The presence and orientation of ecto-5'-nucleotidase in rat liver lysosomes.

Purified rat liver lysosomes contained 5'-nucleotidase activity which was 92 +/- 2% [4]latent. This latency was lost in response to a permeant sugar at a similar rate to that of the lysosomal marker enzyme beta-N-acetylglucosaminidase indicating that the 5'-nucleotidase was genuinely located in the lysosome and not a plasma membrane contaminant. Lysosomal 5'-nucleotidase exhibited the following properties characteristic of ecto-5'-nucleotidase inhibition by specific polyclonal antibodies: binding to a monoclonal antibody; inhibition by 1 mmol/1 alpha beta-methylene ADP; immunoreactive subunits of 70 and 38 kDa. Lysosomes in addition contained immunoreactive species of intermediate molecular mass.

Bromcresol purple method for serum albumin gives falsely low values in patients with renal insufficiency.

In patients with renal insufficiency, the BCP method underestimated the serum albumin. In non-renal patients, the BCP method gave albumin results in good agreement with the immunological method. The underestimation did not appear to be related to the degree of renal impairment. The interferent appears to act by preventing the binding of BCP to albumin. The BCG method is much less susceptible to this interference.

Investigation of the use of impermeable fluid barriers between pelleted and supernatant enzyme activity in a pseudohomogeneous enzyme immunoassay.

We have investigated the feasibility of performing an automated pseudohomogeneous enzyme immunoassay in which a separation step is not apparent to the user. This was achieved using a layer of silicone fluid, which is immiscible with aqueous solutions, as a physical barrier between the pelleted and supernatant enzyme. Initially we produced a manual assay based on the Serozyme T4 assay to demonstrate the feasibility of the approach. This assay showed good precision, parallelism and correlated with 'in house' results on patients' samples. Production of a fully automated assay was made difficult by the design of available equipment but none the less we demonstrated the feasibility of the automated approach by producing a standard curve for T4.

An immunoprecipitation assay for high molecular weight alkaline phosphatase in human serum.

The serum of patients with obstructive liver disease may contain a high molecular weight form of alkaline phosphatase (high Mr alkaline phosphatase). The presence of this form of alkaline phosphatase is associated with hepatic malignancies. We have investigated the use of anti-alkaline phosphatase monoclonal antibodies which do not bind high Mr alkaline phosphatase in assays for high Mr alkaline phosphatase. Direct immunoprecipitation of liver and bone alkaline phosphatase with solid phase anti-liver alkaline phosphatase antibody (which also reacts with bone alkaline phosphatase) and measurement of the residual supernatant alkaline phosphatase activity led to a precise assay. Intestinal alkaline phosphatase interfered in this assay which, consequently, was of little use in the differential diagnosis of liver disease. Indirect precipitation of liver, bone, placental and intestinal alkaline phosphatase by soluble anti-liver alkaline phosphatase (which reacts with liver and bone alkaline phosphatases), soluble anti-intestinal alkaline phosphatase (which reacts with placental and intestinal alkaline phosphatases) and solid phase anti-mouse IgG led to an assay which, although less precise, showed more promise of being useful clinically.

Glycosyl phosphatidyl inositol phospholipase D activity in human serum.

We measured serum glycosyl phosphatidyl inositol phospholipase D (GPI-PLD) by its alkaline phosphatase releasing activity in healthy and diseased individuals. Linearity with respect to serum concentration was obtained only with very low serum volumes (below about 0.2 microL) necessitating a large predilution of serum to avoid potential artefacts. The assay was sufficiently precise for routine use. Patients with liver disease had lower activities and those with renal disease had higher activities than healthy controls. Following liver transplantation there was no correlation between GPI-PLD and conventional markers of liver function but there was a marked correlation with cholesterol concentration. These observations suggest that liver is a major source of GPI-PLD in serum. Its function remains unknown.

A kinetic fluorimetric assay for the measurement of angiotensin-converting enzyme in human serum.

The development and assay performance of a direct kinetic fluorimetric assay for angiotensin-converting enzyme is described. It is based on the substrate developed by Carmel et al. (Clin Chim Acta 1979; 93: 215-20), and applied to a microcentrifugal analyser with fluorescence optics. The method is sufficiently sensitive and precise to detect both normal and pathological activities; the method is linear up to at least three times the upper limit of the reference range. The method correlates well with an established method. Because of interference, the method is unsuitable for use with icteric or haemolysed samples.

A continuous monitoring spectrophotometric method for the measurement of angiotensin-converting enzyme in human serum.

A continuous monitoring spectrophotometric method for the measurement of angiotensin-converting enzyme in human serum is described. It is based on the hydrolysis of furylacrylylphenylalanylglycylglycine and applied to an IL Multistat III centrifugal analyser. The method offers better precision and freedom from interference than a fluorimetric assay we have previously described.

Investigation of the use of bilirubin oxidase to measure the apparent unbound bilirubin concentration in human plasma.

An investigation into the use of bilirubin oxidase to measure the apparent concentration of unbound bilirubin in solutions of bilirubin or bilirubin/human serum albumin demonstrated (1) near linearity of oxidation rate with bilirubin concentration up to 16 mumol/L, (2) linearity with respect to enzyme concentration up to 75 mg/L, (3) specificity of the enzyme for unbound bilirubin, as opposed to bound bilirubin, (4) poor precision. Very small absorbance changes leading to poor precision and the potential for interference by conjugated bilirubin meant that the method was unsuitable for patient samples.

Are there any clinical indications for measuring IgG subclasses?

It is questionable as to whether a low serum concentration of one of the IgG subclasses identifies a disease state. A low IgG(1) concentration is found in primary or secondary immunodeficiency states but does not occur in isolation. Low IgG(2) concentration is associated with an increased risk of bacterial infections but only in some individuals and not in others. Isolated IgG(3) and IgG(4) deficiency have not been convincingly demonstrated. Therefore, the isolated finding of low concentrations of one or more IgG subclass does not identify individuals at risk. In contrast, the finding of low serum concentrations of antibodies to specific bacterial antigens (Haemophilus influenzae type B, pneumococcus, tetanus and diphtheria) does identify individuals at risk and these measurements should be used in preference to IgG subclass measurement.

Volunteer program to assist the elderly to remain in home settings.

A community-based volunteer program was organized to improve the quality of life for elderly individuals in the community. Each elderly client referred for the program from welfare and home health agencies, or from family and friends, was matched with a volunteer who visited regularly. The volunteers also assisted with transportation, sitting, home maintenance, and meal preparation when these services were not available. The goals of the program were to improve the quality of life of elderly in the community, to assist the clients to remain in their home setting despite physical limitations, to encourage positive attitudes toward the elderly by the volunteers, and to increase the community's awareness of the older person's needs. The program also included educational seminars on gerontology for volunteers and community members.

A randomized controlled trial of the effect of sublingual orally disintegrating olanzapine versus oral olanzapine on body mass index: the PLATYPUS Study.

BACKGROUND: Patients with schizophrenia and bipolar disorder have frequently reported weight gain during olanzapine treatment. Previous studies have observed a decrease in weight gain, or weight loss, in patients switching from standard olanzapine tablets (SOT) to orally disintegrating olanzapine (ODO) tablets. The primary objective of this study was to investigate the change in body mass index (BMI) in patients who had previously gained weight with SOT and continued with this therapy during the study period, compared with those patients who switched to ODO during the study period. METHODS: This was a 16-week, multicentre, randomized, double-blind, double-dummy, study of outpatients diagnosed with schizophrenia, schizoaffective disorder, related psychotic disorder or bipolar disorder, who were taking 5-20 mg SOT daily. Patients continued treatment with 5-20 mg olanzapine in a flexible single daily dose, and were randomized to either receive sublingual ODO plus an oral placebo, or sublingual placebo plus SOT. RESULTS: No statistically significant between group differences in mean change from baseline in BMI, weight or waist circumference were observed. Analysis of change in body weight from baseline, by pre-specified category (no change, loss of >or=1.5 kg, gain of >or=1.5 kg), revealed a significant difference between groups, favoring ODO patients, who also experienced a significant reduction in subjective appetite and better treatment compliance, compared to patients in the SOT group. CONCLUSIONS: In this study, patients treated with ODO experienced a similar mean change in BMI and weight from baseline, to those patients treated with SOT.

Elimination of the "chromogen oxidase" activity of bilirubin oxidase added to obviate bilirubin interference in hydrogen peroxide/peroxidase detecting systems.

The use of bilirubin oxidase to remove interference by bilirubin in hydrogen peroxide/peroxidase detecting systems is hampered by its inherent "chromogen oxidase" activity (its ability to oxidize the chromogens used in the systems). This unwanted activity is greater than 99% inhibited by 0.5 mmol/L cyanide, 97% inhibited by 20 mmol/L azide. At these same concentrations, they inhibit bilirubin oxidase activity by 95% and 73%, respectively. Sequential addition of reagents allows the use of bilirubin oxidase without interference by the chromogen oxidase activity.

A kinetic assay for urea in undiluted urine specimens.

We describe a kinetic assay for quantifying urea in undiluted urine samples. The assay linearity extends to urea concentrations of 400 mmol/L, is free from interference from blood (10 mL/L) or bilirubin (1 mmol/L), is sufficiently precise for routine use, and correlates well with an established method for assay of diluted urine samples.