Dianne Baldwin

SUBSTITUTION OF ALUMINIUM SALTS BY MAGNESIUM SALTS IN CONTROL OF DIALYSIS HYPERPHOSPHATAEMIA

For two years all 28 patients undergoing hospital haemodialysis were switched from a dialysate magnesium (Mg) of 0.85 mmol/l to one containing none. Oral aluminium hydroxide was discontinued, and magnesium carbonate was substituted as a phosphate binder. After 24 months on this regimen predialysis aluminium concentration had fallen significantly. There was no significant change in predialysis phosphate, which remained above the normal range; nor was there evidence of increased secondary hyperparathyroidism as judged by parathyroid hormone immunoassay and biochemical or clinical criteria. Predialysis Mg concentrations tended to fall towards the normal range. Aluminium-containing phosphate binders seem to be unnecessary for the control of dialysis hyperphosphataemia. Magnesium carbonate may be an alternative and less toxic compound.

Successful control of hyperparathyroidism in patients on continuous ambulatory peritoneal dialysis using magnesium carbonate and calcium carbonate as phosphate binders.

To avoid the use of aluminium as a phosphate binder, patients on CAPD who were stable were dialysed against a peritoneal dialysis fluid which was magnesium free. A mixture of calcium and magnesium carbonate was used as a phosphate binder over a period in excess of 1 year. Vitamin D analogues were used in the majority. Results show satisfactory control of hyperparathyroidism with mean parathyroid hormone concentration for the group of 121 pg/ml (normal < 100 pg/ml), calcium concentration of 2.41 mmol/l, magnesium 0.97 mmol/l, phosphate 1.36 mmol/l and aluminium 0.35 mmol/l (normal < 0.2 mumol/l). These results were as good as and better in some respects than a minority using calcium carbonate alone or remaining on aluminium hydroxide, the latter remaining on Mg-containing CAPD fluid.

Skeletal muscle protein loss due to D-penicillamine results from reduced protein synthesis

Reports in the literature indicate that the trifunctional amino acid D-penicillamine (D-P) induces a variety of muscle abnormalities, although the mechanisms are unknown. We hypothesised that defects may also arise due to the effects of D-P on rates of protein synthesis, possibly via changes in muscle metal composition. Male Wistar rats were injected with D-P at doses of 50 and 500 mg/kg body weight, i.p. Rats designated as controls were injected with 0.15 mol/l NaCl. After 24 h, there were reductions in muscle protein contents, protein synthetic capacities (RNA:protein ratio), fractional rates of protein synthesis, synthesis rates per unit RNA and synthesis rates per unit DNA in skeletal muscles of D-P treated rats. There were no statistically significant differences between the responses of the muscles containing a predominance of either Type I (represented by the soleus) or Type II (represented by the plantaris) fibres. In general, intracellular amino acids were not significantly affected by D-P treatment. Changes in muscle metals included significant reductions in copper, iron and manganese, without alterations in zinc or magnesium. In liver D-P reduced copper and iron though zinc, manganese and magnesium were unaffected. These effects of D-P on muscle may have been direct, as plasma indices of liver (activities of alkaline phosphatase and alanine aminotransferase) and kidney (urea, creatinine and electrolytes) damage were not significantly altered by D-P treatment. Plasma levels of corticosterone, insulin and free T3 were also not significantly affected by D-P treatment. Muscle protein carbonyl concentrations, an index of free radical activity, were similarly unaffected. This is the first report of reduced rates of muscle protein synthesis in D-P treatment. Our data suggests that the reduced rates of muscle protein synthesis may contribute to, or reflect, the muscle abnormalities observed in patients undergoing D-P treatment.

Histochemical and biochemical determination of calcium in salivary glands with particular reference to chronic submandibular sialadenitis.

Although salivary calcification is relatively common, little is known about the localization and content of the calcium of normal and diseased human salivary glands. We investigated this in chronic submandibular sialadenitis with a variable mixture of relatively normal and extremely atrophic parenchyma and in normal submandibular, parotid and palatal glands. Calcium was localized histochemically in mucous acinar cells of submandibular and palatal glands at moderate to high levels, in serous acinar cells of submandibular and parotid glands at low to moderate or occasionally high levels, in mucous ductal cells at moderate to high levels, and in extremely atrophic parenchyma at low levels or not at all. Calcium was determined biochemically at relatively high levels in the different glands in the order palatal, submandibular, sialadenitis and parotid. However, the differences were small. The results indicate that most salivary calcium is associated with secretory granules; this is the likely source of the calcium involved in salivary calcification

Histochemical and biochemical determination of calcium in salivary glands of cat

Although feline salivary glands have been used in investigations on secretion and microlithiasis and both processes involve calcium, nothing is known about its distribution in these glands. Therefore we have demonstrated the presence of calcium by a histochemical technique using glyoxal bis(2-hydroxyanil) and a biochemical technique using dry ashing. The histochemical technique stained serous acinar cells weakly and rarely found mucous acinar cells strongly in the parotid gland, mucous acinar cells moderately to strongly and serous acinar cells weakly in the sublingual gland, and central and demilunar acinar cells moderately to strongly in the submandibular gland. The biochemical technique revealed less calcium in the parotid than in the submandibular and sublingual glands. Both techniques revealed a decrease of calcium in submandibular and sublingual glands following parasympathetic stimulation. The histochemical distribution of calcium, which corresponds to that of acinar secretory glycoprotein, and the loss of calcium following parasympathetic stimulation, which causes release of secretory granules, indicate the presence of calcium in secretory granules. The concentration of calcium in the different types of acinar cell corresponds to the acidity of the secretory glycoprotein and suggests that calcium is present as a cationic shield to allow the condensation of polyionic glycoprotein in secretory granules.

Histochemical and biochemical determination of calcium in pleomorphic adenoma.

SummaryAlthough calcification seldom occurs in pleomorphic adenoma, it often occurs in salivary glands, and so we decided to investigate the possible role of calcium in this difference. A histochemical method using glyoxal bis(2-hydroxyanil) demonstrated a small amount of calcium outlining lumina and separated cells of epithelial structures and associated with cells of myxoid and chondroid regions in pleomorphic adenoma, and a conspicuous amount in the pcini of the associated salivary glands. A biochemical method using dry ashing demonstrated a significantly higher level of calcium in the glands than in pleomorphic adenoma. The results indicate that the calcium is mainly associated with secretory granules, which are scarce in pleomorphic adenoma, and with proteoglycan present intercellularly and in stromal regions of pleomorphic adenoma. The calcium in secretory granules is of possible importance in calcification in lumina and epithelium, and that bound to proteoglycan is possibly released following necrosis to be of importance in stromal calcification. However, the overall low level of calcium in pleomorphic adenoma is the likely explanation for the usual lack of calcification.