Ornithine assay

Epstein-Barr virus early antigen induction. Methanol extract of the dried leaf, in cell culture at a concentration of 1 pg/mL, was inactive. The assay was designed for tumor-promoting activity . Two diastere-oisomers of 2,7,1 l-cembratriene-4,6-diol (a- and 3-CBT) from the neutral fractions of cigarette smoke condensate, in Raji cells, produced potent inhibitory effects on the induction of Epstein-Barr virus (EBV)-EA by 12-0-tetradecanoylphorbol-13-acetate (TPA). The doses of a- and P-CBT required for 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7 mg/mL, respectively. Application of a- and P-CBT to mouse skin before treatment with TPA, inhibited TPA-induced ornithine decarboxylase activity in a dose-dependent manner. Application of 16.5 pM/mouse of a- and p-CBT resulted... 

Cell transformation, C3H10T14 mouse eells Cell transformation, Syrian hamster embryo eells, elonal assay Cell transformation, Syrian hamster embryo eells, elonal assay Cell transformation, Syrian hamster embryo eells, elonal assay Cell transformation, Syrian hamster embryo eells, elonal assay Cell transformation, Syrian hamster embryo eells, elonal assay Ornithine deearboxylase superinduetion, Syrian hamster embryo eells ... 

RLV/Fischer rat assay without the addition of an exogenous metabolic activation system. In a single study, mouse JB6 epidermal cells were transformed by di(2-ethyl-hexyl) phthalate without activation and in one of two studies a weak response was reported in the CSHIOT A cell transformation assay with di(2-ethylhexyl) phthalate in either the absence or presence of exogenous metabolic activation. BALB/c-3T3 cells were not transformed by di(2-ethylhexyl) phthalate with or without metabolic activation. Di(2-ethylhexyl) phthalate inhibited gap-junctional intercellular communication in Chinese hamster V79 cells in six of seven studies, but not in one study of liver cells of cynomolgus monkeys in vivo. Di(2-ethylhexyl) phthalate treatment of Syrian hamster embryo cells in a two-stage exposure with 12-O-tetradecanoylphorbol 13-acetate resulted in superinduction of ornithine decarboxylase, an early event in morphological transformation no effect was seen after a one-stage treatment with di(2-ethylhexyl) phthalate alone. 

Fig. 2.1.2a-c A Urine amino acids in a patient with cystinuria assayed by an amino acid analyzer (AAA). The indicated peaks are 1 glycine, 2 cystine, 3 ammonia, 4 ornithine, 5 lysine, 6 arginine, i.s. internal standard (S-amino thyl-cysteine). Cystinuria treatment is best followed-up by analyzing an early morning urine specimen, which usually shows the highest amino acid concentrations. b-c see next page... 

Ornithine Decarboxylase Assays. The double-chamber assay system of Moskal and Basu (59) was used to measure enzyme activity in the form of L C] carbon dioxIHe evolution. The assay conditions of O Brien and Diamond (60) were used and consisted of the following components (in micromoles, unless otherwise stated) in a total volume of 100 jul sodium phosphate buffer, pH 7.2, 5.0 EDTA, 1.0 dithiothreitol, 5.0 pyridoxal-5 -monophosphate, 0.2 L-ornithine (specific activity 0.5 x 10° cpm/-jumole), 0.1 and protein, 0.1-0.5 mg. Incubations were carried out at 37°C for 60 min, and the reactions were terminated by the addition of 200 jul of 2M sodium citrate followed by a post-incubation period of 3 hours at 37°C to insure maximal release of radiolabeled carbon dioxide. 

The important odorant, 2-acetyltetrahydropyridine (ACTPY), has already been mentioned in the previous section. ACTPY and ACPY play key roles in the aroma of popcorn.227 Freeze-dried maize contains relatively high amounts of proline (155), whereas ornithine is not detectable (< 5 mg kg ) Schieberle treated a low-molecu-lar-mass fraction of an aqueous extract of maize in different ways and determined ACTPY and ACPY by isotope dilution assay (Table 5.2). Steam-distillation extraction gave 130 times as much ACTPY than ACPY however, in the presence of added 2-oxo-propanal, the amount of the former was multiplied by 4, but that of the latter by 29. Dry-heating, as in popping, increased the latter further, but the former became undetectable. 

Fig. 7. Changes in the contents of specific mRNAs and nuclear receptors in mouse kidney after exposure to testosterone. Female NCS mice were given a single intraperitoneal dose of 10 mg of testosterone at time zero. Thereafter, nuclear androgen receptors were measured, The specific mRNAs of three proteins were also assayed, namely for ornithine decarboxylase (- -), KAP (-0-) and /3-glucuronidase (- -). Redrawn from Catterall et al. [26],...

The assay described for amino acid decarboxylase can be used to quantitate the substrates and products associated with the decarboxylation of arginine, aspartate, 2,6-diaminopimelate, histidine, glutamate, lysine, and ornithine. 

In the assay described by Beeman and Rossomando (1989), a /xBondapak CI8 column (3.9 mm x 300 mm) was used to separate L-[2,3-3H]ornithine from [1,2-3H]putrescine. The mobile phase contained 0.05 M sodium phosphate (pH adjusted to 3.9 with phosphoric acid) containing 0.01 Af SDS and 36% acetonitrile. Fractions were collected and the radioactivity determined by a liquid scintillation counter The flow rate was 1.0 mL/min, and 0.5 mL fractions were collected. 

The reaction mixture contained in a final volume of 1 mL 20 mAf sodium phosphate buffer (pH 5.0), 2.5 mAf dithiothreitol, 0.1 mAf pyridoxal 5 -phosphate, 0.4 /xCi L-[2,3-3H]ornithine, 100 mAf ornithine hydrochloride, and 0.3 mL of either E. coli ornithine decarboxylase or tissue homogenate. The E. coli enzyme was assayed at pH 5.0 and 37°C the pH values of reaction mixtures were adjusted to pH 7.3 before assaying homogenates of mammalian tissues. The reaction was stopped by injection onto the column. 

A question of stability. Pyridoxal phosphate (PLP) is a coenzyme for the enzyme ornithine aminotransferase. The enzyme was purified from cells grovm in PLP-deficient media as well as from cells grown in media that contained pyridoxal phosphate. The stability of the enzyme was then measured by incubating the enzyme at 37°C and assaying for the amount of enzyme activity remaining. The following results were obtained. 

Gatto et al m characterized the mechanism of L-pipecolic acid formation by cyclodeaminase RapL from L-lysine within rapamycin biosynthesis, which is a hybrid NRP—polyketide antibiotic (Figure 25(a)). RapL was characterized by biochemical assays to require cofactor nicotinamide adenine dinucleotide (NAD+) and an oxidative cyclodeamination reaction mechanism corresponding to ornithine cyclodeamination was proposed based on ESI-FTMS analysis of RapL reaction products (Figure 25(b)). 

It must be noted that only few results have been obtained on fresh biopsy specimens most have been from specimens which have been stored in the frozen state for some time or from specimens of liver which have been removed at necropsy at varying unstated periods after death and kept deep frozen at —15°C for various periods of time before analysis. There is some evidence from our results that at least two, carbamyl phosphate synthetase and ornithine transcarbamylase, of the urea cycle enzyme activities fall off on storage at — 15°C for even 1 day, and this decrease continues over longer periods. Thus carbamyl phosphate synthetase activity in fresh mouse liver is in our experience appreciably higher than in liver kept frozen for some days or weeks. This is borne out by a comparison of the enzyme activities found in human liver obtained by biopsy, measured immediately, after storage at —15°C, and finally in liver obtained at necropsy (Fig. 6). Ornithine transcarbamylase activity in a human biopsy specimen of liver is greater when assayed immediately than when it is kept frozen even a short time or... 

Fig. 7. Comparison of ornithine transcarbamylase activities in the human liver assayed immediately after biopsy, after storage at —15°C, and at necropsy.

The substances assayed in the reaction mixture are citrulline, in determining carbamyl phosphate synthetase and ornithine transcarbamylase, and urea in determining argininosuccinate synthetase, argininosuccinate lyase, and arginase. 

The high concentration of OCT is in hepatic tissue relative to other tissues this leads to this enzyme being regarded as a liver-specific enzyme. OCT is localized in the periportal mitochondria and is the second of the five enzymes in the urea cycle. The enzyme measurement should not be confused with ornithine decarboxylase (ODC), which is of interest in studies of polyamine metabolism. The use of the method has been limited by some of technical requirements for the older assays, but newer enzymatic methods may increase its use (Peltenburg et al. 1991 Isobe, Matsuzawa, and Nagamura 1993 Ishikawa et al. 2002). In a number of rat studies, ALT was found to be more predictive of hepatotoxicity than OCT (Bondy et al. 2000). 

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