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Biomedical subjects

I D McCarthy

Publications and source records attributed to I D McCarthy.

48 records · Page 3Linked to original sources
PubMed1986

The vascular system in bone. Its importance and relevance to clinical practice.

Experimentally proven principles on the effect of changes in bone blood flow on molecular transport in bone and on the factors that affect these changes in both flow under physiologic and pharmacologic conditions clarify the changes that occur in bone in response to certain clinical problems, such as the effect of blood flow in fracture healing. The results of using these principles in establishing a method of quantitative bone scanning are presented.

Animals↗
PubMed1985

The variation with flow-rate of the extraction of bone-seeking tracers in recirculation experiments.

Radioactive microspheres were injected into the hearts of anesthetized dogs and the reference organ technique used to determine cardiac output. Blood flow to the leg bones was then obtained from microsphere uptake. Simultaneous injections of the bone-seeking radiotracers 85Sr and, in fewer animals, 18F and 99mTc methylene diphosphonate similarly gave their clearances from the blood by bone over a period of 5 min. The ratio of clearance to flow (extraction ratio) was found to be flow-dependent, falling from near unity at low flow rates to about 0.4 at higher flow rates. The results are in general accordance with the Renkin theory of capillary permeability but do not fit exactly to the concept of a constant product of permeability and surface area, perhaps due to the heterogeneity of the model. The findings confirm conclusions based on tibial nutrient artery perfusion experiments and demonstrate that skeletal blood flow cannot be measured by the clearance of bone-seeking tracers. There were substantial differences of blood flow normalized for weight between the bones of a given animal.

Animals↗
PubMed1985

The effect of induced electric currents on bone after experimental osteotomy in sheep.

We have investigated the effect of currents induced by electromagnetic fields on the healing of the tibia of sheep after osteotomy, using objective and quantifiable criteria wherever possible. A battery-powered, induction apparatus was developed and was enclosed within the cast applied to the limb, so that the treated fractures received pulsed magnetic fields for 24 hours a day while the animals were freely mobile. In all, 13 sheep were treated and 13 were used as controls. The response was assessed by radiography of the limb and of the excised bone, by histology, including measurement of the areas of callus, fibrocallus and cortical bone, and by measurement of the uptake and extraction of bone-seeking mineral. All the bones healed and no statistically significant differences between the treated animals and the controls were discovered except (at only P less than 0.05) in the uptake of bone-seeking mineral; this increased more rapidly in treated animals over the two to three weeks after osteotomy, although at six weeks the uptake in both groups was the same.

Animals↗
PubMed1984

The early effects of sympathectomy on bone blood flow.

Several laboratories, including our own, have investigated the physiology of bone blood flow by perfusion of the tibia via the nutrient artery. Any damage caused to the nerve supply by cannulation of the artery might affect the results. The possible effect of such damage was investigated by measuring blood flow to the dog tibia using a microsphere technique, before and after sympathectomy. No effect was found and the tibial nutrient artery is therefore a suitable vessel for perfusion when estimating nutrient exchange in bone.

Animals↗
PubMed1984

Extraction of ceftazidime in bone.

The extraction of ceftazidime has been measured in bone by means of the outflow dilution technique following injection into the perfused nutrient artery of the canine tibia. The instantaneous extraction was found to be 0.71 +/- 0.18 and the net extraction was 0.55 +/- 0.25 (mean +/- S.D. n = 5). The extraction of this antibiotic is relatively high and this experiment demonstrates the fact that antibiotics leave capillaries in bone and pass into the fluid spaces where they can act on pathogenic organisms.

Animals↗
PubMed1983

The role of skeletal blood flow in determining the uptake of 99mTc-methylene diphosphonate.

The increased uptake of bone-seeking radionuclides following a fracture has been stated to be due to an increase in bone blood flow, resulting in an increase in capillary surface area available for exchange. This paper examines the relationship between the maximum instantaneous extraction of 99mTc-MDP and blood flow in normal canine tibia. The findings, consistent with the model of capillary action proposed for muscle by Renkin and Crone, are applicable to bone. There is no evidence that in normal bone the surface area available for exchange responds to an increase in bone blood flow.

Animals↗
PubMed1980

The accuracy of total body nitrogen determined by neutron activation analysis.

Experiments have been performed to validate the technique of determining total body nitrogen by measuring the induced activity of 13N produced by the reaction of 14 MeV neutrons with nitrogen. Firstly, the accuracy of determining the counts due to nitrogen was studied by measuring the activities of the positron-emitting nuclides of C, Cl, K, P, and O, as well as N, produced by the irradiation of anthropomorphic phantoms with a surface neutron dose equivalent of 0.5 mSv (50 mrem). Secondly, the effect of variation of spatial sensitivity was studied by measuring the activation and detection efficiencies of small samples at many positions within an anthropomorphic phantom, and also by comparing the known amounts of nitrogen within a new type of phantom in which the elements are fixed, with the amounts measured using a calibration based on experiments with a Bush phantom in which the elements are freely diffusible within each phantom part. There was a maximum difference of only 4% between the measured and known amounts of nitrogen. It is therefore concluded that this technique provides a simple and accurate way of measuring total body nitrogen.

Activation Analysis↗
PubMed1979

Assessment of protein nutrition in surgical patients--the value of anthropometrics.

In order to evaluate the reliability of anthropometry in assessing protein stores we have compared, in 10 normal adults and 82 surgical patients with varying degrees of weight loss, measurements of weight/height, arm circumference, arm muscle circumference, and arm muscle area with direct measurements of body nitrogen using in vivo neutron activation analysis. Anthropometry is reliable for the assessment of protein nutrition in groups of patients (for 100 patients 95% confidence limits are +/- 30 g nitrogen) but the magnitude of variance shown makes it inappropriate for assessing the individual as a single measurement (95% confidence limits are +/- 300 g nitrogen). Repeat measurements were made after 2 weeks on 35 patients and there was no correlation between changes in body nitrogen and changes in the anthropometric measurements. Anthropometry is not reliable in following changes in body nitrogen in individual patients over short periods of time.

Adult↗
PubMed1978

A new method for the rapid measurement of body composition in critically ill surgical patients.

A rapid, non-invasive method for the measurement of absolute amounts of fat, protein, minerals and water in the body has been developed which is applicable to very ill patients. The patient is weighed and skinfold thickness is measured with calipers. The body contents of potassium, nitrogen, sodium, chlorine, calcium and phosphorus are measured in a whole-body radiation counter after irradiation with fast neutrons. From these values absolute amounts of body fat, protein, minerals and water are calculated. The procedure, which takes about 40 min, is carried out with the patient lying supine on a couch. The errors in the absolute measurement of the components expressed as percentages of body weight are: for fat, 4.5 per cent; for protein, 1.6 per cent; for minerals, 0.8 per cent; and for water, 4.9 per cent. The radiation dose is equivalent to that of a chest radiograph (50 mrem). We have used this technique (a) to determine the tissue composition of the weight lost in 16 patients after excision of the rectum; (b) to establish that the weight gained by 16 patients receiving intravenous nutrition was mainly water; and (c) to show that in 10 patients who received a simple solution of amino acids for 2 weeks after rectal excision body protein was preserved as efficiently as in 10 similar patients who received a full course of intravenous nutrition. This is the first time body weights of living persons have been broken down into terms of fat, protein, minerals and water, and the method should help to solve a number of metabolic and nutritional problems in clinical surgery.

Adipose Tissue↗
PubMedDate not supplied

Changes in body weight and body protein with intravenous nutrition.

Body weight, protein, fat and water were measured before and after intravenous nutrition in 20 surgical patients. The group included both young and old patients who were suffering from a wide variety of catabolic illnesses and the period of intravenous feeding ranged from 11 to 40 days. Eight of the patients were able to take small amounts of food orally. During the period of intravenous nutrition ten patients gained significant weight although only two of these gained significant protein. Most of the weight gain was due to an increase of water. There was also a gain of water in the patients who lost weight; this water gain occurred in small daily increments over the course of treatment. It is concluded that weight gain can occur without protein gain in patients who are being fed intravenously and that body weight is not a reliable guide to changes in body protein or fat in critically ill patients receiving intravenous nutrition.

Adult↗