Induction of UDPglucose dehydrogenase during development, organ culture, and exposure to phenobarbital. Its relation to levels of UDPglucuronic acid and overall glucuronidation in chicken and mouse.

Liver UDPglucose in early chick-enbryo has, by the 19th day of incubation, reached levels existing in young hatched (White Leghorn) chicks. In developing ASH/TO mouse liver, the dehydrogenase is low, but increases sharply at late foetal and weaning stages; adult activity is greater in females than males. The UDPglucuronic acid content of embryo liver from at least 12 days resembles that of adult chicken; in mouse liver it rises over birth and infancy. These differences in relative rates of development of enzyme and nucleotide in the 2 species can explain why overall glucuronidation by liver appears in chick rapidly after hatching, but in mouse only gradually during infancy. UDPglucose dehydrogenase increases in embryo liver, probably by induction, 2-3-fold during culture with phenobarbital and some 5-fold when exposed to the drug in ovo. Phenobarbital treatment also increases the enzyme in late foetal and adult mice, abolishing the sex difference. Differences between induction of UDPglucose dehydrogenase and UDPglucuronyl transferase during development, culture and phenobarbital treatment indicate that control mechanism for these two enzymes are not directly linked.

Role for c-jun N-terminal kinase in treatment-refractory acute myeloid leukemia (AML): signaling to multidrug-efflux and hyperproliferation.

A relationship was proved between constitutive activity of leukemic cell c-jun-N-terminal kinase (JNK) and treatment failure in AML. Specifically, early treatment failure was predicted by the presence of constitutive JNK activity. The mechanistic origins of this association was sought. A multidrug resistant leukemic cell line, HL-60/ADR, characterized by hyperexpression of c-jun and JNK activity, was transfected with a mutant c-jun vector, whose substrate N-terminal c-jun serines were mutated. Down-regulated expression occurred of c-jun/AP-1-dependent genes, catalase and glutathione-S-transferase (GST) pi, which participate in cellular homeostasis to oxidative stress and xenobiotic exposure. MRP-efflux was abrogated in HL-60/ADR cells with dominant-negative c-jun, perhaps because MRP1 protein expression was also lost. Heightened sensitivity to daunorubicin resulted in cells subjected to this change. Biochemical analysis in 67 primary adult AML samples established a statistical correlation between cellular expression of c-jun and JNK activity, JNK activity with hyperleukocytosis at presentation of disease, and with exuberant MRP efflux. These findings reflect the survival role for c-jun/AP-1 and its regulatory kinase previously demonstrated for yeast in homeostatic response to oxidative stress and in operation of ATP-binding cassette efflux pumps, and may support evolutionary conservation of such function. Thus, JNK and c-jun may be salient drug targets in multidrug resistant AML.

Effects of trimethoprim and sulphonamide preparations on the pituitary-thyroid axis of rodents.

The effects on pituitary-thyroid function of the commonly prescribed anti-bacterial preparations co-trimoxazole and co-trifamole, and their component drugs, have been studied in the rat and compared to the changes caused by propylthiouracil. Co-trimoxazole and co-trifamole, in doses 20-fold in excess of a pharmacological dose administered for 10 days, produced marked changes in hormone levels consistent with blocking of hyperplastic goitre formation, were also demonstrated. Propylthiouracil produced less marked changes of thyroid hormone levels but higher levels of thyroid-stimulating hormone. Pharmacological doses of co-trimoxazole and co-trifamole and sulphamoxole, the sulphonamide component of co-trifamole, caused significant changes in thyroid hormone levels consistent with anti-thyroidal activity. In contrast, there was no evidence that trimethoprim, which is common to both preparations, or sulphamethoxazole, the sulphonamide component of co-trimoxazole, had an anti-thyroidal action, indeed, serum thyroxine levels were significantly increased at pharmacological dosage. We have concluded that the new commonly prescribed combination preparations retain the goitrogenic properties of the earlier sulphonamides.

Diagnostic equipment outside the laboratory.

A questionnaire was circulated to clinical biochemistry laboratories in the North West Thames region of the United Kingdom requesting information on extralaboratory equipment. Data on the types and numbers of instruments in use, their relationship with the laboratory, and quality assurance procedures were obtained. Laboratories were prepared to maintain equipment over which they had no responsibility for purchase, training of users, or use. The quality assurance of these instruments gave even greater cause for concern. Although internal quality control procedures were performed on many of the instruments, laboratories were involved in only a minority of these procedures. Quality control procedures and training of users were undertaken on site in less than 50% of blood gas analysers and bilirubin meters and in less than 25% of glucose meters. External quality assessment procedures were non-existent for all of the instruments in use with the exception of glucose stick meters in two laboratories.

The effects of time delay and temperature on capillary blood gas measurements.

Monitoring of blood gas measurements is an important part of the assessment of patients with chronic lung disease. Increasingly, this is being done in the patients' homes by specialist nurses. This makes it important to know the effect of time delay and storage temperature on the reliability of capillary blood gas analysis results. In this study, the effect of a delay of 1 and 2 h and of storage at both room temperature and in ice, on blood stored in glass capillary tubes was investigated. Samples, initially taken from the earlobes, were transferred to glass capillary tubes and used to provide duplicate initial samples for immediate analysis, and then single samples at 1 and 2 h stored at room temperature or in ice. The duplicate baseline measurements showed good reproducibility. There was a small, but statistically significant, increase in PCO2 when samples were stored in capillaries at room temperature, or in ice, both at 1 and 2 h. Small changes in PO2 were not statistically significant, either in ice or at room temperature. None of the changes was considered to be sufficient to be of clinical significance, thus supporting the use of capillary blood sampling even when there might be a delay of 1-2 h and transport is at room temperature, as might be the case when taking domiciliary samples.

Regional quality assessment of pH and blood gas analysers.

The performance of 41 pH and blood gas analysers in 20 hospitals was assessed using commercially available blood gas ampoules provided by seven manufacturers. The stability of the material and the effect of ambient temperature on Po2 was assessed. The overall mean values were outside the manufacturers' assigned values on eight out of 64 values. Using IL413 analysers as a basis for comparison, significant differences were found for Pco2 on ABL1, Corning 168 and 178 analysers and for Po2 on ABL1 and 2 and Corning 178. No significant differences were found for pH. Poor performers were identified in terms of imprecision. Analysers within or associated with clinical biochemistry departments gave better performance than those outside the laboratory. The five analysers that provided insufficient data for inclusion in the study were all situated outside the laboratory. Analysers from different manufacturers performed equally well provided they were used regularly and in accordance with manufacturers' instructions.

Preparation of material to control precision of calcium selective electrodes.

A simple procedure is described for the preparation of a stable precision quality control material for use in the measurement of level of ionised calcium in serum at or near the reference range. Repeat analyses on a Nova 2 ionised calcium analyser of serum pools stored at different temperatures over a period of three months showed coefficients of variation less of less than 4%.

Predictive value of derived calcium figures based on the measurement of ionised calcium.

The algorithms used in this hospital to assess calcium status are calculated ionised serum calcium and the serum calcium concentration adjusted for albumin. In order to establish their clinical usefulness, they were compared with the ionised calcium concentration measured on the Nova 2 instrument in patients with various calcium and protein abnormalities. Good correlation was found between the measured and calculated values. The predictive values for the calculated results and for total serum calcium concentrations are presented. In this series, the derived values were useful in predicting the serum ionised calcium concentration of the patients studied.

Clinical and laboratory evaluation of four methods of assessing free thyroxine status in thyroid clinic patients.

The clinical value of four laboratory methods of assessing free thyroxine status was compared in 82 consecutive patients newly referred to a thyroid clinic with suspected thyroid dysfunction. The methods of determining free thyroxine used were: (1) free thyroxine index using a thyroid hormone uptake test (FTI (THUT)); (2) a free thyroxine index using thyroxine binding globulin (FTI (TBG)); (3) a kinetic radioimmunoassay (Immophase); and (4) an equilibrium dialysis method. The definitive thyroid status was evaluated by a combination of clinical assessment (including Wayne index), routine tests of thyroid function (total T4, T3, TSH, and TRH tests where appropriate), and by therapeutic trial in one case. The diagnostic efficiency of the tests was markedly dependent upon the method of determining the reference range for euthyroid patients. Best efficiency for each test was achieved using an amended range after excluding outliners. Test efficiency was then 97.6% for FTI (THUT) and the kinetic RIA and 96.8% for FTI (TBG). Misclassification by one or more of these tests occurred in only four patients (mild hypothyroid, euthyroid on phenytoin, euthyroid on oral contraceptive and valium, T3 hyperthyroid). In contrast, free T4 by equilibrium dialysis was much less efficient (86.6%) and was technically the most complex. Overall the kinetic T4 RIA provided similar diagnostic information to the indirect indices. However, further studies of cost benefit in settings other than a thyroid clinic are required to assess whether this method might replace total T4 and/or FTI as a first-line test of thyroid function.

Somatomedins and other serum growth factors: a review of current concepts.

Growth hormone is essential for sustaining longitudinal growth in man. However, during the last 20 years, it has become evident that the actions of growth hormone, at a cellular level, are mediated by specific growth promoting factors. This paper describes the nature and actions of mammalian growth factors and summarises the immense contribution that the measurement of these substances has made towards the elucidation of many problems in the science of human growth and development.

Stick testing: a cause for concern.

A questionnaire was sent to biochemistry laboratories in the NW Thames Region regarding stick testing and the use of reflectance meters for the measurement of blood glucose. Some disturbing facts were reported, particularly with regard to training of staff and the quality of results.

A novel ELISA format for the rapid and sensitive detection of staphylococcal enterotoxin A.

Staphylococcal food poisoning is one of the leading causes of bacterial food poisoning each year. Detection kits for staphylococcal enterotoxins are commercially available and the assays can require from one and a half to twenty-four hours to complete with detection limits ranging from 0.5 to 2 ng enterotoxin per gram of food. We have successfully demonstrated a microsphere-packed capillary (MPC) ELISA for the detection of staphylococcal enterotoxin A (SEA) and have compared it to two commercially available kits. The MPC assay detected a lower amount of SEA in ham, chicken, cheese, and bean sprouts than either of the two commercially available kits. In addition, the novel MPC assay was completed in less than ten minutes, as compared to three and twenty-four hours for the two commercially available kits. This research also demonstrated that the MPC ELISA can contain integrated positive and negative controls and has the potential to simultaneously detect and identify multiple enterotoxins.

Thyroxine and triiodothyronine levels in hyperthyroid patients during treatment with propranolol.

Serum triiodothyronine (T3) and thyroxine (T4) levels were measured in twelve hyperthyroid patients before and after treatment with propranolol, 40 mg four times daily, for 2 weeks. There was a significant fall in serum T3 and a significant rise in serum T4 concentrations in the group as a whole and it was concluded that the clinical effectiveness of propranolol in hyperthyroidism may be mediated in part by its action on the peripheral metabolism of thyroid hormones. Propranolol treatment should be withdrawn gradually as removal of the suppressive action of the drug on thyroid hormone metabolism is potentially hazardous, particularly in patients with ischaemic heart disease.