Australian paediatric journal最新文献

Results of disaccharidase assays in small bowel biopsies from 887 children over a 3 year period were analysed to establish normal values. Abnormal histology, the presence of giardia trophozoites or total absence of sucrase and isomaltase were found in 307 cases and these were excluded from further consideration. The results for maltase, sucrase and lactase from the remaining 580 children have been graphed as percentiles at various ages. They represent results which are as close to normal as it is possible ethically to obtain.

It is important to be able to clearly differentiate between Duchenne (DMD) and Becker (BMD) muscular dystrophies in early childhood in order to offer more accurate prognostic information to parents. In response to this need, biopsies from BMD and DMD patients were compared to see which features, if any, allowed a differentiation to be made. Fifteen biopsies of vastus lateralis muscle from boys with the mild (BMD) X-linked muscular dystrophy were compared with 19 biopsies from patients with the severe (DMD) form using a variety of histochemical and morphometric parameters. Both forms showed many similarities including increases in fibre variation, percentages of Type 1 fibres, internal nuclei counts, split and fragmented fibres and groups of fibres attempting regeneration. Hypercontracted and necrotic fibres, interstitial inflammatory cells and endomysial connective tissue were more commonly increased in DMD. Fibre hypertrophy was initially prominent, particularly in DMD boys until 5 years of age and in BMD patients until approximately 10 years, thereafter the mean fibre sizes became smaller than normal. Type 2B deficiency was again common in DMD as well as occurring in some BMD cases. Nuclear aggregates and small group atrophy were more likely to be found in BMD. In the absence of morphological criteria to accurately discriminate between DMD and BMD, classification of young affected males with muscular dystrophy into one or other groups, remains a difficulty in the first decade of life.

Twenty patients with mitochondrial myopathy were investigated for the presence of peripheral neuropathy. There were clinical features of a mild sensorimotor neuropathy in five patients (25%) and nerve conduction studies were abnormal in 10 patients (50%). Electrophysiological studies of the whole group showed significant impairment of motor and sensory conduction compared with controls. Sural nerve biopsy and morphometric studies were performed on four patients with clinical neuropathy. There was a reduction in density of myelinated fibres and electron microscopic features of axonal degeneration affecting myelinated and unmyelinated fibres were in evidence. Abnormal mitochondria containing paracrystalline inclusions were seen in the Schwann cell cytoplasm of two nerves.

Using standard likelihood linkage techniques, the gene for dystrophia myotonica has been localized to the proximal long arm of chromosome 19. Several large families provided the substrate for detecting linkage of restriction fragment length polymorphisms which were developed in the laboratory from flow-sorted chromosome 19 genomic libraries. In over 500 family members from five families only a single cross-over with ApoC2 was detected. Thus a useful probe for antenatal and preclinical diagnosis is now available. Details of the strategy employed within the framework of clinical diagnosis, genetic epidemiology and recombinant DNA techniques is described.

Medical applications of recombinant DNA technology are reviewed. The main impact of these techniques has been in the diagnosis of genetic disease and analysis of the underlying mutations. Two different methods can be used for the diagnosis of genetic disease. When the gene defect is known and DNA probes are available, it may be possible to establish the diagnosis directly. In many cases, however, the gene is unknown or the mutation cannot be detected easily. In these situations, it may still be possible to make a diagnosis. The genotype can be determined indirectly by linkage analysis using sequence variations which alter restriction sites (restriction fragment length polymorphisms) and DNA probes for loci close to the disease locus. Recombinant DNA techniques have also led to a process of 'reverse' genetics for identification and analysis of the causes of genetic disease. Genes can be located, isolated and characterized without any prior knowledge of their function. The nature of the gene product can then be determined and its role in the disease process defined.

Patients with progressive neuromuscular diseases (PND) suffer from motor disabilities which result not only from muscle weaknesses but also from the response of the upper motor neuron to these weaknesses. A short review of studies of the neurocontrol of posture and gait is given for patients with PND and their importance for the maintenance of ambulation will be reviewed. It is proposed that the newly established procedures for the modification of muscle properties by means of low frequency stimulation can further restore motor activities when used in conjunction with motor studies soon after the onset of PND.

An area centralis and visual streak, specializations of high cell density in the mammalian retinal ganglion cell layer, develop from a more uniform cell distribution. In the wallaby and kangaroo, this transition is first seen 60 days postnatally. Total live cell numbers in this layer fall by approximately one-third as these specializations start to appear and dying cells are seen. However, dying cells have already become concentrated at the retinal rim prior to the emergence of live cell density gradients. Our results suggest that cell death may partially sculpt patterns of live cells, particularly by lowering densities around the entire far periphery. Studies of cell division demonstrate that ganglion cells are generated and enter the ganglion cell layer before the area centralis and visual streak are formed. However, cell addition to the inner and outer nuclear layers continues as cell density gradients become apparent in the ganglion cell layer. Furthermore, this late cell generation ceases first in areas adjacent to the presumptive area centralis. The differential distribution of such prolonged cell addition to the inner and outer nuclear layers may result in an asymmetric expansion of the retina. This process would partially explain the changing topography of cells in the ganglion cell layer. Mathematical analysis of patterns of overall retinal growth support this interpretation.

It has been proposed that a defect in tocopherol transport may lead to a chronic vitamin deficiency in Duchenne muscular dystrophy (DMD). To test this hypothesis, a pilot clinical trial which involved the infusion of tocopherol-laden plasma was carried out. An increased uptake of tocopherol into erythrocyte membranes during infusions failed to produce a significant reduction in plasma enzyme levels or to arrest the dystrophic process in the two children examined. Further studies to investigate treatments with increased amounts of tocopherol, in conjunction with other antioxidants, may prove a more fruitful avenue of research.