Apoptosis precedes necrosis of dystrophin-deficient muscle.

The current view that death of dystrophin-deficient muscle fibers is a necrotic process relies primarily upon the histological appearance of the tissue after the degenerative process is well advanced. Here, we tested this view by examining the possibility that apoptosis is a component of dystrophin-deficient muscle cell death. Three assays for apoptosis were employed in analyzing prenecrotic, peak necrotic and regenerated hindlimb muscle of mdx mice: (1) terminal deoxynucleotidyl transferase (TdT) mediated end-labeling of DNA in nuclei in tissue sections; (2) assays for DNA ladders; and (3) electron microscopic assays for the presence of organelles undergoing structural changes characteristic of apoptosis. At all ages sampled, mdx muscle contained apoptotic nuclei, according to TdT-mediated dUTP labeling of tissue sections. Nuclei in regenerated mdx muscle fibers did not display apoptosis. dUTP-labeled nuclei in control C57 muscles were rare or absent at all ages sampled. DNA from 4-week-old mdx mice was found to be cleaved into fragments indicative of preferential cleavage at internucleosomal sites. Electron microscopic analysis showed that organelle structural changes indicating apoptosis appear before pathological changes diagnostic of necrosis. For example, condensed mitochondria, fragmented sarcoplasmic reticulum and nuclei with chromatin condensations resembling apoptosis appear in fibers that otherwise possess normal morphology. Together, the findings show that apoptosis precedes any detectable necrotic change in mdx muscle, and that apoptotic events continue into the stage of dystrophic pathology that is currently viewed as necrosis. Thus, apoptosis characterizes the onset of pathology in dystrophin-deficient muscle which is followed secondarily by necrotic processes.

Linkage analysis of the genetic determinants of high density lipoprotein concentrations and composition: evidence for involvement of the apolipoprotein A-II and cholesteryl ester transfer protein loci.

We have tested for evidence of linkage between the genetic loci determining concentrations and composition of plasma high density lipoproteins (HDL) with the genes for the major apolipoproteins and enzymes participating in lipoprotein metabolism. These genes include those encoding various apolipoproteins (apo), including apoA-I, apoA-II, apoA-IV, apoB, apoC-I, apoC-II, apoC-III, apoE, and apo(a), cholesteryl ester transfer protein (CETP), HDL-binding protein, lipoprotein lipase, and the low density lipoprotein (LDL) receptor. Polymorphisms of these genes, and nearby highly polymorphic simple sequence repeat markers, were examined by quantitative sib-pair linkage analysis in 30 coronary artery disease families consisting of a total of 366 individuals. Evidence for linkage was observed between a marker locus D16S313 linked to the CETP locus and a locus determining plasma HDL-cholesterol concentration (P = 0.002), and the genetic locus for apoA-II and a locus determining the levels of the major apolipoproteins of HDL, apoA-I and apoA-II (P = 0.009 and 0.02, respectively). HDL level was also influenced by the variation at the apo(a) locus on chromosome 6 (P = 0.02). Thus, these data indicate the simultaneous involvement of at least two different genetic loci in the determination of the levels of HDL and its associated lipoproteins.

Comparison of three immunoassays for the rapid detection of bovine respiratory syncytial virus.

Three enzyme-linked immunosorbent assays (EIA) designed for the detection of human respiratory syncytial virus (RSV) were evaluated for the detection of bovine respiratory syncytial virus (BRSV) in bovine lungs and the results were compared with those obtained by a direct fluorescent antibody assay (DFA). The EIA tests used were Directigen EIA, Kallestad Pathfinder EIA, and Abbott RSV EIA. Homogenates of lung tissues obtained from 64 cattle that had died of respiratory disease were used; 32 were positive by DFA and 32 were negative. All EIA's varied in the amount of labor and time involved but their relative sensitivities were similar ranging between 59 and 66% when compared with DFA. The specificity of Pathfinder EIA was lower than those of the Directigen and Abbott tests. The overall agreement between the three EIA's and the DFA was 66-77% indicating that DFA is still the test of choice for detecting BRSV infection in lung tissues of cattle.