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Biomedical subjects

S Posen

Publications and source records attributed to S Posen.

At least 73 records · Page 4Linked to original sources
PubMed1985

Is parathyroidectomy of benefit in primary hyperparathyroidism?

A retrospective survey was performed on 265 patients with primary hyperparathyroidism who had received three forms of treatment on a non-randomised basis. 'Successful' surgery (normalisation of serum calcium) was carried out in 142 patients, 'unsuccessful' surgery (persistence of hypercalcaemia after neck exploration) in 33 and no surgery in 90. Patients subjected to surgery were significantly younger than patients in the unoperated group and their serum calcium values at the time of decision were approximately 10 per cent higher. The mean follow-up period was significantly longer in the operated groups. The percentages of patients who had died were similar in each group. Clinical events relating to renal stones depended on the presence or absence of calculi at the time of decision rather than on the method of treatment. At the time of follow-up the prevalence of hypertension, renal impairment and vertebral crush fractures were similar in all three groups. Forearm osteo-densitometry showed a higher bone mineral content in the 'successful' group than in the other two groups. In spite of the selection bias inherent in a study of this kind, it is clear that untreated hyperparathyroidism is compatible with long survival and a lack of demonstrable deleterious effects on kidney and bone.

Bone Diseases↗
PubMed1984

Clinical disorders in patients with hyperprolactinaemia. Experience with 59 patients.

Fifty-nine patients with hyperprolactinaemia and presumed, or histologically proven, pituitary tumours were identified within a seven-year period. The wide variety of clinical presentation, the natural history, and the problems associated with therapy are highlighted in several selected case presentations which include both patients with invasive tumours and those with no radiological abnormalities and minimal symptoms. The special considerations involved in a planned pregnancy in a patient with hyperprolactinaemia are emphasized.

Acromegaly↗
PubMed1984

Vitamin D conversion by sarcoid lymph node homogenate.

Recent studies suggest that hypercalcemia of sarcoidosis is due to high blood concentrations of calcitriol and that this compound may be synthesized at an extra-renal site. We report that sarcoid lymph node homogenate metabolized calcifediol to a substance indistinguishable from calcitriol, whereas six nonsarcoid lymph nodes failed to produce this compound.

Calcifediol↗
PubMed1983

Effect of aluminum on normal and uremic rats: tissue distribution, vitamin D metabolites, and quantitative bone histology.

The effects of intraperitoneal aluminum chloride (1.5 mg aluminum/kg/day for 9 weeks) were studied in normal and uremic rats. Parameters measured included tissue aluminum, serum vitamin D metabolites, and quantitative bone histology. Aluminum administration increased tissue concentrations of this metal in uremic and nonuremic animals. Bone aluminum concentrations were higher in uremic rats (121 +/- 27 mg/kg compared to 47 +/- 4), whereas liver values were higher in the nonuremic group (175 +/- 47 mg/kg compared to 100 +/- 36). Serum concentrations of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D were reduced in uremia, but aluminum was without apparent effect on any vitamin D metabolite. Aluminum, in the doses administered, caused no skeletal changes in nonuremic animals. Some uremic, non-aluminum-treated rats developed osteomalacia and marrow fibrosis. However, osteomalacia was more severe and the osteoclast count was higher in the uremic, aluminum-treated rats. In this group of animals the mineral apposition rate was reduced at the metaphyseal endosteum but increased at the periosteum, indicating different control mechanisms at the two sites.

Aluminum↗
PubMed1983

Vitamin D metabolism in nephrotic rats.

Vitamin D metabolites were measured in sera of normal, vitamin D deficient and nonazotemic nephrotic rats. The concentrations of all metabolites were reduced in nephrotic and vitamin D deficient animals although 1,25-dihydroxyvitamin D values remained relatively normal in the nephrotic group. Twenty-four hours after the intravenous injection of tritiated 25-hydroxycholecalciferol, approximately 34% of the injected radioactivity appeared in the urine of the nephrotic animals compared with 0.4% in the controls. In extracts from nephrotic sera subjected to high performance liquid chromatography, the percentage of radioactive counts comigrating with 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol was significantly increased. The various metabolites were present in urine in approximately the same ratios as in serum. Dynamic histomorphometry of tibial metaphyses showed no abnormality. Urinary losses of vitamin D metabolites constitute the major cause for low serum values in nephrotic rats. The apparent synthetic rates are not impaired.

24,25-Dihydroxyvitamin D 3↗
PubMed1983

The vascular lesions associated with skin necrosis in renal disease.

Three renal allograft recipients and one uraemic patient presented with skin necrosis. In all cases, the subcutaneous arteries and arterioles were narrowed or occluded by mural calcification with or without intimal fibrosis. A review of the literature shows that uraemic patients or allograft recipients with skin necrosis involving the trunk or thighs have a poor prognosis while recovery is common in patients with more peripheral lesions. The aetiology of the arterial lesions is unknown. Their relationship to renal disorders and/or hyperparathyroidism is uncertain and therapy remains unsatisfactory.

Adult↗
PubMed1983

Plasma vasopressin in hypercalcaemic states.

Plasma vasopressin was measured by radioimmunoassay in eight normal subjects and in six patients with hypercalcaemia. Vasopressin levels were significantly elevated in the hypercalcaemic patients, although urine osmolalities were lower than in controls. This finding is consistent with a renal resistance to the action of endogenous vasopressin in hypercalcaemia.

Adult↗
PubMed1983

The synthesis of vitamin D metabolites by human melanoma cells.

Two melanin-producing human melanoma cell lines originally established from fresh surgical specimens were incubated with 25 hydroxyvitamin D3 (25 OHD3). Both cell lines produced material comigrating with 1,25 dihydroxy-vitamin D3 (1,25(OH)2D3) and 24,25 dihydroxyvitamin D3 (24,25(OH)2D3) in straight and reverse phase high performance liquid chromatography systems and displacing the relevant labeled ligands in competitive binding assays. The material designated 1,25(OH)2D3 was found almost entirely within the cells, whereas 24,25(OH)2D3 was evenly distributed between cells and medium. The synthesis of dihydroxylated materials was time dependent and was not observed if the cells were boiled before incubation with 25 OHD3. Preincubation with 1,25(OH)2D3 caused an increase in the synthesis of 24,25(OH)2D3 and a decrease in the synthesis of 1,25(OH)2D3. Michaelis-Menten constant (Km) values were 1.4 X 10(-9) mol/liter 25 OHD3 for the 1-alpha-hydroxylase enzyme and 72 X 10(-9) mol/liter for 24-hydroxylase. These studies constitute further evidence for the extrarenal synthesis of 1,25(OH)2D3. The suppressibility of 1 alpha-hydroxylase by preincubation with 1,25(OH)2D3 suggests a regulatory function for this system in the skin.

24,25-Dihydroxyvitamin D 3↗
PubMed1982

Vitamin D metabolism in hypophosphatemic rickets.

Vitamin D metabolites were measured in 21 patients with hypophosphatemic osteomalacia of juvenile onset. In eight patients who had not received any antirachitic treatment, serum 25-hydroxyvitamin D(25-OH-D) and 1,25-dihydroxyvitamin D (1,25-[OH]2D) values were normal, whereas serum 24,25-dihydroxyvitamin D (24,25-[OH]2D) values were lower than in normal subjects. In 13 patients who were receiving ergocalciferol and oral elemental phosphorus, serum 25-OH-D and 24,25-(OH)2D concentrations were elevated and serum 1,25-(OH)2D values were low. The findings in untreated patients supported the hypothesis that vitamin D metabolism is abnormal in hypophosphatemic rickets/osteomalacia. The reduction of serum 1,25-(OH)2D levels with ergocalciferol and phosphate therapy gives further support to a therapeutic role for 1,25-(OH)2D in this disorder.

24,25-Dihydroxyvitamin D 3↗
PubMed1982

The effect of bromocriptine on circulating vasopressin.

1. The oral administration of 2.5 mg of the dopamine (3,4-dihydroxyphenethylamine) agonist bromoergocriptine enhanced the osmotically stimulated rise in plasma [arginine]vasopressin ([Arg]VP) concentrations in five normal human subjects. 2. This finding lends support to the suggestion that the osmotically induced release of [Arg]VP is under dopaminergic control in man.

Adult↗
PubMed1982

Skeletal changes in preterm infants.

The skeletal changes in 19 very low birthweight infants (less than 1500 g) were observed from birth to 10 weeks, by means of clinical, biochemical, and radiological techniques. All infants were receiving a supplement of 800 IU vitamin D a day from age 2 weeks. None of the infants showed any specific physical sign of rickets during the period of study. Six infants showed radiological evidence of skeletal demineralisation; 1 of these had severe changes of rickets and 1 had both rickets and fractures. These 6 infants were of shorter gestational periods and lower birthweights than the infants not showing radiological changes. They tended to have more clinical problems and to reach a predetermined volume of feeds (160 ml/kg a day) later than the unaffected infants. Serum alkaline phosphatase values were significantly higher at 5 weeks in the infants with abnormal radiographs than in those without. There were no significant differences between the two groups in relation to serum calcium, inorganic phosphate, 25 hydroxyvitamin D, and immunoreactive parathyroid hormone. The pathogenesis of the skeletal lesions of very low birthweight infants remains unknown.

25-Hydroxyvitamin D 2↗
PubMed1982

Turnover rate of skeletal alkaline phosphatase in humans.

Two patients with Paget's disease of bone were subjected to plasmapheresis. Alkaline phosphatase activities of serum declined sharply, but returned to preplasmapheresis values within eight to 10 days. The biological half-life of circulating skeletal alkaline phosphatase, as calculated from these experiments, is between 1.12 and 2.15 days.

Aged↗
PubMed1982

Therapeutic problems relating to azotaemic osteodystrophy.

Azotaemic osteodystrophy is a generic term encompassing the different bony lesions found in renal failure. The most important of these are parathyroid osteopathy and osteomalacia which may co-exist or occur singly. Both types of lesions have multifactorial aetiologies. Hyperparathyroidism is caused by hyperphosphataemia, hypocalcaemia and possibly, a lack of 1,25-dihydroxycholecalciferol. Osteomalacia is caused by vitamin D deficiency, a lack of dihydroxylated vitamin D metabolites and aluminium intoxication. Treatment modalities include phosphate binders, a tight control of calcium concentrations in the dialysis fluid, vitamin D and parathyroidectomy. Each of these is associated with certain hazards. In particular, vitamin D and parathyroidectomy may cause deterioration of residual renal function.

Calcium↗
PubMed1981

Paget's disease of bone: experiences with 100 patients treated with salmon calcitonin.

ONe hundred patients with Paget's disease of bone were treated with salmon calcitonin. Seventy per cent of patients who presented with pain reported improvement of symptoms. Side effects which occurred in 53 patients were more severe in women, necessitating the withdrawal of therapy in 30% of women as against 7.5% of men. Five of the patients with intolerable side effects were subsequently able to tolerate porcine calcitonin, while six were unable to tolerate salmon, porcine or human calcitonin. No audiological improvement occurred. Aortic valve lesions were detected in 11 patients. After a mean treatment period of 7.8 months, serum alkaline phosphatase level was reduced by 39.3%. Total 24-hour urinary hydroxyproline was reduced by 46.1% after 11.2 months of treatment.

Alkaline Phosphatase↗
PubMed1981

Hyperparathyroidism: experiences with treated and untreated patients.

During a seven-year period, after the introduction of parathyroid hormone assays, 113 patients with primary hyperparathyroidism were seen at an Australian teaching hospital. In 68, parathyroidectomy was followed by normalization of serum calcium levels. Fifteen patients (six referred from other units) remained hypercalcaemic after their initial neck exploration. Thirty patients with biochemical changes indicative of primary hyperparathyroidism were not referred for surgery, mainly because of old age or lack of symptoms. Those patients who were not submitted to surgery, and those who had undergone unsuccessful neck explorations, were observed (while hypercalcaemic) for a mean period of three years. During the period of observation, no deterioration occurred in the clinical or biochemical status of these patients. It is proposed that patients with non-symptomatic primary hyperparathyroidism may be managed by clinical observation, rather than by immediate parathyroidectomy.

Adult↗