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Biomedical subjects

H Woelders

Publications and source records attributed to H Woelders.

26 records · Page 2Linked to original sources
PubMed1988

Unique relationships between the rates of oxidation and phosphorylation and the protonmotive force in rat-liver mitochondria.

The rate of ATP synthesis (JP) in isolated rat-liver mitochondria was strongly dependent on the magnitude of the protonmotive force (delta mu H+) across the mitochondrial inner membrane. Addition of different concentrations of various uncouplers or malonate to mitochondrial incubations in State 3 led to a depression of delta mu H+ and a concomitant decrease in JP. A unique relationship between JP and delta mu H+ was obtained, which was independent of the way in which delta mu H+ was varied. This unique relationship was observed when K+ (in the presence of valinomycin) was used as a probe for delta psi. Different relationships between JP and delta mu H+ were observed when K+ was used as a probe for delta psi and when K+ was measured after separation of the mitochondria by centrifugation without silicone oil. This led to a serious underestimation of delta psi, specifically when uncouplers were present, and non-unique flow-force relationships were thus obtained. Anomalous relationships between JP and delta mu H+ were also found when TPMP+ was used as a probe for delta psi. However, in uncoupler incubations the presence of TBP- strongly affected the TPMP+ accumulation ratio without any effect on the K+ accumulation or on JP and in the presence of TBP- unique relationships between JP and delta mu H+ were again obtained. This indicates that the accumulation of TPMP+ inside the mitochondria is not a straightforward function of delta psi but also depends on conditions like the presence of TBP- or uncouplers. We conclude that there is a unique relationship between the rate of phosphorylation and the protonmotive force in mitochondria and that under some conditions the behaviour of TPMP+ is anomalous.

Adenosine Triphosphate↗
PubMed1986

Flow-force relationships in mitochondrial oxidative phosphorylation.

The rates of oxidation and phosphorylation in isolated rat-liver mitochondria have a steep dependence on the protonmotive force (delta mu H+) across the membrane. These experimentally observed relationships proved to be independent of the way in which delta mu H+ was varied. These results were obtained when the membrane potential (delta psi) was calculated from the distribution of K+ (in the presence of valinomycin). When triphenylmethylphosphonium (TPMP+) was used as a probe for delta psi, slightly different flow-force relationships were obtained. We conclude that unique relationships exist between delta mu H+ and the rates of oxidation and phosphorylation, and that under some conditions the behaviour of the probe TPMP+ is anomalous.

Animals↗
PubMed1985

The phosphate potential maintained by mitochondria in State 4 is proportional to the proton-motive force.

Evidence is presented for a proportional relationship between the extramitochondrial phosphate potential (delta Gexp) and the proton-motive force (delta mu H+) across the mitochondrial membrane in rat-liver mitochondria oxidising succinate in State 4, when delta mu H+ is varied by addition of uncouplers or malonate. This relationship was found when precautions were taken to minimise interference with the determination of delta Gexp and delta mu H+ by intramitochondrial nucleotides, adenylate kinase activity, the quenching method, and delta mu H+-dependent changes in matrix volume. A non-proportional delta Gexp/delta mu H+ relationship was obtained when these precautions were omitted. Our results do not support mosaic protonic coupling, but are not necessarily in conflict with other localised coupling schemes.

Adenine Nucleotides↗
PubMed1985

On the origin of peritoneal resident macrophages. II. Recovery of the resident macrophage population in the peritoneal cavity and in the milky spots after peritoneal cell depletion.

A kinetic study of the resident macrophage population in the peritoneal cavity and in the milky spots was done in mice depleted of peritoneal cells by repeated peritoneal washing. According to the distribution of the peroxidatic activity, four types of peritoneal macrophages could be distinguished. The size of each of these subpopulations depends on the length of the interval after peritoneal-cell depletion. Tritiated thymidine experiments revealed in the peritoneal cavity and in the milky spots local DNA synthesis by resident and PO-negative macrophages but not by monocytes or exudate macrophages and exudate/resident macrophages. The relationships between the various types of macrophages are discussed. No evidence was found for a relationship between resident macrophages and monocytes or macrophages with PO-positive granules. The PO-negative macrophage population was suggested to be heterogeneous, part of it being derived from monocytes and part having a relationship with the resident macrophages.

Animals↗
PubMed1979

Intracellular cyclic GMP-binding proteins in cellular slime molds.

The complexity of cyclic GMP-binding activity in the 48,000 X g supernatant of three species of the cellular slime molds (Dictyostelium discoideum, Dictyostelium rosarium, and Polysphondylium violaceum) was studied by gel filtration chromatography on AcA 34 Ultrogel. All these species have in common a cyclic GMP-binding protein of molecular weight of about 2.5 X 10(5) which specifically binds this nucleotide. In addition, Scatchard plots of assays carried out with the 48,000 X g supernatant of these species exhibit cyclic GMP-binding activity with an apparent dissociation constant of about 1 nM. None of the cyclic GMP-binding proteins separated by chromatography on AcA 34 Ultrogel was associated to protein kinase activity stimulation. In view of the cyclic GMP function during chemotactic transduction in the cellular slime molds, the possible molecular function for this 2.5 X 10(5)-dalton cyclic GMP-binding protein is discussed.

Carrier Proteins↗
PubMedDate not supplied

The fix vital stain method. Simultaneous determination of viability and acrosomal status of bovine spermatozoa.

A rapid, accurate and precise method for simultaneous determination of acrosomal status and viability of bull spermatozoa is introduced and evaluated. The method involves fixation of semen with glutaraldehyde and subsequent addition of the fluorescent dye Hoechst bisbenzimide 33258 (H33258). Wet mounts were examined using a combination of phase-contrast and fluorescence microscopy (x500) for simultaneous visualization of the acrosomal apical ridge, which is indicative of the presence of an intact acrosome, and H33258-labeled nuclei, which is indicative of membrane-damaged cells. This fix-vital stain method allows differentiation between true acrosome reactions and degenerative postmortem loss of acrosomal membranes. Incubation of frozen-thawed spermatozoa for 60 minutes at 37 degrees C in the presence of calcium ionophore A23187 resulted in an increase in the percentage of true acrosome-reacted spermatozoa. The fix-vital stain method does not contain any processing steps that result in loss, selection, or damage of spermatozoa and therefore allows evaluation of representative semen samples.

Acrosome↗