggested an abnormal steroid metabolism. Patients who had been treated continuously with corticotrophin (for at least 1 year) showed elevated plasma cortisol concentrations and an even greater disparity between plasma and urine concentrations than the untreated controls. Thus, the urinary steroid measurements did not give a useful measure of the degree of adrenal response and should not be used to monitor prolonged corticotrophin therapy.