Yochanan Peled

Isolation and properties of a lipoprotein from the haemolymph of the locust, Locusta migratoria

Abstract A yellow lipoprotein was isolated from the haemolymph of the migratory locust by ethanol precipitation and sucrose gradient centrifugation. The lipoprotein contained 30% lipids, 80% of which were diglycerides and phospholipids. The yellow colour was due to the presence of carotenoids. A mol w of 340,000 ± 50,000 was calculated from sedimentation equilibrium measurements. By electrophoresis in sodium dodecyl sulphate-gels the lipoproteins separated into several polypeptides. The capacity of the purified lipoprotein to promote diglyceride release was lower than that of the haemolymph. Full activity was restored by the addition of a protein from the haemolymph, which by itself showed little activity.

Utilization of 2-acyl-sn-glycerol by locust fat body microsomes: Specificity of the acyltransferase system

Abstract Locust fat-body monoacylglycerol acyltransferase specifically acylates 2-acyl- sn -glycerol; 1-acyl and 2-alkyl- sn -glycerol are poor substrates. The system was activated by Tween 20. Maximal activity was obtained at pH 7.0. Release of free CoA could not be shown.

Halitosis and helicobacter pylori . A Possible Link

The exact pathophysiological mechanism of halitosis is not clear, and in many patients the etiology is an enigma. We followed three couples in which one member or both had halitosis. All the subjects had evidence of Helicobacter pylori infection. All received a treatment course of colloidal bismuth subcitrate four times a day and 250 mg metronidazole three times a day. There was impressive improvement in their symptoms, the halitosis disappearing along with eradication of the organism. We call the attention of physicians to the possible connection between halitosis, H. pylori infection, and familial occurrence. Further studies to confirm this surprising association are in order.

Fat transport in the locust, Locusta migratoria: The role of protein synthesis

Abstract 1. 1. When prelabeled fat body was incubated in the presence of hemolymph, diglycerides were released and incorporated into lipoproteins of the hemolymph. 2. 2. When fat body was incubated with 14 C-labeled amino acids, the acids were incorporated into tissue proteins which were subsequently released into the medium. Protein release was not dependent on the presence of hemolymph. 3. 3. Gel electrophoresis of the released protein showed that the distribution of radioactivity along the gel coincided with the protein bands of the hemolymph. 4. 4. Addition of cycloheximide inhibited the incorporation of amino acids into proteins; the release of preformed proteins was not affected. 5. 5. Cycloheximide did not inhibit the incorporation of 14 C-labeled palmitate into glycerides, neither was the release of glycerides from the “inhibited” tissue affected.

One week triple therapy with omeprazole, clarithromycin and tinidazole for Helicobacter pylori: differing efficacy in previously treated and untreated patients

Background: Triple therapy with omeprazole, clarithromycin, and tinidazole (OCT) has been found to be highly effective against Helicobacter pylori infection. However, its efficacy as a second line regimen for patients who failed metronidazole‐based triple therapy has not been evaluated.

Biliary micellar cholesterol nucleates via the vesicular pathway

Biliary cholesterol nucleates primarily from phospholipid vesicles. In this study, we investigated the mode of nucleation of micellar cholesterol. Ten biles (four human and six model) were examined. The vesicular and micellar fractions of each bile were separated by gel chromatography. The whole biles and their isolated carriers were incubated at 37 degrees C until nucleation time. In whole human biles, the proportion of total cholesterol in vesicles rose throughout the incubation (from zero time to nucleation time) from 15.5 +/- 8.6% to 28.0 +/- 12.5%, and in model biles from 46.8 +/- 22.4% to 75.5 +/- 8.2%. The vesicular isolated fraction remained unchanged throughout incubation. In isolated micelles devoid of vesicles at zero time, new vesicles formed during incubation, carrying increasing proportions of cholesterol. At nucleation time, these vesicles contained 11.0% of originally micellar cholesterol in human biles, and 41.2% in model biles. The new vesicles formed in whole bile and in the micellar fraction were chromatographically and chemically similar to the vesicles originally present in bile. These data suggest that micellar cholesterol nucleates via the neoformation of phospholipid vesicles, which seem to be the final common pathway for cholesterol nucleation in bile.

The distribution of the biliary-anionic polypeptide fraction between cholesterol carriers in bile and its effect on nucleation

The small (7 kD) biliary phospholipid and calcium binding polypeptide (anionic polypeptide fraction/calcium binding protein) has been found in higher concentrations in the bile of patients with pigment stones than in controls. In different model systems it was variously found to promote or retard cholesteral crystalization. In the present study we investigated its distribution between cholesterol carriers in bile and its effect on cholesterol crystalization in native and model biles. On gel chromatography anionic polypeptide fraction/calcium binding protein was found predominantly in three areas: in the vesicular fraction, in the non-vesicular lipid fraction and in another fraction unassociated with biliary lipids. It was much more concentrated in the vesicular than in the non-vesicular fraction, the mean anionic polypeptide fraction/phospholipid molar ratio being 219 +/- 181 vs. 30.4 +/- 16, respectively. Anionic polypeptide fraction/calcium binding protein was added at three dose levels, 0.14, 0.28, 0.42 mg/ml (representing approximately 18%-55% of the physiologic biliary concentration), to 19 human and five model biles. This did not produce any significant changes in the nucleation time. The addition of anionic polypeptide fraction/calcium binding protein at a dose level of 0.42 mg/ml to 13 different human biles did not induce changes in the distribution of cholesterol among its carriers. The present experiments do not support a role for anionic polypeptide fraction/calcium binding protein in the process of cholesterol nucleation in bile. Qualitative changes in the protein molecule, as demonstrated in other human secretions, cannot be excluded.

Acylation of monoglycerides by locust-fat-body microsomes

The synthesis of triglycerides is known to occur by two pathways. The first pathway employs glycerol-3phosphate as acyl acceptor and triglyceride synthesis occurs via the intermediate formation of phosphatidic acid and diglycerides [ 11. The second pathway, known as the monoglyceride pathway, synthesizes triglycerides by the acylation of monoglycerides through a diglyceride intermediate [2,3] . The enzymes of the first pathway are present in a wide variety of tissues and as suggested by Kennedy (1) this is the major route for the biosynthesis of diand triglycerides in all tissues except the mucosa of the small intestine which contains high levels of monoglyceride acyltransferase (EC 2:3: 1 type) [2,3]. In a previous communication [4] we described the presence of the enzymes of the glycerol-3-phosphate pathway in the fat-body of the locust, Locusta migratona In the present communication the occurrence of monoglyceride acyltransferase in the microsomes of the fat body will be demonstrated. The possible role of the monoglyceride pathway in fat mobilization will be discussed.

Phospholipid peroxidation as a factor in gallstone pathogenesis

Phospholipid peroxidation markedly reduces the stability of mixed micellar systems composed of cholate, phosphatidylcholine and supersaturating levels of cholesterol. This suggests that lipid peroxidation is likely to play a significant role in the precipitation of cholesterol from gallbladder bile, thus in the pathogenesis of cholesterol gallstones. This conclusion is supported by studies of the nucleation time of cholesterol in gallbladder biles, which was significantly reduced by exposure to a stream of oxygen. This effect of phospholipid peroxidation on cholesterol solubility may occur in other biological fluids as well. In view of the increased lipid peroxidation in the elderly, it may explain the effect of age on the frequency of various diseases related to cholesterol precipitation.

THE EFFECTS OF DIETARY PHOSPHOLIPIDS ENRICHED WITH PHOSPHATIDYLETHANOLAMINE ON BILE AND RED CELL MEMBRANE LIPIDS IN HUMANS

The role of phospholipids in biliary cholesterol solubilization and crystallization has only recently begun to be appreciated. Phospholipid vesicles are believed to be the metastable carrier from which cholesterol nucleates. Cholesterol crystallization is influenced by the phospholipid species in bile. Feeding rats and hamsters with diets enriched in phospholipids or their precursors, especially ethanolamine, resulted in reduced cholesterol saturation of bile. Although whole phospholipids are normal dietary constituents, the effects and safety of phospholipid components have not been tested in humans. In the present study, we have evaluated the effects of a dietary phospholipid mixture, enriched with phosphatidylethanolamine, on human bile and red blood cell membrane lipid composition. Five ambulatory volunteers having a chronic indwelling T-tube, with an intact enterohepatic circulation, were investigated. Thirty-six grams of phospholipids (54% phosphatidylethanolamine, 54% linoleyl acyl chains) were added to their daily diet for fourteen days. Biliary nucleation time, cholesterol carriers, as well as plasma, red blood cell membrane, and bile lipid compositions, were monitored. Following phospholipid supplementation, the proportion of linoleyl chains (18:2) in biliary phospholipids increased significantly from 31.1±1.2 to 37.7±5.3%, while that of oleyl chains (18:1) decreased from 11.4±1.6 to 9.6±1.1%. These changes were accompanied by an increase of linoleate and its metabolite, arachidonate, in red cell membranes. Phospholipid feeding did not cause any side effects, and no significant changes in biliary nucleation time, cholesterol, phospholipid, or bile salt concentrations, or in the distribution of cholesterol within micelles or vesicles. We conclude that phospholipid feeding is safe, and can be effective as a vehicle for lecithin fatty acyl chain modulation of bile and lipid membranes. These findings may provide a basis for a controlled modulation of biliary phospholipids to increase cholesterol solubility in bile.