Decreased photosynthetic rate under high temperature in wheat is due to lipid desaturation, oxidation, acylation, and damage of organelles.

BACKGROUND: High temperature is a major abiotic stress that limits wheat (Triticum aestivum L.) productivity. Variation in levels of a wide range of lipids, including stress-related molecular species, oxidative damage, cellular organization and ultrastructural changes were analyzed to provide an integrated view of the factors that underlie decreased photosynthetic rate under high temperature stress. Wheat plants of cultivar Chinese Spring were grown at optimum temperatures (25/15 °C, maximum/minimum) until the onset of the booting stage. Thereafter, plants were exposed to high temperature (35/25 °C) for 16 d. RESULTS: Compared with optimum temperature, a lower photosynthetic rate was observed at high temperature which is an interplay between thylakoid membrane damage, thylakoid membrane lipid composition, oxidative damage of cell organelle, and stomatal and non-stomatal limitations. Triacylglycerol levels were higher under high temperature stress. Polar lipid fatty acyl unsaturation was lower at high temperature, while triacylglycerol unsaturation was the same at high temperature and optimum temperature. The changes in lipid species indicates increases in activities of desaturating, oxidizing, glycosylating and acylating enzymes under high temperature stress. Cumulative effect of high temperature stress led to generation of reactive oxygen species, cell organelle and membrane damage, and reduced antioxidant enzyme activity, and imbalance between reactive oxygen species and antioxidant defense system. CONCLUSIONS: Taken together with recent findings demonstrating that reactive oxygen species are formed from and are removed by thylakoid lipids, the data suggest that reactive oxygen species production, reactive oxygen species removal, and changes in lipid metabolism contribute to decreased photosynthetic rate under high temperature stress.

Sensitivity of sorghum pollen and pistil to high-temperature stress.

High temperature (HT) decreases seed set percentage in sorghum (Sorghum bicolor [L.] Moench). The relative sensitivity of pollen and particularly pistil and the mechanistic response that induces tolerance or susceptibility to HT are not well known and hence are the major objectives of this research. The male sterile (ATx399) and fertile (RTx430) lines were exposed to 30/20 °C (optimum temperature), 36/26 °C (HT1 ), and 39/29 °C (HT2 ) from the start of booting to seed set in a controlled environment. Similarly, in the field, HT stress was imposed using heat tents. HT stress decreased pollen germination. Relatively high levels of reactive oxygen species and decreased antioxidant enzyme activity and phospholipid unsaturation were observed in pollen compared to pistil under HT. The severe cell organelle damage was observed in pollen and pistil at 36/26 and 39/29 °C, respectively. The seed set percentage was higher in HT-stressed pistil pollinated with optimum-temperature pollen. Direct and reciprocal crosses indicate that pollen was more sensitive with larger decreases in seed set percentage than pistil under HT stress. The negative impact was greater in pollen than pistil at lower temperatures. Overall, pollen was more sensitive than pistil to HT stress because it is more susceptible to oxidative damage than pistil.

Oral health messages for Australia: A national consensus statement.

BACKGROUND: Oral health promotion initiatives must be evidence-based and consistent with broader health messaging. The Oral Health Messages for the Australian Public were first produced in 2009 and sought to enable a focused, and strategic approach to oral health promotion in Australia. As the evidence base and needs of the Australian population have since changed, this consensus statement was updated in 2022-2023. METHODS: The process of updating the messages consisted of 3 phases (preparatory phase, the Delphi technique, final revision phase). The preparatory phase included public and expert consultation, an umbrella review of published scientific literature and review of available recommendations, policies and guidelines. The Delphi technique used in this study was guided by Guidance on Conducting and REporting DElphi Studies (CREDES) and included 2 voting rounds. There were 70 experts in round 1 and 60 experts in round 2. Delphi participants comprised of experts from a variety of fields to ensure diversity and inclusion, balance expertise and maximize stakeholder representation. Consensus was defined as 75% agreement. RESULTS: A total of 11 messages were included in the 2022 update of Oral Health Messages for Australia. CONCLUSION: The updated oral health messages will support oral health promotion policy and activity at both individual and population level to improve the oral health of Australians.

Arrangement of phosphatidylethanolamine molecular species in Escherichia coli membranes and reconstituted lipids as determined by dimethyl suberimidate cross-linking of nearest neighbor lipids.

Dimethylsuberimidate cross-linking has been used to determine the arrangement of phosphatidylethanolamine (PE) molecular species in Escherichia coli membranes. No large deviations from random mixing were found in wild-type strain AB1623, either in whole cells or in extracted lipids which were reconstituted into multilamellar vesicles. These results suggest, first, that there is little difference in the PE molecular species composition of the three lipid monolayers (the inner and outer monolayers of the inner membrane and the inner monolayer of the outer membrane) which contain significant amounts of PE. Secondly, the results suggest that the molecular species within each monolayer and in the extracted lipids are arranged close to randomly with no tendency for like molecular species to cluster. E. coli strain L8-2, which has a defect in beta-oxidation and a temperature-sensitive mutation in total fatty acid synthesis, was grown on cis-vaccenate (cis-11,12- octadecenate) to enrich the cells in divaccenoyl PE. Again, in whole cells or in lipids extracted from whole cells and reconstituted into multilamellar vesicles, the species were close to randomly arranged. However, a consistent, slight tendency of divaccenoyl species to pair with like species as compared to pairing with the second most common species, vaccenoyl, palmitoleoyl PE, was noted in both extracted lipids and in whole cells.

Lipid arrangement in fluid model membranes: analysis by cross-linking of phosphatidylethanolamines.

Binary mixtures of fluid phase phosphatidylethanolamines at pH 10 were treated with the bifunctional cross-linking reagent dimethylsuberimidate. Analysis of the dimeric species formed demonstrated that the phospholipid species in dimyristoylphosphatidylethanolamine/dielaidoylphosphatidylethanolamine mixtures at 52 degrees C and dielaidoylphosphatidylethanolamine/dilauroylphosphatidylethanolamine mixtures at 41 degrees C were randomly arranged. Analysis of the dimeric species formed in dipalmitoylphosphatidylethanolamine/dioleoylphosphatidylethanolamine mixtures at 68 degrees C showed that this mixture was very close to being randomly arranged, with just a slight propensity of like phospholipid species to cluster.

Membrane penetration depth and lipid phase preference of acyl-labeled dansyl phosphatidylcholines in phosphatidylcholine vesicles.

The dansyl fluors of 1-oleoyl-2-[4-(dansyl)amino]butyl]-sn-glycero-3-phosphocholine (18:1,4-dansyl PC) and 1-palmitoyl-2-[1-[(dansyl)amino)]undecanoyl]-sn-glycero-3-phosphoc holine (16:0,11-dansyl PC) were shown to reside at similar depths in phosphatidylcholine vesicles at pH 7. Analysis of fluorescence emission maxima showed that the dansyl groups of both 18:1,4-dansyl PC and 16:0,11-dansyl PC in phosphatidylcholine vesicles experienced environments more polar than methanol, suggesting that the dansyl group attached to the terminus of the undecanoyl chain must fold back toward the bilayer surface. Fluorescence polarization measurements in solid/fluid lipid mixtures show that both probes partition strongly into fluid phase lipid. The very low polarization values of 16:0,11-dansyl PC in lipid vesicles are consistent with the notion that the dansyl fluor of 16:0,11-dansyl PC existed in an environment allowing a high degree of motional freedom due to folding back of the dansyl group attached to the undecanoyl chain.

Partition of parinaroylphosphatidylethanolamines and parinaroylphosphatidylglycerols in immiscible phospholipid mixtures.

Partitioning of two parinaroyl phosphatidylethanolamines and two parinaroyl phosphatidylglycerols between solid and fluid phase phospholipids was examined. Fluorescence quantum yields and fluorescence polarization measurements were used to calculate Ks/fp, the solid to fluid partition coefficient of each probe (Sklar, L.A., Miljanich, G.P. and Dratz, E.A. (1979) Biochemistry 18, 1707-1716). In the immiscible mixture dipalmitoylphosphatidylcholine and dilinoleylphosphatidylcholine, both 1-palmitoyl-2-trans-parinaroylphosphatidylethanolamine and 1-palmitoyl-2-transparinaroylphosphatidylglycerol partitioned preferentially into solid phase lipid with mean Ks/fp values (calculated from quantum yields) of 3.4 +/- 1.5 and 2.1 +/- 0.7, respectively. In contrast, 1-oleoyl-2-cis-parinaroylphosphatidylethanolamine and 1-oleoyl-2-cis-parinaroylphosphatidylglycerol partitioned preferentially into fluid phase lipid in the same model system with mean Ks/fp values (calculated from quantum yields) of 0.44 +/- 0.26 and 0.16 +/- 0.07, respectively. Fluorescence polarization data on the same four parinaroyl phospholipids in mixtures of solid-phase dimyristoylphosphatidyl ethanolamine and fluid-phase dilinoleoylphosphatidylglycerol were similar to those obtained in the immiscible phosphatidylcholine system, demonstrating that the partitioning of these probes is not strongly dependent on head group. Knowledge of the partition properties of these fluorescent probes is relevant to use of these probes in investigation of the phase behavior of Escherichia coli inner membrane lipids, since phosphatidylethanolamine and phosphatidylglycerol species account for approximately 95% of these lipids.

Cross-linking of phosphatidylethanolamine neighbors with dimethylsuberimidate is sensitive to the lipid phase.

Dimethylsuberimidate was reacted with aqueous dispersions of dipalmitoylphosphatidylethanolamine, dimyristoylphosphatidylethanolamine, dilauroylphosphatidylethanolamine, and dielaidoylphosphatidylethanolamine at pH 10 and at pH 8. The amount of amidine dimer formation was about four times greater above the gel-to-fluid phase transition of each lipid than below the transition. The transition temperature of each phosphatidylethanolamine, measured by steady-state fluorescence anisotropy of cis-parinaric acid, was lower at pH 10 than at pH 8 or in water. The ability of dimethylsuberimidate to discriminate between phosphatidylethanolamines in the fluid and gel phases should allow use of this reagent to identify phosphatidylethanolamine species within the gel or fluid lipid phase.

In vivo substrates and the contribution of the common phospholipase D, PLDalpha, to wound-induced metabolism of lipids in Arabidopsis.

The common plant phospholipase D (PLD), PLDalpha, has been proposed to be involved in wound-induced production of jasmonic acid. To better understand the role(s) of PLDalpha in the wound response, detailed lipid analysis was carried out to determine the in vivo substrates and the contribution of PLDalpha in wound-induced lipid metabolism in Arabidopsis thaliana. Mechanical wounding of Arabidopsis leaves resulted in significantly less hydrolysis of phosphatidylcholine (PC) in PLDalpha-deficient than in wild-type plants. Hydrolysis of phosphatidylethanolamine, phosphatidylglycerol (PG), and phosphatidylinositol within 30 min of wounding was not significantly different in PLDalpha-deficient and wild-type leaves. Phosphatidic acid (PA) levels increased rapidly in wild-type and, to a lesser extent, in PLDalpha-deficient plants. The acyl composition of the PA generated by wounding suggests that the major in vivo substrate of PLD in wild-type leaves was PC, and that PG hydrolysis accounted for 10-15% of the wound-induced PA in wild-type leaves. Comparison of the acyl compositions of the wound-induced PA of wild-type and PLDalpha-deficient leaves indicated that PLDalpha hydrolyzed PG more readily than other PLD isoforms did. Wounding produced substantial increases in free linoleic and linolenic acids in wild-type plants, whereas PLDalpha-deficient plants showed only a slight increase in linoleic acid and no significant increase in linolenic acid. These results demonstrate that PLDalpha and at least one other PLD isoform, as well as other hydrolytic enzymes, are active in mechanically wounded Arabidopsis leaves, and PLDalpha is involved in wound-induced metabolism of polyunsaturated fatty acids.

Phase behavior and arrangement of molecular species in mixtures of a mixed chain and a symmetric phosphatidylethanolamine in the gel and fluid phases.

1-Octadecanoyl, 2-decanoylphosphatidylethanolamine (C(18:0)C(10:0)PE) has been reported to exhibit mixed interdigitated gel-phase packing of the phospholipid acyl chains (Mason, J.T. and Stephenson, F.A. (1990) Biochemistry 29, 590-598). In contrast, ditetradecanoylphosphatidylethanolamine (C(14:0)C(14:0)PE) packs without significant interdigitation of the phospholipid acyl chains across the bilayer center. In this report, the gel-fluid transition temperatures of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in multilamellar dispersions were determined by fluorescence anisotropy of cis-parinaric acid and trans-parinaric acid with a descending temperature scan rate of 0.67 degrees C/min. The transition mid-points detected for C(18:0)C(10:0)PE with cis-parinaric acid were 19 degrees C in water, 18 degrees C at pH 8.1, and 14 degrees C at pH 10. The phase diagram for C(14:0)C(14:0)PE and C(18:0)C(10:0)PE at pH 10 suggests complete mixing in the fluid phase and considerable immiscibility in the gel phase. Cross-linking of equimolar mixtures of C(14:0)C(14:0)PE and C(18:0)C(10:0)PE with dimethylsuberimidate at pH 10 revealed a random arrangement of the two species in the fluid phase, confirming the notion that C(18:0)C(10:0)PE and C(14:0)C(14:0)PE are miscible in the fluid phase, as determined from the phase diagram. In contrast, cross-linking of the equimolar mixture of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in the gel phase at 0 degrees C revealed a non-random arrangement, demonstrating and confirming immiscibility in the gel phase.

Conformational analysis in solution of C(2)-symmetric 1, 1'-binaphthyl derivatives by circular dichroism spectroscopy and cholesteric induction in nematic mesophases

The twisting ability of a series of 1,1'-binaphthalene compounds used as dopants in nematic solvents has been related to the dihedral angle theta between the two naphthalene moieties. While in the case of the more flexible compounds the sign and value of the helical twisting power is affected by several structural features that prevent a simple assignment of the conformation, in the presence of a covalent bridge that restricts the rotation around the C(1)-C(1') bond a reliable estimate of the conformational helicity could be obtained. This technique is complementary to CD spectroscopy that, for the investigated molecules, presents the same exciton patterns irrespective of the actual theta value.

Lipid domains in model and biological membranes.

Lipid domains that occur within biological of model membranes encompass a variety of structures with very different lifetimes. The separation of membrane lipids into compositional domains can be due to lateral phase separation, immiscibility within a single phase, or interaction of lipids with integral or peripheral proteins. Lipid domains can affect the extent and rate of reactions in the membrane and provide sites for the activity of specialized proteins. Domains are likely to be involved in the process of lipid sorting to various cellular membranes, as well as in other processes which involve membrane budding or invagination.

Analysis of dimeric species derived from the reaction of phosphatidylethanolamine with dimethylsuberimidate.

Phosphatidylethanolamines of various fatty acyl species in vortexed lipid dispersions were reacted with dimethylsuberimidate to produce dimeric products. The yield was 34% at pH 10 and 2% at pH 7. The crosslinked phosphatidylethanolamine species were separated from minor products and the reactants by extraction and two-dimensional thin-layer chromatography on silica gel G, gel filtration on lipophilic Sephadex, or C18-reversed phase high-performance liquid chromatography (HPLC). Reversed phase HPLC was also used to resolve the dimers into individual molecular species. Analysis of the dimers revealed the extinction coefficients at 205 nm to be higher than those of the reactant phosphatidylethanolamines. Proton nuclear magnetic resonance spectroscopy and chemical analysis implied that the dimers contain an amidine group.

Coronary artery bypass grafting in patients 70 years of age and older. Early and late results.

Ninety-four patients 70 years of age and older underwent coronary artery bypass grafting (CABG) between 1979 and 1985. Thirty-two percent were females. An internal mammary artery was used in 49% and concomitant cardiac procedures were performed in 51% of the operations. Early mortality was 12%. Five of 11 early deaths were from non-cardiac causes: ascending aortic disease (2), cerebral damage (2) and septicaemia (1). Postoperative morbidity included neurological complications in 16%, reoperation for bleeding in 12%, mediastinitis or sternal dehiscence in 4% and perioperative acute myocardial infarction in 4%. At follow-up, a median of 2.5 years after surgery, 83% were completely free from angina, 5% much improved, 9% improved and 3% had unchanged symptoms of angina. Actuarial survival, inclusive of early mortality, was 84% at 3 years. Female sex and concomitant cardiac surgery were common in elderly patients who had CABG. Early mortality from noncardiac causes and postoperative morbidity were increased but dramatic relief of symptoms was achieved in the majority of survivors.

Role of albumin as a fatty acid carrier for biosynthesis of lens lipids.

Although serum albumin is the major protein component of the aqueous humor and vitreous humor, its possible physiological role(s) in lens metabolism has not yet been determined. BODIPY fatty acid, a fluorescent analogue of a C(12) long chain fatty acid, was bound to serum albumin, then incubated with lenses in culture. After various times of incubation, the lenses were homogenized, lipids extracted, and the extracted lipids resolved by thin layer chromatography. Fluorescence analyses demonstrated that the BODIPY fatty acid--albumin complex was translocated into the lens, where the BODIPY fatty acid was incorporated in a time dependent manner into numerous lipids, including phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin. Together, the results strongly suggest that serum albumin in the aqueous humor and/or vitreous humor facilitates the translocation of long chain fatty acids into the lens, where they are used for the biosynthesis of lens lipids.

Partition of parinaroyl phospholipids in mixed head group systems.

Partitioning of 1-palmitoyl-2-cis-parinaroylphosphatidylcholine, 1-palmitoyl-2-cis-parinaroylphosphatidylethanolamine, 1-oleoyl-2-trans-parinaroylphosphatidylcholine, and 1-oleoyl-2-trans-parinaroylphosphatidylethanolamine between solid-phase phosphatidyelthanolamine and between solid-phase phosphatidylcholine and fluid-phase phosphatidylethanolamine is investigated. The partitioning of these probes is shown to be nearly independent of their head group. Fluorescence polarization of the above probes plus trans-parinaric acid, cis-parinaric acid, 1-palmitoyl-2-trans-parinaroylphosphatidylcholine, 1-oleoyl-2-cis-parinaroylphosphatidylcholine, and 1-oleoyl-2-cis-parinoylphosphatidylethanolamine is examined in phospholipids isolated from LM cell (mouse fibroblast) plasma membranes. A fraction of these phospholipids undergoes a gel-liquid-crystalline phase transition beginning near the physiological temperature. The parinaroyl probes with the highest solid-fluid-phase partition coefficients [Welti, R., & Silbert, D. F. (1982) Biochemistry (preceding paper in this issue)] detect the transition most readily. The degree of response to this transition also appears to depend on the acyl chains of the parinaroyl phospholipid rather than the probe head group. This is further demonstrated with the phosphatidylcholine and phosphatidylethanolamine fractions from LM cell plasma membranes.

Acyl chain specificity of phosphatidylcholine transfer protein from bovine liver.

The specificity of bovine liver phosphatidylcholine transfer protein for various phosphatidylcholine (PC) molecular species was examined at 37 degrees C. The amount of transfer between donor and acceptor vesicles of defined phospholipid composition was determined. Protein-mediated transfer between vesicles of long chain, fluid phase PCs (di-16:1 PC, di-17:1 PC, di-18:1 PC, di-18:2 PC, or egg PC) was markedly higher than transfer between vesicles of solid phase or short chain, fluid phase PCs (di-18:0 PC, di-16:0 PC, or di-14:0 PC). When di-14:0 PC and di-18:1 PC were present in the same vesicle, protein-mediated transfer of di-18:1 PC was still higher, indicating that the protein's specificity toward long chain, fluid phase PCs is based on true acyl chain structure preference rather than a bulk phase physical property of the longer chain PCs. The effect of adding a third type of vesicle to a system which consisted of transfer protein, donor vesicles, and acceptor vesicles was investigated. Addition of solid phase PC vesicles does not affect transfer of the well transferred species, while addition of the poorly transferred short chain, fluid phase PCs does inhibit transfer. These results suggest that the transfer protein has the ability to bind to any fluid phase PC vesicle, although it preferentially extracts and transfers long chain, fluid phase PCs.

Thermotropic behavior of mixtures of glycosphingolipids and phosphatidylcholine: effect of monovalent cations on sulfatide and galactosylceramide.

The thermotropic behavior of both sulfatide (3-sulfogalactosylceramide) and galactosylceramide in dielaidoylphosphatidylcholine (DEPC) liposomes was studied, using steady-state fluorescence polarization of parinaric acid isomers. The glycosphingolipid (GSL) concentration of the liposomes was varied from 0 to 100%, and phase diagrams were constructed. The data indicate that sulfatide and DEPC are immiscible in the gel phase at sulfatide mole ratios of less than 0.30. The temperature of onset of the gel-liquid-crystalline phase transition is higher in K+ -containing buffer than in osmotically equal Na+ -containing buffer. Similar measurements, using galactosylceramide, a neutral GSL, indicated that this lipid and DEPC are immiscible in the gel phase at galactosylceramide mole ratios of less than 0.40. In contrast to the results obtained with sulfatide, onset temperatures are identical in Na+- or K+-containing buffers. The phase properties of sulfatide/DEPC mixtures are shown to depend on the cation only when the sulfatides contain hydroxy fatty acids. Our observations indicate that physiologically relevant concentrations of monovalent cations affect motion and distribution of sulfatide in biological membranes and further implicate this GSL as an important determinant of function of the Na+,K+-ATPase. A preliminary report of these data [Rintoul, D.A., Welti, R., & Song, W. (1988) Biophys. J. 53, 126a].

Partition of parinaroyl phospholipid probes between solid and fluid phosphatidylcholine phases.

The partitioning of parinaroyl phospholipid probes between solid- and fluid-phase phospholipid is examined. The immiscible model system dipalmitoylphosphatidylcholine and palmitoyldocosahexaenoylphosphatidylcholine is used. Fluorescence quantum yields and fluorescence polarization are used to calculate Kps/f, the solid to fluid phase partition coefficient of each probe [Sklar, L. A., Miljanich, G. P. & Dratz, E. A. (1979) Biochemistry 18, 1707-1716]. Like free trans-parinaric acid (9,11,13,15-all-trans-octadecatetraenoic acid) 1-palmitoyl-2-trans-parinaroylphosphatidylcholine and 1-palmitoyl-2-tra-parinaroylphosphatidylethanolamine partition strongly into solid phase with mean Kps/fs of 7 +/- 4 and 9 +/- 5, respectively. Like free cis-parinaric acid (9,11,13,15-cis-trans,trans,cis-octadecatetraenoic acid), another group of phospholipid probes prefer fluid phase just slightly or partition equally between fluid and solid phases. The Kps/f of 1-palmitoyl-2-cis-parinaroylphosphatidylcholine is 0.6 +/- 0.2, that of 1-palmitoyl-2-cis-parinaroylphosphatidylethanolamine is 1.0 +/- 0.3, that of 1-oleoyl-2-trans-parinaroylphosphatidylcholine is 0.6 +/- 0.3, and that of 1-oleoyl-2-trans-parinaroylphosphatidylethanolamine is 0.7 +/- 0.3. Two probes partition more strongly into fluid-phase phospholipid. These are 1-oleoyl-2-cis-parinaroylphosphatidylcholine with a Kps/f of 0.2 +/- 0.1 and 1-oleoyl-2-cis-parinaroylphosphatidylethanolamine with a Kps/f of 0.4 +/- 0.4.