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Biomedical subjects

W R Clarke

Publications and source records attributed to W R Clarke.

At least 109 records · Page 6Linked to original sources
PubMed1981

Load-carrying effects on the adult beagle tibia.

The response of the skeleton to carrying extra weight while exercising was studied in 30 young adult male beagles. Following 34 wk of a caged control period, 18 dogs carried lead-weighted jackets for 1 h and 15 min, 5 d/wk for 2 yr, on a carousel-type treadmill at 3.3 kph. During the next 23 wk, the load carried was gradually increased to 130% of the animal's body weight, and then maintained for 48 wk. The other 12 dogs served as controls. The dogs remained healthy and responded to exercise showing decreased skinfolds and body weight. All dogs showed increases in both tibial mineral content and width with time; but, the exercise group increased significantly more in mineral content than the controls. It is concluded that the gradual increase in bone mineral and width of the tibia is normal in the epiphyseal-closed skeleton of a young adult beagle. Also important is the fact that the intervention of exercise with added weight will increase tibial mineral content above these normal levels.

Animals↗
PubMed1981

Coronary risk factors in children.

Arteriosclerosis and its complications are the leading cause of death in American adults today. There is ample evidence to show that the pathologic process begins process begins in childhood. In addition, coronary risk factors can be identified in childhood and may be maintained to some degree into adulthood. Thus, prevention should logically begin in the childhood years. A small reduction of serum cholesterol levels in all children by a modest change in diet has the potential for reducing coronary risk. More severe dietary restriction, in some cases in conjunction with medication, is recommended for high-risk pediatric populations only. In addition, surveillance of blood pressure, avoidance of cigarette smoking, weight control, and a program of regular physical exercise are prudent recommendations for all children.

Adolescent↗
PubMed1980

Arterial platelet accumulation in experimental hypercholesterolemia.

Accumulation of arterial platelets was calculated from 51Cr radioactivity in the intima-inner media of flushed, perfuse-fixed aortas and branch vessels of cynomolgus monkeys 48 hours after labeling of the blood platelets. In normo-cholesterolemic controls the radioactivity per square centimeter of tissue was consistently higher in aortic branching sites (circumostial aorta) than in the remainder of the aorta. In monkeys given 10 and 100 days of hypercholesterolemic diet radioactivity rose in circumostial aorta in proportion to increases in streaks and in areas of Evans blue uptake. In branch artery inner wall, where intimal changes were minimal and usually absent, counts were significantly greater in animals given 100 days of hypercholesterolemic diet than in controls. After 10 days of hypercholesterolemic diet the mean radioactivity in aortic branch artery inner wall uniformly exceeded control values, but usually nonsignificantly, permitting the speculation that changes in platelet-intima interactions may occur in widespread fashion throughout the arterial tree very early in hypercholesterolemia when lesion formation is incipient or absent.

Animals↗
PubMed1979

Measurement criteria for group echocardiographic studies.

This study reports the reproducibility achieved both within an observer and between observers measuring left heart echocardiographic dimensions using standard measurement criteria in school age children. These criteria define acceptable interfaces as: 1) a single dominant line; 2) continuity at the point of measurement of at least 5 mm in length; and 3) display of specific motion characteristics for the cardiac structure to be measured. The within observer intraclass correlation coefficient for interventricular septum, diastolic dimension, systolic dimension, left ventricular posterior wall, left atrium and aorta averaged 0.94 (range 0.87--0.98). The coefficient of variation averaged 3.6% (range 2--7.5%). The least reproducible dimension was left ventricular posterior wall. The day-to-day variability within a single subject of echocardiographic determined cardiac dimensions was small for all measurements. The standard deviation of error for all variables was no more than 0.3 mm. A system using screening criteria and standardized measurement techniques can provide the degree of precision necessary to begin investigating echocardiographic differences in group studies.

Adolescent↗
PubMed1979

Increased coronary mortality in relatives of hypercholesterolemic school children: the Muscatine study.

From 2,874 school children participating in the 1971 and 1973 Muscatine Coronary Risk Factor Survey, we selected three groups of index cases for detailed family study: the HIGH group (n = 56), with cholesterol levels greater than the 95th percentile twice; the MIDDLE group (n = 46), cholesterol levels between the 5th and 95th percentile; and the LOW group (n = 46), cholesterol levels less than the 5th percentile twice. Coronary mortality determined from death certificates was increased in the young relatives (ages 30-59) of the HIGH group index cases, as follows: twofold excess in HIGH male relatives compared with the MIDDLE or LOW group (p less than 0.05); tenfold excess in the HIGH female relatives compared with the MIDDLE and LOW group combined (p less than 0.01). After correction for years at risk, there was an approximately twofold significantly-increased coronary mortality. Stroke mortality was higher, although not significantly, in the older relatives (ages greater than or equal to 60) of the HIGH index cases. Cancer mortality was not significantly different among the relatives of the three groups of index cases. This study indicates that school children's cholesterol levels cluster with those of their family members and that persistent hypercholesterolemia in children identifies families at risk for coronary artery disease.

Adolescent↗
PubMed1978

Hepatic alpha-adrenergic receptors. Identification and subcellular localization using [3H]dihydroergocryptine.

Recently, several workers have shown that adrenergic control of hepatic carbohydrate metabolism has the characteristics of an alpha-receptor-mediated process. Using the rat liver membrane preparation of Neville (Neville, D. (1968) Biochim. Biophys. Acta 154, 540-552), alpha-adrenergic receptors have been identified using the ligand [3H]dihydroergocryptine. The receptors are saturable and of high affinity. Scatchard analysis yields a KD of 1.8 nM with 1.7 +/- 0.55 pmol of sites/mg of protein. Competition of dihydroergocryptine binding with various pharmacologic agents yields the typical (alpha-adrenergic potency series: (-)-epinephrine greater than (-)-norepinephrine greater than (-)-isoproterenol. (-)-Isomers are more potent than (+)-isomers. The alpha-blocker phentolamine is 3.4 orders of magnitude more potent than the beta-blocker propranolol. To determine subcellular localization of alpha-adrenergic receptors, livers were fractionated into a crude homogenate, a 1500 X g pellet, and the purified membrane preparation used previously for binding. Specific dihydroergocryptine binding, ouabain-inhibitable (Na,K)-ATPase, and F--stimulated adenylate cyclase activities, were followed in these fractions. Specific binding was enriched, relative to that in the crude homogenate, 2.88-fold in the pellet and 6.28-fold in the membranes. Similarly, (Na,K)-ATPase acticity was enriched 2.6-fold in the pellet and 7.1-fold in the membranes while adenylate cyclase activity was enriched 2.9-fold in the pellet and 3.5-fold in the membranes. It is concluded that hepatic alpha-adrenergic receptors are likely concentrated in the plasma membranes.

Adenylyl Cyclases↗
PubMed1978

Blood pressure and its significance in childhood.

Hypertension is an important accelerator of the atherosclerotic process. Detection in childhood may be important although longitudinal data are lacking of the prognosis of blood pressure measurement in childhood through adult life. The blood pressure of children should be measured. In populations where salt intake is high, values for blood pressure increase with age. Populations who eat small quantities of salt are relatively free from hypertension. There is an epidemiological argument for limiting salt intake in children. There are few data to indicate the level of blood pressure in children which should be treated. Children's blood pressures are labile and elevated levels are sustained only in a small minority. In these secondary causes, advice should be sought. In subjects with extreme persistent hypertension drug therapy should be considered; in subjects with values of blood pressure not so extremely raised surveillance should be maintained to prevent the development of sustained hypertension.

Adolescent↗
PubMed1978

Tracking of blood lipids and blood pressures in school age children: the Muscatine study.

In four cross sectional school screens, the Muscatine Study has sampled 8,909 school children; 820 have been studied repeatedly over a six-year period. Tracking of measurements described by the relationship between repeated observations and the relationship between peer rank orderings over the six-year period has been studied. For height and weight, correlations between observations six years apart were approximately 0.74 and about 60% of children initially in the upper quintile were there again six years later. Six-year correlations were 0.65 for skinfold and 0.61 for cholesterol. Four-year correlation for fasting triglyceride was 0.40. Six-year correlations were 0.30 for casual systolic blood pressure and 0.18 for diastolic blood pressure. Peer rank orderings for both blood pressures were highly variable. Height and weight track well, and thus routine measurement of these variables are useful in identifying children with growth perturbing disorders. Cholesterol and, to a lesser degree, triglycerides also track, and a significant proportion of children with initially high values demonstrated consistently high values throughout the study period. Blood pressures do not track as well; consistently high blood pressures are unusual, thus indicating the need for repeated blood pressure measurements to identify children with persistent elevated levels. The future significance of transient blood pressure elevations has yet to be established.

Adolescent↗
PubMed1978

Normal blood pressure and the evaluation of sustained blood pressure elevation in childhood: the Muscatine study.

This study describes the seated blood pressure distributions of 6,622 predominantly white schoolchildren in Muscatine, Iowa. Subjects with seated pressures equal to or greater than the 95th percentile for age and sex or 140 mm Hg systolic or 90 mm Hg diastolic were examined on repeated occasions. Approximately 13% of subjects were found to have blood pressures at these levels when first examined, but less than 1% were found to have persistent blood pressure elevations. Of 41 subjects found to have persistent blood pressure elevations, 23 were obese with relative weights in excess of 120%. Of the 18 lean subjects, 5 had secondary hypertension and 13 were considered to have essential hypertension. Mass screening of school-age children identifies many children with transient elevation of blood pressure and few with fixed high blood pressures. Children's blood pressures should be assessed during their continuing care where pressures can be measured over a period of time to identify those with fixed blood pressure elevations.

Adolescent↗
PubMed1976

Blood pressure, salt preference, salt threshold, and relative weight.

This study was performed to observe the relationships of salt preference, salt threshold, the relative weight to blood pressure. Three groups were selected from 4,800 school children on the basis of mean blood pressure: less than or equal to fifth percentile, in the area of the 50th percentile, and greater than or equal to 95th percentile. Salt threshold was determined by titrating, on each subject's tongue, solutions ranging from 1 to 60 millimols/liter of sodium chloride. Salt preference was tested by the addition of salt by each subject to unsalted tomato juice and beef broth according to individual taste. The samples were then analyzed for sodium concentration. The coefficient of correlation for the amount of salt added to juice and broth was significant (r=0.63). There was no relationship of salt threshold to preference, nor did threshold or preference relate to blood pressure. Relative weight was related to blood pressure range being the most obese.

Adolescent↗
PubMed1976

Effect of gastric bypass on gastric secretion.

Gastric bypass as a 90 per cent gastric exclusion operation was used in 393 patients with massive obesity to limit food intake. Stomal ulcer has occurred in 1.8 per cent of such patients or one ulcer per 140 man years of observation. The studies of indwelling fundic pH and of gastric acid secretion from the excluded stomach indicate that acid secretion is reduced after gastric bypass but that the acid, unbuffered by food in the excluded stomach, results in a lowered gastrin secretion after a meal. Thus, gastric bypass in inhibitory to acid secretion in most morbidly obese patients who do not have known acid peptic disease.

Achlorhydria↗
PubMed1975

Coronary heart disease risk factors in school children: the Muscatine study.

The frequency of coronary risk factors was documented in 4,829 school children in Muscatine, Iowa, over a 14-month period of time. Serum cholesterol levels were similar for children at all ages; the mean serum cholesterol level was 182 mg/dl (SD lus or minus 29). Twenty four percent had levels larger than or equal to 200 mg/dl, 9% were larger than or equal to 220 mg/dl, 3 % were larger than or equal to 240 mg/dl, and 1% were larger than or equal to 260 mg/dl. Casual levels of serum triglyceride increased with age: the mean level was 71 mg/dl (SD plus or minus 36) at age 6 years and 108 mg/dl (SD plus or minus 45) at age 18 years. Only 15% of the children had serum triglyceride levels of 140 mg/dl or more. Blood pressure increased strikingly with age. No child between 6 and 9 years of age had blood pressures larger than or equal to 140 mm Hg systolic or larger than or equal to 90 mm Hg diastolic. In the age group 14 to 18 years, 8.9% had systolic blood pressures larger than or equal to 140 mm Hg, 12.2% had diastolic blood pressures larger than or equal to 90 mm Hg, and in 4.4% both pressures were at or above these levels. Obesity also increased through the school years. At ages 6 to 9 years, 20% had weights relative to those of the group as a whole of larger than or equal to 110%, and 5% were larger than or equal to 130%; in the 14 to 18 years age group, 25% had relative weights of larger than or equal to 110%, and 8% were larger than or equal to 130%. These data indicate that a considerable number of school-age children have risk factors which in adults are predictive of coronary heart disease.

Adolescent↗