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J H Walker

Publications and source records attributed to J H Walker.

At least 109 records · Page 6Linked to original sources
PubMed1982

Presynaptic plasma membranes and synaptic vesicles of cholinergic nerve endings demonstrated by means of specific antisera.

Antisera were raised to cholinergic presynaptic plasma membranes and synaptic vesicles isolated from the electric organ of Torpedo marmorata and tested by immunochemical and immunohistochemical methods. The antisera responded to many antigens not specific to nerve endings, but it was possible to eliminate these antibodies by means of simple absorption procedures with fractions containing the unwanted antigens. After absorption, staining of thin sections of electric organ by immunofluorescence was limited to the region of nerve endings in the tissue. The remaining antibodies responded in the case of the plasma membrane antisera predominantly to a 33,000 molecular-weight polypeptide and a chloroform/methanol-soluble antigen. In cross reactivity studies it was found that this antiserum not only stains cholinergic nerve endings in Torpedo but also those in mammalian tissue. The antigen responsible for the cross reactivity is restricted to the chloroform/methanol-soluble material. The vesicle antiserum labels cholinergic nerve endings in mammalian tissue as well; the relevant antigen in this case is different from the one described above and is likely to be a glycosaminoglycan. The antisera provide valuable markers for cholinergic nerve terminals. In addition, the vesicle antiserum may now be used to study axonal transport and the life cycle of this organelle in the cholinergic neurone.

Animals↗
PubMed1982

Immunohistochemical localization of a synaptic-vesicle antigen in a cholinergic neuron under conditions of stimulation and rest.

An antiserum against a specific component (a glycosamino glycan) of the cholinergic synaptic-vesicle of Torpedo marmorata has been used to investigate the localization of the component in the cell body, its movement within the electromotor axon and its fate within the nerve terminal upon electrical stimulation. After immunofluorescent staining, spots are observed throughout the cytoplasm of the lobe perikarya, although they are concentrated in the region of the axon hillock. Ligation of the electromotor nerves leading from the lobe to electric organ produces a proximal build-up of material which stains readily with the antivesicle antiserum, indicating that the vesicle antigen is transported from the cell body to the nerve terminal. A marked increase in indirect immunofluorescent staining of the electric organ is observed in the nerve ending upon electrical stimulation. We interpret this result as fusion of the vesicles with the presynaptic plasma membrane and exteriorization of the vesicle antigen to the extracellular space, thereby facilitating its staining. After recovery of the system the fluorescence declines, a result that is consistent with the reinternalization of the vesicle antigen into the core of reformed vesicles. The results support a mechanism whereby vesicles recycle within the nerve terminal and transmitter is released by exocytosis.

Animals↗
PubMed1982

Identification of a cholinergic-specific antigen Chol-1 as a ganglioside.

An antiserum specific for cholinergic terminals was used to identify an antigen conserved between Elasmobranchs and mammals. Immunohistochemistry and a cytotoxicity test were used to assay the binding of antibody to mammalian terminals. Torpedo electric organ gangliosides totally abolished antibody binding. The highest inhibitory activity was associated with a single polysialoganglioside band on TLC plates. Neuraminidase altered the migration of the inhibitory activity on TLC plates. Antibody binding was inhibited by ganglioside fractions derived from chicken and mammalian brains. A summary of those tissues in which the antigen has been detected is presented. The possible function of the antigen is discussed.

Animals↗
PubMed1982

Isolation from cholinergic synapses of a protein that binds to membranes in a calcium-dependent manner.

A protein that binds to membranes in a calcium-dependent manner between calcium concentrations of 10(-5) and 10(-6) M has been isolated in large amounts (20 mg/kg tissue) from the entirely cholinergic electric organ of Torpedo marmorata. The protein bound reversibly to membrane fractions in a calcium-specific and saturable manner. The protein also bound to lipids isolated from Torpedo electric organ and to clathrin-coated vesicles prepared from pig brain. The protein bound to a Triton X-100-sensitive site. It had an apparent subunit molecular weight of 32,000 by polyacrylamide gel electrophoresis and of 35,900 by amino acid analysis; a broad isoelectric range of 4.8 to 5.5; and 27% of its amino acids after hydrolysis were observed to be aspartic and glutamic acids. Synaptosomes derived from electric organ were enriched in the protein which is probably localised within the nerve ending. It was localised in the synaptic region of the electric organ by means of immunofluorescence. In the electric lobe, discrete patches of fluorescence were seen within the cell bodies that innervate the electric organ. The protein may be involved in the recognition of membranes within the cholinergic neurone. Proteins with similar purification properties were found in all tissues investigated so far, and polypeptides of subunit molecular weight 32,000 were identified in bovine adrenal medulla and guinea pig brain synaptosomes.

Amino Acids↗
PubMed1981

Immunohistochemical localization of cholinergic nerve terminals.

Most of the published light-microscopic methods for the localization of cholinergic nerve pathways present various difficulties of interpretation. The production and characterization of an antiserum that binds specifically to cholinergic terminals is described. The antiserum was raised to small synaptosomes prepared from the purely cholinergic electric organ of Torpedo marmorata. It was shown to lyse cholinergic synaptosomes in a mixed population derived from guinea-pig cortex. After partial purification by adsorption onto nonspecific antigens, It was used to label nerve endings in several tissues of Torpedo, rat and guinea pigs using indirect immunofluorescence histochemistry. The antiserum appears to provide a highly specific means of localizing cholinergic nerve endings in these tissues.

Acetylcholinesterase↗
PubMed1979

Inverted diverticula of the gastrointestinal tract.

Inverted diverticula of the gastrointestinal tract are rare. This paper briefly presents the roentgen findings of an inverted Meckel's diverticulum and is the first reported case of the roentgen appearance of an inverted colonic diverticulum.

Adult↗
PubMed1978

Choice of precursors for the measurement of protein turnover by the double-isotope method. Application to the study of mitochondrial proteins.

1. The double-isotope concept [Arias, Doyle & Schimke (1969) J. Biol. Chem. 224, 3303--3315] for the measurement of protein turnover was used to estimate the turnover of proteins in subcellular and submitochondrial fractions prepared from rat liver. 2. Double-isotope experiments with [3H]leucine as first precursor and [14C]leucine as second precursor were used to measure the turnover rates of proteins in subcellular and submitochondrial fractions. Solvent extraction procedures designed to remove lipids and nucleic acids from trichloroacetic acid precipitates only changed the isotope ratio of the microsomal fraction. It was not possible to measure turnover of proteins in mitochondrial and submitochondrial fractions with these precursors. 3. Double-isotope experiments were designed to minimize first-precursor reutilization by employing NaH14CO3. [3H]Arginine was used as second precursor. The turnover rates of protein in subcellular and submitochondrial fractions was measured. Solvent extraction procedures designed to remove lipids and nucleic acids showed changes in the isotope ratio for all subcellular fractions, especially in microsomal and detergent-soluble mitochondrial fractions. Isotope ratios of precipitates after solvent extraction indicate that, whereas considerable heterogeneity exists for the average rates of protein turnover in subcellular fractions, little heterogeneity is observed in the average rates of protein turnover in submitochondrial fractions.

Animals↗
PubMed1978

Relative rates of turnover of subunits of mitochondrial proteins.

1. The double-isotope concept [Arias, Doyle & Schimke (1969) J. Biol. Chem. 244, 3303--3315] for the measurement of protein turnover was used to estimate the turnover rates of protein subunits from rat liver submitochondrial fractions resolved by means of polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. NaH14CO3 and [5-3H]arginine were used as first and second precursors respectively. 2. Marked heterogeneity of protein subunit turnover rates is seen for protein subunits from water-soluble, salt-soluble and Tween 20-soluble mitochondrial proteins. 3. Much lower heterogeneity is seen in the turnover of protein subunits in Triton X-100-soluble material not binding to DEAE-cellulose at low ionic strength. The relative rates of turnover of proteins in this fraction are lower than for proteins in any other submitochondrial fraction. This fraction contains the integral membrane proteins. 4. Incorporation of [3H]arginine into subunits of the cytochrome oxidase complex is greatest for subunits with molecular weights in excess of 20000. 5. No correlation is seen between protein subunit size and the rate of turnover of the protein subunits in any of the submitochondrial fractions.

Animals↗
PubMed1978

Diffuse interstitial pneumonitis. Clinicopathologic correlations in 20 patients treated with prednisone/azathioprine.

Twenty patients with diffuse interstitial pulmonary disease diagnosed by open lung biopsy received combined prednisone/azathioprine therapy. Twelve patients demonstrated improvement with therapy. Each patient's clinical presentation, roentgenologic features and pathologic findings were correlated with their therapeutic response. Patients with an illness of one year's duration or less had a more favorable response to therapy than patients with a greater than two year duration of illness. Patients with associated extrathoracic abnormalities (anemia, glomerulitis, hepatopathy) exhibited a better therapeutic response that those with only pulmonary disease. The biopsy material from each patient was quantitatively graded on 20 morphologic variables. Statistical analysis using multiple linear regression revealed that a single variable, degree of interstitial fibrosis, was more that 90 per cent accurate in separating those responsive to therapy from those who failed to respond. Patients who respond to treatment had less interstitial fibrosis. Neither the amount of alveolar septal inflammation nor intra-alveolar cellular reaction was discriminatory in predicting response to therapy. A beneficial response to therapy was reflected in both improved lung volumes and gas exchange. Eight patients appeared to have a selective beneficial effect from azathioprine.

Adult↗
PubMed1978

Financial support for research in general practice.

I have tried to identify all the main sources of financial support for general-practice research and to classify the work and the sources of support.The Department of Health is the biggest single source and the total sums involved exceed pound1 million.About a quarter of the money is spent by academic departments of general practice, about a quarter by research units directed by practising general practitioners, and the remaining half is spent by other academic departments such as social research, medical sociology, or community health.

Family Practice↗
PubMed1977

Paediatric home nursing scheme in Gateshead.

A scheme to provide specialised nursing care for sick children in their own homes was begun in Gateshead in 1974. Selected district nurses were retrained in the paediatric unit on which the scheme was based and nursed at home 22 children referred to them by general practitioners as the alternative to hospital admission and 39 discharged to their care by the hospital. Most of the children were aged 3 years or less and came from working-class homes. Most of the mothers who were asked were in favour of the scheme.

Adolescent↗
PubMed1977

Adenocarcinoma in regional enteritis of the small intestine.

An increased risk for regional enteritis patients of small bowel adenocarcinoma to develop has been suspected but unproved. We have analyzed 49 cases reported since 1957 and two additional ones of our own. These have been compared with a current group of small bowel adenocarcinomas not associated with regional enteritis. The Crohn-associated cancers differed from adenocarcinomas not associated with Crohn disease in that (1) mean age at cancer discovery was less (46 vs 64 years), (2) more cancers arose in the ileum (76% vs 27%), (3) diagnosis and cure were less successful, and (4) they occurred more frequently. The 32 cases reported in the past five years were compared with the expected 0.1 to 5 cases. Regional enteritis patients were found to have an increased risk for the development not only of small bowel adenocarcinoma, but one that is more occult and lethal than that in individuals wihtout Crohn disease.

Adenocarcinoma↗