Mapping the active-site tyrosine of vaccinia virus DNA topoisomerase I.

Site-directed mutagenesis of the vaccinia virus gene encoding a type I DNA topoisomerase implicates Tyr-274 as the active-site residue that forms a covalent adduct with DNA during cycles of DNA-strand breakage and reunion. Replacement of Tyr-274 by phenylalanine results in loss of the ability of the enzyme to relax negatively supercoiled DNA as well as to form the covalent DNA-protein intermediate. Substitution of phenylalanine for tyrosine at nine other sites in the protein has no apparent effect on enzyme activity. Amino acid sequence alignment reveals Tyr-274 to be homologous to Tyr-727 and Tyr-771, respectively, of the type I topoisomerases from Saccharomyces cerevisiae and Saccharomyces pombe; Tyr-727 and Tyr-771 have been shown to represent the active-site tyrosines of those enzymes. Sequence comparison of the active-site regions defines a motif Ser-Lys-Xaa-Xaa-Tyr common to the viral and cellular type I topoisomerases, including the human enzyme.     

Primary hyperparathyroidism and monoclonal gammopathy

Coexistent primary hyperparathyroidism and monoclonal gammopathy, although rare, has been reported previously by a number of investigators. We report four patients with such an occurrence who were seen between 1976 and 1988. Another patient with primary hyperparathyroidism also had multiple myeloma and was in remission for 12 years. These patients represent approximately 1% of the 386 patients with primary hyperparathyroidism seen during the same 12-year period. Although several mechanisms have been proposed to explain this concurrence, we believe it is the result of a chance occurrence. A review of the literature, an estimate of the chance occurrence of coincidental monoclonal gammopathy, benign or malignant, in patients with primary hyperparathyroidism, and some practical implications of this interesting coexistence are presented.     

319例352眼眼外伤疗效观察

采用综合治疗，抗炎，散瞳，局部治疗与全身应用免疫抑制疗法，治疗３１９例３５２眼外伤获得了满意的疗效，眼球挫伤１０４例，眼球穿孔伤９３例，化学烧伤７１例，眼炸伤４６例。眼热烧伤５例，治疗包括及时清创胶粘或缝合，清除前房出血合理用皮质类固醇和免疫抑制剂等。眼球挫伤治愈率９７．１２％，穿透伤９３．１８％，热烧伤６６．６７％。３１９例眼外伤治愈率９４．６７％好转５．３３％，并对各种治疗方法进行了讨论。