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Biomedical subjects

R A Melick

Publications and source records attributed to R A Melick.

At least 37 records · Page 2Linked to original sources
PubMed1978

The effects of digestive enzymes on characteristics of placental insulin receptor. Comparison of particulate and soluble receptor preparations.

The role of the surrounding membrane structure on the binding characteristics of the insulin receptor was studied by using several digestive enzymes. The effects observed with particulate membrane preparations are compared with those from soluble receptor preparations. beta-Galactosidase and neuraminidase had no effect on insulin binding to either particulate or soluble receptors from human placentae. Exposure to 2 units of phospholipase C/ml increased insulin binding to particulate membranes, but was without effect on the soluble receptor preparation. The increase in binding to particulate membranes was shown to be due to an increase in apparent receptor number. After 5 min exposure to 500 microgram of trypsin/ml there was an increase in insulin binding to the particulate membrane fraction, owing to an increase in receptor affinity. After 15 min exposure to this amount of trypsin, binding decreased, owing to a progressive decrease in receptor availability. In contrast, this concentration of trypsin had no effect on the solubilized receptor preparation. Because of the differential effects of phospholipase C and trypsin on the particulate compared with the solubilized receptor preparations, it is concluded that the effects of these enzymes were due to an effect on the surrounding membrane structure. Changes in receptor configuration due to alterations within the adjoining membrane provide a potential mechanism for mediating short-term alterations in receptor function.

Cell Membrane↗
PubMed1978

The effect of growth retardation and of osteomalacia on the uptake of albumin by bone.

125I-labeled rat albumin injected intravenously into rats was taken up by growing bone. Some of this radioactive albumin could be removed from bone by washing with saline, the proportion so removed decreasing from 82.5% at 1 day to 7.4% at 8 days. Both the total radioactivity, and that remaining in bone after saline wash, were reduced when growth was slowed by alteration or restriction of the diet. Although the amount of 125I albumin in rachitic bone was reduced, autoradiography showed that radioactivity was present in rachitic osteoid. Immunoprecipitation using anti-rat-albumin serum showed that about half of the radioactivity released from normal bone by EDTA was still attached to albumin. These results suggest that albumin plays some part in the growth of bone.

Albumins↗
PubMed1977

Clinical, biochemical and histological observations on the effect of porcine calcitonin in Paget's disease of bone.

The response to porcine calcitonin has been assessed in 38 patients with Paget's disease, observed during 44 treatment periods of from three to 42 months. In 36 of the treatment courses significant relief of pain was achieved but the contribution of placebo effect could not be determined. Serum alkaline phosphatase and urinary hydroxyproline levels reached normal in a few patients, but the grouped data indicated a plateau effect above the range of normal. The acute hypocalcaemic response to calcitonin was lost only in those patients whose bone turnover was restored to normal. Quantitative histology on iliac crest bone biopsy samples showed no statisically significant lowering of osteoclast counts. No antibody-based clinical resistance occurred and the incidence of side effects was low. The results indicate that porcine calcitonin is a useful treatment of Paget's disease, and the experience of the study helps in arriving at patient selection and treatment schedules. Treatment is recommended for bone pain and for active disease in the relatively young, using intermittent therapy with course of at least six months duration. Resumption of therapy is based on clinical and biochemical indications.

Adult↗
PubMed1976

Renal calculi and their management.

Any patient presenting with renal colic requires the taking of a detailed history-- with inquiries about diet and drugs, an examination of the urine, intravenous pyelography and measurement of the calcium concentration in serum and urine. Any stone passed should be analysed. Recurrent stone formation warrants more comprehensive metabolic investigation. The cause of renal calculi in most patients is still not known. When a cause is found, specific treatment can prevent or control stone formation. For the majority in whom no abnormality is detected, various methods of reducing stone formation have been tried but results are disappointing. The most important points in management are the early detection and effective treatment of urinary tract infection or obstruction and the maintenance of a high fluid intake.

Bacteriuria↗
PubMed1976

Correlation between insulin receptor binding in isolated fat cells and insulin sensitivity in obese human subjects.

This study examined the relationship between receptor binding of insulin in a metabolically significant target tissue in vitro and sensitivity to insulin in vivo in obese human subjects. Specific insulin binding was measured at 24 degrees C in isolated enlarged fat cells obtained from 16 patients, by observing the effect of increasing concentrations of unlabeled insulin on the binding of [125I]insulin. Scratchard plots of the binding data were curvilinear with an upward concavity, similarity shaped, and essentially parallel. Kinetic studies on the dissociation of [125I]insulin from fat cells indicated that these curvilinear Scratchard plots could be explained by the presence of site:site interactions of the negative cooperative type. Differences in binding between individual patients were predominantly due to differences in the numbers of receptor sites whether expressed in relation to cell number, cell volume, or cell surface area. These findings were not accounted for by differences in [125I]insulin degradation. Acute exposure of adipose tissue to insulin in vitro had no significant effect on [125I]insulin binding to isolated cells. The number of receptor sites was directly correlated with insulin sensitivity in vivo, measured as the rate constant (Kitt) for the fall in blood glucose after intravenous insulin, and was inversely correlated with the level of fasting plasma insulin. These findings corroborate those from other studies using human mononuclear leukocytes and various tissues from the obese mouse, which indicate that decreased insulin binding is a characteristic feature of insulin resistance in obesity.

Adipose Tissue↗
PubMed1975

Paget's disease in identical twins.

Paget's disease of bone was found in each of elderly monozygotic twin sisters. Apart from the skull, which was affected in each twin, different bones were involved by Paget's disease. This is the fifth pair of identical twins reported with Paget's disease of bone.

Diseases in Twins↗
PubMed1975

Prediction of the strength of the neck of femur from its radiological appearance.

In this study 39 male and female cadaveric femoral necks of ages between 21 and 89 years have been radiographed and subsequently mechanically tested to determine failure load. A structural model has been developed, in an attempt to predict the failure load of specimens solely from measurements made from an anteroposterior radiograph of the neck region. Good correlation was obtained between the predicted and experimental values for the range tested. The influence of average bone porosity is discussed. It is believed that this method, with modifications will provide a basis for the quantitative assessment of femoral neck strength in the clinical situation.

Adult↗