PubMed Health⌕ Search

Biomedical subjects

K D Hammond

Publications and source records attributed to K D Hammond.

At least 37 records · Page 2Linked to original sources
PubMed1991

Protein kinases associated with proliferation and differentiation in murine erythroleukaemic cells.

1. The changes in electrophoretic distribution of cytosolic protein kinases have been studied in relation to proliferation, differentiation and transformation in murine erythroleukaemic cells, using a non-denaturing polyacrylamide gel electrophoresis system. 2. Native molecular masses of the major forms were determined by Ferguson plots. 3. A two dimensional electrophoresis method was developed for determination of the subunit molecular masses. 4. These studies suggest that the major bands of activity contain components which may correspond to cGMP dependent protein kinase, cAMP dependent protein kinase and protein kinase C. 5. On hexamethylene bisacetamide induced differentiation of the cells, changes in proportions of the different forms were observed.

Acetamides↗
PubMed1990

Electrophoretic separation of protein kinases: altered mobility with different crosslinking agents in the presence of certain detergents.

Nondenaturing polyacrylamide gel electrophoresis was used to separate protein kinases in crude extracts and subcellular fractions of murine erythroleukemic cells. The kinases were detected using an in situ phosphorylation assay. The electrophoretic patterns obtained using gel bound to GelBond and prepared with AcrylAide differed from those seen without GelBond and with N,N'-methylenebisacrylamide as cross-linker. In an attempt to improve the resolution of the bands in the membrane fractions, detergent-treated preparations were electrophoresed through gels which contained either 0.1% Triton X-100 or 0.1% Nonidet P-40. The resolution of the bands in this fraction was not, however, improved with the inclusion of the nonionic detergent in the gels. When cytosol was electrophoresed through gels containing detergent, a major band of cAMP-dependent protein kinase activity showed a marked shift in mobility. This may have been the result of a structural change, altering the shape and possibly affecting the charge on the molecule, or the enzyme may have formed aggregates with the detergent.

Acetamides↗
PubMed1990

Alkaline phosphatase and phosphoamino acid phosphatases in normal and cancerous tissues of the human larynx.

The activities of alkaline phosphatase and phosphoamino acid phosphatases were measured in normal and cancerous regions of the human larynx. For each larynx, alkaline phosphatase and phosphotyrosine phosphatase activities were higher in the tumor than in the corresponding normal tissue. Phosphothreonine and phosphoserine phosphatase activities were relatively low and there were no consistent trends. The increased alkaline phosphatase activity in the tumors supports histological observations that ossification of cartilage seems to occur at the site of invasion; the phosphatase acting on phosphotyrosine could serve as a regulator of cell differentiation during tumorigenesis.

Adult↗
PubMed1989

Temporal changes in phosphoamino acid phosphatase activities in murine erythroleukaemic cells.

1. The activities of phosphotyrosine, phosphothreonine and phosphoserine phosphatases were measured at various time periods in Friend murine erythroleukaemic (MEL) cells. 2. Effects of DMSO (dimethyl sulphoxide) and HMBA (hexamethylene bisacetamide), inducers of differentiation, were examined. 3. The activities of all three enzymes showed cyclic variation when measured on a daily basis over a period of several days; this was also the case when phosphothreonine phosphatase was determined in cells treated with DMSO or HMBA and when phosphoserine phosphatase was assayed after stimulation of the cells with HMBA. 4. Evidence for rhythmic variation in phosphotyrosine phosphatase activities was also obtained when the activities were determined at hourly intervals both in control cells and those treated with HMBA. 5. The time-dependent changes observed could be significant in that control of dephosphorylation may possibly be achieved by altering the rhythms.

Animals↗
PubMed1989

Phosphoamino acid phosphatases in human normal and leukaemic lymphocytes.

The activities of phosphoamino acid phosphatases were measured in lymphocytes from normal adults. For cells from white individuals the mean value (+/- SD) for phosphotyrosine phosphatase activity was 342 +/- 120 mU/mg protein; mean values for phosphothreonine and phosphoserine phosphatase activities were 35.6 +/- 17.1 and 21.6 +/- 10.2 mU/mg protein, respectively. The corresponding activities were similar to these for both the Indian and Bantu population groups. The activity of phosphotyrosine phosphatase was significantly lower in lymphocytes from white children with acute lymphocytic leukaemia than in cells from normal children or adults. For phosphothreonine and phosphoserine phosphatases, there was no significant difference between activities obtained in lymphocytes from normal and leukaemic children.

Adult↗
PubMed1988

The influence of gestational age and preeclampsia on the presence and magnitude of serum endogenous digoxin-like immunoreactive substance(s).

Digoxin-like immunoreactive substance(s) has been measured in serum during pregnancy. Because of its presence in pregnancy, investigators have suggested that digoxin-like immunoreactive substance may play an etiologic role in the development of preeclampsia. The objectives of this study were to evaluate the relationship between maternal digoxin-like immunoreactive substance and gestational age and compare digoxin-like immunoreactive substance concentrations in patients with and without preeclampsia who were in the third trimester. Two hundred twenty patients were studied during either the first (n = 53), second (n = 56), or third (n = 111) trimester of pregnancy. Digoxin-like immunoreactive substance was undetectable in the serum of patients during the first trimester; however, 11% of second-trimester and 96% of third-trimester patients had measurable levels of serum digoxin-like immunoreactive substance (p less than 0.05). The mean +/- SEM concentration of digoxin-like immunoreactive substance in serum in third-trimester patients was 0.29 +/- 0.01 ng/ml (range 0 to 0.58 ng/ml). Gestational age at delivery was significantly lower in patients with preeclampsia than in those without preeclampsia (36.3 +/- 0.6 versus 38.8 +/- 0.4 weeks; p less than 0.001). In addition, there was no statistical difference in mean +/- SEM concentration of digoxin-like immunoreactive substance between 27 patients without preeclampsia (0.32 +/- 0.02 ng/ml) and 27 patients with preeclampsia (0.30 +/- 0.02 ng/ml; p = 0.47) matched for gestational age. We conclude that (1) digoxin-like immunoreactive substance appearance and increasing serum concentration during pregnancy are correlated with increasing gestational age and (2) there is no difference in digoxin-like immunoreactive substance values between patients with and without preeclampsia, which may exclude digoxin-like immunoreactive substance as a predictor of preeclampsia.

Adolescent↗
PubMed1987

Serum carnitine in children with kwashiorkor.

Concentrations of free and acylcarnitine were measured in serum of children with kwashiorkor and compared with those obtained for well nourished children of similar age. The mean values (S.E.) for both free and acylcarnitine were significantly lower in the kwashiorkor group [32.6 (6.2) and 8.1 (2.2), respectively] than in the controls [53.2 (2.9) and 13.8 (3.1), respectively]. Serum albumin was also low in kwashiorkor patients, but there was no significant correlation with carnitine values.

Beta-Globulins↗
PubMed1987

Glucocorticoid receptors in murine erythroleukaemic cells.

Glucocorticoid receptors in murine erythroleukaemic cells were studied in relation to hexamethylene bisacetamide (HMBA) induced differentiation. Specific binding of dexamethasone was measured. A single class of saturable, high affinity binding sites was demonstrated in intact cells; with cell homogenates or fractions binding was low and could not be reliably quantified. Receptor binding in whole cell suspensions was lower in cells which had been treated with HMBA (36.5 +/- 8.2 pmol/g protein) than in untreated controls (87.9 +/- 23.6 pmol/g protein); dissociation constants were similar in treated (2.7 nM) and untreated cells (2.5 nM). Dexamethasone, hydrocortisone, corticosterone and progesterone competed with tritium-labelled dexamethasone for receptor binding sites; cortisone, deoxycorticosterone and oestradiol had little effect.

Acetamides↗
PubMed1987

Familial hypercholesterolaemia: effect of low density lipoproteins on esterification of cholesterol in lymphocytes from homozygous and heterozygous subjects.

The effect of low density lipoproteins on esterification of cholesterol was studied in lymphocytes from patients with familial hypercholesterolaemia; results were compared with those obtained using cells from normal individuals. Freshly isolated lymphocytes were maintained in lipoprotein-deficient medium for 48 h and the rate of formation of [3H] cholesteryl oleate from [3H] oleate was then determined in the presence or absence of low density lipoproteins. In the absence of low density lipoproteins, incorporation of [3H] oleate was higher in heterozygote and homozygote cells than in normal lymphocytes. Incorporation in the presence of low density lipoproteins was increased relative to that measured in their absence for all of the subjects studied; heterozygotes and homozygotes showed marked changes in some cases but not in others.

Adolescent↗
PubMed1985

Acid phosphatase and phosphoamino acid phosphatases in murine erythroleukaemic cells.

The activities of acid and alkaline phosphatases and phosphotyrosine, phosphoserine and phosphothreonine phosphatases were measured in Friend murine erythroleukaemic (MEL) cells. The effects of treating the cells with dimethyl sulphoxide (DMSO), an inducer of differentiation, were examined. In untreated cells alkaline phosphatase activity was undetectable, though there were significant amounts of acid phosphatase (76 +/- 15 mU/mg protein) and phosphotyrosine phosphatase (16 +/- 0.9mU/mg protein); phosphoserine and phosphothreonine phosphatase activities (9 +/- 0.4 and 7 +/- 0.6mU/mg protein, respectively) were lower than for phosphotyrosine phosphatase. Addition of 1 or 2% DMSO to the culture medium resulted in the expected cell death within 2 weeks. With 0.5% DMSO, cells remained viable for at least 8 weeks, but while some appeared to have smaller nuclei and retained their rounded appearance, others became fibroblastic within several days and adhered to the culture vessel. The treated cells which had kept their morphology showed no difference in acid phosphatase activities as compared with untreated controls; phosphotyrosine phosphatase was lower (9 +/- 0.8mU/mg protein) and phosphoserine and phosphothreonine phophatases higher (11 +/- 0.5 and 10 +/- 0.4mU/mg protein, respectively) than in the controls. The Km values for p-nitrophenyl phosphate were similar in untreated and treated cells (0.069 and 0.068mM, respectively); for phosphotyrosine the Km value was lower in the treated cells (0.97mM) than in the controls (1.9mM).

Acid Phosphatase↗
PubMed1985

Electrophoretic studies of serum gamma-glutamyl transferase from patients with hepatoma.

Activities and isoenzyme patterns of gamma-glutamyl transferase (GGT) were studied in serum samples from fifteen Bantu males suffering from primary hepatoma; the results were compared with those obtained from normal samples. Enzyme activities were significantly higher in hepatoma patients than in controls. Results with Cellogel electrophoresis and the fluorescent substrate gamma-L-glutamine-7-amido-4-methylcoumarin were reproducible; two major bands of activity were observed in normal serum and three bands in hepatoma serum. The additional band seen in hepatoma serum was also detected in serum from patients with certain other disorders. With polyacrylamide gel electrophoresis using either gamma-L-glutamyl-alpha-naphthylamide or gamma-L-glutamyl-p-nitroanilide as substrates, results were inconsistent and difficult to interpret since there was a lack of specificity for GGT.

Adult↗
PubMed1984

Familial hypercholesterolaemia: esterification of cholesterol in lymphocytes from homozygous and heterozygous subjects.

A comparative study of the rates of cholesterol esterification in lymphocytes from healthy subjects and patients with familial hypercholesterolaemia (25 heterozygotes and 10 homozygotes) was carried out. Freshly isolated lymphocytes were incubated at 37 degrees C in medium containing lipoprotein-deficient serum and [3H]oleate-albumin was extracted, isolated by thin layer chromatography and quantitated. Incorporation of [3H]oleate into cholesteryloleate was significantly higher in lymphocytes from both heterozygotes and homozygotes than in cells from normal subjects; there was no significant difference between the values for heterozygotes and homozygotes. For all three groups cholesteryloleate formation was dependent on the concentration of lipoprotein-deficient serum in the medium.

Adolescent↗
PubMed1983

Familial hypercholesterolaemia : effect of low density lipoproteins on cholesterol synthesis in lymphocytes from homozygous and heterozygous subjects.

The effect of low density lipoproteins on cholesterol synthesis was studied in lymphocytes from patients with familial hypercholesterolaemia (10 homozygotes and 11 heterozygotes); results were compared with those obtained using cells from apparently normal individuals. Freshly isolated lymphocytes were maintained in lipoprotein deficient medium for 48 h and the rate of formation of [14C] cholesterol from [14C] acetate then determined in the presence or absence of low density lipoproteins. In the absence of low density lipoproteins, incorporation of [14C] acetate was lower in homozygote cells than in normal lymphocytes; differences between heterozygote and normal cells were not significant. When low density lipoproteins were included, incorporation was considerably reduced in normal cells; in lymphocytes from both homozygotes and heterozygotes results were variable with incorporation being markedly reduced in some cases, but not in others.

Adult↗