Plasma thyrotropin bioactivity in Down's syndrome children with subclinical hypothyroidism.

OBJECTIVE: Subclinical hypothyroidism occurs in a number of children with Down's syndrome (DS). The reason for the mildly elevated plasma thyrotropin (TSH) concentrations is not known. The present study investigated whether decreased TSH bioactivity plays a role in this phenomenon. DESIGN: A retrospective study of plasma specimens from DS children with mildly elevated plasma TSH concentrations and thyroid hormone levels within the reference range, using a TSH receptor-adenylate cyclase mediated bioassay. METHODS: Strain JP26 Chinese hamster ovary (CHO) cells, stable transfected with the human TSH receptor, were incubated with unfractionated plasma (1/10 diluted in hypotonic incubation medium) of 10 DS children with subclinical hypothyroidism and nine euthyroid children with insulin-dependent diabetes mellitus as controls. cAMP released in the incubation medium was measured by RIA. Mock-transfected CHO cells were used to correct for non-specific CHO response. WHO Second International Reference Preparation of human TSH was dissolved and diluted in pooled normal human plasma and simultaneously bioassayed to match patient and control results. RESULTS: Plasma TSH levels were slightly increased in DS (mean +/- S.D., 6.5+/-1.3 mU/l, reference range 0.4-4.0 mU/l). Plasma TSH levels for controls (1.3+/-0.4 mU/l) were within the reference range. Plasma thyroid hormone levels in patients and controls were normal, plasma TSH binding inhibitory immunoglobulin and thyroid peroxidase antibodies were negative. cAMP levels (corrected for non-specific CHO response) in DS patients (18.4+/-3.9 pmol/well) and in controls (14.3+/-1.3 pmol/well) did not significantly differ from cAMP levels generated by patient-TSH equivalent TSH standards (16.3+/-0.9 pmol/well). CONCLUSIONS: The present results demonstrate normal TSH bioactivity in plasma of DS children, indicating that subclinical hypothyroidism in these patients is of primary (thyroidal) origin.

Normal cerebrospinal fluid glutathione concentrations in Parkinson's disease, Alzheimer's disease and multiple system atrophy.

We measured total glutathione concentrations in the cerebrospinal fluid (CSF) of non-demented Parkinson's disease patients (PD; n=71), demented PD patients (PDD; n=13), multiple system atrophy patients (MSA; n=10), Alzheimer's disease patients (AD; n=17) and age-matched controls (n=21). No statistically significant differences in the mean total CSF glutathione concentrations were found between groups and dopaminomimetic treatment was not found to have any effect on total CSF glutathione levels. Our main conclusion is that total glutathione is not useful as a CSF marker for assumed oxidative stress in patients with PD, MSA or AD.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes.

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.

Serum proteinase activities in head and neck squamous cell carcinoma patients.

Proteinases are known to be involved in carcinogenesis, and various substrates are now available to measure the activity of these enzymes. No suitable serum tumour marker for head and neck squamous cell carcinoma (HNSCC) exists at this moment. Therefore, we compared proteinase-activity in serum of 20 untreated HNSCC patients with that of 20 non-cancer individuals. When N-benzoyl-DL-arginine-beta-naphtylamide (BANA) was used as the substrate, proteinase-activity seemed higher among patients, but this difference disappeared after adjustment for alcohol and tobacco consumption. Applying N-a-benzoyloxycarbonyl-L-arginyl-L-arginine-7-amido-4-methylcou marine (ZAAM) as the substrate no difference was found. Addition of E-64, an inhibitor of cysteine proteinase showed that cathepsin B contributed minimally to the ZAAM-specific activity.

Re-evaluation of cerebrospinal fluid angiotensin-converting enzyme activity in patients with 'probable' Alzheimer's disease.

Angiotensin-converting enzyme activity was measured in lumbar cerebrospinal fluid from patients with 'probable' Alzheimer's disease (n = 17) and age-matched controls (n = 19), using a spectrofluorimetric method. In contrast to a previous finding, no statistically significant difference in the mean (specific) angiotensin-converting enzyme activity was found between the two groups. No correlation existed between (specific) enzyme activity and severity of dementia in the Alzheimer's disease patients. We conclude that angiotensin-converting enzyme in cerebrospinal fluid does not appear to be useful as a potential antemortem marker for Alzheimer's disease.

Whole blood monoamine oxidase activity in Parkinson's disease and multiple system atrophy patients.

Monoamine oxidase type B (MAO-B), which catalyses the breakdown of dopamine (DA) in human brain, is said to be involved in the pathophysiology of Parkinson's disease (PD). Activity of MAO-B in PD has been measured in platelets isolated from blood samples in different studies, with contradictory results, possibly due to the differences in substrate used or to differences in platelet isolation. Therefore we measured MAO activity in whole blood, which is almost identical to MAO-B activity in platelets, in 25 drug-naive PD patients, 25 treated PD patients, 9 multiple system atrophy (MSA) patients and 20 controls, using a spectrofluorimetric method with kynuramin as a substrate. No statistically significant differences between groups were found, nor any correlation with the severity or duration of the disease.

Effects of zinc supplementation on zinc status and immunity in haemodialysis patients.

The depression of immunity to various antigens in chronic uremia is a frequently encountered phenomenon. Zinc deficiency might well be an important factor in its genesis. The aim of this study was to investigate the role of zinc deficiency in this reduced immune response. Two groups of 7 patients on haemodialysis who had failed to respond with seroconversion to an earlier vaccination against hepatitis B were revaccinated. One group received zinc by the addition of zinc chloride to the dialysate. Before initiation of the study zinc in plasma and leucocytes was measured. No difference in plasma and leucocyte zinc was observed between the two groups. Zinc in leucocytes was lower in patients than in a group of healthy volunteers (61.5 pmol/10E6 cells +/- 4.6 versus 73.8 +/- 5.6, p less than 0.005). Plasma zinc showed no difference between patients and healthy volunteers. During zinc supplementation zinc in plasma rose in the patient group receiving zinc (10.4 mmol/L +/- 1.5 to 14.2 +/- 1.9, p less than 0.005). However, no rise in leucocyte zinc was seen. At the end of the trial seroconversion had occurred in 2 patients in each group. It is concluded that zinc supplementation in haemodialysis patients does not lead to the restoration of leucocyte zinc to normal levels. Neither did it lead to an enhanced antibody response in our population after revaccination of haemodialysis patients against hepatitis B.

Arginine pharmacokinetics in humans assessed with an enzymatic assay adapted to a centrifugal analyzer.

Arginine is used in supra-physiological concentrations as an insulin secretagogue, in both in vitro and in vivo studies. To investigate the pharmacokinetics of arginine in humans, we have developed a rapid, automated assay of arginine in serum, based on our manual enzymatic method (Clin Chim Acta 1988, 176; 185-94). The limit of linearity of the automated assay was an arginine concentration of 3 mmol/L. Within-run CVs for Ortho control sera with added arginine were 5.5%, 0.8%, and 0.7% at concentrations of 0.16, 1.30, and 2.50 mmol/L, respectively. After 30 min of primed continuous infusions with arginine at infusion rates of 3, 9, 15, and 21 mg/kg per minute, mean (+/- SEM) arginine concentrations in serum from eight volunteers were 1.17 +/- 0.08, 3.44 +/- 0.21, 6.84 +/- 0.58, and 9.25 +/- 0.39 mmol/L, respectively, well within the range of arginine concentrations shown (in vitro) to stimulate insulin secretion. Metabolic clearance of arginine was approximately 11 mL/kg body wt per minute. For the lowest three infusion rates, the half-life (t1/2) of arginine was approximately 15 min and the volume of distribution (Vd) was approximately 290 mL/kg. At the highest infusion rate, t1/2 was significantly increased (27.3 +/- 3.1 min), owing to an increased Vd (446 +/- 83 mL/kg).

Comparison of two latex agglutination test kits for serum myoglobin in the exclusion of acute myocardial infarction.

The Myolex (Orion) and the RapiTex (Behringwerke) latex agglutination tests for the rapid detection of elevated levels of serum myoglobin were studied prospectively in patients suspected of acute myocardial infarction, who were admitted to hospital within 8 h of pain onset. Using admission blood samples drawn 3.4 +/- 2.0 h (mean +/- SD) after onset of symptoms, the negative predictive values of both tests were too low to use these assays in the early exclusion of myocardial infarction in the emergency department. However, the negative predictive values obtained with the second blood samples, drawn 4 h later, indicated that the myoglobin agglutination test could be of value in the exclusion of myocardial infarction.

A kinetic procedure for the estimation of arginine in serum using arginine kinase.

A method for estimation of arginine in 50 microliters serum was developed using commercially available arginine kinase (EC 2.7.3.3). The assay is based on the transformation of arginine and ATP into phospho-arginine and ADP by the enzyme. ADP is measured by two coupling reactions involving pyruvate kinase (EC 2.7.1.40) and lactate dehydrogenase (EC 1.1.1.27) with measurement of NADH consumption at 340 nm. The method involves preincubation of serum in the reaction medium without arginine kinase to eliminate side reactions and a kinetic rate protocol with measurements of absorbance at 60 s and 180 s. Reaction temperature is 30 degrees C. The reaction is linear up to at least 3 mmol/l of arginine. Within-batch CV is less than 3% for arginine levels above 0.75 mmol/l and the between-batch CV is 6.5% or less. The method correlates well with an automatic amino acid analyzer procedure (r = 0.983). The reference range derived from sera of 40 blood donors has been determined to be 0.06-0.20 mmol/l.

A modified kit method and a miniphotometer used for the rapid determination of total bilirubin in neonatal sera.

The results of the determination of total bilirubin in neonatal sera using the Compur kit and miniphotometer are reported. The kit method was modified somewhat by halving the volume of serum. This smaller volume (10 microliters) minimizes the interference of haemoglobin and turbidity. In a study of 68 neonatal sera, the method correlated excellently with the assay according to Hertz et al. ((1974) Scand. J. Clin. Lab. Invest. 33,215-230) and precision was better than 3.5%. The method described is rapid and reliable and ideally-suited for emergency requests for monitoring neonatal hyperbilirubinaemia.

Measurement of antitryptic activity of serum with a centrifugal analyzer.

The Selected Method [Clin. Chem. 20, 396 (1974)] for the enzymatic assay of alpha1-antitrypsin in serum has been adapted for use with the E.N.I.-GEMSAEC. With alpha-N-benzoyl-D,L-arginine-p-nitroanilide as substrate, the difference between the tryptic activity measured with and without addition of serum in the same run has been used to calculate the trypsin-inhibitory capacity. The rate of increase in absorbance at 400 nm of the p-nitroanilide formed, has been evaluated during a reaction time of 140 s. Results correlated well (r = 0.986) for 54 human sera analyzed as described here and by the Selected Method. The adaptation on GEMSAEC can be used in detecting alpha1-antitrypsin deficiency in the newborn.