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Biomedical subjects

T Myers

Publications and source records attributed to T Myers.

At least 55 records · Page 3Linked to original sources
PubMed1994

Influenza B virus infection in pediatric solid organ transplant recipients.

OBJECTIVE: Influenza B virus causes epidemic infection in normal children, but only one case of infection in an immunocompromised solid organ transplant (SOT) recipient has been reported. Characterization of the clinical course of influenza B virus infection in pediatric SOT recipients may increase the utilization of preventive and therapeutic interventions by pediatricians caring for these immunocompromised children. DESIGN: Retrospective chart review of patients whose respiratory viral cultures yielded influenza B from January 1989 through March 1992. PATIENTS: Twelve pediatric SOT recipients with influenza B virus infection were identified. These included five renal, four hepatic, and three cardiac allograft recipients, ranging from 19 months to 17 years 9 months of age (median 6 years 2 months). The posttransplant interval ranged from 6 weeks to 4 years 6 months (average 26.7 months). No patient had been immunized against influenza. Exposure histories were documented for eight children; five of these occurred in the hospital. RESULTS: Clinical symptoms included fever (12/12), respiratory (11/12), or gastrointestinal complaints (8/12). Five patients had neurologic involvement; one died of uncal herniation. Ten children were hospitalized (median duration, 3 days; range, 2 to 79 days). Two patients (post-transplant interval, 3 to 8 months) required mechanical ventilation, and one of these received aerosolized ribavirin. Three children had concurrent allograft rejection. CONCLUSIONS: Influenza B infection is potentially life-threatening in pediatric SOT recipients. We recommend annual immunization of pediatric SOT recipients, their household contacts, and health care workers. Prospective studies are needed to evaluate the efficacy of influenza vaccination in pediatric SOT recipients.

Adolescent↗
PubMed1993

Backtransplantation of chick cardiac neural crest cells cultured in LIF rescues heart development.

The cardiac neural crest is essential for normal development of the cardiovascular system. Cardiac neural crest cells are derived from the neural folds located between the mid-otic placodes and the caudal limit of somite 3. These crest cells can differentiate into a variety of mesenchymal cell types that support cardiovascular development, in addition to neurogenic cells. When cultured, many express alpha-smooth muscle actin or neurofilaments and lose their undifferentiated neural crest phenotype as shown by a decrease in HNK-1 reactivity. We wanted to determine whether cultured cardiac neural crest cells maintained the potency to support normal heart development when backtransplanted into embryos lacking their native cardiac neural crest. Under usual circumstances removal of the cardiac neural crest results in 80-100% incidence of persistent truncus arteriosus. The present study reports a system in which cardiac neural folds are cultured for 3 days and the cells backtransplanted into chick embryos after laser-induced ablation of the intrinsic cardiac neural folds. Rescue of heart development was improved 50% when cultured cells were backtransplanted and almost 200% when the backtransplanted cells had been cultured in leukemia inhibitory factor (LIF). To determine whether the cultured cells are capable of following normal migratory routes, cultured homospecific cardiac neural crest cells were tagged with DiI. Initially, fluorescent cells were found concentrated around the neural tube. By the second day following backtransplantation, the cells had migrated to the circumpharyngeal crest, populated the pharyngeal arches and aortic arch arteries, and were in the region of the cardiac outflow tract. By the third day, the labeled cells had dispersed, but could be found around the neural tube, esophagus, cardiac outflow tract, and within the dorsal root ganglia. Interestingly, a cranial migration to the periphery of the eyes was also noted. With the exception of the cranial migration to the eyes, cultured and backtransplanted cardiac neural crest cells followed normal migratory pathways to the cardiac outflow tract. LIF is used for the in vitro maintenance of the pluripotential phenotype of embryonic stem cells. In an effort to understand why LIF improves the ability of cultured neural crest cells to support normal heart development, we have examined the relationship of neural crest expression of HNK-1 antigen, alpha-smooth muscle actin, and neurofilament protein in neural crest cells cultured in LIF. LIF treatment resulted in an expanded period of expression of HNK-1 antigen, associated with a decrease in expression of alpha-smooth muscle actin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Factors affecting gay and bisexual men's decisions and intentions to seek HIV testing.

OBJECTIVES: This paper describes the relationships of sociodemographic, attitudinal, and behavioral variables to (1) decision to be tested, (2) expressed intention to be tested, and (3) reasons for not being tested for the human immunodeficiency virus (HIV) antibody. METHODS: A sample of 1295 men completed an anonymous questionnaire in gay-identified venues. Factor analysis was used to group reasons for not being tested and logistic and multiple linear regression were used to model the dependent variables. RESULTS: Fifty-three percent of the respondents had been tested, of whom 26% tested positive. Metropolitan residence and anal intercourse most strongly correlated with previous test-seeking. Previous test experience correlated most strongly with intention to be tested. Reasons for not being tested fell into three groups: (1) desire for anonymity, (2) self-perceived health, and (3) no benefit and denial. The odds were lower for gay men than bisexuals and men who did not participate in anal intercourse to express a desire for anonymity. CONCLUSIONS: Public health agencies should be prepared to individualize testing policies and education to deal with specific concerns and fears. Improving access to the test by removing some of the current psychological and physical barriers will enhance its medical and public health value.

AIDS Serodiagnosis↗
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↗
PubMed1987

A pressure-limited critical care ventilator.

We developed a new pressure-limited ventilator system by modifying the Bird #7001M ventilator. Our aims were to free ICU floor space by wall-mounting the ventilator, and to employ a pressure-limited, gas-powered ventilator similar to our transport ventilator to aid in the training of members of our transport team. The system provides a peak pressure of 150 cm H2O and a peak flow of 208 L/min. When coupled with heated pneumatic nebulizers, it quietly provides a maximum gas flow of 208 L/min with nebulized water at 37 degrees C. We successfully used this system for over 4 years to provide a wide range of ventilatory support and oxygen therapy.

Equipment Design↗