Cornel J M Kerkhof

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3-Methyladenine is generally used as an inhibitor of autophagy [P. O. Seglen & P. B. Gordon (1982) Proc. Natl Acad. Sci. USA 79, 1889-1892]. Using isolated hepatocytes, we observed that 3-methyladenine has other effects as well. 1. 3-Methyladenine promoted glycogen breakdown and inhibited flux through phosphofructokinase and pyruvate kinase. These effects(More)
Ecto-nucleotidases are plasma membrane-bound enzymes that sequentially dephosphorylate extracellular nucleotides such as ATP. This breakdown of ATP and other nucleotides obscures the characterization and classification of P2 (nucleotide) receptors. We therefore studied suramin and several of its analogs, divalent cations and ATP gamma S for their ability to(More)
Ecto-ATPase (EC is a plasma membrane-bound enzyme which degrades extracellular triphosphate nucleotides. Although its physiological function is still unclear, the enzyme obscures the study of P2 purinoceptors (i.e. receptors for ATP and other di- and triphosphate nucleotides), since it is capable of metabolizing the pharmacological ligands, such(More)
A sensitive radiochemical method for the determination of the pyruvate dehydrogenase complex (PDHC) activity in skeletal muscle tissue, based on the decarboxylation of [1-14C]-pyruvate to 14CO2, is described. Measurements can be carried out either in muscle homogenate or in 600-g supernatant, both obtainable from a small muscle biopsy specimen (20 mg). In(More)
The role of arachidonic acid metabolism and nitric oxide (NO) in hypoxia-induced changes of vascular tone was investigated in first-order cannulated rat cremaster muscle resistance arteries. Spontaneous tone reduced arterial diameter from 179 +/- 2 micrometer (fully dilated) to 98 +/- 3 micrometer under normoxia (PO(2) = 150 mmHg). Hypoxia (PO(2) 5-10 mmHg)(More)
OBJECTIVE The mechanism of spontaneous myogenic tone was investigated in isolated arteriolar segments. METHODS Arterioles were isolated from rat cremaster muscle. Segments were endothelium-denuded and mounted in a pressure myograph at 75 mmHg. Under this condition, segments spontaneously constricted from a passive diameter of 167 +/- 3 to 82 +/- 4 microns(More)
In this study, we determined whether R75231, (+/-)-2-(aminocarbonyl)-N-(4-amino-2,6-dichlorophenyl)-4-[5,5-bis( 4-fluoro- phenyl)pentyl]-1-piperazineacetamide, and its two enantiomers, all nucleoside transport inhibitors, could play a role as anti-aggregatory agents. First, we determined the binding characteristics of [3H]nitrobenzylthioinosine, also a(More)
An infant with moderate muscular hypotonia and congenital lactic acidosis died suddenly at the age of 3 months. Autopsy revealed no abnormalities responsible for this unexpected death. Measurement of mitochondrial enzymes involved in energy production indicated a severely decreased total pyruvate dehydrogenase complex (PDHC) activity in muscle tissue (0.23(More)
Hypoxia triggers a mechanism that induces vasodilation in the whole heart but not necessarily in isolated coronary arteries. We therefore studied the role of cardiomyocytes (CM), smooth muscle cells (SMC), and endothelial cells (EC) in coronary responses to hypoxia (PO(2) of 5-10 mmHg). In an attempt to determine the factor(s) released in response to(More)
Pyruvate dehydrogenase (E1) catalyzes the rate-limiting step of the pyruvate dehydrogenase complex. Since E1 activity of human muscle tissue is low, a sensitive method is needed for diagnostic purposes. Measurement of 14CO2 production from [1-14C]pyruvate provides a specific and sensitive assay for measuring E1 activity. We use as artificial electron(More)