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K J Ellis

Publications and source records attributed to K J Ellis.

At least 127 records · Page 7Linked to original sources
PubMed1978

What happens when data are fitted to the wrong equation?

In many problems of data analysis it is necessary to fit the data to a mathematical equation. Random errors of measurement will be responsible for deviations between the data and the equation, but superimposed on this there may be deviations that result from the equation being an inadequate description of the system from which the data were obtained. Plots of the residual (i.e. the difference between the experimental and calculated values of the dependent variable) against each of the experimental variables have been previously used to detect a misfit between the data and the equation. In the present paper, we show that the shape of the residual plots may be used as a guide in choosing a more appropriate equation. In addition, residual plots give useful information on the error structure of the data, and hence the weighting factors that should be used in the analysis.

Enzymes↗
PubMed1978

Mercury contamination during pH measurement and its effect on creatine kinase activity.

Inhibition of activity of the enzyme creatine kinase occurs when small volumes of assay mixtures have their pH measured using a combination pH electrode prior to addition of the enzyme. This inhibition can be attributed to diffusion of ionic mercury from the calomel reference electrode through the saturated potassium chloride salt bridge and the ground glass-liquid junction to the test solution. The concentration of mercury accumulating in a solution by this process can be sufficient to affect the activity of an enzyme, and EDTA cannot be used successfully to scavenge mercury ion and avoid the inhibition.

Animals↗
PubMed1978

Studies of whole-body retention and clearance of inhaled noble gases.

The in vivo measurements of 127Xe and 79Kr clearance from the whole body indicate five components, with biologic half-times ranging from 13 sec to 17.04 h. The slowest component correlated highly with percent total-body fat, the half-time varying between 7.59 and 17.04 for xenon and between 4.20 and 9.62 h for krypton. The long-term retention was localized to regions of high fat content as determined by the coincidence mode of the whole-body counter and images obtained with the scintillation camera. The estimated dose based on the retention data of this study would indicate increased doses to body fat and gonads as compared with those previously calculated. These increased doses are due to the longer retention of noble gases in fat. After 10-min inhalations of a mixture of 127Xe and air and 79Kr and air, approximately one third of the total 127Xe and one fifth of the total 79Kr were transferred to the body tissues, extrapolated back to the start of gas washout. Of this amount, approximately 13% of the 127Xe and approximately 9% of the 79Kr were associated with the slowest component.

Adipose Tissue↗
PubMed1977

Comparative skeletal mass and radial bone mineral content in black and white women.

The age-related changes in both skeletal mass and muscle mass were directly measured in normal black women ages 30-80 yr. The levels of total-body calcium (TBCa) were determined with the use of in vivo neutron activation. The muscle mass was measured by wholebody counting of 40K. In the same population, the bone mineral content of the radius was measured using a photon absorptiometric technique. Although there was no significant difference in stature, black women had a greater skeletal mass and bone mineral content of the radius than age-matched white female subjects. When the TBCa values were normalized for body size (i.e., corrected for height and lean body mass), the TBCa was still higher for the black women but not as high as the absolute TBCa values. Clearly, it is the larger muscle mass (as reflected by the 40K measure) in relation to weight and height that accounts for this difference. The lower prevalence of fracture and osteoporosis observed in black women relative to white women is due in part to this greater quantity of skeleton. American black women with a higher bone density (i.e., skeletal mass) maintain mechanical integrity of the skeleton longer than individuals with a lower bone density. It is suggested that the larger muscle mass in black women is, in part, a determinant of their increased skeletal mass and is partly responsible for their apparent resistance to osteoporosis and fracture of the skeleton.

Adult↗
PubMed1977

A facility for in vivo measurement of kidney and liver cadmium by neutron capture prompt gamma ray analysis.

An in vivo method for the determination of Cd levels in human kidney and liver has been developed. The method allows detection of absolute quantities of Cd in the left kidney and Cd concentration in the liver. The limit of detection of cadmium is 2.5 mg for the left kidney and 1.8 microgram/g (wet weight) for the liver, for a localized dose of 670 mrem. The effects of patient positioning, organ geometry and liver-kidney interference on the measurement have been investigated using an Alderson phantom.

Cadmium↗
PubMed1977

Body elemental composition: comparison between black and white adults.

The age-related changes in body chemical composition were measured in a normal black population ranging in age from 30 to 80 yr. The levels of total-body calcium, phosphorus, sodium, and chlorine were measured by in vivo neutron activation. In addition, the lean body mass (total-body potassium) was measured by whole-body counting of 40K. These data were compared with the same data obtained on a normal white population in a previous study. Although there were no significant differences in the height of the two groups, black men and women had significantly higher total-body calcium, phosphorus, sodium, chlorine, and potassium than the sex-and age-matched white population. The increased levels of total-body calcium and potassium when normalized for the weight and height of the subjects were reduced but still remained significantly higher than those of the white population. Clearly specific reference standards for skeletal and muscle mass as well as for sodium and chlorine need to be established for black populations.

Adult↗
PubMed1977

Distribution of calcium in the rat due to chronic renal failure.

During the 12 weeks following 5/6 nephrectomy in rats with moderate uremia (creatinine 0.7-1.2 mg/100 ml, BUN 53-89 mg/100 ml), no significant increases in total soft tissue calcification were observed. The calcium concentration of skeletal muscle remained unchanged at 4, 8, and 12 weeks after surgery. A slight but not significant increase in skin calcium was found. However, a significant decrease in cardiac calcium was found for the uremic animals. Total body calcium as determined by neutron activation analysis was significantly lower in the uremic rat when compared with the age-matched animal. However, when normalized for body weight, the total calcium content in uremic rats did not differ from the controls. Similar findings were observed for the absolute calcium content of the tibia and when normalized for weight. Furthermore, a highly significant linear relationship (r = 0.92, p less than 0.001) was established between absolute levels of total body calcium and tibia calcium which was identical for control and uremic groups.

Animals↗
PubMed1977

Whole-body retention of radioxenon.

The total-body retention of 127Xe, and its variation with time following short, nonequilibrium periods of inhalation, were measured in vivo so as to refine dosimetry calculations. Radioactivity in the chest region and in the recirculating xenon-air mixture was measured continuously during re-breathing of the gas mixture and in the first 5 min of the immediate gas-washout period using a scintillation camera and shielded NaI detector, respectively. Subjects were then counted in a whole-body counter at varying time intervals until background levels were reached, usually in 72 hr. Five components of Xe clearance from the entire body were measured; they had biologic half-times of 21.7+/-12.4 sec, 3.05+/-1.72 min, 0.04+/-0.11 hr, and 2.71+/-0.87 hr, and a long-term component varied between 7.59 and 17.04 hr. The half-time of the last component correlated highly with the percent of total-body fat. After 10-min inhalations of the xenon-air mixture, approximately one-third of the total xenon was transferred to the body tissues, extrapolated back to the start of gas washout. Of this amount, 13% was associated with the slowest component of clearance.

Adipose Tissue↗
PubMed1977

Thallium-201 for medical use. Part 3: Human distribution and physical imaging properties.

Studies were undertaken to determine the biologic distribution of thallium-201 in man. The disappearance from the blood is extremely rapid and intracellular deposition is nearly immediate. The biologic half-time of thallium was measured by both the Brookhaven whole-body counter and the Donner whole-body scanner, with excellent agreement. The effective whole-body half-time of thallium-201 is about 57 hr. Concentration of activity was seen in the heart, kidneys, large bowel, and thyroid. The whole-body radiation dose is 0.21 rads/mCi.

Animals↗
PubMed1976

Total body sodium and chlorine in normal adults.

Absolute levels of total body sodium (TBNa) and total body chlorine (TBCl) were determined in 81 normal adults (39 males, 42 females) by means of total body neutron activation analysis (TBNAA). The ages of the subjects ranged from 30 to 90 yr. The mean values for both TBNa and TBCl remained relatively constant throughout the age span studied for males, but decreased slightly for females over 60 yr of age. In order for the absolute measurements of Na and Cl to be of clinical value, the values must be compared to a predicted value based on the sex and body habitus of the individual. Normalization of TBNa values relative to body dimensions (weight, height, body surface area) were evaluated. In addition, TBNa was related to total body calcium (TBCa), which reflects skeletal mass, and TBK, which reflects muscle, or lean body mass. Normalization in terms of a linear combination of the TBCa and TBK was found to be the most satisfactory of all those studied. Sodium excess, NaES, defined as the amount of body sodium (mEq) in excess of body chlorine (mEq) was determined. Sodium excess correlated well with total body calcium. Values for total body sodium and chlorine obtained in the present study were compared with values previously reported in the literature.

Adult↗
PubMed1976

Changes in body chemical composition with age measured by total-body neutron activation.

Total-body levels of calcium and phosphorus (reflecting skeletal mass) and total-body levels of potassium (reflecting muscle mass) were measured by neutron activation analysis in 39 men and 40 women ages 30-90 yr. In order to intercompare the total body calcium (TBCa) values in a heterogeneous population, such as this, it was necessary to normalize the data for skeletal size. The normalization consisted of dividing the absolute calcium level by the predicted calcium level for each individual matched to a set of critical parameters. The parameter used in the computation of normal values were age, sex, muscle mass, i.e., total body potassium (TBK) and height. For the calcium data of the women, it was necessary to add an age correction factor after the age of 55 yr. The calcium ratio(mean ratio of the predicted to measured TBCa) in men was 1.000 +/- 7.8% and in women 0.996 +/- 7.1%. The TBCa of normal males and females can thus be predicted to +/- 13% (at the 90% confidence level). An exception to this was found in males (70-90 yr) who exhibited a mean calcium ratio greater than 1.13. The derivative of TBCa with time was determined for this population of men and women by taking into account the dependency of calcium on three time dependent variables, height, TBK, and an explicit age correction factor in the case of the women. The mean rate of loss of TBCa in women was 0.37% and 1.1% per year before and after menopause (50 yr). In the males, the average rate of loss of TBCa was 0.7% per year after 50 yr of age. The pattern of total body phosphorus (TBP) loss with age paralleled that of TBCa as the ratio of TBP/TBCa was rather constant with age. The constancy of the ratio suggests that the mineral composition of bone does not change significantly with age. The rate of loss of TBK with age was also related directly to that of TBCa. The mean ratio of TBK/TBCa was 9.9 in females and 8.0 in males and this ratio remained relatively constant from 30-70 yr. Thus, the mechanism responsible for the loss of bone with age, whether nutritional deficiency or decreased gonadal function and physical activity may also be responsible for the loss of muscle mass with age.

Adult↗
PubMed1976

Effect of aging on bone mass in adult women.

Total-body calcium was measured in 40 adult women by total-body neutron activation analysis (TBNAA). Procedures for normalizing the absolute calcium measurements for the parameters of size and age were developed in order to effect a direct comparison of women of age 30-78 yr. The normal total-body calcium (TBCa) for an individual can be predicted by a formula developed in the present study to within +/- 11% (1.62 SD) at the 90% confidence level. The TBCa loss can be characterized by two components: one with a slower rate, 0.37%/yr, and the other with a faster rate, 1.08%/yr. The latter, a more rapid postmenopausal loss, started at 50-60 yr and was superimposed on the slower rate of loss that started in the fourth decade and continued throughout life. The bone mineral content (BMC) of the radius, measured by the absorptiometric technique, correlated well with the total-body skeletal calcium in this population (r = 0.813, P less than .001). However, for intercomparisons of the BMC values of individuals, normalization of the BMC values for size and age is required, as it is for the TBCa data. Normalization provided by the ratio of BMC to radius width is not adequate for comparative studies.

Adult↗