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Biomedical subjects

F Talamantes

Publications and source records attributed to F Talamantes.

At least 145 records · Page 8Linked to original sources
PubMed1983

Development and characterization of a homologous radioimmunoassay for deer mouse (Peromyscus maniculatus bairdii) prolactin.

A highly specific and sensitive homologous radioimmunoassay has been developed for the secreted form of prolactin from the deer mouse Peromyscus maniculatus bairdii. Peromyscus serum and pituitary homogenates displayed parallel dilution response curves, and no cross reaction was seen with either mouse prolactin, mouse growth hormone or rat prolactin. The assay was sensitive to 25 picograms per tube and the intra- and inter-assay coefficients of variation were 5 and 3.6%, respectively. In addition, we have demonstrated that Peromyscus prolactin does not show parallel displacement in a homologous radioimmunoassay utilized for measuring prolactin in the common laboratory mouse.

Animals↗
PubMed1983

Secretion kinetics of prolactin and growth hormone by mouse anterior pituitaries in long term organ cultures.

Long-term organ cultures of mouse anterior pituitaries provides a system for generating an enriched starting material for the purification of prolactin and growth hormone. Culturing 1 anterior pituitary per ml in serum-free medium for 12 days resulted in a total yield of 40.9 micrograms and 6.6 micrograms of prolactin and growth hormone, respectively. This yield represented a 1886% and 18% net increase over the control prolactin and growth hormone content in the unincubated pituitaries. Secondly, culturing of 1-5 anterior pituitaries per ml did not result in a negative feedback autoregulation in the culture system.

Animals↗
PubMed1983

Isolation, purification, and characterization of deer mouse (Peromyscus maniculatus bairdii) prolactin.

Prolactin (PRL) secreted by Peromyscus maniculatus bairdii anterior pituitaries was purified by gel filtration on Sephadex G-100 and ion-exchange chromatography on DEAE-cellulose. Peromyscus PRL (pmPRL) eluted from Sephadex G-100 with an elution-to-void volume ratio of 1.9 and at a salt concentration of 100 mM NaCl on DEAE-cellulose. Electrophoretic homogeneity of the hormone was demonstrated in several gel systems. On 7 1/2% alkaline polyacrylamide gels, pmPRL migrated with an Rf of 0.65. The molecular weight of pmPRL was estimated at 24,000 to 26,000 by sodium dodecyl sulfate electrophoresis and molecular exclusion chromatography. The amino acid composition of pmPRL was similar to other mammalian PRLs including two tryptophan residues and three disulfide bonds. Leucine was found to be the NH2-terminal residue. Circular dichroism (CD) spectra indicated an alpha-helix content of 55 +/- 5%, a value typical for prolactin molecules. However, in the region of side-chain absorption, the CD spectrum displayed a weak, asymmetric, negative band near 299 nm, with the CD returning to slightly positive values at 292 nm. This CD pattern is not typical of other secreted or stored prolactins. In the pigeon crop-sac assay, pmPRL showed a prolactin-like activity of 21 IU/mg.

Amino Acids↗
PubMed1983

Conformational comparison of stored and secreted ovine pituitary prolactin.

Highly purified samples of stored and secreted ovine pituitary prolactin have been compared with regard to those conformational properties evidenced by ultraviolet absorption and circular dichroism measurements. No significant differences were found in any of the optical properties measured. The previously reported absence of tryptophanyl circular dichroism in the secreted forms of rat and mouse prolactins may be typical only of rodent hormones and not a general phenomenon.

Animals↗
PubMed1983

Genetic and litter size effects on serum placental lactogen in the mouse.

Placental lactogen (PL) and progesterone are important hormones of pregnancy in the mouse. The purpose of this study was to investigate the influence of genetic differences and litter size on serum PL levels in the mouse. Serum progesterone levels were also measured in some experiments. Two features of serum PL levels under genetic control were identified: 1) the gestational profile of serum PL and 2) absolute serum PL levels. Breeding combinations that resulted in profound effects on serum PL levels were without significant affect on serum progesterone levels. Serum concentrations of PL and progesterone were directly proportional to litter size. Conceptus number was found to significantly affect ovarian progesterone release. The presence of uterine tissue antagonized the luteotropic actions of the conceptus but did not affect serum PL levels.

Analysis of Variance↗
PubMed1983

Effects of short photoperiod on the ability of golden hamster pituitaries to secrete prolactin and gonadotropins in vitro.

Transfer of male golden (Syrian) hamsters from a 14L:10D (light:dark) to a 5L:19D photoperiod induced significant changes in pituitary function tested in vitro. Within 27 days after transfer to a 5L:19D photoperiod, basal prolactin (Prl) release was significantly depressed and response to dopamine (DA) was significantly enhanced as compared to Prl release by pituitaries from 14L: 10D hamsters. Follicle-stimulating hormone (FSH) release tended to be depressed after 9 or 27 days of 5L:19D exposure, but the effect was not significant. After 77 days of 5L:19D exposure, Prl release was further suppressed, while FSH release surpassed that seen in 14L:10D pituitaries. In vitro FSH response to luteinizing hormone releasing hormone (LHRH) was also enhanced at this time. After 15 weeks of exposure to a short photoperiod, FSH secretion was still elevated above control levels, but Prl release and Prl response to DA were no longer different from that of 14L: 10D controls. Secretion of luteinizing hormone (LH) in vitro, either basal or LHRH stimulated, was not affected by photoperiod at any time tested. From these results, we conclude that short photoperiod exposure does not reduce the pituitary's ability to secrete LH or FSH, although secretion of Prl is severely attenuated.

Animals↗
PubMed1983

Identification and partial characterization of a lactogen from the midpregnant mouse conceptus.

Previously, we demonstrated that measurement of serum lactogenic hormones during pregnancy in the mouse by the rabbit mammary gland radioreceptor assay (RRA) and specific RIAs for mouse PRL (mPRL) and mouse placental lactogen (mPL) showed a large RRA to RIA activity ratio during midpregnancy. The purpose of this study was to begin to characterize this discrepancy in midpregnancy PRL-like activity. The elution profile of serum from midpregnant mice on Sephadex G-100 showed a characteristic peak in RRA activity (elution volume/void volume = 1.5), distinct from either mPRL or mPL (both approximately elution volume/void volume = 2.0). This PRL-like activity was not recognized by antisera to either mPRL or mPL. The source of the midpregnancy lactogen was localized to the conceptus. The hormone was found to have an apparent molecular weight of 50,000 (based on Sephadex G-100 chromatography) and an electrophoretic mobility similar to mPRL (Rf = 0.5-0.6) and to be lactogenic in the in vitro mouse mammary gland explant bioassay. We have demonstrated the existence of a midpregnancy lactogen that is different from mPL and mPRL and is of conceptus origin.

Animals↗
PubMed1983

Midpregnancy elevation of serum androstenedione levels in the C3H/HeN mouse: placental origin.

The purpose of this study was to characterize the serum profile of androstenedione during pregnancy in the C3H/HeN mouse and to determine the site of its production. Serum androstenedione levels were characterized by a prominent midpregnancy elevation and were substantially higher than testosterone levels during pregnancy. The results of our studies support a placental site of production for androstenedione during midpregnancy: 1) uterine venous levels of androstenedione are higher than peripheral androstenedione levels at midpregnancy and during the second half of pregnancy, 2) developmental changes in the in vitro release of androstenedione by conceptuses coincide temporally with serum changes in androstenedione levels, 3) the day 10 placenta releases significantly more androstenedione in vitro than do other endocrine tissues from day 10 of pregnancy, and 4) serum androstenedione levels are maintained after bilateral ovariectomy on day 10 of pregnancy.

Androstenedione↗
PubMed1983

Development of a homologous radioimmunoassay for secreted hamster prolactin.

A specific and sensitive homologous radioimmunoassay has been developed for secreted hamster prolactin. Hamster serum and pituitary extracts showed parallel dilution-response curves with hamster prolactin. The sensitivity of the assay ranged from 0.5 to 1.0 ng/ml, and the intra- and inter-assay coefficients of variation were 6 and 10%, respectively. Additionally we have demonstrated that the rat prolactin radioimmunoassay kit distributed by the National Institute of Arthritis, Metabolism, and Digestive Diseases is an inadequate method for the measurement of hamster prolactin.

Animals↗
PubMed1983

Effects of handling and ether anesthesia on serum prolactin levels in the golden hamster.

The effects of handling and ether stress on serum prolactin (PRL) levels in gonadally active and gonadally regressed male golden hamsters and in females in different stages of the estrous cycle were examined. Males, regardless of reproductive state or photoperiod, showed no significant alterations in serum PRL levels following exposure to ether and cardiac puncture, in contrast to females, which showed a significant elevation in serum PRL following these two procedures. This increase was small and inconsistent in females etherized for 1 min, but it was very pronounced in females etherized for 6 min. In females there was also a slight but significant increase in PRL following transfer from the animal room to the laboratory. Thus, routine experimental manipulations, such as moving the animals to a laboratory and ether exposure, induce significant and variable elevations of serum prolactin in female hamsters.

Animals↗
PubMed1982

Conformational studies of secreted mouse pituitary prolactin.

A secreted form of mouse pituitary prolactin has been shown to contain only a single tryptophan residue. All previously reported prolactins contain two tryptophans. Circular dichroism spectra indicate that secreted mouse prolactin is conformationally similar to stored forms of prolactin previously isolated from several other species, including its alpha-helix content (65%). However, like secreted rat prolactin, secreted mouse prolactin shows no tryptophan signal in its circular dichroism spectrum. All stored forms of prolactin studied to date display distinct tryptophan signals. This suggests the possibility that secretion of prolactin may be accompanied by modification of the protein's tertiary structure.

Animals↗
PubMed1982

Isolation, purification, and characterization of mouse placental lactogen.

Mouse placental lactogen was purified 1840-fold from BALB/c placentae from days 14-18 of gestation with an overall yield of 29%. The purification procedure included alkaline homogenization and extraction, ammonium sulfate precipitation, hydrophobic interaction chromatography on Phenyl-Sepharose, ion-exchange chromatography on CM- and DEAE-cellulose, and gel exclusion chromatography on Sephadex G-100. On 10% alkaline polyacrylamide gels, mouse placental lactogen had an Rf of 0.19. Electrophoresis in gels containing NaDodSO4 showed a single band with a mobility corresponding to a Mr of 23,000 +/- 1000. The isoelectric point, determined by isoelectric focusing in 8 M urea/5% 2-mercaptoethanol, was 7.1. When tested in the pigeon crop sac assay, 10 micrograms of mouse placental lactogen produced stimulation comparable with that evoked by 10 micrograms of ovine prolactin. In the rabbit mammary gland radioreceptor assay, mouse placental lactogen was 150% more potent than ovine prolactin in displacing 125I-labeled ovine prolactin from rabbit mammary gland membranes. Iodinated purified mouse placental lactogen could be displaced from rabbit mammary gland membranes by mouse placental lactogen, mouse prolactin, and ovine prolactin. Ovine prolactin was 45% as avid as mouse placental lactogen is displacing 125I-labeled mouse placental lactogen from rabbit mammary gland membranes. Mouse placental lactogen did not crossreact with antisera to mouse prolactin or mouse growth hormone in a radioimmunoassay.

Animals↗
PubMed1982

Placental and serum hormone changes during the second half of pregnancy in the hamster.

The concentrations of androgen, estrogen, progesterone, and prolactin-like hormones in serum, placentae, and media from placental incubations during the second half of pregnancy in the hamster were determined. Concentrations of prolactin-like activity in serum, placentae, and media from placental incubations increased from Day 8 to Day 14 of gestation. On Day 16 of pregnancy the content and in vitro release of placental prolactin-like activity declined; however, serum prolactin-like activity increased. The in vitro release of 3H-protein by hamster placentae showed gestational changes resembling the pattern of in vitro placental lactogen release. Serum and placental content of progesterone increased from Day 8 to Day 14 of gestation and declined from Day 14 to Day 16. In vitro placental progesterone release increased from Day 8 to Day 12 and declined from Day 12 to Day 16. Serum estrogen levels were elevated during the second half of pregnancy, whereas serum androgen levels were minimal. Neither estrogen nor androgen production by hamster placentae could be detected.

Androgens↗
PubMed1982

Partial characterization of mouse placental lactogen.

Serum, placental, extracts, and placental incubation medium from 12- and 17-day-pregnant mice were fractionated by gel exclusion chromatography on Sephadex G-100. The eluates were monitored for activity by a radioreceptor assay (RRA) for lactogenic hormones that detects placental lactogen (PL) and PRL. RRA activity in serum and placental extracts and incubation medium from both days of gestation eluted in two peaks, the first emerging in the void volume (Vo) and the second with an elution volume (Ve) to Vo ratio of 1.96, which was similar to the Ve to Vo ratio of a human PL marker. Fractions in the second peak stimulated casein synthesis in mouse mammary gland explants. The RRA activity of the eluates was not due to the presence of PRL, as determined by RIA, and therefore the activity in the second peak was identified as monomeric PL. Electrophoresis of mouse placental extracts and incubation medium from both days 12 and 17 of gestation on 10% polyacrylamide gels showed only one band of RRA activity (Rf = 0.22). The present results show there are no differences between the elution profiles on Sephadex G-100 and the electrophoretic mobilities of PL from serum, placental extracts, and placental incubation media from days 12 and 17 of pregnancy in mice.

Animals↗
PubMed1982

The development and characterization of a homologous radioimmunoassay for mouse placental lactogen.

A highly specific and sensitive homologous radioimmunoassay (RIA) has been developed for mouse placental lactogen(mPL). Mouse pregnancy serum and placental extracts showed parallel dilution-response curves, and no significant cross-reaction was seen with either mouse growth hormone or mouse prolactin. The sensitivity of the assay ranged from 0.5 to 1.0 ng/ml, and the intra- and inter-assay coefficients of variation were 5 and 11%, respectively. By RIA, mPL levels were detectable on day 9 of pregnancy (1 ng/ml) and increased until day 14 (100-150 ng/ml) in both C3H and BALB/c strains. On days 14-18 of pregnancy, mPL levels were maintained (95-125 ng/ml) in C3H mice, while they continued to increase (greater than 250 ng/ml) in BALB/c mice. In both strains, a midpregnancy peak in prolactin-like activity was detected by a radioreceptor assay but not by the mPL RIA.

Animals↗
PubMed1982

Gestational effects on placental and serum androgen, progesterone and prolactin-like activity in the mouse.

The concentrations of androgen, progesterone and prolactin-like activity in serum, placentae and media from placental incubations during the second half of pregnancy in the C3H mouse were evaluated. Serum concentrations, placental content and in-vitro placental release of androgen were raised on day 10 of pregnancy. Serum progesterone levels showed minor fluctuations during the second half of gestation, whereas placenta content and in-vitro release of progesterone were increased on day 10 of gestation. The serum profile of prolactin-like activity showed a significant mid-pregnancy increase on day 10 which did not correlate with placental content or in-vitro placental release of prolactin-like activity. The placental content and in-vitro release of prolactin-like activity were low during mid-pregnancy and increased during the latter days of gestation when serum prolactin-like activity was reduced.

Androgens↗