Synthesis, chromatographic purification, and analysis of isomers of biliverdin IX and bilirubin IX.

Neutral solvent systems were developed to isolate the alpha, beta, gamma, and delta isomers of biliverdin IX dimethyl ester by TLC. The individual free acids of biliverdin IX were obtained by saponification of the corresponding dimethyl esters. The bilirubin IX isomers were prepared by reducing the corresponding biliverdin IX isomers with NaBH3CN.

Effects of stem design and material properties on stresses in hip endoprostheses.

With the aid of a three-dimensional finite element stress analysis a parameteric study of the essential aspects of the femoral component of hip endoprostheses was carried out. Various designs were investigated; these included the prosthetic stem length, the existence or non-existence of the prosthetic collar and the elastic modulus of stem and cement. Variations in the stem length have only minor effects on the stress distribution for a stem length greater than 100 mm, but the elastic modulus of the prosthetic stem has a considerable influence on the stresses.

[Stresses on the femur following hip joint replacement].

The stresses in femur after joint replacement have been calculated with the finite element method and the results were checked by using strain gauges glued on the surface of the femur and on the prosthetic stem. The influence of stem length and prosthetic collar on the distribution of the stresses have been investigated. The stem length has only a minor effect on the stress distribution if the stem has a texture which allows transfer of tension and shear at the interface endoprosthesis--bone cement.

Uridine diphosphate-glucuronic acid-independent conversion of bilirubin monoglucuronides to diglucuronide in presence of plasma membranes from rat liver is nonenzymic.

TWO ROUTES HAVE BEEN PROPOSED FOR CONVERSION OF BILIRUBIN MONOGLUCURONIDE TO THE DIGLUCURONIDE: glucuronyl transfer (a) from UDP-glucuronic acid to bilirubin monoglucuronide, catalyzed by a microsomal UDP-glucuronyltransferase, and (b) from one molecule of bilirubin monoglucuronide to another (transglucuronidation), catalyzed by an enzyme present in liver plasma membranes. The evidence regarding the role of the latter enzyme for in vivo formation of bilirubin diglucuronide is conflicting. We therefore decided to reexamine the transglucuronidation reaction in plasma membranes and to study the conversion of bilirubin monoglucuronide to diglucuronide in vivo.

Rearranged glucuronic acid conjugates of bilirubin-IX alpha in post-obstructive bile. Structure elucidation of azopigments beta and gamma as ethyl anthranilate N-glycosides derived from 2-, 3- and 4-o-acyl glucuronides.

Azopigment analysis was performed on conjugates of bilirubin-IXalpha in bile of man and rats obtained after obstruction of the bile duct or in bile incubated under N2. The azopigments beta and gamma, formed by applying a pH 2.7 diazonium reagent containing an excess of ethyl anthranilate, correspond to rearranged ethyl athranilate N-glucuronides having the azodipyrrole acyl group on positions 2, 3 and 4 of the sugar.

Glucuronic acid conjugates of bilirubin-IXalpha in normal bile compared with post-obstructive bile. Transformation of the 1-O-acylglucuronide into 2-, 3-, and 4-O-acylglucuronides.

Structures have been determined for bilirubin-IXalpha conjugates in freshly collected bile of normal rats, dogs and man and in post-obstructive bile of man and rats. The originally secreted conjugate has been characterized as azopigment (I), i.e.

[Radioimmunoassay for secretin].

A simple direct radioimmunoassay for human secretin has been developed by immunizing rabbits with synthetic human secretin. After 1-2 injections antisera with titers up to 1:52000 could be induced. In a dysequilibrium system secretin levels in plasma can be measured down to a concentration of 25 pg/ml plasma.

Separation by thin-layer chromatography and structure elucidation of bilirubin conjugates isolated from dog bile.

1. A system for separation of bile pigments by t.l.

Mass-spectrometric structure elucidation of dog bile azopigments as the acyl glycosides of glucopyranose and xylopyranose.

1. The structures of the alpha(2)- and alpha(3)-azopigments, prepared by diazotization of dog bile with ethyl anthranilate, were shown by mass spectrometry and g.l.

Excretion in dog bile of glucose and xylose conjugates of bilirubin.

1. T.l.

Heterogeneity of bile pigment conjugates as revealed by chromatography of their ethyl anthranilate azopigments.

1. Azopigments derived from conjugated bile pigments by coupling with the diazonium salt of ethyl anthranilate are analysed conveniently by quantitative t.l.