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Biomedical subjects

G Matheis

Publications and source records attributed to G Matheis.

At least 55 records · Page 3Linked to original sources
PubMed1992

Role of L-arginine-nitric oxide pathway in myocardial reoxygenation injury.

In view of the recent findings that NO reacts with superoxide anion to generate hydroxyl radical, the present study was conducted to ascertain the role of endogenous NO in mediating myocardial reoxygenation injury in the hypoxic piglet on cardiopulmonary bypass. Anesthetized piglets were made hypoxic (PaO2 = 20-30 mmHg) for up to 120 min, followed by reoxygenation on cardiopulmonary bypass for 30 min. Reoxygenation caused rapidly developing myocardial injury characterized by decreased contractility (expressed as end-systolic elastance) and increased lipid peroxidation (measured as conjugated dienes). Systemic venous and coronary sinus blood content of NO decreased significantly during hypoxia and increased substantially above prehypoxic levels during reoxygenation on cardiopulmonary bypass. Administration of either the antioxidants mercaptopropionyl glycine and catalase or the NO synthase inhibitor, NG-nitro-L-arginine methyl ester, to the extracorporeal circuit afforded similar and nearly complete protection against myocardial reoxygenation injury. The protective effects of NG-nitro-L-arginine methyl ester were nullified by adding an excess of L-arginine to the pump circuit, suggesting that the L-arginine-NO pathway is involved in myocardial reoxygenation injury.

Animals↗
PubMed1991

Donor hearts with impaired hemodynamics. Benefit of warm substrate-enriched blood cardioplegic solution for induction of cardioplegia during cardiac harvesting.

Brain-dead donors frequently show circulatory deterioration and often require so much inotropic support that the donor heart is of questionable value. This experimental study quantifies the cardiac metabolic consequences of brain death and the role of warm blood cardioplegic solution for induction of cardioplegia to improve the quality of potential donor hearts with impaired hemodynamics. Twelve dogs were subjected to brain death by interrupting cerebral blood flow (ligation of innominate artery, carotid arteries, and superior vena cava) and were followed up for as long as 6 hours. Each showed progressive hemodynamic deterioration, necessitating inotropic support (dopamine, calcium, and epinephrine) and large amounts of volume replacement (hetastarch; Hespan) to support the circulation (maintain mean arterial blood pressure greater than 60 mm Hg). Biopsy specimens were taken after 6 hours, or when irreversible ventricular fibrillation occurred, and were analyzed for adenosine triphosphate, creatine phosphate, glycogen, glutamate, and lactate. In six dogs the aorta was then clamped, and a 10-minute infusion of warm (37 degrees C) substrate-enriched aspartate/glutamate blood cardioplegic solution (with the dog's own blood) was given by roller pump to simulate warm induction during the harvesting process. Biopsies were then repeated. Myocardial metabolism, expressed as percent of control values, during brain death was characterized by the following: (1) moderate energy depletion (adenosine triphosphate fell 25% +/- 8%, creatine phosphate fell 55% +/- 15%; p less than 0.05 versus control: mean +/- standard error of the mean); (2) substrate depletion (tissue glutamate fell 48% +/- 9.5%, glycogen fell 66% +/- 7.5%; p less than 0.05 versus control: mean +/- standard error of the mean); and (3) evidence of anaerobic metabolism (lactate increased 374% +/- 95%; p less than 0.05 versus control: mean +/- standard error of the mean). Warm induction of blood cardioplegia in these energy- and substrate-depleted ischemic hearts showed (1) return of creatine phosphate levels to normal (113% +/- 16.8%), (2) replenishment of glutamate (201% +/- 24% of control; p less than 0.05 versus control: mean +/- standard error of the mean), and (3) 43% +/- 14% reduction in myocardial lactate content; (p less than 0.05 versus brain-dead animals). These data suggest that brain-dead donors requiring inotropic support sustain energy and substrate depletion and ischemic damage that can be reversed by a brief period of induction of cardioplegia with a warm substrate-enriched blood cardioplegic solution before harvesting.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

New surgical repair for an anomalous origin of the left coronary artery adjacent to the pulmonary cusps with numerous large side branches.

A new surgical procedure for anatomical correction of an anomalous origin of the left main coronary artery (LCA) from the pulmonary artery is described for those patients in whom the origin of the LCA is located adjacent to a pulmonary cusp and several side branches are arising immediately behind the ostium of the LCA. Hence the LCA can not be disconnected from the pulmonary artery for either coronary arterial transfer or bypass grafting. A tunnel-type repair may interfere with the movement of the pulmonary leaflets. In those cases our proposed surgical correction consists of an arteriotomy of the pulmonary trunk, end-to-end anastomosis of a vein graft to the ostium of the LCA and its implantation into the ascending aorta. The resulting defect in the pulmonary artery is closed with a pericardial patch avoiding kinking or stenosis of the pulmonary trunk.

Adult↗
PubMed1989

Avoiding reperfusion injury after limb revascularization: experimental observations and recommendations for clinical application.

This study tests the hypothesis that reperfusion injury is the principal cause of limb loss after acute arterial occlusion and that this injury is avoidable. Of 61 isolated hindlimbs amputated at the level of the hip joint, 17 were controls (group I), 5 were perfused without ischemia to establish the validity of the model (group II), and 15 underwent 4 hours of ischemia at room temperature without reperfusion (group III). Acute embolectomy was simulated in 24 limbs after 4 hours of ischemia; 12 were reperfused with standard Krebs-Henseleit solution at 100 mm Hg (group IV), and 12 were reperfused under controlled conditions (i.e., 37 degrees C, 50 mm Hg) with substrate-enriched modified reperfusate (group V). Leg volume, water content, contractile function, and high-energy phosphate content were assessed and data were expressed as mean +/- SD. Four hours of ischemia caused a profound fall in adenosine triphosphate content (4.0 vs 26.0 mmol/L/gm of protein, p less than or equal to 0.001). Uncontrolled reperfusion resulted in severe reperfusion injury; massive edema developed (83% vs 75%, p less than or equal to 0.01), leg volume increased markedly (21.5% above control, p less than or equal to 0.001), and no contractile function followed electrical stimulation. In contrast, controlled reperfusion resulted in normal water content (76.9% vs 75.0%, NS) and minimal change of leg volume (5.5% +/- 5% of control, NS), replenished adenosine triphosphate completely (24.2 vs 26.4 mmol/L/gm of protein, NS), and restored immediate contractile function in all limbs (24.3% +/- 14% of control). This study shows that 4 hours of room-temperature ischemia (18 degrees C) does not produce irreversible damage of the rat hindlimb because the reperfusion injury that follows uncontrolled reperfusion can be avoided. Immediate recovery of contractile function can be restored if the conditions of reperfusion are controlled by gentle reperfusion pressure (50 mm Hg) at 37 degrees C and if a modified substrate-enriched, hyperosmotic, alkalotic, low-Ca++ reperfusate is administered.

Adenine Nucleotides↗
PubMed1986

Noninvasive monitoring of cardiac allograft rejection by intramyocardial electrogram recordings.

Rejection after cardiac transplantation was monitored in nine patients by control of intramyocardial electrogram (IMEG) recordings transmitted by an implanted telemetric pacemaker. Under immunosuppression with cyclosporin A and prednisolone, 33 out of a total of 119 endomyocardial biopsy specimens showed moderate rejection (infiltrate with myocytolysis). Twenty-nine of these rejection episodes could be correctly predicted from IMEG recordings with a voltage drop above 15% used as a criterion (sensitivity 87.9%). Eighty-three of 86 negative biopsy results corresponded to negative IMEG results (specificity 96.5%). In this group of patients, amplitude of body surface electrocardiograms was not useful for the diagnosis of rejection because of the broad range of spontaneous variation. Control of IMEG voltage amplitude appears to be more accurate than body surface electrocardiogram amplitude in the detection of rejection episodes. Thus the onset of rejection during biopsy intervals is more readily detected and treatment is instituted earlier. The method is suitable for ambulatory patient monitoring by the patient's local physician.

Biopsy↗
PubMed1985

Impending paradoxical embolism from atrial thrombus: correct diagnosis by transesophageal echocardiography and prevention by surgery.

During recovery from a posterolateral myocardial infarction, a 56 year old patient developed signs of deep vein thrombophlebitis and subsequently of pulmonary embolism. After conventional echocardiography showed masses in both atria, transesophageal two-dimensional echocardiography clearly revealed an elongated mass overriding an atrial septal defect. Impending paradoxical embolism was confirmed at surgery.

Echocardiography↗
PubMed1985

[Bacterial growth in breast milk under various storage conditions].

To find the best temperature for storing human breast milk in the first test series, bacterial growth was determined and recorded at refrigerator temperatures of 8 to 10 degrees C and at 4 degrees C respectively. During a 3-day observation period, there was a slight decrease in bacterial count (b.c.) at higher temperature whereas the b.c. decrease at the lower temperature was more significant. In another test 72 samples of milk were kept for one month at a temperature of -20 degrees C; the b.c. observed after thawing was substantially smaller than that recorded before freezing. Pasteurized milk samples were found sterile with the method we used (in 0.1 ml). In a third test a measured quantity of specific bacteria was added to the milk samples which were first deep-frozen, thereafter pasteurized and finally stored in a refrigerator for 3 days at 4 degrees C. During this process, a decrease was observed in all the bacteria involved. In our opinion, breast milk is best stored at a constant temperature of 4 degrees C. Pasteurization and freezing are also recommended from a bacteriological point of view.

Bacteriological Techniques↗
PubMed1985

[Bacterial contamination of pump-collected breast milk].

Breast feeding of premature, new-born babies is often difficult when they become sick and are transferred to a children's hospital. The mother's milk should be collected and provided to the child without a loss of quality or too high a bacterial count which could endanger his health. We collected 113 samples of milk using electric vacuum breast pumps and then determined the bacterial contamination. In most cases there was evidence of bacteria normally found on the skin although more than 10(5)/ml of these bacteria were found in only 11.5% of the samples. As potentially pathogenic germs gram-negative bacilli, beta-hemolytic Streptococci Group B and Staphylococcus aureus were found. The electric pumps were cleaned with two different methods: the usual technique (Series I: 41 samples) and second, sterilization or replacement of the various external pump components between the collection of individual milk samples (Series II: 72 samples). The total of bacteria was considerably reduced by these additional hygienic measures; 62.5% of the samples could now be given to the children unpasteurized whereas the former figure was only 29.3%. On the other hand there was no decrease in the number of milk samples containing either beta-hemolytic Streptococci (Group B) or more than 10(5)/ml bacteria normally found on the skin.

Bacteria↗
PubMed1984

31P NMR chemical shifts of phosphate covalently bound to proteins.

31P nuclear magnetic resonance (NMR) spectroscopy for characterizing the nature of covalently bound phosphate in proteins is relatively unexploited by the biochemist. 31P NMR chemical shifts of phosphate covalently bound to naturally occurring phosphoproteins, phosphorylated enzyme intermediates and chemically phosphorylated proteins have been compiled in this review. The chemical shifts (31P NMR) of selected reference compounds are reported to assist in the assignment of 31P resonances of phosphate covalently attached to proteins. 31P NMR chemical shifts of phosphate and phospho compounds non-covalently bound to selected proteins as well as the pH dependence of 31P NMR resonance have also been compiled.

Animals↗
PubMed1979

Multiple forms of soluble monophenol, dihydroxyphenylalanine: oxygen oxidoreductase (EC 1.14.18.1) from potato tubers (Solanum tuberosum). IV. Association and dissociation phenomena.

The soluble phenol oxidase of various potato juices (adjusted from physiological pH to pH 4.5, 7.0 and 7.8) was separated by gel chromatography into multiple molecular forms. In acid or neutral and alkaline potato juices, low-mol.-wt. (less than 150,000 daltons) or high-mol.-wt. (greater than 150,000 daltons) enzyme forms predominate, respectively. Conversion of the low-mol.-wt. enzyme forms into high-mol.-wt. enzyme forms, and vice versa, was achieved by changing the pH values from acidic to neutral or alkaline pH, and vice versa. This substantiated our previous idea that the enzyme multiplicity arises from association of various subunits. In alkaline potato juice, considerable loss of monophenol oxidase activity (assayed at pH 6.0) occurred. This confirmed our previous findings that o-diphenol oxidase is more alkali-stable than monophenol oxidase.

Catechol Oxidase↗
PubMed1979

Multiple forms of soluble monophenol, dihydroxyphenylalanine: oxygen oxidoreductase (EC 1.14.18.1) from potato tubers (Solanum tuberosum). III. Influence of pH on the molecular weight distribution of enzyme activity in potato juice.

Gel chromatography on Sepharose and on Sephadex was used to separate the soluble phenol oxidase in various potato juices into multiple molecular forms ranging from 36,000 to 800,000 daltons. Adjustment of potato juice from physiological pH (ca. 6) to pH 4.5 or to pH 7.8 resulted in the predominance of low-mol.-wt. (less than 150,000 daltons) or high-mol.-wt. (greater than 150,000 daltons) enzyme forms, respectively. This suggests association phenomena of subunits. In potato juice of physiological pH and in potato juice adjusted to pH 4.5, all enzyme forms exhibited both monophenol and o-diphenol oxidase activities (assayed at pH 6.0). In potato juice adjusted to pH 7.8 considerable loss of monophenol oxidase activity (assayed at pH 6.0) occurred. This suggests that o-diphenol oxidase is more alkali-stable than monophenol oxidase. The significance of these findings for enzyme purifications and for the in vivo action of the enzyme is discussed.

Catechol Oxidase↗
PubMed1978

Studies on enzymic browning of potatoes (Solanum tuberosum). IV. Relationship between tyrosine turnover and rate of browning.

Using analytical data from the literature the tyrosine turnover was calculated by a method published previously by us for 72 potato samples with different rates of browning. The samples included 9 varieties grown at three locations in 1969, which were analysed after harvest and after different times of storage at three temperatures. For 58 samples (81%) this calculation led to the same classification of the varieties as did visual observation of the rate of discolouration. It is concluded that enzymic browning of potatoes is correlated rather with tyrosine turnover, which depends on the concentrations of phenol oxidase, tyrosine, chlorogenic acid, and ascorbic acid, than with any single parameter.

Ascorbic Acid↗
PubMed1977

Multiple forms of soluble monophenol, dihydroxyphenylalamine: oxygen-oxidoreductase (EC 1.14.18.1) from potato tubers (Solanum tuberosum). II. Partial characterization of the enzyme forms with different molecular weights.

Gel chromatography on Sephadex G-200 was used to separate a soluble phenoloxidase from potatoes (var. Maritta) into at least six active fractions with dopa (dihydroxyphenylalanine) as substrate. Only high-molecular-weight-enzyme forms exhibited monophenoloxidase activity. Re-chromatography of the highest-molecular-weight form gave the same molecular weight distribution as with the crude enzyme. The molecular weights indicate association phenomena of subunits with a molecular weight of about 36000 daltons. According to polyacrylamide-gel electrophoresis, several monomeric forms with differnt isoelectric points seem to be present. This suggests that the large number of multiple forms of the enzyme arises from various combinations of identical and/or different subunits. SDS polyacrylamide gel electrophoresis failed to show the monomeric forms; the dimer and higher oligomers were obtained.

Catechol Oxidase↗
PubMed1977

[Studies on enzymic browning of potatoes (Solanum tuberosum). II. The quantitative relationship between browning and its causative factors (author's transl)].

Ten potato varieties, with different rates of browning, were analyzed quantitatively for phenoloxidase, tyrosine, chlorogenic acid, caffeic acid, and for reducing substances (ascorbic acid). The rate of tyrosine turnover was calculated from the data. The fact that the further reactions of the primary oxidation products leading to browning only take place after complete oxidation of the reducing substances, was taken into account. This leads to the same classification of the varieties as does visual observation of the rate of discolouration. Thus a clear relationship between browning and potato constituents is demonstrated.

Ascorbic Acid↗
PubMed1977

Studies on enzymic browning of potatoes (Solanum tuberosum). III. Kinetics of potato phenoloxidase (EC 1.14.18.1 monophenol, dihydroxyphenylalanine: oxygen-oxidoreductase).

From initial velocity studies a sequential mechanism for the reactions catalysed by phenoloxidase from potatoes is indicated. The data are in accordance with an ordered addition of oxygen and phenolic substrate to the enzyme, with oxygen being the first substrate bound at thermodynamic equilibrium. The Michaelis constants for L-tyrosine, L-dopa, and chlorogenic acid are 1.4 X 10(-3), 3.3 X 10(-4), and 1.4 X 10(-4) mol/l, respectively. The dissociation constant for the enzyme-oxygen complex is about 10(-3) mol/l. In the presence of chlorogenic acid no lag phase occurs in the course of L-tyrosine oxidation. With increasing amounts of chlorogenic acid the tyrosinase activity goes through a maximum. The significance of these findings for the in vivo action of the enzyme is discussed.

Catalysis↗
PubMed1977

[Studies on enzymic browning of potatoes (Solanum tuberosum). I. Phenoloxidases and phenolic compounds from different varieties (author's transl)].

31 samples of potato varieties with slow, medium and fast rates of browning were studies. Characteristic enzyme patterns were obtained from polyacrylamide gel electrophoresic of the phenoloxidases of varieties with different discolouration rates. The differences lie mainly in the intensities of the enzyme bands. The qualitative determinaiton of the phenols showed no significant differences. Tyrosine, chlorogenic acid and caffeic acid produce coloured oxidation products; the characteristic colour gradations of in vivo browning were only observed in the presence of tyrosine. It is concluded that the same reactions take place during the discolouration of all the varieties.

Catechol Oxidase↗
PubMed1975

Multiple forms of soluble monophenol, dihydroxyphenylalanine: oxygen-oxidoreductase (EC 1.14.18.1) from potato tubers (Solanum tuberosum).

Upon polyacrylamide gel electrophoresis, a soluble phenoloxidase from potatoes (var. Maritta) revealed 17 multiple forms with activity towards dopa and almost all other o-diphenols tested, but only 5 of the forms reacted with monophenols. Isoelectric focusing of the crude enzyme resulted in 2 main peaks with activity towards dopa, having isoelectric points at pH ranges 4.0-4.7 and 5.1-5.4: smaller amounts of the enzyme at higher pI values were also detected. When activity peaks were controlled by polyacrylamide gel electrophoresis, all bands previously detected by electrophoresis of the crude enzyme were recovered, but all peaks were electrophoretically heterogeneous. Gel chromatography of the crude enzyme showed different molecular forms. Their molecular weights indicated monomer, dimer, tetramer, octamer and polymer (at least hexadecamer) forms with a monomer molecular weight of about 36000.

Catechol Oxidase↗