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Biomedical subjects

C L Rutherford

Publications and source records attributed to C L Rutherford.

64 records · Page 4Linked to original sources
PubMed1976

Cell specific activity of trehalose-6-phosphate synthetase during differentiation of Dictyostelium discoideum.

Trehalose-6-P synthetase activity was low at the beginning of the life cycle of Dictyostelium discoideum, reached maximum activity at 20 h, and decreased at late sorocarp. Enzyme activity in developing spore cells increased 10-fold during differentiation from myxamoebae (0 h) to the culmination stage (20 h) and decreased slightly at sorocarp (24 h). Activity was similar in spore cells at the apex of the stalk. The activities in the stalk cells were dependent upon their position in the developing stalk. There was a decreasing gradient of activity from the apex to the base of the stalk.

Dictyostelium↗
PubMed1976

Localization of glycogen synthetase during differentiation of presumptive cell types in Dictyostelium discoideum.

Ultramicrochemical techniques were utilized to assay glycogen synthetase (EC 2.4.1.11) activity in cell samples of Dictyostelium discoideum as small as 0.01 mug (dry weight) in reaction volumes of 0.1 mul. The activity was assayed by an amplification procedure employing the enzymatic cycling of pyridine nucleotides. These techniques were used to determine the extent of localization of glycogen synthetase in the two cell types during differentiation of D. discoideum. Localization studies in developing spore cells revealed decreasing enzyme activity to the culmination stage. During this phase of development, the enzyme required the presence of soluble glycogen for activity. From culmination to sorocarp stage, enzyme activity increased and was independent of the soluble glycogen. In developing stalk cells, synthetase showed a decreasing gradient of activity. In sorocarps, the cells in the stalk apex showed synthetase activity similar to that of the spores. The cells at the bottom of the stalk had no detectable activity.

Cell-Free System↗
PubMed1976

Cell specific events occurring during development.

Ultra-microfluorometric techniques were adapted to follow the time sequence of glycogen degradation during the differentiation of two cell types in Dictyostelium discoideum. Glycogen content, glycogen phosphorylase activity, and inorganic phosphate accumulation were localized in specific cell types during stalk and spore development. Glycogen levels in pre-stalk cells remained constant during the pseudoplasmodium and early culmination stages of development. However, as pre-stalk cells migrated into the position of stalk formation, a cell specific degradation of glycogen was observed. The loss of glycogen from pre-stalk cells was accompanied by an increase in the activity of glycogen phosphorylase. This increase in activity from 0-04 to 0-14 moles/h/kg dry wt. occurred as pre-stalk cells entered the position of stalk formation. An inverse relationship was found between glycogen levels and inorganic phosphate (Pi) levels in the developing stalk. During the process of stalk construction, a gradient of Pi levels occurred from the apex to the base of the developing stalk. Glycogen degradation from pre-spore cells lagged behind that of pre-stalk cells. No change in pre-spore cell glycogen levels was observed until stalk construction was nearly completed. The results emphasize the importance of the physical position of a cell with respect to its composition and fate during development.

Cell Differentiation↗
PubMed1971

Nucleotide metabolism during differentiation in Dictyostelium discoideum.

Energy metabolism in Dictyostelium discoideum was studied by following the incorporation of [(3)H]adenine and [(32)P]Pi into the intracellular adenine nucleotides at two stages of differentiation. That the levels of nucleotides measured represented levels present in vivo was shown by demonstrating that the concentrations determined from cells quickly frozen in liquid nitrogen were identical to those from cells harvested and subsequently killed in perchloric acid. In addition, significant compartmentalization among the nucleoside triphosphates was not observed after 30 min, since uridine triphosphate, guanosine triphosphate, and adenosine triphosphate (ATP) were at radioactive equilibrium after exposure to [(32)P]Pi. At the sorocarp stage of differentiation, the dominant role of adenylate kinase activity is indicated by the observations that (i) adenylate kinase activity was found to be present, (ii) the specific radioactivities of the beta- and gamma-phosphates of ATP were equal, (iii) the increase in specific radioactivity of adenosine diphosphate was one-half that of ATP in the presence of [(32)P]Pi, and (iv) the steady-state equilibrium constant calculated (0.69) from the nucleotide levels equaled that of the apparent equilibrium constant reported in the literature (0.70). By using the same criteria, adenylate kinase activity was not the predominant reaction establishing the adenine nucleotide levels in cells at the pseudoplasmodium stage of differentiation.

Adenine↗