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Biomedical subjects

W L Nicholson

Publications and source records attributed to W L Nicholson.

12 recordsLinked to original sources
PubMed1992

Attempted mechanical transfer of Ehrlichia risticii by tabanids (Diptera: Tabanidae).

The ability of tabanid mouthparts to retain and to transfer mechanically Ehrlichia risticii Holland, Weiss, Burgdorfer, Cole & Kakoma was evaluated by feeding flies on infected and noninfected mice and on capillary tubes containing infected cells and cell-free medium. Flies representing two genera and 29 species were collected at equine boarding stables, farms, and along riding trails in Wake, Johnston, and Duplin counties in North Carolina for the feeding trials. Two species, Tabanus fulvulus Wiedemann and T. pallidescens Philip, fed on mice but failed to transfer the pathogen from infected to susceptible mice. Chrysops vittatus Wiedemann, Tabanus americanus Forster, and T. sulcifrons Macquart transferred E. risticii-infected cells from capillary tubes containing infected cells in medium to tubes containing medium. These studies document that E. risticii-infected cells can be retained on mouthparts and potentially transferred by tabanids.

Animals↗
PubMed1991

Ultraviolet irradiation of DNA complexed with alpha/beta-type small, acid-soluble proteins from spores of Bacillus or Clostridium species makes spore photoproduct but not thymine dimers.

UV irradiation of complexes of DNA and an alpha/beta-type small, acid-soluble protein (SASP) from Bacillus subtilis spores gave decreasing amounts of pyrimidine dimers and increasing amounts of spore photoproduct as the SASP/DNA ratio was increased. The yields of pyrimidine dimers and spore photoproduct were less than 0.2% and 8% of total thymine, respectively, when DNA saturated with SASP was irradiated at 254 nm with 30 kJ/m2; in the absence of SASP the yields were reversed-4.5% and 0.3%, respectively. Complexes of DNA with alpha/beta-type SASP from Bacillus cereus, Bacillus megaterium, or Clostridium bifermentans spores also gave spore photoproduct upon UV irradiation. However, incubation of these SASPs with DNA under conditions preventing complex formation or use of mutant SASPs that do not form complexes did not affect the photoproducts formed in vitro. These results suggest that the UV photochemistry of bacterial spore DNA in vivo is due to the binding of alpha/beta-type SASP, a binding that is known to cause a change in DNA conformation in vitro from the B form to the A form. The yields of spore photoproduct in vitro were significantly lower than in vivo, perhaps because of the presence of substances other than SASP in spores. It is suggested that as these factors diffuse out in the first minutes of spore germination, spore photoproduct yields become similar to those observed for irradiation of SASP/DNA complexes in vitro.

Bacillus↗
PubMed1991

Comparison of an enzyme-linked immunosorbent assay to an indirect immunofluorescence assay for the detection of antibodies to Borrelia burgdorferi in the dog.

An enzyme-linked immunosorbent assay (ELISA) was compared to an indirect immunofluorescence assay (IFA) for detection of IgG antibodies to Borrelia burgdorferi in dog sera. The concordance of the two tests was 93.5% for sera from dogs from Maryland (n = 93), 98.0% for sera from dogs from North Carolina (n = 446), and 97.2% for the combined sample groups (n = 539). Twenty-five of the 27 samples with discordant or low positive results were tested, and showed immunoblot reactions to 1 to 10 different bands. Reaction patterns and intensity of the bands were quite variable, and did not explain a reason for the discordance.

Animals↗
PubMed1991

Borrelia burgdorferi in ticks (Acari: Ixodidae) from coastal Virginia.

Ixodid ticks removed from hosts and from vegetation during March-November 1987 at sites in coastal Virginia and North Carolina were examined for Borrelia burgdorferi. B. burgdorferi was evident in nine (22%) Ixodes cookei Packard removed from rice rats (Oryzomys palustris), a white-footed mouse (Peromyscus leucopus), and raccoons (Procyon lotor); four (6%) Amblyomma americanum (L.) removed from raccoons; and two (3%) Dermacentor variabilis (Say) removed from a raccoon and a rice rat. B. burgdorferi was also detected in Ixodes dentatus Marx removed from a brown thrasher (Toxostoma rufum), a Carolina wren (Thryothoros ludovicianus), and a towhee (Piplio erythrophthalamus); and in Haemaphysalis leporispalustris (Packard) removed from a brown thrasher and a white-throated sparrow (Zonotrichia albicollis) netted at Kiptopeke Beach, Va. Two Ixodes dammini Spielman, Clifford, Piesman & Corwin were collected on Parramore Island; one specimen was examined for spirochetes, and it was infected with B. burgdorferi. No spirochetes were detected in host-seeking A. americanum and Amblyomma maculatum Koch removed from vegetation. The plasma of one P. leucopus and sera obtained from two P. lotor contained antibodies to B. burgdorferi. All infected ticks and the seroreactive hosts were collected from the Eastern Shore of Virginia.

Animals↗
PubMed1991

Indigenous cases of Lyme disease diagnosed in North Carolina.

Between January 1984 and December 1989, 102 indigenous cases of Lyme disease were reported in North Carolina. Lyme disease was reported in each of the three major geographic regions of the state: mountain, piedmont, and coastal plain. One or more diagnoses were made in 42 of 100 counties. Patients ranged in age from 5 months to 78 years (median, 27 years); 58 patients (57%) reported a history of tick exposure within 1 month of the onset of symptoms. Erythema migrans was reported by 93 patients (91%). Arthritis (30%), neurologic symptoms (10%), and cardiac abnormalities (7%) were observed. Thirty of the 102 cases were confirmed serologically by indirect fluorescence microscopy or enzyme-linked immunosorbent assay.

Acute Disease↗
PubMed1991

Catabolite repression of alpha-amylase gene expression in Bacillus subtilis involves a trans-acting gene product homologous to the Escherichia coli lacl and galR repressors.

Expression of the alpha-amylase gene of Bacillus subtilis is controlled at the transcriptional level, and responds to the growth state of the cell as well as the availability of rapidly metabolizable carbon sources. Glucose-mediated repression has previously been shown to involve a site near the transcriptional start-point of the amyE gene. In this study, a transposon insertion mutation was characterized which resulted in loss of glucose repression of amyE gene expression. The gene affected by this mutation, which was localized near 263 degrees on the B. subtilis chromosomal map, was isolated and its DNA sequence was determined. This gene, designated ccpA, exhibited striking homology to repressor genes of the lac and gal repressor family. The ccpA gene was found to be allelic to alsA, previously identified as a regulator of acetoin biosynthesis, and may be involved in catabolite regulation of other systems as well.

Acetoin↗
PubMed1990

Attempted Ehrlichia risticii transmission with Dermacentor variabilis (Acari: Ixodidae).

Larval Dermacentor variabilis (Say) (n = 327) were fed on Balb/C mice inoculated with Ehrlichia risticii, the etiologic agent of equine monocytic ehrlichiosis (Potomac horse fever). All mice displayed clinical signs of E. risticii infection at the time of feeding. After molting, resulting nymphs (n = 74) were fed on susceptible mice. No clinical signs were observed, and the mice remained seronegative for 6 wk after feeding.

Animals↗
PubMed1990

Dramatic increase in negative superhelicity of plasmid DNA in the forespore compartment of sporulating cells of Bacillus subtilis.

Plasmid pUB110, isolated from vegetative cells of Bacillus subtilis, has an average of 34 negative supertwists (tau av = -34). This value falls to -30 early in sporulation, and the plasmid in the mother cell compartment maintains a tau av of -30. However, the plasmid within the developing forespore becomes much more negatively supercoiled, reaching a tau av of -47 in the dormant spore. This increased negative supercoiling in the forespore plasmid takes place in parallel with the synthesis of small, acid-soluble spore proteins, alpha and beta; and the plasmid from spores lacking small, acid-soluble proteins alpha and beta has a tau av of -40. The large increase in negative supercoiling of spore plasmid was also observed with Bacillus megaterium and in B. subtilis containing a plasmid with an origin different from that of pUB110. During spore germination plasmid pUB110 rapidly relaxed back to the tau av value characteristic of vegetative cells. It is possible that the observed changes in forespore plasmid topology are involved in modulating gene expression, DNA photochemistry, or both of these parameters in this compartment.

Bacillus subtilis↗
PubMed1990

Binding of DNA in vitro by a small, acid-soluble spore protein from Bacillus subtilis and the effect of this binding on DNA topology.

The DNA within spores of Bacillus subtilis is complexed with a large amount of alpha/beta-type small, acid-soluble spore protein (SASP). Measurement of the interaction of a purified alpha/beta-type SASP with DNA in vitro by a filter binding assay showed that the binding saturated at one molecule of SASP per approximately 5 bp. SASP-DNA binding did not require a divalent cation, was optimal at pH 6.7, and was unaffected by salt up to 400 mM. Binding of SASP to relaxed plasmid DNA in the presence of topoisomerase I resulted in the introduction of 18 (for plasmid pUC19) or 36 (for plasmid pUB110) negative supertwists, a superhelical density similar to that found in several plasmids isolated from spores. The SASP-dependent introduction of negative supertwists did not require a divalent cation, was unaffected by salt, and also gave a value of one molecule of SASP per approximately 5 bp at saturation. There was at least one slow step in the binding of SASP to DNA as seen in both the filter binding and supercoiling assays.

Bacillus subtilis↗
PubMed1978

Application of statistical methods in quantitative microscopy.

The purpose of the paper is twofold: first, to describe the aspects of quantitative microscopy where statistical ideas are being applied today; and second, to describe some ways in which more complete use of statistics could improve quantitative microscopy. The typical estimation problem in quantitative microscopy is described with emphasis on the modelling of variability in estimation. A Poisson field model for imbedded particulates is used to illustrate the value of theoretical treatments of variability. Sampling, estimation and multivariate analysis are cited as areas of statistics presently used by quantitative microscopists. The potential role of statistics in quantitative microscopy is discussed. Examples from particle sizing and characterization of alveolar lung structure illustrate the value of statistical ideas. Automatic image analysers, while making the collection of large amounts of data feasible, have complicated statistical estimation. An investigation of the size distribution of random chord lengths through alveolar chambers illustrates how statistical methodology must be modified for valid inference.

Animals↗
PubMed1975

Pseudomonas aeruginosa meningitis following stapedectomy.

Meningitis is a rare complication following stapedectomy. Most cases are preceeded by a fistula in the oval window. Although fatalities have been reported, most cases respond to parenteral and intrathecal antibiotics if diagnosed and treated early. Gram-positive organisms are the usual pathogens, but Gram-negative organisms may be found, especially as a superinfection following antibiotics administered prophylacticly or for the treatment of otitis media or mastoiditis. A case of Pseudomonas aeruginosa meningitis five weeks after stapedectomy, successfully treated with gentamicin, is reported. The discussion included the diagnosis of post-stapedectomy fistula and meningitis and current trends in treatment.

Audiometry↗