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The prevalence of congenital myopathies in the United States has not been examined. To address this, we determined the point prevalence of congenital myopathies in a well-defined pediatric population from Southeastern Michigan. The overall point prevalence was 1:26,000. Mutations in RYR1 were the most common cause of congenital myopathies at 1:90,000. Our data broadly agrees with estimates from previous European studies and provides the first estimate of the prevalence of congenital myopathies in the United States. Ann Neurol 2011;70:662-665., (Copyright © 2011 American Neurological Association.)

Virus-like particles (80 mmu to 100 mmu in diameter) occur in the endoplasmic reticulum of germ cells in the ovaries of fetal guinea pigs, and are confined to this population of cells. Using these particles as a marker, the phagocytosis of degenerating germ cells by somatic cells in the cortex of the ovary was traced.

Comparison of the fine structural features of guinea pig adrenocortical cells as seen in thin sections with those revealed by freeze-fracture confirms the structural appearance of steroid-secreting cells as interpreted from thin sections and reveals significant new features of the membranous organelles. Smooth-surfaced endoplasmic reticulum appears as a network of tubules, interwoven or in parallel, and as cisternae, fenestrated and non-fenestrated. These elements are tightly packed in the deeper cortical cells, excluding other organelles from their domain. Tubules and fenestrated cisternae possess randomly distributed intramembranous particles on their PF faces, while closely packed non-fenestrated cisternae possess aggregates of particles interspersed with aparticulate regions on their PF faces. These differences in particle distribution suggest functional specialization among the various forms of reticulum. Mitochondria appear as elongated structures of varying shape. Freeze-fracture reveals that all their cristae have circular origins from the inner membrane. Sinuous tubules, which appear as tubules in section, and straight tubules, which appear as lamellae in section, arise from single sites. Flattened sac-like cristae may have multiple circular origins. Definite contact points seen between inner and outer membranes may facilitate passage of molecules, including steroids, into the mitochondrial compartments. Lysosomes and peroxisomes, which are easily identified in thin sections with the aid of cytochemistry, are difficult to identify with certainty by freeze-fracture. Single membrane-bound granules of slightly smaller diameter than mitochondria may represent lysosomes. Smaller granules interconnected with the tubular reticulum, as well as dilated regions of this organelle, may represent peroxisomes. Plasma membranes show no indication of tight junctions but do have abundant gap junctions which show a zonal differentiation: small gap junctions throughout the cortex, medium-sized regularly shaped gap junctions in zona fasciculata externa, and large irregular gap junctions in zona fasciculata interna and zona reticularis. The large junctions cover planar areas as well as surfaces of projections of one cell into another. Such junctions may allow passage of ions as well as of low-molecular-weight substances between the cells, facilitating or even amplifying the response to trophic hormone stimulation.

Isolated guinea pig adrenocortical cells were maintained in long-term culture in order to perform sequential experiments on the same cell populations. The cells produced fluorogenic steroids, shown by thin-layer chromatography to be at least aldosterone, cortisol, and corticosterone. In addition, they increased production of these steroids when treated with either ACTH or dibutyryl cyclic AMP. Of particular interest was the fact that cultures treated for the initial 24-hour culture period with ACTH maintained enhanced levels of secretion for several days in absence of hormone and had an enhanced response to ACTH later in the culture period. Such enhancement of secretion was not seen following early treatment with dibutyryl cyclic AMP. The fine structure of the ACTH-treated cells was consistent with increased steroidogenesis. They possessed more smooth-surfaced endoplasmic reticulum, larger mitochondrial crystal surfaces, and larger Golgi complexes than the cells in untreated cultures.