Search PubMed⌕ Search

Biomedical subjects

M J Geisow

Publications and source records attributed to M J Geisow.

At least 73 records · Page 4Linked to original sources
PubMed1982

Calcium-dependent binding of cytosolic proteins by chromaffin granules from adrenal medulla.

Purified chromaffin granules from bovine adrenal medulla bound a small group of medullary cell cytosol proteins at micromolar levels of Ca2+ and physiological levels of K+, Mg2+, and Mg-ATP. The bound proteins had molecular weights of 33,000-37,000 and 70,000-71,000 on sodium dodecyl sulphate-polyacrylamide gel electrophoresis and did not correspond with any previously reported cytosolic components of chromaffin cells. The new proteins were eluted from intact granules or resealed granule membranes at 0.1 microM Ca2+; binding was half-maximal at 2.6 microM. Adsorption and elution in this manner resulted in a high degree of purification of the new proteins that were minor components of the original cytosol. Partially purified fractions enriched in the 33,000-37,000 and 70,000-71,000 proteins bound 45Ca2+ at submicromolar levels in the presence of millimolar Mg2+. Calmodulin was also bound by the granule membranes and was present in trace amounts in cytosol eluates from granules, but it did not bind to the new proteins in the presence of calcium ions. The possible significance of the new proteins to calcium-mediated secretion from chromaffin cells is discussed.

Adenosine Triphosphate↗
PubMed1982

Phosphoproteins of the adrenal chromaffin granule membrane.

A fraction of chromaffin granule membranes contained a number of substrates for endogenous protein kinase activity as well as endogenous phosphatase activity. The major 32P-labelled polypeptide of molecular weight 43,000 appeared to be the alpha-subunit of pyruvate dehydrogenase of residual mitochondria. Several polypeptides showed cyclic AMP stimulation of phosphorylation of which the major polypeptide of molecular weight 59,000 shows half-maximal phosphorylation with 0.49 microM cyclic AMP. The phosphorylation of several other polypeptides is inhibited at high cyclic AMP concentrations. From studies with immunoprecipitation and two-dimensional electrophoresis it was found that alpha- and beta-tubulin and actin were absent from the granule membranes. However 32P labelling of a proportion of the copies of dopamine-beta-hydroxylase was demonstrated. The majority of the substrates for endogenous protein kinase activity are probably on the cytoplasmic side of the granule membrane.

Adrenal Medulla↗
PubMed1981

Temporal changes of lysosome and phagosome pH during phagolysosome formation in macrophages: studies by fluorescence spectroscopy.

Intravascular pH was measured within the lysosomes and newly formed phagosomes in cultured mouse peritoneal macrophages. The kinetics of pH change in both vacuolar systems was quantitatively determined within a large cell population by fluorescence spectroscopy. Additionally, pH changes within individual phagosomes were followed semiquantitatively using indicator dyes. Two novel findings were made. Firstly, the pH in new phagosomes was transiently driven alkaline (higher than physiological) even when the external medium was buffered at pH 6.5. Secondly, perturbations of phagosome-lysosome fusion had little effect upon phagosomal pH changes, even though the compounds used markedly altered the pH of the lysosomes in resting and phagocytosing cells.

Amylose↗
PubMed1980

A method for the preparation of human thyroxine-binding globulin; its importance in the establishment of an accurate and specific radioimmunoassay.

Pure thyroxine-binding globulin (TBG) is required in radioimmunoassay to prepare monospecific antisera, [125I]TBG and as primary standard. Homogeneous TBG was prepared by a three-stage affinity chromatography procedure; it could not be dissociated into subunits and its molecular weight by SDS polyacrylamide gel electrophoresis was 59 000. The amino acid composition was in agreement with two earlier reports. The secondary structure determined by circular dichroism in the far U.V. showed it to contain 24% each of alpha-helix and beta-pleated sheet. Serum TBG was determined by a 24-h radioimmunoassay using polyethyleneglycol to separate bound and free TBG. Serum TBG (mg/l, mean +/- S.D.) was: normal men 15.3 +/- 2.11 (n = 34), normal women 18.4 +/- 2.72 (n = 32) (P less than 0.005), in women on oral oestrogens 24.0 +/- 5.0 (n = 23), in normal pregnancy 38.6 +/- 3.0 (n =37), in cord blood 21.7 +/- 3.5 (n = 25) (P less than 0.001) and in euthyroid subjects aged over 60 years 17.8 +/- 4.5 (P n.s.). In women with thyroid disease TBG was reduced in hyperthyroidism: 15.5 +/- 2.5 (n = 28) and elevated in hypothyroidism: 21.0 +/- 4.0 (n = 25). Wider use in TBG-assay of non-denatured TBG of proven composition and structure should decrease the scatter in reference ranges and improve its value as a routine thyroid function test as both a primary measurement and as the T4 : TBG ratio.

Adolescent↗
PubMed1977

Cytosine deaminase: structural modifications studies.

Structural modification studies have been shown that a cysteine, a histidine and possibly an arginine residue are involved in the catalytic process. The enzyme gave a single band on polyacrylamide gel electrophoresis, and the amino acid analysis showed it to contain a high proportion of hydrophobic residues, which was in agreement with the chemical modification results.

Amino Acids↗