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Biomedical subjects

R Haeckel

Publications and source records attributed to R Haeckel.

At least 55 records · Page 3Linked to original sources
PubMed1987

The comparability of ethanol concentrations in peripheral blood and saliva. The phenomenon of variation in saliva to blood concentration ratios.

Ethanol appears to reach a higher peak concentration in saliva than in peripheral blood, and to be eliminated from both compartments at different rates. This phenomenon of different elimination rates, which leads to a cross-over of both concentration versus time curves, can be explained by differences in the water content of both body fluids. When the water content is considered, the salivary ethanol concentration parallels the blood level in the elimination phase, more closely in capillary blood than in venous blood.

Capillaries↗
PubMed1987

Inhibition of mitochondrial carnitine acylcarnitine translocase-mediated uptake of carnitine by 2-(3-methyl-cinnamyl-hydrazono)-propionate. Hydrazonopropionic acids, a new class of hypoglycaemic substances, VI.

The rate of mitochondrial carnitine-carnitine exchange mediated by carnitine acylcarnitine translocase was measured by following the uptake of L-[methyl-14C]carnitine. It was demonstrated that the hypoglycaemic compound 2-(3-methyl-cinnamyl-hydrazono)-propionate causes a concentration-dependent decrease in the rate of the translocase-mediated transport of carnitine in guinea pig liver mitochondria. Apparent initial influx rates were decreased by 20% at 0.3 mmol/1 2-(3-methyl-cinnamyl-hydrazono)-propionate, 38% at 0.5 mmol/l, and 75% at 2.0 mmol/l of this compound. This finding may explain the previously observed inhibitory effects of this substance on long-chain fatty acid oxidation, ketone body production and gluconeogenesis.

Animals↗
PubMed1987

Influence of 2(3-methyl-cinnamyl-hydrazono)-propionate on glucose and palmitate oxidation in human mononuclear leukocytes. Hydrazonopropionic acids, a new class of hypoglycaemic substances, VII.

2-(3-Methyl-cinnamyl-hydrozono)-propionate stimulated glucose oxidation in human mononuclear leukocytes and the stimulation was similar to that by concanavalin A. Both substances must affect glucose metabolism at two sites, the first site being before the pyruvate dehydrogenase step because of the increase of lactate plus pyruvate concentration. The second site is related to pyruvate oxidation. The hydrazone inhibited the conversion of plamitate to CO2. This effect could have caused an activation of the pyruvate dehydrogenase complex, resulting from a decrease acetyl-CoA/CoA ratio. Concanavalin A did not influence fatty acid oxidation. Both substances did not affect the CO2 formation from acetate. Mononuclear leukocytes appear to be a suitable model for the investigation of the influence of hypoglycaemic substances on glucose and fatty acid metabolism in living human cells.

Carbon Dioxide↗
PubMed1986

Analytical performance of the random access analyser Hitachi 737. A multicentre evaluation.

The selective multitest analyser Hitachi 737 was examined according to the ECCLS guidelines in a multicentre evaluation involving 4 laboratories. Twenty routine parameters, including the electrolytes, sodium, potassium and chloride, were measured at 37 degrees C. All of the measured values were included for evaluation without correcting for outliers. The trial, which lasted 4 months and involved over 70 000 analyses, basically yielded the following results: The precision can be termed very good. For the majority of the methods, the day-to-day coefficients of variation were below 2%. The highest coefficient of variation was 6.3% (for creatine kinase) and the lowest below 0.1% (for gamma-glutamyltransferase). The recovery of the assigned values of control sera was very good for most of the parameters (between 95% and 105%). Only with bilirubin, phosphate and chloride did greater deviations occur in a few control sera. Excellent agreement was found between the results obtained from the instruments used in the comparison: the Hitachi 705, a flame photometer and a chloride meter. No drift effects were observed. The same applied to carryover effects, provided that Boehringer Mannheim's recommendations concerning method combinations are observed. Because of the large measuring range, it is necessary to repeat analyses only in exceptional cases. During the entire period of the trial there were no stoppages due to the instrument malfunction. As a result of its reliability, the Hitachi 737 is well suited for routine operation and emergency analysis in medium to large-sized laboratories.

Autoanalysis↗
PubMed1985

Hydrazonopropionic acids, a new class of hypoglycemic substances. 5. Inhibition of hepatic gluconeogenesis by 2-(3-methylcinnamyl-hydrazono)-propionate in the rat and guinea pig.

2-(3-Methyl-cinnamyl-hydrazono)-propionate (MCHP) is a new compound which effectively lowers the blood glucose level in guinea pigs. 0.04 mmol/l MCHP inhibited glucose formation from lactate, pyruvate and alanine, but not from dihydroxyacetone in the perfused guinea pig liver. In the presence of both hexanoic acid and alanine, 0.04 mmol/l MCHP did not effect hepatic gluconeogenesis. Gluconeogenesis was probably reduced by an inhibition of the pyruvate carboxylase: The pattern of hepatic metabolite concentrations indicated a block between pyruvate and the triose phosphates. The intrahepatic concentration of acetyl-CoA was consistently decreased. The decrease of the acetyl-CoA concentration could be explained by an influence of MCHP on the fatty acid oxidations, which occurred at the carnitine palmitoyl transferase (CPT) step. This hypothesis is supported by the fact that a medium chain fatty acid not requiring CPT reversed the inhibition of gluconeogenesis by MCHP. From all results reported it is concluded that transamination and oxidative phosphorylation were not effected to a degree relevant for the inhibition of gluconeogenesis by 0.04 mmol/l MCHP.

Animals↗
PubMed1985

[Statistical problems in comparative clinical chemical analysis. Report of the workshop conference of the German Society for Clinical Chemistry, 12 and 13 January 1984, Bremen].

In continuation of the three previous workshops on this theme, the Passing-Bablok method was recapitulated and compared with standardized main component analysis. Participants in the workshop recommended both methods in place of the classical regression analysis. An essential advantage of the standardized main component is that it is more easily understood by the clinical chemist and his coworkers, and it involves fewer calculation steps. On the other hand, outliers must be recognized and eliminated, and certain other assumptions must be fulfilled. In comparison, the Passing-Bablok method is much more robust, but requires more calculation. The workshop also discussed unresolved questions concerning bases for the comparison of methods: the necessary number of samples, measures of scatter for description of precision, comparison of discrete results and several independent variances. These will be treated in greater depth in subsequent workshops.

Chemistry, Clinical↗
PubMed1985

Multi-centre evaluation of the urine test strip analyser Rapimat.

A multi-centre evaluation of the test strip analyser, Rapimat, was performed by four laboratories following the ECCLS 2nd draft guidelines for the evaluation of analysers in clinical chemistry. Using the Rapignost urine test strip with the test fields for bilirubin, urobilinogen, acetoacetate, ascorbic acid, glucose, protein, nitrite, pH and haemoglobin, the Rapimat was found to be analytically reliable in comparison with other, in most cases quantitative procedures. During the observation period of about 6 months no breakdown occurred in any laboratory. Interferences and sensitivity as discussed for the bilirubin and urobilinogen test field are more related to the test strip than to the instrument. Several improvements for further developments are suggested. This multi-centre study has shown that the ECCLS protocol is applicable to analytical procedures leading to discrete results.

Chemistry, Clinical↗
PubMed1984

Hydrazonopropionic acids, a new class of hypoglycemic substances, 3. Inhibition of jejunal glucose uptake in the rat and guinea pig.

Recently hydrazonopropionate derivatives have been recognized as a new group of compounds with strong hypoglycemic effects in various laboratory animals. The hypoglycemia probably has several causes of which an inhibition of gluconeogenesis and of intestinal glucose uptake could be identified. In the present report, the influence of phenylethylhydrazonopropionate, cyclohexylethylhydrazonopropionate, methylcinnamylhydrazonopropionate and their corresponding hydrazine derivatives on the glucose uptake of rat and guinea pig jejunum has been compared with the well known effects caused by phenformin. All substances tested inhibited the jejunal glucose uptake, phenelzine, methylcinnamylhydrazine and cyclohexylhydrazonopropionate more effective, the other compounds less effective than phenformin. The hydrazine derivatives appeared more effective than the hydrazone compounds used. The cellular ATP/ADP ratio was not influenced by the hydrazonopropionate compounds.

Adenosine Diphosphate↗
PubMed1984

Hydrazonopropionic acids, a new class of hypoglycemic substances. 4. Hypoglycemic effect of 2-(3-methyl-cinnamylhydrazono)-propionate in the rat and guinea pig.

The hydrazone-compound 2-(3-methyl-cinnamylhydrazono)-propionate (MCHP) significantly lowered the blood glucose concentration in fasted guinea pigs and rats. A significant decrease of blood glucose levels was observed in fasted guinea pigs already after an intraperitoneal injection of 20.5 mumol/kg MCHP, while much higher doses (about 1000 mumol/kg) were necessary to produce a hypoglycemic effect in the fasted rat. After oral administration MCHP (82.0 mumol/kg) significantly decreased the blood glucose concentration in guinea pigs. Furthermore MCHP caused a dose-dependent increase of plasma free fatty acid concentrations in guinea pigs and rats. In addition, MCHP decreased the concentrations of blood ketone bodies, plasma cholesterol and intrahepatic acetyl-coenzyme A in the guinea pig. All of these findings appear to be due to a reduced fatty acid utilization in the presence of MCHP resulting presumably in an intramitochondrial deficiency of acetyl-CoA. At hypoglycemic effective doses the intramitochondrial and cytoplasmatic redox ratios as well as the hepatic ATP/ADP ratio were not influenced by MCHP in fasted guinea pigs. Even at large doses (123 mumol/kg) MCHP decreased the activity of monoamino oxidase in guinea pigs only by less than 15%. Furthermore MCHP showed under our experimental conditions no relevant influence on the activity of various liver enzymes in plasma, the plasma concentration of creatinine, the plasma triglyceride-glycerol level and on the intrahepatic triglyceride-glycerol concentration of fasted guinea pigs. It is concluded that MCHP meets basic requirements for a potential oral antidiabetic agent.

Acetyl Coenzyme A↗
PubMed1984

[Statistical problems in comparative clinical chemistry analysis methods].

The previous workshop on this subject put forward recommendations for the use of statistical methods in the comparison of clinical chemical analytical procedures. In particular, standardized principal components analysis was recommended as a replacement for classical regression analysis. In the present workshop, two non-parametric methods were described, and their advantages and disadvantages, compared with standardized principal components analysis, were discussed.

Chemistry, Clinical↗
PubMed1983

Detection of drift effects before calculating the standard deviation as a measure of analytical imprecision.

The sample standard deviation is commonly used as a measure of analytical imprecision, calculated from a series of n data obtained from one sample split for n assays. Drift effects cause an overestimation and consequently a misinterpretation of the standard deviation in clinical chemistry. The r-ratio test is recommended as a simple procedure for detecting drift effects. It has been found necessary to eliminate outliers before drift effects can be recognized.

Analysis of Variance↗
PubMed1982

Evaluation of EMIT adapted to the (Cobas) Bio centrifugal analyzer.

EMIT assays for the determination of phenytoin, methotrexate, disopyramide, digoxin and thyroxine were adapted to the Cobas Bio centrifugal analyzer and compared with the corresponding laboratory routine procedures. Evaluation of the data from the Cobas Bio by 5 different mathematical models showed that the four-parameter logit model correlated best with the comparison procedures and the originally recommended calculation model for the reagent lots used in our study. The precision of the EMIT phenytoin, methotrexate and disopyramide assays was in most cases very good (between-days coefficient) of variation 1.6-7.5%). A lower precision was observed with the EMIT digoxin assay (between-days coefficients of variation 9.2-16.8%) and at low concentrations also with the EMIT thyroxine assay (3.1-21.4%). Calibration curves of the EMIT phenytoin, methotrexate assays were stable for at least one hour. The results from the determination of phenytoin, methotrexate and disopyramide in patient samples by use of the Cobas Bio were in good agreement with those values obtained with the EMIT/LAB. The data determined with the EMIT digoxin assay adapted to the Cobas Bio correlated better with those of a radioimmunoassay than the values measured with the EMIT/LAB system. The results of thyroxin determinations with EMIT by use of the Cobas Bio and the original procedure with an ABA-100 were in good agreement and on average about 12% lower than those measured by radioimmunoassay. The Cobas Bio allows rapid determination with EMIT and a reduction in direct costs of up to 85%.

Centrifugation↗
PubMed1982

A multicentre european evaluation of the Kodak EKTACHEM GLU/BUN analyzer using NCCLS guidelines and other approaches.

This paper describes the field performance of the Kodak EKTACHEM GLU/BUN Analyzer for glucose and urea. NCCLS protocols PSEP-2, 3 an 4 were used which enable manufacturers to establish performance claims concerning the precision and accuracy of an analytical system. This multicentre trial used four analysers in four European countries, United Kingdom, France, West Germany and Italy to assess within and between laboratory performances. Freeze dried control materials were used for the performance check experiment PSEP-2 and for the replication experiment PSEP-3. The replication study, although very time consuming, was straight forward to undertake and the results were comparable between centres. Compliance with the protocol for comparison of methods experiment PSEP-4 in which laboratories used their own hospital patient samples was more difficult. The problems with obtaining suitable samples and the performance of comparative methods are discussed in detail.

Autoanalysis↗