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D D Smith

Publications and source records attributed to D D Smith.

At least 37 records · Page 2Linked to original sources
PubMed1997

Structure-activity studies on position 14 of human alpha-calcitonin gene-related peptide.

A structure-activity study was performed to examine the role of position 14 of human alpha-calcitonin gene-related peptide (h-alpha-CGRP) in activating the CGRP receptor. Interestingly, position 14 of h-alpha-CGRP contains a glycyl residue and is part of an alpha-helix spanning residues 8-18. Analogues [Ala14]-h-alpha-CGRP, [Aib14]-h-alpha-CGRP, [Asp14]-h-alpha-CGRP, [Asn14]-h-alpha-CGRP, and [Pro14]-h-alpha-CGRP were synthesized by solid phase peptide methodology and purified by RP-HPLC. Secondary structure was measured by circular dichroism spectroscopy. Agonist activities were determined as the analogues' ability to stimulate amylase secretion from guinea pig pancreatic acini and to relax precontracted porcine coronary arteries. Analogues [Ala14]-h-alpha-CGRP, [Aib14]-h-alpha-CGRP, [Asp14]-h-alpha-CGRP, and [Asn14]-h-alpha-CGRP, all containing residues with a high helical propensity in position 14, were potent full agonists compared to h-alpha-CGRP in both tissues. Interestingly, replacement of Gly14 of h-alpha-CGRP with these residues did not substantially increase the helical content of these analogues. [Pro14]-h-alpha-CGRP, predictably, has significantly lower helical content and is a 20-fold less potent agonist on coronary artery, known to contain CGRP-1 receptor subtypes, and an antagonist on pancreatic acini, known to contain CGRP-2 receptor subtypes. In conclusion, the residue in position 14 plays a structural role in stabilizing the alpha-helix spanning residues 8-18. The alpha-helix is crucial for maintaining highly potent agonist effects of h-alpha-CGRP at CGRP receptors. The wide variety of functional groups that can be tolerated in position 14 with no substantial modification of agonist effects suggests the residue in this position is not in contact with the CGRP receptor. [Pro14]-h-alpha-CGRP may be a useful pharmacological tool to distinguish between CGRP-1 and CGRP-2 receptor subtypes.

Amino Acid Sequence↗
PubMed1997

Optimization of cellular ELISA for assay of surface antigens on human synoviocytes.

The cellular enzyme-linked immunosorbent assay (CELISA) permits assay of cell surface antigens on intact fixed cells. Using a monolayer of cells as the solid phase, the CELISA offers an inexpensive alternative to flow cytometry. In addition, this protocol has the decided advantages of miniaturization (small numbers of cells) and ease of replication (the 96-well cluster plate format). In efforts to optimize CELISA for detecting surface antigens on human fibroblastlike synoviocytes, the authors found that cell number, serum proteins, choice of culture plate, pipetting technique and fixatives may all impact the results of the CELISA.

Antigens, Surface↗
PubMed1997

Mast cell granules potentiate endotoxin-induced interleukin-6 production by endothelial cells.

Mast cells are constituent cells of vascular tissue and their numbers are increased in atherosclerotic vessels. To gain insight into the role of mast cells in vascular inflammation, the effect of mast cell granules (MCG) on endothelial cell production of interleukin-6 (IL-6) was examined. Human umbilical vein endothelial cells (HUVEC) were cultured with lipopolysaccharide (LPS) in the presence or absence of rat peritoneal MCG and IL-6 production was assayed by enzyme-linked immunosorbent assay. The interaction of MCG with HUVEC in culture was examined by electron microscopy (EM). The EM studies revealed that MCG are internalized by HUVEC and appear intact even after 24 h in culture. Unactivated HUVEC produced little or no IL-6 either in the presence or absence of MCG. Treatment of HUVEC with LPS stimulated IL-6 production in a dose- and time-dependent fashion. Addition of MCG to LPS-activated HUVEC-resulted in the potentiation of IL-6 production at all LPS doses. MCG-induced enhancement of IL-6 production was evident even at a mast cell-to-endothelial cell ratio of 1:32. The enhancement of IL-6 production by MCG was also seen when tumor necrosis factor alpha was used as an activator. Although potentiation was evident when MCG were added 6 h before or after LPS stimulation, the maximum effect was noted when MCG and LPS were added simultaneously. MCG-mediated enhancement of IL-6 production was abrogated by pretreating MCG with protease inhibitors. Although MCG proteases potentiate IL-6 production by HUVEC, they do not degrade secreted IL-6. These results demonstrate that MCG interact with endothelial cells and modulate the production of an important inflammatory cytokine.

Animals↗
PubMed1996

Brain S-adenosylmethionine levels are severely decreased in Alzheimer's disease.

S-Adenosylmethionine is an essential ubiquitous metabolite central to many biochemical pathways, including transmethylation and polyamine biosynthesis. Reduced CSF S-adenosylmethionine levels in Alzheimer's disease have been reported; however, no information is available regarding the status of S-adenosylmethionine or S-adenosylmethionine-dependent methylation in the brain of patients with this disorder. S-Adenosylmethionine concentrations were measured in postmortem brain of 11 patients with Alzheimer's disease. We found decreased levels of S-adenosylmethionine (-67 to -85%) and its demethylated product S-adenosylhomocysteine (-56 to -79%) in all brain areas examined (cerebral cortical subdivisions, hippocampus, and putamen) as compared with matched controls (n = 14). S-Adenosylmethionine and S-adenosylhomocysteine levels were normal in occipital cortex of patients with idiopathic Parkinson's disease (n = 10), suggesting that the decreased S-adenosylmethionine levels in Alzheimer's disease are not simply a consequence of a chronic, neurodegenerative condition. Reduced S-adenosylmethionine levels could be due to excessive utilization in polyamine biosynthesis. The severe reduction in levels of this essential biochemical substrate would be expected to compromise seriously metabolism and brain function in patients with Alzheimer's disease and may provide the basis for the observations of improved cognition in some Alzheimer's patients following S-adenosylmethionine therapy.

Aged↗
PubMed1996

Changes in medical education: the community perspective.

The societal and economic forces driving change in medical education are affecting communities as well as universities. Each of the four authors of this paper is deeply involved in one of the components of their locale's well-developed community-based medical educational system, and each describes how change is influencing his role in that system, whether the role be managing a community hospital, directing a local Area Health Education Center, participating as a family medicine faculty member, or being a community preceptor. They agree on some common themes: (1) that it is good that medical students' education is moving into the community (e.g., this validates the importance of the community hospital to medical education, is an acknowledgment of the importance of generalism, and provides students invaluable learning experiences); (2) that educating medical students in the community is expensive, and more funding and resources are needed so that the area's hospitals, community faculty, preceptors, and support services can be fairly compensated for their commitment; and (3) that their community-based education system can no longer absorb the costs of training more medical students. This is not a criticism of academic medical centers, which are under tremendous financial pressures themselves, but is simply to state the community perspective and to urge fairness in the distribution of resources for medical education. Community institutions and academic medical centers will work individually to create their own integrated health care systems but must work together to create a better, more cost-effective system for educating medical students.

Academic Medical Centers↗
PubMed1996

Cardiovascular actions of trout urotensin II in the conscious trout, Oncorhynchus mykiss.

The central and peripheral cardiovascular effects of synthetic trout urotensin II (UII) were investigated in the conscious rainbow trout. Intracerebroventricular injection of 50 pmol UII produced a slight (3%) but significant (P < 0.05) increase in heart rate but had no effect on mean arterial blood pressure. Injection of 500 pmol UII icv produced a significant (P < 0.05) rise (8%) in blood pressure with no change in heart rate. In contrast to the weak pressor effect of centrally administered UII, intra-arterial injection of UII produced a dose-dependent increase in arterial blood pressure and decrease in heart rate with significant (P < 0.05) effects on both parameters observed at a dose of 25 pmol. Higher doses of the peptide produced a sustained decrease in cardiac output that accompanied the bradycardia and rise in arterial blood pressure. The UII-induced bradycardia, but not the increase in pressure, was abolished by pretreatment with phentolamine. Trout UII produced a sustained and dose-dependent contraction of isolated vascular rings prepared from trout efferent branchial [-log 50% of the concentration producing maximal contraction (pD2) = 8.30] and celiacomesenteric (pD2 = 8.22) arteries but was without effects on vascular rings from the anterior cardinal vein. The data indicate that the pressor effect of UII in trout is mediated predominantly, if not exclusively, by an increase in systemic vascular resistance. The UII-induced hypertensive response does not seem to involve release of catecholamines, but the bradycardia may arise from adrenergic-mediated activation of cardioinhibitory baroreflexes.

Angiotensin II↗
PubMed1996

Survey of current practice patterns for percutaneous transluminal coronary angioplasty. SANDBAG Nursing Coordinators.

BACKGROUND: The increasing complexity of coronary intervention has led to variations in current patterns of nursing practice for patients undergoing routine percutaneous transluminal coronary angioplasty. In preparation for a large study examining the effects of specific nursing practices on complications at the site of vascular access, we surveyed institutions participating in a randomized phase III trial involving 4010 patients to determine current patterns of practice. OBJECTIVE: The purpose of this study was to determine the current patterns of nursing practice for patients undergoing percutaneous transluminal coronary angioplasty. METHODS: An eight-page questionnaire was completed by 70 hospitals participating in the study titled Integrelin to Manage Platelet Aggregation to Prevent Coronary Thrombosis (IMPACT II). RESULTS: The hospitals participating in this study have an average of 500 beds; 34% of the institutions do 500 to 1000 angioplasty procedures annually. At many sites (39%), heparin is infused for 12 to 18 hours after the intervention, but heparin is not infused at all in 31% of the hospitals studied. At 27% of the hospitals, arterial sheaths are removed 12 to 18 hours after angioplasty, and at 15% of the hospitals, sheaths are removed more than 18 hours after the procedure. Typically after angioplasty (36%), patients are transferred to an ICU, with a nurse-patient ratio of 1:2. Eighty-three percent of the hospitals use CareMAPs or care plans for standardization of care. Most hospitals (83%) require complete bed rest for patients who have had angioplasty, with the affected leg restrained to prevent mobility. Ninety-one percent of the hospitals reported continuing to treat the patient with bed rest for an additional 6 hours after the sheath is removed. CONCLUSION: Comprehensive nursing standards of care based on well-designed clinical trials for patients after angioplasty are not available. In the second phase of our study, we hope to correlate nursing practices with clinical outcome data to improve further the care of patients who have had angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1995

Greek key jellyroll protein motif design: expression and characterization of a first-generation molecule.

A protein designed de novo to fold into the Greek key jellyroll structural motif has been studied. Theoretical analyses have indicated that the designed sequence should adopt the beta-strand arrangement of the Greek key jellyroll rather than any other arrangement. A synthetic gene was constructed and the protein expressed in Escherichia coli. Circular dichroism spectroscopy is consistent with the protein folding into the designed conformation and also suggests the presence of tertiary structure. Fluorescence spectroscopy showed the single tryptophan to be partially buried, while denaturation studies showed changes in fluorescence to precede alterations in secondary structure.

Amino Acid Sequence↗
PubMed1995

Interaction between primary and secondary metabolism in Streptomyces coelicolor A3(2): role of pyrroline-5-carboxylate dehydrogenase.

The activity of the proline catabolic enzyme pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12) was induced up to three-hundred-fold by the addition of three hundred proline to the growth medium of the Gram-positive bacterium Streptomyces coelicolor A3(2). Rifampicin, an inhibitor of RNA polymerase activity, abolished induction, implying that regulation was at the level of activation of gene transcription. The enzyme was purified and SDS-PAGE of the highly purified enzyme preparation revealed a single subunit with M(r) 68,000. A single band of protein, which also stained for enzyme activity, was observed after native gel electrophoresis. The M(r) of the enzyme was estimated to be approximately 265,000 by native gel electrophoresis and approximately 305,000 by gel filtration, which indicated that the enzyme had a tetrameric quaternary structure. The apparent Km for pyrroline-5-carboxylate was 109 +/- 7.3 microM, whilst that for NAD+ was 43.3 +/- 2.5 microM. Product inhibition by NADH (apparent Ki 0.6mM) was observed. The observed Vmax was 22.0 +/- 1 mol min-1 (mg protein)-1. Neither 1 nor 5 mM proline had any effect on enzyme activity, whilst glutamate was a very weak inhibitor.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed1995

Prevalence of antibodies to Toxoplasma gondii in wild mammals of Missouri and east central Kansas: biologic and ecologic considerations of transmission.

Sera from 273 wild mammals from Missouri and Kansas (USA), collected between December 1974 and December 1987, were tested for the presence of antibodies to Toxoplasma gondii using the Sabin-Feldman dye test. Sixty-five (24%) had antibodies at titers of > or = 1:8, including 38 (66%) of 58 carnivores, 14 (15%) of 94 omnivores, 13 (11%) of 117 herbivores, and none of four insectivores. The prevalence of antibodies in mice (Mus musculus and Peromyscus spp.) and rats (Rattus norvegicus and Sigmodon hispidus) was low (3%), while medium sized herbivores such as squirrels (Sciurus spp.), rabbits (Sylvilagus floridanus), and muskrats (Ondatra zibethicus) had prevalences of about 18%. Red foxes (Vulpes fulva) and mink (Mustela vison) had the highest prevalence of antibodies with frequencies of 90 and 66%, respectively. In 32 attempts to isolate Toxoplasma gondii from wild mammals with positive (> or = 1:4) titers, only six (19%) were successful: a gray squirrel (Sciurus carolinensis), a beaver (Castor canadensis), an opossum (Didelphis marsupialis), a red fox and two mink. These findings are consistent with the hypothesis that the probability of infection with Toxoplasma gondii, and therefore prevalence of antibodies in wildlife, is greatest in carnivores.

Animals↗
PubMed1995

Four new coccidia (Apicomplexia: Eimeriidae) from anoles (Lacertilia: Polychrotidae) in the Dominican Republic.

Fecal samples from 25 Anolis armouri, 2 Anolis bahorucoensis, 48 Anolis cybotes, and 21 Anolis olssoni (Lacertilia: Polychrotidae) from southern Hispaniola were examined for coccidian oocysts. Two eimerians and 2 isosporans are herein described as new species. Sporulated oocysts of Eimeria schwartzi n. sp. from A. armouri are ellipsoidal, 22.7 (20.8-25.0) x 15.7 (14.6-17.7) microns, with spherical to subspherical sporocysts, 7.9 (6.2-9.4) x 7.4 (6.2-8.3) microns. Sporulated oocysts of Isospora reui n. sp. from A. bahorucoensis are spherical to subspherical, 18.2 (15.6-20.0) x 17.8 (15.6-19.8) microns, with ovoid sporocysts, 11.9 (10.4-12.7) x 8.5 (7.5-9.4) microns. Sporulated oocysts of Isospora hendersoni n. sp. from A. armouri and A. cybotes are spherical to subspherical, 23.2 (20.8-26.0) x 21.1 (18.4-23.9) microns, with ellipsoidal sporocysts, 14.7 (12.5-15.6) x 10.0 (9.2-11.4) microns. Sporulated oocysts of Eimeria avilae n. sp. from A. olssoni are cylindrical, 29.3 (26.0-33.3) x 15.9 (13.5-18.9) microns, with ellipsoidal sporocysts 10.2 (9.4-11.4) x 6.8 (5.2-8.0) microns.

Animals↗
PubMed1995

Advances in genosensor research.

Microfabricated devices containing arrays of nucleic acid hybridization sites, known as genosensors, are being developed for a variety of uses in genomic analysis. A great deal of the overall genosensor development effort involves optimization of experimental conditions in the actual use of genosensors. Here we describe a "low-tech" form of genosensor technology, involving arrays of oligonucleotides on glass microscope slides, which can be used to define optimal operating conditions and to develop applications of hybridization arrays in genome mapping and sequencing. In addition, we describe a porous silicon genosensor, which can be operated in a flowthrough mode, and discuss its advantages over current flat-surface designs. Porous silicon genosensors containing arrays of DNA fragments offer several unique capabilities in genome analysis.

Base Sequence↗
PubMed1994

Solid-phase peptide synthesis and biological activity of bovine thymopoietin II (bTP-II).

Bovine thymopoietin (bTP), a 49 amino acid polypeptide, was synthesized using Merrifield's solid-phase peptide synthesis methodology. The polypeptide was purified using anion-exchange chromatography and reversed-phase HPLC and characterized by mass spectrometry and amino acid analysis of the full-length peptide and of products derived from digestion with Staphylococcus aureus V8 protease. The biological activity of the synthesized product was tested in several assay systems. Synthetic bTP was found to induce the expression of Thy 1.2 antigen on T-lymphocytes from athymic mice, in agreement with previous studies on the biological activity of endogenous bTP. Biological activity at skeletal muscle and neuronal nicotinic acetylcholine receptor sites, as reported by others for bTP, could not be confirmed in our studies. The absence of biological activity at nicotinic receptor sites may be related to the results of a recent report demonstrating the presence of a cobratoxin-like molecule in preparations of natural bTP. These data indicate that synthetic peptides have an important role for the evaluation of the specificity of the biological activity of polypeptides.

Amino Acid Sequence↗