PubMed Health⌕ Search

Biomedical subjects

R Hesp

Publications and source records attributed to R Hesp.

18 recordsLinked to original sources
PubMed1979

A comparison of chromium sesquioxide and [51Cr]chromic chloride as inert markers in calcium balance studies.

1. Chromium sesquioxide (Cr2O3; 1.5 g/day) and [51Cr]chromic chloride [51CrCl3 (0.3 muCi/day)] were compared as continuously administered non-absorbed markers for the correction of faecal recoveries in 14 calcium balance studies each lasting at least 18 days. 2. The mean recoveries of each, 98.4% for Cr2O3 and 101.9% for 51CrCl3, were not significantly different from 100%. 3. The two markers reduced the uncertainity in a typical 3 x 6 day calcium balance study to a similar extent (SD = 1.4 mmol/day for Cr2O3 and SD = 1.5 mmol/day for 51CrCl3. 4. 51CrCl3 is a convenient and satisfactorily alternative to Cr2O3 when the laboratory hazards associated with estimating the latter cannot easily be eliminated.

Calcium↗
PubMed1979

Fractured neck of femur in the elderly: an attempt to identify patients at risk.

1. During a 15-month period, 110 elderly patients admitted with fractured neck of femur were studied in comparison with 72 elderly control patients undergoing elective surgery admitted over the same period to the same orthopaedic wards. 2. A striking finding was the marked similarity of all variables measured in the fracture and control groups. The principal differences between the two populations were that the fracture patients had a lower mean forearm bone mineral content, and that their serum concentrations of albumin, globulin and phosphate were reduced. 3. Neither measurements of radioisotopic calcium absorption, nor those of the serum concentrations of calcium, 25-hydroxy-vitamin D3 nor alkaline phosphatase provided satisfactory discrimination between the groups. 4. Several indices were devised, based on linear combinations of the test results obtained, in an attempt to predict the liability to future fractures of patients being considered for prophylactic therapy with oestrogens or other drugs. However, further work is required to define an index of improved predictive power and to evaluate it prospectively.

Aged↗
PubMed1979

A new method for measuring the body density of obese adults.

1. A new apparatus is described with which it is possible to measure the volume (and hence density) of obese patients without requiring them to immerse totally in water. Replicate measurements of subjects with 6, 23 and 38 kg body fat had a standard deviation not greater than 0.3 kg fat. 2. In nineteen obese women body fat was measured by density, total body water, and total body potassium at the beginning, and again at the end, of a period of 3--4 weeks on a reducing diet, during which they lost 5.43 (SD 1.83) kg in weight. The composition of weight loss was also estimated both by energy balance and nitrogen balance during the interval between the two measurements of body composition. 3. The estimates of fat content of the ninetten women at the start of the balance period were 45.63 (SD 14.50) kg by density, 48.07 (SD 13.88) kg by K and 47.09 (SD 13.85) kg by water. The correlation coefficient between the density and K estimate was 0.949, and for the density and water estimate it was 0.971. 4. It is concluded that measurement of density by the new method provides a convenient method for estimating body fatness, and change in fat content, which compares favourably with estimates based on total body water or total body K. However, these methods cannot be used to provide an accurate estimate of the composition of a small weight loss in an individual since deviations up to 4 kg fat occur between fat loss based on change in density and those based on the more reliable (but more tedious) energy balance method.

Adipose Tissue↗
PubMed1979

Resting metabolic rate, weight, surface area and body composition in obese women.

Resting metabolic rate was measured in 22 women with varying degrees of obesity. Body composition was estimated from total body potassium and from total body water, and creatinine excretion in urine was measured over a period of three weeks while the patients were on a creatinine and creatine-free reducing diet. Resting metabolic rate was highly significantly correlated with body weight, surface area, creatinine excretion and lean body mass calculated either from potassium or water measurements (P less than 0.001). Correlation with adipose tissue was less strong, and when multiple regression of both fat and lean on metabolic rate was performed, the relationship was seen to depend mostly on the mass of lean rather than adipose tissue. In obese people the water content of fat-free tissue is greater than that in normal subjects, so it is not valid to assume that fat content can be calculated accurately from a measurement of total body water.

Adipose Tissue↗
PubMed1978

The feasibility of using a liquid-filled Cerenkov counter of gamma-ray counting of large samples.

The feasibility of detecting gamma rays with energies below 1.5 MeV by means of a large-volume liquid-filled Cerenkov counter has been examined, together with the characteristics and limitations of an experimental counter. Various liquids (water, glycerol, sodium iodide solution; and glycerol plus a wavelength shifter) were investigated as possible Cerenkov media. A rectangular counter containing 1.2 liters of the latter medium could detect 10 nCi of 58Co or 59Fe at 10 cm in a counting time of 1000 s.

Gamma Rays↗
PubMed1976

A model-independent comparison of the rates of uptake and short term retention of 47Ca and 85Sr by the skeleton.

1. A method has been devised for comparing the impulse response functions of the skeleton for two or more boneseeking tracers, and for estimating the contribution made by measurement errors to the differences between any pair of impulse response functions. 2. Comparisons were made between the calculated impulse response functions for 47Ca and 85Sr obtained in simultaneous double tracer studies in sixteen subjects. Collectively the differences between the 47Ca and 85Sr functions could be accounted for entirely by measurement errors. 3. Because the calculation of an impulse response function requires fewer a priori assumptions than other forms of mathematical analysis, and automatically corrects for differences induced by recycling of tracer and non-identical rates of excretory plasma clearance of tracer, it is concluded that differences shown in previous in vivo studies between the fluxes of Ca and Sr into bone can be fully accounted for by undetermined oversimplifications in the various mathematical models used to analyse the results of those studies. 85Sr is therefore an adequate tracer for bone calcium in most in vivo studies.

Bone and Bones↗
PubMed1976

A new tracer method for the calculation of rates of bone formation and breakdown in osteoporosis and other generalised skeletal disorders.

1. Evidence has accumulated that the rate of accretion (A) of calcium to bone is the sum of two fluxes; apposition involving the laying down of new bone and augmentation which is the result of slow exchange of non-surface bone calcium with plasma calcium pools as the result of solid state diffusion. 2. A method has been devised for separating A into its two components. It requires the use of 45Ca or, for clinical studies, 85Sr as a calcium tracer. Studies which are initiated with a combined accretion rate--calcium balance study, are concluded with an estimate of the exponent of the power function which has been found to describe the whole body retention of tracer from the second month onward. 3. The impulse response function of the skeleton for the tracer is then calculated, making the assumption that in any uniform volume of bone, osteoclastic resorption is a first order process. Making in addition certain simplifying assumptions, which are shown to have a modest influence on the final results, a mean rate of bone resorption can be calculated using a development of the well known Stewart-Hamilton formula. The apposition rate is calculated as the sum of the resorption rate and the calcium balance. Augmentation and diminution, defined as equal and opposite exchange processes, are given by the difference between A and the apposition rate. 4. The results of our first thirteen studies in normal subjects and patients with metabolic bone disease are presented, together with analyses of some data from the literature. It is concluded that the development of an atraumatic method for measuring rates of bone formation and resorption in the whole body would be an important advance in the study of metabolic bone disease, and this work is presented so that critical comparisons may be initiated between this tracer method and independent histological methods for measuring these parameters.

Bone Diseases↗
PubMed1976

Anabolic effect of low doses of a fragment of human parathyroid hormone on the skeleton in postmenopausal osteoporosis.

Parathyroid hormone, injected daily in low dosage, exerted anabolic effects on the human skeleton, just as it does in the rat. Four postmenopausal women with primary osteoporosis were treated for six months with a synthetic fragment of human parathyroid hormone (hP.T.H. 1-34), given as a daily injection of 100 mug. This treatment caused a remarkable acceleration of bone turnover, indicated both by isotopic tracer and histological methods. At this normocalcaemic dose level, the increases in bone formation outweighed increases in resorption. Three of the four patients showed more positive calcium balances, and mean increases in calcium and phosphorus balances were statistically significant for the group as a whole, the changes being principally due to increased intestinal absorption of both elements. Many modifications of the present method of hormone administration are possible which could further increase the preponderance of anabolic effects. These results suggest that low doses of hP.T.H. 1-34, alone or in combination with other agents, may prove useful in the treatment of osteoporosis.

Absorption↗
PubMed1975

Total body and serum potassium during prolonged thiazide therapy for essential hypertension.

Serum-potassium and total body potassium (T.B.K.) were measured serially for 1 year in a group of eighteen patients with mild essential hypertension. The patients were receiving a single daily dose of 10 mg. bendrofluazide without potassium supplements. At 12 months the mean value for serum-potassium (3-86 mmol per litre) was significantly lower than the mean pre-treatment value (4-26 mmol per litre). There was no significant decrease in T.B.K. in the same period. Diastolic blood-pressure fell significantly, and there were no apparent side-effects from the medication. In the group as a whole, a reduction of about 1 mmol per litre in serum-potassium was associated with an average reduction of 10% in T.B.K., but there was a large individual variation. The amount of potassium loss during the period of study did not seem to be clinically significant. It is suggested that routine potassium supplements are not essential in the treatment of uncomplicated essential hypertension with thiazide diuretics.

Bendroflumethiazide↗
PubMed1975

Potassium changes in megaloblastic anaemia.

1. Serial measurements of serum potasssium and total-body potassium were made on eighteen patients with megaloblastic anaemia before the start of therapy and during the period of recovery. 2. In those patients who presented with an initial packed cell volume of less than 25%, a mean decrease in serum potassium of 0.4 mmol/1 occurred on average with 2.5 days of the start of therapy. This was followed by a significant increase in serum potassium during the period of recovery. There was a significant increase in total-body potassium in these patients, but this could be explained by increases in erythrocyte mass, erythrocyte potassium concentration and lean body mass.

Adolescent↗