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Biomedical subjects

J C Fischer

Publications and source records attributed to J C Fischer.

At least 37 records · Page 2Linked to original sources
PubMed1985

Differential investigation of the capacity of succinate oxidation in human skeletal muscle.

Procedures are described for the estimation of the succinate:ubiquinone oxidoreductase and succinate:phenazine methosulfate oxidoreductase activities in post-nuclear supernatants of human skeletal muscle homogenates using 2,6-dichlorophenol indophenol as the terminal electron acceptor. The influence of ionic strength and of sucrose upon these assays and upon the succinate:cytochrome c oxidoreductase activity has been investigated. Sucrose markedly interferes with the activation of the succinate dehydrogenase complex. Succinate:cytochrome c oxidoreductase activity and succinate:phenazine methosulfate oxidoreductase activity are inhibited by increasing concentrations of ions and of sucrose. Our results lead us to propose the existence of a single acceptor site for phenazine methosulfate at the succinate dehydrogenase complex, not involved in the physiological electron flux across ubiquinone. Estimation of the enzymatic activities mentioned above allows differential investigation of the functional integrity of a large part of the respiratory chain in patients suspected of suffering from a neuromuscular disorder.

2,6-Dichloroindophenol↗
PubMed1985

Investigation of mitochondrial metabolism in small human skeletal muscle biopsy specimens. Improvement of preparation procedure.

A method is presented which allows the investigation of almost the complete mitochondrial content of small human skeletal muscle biopsy specimens. Thorough mechanical disruption with a chopper apparatus results in the release of about 50% of the mitochondrial content. Subsequent treatment of the 600 x g sediment with trypsin releases another 30% of the total mitochondrial population. The biochemical characteristics of the two mitochondrial fractions obtained in these two successive steps have been compared. No obvious differences could be established. The procedure is well suited for biochemical investigation of muscle biopsy specimens from patients suspected of suffering from a mitochondrial myopathy.

Adenosine Diphosphate↗
PubMed1985

Laser Doppler flowmeter measurements of skin perfusion changes associated with arterial and venous compromise in the cutaneous island flap.

Laser Doppler flowmetry (LDF) is a noninvasive, continuous measure of tissue surface microcirculatory red blood cell (RBC) flux. LDF was calibrated against varying RBC volume fractions and flow rates using extracorporeal perfusion of saphenous island flaps of dogs. The RBC flux was found to be linear with LDF signal. The difference in vascular geometry of the skin appeared to play a minor role in generating the LDF signal compared to changes in the RBC flux. In vivo experiments of varying arterial perfusion pressure, flap venous pressure, and total blood flow of the cutaneous island flap had a linear relationship with LDF signal.

Animals↗
PubMed1985

Computerized calculation of in vitro generation of ATP and creatine phosphate induced by respiration in human muscle mitochondria.

A computer program is presented which calculates the action of adenylate kinase and creatine kinase during the process of adenosine-5'-triphosphate generation by the mitochondria in human skeletal muscle 600 X g supernatants. The results show that the mass action ratios of the two kinase reactions are not influenced by incubation time or decreased rate of oxidative phosphorylation as a result of mitochondrial dysfunction. The program is useful for establishing optimum initial adenosine-5'-diphosphate and creatine concentrations in the assay medium.

Adenosine Triphosphate↗
PubMed1985

Subacute necrotizing encephalomyelopathy (Leigh syndrome) associated with disturbed oxidation of pyruvate, malate and 2-oxoglutarate in muscle and liver.

We studied a 17-year-old girl with subacute necrotizing encephalomyelopathy (Leigh syndrome). Lactate and pyruvate levels were increased in serum and cerebrospinal fluid. The oxidation rates of all substrates tested, i.e. pyruvate in liver, and pyruvate, malate and 2-oxoglutarate in muscle, were decreased, as was the production of adenosine triphosphate plus creatine phosphate. Cytochrome content was normal. The data imply a defect in oxidative phosphorylation, outside the cytochrome region.

Adolescent↗
PubMed1984

Implantable pulsed Doppler cuff for long-term monitoring of free flaps: a preliminary study.

High-frequency (20 mHz) ultra-sonic Doppler in a pulsed mode rather than continuous mode allows blood flow detection in small arteries using a 1-mm crystal embedded in a silastic cuff. The "probe factor" used to determine flow was first established in an in vitro system and found to be reliable. The probe was then tested in five dogs on the saphenous artery and found to be highly responsive to hemodynamic changes in the pedicle. Finally, in 15 long-term studies of island flaps and free flaps, the probes were implanted to obtain daily readings and then removed at 7 days. Except for some dog-related problems and technical errors, the system produced reliable flow data in the percutaneous cable. It is anticipated that such immediate and direct information on the pedicle blood flow would be useful in monitoring flaps.

Animals↗
PubMed1984

Deficiency of cytochromes b and aa3 in muscle from a floppy infant with cytochrome oxidase deficiency.

A girl was presented suffering from generalised weakness and cardiorespiratory insufficiency. She succumbed at the age of 5 months. Lactate levels were elevated in serum, cerebrospinal fluid and urine. Histopathological examination revealed a mitochondrial myopathy. In muscle tissue the cytochrome oxydase activity was strongly reduced. The content of cytochromes b and aa3 was very low. At autopsy a cardiomyopathy was found.

Acidosis↗
PubMed1983

Comparison of two laser Doppler flowmeters for the monitoring of dermal blood flow.

Laser Doppler flowmetry (LDF) is a noninvasive and continuous method of monitoring dermal blood flow in free flaps. There are two LDFs available for clinical application: the LD5000 Laser Doppler Perfusion Monitor and the Periflux Laser Doppler Flowmeter. Varying degrees of arterial (N = 46) and venous (N = 28) occlusion were induced in saphenous island flaps of the dog, while simultaneous measurements with the LD5000 and Periflux LDFs were made. The millivoltage output of both the LD5000 and the Periflux showed a high degree of correlation with arterial and venous occlusion and with each other.

Animals↗
PubMed1983

A mitochondrial myopathy with a defective respiratory chain and carnitine deficiency.

A boy presented suffering from generalised weakness, exercise intolerance and lactic acidosis. The weakness became evident at 2 years. A cerebral CT-scan showed cerebellar atrophy and central and peripheral atrophy of both hemispheres. With trichrome staining about 20% of the muscle fibres showed large areas containing red-staining granular material. Electron microscopic examination showed that this material consisted of areas of mitochondrial proliferation, most of the mitochondria having abnormal ultrastructural characteristics. Pyruvate dehydrogenase complex and citric acid cycle activities were determined by measuring 14CO2 production from various labelled substrates. Diminished oxidation rates were found with the patient's muscle homogenate for all substrates tested, indicating a defect in the respiratory chain. The cytochromes were present in normal quantities. Succinate cytochrome c reductase activity was very decreased. Carnitine concentration was decreased in serum and in muscle as well.

Brain↗
PubMed1979

The reconstruction of a helical structure from projections applied to a phage tail.

A procedure has been described for 3 D-image reconstruction for helical biological structures, if more than one projection will be required to determine the contributing helical density-waves. The method was tested with a helical protein aggregate derived from a bacteriophage. The results showed the feasibility of the proposed scheme and yielded a low resolution picture (about 2.5 nm) of the protein structure.

Bacillus subtilis↗
PubMed1979

Low-dose electron image reconstruction of negatively stained contractile phage sheath from Bacillus subtilis (PBS-Z).

The structure of the contractile sheath of the defective phage from B. subtilis (PBS-Z) has been investigated by low-dose electron microscopy and image reconstruction. The extended and contracted sheath particles were imaged by means of two negative stains which consisted of uranyl- and phosphotungstate-containing solutions of a pH of 4.2 and 7.0 respectively. Images of identical parts of the same type of specimen were recorded at a total electron dose of 80 C/m2 (5 electrons/A2) and 4 x 10(3) C/m2 (250 electrons/A2). The low-dose reconstructions of the extended and contracted sheath structure in the two stains show good correspondence and made it possible to draw the following structural conclusions. The sheath protein in both types of structure has an elongated shape, and in both structures the long molecular axis lies in a plane perpendicular to the helical sheath axis. The orientation of the protein in the extended and contracted sheath is different; the long axes differ by about 35 degrees in orientation. The reconstructions did not permit conclusions about different conformational states of the protein in both structures. These data, together with the packing parameters of the protein subunits in the contractile sheath [1], form the complete structural analysis of this biological structure by electron microscopy. The radiation damage effects which have been monitored in analyzing image pairs to the full extent may be summarized as follows. (1) Diameters of the sheath structure increase, which indicate flattening. (2) There is no loss in resolution, and layerline altitudes of the Fourier-transformed images do not change. (3) Uranyl stain behaves differently compared to phosphotungstate. In both negative stains the structural noise level increases upon irradiation as follows from the increase in phase residuals of the digital layerline data. In uranyl-stained images also more aperiodic noise appears. (4) The Fourier amplitudes of the principal layerline maxima shift towards lower spatial frequencies; phases of corresponding maxima generally remain constant. This pattern is more pronounced in the extended sheath data; there is no rationale describing these positional shifts. Moreover, in the case of contracted sheath the amplitudes of Fourier components also change more in absolute value. Therefore the damage effects also seem to depend on the type of structure embedded in the stain. (5) In the reconstructed images these radiation effects create artificial stain-excluded volumes of a type and at a radius which depend on the stain and structure.

Bacillus subtilis↗