Search PubMed⌕ Search

Biomedical subjects

R Scholz

Publications and source records attributed to R Scholz.

At least 91 records · Page 5Linked to original sources
PubMed1980

Continuous peritoneal dialysis (CPD)--an alternative to hemodialysis in acute renal failure after cardiovascular operations.

In our experience hemodialysis proved to be unsatisfactory in the treatment of acute renal failure after cardiovascular surgical intervention because of its negative influence on the often critical hemodynamic situation of the patients. In 21 cases we performed a continuous peritoneal dialysis (CPD) for 1 to 29 (mean 9.2) days by using a Tenckhoff catheter (16). Treatment was started when anuria occurred or when serum nonprotein nitrogen increased. Satisfactory volume equilibration was established by this treatment. A pathological increase of serum electrolytes could be prevented; serum potassium, in particular, did not exceed 5.6 mVal/l. No dysfunctions in acid-base balance occurred. The serum levels of nonprotein nitrogen decreased: Serum carbamid was diminished from 229 +/- 14 mg% to 160 +/- 10 mg% and serum creatinine from 7.7 +/- 0.6 mg% to 6.0 +/- 0.8 mg% (p < 0.05). Disturbances of hemodynamic and respiratory functions could be avoided by CPD. Peritoneal reactions were noted in 5 cases. In our opinion continuous peritoneal dialysis seems to be a suitable alternative to hemodialysis in the treatment of acute renal failure after open heart surgery.

Acute Kidney Injury↗
PubMed1980

Subcellular distribution of di- and tricarboxylates and pH gradients in perfused rat liver.

The subcellular distribution of malate, 2-oxoglutarate, citrate, aspartate and glutamate and the mitochondrial and cytosolic pH values were determined in perfused livers from fed and fasted rats. The method of fractionation of the freeze-dried tissue in non-aqueous solvents was employed. The following results were obtained: 1) Di- and tricarboxylates are not equally distributed between mitochondria and cytosol. Under the two metabolic conditions studied, the concentrations of citrate and 2-oxoglutarate are higher and those of glutamate and aspartate are lower in the mitochondria than in the cytosol. The distribution of malate varies with the metabolic state. 2) From the distribution of 5,5-dimethyl-2,4-oxazolidinedione it was calculated that the mitochondrial matrix has a more alkaline milieu than the cytosol. The cytosol is also more acidic than the perfusate. The pH difference between mitochondria and cytosol is 0.3 in the fed state and 0.6 in the fasted one, whereas the pH difference between perfusate and cytosol is 0.4 in the fed state and 0.2 in the fasted one. 3) In livers from fed rats, citrate, malate and 2-oxoglutarate appear to be distributed according to the pH gradient across the mitochondrial membrane, whereas in the fasted state, the distribution does not correspond to the pH gradient. Glutamate and aspartate do not follow the pH gradient in either metabolic state. 4) The data indicate that the pH gradient across the mitochondrial membrane does not reflect the membrane potential or the energy state of mitochondria in the intact cell.

Animals↗
PubMed1980

[Flow rates in the isolated perfused rat liver by pulse labeling with radioactive substrates and mathematical analysis of the wash-out kinetics].

The multiple indicator dilution technique (Goresky and Bach) is critically evaluated and its application to the isolated, hemoglobin-free perfused rat liver is described. From the results of pulse labelling experiments using indicator substances for the total aqueous space of the liver ([3H]water and [14C]urea) an for the extracellular space ([14C]sucrose, [3H]-inulin and [3H]dextrane), it is concluded that the mathematical model of the liver in situ according to Goresky and Bach is sufficient to also describe the hemodynamics of the isolated liver perfused with a saline solution. The data indicate that the multiple indicator dilution technique in combination with the available mathematical basis is applicable to the study of transport across the liver cell membrane. The method, however, is restricted to compounds which are metabolized very slowly, such as D-lactate. A possible extension of this method to metabolic processes is discussed in view of pulse labelling experiments with [3H]-and [1-14C]L-lactate. Since the involvement of metabolism in the available mathematical model is not differentiated and the release of products is not taken into consideration, the method in its present state is not applicable to studies of metabolism. Moreover, even the parameters of transport derived by this technique are of limited value, when the transported compounds are rapidly metabolized by reversible reactions. Despite these uncertainties, the present data indicate that the transport of L-lactate is ten times faster than that of D-lactate.

Animals↗
PubMed1979

Transport of D-lactate in perfused rat liver.

The transport of D-lactate across the plasma membrane was investigated in hemoglobin-free perfused rat livers, applying the multiple-indicator dilution technique (pulse labelling of D-lactate and indicator substances). The following results were obtained: 1. The steady state exchange rate at 1 mM D-lactate was 2.5 mumol x min-1 x g wet wt-1. It was proportional to the extracellular concentration in the range between 0.1 and 70 mM. 2. The transport of D-lactate was inhibited by L-lactate and pyruvate; 50% inhibition was observed at 40 mM L-lactate or 5 mM pyruvate. 3. The transport was also inhibited by alpha-cyanocinnamate and 4,4'-diisocyanostilbene-2,2'-disulfonic acid. The inhibition by cyanocinnamate was complete (with 25 mM) and fully reversible, whereas the inhibition by diisothiocyanostilbenedisulfonic acid was incomplete and irreversible; it was dependent upon the amount of diisothiocyanostilbenedisulfonic acid bound by the liver. Maximal inhibition (80%) was observed with 2 mumol diisothiocyanostilbenedisulfonic acid bound per g wet weight. 4. The intracellular concentration (ci) of D-lactate was proportional to the extracellular concentration (ce); the ratio ci/ce was 0.5 throughout the concentration range studied. It decreased in the presence of L-lactate or pyruvate. It is concluded that the transport of D-lactate is carrier-mediated, and, at least partially, electroneutral.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1979

[Rule of antibody structure. Primary structure of a human monoclonal IgAl-immunoglobulin (myeloma protein Tro). VI. Amino acid sequence of the L-chain, lambda-type, subgroup II].

The primary structure of the L-chain of an IgA1-immunoglobulin (Myeloma protein Tro) has been determined by means of cleavage with trypsin and, if necessary, with alpha-chymotrypsin. The tryptic peptides of the variable part were characterized by amino acid analysis, Dansyl-Edman degradation and cleavage with carboxypeptidase; the peptides of the constant part were identified by amino acid analyses and determination of its N- and C-terminal residues. The sequence of the remaining amino acids and the arrangement of the peptides were established in homology to known structures. The protein comprises 216 amino acids. The homology of the variable part clearly characterizes it as belonging to subgroup II of lambda-chains. In positions 27a, b and c, there are the subgroup-specific additional residues and in position 96 is the characteristic deletion. The constant part of the chain is Kern- and Oz- which indicates that it has serine in position 154 and arginine in position 191.

Amino Acid Sequence↗
PubMed1978

Subcellular metabolite concentrations. Dependence of mitochondrial and cytosolic ATP systems on the metabolic state of perfused rat liver.

Mitochondrial and cytosolic contents of adenine nucleotides and phosphate were measured in perfused rat livers employing a technique of fractionation of freeze-fixated tissue in non-aqueous solvents. From the subcellular contents the mitochondrial and cytosolic concentrations of ATP, ADP, AMP and phosphate and the phosphorylation potentials of the subcellular ATP systems were calculated. An attempt was made to elucidate the relationship between mitochondrial and cytosolic adenine nucleotide systems and the dependency on the metabolic state of the liver. The following results were obtained: 1. Under all metabolic conditions studied the mitochondrial ATP/ADP ratios were considerably lower than the cytosolic ratios (mitochondria: 0.1-0.7; cytosol: 2-11). 2. The ATP/ADP ratios calculated from overall tissue contents reflect mainly the cytosolic ratios. 3. An inverse relationship was found between mitochondrial and cytosolic ATP/ADP ratios, i.e. when the mitochondrial ratios tended to increase, the cytosolic ratios decreased and vice versa. 4. The phosphorylation potentials calculated from the subcellular concentrations were higher in the cytosol than in the mitochondria. The potential difference varied between 11 and 3 kj/mol in livers from fed and starved rats, respectively. 5. In the presence of mitochondrial inhibitors, i.e. amytal, dinitrophenol and carboxyatractyloside, the potential difference between the subcellular ATP systems decreased predominantly due to an increase in the mitochondrial ATP/ADP ratios. 6. A correlation between mitochondrial ATP/ADP ratios and the respiratory rates was not observed, but the subcellular ratios appeared to correlate with the rate of glycolysis. When the rate of lactate + pyruvate production was increased, the cytosolic ATP/ADP ratios were increased, too, whereas the mitochondrial ratios tended to decrease. 7. The adenine nucleotides in the cytosol appear to be in near equilibrium catalysed by the adenylate kinase. In the mitochondria, the AMP concentration is much lower than to be expected under equilibrium conditions. These results were discussed with respect to rate control of processes involved in ATP generation, i.e. oxidative phosphorylation, adenine nucleotide translocation and glycolysis.

Adenosine Diphosphate↗
PubMed1978

The effect of fatty acids on the regulation of pyruvate dehydrogenase in perfused rat liver.

The effect of fatty acids on the rate of pyruvate decarboxylation was studied in perfused livers from fed rats. The production of 14CO2 from infused [1-14C]pyruvate was employed as a monitor of the flux through the pyruvate dehydrogenase reaction. A correction for other decarboxylation reactions was made using kinetic analyses. Fatty acid (octanoate or oleate) infusion caused a stimulation of pyruvate decarboxylation at pyruvate concentrations in the perfusate below 1 mM (up to 3-fold at 0.05 mM pyruvate) but decreased the rate to one-third of control rates at pyruvate concentrations near 5 mM. These effects were half-maximal at fatty acid concentrations below 0.1 mM. Infusion of 3-hydroxybutyrate also caused a marked stimulation of pyruvate decarboxylation at low pyruvate concentrations. The data suggest that the mechanism by which fatty acids stimulate the flux through the pyruvate dehydrogenase reaction in perfused liver at low (limiting) pyruvate concentrations involves an acceleration of pyruvate transport into the mitochondrial compartment due to an exchange with acetoacetate. Furthermore, it is proposed that a relationship exists between ketogenesis and the regulation of pyruvate oxidation at pyruvate concentrations approximating conditions in vivo.

Acetoacetates↗
PubMed1978

Fructose, a substrate for energy-yielding metabolism in the heart?

Effects of fructose and glucose on cardiac function and 14CO2 production from radioactive hexoses were studied in isolated working guinea pig hearts perfused at constant filling pressure via the left atrium. When hearts were perfused without exogenous substrates external work declined, indicating exhaustion of endogenous energy sources. It was possible to restore left ventricular function with concentrations of glucose in the physiological range; in order to achieve a similar restoration with fructose as the only exogenous substrate concentrations higher than 40mM were necessary. 14CO2 necessary. 14CO2 production from [U-14C]glucose was half-maximal at about 2mM glucose. On the other hand, 14CO2 production from [U-14C]fructose did not show saturation kinetics and, at concentrations around 2mM, was less than 5% of the rates observed with [U-14C]glucose. Moreover, fructose oxidation was suppressed in the presence of 5mM glucose. The data suggest that fructose cannot serve as a major substrate in the heart under in vivo conditions.

Animals↗
PubMed1978

[Rule of antibody structure: the primary structure of a human monoclonal IgA1-immunoglobulin (myeloma protein Tro), I. Purification and characterization of the protein and its L- and H-chains (author's transl)].

Myeloma protein Tro was prepared from the serum of a myeloma patient by ammonium sulfate precipitation. It was purified by gel filtration and ion exchange chromatography or by Pevikon block electrophoresis. The purity of the preparation was tested by several electrophoretic or immunoelectrophoretic methods. L- and H-chains of the purified protein after reduction and alkylation were separated by gel chromatography. The protein and its L- and H-chains were characterized by amino acid analyses and end-group determinations.

Amino Acid Sequence↗
PubMed1977

Interaction of glycolysis and respiration in perfused rat liver. Changes in oxygen uptake following the addition of ethanol.

The effect of ethanol on hepatic respiration and glycolysis was studied in perfused rat livers. 1. Ethanol increased the rate of oxygen uptake in livers from fed rats, but decreased the rate in livers from fasted animals perfused in the absence of added substrates. 2. Addition of ethanol decreased the rate of lactate + pyruvate production reflecting an inhibition of glycolysis irrespective of whether glycogen or added glucose was the substrate. 3. Half-maximal stimulation of respiration and inhibition of glycolysis were observed at ethanol concentrations between 0.2 and 0.4 mM. 4. A stoichiometric relationship of one mole of stimulated oxygen uptake to 3.6 mol of decreased lactate + pyruvate production was observed under a variety of experimental conditions. 5. The effects of ethanol on oxygen uptake and lactate + pyruvate production were abolished by the addition of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, but were unaffected by aminooxyacetate, an inhibitor of hydrogen transport across the mitochondrial membrane. 6. Carboxyatractyloside, an inhibitor of adenine nucleotide translocase, largely abolished the increase in oxygen uptake due to ethnol, but had little effect on the inhibitory action of ethanol on glycolysis. These data indicate that the ethanol-stimulated oxygen uptake is due to an increased flux through the mitochondrial respiratory chain and that it involves the NAD+-dependent oxidation of ethanol by alcohol dehydrogenase. The data are consistent with the hypothesis that the ethanol-stimulated respiration results from an increased demand for mitochondrial oxidative phosphorylation as a consequence of the decreased extramitochondrial ATP generation following inhibition of glycolysis by ethanol.

Aminooxyacetic Acid↗
PubMed1977

[Myxochondrosarcoma of the hand].

First description of repeated recurrence of a myxochondrosarcoma of the second metacarpal, most probably beginning as a central chondrosarcoma and within few months, after destroying the cortex, spreading into the soft tissues as a myxosarcoma. As it consisted mainly of chondroid material it is to be classified as a chondrosarcoma while histologically it showed small spindle cell and angiomatous areas. The rarity, pathological anatomy and clinical therapeutic experience with chondrosarcoma oft the hand with its greater tendency to metastasize from there than from other locations are discussed. The morphological differences between the common secondary myxoid degeneration of chondrosarcoma and the rare primary myxosarcoma are accentuated.

Adolescent↗
PubMed1977

[Gluconeogenesis in perfused rat liver following preservation in various temperature ranges].

Experiments with perfused rat livers have shown that rates of various metabolic processes are influenced by changes in temperature in different ways. Cytosolic processes exhibit a linear temperature dependence when plotted in an Arrhenius-diagram in the range between 37 degrees and 1 degree C. In contrast, processes which are bound to mitochondrial membranes show phase changes at 22 degrees C. Furthermore, with gluconeogenesis another phase was observed at 11 degrees C. After 24 hour of perfusion at 11 degrees C the livers produced more glucose from gluconeogenic precursors when perfused at 37 degrees C than after perfusion at 4 degrees C. The importance of the balance of metabolism during hypothermia is discussed by comparison with metabolism of poikilothermic animals.

Animals↗
PubMed1976

Metabolism of maltose in perfused rat liver and in isolated hepatocytes.

The conversion of 14C-maltose into glucose, lactate and 14 CO2 was studied in perfused livers from fed and fasted rats and in isolated hepatocytes. Maximal glucose production was 30 mM x g-1 x h-1; half-maximal rates were found with 3 mM maltose. About 0.01 % of the radioactivity infused was recovered as 14CO2. The addition of maltose had no effect on rates of oxygen consumption, lactate production or ketogenesis. The data suggest that maltose did not serve as a major substrate for biosynthetic or energy producing processes under the conditions of the perfused rat liver.

Animals↗