Evaluation of the Boehringer Mannheim ES 300 immunoassay analyzer and comparison with enzyme immunoassay, fluorescence polarization immunoassay, and radioimmunoassay methods.

The ES 300 (Boehringer Mannheim Diagnostics, Indianapolis, IN) is a new automated immunoassay analyzer intended for the quantitative determination of a wide range of analytes. We compared its performance to enzyme immunoassay (EIA), fluorescence polarization immunoassay (FPIA), and radioimmunoassay (RIA) methods for cortisol, digoxin, ferritin, prolactin, T4-uptake, total-T3, and TSH. The ES 300 methods showed excellent precision and the manufacturers' linearity claims were met in all cases. Cortisol, prolactin, total-T3, and TSH showed no bias and acceptable correlation with other methods. Digoxin, ferritin and total T4 showed positive bias but acceptable correlation. The ES 300 T4-uptake correlated poorly with the TDx method and showed positive bias; however, these assays appear comparable (although deficient) in diagnostic sensitivity when compared to TSH and T4 data for the same patient population. In all, we found the ES 300 to be an acceptable instrumental alternative for the high volume immunoassay laboratory.

Prevalence and properties of the intestinal alkaline phosphatase identified in serum by cellulose acetate electrophoresis.

We investigated the prevalence and characteristics of intestinal alkaline phosphatase (ALP; EC 3.1.3.1) identified in human serum by cellulose acetate electrophoresis in 8% of fasting serum samples from hospital patients (n = 500) and in 35% of fasting serum samples from patients with diabetes mellitus (n = 106; not differentiated between types 1 and 2). The intestinal ALP electrophoretic band was usually heterogeneous and contained two major subtypes of ALP. Isoelectric focusing of intestinal-ALP-positive serum treated with levamisole and neuraminidase (EC 3.2.1.18) revealed two distinct regions of enzymatic activity that comigrated with ALP extracted from small intestinal and colonic mucosa. Anodic intestinal ALP was resistant to treatment with levamisole and neuraminidase and comigrated with ALP from small intestinal mucosa. The more-cathodic intestinal ALP, which comigrated with ALP from colonic mucosa, was completely inhibited by levamisole and converted by neuraminidase to a species with a more basic pI than that of neuraminidase-digested tissue-nonspecific form. This component of intestinal ALP may be of vascular origin.

Comparison of a commercial method for total protein with a candidate reference method.

The biuret method for total protein has been compared on the Boehringer Mannheim Diagnostics (BMD) Hitachi 717 Analyzer with a candidate reference method in efforts to standardize the BMD method. The methods were compared using 115 paired serum specimens collected during morning rounds at the Roger Williams Hospital. Results from the test method were compared to the reference method using a statistical procedure for quantifying bias between analytical methods. Linear regression statistics were also calculated. The Hitachi 717 biuret method shows no bias when compared to the reference method (z = -0.90), and there is acceptable correlation between the two methods (y = 0.86, m = 0.86, r = 0.896). The Hitachi method is linear to 15.0 g per dL and demonstrates excellent precision (CV less than or equal to 2.14 percent, N = 140). The Hitachi 717 biuret method has been found to be excellent in all respects and its use is recommended as a convenient and accurate means of measuring total protein.

Cell culture of the mucinous variant of human colorectal carcinoma.

Two cell lines, RW-2982 and RW-7213, have been established for the first time from the mucinous variant of human colorectal carcinoma, which is a distinctive and important subtype that has a worse prognosis than the more common nonmucogenic large bowel carcinoma. Methods of establishment and observations made during 7 and 3 years, respectively, of continuous culture are described. These cell lines required 4-9 months of adaptation to tissue culture conditions before noticeable growth occurred. Both cell lines have the following unique properties: (a) growth in vitro as delicate branching three-dimensional tumor particles within a wide gel of insoluble, often translucent mucus (proteoglycan); (b) production of large quantities of carcinoembryonic antigen; (c) ability to survive or adapt to growth in media free of serum, hormones, growth factors, and all protein; and (d) tumorigenicity in multiple sites in nude mice, including liver, with especially rapid growth in the peritoneal cavity as gelatinous material that is nonadherent and noninvasive and thus resembles pseudomyxoma peritonei. Unlike other reported colorectal cell lines, these mucus-coated particulate cell lines will not readily grow as monolayers and grow much more slowly with a doubling time of 2 weeks or more. A serially transplantable tumor from the RW-7213 surgical specimen has also been maintained in nude mice since August 8, 1984. This tumor retains properties of the original specimen. Observations made on the tumor biology of mucogenic colorectal carcinoma using these cell lines are discussed.

The in vitro serum protein-binding characteristics of bis-(2-ethylhexyl) phthalate and its principal metabolite, mono-(2-ethylhexyl) phthalate.

The metabolism and toxicity of the ubiquitous plasticizer, bis-(2-ethylhexyl) phthalate (DEHP), and its principal metabolite, mono-(2-ethylhexyl) phthalate (MEHP), have been extensively investigated. In an attempt to understand their disposition in man, we studied the in vitro serum protein-binding characteristics of these compounds, using ultracentrifugation and agarose gel electrophoresis. The association of DEHP and lipoproteins was shown to be highly dependent upon, and proportional to, the lipid concentration of the serum. It appears that more than half of the serum DEHP is bound to proteins with density greater than 1.21 g/mL when the concentration of cholesterol is below 300 mg/dL or the cholesterol and triglyceride total concentration is less than 600 mg/dL. As the cholesterol and triglyceride concentrations increase, the percent DEHP bound to VLDL, IDL, and LDL increases. MEHP is bound principally to nonlipoprotein constituents in the serum, and this binding distribution is unaffected by lipid concentration. The percent binding of DEHP and MEHP to individual proteins was also found to be unaffected by their concentrations in serum. These data indicate that the protein-binding characteristics of these compounds, in vitro, is somewhat more complex than previously reported.

The significance of beta-2 microglobulinuria associated with gentamicin therapy.

Gentamicin is a nephrotoxic agent known to damage the proximal tubule,--a site of low molecular weight (LMW) protein reabsorption and catabolism. The effect of gentamicin was investigated on three LMW proteins--amylase, light chains, and beta 2 microglobulin--and the effects were correlated on the latter to renal function as determined by creatinine clearance (GFR). The renal excretion of beta 2 microglobulin (beta 2M) was studied in 18 patients receiving gentamicin and eight control patients. Both gentamicin and control patients had similar mean ages and serum beta 2M. Twelve of the 18 gentamicin treated patients had marked increases in beta 2M excretion. The mean daily 2 beta microglobulin excretion for the gentamicin treated group was 10,511 microgram while that of the control group was 102 microgram. Serial determinations in 10 of the gentamicin treated patients revealed an increase in beta 2M excretion within 48 hours of starting therapy. No deterioration of GFR was seen in any patient. In four patients, beta 2M excretion decreased while still receiving gentamicin. The renal handling of amylase was found to be normal in four patients and mildly abnormal in three patients receiving gentamicin who also had increased beta 2M excretion. Urinary light chains were determined in four of these seven patients and found to be normal. It is concluded that gentamicin induces an early and often transient tubular proteinuria. This tubular proteinuria is not associated with clinical nephrotoxicity.