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F Talamantes

Publications and source records attributed to F Talamantes.

At least 55 records · Page 3Linked to original sources
PubMed1994

Mouse placental cells secrete immunoreactive growth hormone-releasing factor.

The initial objective of this study was to establish a placental cell culture system in which the secretion of mouse growth hormone-releasing factor (mGHRF) could be examined during a several-day period. To determine when during pregnancy placental cells begin to express mGHRF, Northern blot analysis was carried out on total RNA from placentas collected on Days 6, 9, 11, 13, 15, 17, and 18 of pregnancy. Mouse GHRF mRNA could be detected as early as Day 11 of pregnancy. Its steady-state levels increased to maximum values on Days 15-17 and then declined slightly on Day 18. Placentas from Day 12 of pregnancy were selected for cell culture. The basal zone and labyrinth were dispersed in collagenase, and the cells were fractionated on a Percoll gradient. Two bands of cells were selected for further study. Both released significant amounts of immunoreactive mGHRF during a 5-day culture period. Effects of prolonged exposure of the cells to 8-bromo-cAMP and to agents that elevate intracellular cAMP concentration were then examined. Treatment of the cells with 0.5 mM 8-bromo-cAMP resulted in a significant decrease in the mGHRF concentration of the medium by the second day of culture. Mouse GHRF secretion was also inhibited by treatment of the cells with 100 ng/ml cholera toxin or 0.1 mM forskolin. The effect of 8-bromo-cAMP was concentration-dependent, with 0.1 mM being the lowest concentration that was active. 8-Bromo-cAMP treatment also reduced the steady-state level of mGHRF mRNA in the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Mouse growth hormone-binding protein and growth hormone receptor transcripts are produced from a single gene by alternative splicing.

Serum contains a soluble growth hormone-binding protein which is produced in some species by proteolytic cleavage of the extracellular domain of the growth hormone receptor. The hypothesis that a growth hormone-binding protein messenger RNA is produced in other species by alternative splicing of nascent growth hormone receptor transcripts was confirmed by analysis of the mouse growth hormone receptor gene. An exon that encodes the hydrophilic tail of the binding protein is located between an exon encoding the final portion of the hormone binding domain and an exon encoding the hydrophobic transmembrane domain of the receptor.

Amino Acid Sequence↗
PubMed1994

Expression of growth hormone-binding protein with a hydrophilic carboxyl terminus by the mouse placenta: studies in vivo and in vitro.

GH-binding protein (GHBP) or GH receptor is present in numerous extrahepatic tissues in the rodent. From mid- to late gestation in the mouse, the maternal serum concentration of GHBP increases 30- to 50-fold. We have investigated whether the placenta might synthesize GHBP and potentially contribute to this increase. RNA was isolated from placentas and subjected to Northern analysis using a cDNA probe to the shared region of GHBP and GH receptor-encoding mRNAs. From day 8 to day 18 of gestation, the GHBP-encoding mRNA (1.4 kb) increased 45-fold in quantity. The GH receptor-encoding mRNA (4.2 kb) increased sixfold by day 14 and then remained steady until day 18. These changes which were not co-ordinated parallel reported changes in the steady-state concentrations of 1.4 and 4.2 kb mRNAs in maternal liver, suggesting shared regulatory factors. Extracts of freshly isolated trophoblasts were assayed for GHBP with a radioimmunoassay specific for GHBP with a hydrophilic carboxyl terminus. The cytosolic content of immunoreactive GHBP increased fourfold from mid- to late gestation. Trophoblasts were isolated from placentas and cultured for 2 days on collagen gels in defined medium. Cultured cells were at least 90% viable and secreted mouse placental lactogen-II (mPL-II). Immunocytochemistry was carried out simultaneously on cells cultured from day 7 to day 17 of gestation using a monoclonal antibody (MAb 4.3), which recognizes the hydrophilic C-terminus of GHBP. Cell-localized GHBP was present in trophoblasts cultured for 2 days, but GHBP was not detectable by radioimmunoassay or by immunoprecipitation in concentrated culture media from cultures treated with 100 ng mouse GH/ml or 100 ng mPL-II/ml or from untreated cultures. RNA was isolated from cells cultured in an identical manner to those analysed by immunocytochemistry. Three GH receptor/GHBP mRNA species of 8, 4.2 and 1.4 kb were observed. The quantity of 4.2 and 1.4 kb mRNAs did not change significantly in cultures from day 7 to day 15 of gestation but, in cultures from day 17 of gestation, the amount of 1.4 kb mRNA dropped significantly, while that of the 4.2 kb mRNA remained unchanged. GHBP- and GH receptor-encoding mRNAs are not co-ordinately regulated in vivo or in vitro. Although mPL-II was secreted into the medium by cultured trophoblasts, secretion of GHBP could not be detected. The culture medium may not contain the specific factors required for secretion of placental GHBP, or placental GHBP may not be destined for secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Selective inhibition of mouse placental lactogen II secretion by tumour necrosis factor-alpha.

The placental members of the prolactin-GH-placental lactogen (PL) gene family of the mouse include mPL-I, mPL-II, proliferin (PLF) and proliferin-related protein (PRP). The aim of the present study was to assess the effects of tumour necrosis factor-alpha (TNF-alpha) on the secretion of these proteins in primary cultures of placental cells from days 7, 9 and 12 of pregnancy. The effects of epidermal growth factor (EGF) on the secretion of PLF and PRP were also determined. EGF has previously been shown to stimulate mPL-I and inhibit mPL-II secretion. Incubation of placental cells from day 7 of pregnancy for 5 days with 10 nmol human (h)TNF-alpha/l did not affect the mPL-II concentration of the medium, but similar treatment of cells from days 9 or 12 of pregnancy resulted in a significant reduction in the mPL-II concentration of the medium by the second or third day of culture. The intracellular concentration of mPL-II, the number of cells that released mPL-II as assessed by reverse haemolytic plaque assay, and steady-state levels of mPL-II mRNA as assessed by Northern analysis were also reduced by hTNF-alpha treatment. The lowest concentration of hTNF-alpha that significantly inhibited mPL-II secretion by cells from day 12 of pregnancy was 0.01 nmol/l. hTNF-alpha treatment did not affect the secretion of mPL-I, PLF or PRP, as assessed by the concentrations of these proteins in the medium during a 5-day incubation. Incubation of the cells with 20 ng EGF/ml also did not affect the PLF or PRP concentration of the medium during 5 days of culture. To determine whether the effect of hTNF-alpha on mPL-II secretion was mediated by interleukin-6 (IL-6), the IL-6 concentration of the medium of control and hTNF-alpha-treated cells was determined. Bioactive and immunoreactive IL-6 could not be detected in medium from either treatment group. The presence of binding sites for hTNF-alpha was assessed in cells from day 12 of pregnancy. Scatchard analysis detected a single class of binding sites having a Kd of 1.61 +/- 0.34 nmol/l, with about 1350 sites per cell. The results of this study demonstrate that hTNF-alpha inhibits the secretion of mPL-II by placental cells from days 9 and 12 of pregnancy, suggesting that TNF-alpha may be one of the factors that regulate the production of this hormone in vivo.

Animals↗
PubMed1994

The structure and regulation of expression of the mouse growth hormone receptor and binding protein.

The mouse growth hormone receptor (mGHR) and the mouse growth hormone-binding protein (mGHBP) are products of a single gene which are generated by alternative splicing. The factors that regulate the expression of mGHR and mGHBP mRNA and protein during pregnancy in the mouse are incompletely understood. During pregnancy in the mouse, there are parallel increases in circulating mouse growth hormone (mGH), liver mGHR, and serum mGHBP. The increase in both hepatic mGHR and serum mGHBP begins on Day 9 of gestation and by late gestation the hepatic mGHR content has increased 8-fold and serum mGHBP has increased 30-fold compared with values in nonpregnant controls. A parallel increase occurs in the steady state levels of liver GHR and GHBP encoding mRNAs. The increase in both messages begins on Day 9 of gestation; however, the GHR mRNA reaches maximum levels by Day 13, while the GHBP mRNA continues to increase until the end of pregnancy. The magnitude of the increase in the GHR-encoding message is 15- to 20-fold between nonpregnant and late pregnant mice, and the magnitude of the increase in the GHBP-encoding message is 30- to 50-fold. Both pituitary mGH and the number of conceptuses influence the receptors and binding protein for mGH during pregnancy.

Alternative Splicing↗
PubMed1994

Serum growth hormone binding protein and hepatic GH binding sites in the Lewis dwarf rat: effects of IGF-I and GH.

A radioimmunoassay (RIA) for the rat growth hormone binding protein (GHBP) was developed using a synthetic peptide (corresponding to the hydrophilic carboxyl-terminal sequence of mouse GHBP) as standard and a monoclonal antibody (MAb 4.3) reactive with this peptide as the primary antibody. The values for GHBP concentration obtained for normal rats using this assay compare favourably with those obtained by gel filtration and ELISA methods. The concentration of GHBP in normal male rats at 11 weeks of age (680 +/- 30 ng/ml, SEM, n = 9) was significantly less than the concentration in normal females (943 +/- 47 ng/ml, SEM, n = 25). In 11-week-old dwarf male rats the concentration of GHBP was 423 +/- 35 ng/ml (n = 8); less than in dwarf females (542 +/- 32, P < 0.05, n = 9) and normal males (680 +/- 30, P < 0.001, n = 9). The GHBP concentration in dwarf rats was not age-dependent, whereas in normal females the concentration of GHBP increased with age. The availability of an RIA which is not susceptible to interference by endogenous GH, will facilitate further studies on hormonal and nutritional regulation of the rat GHBP. The assay was applied to studying the effects of IGF-I infusion (240 micrograms/day for 1 week) and GH injection (65 micrograms/100 g body weight, twice daily for 1 week and 4 weeks) on the serum concentration of GHBP in 11-week-old Lewis dwarf rats. Hepatic GH binding sites were also measured in desaturated membranes from the same animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Interleukin 6 inhibits mouse placental lactogen II but not mouse placental lactogen I secretion in vitro.

The mouse placenta produces several polypeptides belonging to the prolactin-growth hormone gene family, including mouse placental lactogen (mPL) I and mPL-II. The present study was undertaken to determine whether the secretion of mPL-I and mPL-II is regulated by interleukin 6 (IL-6), which is present in the placenta and has previously been reported to stimulate the secretion of pituitary members of this gene family. Effects of human and mouse IL-6 on mPL-I and mPL-II secretion were examined in primary cultures of placental cells from days 7, 9, and 12 of pregnancy. IL-6 caused a dose-dependent reduction in the mPL-II concentration in the medium of cells from days 9 and 12 of pregnancy but did not affect the mPL-II concentration in the medium of cells from day 7 of pregnancy or the mPL-I concentration in the medium of cells from days 7 or 9 of pregnancy. The lowest concentration of human IL-6 that significantly inhibited mPL-II secretion was 250 pM. The effect of IL-6 on the mPL-II concentration in the medium was due primarily to inhibition of mPL-II synthesis, which resulted at least partly from a decrease in the steady-state level of mPL-II mRNA. These data raise the possibility that IL-6 may regulate mPL-II production after midpregnancy in vivo.

Animals↗
PubMed1993

Kinetics of mammary epithelial cell proliferation in pituitary isografted BALB/c mice.

Recently, we have published that treatment of pituitary isografted BALB/c mice with a single injection of N-methyl-N-nitrosourea (MNU) leads to the rapid development of mammary tumors in over 90% of the animals (Guzman et al., Cancer Res., 52, 5732-5737). In the present study, we characterized the changes in proliferative activity and lobulo-alveolar differentiation of MECs at different time intervals after isografting animals with pituitary glands. Virgin BALB/c mice 1, 3, 5 or 8 weeks after pituitary isografting were either pulse-labeled for 2 h or continuously infused with bromodeoxyuridine (BrdU) and the percentage of BrdU-labeled MECs was assessed. The S-phase duration (TS) of MECs was evaluated by double labeling with [3H]thymidine and BrdU. The population potential doubling time (TP) was calculated from the values of BrdU-LI and TS. Three stages of proliferation and differentiation of MECs in pituitary isografted virgin BALB/c mice were observed: (i) A sharp increase in the percentage of proliferating MECs of the terminal ducts and ductal branchings in the first 1-2 weeks, (ii) Development of lobulo-alveolar structures from the terminal ductal and alveolar buds, between weeks 3 and 5 with the highest BrdU-LI in week 3 and (iii) Multiplication of the alveolar structures and decrease in the BrdU-LI between weeks 5 and 8. The BrdU-LIs of alveolar cells 5 weeks after isografting the animals were significantly higher than those of the ductal cells. The continuous administration of BrdU for 3, 5 or 7 days by using osmotic pumps revealed zones in the ducts where almost all MECs were labeled as well as zones lacking proliferate activity. When the BrdU administration was extended for 10-14 days, almost all (> 95%) ductal and lobular epithelial cells were labeled. A small percentage (< 5%), of ductal and lobulo-alveolar MECs cells, remained unlabeled even after 14 days infusion of BrdU. The TS and TP values were shorter in pituitary isografted animals than in controls, but no significant difference was found for either values between the ductal and alveolar cells in either isografted or control mice. Changes in proliferation kinetics of mouse MECs in pituitary isografted animals correlated with the circulating concentrations of prolactin, progesterone and 17 beta-estradiol, but not with corticosterone, growth hormone or thyroxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Effect of homologous placental lactogens, prolactins, and growth hormones on islet B-cell division and insulin secretion in rat, mouse, and human islets: implication for placental lactogen regulation of islet function during pregnancy.

Up-regulation of maternal islet function is essential to accommodate the increased demand for insulin during pregnancy. Previously, we suggested that lactogenic activity regulates islet function during pregnancy. However, this hypothesis was based on the effect of homologous PRLs on islets, since the homologous placental lactogens (or islets) were unavailable. In this study we examine the direct effects of homologous placental lactogens (PL), PRL, and GH on insulin secretion and B-cell division in rat, mouse, and human islets in vitro. Neonatal rat islets were cultured for 8 days in the presence of 0-1000 ng/ml rat PL-I (rPL-I), rPRL, or rGH. Media were changed daily, and the insulin concentration was determined. rPL-I and rPRL (500 ng/ml) treatment resulted in a 2-fold increase in insulin secretion. rGH (1000 ng/ml) elicited a 30% increase in insulin secretion. Similarly, cell replication, as indicated by BrdU incorporation into B-cells, was increased 4-fold in the presence of rPL-I and rPRL. The ED50 for insulin secretion and 5'-bromo-2'-deoxyuridine (BrdU) incorporation was 70 ng/ml for rPL-I and 150 ng/ml for rPRL. Similarly, in adult rat islets, insulin secretion was increased 1.6-fold, and B-cell replication increased 3-fold in the presence of the lactogenic hormones. Neonatal mouse islets were cultured for 8 days in the presence of 500 ng/ml mouse (m) PL-I, mPL-II, mPRL, or mGH. mPL-I, mPL-II, and mPRL treatment resulted in a 2-fold increase in insulin secretion. mGH elicited a 30% increase in insulin secretion. BrdU incorporation into B-cells was increased 3-fold in the presence of mPL-I and mPRL and 2-fold in the presence of mPL-II. Adult human islets were cultured for 8 days in the presence of 1 microgram/ml human (h) PL, hPRL, or hGH. For human islets isolated from six pancreata obtained from females, hPL (138 +/- 10%), hPRL (133 +/- 9%), and hGH (117 +/- 3%) significantly increased insulin secretion compared to that from control islets. This study compares the direct effects among homologous PLs, PRLs, and GHs on insulin secretion and B-cell division in rat, mouse, and human islets. The results indicate that placental lactogen directly regulates islet function in several species and is probably the principal hormone responsible for the increased islet function observed during normal pregnancy.

Adult↗
PubMed1993

Growth hormone receptor and growth hormone-binding protein messages in mouse placenta contain the exon analogous to human exon 3.

Growth hormone receptor (GHR)-encoding messages from the human placenta and other tissues have been recently characterized by several investigators. Of particular interest is the finding that exon 3 is deleted from the mRNA encoding GHR in human placenta, but not in maternal tissues. We have used a reverse transcriptase-polymerase chain reaction (RT-PCR) technique to amplify the distinct mRNAs encoding GHR and GH-binding protein (GHBP) in the mouse placenta and liver, followed by restriction analysis, to determine whether an analogous deletion exists in these mRNAs. The restriction analysis and sequencing of the PCR products shows that the mRNAs encoding GHBP and GHR in the mouse placenta do not have a deletion analogous to that found in human placental GHR mRNA.

Animals↗
PubMed1993

Growth hormone-releasing hormone peptide and mRNA are overexpressed in GH-deficient Ames dwarf mice.

Hypothalamic expression of growth hormone-releasing hormone (GHRH) was quantified morphologically in dwarf mice which exhibit spontaneous genetic GH absence. Mouse GHRH mRNA was assessed by in situ hybridization; densitometric evaluation of total mRNA in dwarfs showed levels 2.3-fold higher than in phenotypically normal siblings (p < 0.01); assessment of mRNA per neuron by autoradiographic grain counting indicated a 2.5-fold increase per cell in dwarfs (p < 0.005). GHRH peptide was evaluated immunocytochemically using a new mouse-specific antiserum; numbers of neurons containing detectable levels were 3-fold higher in dwarfs (p < 0.005). The increase in GHRH mRNA corroborates that reported previously in the GH-deficient little mouse, and after hypophysectomy in rats; GHRH peptide increase contrasts with previous reports of the effect of acute GH removal by hypophysectomy, in which GHRH levels fell. The results suggest that chronic GH deficiency is accompanied by increased translation as well as transcription of GHRH.

Animals↗
PubMed1992

Epidermal growth factor stimulates mouse placental lactogen I but inhibits mouse placental lactogen II secretion in vitro.

This study was undertaken to determine whether epidermal growth factor (EGF) regulates the secretion of mouse placental lactogen (mPL)-I and mPL-II. Primary cell cultures were prepared from placentas from days 7, 9, and 11 of pregnancy and cultured for up to 5 days. Addition of EGF (20 ng/ml) to the medium resulted in significant stimulation of mPL-I secretion by the second day of culture in cells from days 7 and 9 of pregnancy and significant inhibition of mPL-II secretion by the third or fourth day of culture in cells from days 7, 9, and 11. Dose-response studies carried out with cells from day 7 of pregnancy demonstrated that the minimum concentration of EGF that stimulated mPL-I secretion and inhibited mPL-II secretion was 1.0 ng/ml. EGF did not affect the DNA content of the cells or cell viability, assessed by trypan blue exclusion, nor did it have a general effect on protein synthesis. There are three types of PL-containing giant cells in mouse placental cell cultures: cells that contain either mPL-I or mPL-II and cells that contain both hormones. Immunocytochemical analysis and the reverse hemolytic plaque assay indicated that EGF treatment was accompanied by a significant increase in the number of cells that produce mPL-I, but among the PL cells that contained mPL-I, there was no change in the fraction of cells that contained only mPL-I or the fraction that contained both mPL-I and mPL-II. In contrast, EGF treatment did affect the distribution of mPL-II among PL cells. In control cultures, about 75% of the cells that contained mPL-II also contained mPL-I, but in EGF-treated cultures, all of the cells that contained mPL-II also contained mPL-I. These data suggest that EGF regulates mPL-I and mPL-II secretion at least partly by regulating PL cell differentiation.

Animals↗
PubMed1992

Evidence for association of the cloned liver growth hormone receptor with a tyrosine kinase.

The ability of the cloned liver growth hormone (GH) receptor, when expressed in mammalian cell lines, to copurify with tyrosine kinase activity and be tyrosyl phosphorylated was examined. 125I-human growth hormone-GH receptor complexes isolated from COS-7 cells transiently expressing high levels of the cloned liver GH receptor bound to anti-phosphotyrosine antibody, suggesting that the cloned GH receptor is tyrosyl phosphorylated in vivo. GH-GH receptor complexes purified from transfected COS-7 cells using anti-GH antibody incorporated 32P when incubated with [gamma-32P]ATP, indicating association of tyrosine kinase activity with cloned liver GH receptor. The level of phosphorylation of the GH receptor was very low, as compared with the endogenous GH receptor in 3T3-F442A cells, suggesting that tyrosine kinase activity is not intrinsic to the cloned GH receptor but rather resides with a kinase present at low levels in the COS-7 cells. To test whether a higher level of GH receptor phosphorylation would be observed when the GH receptor was expressed in a different cell line, GH receptor cDNAs were stably transfected into mouse L and CHO cells, which have few or no endogenous GH receptors, and RIN5-AH cells, which do express endogenous GH receptors. In vivo tyrosyl phosphorylation of the cloned GH receptor in mouse L cells and in vitro phosphorylation of the cloned GH receptor in both L and CHO cells were higher than in transfected COS-7 cells but still substantially lower than in untransfected 3T3-F442A cells. Significantly increased 32P incorporation into tyrosyl residues in GH receptors in the in vitro kinase assay was demonstrated for GH receptors isolated from the transfected RIN5-AH cells. These studies show that the cloned liver GH receptor can be tyrosyl phosphorylated when expressed in a variety of cell types. The finding that the level of phosphorylation of GH receptor appears to vary with cell type is consistent with the cloned liver GH receptor being a substrate for an associated tyrosine kinase and with the amount of such a GH receptor-associated tyrosine kinase being cell type-specific.

3T3 Cells↗
PubMed1992

Seasonal fluctuations in hormones and behavior of free-living male California ground squirrels (Spermophilus beecheyi).

Plasma testosterone (T), prolactin (PRL), and behavior were monitored concurrently in free-living male California ground squirrels (Spermophilus beecheyi). Male plasma T peaked in January, 2-3 months after males emerged from their annual period of estivation. PRL peaked 6 to 10 weeks after T. Temporal patterns of space use by males were directly correlated with plasma T levels, but seasonal maxima in rates of most monitored male behaviors occurred 4 weeks after the T peak. No monitored behavior rates were correlated with plasma PRL values. Yearling and adult males did not differ with respect to circulating levels of either T or PRL. Both groups of males mated in our study population, and did not differ significantly with respect to rates of most monitored behaviors. However, yearlings pursued fewer females, mated less frequently, and required more mounts to complete each copulation than did adults. We suggest that T serves an important priming function for various seasonally fluctuating behaviors, but also that mating experience might influence the efficiency of copulatory behavior in this species.

Animals↗
PubMed1992

The insulin-like effects of mouse growth hormone on adipose tissue from virgin and pregnant mice.

The abilities of mouse prolactin (mPRL), growth hormone (mGH), placental lactogen (mPL)-I, and mPL-II to stimulate glucose oxidation were investigated, using adipose tissue from both virgin and pregnant mice. In separate experiments, adipose tissue segments from the parametrial fat pads of virgin and pregnant mice were collected on days 7, 13, and 17 of gestation. Tissue segments were first preincubated at 37 degrees C for 3 hours in Krebs-Ringer-HEPES (KRH) buffer without any added hormones. Following the preincubation, mPRL, mGH, recombinant mPL-I, mPL-II (1 microgram/mL), and porcine insulin (plns) (1 ng/L) were added to the incubations, along with 0.5 microCi/mL D-[U-14C]glucose, and incubated for an additional 2 hours. After the second incubation, the 14CO2 produced by the oxidation of the D-[U-14C]glucose was collected and counted. Both mGH and plns significantly stimulated glucose oxidation in adipose tissue from virgin and pregnant mice. However, mPRL, mPL-I, and mPL-II failed to stimulate glucose oxidation in adipose tissue from either virgin or pregnant mice. Preincubating adipose tissue, from day 13 of gestation, with 0.5 microgram/mL epinephrine (Epn) increased basal glucose oxidation and decreased both mGH- and plns-stimulated glucose oxidation. Preincubating adipose tissue, from day 13 of gestation, with 0.11 microgram/mL dexamethasone (Dex) significantly decreased the ability of the tissue to oxidize glucose. However, the Dex-treated tissue retained its ability to increase glucose oxidation in response to mGH and plns. These results indicate that mGH, but not mPRL, mPL-I, or mPL-II, has insulin-like effects on adipose tissue, and that mGH and plns may affect glucose oxidation through similar pathways.

Adipose Tissue↗
PubMed1992

Mammary gland differentiation in hypophysectomized, pregnant mice treated with corticosterone and thyroxine.

Swiss Webster mice were hypophysectomized or sham-operated on Day 11 of pregnancy. The animals were fitted s.c. with osmotic minipumps containing either corticosterone (B) dissolved in Molecusol (Pharmatec, Alachua, FL) or the vehicle alone immediately after they were hypophysectomized. Animals in some of the experimental groups also received thyroxine (T4) in their drinking water. The mice were killed on Day 18 of gestation, and mammary tissue was homogenized and extracted for assessment of DNA, RNA, alpha-lactalbumin, and alpha-casein. Serum was assayed for placental lactogen-I (PL-I), and placental lactogen-II (PL-II), B, and T4. The concentration of PL-II in serum was elevated in the hypophysectomized mice, whereas the PL-I concentration did not differ among experimental groups. Hypophysectomy decreased both T4 and B concentrations in serum, and administration of these hormones restored their serum concentrations to normal or, in some cases, somewhat higher than normal levels. Hypophysectomy reduced the total RNA content and RNA/DNA ratio of the mammary gland, but treatment with B alone or with B and T4 restored RNA levels to those of sham-operated animals. T4 alone was ineffective in restoring RNA levels. Sham-operated animals that received hormonal treatment (B and T4) had the highest levels of RNA in the mammary tissue. Hypophysectomized animals had reduced content and concentration of alpha-lactalbumin in the mammary gland as compared to all other experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A mouse growth hormone-binding protein RIA: concentrations in maternal serum during pregnancy.

A RIA for mouse growth hormone-binding protein (mGHBP) was developed. A 28-amino acid synthetic peptide corresponding to the carboxyl-terminal 27 amino acids of mGHBP plus an additional cysteine residue at the amino-terminus was coupled to keyhole limpet hemocyanin and used as the antigen for antiserum production. The ability of the antiserum to recognize mGHBP was demonstrated by incubating mouse serum with 125I-iodomouse GH (mGH) in the presence of increasing concentrations of antiserum and subsequent immunoprecipitation. The antiserum precipitated mGHBP in a dose-dependent manner. The uncoupled synthetic peptide was used as the standard and radioligand in the RIA. Serial dilutions of sera from non-pregnant or 17-days-pregnant mice yielded displacement curves parallel to the synthetic peptide, with serum from 17-days-pregnant mice being 32 times more effective than serum from non-pregnant mice for a given dilution. The relative concentration of mGHBP in maternal serum on days 5, 11, and 15 of pregnancy was 1, 17, and 39, respectively.

Animals↗