Intracellular nickel is required by Escherichia coli as a cofactor for a number of enzymes and is necessary for anaerobic respiration. However, high concentrations of nickel are toxic, so both import and export systems have evolved to control the cellular level of the metal. The nik operon in E. coli encodes a nickel-uptake system that includes the periplasmic nickel-binding protein NikA. The crystal structures of wild-type NikA both bound to nickel and in the apo form have been solved previously. The liganded structure appeared to show an unusual interaction between the nickel and the protein in which no direct bonds are formed. The highly unusual nickel coordination suggested by the crystal structure contrasted strongly with earlier X-ray spectroscopic studies. The known nickel-binding site has been probed by extensive mutagenesis and isothermal titration calorimetry and it has been found that even large numbers of disruptive mutations appear to have little effect on the nickel affinity. The crystal structure of a binding-site mutant with nickel bound has been solved and it is found that nickel is bound to two histidine residues at a position distant from the previously characterized binding site. This novel site immediately resolves the conflict between the crystal structures and other biophysical analyses. The physiological relevance of the two binding sites is discussed.
such as vascular prosthesis implantation or endovascular aneurysm repair (EVAR); so far, no medical therapy has been established. 7-9 Surgical treatment is highly invasive, and even elective surgery is associated with a 30-day mortality rate of 5.4%. 7 Surgical treatment is therefore indicated only for cases in which the risk of rupture is higher than the operative mortality rate.The maximum axial diameter (MAD) of the aneurysm is an indicator of rupture risk in fusiform AAA; the greater the MAD, the higher the risk of rupture. 7,8,10 In Europe and the USA, comparisons of the rate of rupture and postoperative mortality rate have led to the surgical indication of MAD ≥55 mm; in Japan, the common surgical indication is ≥50 mm, which takes body size into consideration. 7,8,11 For women, the surgical indication is sometimes taken as MAD ≥45 mm because the rupture risk in women has been reported to be 3-fold higher than in men. 11 Patients with smaller AAA (MAD <50 mm), for whom surgery is not A bdominal aortic aneurysm (AAA) is a pathological condition in which the abdominal aorta has a diameter >30 mm, or 1.5-fold greater than normal at the level of the renal artery. 1 Most AAA are asymptomatic, but once rupture occurs, the condition has a mortality rate of 65-85% and is ranked as the 16th most prominent cause of death in the USA in individuals aged ≥65 years. 2,3 In Europe and the USA, the prevalence of the condition is 2% in men aged ≥65 years, with major risk factors for morbidity including male sex, age, history of smoking, and Caucasian race. 3,4 The etiology in the majority of AAA is considered to be atherosclerosis, but a causal relationship with the typical risk factors for atherosclerosis, such as hypertension, dyslipidemia, and diabetes mellitus, remains unclear. 5 Indeed, a negative correlation with diabetes mellitus has been shown, suggesting that AAA is a pathological state distinct from atherothrombosis. 4-6The only treatment option for this condition is surgery, The maximum axial diameter (MAD) of a fusiform abdominal aortic aneurysm (AAA) is an indicator of the risk of expansion or rupture. Apart from smoking and MAD itself, few expansion risk factors have been reported. In this study, we investigated expansion risk factors for AAA.
The present study reports a case of an occult basal cell carcinoma that arose in seborrheic keratosis. The patient was a fifty-six-year-old male who presented with a dark brown plaque on his back. Clinically, the lesion demonstrated no nodules or ulcerations suggesting that it was malignant. However, histopathological analysis of the lesion revealed an atypical basaloid cell mass that appeared to be a solid basal cell carcinoma beneath and surrounded by a seborrheic keratosis lesion. Thus, the coexistence of basal cell carcinoma and seborrheic keratosis is possible and should be considered when a malignant change in seborrheic keratosis is apparent.
We report the use of dynamic hepatic scintigraphy in the assessment of the hepatic status of psoriatic patients before and during methotrexate therapy. Eighty-seven paired dynamic scans and percutaneous liver biopsies were performed in 63 patients. The liver biopsies were graded according to Warin et al. with fibrosis of grade 2 or worse being a strong indication for withdrawal of methotrexate. The sensitivity of dynamic hepatic scintigraphy in detecting fibrosis of grade 2 or worse was 83.3% and the specificity was 81.5%. The predictive value of a normal scan for fibrosis of grade 0-1 was high (98.5%) although the predictive value of an abnormal scan for fibrosis of grade 2 or worse was low (25%). Dynamic hepatic scintigraphy may therefore offer a means to reduce the number of liver biopsies necessary in patients receiving methotrexate for psoriasis.
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