Chemical characterization of isocyanate-protein conjugates.

The rates of reaction of toluene diisocyanate (TDI) and hexamethylene diisocyanate (HDI) with the protein, human serum albumin, were studied. The reaction of TDI with protein was assessed by determining the total number of TDI residues bound as well as those bound in a monoureido linkage. There was a 3.5-fold greater number of residues bound in the bisureido linkage as compared to the monoureido linkage. The reaction of HDI with human serum albumin was quantified by combined assays of gas chromatography of the hexamethylenediamine formed after acid hydrolysis of the conjugate and by amino acid analyses of the protein. HDI isocyanate groups reacting with the lysyl residues and other sites on the protein molecule formed at least two reaction products, one which was easily hydrolyzable by acid and the other resistant to hydrolysis. The chemical structures proposed by these observations are similar to those of classical hapten derivatives and suggest that such derivatives may be immunogenic and/or allergenic in some workers exposed to the vapors of these reagents.     

Ageing blunts the effects of nitric oxide on myocardial O2 consumption

1. In the present study, we tested the hypothesis that the negative myocardial metabolic effects of nitric oxide (NO) were reduced in old hearts. 2. Studies were conducted in 17 young (approximately 6 months) and 18 old (> 36 months) New Zealand anaesthetized open-chest rabbits. Either vehicle or s-nitroso-N-acetylpenicillamine (SNAP; 10-4 mol/L; a NO donor) was applied to the epicardial surface of the left ventricle. Coronary blood flow (microspheres) and artero-venous (a-v) O2 difference (microspectrophotometry) were used to determine subepicardial (EPI) and subendocardial (ENDO) O2 consumption. Wall thickening was determined ultrasonically. Cyclic GMP and guanylyl cyclase activity were also determined. Myocardial a-v O2 difference, flow, O2 consumption and wall thickening were comparable in young and old hearts. 3. The EPI and ENDO O2 consumption of SNAP-treated young hearts decreased significantly (> 25%) compared with vehicle (saline). However, SNAP had no significant effects on the O2 consumption of old hearts. In addition, SNAP decreased the percentage wall thickening in young (from 18.0 +/- 1.7 to 13.4 +/- 1.6%), but not old (from 14.5 +/- 0.9 to 11.4 +/- 1.6%), hearts. Basal cGMP levels in old hearts were greater (approximately 70%) than those in young hearts (15.7 +/- 2.0 vs 9.0 +/- 0.8 pmol/g, EPI). s-Nitroso-N-acetylpenicillamine increased cGMP in EPI (13.7 +/- 1.8 pmol/g) and ENDO of young, but not old (18.7 +/- 2.3 pmol/g, EPI), hearts. Similar results were also obtained using another NO donor, namely sodium nitroprusside (SNP; 10-4 mol/L). Guanylyl cyclase activity was elevated in old rabbit hearts with 0.5 mmol/L SNP (131 +/- 12 vs 80 +/- 12 pmol/min per mg protein for old and young rabbits, respectively). 4. Thus, while older hearts had similar O2 consumption and wall thickening compared with young hearts, they responded less well to NO and had significantly elevated basal levels of myocardial cGMP.     

Prevalence and spectrum of p53 mutations associated with smoking in breast cancer

To explore the role of smoking in breast cancer, we undertook a population-based study to evaluate the prevalence and spectrum of p53 mutations in the breast tumors of smokers and nonsmokers. We evaluated 456 archival invasive breast tumors for mutations in exons 4-8 of the p53 gene, using single-strand conformational polymorphism analysis and manual sequencing. Statistical analyses were performed to determine the association of p53 mutations with clinical and smoking characteristics. Of 108 mutations identified, 77 (71%) were point mutations and 31 (29%) were deletions or insertions. A higher prevalence of p53 mutations was found in the breast tumors of current smokers (36.5%; P = 0.02) compared with never smokers (23.6%), whereas fewer mutations were found in former smokers (16.2%; P = 0.09). After adjustment for age, race, menopausal status, clinical stage, tumor size, and family history of breast cancer, current smokers were significantly more likely to harbor any p53 mutation [odds ratio (OR), 2.11; 95% confidence interval (CI), 1.17-3.78], p53 transversions (OR, 3.37; 95% CI, 1.03-11.06), and G:C-->T:A transversions (OR, 10.53; 95% CI, 1.77-62.55) compared with never smokers. Stage at diagnosis did not account for the increase in p53 mutation-positive breast cancer among current smokers. Former smokers were also more likely than never smokers to harbor G:C-->T:A transversions (OR, 2.43; 95% CI, 0.37-15.73), although this association was not statistically significant. Among former smokers, the prevalence of p53 mutations varied with time since quitting: former smokers who quit smoking for longer than 1 year had a lower prevalence of p53 mutations (10.5% for 1-5 years and 12.9% for >5 years) than those who had stopped smoking within the year of their cancer diagnosis (26.3%). Our results indicate that cigarette smoking appears to modify the prevalence and spectrum of p53 mutations in breast tumors. Moreover, the difference in mutational spectra observed between smokers and nonsmokers is suggestive of the genotoxic effects of smoking in breast tissue.     

A comparative study of Y chromosome microdeletions in infertile males from two Chinese populations

Purpose : To compare the prevalence and type of Y-microdeletions in Hong Kong and Shanghai men with severe male-factor infertility. Methods : Seven Y-linked sequence tagged site (STS) primers and seven gene-specific primers were screened in 293 infertile males (139 from Hong Kong and 154 from Shanghai) and 161 fertile men (61 from Hong Kong and 100 from Shanghai). Serum FSH, LH, and testosterone levels were also measured in these men. Results : The incidence of Yq microdeletions in nonobstructive azoospermic men from Hong Kong (8.5%) and Shanghai (6%) was similar. Yq microdeletions were observed in severe oligospermic patients (8.5%) from Hong Kong but not from Shanghai. Among the 9 Hong Kong men with Y-microdeletions, 8 had AZFc deletion and one had AZFb deletion. In contrast, 6 of 9 men from Shanghai with Y-microdeletions had AZFb deletion. The incidence of AZFb deletion among Y-microdeleted men was statistically different between the two populations. Two of the men with AZFb deletion also had AZFa and AZFc deletions. Conclusions : Regional variations in the type of Y-microdeletion existed between Hong Kong and Shanghai infertile males.