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Biomedical subjects

H A Bern

Publications and source records attributed to H A Bern.

At least 73 records · Page 4Linked to original sources
PubMed1989

17 beta-estradiol increases plasma calcitonin levels in salmonid fish.

The functional role of calcitonin in teleost fish is in question. Data on the role of calcitonin in calcium regulation are inconsistent, and while a participation in some aspects of sexual maturation has been strongly indicated, the exact function is not known. To establish if there exists a functional relationship between 17 beta-estradiol (E2) and calcitonin in salmonid species, rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar), and coho salmon (Oncorhynchus kisutch) were injected ip with a single or repeated doses of E2. It is concluded that E2 treatment increases plasma calcitonin levels directly or indirectly, and that it is possible that E2 is responsible for the rise in calcitonin levels during late sexual maturation of female salmonids. In accord with earlier studies, no correlation was found between changes in calcitonin levels and free plasma calcium levels. It seems clear that changes in free plasma calcium levels are not the primary cause of the plasma calcitonin changes in teleost fish. It is possible that calcitonin is involved in mobilizing calcium or directing its mobilization by protection of certain calcium pools during vitellogenesis. However, the increase in calcitonin occurs so close to ovulation that a reproductive role other than a calcium regulatory one is likely. The possibility of transfer of calcitonin itself to the developing oocytes and a subsequent role in embryonic development must also be considered.

Animals↗
PubMed1989

Prolactin sensitivity of mammary epithelial cells from mice exposed neonatally to diethylstilbestrol.

We examined the responsiveness to prolactin and growth hormone of mammary epithelial cells from mice exposed neonatally to diethylstilbestrol (DES) and from control mice. The mammary epithelial cells were cultured inside collagen gels with serum-free medium containing insulin, epidermal growth factor, and linoleic acid. This produces prolactin-sensitive cells with low levels of casein production, as measured in cellular homogenates with a specific enzyme-linked immunosorbent assay for alpha-casein. The collagen gels containing these cells were then released and the medium supplements changed to insulin, linoleic acid, and prolactin at concentrations from 10 to 1000 ng/ml and growth hormone at 0, 10, or 100 ng/ml. This second phase of the culture, the differentiation phase, allows the cells to accumulate casein if they have this capacity. When cultured with prolactin only (no growth hormone), the cells from DES-exposed mice consistently accumulated 50-100% of the casein content of normal cells, but never more. Growth hormone, when added to prolactin-containing medium, increased casein accumulation above the levels seen with prolactin alone. Combinations of prolactin and growth hormone enhanced the difference between casein accumulation in DES-exposed and control cells, and DES-exposed cells were much less responsive to growth hormone. In our studies, the isolated mammary epithelial cells of estrogen-exposed mice are not more sensitive to prolactin than cells from normal animals as previous reports reports had suggested, but rather are generally less sensitive to hormonal stimulants.

Animals↗
PubMed1988

Vaginal abnormalities in ovariectomized BALB/cCrgl mice after neonatal exposure to different doses of diethylstilbestrol.

Newborn BALB/cCrgl female mice received five daily injections of various doses of diethylstilbestrol (DES), 0.0001-10 micrograms. Mice were killed at 6 days of age or at 4 months after ovariectomy at 40-42 days. Subepithelial nodules of polygonal cells in the upper (Mullerian) vagina during early postnatal life were associated with the later occurrence of ovary-independent persistent stratification with or without cornification in mice treated neonatally with 0.1-10 micrograms DES and thus are a possible predictor of this phenomenon. The thresholds for the induction of ovary-independent epithelial pegs, downgrowths and adenosis (glandular formations) were 0.1 microgram and 0.5 microgram DES/day, respectively.

Age Factors↗
PubMed1988

Complete amino acid sequences of a pair of fish (tilapia) prolactins, tPRL177 and tPRL188.

The complete amino acid sequences of a pair of tilapia (Oreochromis mossambicus) prolactins (PRLs) were determined. The larger PRL of molecular mass 20,836 Da consists of 188 amino acid residues. The smaller PRL of molecular mass 19,584 Da is 11 residues shorter. On alignment of the two sequences, the 19.6-kDa PRL (tPRL177) has two conspicuous deletions on the NH2-terminal side of the disulfide bond which connects the first and second cysteine residues. The degree of similarity between the two PRL sequences is unexpectedly low (130 identical residues, 69%) compared with that between the variants of other teleostean PRLs. Circular dichroism spectra and hydropathy profiles suggest structural similarity of the two PRLs. The sequence of the 20.8-kDa PRL (tPRL188) has 69% identity with that of salmon PRL. The sequence of tPRL177 is 56% identical with that of salmon PRL. Each tilapia PRL is equally similar to mammalian PRLs (about 30% identical residues). Regions highly conserved among teleostean and mammalian PRLs were identified on the COOH-terminal side of the disulfide bond connecting the first and second cysteine residues.

Amino Acid Sequence↗
PubMed1988

Novel effect of vasoactive intestinal polypeptide and peptide histidine isoleucine: inhibition of in vitro secretion of prolactin in the tilapia, Oreochromis mossambicus.

The effects of vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) on the in vitro secretion of two prolactins (PRL) from the rostral pars distalis (RPD) and of growth hormone (GH) from the proximal pars distalis (PPD) of the pituitary of the tilapia (Oreochromis mossambicus) were studied. RPDs were incubated for 20 hr in hypoosmotic (280-300 mOsm) or hyperosmotic (340-350 mOsm) Krebs-Ringer bicarbonate medium with added peptide concentrations of 0 (control), 0.3, 3.0, 30, and 300 nM; similarly, PPDs were incubated with the same peptide concentrations in isoosmotic (325 mOsm) medium supplemented with cortisol. PRL and GH in the tissue and secreted into the medium were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by soft laser densitometry of the protein band(s). Neither VIP nor PHI has a detectable effect on the secretion of GH. Secretion of the two PRLs is significantly inhibited by VIP and PHI in both hyperosmotic and hypoosmotic medium. In hyperosmotic medium, 300 nM VIP inhibits secretion of both PRLs by 47%, whereas in hypoosmotic medium, 300 nM VIP inhibits their secretion by 27%. PHI inhibits their secretion by ca. 65% in hyperosmotic medium and by 40% in hypoosmotic medium. There is preliminary immunocytochemical evidence for some VIP-like immunoreactivity (IR), but no conclusive indication of PHI-like IR, in the hypothalamo-hypophysial area. The inhibitory actions of VIP and PHI on PRL secretion in tilapia are in contrast to the known stimulatory actions of VIP and PHI on PRL secretion in tetrapods.

Animals↗
PubMed1988

Effects of salinity, hypophysectomy, and prolactin on whole-animal transepithelial potential in the tilapia Oreochromis mossambicus.

We have examined whether two recently isolated forms of tilapia (Oreochromis mossambicus) prolactin exert similar effects on osmoregulatory physiology. The effects of salinity, hypophysectomy, and replacement therapy with tilapia prolactins on whole-animal transepithelial potential (TEP), gill Na+, K+-ATPase activity, and plasma ions were determined. When intact fish adapted to 25% seawater (SW) were transferred to different salinities, TEP reached a steady state after 10 hr; TEP increased with increasing salinity from fresh water (FW) to 75% SW but was stable from 75 to 125% SW. Plasma osmolality, [Na+], and [Cl-] of these fish 24 hr after salinity change showed that fish in 100 and 125% SW had greater osmotic perturbation than those transferred to lower salinities. Following a 5-day recovery period in 25% SW, hypophysectomized fish transferred to FW for 10 hr had significantly lower TEP and plasma ion levels than either sham-operated fish or intact fish under the same conditions. Injection of hypophysectomized fish with "small" prolactin (tPRL177), "large" prolactin (tPRL188), or a combination of both (0.5 micrograms/g body weight) 22 hr and again 20 min prior to transfer from 25% SW to FW, restored TEP and plasma ion levels to those of sham-operated fish. Neither prolactin affected the TEP or plasma ions of sham-operated (intact) fish. Hypophysectomized fish had lower gill Na+,K+-ATPase activity than sham-operated fish in FW, but prolactin injections as described above did not affect gill Na+,K+-ATPase activity in either hypophysectomized or sham-operated fish. Our results indicate that the two forms of prolactin are indistinguishable with regard to several aspects of tilapia osmoregulation.

Animals↗
PubMed1988

Aromatase is concentrated in the proximal pars distalis of tilapia pituitary.

Aromatase has been identified in the telostean, avian, and mammalian pituitaries, although its cellular location(s) is not yet certain. To address this question, experiments were performed in tilapia (Oreochromis mossambicus), a species which has been well characterized with respect to the intraglandular distribution of the different pituitary cell types. To estimate aromatase, glands were microdissected into rostral pars distalis (RPD), proximal pars distalis (PPD), and neurointermediate lobe (NIL) and organs were cultured in the presence of [3H]androstenedione for 16-24 hr. [3H]Estrogen products were isolated and quantified after ether extraction, hydrolysis with glucuronidase-sulfatase, thin-layer chromatography, and phenolic partition. Authentic estrone or estradiol-17 beta were produced by all pituitary regions and also by the urophyseal region of the spinal cord. Aromatase was two to five times higher in PPD than in RPD or NIL and similar to activity in adjacent hypothalamus-preoptic area (HPOA). Much lower estrogen yields were obtained in cultures of cerebellum, urophysis, and other cord regions. Since the PPD contains most of the somatotropes, these data are consistent with earlier studies implicating GH3/GH4 cell strains as an enriched enzyme source, although its presence in other cell types cannot be ruled out. The unusually high and localized aromatase in tilapia pituitary renders this species a useful model for studying the targets and functional importance of estrogen as a parahormone in the pituitary.

Androstenedione↗
PubMed1988

Neonatal administration of prolactin antiserum alters the developmental pattern of T- and B-lymphocytes in the thymus and spleen of BALB/c female mice.

We have evaluated the effect of neonatal administration of mouse prolactin (PRL) antiserum on the developmental expression of T- and B-lymphocytes in the thymus and spleen of female BALB/c mice. Newborn female mice were injected subcutaneously with a 50-microliters aliquot of PRL antiserum or normal rabbit serum on days 1, 2, and 3. On neonatal day 5, the PRL antiserum-treated group had a significantly (P less than 0.05) increased population of cells in the thymus and the spleen that were positive for Thy-1.2 and for L3T4. Increases in Thy-1.2- and L3T4-positive cells in the thymus were detectable also on days 8 and 14 in mice that received the PRL antiserum and in mice injected with bromocriptine, a dopamine agonist that inhibits PRL release from the anterior pituitary. On neonatal days 21, 28, and 32, there were no significant differences in the percentage of cells positive for Thy-1.2, Ly-2 (formerly Lyt-2), or L3T4 antigens in the thymus. However, there were significant increases in the percentage of Thy-1.2- and L3T4-positive spleen cells in the bromocriptine-treated group at all times monitored and in the PRL antiserum-treated group except on day 14. In addition, the percentage of splenocytes that were positive for IgG was significantly increased in the PRL antiserum-treatment group on days 8-28, although not on neonatal day 32. Of tissues known to contain PRL receptors, neonatal administration of PRL antiserum or bromocriptine resulted in a significant alteration in the wet weight of spleen and liver, with no significant effect in thymus, heart, and kidney. Pituitary implants also resulted in a significant increase in both concanavalin A- and lipopolysaccharide-stimulated thymidine incorporation into murine splenic lymphocytes prepared from 45-day-old female mice. These data extend the role of PRL as an immunomodulator of adult lymphocyte function to a role in the developmental expression of T- and B-lymphocyte populations in the thymus and spleen of mice.

Animals↗
PubMed1988

The influence of urotensin II on calcium flux in rat aorta.

The fish neuropeptide urotensin II (UII, 10 nM) caused a 51% increase in uptake of 45Ca by segments of rat aorta; this increase was abolished by the Ca channel blocking drug nitrendipine (200 nM). 45Ca efflux was unchanged in the presence of UII, but was significantly increased following washout of the peptide; again, this increase was not observed in the presence of nitrendipine. The results provide direct evidence that the nitrendipine-sensitive component of the contractile response of rat aorta to UII involves mobilization of extracellular Ca, with subsequent activation of a Ca-induced, Ca-release process intracellularly. The mechanisms responsible for the nitrendipine-resistant component of the contractile response to UII remain to be established.

Animals↗
PubMed1987

Long-term alterations in histology and steroid receptor levels of the genital tract and mammary gland following neonatal exposure of female BALB/cCrgl mice to various doses of diethylstilbestrol.

The relation of the dosage of diethylstilbestrol (DES) administered neonatally to the incidence and severity of genital tract and mammary gland lesions and to the levels of sex hormone receptors was examined using a mouse model for human intrauterine DES exposure. Female BALB/cCrgl mice received various doses of DES (ranging from 5 X 10(-1)-10(-5) micrograms daily for the first 5 days of life) or the sesame oil vehicle alone. In the vagina, at all ages examined (1, 2, 6, and 12 months) cytosolic estrogen receptors are consistently decreased after high doses of neonatal DES (10(-1) and 1 microgram). In contrast, at the same ages, vaginal cytosolic progestin receptors increase after identical doses. In the uterus, the 1-microgram dose of neonatal DES also consistently decreases cytosolic estrogen receptors while increasing cytosolic progestin receptors at 1, 2, and 6 months of age. Histologically, neonatal doses of 5 X 10(-2) micrograms DES result in vaginal lesions at 2 months. With age, this threshold level decreases, implying interaction with an altered hormonal milieu. The uterus shows a sensitivity similar to that of the vagina in regard to the histopathological effects of neonatal DES. The ovary and mammary glands are 10- to 100-fold more sensitive to neonatal DES exposure.

Age Factors↗
PubMed1987

A double sequential immunofluorescence method demonstrating the co-localization of urotensins I and II in the caudal neurosecretory system of the teleost, Gillichthys mirabilis.

A double immunofluorescence method was devised to localize simultaneously urotensin-I (UI) and -II (UII) immunoreactivities in the caudal neurosecretory system of the goby, Gillichthys mirabilis. In a sequential fashion, sections of the posterior spinal cord and urophysis were treated with antiserum to corticotropin-releasing factor (CRF) that cross-reacts with UI, fluorescein-conjugated sheep anti-rabbit IgG, biotinylated anti-UII and rhodamine-conjugated avidin. UI and UII immunoreactivities appeared to coexist in some neurons and in most fibers and urophysial tissue; the remainder of the fibers and urophysis and the majority of neurons were immunoreactive for CRF/UI only. No convincing evidence of immunoreactivity for UII only was found. A few nonreactive cells were seen, but these may not be neurosecretory neurons. The two immunoreactive cell types were not segregated topographically, and the intensity of perikaryal immunofluorescence for CRF/UI was variable. To explain these results a hypothesis that all caudal neurosecretory cells may synthesize both UI and UII and that immunoreactive differences may reflect different states of cellular activity, is suggested. This sequential double immunofluorescence method offers several advantages over other techniques and is especially useful for co-localization studies when primary antisera from different species are not available.

Animals↗
PubMed1987

Growth of mouse vaginal epithelial cells in culture: effect of sera and supplemented serum-free media.

Normal mouse vaginal epithelial cells isolated from ovariectomized ca. 35-d-old BALB/cCrgl mice were grown in primary culture using collagen gel matrix and a serum-free medium composed of a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12 (D:H) medium supplemented with insulin (IN), epidermal growth factor (EGF), cholera toxin, transferrin, and bovine serum albumin V (BSA). Three-dimensional cellular outgrowths occurred inside the collagen gel matrix. The contribution of each factor to cell growth was examined by individual addition to the basic D:H medium and by individual deletion from the complete serum-free medium. When added individually, only IN promoted growth. Deletion of IN from the complete serum-free medium markedly diminished growth; deletion of EGF or BSA slightly diminished growth. When horse, fetal bovine, or chicken serum was added to the basal D:H medium, only with increasing doses of horse serum was there enhanced cell growth. The effect of 17 beta-estradiol and diethylstilbestrol on the growth of cells was also tested, using a suboptimal medium of D:H supplemented with BSA and IN, or a minimal medium supplemented with IN alone. During the 8-d time period, addition of estrogen did not enhance cell growth in either medium. To date, we have been unable to demonstrate a mitogenic effect of estrogen; rather a dose-dependent inhibition of proliferation is seen.

Animals↗
PubMed1987

Effects of hypophysectomy and subsequent hormonal replacement therapy on hormonal and osmoregulatory status of coho salmon, Oncorhynchus kisutch.

This study investigates the effects of hypophysectomy and subsequent hormone replacement therapy upon the hormonal and osmoregulatory status of coho salmon, Oncorhynchus kisutch, in 7% seawater (SW) and SW. Following hypophysectomy, coho salmon were injected every 2 days for 8 days with thyroxine, growth hormone, and cortisol, alone or in combinations, and sampled 2 days after the final injection. Increased environmental salinity raises plasma sodium, calcium, and magnesium levels, as well as plasma osmolality. Cortisol is hypercalcemic and thyroxine is hypocalcemic in hypophysectomized salmon, but it is unclear whether these effects are due directly to calcium regulation or are the consequence of general effects on the plasma osmotic/ionic balance. Growth hormone and thyroxine together, but not separately, decrease and increase magnesium levels, at low and high environmental salinities, respectively, indicating a complex endocrine control of plasma magnesium. Gill Na+, K+-ATPase activity in hypophysectomized salmon is stimulated by growth hormone and cortisol, but inhibited by thyroxine and raised environmental salinity. This implies a complex endocrine control and indicates that hormonal support is needed to sustain or raise gill Na+, K+-ATPase activity in seawater. Increased environmental salinity induces elevation of plasma cortisol levels in apparent absence of pituitary control, indicating that the interrenals may respond to changes in external and/or internal environment, either directly or indirectly through extrapituitary hormonal or nervous control. Cortisol is a potent inhibitor of calcitonin secretion, as seen by the large decrease in plasma calcitonin levels in cortisol-treated hypophysectomized fish. The study was carried out at a time when thyroxine plasma levels were low. These basal levels were not affected by hypophysectomy, possibly indicating a basal release of thyroxine from the thyroid without stimulatory support of the pituitary gland.

Animals↗
PubMed1987

Effects of cortisol and growth hormone replacement on osmoregulation in hypophysectomized coho salmon (Oncorhynchus kisutch).

Both cortisol and GH were able to reverse partially the effects of hypophysectomy on coho salmon (Oncorhynchus kisutch) as judged by improved seawater (SW) tolerance after long-term treatment; however, neither hormone significantly restored gill Na+, Na+,K+-ATPase activity. In the first experiment, gill Na+,K+-ATPase activity remained low in hypophysectomized (Hx) coho treated with cortisol (15 micrograms/g body wt, suspended in cocoa butter) for 96 hr (48 hr in fresh water followed by 48 hr in seawater). In addition, plasma sodium levels were higher in the cortisol-treated Hx animals compared with those in untreated controls. In the second experiment, treatment with cortisol-filled Silastic capsules and implants of bovine GH (mixed with cholesterol in a ratio calculated to yield a dose of 1.5 microgram/g body wt/week) for 12 days also failed to alter gill Na+,K+-ATPase activity, but did reduce plasma sodium levels in animals transferred to SW for 48 hr. These results suggest that these hormones may be involved in the development of hypoosmoregulatory ability in coho salmon. However, the failure of either hormone to restore gill Na+,K+-ATPase activity suggests that a combination of these hormones and/or an additional hormone(s) acting in a synchronized fashion may be required for full effectiveness.

Animals↗
PubMed1987

Studies on the regulation of growth hormone release from the proximal pars distalis of male tilapia, Oreochromis mossambicus, in vitro.

The in vitro effects of several factors, including cortisol, somatostatin (SRIF), and medium osmotic pressure, on growth hormone (GH) release from the tilapia pituitary were examined in relation to fish size. Spontaneous GH release from the proximal pars distalis (PPD) of approximately 60-g fish was significantly less than that from tissue of fish weighing either approximately 120 or approximately 280 g when incubated in 340 m phi smolal medium. While GH content of the PPD cultures (tissue + medium measured by densitometry) increased consistently with fish size, GH concentration (per microgram of tissue protein) was variable, being highest in 120-g fish and lowest in 280-g fish. Moreover, GH concentration was not related to GH release. Fish size also appeared to be important in the responsiveness of GH cells to stimulation by cortisol (Nishioka et al., 1985) and by increased osmotic pressure. In cultures of PPD from approximately 60-g fish, in which spontaneous release was relatively low, cortisol and increased medium osmotic pressure significantly enhanced release. Cortisol and hyperosmotic medium were without significant effect, however, on GH release from PPD of approximately 120-g fish, which showed high spontaneous release. In contrast, SRIF, a potent inhibitor of GH secretion, was effective in lowering GH release regardless of fish size. Nevertheless, SRIF was apparently more effective in inhibiting GH release from tissue of 60-g fish than from tissue of 120-g fish. Our data suggest that GH secretion may be augmented when smaller tilapia (approximately 60 g) are transferred to seawater, a situation in which blood cortisol and osmotic pressure would presumably be elevated.

Adaptation, Physiological↗
PubMed1987

Effects of somatostatin-25 and urotensin II on lipid and carbohydrate metabolism of coho salmon, Oncorhynchus kisutch.

Salmon (Oncorhynchus kisutch) somatostatin (sSS; 4 or 8 ng/g body wt) or synthetic Gillichthys urotensin II (UII; 2 or 4 ng/g body wt) were injected intraperitoneally into juvenile freshwater coho salmon. Both sSS and UII caused a dose-dependent increase in plasma free fatty acids (FFA) which diminished with time. sSS induced an initial (1 hr) transient hyperglycemia. By contrast, UII tended to induce hypoglycemia, this effect being significant 5 hr after injection of the higher dose. Both sSS and UII depressed plasma insulin titers 1 hr after injection. By 3 hr, the sSS-associated insulin depression was no longer observed. UII treatment induced a hyperinsulinemia which was present 3 and 5 hr after peptide administration. Although no decreases in liver total lipid concentration or in mesenteric fat total tissue mass were observed, lipolytic enzyme activity within each depot was significantly enhanced by both peptides. Neither sSS nor UII altered 3H2O incorporation into fatty acids or neutral lipids. However, enhanced lipogenesis, particularly by UII, was indicated by increased NADPH production resulting from glucose-6-phosphate dehydrogenase activity. Both sSS and UII enhanced glucose mobilization, as indicated by decreased liver glycogen content and increased liver glucose-6-phosphatase activity. UII, but not sSS, stimulated glycogen synthetase activity. These results suggest that both sSS and UII stimulate hyperlipidemia by enhancing depot lipase activity and that although both factors are potentially gluconeogenetic, sSS seems to be glycogenolytic and hyperglycemic, whereas UII may channel glucose to FFA synthesis.

Animals↗
PubMed1987

Growth of mouse vaginal epithelial cells in culture: functional integrity of the estrogen receptor system and failure of estrogen to induce proliferation.

Normal mouse vaginal epithelial cells isolated from ovariectomized ca. 40-day-old BALB/cCrg1 mice were purified by Percoll density gradient centrifugation and grown in primary culture using a collagen gel matrix and a serum-free complete medium. During the 9-day culture period, a 6-fold increase in cell number was observed. Addition of estrogen to the medium did not enhance epithelial cell proliferation. In fact, all doses of estrogen (180 fM to 18 nM) were inhibitory, resulting in only a 3- to 4-fold increase in cell number by day 9 of culture. Continuous exposure to estradiol (1.8 nM) for 9 days in the serum-free complete medium resulted in a decrease in cytosolic estrogen receptors with associated nuclear accumulation of estrogen receptors. A corresponding increase of cytosolic progestin receptors was also observed, indicating that no qualitative modification of the estrogen receptor system had occurred. Thus, despite its effectiveness in specific product synthesis (progestin receptors), estrogen does not stimulate proliferation of vaginal cells in this culture system, but rather inhibits epithelial cell proliferation.

Animals↗