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Biomedical subjects

T Myers

Publications and source records attributed to T Myers.

At least 19 recordsLinked to original sources
PubMed1992

Biomechanical properties of human lumbar spine ligaments.

Biomechanical properties of the six major lumbar spine ligaments were determined from 38 fresh human cadaveric subjects for direct incorporation into mathematical and finite element models. Anterior and posterior longitudinal ligaments, joint capsules, ligamentum flavum, interspinous, and supraspinous ligaments were evaluated. Using the results from in situ isolation tests, individual force-deflection responses from 132 samples were transformed with a normalization procedure into mean force-deflection properties to describe the nonlinear characteristics. Ligament responses based on the mechanical characteristics as well as anatomical considerations, were grouped into T12-L2, L2-L4, and L4-S1 levels maintaining individuality and nonlinearity. A total of 18 data curves are presented. Geometrical measurements of original length and cross-sectional area for these six major ligaments were determined using cryomicrotomy techniques. Derived parameters including failure stress and strain were computed using the strength and geometry information. These properties for the lumbar spinal ligaments which are based on identical definitions used in mechanical testing and geometrical assay will permit more realistic and consistent inputs for analytical models.

Adult↗
PubMed1992

HIV, substance use and related behaviour of gay and bisexual men: an examination of the talking sex project cohort.

This paper reports on the substance use of 612 gay and bisexual men who participated in an HIV risk reduction project. Use/non-use, level of substance use, and reported frequency of use prior to sexual activity were examined in relation to number of sexual partners, sexual activities, HIV antibody test seeking behaviour and known HIV status. The use of substances among the study cohort appear to be higher than in a comparable heterosexual male group. An association was found between substance use, and both number of sexual partners and sexual activities. However, no significant difference was found in substance use between men participating in protected versus unprotected anal sex. Similarly, no significant difference was found in the reported frequency of substance use prior to sex by those participating in protected and unprotected anal intercourse. Greater drug use was reported among those who were known to be HIV antibody positive. These findings raise issues for further research. The high use of alcohol and drugs by gay and bisexual men may pose significant health risks for this group of men.

AIDS Serodiagnosis↗
PubMed1992

Lack of effect of maternal cocaine administration on myometrial electromyogram and maternal plasma oxytocin concentrations in pregnant sheep at 124-146 days' gestational age.

Although cocaine abuse during human pregnancy is associated with an increased incidence of preterm labor, there are few reports on the effects of cocaine on myometrial activity during pregnancy in experimental animals. Cocaine (0.5, 1, or 2 mg/kg) or vehicle was randomly administered intravenously to 15 pregnant ewes between 124-146 days' gestation (term is 147 days). Neither cocaine nor vehicle administration altered total myometrial electromyographic activity from pre-dose levels 1 or 6 hours after administration. Maternal arterial plasma oxytocin did not change during the study. Using a positive control, we confirmed observations of other investigators that administration of 2 mg/kg cocaine significantly increases maternal arterial blood pressure. The results indicate that cocaine does not stimulate myometrial contractility significantly in late pregnancy in sheep.

Animals↗
PubMed1991

Inhibition of cellular transformation by the adeno-associated virus rep gene.

The replication, or rep, gene of the human parvovirus, adeno-associated virus (AAV), is a pleiotropic effector of numerous viral functions. The rep gene trans-regulates viral DNA replication, mRNA transcription, and assembly of the infectious virion. In addition to its roles in the virus life cycle the rep gene also represses gene expression from viral or cellular transcription promoters in both transient and long-term assays. In this report we have investigated the ability of the rep gene to inhibit cellular transformation mediated by SV40 DNA or the adenovirus E1a and human ras oncogene pair. In DNA transfection assays, the complete AAV rep gene inhibited SV40 DNA and E1a/ras gene-mediated transformation of mouse fibroblasts. AAV DNA plasmids that expressed the Rep68/40 or Rep52/40 proteins alone did not suppress transformation. AAV DNA replication was not required for suppression. Due to the antiproliferative effect of the AAV rep gene, we propose that it acts a viral analogue of cellular anti-oncogenes and is a useful model system for studying the regulation of cellular proliferation.

Adenovirus Early Proteins↗
PubMed1991

Cocaine in pregnancy: the effect of maternal administration of cocaine on the maternal and fetal pituitary-adrenal axes.

The effects of cocaine on the maternal and fetal pituitary-adrenal axis in vivo during pregnancy have not been reported. Six pregnant ewes and their fetuses underwent instrumentation at 113 to 119 days' gestation. Ewes were assigned to receive an intravenous bolus injection of vehicle or cocaine (0.5, 1.0, or 2.0 mg.kg-1) at 124 to 136 days' gestation. Maternal arterial blood gases, fetal pH and fetal PCO2 were unchanged after injection of cocaine or vehicle. After administration of 2.0 mg.kg-1 cocaine, arterial fetal PO2 fell 3.2 +/- 1.72 mm Hg (p less than 0.05) at +5 minutes, returning to baseline by +15 minutes. Maternal and fetal adrenocorticotropin levels rose within 5 minutes after the highest cocaine dose (p less than 0.05). There was a significant (p less than 0.05) increase in maternal cortisol at all doses of cocaine and in fetal cortisol at +15 minutes after the 2.0 mg.kg-1.

Adrenocorticotropic Hormone↗
PubMed1990

Stable rightward shifts of the oxyhemoglobin dissociation curve induced by encapsulation of inositol hexaphosphate in red blood cells using electroporation.

Rightward shifts of 50-100% of the P50 values in the oxygen dissociation curve of intracellular hemoglobin are obtained after encapsulation of inositol hexaphosphate in mouse and dog red blood cells (RBC) by electroporation. Life spans of mouse RBC-myo-inositol hexaphosphate in circulation are unchanged from the normal RBC values.

Allosteric Regulation↗
PubMed1989

Variation in myometrial response to intravenous oxytocin administration at different times of the day in the pregnant rhesus monkey.

To assess a potential underlying rhythm in the sensitivity of the pregnant primate myometrium to oxytocin we infused five pregnant rhesus monkeys (gestational age, 121-142 days) with oxytocin at three different periods of the 24-h day, in the order night, afternoon, and morning, via the maternal inferior vena cava. Oxytocin was administered for 1 min every 5 min over 30 min at four doses 400, 800, 2000, and 4000 pg/min.kg. The response of the myometrium, evaluated as the number of contractions per pulse of oxytocin, was greatest in the early hours of darkness. Studies in three additional monkeys in which the order of the oxytocin challenge tests was changed, again showed that the response to oxytocin was greatest in the hours of darkness. We conclude that an underlying, as yet undefined, rhythm exists in the sensitivity of the pregnant primate myometrium to oxytocin at different times of the 24-h day. This change in myometrial sensitivity may be due to variation in one or more of the many potential regulatory sites of oxytocin's action at the cellular level. We hypothesize that this difference in myometrial sensitivity to oxytocin plays a role in the switch from myometrial contractures to contractions that occurs around the hours of darkness, e.g. postsurgery, during food withdrawal, and before delivery.

Animals↗
PubMed1988

Leuprolide acetate: serum and follicular fluid concentrations and effects on human fertilization, embryo growth, and granulosa-lutein cell progesterone accumulation in vitro.

Data from various animal models have demonstrated significant extrapituitary effects of gonadotropin-releasing hormone agonists. The purpose of this study was to determine the effects of therapeutic concentrations of leuprolide acetate on human granulosa-lutein cell steroidogenesis, fertilization, and embryo growth rates in vitro. During leuprolide administration, mean serum concentrations of leuprolide were less than 50 ng/ml and were undetectable 48 hours after cessation of administration. There was no effect of leuprolide on progesterone (P) secretion by granulosa-lutein cells cultured in the presence or absence of human chorionic gonadotropin. The effect of leuprolide on embryo growth rates was evaluated with the mouse two-cell embryo culture model and a retrospective review of early embryo growth rates in humans receiving adjunctive leuprolide therapy. There was no measurable effect of leuprolide on early embryo growth in either species. These data indicate that (1) serum and follicular and peritoneal fluid concentrations are undetectable 2 days after discontinuation of leuprolide; (2) there is no measurable effect of leuprolide on human or murine embryo growth rates up to the 8 cell stage in vitro; and (3) there is no measurable effect of leuprolide on granulosa-lutein cell P accumulation.

Animals↗
PubMed1987

Psychological factors predict symptoms of severe recurrent genital herpes infection.

In a group of patients with severe recurrent genital herpes infection, we measured symptoms (pain and itching), psychological factors (depression, anxiety, somatisation, interpersonal sensitivity, and life change) and objective indices of disease (number of recurrences in the previous year, total number of recurrences, duration of recurrences, number of lesions per recurrence). Psychological factors were more predictive of pain and itching than were somatic indices, even after correcting for sex.

Adult↗
PubMed1986

An analysis of context and alcohol consumption in a group of criminal events.

The aim of this analysis was to demonstrate the importance of examining the context of alcohol consumption with regard to a criminal event. The paper explores information which was part of a larger study of alcohol use by violent and non-violent offenders. Data were collected by interview from the offenders and correlated with other reports. Earlier findings of the study which have been reported suggested that level of consumption was associated with the type of offence. In this paper a more complex drinking/drinking context and crime relationship is shown to exist. The circumstances at the time of the crime were related more to the level of alcohol consumption than to the violent or non-violent nature of the crime. Type of beverage, companionship and time of day were found to be particularly good indicators of the amount of alcohol consumed.

Alcohol Drinking↗
PubMed1983

Cause-and-effect relationship between motilin and migrating myoelectric complexes.

We investigated the cause-and-effect relationship between plasma motilin levels and migrating myoelectric complexes (MMCs). Each dog was implanted with a set of eight bipolar electrodes on the small intestine. Premature phase IIIs were initiated by morphine bolus injections. Plasma samples were assayed for motilin and gastrin. All spontaneous and morphine-initiated phase IIIs were associated with peaks of plasma motilin, which always occurred after phase IIIs had started in the proximal duodenum. The plasma motilin level decreased consistently during phase I and started to increase again only after phase II had started in the duodenum. Either a meal or somatostatin infusion disrupted MMC cycling, but morphine boluses overcame this disruption and initiated phase IIIs that propagated distally. The phase IIIs thus initiated were associated with peaks in plasma motilin levels. In contrast, bolus injections of motilin did not initiate phase IIIs during the fed state or during somatostatin infusion. Our findings suggest that endogenous motilin does not initiate spontaneous MMCs. Instead, MMC contractions release motilin. The physiological role of motilin, thus released, may be to act as an endocrine agent to coordinate secretory and motor events with the start of phase III activity in the upper small intestine.

Animals↗