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Biomedical subjects

N Weber

Publications and source records attributed to N Weber.

At least 91 records · Page 5Linked to original sources
PubMed1985

Semi-synthetic preparation of 1-O-[1'-14C]hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) using plant cell cultures.

Incubation of photomixotrophic cell suspension cultures of rape (Brassica napus) and heterotrophic cell suspension cultures of soya (Glycine max) with 1-O-[1'-14C]hexadecyl-sn-glycerol or rac-1-O-[1'-14C]hexadecylglycerol leads in high yield (up to 78%) to labeled 1-O-hexadecyl-2-acyl-sn-glycero-3-phosphocholines. Alkaline hydrolysis of the choline glycerophospholipids yields pure 1-O-[1'-14C]hexadecyl-sn-glycero-3-phosphocholine. 1-O-[1'-14C]Hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) is obtained by acetylating the lyso compound. The semi-synthetic preparation described leads to labeled platelet activating factor in an overall yield of 50-60% without loss of specific activity.

Brassica↗
PubMed1985

Metabolism of orally administered rac-1-O-[1'-14C]dodecylglycerol and nutritional effects of dietary rac-1-O-dodecylglycerol in mice.

The metabolism of orally administered rac-1-O-[1'-14C]dodecylglycerol was investigated in mice. The substrate was rapidly absorbed in the intestine and then incorporated into ether glycerolipids of various organs and tissues in high proportions. In intestine and liver, however, large amounts of rac-1-O-[1'-14C]dodecylglycerol were catabolized by oxidative cleavage of the ether bond followed by degradation of the radioactive cleavage product, i.e., lauric acid, to water-soluble metabolites that were excreted in the urine at a fast rate. The feeding of a rac-1-O-dodecylglycerol-containing diet (1 g rac-1-O-dodecylglycerol/kg body weight X day) given over a period of 4 weeks did not significantly alter body weights or organ weights of mice. Analysis of total lipids revealed that high proportions of the substrate were incorporated into ether lipids of all organs and tissues during the feeding period, generally accompanied by a remarkable increase in saturated acyl moieties and a concomitant decrease of linoleoyl moieties of total lipids. Yet, 4 weeks after removal of the rac-1-O-dodecylglycerol-containing diet, the lipids of murine organs and tissues showed a close resemblance to those of the control group.

Animals↗
PubMed1984

Metabolism of orally administered alkyl beta-glycosides in the mouse.

The metabolism of octyl beta-D-[U-14C]glucoside, ]1-14C]dodecyl beta-D-maltoside and [1-14C]hexadecyl beta-D-glucoside was studied after oral administration to mice. The beta-glycosidic bond was rapidly hydrolyzed in intestine and liver. The cleavage products, sugars and long-chain alcohols, entered the pathways of lipid and carbohydrate metabolism. It appears that alkyl beta-glycosides are suitable as additives in food and feed.

Animals↗
PubMed1982

Formation of ether lipids and wax esters in mammalian cells. Specificity of enzymes with regard to carbon chains of substrates.

The incorporation of radioactivity from individual constituents of an equimolar mixture of saturated straight-chain alcohols (14:0, 16:0, 18:0, 20:0) and of nearly uniform mixtures of isomeric cis- or trans-octadecenols (delta 8-delta 16) into alkyl, alk-1-enyl and acyl moieties of diradylglycerophosphocholines and diradylglycerophosphoethanolamines and into alkyl and acyl moieties of wax esters was studied in rat brain as well as in L 1210 and S 180 ascites cells. The pattern of incorporation of radioactivity from the substrates into alkyl and alk-1-enyl moieties of ether phospholipids and into alkyl moieties of wax esters reveals the following: (1) The enzymes catalyzing the biosynthesis of alkylacylglycerols, the common intermediates of cholinephospholipids and ethanolaminephospholipids, have no substrate specificity with regard to position of the double bond of either cis- or trans-octadecenols or of intermediate ether lipids derived therefrom. (2) CDPcholine:diradylglycerol cholinephosphotransferases exhibit a strong preference for alkylacylglycerols with cis-8, cis-9 and cis-10-octadecenyl moieties, but no preference for the double bond position in the trans-octadecenylacylglycerols. (3) CDPethanolamine:diredylglycerol ethanolaminephosphotransferases have no substrate specificity with regard to position of the double bond in cis- or trans-octadecenyl moieties of alkylacylglycerols. (4) THe enzyme systems catalyzing the biosynthesis of alkylacylglycerophosphocholines and alkylacylglycerophosphoethanolamines exhibit substrate specificity with regard to chain-length of saturated alcohols and intermediate ether lipids derived therefrom. (5) Alkylacylglycerophosphoethanolamine desaturase and (6) wax ester synthase are highly specific for alkylacylglycerophosphoethanolamines and long-chain alcohols, respectively, with regard to chain-length of saturated alkyl moieties, but not with regard to position of double bonds of cis- or trans-octadecenyl moieties.

Animals↗
PubMed1981

Formation of ether lipids from isomeric cis-octadecen-1-ols in normal and neoplastic cells: substrate specificity of enzymes with regard to position of double bonds.

The pattern of incorporation of isomeric cis-[1-14C]octadecen-1-ols into alkyl moieties of glycerophospholipids of rat brain as well as of L 1210 and S 180 murine ascites cells revealed the following: 1) The enzymes involved in the biosynthesis of acylalkylglycerophospholamines have no substrate specificity with regard to position of the double bond of either cis-oectadecen-1-ols or of intermediate ether lipids derived therefrom. 2) CDPcholine: diradylglycerol cholinephosphotransferases exhibit a strong preference for acylalkylglycerols with cis-8, cis-9 and cis-10-octadecenyl moieties as substrates.

Animals↗
PubMed1980

Therapy of solid Walker carcinosarcoma 256 with bleomycin after synchronization with hydroxyurea.

Rats with the solid Walker carcinosarcoma 256 were synchronized with hydroxyurea (6 x 50 mg/kg or 1 x 300 mg/kg body weight) and treated with bleomycin (32 mg/kg body weight) at different time points thereafter. Bleomycin clearly affects Walker carcinosarcoma cells at the G1/S boundary or in S-phase. The improvement in the results of bleomycin therapy after pretreatment with hydroxyurea can mainly be accounted for by the synchronization of the tumour cells.

Animals↗
PubMed1980

Competing pathways in the formation of alkyl, alk-1-enyl and acyl moieties in the lipids of mammalian tissues.

The distribution of radioactivity from intravenously administered cis-9[1-14C]octadecenol into various tissues of the rat was studied as a function of time. The pattern of incorporation of radioactivity into alkyl, alk-1-enyl and acyl moieties of the lipids in heart, lungs, liver, intestine, kidney, brain and plasma revealed that oxidation of the long-chain alcohol and esterification of the resulting fatty acid to a wide variety of lipids are by far the most predominant reactions. Acylation of the long-chain alcohol is observed especially in liver, which appears to be the major site of biosynthesis of wax esters. Alkylation of the long-chain alcohol to alkoxylipids occurs in most tissues, most predominantly in the heart.

Acylation↗
PubMed1980

[Studies in vivo and in vitro on the influence of 5-fluorouracil and n'-(2'-furanidyl)-5-fluorouracil on the walker carcinosarcoma 256 in the rat (author's transl)].

We compare the effects of 5-fluorouracil and N'-(2'-furanidyl)-5-fluorouracil (Ftorafur) in vivo (tumor size) and in vitro ([6-3H]-deoxyuridine incorporation) on solid Walker carcinosarcoma of the rat. 5-Fluorouracil and Ftorafur have a dose-dependent effect on tumor size and on [6-3H]-deoxyuridine incorporation in vitro. The in vivo effects on tumor size are similar when the dose of Ftorafur calculated by its molecular weight is about 3 times higher than that of 5-fluorouracil. In vitro an about 650 times higher dose of Ftorafur is required to achieve a comparable reduction of [6-3H]-deoxyuridine incorporation in the tumor cells.

Animals↗
PubMed1979

[Influence of the thymus hormone on radioleucosis in mice].

A partially purified thymic extract has determined the development of leucosis in 10 thymectomized irradiated CC57Bl mice out of 25. The pure hormone isolated from the same extract prevented the development of leucosis in intact irradiated Mice. This seems to indicate the presence of a second active substance in the extract (enhancing the development of the leucosis).

Animals↗
PubMed1978

[Noninvasive assessment of left ventricular dynamics (author's transl)].

ECG triggered scintiphotography has established itself as a reliable, reproducible, noninvasive method for the determination of ventricular volumes, left ventricular ejection fraction, and regional ventricular wall motion. It can be used with sufficient precision and accuracy in severely ill patients who are not suitable for invasive diagnostic procedures. The method is useful for follow-up investigations of known heart disease. In comparison with left ventricular cineangiocardiography a correlation coefficient of r=0.78 could be found for enddiastolic voluumes, of r=0.92 for endystolic volumes, and of r=0.91 for ejection fraction. The sensitivity of the method for recognition of disturbances of regional ventricular wall motion is 94%, the specificity 86%. In comparison with left ventricular cineangiocardiography the resulting accuracy is 90%.

Adult↗
PubMed1977

Uptake and metabolism of fatty acids by soybean suspension cells.

Soybean suspension cultures very rapidly take up C16 and C18 fatty acids by a nonspecific, nonenzymic binding of exogeneously added fatty acids to cell walls and by a subsequent transfer into the cell where they are rapidly incorporated into triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines. 14C-Palmitic and 14C-stearic acids follow this sequence but are not desaturated, wherease 14C-oleic and 14C-linoleic acids are transferred more rapidly than the saturated fatty acids and are then further modified. All the data fit a sequence of events by which free oleic acid is first activated to a CoA thioester, and then desaturated to linoleyl-CoA; both thioesters are then transferred to triacylglycerols, phosphatidylcholine, and phosphatidylethanolamine.

Acetates↗
PubMedDate not supplied

Alveolar deposition of monodisperse aerosol particles in the lung of patients with chronic obstructive pulmonary disease.

Knowledge about the regional deposition of aerosol particles is essential in order to perform efficient inhalation therapy or to minimize health risks due to environmental or occupational aerosol particles. In this study, 2 techniques were used to measure thoracic deposition and to differentiate between bronchial and alveolar deposition. The first technique was the clearance-derived regional deposition (CRD) technique and the second the single-breath regional deposition (SBRD) technique. Deposition was measured in 12 patients with alpha1-antitrypsin deficiency and symptoms of moderate to severe chronic obstructive pulmonary disease (COPD) using monodisperse test particles with aerodynamic diameters of 2, 3, and 4 microm. In CRD, the kinetic of particle clearance within the first 24 hours after inhalation was used to determine bronchial and alveolar deposition. In SBRD, the longitudinal distribution of deposited inert test particles was used to calculate the particle fraction deposited within and distal to the dead space. Both techniques delivered very similar mean values for total and alveolar deposition. Due to controlled slow and deep inhalations, alveolar deposition was as much as 50%. Therefore, SBRD can be considered as an easy tool to study alveolar deposition in patients.

Aerosols↗