In vitro inhibition of lipase activity by malonaldehyde,formaldehyde and propionaldehyde

The in vitro inhibition of bovine pancreatic lipase by malonaldehyde, formaldehyde and propionaldehyde was investigated. Malonaldehyde, as sodium 3-oxy-prop-2-enal (MA-Na), was found to be the most inhibitory at pH values below 7. Its reaction with lipase appeared to be two part: the first was rapid and a function of the MA-Na concentration; the second part was slower and related linearly to the MA-Na concentration. Methanol-free formaldehyde was a much less effective inhibitor. Low concentrations (0.01 M) had little effect on lipse activity. Propionaldehyde produced the least inhibition. A break point in the reaction of propionaldehyde with lipase occurred with time. After the break point, the inhibition nearly parallelled that seen in the control. Technical Paper No. 1859, Oregon Agricultural Experiment Station, Corvallis, Oregon.     

Uptake and oxidation of malonaldehyde by cultured mammalian cells

Primary cultures of rat skin fibroblasts were used as a model system to investigate the cellular uptake and oxidation of malonaldehyde (MA). The cells were grown in a medium containing 10⁻⁵ M, 10⁻⁴ M or 10⁻³ M concentrations of [1,3-¹⁴C]MA. There was a limited, concentration-dependent uptake of MA by 24 hr (∼4% at all concentrations). The uptake of [1,2-¹⁴C]acetate by 24 hr was ∼24%; 83–89% of the¹⁴C in the MA taken up was oxidized to¹⁴CO₂ by 24 hr and ∼5% was recovered in the major lipids. Despite its low uptake and rapid oxidation to CO₂, pretreatment of the cells with 10⁻³ M MA for 24 hr produced a latent inhibition of [¹⁴C]glucose oxidation. Limited cellular uptake of MA may explain the tolerance of cells grown in culture to relatively high MA concentrations.     

Radioprotection of mice by dietary squalene

Male C3H mice were fed a diet containing 2% squalene for 14 d prior to and 30 d subsequent to exposure to 6, 7 or 8 Gy of whole body γ-irradiation (Cesium-137). After 14 d on squalene-supplemented diet, plasma and jejunal tissue squalene levels were 2X and 15X that of controls. Seven days after irradiation, total white cell counts and total lymphocyte counts were substantially depressed in a radiation dose-dependent manner. Although counts in the squalene group were consistently (18–119%) higher than those in the corresponding dietary control group, the differences between dietary groups at any single dose were not significant. Nuclear area of villus cells in the jejunum of both dietary groups was significantly reduced (20%) by day 11 post-irradiation but the nuclear area in squalene-fed mice was significantly greater (15%) than in controls, before and after irradiation. There were no differences in body weight as a function of either diet or radiation dose prior to the first observations of animal lethality. Animal survival was decreased from 100 to 0% at 30 d post-irradiation by radiation doses of 6–8 Gy, with the greatest difference between dietary groups being observed at 7 Gy (median survival times of 12 and 16 d for control and squalene groups, respectively). Overall, survival of squalene-fed mice was significantly prolonged compared with control-fed mice (P=0.0054 by censored multiple regression analysis). It is concluded that squalene conferred some cellular and systemic radioprotection to mice receiving these lethal whole-body radiation doses.     

Regulation of squalene synthetase and squalene epoxidase activities insaccharomyces cerevisiae

Squalene synthetase (EC 2.5.1.21) and squalene epoxidase (EC 1.14 99.7) activities have been measured in cell-free extracts of wild type yeast grown in aerobic and semianaerobic conditions as well as in sterol-auxotrophic mutant strains grown aerobically. The results show that both enzymes are induced resulting in an almost two- to five-fold increase in enzymatic activities in mutant strains containing limited sterol amounts and are repressed in the wild type strain cultured in anaerobiosis in excess of sterol. The results show also that squalene epoxidase is repressed by lanosterol, and that the mevalonic acid pool may regulate squalene synthetase levels. The large change in the activities of the two enzymes, depending on the sterol needs of the cells, as well as their low specific activities in comparison with those of the enzymes involved in the early stages of sterol synthesis strongly suggests that squalene synthetase and squalene epoxidase are of importance in regulating the amount of sterol synthesized by yeast.     

Modulation of platelet thromboxane and malonaldehyde by dietary vitamin E and linoleate

Thromboxane (TXB₂) and malonaldehyde (MDA) production by thrombin-stimulated washed platelet were evaluated in rats fed 6 combinations of dietary vitamin E (0, 100, 1000 ppm) and linoleate (6.5 and 17.0 en%) for 23 weeks. The molar ratio of MDA:TXB₂ was consistently near 3 in all groups studied. In animals receiving the lower linoleate diets, TXB₂ and MDA synthesis were inversely related to the dietary vitamin E concentrations and the levels of MDA and TXB₂ were positively correlated (r=0.99) with decreasing vitamin E in the diet. High dietary linoleate (17.0 en%), independent of vitamin E status, reduces TXB₂ and MDA synthesis. The importance of dietary antioxidant on platelet prostanoid synthesis is discussed.     

Preparation of malonaldehyde acetals by ozonolysis of polyunsaturated fatty esters

Malonaldehyde acetals were prepared in more than a 70% yield by ozonolysis of the methyl esters of linseed oil, safflower oil and linoleic acid, and by ozonolysis of linseed oil alone. Malonaldehyde tetramethyl acetal could not be separated readily from caproaldehyde dimethyl acetal by fractional distillation. However, conversion of the methyl acetals to propylene glycol acetals resulted in sufficient spread in boiling points for their effective separation by distillation. Presented at the AOCS Meeting, Minneapolis, 1963. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA.     

Reaction of cysteine and methionine with malonaldehyde

Malonaldehyde (M), a product of polyunsaturated fatty acid oxidation, reacted with the sulfhydryl as well as with the amino groups of cysteine (cys). The cys-M product had an absorption maximum at 310 mμ, and the extinction coefficient at pH 7.0 was 2.3 × 10⁴. Elementary analysis of the cys-M product agreed with a structure in which 2 moles of cysteine had reacted with 3 moles of malonaldehyde. The molecular weight of cys-M preparations increased on storage and the UV absorption changed from 310 to 315–320 mμ, with a consequent shift to longer wavelength in the visible. Methionine (meth) reacted with malonaldehyde under the same reaction conditions only at the α-amino group, similar to glycine (gly). The apparent pK_a of the carboxyl group of gly-M increased to 3.36 and that of meth-M to 3.19, representing an increase of about one pK_a unit over the natural amino acids. For gly-M and meth-M the respective absorption maxima were 272 and 282 mμ. The spectral shifts from 267 to 315 mμ of the amino acid-M products with respect to β-oxyacrolein were explained in terms of increasing substitution at the β-carbon of the α,β-unsaturated carbonyl system. When the α-amino-malonaldehyde condensation products of methionine and glycine reacted with semicarbazide the original amino acids and disemicarbazone of malonaldehyde were formed.     

Specific determination of malonaldehyde by N-methyl-2-phenylindole or thiobarbituric acid

Reactivity of a commercially available test kit (LPO-586), based on N-methyl-2-phenylindole, toward aldehydes was characterized and compared with that of thiobarbituric acid (TBA). In hydrochloric acid, LPO-586 produced a violet pigment with malonaldehyde (MA) but not with other tested aldehydes. In methane sulfonic acid, LPO-586 produced the violet pigment with MA and 4-hydroxynonenal (HNE), but not with other tested aldehydes. Pigment formation with MA was not inhibited by other aldehydes, but that with HNE was inhibited by alka-2,4-dienals. TBA produced a red pigment with MA but not with other tested aldehydes in hydrochloric acid or in acetate with ethylenediaminetetraacetic acid (EDTA). Both the LPO-586 test in hydrochloric acid and the TBA test in hydrochloric acid or in acetate with EDTA can be used for specific measurement of MA in oxidized lipid samples.     

Urea formaldehyde resin with low formaldehyde content modified by phenol formaldehyde intermediates and properties of its bamboo particleboards

Phenol formaldehyde reaction solution (PFS) was used to synthesize urea–formaldehyde resins (PFSUF resins) with low formaldehyde content. In addition, the prepared PFSUF resins were used as adhesives to bond bamboo particleboards. Mechanical properties, fracture morphology, water absorption ratio, and dimensional stability of bamboo particleboards have been studied by tensile tests, SEM tests, water absorption analysis, and swelling ratio analysis, respectively. The results demonstrate that the main ingredient of PFS is phenol formaldehyde intermediate 2,4,6‐trimethylolphenate and proper amount of PFS can be used to reduce the formaldehyde content of UF resins effectively. The results also show that bamboo particleboards bonded with PFSUF resins exhibit better mechanical properties, water resistance, and dimensional stability than that bonded with pure UF resin. However, the results of TG and mechanical properties analysis exhibit that alternative curing agents to ammonium chloride should be studied to improve the curing properties of the PFSUF resins with low formaldehyde content. Taken together, this work provides a method of preparing environment‐friendly PFSUF resins with low phenol and low formaldehyde content and the prepared resins have potential application in wood industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42280.     

Metabolism of malonaldehyde in vivo and in vitro

The metabolism of malonaldehyde (MA) was investigated in vivo using male Wistar rats and in vitro using rat liver mitochondria. Twelve hr after intubation with [1,3-¹⁴C] MA, 60–70%, 5–15% and 9–17% of administered radioactivity was recovered in expired CO₂, feces and urine, respectively. In rats intubated with [1,2-¹⁴C] acetate, the corresponding values were 68–82%, 1–2% and 2–3%.¹⁴CO₂ evolution was initially slower after¹⁴C-MA administration than after¹⁴C-acetate administration and more radioactivity was excreted in the feces and urine. In vitro experiments using [1,3-¹⁴C] MA showed that MA is metabolized primarily in the mitochondria via reactions involving O₂ utilization and¹⁴CO₂ production. The apparent K_m and V_max were 0.5 mM and 9.3 nmol/min/mg protein for O₂ uptake, respectively, and 2.0 mM and 2.4 nmol/min/mg protein for¹⁴CO₂ production. Addition of malonic acid to mitochondrial incubates at concentrations inhibitory to succinate dehydrogenase did not affect MA-induced O₂ uptake but enhanced¹⁴CO₂ production from¹⁴C-MA.¹⁴C-Acetate appeared to be the major accumulating metabolite in rat liver mitochondrial preparations following a 120-min incubation with¹⁴C-MA. A probable biochemical route for MA metabolism involves oxidation of MA by mitochondrial aldehyde dehydrogenase followed by decarboxylation to produce CO₂ and acetate.     

Surface modification of polypropylene by a combination of photooxidation and photosubstitution reactions

An efficient photoprocess has been developed to increase polypropylene surface wettability by insertion of acid, ester, and amide functionalities. A systematic study of polypropylene surface irradiations indicates that photoxidations always precede the photosubstitution reactions that occur at the carbonyl site to form carboxyl, ester, and amide groups. Irradiations with amines to form amide groups always achieved the highest level of wettability improvement without changing bulk morphology. This process may be very beneficial in facilitating the fabrication of composite membranes with hydrophilic barriers on top of a hydrophobic polymeric support such as polypropylene. The high chemical resistance of polypropylene matrix to various solvents makes the partially hydrophilized polypropylene an ideal membrane support when hydrophilic membrane barriers made by interfacial polymerization/crosslinking are needed for a variety of separation application. © 1995 John Wiley & Sons, Inc.     

Inhibition of malonaldehyde formation by antioxidants from ω3 polyunsaturated fatty acids

The inhibitory effect of α-tocopherol, β-carotene, 2″-O-glycosyl isovitexin (2″-O-GIV), and butylated hydroxytoluene (BHT) on malonaldehyde (MA) formation from ω3 polyunsaturated fatty acids (PUFA) was determined by gas chromatography. The levels of MA formed from 1 mg each of octadecatetraenoic acid (ODTA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) upon oxidation with Fenton's reagent were 29.8±1.5, 17.2±1.5, and 22.0±0.7 nmol, respectively. BHT was most effective toward protecting all three ω3 PUFA, whereas β-carotene did not exhibit any inhibitory effect. 2″-O-GIV inhibited MA formation from EPA and DHA by 56 and 43%, respectively, showing the second greatest inhibitory activity after BHT. α-Tocopherol inhibited MA formation from ODTA and DHA by 67 and 28%, respectively, but it did not show any activity toward EPA oxidation. The naturally occurring antioxidant, 2″-O-GIV, may be useful to prevent oxidation of ω3 PUFA.     

Stimulation of hepatic squalene and triglyceride synthesis by dimethylsulfoxide,in vitro

The incorporation of [¹⁴C] mevalonate and [¹⁴C] acetate into squalene by rat liver slices was increased over 7-fold by the presence of 5% dimethylsulfoxide (DMSO) in the incubation medium. The stimulation of squalene synthesis was dose-related over the concentration range of 1–5% DMSO and did not affect the incorporation of [¹⁴C] mevalonate, into the C₂₇-sterol fraction (cholesterol) but did increase (about 50%) incorporation into C₃₀-sterol (lanosterol) at a level, of 5% DMSO. The stimulation of squalene synthesis was observed under both anaerobic (N₂ atmosphere) and aerobic (ambient air or 95% O₂/5% CO₂) conditions and may represent a direct effect of DMSO on squalene synthetase. At a level of 5%, DMSO also stimulated 7-fold the incorporation of [¹⁴C] acetate into triglycerides by liver slices; this occurred without changes in incorporation into the phospholipid or free fatty acid fractions. The disproportionate increase in lipid labeling from [¹⁴C] acetate suggests that the effects of DMSO are not simply a matter of increasing [¹⁴C] acetate entry into the tissue.     

Blends of nylon 6 with a polyethylene functionalized by photooxidation

An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved by chemical modification of the polyolefines chains. This step could be very expensive.     

Heterogeneous photooxidation of solid polymers

Photooxidation of polymer can undergo heterogeneous effects, a complication which impacts attempts to extrapolate artificial accelerated tests to natural outdoor exposures. The main cause of heterogeneous degradation results from oxygen diffusion-limited effects. Several experimental techniques can be used to monitor macroscopic heterogeneous oxidation in polymers. These techniques are based on i.r. spectroscopy: micro FTi. r. spectroscopy permits to determine oxidation profiles in polymer materials till a resolution around 10 microns and photoacoustic (PAS) -FTi. r. spectroscopy is an interesting method for analyzing the oxidation of the surface layers.     

Inhibition of rat hepatic sterol formation from squalene by plasma lipoproteins

The conversion of³H-squalene to sterols by rat liver microsomes and cytosol was inhibited by individual rat and human plasma lipoproteins at various concentrations. This inhibition was also observed with added human high density apolipoprotein, but triglycerides, cholesterol or cholesteryl esters had no inhibitory effects. Lipoproteins and apo high density lipoprotein (HDL) were demonstrated to bind³H-squalene in vitro. The binding of³H-squalene by apo HDL could be reversed by increasing concentration of liver cytosol containing sterol carrier protein.