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Biomedical subjects

J W Nelson

Publications and source records attributed to J W Nelson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Mucinophilic and chemotactic properties of Pseudomonas aeruginosa in relation to pulmonary colonization in cystic fibrosis.

Representative isolates of nonmucoid Pseudomonas aeruginosa were studied to investigate the hypothesis that mucinophilic and chemotactic properties in this species act as potential factors in the initial stages of pulmonary colonization in patients with cystic fibrosis (CF). Transmission electron microscopy with a surfactant monolayer technique was used in a novel manner to demonstrate the adhesion of all 10 P. aeruginosa strains examined to porcine gastric mucin and tracheobronchial mucin from a patient with CF. Control experiments showed that Escherichia coli K-12 and single representatives of Proteus mirabilis and Klebsiella aerogenes did not bind to these mucins. The Adler capillary technique, used to measure bacterial chemotactic response, showed that purified CF mucin acted as a chemoattractant for most P. aeruginosa strains, with the exception of the nonmotile mutant M2Fla- and the nonchemotactic mutant WR-5. The ability of the major sugar and amino acid components of mucin to act as chemoattractants was investigated. The degree of chemotaxis was strain specific; optimum chemotaxis was observed toward serine, alanine, glycine, proline, and threonine. No strain showed chemotaxis to N-acetylneuraminic acid, but all strains showed a strain-dependent chemotactic response to the sugars L-fucose, D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine. These results provide new information on the mucinophilic and chemotactic properties of nonmucoid P. aeruginosa and support the hypothesis that these properties could play a role in the initial stages of pulmonary colonization in patients with CF.

Amino Acids↗
PubMed1989

Persistence of the alpha-helix stop signal in the S-peptide in trifluoroethanol solutions.

alpha-Helix formation in the S-peptide (residues 1-19 of ribonuclease A) was studied in detail by use of two-dimensional 1H nuclear magnetic resonance to monitor the effects of 2,2,2-trifluoroethanol (TFE) at 0 degrees C and pH* 2.07. TFE stabilizes the S-peptide alpha-helix. Helix formation by a particular amino acid was monitored by the chemical shifts of the C alpha, C beta, and C gamma protons while increasing the concentration of TFE: large changes in chemical shift of a particular residue indicate that it is induced to go helical, whereas small chemical shift changes indicate little helix formation. Residues Thr-3 to Met-13 undergo chemical shift changes consistent with helix formation, whereas the other residues do not. Earlier work [Kim, P. S., & Baldwin, R. L. (1984) Nature 307, 329-334] reported that residues Thr-3 to His-12 become helical in aqueous solution. The existence of a "helix stop signal" was inferred from this behavior. We thus conclude that this helix stop signal persists in TFE solutions.

Amino Acids↗
PubMed1986

Methylation and restriction endonuclease cleavage of linear Z-DNA in the presence of hexamminecobalt (III) ions.

These studies employed the synthetic linear DNA, poly dGdC, in the B and cobalt hexammine chloride (Co)-induced Z form to determine the effect of conformation on protein-DNA interactions. The rate of the reaction of the restriction endonucleases, Hha I and Cfo I, are reduced with Z DNA as compared to B DNA. The ability of both restriction endonucleases to react with an aggregate form of Z DNA (Z* DNA) is found to depend upon how the Z* DNA is formed. When Z* DNA is induced by low concentrations of Co (50 microM), the endonucleases remain active. In the presence of 100 microM Co, which causes increased aggregation, the endonucleases are inactive. The Hha I DNA methyltransferase reacts at equal rates with the B, Z and low cobalt Z* forms and at a greatly reduced rate with the high cobalt Z* form. These results are significantly different than those observed with Z form dGdC tracts inserted into circular DNA molecules.

Chlorides↗
PubMed1986

Stabilization of the ribonuclease S-peptide alpha-helix by trifluoroethanol.

The effects of trifluoroethanol (TFE) on the stability of the alpha-helix formed by ribonuclease S-peptide, residues 1-19 of ribonuclease A, were studied by measuring circular dichroism as a function of TFE concentration, pH, and temperature. The S-peptide forms an unusually stable alpha-helix, which is known to be stabilized by TFE. The magnitude of the effect of charged groups on the peptide, manifested by the change in alpha-helix stability as a function of pH, was not altered significantly by either TFE concentration or temperature, indicating that the lower dielectric constant of TFE is not important in the stabilization of this alpha-helix. This suggests that the alpha-helix might be stabilized by many interactions in addition to the effects of charges. The titration curve of circular dichroism vs. TFE concentration appears to be cooperative at 0 degree C, but becomes progressively less cooperative at temperatures between 25 and 75 degrees C. The properties of the TFE stabilization indicate that TFE might be a useful probe with which to measure the stability of marginally stable peptides and small proteins.

Circular Dichroism↗
PubMed1985

Ethidium ion binds more strongly to a DNA double helix with a bulged cytosine than to a regular double helix.

Thermodynamic parameters for ethidium intercalation were determined for the double helices formed by the oligonucleotides dCA6G + dCT6G, which form a normal helix, and dCA3CA3G + dCT6G, which form a double helix with the middle cytosine bulged outside of the helix. Ethidium intercalation was measured by monitoring the absorbance at 260 and 283 nm as a function of temperature for a number of concentrations of ethidium. The binding to the normal helix occurs equally at all the intercalation sites, with an enthalpy of binding of -8 kcal mol-1, an entropy of binding of -6 eu, and an equilibrium constant at 25 degrees C of 2.2 X 10(4) M-1. The binding to the bulged double helix was considerably stronger and is consistent with a model in which the intercalation sites on either side of the bulged base bind 10 times stronger than the other sites. Thus, there are two strong binding sites on the perturbed helix with equilibrium constants for binding of 2 X 10(5) M-1 at 25 degrees C in addition to five normal sites. Several other binding models were tested but did not fit the data satisfactorily.

Calorimetry↗
PubMed1985

Clear cell myeloma.

We report a case of clear cell myeloma misinterpreted at initial biopsy as liposarcoma. The patient had lytic skeletal lesions and monoclonal IgA, kappa, serum immunoglobulin. The tumor cells contained cytoplasmic vacuoles that produced a clear histologic appearance. The light-microscopic and ultrastructural findings are compared with those of other cases of lymphoplasmacytic disorders with prominent cytoplasmic inclusions.

Aged↗
PubMed1983

Resurgence of yaws in Ghana.

This paper reports on the first 1 1/2 years of a new effort to control yaws in Ghana, where the disease has been resurgent since a previous mass campaign ended over 10 years ago.

Adolescent↗
PubMed1982

Comparison of the kinetics of ribooligonucleotide, deoxyribooligonucleotide, and hybrid oligonucleotide double-strand formation by temperature-jump kinetics.

The kinetics of double-strand formation were measured by using temperature-jump kinetic techniques for the DNA oligonucleotides dCA5G + dCT5G, the analogous RNA oligonucleotides rCA5G + rCU5G, and the hybrid rCA5G + dCT5G. The DNA oligonucleotides have a faster rate of recombination and a slower rate of dissociation at 12.0 degrees C than the RNA oligonucleotides; the hybrid has about the same recombination rate and a slightly faster dissociation rate than the RNA oligonucleotides. The activation energies for recombination for the DNA and RNA oligonucleotides are both near 0 kcal/mol. The difference in dissociation and recombination activation energies is consistent with the thermodynamic results obtained earlier. The relaxation process is composed of two exponential components for the RNA and hybrid oligonucleotides at temperatures of 12.0 degrees C and lower. One exponential component is observed for these oligonucleotides above 12.0 degrees C and for the DNA oligonucleotides at all temperatures.

Kinetics↗
PubMed1980

Traumatic rupture of the diaphragm: a method of diagnosis.

Traumatic rupture of the diaphragm is often difficult to diagnose and is frequently missed preoperatively. A new method of diagnosis is discussed in the following case presentation of traumatic rupture of the right hemidiaphragm.

Adult↗
PubMed1979

Manufacture of antithymocyte globulin (ATGAM) for clinical trials.

Methods are described for preparing large amounts of horse anti-human thymocyte globulin (ATG, ATGAM; The Upjohn Company) for clinical use. These methods have been used since 1968 to provide material for clinical trials. Characteristics of 40 lots of ATG are summarized.

Animals↗
PubMed1978

Copper metabolism in American retinitis pigmentosa patients.

Serum copper, serum caeruloplasmin, and urinary copper excretion were measured in 38 American patients (and 15 family members) with recessive, dominant, and X-linked forms of retinitis pigmentosa. No abnormalities were found, in contrast to the findings of a recent study on Indian patients. Our data argue against a role for copper metabolism in ordinary retinitis pigmentosa.

Adolescent↗
PubMed1977

Proton-induced x-ray emission analysis of single human hair roots.

Collimated beams of 3.75 million electron volt protons were used to examine a 2-millimeter length of the root end of human hair; the concentrations of some hair root elements were correlated with the results of standard clinical assays of blood samples. The technique should be useful for the analysis of micro amounts of biological tissue.

Calcium↗
PubMed1977

Simplified micro-scale procedure for preparing samples for theophylline determination by liquid chromatography.

We describe an improved procedure for the preparation of plasma or serum for determination of theophylline by reverse phase high-performance liquid chromatography. Quantitative results are available in less than 30 min from receipt of sample. The chromatogram is complete in 8 to 16 min, which includes the use of an internal standard. Sample preparation consists of simple solvent denaturation of the sample proteins, and centrifugation to remove protein before chromatography. No precolumn is required to pretect the separating column. No interference was noted when sodium or lithium heparin or ethylenediaminetetraacetate were used as anticoagulants, but citrate treatment proved to be unsatisfactory because of a highly absorbing band that eluted with the same retention volume as theophylline.

Analysis of Variance↗