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Biomedical subjects

H Davis

Publications and source records attributed to H Davis.

At least 37 records · Page 2Linked to original sources
PubMed2000

Human hip and knee torque accommodations to anterior cruciate ligament dysfunction.

It has been postulated that the adaptations of lower extremity function exhibited by anterior cruciate ligament (ACL) deficient and post-ACL surgical patients represent early accommodations to the loss of ACL function after injury so that excessive anterior displacement of the tibia is prevented. Prior studies have suggested that compensation patterns in ACL deficient and post-ACL surgical subjects may affect joint moments of the knee as well as the hip. However, the variance in knee and hip forces between ACL deficient, post-surgical ACL and uninjured groups has not been clearly elucidated. The purpose of this study was to assess hip:knee extensor torque ratios relative to anterior tibia shear in pre-surgical-ACL deficient, post-surgical and uninjured subjects. Measurements of hip and knee joint moments and anterior tibia shear were recorded from 45 injured and uninjured subjects (21 men, 24 women) during lower extremity, variable resistance exercise. Anterior tibia shear was computed by decomposing joint moments and reaction forces according to a model derived from cadaver knee dissections and radiography, in combination, to estimate the tibio-femoral compressive and shear forces generated by the patellar tendon at various angles throughout the knee joint range. Three groups of subjects were studied: recently injured ACL deficient pre-surgical subjects who were scheduled for immediate surgery (PRE; n = 15); postsurgical subjects who had undergone ACL reconstructive surgery at least 1 year prior to testing (POST; n = 15); and uninjured controls (CON; n = 15). All PRE and POST subjects had a normal contralateral limb. Tests were conducted under six conditions: 1 and 1.5 Hz cadence and maximal speed at 33% and 50% one repetition maximum resistance. The results revealed that the hip:knee ratios were significantly greater for the post-ACL surgical group than the PRE and CON groups (P<0.01; P<0.03). There were significant negative correlations between the hip extensor:knee extensor torque ratios and maximal anterior tibia shear across all groups. The hip:knee extensor torque ratio increased with decreased anterior tibia shear in all groups with significant correlations ranging from -0.55 to -0.88 (P<0.01) for the injured limbs of PRE and POST groups, and -0.64 to -0.78; (P<0.01) for the CON group. The highest overall correlations were found for the post-surgical subjects. The results revealed that anterior tibia shear declined significantly with speed (P<0.01) in all groups. However, the converse was true for the hip:knee extensor torque ratio across speeds. The ratio increased significantly with speed (P<0.001) for all groups at the 33% and 50% resistances. The results suggest (1) that post-ACL surgical subjects appear to accommodate to ACL substitution by using hip extensors to a significantly greater extent than the uninjured controls in closed-chain lower extremity exercise; (2) that the hip:knee extensor torque ratio is significantly related to the magnitude of anterior tibia shear; and (3) that the anterior tibia shear is significantly reduced as speed increases in closed-chain lower extremity exercise.

Adaptation, Physiological↗
PubMed2000

Racial differences in endothelin-1 at rest and in response to acute stress in adolescent males.

Blacks exhibit greater vasoconstriction-mediated blood pressure (BP) increases in response to stress than do whites. Endothelin-1 (ET-1), a potent vasoconstrictive peptide, has been proposed as having a role in racial differences in stress reactivity. We evaluated the hemodynamic and plasma ET-1 levels of 41 (23 whites, 18 blacks, mean age 18.6 years) normotensive adolescent males at rest and in response to a video game challenge and forehead cold stimulation. Measurements were performed at catheter insertion and before and immediately after the 2 stressors, which were separated by 20-minute rest periods. Blacks exhibited higher absolute levels of diastolic blood pressure, total peripheral resistance index, or both in response to catheter insertion and to the video game challenge and during recovery from video game challenge and cold stimulation (P<0. 05 for all). Blacks exhibited higher absolute levels of ET-1 at every evaluation point (P<0.05 for all) and greater increases in ET-1 in response to both stressors (ps<0.05). These findings suggest that altered endothelial function may be involved in racial differences in hemodynamic reactivity to stress and possibly in the development of essential hypertension.

Acute Disease↗
PubMed2000

Ethnicity and socioeconomic status: impact on cardiovascular activity at rest and during stress in youth with a family history of hypertension.

OBJECTIVE: The purpose of the present study was to examine the potential interaction of ethnicity and SES on hemodynamic functioning at rest and during acute stress in normotensive adolescents with a family history of essential hypertension (EH). DESIGN: The influences of ethnicity and socioeconomic status (SES) on cardiovascular function were evaluated at rest and in response to five different laboratory stressors. METHODS: 110 (50 female) Caucasian and 162 (85 female) African-American normotensive youth (initial age 11.2+/-2.4 years) with a family history of essential hypertension (EH) were tested on two occasions, an average of 2.5 years apart. Based on previous findings, it was predicted that African Americans, particularly those of low SES, would exhibit higher resting blood pressure (BP) and greater cardiovascular reactivity to acute laboratory stressors than would Caucasians. RESULTS: As predicted, African-American youth exhibited higher resting diastolic blood pressure (DBP) and total peripheral resistance (TPR) than Caucasians on both visits (both Ps<.04). African Americans exhibited greater systolic blood pressure (SBP) reactivity than did Caucasians to the video game stressor during both lab visits (both Ps<.02) and greater heart rate reactivity during the first lab visit (P<.01). African Americans exhibited greater SBP and/or DBP, and TPR reactivity to the cold pressor during the first lab visit and the parent-child discussion during the second visit (all Ps<.03). CONCLUSION: As predicted, African Americans exhibited higher resting BP and TPR, and greater cardiovascular reactivity than Caucasians. Although not in the predicted direction, a pattern of interactions began to emerge on the second evaluation. For example, upper SES youth exhibited greater heart rate reactivity compared to all other groups on the social competence interview and parent-child discussion stressors. Further study is needed to clarify the role cardiovascular reactivity may play in the link between ethnicity, SES, and cardiovascular disease risk.

Adolescent↗
PubMed2000

Can rabbits tell humans apart?: Discrimination of individual humans and its implications for animal research.

To predict when food reward was available, 12 New Zealand White rabbits were trained to discriminate between two humans. All subjects had significantly higher response rates and greater behavioral arousal in the presence of the positive stimulus person. The ability to discriminate between individual humans sets the stage for unanticipated Pavlovian conditioning, which may have considerable implications for animal research in behavioral and biomedical settings.

Animals↗
PubMed2000

The wandering psychiatric emergency room--design, location and transformations.

We describe the changes in location and philosophy of a psychiatric emergency room over a period of 20 years. Four phases are described in which location, size, modes of access as well as internal and external boundaries reflect philosophies of treatment and the evolving identity of a psychiatric emergency room. The four phases include an early embryonic stage, a second stage involving rapid development of services, a third stage involving regression and consolidation and a fourth stage representing a fully developed independent service. The authors stress both external and rational considerations, such as mental health policies and budget, as well as unconscious irrational processes, which reflect the dynamic forces within the organization.

Emergency Services, Psychiatric↗
PubMed1999

Patterns of body fat deposition in youth and their relation to left ventricular markers of adverse cardiovascular prognosis.

The patterns of body fat deposition in healthy youth and their relation to future development of cardiovascular disease remain incompletely understood. To further evaluate these patterns, we measured indirect indexes of central and general fat deposition in healthy adolescents (mean age 15.4+/-2.3 years) with family histories of hypertension. We examined the relation between these indexes and echocardiographic markers of adverse prognosis as well as the effect of gender and ethnicity. All 225 subjects (64% black and 48% female) had > or =1 biologic parent and 1 grandparent with hypertension. Skinfold thicknesses, waist-to-hip girth ratio, Quetelet index, Ponderal index, conicity, and Z score weight - Z score height were measured. Left ventricular (LV) mass, indexed LV mass, relative wall thickness (RWT), and midwall fractional shortening (MFS) were determined using echocardiography. In both black and white subjects, the adiposity indexes were significantly correlated with posterior wall thickness, total LV mass, and indexed LV mass (p <0.05 for all). Additionally, in black subjects, central adiposity was inversely related to MFS and directly related to RWT and septal thickness. General adiposity independently predicted indexed and nonindexed LV mass, whereas central adiposity predicted MFS and RWT. Compared with subjects with normal LV geometry, those with abnormal geometry were heavier and fatter based on every index of obesity (p <0.03 for all). Thus, indexes of fat deposition are significantly correlated with LV markers of adverse prognosis in healthy youth.

Adolescent↗
PubMed1999

Effects of race, sex, and socioeconomic status upon cardiovascular stress responsivity and recovery in youth.

Cardiovascular (CV) responsivity to and recovery from acute laboratory stressors, as derived from aggregate scores of CV functioning during and after postural change, video game challenge, social competence interview, and parent-child conflict discussion, were evaluated in 272 youths [mean age 13.5 +/- 2.6 years; 162 Blacks (77 males, 85 females), 110 Whites (60 males, 50 females)], all with a positive family history of essential hypertension. Blacks demonstrated greater systolic and diastolic blood pressure (SBP, DBP) and lower heart rate responsivity compared to Whites (all P values < 0.05). A race by neighborhood socioeconomic status (SES) interaction for SBP responsivity was also observed where low SES Whites and high SES Blacks had the greatest responsivity compared to their same race cohorts. Additionally, upper SES Whites had the lowest total peripheral resistance responsivity. For recovery, Blacks and males exhibited higher SBP during recovery compared to Whites and females, respectively. These findings extend previous studies and provide further support for the hypothesis that recovery from stress is a potentially informative component of the contribution of stress responsivity to cardiovascular disease.

Adolescent↗
PubMed1999

Prospective evaluation of accuracy, precision, and reproducibility of an at-home hemoglobin A1c sampling kit.

BACKGROUND: The measurement of hemoglobin A1c (HbA1c) is critical to the optimal therapeutic management of diabetes. To be most useful, the HbA1c value should be available at the clinical visit. Recently, a number of at-home sampling kits have been developed that facilitate the timely availability of HbA1c results. This is a report of the accuracy, precision (among-subject), and reproducibility (within-subject) of one such kit, B-D A1c, At-Home-Test, which combines a filter paper technique for spotting capillary blood with an immunoturbidometric assay (a variation of the Cobas Integra Hemoglobin A1c method also referred to as Roche Unimate). METHODS: The B-D A1c At-Home test kit was evaluated in a clinical trial using 1625 dried blood spot samples from 59 subjects diagnosed with type 1 or type 2 diabetes collected in an in-clinic setting. Data for replicate samples were compared against those from the standard Cobas Integra Hemoglobin A1c assay and from the BioRad Variant high-performance liquid chromatography [HPLC] assay. The effects of subjecting the dried spotted blood samples to prolonged elevated temperatures was evaluated in a separate laboratory analysis. RESULTS: The B-D A1c At-Home results, which are highly correlated with the standard Cobas Integra Hemoglobin A1c assay, (r2 = 94.7%), demonstrate excellent within-subject reproducibility for 3- to 10-day-old samples (coefficient of variation = 2.7%), and provide a coefficient of variation for among-subjects that is 3.9%. There were no clinically significant differences (i.e., < 0.3 units) in samples aged 3 to 10 days, between venous or capillary blood samples, or from freezing and thawing or prolonged exposure of B-D A1c At-Home dried blood samples to elevated temperatures before assay. CONCLUSIONS: The B-D A1c At-Home kit combines the accuracy, precision, and reproducibility of a clinical laboratory test with the convenience of at-home sample collection. This product may add to the convenience of both patient and health care provider by making it easier for patients to obtain their HbA1c values and have them available at their visit to the clinician.

Adult↗
PubMed1999

Temporal stability of ambulatory blood pressure and heart rate in youths.

BACKGROUND: The use of ambulatory blood pressure monitoring for pediatric populations is increasing. OBJECTIVE: ; To determine the 2-year stability of ambulatory blood pressure in youths. METHODS: We evaluated 2-year stabilities of resting and ambulatory blood pressures in 197 youths (aged 13.9+/-2.3 years at initial evaluation). Readings were taken every 20 min during the daytime (0800-2200 h) and every 30 min at night (0000-0600 h). RESULTS: Daytime and night-time systolic blood pressure increased (P < 0.01 for both) as did resting systolic blood pressure (P < 0.05). Measures of diastolic blood pressure did not change. Changes in systolic blood pressure were related to changes in body size. Estimates of stability for resting and ambulatory measurements were similar, ranging from 0.65 to 0.75. In addition, correlation coefficients for relationships between first and second readings for resting and ambulatory measurements were similar ranging from 0.43 and for resting heart rate to 0.72 for 24h systolic blood pressure (P < 0. 001 for each). The only significant correlation between change scores for resting and ambulatory values was that between resting and night-time diastolic blood pressures (r = 0.33, P < 0.001). CONCLUSION: Measures of blood pressure derived from ambulatory blood pressure monitoring reflect changes in blood pressure in youths at least as well as do changes in resting blood pressure despite the high degree of variability in levels of physical activity and affective states of the children during the ambulatory recordings.

Adolescent↗
PubMed1998

Subchronic toxicity of benzothiophene on rats following dietary exposure.

The systemic and neurobehavioral effects of benzo[b]thiophene (routinely referred to as benzothiophene) were studied in rats following 13-wk oral exposure. Male (170 +/- 16 g) and female (146 +/- 12 g) Sprague-Dawley rats (10 animals per group) were fed diet containing 0.5, 5, 50, or 500 ppm benzothiophene for 13 wk. Control animals were given rat feed plus vehicle (corn oil) only. No clinical signs of toxicity and neurobehavioral effects were observed using screening tests that included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. Elevated serum aspartate aminotransferase activity and bilirubin level were observed in highest dose females. Except for a statistically significant decrease in hematocrit in the highest dose males, benzothiophene exerted no marked effects on hematological parameters. Benzothiophene exposure did not result in alterations in hepatic alkaline phosphatase activity, or the typical hepatic phase I (aniline hydroxylase, ethoxyresorufin O-deethylase, pentoxyresorufin O-dealkylase, aminopyrine N-demethylase) and phase II (UDP-glucuronosyltransferase, glutathione S-transferase) drug-metabolizing enzyme activities. No significant elevation in urinary ascorbic acid, protein, and N-acetylglucosaminidase activity was detected in the treated animals. Peribiliary fibrosis was the most significant histological change and occurred in the liver of females in the 50 and 500 ppm groups. Mild epithelial hyperplasia in the renal pelvis was detected in the majority of 5 and 50 ppm females, with epithelial hyperplasia in the urinary bladder observed in the 50 ppm females. In males, increased incidence and severity of mild binucleation of hepatocytes and mild thickening of the basement membrane in kidney cortex were observed at 500 ppm. Benzothiophene was not detected in the urine of high-dose animals at the termination of the experiment. Based on the kidney, hepatic, and hematocrit changes, the no-observed-adverse-effect level (NOAEL) in the diet was determined to be 0.5 ppm (0.04 mg/kg/d) for females and 50 ppm (3.51 mg/kg/d) for males.

Animals↗
PubMed1998

The GalR2 galanin receptor mediates galanin-induced jejunal contraction, but not feeding behavior, in the rat: differentiation of central and peripheral effects of receptor subtype activation.

The neuropeptide galanin mediates a diverse array of physiological functions through activation of specific receptors. Roles of the three recently cloned galanin receptors (GalRs) in rat intestinal contraction and food intake were examined using GalR-selective ligands and the results were compared with the pharmacological profiles of defined GalRs. The action profile of these ligands in jejunal contraction resembled only that of GalR2 and only a high level of GalR2 mRNA was detected in the tissue, supporting GalR2 as the receptor mediating jejunal contraction. The action profile for food intake in rats excluded GalR2, GalR3 and the putative pituitary galanin receptor as the 'feeding receptor', suggesting that either GalR1 or an unidentified GalR is responsible for mediating this function.

Animals↗
PubMed1998

Randomised trial of isoniazid versus rifampicin and pyrazinamide for prevention of tuberculosis in HIV-1 infection.

BACKGROUND: Tuberculosis is a common complication of HIV-1 infection, especially in developing countries. Practical and effective chemoprophylaxis regimens for HIV-1-related tuberculosis are needed. Our aim was to test the efficacy of isoniazid versus rifampicin with pyrazinamide for prevention of tuberculosis in HIV-1-positive individuals. METHODS: We compared the efficacy of 6 months of isoniazid with 2 months of rifampicin and pyrazinamide for prevention of tuberculosis in HIV-1-seropositive individuals. Eligible participants were aged 16-77 years, HIV-1 seropositive, had a positive purified-protein derivative (PPD) skin test reaction of at least 5 mm, and had a normal chest radiograph. Participants were randomly assigned partially supervised twice weekly isoniazid for 24 weeks or twice weekly rifampicin and pyrazinamide for 8 weeks. Participants were followed up for up to 4 years for the development of tuberculosis and survival. FINDINGS: Tuberculosis developed in 14 (3.8%) of 370 participants assigned isoniazid and 19 (5.0%) of 380 participants assigned rifampicin and pyrazinamide (Cox model rate ratio 1.3 [95% CI 0.7-2.7]). The Kaplan-Meier estimate of the risk of tuberculosis during the first 10 months after entry was 3.7% among participants who received rifampicin and pyrazinamide compared with 1.0% (p=0.03) among participants who received isoniazid, and 5.4% versus 5.1%, respectively (p=0.9) at 36 months after entry. Higher rates of tuberculosis were observed in people with baseline CD4 percentages (of total lymphocytes) of less than 20 (rate ratio 4.0 [95% CI 1.8-9.0]). There were no significant differences in total mortality at any time. INTERPRETATION: Twice-weekly isoniazid preventive therapy for 6 months or rifampicin and pyrazinamide for 2 months provided similar overall protection against tuberculosis in HIV-1-infected, PPD-positive adults. The better protection among recipients of isoniazid during the first 10 months was most likely secondary to the longer duration of chemoprophylaxis. Preventive therapy for HIV-1-seropositive, PPD-positive individuals could be practical in developing countries with a once weekly clinic visit, but optimum duration of chemoprophylaxis has not been determined.

AIDS-Related Opportunistic Infections↗
PubMed1998

Synthesis of C3 heteroatom-substituted azetidinones that display potent cholesterol absorption inhibitory activity.

The C3 phenylpropyl side chain of N-phenylazetidinones related to SCH 56524 was modified by replacing the hydroxymethylene with various isoelectronic or isosteric groups. Modifications at the 3' position led to less-active compounds; however, modifications at the 1' position provided compounds with improved cholesterol absorption inhibitory activity. An enantioselective route for the synthesis of C3 1'-sulfur-substituted azetidinones and the development of structure-activity relationships for this series of compounds are presented.

Animals↗
PubMed1998

Use of computerized health claims data to monitor compliance with antibiotic prophylaxis in sickle cell disease.

OBJECTIVE: To demonstrate how computerized claims data can be used to identify children with sickle cell disease probably having low compliance with antibiotic prophylaxis of pneumococcal disease. METHODS: The study included under-5-year-old children with sickle cell disease who were on antibiotic prophylaxis and covered by Medicaid in Michigan (N=158), Missouri (N=64), and New York (N=297). Medicaid pharmacy claims from 10-month periods were used to estimate the total days' supply of antibiotics dispensed for each child. Low compliance was defined as a ratio less than 0.33 for the child's estimated total days' supply of antibiotics divided by days in the child's study period. Two slightly different methods of estimating antibiotic supplies were used to generate a low and high estimate of the percentage of children having low compliance. RESULTS: Low and high estimates of the percentage of children having low compliance were 20% and 25% in Michigan, 19% and 31% in Missouri, and 16% and 24% in New York. With each method of estimating antibiotic supplies, low compliance was not associated with age in any state. CONCLUSIONS: Computerized claims data can be used, potentially by Medicaid programs and managed care organizations, to identify children with sickle cell disease who probably have low compliance with antibiotic prophylaxis.

Journal Article↗
PubMed1998

The evaluation and hazard classification of toxicological information for workplace hazardous materials information system material safety data sheets

Hazardous materials used occupationally in Canada are subject to the legislated requirements of the Workplace Hazardous Materials Information System (WHMIS). This paper describes the administrative framework of WHMIS and how toxicological data are evaluated to determine if a substance triggers WHMIS classification for the toxicological endpoints of acute toxicity, skin irritation, eye irritation, corrosion, dermal sensitization, respiratory sensitization, chronic toxicity, mutagenicity, teratogenicity/embryotoxicity, and carcinogenicity. Problems encountered with the information on material safety data sheets are also discussed for each of the toxicological endpoints. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Psychological distress in patients with chronic, nonalcoholic, uncomplicated liver disease.

To study whether the presence of significant disease in a major organ, possibly with minimal or no clinical symptoms, would be associated with psychological disturbance, 80 subjects suffering from chronic hepatitis or cirrhosis, of nonalcoholic etiology were interviewed. Of these, 64 had either minimal or no physical symptoms. Patients completed the Brief Symptom Inventory (BSI) and the Impact of Event Scale (IES), questionnaires, which measure symptoms of psychological distress. It was found that 50% of the liver subjects were defined as cases by the BSI criteria including 15% who were defined as severe cases. There were no gender differences. Forty-five percent of asymptomatic liver subjects were defined as cases. Psychological distress was significantly pronounced in subjects with less than 12 years of education. This study points to a significant incidence of psychological distress, even in clinically asymptomatic subjects, suffering from chronic, nonalcoholic, uncomplicated liver disease.

Adult↗