The magnesium-GTP interaction in microtubule assembly

Microtubule-associated-protein-dependent assembly of tubulin with GDP in the exchangeable site (tubulin-GDP) can occur with minimal free Mg2+ (< 3 microM). This reaction is totally inhibited by EDTA and by GTP concentrations over 2 mM and stimulated by MgCl2. Quantitative aspects of this stimulation are affected by both the Mg2+ and GTP concentrations but no relationship exists between reaction rates and relative amounts of different magnesium and GTP species. GTP binding to tubulin-GDP, while maximally stimulated 2-3-fold by exogenous MgCl2, was inhibited less than 50% by EDTA, and the amount of GTP bound increased as its concentration rose to levels that inhibited polymerization. Studies on the binding of Mg2+ to tubulin-GDP in the presence and absence of GTP showed that the increase in the amount of tubulin-associated Mg2+ was substoichiometric to the amount of GTP bound (maximum stoichiometry of additional Mg2+ to GTP bound, 0.7). Upon polymerization the increased Mg2+ content of tubulin was reduced, indicating its loss during GTP hydrolysis. Mg2+ thus plays a critical role in assembly distinct from its enhancement of GTP binding to the exchangeable site. If magnesium is present in trace amounts, this role must either be catalytic during polymerization or limited to nucleation.

Acute sporadic hepatitis E in Kuwait

Fifty-seven adult patients with acute hepatitis and 34 comparison patients without liver disease were evaluated using a newly developed Western blot assay for IgM antibody to hepatitis E virus. The mean age of patients with hepatitis was 32 years (range, 18-55 years); 88% were male. Among patients with acute hepatitis, hepatitis A (anti-HAV IgM positive) was diagnosed in two (4%), hepatitis B (anti-HBc IgM positive) in three (5%), and hepatitis E (anti-HEV IgM positive) in 34 (60%). One hepatitis patient had CMV IgM, another had EBV IgM, and 16 others (28%) were negative for all serologic markers of acute viral hepatitis. No patient with acute hepatitis A or B and none of the comparison patients without acute hepatitis had anti-HEV IgM. All but one case of acute hepatitis E were found among expatriates of Asian origin, and acute hepatitis E was associated significantly with recent travel to the Indian subcontinent. These data suggest that acute hepatitis E is common among foreign workers in Kuwait but that little HEV transmission is occurring directly in Kuwait.

The presence of a human chorionic gonadotropin-like protein and its binding site in Saccharomyces cerevisiae

In this study, we characterize from Saccharomyces cerevisiae: 1) a protein that has immunological similarities to human chorionic gonadotropin (hCG), and 2) a binding site for this hCG-like protein which also binds hCG and human luteinizing hormone (hLH). Saccharomyces cerevisiae chorionic gonadotropin-like protein (ScCGLP) was purified in several steps. This protein when analyzed by SDS-PAGE, under nondenaturing conditions, produced two bands, one at 110-kDa, and another at 57.5-kDa. Under denaturing conditions, only the 57.5-kDa band appeared. This 57.5-kDa band also reacted in a Western blot, using a polyclonal antibody directed against hCG. Purified ScCGLP reacted in the following hCG immunoassays: 1) polyclonal rabbit anti-hCG equilibrium assay, 2) carboxyl-tail hCG equilibrium assay, 3) two equilibrium assays using monoclonal antibodies, and 4) free alpha-chain subunit equilibrium assay using a monoclonal antibody. Characterization of hCG/hLH binding sites in Saccharomyces cerevisiae was performed, and the ability of the ScCGLP to displace I125-hCG was also shown. Human CG and hLH were able to compete for I125-hCG binding to Saccharomyces cerevisiae blastospores (Kds of approximately 10(-8) M), while ScCGLP competed with higher affinity (Kd = 9.41 x 10(-10) M). The hCG-like immunoactivity was also present in Saccharomyces growth media, as well as in all brands of commercial beer studied.

Serodiagnosis of extrapulmonary tuberculosis by ELISA

This study aims at evaluating the specificity and sensitivity of ELISA test in detection of Mycobacterial Antibodies using A60 antigen. Sera from 100 clinically suspected cases of extrapulmonary tuberculosis were studied along with 10 sputum positive cases 25 age and sex matched healthy control. Overall positivity of the test was 80.00 per cent with 100 percent sensitivity and 92 per cent specificity. The present study recommends ELISA as an adjunct to other investigative procedures.

Recruitment of antigen-nonspecific cells plays a pivotal role in the pathogenesis of a T cell-mediated organ-specific autoimmune disease, experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) is a prototypic T cell-mediated autoimmune disease, whose target tissue is the neural retina, that is used as a model for a number of human blinding ocular diseases of a presumed autoimmune nature. EAU in rats can be induced by adoptive transfer of small numbers of retinal antigen-specific CD4+ T cell lines. Although recruitment mechanisms were assumed to play a role in the immunopathogenesis of uveitis, there is no direct evidence that would permit assessment of the importance of recruited non-antigen-specific T cells in retinal autoimmunity. In the present study, we addressed this question by using congenitally athymic Lewis rats (LEW.rnu/rnu), that are deficient in functional endogenous T cells, but are otherwise syngeneic with the euthymic Lewis rats that develop characteristically severe EAU. The uveitogenic stimulus was delivered in the form of phenotypically and functionally homogeneous pathogenic T cell lines, specific to the major pathogenic epitope of either the intracellular photoreceptor protein, S-Ag, or the extracellular photoreceptor matrix protein, IRBP. Depending on the T cell line used, EAU in athymic rats was either drastically reduced in severity (IRBP), or essentially absent (S-Ag). Susceptibility was restored when the athymic animals were reconstituted with immunocompetent T cells from syngeneic euthymic donors. While the intraocular infiltrate in euthymic rats was predominantly lymphocytic, with smaller numbers of monocyte/macrophages and even fewer neutrophils, the sparse infiltrate in athymics was largely monocytic, and with a relatively high proportion of neutrophils and eosinophils. Reconstituted animals had an intermediate histological picture with respect to the infiltrating cell types and disease severity. Our data are consistent with the interpretation that recruitment of naive T cells constitutes an amplification mechanism that is central to the expression and pathogenesis of uveitis. The extent of dependence on this phenomenon appears to be influenced by the antigenic specificity of the T cell line, and could be connected to the 'accessibility' of the target antigen in vivo.

Modified taxols, 9. Synthesis and biological evaluation of 7-substituted photoaffinity analogues of taxol

The 7-substituted taxol analogues 7, 19, 27, and 32 have been prepared as potential photoaffinity-labeled derivatives for studies of the nature of the binding site of taxol on polymerized tubulin. The analogue 32 has been prepared in both deuterium- and tritium-labeled versions. Tubulin-assembly studies were carried out with these compounds, and it was found that they showed some but not all of the properties of taxol. We conclude that these specific taxol analogues labeled at the 7 position are not ideal derivatives for photoaffinity labeling studies.

Patterns of inheritance of ovarian cancer. An analysis from an ovarian cancer screening program

BACKGROUND

A variety of inheritance patterns for familial ovarian cancer have been proposed including an autosomal dominant inheritance, a breast-ovary cancer syndrome and Lynch Cancer Family Syndrome (involving breast, bowel, ovary, and endometrial cancers).

METHODS

Women participating in an ovarian cancer screening study completed a questionnaire concerning their family history of ovarian and other malignancies (in particular breast, bowel, and endometrial cancer). Confirmation of the diagnosis was sought when there was uncertainty.

RESULTS

Two hundred forty women with a first-degree relative with ovarian cancer participated in the study. Nine percent of these women (representing 13 families) gave a definite history of two or more affected first-degree relatives. Two families had a pedigree consistent with an autosomal dominant inheritance. A breast-ovary cancer family and a Lynch cancer family syndrome were suspected in one family each, although 34% of all women gave a history of at least one other first-degree relative with either breast, bowel, or endometrial cancer.

CONCLUSIONS

Only a small number of women with a family history of ovarian cancer fit into the recognized hereditary patterns. Difficulty in recognizing the inheritance patterns and the lack of definitive genetic markers poses problems in providing adequate counseling regarding screening and prophylactic oophorectomy.

A bacterial protein has homology with human chorionic gonadotropin (hCG)

Studies from our laboratory have demonstrated the presence of a 48.5 kD cell wall protein in the bacterium, Xanthomonas maltophilia, which immunologically resembles the beta subunit of human chorionic gonadotropin. Primers were designed from the amino acid sequences of enzymatically cleaved peptide fragments of this protein. These primers were used to obtain PCR amplified products, which were subsequently cloned in a PCR11TA cloning vector, and a 492 base pair nucleotide sequence was obtained with a 164 amino acid open reading frame. When this nucleotide sequence was aligned with exon 2 of genes 5 and 6 of the beta hCG gene, a 53% homology was observed. The translated protein sequence had a 35% homology with hCG and a 25% homology with human luteinizing hormone.

Partial nucleotide sequence of the Xanthomonas maltophilia chorionic gonadotropin-like receptor

Xanthomonas maltophilia possesses a unique high-affinity binding site which binds human chorionic gonadotropin (hCG), but not human luteinizing hormone (hLH) or other glycoprotein hormones. We designed primers from the known nucleotide sequence of the human LH/CG receptor, spanning an area extending from transmembrane region 2 to transmembrane region 6. Genomic DNA extracted from Xanthomonas maltophilia was used to obtain a PCR amplified product using the above primers. The primary amplification product was cloned in a pCR11 TA cloning vector, and the partial nucleotide sequence of the gene determined. This determined sequence showed 73% identity with the human, as well as the rat LH/CG receptor. Comparison of the translated protein sequence with the human, rat and porcine receptor protein sequences showed a 52% similarity.

Characterization of the 48.5 kDa chorionic gonadotropin-like protein from Xanthomonas maltophilia

Our laboratory has previously reported the isolation of a 48.5 kDa membrane protein from Xanthomonas maltophilia (ATCC 13637) which immunologically cross-reacts with the beta-subunit of human chorionic gonadotropin (hCG) in both polyclonal and monoclonal radioimmunoassays (RIA) (1). The protein showed no reaction in RIAs for human LH, TSH, or the free alpha subunit of hCG. We have now improved the protein purification procedure and have obtained adequate bacterial protein to characterize the pure protein (designated xCG) in RIAs and also to obtain amino acid composition and partial sequence. We present these data and compare homology to hCG. An RIA for the bacterial protein has also been developed.

Role of copper in Indian childhood cirrhosis

One hundred and twenty cases of Indian childhood cirrhosis (ICC) were studied. Most of the children presented in the clinical and histological grade II of the disease. Serum copper values in 32 prospective patients were significantly raised in comparison with values in normal controls. Hepatic copper content estimated in 82 liver biopsies revealed an increase in hepatic copper content showing a significant correlation with the histological grade of the disease. All cases were breastfed. Use of brass utensils to boil or store milk fed to ICC children was not seen in 46% of cases, although their serum copper values were raised. Serum and hepatic copper is raised in ICC. Dietary copper as a source of this raised copper seems unlikely. The most probable cause could be a defect in the metabolism of copper in ICC patients.

The effect of the menstrual cycle on serum CA 125 levels: a population study

OBJECTIVE

Our objective was to assess the effect of the menstrual cycle on CA 125 levels in a population study.

STUDY DESIGN

Serum CA 125 was measured in 1478 women, with day of menstrual cycle noted in 574 women. Repeat examination was performed in women with elevated results, and 40 of these women were tracked by weekly examination of CA 125 levels.

RESULTS

A significant difference was demonstrated when midcycle samples were compared with day 1 and day 28 samples (p < 0.05). In spite of this significance the difference was not clinically useful. Elevated serum CA 125 (> 35 U/ml) levels were present in 77 (5.2%) of the premenopausal women. A significant variation was demonstrable with higher CA 125 levels about the time of menstruation in 29 of the 40 women tracked.

CONCLUSION

This study suggests that in the population as a whole the effect of the menstrual cycle on serum CA 125 is not clinically significant, but single elevated levels in an individual may represent menstrual fluctuation.

Chloroacetates of 2- and 3-demethylthiocolchicine: specific covalent interactions with tubulin with preferential labeling of the beta-subunit

We synthesized two chemically reactive A ring modified analogs of colchicine, 2-chloroacetyl-2-demethylthiocolchicine (2-CTC) and 3-chloroacetyl-3-demethylthiocolchicine (3-CTC). Both are similar to colchicine as inhibitors of tubulin polymerization and act as competitive inhibitors of colchicine binding (apparent Ki values, 3 microM). [14C]-labeled 2-CTC and 3-CTC bound to tubulin at 37 degrees C but not at 0 degree C, and bound drug formed covalent bond(s) with tubulin. The binding and covalent reactions were inhibited by podophyllotoxin. About 60% of the bound 3-CTC rapidly formed a covalent bond with tubulin. With 2-CTC the covalent reaction was slower than the binding reaction, and only one-third of the bound 2-CTC reacted covalently with tubulin. The ratio of radiolabel in beta-tubulin to that in alpha-tubulin was about 4:1 with both 2-CTC and 3-CTC.

Factors influencing serum CA 125 levels in normal women

Serum CA 125 levels were studied in 2544 healthy women. Menopausal status and a history of hysterectomy were both highly significant influences on the CA 125 level (P less than .0001 for both factors). A history of hormone replacement therapy was also highly significant in reducing CA 125 levels (P = .002) in postmenopausal women. Other factors such as parity, history of unilateral oophorectomy or oral contraceptive usage, or family history of ovarian cancer were not significant influences when analysis of covariance was performed. When premenopausal women were assessed separately, age was significant (P = .04). The number of years since menopause did not influence CA 125 levels. Both hysterectomy and menopausal status have a clear effect on serum CA 125 levels and must be considered if serum CA 125 is to be used as a screening test.

Partial characterization of the 30 kD Ig-binding protein from Pseudomonas maltophilia

We have previously demonstrated that Pseudomonas maltophilia (ATCC 13637) possess a 30 kDa cell wall protein which binds various subclasses of IgG's and IgA by their Fc region. The protein was solubilized by papain and purified by affinity chromatography on cyanogen bromide activated sepharose beads conjugated with human IgG. The eluent was electrophoresed on a 12% polyacrylamide gel under denaturing conditions, and the immunoactive bands identified by Western blot analysis, a second gel was stained with Coomassie blue. The affinity purified eluent was electrophoresed on a one-dimensional 15% polyacrylamide gel and stained with Coomassie blue. The protein band of interest was cut. The protein band was then digested in situ with Staphylococcus aureus V-8 protease. The peptide bands were separated by electrophoresis on a second one dimensional 15% polyacrylamide gel and then electroblotted into a polyvinylidine difluoride membrane. The bands were visualized by staining with Coomassie blue, cut out, and sequenced using an automated gas phase sequencer. Minimal amino acid composition was determined in a similar fashion. We have thus obtained partial N-terminal amino acid sequence data from the above method.

Stimulation of Candida albicans transition by human chorionic gonadotrophin and a bacterial protein

Candida albicans, a dimorphic fungus, is involved commonly in human infections with the mycelium form more associated with pathogenicity. The influence of various hormones and a bacterial protein on the transition from blastospore to mycelium was assessed. Human luteinizing hormone (hLH), chorionic gonadotrophin (hCG), and an hCG-like material purified from a bacteria, Xanthomonas maltophilia (PCG), were able to increase the rate of transition when compared with the controls. The effect of the two hormones and the bacterial peptide were specific, as human follicle stimulating hormone (hFSH), thyroid stimulating hormone (hTSH), growth hormone (hGH), prolactin (hPrl) and rat and bovine LH (rLH, bLH), and bovine albumin and gamma globulin did not affect the transition. The binding of 125I-hCG or 125I-LH to spheroplasts of Candida albicans were competitively displaced by hCG, hLH, and PCG. Scatchard analysis of binding of all three ligands revealed two binding sites with a high-affinity nM Kd. Thus, hCG, hLH, and PCG induce transition of Candida albicans from a blastospore state to a mycelium form, suggesting that these hormones may modify the pathogenicity of Candida albicans.

Ultrasensitive, specific, two-antibody immunoradiometric assay that detects free alpha subunits of glycoprotein hormones in blood of nonpregnant humans

This noncompetitive, sensitive, immunoradiometric assay of the free alpha subunit of human pituitary glycoprotein hormones is based on two monoclonal antibodies and an avidin-biotin separation system. The affinity of the first antibody, mouse anti-alpha subunit covalently conjugated to biotin, is 3.8 x 10(11) L/mol. The second antibody, radiolabeled with 125I, has an affinity of 5.4 x 10(11) L/mol. A polystyrene ball coated with avidin serves as the separation system. Tests of "purified" immunochemical-grade intact human glycoprotein hormones yielded cross-reactions of approximately 2% in the assay. Sephadex G-100 column chromatography showed that this "cross-reaction" was caused by contamination of the various hormone preparations with free alpha subunit. When the intact glycoprotein hormones were further purified with specific anti-alpha monoclonal antibody, their reaction in the alpha subunit assay was undetectable (less than 0.01%). Interassay CV averaged 3.5%, and intra-assay CV averaged 7.5% at low concentrations of subunit. The detection limit of the assay (0.01 micrograms/L) is adequate to detect free alpha subunit in the blood of normal humans. Mean (SD) concentrations of free alpha subunit in normal humans were as follows: eugonadal men = 437 (35) ng/L; postmenopausal women = 1231 (40) ng/L; eugonadal women, follicular phase = 1061 (40) ng/L; eugonadal luteal phase = 780 (45) ng/L.

Isolation of a 30 kDa immunoglobulin binding protein from Pseudomonas maltophilia

We have demonstrated that Pseudomonas maltophilia (ATCC No. 13637) possesses an exposed, immunologically accessible protein which binds to the Fc region of several species of immunoglobulins. Whole bacteria suspensions were incubated for 18 h with purified 125I-labelled antibodies with and without added non-labelled immunoglobulins. The suspensions were centrifuged for 30 min and the pellet containing bacteria was assessed for radioactivity. Using this crude assay, the whole organism bound 125I-labelled rabbit and mouse immunoglobulins and the purified Fc portion of human IgG. All of these labelled preparations were competitively displaced by unlabelled rabbit and mouse immunoglobulins, and Fc of human IgG, as well as human immunoglobulin subclasses. The organism was sonicated to solubilize this immunoglobulin binding protein. Using this sonicated preparation, it was shown that unlabelled Fc of IgG, unlabelled mouse and rabbit immunoglobulins, all competitively displaced 125I-labelled human Fc of IgG in a dose-response manner. A partially purified protein was prepared by Sephacryl S-300 followed by Sephadex G-100 column chromatography. This preparation was incubated with 125I-Fc gamma and with the following purified unlabelled preparations: F(ab')2 of IgG, Fc of IgG, murine monoclonal IgA, IgG1, IgG2, IgG3, and IgG4. All except F(ab')2 of IgG produced dose response competitive displacement. The molecular weight, as estimated by SDS-PAGE and Western blot, was 30,000 daltons. In Western blots, Fc gamma, murine monoclonal IgA, and human immunoglobulin subclasses, all showed affinity for the immobilized protein. Human F(ab')2 fragments did not show affinity for the protein. Radioiodinated pseudomonal Ig-binding protein showed affinity for human IgG coupled to Sepharose, and was displaced by unlabelled pseudomonal Ig-binding protein. Scatchard analysis of binding showed two binding affinities: two distinct types of Ig-binding proteins were obtained, a high affinity with Kd = 1.54 x 10(-10) and a lower affinity with Kd = 2.36 x 10(-8). This immunoglobulin binding protein may be useful in immunoglobulin purification or identification.

Isolation of a 48.5-kDa membrane protein from Pseudomonas maltophilia which exhibits immunologic cross-reaction to the beta-subunit of human chorionic gonadotropin

In separate studies we have shown that Pseudomonas maltophilia (American Type Culture Collection 13637) possesses an immunoglobulin Fc-binding protein. We have found that this protein prevents the application of immunoassays using monoclonal antibodies to study possible production of a CG-like material by this bacteria. Employing an immunoglobulin saturation technique to block this protein as well as a zwitterion detergent membrane solubilization technique, we now report the isolation of a membrane protein from Pseudomonas maltophilia which shows immunological relationships to the beta-subunit and carboxyl tail of human pregnancy CG. This pseudomonas immunoreactive material produced dose-response curves in the following CG immunoassays: 1) a polyclonal rabbit anti-CG equilibrium assay, 2) carboxyl tail CG equilibrium assay, and 3) two CG equilibrium assays using monoclonal antibodies. The pseudomonas CG-like protein did not react in equilibrium assays for human TSH, human LH, or free alpha-subunit of CG. The pseudomonas CG-like protein was purified by affinity chromatography. The purified protein showed only 0.25% cross-reaction with pregnancy CG in the monoclonal antibody equilibrium assays. Furthermore, the purified protein showed no binding to rat testicular CG/LH receptors, but showed avid binding to the pseudomonas CG-binding protein previously described by Richert and Ryan. The pseudomonas protein showed no binding to Concanavalin-A, which avidly binds pregnancy CG. When assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting, this protein had a mol wt of 48,500 daltons, which is larger than the mol wt of the unglycosylated beta-subunit of pregnancy CG. We conclude that pseudomonas contain a protein that has partial homology to the beta-subunit of pregnancy CG. This material does not bind to mammalian CG receptors, but does bind to a pseudomonas CG-binding site. The latter suggests it has a function, as yet unknown, in pseudomonas.

HIV antibody screening among immigrants: a cost-benefit analysis

To assess the economic impact of HIV (human immunodeficiency virus) antibody screening among potential immigrants on Canada's health care system we estimated the costs and benefits of such screening among the 160 135 immigrants who entered Canada in 1988 using the in-hospital costs of treating AIDS (acquired immune deficiency syndrome) over the 10 years after immigration. This economic model was based on current international HIV seroprevalence data, Canadian immigration statistics and estimates of disease progression. Between 343 and 862 of the immigrants were estimated to have been HIV seropositive; with the use of the enzyme-linked immunosorbent assay and the Western blot technique 310 to 780 of them would have been correctly identified as being seropositive, and 33 to 82 would have been incorrectly classified as being seronegative. Another 16 would have been falsely classified as being seropositive. There would have been 151 to 379 cases of AIDS from 1988 to 1998 among the immigrants identified as being HIV-positive. The estimated total cost of screening would have been $3.3 to $3.4 million. The in-hospital costs of treating HIV-infected immigrants in whom AIDS developed between 1989 and 1998 would have been $5.0 to $17.1 million. Accordingly, screening would have saved $1.7 to $13.7 million over the 10 years after immigration. However, we do not advocate screening on the basis of economic analysis alone and acknowledge that any policy regarding such screening must also incorporate social, legal and ethical considerations.

ELISA for diagnosis of tuberculosis

Antigen A 60 of Mycobacterium bovis is a cell wall antigen with almost complete cross reactivity with antigen A 60 of Mycobacterium tuberculosis. This antigen was used for the ELISA technique for 100 cases suspected of childhood tuberculosis to evaluate the usefulness of the method in the diagnosis. The positivity rate in pulmonary tuberculosis was 65.1%, in central nervous system tuberculosis 50.0% and in the miscellaneous group 76.4%. The overall positivity was 61.0%, proving the utility of the method for diagnosis.