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Biomedical subjects

H Papkoff

Publications and source records attributed to H Papkoff.

At least 109 records · Page 6Linked to original sources
PubMed1976

Isolation and characterization of follicle-stimulating hormone and luteinizing hormone and its subunits from snapping turtle (Chelydra serpentina) pituitaries.

Highly purified luteinizing hormone and follicle-stimulating hormone have been isolated from extracts of snapping turtle (Chelydra serpentina) pituitaries. Both hormones are potent in non-mammalian gonadotropin bioassays (1.8 X NIH-LH-S1 and 30 X NIH-FSH-S1). The materials have been characterized by polyacrylamide gel electrophoresis, amino terminal group analysis, amino acid and carbohydrate content, and, in the case of turtle luteinizing hormone, ultracentrifugation. The luteinizing hormone was shown to dissociate and subunits were prepared by the countercurrent distribution technique and characterized. Biological activity of the hormone could be regenerated by recombination of the subunits. In addition, it was shown that the snapping turtle luteinizing hormone subunits could be combined with subunits from ovine luteinizing hormone with generation of significant biological activity. Comparisons in properties of the turtle gonadotropins have been made with ovine gonadotropins, showing, in many cases, similarities in properties, suggesting structural features which have been conserved during evolution.

Animals↗
PubMed1976

A new radioimmunoassay for follicle-stimulating hormone in macaques: ovulatory menstrual cycles.

A sensitive and specific radioimmunoassay system for macaque follicle-stimulating hormone (mFSH) was developed utilizing an antiserum (H-31) prepared in a rabbit against purified ovine FSH as the immunogen. Sera from castrated female, adult male, and juvenile rhesus monkeys, as well as urinary extracts from castrated rhesus and bonnet monkeys, were used to demonstrate parallelism with a standard of partially purified monkey pituitary gonadotropins (LER-M-907-D). An extract of baboon pituitary tissue also showed parallelism with the reference standard. A highly purified pituitary extract (WP-X-105-28), containing approximately 75% macaque luteinizing hormone (mLH) and 1% mFSH, was used to demonstrate the specificity of this mFSH assay system. Sera and urinary extracts obtained from hypophysectomized monkeys did not show cross-reactivity in the assay. Macaque chorionic gonadotropin (mCG) did not produce an inhibition curve in the assay, as determined from serum samples and urinary extracts collected from pregnant monkeys at the time of peak mCG secretion. Serum concentrations of mFSH were suppressed in ovariectomized monkeys by the administration of ethinyl estradiol for 3 days, but returned to near pretreatment values by 96 h after the last estradiol administration. The determination of serum mFSH concentrations in daily blood samples obtained from 20 rhesus monkeys throughout ovulatory menstrual cycles revealed a pattern similar to that previously reported for the rhesus monkey and the woman. The peak value of serum mFSH during the menstrual cycle coincided with the midcycle surge of mLH in each case. The gonadotropin peaks were preceded by increasing serum concentrations of estradiol and followed by rises in the serum concentrations of progesterone. The follicular phase of the menstrual cycle was characterized by continuously decreasing serum concentrations of mFSH, reaching a preovulatory nadir 48 h prior to the midcycle mFSH and mLH surges. Serum mFSH concentrations following the midcycle gonadotropin surges decreased progressively as serum progesterone concentrations increased and reached a plateau, and then increased during the last week of the menstrual cycle as corpus luteum function was waning. We have prepared a large pool of antiserum for distribution under the aegis of the Contraceptive Development Branch of the Center for Population Research, the National Institute of Child Health and Human Development.

Animals↗
PubMed1976

Purification and properties of reptilian and amphibian growth hormones.

Highly purified growth hormone was isolated from the pituitaries of two reptilian species, the snapping turtle and the sea turtle, and two amphibian species, the bullfrog and the leopard frog. Characterization studies were performed with these growth hormones in comparison with mammalian and avian growth hormones. Great similarities among these species were found in chromatographic behavior, Ve/Vo ratios (2.0) on gel filtration, disc electrophoretic patterns, terminal amino acid residues and immunochemical reactivity with snapping turtle growth hormone antiserum. Species differences were noted in amino acid composition and immunoactivity measured by rat growth hormone antiserum, and these appeared to reflect the phylogenetic relationships among the four tetrapod species. The turtle and frog growth hormones gave parallel dose responses in the rat tibia assay. All were less potent than the bovine growth hormone standard except the bullfrog growth hormone which was equipotent if not more active. The data indicate that many elements of growth hormone structure have been strongly conserved during evolution.

Amino Acid Sequence↗
PubMed1976

Stimulation of aromatization of exogenous and endogenous androgens in ovaries of hypophysectomized rats in vivo by follicle-stimulating hormone.

The role of follicle-stimulating hormone (FSH) in the regulation of estrogen biosynthesis in vivo has been investigated in immature hypophysectomized rats, utilizing uterine weight and histologic responses, and ovarian estradiol-17beta concentrations as indicators of estrogen secretion. A highly purified FSH preparation produced only borderline increases in uterine weights and in ovarian estradiol-17beta contents when administered alone at 2.5 mug/day for 3 days. Testosterone or androstenedione (5 mg/day), when administered in the absence of FSH, produced typically androgenic stimulation of uteri, and did not increase ovarian estradiol-17beta concentrations. When administered concomitantly with FSH, the uterine weight-stimulating activity of these aromatizable androgens was substantially increased, accompanied by marked hypertrophy of the endometrial mucosal cells, and ovarian estradiol-17beta concentrations were increased 20- to 200-fold. The administration of the non-aromatizable androgen, 17beta-OH-5alpha-androstan-3-one (DHT) (5 mg/day, by itself produced uterine weight increases similar to those caused by testosterone alone; however, no evidence of increased estrogen secretion resulted from the combined treatment of DHT wtih FSH. A highly purified luteinizing hormone (LH) preparation was equally as effective as exogenous androstenedione in increasing ovarian concentrations of immunoreactive androgen (testosterone + DHT) but evoked none of the above signs of estrogen secretion unless administered together with FSH. The weights of ovaries were not affected by the administration of LH or of any of the androgens by themselves, but were approximately doubled by FSH alone. Ovarian weights were increased still further when FSH was administered concomitantly with LH, testosterone , or androstenedione, but not with DHT. It is concluded that FSH and LH regulate ovarian estrogen secretion in vivo by acting at biochemically distinct sites--LH stimulating the synthesis of C19-steroids, which are then converted to estradiol-17beta under specific stimulation by FSH.

Androgens↗
PubMed1975

Pituitary growth hormones: further evidence for evolutionary conservatism based on immunochemical studies.

Immunochemical relatedness of preparations of purified somatotropins (growth hormones) of somatotropins in pituitary extracts from various vertebrate species was investigated by applying an antiserum to a purified somatotropin from a submammalian species, the snapping turtle. With the exception of monkey somatotropin, all mammalian, reptilian, and avian preparations tested showed reactions of identity or near identity by immunodiffusion studies in agar gel. Radioimmunoassay employing labeled rat somatotropin as a tracer and for standards, revealed that these same pituitary preparations gave steep inhibition slopes that were parallel or nearly parallel to each other. Purified somatotropins or somatotropins in pituitary extracts of subreptilian species, including an amphibian and existing primitive fishes, showed partial yet substantial relatedness to mammalian (ray) or reptilian (turtle) somatotropins by both immunodiffusion and radioimmunoassay. Our evidence indicates that the immunochemical relatedness of somatotropins from various vertebrate species appears to be even closer than has been suggested previously, and that a high degree of conservation of structure occurs during evolution.

Animals↗