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Biomedical subjects

M Stephenson

Publications and source records attributed to M Stephenson.

At least 37 records · Page 2Linked to original sources
PubMed1993

Evidence for human meiotic recombination interference obtained through construction of a short tandem repeat-polymorphism linkage map of chromosome 19.

An improved linkage map for human chromosome 19 containing 35 short tandem repeat polymorphisms (STRPs) and one VNTR (D19S20) was constructed. The map included 12 new (GATA)n tetranucleotide STRPs. Although total lengths of the male (114 cM) and female (128 cM) maps were similar, at both ends of the chromosome male recombination exceeded female recombination, while in the interior portion of the map female recombination was in excess. Cosmid clones containing the STRP sequences were identified and were positioned along the chromosome by fluorescent in situ hybridization. Four rounds of careful checking and removal of genotyping errors allowed biologically relevant conclusions to be made concerning the numbers and distributions of recombination events on chromosome 19. The average numbers of recombinations per chromosome matched closely the lengths of the genetic maps computed by using the program CRIMAP. Significant numbers of chromosomes with zero, one, two, or three recombinations were detected as products of both female and male meioses. On the basis of the total number of observed pairs of recombination events in which only a single informative marker was situated between the two recombinations, a maximal estimate for the rate of meiotic STRP "gene" conversion without recombination was calculated as 3 x 10(-4)/meiosis. For distances up to 30 cM between recombinations, many fewer chromosomes which had undergone exactly two recombinations were observed than were expected on the basis of the assumption of independent recombination locations. This strong new evidence for human meiotic interference will help to improve the accuracy of interpretation of clinical DNA test results involving polymorphisms flanking a genetic abnormality.

Base Sequence↗
PubMed1992

3-Methoxybutylcyanoacrylate: evaluation of biocompatibility and bioresorption.

The biocompatibility and bioresorption of 3-methoxybutylcyanoacrylate (MBCA) was evaluated in vivo using female Wistar albino rats. MBCA was found to elicit slight to moderate tissue reaction similar to isobutylcyanoacrylate (iBCA) which has been sold commercially as a surgical adhesive (Bucrylate, Ethicon). MBCA was judged less reactive to tissue than ethylcyanoacrylate (ECA). The MBCA implants in rat gluteal muscles also resorbed within approx. 16 wk while iBCA implants remained essentially unchanged at 36 wk in vivo. In vitro resorption in phosphate buffer (pH 7.2) at 37 degrees C showed the same trend. The MBCA performed similarly to iBCA as a haemostat on excised rat livers and as an adhesive on rat skin incisions and had comparable adhesive bond strength.

Absorption↗
PubMed1990

Plasmid transfer between strains of Bacillus thuringiensis infecting Galleria mellonella and Spodoptera littoralis.

To determine the possibility of plasmid transfer occurring between strains of Bacillus thuringiensis in infected lepidopterous larvae, Galleria mellonella and Spodoptera littoralis were infected with two or more strains of B. thuringiensis and the resulting bacteria from the dead insects were examined for plasmid transfer. Transfer rates of plasmids coding for crystal production and tetracycline resistance were high, reaching levels similar to those obtained in laboratory broth cultures. Transfer was higher in G. mellonella than S. littoralis, probably due to the greater ability of B. thuringiensis to colonize the larvae. In broth cultures, B. thuringiensis was also able to transfer plasmids into sporeforming bacteria present in soil samples. The results suggest that plasmid transfer between strains of B. thuringiensis occurs in nature, resulting in the production of new combinations of delta-endotoxins within populations of the bacteria.

Animals↗
PubMed1989

Fatty Acid Acylated Proteins of the Halotolerant Alga Dunaliella salina.

The unicellular, wall-less alga Dunaliella salina has been shown to contain an array of proteins modified by the covalent attachment of fatty acids. Myristic acid (14:0) comprised approximately 80% by weight of the protein-linked acyl groups in samples derived from cells cultured in medium containing 1.7 molar NaCl and 93% in samples from cells grown in medium containing 3.0 molar NaCl. Palmitic and stearic acids accounted for most of the remaining protein-bound acyl chains. Approximately 0.2% of the incorporated radioactivity was estimated to be in linkage with protein. The bulk of acyl chains (about 99%) were resistant to cleavage by alkali, indicating a preponderance of amide bonding. The sodium dodecyl sulfate-polyacrylamide electrophoresis labeling pattern of proteins from [(3)H]myristic-labeled cells was significantly different from that of proteins from cells exposed to [(3)H]palmitate. The appearance of radioactivity in certain proteins was also influenced by the salinity of the culture medium. Thus growth in moderate (1.7 molar) salt favored the acylation of a 48-kilodalton polypeptide whereas in high (3.0 molar) salt, a 17-kilodalton polypeptide was more heavily labeled.

Journal Article↗
PubMed1989

Interaction of campylobacter species with antibody, complement and phagocytes.

The opsonisation of four different campylobacter species for human neutrophils was studied using a chemiluminescence system and electron microscopy. Opsonisation of Campylobacter fetus, Campylobacter coli, and Campylobacter jejuni was mediated by antibody and enhanced by complement. Antibody was not, however, required for the phagocytosis of Campylobacter pylori because it activates the classical pathway of complement directly. This unusual property may be important in the pathogenesis of C pylori associated gastritis and duodenal ulcer.

Anaphylatoxins↗
PubMed1987

Single-dose treatment of bacteriuria in pregnancy.

Comparison of the results of single-dose treatment of urinary tract infection in women is confused by differences between published series in the duration of follow-up and in the diagnosis of infection. Pregnancy allows prolonged follow-up in a motivated population, but increases the possibility of false positive diagnosis of infection from midstream urines due to increased vulvovaginal contamination. Suprapubic aspiration (SPA) is safe in pregnancy and accurately confirms the presence or absence of bacteria in the bladder urine. Bacteriuria was diagnosed by SPA in 86 pregnant women. Thirty-seven of these were treated with a single dose of 3 g cephalexin and 49 with 3 days of cephalexin 1 g or of a combined preparation of pivmecillinam-pivampicillin. Both single-dose and 3-day treatments prevented further bacteriuria in 65% of the patients for the remainder of their pregnancies. This is similar to the results achieved with 10-day treatment. If extended trials confirm that single-dose treatment is as effective as conventional treatment with the same drug, then single-dose treatment has the advantages in pregnancy of minimal medication, good patient compliance and lack of side-effects.

Amdinocillin↗
PubMed1982

Temporal integration and presbycusis.

On 8 presbycusic Ss with similar sensorineural hearing losses, temporal integration (TI) was estimated by comparing HTLs for signal durations of 500 and 20 msec, at frequencies .5-6 kc/s. Normal-hearing young adult controls were also tested. Degree of group hearing loss for the presbycusic Ss was related to group TI data, but did not account for the amount of decrease in TI with these older Ss. Slightly reduced TI (6 db) was found in Ss' area of normal hearing even though the test frequency and adjacent frequencies were within a normal-hearing range. Reduced TI occurred most consistently in Ss with HTLs greater than or equal to 40 db. Individual variance suggested caution in using TI as a diagnostic clinical procedure.

Acoustic Stimulation↗
PubMed1971

Metabolic disease in mental retardation: a study in Texas.

Reported are the results of a study of patients admitted to the State Schools for the Mentally Retarded in Texas, over a two-year period from 1968-1970. Of 2029 cases, 185 were found on a detection battery screening to have possible metabolic disease. The report summarizes the findings on 93 cases studied in the metabolic ward at the Texas Research Institute.

Female↗