Centronuclear myopathy--morphological relation to developing human skeletal muscle: a clinicopathological evaluation.

Centronuclear myopathy (CNM), an uncommon condition, is one of the congenital myopathies. It is believed to arise as a result of maturational arrest, with persistence of myotubes postnatally. However, denervation being the basic disease process and its possible influence on central nervous system causing defect in nuclear migration has also been postulated. Keeping in view these existing controversies, we have studied 17 cases of CNM (neonatal - 1, childhood - 13, adulthood - 3) during the last twelve and a half years. Diagnosis was based on histological and enzyme histochemical findings of muscle biopsy along with clinical data. Ultrastructural characterstics of muscle have been studied in 10 cases. The affected muscle fibres showed a central nucleus (40-99%) with perinuclear halo. Type I fibre predominance with hypoplasia was consistently seen. Fibre type disproportion was noticed in 7 cases. The neonatal form revealed dense oxidative enzyme reaction product in the centre. The morphological features of CNM were compared with foetal skeletal muscles obtained at gestational ages ranging from 9 weeks - 36 weeks (n = 18). In the severe neonatal form th myofibres resembled the foetal myotubes. In the less severe childhood and adult form of CNM, aberrant organization of cytoskeletal network might have played a pathogenetic role in causing the disease.

Chediak-Higashi syndrome--a case report with ultrastructural and cytogenetic study.

We report the ultrastructural abnormalities of the leukocyte granules and the cytogenetic findings in a patient of Chediak-Higashi syndrome (CHS), who presented with cutaneous melanosis as the only clinical feature. The diagnosis of CHS was established by peripheral smear and bone marrow examination. Chediak-Higashi syndrome, a rare autosomal recessive disorder is characterized by enlarged abnormal organelles in leukocytes and other cells. An interesting aspect of our patient was the absence of recurrent infections or any other clinical stigmata. Ultrastructurally, the leukocytes and their precursors in the bone marrow showed characteristic homogenous and heterogenous giant inclusions of variable sizes and shapes. These represent the primary granules which enlarge to attain the giant abnormal size by fusion with other primary or secondary granules. Cytogenic study of the bone marrow cells showed monosomy of chromosomes 8 and 17 in 20 percent of the metaphases. Neither the gene nor the chromosomal abnormalities specific for CHS have been identified as yet and thus the significance of our cytogenetic finding is presently not clear.

A modified technique to process peripheral nerves for light microscopy.

A new technique is described to fix, paraffin embed and cut routine peripheral nerve biopsies for light microscopy. Buffered glutaraldehyde pH 7.4 is used as a common fixative for both light and electron microscopy. The nerve bits for LM are embedded in paraffin using the 'reverse embedding' method and blocks are trimmed to cut sections on the ultra microtome using glass knives. The uniformly thin sections can be utilised for any special stain and the good resolution of these thin sections facilitates better observation and documentation.

Ultrastructural variations in frog muscles subjected to sciatectomy.

Fine structural variations in two different types of muscles of frog (Rana cyanophlictis) subjected to sciatectomy were studied electronmicroscopically. Gastrocnemius muscle showed marked myofibrillar disarray and degeneration due to sciatectomy, while sartorius muscle was relatively less affected. The extent of sciatectomy induced fine structural variation was in proportion to the degree of denervation atrophy (as reflected by loss of wet muscle weight) in these muscles. Differences in the degree of degenerative changes in atrophying muscles may be attributed to variations in fiber type composition and stretch effects imposed during swimming movements.