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Biomedical subjects

D Porter

Publications and source records attributed to D Porter.

At least 109 records · Page 6Linked to original sources
PubMed1987

Specificity of amphibian and reptilian pituitaries for various forms of gonadotropin-releasing hormones in vitro.

In vitro perifusion was employed to compare the potencies of mammalian, avian, salmon, and lamprey gonadotropin-releasing hormones (GnRHs) on the release of luteinizing hormone (LH) from the pituitaries of an amphibian (Rana pipiens) and a reptile (Chrysemys picta). The chicken-I and salmon GnRH variants were equipotent with mammalian GnRH in both the frog and the turtle glands. By contrast, the lamprey GnRH was inactive (less than 1% as potent as the others). Lamprey GnRH also failed to stimulate LH release or to induce GnRH priming when administered chronically to the frog gland. These results support the hypothesis that the GnRH receptors on nonmammalian pituitary cells are much less specific than those of the mammal with regard to the amino acid at position 8 of the GnRH molecule. These data suggest that the native GnRH variant or the one most like that found in the brain of a species is not necessarily the most potent biologically in that species. However, the nonmammalian pituitary does show some specificity with regard to the structure of natural GnRHs in that none of the tetrapod species studied is responsive to lamprey GnRH.

Animals↗
PubMed1987

Growth of bacteria with dimorphic vegetative cell cycles.

A mathematical model of the growth of bacteria with dimorphic cell cycles is described. In these bacteria motile swarmer cells differentiate to stalked reproductive cells and the proportions of these cell types change in a characteristic fashion during growth. The selection of parameters to fit the model to experimental data can result in the elucidation of the factors controlling the differentiation of swarmer cells.

Bacteria↗
PubMed1985

Energy expenditure during front crawl swimming: predicting success in middle-distance events.

Male (n = 25) and female (n = 14) competitive swimmers were studied during tethered (breaststroke) and free (front crawl) swimming to determine the validity of calculating exercise oxygen uptake (VO2) from expired gas samples taken immediately after the activity. Based on a single 20-s recovery VO2, the swimmers' VO2 max was correlated with performance in a 400-yd (365.8-m) front crawl swim. The best predictors of VO2 max for trained swimmers were lean body weight and stroke index (r = 0.97). The single best predictor of performance in the 365.8-m front crawl swim was the distance per stroke (r = 0.88), whereas the combination of distance per stroke and VO2 max (ml/kg LBW/min) correlated 0.97 with performance in the swim. This study demonstrates that it is possible to accurately determine the VO2 during maximal and submaximal swimming using a single, 20-s expired gas collection taken immediately after a 4-7 min swim. These findings demonstrate the importance of stroke technique on the energy cost and variations in performance during competitive swimming.

Adolescent↗
PubMed1985

E1a regions of the human adenoviruses and of the highly oncogenic simian adenovirus 7 are closely related.

Simian adenovirus 7 (SA7) is a highly oncogenic virus, capable of causing tumors in hamsters upon the direct injection of viral DNA. We determined the transcriptional organization of the transforming region and compared it with that of the human adenoviruses. This analysis demonstrated that there are two independently promoted transcription units similar to the E1a and E1b regions of the human adenoviruses. The nucleotide sequence of the SA7 E1a region demonstrated considerable homology with the human adenoviruses, both in the sequences that regulate E1a expression and in the encoded polypeptides. The amino acid homology was reflected in the ability of SA7 to complement the growth of human adenoviruses mutant in the E1a region. Furthermore, we found two regions of amino acid homology unique to SA7 and the highly oncogenic human adenovirus 12.

Adenoviridae↗
PubMed1982

Rapid method for determining antimicrobial susceptibility of Haemophilus influenzae.

A method was developed to determine the susceptibility of Haemophilus influenzae to ampicillin, cefamandole, and chloramphenicol by using the MS-2 system (Abbott Laboratories) for determining minimum inhibitory concentrations (MIC). The MS-2 results for 132 strains of H. influenzae were compared with the results of agar disk diffusion, agar dilution, and beta-lactamase tests. Twenty-four strains (18.2%) of H. influenzae were resistant to ampicillin by the agar dilution method, as opposed to 25 strains by the MS-2 method. For a beta-lactamase-negative strain, the agar dilution MIC was 4 micrograms/ml, and the MS-2 MIC was 16 micrograms/ml. Twenty-one strains produced beta-lactamase; two beta-lactamase-negative strains were resistant by MS-2, agar dilution, and agar disk diffusion. In addition, one beta-lactamase-negative strain, for which the agar dilution MIC was 32 micrograms/ml and the MS-2 MIC was 16 micrograms/ml, was sensitive by agar disk diffusion. Overall, the MS-2 method compared favorably with the agar dilution method for determining the MIC of ampicillin, cefamandole, and chloramphenicol for H. influenzae.

Ampicillin↗
PubMed1981

Computerized radiologic reporting with voice data-entry.

The accurate, voice entry of radiologic reports into a computer takes significantly longer than entry by keyboard. Careful speech and considerable patience are required to avoid an unacceptably high error-rate. With improvements in the future, this technology may compete with the conventional technology.

Computers↗