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Biomedical subjects

R Hesp

Publications and source records attributed to R Hesp.

88 records · Page 5Linked to original sources
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↗
PubMed1974

Effects of therapy on rate of absorption of calcium from gut in disorders of calcium homoeostasis.

A development of the double-tracer calcium absorption test, in which a function is derived for single-passage entry rate from the gut with time, has been assessed in various disorders of calcium homoeostasis. Single tests are diagnostically useful in calcium malabsorption but because of the wide spectrum of normal values a single test can only moderately enhance the accuracy of the diagnosis of hypercalcaemic states made primarily by other methods. On the other hand serial studies in the same subject can be much more informative because the test is normally highly reproducible if conditions are unchanged. Serial studies play an important part in assessing the efficacy of established methods of treatment in disorders of calcium homoeostasis and should be particularly helpful in studying the effects of new forms of therapy on the absorption process.

Adult↗
PubMedDate not supplied

Spinal and somatic growth in patients with juvenile chronic arthritis treated for up to 2 years with deflazacort.

We previously reported a double-blind controlled trial of Deflazacort vs Prednisone in patients with Juvenile Chronic Arthritis who had required corticosteroid therapy for at least one year. This paper presents further results on an additional 11 patients, making 26 altogether, who were treated for one year with deflazacort. Fourteen of these went on to a second year of deflazacort treatment. As previously reported, the relative rate of spinal bone mineral growth in the first year was greater for the spinal bone mineral content than for the body surface by about 70%. In the second year of treatment spinal bone mineral continued, with wide variations, to grow at the same or a very slightly greater rate. However, somatic growth recovered so that there was no significant difference between the relative growth rates in the spinal bone mineral and the body surface area in year 2 (P = 0.78). Deflazacort therapy appears to permit appropriate growth of the spine in relation to the rest of the body against a background of variable growth impairment due to the disease process and the treatment required to control it.

Anti-Inflammatory Agents↗