Human pancreatic lipase: a glycoprotein.

Human lipase has been purified from pancreatic juice. The protein has a molecular weight of 48 000 and an N-terminal residue of lysine. It has been characterized as a glycoprotein containing 4.7 mol of glucosamine, 2.8 mol of mannose, 2.9 mol of fucose, 3.0 mol. of galactose and 1.1 mol of glucose per mol of protein. Two isolipases have been separated by polyacrylamide gel electrophoresis. Their isoelectric points are 5.80 and 5.85, respectively and both are glycoproteins. Immunological cross reactions have been obtained between human lipase and other mammalian lipases (porcine, bovine, ovine, canine and rat).

beta-Muricholic acid; potentiometric and cholesterol-dissolving properties.

Some physicochemical properties of beta-muricholic acid (3 alpha,6 beta,7 beta-trihydroxy-5 beta-cholanic acid), a major bile acid biosynthesized by rat liver, were determined and compared to those of ursodeoxycholic and chenodeoxycholic acids. From potentiometric studies, the following characteristics of beta-muricholic acid were shown: a low monomer solubility (13 microM), a high equilibrium precipitation pH (7.92 for 30 mM solution), an apparent critical micellar concentration of 4 mM, and a very low micellar capacity of the bile salt to dissolve the protonated bile acid. Sodium beta-muricholate solution (30 mM) poorly solubilized cholesterol, as indicated by a bile salt/cholesterol molar ratio of 1430, whereas saturation ratios obtained with chenodeoxycholate and ursoseoxycholate were 24 and 384, respectively. Sodium beta-muricholate (30 mM)/phosphatidylcholine/cholesterol mixtures contained non-micellar aggregates from very low cholesterol concentrations. At physiological phosphatidylcholine concentrations, sodium beta-muricholate (100 mM) dissolved cholesterol crystals via essentially lamellar liquid-crystal formation. These solubilizing properties might have important physiological relevance to the dissolution of cholesterol gallstones in man.

Isolation and properties of prophospholipase A2 from human pancreatic juice.

Human prophospholipase A2 was purified from pancreatic juice. The protein has a molecular weight of 14500 and a free N-terminal residue identified as aspartic acid (or asparagine). The amino acid composition was determined. Partial immunological identity has been obtained between human and porcine prophospholipase A2. As other phospholipases, the human enzyme requires the presence of calcium for its activity. However, the activity of human phospholipase A2 on egg yolk emulsion is partially inhibited at 0.4 mM calcium concentration, which differs from the porcine homologous enzyme. Kinetics of activation of the two zymogens (human and porcine) by 4 different trypsins (bovine, porcine and human) indicate a difference between the two zymogens only when activated by human trypsins, which suggests a marked specificity of both human trypsins for human prophospholipase.

Zone electrophoresis study of the bile lipoprotein complex.

Sucrose gradient column electrophoresis was performed with human hepatic and gallbladder bile. It is shown that bile phosphatidylcholines exhibit a more rapid anodic mobility than do bile salts and serum albumin. This high mobility of bile phosphatidylcholines is not due to the negatively charged lipids which are present in bile, i.e. bile salts or free fatty acids. It is demonstrated that phosphatidylcholines are associated with anionic polypeptides. Electrophoresis of reassociations between these purified polypeptides and dilaurylphosphatidylcholine showed that these anionic polypeptides are primarily responsible for the high anodic mobility of the bile lipoprotein complex. This work describes a procedure for the purification of the bile lipoprotein complex which can be useful for the study of other kinds of lipid-polypeptide associations.

Glycodihydrofusidate: biliary excretion and its effect on biliary secretion of the rat.

Glycodihydrofusidate, which has the same detergent properties a bile salts, is excreted almost exclusively by the bile duct after intravenous injection in the rat. As with bile salts, it leads to a significant (P less tthan or equal to 0.05) increase in excretion of lecithins and cholesterol (0.15 mumol lecithin and 0.026 mumol cholesterol per 1 mumol of glycodihydrofusidate excreted). In addition, this drug simulataneously inhibits excretion of both endogenous bile salts and bile pigments.

Dissolving agents of human mixed cholesterol stones.

Methyl tert-butyl ether which is a powerful cholesterol monohydrate solvent does not completely dissolve mixed cholesterol gallstones when directly infused into the biliary tree. In this work, we compared the effect of various solvents containing different proportions of methyl tert-butyl ether and dimethylsulfoxide in anhydrous and aqueous systems on the in vitro solubilization of human cholesterol stones. The dissolution rates of cholesterol obtained in the presence of methyl tert-butyl ether was markedly decreased when 10 p. 100 water was added. In contrast, the addition of dimethylsulfoxide (30 p. 100) to methyl tert-butyl ether-water system enhanced the stone-solvent contact, improved the cholesterol dissolution rates and left less stone debris. A subsequent dissolution with an alkaline, pH = 8.8, aqueous dimethylsulfoxide-ethylenediaminetetraacetic acid solution strongly reduced the non cholesterol residues. In vivo, nearly complete dissolution of human cholesterol stones implanted in the gallbladder of rabbits was obtained within 8 hours when methyl tert-butyl ether/dimethylsulfoxide (70/30) solvent was infused at a rate of 0.6 ml/h/kg. With methyl tert-butyl ether, only 84 p. 100 of the original stone weight was dissolved. The infusion of these solvents leads to morphological changes in the gallbladder wall with some focal ulcerations. These alterations can be almost completely recovered after two weeks. No histologic evidence of hepatic, duodenal or renal damage was found. We conclude that the mixture methyl tert-butyl ether/dimethylsulfoxide (70/30) constitutes a good solvent for mixed cholesterol stones. Compared with pure methyl tert-butyl ether, the mixed system allows for a more rapid and a more complete dissolution of gallstones.

[Differential thermal analysis of the organic fraction of bone]. / Sur l'analyse thermique différentielle de la fraction organique de l'os.

Thermal decomposition analysis of Bovine femur bone has been carried out by means of a Micro Differential Thermal Analyser. The analysis of both thermograms and amino acid compositions has revealed the complexity of collagen degradation mechanisms.

Dissolution of human brown pigment biliary stones.

The chemical dissolution of human brown pigment stones was studied using various monophasic multicomponent solvents. Among the nine solutions tested for stone powder dissolution capacity, the two most active were retained for further analysis. The solvent containing 26 mM ethylenediaminetetraacetate, 40 mM sodium deoxycholate, 10 mM monoolein and 30% dimethylsulfoxide was efficient for calcium and bilirubin solubilization. The other solvent containing dimethylsulfoxide/methyl tert-butyl ether (70:30) had a high capacity for dissolution of cholesterol and bilirubin. From in vitro stone dissolution experiments, we found that alternating treatment every 2 h with these two mixtures was more effective than using these solvents separately. Within 24 h, 90% of cholesterol, 80% of bilirubin, and 70% of calcium were dissolved. In vivo, we studied the dissolution of human stones surgically implanted in the gallbladder of 6 rabbits. Alternating perfusions with the solvents selected led to complete disappearance of stones within 16 h in 5 out of 6 cases. The residual histological toxicity in the gallbladder wall, 15 days after perfusion, was low and blood parameters did not differ from the normal values.

Two human trypsinogens. Purification, molecular properties, and N-terminal sequences.

The two human trypsinogens have been isolated from human pancreatic juice in a sufficient amount to study molecular and structural properties. The purification procedure included filtration on Sephadex G-100 followed by ion-exchange chromatography on DEAE-cellulose. The two trypsinogens represent 19% of total proteins of pancreatic juice. Trypsinogen 1, the major form, is present in a quantity twice that of trypsinogen 2, which is the most anionic protein in human pancreatic juice. The two proteins have partial immunological identity, close molecular weights (23 438 and 25 006 for trypsinogens 1 and 2, respectively) and similar amino acid compositions. The N-terminal sequences are the same for the first 9 residues: Ala-Pro-Phe-Asp4-Lys-Ile. The two proteins differ in the activation peptides released during the transformation to trypsins. Trypsinogen 2 liberates one octapeptide Ala-Pro-Phe-Asp4-Lys while trypsinogen 1 liberates two peptides, the same octapeptide and the pentapeptide (Asp)4-Lys.