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Biomedical subjects

H Leweling

Publications and source records attributed to H Leweling.

11 recordsLinked to original sources
PubMed1992

Haemodilution in acute ischaemic stroke comparison of two haemodilution regimen.

In a prospective study we randomly allocated 50 patients with acute ischaemic stroke in the area of the middle cerebral artery within 12 hours after onset to two moderate hypervolemic haemodilution regimen consisting of 500 ml of 10% hydroxyethyl starch per day for 10 days. In the high haematocrit group the target haematocrit of 41-42% was achieved by 0-3 phlebotomies and additional replacement of that volume with the colloid in 3 days. In the low haematocrit group with 1-4 phlebotomies a target haematocrit of 37-38% was reached in 4 days. The groups did not differ regarding age, risk factors, haematocrit and neurological score. The improvement of the disturbed blood rheology was more pronounced in the low haematocrit group. One death occurred in each group. The neurological score showed a significantly greater increase in the low haematocrit group with +59% at day 5 and +125% at day 11; the data for the high haematocrit group were +34% and +89% respectively. We calculated a correlation (r = 0.36, p less than 0.02) between the rise in neurological score and the reduction of haematocrit. Our data suggest but not do prove that an early start on moderate hypervolemic haemodilution is beneficial in patients with acute ischaemic stroke and disturbed blood rheology.

Aged↗
PubMed1989

Intra- and extracellular amino acid concentrations in portacaval-shunted rabbits. Role of hyperammonemia and effects of branched-chain amino acid-enriched parenteral nutrition.

Intra- and extracellular amino acid concentrations were measured in rabbits in order to elucidate the possible role of hyperammonemia in lowering the postabsorptive plasma levels of branched-chain amino acids (BCAA) and to assess the effects of BCAA-enriched total parenteral nutrition (TPN) on the amino acid pattern of muscle. The pathophysiological part of this paper deals with portacaval anastomosis (PCA) and is aimed at substantiating or rejecting our hypothesis that excessive ammonia-by stimulating glutamine synthesis-reduces the intracellular glutamate pool which is then restored, at least in part, by an intensified BCAA degradation. Regarding infusion therapy, we were mainly interested in whether an amino acid solution adapted to the metabolism in liver cirrhosis causes an accumulation of BCAA in muscle or modifies the intracellular content of glutamate and glutamine. Eighteen rabbits did not undergo surgery and served as controls (group A), while 30 were given a portacaval end-to-side anastomosis (group B). Two weeks after creating the PCA, venous blood samples were taken and muscle biopsies (Bergström's technique) were performed postabsorptively. An 18-h TPN was then started, the regimen administered included dextrose, fat and, in addition, either a conventional (group B1, n = 15) or an adapted amino acid solution (group B2, n = 15). We obtained second blood specimens and muscle biopsies at the end of the infusion period. With the control animals, the same time schedule for blood sampling and muscle biopsies was followed. Fourteen days after the operation, the PCA rabbits displayed a mean plasma ammonia level 5.1 times higher than that measured in the controls (p less than or equal to 0.001). Conventional blood chemistry did not reveal any impairment of liver cell integrity or over-all hepatic function, whereas the nutritional state of the shunted animals worsened, as indicated by body weight and biochemical variables. Since in the PCA rabbits, the total amino acid pools of muscle and plasma were seen to be increased and decreased, respectively, the results concerning the individual amino acids are given in terms of both the absolute and percentage values, the latter more often revealing high levels of statistical significance. PCA induced a marked rise in the intra- and extracellular concentrations of glutamine, while the values of glutamate and alanine showed a decline in muscle and plasma. The extracellular levels of methionine, phenylalanine, and tyrosine were raised, while those of the BCAA were diminished.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1989

[Effect of hemodilution with 10% hydroxyethyl starch solution (MW 200,000/9.5) on the flow properties of blood, arterial blood gases and conjunctival oxygen partial pressure in patients with cerebral infarct].

Hemorheological parameters, arterial blood gases and conjunctival oxygen tension were measured in 15 patients with acute ischemic stroke and compared with values obtained in an age matched reference group. Since the conjunctival capillary bed is perfused by the ophthalmic artery, it reflects the oxygen delivery to the areas supplied by the internal carotid artery. Measurements of conjunctival oxygen tension are simple and safe. Patients with acute ischemic stroke showed a lowered conjunctival oxygen tension; this holds true especially to the ipsilateral side, i.e. the side where the attack occurred, and to a lesser extent to the other side. By contrast, the ratio of arterial/conjunctival pO2 was disturbed only on the ipsilateral side. Furthermore, these patients had pathologically elevated values for red cell aggregation, whole blood and plasma viscosity. After infusing 500 ml 10% middle-molecular-weight hydroxyethyl starch (10% HAES-steril) and phlebotomy (250 ml) blood fluidity was normalized, although the hematokrit was only slightly reduced. Arterial pO2 improved slightly while pCO2 remained unchanged. Conjunctival oxygen tension improved by 30% on the ipsilateral and by 10% on the contralateral side, the ipsilateral values always remaining significantly lower. The ratio conjunctival/arterial pO2 raised only on the ipsilateral side where it was below the reference range before hemodilution. In addition to the well known improvement of blood fluidity and augmentation of cerebral blood flow following hemodilution in patients with acute ischemic stroke, there seems to be an increase in oxygen supply in the territories of both internal carotid arteries, especially on the ipsilateral side as indicated by the values of conjunctival oxygen tension and the ratio of conjunctival to arterial pO2.

Blood Viscosity↗
PubMed1987

[Intracellular amino acid concentrations in the musculature of 3 species of animals under physiologic, pathophysiologic and infusion therapy conditions].

In the first part of this paper methodological aspects of intracellular amino-acid analysis in three species of animals, i.e. in rats, rabbits, and cats are dealt with. The genetic homogeneity as well as the age of the animal groups, metabolic differences between carnivores and herbivores, the length of the intestine and, thus, the time elapsing before the postabsorptive state is reached, furthermore, the body size which, in studies with muscle biopsies, makes correlated samples either possible or impossible; all these factors are experimental variables potentially affecting the evidence of the results obtained. Amino acids being involved in ammonia detoxification or showing raised plasma levels in hepatic failure form the subject of the subsequent parts of this paper. In the muscle cells of the three above species investigated after an overnight fast, the concentration of glutamine was about 5.5 times and that of glutamate about 4.1 times higher than in human muscle. Regarding glutamine and glutamate, there were no marked differences between the three species. As to the other amino acids measured in the rats, rabbits, and cats, alanine, the branched-chain amino acid (BCAA) as well as methionine and phenylalanine had intracellular values similar to those observed in humans. To test the hypothesis that ammonia lowers the BCAA plasma levels by considerably increasing glutamine synthesis and decreasing the intracellular glutamate pool with consecutively intensified transamination of BCAA for partial replenishment of this pool, we infused ammonium salts and created portocaval shunts in animal experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1986

[Amino acid uptake and release by colorectal cancer in man].

Little information is available regarding the amino acid exchange by human tumors. To characterize this exchange in vivo, 21 patients with resectable colorectal carcinomas were studied during curative operations. Concerning the amino acid uptake and release by peripheral tissues, 20 non-cancer patients served as controls. Both groups of subjects were well-nourished, as indicated by anthropometric and biochemical variables. In the cancer patients, we cannulated a peripheral artery and vein as well as a central tumor-draining vein and the portal vein. Plasma concentrations and concentration differences were determined in mumol/l and in percentages of the total amino acid amounts. Peripheral glutamate uptake per liter plasma was reduced in the cancer patients (p = 0.02). In these patients, the central tumor-draining vein contained less glutamine (p = 0.002) and more glutamate (p = 0.002) than the peripheral vein. Glutamine uptake by the tumor occurred more often than glutamine release, while glutamate had a negative balance across the tumor in all but three cases. The qualitative differences between the peripheral tissues and the tumors with respect to glutamine and glutamate exchange reached high levels of significance (p = 0.002 for both of the amino acids). In addition, the tumors released more glycine, ornithine, and tyrosine than the periphery. As to glutamine and glutamate metabolism, there was a significant difference between the tumors and the portal-drained organs (p greater than or equal to 0.05). The discussion of the results emphasizes the contributions made by the periphery and the tumor to the plasma amino pattern. The role of glutamine as a potential high importance energy source for neoplastic tissues is delineated.

Aged↗
PubMed1979

[Use of different parenterally administered amino acid solutions with healthy test subjects].

We studied the alterations in the pattern of free serum amino acids during continuous parenteral infusion of 4 different standardised L-amino acid solutions. Nearly for all amino acids, a dose-dependent steady state could be established, usually as early as 30 or 60 minutes after starting the infusion. Amino acid solutions that caused the smallest changes of the amino acid pattern in plasma during infusion produced always the smallest increase of total amino acid nitrogen and the greatest rate of amino acid transfer. So we conclude that these solutions are utilised most effectively.

Adult↗