Dimerization of human growth hormone by zinc

Size-exclusion chromatography and sedimentation equilbrium studies demonstrated that zinc ion (Zn2+) induced the dimerization of human growth hormone (hGH). Scatchard analysis of 65Zn2+ binding to hGH showed that two Zn2+ ions associate per dimer of hGH in a cooperative fashion. Cobalt (II) can substitute for Zn2+ in the hormone dimer and gives a visible spectrum characteristic of cobalt coordinated in a tetrahedral fashion by oxygen- and nitrogen-containing ligands. Replacement of potential Zn2+ ligands (His18, His21, and Glu174) in hGH with alanine weakened both Zn2+ binding and hGH dimer formation. The Zn(2+)-hGH dimer was more stable than monomeric hGH to denaturation in guanidine-HCl. Formation of a Zn(2+)-hGH dimeric complex may be important for storage of hGH in secretory granules.     

Bovine growth hormone: human food safety evaluation

Scientists in the Food and Drug Administration (FDA), after reviewing the scientific literature and evaluating studies conducted by pharmaceutical companies, have concluded that the use of recombinant bovine growth hormone (rbGH) in dairy cattle presents no increased health risk to consumers. Bovine GH is not biologically active in humans, and oral toxicity studies have demonstrated that rbGH is not orally active in rats, a species responsive to parenterally administered bGH. Recombinant bGH treatment produces an increase in the concentration of insulin-like growth factor-I (IGF-I) in cow's milk. However, oral toxicity studies have shown that bovine IGF-I lacks oral activity in rats. Additionally, the concentration of IGF-I in milk of rbGH-treated cows is within the normal physiological range found in human breast milk, and IGF-I is denatured under conditions used to process cow's milk for infant formula. On the basis of estimates of the amount of protein absorbed intact in humans and the concentration of IGF-I in cow's milk during rbGH treatment, biologically significant levels of intact IGF-I would not be absorbed.     

Plasminogen: purification from human plasma by affinity chromatography

Plasminogen was prepared from human plasma by affinity chromatography on L-lysine-substituted Sepharose. Thirty milligrams of plasminogen, with a specific activity of 100 caseinolytic units (Committee on Thrombolytic Agents) per milligram of nitrogen, were obtained from 340 milliliters of plasma. This corresponds to over 200-fold purification from plasma. Disc-gel electrophoresis at pH 8.3 indicated seven distinct bands, all of which contained activity.     

Receptor and antibody epitopes in human growth hormone identified by homolog-scanning mutagenesis

A strategy, termed homolog-scanning mutagenesis, was used to identify the epitopes on human growth hormone (hGH) for binding to its cloned liver receptor and eight different monoclonal antibodies (Mab's). Segments of sequences (7 to 30 residues long) that were derived from homologous hormones known not to bind to the hGH receptor or Mab's, were systematically substituted throughout the hGH gene to produce a set of 17 chimeric hormones. Each Mab or receptor was categorized by a particular subset of mutant hormones was categorized by a particular subset of mutant hormones that disrupted binding. Each subset of the disruptive mutations mapped within close proximity on a three-dimensional model of hGH, even though the residues changed within each subset were usually distant in the primary sequence. The mapping analysis correctly predicted those Mab's which could or could not block binding of the receptor to hGH and further suggested (along with other data) that the folding of these chimeric hormones is like that of HGH. By this analysis, three discontinuous polypeptide determinants in hGH--the loop between residues 54 and 74, the central portion of helix 4 to the carboxyl terminus, and to a lesser extent the amino-terminal region of helix 1--modulate binding to the liver receptor. Homolog-scanning mutagenesis should be of general use in identifying sequences that cause functional variation among homologous proteins.     

Expression of an exogenous growth hormone gene by transplantable human epidermal cells

Retrovirus-mediated gene transfer was used to introduce a recombinant human growth hormone gene into cultured human keratinocytes. The transduced keratinocytes secreted biologically active growth hormone into the culture medium. When grafted as an epithelial sheet onto athymic mice, these cultured keratinocytes reconstituted an epidermis that was similar in appearance to that resulting from normal cells, but from which human growth hormone could be extracted. Transduced epidermal cells may prove to be a general vehicle for the delivery of gene products by means of grafting.     

Pulsatile growth hormone secretion: suppression by hypothalamic ventromedial lesions and by long-acting somatostatin

Sequential blood samples, obtained from freely behaving, nonstressed male rats, showed a pulsatile pattern of growth hormone secretion with a mean interval between peaks of 68 minutes. The bursts of secretion were blocked by lesions of the hypothalamic ventromedial nuclei and by administration of a longacting preparation of synthetic somatostatin.     

Paradoxical elevation of growth hormone by intraventricular somatostatin: possible ultrashort-loop feedback

Somatostatin, the growth hormone-inhibiting factor, when microinjected into the third ventricle of the rat brain, paradoxically induced the release of growth hormone. A pituitary site of action having been ruled out, this result supports the concept that exogenous somatostatin within the hypothalamus acts either to suppress the release of somatostatin from somatostatin-containing neurons, possibly via an ultrashort-loop feedback mechanism, or to augment release of hypothalamic growth hormone-releasing factor, thereby inducing a release of growth hormone. Injection of somatostatin into the third ventricle also decreased plasma concentrations of luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone, probably by inhibiting the release of luteinizing hormone-releasing factor and thyrotropin-releasing factor.     

Prenatal cerebral development: effect of restricted diet, reversal by growth hormone

Caloric restriction of rats from day 10 to day 20 of pregnancy results in significant decreases in body weight, placental weight, cerebral weight, cerebral DNA, and cerebral protein of the offspring at birth. These decreases did not usually occur if mothers on the restricted diet were treated concomitantly with bovine growth hormone. If growth hormone did not cross the placenta, then, it is postulated, at least one effect of growth hormone was the mobilization of maternal nutrient reserves.     

Permeability of a nuclear membrane: changes during normal development and changes induced by growth hormone

The ion permeability of the nuclear membrane envelope of salivary gland cells (of the midge Chironomus thummi) undergoes changes during development. Following the early fourth instar stage, permeability falls to about one-fifth of its base value over a period of 3 to 5 days of development of the animal, and then rises again over the next 2 to 4 days. The falling phase of the change can be reproduced within 1 hour by injections of the growth hormone ecdyson.     

"Helium spots": caused by a diapiric magma from the upper mantle

"Helium spots," where a significant amount of helium is present in the soil [up to 350 parts per million with a high (3)He to (4)He ratio of (8.90 +/- 0.31) x 10(-6)], have been found along the fault zone formed by the 1966 Matsushiro swarm earthquakes. The formation of the "helium spots" and the occurrence of the earthquakes are interpreted as the results of a diapiric uprise of a magma approximately 1 kilometer in diameter.     

Human brain tumor--derived cell lines: growth rate reduced by human fibroblast interferon

The biological response modifier human beta-interferon had pronounced antigrowth effects on various histologic types of human brain tumor cells but no effects on a nontransformed cell line, MRC-5. The cultures of brain tumor cells showed severe alterations indicative of cell injury and death after exposure to beta-interferon for 2 to 6 days. Similar results were obtained with cells freshly explanted from human brain tumors. The results indicate that it may be possible to use fresh, explanted tumor tissue to identify patients who might benefit from therapy with beta-interferon.     

Bone marrow colonies: stimulation in vitro by supernatant from incubated human blood cells

A substance which stimulates growth of granulocytic and mononuclear cell colonies from mouse and human bone marrow was produced by incubated human blood cells. It is resistant to heat and freezing and is not dialyzable. Intact irradiated and unirradiated cells had very little activity, and sonically disrupted cells had no activity. The addition of plasma or sonically disrupted cells to the cell supernatant decreased its activity.     

Genetic Diversity of <Emphasis Type="Italic">E. coli O157:H7</Emphasis> Isolated from Some Leafy Greens,Irrigated by Aleppo River,Using Random Amplified Polymorphic DNA (RAPD) Marker

In recent years, fresh fruits and vegetables have been linked to numerous foodborne illness outbreaks in different regions of the world. In Syria, there is not a lot of research that study E. coli and its serotypes by PCR technology. In this study, we have fulfilled a total count of bacteria, the census total coliform group, and Escherichia coli, as well as the serotype E. coli O157:H7 on some leafy greens (Spinacia oleracea, Beta vulgaris) irrigated by Aleppo River. The molecular characterization was done for ten strains of E. coli isolated from collected samples. The samples were inoculated on blood agar and suspicious colonies, then transferred to EMB and MacConkey agar using a primer (COL 1) in RAPD technic. Molecular characterization also performed ten strains of serotype E. coli O157:H7 isolated in medium (Sorbitol-MacCONKEY Agar), then by primers (OPA-03, OPA-13 OPC-12, OPE-20) in RAPD technic. The results showed significant differences between collected samples. The total count of bacteria in the first site (Handarat) for spinach and chard were the lowest, but in the fourth site (Jezraya) it was the highest among all samples. The results showed also the existence of E. coli in all sites except the first one in riverbed Handarat, and E. coli O157:H7 was found only in Jezraya village. Extracted DNA from samples was amplified by RAPD. after electrophoresis in the gel agarose, eleven different bands were detected from isolated strains of E. coli. These results refer to the great genetic diversity of Escherichia coli. For serotype E. coli O157:H7 thirty-four different bands were detected. RAPD analysis had the high discriminatory capacity for typing E. coli isolates. Because of its simplicity and rapidity, RAPD analysis appears to be a highly valuable tool for studying E. coli molecular epidemiology.