Biomedical subjects
Publications and source records attributed to R Haeckel.
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1. In fed rats various nucleosides and their monophosphates caused a strong glucose release from perfused livers. 2. This effect was further studied with inosine and found depending on the rat strain used; it was much less pronounced in the Wistar strain WU than in the Hannover Wistar or the Sprague Dawley strain. In animals fasted 48 hours less glucose was released in the presence of inosine; no difference was observed between the various strains. 3. In fasted rats of all three strains inosine led to gluconeogenesis probable by its ribose moiety. In addition, 60% of the hepatic glucose output caused by inosine was derived from glycogen in fed Hannover Wistar rats. 4. The reduction of the hepatic blood flow after the addition of nucleosides, which could cause glycogenolysis by hypoxia, cannot explain their glucose releasing effect.
The structural relationship model is recommended for the comparison of analytical methods in clinical chemistry. This model is based on the partition of the observed measurements of the different methods in 2 hypothetical random variables: the "expected values", which represent the correct value of the analyte with no error of measurement, and the "error term" representing the measurement errors. it is assumed, that both these variables are normally distributed. There exists a linear structural relation between different analytical methods for the same analyte, provided the correlation coefficient between each pair of the expected values of these models is 1. This linear structural relationship is expressed by the mean values mui and standard deviations alpha i of the expected values, whereas the standard deviations of the error terms determine the precision of the methods. As a measure of the precision the coefficient of determination R(2)i is recommended. The model of structural relationship is an extension of th well known regression models and gives a more realistic approach to the comparison of 2 or more analytical methods. With 2 methods the standardized principle component should therefore replace the regression analysis. The slope of this principle component is identical with the ratio sy/sx. Statistical methods for the estimation and for the tests of hypotheses of the parameters are derived and demonstrated with an example.
An increase of the serum uric acid concentration of pregnant women can indicate an EPH gestosis with a high risk. Above a uric acid level of 270 mumol/l (and of 315 mumol/l after the 32nd. week of pregnancy) and gestosis has become moderate. An increased risk for mother and fetus must then be assumed. This decision point is estimated by comparing three techniques: The ROC-curve-method and the determination of the maximal efficiency and of the maximal information content.
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Phenylethylhydrazono-propionic acid (PEHP) and cyclohexyl-ethylhydrazono-propionic acid (CHEHP) has been shown to lower blood glucose concentrations in various laboratory animals after intraperitoneal or oral application. The present study has been conducted to investigate, if these hydrazones may induce lactic acidosis like the biguanides or may cause unwanted side reactions due to an inhibition of monoamino oxidase like the corresponding hydrazines. It was found that intramitochondrial and cytoplasmatic redox ratios were not influenced at a hypoglycemic effective dosage (145 mumol/kg body weight) of these substances in fasted guinea pigs. An effect on the acid base status was not observed. Both substances lowered the concentration of ketone bodies in fasted guinea pigs. In vitro the activity of monoamino oxidase purified from guinea pig liver was much less inhibited by the hydrazones than by one of the corresponding hydrazines (phenelzine). Furthermore CHEHP (145 mumol/kg body weight) did not influence the serum activity of various liver enzymes and the concentration of triglycerides, cholesterol and uric acid in plasma of fasted guinea pigs. It is concluded that CHEHP meets basic requirements for a potential oral antidiabetic agent.
A spectrophotometric method is described for the determination of 5'-nucleotidase. In combination with the enzymes nucleoside phosphorylase and xanthine oxidase, inosine, formed by hydrolysis of 5'-IMP by 5'-nucleotidase, is cleaved phosphorolytically to hypoxanthine, which is oxidized to uric acid. In the presence of ethanol, the hydrogen peroxide formed is reduced by catalase and equivalent amounts of acetaldehyde are produced. The aldehyde is dehydrogenated (NADP-dependent) by aldehyde dehydrogenase and the production rate of NADPH is recorded at 334 nm. The inhibition of the unspecific cleavage of 5'-IMP by phosphatases is examined critically.
The procedures using Fuller's earth for the specific determination of creatinine were further simplified without loss of reliability. Four routine purposes, deproteinization can be omitted if lipemic sera are excluded. the modification with deproteinization is recommended as a candiate for a selected method. Good correlation with an enzymatic procedure and the lack of relevant interference indicate a high analytical specificity. The Fuller's earth procedure is cheaper and more precise than the enzymatic method and slightly faster than the fading fraction method. Urine samples should also be treated with Fuller's earth before they are subjected to the Jaffé reaction.
In planning the internal organization of central laboratories, the future needs for clinical chemistry in hospitals must be considered. For the next decade the medical laboratory will primarily be concerned with the interpretation of laboratory data and with organizational problems, such as sample identification, specimen splitting and especially the timing of its service. The consequences for instrumentation, newer technology for routine clinical chemistry, and recommendations for the future development of analytical systems are discussed.
Despite published recommendations and experimental protocols for the evaluation of clinical chemical analytical methods, the statistical evaluation of results still leaves many questions unanswered. The purpose of the workshop conference was to produce, and submit to discussion, recommendations for suitable statistical procedures, in particular for the comparison of different analytical methods.
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