长春净月潭地区土壤跳虫的生态分布

土壤动物直接参与土壤形成,它与土壤微生物的相互配合,对植物凋落物的分解起着十分重要的作用。土壤跳虫是土壤动物中最重要的类群之一。关于它的生态分布,目前国内报道不多。东北师范大学和日本九州大学合作,对长春净月潭地区的土壤跳虫进行了初步调查。     

The mutation rates of di-, tri- and tetranucleotide repeats in Drosophila melanogaster

In a recent study, we reported that the combined average mutation rate of 10 di-, 6 tri-, and 8 tetranucleotide repeats in Drosophila melanogaster was 6.3 x 10(-6) mutations per locus per generation, a rate substantially below that of microsatellite repeat units in mammals studied to date (range = 10(-2)-10(-5) per locus per generation). To obtain a more precise estimate of mutation rate for dinucleotide repeat motifs alone, we assayed 39 new dinucleotide repeat microsatellite loci in the mutation accumulation lines from our earlier study. Our estimate of mutation rate for a total of 49 dinucleotide repeats is 9.3 x 10(-6) per locus per generation, only slightly higher than the estimate from our earlier study. We also estimated the relative difference in microsatellite mutation rate among di-, tri-, and tetranucleotide repeats in the genome of D. melanogaster using a method based on population variation, and we found that tri- and tetranucleotide repeats mutate at rates 6.4 and 8.4 times slower than that of dinucleotide repeats, respectively. The slower mutation rates of tri- and tetranucleotide repeats appear to be associated with a relatively short repeat unit length of these repeat motifs in the genome of D. melanogaster. A positive correlation between repeat unit length and allelic variation suggests that mutation rate increases as the repeat unit lengths of microsatellites increase.      

Scleroderma-polymyositis overlap syndrome versus idiopathic polymyositis and systemic sclerosis: a descriptive study on clinical features and myopathology

Introduction

The objective was to characterize the clinical and myopathologic features of patients with scleroderma-polymyositis (SSc-PM) overlap compared with a population of patients with systemic sclerosis (SSc) and polymyositis (PM).

Methods

A three-way comparison of patients with SSc-PM overlap (n = 25) with patients with SSc (n = 397) and PM (n = 40) on clinical and myopathologic features and causes of death. One neuropathologist blinded for the diagnosis evaluated all recent available muscle biopsies. Biopsies were scored for presence of inflammation, necrotic muscle fibers, rimmed vacuoles, fibrosis, and immunohistochemical staining. Clinical or myopathologic characteristics were compared by using the χ² test or one-way analysis of variance (ANOVA).

Results

The prevalence of SSc-PM overlap in the Nijmegen Systemic Sclerosis cohort was 5.9%. The mortality was 32% (eight of 25) in SSc-PM, of which half was related to cardiac diseases. The prevalence of pulmonary fibrosis was significantly increased in SSc-PM (83%) (P = 0.04) compared with SSc (49%) and PM (53%). SSc or myositis-specific antibodies were nearly absent in the SSc-PM group. In almost all biopsies (96%) of SSc-PM patients, necrotic muscle fibers were present, which was significantly increased compared with PM patients (P = 0.02).

Conclusions

Patients with SSc-PM have increased prevalence of pulmonary fibrosis and cardiac disease as the cause of death compared with patients with SSc and PM . In addition, we found that necrotizing muscle fibers with inflammation characterize SSc-PM overlap in muscle biopsies. Further research should focus on underlying mechanisms causing necrosis, inflammation, and fibrosis and their relation to pulmonary involvement and mortality in patients with SSc-PM overlap.