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Biomedical subjects

G Arnold

Publications and source records attributed to G Arnold.

At least 163 records · Page 9Linked to original sources
PubMed1982

[Experimental studies on the biomechanical reaction of collagenous fibres during impulse mechanical strain working conditions (author's transl)].

A wide spectrum of stress-strain factors of varying directions and magnitudes are acting on collagenous fibres. Bundles of parallel collagen fibres in tendons and ligaments are mainly subject to tension forces. Single twitches and unfused tetanus of muscles fibres are giving rise to impulse strains on tendon fibres. Tendon reflexes are causing contractions of the muscle and sudden extensions of the corresponding collagenous fibres. In vitro studies were performed on tendon fibres. Tendon reflexes are causing contractions of the muscle and sudden extensions of the corresponding collagenous fibers. In vitro studies were performed on tendon fibre bundles. Systematic impulse extensions were applied as input functions. The force resp. stress impulses were recorded as output functions. When linear extensions with superimposed impulse strains were applied, the force-elongation curve showed a stepwise increase of the force impulse initially. Under consecutive isometric conditions an impulse relaxation curve arises. After partial deloading and subsequently isometric conditions an impulse force recovery function emerges. The output force impulses are dependent on the frequency of the input strain impulses. The effects are called frequency dependent force impulse relaxation and recovery. The findings are briefly discussed in correlation with functional anatomy and muscle physiology.

Animals↗
PubMed1982

[Valve replacement for mitral in incompetence in a patient with osteogenesis imperfecta (author's transl)].

Reports on aortic and mitral valve alterations in patients with osteogenesis imperfecta, a congenital connective tissue disorder, are sparse in the literature. Aortic valve incompetence is more common than mitral valve dysfunction. Though the clinico-pathological and histological features of valve alterations are very similar to those seen in Marfan's Syndrome, valve dysfunctions in osteogenesis imperfecta are rarer than in Marfan's Syndrome. In a 23-year-old patient with typical clinical feature of osteogenesis imperfecta, mitral incompetence was detected by echo- and angiography. Patient was provided with a St.-Jude-Medica prosthesis and postoperative course was without any complications.

Adult↗
PubMed1981

[The prognostic significance of determining bioelectric brain maturity in newborn infants with perinatal complication (author's transl)].

92 infants were studied in order to determine the prognostic value of bioelectric brain maturity assessment during newborn period. Psychomotor development was followed up until infants were at least one year old. Infants with abnormal follow-up examination findings showed a statistically significant retardation of "EEG-maturity" in comparison with infants who developed normally. The more unfavourable the psychomotor development was, the more immature was the EEG-pattern. The prognosis of 6 infants whose "EEG-maturity" was extremely retarded (= 4 weeks immature) was severe; their follow-up examination revealed either definite pathological findings or severe cerebral damage. All newborns whose abnormal electroencephalogram recording did not allow assessment of "EEG-maturity" developed severe cerebral damage. Comparing the prognostic value of risk factors with the bioelectric brain maturity the last method proved to be more valuable. Especially in infants with perinatal hypoxia this method showed the highest prognostic value.

Brain Damage, Chronic↗
PubMed1981

[Mechanical function of the liver capsule].

Histomechanical experiments were performed on human and bovine liver capsules. On strain processes, the mechanical resistance force increases slowly at the beginning, and then with a continuous change rapidly. The relaxation processes approximate to a constant form at equal stains with interponed isometrical phases. This indicates that the tissue has a trend towards a viscoelastic equilibrium (balance behaviour, steady state). In further experiments the following histomechanical properties could be demonstrated: Upper and lower summit decrease at dynamical (cyclic) relaxation, and cascade dynamical (cyclic) force recovery with stepwise reduced force amplitudes.

Animals↗
PubMed1980

Failure to detect naturally occurring serum inhibitors of hepatitis B virus deoxyribonucleic acid polymerase.

Sera of patients with past or ongoing hepatitis -B virus infection were tested for the presence of inhibitors of hepatitis -B virus-specific deoxyribonucleic acid (DNA) polymerase activity. None of the sera tested, which included those from anti-hepatitis B surface- and anti-hepatitis B core antigen-positive hemophiliacs, anti-hepatitis Bc antigen-positive hepatitis B surface antigen carriers, patients with hepatitis B surface antigen-positive chronic active hepatitis, hepatitis B surface antigen-positive hemodialysis patients, tumor patients with minimal hepatitis, patients with acute type B, type A, and type non-A, non-B hepatitis and individuals with autoimmune phenomena, contained inhibitors of DNA polymerase activity. This implies that the DNA polymerase test is not affected when utilized to quantitate DNA-containing Dane particles. In addition, there is no evidence that inhibitors of DNA polymerase activity play some pathogenic role in the course of hepatitis B virus infection.

Carrier State↗
PubMed1980

Ultrastructural localization of alpha-OH acid oxidase in peroxisomes with the CeCl3 technique.

alpha-OH acid oxidase activity was demonstrated in peroxisomes of glutaraldehyde-fixed tissues using the CeCl3 cytochemical method. For kidney, alpha-OH butyrate or alpha-OH valerate were used as substrates. These substrates gave much less reaction product in liver peroxisomes. Liver peroxisomes were more reactive with glycolate as substrate. Glycolate gave little or no reaction product in kidney peroxisomes. alpha-keto-glutarate inhibited activity of the enzyme with alpha-OH butyrate as substrate.

Alcohol Oxidoreductases↗
PubMed1979

Ultrastructural localization of D-amino acid oxidase in microperoxisomes of the rat nervous system.

A recently developed procedure for the localization of D-amino acid oxidase (D-AAO) has been used to investigate the distribution of this enzyme in rat nervous tissue. Initial studies were carried out on kidney to validate the methods. The cytochemically demonstrable enzyme in kidney is inhibited by kojic acid, a known competitive D-AAO inhibitor. Omission of the catalse inhibitor, aminotriazole, from the cytochemical medium produces a marked diminution of D-AAO reaction product in kidney peroxisomes. This would be expected if catalase and D-AAO are present in the same particles. In brain, kojic acid-inhibitable D-AAO is demonstrable in numerous bodies within astrocytes especially in the cerebellum, a brain region known from biochemistry to contain particularly high levels of the oxidase. In preparations incubated for catalase, far fewer positive bodies are seen in the cerebellum. Moreover, omission of aminotriazole has little evident effect on the D-AAO reaction. Thus, the oxidase-containing cerebellar bodies may be relatively poor in catalse. In contrast, several nervous system cell types that contain relatively numerous catalase-positive bodies, contain none with detectable D-AAO. Such heterogeneity of peroxisome enzyme content is in accord with reports from biochemical studies of brain.

Animals↗
PubMed1979

[Is hemoperfusion effective in the treatment of digoxin intoxication? (author's transl)].

Digitalis therapy is frequently accompanied by adverse drug reactions. Severe digitalis intoxications are still a problem. Therapeutical methods, which could be used in the case of a life threatening digoxin intoxication, are known, but not yet generally available. Hemodialysis has only a minor effect on digoxin excretion. This study was planned to test the hypothesis that hemoperfusion across dextran-cocoated charcoal or the resin Amberlite XAD 4 could be more effective in the therapy of digoxin intoxications. The ability of hemoperfusion to eliminate digoxin was tested in a patient who had to undergo treatment beacuse of a severe bromcarbamide intoxication. Additionally we compared the effect of several modifications on this method in 12 dogs, which had received 0.05 mg/kg body weight per day for three days prior to the experiment. Although hemoperfusion across Amberlite XAD 4 may eliminate as much digoxin as normal human kidneys during the few hours of treatment, the amount of digoxin removed after all is only a small percentage of the total body pool. Thus compared to the risks of hemoperfusion as an invasive treatment its effect is small. According to our results, hemoperfusion cannot be recommended as a standard therapy of severe digoxin intoxications.

Adult↗
PubMed1978

Microperoxisomes in the central nervous system of the postnatal rat.

The distribution of catalase-containing microperoxisomes was studied in the central nervous system of rats during the early postnatal period when the processes of myelination and cell differentiation are active. The regions selected for study included a region previously found in adult animals to contain substantial numbers of reactive microperoxisomes, as well as areas where few such bodies were seen. Microperoxisomes were relatively numerous in all areas during the first two postnatal weeks; at later times they occurred less frequently, or, in some areas, were almost entirely absent. In early postnatal CNS, catalase-positive microperoxisomes were found in all cell types in all regions studied. Neurons of both cerebrum and cerebellum contained catalase-positive microperoxisomes during the first two postnatal weeks; few such neuronal bodies are found in these areas after the third postnatal week. During the period of active myelination, catalase-positive microperoxisomes were found in oligodendrocyte cell bodies, and also in oligodendrocyte processes associated with forming myelin sheaths in all areas. In several areas during the first 3 postnatal weeks, catalase-positive bodies were seen in synaptic terminals, a location where they are seldom observed in mature tissue. Cells of postnatal choroid plexus also were found to contain modest numbers of reactive microperoxisomes.

Age Factors↗
PubMed1978

[Histomechanical studies on test specimens from hyaline cartilage under compressive loading with regard to rheology (author's transl)].

Modified rheological methods from high polymer physics (biorheology, historheology) have been applied to the testing of hyaline cartilage histomechanics. The following histomechanical properties of cartilage are discussed: transient behaviour, the influence of the mechanical history on the subsequent force-deformation processes, viscoelastic equilibrium status (histomechanical steady state), and relaxation phenomena in the pressure and tension range under alternating pressure-tension loading. Pressure force-time input and output curves in a closed loop system and the amplitude-increasing phenomenon under uniform sinus deformations with increasing superimposed linear deformation input were also demonstrated. The results are discussed from the point of view of functional anatomy.

Animals↗