Quantitation of ochratoxin A: use of reverse phase thin-layer chromatography for sample cleanup followed by liquid chromatography or direct fluorescence measurement.

An improved procedure for sample preparation and quantitation of ochratoxin A in moldy grain was developed. Grain samples were acidified and extracted, and extracts were subjected to reverse phase thin-layer chromatography (RPTLC). The separated spots, which were identified under UV light, were scraped and collected into recovery devices. Ochratoxin A was eluted from the adsorbent and analyzed by either liquid chromatography with fluorescence detection or direct spectrofluorometric measurement. The method yielded values that were proportional to the concentrations of toxin in the sample, had relatively high levels of recovery (94%), and required considerably less volume of solvents and preparation time than a standard packed column method.

Ochratoxin A in blood from slaughter pigs in western Canada.

Twelve hundred blood samples were obtained in 1986 from pigs slaughtered in western Canada. The samples were assayed for ochratoxin as it is a potential contaminant in the food system. Blood ochratoxin concentration is a good indicator of tissue concentrations, particularly those in the liver and kidney. High performance liquid chromatography analysis of serum for ochratoxin demonstrated that 3.6 and 4.2% of the blood samples collected in February and March (n = 194) and May, June and July (n = 1006), respectively, had ochratoxin concentrations that exceeded 20 ng/mL. Overall the percent of samples that had concentrations of greater than 10, 20, 50, 100 and 200 ng/mL serum were 11.3, 4.1, 1.25, 0.42 and 0.08%, respectively. Samples that had ochratoxin concentrations that were greater than 20 ng/mL of serum were confirmed using two independent methods: liquid chromatography-mass spectrometry analysis and methyl ester derivatization followed by high performance liquid chromatography analysis.

Energy production and utilization in contractile failure due to intracellular calcium overload.

Intracellular calcium overload was produced by perfusing the Ca2+- deprived rat hearts for 5 or 10 min with normal medium containing 1.25 mM Ca2+ for 10 min and changes in the myofibrillar and membrane ATPase, sarcolemmal adenylate cyclase, mitochondrial oxidative phosphorylation and high energy phosphate stores in failing hearts were examined. Myocardial creatine phosphate and ATP were decreased by the intracellular calcium overload whereas the myofibrillar, mitochondrial and microsomal ATPase activities were not altered. The intracellular calcium overload markedly depressed the mitochondrial oxidative phosphorylation as well as sarcolemmal Ca2+ ATPase, Mg2+ ATPase, Na+ - K+ ATPase and adenylate cyclase. These results suggest that abnormalities in the process of energy production rather than energy utilization may primarily account for the depressed energy state of hearts failing due to an intracellular calcium overload.

Distribution of conduritol B epoxide in the animal model for Gaucher's disease (Gaucher mouse).

The time course of the distribution of the beta-glucosidase inhibitor [3H]conduritol B epoxide was determined in various organs of mice, which had received a single interperitoneal dose of the inhibitor. The epoxide is rapidly distributed over all tissues except brain where its concentration is only one-tenth of the average. This is considered an indication that the epoxide can pass the blood/brain barrier only with difficulty. A 4-fold enrichment is seen in the kidney. The inhibitor is excreted with a half-life of about 7 h; it is not metabolized. A parallel determination of beta-glucosidase activity in the tissues showed greater than 90% inhibition within 1 and 2 h and a beginning recovery between 4 and 12 h. The only exception was brain, where no effects could be seen after 1 h and where a subsequent decrease to 37% of normal was observed after 12 h.

Studies on the possible identity of particulate beta-glucosidase and beta-xylosidase of mouse liver.

Mouse liver beta-glucosidase (beta-D-glucosidase glucohydrolase, EC 3.2.1.21) and beta-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) activities were studied under different conditions of incubation in an attempt to determine whether these two activities are due to a single enzyme or two separate enzymes. The results showed that: (a) Particle-bound beta-glucosidase and beta-xylosidase activities exhibit similar characteristics with different buffers and at various pH values, in the presence or absence of taurocholate. (b) Both activities are inhibited by gluconolactone and conduritol B eposice. beta-Glucosidase activity is inhibited competitively by the two inhibitors, but beta-xylosidase activity is inhibited non-competitively. (c) Xylonolactone was a very poor inhibitor of both activities, but the inhibition of beta-xylosidase activity was more pronounced than that of beta-glucosidase. (d) The presence of glucosides or xylosides simultaneously in the incubation medium suggested the presence of one enzyme with both activities. These results, together with the mode of inhibition produced by gluconolactone and conduritol B epoxide also suggest the presence of two different binding sites for the beta-D-glucoside and beta-D-xyloside, respectively.

Defective membrane systems in dystrophic skeletal muscle of the UM-X7.1 strain of genetically myopathic hamster.

1. The function of mitochondria, sarcotubular membranes (heavy microsomes), sarcolemma and myofibrils from the hind-leg skeletal muscle of about 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters was examined. 2. The mitochondrial calcium uptake as well as mitochondrial phosphorylation and respiratory rates were lower in 60-day-old myopathic skeletal muscle, unlike 150-day-old myopathic animals, when pyruvate-malate and glutamate-malate were used as substrates. However, mitochondria from 150-day-old myopathic animals showed depressed glutamate-dependent respiratory and phosphorylation rates and succinate-supported initial rate of calcium uptake. 3. The microsomal calcium-uptake, but not calcium-binding, and Ca2+-stimulated adenosine triphosphatase (ATPase) activity of the 150-day-old myopathic skeletal muscle were lower than the control values. Although microsomal calcium-binding, calcium-uptake and ATPase activities of the 60-day-old myopathic muscle were not depressed significantly, the initial rate of calcium uptake was less than the control. 4. The sarcolemmal Ca2+-ATPase, but not Mg2+-ATPase or Na+ +K+-ATPase, activity was higher in 60-day-old myopathic muscle whereas the activities of all these enzymes from 150-day-old myopathic animals were higher than the control. On the other hand, the Na+ +K+-ATPase activities from 60- and 150-day-old myopathic animals were inhibited by ouabain to a lesser extent in comparison with the respective control values. 5. The myofibrillar Ca2+-ATPase and Mg2+-ATPase activities as well as inhibition of Mg2+-ATPase due to Na+ and K+ in myopathic muscle were no different from the control values. 6. The results reported here give further support to the view that different membrane systems of the dystrophic muscle are defective.