PubMed Health⌕ Search

Biomedical subjects

W R Davis

Publications and source records attributed to W R Davis.

At least 19 recordsLinked to original sources
PubMed2004

Injury patterns in big ten conference football.

BACKGROUND: In 1998, the National Collegiate Athletic Association legislated a decrease in the number of scrimmages and full-contact practices allowed during the spring season. HYPOTHESIS: A significantly increased risk of injury faced by the same player during the spring versus fall practice sessions does exist, but the National Collegiate Athletic Association regulations will not have the intended effect of reducing injury rates to equal or below those of the fall practice sessions. STUDY DESIGN: Retrospectively analyzed, descriptive study of prospectively collected injury surveillance data followed by a prospective, controlled, repeated-measures study after the rule change. METHODS: Phase 1: the Big Ten Conference Sports Injury Surveillance System database was reviewed from spring 1992 through fall 1997 for all reportable injuries. Phase 2: a prospective investigation was instituted from spring 1998 through fall 2000. This protocol was modified to also document updated individual player position descriptions and string as well as exposures for the old fall and spring practice categories (scrimmages, full contact, and limited contact) and the new spring practice designations (full pads with and without tackling, helmets only, spring game, and other scrimmages). RESULTS: Phase 1: There were 3950 fall injuries and 1007 spring injuries, with 469 of the 1007 attributable to the "spring risk factor." There was a statistically significant increase in injury rate in the spring (19.8) versus fall (10.6). Scrimmages (incidence density ratio = 2.4) and limited-contact practices (incidence density ratio = 2.5) showed more than twice the fall injury rate. Phase 2: There were 1502 fall injuries and 648 spring injuries, with 192 attributable to the spring risk factor. There was a 3-fold increase in injury rate in the spring (incidence density ratio = 3.2). Although the noncontact, helmets-only practices produced the lowest injury rates, the nonspring game scrimmages and the limited-contact practices defined as "practice with pads but without tackling" displayed the highest injury rates. In both spring and fall, nonplayers exhibited the highest injury rates for all string groups. CONCLUSIONS: There was and still is a statistically significant increase in spring practice injury risk. The 1998 rule change resulted in an even greater increase in spring practice injury risk. If the goal is to minimize the number of spring practice injuries, it will be best accomplished by limiting the number of scrimmages and limited-contact sessions.

Adult↗
PubMed2001

Supporting the habit: income generation activities of frequent crack users compared with frequent users of other hard drugs.

US Federal sentencing guidelines punish possession of crack cocaine very differently from powder cocaine, based partially upon the assumption that crack users engage more frequently in criminal behavior to pay for their habit. This article analyzed frequent users (those who have used at least 15 of the last 30 days) of crack with subgroups of less frequent hard drug users in terms of various income generation activities reported during the past 30 days. The sample consists of 602 African-Americans who were current (in past 30 days) users or sellers of cocaine powder, crack, and heroin. They were carefully recruited from randomly selected blocks in the Central Harlem area of New York City and interviewed extensively in 1998-1999. Their IGAs were classified into six categories. Compared with not-frequent (less than 15 days) hard drug users, frequent crack and multiple hard drug users were equally likely to be involved in drug distribution activities, but were significantly less likely to have full-time jobs, part-time jobs, aid to families with dependent children or welfare support. They had much higher odds ratios for non-drug related illegal (theft mainly) income generation activities and sex work among women. Often, gender and birth cohort variables had higher odds ratios with specific income generation activities than the frequent use of the primary drug(s). This evidence suggests that very frequent crack users have been stigmatized by, are largely excluded from, and perform very marginal economic roles in the legal economic system (jobs and welfare), the illegal economic system, and even in the hard drug distribution system.

Adult↗
PubMed2001

Gout, bradycardia, and hypercholesterolemia after renal transplantation.

Approximately 17,000 solid organ transplantations are done annually in the United States. Increasingly, care of these patients will be provided by primary care physicians. In this report, we illustrate the complexity of common medical problems in a patient who had cellulitis and who had had a cadaveric renal transplantation 10 years earlier. Immunosuppressive therapy was cyclosporine (100 mg twice a day) and prednisone (10 mg once a day). The patient's hospital course was complicated by acute gout and symptomatic bradycardia. In both instances, usual treatment--full-dose indomethacin for gout and withholding verapamil for bradycardia--could have had significant interaction with the cyclosporine. At the time of discharge, a therapeutic plan for long-term management of hypercholesterolemia included possible drug interactions with cyclosporine. The potential for drug toxicity in the transplant patient necessitates careful monitoring of immunosuppressive drug levels. Ongoing communication with the transplant center is also needed.

Bradycardia↗
PubMed2000

Inhibition of HIV-1 reverse transcriptase-catalyzed DNA strand transfer reactions by 4-chlorophenylhydrazone of mesoxalic acid.

DNA strand transfer reactions occur twice during retroviral reverse transcription catalyzed by HIV-1 reverse transcriptase. The 4-chlorophenylhydrazone of mesoxalic acid (CPHM) was found to be an inhibitor of DNA strand transfer reactions catalyzed by HIV-1 reverse transcriptase. Using a model strand transfer assay system described previously [Davis, W. R., et al. (1998) Biochemistry 37, 14213-14221], the mechanism of CPHM inhibition of DNA strand transfer has been characterized. CPHM was found to target the RNase H activity of HIV-1 reverse transcriptase. DNA polymerase activity was not significantly affected by CPHM; however, it did inhibit the polymerase-independent RNase H activity with an IC(50) of 2.2 microM. In the absence of DNA synthesis, CPHM appears to interfere with the translocation, or repositioning, of RT on the RNA.DNA template duplex, a step required for efficient RNA hydrolysis by RNase H. Enzyme inhibition by CPHM was found to be highly specific for HIV-1 reverse transcriptase; little or no inhibition of DNA strand transfer or DNA polymerase activity was observed with MLV or AMV reverse transcriptase, T7 DNA polymerase, or DNA polymerase I. Examination of additional 4-chlorophenylhydrazones showed that the dicarboxylic acid moiety of CPHM is essential for activity, suggesting its important role for enzyme binding. Consistent with the role of the dicarboxylic acid in inhibitor function, Mg(2+) was found to chelate directly to CPHM with a K(d) of 2.4 mM. Together, these studies suggest that the inhibitor may function by binding to enzyme-bound divalent metal cofactors.

Animals↗
PubMed1999

Inhibitors of DNA strand transfer reactions catalyzed by HIV-1 reverse transcriptase.

The discovery and characterization of new inhibitors of HIV-1 reverse transcriptase (RT) is an important step toward understanding the mechanism of this multifunctional polymerase. We describe the identification of novel inhibitors of HIV-1 RT-catalyzed reactions utilizing a nucleic acid model system designed to mimic the essential features of DNA strand transfer reactions catalyzed by HIV-1 RT. This reaction requires the DNA polymerase and RNase H activities of RT, as well as the translocation of DNA from one template strand to another. In addition to the discovery of new inhibitors of DNA polymerase activity, two classes of inhibitors were identified that inhibit different steps of the DNA strand transfer reaction. One class of these, exemplified by actinomycin D, inhibits DNA strand transfer by interfering with the transfer of the DNA intermediate onto the acceptor template. The second class of strand transfer inhibitor, exemplified by the chlorophenylhydrazone of mesoxalic acid, was found to inhibit the ribonuclease H (RNase H) activity of HIV-1 RT under strand transfer conditions. This inhibitor is a potent and specific inhibitor of RNase H activity, which displays no inhibition of either DNA-dependent or RNA-dependent DNA polymerase activity. Together, these three inhibitors block different steps reverse transcription and will be valuable in studying the mechanism of multistep reactions such as DNA strand transfer. In addition, these new inhibitors of in vitro reverse transcription point to new strategies for the intervention of retroviral DNA replication and could be useful in the development of new HIV-1 therapeutic strategies.

Anti-HIV Agents↗
PubMed1999

A demographic and behavioral profile of homeless youth in New York City: implications for AIDS outreach and prevention.

Rapid changes in the world market economy have served to destabilize many local institutions, widening the gap between the rich and the poor and undermining viability of key social and economic institutions such as family and household. Among those most deeply affected by this displacement are children and adolescents, many of whom are forced to leave family institutions before they have acquired the skills and maturity needed to become economically self-sufficient. Fending for themselves amid the vagaries of the underworld of virtually every major city in the world, these youths are at exceptional risk for a wide range of poor health outcomes and premature death. While perhaps a familiar sight in many non-Western countries, this phenomenon also has emerged in the industrialized world, a fact that accounts for the rise in exposure to violence and disease among street-involved youth and young adults in nations such as the United States. There are as yet few empirical data available about the nature of these youth populations or the constellation of behaviors that place them at increased risk for disease outcomes. In this report we construct a demographic and behavioral profile of the homeless youth population in New York City, particularly as behavioral patterns relate to risk associated with HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Actinomycin D inhibition of DNA strand transfer reactions catalyzed by HIV-1 reverse transcriptase and nucleocapsid protein.

Actinomycin D was found to be a potent inhibitor of HIV-1 reverse transcriptase catalyzed DNA strand transfer reactions. Using an oligonucleotide model system, actinomycin D inhibition of DNA strand transfer was examined to elucidate the mechanism of inhibition and further define the mechanism of DNA strand transfer. Our results show that actinomycin D inhibits HIV-1 reverse transcriptase catalyzed DNA strand transfer without inhibiting RNA-dependent or DNA-dependent DNA polymerase activity. Actinomycin D was found to strongly inhibit annealing of a primary DNA product to the DNA acceptor template, preventing the formation of a key reaction intermediate. The HIV-1 nucleocapsid protein has been shown to participate in catalytic events during reverse transcription including DNA strand transfer. Recombinant nucleocapsid protein was used in conjunction with actinomycin D in this model system to investigate how NC may participate in the mechanism of inhibition by actinomycin D and in DNA strand transfer. The inclusion of nucleocapsid protein was found to partially relieve both DNA annealing and strand transfer inhibition caused by actinomycin D. This study suggests a potential new mechanism for inhibiting retroviral replication by preventing the formation of replication intermediates.

Catalysis↗
PubMed1997

Gender differences and other factors associated with HIV testing in a national sample of active drug injectors.

Gender, health, HIV risk, and demographic factors were examined with chi-square and logistic regression analyses to assess which of these factors are most predictive of active injection drug users' (IDUs') getting tested for HIV. Analyses were based on 36,898 IDUs recruited to participate in a nationwide multisite HIV prevention project. Women IDUs were recently tested (prior 6 months) more than men IDUs. Health factors, particularly for women IDUs, predicted who got tested for HIV more than risk or demographic factors. HIV testing usually occurred when disease symptomatology developed, after a long period of being capable of transmitting HIV to others, and when the benefits of AZT and other interventions may be reduced. Preventive interventions with IDUs are needed that emphasize the possible benefits of HIV testing and that encourage testing before symptoms develop.

AIDS Serodiagnosis↗
PubMed1996

HIV risk behaviors among Dominican brothel and street prostitutes in New York City.

Latina women are overrepresented among AIDS cases in the United States. To assist in developing appropriate prevention and intervention programs, information regarding HIV risk behaviors is needed on the many diverse Latina subgroups. This study examined sociodemographic characteristics and HIV risk behaviors of Dominican female prostitutes, comparing those who worked primarily in brothels with those who were street workers. A total of 77 Dominican prostitutes (54 brothel; 23 street) were recruited in New York City to participate in a structured interview and were offered HIV testing. Ethnographic interviews were conducted with a subscale. Results indicated that there were many significant differences in demographics and risk behaviors between the two groups, and those working in brothels engaged in lower levels of risk behaviors. In addition, those working in brothels had closer ties to the Dominican and Spanish cultures. Implications for AIDS prevention efforts are discussed.

AIDS Serodiagnosis↗
PubMed1995

Outcomes of a risk-reduction intervention with high-risk populations: the Harlem AIDS project.

Many studies of interventions with high-risk populations have reported reductions in risk behaviors. To assess effectiveness of interventions, data are also needed on the characteristics of subjects lost to follow-up, and on follow-up risk behaviors for subjects who were not participants in the intervention. This paper reports on a study conducted in Harlem, New York, recruiting 1,770 injection drug users (IDUs) and sex partners of IDUs, randomly assigned to two interventions. Repeated-measures analyses for the two intervention groups and those who participated in no intervention indicated that all groups reported significant reductions in risk behaviors, with no group effect. Comparisons of those followed-up and not followed-up indicate that those followed-up were less likely to: be homeless, be Latinos, and to use "shooting galleries." The discussion focuses on the need to assess outcomes for all types of participants, and to distinguish the impact of interventions from other explanations for behavior changes.

Acquired Immunodeficiency Syndrome↗
PubMed1994

The risk of HIV infection in a national sample of women with injection drug-using partners.

OBJECTIVES: This study reports on a large, national cohort of women with injection drug-using sex partners. Information is provided on demographic characteristics; human immunodeficiency virus (HIV) risk factors, including unprotected sex and incidence of sexually transmitted diseases; use of noninjected drugs; HIV serostatus; and other selected health variables. METHODS: A sample of 5162 heterosexual women was recruited for a national acquired immunodeficiency syndrome (AIDS) research and demonstration project. A structured interview was administered, and the women had the option of undergoing HIV testing. Statistical analyses compared three groups on variables of interest: women with single sex partners, women with multiple partners, and women with multiple partners who exchanged sex for drugs and/or money. RESULTS: These groups differed significantly on virtually all of the demographic and risk variables examined. Women with multiple partners who exchanged sex for drugs and/or money were at higher risk for HIV than women in the other groups, even when selected demographic variables were controlled. CONCLUSIONS: Research is needed on the efficacy of prevention efforts involving these diverse groups of women at risk for AIDS.

Adult↗
PubMed1992

Pharmacologic suppression of atrial flutter induced by atrial stimulation.

To examine the electrophysiologic properties of human atrial flutter and its response to various classes of antiarrhythmic drugs, 39 patients were identified as having inducible sustained atrial flutter with atrial extra-stimulation techniques. Measurement of intra-atrial, interatrial, atrioventricular node and His-Purkinje-conduction intervals, atrial refractory periods, and atrial flutter-cycle length were made before and after intravenous administration of verapamil, ouabain, or cedilanid, propranolol, and procainamide in these 39 patients, as well as in seven control patients. Verapamil significantly shortened flutter-cycle length but suppressed atrial-flutter induction in only one of seven patients. Two of nine patients who received propranolol proved resistant to flutter provocation; the seven patients who remained nonsuppressible exhibited greater prolongation of interatrial-conduction time. Ouabain and cedilanid suppressed flutter inducibility in four of seven patients, and flutter-cycle length increased in those patients remaining inducible. Procainamide suppressed flutter induction in nine of 11 patients. These results suggest that procainamide is the most effective agent of those agents tested in suppressing atrial flutter induced by atrial extra-stimulation. Verapamil and propranolol proved quite ineffective in suppressing inducible atrial flutter.

Adult↗
PubMed1992

AIDS outreach workers: an exploratory study of job satisfactions/dissatisfactions.

AIDS outreach workers operate at the frontlines of the AIDS epidemic to provide information and education to high-risk individuals. Recent reports indicate that these workers have been effective in helping to reduce high-risk behaviors. However, a review of retention data for 62 outreach workers employed from 1986 to 1988 at a private nonprofit research institute indicated a high rate of turnover, especially among males. The literature provides little information regarding the demographic characteristics of outreach workers and their sources of job satisfaction and dissatisfaction. This exploratory investigation was undertaken to address these topics. Structured interviews were conducted with 20 currently active outreach workers. Results indicate that altruistic motives were most frequently cited as reasons why people became outreach workers and also provided the primary source of satisfaction. Stress was most frequently mentioned as a source of dissatisfaction and also as a reason previous workers had left outreach work. Conclusions focus on the outreach workers' suggestions for job improvements. These included: improvement in the terms of employment (e.g., salary, benefits); more education and training opportunities; and more support groups or help with recovery.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Humoral factors determining the blood pressure response to converting enzyme inhibition and calcium channel blockade.

Renin and catecholamine levels were determined in patients with mild to moderate hypertension before and after treatment with sustained release diltiazem or captopril and were correlated with the blood pressure response to these antihypertensives. Eight weeks of treatment with either agent led to equal decreases in both systolic and diastolic blood pressure. Pretreatment plasma renin activity (PRA) and plasma norepinephrine did not predict the blood pressure response to either agent. Diltiazem significantly increased both PRA and supine norepinephrine levels. However, in the diltiazem treated patients, there was no correlation between the change in plasma norepinephrine and the change in systolic or diastolic blood pressure. In contrast, there was a negative correlation (P less than .05) between the reactive rise in PRA and the decrease in systolic blood pressure. Thus, the antihypertensive response to a calcium channel blocker may be determined, in part, by the reactive response of pressor systems.

Adult↗
PubMed1990

Effects of calcium channel blockade on calcium homeostasis in mild to moderate essential hypertension.

Calcium channel blockers may alter parathyroid hormone secretion in vitro, which would alter calcium homeostasis. To determine the chronic effect of calcium channel blockade in vivo, we conducted a randomized, double blind, 16 week study comparing the effects of two pharmacologic antihypertensive agents, the calcium channel blocker diltiazem and the angiotensin-converting enzyme inhibitor captopril on parameters of calcium homeostasis. Both diltiazem and captopril lowered blood pressure to a similar degree. Neither drug produced any significant change in blood levels of total and ionized calcium, magnesium, or phosphorus, which affect the regulation of parathyroid hormone and vitamin D. In addition, at eight or 16 weeks following initiation, neither drug altered the serum levels of parathyroid hormone (PTH) or 1,25-(OH)2-vitamin D3 (1,25-D). Chronic calcium channel blockade with diltiazem does not alter serum parameters of calcium homeostasis and, thus, should not affect bone mineralization.

Adult↗