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Biomedical subjects

D R Hall

Publications and source records attributed to D R Hall.

At least 73 records · Page 4Linked to original sources
PubMed1995

Stabilizing effect of sucrose against irreversible denaturation of rabbit muscle lactate dehydrogenase.

Measurements of the kinetics of activity loss by rabbit muscle lactate dehydrogenase in acetate-chloride buffer, pH 5.0, I 0.20, have shown that the enzyme exhibits greater stability against irreversible inactivation when the buffer is supplemented with sucrose (0.1 M-0.5 M). On the basis of sedimentation equilibrium distributions obtained for enzyme in the absence and presence of sucrose (0.5 M), the lactate dehydrogenase is essentially dimeric in both environments. The observed stabilization of enzyme activity has therefore been considered in terms of the space-filling effects of sucrose on an isomerization equilibrium between native and unfolded forms of dimeric lactate dehydrogenase, which precedes irreversible inactivation of the unfolded isomer. Interpretation of the kinetic results on that basis has led to the conclusion that the initial stage of enzyme unfolding entails a minor change in volume and/or asymmetry of the lactate dehydrogenase that gives rise to a 4% increase in the second virial coefficient describing excluded volume interactions between dimeric enzyme and sucrose.

Animals↗
PubMed1994

Embryo transfer in fallow deer (Dama dama): superovulation, embryo recovery and laparoscopic transfer of fresh and cryopreserved embryos.

Multiple ovulation-embryo transfer (MOET) protocols for farmed fallow deer (Dama dama) were investigated in a series of 3 experiments. A total of 37 donors, of either European (D.d. dama ; n = 30) or Mesopotamian hybrid (D.d. mesopotamica x D.d. dama ; n =7) genotype, each received an intravaginal silastic device containing 0.3 g progesterone (CIDR-type G device) for 14 d and injections of 0.5 units ovine FSH (8 x 0.06 unit injections from Days 10 to 14 of device insertion) and 100 IU PMSG (either with the first or last FSH injection). All donors received laparoscopic intrauterine inseminations of fresh semen (50 x 10(6) spermatozoa) from a Mesopotamian sire 36 h after withdrawal of CIDR devices. Embryos were recovered by laparotomy on Day 6 (Day 0 = estrus). Mean ovulation rates for the 3 experiments were 8.1, 9.8 and 7.0, with no effect of PMSG timing (P>0.10). However, embryo recovery rates, albeit low throughout the study (29.6%), were significantly improved with later PMSG administration (33.9 vs 20.1%; P<0.05). Hybrid and European donors performed in a similar manner. A range of embryo development stages was recovered throughout the study. In 2 experiments laparoscopic transfer of embryos to 48 recipient does treated previously with intravaginal CIDR devices for 14 d yielded a total pregnancy rate of 37.5%. In the experiment with fresh embryos, the use of clenbuterol to reduce uterine turgidity resulted in a higher proportion of does conceiving (3/4 ; 75%) compared with that of the untreated does (0/6 , 0%; P<0.05). In the second experiment, in which all the does routinely received clenbuterol, 10/19 (53%) and 5 19 (26%) does conceived following the transfer of fresh and cryopreserved embryos, respectively (P<0.05). While the overall efficiency of the MOET program was low (equivalent of 0.9 to 1.0 surrogate pregnancies per donor), improvements in the recovery rate of transferable embryos have considerable potential for genetic improvement of farm stock and captive propagation of endangered Mesopotamian fallow deer through maternal surrogacy programs.

Journal Article↗
PubMed1994

Laparoscopic transfer of ovine and cervine embryos using the transpic technique.

A transpic technique was developed to transfer embryos to 352 sheep and 4 deer recipients using a laparoscope, a modified pair of Allis forceps and a modified Cassou aspic normally used for laparoscopic uterine insemination. The overall proportion of uncomplicated transfers in Experiment 1 in 216 recipient ewes was 90.7% (range between groups 80 to 100%), 3.7% of the transfers were presumed to be loss of embryos during expulsion from the transpic, and 5.6% were apparent transfers into the uterine wall. In Experiment 2,83% of transfers into 136 ewe recipients were uncomplicated, 5% were presumed to be loss of embryos during expulsion, 1% was apparent transfer into the uterine wall, and 11% involved 2 attempts at transfer. Only 34% of 116 recipients receiving low-quality frozen-thawed embryos were pregnant and 24% of the 226 embryos survived to term. In contrast, high pregnancy rates (>80%) and embryo survival rates (>70%) were achieved following uncomplicated and twice attempted transfers of fresh embryos. Pregnancy rates and embryo survival rates were low (<2%) following the presumed loss of embryos during expulsion and apparent transfers into the uterine wall. All 4 deer transfers were uncomplicated and 2 2 good-quality embryos survived to term compared with 0 2 low-medium quality embryos. The transpic technique is a moderately invasive technique which permits fast (15 to 20/h) and reliable transfer of embryos in small ruminants. With appropriate care, nearly all of the embryos can be correctly placed in the uterus, and high pregnancy rates and embryo survival rates can be achieved using this technique.

Journal Article↗
PubMed1991

Attraction of Glossina longipalpis (Diptera: Glossinidae) in Guinea-Bissau to odor-baited biconical traps.

The catches of tsetse flies, Stomoxys, and tabanids in biconial traps baited with different synthetic odors were compared in the Jopá-Cobiana Forest, northwestern Guinea-Bissau. Thirty-six traps, the baits of which were randomly interchanged each of 10 sampling days, were baited either with (a) 1-octen-3-ol (octenol) + phenols [4-methylphenol + 3-propylphenol] + acetone + N'dama cow urine ("urine"), (b) octenol + phenols + acetone, (c) octenol + phenols, (d) acetone, (e) acetone + urine, or (f) urine. Six of the traps were not baited (controls). A total of 3,172 tsetse flies (96% Glossina longipalpis Widemann, 3% G. morsitans submorsitans Newstead, and 1% G. palpalis gambiensis Vanderplank), 286 Stomoxys, and 571 Tabanidae was captured. G. longipalpis was caught in statistically greater numbers in traps baited with octenol + phenols + acetone. Traps baited with octenol + phenols, with or without acetone, caught the greatest numbers of tabanids. N'dama urine did not increase the catch of G. longipalpis. Stomoxys was not significantly attracted to any of the odors.

Animals↗
PubMed1986

Uridine monophosphate kinase and susceptibility to invasive Haemophilus influenzae type B disease.

A polymorphic genetic variant of the pyrimidine pathway enzyme, uridine monophosphate kinase-3 (UMPK-3), was positively associated with invasive Hib disease. All UMPK 3-3 homozygotes in this study were Hib cases, and we found that in cases and controls, there was no difference between UMPK phenotype and serum levels of total Hib antibody as measured by radioimmunoassay. This suggests that UMPK-3 may play a role in mediating the non-humoral immunity to Hib. However, unlike other enzyme variants in the nucleoside synthesis pathways which result in syndromes of severe immunodeficiency, this gene appears to confer a more subtle disease susceptibility. Thus, the UMPK-3 allele, although rare in Caucasians, is associated with an increased risk of invasive Hib infection in Alaskan Eskimos.

Alaska↗
PubMed1979

Effect of posture on lung volume: airway closure and gas exchange in hemidiaphragmatic paralysis.

The effects of posture on lung volume, airway closure, and gas exchange were studied in eight patients with hemidiaphragmatic paralysis. The mean vital capacity in the sitting position was 81% of predicted normal, and in the supine posture fell by a further 19% in right-sided but only 10% in left-sided paralysis. The mean arterial oxygen tension was less than predicted in the sitting posture and fell significantly on lying. Single breath gas transfer factor was normal in all cases whereas the diffusion coefficient was greater than predicted in the sitting posture and rose even further on lying. Closing volume showed no positional change but closing volume as a percentage of vital capacity was higher in the supine position. Regional airways closure was expressed as the relationship expiratory reserve volume minus closing volume. Negative values were found in only two of the subjects in the sitting position but seven had negative values supine, indicating significant airway closure during tidal breathing in this position.

Adult↗
PubMed1976

Abnormalities of lung function in hay fever.

Twenty subjects with symptoms of hay fever were studied to see whether abnormalities could be detected in the function of small airways. The investigations included dynamic compliance at varying respiratory frequencies, closing capacity, residual volume, transfer factor, and maximal expiratory flow-volume curves. The tests were repeated in the winter when symptoms had resolved. Frequency dependence of compliance was found in eight subjects with symptoms (40%), closing capacities being abnormal in only two instances. Conventional pulmonary function tests, including expiratory flow rates at mid vital capacity, were within the predicted range of all subjects. When tests were repeated in the winter, frequency dependence of compliance was no longer present in subjects whose symptoms had resolved. The study suggests that reversible small airway abnormalities are present in a significant proportion of subjects with symptoms of hay fever and that such abnormalities are best detected by the measurement of dynamic compliance at varying respiratory frequencies.

Adolescent↗