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Biomedical subjects

F Talamantes

Publications and source records attributed to F Talamantes.

162 records · Page 9Linked to original sources
PubMed1981

Isolation and partial characterization of secreted hamster pituitary prolactin.

PRL secreted by hamster anterior pituitaries was purified by gel filtration on Sephadex G-100 and ion exchange chromatography on DEAE-cellulose. Hamster PRL eluted from Sephadex G-100 with an elution volume to void volume ratio of 1.85 and at a salt concentration of 0.13 M NaCl on DEAE-cellulose. Electrophoretic homogeneity of the hormone was demonstrated in several gel systems, and electrophoresis in the presence of sodium dodecyl sulfate indicated a molecular weight of 22,000 +/- 2,000. Hamster PRL did not cross-react with antiserum to mouse PRL. Hamster PRL displayed lactogenic activity in an in vitro mouse mammary gland assay. Hamster PRL displaced [125I]iodo-PRL from lactating rabbit mammary gland receptors. Thus, with respect to its exclusion properties on SEphadex G-100, its molecular weight, and its biological activity, hamster PRL closely resembles other mammalian PRLs.

Animals↗
PubMed1981

Multiple forms of growth hormone: detection in medium from cultured pituitary adenoma explants.

Three pituitary adenomas obtained from patients wtih acromegaly were maintained in organ explant culture for a period of 12 days in a defined culture medium. Lyophilized culture medium from each was then examined by electrophoresis to determine which forms of growth hormone were secreted by the explants. All three explants secreted principally the major form of growth hormone. One adenoma however secreted unusually large amounts of two slowly migrating forms which were in low concentration in the GH-containing granules of normal pituitaries. On the other hand the adenoma produced a much lower amount of a 20,000-dalton variant than was seen in normal pituitary glands. The other two adenomas did not secrete the relatively large amounts of the slowly migrating forms although the quantity of the 20,000-dalton form was less than the amount seen in the normal pituitary. There was no evidence of proteolytic alteration of the growth hormone during the culturing process. In companion experiments with rat pituitary glands the growth hormone did not undergo proteolytic degradation in the gland left in situ for 96 h at 5 degrees C.

Adenoma↗
PubMed1980

The lactogenic response of mouse mammary explants to mose prolactin and growth hormone.

The lactogenic response of mouse mammary explants to mouse prolactin (mPRL) and mouse growth hormone (mGH) was studied. Mouse mammary explants were cultured, in a defined medium, in the presence of varying concentrations of either mPRL or mGH and the rate of 3H amino acid incorporation into casein was measured. The lactogenic activity of mPRL was compared with that of ovine prolactin (oPRL) and found to be directly comparable. MGH, when compared to oPRL, was found to be less active in stimulating casein synthesis.

Animals↗
PubMed1980

Phylogenetic distribution, regulation of secretion, and prolactin-like effects of placental lactogens.

The occurrence of placental lactogens has been reported for members of 4 orders, 7 families, and 15 genera, while its absence has been documented in representatives from 4 orders, 5 families, and 5 genera. Placental lactogens from several genera have been isolated, purified, and characterized biochemically. The cellular sites of production and patterns of secretion of placental lactogens have been described. The regulation of placental lactogen secretion is not understood, although its synthesis and release can be modified experimentally by altering metabolic, ionic, and hormonal factors in the placental environment. Placental lactogens stimulate lactogenesis and steroidogenesis. The mechanism underlying placental lactogen's role in these processes has not been clarified.

Animals↗
PubMed1979

Lactogenic response of mouse mammary explants from different days of pregnancy to placental lactogen and pituitary prolactin.

The lactogenic response of mouse mammary gland explants to human placental lactogen (hPL) and ovine pituitary prolactin (oPRL) was examined on days 10 to 18 of pregnancy by measuring 3H-amino acid incorporation into calcium-rennin precipitable casein. To determine the lactogenic response of the explants, the mean slopes of dose-response curves were calculated for each hormone treatment. Slope means of dose-response curves for oPRL and hPL did not differ from each other on any day of pregnancy examined. A triphasic pattern of response was suggested when slope means of dose-response curves for both hormones were plotted as a function of day of gestation. Peak responses were observed on days 10, 13 and 17-18. Combinations of oPRL and hPL, in ratios of oPRL:hPL = 2:1 and oPRL:hPL = 1:2, also produced a triphasic pattern of sensitivity very similar to that produced by either hormone alone. These results suggest that mouse mammary explants may be more sensitive to oPRL and hPL on days 10, 13 and 17-18 of pregnancy.

Animals↗
PubMed1978

Isolation and partial characterization of secreted mouse pituitary prolactin.

Prolactin secreted by mouse anterior pituitaries was purified by gel filtration on Sephadex G-100. Electrophoretic homogeneity of the purified hormone was demonstrated in several gel systems, and electrophoresis in the presence of sodium dodecyl sulfate indicated an apparent molecular weight of 21 000 +/- 2000. Mouse and ovine prolactin displayed parallel dose vs. response curves in radio-receptor binding studies, indicating that these two hormones compete for identical receptor sites on rabbit mammary membranes. Comparative peptide mapping studies carried out on tryptic digests of mouse and ovine prolactin suggested only partial homology between the two hormones. Internally labeled monomeric mouse prolactin was observed to undergo aggregation following storage at --20 degrees C for 2 months.

Animals↗
PubMed1977

Effects of chlordane isomers administered to female mice during the neonatal period.

In consideration of the influence that chlorinated hydrocarbon insecticides may exert on mammalian physiology, the present study was performed to investigate the effects of neonatal chlordane administration on body growth and endocrine development in female mice. Mice receiving 0.075 or 0.15 mg of alpha or gamma chlordane on day 2, 3, and 4 of life were observed to have growth rates depressed to varying extents depending on the concentration or the type of isomer that was utilized. Eye and vaginal opening in the neonatally treated mice were observed to be delayed to varying degrees, which were dependent on which isomer was used. The total effects observed in the neonatally treated mice were not found to reflect a dose-related response.

Age Factors↗
PubMedDate not supplied

Development of a placental cell culture system for studying the control of mouse placental lactogen II secretion.

Fetal placental tissue from 11 days pregnant mice was dissociated in collagenase and DNase solution and then separated on a 40 per cent Percoll gradient. Trophoblast cells banded at a density of 1.05 g/ml. When cultured on rat tail collagen, these cells formed colonies of mono- and binucleate cells varying in size from 40 to 70 microns. At the time of plating, about 13 per cent of the trophoblast cells secreted mouse placental lactogen II (mPL-II) as determined by reverse haemolytic plaque assay. The ratio of mPL-II-producing cells increased significantly in culture and reached 63 per cent after 48 h. The secretion of mPL-II increased continuously during six days of culture, whereas the total protein release was highest after the first day, declined the second day and then remained relatively constant for the last four days of culture. The DNA content of the cells did not change significantly during the six-day period. When the trophoblast cells were incubated with insulin (1 ng/ml to 5 micrograms/ml), a modest but significant reduction in mPL-II secretion was observed. No change in the mPL-II secretion was seen when epidermal growth factor was administered to the culture in concentrations from 1 ng/ml to 10 micrograms/ml. It is concluded that this in vitro culture system is suitable for studying both mPL-II secretion and the differentiation of mPL-II-producing cells.

Animals↗
PubMedDate not supplied

Characterization of the mouse placental epidermal growth factor receptor: changes in receptor number with day of gestation.

The epidermal growth factor (EGF) receptor is present in the mouse placenta in both a low- and a high-affinity form having approximate values for Ka of 10(7) M-1 and 10(9) M-1, respectively. No significant difference (P greater than or equal to 0.05) in the number of receptors existed between placental membrane preparations from days 10 and 17, both for the low- and the high-affinity receptor. The number of both high- and low-affinity receptors was significantly lower (P less than 0.05) for day 14 placental membranes than for either day 10 or day 17 placental membranes. Cross-linking of 125I-EGF to placental membranes resulted in the specific labelling of two major receptor forms with approximate molecular weights of 170,000 and 154,000, as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

Animals↗
PubMedDate not supplied

Estradiol and testosterone concentrations increase with fasting in weaned pups of the northern elephant seal (Mirounga angustirostris).

Although neonatal development is generally associated with increased levels of circulating testosterone (T) and estradiol (E2), food deprivation may inhibit steroidogenesis. Therefore, these potentially conflicting stimuli were examined in fasting weaned northern elephant seal (Mirounga angustirostris) pups by measuring serum concentrations of T, E2, progesterone (P4), and luteinizing hormone (LH) by either radioimmunoassay (P4, LH) or enzymeimmunoassay (T, E2). Blood samples were obtained from 20 male and 20 female pups at both early (<1 wk postweaning) and late (6-8 wk postweaning) periods during their natural postweaning fast. T in males (early: 2.9 +/- 0.4 ng/mL; late: 16 +/- 2 ng/mL; P < 0.0001) and E2 in females (early: 42 +/- 6 pg/mL; late: 67 +/- 5 pg/mL; P < 0.01) increased between the two measurement periods, while P4 (early: 2.5 +/- 0.3 ng/mL; late: 2.1 +/- 0.3 ng/mL; P > 0.05) did not. LH increased (early: 46 +/- 4 pg/mL; late: 65 +/- 6 pg/mL; P < 0.05) in males but not in females (early: 69 +/- 9 pg/mL; late: 65 +/- 6 pg/mL; P > 0.05). Increases in LH and T suggest that LH may stimulate T secretion. Alternatively, relatively low concentrations of LH in both males and females may reflect negative feedback inhibition imposed by elevated T and E2 concentrations. Despite the inherent postweaning fast, concentrations of T and E2 increased, suggesting that they may be critical for the continued development of pups. Therefore, compensatory mechanisms may exist that alleviate the fasting-induced inhibition of gonadal steroidogenesis during neonatal development in elephant seal pups.

Age Factors↗
PubMedDate not supplied

Changes in the parous rat mammary gland environment are involved in parity-associated protection against mammary carcinogenesis.

Parity in rats results in protection from methylnitrosourea (MNU)-induced mammary cancer. Our goal was to determine if systemic alterations in the mammary gland environment after a full-term pregnancy rendered the parous rat an inadequate host for promotion of initiated mammary epithelial cells to become cancerous. Lewis rat MNU-treated mammary epithelial cells were transplanted into uniparous (UP), age-matched virgin (AMV) (both 130-150 d), or young virgin (YV) (50-60 d) syngeneic hosts to examine if differences in the systemic environments of the three hosts had an effect on hyperplasia and cancer formation. More transplants in YV and AMV hosts contained hyperplasias and adenocarcinomas as compared to transplants in UP hosts. In addition, UP host transplants had significantly fewer numbers of hyperplastic lesions than transplants from the virgin hosts. The evidence presented here shows that the uniparous host environment is less supportive than that of the virgin host for hyperplasia and cancer development.

Animals↗