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Biomedical subjects

J E Jenkins

Publications and source records attributed to J E Jenkins.

10 recordsLinked to original sources
PubMed1998

The relationship of family structure to adolescent drug use, peer affiliation, and perception of peer acceptance of drug use.

This study examined the relationship of family structure to adolescent gateway drug use and peer-related factors. The sample consisted of 2,121 randomly selected students in grades 8, 10, and 12 from seventeen school districts in northeastern Ohio. Students were administered a self-report instrument containing items measuring drug use and psychosocial variables. For purposes of analysis, the dependent variables included frequency of use of five gateway drugs, degree of affiliation with drug-using peers, and perceptions of peer acceptance of drug use. Comparison groups included single-parent (both mother- and father-headed), stepparent, and intact families. Analyses were conducted separately by grade level. Significant differences were found between groups on the drug-use variables at grades 8 and 10, with adolescents from intact families reporting less frequent drug use, fewer drug-using friends, and perceptions of more peer disapproval of drug use. Interestingly, there were several statistically significant group differences on perceptions of peer acceptance of drug use and the number of drug-using friends at the 8th-grade level. The largest differences were found between the single-parent (father-headed) and intact groups, with adolescents from father-headed families showing more frequent beer and liquor consumption at the 10th-grade level.

Adolescent↗
PubMed1996

Moving beyond a project's implementation phase.

Often, much time is spent planning a project's stages. While essential, this emphasis often leaves little energy for the implementation phase. Following three detailed stages helps illustrate points, defuse conflict and find common ground.

Humans↗
PubMed1996

The influence of peer affiliation and student activities on adolescent drug involvement.

This study examined the importance of students' academic performance level and extracurricular activities as predictors of drug involvement relative to peer influence. Social development theory provided the theoretical rational for the study. Data were obtained from 2,229 randomly selected students in the eighth, tenth, and twelfth grades from seventeen school districts in northeastern Ohio. At all three grade levels, involvement in extracurricular activities and academic level were significantly correlated with students' gateway and hard drug use. Consistent with prior research, the strongest correlate of gateway and hard drug use across all grade levels was affiliation with drug-using friends. Having a job after school was marginally related to self-reported gateway drug use at grade level ten. Multiple regression analysis revealed that extracurricular involvement and academic performance level make small, but unique contributions to the prediction of adolescents' gateway drug use beyond affiliation with drug-using peers at all three grade levels. The findings of this study suggest that students' academic performance and extracurricular involvements are significantly related to adolescent gateway and hard drug use, but have less predictive significance relative to peer relationships.

Achievement↗
PubMed1993

Submaximal, aerobic exercise training exacerbates the cardiomyopathy of postweanling Cu-depleted rats.

To determine the dual effect of exercise training and copper depletion on myocardial function and ultrastructure, postweanling rats were either trained or sedentary while fed copper-adequate or copper-deficient diets for 8 wk. Rats developed characteristic myocardial subcellular degeneration and increased cardiac mitochondrial volume density when copper depleted, despite lack of overt cardiac hypertrophy, hypertension, or anemia. Training combined with copper depletion induced mild left ventricular hypertrophy. Basal laminae appeared fractionated in areas at capillary-myocyte interface, with focal pericapillary and interstitial collagen accumulation, whereas overt fibrosis was absent or minimal. Electrocardiograms revealed increased QRS wave and QT duration and notching of QRS complex with copper depletion, consistent with intraventricular conductance disturbances. The oxidative capacity of soleus muscle increased with training in copper-adequate rats, but was reduced with progressive copper depletion. These data suggest that copper depletion and training are synergistic in effecting focal accumulation of collagen, with deleterious effect on exercise capacity.

Aerobiosis↗
PubMed1993

Diets containing corn oil, coconut oil and cholesterol alter ventricular hypertrophy, dilatation and function in hearts of rats fed copper-deficient diets.

Cardiac hypertrophy and function were evaluated in rats fed diets containing deficient, marginal or adequate levels of copper. The fat concentration of the diets was either 10 g/100 g corn oil, 10 g/100 g coconut oil or 10 g/100 g coconut oil + 1 g/100 g added cholesterol. Left ventricular (LV) wall thickening of hearts in rats fed copper-deficient diets was characterized by greater (P < 0.05) LV free wall width, regardless of dietary fat type, and greater intraventricular septum width in the rats fed corn oil. Rats fed the copper-deficient diet with coconut oil + cholesterol had LV chamber volumes that were twofold larger than those of rats fed the copper-deficient diet with coconut oil or corn oil. Copper deficiency reduced LV chamber volume only in rats fed coconut oil + cholesterol. Cardiac LV end diastolic pressure in rats fed copper-deficient diets was twofold larger than in copper-adequate and copper-marginal groups fed corn oil or coconut oil. Hearts from rats fed the copper-deficient diet with corn oil compared with those from rats fed the copper-deficient diet with coconut oil + cholesterol had greater right ventricular (RV) and LV end diastolic pressures, LV pressures and LV and RV maximal rates of positive pressure development. Our data suggest that cardiac adaptations in rats fed copper-deficient diets are influenced by dietary fat type: 1) hearts of rats fed the copper-deficient diet with corn oil were concentrically hypertrophied, whereas cardiac contractility was maintained in the presence of high preload; 2) preload and contractility in hearts of coconut oil-fed rats was greater than cardiac response to cholesterol addition to the coconut oil diet; 3) hearts in copper-deficient rats fed coconut oil + cholesterol exhibited eccentric hypertrophy and ventricular dysfunction.

Animals↗
PubMed1993

A unified perspective on copper deficiency and cardiomyopathy.

Dietary copper restriction in rats results in cardiomyopathy. In rats fed copper-restricted diets from weaning for 5 to 8 weeks, a concentric hypertrophy is apparent, whereas postweaning copper restriction does produce cardiomyopathy without apparent hypertrophy. Both sets of circumstances appear to affect the integrity of the basal laminae of cardiac myocytes and capillaries. In rats fed copper-restricted diets from weaning, decreases in cytochrome c oxidase are related not only to copper's role as a coenzyme, but also to a marked decrease in the nuclear encoded subunits of the enzyme complex. Decreased levels of the delta-subunit of ATP synthase have been observed. However, such aberrations in mitochondrial enzymes, as well as morphologic alterations, apparently do not affect cardiac levels of ATP. This review suggests mechanisms of cardiac adaptation and initiation factors leading to cardiac hypertrophy. We present a hypothetical working model explaining the events leading to cardiac failure in the copper-deficient rat heart based on the present body of knowledge, and compare the pathology with other models of cardiomyopathies.

Animals↗
PubMed1992

Effects of enalapril and clonidine on glomerular structure, function, and atrial natriuretic peptide receptors in SHHF/Mcc-cp rats.

Seven-month-old, lean male SHHF/Mcc-cp rats, a model of spontaneous hypertension, progressive renal dysfunction, and congestive heart failure (CHF), were treated with either clonidine (CL) or enalapril (EN) or received no treatment (CON) for 20 weeks. CL significantly decreased systolic blood pressure (SBP), kidney weights, and severity of renal lesions as compared with untreated CON. EN produced a decrease in SBP comparable to that in CL. Kidney weights and severity of renal histologic changes in the EN group were intermediate between those of the CL and CON groups. Despite similar plasma atrial natriuretic peptide (ANP) concentrations, CL treatment resulted in a significant increase in the density of guanylate cyclase-linked glomerular ANP receptors, whereas EN treatment resulted in a significant decrease in the total number of ANP receptors and in the number of nonguanylate cyclase-linked receptors and an increase in overall binding affinity. These findings demonstrate that antihypertensive agents will slow progression of renal injury in SHHF/Mcc-cp rats and that CL is more effective than EN in alleviating progressive kidney damage in this model. Furthermore, different classes of antihypertensive drugs may alter the density or ratio of biologically active and clearance ANP receptor sites in the glomerulus.

Animals↗