Expression and kinetic characterization of methylmalonyl-CoA mutase from patients with the mut- phenotype: evidence for naturally occurring interallelic complementation

L-Methylmalonyl-CoA mutase (MUT) is an adenosylcobalamin (AdoCbl)- requiring mitochondrial matrix enzyme that catalyzes the isomerization of L-methylmalonyl-CoA to succinyl-CoA. Inherited defects in the gene encoding this enzyme result in the mut forms of methylmalonic acidemia. Expression of mature human MUT cDNA in Escherichia coli at a post- induction cultivation temperature of 12 degrees C, rather than 37 degrees C, led to the folding of the majority of the synthesized protein to a soluble form, with an activity of 0.2-0.3 U/mg protein in the cell-free extract, 10-15 times higher than that in human liver homogenate. Six missense mutations, producing the amino acid changes G94V, Y231N, R369H, G623R, H678R and G717V, were detected in MUT cDNA of patients suffering from the mut- form of methylmalonic acidemia, resulting from defective AdoCbl binding. Two (G623R and G717V) had been reported in other patients. Three (G94V, Y231N and R369H) are the first changes in the NH2-terminal part of the enzyme reported to cause the mut- phenotype. Enzymes with the mutations were individually expressed, and their kinetic parameters were generally in accord with published biochemical data from extracts of fibroblasts from these patients. The mutations increased the K(m) for AdoCbl by 40- to 900-fold, while V(max) values varied from 0.2% to nearly 100% of that of wild-type protein. In one case of a doubly heterozygous cell line, however, neither of the constituent mutant enzymes had a K(m) corresponding to the lower of the two estimated from the extract data. This finding may reflect the natural occurrence of interallelic complementation in vivo in this cell line.      

Bacterial pyrogenic exotoxins as superantigens.

The recent discovery of the mode of interaction between a group of microbial proteins known as superantigens and the immune system has opened a wide area of investigation into the possible role of these molecules in human diseases. Superantigens produced by certain viruses and bacteria, including Mycoplasma species, are either secreted or membrane-bound proteins. A unique feature of these proteins is that they can interact simultaneously with distinct receptors on different types of cells, resulting in enhanced cell-cell interaction and triggering a series of biochemical reactions that can lead to excessive cell proliferation and the release of inflammatory cytokines. However, although superantigens share many features, they can have very different biological effects that are potentiated by host genetic and environmental factors. This review focuses on a group of secreted pyrogenic toxins that belong to the superantigen family and highlights some of their structural-functional features and their roles in diseases such as toxic shock and autoimmunity. Deciphering the biological activities of the various superantigens and understanding their role in the pathogenesis of microbial infections and their sequelae will enable us to devise means by which we can intervene with their activity and/or manipulate them to our advantage.     

Shoulder joint: arthrographic CT and long-term follow-up, with surgical correlation

One hundred two computed tomographic (CT) arthrograms of the shoulder were retrospectively reviewed and compared with conventional double-contrast arthrograms from 101 patients (24 females and 77 males aged 9-70 years). One- to 4-year follow-up was obtained in 84 patients, 40 of whom underwent open-shoulder surgery or arthroscopy. Morphology of the normal portions of each labrum was categorized according to length, width, and tip shape. Correlation between morphology and age was weak, but abnormal labra were more common in younger patients. Conventional radiography was more accurate for detecting bony glenoid margin fractures, but CT was more accurate for detecting Hill-Sach fractures. CT was also more reliable than conventional arthrography in the detection of rotator cuff tears. Hence, few if any conventional radiographs are necessary between contrast material injection and CT imaging. A reduction in the number of images obtained will result in decreased radiation dose, less cost, and shorter examination time without loss of diagnostic accuracy.     

Ruptured intracranial dermoid cysts

Summary Rupture of intracranial dermoid cysts (RICDC) is a rare phenomenon. The mechanism of rupture, pathophysiology of fat in the ventricles and subarachnoid spaces, possible complications, and proper management of such conditions are proposed on the basis of a review of the literature and experience with two cases of ruptured intracranial dermoid cysts (One was in the pineal region, while another was in the fourth ventricle). It is concluded that rupture of intracranial dermoid cysts is usually spontaneous and non-fatal. Persistence of fat in the subarachnoid spaces postoperatively may last asymptomatically for years. Surgery is the only way to deal with these benign lesions. If the capsule is adherent to vital areas, incomplete removal is advised as recurrence and malignant transformation are unlikely to occur.     

早期慢性肾病患者血管内皮功能及肾脏病理相关性研究

目的：研究早期慢性肾病患者的血管内皮功能损害程度及其与肾脏病理损伤的关系。方法：60例研究对象分为3组：A组为20例正常对照组;B组为20例早期慢性肾病患者血压正常组;C组为20例早期慢性肾病患者肾性高血压组。对各组患者应用高频超声检测肱动脉充血前后管径变化率,评价早期慢性肾病患者血管内皮功能损害程度。对病例组行超声引导下穿刺活检,并对肾组织损伤程度行半定量积分,分析血管内皮功能与年龄、血压、肾脏病理损伤的关系。结果：①C组血流介导的血管舒张功能（Flow-mediated dilation,FMD）低于A组和B组（P＜0.05）,A组与B组之间FMD无差异性（P＞0.05）;②FMD与收缩压、肾小球损伤积分、肾间质损伤积分有相关性（P＜0.05）,与年龄、舒张压无相关性（P＞0.05）。结论：①肾性高血压患者在肾功能损害之前已经存在血管内皮功能的异常;②血管内皮功能紊乱对肾脏的病理损伤有一定的促进作用;③高频超声早期检测慢性肾病患者的血管内皮功能有重要的临床意义。