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Biomedical subjects

H C Davis

Publications and source records attributed to H C Davis.

At least 19 recordsLinked to original sources
PubMed1999

Hemodynamic function at rest, during acute stress, and in the field: predictors of cardiac structure and function 2 years later in youth.

Left ventricular hypertrophy is an independent predictor of cardiovascular morbidity and mortality. However, predictors of cardiac structure and function in youth are not completely understood. On 2 occasions (2.3 years apart), we examined 146 youth aged initially 10 to 19 years (mean age, 14.2+/-1.8 years). On the initial visit, hemodynamic function was assessed at rest, during laboratory stress (ie, orthostasis, car-driving simulation, video game, and forehead cold), and in the field (ie, ambulatory blood pressure). Quantitative M-mode echocardiograms were obtained on both visits. On both visits, black compared with white youth had higher resting laboratory systolic blood pressure (P<0.02), greater relative wall thickness (P<0.003), greater left ventricular mass indexed by either body surface area or height(2.7) (P<0.01 for both), and lower midwall fractional shortening ratio (P<0.05). Hierarchical stepwise regression analysis indicated that significant independent predictors of follow-up left ventricular mass/height(2. 7) were the initial evaluation of left ventricular mass/height(2.7), body mass index, gender (males more than females), and supine resting total peripheral resistance (final model R(2)=0.53). Left ventricular mass/body surface area was predicted by initial left ventricular mass/body surface area, weight, gender, mean supine resting total peripheral resistance, and systolic pressure response to car-driving simulation (final model R(2)=0.48). Midwall fractional shortening was predicted by initial midwall fractional shortening, race (white more than black), and lower mean supine total peripheral resistance (final model R(2)=0.13). The clinical significance of these findings and their implications for improved prevention of cardiovascular diseases are yet to be determined.

Adolescent↗
PubMed1999

Assessment of self-reported anger expression in youth.

Internal consistency, temporal stability, and principal components structures of two self-report anger expression scales used in pediatric health research were examined in 415 youth (216 White, 199 Black; 191 boys, 224 girls; mean age 14.7 years). Participants completed the Anger Expression Scale (AXS) and the Pediatric Anger Expression Scale (PAES) on two occasions separated by approximately 1 year. Psychometric properties of the two scales were examined and compared with those reported by the scale authors. For both the AXS and the PAES, estimates of internal consistency (Cronbach s alpha) were acceptable and comparable to values reported by scale authors. Temporal stability of both scales was significant over 1 year. Principal components structures for both scales were similar to those reported by scale authors. Results were generally consistent for age groupings (<13, 13 years), ethnicity, and gender. It is concluded that further research using the AXS and PAES is warranted. The stability of anger expression over time and the assessment of anger suppression is discussed.

Adolescent↗
PubMed1997

"How do you remember you ate...?": a Delphi technique study to identify retrieval categories from fourth-grade children.

OBJECTIVE: To develop and validate a consensus set of retrieval categories for how children remember what they have eaten, and to relate retrieval categories to accuracy of reporting items eaten during school lunch. DESIGN: A Delphi technique study was conducted using 10 psychologists. The subject matter consisted of responses transcribed from interviews conducted with 89 randomly selected fourth graders within 90 minutes of eating. Retrieval categories were evaluated for accuracy by comparing students' self-reported lunch intake with observation. STATISTICAL ANALYSES: For round 1, a centroid hierarchical cluster analysis was used to identify common sets of rating pairs to propose categories for reaching consensus. For rounds 2 and 3, percent of agreement was calculated. Accuracy was tabulated across meal items and student use by retrieval category. RESULTS: After round 3, we found that 23 "near-consensus" categories were used by at least eight raters. Six categories were used 60% of the time, 4 were used 20% of the time, and 5 were used 15% of the time. Less frequently used categories were combined with similar, more frequently used categories for a total of 16 categories. Students used a large variety of retrieval categories when accurately reporting consumption. Of the 16 categories, 12 were used similarly by both accurate and inaccurate students. Where there were differences in accuracy by retrieval category, the more accurate students used "taste/smell/texture" and "visual" in deference to "order items consumed" and "oral cue still present." APPLICATIONS: These categories provide insight into the broad range of retrieval categories that children use and provide direction for researchers to design and study specific cues to enhance the accuracy of children's self-reports of diet.

Child↗
PubMed1997

Impact of gender, ethnicity, meal component, and time interval between eating and reporting on accuracy of fourth-graders' self-reports of school lunch.

OBJECTIVE: To validate fourth-graders' self-reports of school lunch by comparing their reports to lunch observations, and to determine the impact on accuracy of gender, ethnicity, meal component, and time interval between eating and reporting. DESIGN: Students were randomly selected, observed eating lunch, and interviewed the same day, next day, or Monday regarding Friday's lunch. Accuracy of reporting items was determined by tallying matched foods (items reported and observed), phantom foods (items reported but not observed), and omitted foods (items not reported but observed). Accuracy of reporting amount eaten was determined by calculating absolute and arithmetic differences. SUBJECTS: Subjects were 260 students: 89 same-day, 148 next-day, and 23 Monday recalls; 59 whites (30 boys) and 201 blacks (103 boys) from four schools. STATISTICAL ANALYSES: Rates for matched, phantom, and omitted foods; analysis of variance; Friedman's nonparametric analog of analysis of variance; Student-Newman-Keuls' post hoc comparisons. RESULTS: In regard to reporting items, the respective rates for matched, phantom, and omitted foods were 84%, 5%, and 16% for same-day recalls; 68%, 13%, and 32% for next-day recalls; and 38%, 48%, and 62% for Monday recalls. Rates for omitted and phantom foods were higher for Monday recalls than for next-day recalls, which were higher than for same-day recalls (P < .05 for all). In regard to reporting amounts, analysis by gender, ethnicity, and time interval failed to yield significant main or interaction effects. When children correctly reported items eaten, they were quite accurate in reporting amounts eaten. Omitted food rates were lowest for beverage, followed by entree, and highest for miscellaneous and condiment. APPLICATIONS: Even under the best conditions (ie, reporting within 90 minutes after eating school lunch), children have difficulty accurately reporting what they have eaten. As the time interval between eating and reporting increases, accuracy decreases markedly. Techniques that improve reporting of items eaten should result in improved accuracy of reporting amounts eaten.

Analysis of Variance↗
PubMed1997

Ventilator management of infants before extracorporeal membrane oxygenation.

The aim of this project was to review the course of infants referred for consideration of extracorporeal membrane oxygenation (ECMO) to identify maximal ventilator settings that, when exceeded, did not provide clinical benefit to the patient. These settings might then be used in defining failure of conventional mechanical ventilation. We reviewed referral records and hospital charts of all infants treated for severe respiratory failure due to meconium aspiration syndrome during the 52.5 month period from March 15, 1985, to August 1, 1989. At an inspiratory pressure > 35 cm H2O, 75% (43/57) of patients eventually required ECMO, and 28% (4/14) of the infants who did not receive ECMO died. When the inspiratory pressure was > or = 40 cm H2O, 39/49 patients required ECMO, and 30% (3/10) of those not treated with ECMO died. Once the inspiratory pressure was > 45 cm H2O, 91% (29/32) of patients required ECMO, and only one third of those not treated with ECMO survived. Although the limitations for conventional therapy suggested in this paper may be helpful to clinicians, each center needs to establish guidelines for maximal conventional ventilator support. If these guidelines are clearly defined, alternative methods of therapy can be used once these criteria are achieved.

Apgar Score↗
PubMed1996

A measure of stages of change in fruit and vegetable consumption among fourth- and fifth-grade school children: reliability and validity.

OBJECTIVE: We developed, pilot-tested, and field-applied a stages of change questionnaire regarding fruit and vegetable (F&V) consumption among fourth- and fifth-grade students. METHODS: The design included cross-sectional assessment of internal consistency and construct validity, and 2-week and 7-week longitudinal assessment of test-retest reliability. Subjects included 134 students from one school for pilot-testing and 252 from two schools for field application. Thirty-two questions from McConnaughy et al's stages of change questionnaire were adapted and pilot-tested; minor revisions were made for field application. Statistical analyses included principal components analysis to identify subscales; cluster analysis to identify subgroups within students; Cronbach's alpha coefficient to assess internal consistencies; Pearson product-moment correlations to assess test-retest reliabilities; and oneway ANOVA's by F&V stages of change clusters with actual F&V consumption, F&V self-efficacy subscales, F&V preferences, and F&V outcome expectations subscales to determine construct validity. RESULTS: Principal components analysis from the field application indicated two subscales (precontemplation and beyond precontemplation) accounting for 39.5% of variance. Cluster analysis indicated 6 interpretable clusters; 2 (n = 63) provided responses inconsistent with the stages of change theory and 4 (n = 189) provided responses consistent with the theory. Internal consistencies and test-retest reliabilities were acceptable. Students in the "beyond precontemplation" clusters had higher levels of self-efficacy and outcome expectations regarding eating F&V. CONCLUSIONS: Measuring stages of change other than the precontemplation stage in F&V consumption among elementary school children is problematic. Perhaps the theoretical concept does not apply to children, or elementary school children lack the ability to comprehend the questions measuring the concept, or the approach used was not entirely appropriate.

Attitude to Health↗
PubMed1993

Factors affecting cure at depths within light-activated resin composites.

When confronted with all the variables that are influential in maximizing the cure in light-activated resin composites, a practitioner may require information that ranks the relative importance of these parameters, so that clinical time can be best utilized. The purpose of this study was to determine simultaneously the relative impact of filler type (hybrid or microfill), composite shade (universal or gray), exposure duration (20, 40, 60 and 80 seconds) and source intensity (800, 578, 400 and 233 mW/cm2) on the extent of cure in light-activated composite at selected depths (top surface, 1, 2, and 3 mm) of a simulated restoration. Thin wafers of composite (P-50 and Silux Plus) were made between a cured composite underlay and varying thicknesses of cured overlay to obtain a wafer that reproduced the curing environment within a cylinder of composite. The monomer conversion of each specimen was obtained by infrared spectroscopic techniques. Analysis of variance was used to determine the significance of factors contributing to the cure of composite at each thickness of overlay used. At the surface, filler type, exposure duration and resin shade predominated as the most influential factors respectively. At 1 mm depth, the order of influential factors were exposure duration, filler type and source intensity. At depths of 2 mm and more, the overwhelming influences on cure were related solely to source intensity and exposure duration. Resin shade and filler type exerted minimal influence at these depths.

Analysis of Variance↗
PubMed1992

The effect of tensile strength on the clinical effectiveness and patient acceptance of dental floss.

This study compared the clinical effectiveness and subjective approval of 2 waxed dental flosses that differed significantly in tensile strength and wax content. At the initial appointment, subjects (20 1st-year dental students) were instructed to stop interproximal cleaning on 2 contralateral quadrants in order to allow plaque to accumulate on these surfaces for 1 week. 1 week later, subjects were instructed to begin flossing these 2 contralateral quadrants with 1 of the 2 types of floss for the next 1-week period, while withdrawing interproximal cleaning on the opposite 2 contralateral quadrants. After flossing these 2 quadrants for 1 week, the subjects began flossing the opposite 2 contralateral quadrants with the same floss. After 2 weeks of flossing contralateral quadrants, the 1st floss was withdrawn and replaced with the alternative floss for another similar 2-week trial period. At the end of each 2-week trial period, subjects completed subjective questionnaires concerning the floss they had used during the previous 2-week period. Pre- and post-flossing plaque indices were calculated for each week for both flosses, and compared statistically by a repeated measures analysis of variance. The results showed that both flosses significantly reduced interproximal plaque deposits, and had equal subjective approval. However, neither the greater-strength nor the lower-wax content of the experimental floss was associated with an increase in clinical effectiveness or with a change in subjective approval.

Adult↗
PubMed1991

Derivation and implications of MMPI cluster groups in clinically depressed inpatient females.

The purpose of this study was to subclassify clinically depressed patients based on a cluster-analytic examination of the MMPI. Subjects were 79 female inpatients with major depression. A cluster analysis of the MMPI validity and clinical scales resulted in three clusters labeled psychotic (287 MMPI profile), hostile (24 MMPI profile), and histrionic (32 MMPI profile) depression. The psychotic group exhibited the greatest depression as measured by the Beck Depression Inventory (BDI). The psychotic and hostile groups, however, did not differ on other associated aspects of depression, such as negative cognitions, nonassertiveness, or personality style. The hostile group reported the fewest physical difficulties and the most excessive alcohol use. The groups, however, did not differ on other aspects of depression history or presentation such as family history of depression or previous hospitalizations. A repeated measures ANOVA for the three cluster groups on the BDI at admission, discharge, and 6 months after discharge indicated that all groups showed improvement at discharge but that only the hostile depressive group continued to show improvement at the 6-month follow-up.

Adult↗
PubMed1989

Effect of fetal sex and race on amniotic fluid lecithin concentration.

Amniotic fluid lecithin phosphorus concentration (AF-Lec) was measured in 209 healthy women at 31.7-42.7 weeks gestation. The patients were divided into four groups according to race and fetal sex. No differences in AF-Lec between black and white nor between male and female fetuses were found. The relationship of AF-Lec to gestational age and the incidence of "mature" AF-Lec was not different among the four groups. We conclude that there is no effect of fetal sex, race, or the interaction between them on fetal lung development as measured by AF-Lec.

Adult↗
PubMed1989

Cholinergic and serotonergic effects on the P3 potential and recent memory.

The effects of scopolamine (anticholinergic) and methysergide (antiserotonergic) on memory and long-latency auditory cognitive evoked potentials (EPs) were tested in 16 normal adults. Recent memory was impaired by both drugs. In contrast, scopolamine, but not methysergide, significantly delayed P3 latency and decreased P3 amplitude. Immediate memory and the earlier EP components (i.e., N1 and P2) were unaffected. The findings support the hypothesis that cholinergic neurons are important in the neuronal networks generating the P3 potential. Serotonergic neurons do not appear to play a major role in the networks that generate the P3.

Adult↗
PubMed1987

The reliability and clinical use of a rapid phosphatidylglycerol assay in normal and diabetic pregnancies.

Lecithin phosphorus concentration, the standard fetal lung maturity test in our institution, and phosphatidylglyercol were assayed in 69, 29, and 45 amniotic fluid samples from normal (GI), gestational (GII), and insulin-dependent diabetic (GIII) women by means of thin layer chromatography and Amniostat-FLM, respectively. Lecithin phosphorus concentration greater than or equal to 0.1 mg/dl and positive or strong positive Amniostat-FLM results were considered mature. The results of both assays were concordant in 79% of the samples. The discordance rate was highest in GIII patients. In our experience, respiratory distress syndrome did not develop in neonate infants of diabetic women delivered after a mature lecithin result. With lecithin phosphorus concentration as the reference standard, the predictive value of a mature Amniostat-FLM result was 96.2%, whereas that of an immature result was 58.5%. Respiratory distress syndrome occurred in only two GIII neonates who were delivered within 72 hours of both immature lecithin and Amniostat-FLM results. These findings support the use of Aminostat-FLM as a screening test for fetal lung maturity in both normal and diabetic pregnancies. Additional tests will be necessary to evaluate further fetal lung maturity only if the results are negative.

Adult↗
PubMed1987

Central cholinergic systems and the P3 evoked potential.

A cognitive evoked potential, the P3, is commonly altered in dementia states but little is known of the specific neuronal generators that are the source of this potential. Event-related evoked potentials and neuropsychological testing were obtained in six normal subjects during neuropharmacological manipulation of the central cholinergic system. Scopolamine (an anticholinergic) impaired recent memory, prolonged P3 latency and decreased P3 amplitude. These abnormalities were partially reversed by physostigmine (an anticholinesterase). The results imply that the cholinergic system is involved in the generation of the P3 potential.

Adult↗
PubMed1986

Effect of maternal-fetal disorders on lung maturation. I. Diabetes mellitus.

Amniotic fluid for fetal lung maturity studies was obtained from 287 healthy and 198 diabetic women. Classes of diabetes were as follows: Class A, 111; Class B, 58; Class C, 13; Class D, 11; Class F, 4; and Class R, 1. The regression lines representing the relationship of amniotic fluid lecithin phosphorus concentration to gestational age at amniocentesis in each of the groups of diabetic patients were not statistically different from those of the control subjects. Each of the diabetic patients was then matched with a control subject of the same race, sex of newborn infant, and gestational age at amniocentesis. The regression lines of the nonhypertensive, hypertensive, and all diabetics were not different from those of their respective matched control subjects. Also there was no difference in the proportion of mature lecithin phosphorus concentrations at different weeks between diabetic and normal women. The absence of a significant influence of diabetes on fetal lung maturation is probably due to improvement in diabetic control resulting in normalization of the fetal metabolic environment.

Amniocentesis↗
PubMed1984

Regression analysis in medical research.

Even the most respected medical journals continue to publish articles containing unwarranted conclusions, which thus appear validated. This often results from the unfamiliarity of medical investigators with statistics leading to improper study design, data collection, analysis, and presentation. The increased use of multivariate analysis adds to the perplexity of medical readers not adequately prepared to judge the statistical method. This article attempts to acquaint readers with the terminology of regression analysis and how to use regression formulas.

Methods↗
PubMed1984

Relationship of unbound bilirubin concentration to reserve albumin-binding concentration for bilirubin in human neonatal plasma.

We examined the relationship of plasma unbound bilirubin concentration and reserve albumin-binding concentration for bilirubin in a sample of 545 neonates. Plasma unbound bilirubin concentration and total bilirubin-binding concentration were determined with the peroxidase assay. Contrary to published reports, we found that plasma unbound bilirubin concentration and plasma reserve albumin for bilirubin-binding concentration are highly correlated (r = -0.706; p less than 0.001) and that the relationship between these two parameters is dependent upon the total bilirubin-binding concentration. That these measured parameters correlate in the same manner as predicted for free bilirubin and free albumin by the law of mass action, suggests that these measurements may be meaningful.

Bilirubin↗
PubMed1983

Predicting the need for exchange transfusion in newborn infants. A comparison of five methods.

The need for exchange transfusion was analyzed retrospectively using several different methods (total bilirubin binding capacity, birth weight, plasma protein level, and two published charts). These predictive methods were applied to 175 jaundiced infants for whom all the data were available and to 19 infants who were actually exchanged. Most of the patients were sick, premature infants. This study demonstrates the lack of agreement among the predictive methods.

Bilirubin↗