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Biomedical subjects

G E Hoffmann

Publications and source records attributed to G E Hoffmann.

At least 37 records · Page 2Linked to original sources
PubMed1987

Activity of phospholipase A compared in serum of patients with pancreatic and nonpancreatic diseases.

Phospholipase A (PLA) activity was measured with a semi-automated photometric test system that is based on liberation of fatty acids from phosphatidylcholine by phospholipases A1 (EC 3.1.1.32) and A2 (EC 3.1.1.4). We studied 528 serum samples from 86 patients whose lipase activities were increased owing to pancreatitis, pancreatic carcinoma, and extrapancreatic diseases. PLA activity showed no correlation with lipase or amylase activities or with the primary cause of the disease, but was clearly related to prognosis. Noncomplicated acute pancreatitis was characterized by "normal" PLA activities (0-10 U/L), whereas the values (50-137 U/L) were highest in necrotizing pancreatitis and septicemia with a lethal outcome. Changes in lipase and phospholipase A activities exhibited completely different time courses in the various diagnostic groups.

Acute Disease↗
PubMed1986

Sexually dimorphic opioid distribution in the preoptic area: manipulation by gonadal steroids.

A striking sexual dimorphism has been found in the density of Met-enkephalin immunoreactive fibers in the periventricular region of the preoptic area in the rat: the enkephalinergic fiber system is much denser in females. The expression of this female-typical fiber plexus is regulated by the actions of gonadal steroids both during development and in adulthood. In light of abundant evidence demonstrating the ability of the opioid peptides to modulate various sexually differentiated neuroendocrine processes and behaviors, this dimorphic system may represent an important anatomical substrate underlying these functions.

Animals↗
PubMed1986

Fatty-acid biosynthesis in man, a pathway of minor importance. Purification, optimal assay conditions, and organ distribution of fatty-acid synthase.

Fatty-acid synthase has been purified to homogeneity from human liver by a 3-step procedure including protamine sulfate/ammonium sulfate fractionation, affinity chromatography on 2',5'-ADP-Sepharose 4B and gel filtration on Sephacryl S-300. Both the human and rat fatty-acid synthase had similar characteristics regarding molecular mass, subunit structure, amino-acid composition, and substrate affinities. In order to measure the fatty-acid synthase activities in small tissue samples it was necessary to improve the sensitivity of an isotopic assay using [14C]malonyl-CoA as tracer. Special attention was paid to the dual role of free CoASH as an activator and inhibitor of the enzyme. Considerable differences existed between the specific activities of the fatty-acid synthase complex measured in human and rat lipogenic organs. Only negligible values of about 1 mU/mg protein were found in human liver and adipose tissue, while the corresponding activities were 10- to 50-fold higher in young lean rats. Less pronounced but still remarkable differences were determined for the activity of the acetyltransferase which catalyses the initial primer reaction of the fatty-acid synthase complex. In some selected cases under long-term fat-free diet (alcoholism, parenteral nutrition) elevated values of fatty-acid synthase activities were detected in human tissues. Under usual diet, with a relatively high fat content of up to 40 percent, and even after a carbohydrate-rich diet for three days, fatty-acid synthase activity remained low. It is concluded that under the dietary conditions, common for the industrialized world, de novo lipogenesis in man is negligible.

Adipose Tissue↗
PubMed1986

Photometric determination of phospholipase A.

A photometric method for the determination of phospholipase A is described, in which fatty acids are liberated from phosphatidylcholine and measured by a discontinuous enzymatic test. Optimal test conditions were evaluated using purified phospholipase A from human and porcine pancreas. The enzyme activities measured in normal human sera are in the range of 0 to 10 U/l. Pathological values reach more than 100 U/l. There is no correlation with the activities of lipase or amylase in cases of acute pancreatitis.

Amylases↗
PubMed1986

Multicentre evaluation of an enzymatic method for creatinine determination using a sensitive colour reagent.

A new enzymatic colorimetric method for the determination of creatinine in serum and urine (Creatinine PAP, Cat. No. 839434 and 836885, Boehringer Mannheim GmbH, Mannheim, FRG) was evaluated in 16 clinical chemistry laboratories and the manufacturer's testing laboratory. The test is based on the enzymatic degradation of creatinine and its reaction products by creatininase, creatinase and sarcosine oxidase. The H2O2 produced by the oxidation of sarcosine is determined using a modified Trinder reaction. The test can be carried out either manually or in mechanized analysers which enable the pipetting of a starter reagent to be made. The following results were obtained: Depending on the analyte concentration (range 40 to 1240 mumol/l), medians for the coefficients of variation were: 4.6-0.9% within-run and 6.4-2.8% between-day. At 546 nm the linear measuring range extended from 13 mumol/l (detection limit) to 1780 mumol/l, at 510 nm from 9 to 890 mumol/l. Recoveries in aqueous and human serum based standards as well as method comparisons with Fuller's earth methods and an enzymatic UV test indicate a high accuracy of this new enzymatic method in serum and urine. No interference was observed with haemolysed and lipaemic sera. This also applied to anticoagulants and to 36 drugs at therapeutic concentrations, with the exception of calcium dobesilate, which led to decreased values. Icteric samples containing 120-310 mumol/l bilirubin invariably led to decreased creatinine values (10-50 mumol/l lower). In a collaborative study substantially better interlaboratory agreement was observed with the new colorimetric enzymatic test than with the comparison methods (enzymatic UV test and various Jaffe procedures). In conclusion, this new enzymatic colorimetric test permits a precise and specific determination of creatinine in serum and urine. It makes a considerable contribution to improving the interlaboratory comparability of creatinine determinations and is suitable for routine use.

Bilirubin↗
PubMed1986

An enzymatic method for calibration of serum lipase assays.

An enzymatic method for the calibration of a turbidimetric lipase assay is described, based on measurement of free fatty acids liberated by the action of lipase. The substrate of the turbidimetric assay is a colipase-containing triolein emulsion. For determination of the free fatty acids a commercial test kit including acyl-CoA synthetase, acyl-CoA oxidase, and peroxidase is used. Intra- and interassay imprecision (CV) is about 5% at above-normal lipase activities, about 10% at normal values. Temperature coefficients are 1.24 and 1.45, respectively, for measurements at 30 and 37 degrees C vs 25 degrees C.

Animals↗
PubMed1985

Five methods for measuring low-density lipoprotein cholesterol concentration in serum compared.

Five methods for the quantification of low-density-lipoprotein cholesterol were compared: ultracentrifugation, electrophoresis, precipitation with polyvinyl sulfate or heparin, and an indirect calculation procedure (Friedewald formula). Excellent agreement of results was obtained with all procedures for 49 of 51 sera. Discrepancies were as much as 1.69 g/L for the remaining two cases, which contained appreciable amounts of "floating" beta-cholesterol as detected with a combination of ultracentrifugation and electrophoresis.

Chemical Precipitation↗
PubMed1985

[Reaction of unconjugated and conjugated bilirubin with Fast Red TR and related diazonium salts].

In the present study, the reaction of 15 different diazonium salts with serum bilirubin is examined. It is shown that the selectivity of the determination of non-conjugated and total bilirubin greatly depends on two conditions: the pH-value of the reaction mixture and the nature and position of substituents within the benzene ring. Introduction of "electron-pushing" groups such as the o-methyl group of Fast Red TR will change the reactivity of the diazonium cation towards bilirubin in such a way that the co-reaction of the conjugated fraction becomes negligible at pH-values between 2 and 5. After neutralization to pH 7 the total bilirubin can be determined.

Adult↗
PubMed1983

Influence of bilirubin on the determination of acid phosphatase in serum.

Bilirubin interferes greatly in the continuous measurement of acid phosphatase, using alpha-naphthyl phosphate as substrate and diazotized 2-amino-5-chlorotoluene (Fast Red TR) as the colorimetric reagent. Fast Red TR and the so-called "direct" (but not "indirect") bilirubin form a coloured azo-compound which absorbs light above 480 nm. Negative absorbance changes are observed at 405 nm, which is used in the determination of acid phosphatase. This leads to apparently negative activities.

Acid Phosphatase↗
PubMed1982

Comparison of two methods for very low density and low density lipoprotein cholesterol determination.

It is shown that VLDL-cholesterol cannot be calculated from serum triacylglycerol at elevated triacylglycerol concentrations (above 2 g/l). Using the method of Friedewald et al. ((1972) Clin. Chem. 18,499-502), VLDL-cholesterol is usually overestimated in these sera and, consequently, LDL-cholesterol underestimated. Quantitative lipoprotein electrophoresis according to Wieland & Seidel ((1979) Innere Medizin 5,290-300), on the other hand, yields VLDL-cholesterol values which correspond to ultracentrifugation data within narrow limits, even in sera with high triacylglycerol contents. A nomogram has been developed for the evaluation of electropherogram.

Chemical Precipitation↗
PubMed1980

Properties and organ distribution of ATP citrate (pro-3S)-lyase.

1. The lipogenic enzyme ATP citrate lyase (ATP:citrate oxaloacetate-lyase (pro-3S-CH2COO-acetyl-CoA; ATP-dephosphorylating), EC 4.1.3.8) is partially purified from human liver by ammonium sulfate fractionation and anionexchange chromatography. 2. Km values for the substrates are 1.1 x 10(-5) 1.3 x 10(-3), and 1.2 x 10(-4) M for CoASH, ATP and citrate, respectively. The hypolipidemic drug L(-)-hydroxycitrate is a competitive inhibitor with respect to citrate (Ki = 3 x 10(-4) M). 3. Specific activities measured in liver, adipose tissue and intestinal mucosa (autopsic and biopsic material) are in the range of 1 mU/mg protein suggesting that the citrate pathway does not significantly contribute to human lipogenesis. No stimulation is found after a 3-day carbohydrate-rich diet. 4. Specific activities of other key-enzymes of the acetyl-CoA production from carbohydrates (pyruvate dehydrogenase, cytosolic acetyl-CoA synthetase) are of the same low magnitude.

ATP Citrate (pro-S)-Lyase↗
PubMed1980

Overestimation of glucose in uranyl acetate-treated samples: modification of the deproteinization method.

It is demonstrated that uranyl ions remaining in deproteinized supernatants of blood, serum, or liquor cerebrospinalis lead to falsely elevated glucose values by forming insoluble precipitates of uranyl phosphate. Furthermore, glucose is overestimated in hemolytic blood samples because of the UV-absorption of incompletely precipitated hemoglobin. A modified deproteinization method is recommended which overcomes these problems: the specimen volume is reduced to one half of the usual volume (0.05 instead of 0.1 ml) and excess uranyl ions are removed from the deproteinized supernatant by precipitation as uranyl phosphate, using phosphate-coated tubes. The supernatant obtained after centrifugation is free of uranyl ions and hemoglobin. Therefore, a sample blank may be omitted.

Blood Glucose↗
PubMed1980

Specific serum pancreatic lipase determination, with use of purified colipase.

We show that the turbidimetric method of Ziegenhorn et al. (Clin. Chem. 25: 1067, 1979) for determination of pancreatic lipase is not influenced by lipoprotein lipase. This improved specificity as compared to standard lipase methods is explained by the presence of purified colipase and the high concentration of bile acids in the substrate emulsion.

Bile Acids and Salts↗