Biomedical subjects
Publications and source records attributed to J Mallet.
The expression of tyrosine-hydroxylase (TH) gene was analysed in tissue sections of bovine adrenal glands, by in situ hybridization using a single-stranded cDNA probe. Tissue fixation and hybridization conditions were found that led to a specific and sensitive detection of TH.
The study concerns the results at the end of growth of an homogeneous series of congenital dislocation hips, treated by slow reduction, and secondary femoral neck osteotomy. Some of these hips were initially treated orthopaedically, others were operated for open reduction, more often, on account of a principle of treatment than due to necessity. The comparison of these two series allows the conclusion that the nocivity of the surgical procedure was demonstrated in most cases. The study demonstrated some harmful actions in the treatment of congenital dislocation hip at the age of walking. According to the authors, they aggravate the rate of deformities due to vascular lesions. The authors stress some therapeutic necessities, and describe their present attitude towards these hip dislocations. Their attitude is based upon a mild reduction, under progressive traction, abduction, and medial rotation. Tenotomies are, if necessary, performed previously. A plaster immobilization is then applied, until a sufficient penetration of the femoral head into covering acetabulum. In most cases, an abnormal femoral neck orientation was corrected by an osteotomy. An innominate osteotomy to improve the cover of the head was only performed when the centering of the head remained imperfect. By modifying an already ancient technique, which was proved by 84% good results in a series of 112 hips reviewed at the end of growth, the authors expect an actual decrease of the late trophic deformities.
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The authors have analysed the results of treatment of 112 congenitally dislocated hips at the end of growth. They had been treated at walking age by progressive reduction and femoral osteotomy. Any hips that required open reduction were excluded from the study. Over the years, the principles of treatment remain the same but the technique was improved. Most of the poor results were related to trophic or vascular complications. Satisfactory results were obtained in 84 p. 100 of cases. Improvements in technique suggest to the authors that better results may be expected in the future.
Five recombinant DNA plasmids have been constructed that contain structural gene sequences for rat tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2]. Rat pheochromocytoma PC 12 cell line, which contains relatively high levels of catecholamine-synthesizing enzymes, was used to purify RNA. TyrOHase cDNA clones were identified by screening 350 cDNA clones constructed from partially purified TyrOHase mRNA. A rapid and powerful screening of the recombinant clones by differential colony hybridization was possible because TyrOHase is a tissue-specific protein. The final selection relied on the ability of cDNA inserts to hybridize specifically to TyrOHase mRNA as judged by cell-free translation and immunoprecipitation. Blot hybridization analysis of polyadenylylated RNA from PC 12 cells indicated a major mRNA species of 1.9 kilobases. A species of the same size was identified from a human pheochromocytoma tumor, indicating a crossreactivity between rat TyrOHase cDNA and human TyrOHase mRNA.
RNA from PC 12 cells was translated in a cell-free system and the peptides synthesized in vitro were analyzed by immunoprecipitation with an anti-T.H. serum raised in Rabbit. Analysis of the immunoprecipitate on a SDS-polyacrylamide gel reveals a major band with a molecular weight of 62000 dalton. A protein of the same molecular weight was also precipitated from a PC12 cell lysate. This molecular weight of 62000 dalton corresponds to the reported for tyrosine hydroxylase purified from PC12 cells.
A preparation highly enriched in isolated Purkinje cell perikarya was obtained from the developing rat cerebellum. The technique, which also yields a fraction enriched in differentiated astrocytes, involved the removal of heterogeneously-sized replicating cells in vivo by treatment with hydroxyurea prior to dissociation of cells with mild trypsinization and fractionation by sedimentation at unit gravity. Fractions were monitored in terms of particle size and by light and electron microscopy. Pooled fractions containing at least 50% perikarya of > 14.5 micron diameter were enriched in cells resembling Purkinje neurons. Definitive identification of these cells was obtained using an antiserum specific to Purkinje cells. In immunocytochemical studies about 80% of the cells in the fraction enriched in large cells reacted with the antiserum vs about 4% in the unfractionated cell suspension, whilst most of the other cells were identified as astrocytes containing glial fibrillary acidic protein.
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The protein composition of subcellular fractions of the cerebella of normal and weaver, staggerer and nervous mutant mice and of X-irradiated rats are studied by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. The patterns observed are compared with those of granular and Purkinje cells purified from rat cerebella. In particulate fractions from weaver and X-irradiated rat cerebella, several protein bands are missing. These bands are present in purified rat granular cells. The most obvious deficit concerns a nuclear protein of apparent molecular weight 30,000, presumably the F1 histone. In these agranular cerebella the total DNA content is approximately 7 times lower than in the control animals and the DNA to protein ratio decreases approximately by a factor of two. In the cerebella from homozygous staggerer and nervous mutant mice, where the Purkinje cells are either abnormal or absent, a protein of apparent molecular weight 400,000 is markedly reduced. This membrane-bound protein is present in preparations of purified Purkinje cells.
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