Biomedical subjects
Publications and source records attributed to U Wosiewitz.
Freshly precipitated unconjugated bilirubin (UCB) is solubilized rapidly and to a large extent by the sodium salts of di- and trihydroxy bile acids. The solubilization effect depending on bile salt concentration, pH and ionic strength is based on micellar mechanisms.
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Radiolucent (33 cases) and radiopaque (17 cases) black pigment gallstones from patients who underwent cholecystectomy were studied using several spectroscopic and chromatographic methods. Radiolucent pigment stones (mean Ca percentage 2.1%) are composed chiefly of degenerated tetrapyrrolic bile pigments (mean 85.3%) deriving from bilirubin and bilirubinates. Degeneration includes both polymerization and bacterial reduction and leads to products of different grade of polymerization. Final extraction residues (mean 55.5%), called the 'black pigments' are considered to be degenerated bile pigments of high molecular weight. The mean percentage of bilirubin (free and inorganic bound bilirubin) was 8.5%, while the percentage of lipids was very low (mean of total lipids approximately 2.7%). Radiopaque black pigment stones (Ca: 12.4%) were composed of 'black pigments', too, but contained large amounts of calcium phosphate (carbonate apatite) and/or calcium carbonate. 65% of the radiopaque stones were calcified by calcium phosphate. 'Black pigments' were degraded by chromate to maleimides and 2,5-pyrroledialdehyde. These degradation products can be prepared in the same way from normal bile pigments with a tetrapyrrole structure. Polymerized dipyrrolic bile pigments like polymer propentdyopent or 'mesobilifuscin' did not give 2,5-pyrroledialdehydes during chromate oxidation. Thus we conclude that the formation of 'black pigments' starts from the polymerization of tetrapyrrolic, but not from dipyrrolic units. Accumulation of unconjugated bilirubin and bilirubinates within the gallbladder will precede the development of 'black pigments' which play an important role in pigment gallstone formation.
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Pigment gallstones may be subdivided into three different types: radiolucent and radioopaque stones in the gallbladder and radiolucent stones in the common bile duct. 35 of our patients had radiolucent pigment stones in the gallbladder; 21 of these were followed for years by repeated X-ray examination. There is only little enlargement of these stones as time passes by, however the number of these stones increases continuously. Chemical analysis could be done on such stones in 24 cases. The stones were composed of granular calcium bilirubinate and of asphalt-like products derived from abnormal bilirubin degradation. 5 patients had pigment stones in the common bile duct. These stones contained little cholesterol and exhibited a spongy microstructure characterized by small tubules with a diameter of 1 micrometer. They contained more lipids and bilirubin than the stones collected from the gallbladder and on extraction with organic solvents no asphalt-like residues could be obtained.
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Ca-palmitate is an abundant secondary constituent of cholesterol gallstones, especially of "multiple facet" and "barrel" stones. 60% of the 146 stones obtained by operation or autopsy contained crystalline Ca-palmitate. From these 70% were multiple and 11% solitary stones. The average percentage of Ca-palmitate calculated from 30 quantitative analyses amount to 1,75% with regard to the dry weight of stones. The occurrence of Ca-palmitate in gallbladder stones mainly depends on concrements which undergo structural alterations (formation of fissures for example) during their stay in the gallbladder and which are impregnated by bile. Ca-palmitate crystallizes within the fissures of these stones after concentration of included bile. There is no important hint that Ca-palmitate plays a role in stone nucleation. The occurence of Ca-palmitate in bile may be favoured by decreased micellar solubilization of palmitinic acid and by increased concentration of Ca as a result of inflammation.
The enamel sealant Nuva Seal was tested in model tests on caries-free human molars and premolars. Under the scanning electron microscope the acid-etched enamel areas (natural and ground surfaces) and the corresponding Nuva Seal matrices were studied. In the evaluation, the surface reliefs of the objects were compared. Thus, information on flow capacity, wetting and polymerization behavior of the adhesive was obtained. Evaluation of pairs of stereo pictures of the inverse surface reliefs in the enamel/adhesive contact zone suggests that the sealant has an average measurable depth of penetration of 7 mum. Peg-shaped elevations 10-20 mum in size that can sometimes be observed in the Nuva Seal impressions are interpreted as representing enamel defects.
Electronmicroscopic examinations - analogous to those of the previous investigation [4] - suggest a relatively good interlocking of the adhesive with the conditioned dental enamel. In the demineralized microsections, clear differences are found among the strands of resin, in the light microscope. While they reach a length of 10 to 20 mum after UV light polymerisation, they become 100 to 200 mum long after exposure to laser light. First advantages resulting from these experiments are explained and critically discussed.
Eighty in vitro experiments were performed with single (n = 51) or multiple (n = 29) gallstones in order to find out which parameters are of prime importance for their disintegration by extracorporeal shock waves. A Dornier lithotripter and an upper limit of 1,500 discharges were employed. Although computed tomography density was significantly lower in cholesterol stones than in the noncholesterol stones (p less than 0.0001) and although the latter were significantly more often radiopaque (p less than 0.0001), we found no clear-cut correlation between the cholesterol content or computed tomography density and the degree of fragmentation of the stones. The most important variable which limited successful disintegration was the total stone volume. In stones with a mean total volume of 0.83 ml +/- 0.25 S.E. (diameter for single stones = 11.5 +/- 0.9 mm), none of the fragments exceeded 2 mm, whereas in stones with a mean volume of 3.6 ml +/- 0.64 (diameter = 17.2 +/- 1.5 mm) at least one fragment larger than 2 mm remained (p less than 0.002). Under the in vitro conditions, fragmentation was similar in multiple and solitary stones, provided the volume of the stones was comparable. These data show that, in general, the number and size of the stones, i.e. their total volume, and much less significantly their chemical composition are the major determinants of fragmentation by extracorporeal shock waves.