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Biomedical subjects

A Baird

Publications and source records attributed to A Baird.

At least 181 records · Page 10Linked to original sources
PubMed1987

Isolation and partial characterization of basic fibroblast growth factor from bovine testis.

A basic fibroblast growth factor (FGF) has been purified to homogeneity from bovine testis, using ammonium sulfate precipitation of the crude extract followed by three chromatographic steps, involving cation-exchange, heparin-Sepharose, and reversed-phase HPLC. Gas-phase sequence analysis showed the amino-terminal amino acid sequence of the isolated polypeptide as His-Phe-Lys-Asp-Pro-Lys-Arg-Leu-Tyr-, which is identical to the amino-terminal of the (16-146) fragment of basic FGF previously characterized from corpus luteum, adrenal, and kidney. The purified FGF was shown to have the same biological activity as that of basic FGF (1-146). This finding suggests that basic FGF is present in testis and may act as a local regulator of testicular function. In addition, testicular FGF might play an important role in spermatogenesis and/or the development of testis.

Amino Acid Sequence↗
PubMed1987

Multiple influences of a heparin-binding growth factor on neuronal development.

Heparin-binding growth factor-2 (HBGF-2; also known as basic fibroblast growth factor) is mitogenic for most anchorage-dependent cells. It is shown here that HBGF-2 stimulates cell-substratum adhesion and neurite extension in the sympathetic nerve cell line PC12. When HBGF-2 is adsorbed to artificial extracellular matrices consisting of heparin or chondroitin sulfate, it causes the formation of cellular aggregates or circles of cells, respectively. HBGF-2 is also a nerve cell survival molecule, for it potentiates the survival of primary cultures of embryonic chick ciliary ganglion cells but not of embryonic neural retina cells. Finally, a series of synthetic peptides from the HBGF-2 sequence is described that selectively alter the biological effects of HBGF-2. The amphiphilic nature of one of these peptides is discussed with respect to its ability to stimulate cell adhesion.

Adrenal Gland Neoplasms↗
PubMed1987

The inhibition of low density lipoprotein metabolism by transforming growth factor-beta mediates its effects on steroidogenesis in bovine adrenocortical cells in vitro.

Transforming growth factor-beta (TGF beta) has a differential effect on the growth and function of bovine adrenocortical cells in vitro. TGF beta inhibits basal as well as ACTH- or angiotensin II-stimulated steroid formation, with no evidence of change in cell growth. The major inhibitory effect of TGF beta occurs at a step before cholesterol formation, since treatment of adrenocortical cells with TGF beta decreased not only delta 4-steroid levels but also delta 5-steroid levels. The addition of cholesterol reverses the suppression of steroidogenesis induced by TGF beta. To determine the mechanism of this inhibition, the effect of TGF beta on low density lipoprotein (LDL) metabolism was investigated. Cells treated with TGF beta showed a significant suppression of [125I]iodohuman LDL ([125I]LDL) binding to the cell surface, followed by decreases in internalization and proteolytic degradation of [125I]LDL. Maximal inhibition of LDL metabolism was observed at a concentration of 1 ng/ml (4 X 10(-11) M) TGF beta. The stimulation of LDL metabolism by ACTH was also inhibited by TGF beta, and the inhibition observed correlated well with the inhibition of steroidogenesis. The inhibitory effect of TGF beta on [125I]LDL binding results from the decrease in the maximal LDL-binding capacity. The stimulation of LDL uptake induced by Bu2cAMP, cholera toxin, forskolin, and Ang II was also decreased by treatment with 1 ng/ml TGF beta. The specificity of this effect is quite high, since the inhibitory effects of TGF beta on LDL metabolism were not observed with either inhibin A or activin, two molecules that have considerable structural homology to TGF beta. We conclude that TGF beta specifically suppresses LDL metabolism in bovine adrenocortical cell cultures and that this step may mediate, at least in part, its role as a potent inhibitor of steroidogenesis.

Adrenal Cortex↗
PubMed1986

Fibroblast growth factor as an intraovarian hormone: differential regulation of steroidogenesis by an angiogenic factor.

The potential role of fibroblast growth factor (FGF) in the regulation of granulosa cell differentiation was investigated because of its recent identification as the corpus luteum angiogenic factor. Treatment of rat ovarian granulosa cells with FGF inhibits the capacity of follicle stimulating hormone to stimulate estrogen production and to induce luteinizing hormone receptors. In contrast, although incubations with FGF can inhibit the estrogen-sensitive component of progesterone synthesis, the presence of FGF with suboptimal concentrations of follicle stimulating hormone significantly enhances the synthesis of progesterone. This capacity to differentially regulate steroidogenesis in the granulosa cell is comparable to the potency of FGF (ED50 = 30 pg/ml, 10(-12) M) in other in vitro assays. The observation that an angiogenic factor, like FGF, can specifically increase the sensitivity of progesterone synthesis and simultaneously inhibit estrogen formation supports the hypothesis that this growth factor plays an important role in the development and maintenance of a functional corpus luteum. As such, FGF may be involved in the local regulation of follicular selection, growth and atresia by simple virtue of its capacity to induce a neovascular response on one hand and by its ability to modulate the differentiated response to gonadotropins on the other.

Angiogenesis Inducing Agents↗
PubMed1986

Purification and partial characterization of a mitogenic factor from bovine liver: structural homology with basic fibroblast growth factor.

Two mitogenic peptides in bovine liver extract were purified to apparent homogeneity by monitoring the purification steps with two in vitro bioassays; one based on stimulation of adult bovine aortic arch endothelial cell proliferation and the other incorporation of [3H]thymidine to mouse fibroblast 3T3 cells. The purification procedure involved cation-exchange chromatography followed by affinity chromatography on heparin-Sepharose and two steps of reversed-phase HPLC. The purified material showed the same biological activity as pituitary basic fibroblast growth factor (FGF). Amino acid analyses of the purified mitogen yielded a similar, but not identical composition to that of bovine pituitary basic FGF(1-146) reported previously. Gas-phase microsequencing identified two sequences in equal amounts in the purified preparation. Furthermore, the sequencing results are in accord with the theoretical data obtained when two truncated forms of basic FGF, corresponding to FGF(12-146) and (16-146), are being sequenced simultaneously. Basic FGF(12-146) is a novel truncated form of basic FGF which has not been isolated before although the (16-146) fragment has been found previously in kidney, corpus luteum, and adrenal. SDS-PAGE analysis could not separate the two forms and showed that both migrated as a protein of about 15,100 daltons, which is slightly smaller than intact basic FGF(1-146) (16,200 daltons). These results, taken together, indicate that at least some of the mitogenic activity in liver may be derived from basic FGF-related polypeptides.

Amino Acid Sequence↗
PubMed1986

Isolation of an amino terminal extended form of basic fibroblast growth factor.

Extraction of bovine pituitaries in the presence of enzyme inhibitors (2 mM PMSF, 2 mM sodium tetrathionate, 15 microM pepstatin A, and 1 mM EDTA) resulted in the isolation of two distinct forms of basic fibroblast growth factor. Partial characterization of both molecules showed one form to be identical to basic FGF(1-146) which has already been reported by our laboratory. The second form was estimated by SDS-PAGE to have a molecular weight of 17,000 Daltons which is slightly larger than that of basic FGF(1-146). Amino acid analysis shows the presence of 8 new residues more than basic FGF(1-146) which accounts for the difference in molecular weight. Gas-phase sequencing of this molecule indicated that it bears a blocked amino terminus. Furthermore, this higher molecular weight form of basic FGF did not show immunoreactivity with antibodies specific for the amino terminus of basic FGF(1-146) but cross reacted with antibodies generated against midportion fragments of basic FGF(1-146), indicating that the molecule is amino terminally extended. Like basic FGF(1-146), the molecule is a potent mitogenic factor for vascular endothelial cells. Taken together these results demonstrate the existence of a precursor form of basic FGF which is extended by 8 residues at the amino terminus with the first residue being blocked.

Amino Acids↗
PubMed1986

Inhibition of endothelial cell proliferation by type beta-transforming growth factor: interactions with acidic and basic fibroblast growth factors.

TGF beta is a potent (ED50 approximately 10(-11) M) inhibitor of the proliferative activities of both acidic and basic FGF on vascular and capillary endothelial cells in vitro. The inhibition of cell growth is dose-dependent and characteristic of a non-competitive interaction. The results demonstrate that TGF beta and FGF can interact at the cellular level to modulate growth and suggest that many of the biological activities of FGF observed in vitro and in vivo (ie angiogenesis, cell growth, cell differentiation) may be regulated by the presence of TGF beta and related proteins (ie inhibin) in the local cellular milieu. The possible identity of TGF beta with the inhibitors of endothelial cell growth detected in in vitro assays of crude extracts is discussed.

Animals↗
PubMed1986

Type beta transforming growth factor (TGF-beta) is a potent stimulator of the basal secretion of follicle stimulating hormone (FSH) in a pituitary monolayer system.

In view of striking similarities between TGF-beta and inhibin, we investigated the possibility that TGF-beta might modulate pituitary hormone release in vitro. Long term incubations of beta transforming growth factor (TGF-beta) with rat anterior pituitary cells for 48 hr stimulates the basal secretion of FSH in a dose-dependent manner. The secretion of LH, TSH, GH, ACTH and PRL is not modified by TGF-beta. The minimal effective concentration of TGF-beta is 10 pg/ml (less than 500 attomolar) and is dose dependent over a range from 1 pg to 10 ng/ml. Treatment of cells with TGF-beta for short incubation times (4 hr) in assays similar to that used for hypophysial releasing factors is not effective, indicating that TGF-beta acts through a cellular mechanism distinct from that of LRF. Inhibin-A, recently characterized on the basis of its capacity to specifically inhibit the secretion of FSH in the 48 hr bioassay system inhibits the stimulatory effect of TGF-beta on FSH-release. Analyses of the dose response curves indicate that the interaction occurs in a typical non-competitive manner. The results suggest that a TGF-beta-like molecule, present in follicular fluid, may be responsible for the FSH-releasing activity ("anti-inhibin" activity) observed by us and others during the process of isolating inhibin from follicular fluids. They also suggest an important role for inhibin and the TGF-beta related molecules in modulating pituitary gonadotropin release.

Animals↗
PubMed1986

Immunoreactive fibroblast growth factor (FGF) in a transplantable chondrosarcoma: inhibition of tumor growth by antibodies to FGF.

Using a radioimmunoassay for bovine pituitary fibroblast growth factor (FGF), we have established the presence of the immunoreactive mitogen in extracts of a transplantable mouse chondrosarcoma. Both neutral and acidic extracts of the tumor contain an immunoreactive FGF (ir-FGF) that cross-reacts in a parallel and dose-dependent fashion in the radioimmunoassay. The ir-FGF is retained on heparin-Sepharose affinity columns and can be detected in the same molecular weight forms as rat pituitary FGF. Mice (C57/Bl) inoculated with the tumor (10 mg, im) show a decreased rate of tumor growth when passively immunized with the antiserum to FGF. The results establish the presence of FGF in this tumor and implicate its role in the etiology of its development.

Animals↗
PubMed1986

Basic fibroblast growth factor induces angiogenesis in vitro.

Fibroblast growth factors (FGFs) are potent mitogens for vascular and capillary endothelial cells in vitro and can stimulate the formation of blood capillaries (angiogenesis) in vivo. A crucial event in this process is the invasion of the perivascular extracellular matrix by sprouting endothelial cells. Using a recently developed in vitro model of angiogenesis, we show here that highly purified basic pituitary FGF can induce capillary endothelial cells to invade a three-dimensional collagen matrix and to organize themselves to form characteristic tubules that resemble blood capillaries. We also show that basic FGF concomitantly stimulates endothelial cells to produce a urokinase-type plasminogen activator, a protease that has been implicated in the neovascular response. The results demonstrate that basic FGF can stimulate processes that are characteristic of angiogenesis in vivo, including endothelial cell migration, invasion, and production of plasminogen activator.

Animals↗
PubMed1986

Differential effects of transforming growth factor type beta on the growth and function of adrenocortical cells in vitro.

Transforming growth factor type beta (TGF-beta) suppresses basal as well as corticotropin (ACTH)-stimulated steroid formation by bovine adrenocortical cells in culture. The effect is dose dependent and is not accompanied by any change in adrenocortical cell growth. The minimum effective dose of TGF-beta is 4 X 10(-13) M (10 pg/ml), and maximal inhibition is observed at a concentration of 4 X 10(-11) M (1 ng/ml). A 16- to 20-hr incubation with TGF-beta is required to decrease steroidogenesis, and 12-18 hr are required before cells treated with TGF-beta recover complete responsiveness to corticotropin. Increases in cAMP mediated by corticotropin, forskolin, and isobutylmethylxanthine are not modified by the addition of TGF-beta; thus adenylate cyclase activity is unaffected by TGF-beta. Although TGF-beta inhibits the formation of all of the delta 4-steroids measured (including cortisol, corticosterone, aldosterone, and androstenedione), its effect can be completely reversed by the addition of 25-hydroxycholesterol, pregnenolone, or progesterone to the cells. In contrast, the addition of low density lipoprotein has no effect suggesting that TGF-beta targets the conversion of cholesterol precursors to cholesterol. The results demonstrate a highly potent effect of TGF-beta on the differentiated function of the adrenocortical cell. The inhibition of steroidogenesis can be dissociated from any effect on cell proliferation, and it occurs distal to the formation of cAMP but proximal to the formation of cholesterol. The results suggest that in the adrenal, TGF-beta or TGF-beta-like proteins may be playing an important role in modifying the differentiated state of the adrenocortical cell.

Adrenal Cortex↗
PubMed1986

Fibroblast growth factor promotes survival of dissociated hippocampal neurons and enhances neurite extension.

Basic fibroblast growth factor (FGF) has been found to increase neuronal survival and neurite extension in a highly purified population of fetal rat hippocampal neurons under well-defined serum-free cell culture conditions. In the presence of FGF, neuronal survival after 7 days in culture on a simple plastic substrate is increased 4-fold, to 54% of the initial population. Survival is increased 2-fold to 40% on polyornithine-laminin. When FGF was bound to plastic or heparin substrates, neurite outgrowth was significantly increased to lengths comparable to those seen with laminin; however, FGF produced no further increase in neurite outgrowth on laminin. Half-maximal survival was observed at FGF concentrations of about 15 pg/ml (1 pM); half-maximal process outgrowth occurred at about 375 pg/ml (20 pM). The responsive cells were identified as neurons by their labeling with tetanus toxin and by antibodies to neurofilaments and to the neuron-specific enolase. Astrocytes, identified by the presence of glial fibrillary acidic protein, constituted about 10% of cells present at 1 week both in the presence and in the absence of FGF. These results strongly suggest that, in addition to its known mitogenic effects on nonneuronal cells, FGF possesses neurotrophic activity for hippocampal neurons.

Animals↗
PubMed1986

Relative potencies of human, rat, bovine/caprine, porcine and ovine hypothalamic growth hormone-releasing factors to release growth hormone by the rat anterior pituitary in vitro.

Synthetic rat, human, bovine/caprine, porcine and ovine growth hormone-releasing factor (GRF) were tested for their capacity to release growth hormone (GH) by the rat anterior pituitary in vitro. All peptides elicited parallel and dose-dependent increases in GH release and produced similar maximal GH secretion. Rat GRF was 3-6 times more potent in stimulating the release of GH than all other GRFs, while human, bovine/caprine, porcine and ovine GRF had potencies that were not statistically different. The increased potency of both rat GRF(1-27)NH2 and rat GRF(1-23)NH2 when compared to human GRF(1-27)NH2 and human GRF(1-23)NH2, respectively, suggests that the increased potency of this molecule resides in structural differences in the amino terminal of native GRF. The results demonstrate increased sensitivity of rat pituitary cells for their homologous releasing factor.

Animals↗
PubMed1986

Growth hormone-releasing factor: a new chapter in neuroendocrinology.

The isolation and characterization of growth hormone-releasing factor (GRF) has initiated a new and exciting era in our understanding of the neuroendocrine regulation of pituitary growth hormone (GH) secretion. This report briefly describes the isolation and characterization of GRF, factors which modulate the GH response to GRF and the effects of chronic administration and deprivation of GRF on somatic growth. The intent of this report is to serve as a general introduction on biochemical and physiological aspects of GRF. The following reports from this symposium will then cover many of these topics in much greater detail.

Animals↗
PubMed1986

Immunohistochemical evidence that growth hormone-releasing factor (GRF) neurons contain an amidated peptide derived from cleavage of the carboxyl-terminal end of the GRF precursor.

Antisera were raised against synthetic replicates of the carboxyl-terminal (C-terminal) fragment of the precursor to human GH-releasing factor (GRF) (pre-proGRF) whose structure was predicted from the complementary DNA cloned from a pancreatic tumor. These antisera were used along with antisera to human GRF itself to search for the presence of related molecules in the human hypothalamus, with an immunohistochemical approach. The antisera to pre-proGRF that recognize specifically the C-terminal amidated form of pre-proGRF stain GRF neurons in their cell bodies, fibers, and nerve endings that are in contact with portal capillaries of the median eminence. Antisera against the nonamidated form of the molecule did not give any staining in the hypothalamus. These results strongly suggest that human hypothalamic GRF derives from a precursor immunologically related (and probably identical) to the tumorous one and that this precursor is cleaved inside GRF cell bodies to give, in addition to the GRF-44-NH2 a second amidated peptide, the C-terminal pre-proGRF that is transported distally to nerve endings and most probably coreleased with GRF into portal capillaries.

Adult↗
PubMed1986

Isolation of fibroblast growth factor from bovine adrenal gland: physicochemical and biological characterization.

The angiogenic growth factors present in the bovine adrenal gland have been purified by a combination of differential salt precipitation, ion exchange chromatography, and heparin-Sepharose chromatography. They consist of 2 single chain polypeptides with apparent mol wt of 16,000 and 15,000. Sequence analysis of the first 14 residues of both peptides identified the sequences as Pro-Ala-Leu-Pro-Glu-Asp-Gly-Gly-Ser-Gly-Ala-Phe-Pro-Pro for 1 of the peptides and His-Phe-Lys-Asp-Pro-Lys-Arg-Leu-Tyr-x-Lys-Asn-Gly-Gly for the other. The first sequence is identical to residues 1-14 of bovine pituitary and brain fibroblast growth factor (FGF), while the second is identical to residues 1-14 of the corpus luteum (CL) FGF, which is an amino-terminally truncated form of FGF and is otherwise similar, if not identical, to FGF. The biological activity of adrenal FGF is indistinguishable from that of pituitary or brain FGF and CL FGF. They are highly active in triggering the proliferation of culture bovine vascular endothelial cells derived from either large vessels (aortic arch) or CL and adrenal cortex capillaries (half-maximal stimulation at 20-40 pg/ml and saturation at 400-600 pg/ml). In vivo implants containing 50 ng to 1 microgram adrenal-derived growth factors stimulate neovascularization in the chorioallantoic membrane of the chick embryo. In addition to being mitogenic for vascular endothelial cells, adrenal FGFs stimulate the proliferation of a wide variety of mesoderm- and neuroectoderm-derived cells, including vascular smooth muscle cells, granulosa and adrenal cortex cells, rabbit costal chondrocytes, and corneal endothelial cells.

Adrenal Cortex↗
PubMed1986

The molecular weight forms of rat growth hormone secreted in response to growth hormone-releasing factor.

The different molecular weight forms of immunoreactive growth hormone (irGH) secreted by the anterior pituitary of rats were evaluated during basal and stimulated secretion in vitro and in vivo. Anterior pituitary cells maintained in a monolayer culture system secreted only a 22,000-Da form of GH based on Sephacryl S-200 column chromatography. This was also true for the irGH secreted in response to growth hormone-releasing factor and prostaglandin E2 stimulation. In contrast, the molecular weight forms of irGH found in plasma under basal conditions included an approximately 90,000-Da form as well as the expected 22,000-Da form. The concentrations of both forms increased following growth hormone-releasing factor stimulation although there was a shift in the ratio of the forms secreted. These results suggest that the larger molecular weight forms of rat GH observed in plasma may be the result of some postsecretory process which occurs in blood and suggests a possible regulatory function for the larger molecular weight forms as it pertains to the bioavailability of GH in vivo.

Animals↗