Stapler-facilitated rectal eversion.

Sphincter-preserving procedures have come to play an increasingly important role in colon and rectal surgery. In certain situations, rectal eversion can be an invaluable aid in performing a sphincter-saving operation. We present a new method to evert the rectum using the curved circular stapler.

Relative bioavailability of RRR- and all-rac-alpha-tocopheryl acetate in humans: studies using deuterated compounds.

Vitamin E in nutritional supplements in its most common form is alpha-tocopheryl acetate. Available stereoisomeric forms are RRR- (1 stereoisomer) and all-rac- (8 stereoisomers). We evaluated the relative bioavailability of RRR- and all-rac-alpha-tocopheryl acetate using the deuterium-labeled isotopes [5-CD3] 2R, 4'R and 8'R-alpha-tocopheryl acetate (d3), and [5,7-(CD3)2]-all-rac-alpha-tocopheryl acetate (d6). Six adults (three males, three females), aged 25-59 y, received 150 mg each of d3 and d6 for 11 consecutive days. Blood samples were collected on days -1, 0, 1-11, 13, 14, 20, 25, 30, 60, 74, 88, 102, 122, and 137. Plasma and red blood cell tocopherol were evaluated by using HPLC and gas chromatography/mass spectrometry to distinguish between d3 and d6 tocopherols. Cholesterol, triglycerides, and LDL and HDL cholesterol were measured. Relative bioavailability of d3 when compared with d6 was 2.0 +/- 0.06 when area under the plasma time concentration curve (AUC d3/d6) by trapezoidal rule (P < 0.05) was used. Correcting for lipid yielded the same finding. Unlabeled tocopherol (d0) decreased (P < 0.05) with vitamin E administration. It was concluded that the ratio of bioavailability of RRR-/all-rac-alpha-tocopheryl acetate is significantly greater than the currently accepted ratio of 1.36.

Transient and steady-state kinetic studies of sodium-potassium adenosine triphosphatase using beta-(2-furyl)acryloyl phosphate as chromophoric substrate assay.

A convenient and highly specific continuous spectrophotometric assay for sodium-potassium adenosine triphosphate activity utilizing the rapidly hydrolyzed and high-affinity chromophoric substrate beta-(2-furyl)acryloyl phosphate (FAP) is described. The Na/K-ATPase-catalyzed hydrolysis of FAP is faster than that for ATP under all ionic conditions. The rate is neither inhibited nor activated by Na+; it is dependent on [K+] and on [Mg2+]. The hydrolysis of FAP to furylacrylate is accompanied by a large shift in the UV absorbance maximum. The spectrum of FAP, but not furylacrylate, is sensitive to noncovalent ligation with Mg2+, a happenstance which permits the identification of Mg2+FAP, and consequently allows for a probe of the role of Mg2+ in the catalysis. Mg2+ binding to the active site is essential for catalysis. MgFAP is more tightly bound to the site than is FAP2-, but the complex is not obligatory for catalysis. The formation of a phosphoryl-enzyme intermediate is not evident in the reaction of FAP with the enzyme. Transient kinetic experiments, utilizing an excess of MgFAP, demonstrate a unique steady-state rate-limiting production of furylacrylate. These results indicate that the pathway demonstrated with ATP is not appropriate to the FAPase mechanism. The results suggest that acyl phosphates are good "phosphatase" substrates either because they are analogues of the phosphatase-specific phosphoryl-enzyme or because they react exclusively with the isomerized "E2" form of the enzyme.