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Biomedical subjects

P Mann

Publications and source records attributed to P Mann.

At least 37 records · Page 2Linked to original sources
PubMed1994

Analysis of beta-glucans and chitin in a Saccharomyces cerevisiae cell wall mutant using high-performance liquid chromatography.

We have previously shown that mutations in the yeast KNR4 gene resulted in pleiotropic cell wall defects, including resistance to killer 9 toxin, elevated osmotic sensitivity to SDS and increased resistance to zymolyase, a (1-->3)-beta-glucanase. In this report, we further demonstrated that knr4 mutant cells were more permeable to a chromogenic substrate, X-GAL, suggesting that the mutant cell walls were leakier to certain non-permeable molecules. To determine if these defects resulted from structural changes in the cell walls, we analysed the alkali-insoluble cell wall components using HPLC assays developed for this purpose. Comparative analysis using four isogenic strains from a 'knr4 disrupted' tetrad demonstrated that mutant cell walls contained much less (1-->3)-beta-glucan and (1-->6)-beta-glucan; however, the level of chitin, a minor cell wall component, was found to be five times higher in the mutant strains compared to the wild-type strains. The data suggested that the knr4 mutant cell walls were dramatically weakened, which may explain the pleiotropic cell wall defects.

Cell Wall↗
PubMed1994

Cloning and characterization of KNR4, a yeast gene involved in (1,3)-beta-glucan synthesis.

k9 killer toxin from Hansenula mrakii was used to select a number of resistant mutants from Saccharomyces cerevisiae. Preliminary biochemical and genetic studies showed that some of them acquired structural defects in the cell wall. One of these mutants, the knr4-1 mutant, displays a number of cell wall defects, including osmotic sensitivity; sensitivity to cercosporamide, a known antifungal agent; and resistance to Zymolyase, a (1,3)-beta-glucanase. We report here the isolation and analysis of the KNR4 gene. DNA sequence analysis revealed an uninterrupted open reading frame which contains five potential start codons. The longest coding template encodes a protein of 505 amino acids with a calculated molecular mass of 57,044 Da. A data base search revealed 100% identity with a nuclear protein, SMI1p. Disruption of the KNR4 locus does not result in cell death; however, it leads to reduced levels of both (1,3)-beta-glucan synthase activity and (1,3)-beta-glucan content in the cell wall. The gene was mapped to the right arm of chromosome VII.

Amino Acid Sequence↗
PubMed1992

Characterization of the chromosomal aac(6')-Ic gene from Serratia marcescens.

The DNA sequence of the chromosomal aac(6')-Ic gene from Serratia marcescens, which had been previously cloned (H. M. Champion, P. M. Bennett, D. A. Lewis, and D. S. Reeves, J. Antimicrob. Chemother. 22:587-596, 1988) was determined. High-pressure liquid chromatographic analysis of extracts prepared from Escherichia coli carrying the chromosomal aac(6')-Ic gene on a plasmid confirmed the presence of 6'-N-acetyltransferase activity in this strain, which was suggested by the aminoglycoside resistance profile. DNA sequence analysis of the cloned 2,057-bp PstI fragment revealed several regions of homology to previously characterized sequences from GenBank, including the rpoD and tRNA-2 genes of E. coli. Subcloning experiments confirmed the coding sequence of the aac(6')-Ic gene to be at positions 1554 to 1992. The predicted amino acid sequence of the AAC(6')-Ic protein suggested that it was the third member of a family of AAC(6') proteins which included a coding region identified between the aadB and aadA genes of Tn4000 and an AAC(6') protein encoded by pUO490, which was isolated from Enterobacter cloacae. Primer extension analysis suggested that the -35 region of the aac(6')-Ic promoter overlapped a large palindromic sequence which may be involved in the regulation of the aac(6')-Ic gene. Hybridization experiments utilizing a restriction fragment from the aac(6')-Ic gene showed that all S. marcescens organisms carried this gene whether or not the AAC(6')-I resistance profile was expressed. Organisms other than Serratia spp. did not hybridize to this probe.

Base Sequence↗
PubMed1991

Correlation between aminoglycoside resistance profiles and DNA hybridization of clinical isolates.

DNA hybridization data and aminoglycoside resistance profiles (AGRPs) were determined for 4,088 clinical isolates from three studies (United States, Belgium, and Argentina). The correlation between susceptibility profiles and hybridization results was determined with nine DNA probes. For each of the seven aminoglycoside resistance profiles which we were able to test, the data suggested at least two distinct genes could encode enzymes which lead to identical resistance profiles. Furthermore, the DNA hybridization data showed that individual strains carried up to six unique aminoglycoside resistance genes. DNA hybridization revealed interesting differences in the frequencies of these genes by organism and by country.

Acinetobacter↗
PubMed1989

Xeroradiographic evaluation of the equine larynx.

The normal radiographic anatomy of the equine larynx was determine by use of xeroradiography and dissection. The body and laminae of the thyroid cartilage, the muscular process of the arytenoid cartilages, and the dorsal lamina and arch of the cricoid cartilage had radiographic evidence of mineralization (calcification) and/or ossification in clinically normal horses. There was a significant (P less than 0.01) increase in the degree of mineralization of the thyroid and arytenoid cartilages with advancing age. Horses with diagnosis of arytenoid chondrosis (arytenoid chondral dysplasia, arytenoid chondropathy) by use of endoscopy had radiographic changes that included: enlargement with increased density of the arytenoid cartilage region, abnormal patterns of mineralization (dystrophic mineralization or osseous metaplasia), abnormal contour of the corniculate process(es) and laryngeal masses, sometimes obliterating part or all of the lateral laryngeal ventricles.

Aging↗
PubMed1986

Concentration of doxycycline in human gingival fluid.

Doxycycline is a synthetic tetracycline compound whose main advantages over tetracycline hydrochloride are increased oral absorption, prolonged serum half-life and decreased gastrointestinal side-effects. The purpose of this study was to measure the concentration of doxycycline in gingival fluid and blood after oral administration. 4 volunteers were given doses of 100 mg doxycycline every 12 h on the first day of antibiotic administration followed by a maintenance dose of 100 mg per day for an additional 4 days. 3 of these volunteers were also given tetracycline hydrochloride every 6 h for 5 days either 1 month before or after doxycycline administration to compare gingival fluid levels of these 2 tetracycline compounds. Gingival fluid was sampled from 4 gingival sites in each volunteer at hourly intervals from hours 0 to 6, 9, 24, 27, 48 to 54, 57, 72, 75, 96 to 102 and 105. Blood was sampled by finger puncture at hours 0, 3, 6, 24, 48, 54, 72, 96 and 102. Antibiotic levels in gingival fluid and blood were measured using an agar diffusion assay method. The results demonstrated that doxycycline achieved much higher levels in the gingival fluid than in blood and yielded comparable gingival fluid levels to those achieved by tetracycline hydrochloride. Doxycycline levels in gingival fluid ranged between 1.2 micrograms/ml and 8.1 micrograms/ml in the first 24 h and generally achieved 3-10 micrograms/ml after 48 h. Blood levels after 48 h ranged between 2.1 micrograms/ml and 2.9 micrograms/ml. Tetracycline hydrochloride in gingival fluid after 48 h was generally in the range of 4 micrograms/ml-10 micrograms/ml with blood levels between 2.2 micrograms/ml and 3.4 micrograms/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1982

Senescence related changes in brain diazepam binding and motor performance.

Senescent mice showed attenuation of habituation in locomotor activity and marked deficit in the motor performance requiring limb coordination. Also, the binding of 3H-diazepam to the crude synaptosomal fraction prepared from cerebral cortex of the senescent mice was significantly altered. The binding maximum (Bmax) was significantly greater in the aged (23-26 months) mice, but no change was found in the apparent dissociation constant (Kd). Senescent related changes appear to include neurochemical alteration of the endogenous benzodiazepine system (increased receptor sites without any change in receptor affinity) and, perhaps, related physiological deficits in the limb coordination and/or strength.

Aging↗