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R Smith

Publications and source records attributed to R Smith.

At least 865 records · Page 48Linked to original sources
PubMed1991

Conformation of sarafotoxin-6b in aqueous solution determined by NMR spectroscopy and distance geometry.

The solution structure of sarafotoxin-6b in water has been determined using high-resolution NMR spectroscopy. 127 proton-proton distance measurements and three phi dihedral angle constraints derived from NMR spectra were used to calculate the solution structure using a combination of distance geometry and restrained molecular dynamics. The major structural feature of the resulting family of five structures was a right-handed alpha-helix extending from K9 to Q17. In contrast, the C-terminal region of the peptide appears not to adopt a preferred conformation in aqueous solution. The present structure is compared with those previously determined for endothelin peptides in non-aqueous solvents.

Amino Acid Sequence↗
PubMed1991

Interleukin 7 receptor ligation stimulates tyrosine phosphorylation, inositol phospholipid turnover, and clonal proliferation of human B-cell precursors.

Functional interleukin 7 (IL-7) receptors are expressed on the surface of multiphenotypic, biphenotypic, and immature B-lineage human lymphoid precursor cells with germ-line immunoglobulin heavy-chain genes but not on more mature B-lineage lymphoid cells with rearranged and/or expressed immunoglobulin heavy-chain genes. Thus, IL-7 may have an important regulatory role during the earliest stages of human B-cell ontogeny. The engagement of the surface IL-7 receptors on immature B-cell precursor cells with recombinant human IL-7 (rhIL-7) results in enhanced tyrosine phosphorylation of multiple phosphoproteins, stimulates inositol phospholipid turnover and DNA synthesis, and promotes their clonal proliferation. These effects are (i) specific for rhIL-7, since rhIL-3, rhIL-4, rhIL-5, rhIL-6, and recombinant human granulocyte colony-stimulating factor do not elicit similar activities on IL-7 receptor-positive human pro-B cells; and (ii) mediated by IL-7 receptors, since they are not observed in IL-7 receptor-negative B-lineage lymphoid cell populations. rhIL-7-induced tyrosine phosphorylation on the 35-, 53-, 55-, 62-, 69-, 76-, 94-, 150-, 170-, and 190-kDa substrates as well as rhIL-7-induced stimulation of inositol phospholipid turnover are abrogated by the tyrosine kinase inhibitor genistein. These results demonstrate that the IL-7 receptor on immature human B-cell precursor populations is intimately linked to a functional tyrosine kinase pathway and tyrosine phosphorylation is an important and perhaps mandatory step in the generation of the IL-7 receptor-linked transmembrane signal.

B-Lymphocytes↗
PubMed1991

Corneal ulcer and adverse reaction rates in premarket contact lens studies.

We analyzed clinical data on 22,739 contact lens wearers who were studied and whose lenses were approved under 48 manufacturer-sponsored studies for the Food and Drug Administration between 1980 and 1988. The incidence of corneal ulcers was low in the cosmetic (nontherapeutic) daily-wear soft and rigid gas-permeable lens wearers (1/1,923 and 1/1,471 patient-years, respectively). Corneal ulcers and severe adverse reactions occurred two to four times more frequently in extended-wear cosmetic soft and rigid gas-permeable lens wearers than in cosmetic daily-wear lens wearers. Aphakic extended-wear soft lens users were nine times more likely to develop a corneal ulcer when compared to the soft daily-wear cosmetic group. Corneal abrasions and keratitis accounted for 81 of 159 severe adverse reactions, whereas corneal ulcers accounted for 28 of 159 adverse reactions. The data indicate that overnight extended wear of contact lenses is associated with a greater risk of serious, sight-threatening complications than daily wear.

Aphakia↗
PubMed1991

Comparison of the calf suckling technique and milk oxytocin test for estimation of milk yields.

The calf suckling technique and milk oxytocin test were compared as methods to quantify lactation yields in Sanga-type cows in the multi-purpose livestock sector of central Zambia. There was no significant difference between the overall means derived from 154 observations. The oxytocin method interferes less with the multi-purpose system of management, is less time consuming and does not require expensive calf weight scales.

Analysis of Variance↗
PubMed1991

Effect of dry season supplementation of Sanga cattle in Zambia.

Supplementation of lactating Sanga cows in central Zambia with low cost crop residues and urea-mineral licks resulted in significant increases in milk offtake (79%), total daily milk (86%), and daily liveweight gain of their calves (86%). At 1988 market prices the value of the additional milk (ZK54.00) and of liveweight of both cow and calf (ZK189.00) over the 13 weeks exceeded the estimated costs of inputs by ZK180.00.

Animal Feed↗
PubMed1991

Nitric oxide hemoglobin in mice and rats in endotoxic shock.

Mice given ip bacterial endotoxin (LPS) at 10 mg/kg showed a statistically significant decrease in plasma glucose and an increase in hematocrit at 2 h after injection. Glucose was still decreased at 4 h, but the hematocrit had returned to control values. Nitrosylated hemoglobin (HbNO) was detected at 3, but not at 2 h. By 4 h it had increased 5-fold. When N-monomethylarginine (NMMA) at 100 mg/kg, ip was given 2 h after LPS in mice, the HbNO concentration at 4 h was significantly reduced, but the hypoglycemia was worsened because NMMA itself produced a significant hypoglycemia. Rats given iv LPS, 20 mg/kg, showed a fleeting, transient rise in mean arterial pressure (MAP) lasting only a few min. Thereafter, the MAP tended to drift slowly downward over 4 h, but when the MAP at 30 min intervals was compared to the pre-LPS MAP, there were no significant differences. Plasma glucose in unanesthetized rats was significantly elevated at 1 h, back to control at 2 h, and significantly decreased at 3 h. HbNO was detected as early as 1 h after injection. By 2 h the HbNO concentrations exceeded the highest levels found in mice, and they were still increasing as late as 5 h after injection. Unanesthetized rats showed toxic signs and 3/12 rats died within 4 hours of LPS administration. These results are consistent with a model for endotoxic shock in which LPS stimulates an inducible pathway for NO synthesis.

Animals↗
PubMed1991

Neuroendocrinology of the hypothalamo-pituitary-adrenal axis in pregnancy and the puerperium.

Plasma cortisol, adrenocorticotrophic hormone (ACTH), beta-endorphin and corticotrophin releasing hormone or factor (CRF) all rise progressively as pregnancy advances, and fall postnatally. The placenta produces large amounts of CRF in the third trimester and this is released into the maternal circulation. Present evidence suggests that it stimulates the maternal pituitary to produce ACTH while desensitizing the maternal pituitary to further stimulation with CRF. Maternal control of ACTH production is retained, allowing a persistent response to stress and a diurnal rhythm, perhaps through the secretion of vasopressin. The placenta also produces pro-opiomelanocortin peptides; however, the nature of the fragments produced from the precursor differs from that formed in the anterior pituitary of the mother and the role of these fragments in the control of maternal adrenal function is unclear. These changes in the hypothalamo-pituitary-adrenal axis during pregnancy are associated with loss of the normal suppression of cortisol by dexamethasone and elevated basal levels of cortisol with preservation of a diurnal rhythm, features also found in some patients with endogenous depression. Several studies have suggested a relationship between alterations in maternal concentrations of cortisol and beta-endorphin and the development of postnatal mood disturbances.

Adrenal Glands↗