Dihydrotachysterol: a calcium active steroid not dependent upon kidney metabolism.

The activity of dihydrotachysterol and cholecalciferol was determined in nephrectomized or sham-operated vitamin D-depleted rats using in vitro transport of calcium and phosphate by everted intestinal preparations as the index of physiologic response. The activity of dihydrotachysterol was not reduced by absence of the kidneys whereas that of cholecalciferol was markedly inhibited so that at least a 10-fold greater dose of the latter was necessary to produce an equivalent effect in the nephrectomized rat as in the control. Dihydrotachysterol is therefore equipotent with cholecalciferol in the anephric rat although much less active in the intact animal.

Properties of ICI 128,436, a novel aldose reductase inhibitor, and its effects on diabetic complications in the rat.

ICI 128,436 (3-(4-bromo-2-fluorobenzyl)-4-oxo-3H-phthalazin-1-ylacetic acid) is a chemically novel, potent inhibitor of aldose reductase. It inhibits partially purified aldose reductase isolated from a number of sources including human tissue (human lens - IC50 2.0 X 10(-8) mol/L). Dulcitol accumulation in erythrocytes and sciatic nerves of galactose loaded rats was inhibited by five days of treatment with ICI 128,436 (oral ED50's 2.21 mg/kg and 8.56 mg/kg, respectively). On oral administration for five days to streptozotocin diabetic rats, ICI 128,436, reduced sorbitol levels in sciatic nerve, lens, retina, and renal cortex. The ED50 for inhibition of nerve sorbitol accumulation was 5 mg/kg. The effect of a single dose of ICI 128,436 in diabetic rats was prolonged, with little increase in nerve sorbitol for 48 hours. No tolerance to the ability of ICI 128,436 to reduce nerve sorbitol was found on treatment for 74 days. ICI 128,436 was effective in rodent models of the neural and lenticular complications of diabetes. At doses as low as 25 mg/kg/d it completely prevented the development of cataracts in diabetic rats. The deterioration in motor nerve conduction velocity velocity found in diabetic rats was ameliorated by treatment with ICI 128,436 (3.125 mg/kg/d). Thus, ICI 128,436 constitutes a chemically novel aldose reductase inhibitor that is now being assessed for therapeutic value in the diabetic patient.

Recent advances in calcium metabolism. I. Mechanisms of calcium homeostasis.

Within recent years newly acquired knowledge has provided a clearer understanding of some aspects of the complex mechanisms that collectively maintain calcium homeostasis within body fluids and it is our intent to define current concepts of the interrelationship of these various factors to the end that fuller understanding may be available concerning the maintenance of calcuim homeostasis in health as well as features which result in its disruption and the consequent effects of imbalances of calcium in various disease states. In this first section dealing with the physiologic state, there are included descriptions of: (1) the metabolism of vitamin D, the synthesis of its active metabolites, 25 OHD3 and1.25(OH)2D3, and the metabolic actions of the active vitamin D metabolite and analogues upon gastrointestinal, bone, and kidney functions; (2) the synthesis, secretion, and metabolic activity of parathyroid hormone and the difficulties with the radioimmunoassay of PTH related to the number of PTH-like peptides in the circulation; and (3) the chemistry, metabolism, and biologic activities of calcitonin, a hypocalcemic principle derived from the parafollicular cells of the thyroid gland. It is emphasized that under normal circumstances these humoral mechanisms act in an integrated manner to maintain serum concentrations of total and ionized calcium within narrowly defined limits.

Growth hormone therapy in a poorly growing child with hypophosphatemic rickets.

We treated a 10 6/12 year old prepubertal male with hypophosphatemic rickets, who was growing poorly despite appropriate treatment with calcitriol and phosphate, with exogenous growth hormone (for an initial trial period of 4 months, followed by 14 months of continuous treatment at a dose of 4 IU three times weekly) even though his growth hormone testing proved to be normal. His growth rate increased significantly during treatment with synthetic growth hormone (from a basal rate of 3.9 cm/yr to 9 cm/yr during the first 4 months of therapy and from 2.7 cm/yr to 6.0 cm/yr during next 14 months of treatment) and his predicted adult height increased as well. Slight metabolic changes were detected in this patient during treatment, with an increase in serum phosphorus and a decrease in twenty-four hour urine calcium concentrations. It would seem reasonable to evaluate the growth hormone status of children with hypophosphatemic rickets who are growing poorly despite appropriate therapy with calcitriol and phosphate and to consider a trial period of therapy with growth hormone in some of them.

Recent advances in calcium metabolism. II. Disorders of calcium homeostasis.

Abnormalities of calcium and mineral metabolism are described in relation to the differential diagnosis, clinical characteristics, diagnostic procedures, and treatment of infants and children with hypocalcemia, hypercalcemia, rickets, chronic renal insufficiency, and other disorders of calcium metabolism. Understanding of the basic pathogenesis of each abnormality of calcium homeostasis is essential for the rational management of affected patients.

Fanconi syndrome following bowel surgery and hepatitis reversed by 25-hydroxycholecalciferol.

A permature male infant required intravenous alimentation for six weeks following extensive surgery for ileal and cecal necrosis. At 3 months he developed evidence of hepatitis. Subsequently osteoporosis and the Fanconi syndrome appeared. Urine phosphate clearance was 83 percent of creatinine clearance at a serum phosphate concentration of 1.6 mg/dl. Concentration of plasma immunoreactive parathyroid hormone was elevated at 550 pg/ml. 25-Hydroxycholecalciferol was given at 240 mug/day. Aminoaciduria disappeared and bone healing occurred. Serum phosphate rose to 6.5 mg/dl and phosphate clearance fell to 2 percent of creatinine clearance. Upon cessation of 25-OHCC therapy, the Fanconi syndrome recurred despite administration of vitamin D2. 25-OHCC was then administered at 40 mug/day, and the urine abnormalities were reversed. The patient probably developed hyperparathyroidism, secondary malabsorption, and hepatitis. The Fanconi syndrome was the consequence of the hyperparathyroidism. 25-OHCC therapy was more effective than vitamin D in reversing the disordered state, possibly because of impaired hepatic metabolism of vitamin D2.

Vascular prostacyclin release and metabolic derangement in diabetes.

Diabetic patients have a high susceptibility to microangiopathy, atherosclerosis and thrombosis. Platelet hyper-reactivity, possibly related to an imbalance in platelet/vessel wall arachidonic acid metabolism may be involved. Release of prostacyclin (PGI2) by aorta and renal cortex from diabetic rats and arteries from diabetic patients was significantly depressed. Blood glucose levels in rats at sacrifice did not correlate well with aortic PGI2 release, although in no case was a high rate of PGI2 production found in an animal with a high blood glucose level. Insulin treatment (8 days) restored PGI2 release in tissues from diabetic rats. PGI2 generation by arteries from diabetic patients taking oral hypoglycemic agents was significantly lower than that of diabetics treated with insulin. PGI2 stimulatory activity was increased in plasma from diabetic rats and patients, but diabetic rat aortas were less responsive than those of controls to diabetic plasma. This suggests that decreased values PGI2 release in diabetes is not due to lack of stimulatory plasma factors but may be due to a defect in the vessel wall. Impaired PGI2 release by tissues that develop angiopathy and its normalization in rats by insulin, suggests that depressed PGI2 production may play a role in the vascular complications of diabetes.

Effect of insulin treatment on prostacyclin in experimental diabetes.

Diabetic patients have a high susceptibility to microvascular complications, atherosclerosis and thrombosis. Platelet hyperreactivity possibly related to an imbalance in arachidonic acid metabolism may be involved. Aortic rings or renal cortex produced a potent inhibitor of platelet aggregation, identified as prostacyclin (PGI2). Release of PGI2 by tissues from streptozotocin -- diabetic rats (aorta: 0.07 +/ 0.1 ng/mg wet weight; renal cortex 0.004 +/- 0.001 ng/mg wet weight) was significantly depressed when compared with controls (aorta: 0.26 +/- 0.07 ng/mg wet weight; renal cortex: 0.009 +/- 0.001 ng/mg wet weight). Treatment of diabetic animals with insulin for 8 days restored PGI2 production to normal. The finding that PGI2 is depressed in the aorta and in the kidney, tissues which develop angiopathy, and that this is normalised by insulin, suggests that impaired PGI2 production, perhaps associated with platelet hyperreactivity may play a role in the vascular complications of diabetes.

Aldose reductase in the etiology of diabetic complications: 2. Nephropathy.

The progression of diabetic nephropathy can be arrested by an improvement in diabetic control. High glucose concentrations increase the flux through the aldose reductase pathway, and it has been proposed that this may contribute to renal damage. Aldose reductase is present in both the glomerulus and the renal tubule. Biochemical changes associated with increased sorbitol production have been demonstrated in animal models, including myo-inositol depletion, reduced Na+-K+ ATPase activity, and activation of the pentose phosphate and glucuronate-xylose pathways. Selective inhibition of aldose reductase reverses these biochemical changes and prevents some of the structural and functional abnormalities in diabetic rats. The potential beneficial effects of aldose reductase inhibitors on diabetic kidney disease in man are at present being investigated.

Efficacy of twice-daily dosing of amoxycillin/clavulanate in acute otitis media in children.

Children with acute otitis media (AOM), aged 2-12 years, were randomised to 10 days treatment with amoxycillin/clavulanate (A/C) 70/10 mg/kg/day given b.i.d. (231 patients) or to A/C 60/15 mg/kg/day given t.i.d. (232 patients). Clinical success rates at end of therapy (10-17 days) were 91.8% for the b.i.d. group and 90.5% for the t.i.d. group and at follow-up (28-42 days) were 80.1% for the b.i.d. group and 77.6% for the t.i.d. group, indicating that the b.i.d. regimen was as effective as the t.i.d. regimen. There was no statistically significant difference in incidence of adverse experiences between the two groups. The overall incidence of protocol defined diarrhoea assessed from diary booklets was low, with a lower incidence in the b.i.d. group (6.7%) than in the t.i.d. group (10.3%). Significantly more patients in the b.i.d. group (83.1%) than in the t.i.d. group (72.8%) had at least 80% compliance over a 7-10 day treatment period. A/C given twice or three-times daily was highly effective in the treatment of AOM in children. The two regimens showed equivalent clinical efficacy, both were well tolerated, and there was evidence of improved compliance with the b.i.d. regimen.

Efficacy of twice-daily amoxycillin/clavulanate ('Augmentin-Duo' 400/57) in mild to moderate lower respiratory tract infection in children.

A new amoxycillin/clavulanate regimen ('Augmentin-Duo' 400/57), to be given orally in two divided doses, has been proposed to overcome the inconvenience of tid dosing. This observer-blind, multicentre study randomised children aged two to 12 years with lower respiratory tract infection to seven days' treatment with either amoxycillin/clavulanate bid at a dose of 25/3.6mg/kg/day (221 patients) or the currently prescribed amoxycillin/clavulanate regimen of 20/5mg/kg/day tid (216 patients). Clinical success (cure) rates at follow up were 81.0% for the bid group and 77.8% for the tid group [difference 3.2%; 95% CI (-4.36, 10.80)], indicating that the regimens were of equivalent efficacy. Both regimens were well tolerated, and there was no statistically significant difference in the incidence of adverse experiences between the two groups. Compliance with study medication was high and similar for both groups (80% compliance: bid 90.0%; tid 87.0%).

A possible genetic defect in 25-hydroxylation as a cause of rickets.

We examined two siblings who had severe rickets at ages 2 and 7 years, respectively, despite a history of adequate vitamin D intake. The patients' sera had calcium concentrations at the lower limits of normal, low phosphate concentrations, elevated alkaline phosphatase activity, and low levels of 25-hydroxyvitamin D. Treatment with high doses of vitamin D2 resulted in resolution of the biochemical abnormalities and radiographic deformities; pharmacologic doses of vitamin D2 were required to maintain normal concentrations of 25-hydroxyvitamin D in the serum even though vitamin D absorption was normal. These children may have a genetic defect of the 25-hydroxylation step in vitamin D activation.

Transfer from animal insulins to semisynthetic human insulin: a study in four centres.

The effects of transfer from animal insulin to semisynthetic human insulin on glycaemic control, insulin dose and anti-insulin antibodies were investigated in a total of 108 patients at four centres in a double-blind controlled study of eight months duration. Six months after transfer from porcine to human insulin there was a mean (+/- SE) increase in pre-breakfast blood glucose of 1.1 +/- 0.6 mmol l-1 (vs a reduction of 1.6 +/- 0.7 mmol l-1 in controls) (p less than 0.01), and a mean increase of pre-lunch blood glucose of 0.9 +/- 0.7 mmol l-1 (vs a reduction of 1.14 +/- 0.7 mmol l-1 in controls) (p less than 0.05). Six months after transfer from bovine to human insulin, there were no significant changes in blood glucose. Glycated haemoglobin showed no significant change six months after transfer from either bovine or porcine to human insulin. Hypoglycaemic symptoms, the total daily insulin dose, and the ratio of short- to intermediate-acting insulin did not change significantly after transfer from either bovine or porcine to human insulin. Transfer from bovine to human insulin resulted in a significant decline in anti-human insulin antibodies (mean (range): 50.5(14.8-125)% of initial levels), vs controls (113(43.4-234)% of initial levels; p = 0.034), and a non-significant decline in anti-bovine insulin antibodies (52.2(25.8-111)% vs 81.7(42.5-128)%; p = 0.082).