Haematological side effects of clozapine: patient characteristics.

AIM: To determine the prevalence of neutropenia and agranulocytosis in patients taking clozapine since its introduction into New Zealand in April 1988. METHOD: Data was collected by Sandoz Pharma (NZ) Ltd on blood counts from all patients prescribed clozapine as part of its worldwide monitoring programme for this drug. The data was analysed by one of the authors (AEC). Case histories to illustrate the principal ways in which falls in white cells present. RESULTS: A total of 693 patients have been exposed to clozapine between April 1988 and June 1995. The cumulative agranulocytosis rate for the first 7 years of use was 1.15%. There were eight cases of agranulocytosis and no deaths. An additional 14 cases neutropenia were reported (2.02%). CONCLUSIONS: The agranulocytosis and neutropenia rates reported from New Zealand compare favourably with those from larger overseas studies though the exposed patient base is modest.

The basidiomycete ganoderma and asthma: collection, quantitation and immunogenicity of the spores.

Ganoderma fungal spores are a major component of the Auckland air-spora. Previous studies of ganoderma involvement in allergic asthma and rhinitis were extended by locating the sporophores (fruiting bodies) in the Auckland area and systematically collecting the ejected spores. Maximum production by one sporophore was 5 gram dry weight of spores in one week, equivalent to 11 billion spores. We have estimated that between 400 and 1200 sporophores would account for previously reported levels of ganoderma spores collected from the air by Burkhard spore traps. Both whole spores and extracts of spores were strongly immunogenic in rabbits. Of the 115 asthma patients who were skin prick tested with a variety of fungal extracts, 32 (28%) were positive to one or more fungi. Of these, 18 (16%) reacted positively to ganoderma extracts. A theory proposing how ganoderma might contribute to allergic hyperreactivity in susceptible patients is developed.

A reappraisal of the binding characteristics of human thyroxine-binding globulin for 3,5,3'-triiodothyronine and thyroxine.

The binding characteristics of T4 and T3 to dilute plasma were studied separately in five normal euthyroid subjects with normal levels of thyroxine-binding globulin (TBG). Scatchard analyses of these data revealed similar mean affinity constants for T4 [2.0 +/- 0.7 (SD) X 10(9) M-1] and T3 (2.0 +/- 0.7 X 10(9) M-1), but a 5-fold higher capacity for T4 (0.75 +/- 0.18 mol T4/mol TBG) than for T3 (0.14 +/- 0.06 mol T3/mol TBG). Similar results were obtained using various assay buffers, pH concentrations, or separation methods. This characteristic pattern of T4 and T3 binding was retained by thyroid hormone free plasma, with the only difference being a slight parallel shift to the left of the Scatchard plots for both T4 and T3. The calculated affinities (Ka) for T4 and T3 were 5.2 X 10(9) M-1 and 5.2 X 10(9) M-1, respectively. High affinity T4 and T3 binding was abolished in plasma selectively depleted of TBG, but was retained after selective depletion of either prealbumin or albumin. Highly purified TBG, prepared from normal serum, demonstrated binding characteristics for T3 and T4 similar to dilute plasma. Displacement of [125I]T4 from dilute plasma by unlabeled T3 or T4 revealed a binding potency of T3 relative to T4 of 9%. Binding affinities derived from analog displacement studies appear invalid as these calculations assume equal binding capacities of TBG for T4 and T3. It seems clear from these studies, that the binding characteristics of human TBG are inconsistent with a single competitive binding site for thyroid hormones.

Deiodination of reverse 3, 3', 5'-triiodothyronine by hepatic nuclear protein preparations.

A reassessment of the binding characteristics of [125I]rT3 to putative receptors in nuclear protein extracts of rat and pig liver revealed that significant deiodination of radioligand occurred during incubation. When previously reported separation procedures are used, released radioiodine is included in the protein-bound [125I]rT3 fraction during separation of protein bound from free hormone by Sephadex G-25 chromatography. This misclassification produces artefacts in binding curves and Scatchard plots used to calculate binding affinity and capacity. Previously reported affinities and capacities derived by this methodology are therefore erroneous. Deiodination of rT3 in the nuclear protein extracts appears to be mediated by outer ring deiodinase. Whereas dithiothreitol markedly enhanced radioiodine generation, the enzyme inhibitors ipodate and salicylate reduced iodine production. These effects produced dramatic changes in apparent binding curves for the radioreceptor assay. When [125I]T3 was incubated with nuclear protein extract, no significant deiodination was detected. Whereas it is likely that the deiodinase is a microsomal contaminant of the nuclear preparation, as suggested by the presence of glucose-6-phosphatase in the nuclear protein preparation, the possibility of an intrinsic nuclear-linked deiodinase cannot be overlooked.

LDH Calcutta-1: a mutation of the B subunit of human lactate dehydrogenase.

The electrophoretic variant of human LDH, Calcutta-1, occurs at phenotypic frequencies of 0-4% throughout India. The variant was examined by various electrophoretic techniques and by heat stability studies. The LD1 (B4) isoenzyme was purified from normal and variant bloods by affinity chromatography and ion-exchange chromatography. A minimum of five Calcutta-1 LD1 bands was demonstrated by isoelectric focusing. Electrophoresis of variant LD1 in high-molar urea-acrylamide denaturing gels resulted in two Calcutta-1 B subunit bands, while normal gels yielded only a single band. Homozygote Calcutta-1 LDH from red cells demonstrated a decreased heat stability, while heterozygote variant LDH showed a normal heat stability. This effect was confirmed when purified LD1's were compared. Evidence is presented suggesting a B-subunit variant showing thermolability in the homozygous form.