Chondrex: new marker of joint disease.

Chondrex, a major secretory protein of human chondrocytes and synovial fibroblasts, is increased in serum of patients with joint and cartilage disease. We have developed a sandwich-type ELISA for quantifying chondrex in serum. The interassay CVs were 2.8-3.7% and the average within-run and total CVs were 3.6% and 5.4%, respectively. The limit of detectability by linear dilution was 20 micrograms/L, recovery upon dilution was 102% +/- 5%, and analytical recovery (of added analyte) was 98% +/- 11%. The reference interval (central 90% interval) for chondrex in healthy adults was 25-95 micrograms/L. Chondrex values for patients with active rheumatoid arthritis or osteoarthritis were significantly greater than in healthy adults, inactive rheumatoid arthritis patients, and diabetes patients (P < 0.05). In patients treated with disease-modifying antirheumatic drug therapy, decreasing chondrex values reflected the clinical improvement observed in responders, whereas the values were maintained or increased in nonresponders. In conclusion, chondrex may be a useful marker in the clinical investigation of arthritis.

Isolation and quantification of soluble Alzheimer's beta-peptide from biological fluids.

Cerebral deposition of the beta-amyloid peptide (A beta) is an invariant feature of Alzheimer's disease. Since the original isolation and characterization of A beta (ref. 1) and the subsequent cloning of its precursor protein, no direct evidence for the actual production of discrete A beta has been reported. Here we investigate whether A beta is present in human biological fluids using antibodies specific for an epitope within A beta that spans the site of normal constitutive cleavage. These antibodies were used to construct a sandwich-type enzyme-linked immunosorbent assay that detects A beta in cerebrospinal fluid, plasma and conditioned medium of human mixed-brain cells grown in vitro (see also ref. 14). By affinity chromatography, we have purified and sequenced A beta and a novel A beta fragment from human cerebrospinal fluid and conditioned medium of human mixed-brain cell cultures. These findings demonstrate that A beta is produced and released both in vivo and in vitro. These observations offer new opportunities for developing diagnostic tests for Alzheimer's disease and therapeutic strategies aimed at reducing the cerebral deposition of A beta.

Relative binding properties of fluorescein and 9-hydroxyphenylfluoron (HPF) with murine monoclonal anti-fluorescein antibodies.

Contribution of the fluorescein (F1) carboxyl group to hapten binding by idiotypically related murine monoclonal anti-F1 antibodies 4-4-20, 9-40 and 12-40 was studied by comparing relative liganded active site properties with bound Fl or 9-hydroxyphenylfluoron (HPF). Kinetic studies revealed similar association rate constants between Fl and HPF to 4-4-20 (approximately 1.1 x 10(7) M-1 s-1); however, the 4-4-20 dissociation rate for Fl was approximately 200 times slower, relative to HPF, which resulted in relative intrinsic affinity values of 1.2 x 10(10) and 6.5 x 10(7) M-1, respectively. Mabs 9-40 and 12-40 also displayed a reduced affinity for HPF and affinity constants of 5.5 x 10(5) M-1 and 6.7 x 10(5) M-1 were obtained from a competitive ELISA. Additionally, previous studies revealed that upon binding Fl, Mabs 4-4-20 (92.1%), 9-40 (44.7%) and 12-40 (73.4%) quenched Fl fluorescence. Similar analyses with HPF resulted in 64.4% and 2.0% fluorescence quenching by 4-4-20 and 12-40, respectively; however, 9-40 increased HPF fluorescence by approximately 24%. Steady-state fluorescence polarization experiments revealed that in solution, Fl (P = 0.019) and HPF (P = 0.048) were polarized to different degrees. When bound, however, Fl and HPF expressed similar polarization values (P approximately 0.455), except 9-40 bound HPF which was significantly depolarized (P = 0.428). Fluorescence lifetime experiments revealed Fl to possess two discrete lifetimes: a 3.96 ns component (free Fl) and either a 0.52 ns (4-4-20), 2.23 ns (9-40) or 0.96 ns (12-40) short component that corresponded to bound Fl. HPF, however, when bound by 4-4-20 or 9-40, was best fit by three discrete exponentials: a relatively long 4.0 ns component, a 1.11 ns lifetime (free HPF) and either a 0.52 ns (4-4-20) or 2.23 ns (9-40) component. Finally, HPF bound by Mab 12-40 exhibited a single lorenzian distributed lifetime of 1.36 ns (+/- 0.43 ns). Results are discussed in terms of Mab active site structure and conformational state dynamics.

Fluorescence measurements of immune complexes of Mab 4-4-20 with isomeric haptens.

Relative differences in the active site environment of a monoclonal antibody when covalently bound to two isomeric haptens were studied using fluorescence quenching and lifetime measurements. Murine monoclonal antibody 4-4-20, a well-characterized high affinity antifluorescein antibody, served as the model IgG protein. Isomeric haptenic probes comparatively studied were fluorescein-5-isothiocyanate (FITC I, the immunogen) and fluorescein-6-isothiocyanate (FITC II). In kinetic binding studies, the association rate for the interaction of 4-4-20 with FITC I was greater than 2,000 times faster than the reaction with FITC II. Fluorescence lifetimes for FITC I covalently bound to 4-4-20 were 3.89 ns and 0.37 ns, indicative of hapten bound outside and inside the active site, respectively. Fluorescence lifetime for FITC II within the active site was indistinguishable from bound FITC I, indicating that interactions with active site residues which resulted in a decreased lifetime were similar for both isomers. A decreased lifetime for active site bound FITC I was consistent with the 90-95% quenching of fluorescein fluorescence. Dynamic fluorescence quenching experiments with iodide and FITC I in the active site showed no solvent accessibility, whereas bound FITC II showed significant accessibility. These results suggest that the difference in bond angle which accompanies binding of isomer II relative to isomer I within the active site probably leads to steric constraints resulting in a more open configuration of the 4-4-20 active site.

Interstitial deletion of the long arm of chromosome 2 with normal levels of isocitrate dehydrogenase.

We report a 16 year old boy with the abnormal karyotype 46,XY,del(2)(q32.2q33.1) who has mental retardation, microcephaly, epilepsy, craniofacial dysmorphism, distinctive scalloped skin pigmentation, and normal levels of isocitrate dehydrogenase.

Isoelectric focusing of serum in genetic counselling of families with cystic fibrosis.

The high incidence of carriers of cystic fibrosis in the general population allows application of a less than perfect test to genetic counselling of relatives of children with the disorder and their spouses. In the absence of a definitive carrier detection test, we employ isoelectric focusing of serum in this way and include the a priori chance of carrier status in calculating the risk. The test will eventually be replaced but for the present is preferable in our hands to counselling based simply on the known gene frequency.

Serum protein polymorphisms in a village community from the Gambia, West Africa (Hp, Tf, and Gc).

Serum samples from 857 inhabitants of the village of Keneba, The Gambia, West Africa, were examined by means of polyacrylamide gel electrophoresis. In 203 cases no haptoglobin could be detected, whilst in the remaining 654 samples the three common haptoglobin phenotypes were found with gene frequencies of 0.651 (Hp1) and 0.349 (Hp2). The D1 transferrin variant gene was found with a frequency of 0.025. In the serum Gc system the fast variant Gc-Ab was detected, the gene frequencies being: Gc1, 0.943; Gc2, 0.044; and GcAb, 0.013.

The relationship between concentrations of glycosylated haemoglobins and of serum high-density-lipoprotein cholesterol in diabetic patients.

1. Concentrations of high-density-lipoprotein cholesterol and of glycosylated haemoglobins [HbA1(a+b+c)] were measured in non-fasting blood samples taken from 171 diabetic patients. 2. Mean concentrations of high-density-lipoprotein cholesterol were lower in men, and in patients not requiring insulin. 3. There was no correlation between concentrations of high-density-lipoprotein cholesterol and of HbA1(a+b+c) in the patients as a whole, but a significant positive correlation was found between these values in male diabetics not requiring insulin. 4. Changes in the concentrations of HbA1(a+b+c) were not correlated with changes in concentrations of high-density-lipoprotein cholesterol.

Isoelectric focusing of human red cell phosphoglucomutase: the distribution of variant phenotypes in a village population from the Gambia, West Africa.

A total of 637 individuals from the rural village of Keneba in The Gambia, West Africa, have been typed for red cell PGM using isoelectric focusing (pH 5--7) in polyacrylamide gels. Eight different phenotypes have been detected. The frequency of the four alleles at the PGM1 locus was found to be PGM1+(1) 0.795, PGM1-(1) 0.053, PGM2+(1) 0.133, AND PGM2-(1) 0.019. A study of the PGM phenotypes in 89 families confirmed the simple Mendelian codominant inheritance of the four alleles. Comparative population data suggest that red cell PGM typing by isoelectric focusing might prove to be a useful genetic marker in anthropological studies.

A comparison of the isoenzymes, soluble proteins, polypeptides and free amino acids from ten isolates of Trypanosoma evansi.

1. Soluble extracts from different strains of Trypanosoma evansi were compared by several analytical procedures. 2. No isoenzymic differences were detected. 3. Some clear intraspecies differences in protein isoelectric points, in polypeptide sizes and in free amino acid contents were found.