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Biomedical subjects

H J Baker

Publications and source records attributed to H J Baker.

At least 55 records · Page 3Linked to original sources
PubMed1979

The gangliosidoses: comparative features and research applications.

Ganglioside storage diseases are inherited defects of lysosomal hydrolases that result in intralysosomal accumulation of gangliosides and other complex metabolites. Gangliosidoses occur in man, cats, cattle, dogs and swine. In all species, these diseases are characterized clinically by relentlessly progressive neurological deterioration. Lysosomal hypertrophy with characteristic ultrastructural inclusions occur in neurons, endothelial and other cells. Definitive diagnosis requires biochemical identification of the storage product and enzyme deficiency. Gangliosidoses in animals are important models of human lysosomal diseases and may be a significant complication in the maintenance of certain purebred stocks of domestic animals.

Animals↗
PubMed1978

Rapid accumulation of vitellogenin messenger RNA during secondary estrogen stimulation of Xenopus laevis.

Accurate quantitation of low concentrations of vitellogenin mRNA by hybridization to vitellogenin cDNA allows analysis of the accumulation of new vitellogenin mRNA sequences throughout secondary estrogen stimulation. Administration of a secondary injection of estradiol-17 beta to male Xenopus laevis which have been withdrawn from estrogen for 60 days results in synthesis of complete vitellogenin mRNA molecules in as little as 1 h after restimulation. Vitellogenin mRNA accumulates at a rate of 13 molecules/cell/min--at least four times the rate observed in primary estrogen stimulation and peaks at a level twice that observed in primary stimulation. Administration of estrogen to male Xenopus laevis evokes stable long lived changes in the pattern of vitellogenin gene expression and constitutes a type of cellular "memory effect."

Animals↗
PubMed1978

Fine structure of meganeurites and secondary growth processes in feline GM1-gangliosidosis.

Electron microscope studies were carried out on neurons of the hippocampal formation in a feline mutant with beta-galactosidase deficiency and GMI-gangliosidosis. Fusiform processes with characteristics similar to meganeurites of Golgi studies were identified between cell bodies and axons of pyramidal and granule cells. The presence of dense material subjacent to the plasma membrane at the meganeurite-axon junction provides evidence that meganeurites form at the axon-hillock region and displace the initial axonal segment distally. Meganeurites of hippocampal neurons exhibited pleomorphic secondary processes with fine structural features of growth cones. Spines and spine-synapses were abundant on perikarya and meganeurites. Numerous membranous cytoplasmic bodies (MCBs) were encountered amongst otherwise normally appearing organelles of the cell body. MCBs were densely packed in meganeurites except near their peripheral area. They were less common in dendrites and rare in synapses of the neuropil. The observations provide further support for the view that meganeurites of mature cortical neurons in ganglioside storage diseases have embryonic growth characteristics.

Animals↗
PubMed1978

Meganeurites and other aberrant processes of neurons in feline GM1-gangliosidosis: a Golgi study.

Golgi studies were carried out on neurons in several forebrain structures of young adult mutant cats with inherited beta-galactosidase deficiency and neurobehavioral deterioration due to GM1-ganglioside storage disease. Meganeurites similar to those observed in several human gangliosidoses were present on small and medium pyramidal neurons, granule cells of the fascia dentata and spiny neurons of the caudate nucleus. Large and giant pyramidal cells of the motor cortex exhibited prominent somatic spines but lacked meganeurites. Cortical non-pyramidal neurons and aspiny caudate cells were relatively normal in appearance although they showed variable increases in cell body diameter. The range of morphological alterations in different types of cortical neurons in feline GM1-gangliosidosis was identical to that found in human ganglioside storage diseases. Neurite outgrowth from meganeurites was particularly prominent in the feline mutant. The extensive proliferation of neurites confined to meganeurites indicates that the latter have growth properties typical of embryonic neuronal elements. The demonstration of neurite outgrowth from meganeurites of mature cortical neurons in feline GM1-gangliosidosis suggests a possible role for gangliosides in neurite formation during neuronal differentiation and synaptogenesis.

Animals↗
PubMed1978

Purification and characterization of GM1 ganglioside beta-galactosidase from normal feline liver and brain.

GM1 ganglioside beta-galactosidase (GM1-beta-galactosidase) was purified from normal cat brain and liver by a combination of classical and affinity procedures. The final preparation of brain GM1-beta-galactosidase was enriched over 2000-fold with a 36% yield. However, the product was shown to contain several components by disc gel electrophoresis. GM1-beta-galactosidase was also purified from liver with greater than a 30 000-fold enrichment and 40% yield. The liver enzyme was judged homogeneous by disc gel electrophoresis at pH 4.3, 8.1, and 8.9 and by gel chromatography. Both liver and brain GM1-beta-galactosidase(s) eluted as sharp symmetrical peaks from Sephadex G-200 with molecular weights of 250 000 +/- 50 000. The apparent Km determined for 4-methylumbelliferyl beta-D-galactopyranoside (4-MU-Gal) using partially purified brain GM1-beta-galactosidase was 1.73 X 10(-4) M. Liver GM1-beta-galactosidase gave a Km with 4-MU-Gal of 3.25 X 10(-4) M and for [3H]GM1 ganglioside a Km of 4.51 X 10(-4) M was calculated. The pH optima of brain and liver GM1-beta-galactosidase using 4-MU-Gal was 3.8-4.5. By contrast, liver GM1-beta-galactosidase gave a sharp activity peak at pH 4.2 with [3H]GM1 ganglioside. Inhibition by mercuric chloride and sensitivity to hydrogen peroxide and persulfate suggest the involvement of a sulfhydryl in catalysis.

Animals↗
PubMed1977

GM2 ganglioside lysosomal storage disease in cats with beta-hexosaminidase deficiency.

Two kitteens with progressive neurologic disease had increased concentrations of GM2 ganglioside in their cerebral cortex. Examination under the light microscope revealed cytoplasmic vacuolation of neurons and hepatocytes. Transmission and scanning electron microscopy demosntrated cytoplasmic inclusions encompassed by membranes in various central nervous system cell types and in hepatocytes. Beta-D-N-acetyl-hexosaminidase activity was reduced to about 1.0 percent of normal in brain, liver, and cultured skin fibroblasts of the diseased kittens; both major electrophoretic forms, A and B, of the enzyme were deficient. In fibroblasts from the parents of the diseased kittens, this enzyme activity was intermediate between that of affected and normal cats, suggesting an autosomal recessive mode of inheritance of the enzyme defect. Histopahtological and ultrastructural lesions, glycolipid storage, enzyme defect, and pattern of inheritance are similar to those of human GM2 gangliosidosis type 2.

Animals↗
PubMed1976

In vitro translation and estradiol-17beta induction of Xenopus laevis vitellogenin messenger RNA.

Administration of estradiol-17beta to male Xenopus laevis induces synthesis and secretion by the liver of the egg yolk precursor protein vitellogenin. RNA extracted from livers of estradiol-17beta-treated Xenopus laevis directs the synthesis of the entire 200,000-dalton vitellogenin monomer in a cell-free protein synthesizing system derived from rabbit reticulocytes. Vitellogenin synthesized in vitro was isolated and quantitated by indirect immunoprecipitation and identified by comparison to authentic [14C]vitellogenin. The in vitro product and [14C]vitellogenin co-migrate on electrophoresis in sodium dodecyl sulfate-polyacrylamide gels and they exhibit identical immunoprecipitation curves. Xenopus laevis vitellogenin messenger RNA has a sedimentation coefficient of approximately 30 S in sucrose density gradients. It can be purified approximately 60-fold from cell RNA by poly(U)-Sepharose chromatography and therefore appears to contain a polyadenylate sequence. Vitellogenin mRNA and vitellogenin synthesis in vivo could not be detected in unstimulated male Xenopus laevis. The relative rate of vitellogenin synthesis and the level of vitellogenin mRNA were determined at various times following the administration of estradiol-17beta. Vitellogenin synthesis is maximal 12 days after estradiol-17beta administration when it comprises approximately 70% of cell protein synthesis. The level of vitellogenin mRNA and the intracellular rate of vitellogenin synthesis exhibit a close correspondence from 4 to 16 days after administration of estradiol-17beta.

Animals↗
PubMed1976

Enhancement of natural and experimental respiratory mycoplasmosis in rats by hexamethylphosphoramide.

Hexamethylphosphoramide (HMPA) was given orally (100 mg/kg/day) to: a) conventional rats of Sprague-Dawley and Long-Evans substrains known to have indigenous Mycoplasma pulmonis infection, b) uninfected pathogen-free (PF) Fischer rats, and c) PF and axenic Fischer rats inoculated intranasally with M. pulmonis strains having a wide range of virulence. Treated rats infected with virulent M. pulmonis, either naturally or experimentally, developed severe clinical signs of murine respiratory mycoplasmosis (MRM) with mortalities of 25 to 60% compared to relatively mild MRM and no deaths in untreated, infected controls. Deaths were attributed to unusually severe lung lesions of MRM (extreme neutrophilic exudation into major bronchi and bronchiectasis) with ulceration of respiratory mucosa and hemorrhage. Rhinitis also was increased in severity by HMPA in conventional rats, but not in experimentally infected PF or axenic rats. Severity of otitis media and tracheitis was not affected by HMPA. Incidence of lesions of MRM was unchanged except for increased frequency of gross lung lesions. In the absence of M. pulmonis infection, HMPA treatment of rats caused thinning and microulceration of respiratory epithelium in major bronchi without inflammatory lung disease. Other effects induced by HMPA, with or without the infection, were destruction and fibrous replacement of olfactory epithelium, atrophy of testes, and reduced weight gains. It was concluded that HMPA markedly enhances both rate of progression and severity of the pneumonia while inconsistently potentiating the rhinitis of MRM in rats. Previous studies of HMPA are emphasized as an additional example in which the synergistic effects of an experimental chemical and an indigenous pathogen of laboratory rats have given misleading experimental results.

Animals↗
PubMed1975

Male transsexualism. Confirmation of a hypothesis?

Persistent confusion and the grouping together of similar disorders of differing origins confuse the question of genetic influences of male transsexualism. A 27-year-old adopted biological male transsexual was seen for psychiatric referral. At the time of the initial interview, events of her early development were unknown to her, and were elucidated by her adoptive mother. Her history seems to sever the genetic link between parent and child, while maintaining the psychoenvironmental continuity seen in patients who have been diagnosed as having transsexualism.

Adoption↗
PubMed1975

Pathogenic leptospiras isolated from Malaysian surface waters.

Pathogenic leptospiras (1,424) isolated from natural waters and wet soils in Malaysia comprised 29 different serovars (synonym serotypes). All except two of the serovars had been found previously in Malaysia. The exceptional serovars were werrasingha, an Autumnalis serogroup member originally isolated in Ceylon, and a new serovar designated evansi. Serovar evansi had serological affinities with serovar ranarum which was isolated from the kidney of a frog in Iowa. The large variety of serovars found in jungle areas was consistent with similar previous findings of diverse serovar infections in troops who had operated in Malaysian jungles.

Agglutination Tests↗
PubMed1974

Treatment of the severely burned child with skin transplantation modified by immunosuppressive therapy.

The IgG fraction of equine antithymocyte globulin administered by the intravenous and intramuscular route to two patients with severe thermal injury was associated with survival of the skin allografts to 19 and 42 days. In the second patient the IgG fraction was discontinued 28 days after skin grafting and rejection occurred 14 days later while the patient was receiving azathioprine and 1% topical hydrocortisone cream to the skin allografts. Although no comparison can be made between the immunosuppressive properties of antithymocyte globulin, azathioprine and topical steroids, skin allograft survival was prolonged temporarily until autograft skin from previous donor sites could be obtained. The use of skin allografts protected by immunosuppressive therapy in patients with severe thermal injury deserves further consideration.

Animals↗