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Biomedical subjects

K J Ellis

Publications and source records attributed to K J Ellis.

161 records · Page 9Linked to original sources
PubMedDate not supplied

Reference man and woman more fully characterized. Variations on the basis of body size, age, sex, and race.

Total body neutron activation analysis, prompt-gamma neutron activation analysis, and whole body counting have been used to determine the elemental composition of the human body. The total body elements measured were potassium, nitrogen, calcium, sodium, chlorine, and phosphorus. Total body water was also determined by the dilution principle using tritiated water. Observations were made in an adult US population that totaled 1374 and ranged in age from 20 to 90 yr. The dataset for the white population consisted of 175 males and 1134 females observations; for the black population, it consisted of 30 male and 35 female observations. The variation in the elemental composition of both males and females in any 5-yr age group was large and ranged up to 20% (SD). Age-, race-, sex-, and size-specific differences were evident. When equations were developed that predicted the elemental composition of the adult on the basis of age, weight, and height, the variation in the age groups was reduced approximately in half. Age-specific mean values for the 20- to 29-yr-old white population were also compared with values for the International Commission on Radiological Protection (ICRP)-23 Reference Man. The "average" young adult male was larger than Reference Man; the in vivo data also indicated a larger skeletal mass, more lean tissues and body water, but lower body sodium. When in vivo prediction equations were used to adjust for size differences, good agreement was found between the expected values and those for Reference Man. The ICRP-23 does not contain elemental data for Reference Woman; therefore, the in vivo data in the present study provide the first estimates of body composition for Reference Woman.

Adult↗
PubMedDate not supplied

Bioelectrical impedance methods in clinical research: a follow-up to the NIH Technology Assessment Conference.

In 1994, the National Institutes of Health (NIH) convened a Technology Assessment Conference "to provide physicians with a responsible assessment of bioelectrical impedance analysis (BIA) technology for body composition measurement." In 1997, Serono Symposia USA, Inc., organized an invited panel of scientists and clinicians, with extensive research and clinical experience with BIA, to provide an update. Panel members presented reviews based on their own work and published studies for the intervening years. Updates were provided on the single and multifrequency BIA methods and models; continued clinical research experiences; efforts toward establishing population reference norms; and the feasibility of establishing guidelines for potential diagnostic use of BIA in a clinical setting. This report provides a summary of the panel's findings including a consensus on several technical and clinical issues related to the research use of BIA, and those areas that are still in need of additional study.

Body Composition↗
PubMedDate not supplied

Whole-body phantoms with anthropomorphic-shaped skeletons for evaluation of dual-energy X-ray absorptiometry measurements.

We have developed a set of four whole-body phantoms with anthropometric-shaped skeletons constructed of CaHPO4-doped epoxy resin, to simulate average body sizes of children at ages 4, 10, 15, and 18. Each phantom was measured on a Hologic QDR-2000 instrument with and without a set of polyethylene overlays to simulate excess body fat, and with and without a 0.6% NaCl/water mixture to simulate differences in lean tissue composition. Precision of total body BMC, based on 4 scans over 2 wk, were 0.5%-1.8%, and were correlated (r2 = 0.999, p < 0.001) with the chemical Ca content of the simulated skeleton. The addition of overlays to the phantoms to simulate increased body size and/or body fat resulted in small but significant increases in the measured values for BMC and bone area, but not that of BMD.

Absorptiometry, Photon↗
PubMedDate not supplied

Effects of elevated lead and cadmium burdens on renal function and calcium metabolism.

To assess the pathophysiologic significance of increased body burdens of lead and cadmium, detailed renal function studies and evaluation of calcium, phosphorus, and vitamin D metabolism were carried out in 38 industrial workers exposed to lead and cadmium for 11 to 37 yr. Body burden of lead, as assessed by x-ray fluorescence measurement of tibia lead content, was elevated in 58% of the men and, when assessed by excretion of lead after Ca-EDTA infusion, was elevated in 36%. Liver or kidney cadmium burden, as assessed by neutron activation analysis, was elevated in 31%. Creatinine clearance was normal in all workers. One worker was hyperuricemic and two were proteinuric; three had increased beta 2 microglobulin excretion and one had diminished urinary acidifying ability. Maximal urinary concentrating ability was abnormal in a significant fraction, i.e., 52% of the men. Individuals with a high lead burden had a slight decrease in mean serum phosphorus but no accompanying phosphaturia. There was no abnormality of serum calcium. Twenty-two percent of subjects were hypercalciuric and two had low vitamin D levels, but these abnormalities bore no relation to heavy metal burden. In this carefully characterized group of men with chronic lead and calcium exposure, definite, if subclinical, effects on renal function and serum phosphorus but not calcium or vitamin D metabolism were demonstrable.

Adult↗
PubMedDate not supplied

Body composition of the preterm infant.

The body composition of 23 infants was examined at postmortem. All infants were live births and lived from 1 to 192 days. Their body weights at birth ranged from 480 to 3280 g; gestational ages ranged from 24 to 42 weeks. Total body composition was determined using the nondestructive in-situ procedures of 40K counting and neutron activation analysis. The absolute amounts of K, Ca, P, Na, and Cl were measured. Although body Cl was in general agreement with estimates for the reference fetus model, body K and Na values were lower. Body Ca content was higher than the reference fetus at body weights above 2 kg, yet body P levels agreed with the reference fetus. Furthermore, those infants whose survival was brief had reduced body K, an index of body cell mass. All elements except body Cl were linearly related to fat-free mass (FFM). The correlations with gestational age were non-significant when the variation in elemental content was accounted for by FFM or body weight. The two preterm infants who survived for more than 10 weeks had significantly reduced bone growth as shown by their Ca and P deficiences.

Adipose Tissue↗
PubMedDate not supplied

Silicon measurement in a lung phantom by neutron inelastic scattering.

A study was made to assess the feasibility of determining the silicon level in human lungs in vivo by measuring the gamma rays arising from the neutron inelastic scattering reaction 28Si(n, n' gamma)28Si. Neutron energies in the range 5--8 MeV represent the best compromise between the conflicting requirements of high energy for good detection statistics and low energy to minimize the dose to the subject. The sensitivity of measurement was enhanced by pulsing the neutron beam and counting only during the period of bombardment. This effectively reduced the background counts emanating from thermal neutron reactions in the phantom and from the fast neutron reaction 31P(n, alpha)28 A1. In measurements with an anthropomorphic phantom, no interference peaks from other prompt inelastic scattering reactions were observed. With one Ge(Li) detector of 19% relative efficiency, a detection limit of 0.6 g of silicon per 10 mSv was obtained. On this basis, it is estimated that six Ge(Li) detector of 25% efficiency each would be capable of measuring 0.15 g of silicon in the lungs, the average level found in nonoccupationally exposed adults.U

Humans↗
PubMedDate not supplied

Feasibility of noninvasive analysis of lead in the human tibia by soft x-ray fluorescence.

A postmortem study was conducted to assess the feasibility of measuring bone lead concentrations noninvasively in vivo. Characteristic L x rays were induced with an external source of 125I in the superficial tibial cortex of the intact legs of six adults who had no history of occupational exposure to lead. Tibial lead concentrations in the same bones subsequently determined by flameless atomic absorption spectroscopy varied from 15 to 35 micrograms Pb/g wet weight. The upper limit for the modern normal range of lead in the bone is about 25 mg Pb/g wet tissue. The linear correlation coefficient (r) between the measurements made with x-ray fluorescence and lead concentration by absorption spectroscopy was 0.90. Radiation doses of 10 mGy (1 rad) to 1 cm2 of skin, with associated doses to the marrow of adjacent bone of about 0.6 mGy (60 mrad), yielded net lead fluorescence signals ranging from one to seven times the standard deviation of background.

Humans↗
PubMedDate not supplied

In vivo measurement of lithium in the body by a neutron activation analysis technique.

A technique has been developed for in vivo determination of lithium content in the head (and potentially in the whole body and in selected organs) of patients undergoing lithium therapy. It is based on the measurement of tritium induced by the 6Li(n,alpha)T nuclear reaction after neutron irradiation of the body. The fraction of tritium exhaled in the expired air in the form of HT is collected, separated from the other gases, and counted in a high-sensitivity beta counter. The feasibility of the technique was demonstrated by measurements of lithium in the head of a sheep and in the whole body of rats, following the administration of 6LiCl (enriched 6Li isotope, 95.46% abundancy). The precision of the technique is acceptable for clinical applications based on a maximum propagated error of 8.4%. The sensitivity is 1 count/d (from T activity) per 10 mSv (total dose) and 1 microgram of 6Li. This indicates that studies on patients under 6Li treatment can be performed successfully with a radiation dose to the head of 1-2 mSv.

Animals↗