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PubMedDate not supplied

The role of lingual lipase in neonatal fat digestion.

Lingual serous glands (von Ebner) contain a potent lipase that hydrolyses triglycerides to a mixture of partial glycerides (di- and monoglycerides), glycerol and free fatty acids. Studies in man and in rat have shown that similar lipolytic activity is present in oesophageal and gastric aspirates and suggest that the intragastric digestion of dietary fat is initiated by lingual lipase. In the rat the lingual serous glands are initiated in 19- to 20-day fetuses; lipase activity is first detected in 20-day-old fetuses and increases 14-fold by birth. The data suggest that in the fetus lipase activity originates predominantly in the serous demilune cells of mucous glands whereas after birth the enzyme is synthesized and stored in the rapidly differentiating serous glands. In man lipolytic activity is present in gastric aspirates as early as 26 weeks of gestational age. Our studies suggest that the lipolytic activity has characteristics similar to those of adult human and rat lingual lipase; the enzyme is present in the oesophageal pouch of infants with oesophageal atresia indicating that in infants, as in adults, it probably originates in the lingual serous glands. Since the enzyme is active in the absence of bile salts and has a low pH optimum it is ideally suited to act in the stomach and probably compensates in the premature for low pancreatic lipase activity. The lipolytic activity could be important, not only in the digestion of dietary fat, but in helping to overcome the temporary bile salt deficiency and to solubilize dietary fat through the formation of amphiphilic reaction products.

Animals↗
PubMed1976

Scanning electron microscopic study of chylomicrons incubated with lipoprotein lipase.

The effects of lipolysis on the structure of chylomicrons were studied with the scanning electron microscope using rat chylomicrons incubated with purified bovine milk lipoprotein lipase for 20 minutes at pH 8.1. Since the amount of albumin added to the medium was limited, some of the free fatty acids and partial glycerides formed by lipolysis accumulated in the chylomicrons. Lipolyzed chylomicrons fixed with OSO4 at pH 7.4 appeared in scanning electron micrographs as spheres with multiply idented irregular surfaces, while those fixed at pH 5.5, AS WELL AS CONTROL CHYLOMICRONS FIXED AT BOTH PHs, appeared as spheres with smooth surfaces. Sections of OSO4-fixed specimens, viewed with the transmission electron microscope, showed that the core of lipolyzed chylomicrons fixed at pH 7.4 contained numerous circular electron-lucent areas at the periphery, thus accounting for the indented surfaces observed above, while the core surfaces of the other specimens were circular and smooth. These findings confirm an earlier report that aqueous spaces form in chylomicrons during lipolysis when albumin in the medium is limited, and that the aqueous spaces disappear when specimens are prepared at pH 5.5 for microscopy. Thin sections of specimens that had been prepared for scanning electron microscopy showed that the gold-palladium coating was desposited directly on the indented surface of the lipid core of lipolyzed chylomicrons fixed at pH 7.4. It is concluded that vacuum dehydration during specimen preparation ruptures the outer wall of the aqueous spaces in lipolyzed chylomicrons and thereby exposes the interior of the spaces to gold-palladium coating and viewing with the scanning electron microscope.

Animals↗
PubMed1990

[Preparation of theophylline-sodium salicylate suppositories and determination of factors influencing the in vitro dissolution of the active agents].

Suppositories of theophylline-sodium salicylate were prepared with 10 different vehicles and also with tensids and softeners. With the dynamic diffusion method the drug dissolution and the in vitro diffusion were measured. It was established that proper choice of the vehicle is very important. The highest relative in vitro availability was measured in the case of glyceride base with low hydroxyl value. The diffusion of the active agent can be described by an exponential function.

Chemical Phenomena↗
PubMed1986

Identification and quantification of octanoyl glucuronide in the urine of children who ingested medium-chain triglycerides.

In addition to the previously described metabolites, octanoyl glucuronide was identified in the urine of four children who received medium-chain triglycerides. Octanoyl glucuronide in the urine of a child after ingestion of medium-chain triglycerides (C8:C10, 3:1) was quantitated as octanoic acid after glucuronidase treatment by means of gas chromatography/mass spectrometry. The urinary excretion increased rapidly to a maximum 1-2 h after ingestion, and decreased thereafter. During 0-3 h, 6.11 mumol of octanoyl glucuronide was excreted, which comprised 0.034% octanoic acid administered as glyceride, and 0.07% octanoic acid was postulated to be excreted as glucuronide within 24 h. Neither decanoyl glucuronide nor hexanoyl glucuronide was detected. Glucuronidation of branched medium-chain fatty acids, whose beta-oxidation is hindered, has been described previously. The present findings show that even straight-chain fatty acids undergo glucuronidation, although to a lesser extent, in addition to omega-oxidation and beta-oxidation.

Caprylates↗
PubMed1977

Study on the chemical nature of sterols contained in Bulgarian sunflower oil.

The free sterols, the sterol esters and the sterol glycosides of the crude sunflower oil as well as those of the technical lecithin, the pitch and the deodorizer distillate of the latter oil were isolated by preparative TLC. The nature of sterols contained in the isolated sterol derivatives was elucidated by GLC and combinded GLC-MS. Major sterols of all examined sterol fractions are sitosterol, campesterol and stigmasterol, the amount of sitosterol being prevalent. Unknown sterol with a molecular weight of 428 is present in sterols of the crude oil and the deodorizer distillate. Sterols of the deodorizer distillate contain an unknown sterol with a molecular weight of 430. Stigmasterol is present in the sterol fraction of the deodorizer distillate in high amounts. It was established that delta7-sterols of the crude oil occur only in esterified form. The hydrolysis of the sterol derivatives in acid medium leads to dehydration products known as steroid dienes and disteroid ethers. Hydrolysis without dehydration was achieved by enzyme preparations. Some sterols of the crude oil were esterified with the same higher fatty acids contained in the glycerides of the sunflower oil.

Chromatography, Gas↗
PubMed1977

Sterol composition of Bulgarian soya and corn oils.

The free sterols, the sterol esters and the sterol glycosides of the raw soya and corn oils as well as those of the technical lecithin and the deodorizer distillated of the latter oils were isolated by preparative TLC. The composition of each of the isolated sterol derivatives was determined by GLC and MS. Sitosterol, campesterol, stigmasterol and an unknown sterol with a molecular weight of 428 are contained in almost all of the examined fractions of the soya oil and its refinement byproducts. Dehydrocampesterol is present in the free sterols of the raw soya oil and the soya lecithin. Stigmasterol is contained in the soya deodorizer distillate in high amounts. It was established that cholesterol was present in the sterol esters of the raw soya oil high amounts. Delta7-stigmastenol occurs only in the sterol esters of the latter oil. Sitosterol, campesterol and stimgasterol are the main components of all sterol fractions of the corn oil and its refinement products. Dehydrocampesterol and unknown sterols with molecular weights of 428 are present in the free sterols of the raw corn oil. Some sterol glycosides of the soya and corn lecithin are esterified with the same major fatty acid components of the glycerides, palmitic acid being the main one. The fatty acid compositon of sterol esters of the raw soya and corn oil roughly corresponds to the fatty acid composition of oils.

Chromatography, Gas↗
PubMed1991

Increased ether lipid cytotoxicity by reducing membrane cholesterol content.

Ether-linked glycerophospholipids (ether lipids, EL) are selectively toxic and anti-proliferative agents against cancer cells in vitro. The reason for such selectivity is not completely clear. Their mechanism of action is mediated through an interaction with the plasma membrane and the membrane lipid composition may modulate it. As a continuation of previous reports, we now present data showing that cholesterol concentration modulates EL toxicity in the K562, U937 and MOLT4 leukemic cell lines in vitro. Cells become sensitive to otherwise ineffective doses of EL when their cholesterol content is lowered. Cell cholesterol levels were reduced by exposure to an egg lipid mixture (neutral glycerides, phosphatidylcholine and phosphatidylethanolamine, AL721). The data contribute to an understanding of the EL mechanism of action on membranes and suggest that the cellular cholesterol concentration must be considered a major factor in modulating the cytotoxic effects of EL.

Cholesterol↗
PubMed1983

Prolipoprotein signal peptidase of Escherichia coli requires a cysteine residue at the cleavage site.

A signal peptidase specifically required for the secretion of the lipoprotein of the Escherichia coli outer membrane cleaves off the signal peptide at the bond between a glycine and a cysteine residue. This cysteine residue was altered to a glycine residue by guided site-specific mutagenesis using a synthetic oligonucleotide and a plasmid carrying an inducible lipoprotein gene. The induction of mutant lipoprotein production was lethal to the cells. A large amount of the prolipoprotein was accumulated in the outer membrane fraction. No protein of the size of the mature lipoprotein was detected. These results indicate that the prolipoprotein signal peptidase requires a glyceride modified cysteine residue at the cleavage site.

Bacterial Outer Membrane Proteins↗
PubMed1988

Evidence for high affinity binding-protein dependent transport systems in gram-positive bacteria and in Mycoplasma.

Gram-negative bacteria are surrounded by two membranes. In these bacteria, a class of high affinity transport systems for concentrating substrates from the medium into the cell, involves a binding protein located between the outer and inner membranes, in the periplasmic region. These 'periplasmic binding-proteins' are thought to bind the substrate in the vicinity of the inner membrane, and to transfer it to a complex of inner membrane proteins for concentration into the cytoplasm. We report evidence leading us to propose that a Gram-positive bacterium, Streptococcus pneumoniae, and a mycoplasma, Mycoplasma hyorhinis, which are surrounded by a single membrane and have therefore no periplasmic region, possess an equivalent to the high affinity periplasmic binding-protein dependent transport systems, i.e. extra-cytoplasmic binding lipoprotein dependent transport systems. The 'binding lipoproteins' would be maintained at proximity of the inner membrane by insertion of their N-terminal glyceride-cysteine into this membrane.

Amino Acid Sequence↗
PubMedDate not supplied

Effect of corticosterone on rat epididymal lipids.

Corticosterone-induced changes in serum hormone profiles and the lipid composition of the caput and cauda epididymidis were studied. The analysis was conducted in both unwashed and washed (free from fluids and spermatozoa) epididymal tissues. Corticosterone treatment significantly depressed serum prolactin and testosterone but gonadotropins were unaltered. In the unwashed caput region, lipid analysis showed a significant decrease in total lipids, as well as in cholesterol, phospholipid, and the phosphatidyl inositol, phosphatidyl choline, and phosphatidyl ethanolamine fractions. However, in the unwashed cauda region, the total lipid and cholesterol content was not altered while total phospholipid and phospholipid fractions were significantly decreased. On the other hand, in the washed caput and cauda regions, corticosterone induced a significant increase in total lipid, glyceride, and the mono, di, and triglyceride fractions, leaving total phospholipid and its fractions unaltered. Following 20-day withdrawal of corticosterone treatment, all lipid classes returned to normal along with serum hormone profiles. Our findings imply that an excess of corticosterone influences epididymal lipids. These changes in the epididymal lipid pattern probably are reflected in fertility disorders in patients with glucocorticoid excess.

Animals↗
PubMed2003

Structure of the tarsi in some Stenus species (Coleoptera, Staphylinidae): external morphology, ultrastructure, and tarsal secretion.

SEM studies show that the differentiation among Stenus species with respect to the formation of the tarsi (wide bilobed vs. slender tarsomeres) takes place with a considerable augmentation of tarsal ventral setae in wide bilobed tarsomeres. The structural diversity of ventral tarsal setae among and within species is discussed with respect to 1) their different roles as mechanosensilla and tenent setae, respectively, and 2) the different selection pressures in terms of adhesive requirements along the longitudinal tarsus axis. The tarsi are provided with four groups of tarsal mechanosensilla, comprising hair and bristle sensilla, campaniform sensilla, and scolopidia. The tarsus wall is supported by an epidermis, which forms three different types of glands pouring their secretion via different exit paths onto the outer cuticle. The organization and ultrastructure of each of these glands is described. Only one (unicellular) gland is directly associated with the ventral tenent setae and is thus considered to form the main part of the adhesive secretion. The beetles appear to release the tarsal secretion through mediation of the tenent setae, which contains a lipid and a proteinaceous fraction. I propose that the secretion is discharged to the outside via a system of very fine pore canals in the wall of the setal shaft. Gas chromatography and infrared spectroscopy revealed that the lipid fraction of the secretion is a mixture of unsaturated fatty acid glycerides and aliphatic hydrocarbons whose spectra are similar to those of extractions of the superficial lipid coating of the body surface.

Animals↗
PubMed1990

Influence of the hydrophilicity of suppository bases on rectal absorption of carprofen, a lipophilic nonsteroidal anti-inflammatory drug.

The influence of the hydrophilicity of fatty suppository bases on the rectal absorption of the lipophilic drug carprofen (octanol-buffer, pH 7.4; partition coefficient, 40) was investigated in dogs. Five animals received each of six carprofen formulations in a random sequence: intravenous, oral, and rectal solutions, and three suppository formulations. The suppository vehicles tested were semisynthetic glycerides containing saturated fatty acids mainly in the range of C10 to C18 [Massa Estarinum A (MEA), Massa Estarinum B (MEB), and Massa Estarinum 299 (ME299)]; their hydroxyl values increased from 1 for ME299, through 24 for MEB, to 45 for MEA. Following every drug administration, blood samples were collected over a period of 104 h and carprofen plasma concentrations were measured by a specific HPLC method with UV detection. The rate and extent of carprofen absorption were characterized by evaluation of the maximum plasma concentrations (Cmax), the time of their occurrence (tmax), absolute bioavailabilities, statistical moments, and by deconvolution. Carprofen was rapidly and completely absorbed from the oral solution. The maximum concentrations obtained with oral solutions were significantly higher than those observed with rectal solutions and with the three suppository formulations. Results obtained with the rectal solution exhibited a high degree of intersubject variability. After rectal administration of suppositories, the rate and extent of carprofen absorption increased with the hydroxyl value of the suppository base; the mean absorption times (MAT) and tmax were shorter with MEA (2.15 and 1.7 h, respectively) than with the less hydrophilic vehicles (MEB: 4.09 and 2.1 h, respectively; ME299: 4.22 and 2.4 h, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Proton NMR spectroscopy in myocardial ischemic insult.

Proton NMR methods can monitor mobile lipids (e.g., fatty acids and glycerides) in intact tissue. Lipids play a major role in cardiac energy production, and elevated levels of myocardial lipids have been reported following an ischemic insult. The present study examines the potential of high-resolution 1H NMR spectroscopy to monitor lipid alterations 24 h following coronary occlusion in dogs, and to correlate these finds with regional myocardial blood flow (RMBF) measured by radiolabeled microspheres. The dogs were killed, and samples of excised myocardium were studied by high-resolution 1H NMR spectroscopic analysis using solvent suppression in combination with the Hahn spin-echo pulse sequence. Mobile lipids levels in myocardium with moderate blood flow reduction (28.6 +/- 7, integral values, arbitrary units; flow 5-50% of control) were significantly elevated compared to the mobile lipid levels in control myocardium (5.3 +/- 8, P less than 0.001) and in myocardium with severe flow reduction (7.2 +/- 10, P less than 0.001; flow less than 5% of control). The mobile lipids in myocardium with severe flow reduction were not elevated significantly relative to control tissue. As anticipated, depression in the level of creatine paralleled the microsphere determined degree of ischemia, i.e., compared to control (9.0 +/- 3); creatine levels were moderately decreased with flows 5-50% of control (5.5 +/- 4, P less than 0.001) and markedly decreased with flows less than 5% of control (1.0 +/- 2, P less than 0.001). This study suggests that high-resolution 1H NMR spectroscopy may be used to evaluate alterations in myocardial lipid levels following an ischemic insult.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Direct identification and quantitative determination of costunolide and dehydrocostuslactone in the fixed oil of Laurus novocanariensis by 13C-NMR spectroscopy.

The fixed oil of Laurus novocanariensis (previously L. azorica) contains mostly glycerides together with minor non-saponifiable compounds. The direct identification and quantitative determination of costunolide and dehydrocostuslactone, two sesquiterpene lactones components of the oil that exhibit biological activities, is described. The analysis was carried out using 13C-NMR spectroscopy (signal acquisition with inverse gated decoupling of protons; diglyme as internal standard) without separation, derivatisation or any sample preparation.

Lactones↗
PubMed1994

Computer modeling of substrate binding to lipases from Rhizomucor miehei, Humicola lanuginosa, and Candida rugosa.

The substrate-binding sites of the triacyl glyceride lipases from Rhizomucor miehei, Humicola lanuginosa, and Candida rugosa were studied by means of computer modeling methods. The space around the active site was mapped by different probes. These calculations suggested 2 separate regions within the binding site. One region showed high affinity for aliphatic groups, whereas the other region was hydrophilic. The aliphatic site should be a binding cavity for fatty acid chains. Water molecules are required for the hydrolysis of the acyl enzyme, but are probably not readily accessible in the hydrophobic interface, in which lipases are acting. Therefore, the hydrophilic site should be important for the hydrolytic activity of the enzyme. Lipases from R. miehei and H. lanuginosa are excellent catalysts for enantioselective resolutions of many secondary alcohols. We used molecular mechanics and dynamics calculations of enzyme-substrate transition-state complexes, which provided information about molecular interactions important for the enantioselectivities of these reactions.

Binding Sites↗
PubMed1994

Accumulation of fatty alcohol in MCF-7 breast cancer cells.

The MCF-7 cell line (human breast epithelial cells) accumulates fatty alcohols. The fatty alcohols were identified as C16:0, C18:0, and C18:1 alcohols by thin-layer chromatography and gas chromatography/mass spectrometry. This accumulation of alcohols in MCF-7 was found in cultures of MCF-7 cells obtained from other laboratories but not in a variety of unrelated cell lines. The presence of the alcohols suggested an aberrant ether lipid metabolism in the MCF-7 cells. Therefore, the capacity for either lipid biosynthesis was evaluated using cells incubated with either [14C]stearyl alcohol or [14C]stearic acid. MCF-7 cells incorporated less than 0.4% of the [14C]alcohol into ether-linked phospholipids, whereas the AB589 breast epithelial cells, used as a "normal control" for comparisons, did not accumulate fatty alcohol and incorporated approximately 20% of the radiolabeled alcohol into phospholipids containing ether linkages. Although the MCF-7 cells were unable to effectively incorporate the fatty alcohol into ether linkages, the cells were able to oxidize the alcohol to fatty acid. When incubated with [14C]stearic acid, the conversion to radiolabeled fatty alcohol in MCF-7 cells was approximately four times higher than the alcohol levels found in AB589 cells. While deficient in the ability to synthesize ether linkages, the MCF-7 cells did incorporate radiolabeled hexadecylglycerol, a precursor containing an ether linkage, into phospholipids. Collectively, the data indicate that the MCF-7 cells possess a deficiency in the alkyl DHAP synthase activity. A near absence of ether-linked lipids in the MCF-7 cells was indicated by the radiolabeling studies, and this finding was corroborated by results from HPLC analysis. Analyses of the partial glycerides, obtained from the enzymatic hydrolysis of cellular phospholipids, found only trace levels of ether lipids in the MCF-7 cells. The aberration in ether lipid biosynthesis did not correlate with the expression of the multidrug resistance phenotype in a series multidrug resistant MCF-7 variants. The results are discussed relative to the use of the MCF-7 cells as a model for investigations of ether lipid biosynthesis and the cellular physiology of ether lipids.

Breast Neoplasms↗
PubMed1997

Radiolabeling of the lipids of chinese hamster ovary cells with the probe [3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine].

[125I]TID [3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine] is a commercially available, hydrophobic, photoactivatable, gamma-emitting reagent mostly used to label protein hydrophobic domains. It has also been used to radiolabel the phospholipids of lung surfactant (Gilliard et al., Anal. Biochem. 193, 310-315, 1991). Since a nonspecific, highly sensitive, lipid-labeling probe would be a very useful tool to investigate lipid-protein interactions in biological membranes, we characterized further the [125I]TID-labeling products of lipids from cultured Chinese hamster ovary cells (IR-CHO). After labeling of whole cells, TLC analysis followed by autoradiography enabled detection of sphingomyelin, phosphatidylcholine, phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, cardiolipin, diglycerides, cholesterol and its esters, and triglycerides. Analysis of the radioactivity associated with the saponification products of different lipids showed that [125I]TID was mostly (80%) extracted with the fatty acid moiety of the lipids whereas 20% remained associated with the hydrosoluble moiety. Similar radioactivity profiles were observed after labeling of whole cells or extracted and liposome-reconstituted lipids; the [125I]TID probe was able to diffuse in all intracellular organelles. Labeling was not equivalent between the different lipid classes, and it appeared that the amount of associated radioactivity correlated well with the degree of lipid unsaturation. This was confirmed by studying [125I]TID incorporation in phosphatidylcholines of different chain length and unsaturation. Taken together, our data demonstrate that [125I]TID can be used as a radiolabel for lipids in cultured cells. It is rapidly incorporated in the hydrophobic part of membranes, diffuses into all cellular compartments, and labels all lipid classes, including phospholipids, cholesterol, and glycerides, with a sensitivity in the nanomolar range.

Animals↗
PubMed2002

Osmoregulatory isoform of dihydroxyacetone phosphate reductase from Dunaliella tertiolecta: purification and characterization.

The osmoregulatory isoform of dihydroxyacetone phosphate (DHAP) reductase (Osm-DHAPR) is an enzyme unique to Dunaliella, photosynthetic unicellular green algae adapted to extreme environments. This is the first report of purification of an isoform of DHAP reductase from Dunaliella, specifically the osmoregulatory isoform that is involved in the synthesis of free glycerol for osmoregulation in extreme environments, such as high salinity. The Osm-DHAPR is cold labile, inactivated by ammonium sulfate, forms a strong complex with Rubisco, and is unstable in the absence of glycerol. These difficulties have been addressed, and a four-step procedure has been developed to purify the Osm-DHAPR from Dunaliella tertiolecta: precipitation of Rubisco by polyethylene glycol, followed by successive chromatography on DEAE cellulose, Sephacryl S-200, and Red Agarose. Yield of the purified enzyme was 3.6%, with a specific activity of 938 micromol.min-1.mg-1 of protein and a subunit molecular mass of approximately 38 kDa. A maximum specific activity of 2580 micromol.min-1.mg-1 of protein could be achieved by assay with 150 mM NaCl. The Osm-DHAPR had little preference for NADH or NADPH, but it is highly specific for DHAP. Other metabolites of glycolysis, the tricarboxylic acid cycle, and the C3 reductive photosynthetic carbon cycle were not reduced by the enzyme. The purified enzyme was stimulated three-fold by 150 to 250 mM NaCl/KCl and by 25 mM MgCl2. Detergents, lipids, or long-chain acyl CoA derivatives, all of which inhibited the chloroplastic glyceride form of DHAP reductase, did not affect the activity of Osm-DHAPR. The Osm-DHAPR has different properties than the other chloroplastic isoform of DHAP reductase from plants and algae for glycerol phosphate formation and triglyceride synthesis.

Chlorophyta↗