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Biomedical subjects

F Talamantes

Publications and source records attributed to F Talamantes.

At least 91 records · Page 5Linked to original sources
PubMed1990

Transplantable rat choriocarcinoma cells express placental lactogen: identification of placental lactogen-I immunoreactive protein and messenger ribonucleic acid.

The purpose of this investigation was to evaluate the abilities of a transplantable rat choriocarcinoma (Rcho) to produce placental PRLs. The Rcho tumor was analyzed biochemically and histologically for the expression of placental PRLs. Expression of placental PRL mRNAs was determined by Northern blot and in situ hybridization analyses. Expression of placental PRL proteins was determined by Western blot and immunocytochemical analyses. Histologically, Rcho tumors were characterized by the appearance of giant cell surrounding hemorrhagic regions. Female rats bearing the Rcho tumor beneath their kidney capsule showed extensive mammary gland development. The Rcho tumors expressed placental lactogen-I (PL-I) mRNA and protein, but there was no evidence of placental lactogen-II (PL-II), PRL-like protein-A (PLP-A), or PRL-like protein-B (PLP-B). Rcho PL-I mRNA and proteins migrated as a 1-kilobase species and a 36- to 40-kDa species similar to those expressed by normal rat trophoblast tissues. The cell type responsible for Rcho PL-I production was the giant cell, similar to that observed in normal rat trophoblast tissues. In summary, we have demonstrated the production of PL-I by a transplantable rat choriocarcinoma (Rcho). The Rcho tumor resembles rat trophoblast tissue at early postimplantation stages (days 6-10 of gestation) and may be a useful tool for studying placental PRL expression during trophoblast differentiation.

Animals↗
PubMed1989

Antipeptide antibodies reveal structural and functional characteristics of rat placental lactogen-II.

The purpose of this investigation was to develop specific immunologic probes to rat placental lactogen-II (PL-II) and to use the immunologic probes to further characterize rat PL-II. Five oligopeptides corresponding to different regions of rat PL-II (amino acids 1-13, 56-70, 89-103, 107-118, 150-164) were chemically synthesized by solid phase methods and purified to homogeneity by reverse phase high performance liquid chromatography. The synthetic peptides were coupled to keyhole limpet hemocyanin (KLH) and the peptide-KLH conjugates were used to immunize rabbits. Antibody production was monitored by enzyme-linked immunoassay (EIA), electrophoresis and immunoblotting analyses. Each of the antipeptide antisera showed reactivity with the entire rat PL-II protein; however, the extent of the reactivities of each antiserum with rat PL-II was dependent on the conformational state of rat PL-H. Antisera directed to amino acids 56-70 showed the best reactivity toward each of the conformational states of rat PL-II tested. Antibodies generated to the entire rat PL-II protein specifically recognized the 56-70 amino acid sequence but showed limited reactivity with synthetic peptide corresponding to amino acids 1-13, 89-103, 107-118, and 150-164 of rat PL-II. Antisera to amino acids 56-70 of rat PL-II were specific for PLs as demonstrated by their recognition of rat PL-II, mouse PL-II and human PL and by their lack of reactivity with rat pituitary prolactin and growth hormone and with a series of other synthetic peptides to rat PL-II and rat prolactin-like protein-A. The immunorecognition of human PL was restricted to antipeptide antibodies directed to amino acids 56-70 of rat PL-II. The chemically synthesized peptides representing various regions of rat PL-II did not show significant interactions with prolactin receptors, and antisera directed to the peptides failed to interfere with the binding of either rat PL-II or human PL to prolactin receptors. In summary, we have generated a series of immunologic probes for studying the structure of rat PL-II. The sequence comprising amino acids 56-70 of rat PL-II was shown to make up at least part of an epitope for rat PL-II and to be a region of significant structural homology with mouse PL-II and human PL.

Amino Acid Sequence↗
PubMed1989

Mammary gland development and alpha-lactalbumin production in hypophysectomized, pregnant mice.

Swiss Webster mice were hypophysectomized on Day 10 of pregnancy and the effect of the ablation on mammary gland development was estimated by measuring the total weight and the DNA, RNA, and alpha-lactalbumin contents and concentrations of the mammary gland on Days 14 and 18 of gestation. Although a significant increase in mammary gland weight occurred in the hypophysectomized animals between Days 10 and 18 of pregnancy, the mammary gland weight of the hypophysectomized mice was significantly reduced when compared with intact and sham-operated mice on both Days 14 and 18 of pregnancy. The total RNA content of the mammary gland was also reduced in the hypophysectomized mice, although it increased significantly from Day 10 to Day 18. The alpha-lactalbumin content of the mammary gland increased only slightly between Days 10 and 14 of gestation in the intact and sham-operated mice, but a large increase was found on Day 18 in both groups. There was, on the other hand, no increment in the alpha-lactalbumin content of the mammary gland in the hypophysectomized mice either on Day 14 or 18 of gestation. The DNA content of the mammary gland was not affected by hypophysectomy when estimated on Days 14 and 18 of pregnancy. The effects of hypophysectomy on the concentrations of mouse placental lactogen II (mPL-II), progesterone, corticosterone, and thyroxine in the maternal serum were also assessed. The concentration of mPL-II was significantly elevated in the hypophysectomized mice, whereas the circulating concentrations of both corticosterone and thyroxine were greatly reduced. The serum progesterone concentration was not significantly altered by hypophysectomy. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Ethanol consumption during pregnancy in mice: effects on hormone concentrations.

Hormonal and metabolic responses to ethanol consumption were studied in pregnant Swiss Webster mice and their fetuses. On day 10 of pregnancy, mice were assigned to one of three liquid diet groups: 36% ethanol-derived calories fed ad libitum (ETOH); control liquid diet fed ad libitum (control); control liquid diet administered in the same amount as that consumed by the ETOH group on the same day of pregnancy [pair-fed controls (PF)]. Dams were killed on days 14-18 of pregnancy, and fetuses were collected on days 16-18. Serum mouse placental lactogen-II (mPL-II), prolactin (mPRL), growth hormone (mGH), insulin, and glucose concentrations were determined for each group. Ethanol consumption resulted in a significant reduction in fetal weight on day 18 of pregnancy. The maternal serum mPRL concentration was reduced in ETOH mice on days 16 and 17 of pregnancy when compared with control mice, but when compared with PF mice, it was significantly reduced only on day 16. Maternal and fetal serum insulin concentrations were reduced in ETOH mice when compared with control mice, but it is unclear whether this was a specific effect of ethanol consumption or due to reduced food intake. Maternal serum glucose concentrations were reduced in the ETOH mice but not as severely as in the PF mice. Ethanol consumption had no effect on maternal or fetal serum mPL-II and mGH concentrations. These data confirm that ethanol consumption during pregnancy results in fetal growth retardation, but they do not indicate any major effects of ethanol on mPL-II, mPRL, mGH, and insulin concentrations in either the mother or fetus.

Alcohol Drinking↗
PubMed1989

High molecular weight forms of placental lactogen: evidence for lactogen-macroglobulin complexes in rodents and humans.

Gel filtration chromatography of maternal plasma from late pregnant hamsters demonstrated that approximately 90% of hamster placental lactogen-II (PL-II) is present as high mol wt (Mr) forms. A major peak of immunoactive hamster PL-II with a Mr of 600,000 and a smaller peak (Mr, 210,000) were observed. The major high Mr form of hamster PL-II in plasma had a Mr of 360,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). High Mr forms also predominate in placental extracts, but differ from the plasma forms. 125I-Labeled monomeric hamster PL-II (Mr, 22,000) formed a disulfide-bonded complex (Mr, 720,000 by gel filtration and 360,000 by SDS-PAGE) when incubated in vitro with serum of male, nonpregnant female, or pregnant hamsters. The in vitro complex was also formed with unlabeled hamster PL-II. Similar high Mr complexes were formed, but to a lesser extent, when 125I-labeled mouse PL-II and human PL were incubated with the homologous late pregnant serum. High Mr complexes (Mr, 360,000 by SDS-PAGE) were also formed when the three 125I-labeled PLs were incubated with purified human alpha 2-macroglobulin. The most prominent circulating high Mr form of hamster PL-II had a Mr similar to that of alpha 2-macroglobulin by both gel filtration and SDS-PAGE. In addition, it had a mobility similar to that of alpha 2-macroglobulin on nondenaturing polyacrylamide gels, and it was about 10% asparagine-linked carbohydrate by weight, as is alpha 2-macroglobulin. These similarities and the ability of hamster PL-II to form a disulfide-bonded complex with alpha 2-macroglobulin in vitro suggest that the major circulating form of PL-II in the hamster may be a disulfide-bonded complex of one or more PL monomers with alpha 2-macroglobulin or a related plasma protein. Similar complexed forms of PL may be present in mice and humans.

Animals↗
PubMed1989

Mouse placental lactogen-I: RIA and gestational profile in maternal serum.

A RIA for mouse placental lactogen-I (mPL-I) was developed using recombinant mPL-I as the standard, radioligand, and antigen for antiserum production. Displacement curves for dilutions of serum and placental extracts from pregnant mice were parallel to the recombinant mPL-I standard curve. Serum from male and nonpregnant female mice and high concentrations of mouse PRL, GH, PL-II, proliferin, and proliferin-related protein did not cross-react in the assay. mPL-I appeared in maternal serum on day 6 of pregnancy. Its concentration remained low until day 8 and them increased to a very large peak on days 9-11 (maximum concentration, approximately 8 micrograms/ml). The mPL-I concentration declined after day 11, but the hormone could be detected at low concentration in maternal serum until the end of pregnancy. On day 10 of pregnancy, the mPL-I concentration of maternal serum was correlated with litter size. Fractionation of serum from 10-day pregnant mice by size exclusion chromatography indicated the absence of high mol wt forms of mPL-I in the circulation.

Animals↗
PubMed1989

Recombinant mouse placental lactogen-I binds to lactogen receptors in mouse liver and ovary: partial characterization of the ovarian receptor.

The binding of recombinant mouse placental lactogen-I (mPL-Ir) to liver and ovarian membranes was investigated in virgin and pregnant mice. Competitive binding assays demonstrated that mPL-Ir, mouse placental lactogen-II (mPL-II), and mouse PRL (mPRL) bind to the same receptors in ovarian membranes. The relative abilities of the three hormones to displace [125I]iodo-mPL-Ir from the ovarian lactogen receptors was mPL-II greater than mPL-Ir much greater than mPRL. Scatchard analysis of mPL-Ir binding to ovarian membranes from day 10 pregnant mice showed a Ka of 2.0 x 10(9) M-1 and a binding capacity of 3.2 x 10(-14) mol/mg membrane protein. The specific binding of [125I]iodo-mPL-Ir to ovarian membrane preparations was significantly higher on day 17 than on day 10 of gestation. Dissociation of endogenous hormones with 4 M MgCl2 increased the binding of [125I]iodo-mPL-Ir to ovarian membranes but not to liver membranes. Affinity cross-linking of [125I]iodo-mPL-Ir to liver and ovarian membranes resulted in the specific labeling of proteins with receptor mol wt (Mr) of 44K and 40K (nonreduced) and 50K and 42K (reduced), as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The lactogen receptors from liver and ovary appeared structurally homologous, producing fragments with similar Mr when treated with proteolytic enzymes and undergoing similar reductions in Mr when treated with glycolytic enzymes. The ability of mPLs to bind specifically and with high affinity to receptors in mouse ovarian membranes suggests that these hormones may regulate ovarian function during gestation.

Animals↗
PubMed1989

Hamster placental lactogen-II contains a structural feature unique among the growth hormone-prolactin-placental lactogen family.

Sequence analysis of cDNA for hamster placental lactogen-II (PL-II) revealed that while this protein has a high degree of sequence homology to mouse and rat PL-II it contains a pair of cysteine residues not present in the mouse and rat proteins or in any other known member of the GH-PRL-PL protein family. This unique pair of cysteine residues may be responsible for the extreme tendency of hamster PL-II, compared to other members of the GH-PRL-PL family, to form disulfide-bonded hormone-serum protein complexes.

Amino Acid Sequence↗
PubMed1989

Mouse serum growth hormone (GH) binding protein has GH receptor extracellular and substituted transmembrane domains.

Predicted amino acid sequences for the mouse GH receptor and the related serum GH binding protein were deducted from cDNAs. Two types of cDNA clones were isolated. Both types coded an identical peptide domain with extensive homology to the extracellular domains of the recently cloned human and rabbit GH receptors. However, while one type of clone also encoded regions with homology to the transmembrane and cytoplasmic domains of the human and rabbit GH receptors, the other encoded a short hydrophilic carboxyl-terminal region in place of the transmembrane domain. It is speculated that these two types of clones encode the high and low molecular weight variants of the mouse GH receptor/serum binding proteins, respectively. The low molecular weight variant has been previously found to constitute the majority of the serum GH binding activity in mice. It is proposed that the substitution of the hydrophilic tail for the transmembrane domain may give the low molecular weight variant its soluble nature and account for its presence in serum.

Amino Acid Sequence↗
PubMed1988

Effects of perinatal exposure to a synthetic estrogen and progestin on mammary tumorigenesis in mice.

The effects of perinatal exposure to synthetic estrogens and progestins on mammary tumorigenesis were studied in female C3H/HeN/MTV + mice. Mice were treated neonatally with 0.001 microgram/day diethylstilbestrol (DES), with 15 micrograms/day 17 alpha-hydroxyprogesterone caproate (HPC), or with oil on days 1-5 of life (birth = day 1). As adults, neonatally hormone-treated mice received long-term treatment with a synthetic estrogen and progestin combination or vehicle. Animals were palpated weekly for mammary gland tumors. The effect of treatment on the probability of tumor development was examined. Neonatal treatment with a low dose of DES increased the probability of mammary-gland tumor formation, whereas neonatal treatment with HPC had a slightly protective effect on tumorigenesis. Subsequent treatment of adult mice with synthetic steroids did not affect mammary gland tumorigenesis in neonatally DES-treated or oil-treated animals. There was a significant interaction between the effect of neonatal HPC treatment and subsequent steroid treatment on mammary tumorigenesis but examination of the data indicated that this interaction was due to the protective effect of HPC in the absence of subsequent exposure to synthetic steroids and the probability of tumor appearance in mice treated with both HPC and synthetic steroids as adults did not differ from that of neonatally oil-treated controls.

17 alpha-Hydroxyprogesterone Caproate↗
PubMed1988

Development and retention of phenotypically specialized cells in pituitary allografts in the hamster (Mesocricetus auratus).

We used immunohistochemistry to identify cells present in pituitary allografts in the hamster. Hypophyses removed from neonatal hamsters or adenohypophyses removed from adult females were placed beneath renal capsules of hypophysectomized adult females. Serum PRL, LH, and GH concentrations were measured at two, five and eight weeks after placement of allografts. Allografts were removed after eight weeks and stained for cells containing PRL, LH, FSH, GH, or ACTH. Allografts did not release LH or GH. Those of adult adenohypophyseal tissue released significantly more PRL. The morphology of allografts of neonatal hypophyseal tissue resembled that of the adult adenohypophysis in situ. Lactotrophs, corticotrophs, somatotrophs and LH-cells were observed; very few FSH-cells were present. Allografts of adult adenohypophyseal tissue contained pituitary cells, numerous cavities, often enclosing lymphoid cells, and fibrous tissue. Atypical lactotrophs were the numerically dominant cells in these allografts; all other cells were present. The LH-cells outnumbered FSH-cells. These observations suggest that: (a) development of normal adenohypophyseal morphology can occur in an ectopic position; (b) intracellular hormones are present in cells in an ectopic site; (c) development and retention of intracellular FSH is more dependent on occupation of the normal position of the adenohypophysis than is retention of intracellular LH; and (d) release of PRL occurs from atypical cells in allografts of adult adenohypophyseal tissue.

Animals↗
PubMed1988

Circulating prolactin in free-living California ground squirrels (Spermophilus beecheyi).

During a long-term field study of a free-living population of California ground squirrels (Spermophilus beecheyi), blood samples were drawn at regular intervals from marked animals via femoral venipuncture, and plasma prolactin (PRL) was measured by homologous radioimmunoassay. Marked fluctuations with season and reproductive condition occurred in circulating PRL levels in both males and females, with peak levels occurring during the spring breeding season. Peak PRL levels in females were reached 4 weeks after peak male levels, but mean peak values did not differ significantly between the sexes. Among females, juveniles had lower mean PRL levels than adults, and yearlings had lower mean levels throughout their initial reproductive episodes than did older females.

Animals↗
PubMed1988

The kinetics of disappearance of endogenous mouse placental lactogen-II in intact and hypophysectomized pregnant mice.

The kinetics of disappearance of endogenous mouse placental lactogen-II (mPL-II) were determined in day 12 and day 16 pregnant Swiss Webster mice and in day 16 pregnant mice that had been hypophysectomized (hypox) on day 12. Blood samples from anesthetized animals were taken at different time intervals after bilateral hysterectomy and the maternal serum mPL-II concentration was measured by homologous radioimmunoassay (RIA). Disappearance curves of mPL-II for day 12 and day 16 pregnant mice were resolved into two exponential components: a rapid phase of disappearance, followed by a slow phase. Although the serum mPL-II concentration was higher on day 16 of pregnancy than on day 12, the alpha rate constant for the fast component of the disappearance curve for day 12 pregnant mice (0.054 +/- 0.005 ml/s) was similar to the value observed for day 16 animals (0.052 +/- 0.005 ml/s). The half-life of the fast component of the disappearance curve for day 12 and day 16 pregnant mice was 13.3 +/- 0.9 s and 14.8 +/- 1.5 s, respectively. The slow component of the disappearance curves for day 12 and day 16 pregnant mice had a beta rate constant of 0.00088 +/- 0.00017 ml/s and 0.00083 +/- 0.00009 ml/s, respectively. The half-life of the slow phase of the disappearance curves for day 12 pregnant mice was 1216.4 +/- 376.0 s, while the slow phase of day 16 disappearance curves displayed a half-life of 954.4 +/- 102.7 s.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Detection of two growth hormone receptor mRNAs and primary translation products in the mouse.

Two mouse growth hormone-receptor primary translation products of Mr 95,900 and 31,800 were identified from in vitro-translated late pregnant mouse liver mRNA. RNA isolated from mouse liver was translated in a rabbit reticulocyte lysate system containing [35S]methionine, and the growth hormone receptor primary translation products were identified by immunoprecipitation with anti-mouse growth hormone receptor antiserum followed by sodium dodecyl sulfate/PAGE and fluorography. Detectable amounts of the Mr 95,900 and 31,800 proteins were not present in in vitro-translated nonpregnant mouse liver mRNA. This result is consistent with previous observations of the up-regulation of growth hormone receptors in the liver during pregnancy in the mouse. Northern (RNA) blot analysis of mouse liver and adipose tissue RNA with a rabbit growth hormone receptor cDNA probe revealed two hybridizing mRNAs of approximately 3.9 and 1.2 kilobases. These two RNAs were greatly up-regulated in liver, but not in adipose tissue, during pregnancy. The sizes of these mRNAs closely matched predictions of the sizes of the mRNAs coding for the proteins of Mr 95,900 and 31,800 made by in vitro translation of size-fractionated late-pregnant mouse liver poly(A)+RNA. These results suggest a mechanism for the generation of both the heterogeneous forms of the growth hormone receptor identified in mouse liver membrane preparations and the mouse serum growth hormone-binding protein.

Animals↗
PubMed1988

Patterns of progesterone secretion in free-living California ground squirrels (Spermophilus beecheyi).

During a long-term field study of a free-living population of California ground squirrels (Spermophilus beecheyi), blood samples were drawn at regular intervals from marked females via femoral venipuncture, and plasma progesterone (P) and prolactin (PRL) were measured by radioimmunoassay. Marked fluctuations with season and reproductive condition occurred in circulating levels of both hormones, with peak levels occurring during the spring breeding season. Two peaks in P concentrations were observed each spring, the first occurring during pregnancy, and the second during lactation. Peak PRL levels in females were also reached during the lactation interval, midway between the two P peaks. Analysis of repeated measures from individual females showed a marked decline in circulating P around the time of parturition. Juveniles had lower mean P levels than adults, and yearlings had lower peak levels during their initial reproductive episodes than older females did. The observed pattern of P secretion in S. beecheyi differs from that known for most mammals, but resembles those reported for other ground-dwelling sciurid rodents.

Animals↗
PubMed1988

Hepatic placental lactogen receptors during pregnancy in the mouse.

The binding sites for mouse placental lactogen-II (mPL-II) in virgin and pregnant mouse hepatic membranes were analyzed by Scatchard analysis and affinity cross-linking. Competitive binding studies showed that mPL-II and mouse PRL (mPRL) bound to the same receptors in all liver membrane preparations, although the affinity of mPRL binding was lower than that of mPL-II binding. Two classes of receptors for mPL-II, high and low affinity, were found by Scatchard analysis. The concentration of both types of sites in liver membranes increased during pregnancy. In contrast, the affinity of both sites for mPL-II was highest in virgin female mice and declined during pregnancy. Cross-linking of [125I]iodo-mPL-II to maternal liver membranes resulted in the specific labeling of one major protein species of 67,000 daltons as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Under nonreducing conditions, two bands of approximately 63,000 and 60,000 daltons were apparent. Subtraction of the mol wt of mPL-II (22,000, reduced; 20,000, nonreduced) from the mol wt of the cross-linked complex indicated that the mol wt of the receptor was 45,000 under reducing conditions and 43,000 and 40,000 under nonreducing conditions. These observations suggest that mPL-II receptors may be present in mouse liver membranes in at least two forms.

Animals↗