Biomedical subjects

H Davis

Publications and source records attributed to H Davis.

At least 55 records · Page 3Linked to original sources

PubMed1998

Explanatory style among elite ice hockey athletes.

Mentally tough' athletes show resilience and an ability to compete during adverse conditions. The present study investigated mental toughness and assessed causal explanations for positive and negative reactions to imagined events using Seligman's Attributional Style Questionnaire. Pessimistic Explanatory style on this scale is a risk factor for negative affect and behavior following negative events. 38 elite athletes in ice hockey were rated for mental toughness by the National Hockey League's scouts on consensually derived criteria. The comparison of players above and below the median split on mental toughness showed composite explanations for negative events that were more internal, stable and global for players above the median. Contrary to predictions, these results suggest that a Pessimistic Explanatory style may benefit hockey performance.

Adaptation, Psychological↗

PubMed1998

The risk for outpatient antibiotic-treated infections following a course of oral corticosteroids among children with asthma.

Short courses of oral corticosteroids are widely used to treat asthma. The objective of this study was to assess if one course of oral corticosteroids increases asthmatic children's risk for infections treated with outpatient antibiotics. Using New York State Medicaid claims data on asthmatic children 2-15 years old, we made cohorts of oral corticosteroid users and nonusers. We determined the percentage of children who filled antibiotic prescriptions in the 30 days after index dates. Index dates were dates oral steroids were started (for steroid users) or matched dates (for nonusers). Odds ratios were adjusted for age, month of index date, and prior antibiotic use. Among children not receiving antibiotics on index dates, antibiotic prescriptions were filled in the next 30 days for 438 (20%) of 2145 steroid nonusers and 130 (19%) of 698 steroid users (p=0.30); compared to nonusers, steroid users had an adjusted odds ratio of subsequent antibiotic use of 0.92 (95% confidence interval [CI] 0.73-1.15). Among children receiving antibiotics on index dates, antibiotic prescriptions were filled in the next 30 days for 116 (26%) of 451 steroid nonusers and 50 (19%) of 260 steroid users (p=0.05); compared to nonusers, steroid users had an adjusted odds ratio of subsequent antibiotic use of 0.65 (95% CI 0.53-0.97). We conclude that one course of oral corticosteroids does not increase asthmatic children's risk for infections treated with outpatient antibiotics.

Administration, Oral↗

PubMed1998

Cultural feasibility studies in preparation for clinical trials to reduce maternal-infant HIV transmission in Haiti.

A cultural feasibility study is defined as one that investigates scientific as well as ethical, behavioral, and social issues in the design of clinical trials. The value of such a broadly defined assessment is illustrated through the presentation of two case studies conducted to prepare for clinical trials to reduce maternal-infant HIV transmission on Cité Soleil, Haiti. The first study addressed issues surrounding a trial of breast-feeding and exclusive bottle-feeding among HIV seropositive mothers. The second study focused on the implementation of a double-blind trial of HIV immune globulin and standard immune globulin to be administered to infants of seropositive mothers shortly after birth. Both cases used focus group interviews with mothers and in-depth interviews with key informants to investigate AIDS-related beliefs, acceptability of trial participation, risks to subjects, and community reactions and repercussions to the trial. Findings point to the difficulties posed by attempts to conduct trial involving complex research designs in socially disadvantaged populations. Recommendations highlight the need to consider the community-wide impact of a trial, and the need to undertake extensive educational preparation of participants to ensure informed consent and adherence to protocols.

Bottle Feeding↗

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.

Carcinogenicity Tests↗

PubMed1998

Parent counselling: an evaluation of a community child mental health service.

Health visitors and Clinical Medical Officers (CMOs) were trained in parent counselling and worked at home in a highly deprived area with parents of pre-school children with multiple psychosocial problems. Their basic aims were to establish a mutually respectful partnership and to support parents in managing their diverse problems. Detailed evaluation indicated that the Service was highly valued by both parents and referrers, and suggested significant changes, including: improvements in the severity of problems; increased parental self-esteem; decreased levels of parental stress and emotional difficulties; more positive constructions of their children; improvements in the home environment; and decreased child behavioural problems.

Adult↗

PubMed1998

The role of maternal hostility and family environment upon cardiovascular functioning among youth two years later: socioeconomic and ethnic differences.

Two hundred sixty-eight African-American and white children and their biological mothers participated in the study. The purpose of the study was to examine the potential collective impact of maternal hostile coping styles and perceptions of family functioning upon youths' cardiovascular (CV) functioning 2.4 years later, within the context of SES and ethnicity. The mother completed a set of questionnaires that included the Cook-Medley Hostility Scale and three scales from the Family Environment Scale (FES). Childrens' systolic and diastolic blood pressure (SBP and DBP) and impedance cardiography derived total peripheral resistance (TPR) was measured at rest two years later. Mothers with lower SES and African-American mothers reported higher levels of hostility compared to those with higher SES and white mothers, respectively. Lower SES mothers reported lower levels of family cohesion and expressiveness than higher SES mothers. Whites reported more family conflict and expressiveness than African Americans. African-American and lower SES youth exhibited higher SBP and DBP values than whites and higher SES youth. Among lower SES African-American youth, CV functioning tended to be impacted negatively when their mothers rated themselves high in hostility. Findings suggest that ethnicity and SES may have independent as well as interactive impacts on the influence of maternal coping styles on the CV functioning of their children, particularly those from lower SES backgrounds.

Adaptation, Psychological↗

PubMed1997

Relationships between children's cardiovascular stress responses and resting cardiovascular functioning 1 year later.

Resting cardiovascular parameters were predicted from anthropometric data, resting baseline cardiovascular data, and cardiovascular responses to three laboratory stressors completed 1 year earlier. Subjects were 106 male and female children (72 Whites, 34 Blacks) aged 6-7 years at the initial evaluation. During initial testing, blood pressure, heart rate, cardiac output, and total peripheral resistance were assessed at rest and also during a forehead cold pressor task, postural change, and treadmill exercise. The same cardiovascular parameters were then assessed at rest 1 year later. After controlling for significant anthropometric measures and the pertinent previous year's resting data, systolic and diastolic responses to the cold pressor were predictive of respective follow-up resting levels. Postural change heart rate responses were predictive of follow-up resting heart rate after controlling for initial resting levels. Exercise cardiac index reactivity predicted follow-up cardiac index after controlling for earlier resting levels and adiposity. Follow-up total peripheral resistance index was predicted by earlier resting levels.

Blood Pressure↗

PubMed1997

Leptin increases energy expenditure and selectively promotes fat metabolism in ob/ob mice.

Obesity occurs whenever energy intake exceeds energy expenditure. The ob gene product leptin is a potent anorectic agent when administered to ob/ob mice, but its effects on energy expenditure have not been investigated in detail. The present study was designed to analyze the acute metabolic effects of leptin in vivo. Analysis of oxygen consumption in ob/ob mice demonstrated a reduction in energy expenditure compared with lean controls; this reduction showed a diurnal fluctuation and was most evident during the light cycle. A single intraperitoneal dose of leptin increased oxygen consumption during the light cycle in ob/ob mice, ablating the circadian fluctuation in this parameter. In addition, leptin had a profound effect on fuel selection: the respiratory quotient was markedly reduced, indicating a reduction in carbohydrate oxidation and an increase in fat oxidation. These acute effects of leptin on metabolic parameters are consistent with the selective loss of body fat observed on chronic leptin treatment and suggest that increased energy utilization plays an important role in the anti-obese actions of leptin.

Analysis of Variance↗

PubMed1997

National trends in the mortality of children with sickle cell disease, 1968 through 1992.

OBJECTIVES: This paper describes national trends in mortality of children with sickle cell disease and the settings in which death occurred. METHODS: United States death certificate data from 1968 through 1992 were used to calculate mortality rates of Black children with sickle cell disease 1 to 14 years old. Deaths from trauma, congenital anomalies, and perinatal conditions were excluded. RESULTS: Between 1968 and 1992, mortality rates of Black children with sickle cell disease decreased 41% for 1- to 4-year-olds, 47% for 5- to 9-year-olds, and 53% for 10- to 14-year-olds. During 1986 through 1992, children who died before hospital admission accounted for 41% of deaths among 1- to 4-year-olds, 27% among 5- to 9-year-olds, and 12% among 10- to 14-year-olds. CONCLUSIONS: Survival of Black children with sickle cell disease has improved markedly since 1968. A substantial proportion of deaths continue to occur prior to hospital admission. Trends in sickle cell mortality can be monitored inexpensively with death-certificate data.

Adolescent↗

PubMed1997

Validation of the MCMI-III PTSD scale among combat veterans.

The new MCMI-III Posttraumatic Stress Disorder (PTSD) scale was validated on 104 combat veterans who were divided into two groups, PTSD Treatment Group and Non-PTSD Treatment Group. PTSD status was carefully determined by clinical interview and therapists' reports. The Combat Exposure Scale, the Mississippi Scale for Combat-related PTSD, and the Impact of Events Scale were also given. Analysis showed that the MCMI-III PTSD scale had a low internal consistency, but that it significantly differentiated the two groups and significantly correlated to those on other PTSD self-report scales. This scale appeared to be influenced by an acquiescent response style. Further validation studies are needed.

Adult↗

PubMed1997

Effects of benzothiophene on male rats following short-term oral exposure.

The systemic toxicity of benzothiophene, a sulfur-containing heterocyclic present in petroleum, coal, and their derived products, was studied in male rats following short-term oral exposure. Male Sprague-Dawley rats (130 +/- 20 g) (n = 5 per dose group) were treated with benzothiophene by gavage at dosages of 0, 2, 20 or 200 mg/kg/d for 21 d. In another study, male rats were treated with 0, 100, or 500 ppm benzothiophene via the diet for 28 d. In the gavage study, the 200 mg/kg/d rats showed depressed weight gain, increased relative liver and kidney weights, decreased relative thymus weights, and elevated levels of serum gamma-glutamyltransferase (gamma-GT), hepatic aniline hydroxylase (AH), aminopyrine N-demethylase (APDM), pentoxyresorufin O-dealkylase (PROD), glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT) activities. A 4.5-fold increase in urine volume on d 14-21 and a transient, 4-fold increase in urinary ascorbic acid on d 1 were also detected. No treatment related changes in urinary N-acetylglucosaminidase (NAGA) activity were observed. Benzothiophene residues were not detected in adipose tissue, liver, and serum of rats in the 200 mg/kg rats, but a small quantity was detected in the urine. In the diet study, animals fed the 500 ppm diet had increased absolute and relative liver weights, elevated AH, APDM, and GST activities, decreased red blood cell count, and minor increases in serum urea nitrogen and glucose. In summary, benzothiophene produced adverse effects in male rats that included increased relative liver and kidney weights and increased urine output. Benzothiophene also caused increases in hepatic drug metabolizing enzyme activities of a phenobarbital type and a transient elevation in urinary ascorbic acid.

Administration, Oral↗

PubMed1996

Anthropometric, demographic, and cardiovascular predictors of left ventricular mass in young children.

Left ventricular (LV) mass is a strong independent predictor of cardiovascular morbidity and mortality. Few longitudinal studies have examined predictors of LV mass in children. This study assessed the contributions of anthropometric, demographic, and cardiovascular parameters (at rest and after exposure to laboratory stressors) as predictors of LV mass 3.6 years after the initial examination in a sample of 68 Caucasian and African-American children 7.9 +/- 0.7 years old. At the initial examination, all subjects had standard anthropometrics measured and hemodynamics assessed at rest and during 3 stressors: postural change, forehead cold stimulation, and treadmill exercise. On the follow-up examination 3 to 4 years later, echocardiographic evaluations were conducted to estimate LV mass and related LV geometry. LV mass and LV internal diameter in diastole were adjusted for linear growth (LV mass/height2.7 and LV internal dimension during diastole/height0.80, respectively). Hierarchical stepwise multiple regression analyses were conducted using parameters significant in univariate comparisons (p < 0.05). Initial weight (R2 = 0.38), height (R2 = 0.42), and cardiac output reactivity to standing and treadmill exercise (final model R2 = 0.55) were significant predictors of LV mass, whereas LV mass/height2.7 was predicted by initial adiposity (R2 = 0.07) and cardiac output and systolic pressure reactivity to postural change (final model R2 = 0.25). Follow-up relative wall thickness was significantly predicted by ethnicity (African-Americans greater than Caucasians, R2 = 0.15), adiposity (R2 = 0.20), and systolic pressure reactivity to postural change (final model R2 = 0.28). These findings suggest the potential benefit of weight control in childhood as a primary prevention for later onset of cardiovascular disease.

Anthropometry↗

PubMed1996

Cloning and sequencing of human gp330, a Ca(2+)-binding receptor with potential intracellular signaling properties.

We present here the complete primary structure of human gp330, the human variant of the principal kidney autoantigen causing Heymann membranous glomerulonephritis in rats. The deduced 4655 amino acid residues give a calculated molecular mass of 519636 Da for the mature protein and consists of a probable 25-amino-acid N-terminal signal peptide sequence, an extracellular region of 4398 amino acids, a single transmembrane-spanning domain of 23 amino acids, and an intracellular C-terminal region of 209 amino acid residues. Three types of cysteine-rich repeats characteristic of the low density lipoprotein receptor (LDLR) superfamily are present in human gp330. In the extracellular region, there are a total of 36 LDLR ligand-binding repeats, comprising four distinct domains, 16 growth factor repeats separated by eight YWTD spacer regions, and one epidermal growth factor-like repeat. No consensus cleavage sequence for the processing endoprotease furin is detected in human gp330. The intracellular tail contains not only two copies of the F(X)NPXY coated-pit mediated internalization signal characteristic of LDLR superfamily members, but also intriguing and potentially functional motifs including several Src-homology 3 recognition motifs, one Src-homology 2 recognition motif for the p85 regulatory subunit of phosphatidylinositol 3-kinase, and additional sites for protein kinase C, casein kinase II and cAMP-/cGMP-dependent protein kinase. There is approximately 77% amino acid identity between human and rat gp330 with minor differences between the extracellular and intracellular regions. Recently gp330 has been implicated in Ca2+ regulation in the parathyroid, the placenta, and the renal tubule, but its overall physiological and pathological role still remains uncertain.

Amino Acid Sequence↗

PubMed1996

Systemic toxicity of a bitumen upgrading product in the rat following subchronic dermal exposure.

The subchronic toxicity following dermal exposure to a synthetic fuel, heavy gas oil No. 2 fraction of bitumen upgrading product (B-HGO II) was studied in the rat. B-HGO II was applied on the dorsal skin of rats at doses of 8, 20, 50 and 125 mg/kg bw/day daily for 13 weeks. Control animals received normal saline and positive controls received a medium-boiling coal liquefaction product (CLP) at 125 mg/kg bw/day. Both male and female rats in the treatment groups had reduced body weight gain, and males in the highest dose group were terminated in the 5th week due to overt toxicity. Increased liver weight relative to body weight was observed in males and females starting at 8 mg/kg. Increased relative heart and spleen weights were observed in males and females starting at the two intermediate doses (20, 50 mg/kg). Increased relative kidney weight was detected in males at 50 mg/kg and females at 125 mg/kg. Increased serum cholesterol was observed in both sexes starting at 50 mg/kg while elevated serum glucose was present in females starting at 8 mg/kg. Significant changes in AH, APDM and EROD activities were observed in treated rats of both sexes. Reduced red blood cell counts were detected in males starting at 8 mg/kg and females at 20 mg/kg. Microscopic examination of blood smears, spleen and hemosiderin accumulation patterns, as well as analysis of FEP and serum TIBC levels indicated that the cause of anemia was primarily intravascular hemolysis and secondarily iron deficiency. Marked thymic atrophy and thyroid abnormalities were the most prominent histological changes followed by changes in bone marrow (myelofibrosis) and liver. Both B-HGO II and CLP (positive control) caused kidney changes characterized by cytoplasmic inclusions and lesions in the tubular cells, which were observed in 50 mg/kg males but not in the females. B-HGO II was considered to be toxic at a subchronic dermal exposure level as low as 8 mg/kg/day.

Aminopyrine N-Demethylase↗

PubMed1996

Inhibitors of acyl CoA:cholesterol acyltransferase.

Conformational restriction of previously disclosed acyclic (diphenylethyl)diphenylacetamides led to the discovery of several potent inhibitors of acyl CoA:cholesterol acyltransferase (ACAT). cis-[2-(4-Hydroxyphenyl)-1-indanyl]diphenylacetamide (4a) was the most potent ACAT inhibitor identified (IC50 = 0.04 microM in an in vitro rat hepatic microsomal ACAT assay, ED50 = 0.72 mg/kg/day in cholesterol-fed hamster.

Animals↗

PubMed1996

DNA-based immunization against the envelope proteins of the hepatitis B virus.

Intramuscular injection in mice of DNA expression vectors encoding the envelope proteins of the hepatitis B virus induced humoral responses specific to several antigenic determinants of the viral envelope. The use of different promoter elements in the plasmid vectors influenced the kinetics and specificity of antibodies produced to the envelope proteins. The first antibodies appeared within 1-2 weeks after injection of DNA and included antibodies of the IgM isotype. Over the following weeks, an IgM-to-IgG class switch occurred, indicating helper T-lymphocyte activity. Peak IgG titers were reached by 4 weeks after a single DNA injection and were maintained for at least 6 months without further DNA injections. The antibodies to the envelope proteins reacted with both group- and subtype-specific antigenic determinants of the HBV surface antigen (HBsAg). The nature of the immune response to the envelope proteins provides indirect evidence that the proteins have adopted a native conformation and have probably been assembled into particles after intramuscular expression from the plasmid vectors. These results indicate that it may be possible to rationally design DNA expression vectors to induce a particular type of immune response for vaccination against hepatitis B or other pathogens.

Animals↗

PubMed1996

Underestimating the rat's intelligence.

Although rats are a much maligned species, it appears that their intelligence has been underestimated. This paper surveys evidence of cognition in rats from traditional categories (e.g. temporal and numerical competence) as well as from less ordinary test situations (e.g. transitive inference; recognition of individual humans). Although rats may not approach cognitive tasks using strategies observed in human subjects, they are frequently successful on their own terms. Indeed, rats are adept at exploiting procedural loopholes and confounded variables overlooked by human test designers. While not lending itself to the conventional classification of intelligence, this form of 'intellectual optimal foraging' may be an apt general description of the rat's cognitive prowess.

Animals↗

PubMed1996

An improved training procedure as a precursor to testing young children with the Frisby Stereotest.

We describe a modified version of the Frisby Stereopsis Screening Test which enables a light to be flashed behind the stereo target when the child being tested makes an appropriate pointing or reaching response. The light can be flashed to gain the interest of the child during a training phase in which they are familiarised with the test and its requirements. This phase is then followed by a test phase in which the child is encouraged to demonstrate unaided clear pointing responses to the target to gain a light flash while the plate is held in two or three different positions. This device has proved effective in increasing the chances of administering the test successfully to a sample of 30 very young children (age range 7-23 months).

Depth Perception↗