Immunoelectron microscopic localization of dystrophin in myofibres

Duchenne muscular dystrophy, a common X-linked recessive human disease, has recently been shown to be caused by the deficiency of a large, low abundance protein called 'dystrophin'. Biochemical techniques have shown dystrophin to be membrane-associated in skeletal muscle, with enrichment of dystrophin in the t-tubules of 'triads'. Other studies using immunohistochemistry on thick (10 micron) sections have shown dystrophin to be located at the periphery of muscle fibres, possibly at the plasma membrane. These results have been interpreted as being either consistent and complementary, or contradictory. To localize dystrophin more precisely relative to these membrane systems we have employed highly sensitive and spatially accurate immuno-gold electron microscopy of ultra-thin (70-100 nm) cryosections. The major distribution of dystrophin was on the cytoplasmic face of the plasma membrane of muscle fibres, and possibly on the contiguous t-tubule membranes. The presented data, taken together with recently accumulated information regarding the primary structure of dystrophin, suggests that dystrophin is a component of the membrane cytoskeleton in myogenic cells. Thus, myofibre necrosis in patients affected with Duchenne muscular dystrophy is likely the result of plasma membrane instability.     

Phosphors?ure

Ohne Zusammenfassung     

Nonspecific laryngeal granuloma: A case study of a professional singer

A professional singer with laryngeal granuloma underwent surgery following failed response to conservative treatments. Two primary findings emerged. First, although a sizable lesion was present initially, presurgical voice measures were largely normal or superior. The exception was elevated phonatory effort during singing. Second, postsurgical voice functions were entirely normal or superior (including phonatory effort), despite demanding singing performances a few weeks following surgery. The results add to the limited corpus of quantitative, normative-referenced data on voice in patients with granulomas and are inconsistent with previous reports of voice abnormalities in such patients and poor functional response to surgery.     

Permutation-matrix groups with positive sum

Explicit forms are given for all commutative sets of permutation matrices which sum to a positive matrix, and for nonabelian groups of permutation matrices of order twice an odd prime which sum to the matrix of all ones. A relationship to circulants of level k is indicated.     

Exact kinetics for “almost random” irreversible filling of lattices

A variety of processes can be modeled by the irreversible cooperative filling of lattice sites. We consider here cases where the filling rate is independent of the state of the surrounding sitesexcept when all nearest neighbors are already filled (where a generally different rate operates) and indicate some applications for such choices. Exact solutions are obtained to the hierarchical form of the master equations for subconfiguration probabilities for a lattice of arbitrary dimension or coordination number. Analogous irreversible coadsorption processes and processes with longer-range cooperative effects, also amenable to exact solution, are discussed.Ames Laboratory is operated for the U.S. Department of Energy under Contract No. W-7405-ENG-82. This work was supported by the Office of Basic Energy Sciences.     

The effect of ion preparation on kinetic energy release: Substituent and leaving group effects on the reactivity of the [C6H5CO]+ ion

Ion kinetic energy spectrometry has been utilized to investigate the loss of CO from [p-Z-C₆H₄-CO]⁺ and [C₆H₅CO]⁺ ions generated from substituted acetophenones and benzo-phenones. The variation of the leaving group in forming the [C₆H₅CO]⁺ ion has no detectable effect on the kinetic energy release observed in the subsequent decomposition reaction. A substituent effect consistent with the assumption that substituted benzoyl ions have no memory of their origin is also observed.