Search Results

You are looking at 1 - 6 of 6 items for

  • Author: FRANCESCA STEWART x
  • Refine by access: All content x
Clear All Modify Search
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
and
C. H. TYNDALE-BISCOE
Search for other papers by C. H. TYNDALE-BISCOE in
Google Scholar
PubMed
Close

Prolactin and LH receptor concentrations in tammar wallaby corpora lutea (CL) have been examined and related to the control of luteal function in this and other marsupial species. During embryonic diapause, quiescent CL contained high concentrations of prolactin receptors. This was consistent with an earlier suggestion that prolactin may act directly on the CL to maintain its quiescent state. However, despite an apparent seasonal change in the mechanism by which the CL is maintained in quiescence, the number of luteal prolactin receptors remained constant throughout the year. Reactivation of quiescent CL led to an approximate halving of prolactin receptors on a per cell basis, but pregnancy had no effect. None of the wallaby CL showed any significant degree of LH binding, although wallaby follicles and testicular tissue did show binding. This lack of LH binding was consistent with previous findings that quiescent wallaby CL reactivate in response to hypophysectomy and are refractory to LH when cultured in vitro. Parturition, which occurs approximately 2 days before ovulation in this species, had no effect on numbers of either prolactin or LH receptors despite the occurrence of a peak of plasma prolactin at this time. The red kangaroo, which also exhibits embryonic diapause, showed a similar pattern of luteal receptor numbers with high prolactin and negligible LH binding, whereas the brush-tailed possum, which does not exhibit embryonic diapause, gave a pattern more like that seen in Eutheria with many more LH than prolactin receptors.

Restricted access
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
,
W. R. ALLEN
Search for other papers by W. R. ALLEN in
Google Scholar
PubMed
Close
, and
R. M. MOOR
Search for other papers by R. M. MOOR in
Google Scholar
PubMed
Close

SUMMARY

Specific radioreceptor assays for FSH and LH, which employ tissue receptors from rat testis and highly purified human FSH (LER 1575-C) and LH (Hartree IRC-2, 24/6/69) as standards, have been developed to determine the FSH-like and LH-like activities in pregnant mare serum gonadotrophin (PMSG). Measurements of FSH and LH concentrations in the serum of six pregnant Pony mares showed that the ratio of these two activities did not vary significantly between mares and remained constant between days 40 and 80 of gestation with a value of 1·45 ± 0·04 (s.e.m.). The FSH:LH ratio of PMSG produced by cultured equine trophoblast cells was found to be 0·72 ± 0·03 (s.e.m.) and that of partially purified serum extracts of PMSG 1·08 (range 0·87–1·30).

Restricted access
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
,
R. L. SUTHERLAND
Search for other papers by R. L. SUTHERLAND in
Google Scholar
PubMed
Close
, and
C. H. TYNDALE-BISCOE
Search for other papers by C. H. TYNDALE-BISCOE in
Google Scholar
PubMed
Close

The interactions of several mammalian follicle-stimulating hormones and luteinizing hormones with specific gonadotrophin receptors in macropodid marsupial testicular homogenates were investigated with a view to developing radioreceptor assays for marsupial FSH and LH. Testes from Eastern grey kangaroos and tammar wallabies possessed high affinity (dissociation constant ≃10−10 mol/l) saturable receptor sites which were highly specific for LH or FSH. Luteinizing hormone receptor sites bound only highly purified LH preparations (human, ovine and rat) but did not bind highly purified FSH, TSH or prolactin while FSH receptor sites were equally specific for highly purified FSH preparations. These sites demonstrated a degree of species specificity in that marsupial pituitary extracts were relatively more potent in these assays than in assays using gonadotrophin receptors from rat testes. Serum from hypophysectomized female tammar wallabies had little effect on the slope and position of the LH standard curve but significantly depressed the dose–response curve for FSH. For this reason it was not possible to develop a radioreceptor assay for serum FSH using marsupial testicular FSH receptors. However, gonadotrophin receptors from both rat and marsupial testes have been emplpyed in the successful development of radioreceptor assays for marsupial pituitary LH and FSH and marsupial serum LH.

Restricted access
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
,
W. R. ALLEN
Search for other papers by W. R. ALLEN in
Google Scholar
PubMed
Close
, and
R. M. MOOR
Search for other papers by R. M. MOOR in
Google Scholar
PubMed
Close

SUMMARY

Rat testicular radioreceptor assays specific for FSH and LH were used to determine the FSH: LH ratio of PMSG produced by horse, donkey, mule and hinny conceptuses. Measurements of FSH and LH activities in PMSG produced both in vivo and in vitro by the four types of conceptuses showed that the genotype of the foetus markedly influences the FSH: LH ratio of PMSG. The FSH: LH ratio of PMSG produced by the horse conceptus was around unity whereas the ratio of PMSG produced by the donkey conceptus was as low as 0·2. Furthermore, the hybrid mule and hinny conceptuses both produced PMSG with an FSH: LH ratio which was approximately midway between those of the horse and donkey.

Restricted access
RATNA C. SHOWNKEEN
Search for other papers by RATNA C. SHOWNKEEN in
Google Scholar
PubMed
Close
,
ANNE STOCKELL HARTREE
Search for other papers by ANNE STOCKELL HARTREE in
Google Scholar
PubMed
Close
,
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
,
K. MASHITER
Search for other papers by K. MASHITER in
Google Scholar
PubMed
Close
, and
V. C. STEVENS
Search for other papers by V. C. STEVENS in
Google Scholar
PubMed
Close

SUMMARY

Highly purified human pituitary FSH was partially dissociated by treatment with 8 m-urea, and α- and β-subunits were isolated by ion-exchange chromatography and gel filtration. Tests of biological activity by in-vivo assays and in-vitro radioreceptor assays were in good agreement and showed that preparations of isolated α-subunit had less than 1%, and β-subunit from 2 to 10% of the FSH activity of the intact hormone. In contrast to results reported elsewhere, most of the subunit preparations reassociated with counterpart subunit to regain biological activity equal to that of intact FSH (around 160 mg NIH-FSH-S1/mg). The intact FSH recovered as a by-product after isolation of subunits was of high biological activity, and its LH contamination was reduced by more than 90% when compared with the purified FSH starting material. The subunits are relatively inactive in a radioimmunoassay specific for intact FSH. Sialic acid and tryptophan determinations indicated that both subunits contain sialic acid and that tryptophan is present only in the β-subunit.

Restricted access
B. B. AGGARWAL
Search for other papers by B. B. AGGARWAL in
Google Scholar
PubMed
Close
,
SUSAN W. FARMER
Search for other papers by SUSAN W. FARMER in
Google Scholar
PubMed
Close
,
HAROLD PAPKOFF
Search for other papers by HAROLD PAPKOFF in
Google Scholar
PubMed
Close
,
FRANCESCA STEWART
Search for other papers by FRANCESCA STEWART in
Google Scholar
PubMed
Close
, and
W. R. ALLEN
Search for other papers by W. R. ALLEN in
Google Scholar
PubMed
Close

Serum of the pregnant donkey, like that of the mare, contains a gonadotrophin of chorionic origin. The chorionic gonadotrophin of the donkey (dCG) has been isolated in purified form from the serum of pregnant donkeys using methodology previously employed for the purification of pregnant mare chorionic gonadotrophin (eCG). Unlike eCG, dCG is predominantly an LH in biological tests. In the in-vitro rat Leydig cell assay, dCG was as active as eCG, but in the in-vitro rat seminiferous tubule assay for FSH and in the augmentation assay, dCG was considerably less potent than eCG (1–10%). Specific rat testis radioreceptor assays for LH and FSH also showed dCG to be at least nine times more potent in LH than in FSH activity. Chemically, dCG was found to be similar to eCG in fractionation behaviour and glycoprotein nature. However, dCG had significantly less carbohydrate (31%) than had eCG (45%) and several differences were noted in a comparison of amino-acid compositions. A single amino-terminal residue, phenylalanine, was detected in dCG. Immunologically, dCG cross-reacted in homologous radioimmunoassays for eCG, equine LH and equine FSH, but its inhibition curves were all non-parallel with those of the respective equine gonadotrophin standards.

Restricted access