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Biomedical subjects

K H Wilson

Publications and source records attributed to K H Wilson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Adenomas induced by polycyclic aromatic hydrocarbons in strain A/J mouse lung correlate with time-integrated DNA adduct levels.

The induction of DNA adducts and adenomas in the lungs of strain A/J mice has been investigated following the single i.p. administration of each of the following polycyclic aromatic hydrocarbons (PAH): pyrene, dibenz[a,h]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, 5-methylchrysene, and cyclopenta[c,d]pyrene. DNA adducts were measured by 32P-postlabeling at times between 1 and 21 days following injection, while adenomas were counted at 240 days after treatment. Pyrene did not induce either DNA adducts or lung adenomas at any of the doses examined. Each of the remaining PAH induced both adenomas and DNA adducts in a dose-dependent manner, with dibenz[a,h]anthracene > 5-methylchrysene > cyclopenta[c,d]pyrene > benzo[a]pyrene > benzo[b]fluoranthene. DNA adducts reached maximal levels between 3 and 9 days after injection, followed by a gradual decrease. The time-integrated DNA adduct level (TIDAL) was calculated by numerically integrating the areas under the adduct persistence curves extrapolated to 240 days for each PAH at each dose level. This value represents the effective total molecular dose of PAH that was delivered to the lung DNA over the entire course of tumorigenesis. A strong correlation of lung adenoma induction with the TIDAL values was observed for each PAH. The slopes of the tumors versus TIDAL value relationships were essentially identical for 5-methylchrysene, cyclopenta[cd]pyrene, benzo[a]pyrene, and benzo[b]fluoranthene. The slope of this relationship for dibenz[a,h]anthracene was markedly greater. The essentially identical induction of adenomas as a function of TIDAL values for these PAH suggests that the formation and persistence of DNA adducts determines their carcinogenic potency.

Adenoma↗
PubMed1995

Bartonella henselae: etiology of pulmonary nodules in a patient with depressed cell-mediated immunity.

We describe an immunocompromised renal transplantation patient with opportunistic lung infection due to Bartonella henselae (formerly Rochalimaea henselae) and provide evidence suggesting transmission from a pet cat. Computed tomographic scans of the chest and lung biopsies provided material for diagnosis. The etiology was established by polymerase chain reaction and sequencing of a 16S ribosomal DNA segment from infected lung tissue. Histopathologic and serological evidence supported the molecular data. B. henselae was isolated from the blood of eight of the patient's many cats. The patient responded to prolonged therapy with doxycycline, and relapse did not occur during a 1-year follow-up. B. henselae joins a long list of pathogens that can cause lung infections in association with cell-mediated immunodeficiency states. Molecular methods are useful in diagnosis of this infection in light of the bacterium's fastidious growth characteristics. If an immunocompromised patient has lung nodules and a history of exposure to cats, B. henselae should be sought in biopsy specimens.

Adult↗
PubMed1995

Molecular biology as a tool for taxonomy.

Bacterial taxonomy based on phenotypic properties has encountered several problems: many organisms grow to poorly under laboratory conditions to be studied; the same phenotypic property often arises independently in more than one branch of a phylogenetic tree; and phenotypic schemes sometimes become unwieldy. Thus, molecular approaches have found a niche in taxonomy. Measurement of DNA hybridization between strains is the single most definitive tool for defining a species. Data on sequences of DNA and amino acids can be used to infer phylogeny. The molecular phylogenetic approach is most useful at levels ranging from kingdom to species. Restriction fragment length polymorphisms or variability in random polymerase chain reactions often differentiates strains. In the majority of cases, different molecular approaches tend to confirm established taxonomic schemes for bacteria. However, discrepancies between standard taxonomy and molecular data are not rare, especially when dealing with anaerobes. The contemporary approach to taxonomy takes into account both standard and molecular data.

Bacteria↗
PubMed1995

Prolonged Bartonella bacteremia in cats associated with cat-scratch disease patients.

Recent evidence supports a causal relationship between Bartonella (Rochalimaea) henselae, cat-scratch disease (CSD), and bacillary angiomatosis. Cats appear to be the primary reservoir. Blood from 19 cats owned by 14 patients diagnosed with CSD was cultured. Blood samples from cats owned by veterinary students (n = 25) having no association with CSD or bacillary angiomatosis were cultured as controls. Eighty-nine percent (17 of 19) of cats associated with CSD patients and 28% (7 of 25) of controls were bacteremic with Bartonella species (chi-square = 16.47; P < 0.001). Twenty-three isolates were characterized as B. henselae, while one isolate from the cat of a CSD patient appeared to be a new Bartonella species. Thirteen cats remained culture positive during the ensuing 12-month period. Our results support the conclusion that B. henselae is the predominant species involved in CSD and is transmitted by cats. The incidence of Bartonella bacteremia in control cats suggests that B. henselae bacteremia is prevalent among the domestic cat population in the United States.

Adolescent↗
PubMed1995

Genetic variability of Bacillus anthracis and related species.

We evaluated the abilities of pulsed-field gel electrophoresis (PFGE) and sequences of intergenic spacer regions (ISRs) between two highly conserved genes, 16S-23S rDNA and gyrB-gyrA ISRs, to detect variation in strains of Bacillus anthracis as well as two closely related species, B. cereus ATCC 14579 and B. mycoides ATCC 6462. For each restriction enzyme, (NotI, SfiI, and SmaI), the PFGE banding patterns for three B. anthracis strains (Ames, Vollum, and Sterne) were identical. However, closely related species could be differentiated from B. anthracis and from each other. PCR amplification of the 16S-23S rDNA ISR yielded a 143- to 144-bp fragment, showing identical sequences for B. anthracis strains, one nucleotide deletion between B. cerus and B. anthracis, and 13 nucleotide differences between B. mycoides and B. anthracis. The gyrase ISR sequences (121 bp) in B. anthracis strains were also identical, but those in B. cereus and B. mycoides differed from that in B. anthracis by 1 and 2 nucleotides, respectively, and from each other by only 1 nucleotide. Given the diverse geographic origins of these B. anthracis strains, this species is very homogenous. We conclude that methods such as PFGE and sequences of ISRs may be useful in separating B. anthracis from closely related species, but more sensitive methods are needed for strain identification of B. anthracis.

Bacillus↗
PubMed1995

Cloning and pharmacological characterization of human alpha-1 adrenergic receptors: sequence corrections and direct comparison with other species homologues.

We have cloned cDNAs encoding three human alpha-1 adrenergic receptor (AR) subtypes and characterized pharmacological properties of the expressed receptor protein. A number of significant sequence corrections have been identified and compared with previously published data, at both nucleotide and amino acid levels; the most major differences occur for the human alpha-1a/dAR. Pharmacological characterization was performed simultaneously using six cloned alpha-1AR subtypes (human and rat alpha-1a/d, human and hamster alpha-1b, human and bovine alpha-1c) stably expressed in rat-1 fibroblasts at approximately equal receptor concentrations (1-2 pmol/mg of total protein). In general, human alpha-1AR subtypes have similar pharmacology compared to their rat, hamster and bovine homologs, although a few minor species differences important for alpha-1AR classification are noted. In addition, much lower inactivation (approximately 20%) by the alkylating agent chloroethylclonidine is noted in this study compared to previous reports for both human and bovine alpha-1cAR membrane preparations. All six alpha-1AR subtypes couple to phosphoinositide hydrolysis in a pertussis toxin-insensitive manner, including the cloned human alpha-1a/dAR which had not been expressed previously. In spite of significant sequence differences between human alpha-1ARs and their other species counterparts, previously established ligand selectivity remains fairly comparable. In summary, these data represent the first side-by-side comparison of pharmacological properties between species homologs of alpha-1AR subtypes and should facilitate the development of alpha-1AR subtype selective drugs for clinical use.

Amino Acid Sequence↗
PubMed1994

Tumor multiplicity, DNA adducts and K-ras mutation pattern of 5-methylchrysene in strain A/J mouse lung.

This study was undertaken to evaluate the carcinogenic potential of 5-methylchrysene (5-MeC) in strain A/J mouse lung and to correlate the 5-MeC-DNA adduct profile in lung tissue with the mutation spectrum in the K-ras gene of lung tumors. Strain A/J mice received a single i.p. injection of 5-MeC at doses of 10, 50, 100 and 200 mg/kg and after 24, 48 and 72 h their lungs were collected for DNA adduct analysis. Eight months later, lungs from the remaining mice were harvested and the lung tumors counted and collected for subsequent mutational analysis of the K-ras gene. 5-MeC was found to be a potent lung carcinogen in strain A/J mice, inducing more than 100 tumors/mouse at a concentration of 200 mg/kg. Six 5-MeC-DNA adducts were observed; one adduct comigrated with the standard N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I [1R,2S,3S-trihydroxy-4R-(N2-deoxy-guanosyl-3'-phosphate)- 1,2,3,4-tetrahydro-5-methyl-chrysene], derived from the bay-region diol-epoxide of 5-MeC. DNAs isolated from 5-MeC-induced lung tumors were evaluated for activating mutations in the K-ras gene by polymerase chain reaction-single strand conformation polymorphism and direct DNA sequencing analysis. Mutations were detected in 44 of 49 (90%) 5-MeC-induced tumors and the mutations were GGT-->TGT (50%), GGT-->GTT (23%) and GGT-->CGT (27%) in codon 12 of the gene. These results suggest that the N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I may be one of the promutagenic adducts of 5-MeC in strain A/J mouse lung.

Animals↗
PubMed1994

Detection of culture-resistant bacterial pathogens by amplification and sequencing of ribosomal DNA.

Molecular phylogeny is profoundly influencing the field of bacterial evolution. New knowledge in this area has led to an exciting ability to detect and classify bacteria without culturing them. The process involved consists of either amplification or cloning of ribosomal DNA from a bacterial population, sequencing of this ribosomal DNA, and phylogenetic analysis of the sequences obtained. This approach has so far been applied successfully to four infectious diseases: bacillary angiomatosis, human ehrlichiosis, Whipple's disease, and Tyzzer's disease. Interpretation of data obtained by this method has been straightforward.

Angiomatosis, Bacillary↗
PubMed1994

Molecular phylogeny of the Mycobacterium avium complex demonstrates clinically meaningful divisions.

Phylogenetic analysis of nucleotide sequence data is widely used for viral epidemiology. To explore its use in bacterial strain differentiation, the variable 16S-23S rDNA internal transcribed spacer (ITS) in 24 clinical isolates originally identified as Mycobacterium avium complex (MAC) was sequenced. Three isolates had an identical sequence that differed greatly from the rest. They belonged to the recently described Mycobacterium celatum. The 21 MAC clinical isolates gave 6 ITS sequences, each defining a sequevar. Thirteen isolates from 11 AIDS patients with disseminated MAC disease belonged to 2 sequevars, which differed in ITS sequence by 1 nucleotide. In contrast, 7 pulmonary-source MAC isolates were genetically more diverse. They belonged to 4 sequevars, which differed from each other by 6-20 nucleotides and from the disseminated disease-associated sequevars by at least 12 nucleotides. The single urine MAC isolate had the same sequence as 1 of the pulmonary isolates. Because the disseminated disease-associated MAC strains were distinct by ITS sequence analysis, it should be possible to develop a molecular assay to detect them directly in clinical specimens or in environmental samples. Molecular phylogeny at the strain level may be widely useful in studies of bacterial epidemiology and virulence.

Adult↗
PubMed1994

Preliminary study using species-specific oligonucleotide probe for rRNA of Bilophila wadsworthia.

Portions of the 16S RNA from a urease-positive Bilophila wadsworthia strain were sequenced, and a probe was constructed. The probe was end labeled with [32P]ATP and polynucleotide kinase and hybridized on a nylon filter (by dot blot hybridization) to the immobilized rRNA of 12 B. wadsworthia strains and eight other anaerobic isolates. The probe efficiently hybridized only to the Bilophila strains. Cross-reactivity at high RNA levels (2,000 ng) was observed with one strain of Bacteroides thetaiotamicron and one strain of Bacteroides fragilis (with 10x SET buffer [20x SET buffer is 0.5 M NaCl, 0.03 M Tris, and 2 mM EDTA]) but was not seen at lower RNA levels or with 5x SET buffer. When tested against mixed cultures of aerobic and anaerobic isolates representative of appendiceal abscess flora, the probe did not react with mixed cultures containing no Bilophila cells and could detect > or = 10(5) Bilophila CFU/ml when the mixture was seeded with Bilophila cells. This probe is of potential use in the rapid identification of pure isolates and in the direct identification of B. wadsworthia in clinical specimens.

Base Sequence↗
PubMed1994

Extensive DNA sequence conservation throughout the Mycobacterium tuberculosis complex.

The Mycobacterium tuberculosis complex includes the four species M. tuberculosis, M. bovis, M. africanum, and M. microti. We sequenced 13 M. tuberculosis complex strains in the 16S-to-23S rDNA internal transcribed spacer (ITS). The ITS has a high rate of nucleotide substitution. Previous reports found three nucleotide substitutions in the ITS between two M. tuberculosis complex strains. In contrast, we found the same ITS sequence in all 13 M. tuberculosis complex strains (including all four species and M. bovis BCG). This finding confirms the conservation of 16S rDNA sequence and the high DNA-DNA relatedness found in previous studies. By the usual criteria, the four species of the M. tuberculosis complex would be considered a single species. In a phylogenetic analysis based on the ITS sequence, the four species of the M. tuberculosis complex were distinct from nontuberculous mycobacteria. The ITS contains at least seven potential sites for oligonucleotide probes with specificity for the M. tuberculosis complex.

Base Sequence↗
PubMed1993

The microecology of Clostridium difficile.

An understanding of the microecology of Clostridium difficile provides for a better understanding of the disease that this organism causes. C. difficile is not a significant component of the microflora in the colon of healthy adult humans or animals; however, it can establish large populations in antibiotic-treated or gnotobiotic animals and in infants before they acquire a complete flora. Major factors that determine whether or not disease develops are: (1) the size of the C. difficile populations; (2) the toxigenicity of the colonizing strain; (3) the presence of other organisms that affect toxin expression or activity; (4) susceptibility of the host; and possibly (5) a strain's adhesion to colonic epithelium. The rest of the colonic flora determines the size of the C. difficile population, at least in part by limiting available nutrients. In outbreaks, most C. difficile disease is caused by nosocomial strains. Environmental contamination with spores and spread via the hands of health care workers have been implicated in transmission. Information with regard to this organism's microecology suggests alternative approaches to the control of disease.

Animals↗
PubMed1993

Assignment of the agent of Tyzzer's disease to Clostridium piliforme comb. nov. on the basis of 16S rRNA sequence analysis.

The small-subunit rRNA (16S rRNA) sequence of Tyzzer's bacillus (also known as "Bacillus piliformis") was elucidated by using the polymerase chain reaction followed by reverse transcriptase sequencing. By using maximum-likelihood analysis, a phylogenetic tree was constructed from this and other 16S rRNA sequences available from the first release of the Ribosomal Database Project (G. J. Olsen, R. Overbeek, N. Larsen, T. L. Marsh, M. J. McCaughey, M. A. Maciukenas, W.-M. Kuan, T. J. Macke, Y. Xing, and C. R. Woese, Nucleic Acids Res. 20:2199-2200, 1992). Tyzzer's bacillus grouped with a specific set of anaerobic bacteria, most of which are Clostridium spp. The closest identified relatives are Clostridium coccoides, Clostridium oroticum, Clostridium clostridiiforme, Clostridium symbiosum, and Streptococcus hansenii. Clostridium amino-valericum and "Acetitomaculum ruminis" are also solidly allied with this ensemble. We propose that Tyzzer's bacillus be reclassified as Clostridium piliforme on the basis of its 16S rRNA sequence.

3T3 Cells↗
PubMed1993

Sequence-based differentiation of strains in the Mycobacterium avium complex.

The complete 16S-23S rDNA internal transcribed spacer (ITS) was sequenced in 35 reference strains of the Mycobacterium avium complex. Twelve distinct ITS sequences were obtained, each of which defined a "sequevar"; a sequevar consists of the strain or strains which have a particular sequence. ITS sequences were identified which corresponded to M. avium (16 strains, four ITS sequevars) and Mycobacterium intracellulare (12 strains, one ITS sequevars). The other seven M. avium complex strains had ITS sequences which varied greatly from those of M. avium and M. intracellulare and from each other. The 16S-23S rDNA ITS was much more variable than 16S rDNA, which is widely used for genus and species identification. Phylogenetic trees based on the ITS were compatible with those based on 16S rDNA but were more detailed and had longer branches. The results of ITS sequencing were consistent with the results of hybridization with M. avium and M. intracellulare probes (Gen-Probe) for 30 of 31 strains tested. Serologic testing correlated poorly with ITS sequencing. Strains with the same sequence were different serovars, and those of the same serovar had different sequences. Sequencing of the 16S-23S rDNA ITS should be useful for species and strain differentiation for a wide variety of bacteria and should be applicable to studies of epidemiology, diagnosis, virulence, and taxonomy.

Base Sequence↗
PubMed1992

Bacillary angiomatosis in a child undergoing chemotherapy.

Bacillary angiomatosis is an infectious disease of the skin and viscera characterized by vascular lesions, originally described in patients with human immunodeficiency virus infection. There are also case reports of bacillary angiomatosis occurring in immunocompetent patients and in noninfected patients with suppressed immune function. We report a case of bacillary angiomatosis in a child undergoing chemotherapy for acute leukemia.

Angiomatosis, Bacillary↗