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Biomedical subjects

M Wikström

Publications and source records attributed to M Wikström.

213 records · Page 12Linked to original sources
PubMed1978

Proton-translocating cytochrome c oxidase in artificial phospholipid vesicles.

The proton translocating properties of cytochrome c oxidase have been studied in artificial phospholipid vesicles into the membranes of which the isolated and purified enzyme was incorporated. Initiation of oxidation of ferrocytochrome c by addition of the cytochrome, or by addition of oxygen to an anaerobic vesicle suspension, leads to ejection of H+ from the vesicles provided that charge compensation is permitted by the presence of valinomycin and K+. Proton ejection is not observed if the membranes have been specifically rendered permeable to protons. The proton ejection is the result of true translocation of H+ across the membrane as indicated by its dependence on the intravesicular buffering power relative to the number of particles (electrons and protons) transferred by the system, and since it can be shown not to be due to a net formation of acid in the system. Comparison of the initial rates of proton ejection and oxidation of cytochrome c yields a H+/e- quotient close to 1.0 both in cytochrome c and oxygen pulse experiments. An approach towards the same stoichiometry is found by comparison of the extents of proton ejection and electron transfer under appropriate experimental conditions. It is concluded that cytochrome c oxidase is a proton pump, which conserves redox energy by converting it into an electrochemical proton gradient through electrogenic translocation of H+.

Aerobiosis↗
PubMed1975

A spectral shift in cytochrome a induced by calcium ions.

Ca2+ induces a red shift in the absorption spectrum of ferrocytochrome a when added to uncoupled mitochondria, sub-mitochondrial particles or isolated cytochrome aa3. The shift is identical within experimental error to the previously reported energy-linked shift in intact mitochondria (Wikström, M. K. F. (1972), Biochim. Biophys. Acta 283, 385-390). One mol of calcium produces the shift in one mole of cytochrome a, the KD being approx. 20-30 muM. The calcium-induced shift is readily reversed by chelating agents such as EDTA, ethyleneglycol-bis-(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA) and ATP and is insensitive to uncoupling agents and inhibitors of calcium transport (La3+ and ruthenium red). It is shown that the binding site for calcium that is responsible for the spectral shift is located on the outside of the permeability barrier of the mitochondrial cristae membrane. It is proposed that calcium simulates the energy-linked shift in cytochrome a by binding to a site of cytochrome aa3 that is occupied by protons in energized mitochondria and that is located at the external surface of the mitochondrial membrane.

Adenosine Triphosphate↗
PubMedDate not supplied

Abdominal CT in familial Mediterranean fever: a case report.

In order to clarify abnormal findings at abdominal ultrasound (suspicion of late abscess subsequent to appendectomy) in a young male patient with known familial Mediterranean fever (FMF), a helical CT examination of the abdomen was performed. At CT, extensive serositis of the lower abdomen was detected. Findings at CT were verified 2 weeks later at laparoscopy.

Adolescent↗
PubMedDate not supplied

What is the essential proton-translocating molecular machinery in cytochrome oxidase?

Pulses of O2 added to anaerobic mitochondria in the presence of antimycin, but in the absence of exogenous reductants, led to H+ translocation until the amount of oxidizing equivalents exceeded the number of endogenous reducing equivalents capable of rapid reduction of cytochrome oxidase. This demonstrates that either the heme of cytochrome alpha or that CuA is the redox center, the function of which is coupled to proton translocation in cytochrome oxidase. Chemical labeling of subunit III of cytochrome oxidase by dicyclocarbodiimide (DCCD), or removal of this subunit by treatment of the enzyme at high pH, results in loss of proton translocation by the isolated and membrane-reconstituted enzyme. Possible roles of subunit III in proton translocation are discussed.

Animals↗
PubMedDate not supplied

Pumping of protons from the mitochondrial matrix by cytochrome oxidase.

The stoichiometry and mechanism of redox-linked proton translocation by the mitochondrial respiratory chain is a major issue of debate in membrane bioenergetics. The function of cytochrome oxidase is a focal point of disagreement. In 1977 it was suggested that the terminal component of the respiratory chain, cytochrome oxidase, functions as a redox-linked proton pump. That and subsequent studies were based mainly on measurements of proton ejection from mitochondria or from vesicles reconstituted with isolated cytochrome oxidase, or on measurements of translocation of electrical charge equivalents across mitochondrial and vesicle membranes. This proton-translocating function of cytochrome oxidase is confirmed here by a quantitative determination of proton uptake from the inside (matrix) of intact mitochondria.

Antimycin A↗
PubMedDate not supplied

Stereoscopic MR imaging.

The visual fusion of two projection or slice-selective magnetic resonance (MR) images taken at two oblique angles imparts three-dimensional (3D) information within the projection or slice. This approach to 3D MR is rapid and straightforward, requiring only two oblique images and, at most, only a simple optical stereoscope for viewing. Stereoscopic images of the vascular system of a rat were obtained using the intravascular contrast agent albumin-(Gd-diethylenetriaminepentaacetic acid). Stereoscopic images of the human head showing CSF distribution were acquired using a long echo time sequence. These images illustrate the potential clinical applications of this technique.

Animals↗
PubMedDate not supplied

Computed tomography in the determination of leg geometry.

In 286 adults with misalignment of the lower limb the length and torsional angles of the femur and tibia were determined using a method based on computed tomography. Depending on the location of the axial scan values for femoral antetorsion changed substantially. Normal values obtained in non injured extremities by this technique were an internal torsion of 23.5 +/- 8.6 degrees (mean +/- SD) in the femur and an external torsion of 34.9 +/- 8.6 degrees in the tibia. Mean intraindividual side differences in the femur and tibia were 4 degrees, the 95% confidence interval was 11.0 degrees in the femur and 12.3 degrees in the tibia. CT-methods can only be used for the determination of torsional angles in the femur and tibia if reproducible and standardized locations for the acquisition of axial scans are defined.

Adolescent↗