SEARCH · Search PubMed

Results for “Diglycerides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources

PubMed1993

[Determination of mono-, di- and triglycerides using HPLC].

The determination of monoglycerides, diglycerides and triglycerides in the normal phase system: Separon SGX-CN (silica gel with phase-bonded cyanoethyl) and mobile phase hexane-isopropanol-formic acid by HPLC with refractometric detection, is described. It was found that the separation was according to the molecular mass of glycerides, i.e. in groups. This was demonstrated with palmitic, oleic and linoleic acids. The diglycerides and especially monoglycerides of olive and sunflower oils were partly separated according to the ECN1 values of the glycerides. The response factors related to triglycerides were estimated for the glycerides of the fatty acids and oils mentioned above. The value of response factors depends on the number of double bonds of the fatty acids.

Chromatography, High Pressure Liquid↗

PubMed1979

Effect of plastocyanin and phycocyanin on the photosensitivity of chlorophyll-containing bilayer membranes.

Photovoltaic effects were studied in bilayer membranes constructed from phosphatidyl choline, monogalactosyl diglyceride, chlorophyll alpha and beta-carotene. It was demonstrated that the biliprotein C-phycocyanin enhanced the photosensitivity of these membranes. Plastocyanin, an important photosynthetic electron transfer protein, was also found to be effective in enhancing the membrane photovoltage. The C-phycocyanin and plastocyanin were effective on opposite sides of the membrane. Plastocyanin operates to transfer electrons into the membrane, while C-phycocyanin directs electron transfer from the membrane. Membranes containing monogalactosyl diglyceride were found to be extremely stable and were most susceptible to enhancement of photosensitivity by introduction of the proteins. The plastocyanin and C-phycocyanin when used together appeared to operate synergistically.

Carotenoids↗

PubMedDate not supplied

A new method for studying the incorporation of nonesterified fatty acids into cardiac lipids by using deuterium-labelled palmitate.

A new method for measuring the incorporation of exogenous fatty acids into myocardial lipids of working rat hearts using deuterium-labelled palmitate has been developed. After perfusing isolated hearts, the fatty acid composition of triglycerides, diglycerides, monoglycerides, cholesterol esters, and nonesterified fatty acids (NEFA) was measured by a mass fragmentographic method. Hearts perfused only with 5 mM glucose and 1 mM lactate perfusion as basic substrates showed a significant decrease of triglyceride content, while the other lipids were not found to be significantly reduced. The fatty acid composition of all lipids were not affected. An addition of D31-palmitate complexed to albumin at a molar ratio of 5:1, caused a dose-dependent incorporation into triglycerides and diglycerides which suggested saturation kinetics. The tissue content of nonesterified D31-palmitate was found to be linearly related to its concentration in the perfusate. It may be of note that the concentration of the other NEFA was significantly affected neither by a fatty-acid-free perfusion nor by a perfusion with D31-palmitate. A significant incorporation of the supplied fatty acid into cholesterol esters and monoglycerides could not be detected.

Animals↗

PubMed1980

Microsomal phosphatidic acid phosphohydrolase of rat mammary tissue: I. General properties.

The microsomal bound phosphatidic acid phosphohydrolase from lactating rat mammary tissue had a specific activity of six nmoles per mg protein per minute. The optimum pH was 7.0; magnesium at 1.3 mM was required for maximum activity, and at low substrate concentrations magnesium lowered the Km of the enzyme for phosphatidic acid. Diglycerides exerted little effect while diglyceride ether stimulated enzyme activity. Inorganic salts, i.e., potassium phosphate and potassium chloride, enhanced rates of phosphatidic acid hydrolysis under standard assay conditions.

Animals↗

PubMed1995

Leukotriene B4 stimulation of an early elevation of phosphatidic acid mass in human neutrophils.

The signal transduction pathway of leukotriene B4 involves phospholipase D activation in cytochalasin B-primed neutrophils, but leukotriene B4 stimulation of increased phosphatidic acid mass in neutrophils has not been demonstrated. Employing the NIH Image program, we have examined the effect of leukotriene B4 on phosphatidic acid mass in human neutrophils incubated with or without cytochalasin B. Our results show that 0.15 microM leukotriene B4 without cytochalasin B was capable of increasing phosphatidic acid mass in neutrophils by 2-fold after 5 s, 2.5-fold after 1 min, and 2-fold after 5 min incubation. Leukotriene B3, leukotriene B4, and leukotriene B5 were equipotent stimuli for phosphatidic acid mass elevation. Leukotriene B4 induced phosphatidylethanol formation at the expense of phosphatidic acid in cells preincubated with 0.25-1% ethanol, indicating phospholipase D activation. Cytochalasin B enhanced leukotriene B4 stimulation of phosphatidic acid mass elevation and phosphatidylethanol formation. There were no measurable changes in 1,2-diglyceride mass after 5 s, but a 1.7-fold increase occurred after 1 min and declined thereafter. Leukotriene B4 stimulation of [3H]glycerol incorporation into phosphatidic acid, diglyceride and phosphatidylinositol was detectable after a 1-min incubation, suggesting increased de novo synthesis of these lipids. These results suggest that leukotriene B4 stimulation of phospholipase D activity contributes to part of the early increased phosphatidic acid mass and that combined actions of stimulated phospholipases C and D, and de novo phosphatidic acid synthesis contribute to the total increased phosphatidic acid mass.

Cytochalasin B↗

PubMed1987

Biochemical and scanning electron microscope study of lipids chloroform-methanol extracted from unerupted and erupted human tooth enamel.

Almost twice as much fatty acid was extracted without demineralization from the mature enamel of erupted teeth treated with 2:1 chloroform-methanol as from the enamel of unerupted teeth (32.64 micrograms/g versus 15.60 micrograms/g). Palmitic C16:0, stearic C18:0, oleic C18:1 omega 9 and linoleic acids C18:2 omega 6 were the chief fatty acids detected by gas-liquid chromatography. The percentage of free fatty acids and diglycerides was larger in unerupted than erupted teeth, whereas that of triglycerides, phosphatidylethanolamine and phosphatidylcholine was larger in erupted teeth. These changes may be due to bacteria and other contaminants (saliva and pellicle). The large amounts of free fatty acids, diglycerides, cholesterol and phospholipids as intrinsic components were probably due to the persistence of membrane remnants entombed during enamel formation, as indicated by the visualization of holes and by the increase in the size and number of focal holes after lipid-solvent interaction with the enamel surface. These defects always occurred in rods and never in inter-rod material. Other minute defects, including empty-widened intercrystal spaces, were also observed inside some rods.

Adolescent↗

PubMed1978

Galactolipid formation in chloroplast envelopes. I. Evidence for two mechanisms in galactosylation.

Two different enzymes for galactosylation occur in isolated chloroplast envelopes of spinach leaves, UDPgalactose-diglyceride galactosyltransferase and galactolipid-galactolipid galactosyltransferase. The first enzyme is responsible for the biosynthesis of monogalactosyldiglyceride, UDPgalactose being donor of the galactosyl moiety. The second enzyme is responsible for the biosynthesis of digalactosyldiglyceride and higher homologues. The optimum pH for monogalactosyldiglyceride synthesis was found to be 7.5, for digalactosyldiglyceride synthesis 6.5. After incubation at pH 7.4 a Lineweaver-Burk plot indicated two binding sites for UDPgalactose on the UDPgalactose-diglyceride galactosyltransferase with different affinities for UDPgalactose and different activities. Indirectly the galactolipid-galactolipid galactosyltransferase was shown to respond similarly to various UDPgalactose concentrations. However, the second reaction also proceeds in absence of UDPgalactose. It was concluded that the second enzyme does not require the presence of UDPgalactose, but that galactosyl transfer proceeds by direct exchange of galactosyl groups between molecules of galactolipids, or via unknown lipid intermediates, not detected in our system. Results of other investigations will be discussed in the light of the present data.

Chloroplasts↗

PubMed1991

Differential actions of diacyl- and alkylacylglycerols in priming phospholipase A2, 5-lipoxygenase and acetyltransferase activation in human neutrophils.

One aspect of human neutrophil (PMN) function during inflammation is formation of platelet-activating factor (PAF), leukotriene B4 (LTB4), and 5-hydroxyeicosatetraenoic acid (5-HETE), but production of these lipid mediators is limited if PMN are directly stimulated with soluble, physiologic agonists. In vitro, PMN activities can be enhanced by the process of primed-stimulation where cells are sequentially treated with non-stimulatory concentrations of different agonists. Many agents that prime PMN also induce production of 1,2-diacyl- and 1-O-alkyl-2-acylglycerols. Therefore, we investigated whether diglycerides were involved in priming PMN for production of lipid mediators. We previously described the ability of the diacylglycerol, 1-oleoyl-2-acetylglycerol (OAG), and its alkylacylglycerol analog, 1-O-octadecenyl-2-acetylglycerol (EAG), to prime phospholipase A2 (PLA2) for subsequent activation by a second stimulus. However, while OAG also primed 5-lipoxygenase activity (LTB4 and 5-HETE production), EAG priming inhibited LTB4 and 5-HETE formation. We now report the effects of diglyceride priming on acetyltransferase activation (PAF formation). PMN, prelabeled with 1-O-[9',10'-3H]hexadecyl-2-lyso-sn-glycero-3-phosphocholine, were primed with OAG or EAG before stimulation. Neither OAG nor EAG induced formation of labeled PAF. Treatment of PMN with the chemotactic peptide, N-formyl-met-leu-phe (FMLP), induced low but significant production of PAF; PAF formation doubled in PMN primed with 20 microM OAG before FMLP stimulation while priming with 20 microM EAG more than tripled the level of PAF. Calcium ionophore strongly induced PAF formation; OAG priming before ionophore challenge had no effect but EAG priming further enhanced PAF formation. These results suggests a role for alkylacylglycerols in modulating the production of lipid mediators of inflammation.

Acetyltransferases↗

PubMed1985

Kinetic evidence that 1,2-diolein inhibits phorbol ester binding to protein kinase C via a competitive mechanism.

Diacylglycerols inhibit binding of [20-3H]phorbol 12,13-dibutyrate ([3H]PDBu) to protein kinase C (the phorbol ester receptor). This inhibition could reflect competitive binding by the diglyceride. Alternatively, it might simply represent perturbation of the lipid environment required for binding activity. As predicted for a competitive mechanism, we report here that inhibitory concentrations of the diglyceride 1,2-diolein do not affect the off-rate of [3H]PDBu from its receptor. This behavior contrasts with that of arachidonic acid, which appears to interact via a mixed mechanism.

Arachidonic Acid↗

PubMed1989

Diacylglycerol modulates action potential frequency in GH3 pituitary cells: correlative biochemical and electrophysiological studies.

We have investigated the involvement of enhanced phosphoinositide metabolism in mediating TRH-induced alteration of electrophysiological events related to prolactin secretion by GH3 cells (a line of pituitary origin). Patch-clamp recording (in the current clamp, whole-cell configuration) showed that a few seconds after TRH application there was a brief period (about 30 s) of membrane hyperpolarization followed by several minutes of increased calcium-dependent action potential frequency. In parallel experiments cells were labeled for 24 h with either [3H]myo-inositol or [3H]arachidonate. Application of TRH resulted in rapid increases in levels of inositol phosphates and diacylglycerol. The time course of elevation of inositol 1,4,5-triphosphate (maximal by 5 s) is compatible with an initial burst of intracellular calcium mobilization associated with a transient phase of TRH-induced prolactin release. Application of TRH was also followed by a rapid but more sustained (several minutes) period of elevated diglyceride accumulation; a time course corresponding to a prolonged period of prolactin release which is dependent on the influx of external calcium. A causal relationship between diglyceride release and increased action potential frequency was demonstrated since local application (via a U-tube apparatus) of either 2 microM phorbol ester (phorbol 12,13-dibutyrate or phorbol 12-myristate 13-acetate) or 60 microM 1-oleoyl-2-acetyl-glycerol to patch-clamped cells could mimic this aspect of the TRH effect. In contrast, the inactive phorbol ester, 4 alpha-phorbol, was unable to elicit this response.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1978

Differential scanning calorimetry studies of some analogs for the lipid component of biological membranes.

The melting behavior of members of newly synthesized series of rac-1,2-diglycerides with substituted phenyl groups or a benzyl group on the 3-position was investigated with differential scanning calorimetry (DSC). Solution crystallized samples had single melting temperatures, higher than those of the quenched or annealed specimens. Quenched samples exhibited polymorphic behavior; some melted and recrystallized during slow heating. This behavior is similar to that of lecithins and suggests that X-ray diffraction studies of the substituted diglycerides may be useful for understanding membrane structure and functions.

Calorimetry↗

PubMed1984

RHC 80267 inhibits thyrotropin-stimulated prostaglandin release from rat thyroid lobes.

In the present report, we studied the effect of the diglyceride (DG) lipase inhibitor, RHC 80267 on basal and thyrotropin (TSH)-stimulated prostaglandin (PG) release from rat thyroid lobes Further, we tested the effect of RHC 80267 on phosphatidylinositol phospholipase C (PIPLC), DG lipase, and arachidonate cyclo-oxygenase activities in rat thyroid cytosol, plasma membrane, and whole homogenate preparations, respectively. Whereas RHC 80267 inhibited DG lipase activity in a dose-related manner from 0.5-10 microns (17-80% inhibition), it failed to inhibit either PIPLC or arachidonate cyclo-oxygenase activities by more than 9% when tested at 5 and 10 microns (n = 3). RHC 80267 reduced TSH-stimulated 6-keto-PGF1alpha and PGF2alpha release by 100 +/- 14% and 57 +/- 12%, respectively (means + S.E.; p less than 0.01 for both; n = 10-12); the diglyceride lipase inhibitor did not reduce basal release of either PG. These data provide additional evidence which implicate a PIPLC-DG lipase pathway in TSH-stimulated PG synthesis in thyroid.

Animals↗

PubMed1982

A micromethod for the determination of ceramide.

An enzymatic micromethod for the determination of ceramide is presented. The enzyme, E. coli diglyceride kinase was used to phosphorylate ceramide, as well as diglyceride with high specific activity gamma-[32P]ATP, and the two products are differentiated by their alkali stability. This method was applied to the detection of endogenous phospholipases and sphingolipases in several membrane systems and could have wide application.

Animals↗

PubMed1992

Regulation of diacylglycerol levels in carbachol-stimulated pancreatic acinar cells: relationship to the breakdown of phosphatidylcholine and metabolism to phosphatidic acid.

Rat pancreatic acinar cells prelabeled with [14C]palmitic acid and then exposed to carbachol (CCh) exhibited a time-dependent increase in 1,2-[14C]diacylglycerol ([14C]DAG) levels, which was first detected at 2 min and then continued to rise in a linear manner. There was a concomitant increase in [14C]phosphatidic acid, which plateaued after 2 min and then remained at steady-state levels. CCh also promoted the release of phosphocholine, but not choline, within 60 s and caused a decrease in [14C]phosphatidylcholine in cells prelabeled with [14C]glycerol after 15 min. The inability to detect a rise in [14C]phosphatidylethanol accumulation and a fall in [14C]phosphatidate levels in [14C]palmitate prelabeled cells after exposure to CCh plus ethanol documented the absence of a phospholipase D-mediated pathway. The rapid phosphorylation of diglyceride in homogenates from unstimulated and carbachol-treated cells increased with increasing concentrations of exogenous substrate, thereby affirming that carbachol stimulates the phosphorylation of DAG by promoting the accumulation of the diglyceride. These collective findings provide evidence for the existence of an integrative control mechanism for regulating endogenous DAG levels during pancreatic acinar cell activation involving phosphatidylcholine-specific phospholipase C and DAG kinase.

Animals↗

PubMed2005

A chronic dietary toxicity study of DAG (diacylglycerol) in Beagle dogs.

The potential chronic toxic effects of DAG (diacylglycerol) when administered orally for 12 months were evaluated in this dietary study in Beagle dogs. DAG is a cooking oil which contains >80% diglycerides, <20% triglycerides and 5% monoglycerides. For this study, a special diet was prepared with no dietary fat so that all of the dietary fat could be provided by DAG, at various concentrations together with a control oil. The control oil, TG (triacylglycerol), was prepared to contain >85% triglycerides, <10% diglycerides and 5% monoglycerides. The fatty acid composition for DAG and TG was closely matched. Dietary concentrations of 0% DAG/9.5% TG (TG control), 1.5% DAG/8.0% TG, 5.5% DAG/4.0% TG, and 9.5% DAG/0% TG were presented daily, seven days per week, for 52 weeks. A second concurrent control group received the standard basal diet (Certified Canine LabDiet 5007, which has a fat content of 9.5%). The basal diet, control article-treated and DAG-treated groups each consisted of four male and four female dogs. Treatment was initiated in prejuvenile (2.5-month-old) dogs. Statistical evaluations compared the DAG-treated groups both to the basal diet and 9.5% TG control groups. The clinical condition of the animals, body weights, body weight gains and food consumption were unaffected by DAG. Hematology and urinalysis parameters were unaffected. No serum chemistry changes indicative of a toxic effect were observed. There were no effects noted on ECG data. No test article-related gross or histopathologic findings or changes in organ weights were observed. While there were no identifiable differences between the effects of TG and DAG, both caused some differences relative to the basal diet (lower food consumption, higher alkaline phosphatase, cholesterol and triglycerides). These differences were not toxicologically significant and were attributed to the differences in the diet rather than the fat source. Thus, DAG at dietary concentrations up to 9.5% for one year had no effect on normal canine growth and development, in comparison to TG.

Administration, Oral↗

PubMed1998

Differential activation of human neutrophil cytosolic phospholipase A2 and secretory phospholipase A2 during priming by 1,2-diacyl- and 1-O-alkyl-2-acylglycerols.

We have shown previously that both 1,2-diacylglycerol (AAG) and 1-O-alkyl-2-acylglycerol (EAG) prime neutrophil release of arachidonic acid via uncharacterized phospholipases A2. Therefore, we investigated the actions of EAG and AAG specifically on neutrophil cytosolic (cPLA2) and secretory (sPLA2) phospholipase A2s. We hypothesized that AAG as a protein kinase activator would activate cPLA2 via phosphorylation events. EAG is antagonistic to the AAG activation of PKC, thus it was not expected to act via phosphorylation of cPLA2. Neutrophils were primed with either AAG or EAG and then stimulated with fMLP. When neutrophils were primed with 5-20 microM 1,2-diacylglycerol, a shift was observed in cPLA2 migration on SDS-PAGE gels, consistent with phosphorylation of the protein. This gel shift was not seen after exposure to EAG. AAG also caused a parallel increase in enzymatic activity of cPLA2 that was not seen with EAG. We also investigated whether either diglyceride would cause similar priming or direct secretion of sPLA2. Both AAG and EAG directly caused significant secretion of neutrophil sPLA2. EAG also increased the release of sPLA2 in cells subsequently stimulated with fMLP. Thus, AAG activated cPLA2 and stimulated secretion of sPLA2. In contrast, EAG did not activate cPLA2, but directly activated secretion of sPLA2. We also demonstrated that human synovial fluid sPLA2 increased AA release from resting and fMLP-stimulated neutrophils. Given that diglycerides prime for release of AA, PAF, and LTB4, these current data support the hypothesis that such priming may be mediated by phosphorylation dependent (cPLA2) or phosphorylation independent (e.g. secretion of sPLA2) events.

Arachidonic Acid↗

PubMed1984

The stereospecific activation of protein kinase C.

Protein kinase C is synergistically activated by the presence of calcium, certain phospholipids and a diacylglycerol. The physiological activation of the enzyme appears to be determined by the availability of the diacylglycerol which is itself a product of (poly) phosphoinositol turnover. It is shown here that the diacylglycerol activation effect is stereospecific, with only the 1,2-sn-diglycerides being active. This demonstrates for the first time a stereospecific effector role for a membrane-bound lipid. Furthermore, this work strengthens the link forged between the highly potent and specific tumor promoters (such as the phorbol esters) and the diglycerides as activators of protein kinase C.

Animals↗

PubMed2003

Minocycline effect on meibomian gland lipids in meibomianitis patients.

The objective of this research was to determine the effect of oral minocycline on the meibomian gland nonpolar and free fatty acid lipids of chronic blepharitis patients. Patients--seborrheic blepharitis (SBBL), acne rosacea (AR) without ocular involvement, and acne rosacea with meibomianitis (AR-MKC). Minocycline treatment--50mg orally for 2 weeks followed by 100mg to the end of 3 months; this was followed by 3 more months with no treatment. Meibomian gland secretions (meibum) were collected before treatment, at the end of the 3 months on treatment, and 3 months after stopping treatment. Lipids were separated and analyzed for wax and sterol esters, triglycerides, diglycerides, free cholesterol and free fatty acids. Data were analyzed statistically by ANOVA. Minocycline treatment resulted in decreased diglycerides and free fatty acids in the group AR-MKC, which continued into the second 3 months (off treatment) and was significant. Cholesterol decreased, but triglycerides initially decreased with treatment and then increased when treatment in the group was discontinued (second 3 months); these results, however, were not significant. Thus, minocycline has its greatest effect on lipid types, which result from degradation (lipase) reactions, suggesting a lipase inhibition effect and/or direct effect on ocular flora. This minocycline effect continues even after treatment is discontinued, suggesting a more lasting effect on ocular microflora. Minocycline may be most effective when the treatment period is longer than 3 months. These results give insight into disease mechanisms associated with chronic blepharitis.

Analysis of Variance↗