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PubMed1988

Effects of mezerein and diglycerides on ornithine decarboxylase activity in mouse mammary gland explants.

One of the most rapid actions of prolactin in mouse mammary gland explants is the stimulation of ornithine decarboxylase (ODC) activity. Several protein kinase C activators including mezerein, dicaprin, diolein, and 1-oleoyl-2-acetyl-rac-glycerol were found to stimulate ODC activity as does prolactin. Both mezerein and the diglycerides produced nonadditive responses when tested with maximum stimulatory concentrations of prolactin. The results of these studies therefore provide further evidence that the prolactin stimulation of ODC activation in the mammary gland may involve an activation of protein kinase C.

Animals↗
PubMed1992

Alpha-thrombin stimulates nuclear diglyceride levels and differential nuclear localization of protein kinase C isozymes in IIC9 cells.

The mechanism by which an agonist, binding to a cell surface receptor, exerts an effect on events in the nucleus is not known. We have previously shown (Leach, K. L., Ruff, V. A., Wright, T. M., Pessin, M. S., and Raben, D. M. (1991) J. Biol. Chem. 266, 3215-3221) that alpha-thrombin treatment of IIC9 cells results in increased levels of cellular 1,2-diacylglycerol (DAG) and activation of protein kinase C (PKC). Here, we have examined whether changes in nuclear PKC and nuclear DAG also are induced following alpha-thrombin treatment. IIC9 cells were treated with 500 ng/ml alpha-thrombin, and nuclei were then isolated. Western blot analysis using isozyme-specific antibodies demonstrated the presence of PKC alpha, but not PKC epsilon or zeta in the nuclei of cells treated with either phorbol 12-myristate 13-acetate or alpha-thrombin. The increase in nuclear PKC alpha levels was accompanied by a 10-fold increase in nuclear PKC specific activity and stimulated phosphorylation of at least six nuclear proteins. The rise in nuclear PKC levels occurred rapidly and reached a maximum at 30-60 s, which was followed by a decline back to the control level over the next 15 min. In addition, alpha-thrombin treatment resulted in an immediate rise in DAG mass levels in the nuclear fractions. Kinetic analysis indicated that a maximum increase in DAG levels occurred 2.5-5 min after the addition of alpha-thrombin and remained elevated for at least 30 min. In cells labeled with [3H]myristic acid, alpha-thrombin treatment induced an increase in radiolabeled nuclear diglycerides, suggesting that the stimulated nuclear DAGs are derived, at least in part, from phosphatidylcholine. Our results suggest that increases in both nuclear DAG levels and PKC activity following alpha-thrombin treatment may play a role in mediating thrombin-induced nuclear responses such as changes in gene expression and cellular proliferation.

Animals↗
PubMed1992

Formyl peptide stimulates and ATP gamma S potentiates [3H]cytidine 5'-diphosphate diglyceride accumulation in human neutrophils.

Although it is evident that the chemotactic peptide FMLP activates O2-formation in neutrophils via the phosphoinositidase-mediated second messenger system, it is less clear how endogenous priming agents such as ATP and platelet activating factor potentiate FMLP action. In our study, we have examined the possible effects of the stable ATP analog adenosine 5'-O-[3-thiotriphosphate] (ATP gamma S) on cellular levels of inositol 1,4,5-trisphosphate, [Ca2+]i and diglyceride (DG), in resting and in FMLP-stimulated neutrophils. Although all three measures were increased in the presence of FMLP, only the increase in DG was enhanced by pretreatment (priming) with ATP gamma S. We also measured the accumulation of the phosphoinositide cycle intermediate cytidine 5'-diphosphate (CDP)-DG to assess possible effects of priming on phosphoinositide resynthesis. The addition of FMLP to [3H]cytidine-prelabeled neutrophils elicited an increase in the accumulation of [3H]CDP-DG that was maximally enhanced in cells that were pretreated with cytochalasin B. The stimulated accumulation of [3H]CDP-DG was completely reversed by the addition of myo-inositol. Treatment of [3H]cytidine-prelabeled neutrophils with ATP gamma S (10-100 microM) resulted in a dose-dependent synergistic increase in FMLP-stimulated [3H]CDP-DG accumulation, whereas ATP gamma S alone had no effect. The observed increases in DG and in [3H]CDP-DG, in contrast to inositol 1,4,5-trisphosphate and [Ca2+]i responses, correlates well with the ATP gamma S-priming of FMLP-induced O2-formation. A similar potentiation of FMLP-induced stimulation of CDP-DG formation was also observed with platelet-activating factor. It is proposed that the priming of FMLP responses in neutrophils proceeds via a mechanism that selectively enhances DG production through a mechanism that is independent of FMLP-induced breakdown of phosphatidylinositol bisphosphate.

Adenosine Triphosphate↗
PubMed1990

Urokinase secretion from human colon carcinomas induced by endogenous diglycerides.

Colon tumor cells are more responsive to certain growth modulators in their local environment in vivo than are normal colonocytes. Examples of this class of compounds are the fecal diglycerides (DGs)(E. Friedman et al., Cancer Res., 49: 544-548, 1989), which may act as endogenous tumor promoters. At the concentration found in vivo, fecal DGs composed of oleic, myristic, and palmitic fatty acids induced mitogenesis of all classes of benign tumor cells and of half of the resected carcinomas tested in primary culture, but induced no detectable mitogenesis of normal colonocytes. Colon tumor cells also exhibit selective responses to these endogenous modulators as measured by another biological parameter, secretion of urokinase from carcinomas than from normal colonocytes. Fecal DGs also induced a 13-fold increase in urokinase mRNA synthesis in colon carcinoma cells and induced secretion of active urokinase from each of five resected carcinomas. Colon carcinomas, at both the primary site and metastatic to the liver, secreted the Mr 55,000 form of urokinase constitutively and secreted the same form upon treatment with fecal DGs. An increase in the steady-state level of urokinase secretion by saturated-chain DGs exhibited a strong dependency on the chain length of the fatty acid residues, those of 14 and 16 carbons having the greatest activity. Thus, fecal DGs composed of oleic, myristic, and palmitic acid residues induce two biological activities selectively in colon tumor cells, each of which would enhance tumor development. Selective mitogenesis would increase adenoma and carcinoma cell number relative to normal colonocyte number, and induction of the proteolytic enzyme urokinase would aid local invasion of the carcinoma within the bowel wall.

Blotting, Western↗
PubMed1990

Rapid protein kinase C-dependent activation of phospholipase D leads to delayed 1,2-diglyceride accumulation.

We have shown previously that the major source of diglyceride (DG) formed following muscarinic receptor (mAChR) stimulation of 1321N1 astrocytoma cells is phosphatidylcholine (PC) rather than the phosphoinositides (Martinson, E. A., Goldstein, D., and Brown, J. H. (1989) J. Biol. Chem. 264, 14748-14754). We have also noted that there is a delay of several minutes before significant DG accumulation is observed. In the present work, we examine the time course and mechanism of PC hydrolysis in response to mAChR stimulation. Treatment of 1321N1 cells with carbachol results in increases in radiolabeled choline, phosphatidic acid (PA) and phosphatidylethanol (PEt), metabolites that are products of phospholipase D (PLD) action on PC. These products are all formed within 15 s of mAChR stimulation and reach a plateau within 30-60 s. The time course of PEt formation suggests that PLD is no longer activated after several minutes of mAChR stimulation. Thus there is a discrepancy between the rapid and transient activation of PLD and the delayed accumulation of DG. It appears that most of the DG is formed through the action of PLD, since propranolol (which inhibits the conversion of PA to DG) and down-regulation of protein kinase C (which prevents activation of PLD by carbachol) both markedly inhibit DG production. Using a protocol in which cells are stimulated with carbachol for only one minute (a period during which PLD and PA formation are maximally activated), we show that DG mass continues to increase following removal of agonist. We suggest that the rapid and transient activation of PLD results in delayed accumulation of DG due to the relatively slow conversion of PA to DG by PA phosphatase.

Animals↗
PubMed1989

Choline-linked phosphoglycerides. A source of phosphatidic acid and diglycerides in stimulated neutrophils.

Stimulation of human polymorphonuclear leukocytes (PMN) may result in the metabolism of phospholipids other than phosphoinositides to generate second-messenger intermediary metabolites. We investigated agonist-induced breakdown of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (1-O-alkyl-2-acyl-GPC), which constitutes almost half the diradyl-GPC fraction in human PMN (Mueller, H. W., O'Flaherty, J. T., Green, D. G., Samuel, M. P., and Wykle, R. L. (1984) J. Lipid Res. 25: 383-388), in cells prelabeled with 1-O-[3H] alkyl-2-acyl-GPC. We also utilized normal-phase high pressure liquid chromatography to quantitate the accumulation of diradylglycerols (1-O-alkyl-2-acylglycerols and diacylglycerols) in stimulated PMN. Phorbol-12-myristate-13-acetate (PMA), 1-oleoyl-2-acetyl-sn-glycerol-, calcium ionophore A23187-, and f-methionyl-leucyl-phenylalanine (fMLP) stimulation of PMN resulted in a time- and concentration-dependent hydrolysis of 1-O-[3H]alkyl-2-acyl-GPC and the formation of 1-O-[3H]alkyl-2-acyl-phosphatidic acid (PA) and 1-O-[3H]alkyl-2-acylglycerol. In all cases formation of 1-O-[3H]alkyl-2-acyl-PA preceded that of 1-O-[3H]alkyl-2-acylglycerol. The times between addition of stimulus and appearance of 1-O-[3H] alkyl-2-acylglycerol varied for PMA (40 s at 1.6 microM), A23187 (5 min at 5 microM), and fMLP (30 sec at 1 microM). Preincubation of cells with 1 microgram/ml pertussis toxin (PT) inhibited the breakdown of 1-O-[3H]alkyl-2-acyl-GPC in cells stimulated with 1 microM fMLP, indicating a role for a PT-sensitive G protein with this stimulus. Quantitation of diglycerides as diradylglycerobenzoates in PMN stimulated with PMA (10 min), A23187 (10 min), or fMLP demonstrated marked accumulation of both 1-O-alkyl-2-acylglycerols and diacylglycerols. The highest increases over controls were observed for fMLP (33-fold for 1-O-alkyl-2-acylglycerols and 17-fold for diacylglycerols). In stimulated PMN prelabeled with 1-O-[3H]hexadecyl-2-acyl-GPC and 1-O-alkyl-2-acyl-sn-glycero-3-[32P]phosphocholine, the ratio of 3H to 32P in 1-O-alkyl-2-acyl-PA compared to 1-O-alkyl-2-acyl-GPC suggested the involvement of a phospholipase D in the hydrolysis of 1-O-[3H]-alkyl-2-acyl-GPC. Thus, stimulation of human PMN results in the hydrolysis of 1-O-[3H]alkyl-2-acyl-GPC to yield 1-O-[3H] alkyl-2-acyl-PA and 1-O-[3H]alkyl-2-acylglycerol possibly initiated by activation of a phospholipase D.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcimycin↗
PubMed1989

Regulation of phospholipase D in HL-60 granulocytes. Activation by phorbol esters, diglyceride, and calcium ionophore via protein kinase- independent mechanisms.

It has recently been demonstrated that the chemotactic peptide N-formyl-Met-Leu-Phe activates phospholipase D (PLD) in dimethyl sulfoxide-differentiated HL-60 granulocytes to produce phosphatidic acid (PA) and, in the presence of ethanol, phosphatidylethanol (PEt) (Pai, J.-K., Siegel, M. I., Egan, R. W., and Billah, M. M. (1988) J. Biol. Chem. 263, 12472-12477). We now report that biologically active phorbol esters, a cell-permeable diacylglycerol, 1-oleoyl-2-acetylglycerol (OAG), and calcium ionophore A23187 are also potent inducers of PLD in these HL-60 granulocytes. HL-60 granulocytes have been selectively labeled in 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (alkyl-PC) with 32P by incubating the cells with alkyl-[32P]lyso-phosphatidylcholine (PC). When these labeled cells are treated with phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-dibutyrate, OAG, or A23187, alkyl-[32P]PA is formed. Because cellular ATP has not been labeled with 32P, the formation of alkyl-[32P]PA conclusively demonstrates PLD activation by these agents. In the presence of 0.5% ethanol, phorbol esters, OAG, and A23187 also induce formation of alkyl-[32P]PEt, demonstrating that the activated PLD catalyzes transphosphatidylation between the phosphatidyl moiety of the alkyl-[32P]PC and ethanol. Formation of alkyl-[32P]PA and alkyl-[32P]PEt in response to these various agents occurs in a time- and dose-dependent manner and exhibits differential Ca2+ requirements. Based on experiments with both [3H]alkyl-PC and alkyl-[32P]PC, it is concluded that alkyl-PA and alkyl-PEt formed in response to PMA, OAG, or A23187 are derived exclusively from PLD action on alkyl-PC. Furthermore, subthreshold concentrations of PMA (0.5-2.0 nM) or OAG (1.0-25 microM) combined with subthreshold levels of A23187 (15-60 nM) induce the formation of alkyl-[32P]PA and alkyl-[32P]PEt, suggesting that receptor-mediated activation of PLD might involve cooperative interactions between Ca2+ and diglyceride. Although PLD is activated by agents that also activate protein kinase C, the protein kinase C inhibitor, K252a, inhibits PMA-induced protein phosphorylation but causes only partial inhibition of PLD activation. We conclude that phorbol esters, OAG, and A23187 activate PLD in HL-60 granulocytes via protein kinase-independent as well as protein kinase-dependent mechanisms.

Calcimycin↗
PubMed1989

Fecal diglycerides as selective endogenous mitogens for premalignant and malignant human colonic epithelial cells.

Diglycerides (DGs) have been found in fecal extracts at concentrations which induce mitogenesis of adenoma and some carcinoma cells but not normal cells in primary culture. DGs containing stearic, oleic, palmitic, and myristic acid side chains were found in fecal extracts from each of eight subjects. Synthetic 1,2-DGs, containing the fatty acids found in endogenous fecal DGs, induced mitogenesis in cultures of premalignant cells from each of 13 adenomas, covering all histological classes, and in cultures from two of four carcinomas. The potent adenoma mitogen, dimyristin, had no mitogenic activity on cultures of normal colonic epithelial cells from seven different subjects. These results suggest DGs may act as endogenous mitogens in the development of human colon cancer. The extent of adenoma mitogenesis was correlated with the chain length of the saturated R-groups: 16 greater than 14 greater than 12 greater than 10 greater than 8 much greater than 18. DGs with oleic acid residues, C18:1, were among the most active, while substitution of even one fatty acid residue with a stearic acid residue, C18:0, reduced or eliminated mitogenic activity. Dimyristin also induced enhanced levels of urokinase secretion from carcinoma cells, in parallel to the phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. These results imply that DGs found in the colon induce a selective growth of benign colonic tumors and some carcinomas, and may enhance the invasive capacity of carcinomas, while leaving normal cells unaffected.

Adenoma↗
PubMed1988

Selective priming of rate and duration of the respiratory burst of neutrophils by 1,2-diacyl and 1-O-alkyl-2-acyl diglycerides. Possible relation to effects on protein kinase C.

Both 1,2-diacyl- and 1-O-alkyl-2-acyl-sn-glycerols are released during stimulation of human polymorphonuclear leukocytes (PMNL). 1,2-Diacylglycerols have received intense interest as intracellular "second messengers" due to their ability to activate protein kinase C (Ca2+ phospholipid-dependent enzyme). However, little is known about bioactivities of the alkylacylglycerols. This study compared the ability of 1,2-diacyl- and 1-O-alkyl-2-acylglycerols to modulate the respiratory burst of stimulated PMNL, a response which depends on the activation of an NADPH oxidase to generate bactericidal species of reduced oxygen. Direct stimulation by N-formyl-Met-Leu-Phe caused an abrupt release of H2O2 which ceased within 2.5 min. Preincubation with diacylglycerols (1-oleoyl-2-acetylglycerol,5-30 microM, and 1,2-dioctanoylglycerol,2-5 microM) caused a decrease in lag time, 3-fold increase in initial rate of H2O2 release, and marked prolongation of the response to N-formyl-Met-Leu-Phe (features characteristic of a priming effect). Preincubation with alkylacylglycerols (1-O-delta 9-octadecenyl-2-acetylglycerol, 5-30 microM, and 1-O-octyl-2-octanoylglycerol, 20-50 microM) primed initiation (shortened lag time and increased velocity) but, in contrast to diacylglycerols, did not alter duration of H2O2 release. While low concentrations of diacylglycerols (5-30 microM) primed PMNL, higher concentrations (greater than or equal to 70 microM) stimulated the cells directly. In contrast, higher (70-100 microM) concentrations of alkylacylglycerols did not prime the responses but, in fact, inhibited priming (especially of duration) induced by diacylglycerol. The high concentrations of alkylacylglycerol also inhibited direct stimulation induced by high concentrations of diacylglycerol. Direct stimulation by high concentrations of diacylglycerol probably involves activation of protein kinase C, whereas alkylacylglycerol was found to inhibit activation of protein kinase C by diacylglycerol in vitro. Thus, diacylglycerols are complete priming agonists, altering both rate and duration of the response. In contrast, alkylacylglycerols may have biphasic, concentration-related effects in modulation of functions of PMNL. At low concentrations, they may facilitate initiation of functional events; however, as their concentration increases, they may serve to terminate responses. The distinct priming effects of these diglycerides also reveal that priming can involve at least two distinct events: 1) initiation and 2) prolongation.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytosol↗
PubMed1979

Synthesis of all-cis-1,3-diacylcyclopentane-1,2,3-triol-2-phosphate via acyl group migration in a cyclic diglyceride analog.

The acid-catalyzed isomerization of the diglyceride analog (1,2,3/0)-1,2-dipalmitoylcyclopentane-1,2,3-triol has been used to generate syn-syn-1,3-diacyl-cyclopentane-1,2,3-triol, a required intermediate in the synthesis of a symmetrical all-cis-1,2,3/0-2P cyclopentanoid phosphatidic acid analog. The all-cis cyclo-phosphatidic acid analog has therefore been obtained in the free acid form and as the diphenyl ester, dimethyl ester, and dipotassium salt derivatives. The compounds have been characterized by microanalysis and spectroscopic methods. The 1,2,3/0-2P analog is now available for comparative studies with the corresponding all-trans cyclophosphatidic acid (1,3/2-2P).

Cyclopentanes↗
PubMed1981

Gravimetric determination of ethoxylated mono- and diglycerides in bread.

A gravimetric method is described for the quantitative determination of ethoxylated mono-and diglycerides (EMGs) in bread at levels as low 0.42% (dry sample). The air-dried pulverized samples are Soxhlet-extracted 22 h with an azeotropic mixture of n-propanol-water. The contents are evaporated to dryness, and then treated with 5% HCl in methanol to trans-esterify the fatty acids present which are then removed by petroleum ether extraction. The EMGs are subsequently precipitated from aqueous solution with phosphomolybdic acid in the presence of barium ions. The precipitate is weighed and compared with known amounts of standard carried through the same procedure.

Bread↗
PubMed1993

Platelet-activating factor stimulates phosphatidic acid formation in cultured rat mesangial cells: roles of phospholipase D, diglyceride kinase, and de novo phospholipid synthesis.

Platelet-activating factor (PAF) stimulates phospholipase C (PLC)-induced hydrolysis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2). Yet, PAF-stimulated diglycerides (DG) are still elevated at time points where inositol polyphosphates have returned to basal levels. Thus, other signal transduction pathways that hydrolyze phosphatidylcholine (PtdCho) or phosphatidylethanolamine (PtdEth) and form DG and phosphatidic acids (PA) through either PLC or phospholipase D (PLD) may also mediate PAF-stimulated cellular responses. Initially the effects of PAF upon 32P-PA generation in mesangial cells (MC) were assessed. PA formation may be indicative of several metabolic pathways including PLD and DG kinase activities as well as de novo phospholipid synthesis. PAF (10(-7) M) increased 32P-PA formation as early as 5 seconds and this elevation persisted up to 15 minutes. When MC were pretreated with the DG kinase inhibitor-R59022, PAF-induced 32P-PA formation was diminished at early but not late time points, demonstrating that the initial component of PA formation may be due, in part, to PLC activation and subsequent phosphorylation of DG. The reciprocal reaction, PA phosphohydrolase, which dephosphorylates PA to from DG was not stimulated by PAF, suggesting that the sustained elevation of DG induced by PAF is primarily a reflection of PLC. 3H-glycerol pulse-labeling experiments suggest that PAF also stimulates de novo phospholipid synthesis which also contributes to PA formation. Conclusive proof for PLD in the generation of PA was obtained by assessing the formation of 3H-phosphatidyl-ethanol (PEt) from 3H-alkyl-lyso-glycero phosphocholine (GPC) and exogenous ethanol. PAF stimulated alkyl-PEt generation in the presence but not the absence of 0.5% ethanol. Also, PAF induced a concomitant elevation of alkyl-PA at 15 minutes and this elevation of alkyl-PA was reduced when the cells were exposed to exogenous ethanol, reflecting the formation of PEt. Corroborating evidence suggests that PAF stimulates 3H-choline and 3H-ethanolamine release, suggesting that PtdCho and PtdEth are substrates for PLD. Thus, these data demonstrate that MC respond to PAF with elevated PLD and DG kinase activities as well as with an increased rate of de novo lipid synthesis which increases PA, a potential intracellular signal.

Animals↗
PubMed1982

Diglyceride kinase from Escherichia coli. Modulation of enzyme activity by glycosphingolipids.

Diglyceride kinase was purified from membranes of Escherichia coli K-12 using organic solvents. The enzyme apoprotein depended on lipids, such as cardiolipin (diphosphatidylglycerol), phosphatidylcholine or 1-monooleoylglycerol, for activity with 1,2-dipalmitoylglycerol. Mixed brain cerebrosides and gangliosides as well as defined ganglioside fractions and synthetic lactocerebroside were devoid of lipid cofactor activity. However, all these glycosphingolipids were strong inhibitors of activation by phosphatidylcholine. When cardiolipin was used as lipid activator with the detergent, Triton X-100, as solubilizing agent, the addition of mixed or purified gangliosides first (at about 0.4 mM) resulted in additional activation, but higher ganglioside concentrations were strongly inhibitory. Both effects were absolutely dependent on the presence of lipid-bound sialic acid and were not given by cerebrosides, by free sialic acid or by sialyl-lactose. The stimulating and inhibitory effects of glycosphingolipids could also be demonstrated when 1-monooleoylglycerol was used as substrate, lipid activator and solubilizing agent at the same time. The modulation of kinase activity by glycosphingolipids is discussed at the level of lipid/protein interactions.

Cardiolipins↗
PubMed1984

Absence of diglyceride kinase activity in the photoreceptor cells of Drosophila mutants.

Diglyceride kinase (DG) activity was found to be almost absent in the photoreceptor cells of Drosophila vision mutants, norpA (no receptor potential A). Other enzymes related to the phosphatidic acid (PA) metabolism, such as monoacyl-glycerophosphate acyltransferase and PA phosphatase, were normal in the mutant. The deficiency in PA content in the retinular cells of norpA, demonstrated by 32P incorporation in vivo is, therefore, due to abnormal reduction in DG kinase activity. The DG kinase was found to be localized in the retinular cell by assaying its activity in the mutants rdgA (receptor cells degenerated) and sine oculis (compound eyes absent).

Animals↗
PubMed1996

Cloning of the Pseudomonas aeruginosa gene encoding CDP-diglyceride synthetase.

The CDP-diglyceride synthetase (CDS)-encoding gene (cds) from Pseudomonas aeruginosa PAO1 was cloned and sequenced. The gene possessed an open reading frame of 813 bp capable of encoding a putative polypeptide of 271 amino acids (aa) (28 699 Da). The deduced aa sequence of CDS revealed a 67% similarity (45% identity) to Escherichia coli CDS.

Amino Acid Sequence↗
PubMed1991

High-performance liquid chromatographic analysis of 3'-azido-3'-deoxythymidine monophosphate diglyceride, an anti-HIV glycerophospholipid.

A reversed-phase chromatographic method is described for the analysis of an experimental anti-AIDS drug 3'-azido-3'-deoxythymidine monophosphate diglyceride (AZT-MP-DG) [J.M. Steim et al., Biochem. Biophys. Res. Commun. 171, 458-464 (1990)] [1], a phosphatidic acid derivative of AZT. Analytical conditions were based upon conventional separations of glycerophospholipid species. Where AZT-MP-DG was monitored by UV absorption, there were two wavelength maxima. The response was linear in the concentration range used in this study. The peak was characterized by absorbance ratios with a rapid scanning UV detector.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Effect of the diglyceride lipase inhibitor, RG80267, on epithelial chloride secretion induced by various agents.

We previously reported that a diglyceride lipase inhibitor, RG80267, inhibits chloride secretion stimulated by adenosine agonists, stimuli whose effects appear unrelated to cAMP, cGMP or cytosolic calcium. Here, the effect of RG80267 on Cl- secretory responses to agents which do utilize these messengers was examined. RG80267 inhibited responses to vasoactive intestinal polypeptide, forskolin (cAMP-dependent) and E. coli heat stable enterotoxin (cGMP-dependent), but not to prostaglandin E1 or cholera toxin (cAMP-dependent). RG80267 enhanced responses to histamine (calcium-dependent). The inhibitory effect of RG80267 was not due to inhibition of cAMP accumulation. Arachidonic acid release may participate in chloride secretion. Vasoactive intestinal polypeptide, but not prostaglandin E1, released radiolabel from cells preloaded with [3H]arachidonic acid. There may thus be differences between mechanisms of various cyclic nucleotide-dependent chloride secretory responses. Arachidonic acid release may modulate the extent of secretion elicited by some secretagogues.

Alprostadil↗
PubMed1966

Bacterial glycolipids. Glycosyl diglycerides in gram-positive bacteria.

1. The lipids of ten Gram-positive bacteria have been isolated and the presence in each of a glycosyl diglyceride was established. 2. The glycolipid fractions were isolated and deacylated to give water-soluble glycosides which were purified by paper chromatography. Partial structures for the glycosides have been deduced from chemical and enzymic studies. 3. Nine of the glycosides were disaccharides glycosidically linked to the 1-position of glycerol: the remaining glycoside contained a trisaccharide similarly linked to glycerol.

Bacillus subtilis↗