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Biomedical subjects

M Turner

Publications and source records attributed to M Turner.

At least 163 records · Page 9Linked to original sources
PubMed1995

Motion sickness incidence during a round-the-world yacht race.

Motion sickness experiences were obtained from participants in a 9 month, round the world yacht race. Race participants completed questionnaires on their motion sickness experience 1 week prior to the start of the race, during the race, and following the race. Yacht headings, sea states, and wind directions were recorded throughout the race. Illness and the occurrence of vomiting were related to the duration at sea and yacht encounter directions relative to the prevailing wind. Individual crewmember characteristics, the use of anti-motion sickness drugs, activity while at sea, and after-effects of yacht motion were also examined with respect to sickness occurrence. Sickness was greatest among females and younger crewmembers, and among crewmembers who used anti-motion sickness drugs. Sickness varied as a function of drug type and activity while at sea. Crewmembers who reported after-effects of yacht motion also reported greater sickness while at sea. The primary determinants of motion sickness were the duration of time spent at sea and yacht encounter direction to the prevailing wind.

Adult↗
PubMed1995

Shiftwork strategies.

Nurses who learn to manage their sleep and diet while rotating shifts may feel a lot better. A pilot project aimed at improving shiftworkers' sleeping patterns and diet resulted in significant improvements in sleep, general health and psychological well-being. The five-month project, involving 10 oncology nurses in Edmonton, Alberta, included a workshop on sleep and diet, and strategies to address individual shiftwork-related problems.

Diet↗
PubMed1994

Midwife managed delivery unit: a randomised controlled comparison with consultant led care.

OBJECTIVE: To examine whether intrapartum care and delivery of low risk women in a midwife managed delivery unit differs from that in a consultant led labour ward. DESIGN: Pragmatic randomised controlled trial. Subjects were randomised in a 2:1 ratio between the midwives unit and the labour ward. SETTING: Aberdeen Maternity Hospital, Grampian. SUBJECTS: 2844 low risk women, as defined by existing booking criteria for general practitioner units in Grampian. 1900 women were randomised to the midwives unit and 944 to the labour ward. MAIN OUTCOME MEASURES: Maternal and perinatal morbidity. RESULTS: Of the women randomised to the midwives unit, 647 (34%) were transferred to the labour ward antepartum, 303 (16%) were transferred intrapartum, and 80 (4%) were lost to follow up. 870 women (46%) were delivered in the midwives unit. Primigravid women (255/596, 43%) were significantly more likely to be transferred intrapartum than multi-gravid women (48/577, 8%). Significant differences between the midwives unit and labour ward were found in monitoring, fetal distress, analgesia, mobility, and use of episiotomy. There were no significant differences in mode of delivery or fetal outcome. CONCLUSIONS: Midwife managed intrapartum care for low risk women results in more mobility and less intervention with no increase in neonatal morbidity. However, the high rate of transfer shows that antenatal criteria are unable to determine who will remain at low risk throughout pregnancy and labour.

Consultants↗
PubMed1994

Characterization of ligand binding by the human p55 tumour-necrosis-factor receptor. Involvement of individual cysteine-rich repeats.

Two soluble tumour-necrosis-factor-alpha(TNF)-binding proteins are derived from the extracellular domains of the p55 and p75 TNF receptors. They are considered to play a pivotal regulatory role in TNF-mediated inflammatory processes, including diseases such as rheumatoid arthritis, by competing with the cell surface receptors for TNF and lymphotoxin (LT, tumour-necrosis factor beta). The extracellular domains of the two receptors each contain four similar cysteine-rich repeats of about 40 amino acids, in common with several other cell surface proteins including the p75 nerve-growth-factor receptor and the CD40 and Fas antigens. The aim of this study was to characterize the involvement of the four cysteine-rich repeats of the human p55 TNF receptor in TNF and LT binding by both membrane-bound and soluble forms of the receptor. Individual repeats were systematically deleted by PCR mutagenesis and the variants transiently expressed in COS cells. Immunoprecipitated receptor variants exhibited the expected sizes on SDS/PAGE gels, and bound a panel of conformation-dependent anti-(TNF receptor) antibodies. Binding of TNF by the four soluble derivatives was compared with binding by the wild-type soluble receptor using a TNF-affinity column and a BIAcore Biosensor, by measurement of their ability to inhibit TNF cytotoxicity on WEHI cells, and 125I-TNF binding to U937 cells. delta 4, which lacks the fourth cysteine-rich repeat, bound TNF comparably with the full-length soluble receptor. TNF-binding affinity was unaltered by deletion of the fourth membrane-proximal cysteine-rich repeat, as determined by Scatchard analysis of the transmembrane derivatives. We conclude that the fourth cysteine-rich repeat is not required for TNF binding. In contrast, both the soluble and the transmembrane derivatives lacking any one of the first, second or third repeats failed to bind TNF. Although we cannot entirely exclude the possibility that this may be due to indirect conformational change, rather than the removal of essential epitopes, our results suggest that the first three repeats are each required for TNF binding by both the soluble and the cell-surface receptor.

Antibodies, Monoclonal↗
PubMed1994

Applications of capillary zone electrophoresis in clinical chemistry. Determination of low-molecular-mass ions in body fluids.

Investigations were carried out on parameters influencing separation selectivity in the capillary zone electrophoresis of inorganic cations. Copper sulphate can be recommended as a carrier electrolyte salt for the separation of alkali and alkaline earth metal ions. Its separation selectivity is different from that of the widely used aromatic amines and it is compatible with indirect UV detection at 214 nm. The addition of organic solvents to the electrolyte results in a general increase in the migration times of divalent cations relative to monovalent cations. Ion-pairing reagents such as sodium dodecyl sulphate were found to exhibit specific effect son some ions (especially strontium and barium), but are less useful owing to interferences with the separation of alkali metal ions by sodium introduced with the ion-pairing reagent. Applications to the determination of cations relevant in clinical chemistry are demonstrated for serum samples. Further, the determination of anions in serum was investigated using chromate as electrolyte. Generally, the advantage of capillary zone electrophoresis over ion chromatography can be seen in the fact that proteins need not be removed from the sample and do not interfere with the separation of low-molecular-mass ions.

Body Fluids↗
PubMed1994

Evaluating the effects of an alpha-2 adrenoceptor antagonist on erectile function in the human male. 1. The erectile response to erotic stimuli in volunteers.

The effects of a new alpha-2 adrenoceptor antagonist on erectile function was assessed in 12 normal volunteers (mean age 28.7, range 20-42), using a double blind, placebo controlled design with two doses of drug and three testing sessions. The drug was administered by intravenous infusion and erectile responses to erotic fantasy and films were monitored by a Rigiscan device. Four effects of the drug were observed; (i) an increase in spontaneous erections; (ii) increased subjective ratings of sexual arousal, before presentation of erotic stimuli; (iii) increased duration of erectile response to erotic stimuli; and (iv) increases in systolic BP and HR both before and during erotic stimulation. These effects were largely restricted to the high dose of the drug. Adverse effects of the drug were minimal.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1994

Reperfusion enhances the local release of endothelin after regional myocardial ischemia.

The role of endothelin, a potent long-acting vasoconstrictor peptide, in the pathogenesis of the "no-reflow" phenomenon was investigated in nine closed-chest mongrel dogs undergoing 90 minutes of proximal left anterior descending artery occlusion and 3.5 hours of reperfusion. Endothelin levels were measured serially from the coronary sinus (CS) and aorta (Ao) by radioimmunoassay and correlated with regional myocardial blood perfusion. Prolonged anesthesia, surgery, and vascular instrumentation did not change endothelin levels in four sham animals. A progressive and parallel increase in CS and Ao endothelin levels occurred during coronary occlusion. A further increase in CS levels was observed during the reperfusion period, resulting in significantly higher values of the peptide at 30 and 60 minutes (30 minutes: CS 22.1 +/- 3.5 vs Ao 15.1 +/- 5.1 pg/ml; 60 minutes: CS 21.1 +/- 4.5 vs Ao 15.0 +/- 3.6 pg/ml; p < 0.05 by analysis of variance). Microvascular perfusion determined semiquantitatively with fluorescent beads was significantly reduced in the central ischemic zone (CIZ) compared with that in the nonischemic zone (NIZ) (CIZ endocardium 1.14 +/- 0.4 beads/m2, CIZ midmyocardium 1.19 +/- 0.3 beads/m2, NIZ 3.8 +/- 0.6 beads/m2; p < 0.05). A significant correlation was noted between mean reperfusion levels of endothelin in the CS and endocardial flow in the CIZ (r = -0.88; p = 0.009). This study demonstrates that reperfusion per se enhanced the spillover of endothelin from the cardiac interstitium. Local release of endothelin may contribute to the progressive decrease in microvascular flow in the reperfused bed.

Animals↗
PubMed1994

Sexual maturation in male prairie voles: effects of the social environment.

The effects of various social contexts on sexual maturation in captive male prairie voles were investigated. Sexual maturity was assessed as the ability of a young male to produce urine capable of activating a diestrous adult female into estrus, as females remain anestrus until they ingest a male urinary chemosignal. In five experiments the postweaning social environments of developing males were manipulated (e.g., presence or absence of dam, sire, or junior litter, exposure to unfamiliar adult voles, social isolation) to determine if the age at which males begin to produce potent urine was sensitive to social effects. In general, there was no difference in the age of potent urine production as a function of social environment. Findings are discussed in the context of dispersal, inbreeding avoidance, and mate acquisition.

Animals↗
PubMed1994

Fine mapping of the locus for nevoid basal cell carcinoma syndrome on chromosome 9q.

The nevoid basal cell carcinoma syndrome is an autosomal dominant disorder characterized primarily by multiple basal cell carcinomas, odontogenic keratocysts, and pits of the palms and soles. Tumor deletion studies and linkage analysis in Caucasians have revealed that the gene is on chromosome 9q. To further refine the location of the nevoid basal cell carcinoma syndrome locus, we tested linkage to this region in three families. Evaluation of recombinants suggested that the nevoid basal cell carcinoma syndrome locus lies in the interval defined distally by D9S127. Our data, together with existing published data defining D9S12 as a proximal flanking marker, refine the location of nevoid basal cell carcinoma syndrome to an 8.3-cM interval. Two of the families studied were African-American and show a notable variation in phenotypic expression in which affected individuals developed few skin cancers. However, despite clinical heterogeneity, our data are consistent with the hypothesis that the same locus is involved in these African-American families.

Adolescent↗
PubMed1994

Differential regulation of cholesterol side-chain cleavage (P450scc) and aromatase (P450arom) enzyme mRNA expression by gonadotrophins and cyclic AMP in human granulosa cells.

The co-ordinated biosynthesis of progesterone and oestradiol in the human ovary is critical for reproductive cyclicity and eventual pregnancy. The crucial regulatory enzymes for progesterone and oestradiol biosynthesis in granulosa cells are the cholesterol side-chain cleavage (P450scc) and aromatase (P450arom) enzymes respectively. We utilized the cDNA sequences encoding P450arom and P450scc to examine the roles of FSH and LH, and their intracellular second messenger, cyclic AMP (cAMP), in regulating steroidogenic gene expression. Mature granulosa cells (aspirated before the onset of the endogenous LH surge) and granulosa lutein cells (obtained after an ovulatory dose of human chorionic gonadotrophin) were cultured for 4 days with FSH, LH or dibutyryl cAMP (dbcAMP). After the period of culture, total RNA was extracted from granulosa cells and Northern analyses were performed utilizing 32P-labelled cDNAs encoding P450arom and P450scc. Spent culture media were analysed for steroid and cAMP content. Both FSH and LH strongly stimulated P450arom mRNA expression and oestradiol production in mature granulosa cells. On the other hand, P450scc mRNA expression and progesterone biosynthesis were weakly induced by FSH; maximal synthesis occurred only in the presence of LH. With both gonadotrophins at equivalent concentrations, LH generated a 30-fold higher level of cAMP than FSH. Furthermore, the differential effects of FSH and LH on P450 mRNA expression were reproduced by the presence of low and high concentrations of dbcAMP respectively. LH (and high levels of dbcAMP) increased P450arom mRNA expression in mature granulosa cells but inhibited its accumulation in granulosa lutein cells. In contrast, it stimulated P450scc mRNA expression and progesterone synthesis in both mature granulosa and granulosa lutein cells. Therefore, FSH/low cAMP levels stimulated P450arom gene expression and oestradiol production, while LH/high cAMP levels maximally induced P450scc gene expression and function, in a development-related manner consistent with steroid production in vivo. These findings support the hypothesis that one set of genes (like P450arom) in human granulosa cells is regulated by FSH/low cAMP levels and another (like P450scc) by LH/high cAMP levels.

Aromatase↗
PubMed1994

The spontaneously hypertensive rat Y chromosome produces an early testosterone rise in normotensive rats.

OBJECTIVE: To investigate the relationship between testosterone and blood pressure during the rapid development phase of blood pressure rise in four strains of rats: Wistar-Kyoto (WKY) rats; spontaneously hypertensive rats (SHR); SHR/y, a substrain with an SHR Y chromosome and WKY rat autosomes and X chromosomes; and SHR/a, a substrain with SHR autosomes and X chromosomes and the WKY rat Y chromosome. METHODS: Blood pressure was measured every 2 weeks by the tail-cuff method, and was verified in selected rats at 23 weeks by aortic telemetry. Serum testosterone was measured, by radioimmunoassay, every 2 weeks from 5 to 23 weeks of age. RESULTS: During the rapid phase of blood pressure rise, between 5 and 9 weeks of age, there was a significantly larger rise in serum testosterone in SHR and SHR/y than in WKY rats and SHR/a groups. The hypertensive Y chromosome in the SHR and SHR/y accelerated peak testosterone approximately 4 weeks earlier, and blood pressure was increased in these two groups compared with the SHR/a and WKY rat groups, respectively. A gene on the SHR Y chromosome (Tty) affecting the timing of testosterone in development is proposed. At approximately 15 weeks of age testosterone levels decreased sharply towards prepubertal levels in WKY rats and at 23 weeks in SHR/y, whereas testosterone levels were maintained in SHR and SHR/a, which suggests an autosomal component. CONCLUSION: The SHR Y chromosome may accelerate the start of puberty and a cascade of molecular and neuroendocrine events that raise blood pressure.

Aging↗
PubMed1993

cGMP mobilizes intracellular Ca2+ in sea urchin eggs by stimulating cyclic ADP-ribose synthesis.

Many hormones or neurotransmitters act at cell surface receptors to increase the intracellular free calcium concentration, triggering a wide range of cellular responses. As the source of this Ca2+ is often internal stores, additional messengers are required to convey the hormonal message from the plasma membrane. Cyclic ADP-ribose (cADPR) has been proposed as the endogenous activator of Ca(2+)-induced Ca2+ release by the ryanodine receptor in sea urchin eggs and in several mammalian cell types. A second messenger role for cADPR requires that its intracellular levels be under the control of extracellular stimuli. Here we demonstrate a novel action of 3',5'-cyclic guanosine monophosphate (cGMP) in stimulating the synthesis of cADPR from beta-NAD+ by activating its synthetic enzyme ADP-ribosyl cyclase in sea urchin eggs and egg homogenates. We suggest that cADPR may transduce signals generated by cell surface receptors or gaseous transmitters linked to cGMP production.

Adenosine Diphosphate Ribose↗
PubMed1993

Home truths.

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Aftercare↗
PubMed1993

Ventriculo-gallbladder shunts in children.

Ventriculoperitoneal shunts are the most common procedure for the treatment of hydrocephalus. Ventriculoatrial shunts are effective but are subject to a higher incidence of potentially serious complications. We report our experience with ventriculo-gallbladder shunts in children. Ventriculo-gallbladder shunts are safe, effective, and technically easy to perform. We recommend their use when ventriculoperitoneal shunts have failed or the peritoneal cavity is not adequate for shunting.

Adolescent↗