Sterols in seeds and leaves of oats (Avena sativa L.)

In seeds and leaves of oats (Avena sativa L.) 12 different sterols (cholesterol, cholstanol, ⁷-cholestenol, campesterol, campestanol, stigmasterol, lophenol, sitosterol, stigmastanol, ⁵-avenasterol, ⁷-avenasterol and ⁷-stigmastenol) have been identified. The sterol pattern is qualitatively the same, but the relative composition is different in leaves and in seeds. Leaves contain mainly sitosterol, stigmasterol, cholesterol and campesterol, but only minor portions of avenasterols. Seeds contain sitosterol, ⁵- and ⁷-avenasterol, campesterol, but only minor amounts of stigmasterol and cholesterol. In leaf lipids 1-hexacosanol (2.35 wt % of total lipid) has also been identified.     

Average phase difference theory and 1∶1 phase entrainment in interlimb coordination

The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency _c was varied by a metronome, and scaled to the eigenfrequency _v of the coupled system K was assumed to vary inversely with _c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is _c/_v rather than _c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.     

Electrochemical potential of protons in vesicles reconstituted from purified,proton-translocating adenosine triphosphatase

Summary Measurements were made of the difference in the electrochemical potential of protons ( ) across the membrane of vesicles reconstituted from the ATPase complex (TF ₀ ·F ₁) purified from a thermophilic bacterium and P-lipids. Two fluorescent dyes, anilinonaphthalene sulfonate (ANS) and 9-aminoacridine (9AA) were used as probes for measuring the membrane potential () and pH difference across the membrane ( pH), respectively.In the presence of Tris buffer the maximal and no pH were produced, while in the presence of the permeant anion NO ₃ ^– the maximal pH and a low were produced by the addition of ATP. When the ATP concentration was 0.24mm, the was 140–150 mV (positive inside) in Tris buffer, and the pH was 2.9–3.5 units (acidic inside) in the presence of NO ₃ ^– . Addition of a saturating amount of ATP produced somewhat larger and pH values, and the attained was about 310 mV.By trapping pH indicators in the vesicles during their reconstitution it was found that the pH inside the vesicles was pH 4–5 during ATP hydrolysis.The effects of energy transfer inhibitors, uncouplers, ionophores, and permeant anions on these vesicles were studied.     

Effects of competition and N and P supply on carbon isotope discrimination and <Superscript>15</Superscript>N-natural abundance in four grassland species

The effect of interspecific competition and element additions (N and P) on four grassland species (Poa pratensis, Lolium perenne, Festuca valida, Taraxacum officinale) grown under field conditions was studied. Two grasses (L. perenne, F. valida) grown in monoculture (absence of competition) showed lower carbon isotope discrimination (¹³C) and enriched ¹⁵N values. Nitrogen addition (as urea) had inconsistent effects on species ¹³C while caused enrichment of ¹⁵N of P. pratensis and F. valida but strong depletion of ¹⁵N of T. officinale. Phosphorous had no significant effect on ¹³C but depleted ¹⁵N of all species.     

Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela

Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (), hydrogen isotope ratio (D) and N-levels, and with altitude were assessed. In the samples, where values of above 15 indicate predominant performance of C₃ photosynthesis, there were slight tendencies of increasing , D and N-levels with increasing altitude and of increasing with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of with altitude in the samples, where values of below 10 indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C₃-CAM transitions in C₃/CAM intermediate species, low availability of water is the most important.     

The ability of acidic pH,growth inhibitors,and glucose to increase the proton motive force and energy spilling of amino acid-fermenting <Emphasis Type="Italic">Clostridium sporogenes</Emphasis> MD1 cultures

Clostridium sporogenes MD1 grew rapidly with peptides and amino acids as an energy source at pH 6.7. However, the proton motive force (p) was only –25 mV, and protonophores did not inhibit growth. When extracellular pH was decreased with HCl, the chemical gradient of protons (ZpH) and the electrical membrane potential () increased. The p was –125 mV at pH 4.7, even though growth was not observed. At pH 6.7, glucose addition did not cause an increase in growth rate, but increased to –70 mV. Protein synthesis inhibitors also significantly increased . Non-growing, arginine-energized cells had a of –80 mV at pH 6.7 or pH 4.7, but was not detected if the F₁F₀ ATPase was inhibited. Arginine-energized cells initiated growth if other amino acids were added at pH 6.7, and and ATP declined. At pH 4.7, ATP production remained high. However, growth could not be initiated, and neither nor the intracellular ATP concentration declined. Based on these results, it appears that C. sporogenes MD1 does not need a large p to grow, and p appears to serve as a mechanism of ATP dissipation or energy spilling.Mandatory disclaimer: Proprietary or brand names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product, and exclusion of others that may be suitable.     

The mitochondrial membrane potential (deltapsi(m)) in apoptosis; an update

Mitochondrial dysfunction has been shown to participate in the induction of apoptosis and has even been suggested to be central to the apoptotic pathway. Indeed, opening of the mitochondrial permeability transition pore has been demonstrated to induce depolarization of the transmembrane potential (_m), release of apoptogenic factors and loss of oxidative phosphorylation. In some apoptotic systems, loss of _m may be an early event in the apoptotic process. However, there are emerging data suggesting that, depending on the model of apoptosis, the loss of _m may not be an early requirement for apoptosis, but on the contrary may be a consequence of the apoptotic-signaling pathway. Furthermore, to add to these conflicting data, loss of _m has been demonstrated to not be required for cytochrome c release, whereas release of apoptosis inducing factor AIF is dependent upon disruption of _m early in the apoptotic pathway. Together, the existing literature suggests that depending on the cell system under investigation and the apoptotic stimuli used, dissipation of _m may or may not be an early event in the apoptotic pathway. Discrepancies in this area of apoptosis research may be attributed to the fluorochromes used to detect _m. Differential degrees of sensitivity of these fluorochromes exist, and there are also important factors that contribute to their ability to accurately discriminate changes in _m.     

Lactate conversion to acetate,CO2 and H2 in cell suspensions of Desulfovibrio vulgaris (Marburg): indications for the involvement of an energy driven reaction

Cell suspensions of Desulfovibrio vulgaris were found to catalyze, in the absence of sulfate, the complete conversion of 1 lactate to 1 acetate, 1 CO₂, and 2 H₂ (G₀=-8.8 kJ/mol) and of 1 pyruvate to 1 acetate, 1 CO₂, and 1 H₂ (G₀=-52 kJ/mol). Protonophores, the proton translocating ATPase inhibitor N,N-dicyclohexylcarbodiimide, and arsenate specifically inhibited H₂ formation from lactate but not from pyruvate. The results suggest that lactate oxidation to pyruvate and H₂ (G ₀=+43.2 kJ/mol) is energy driven.     

Foam behavior of biological media

Summary The influence of the alcohol concentration on the foaminess, , of-BSA-solutions is considered. This effect is calculated by means of the function (C_BSA . f), where f=1 for pure protein solutions and f>1 for alcohol solutions. f is calculated by f = 2^TT_eff. Here, where T_T is the turbidity temperature change due to solvent structure effects and T_D, the temperature correction due to alcohol-protein interaction. The constants necessary to calculate T_T and T_D are tabulated. The agreement between the calculated and measured foaminess , as a function of the n-propanol concentration is satisfactory and for methanol or ethanol excellent.     

Preparation of a series of sulfated tetrasaccharides from shark cartilage chondroitin sulfate D using testicular hyaluronidase and structure determination by 500 MHz1H NMR spectroscopy

Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz¹H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All the seven tetrasaccharides shared the common core structure GlcA1-3GalNAc1-4GlcA1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GlcA1-3GalNAc(4-sulfate) and/or GlcA1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA1-3GalNAc(4-or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum -N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.Abbreviations NFU National formulary unit - COSY correlation spectroscopy - HOHAHA homonuclear Hartmann-Hahn - 1D or 2D one- or two-dimensional - IdoA l-iduronic acid - GlcA d-gluco-4-enepyranosyluronic acid - Di-0S GlcA1-3GalNAc - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-diS _d GlcA(2-sulfate)1-3GalNAc(6-sulfate) - Di-diS_E GlcA1-3GalNAc(4, 6-disulfate) - U G, U, 2S, 4S, and 6S represent GlcA, GalNAc, GlcA, 2-O-sulfate, 4-O-sulfate, and 6-O-sulfate, respectively     

Desaturation of oxygenated fatty acids in Lesquerella and other oil seeds

Species of the genus Lesquerella, within the Brassicaceae family, have seed oils containing hydroxy fatty acids. In most Lesquerella species, either lesquerolic (14-hydroxy-eicosa-11-enoic), auricolic (14-hydroxy-eicosa-11,17-dienoic) or densipolic (12-hydroxy-octadeca-9,15-dienoic) acid dominates in the seed oils. Incubations of developing seed from Lesquerella species with 1-¹⁴C-fatty acids were conducted in order to study the biosynthetic pathways of these hydroxylated fatty acids. [¹⁴C]Oleic (octadeca-9-enoic) acid, but not [¹⁴C]linoleic (octadeca-9,12-dienoic) acid, was converted into the hydroxy fatty acid, ricinoleic (12-hydroxy-octadeca-9-enoic) acid, which was rapidly desaturated to densipolic (12-hydroxy-octadeca-9,15-dienoic) acid. In addition, [¹⁴C] ricinoleic acid added to Lesquerella seeds was efficiently desaturated at the 15 carbon. A pathway for the biosynthesis of the various hydroxylated fatty acids in Lesquerella seeds is proposed. The demonstration of desaturation at position 15 of a fatty acid with a hydroxy group at position 12 in Lesquerella prompted a comparison of the substrate recognition of the desaturases from Lesquerella and linseed. It was demonstrated that developing linseed also was able to desaturate ricinoleate at position 15 into densipolic acid. In addition, the linseed 15 desaturase was able to desaturate vernolic (12,13-epoxy-octadeca-9-enoic) acid and safflower microsomal 12 desaturase was able to desaturate 9-hydroxy-stearate. Thus, hydroxy and epoxy groups may substitute for double bonds in substrate recognition for oil-seed 12 and 15 desaturases.Abbreviations GLC gas-liquid chromatography - lysoPC palmitoyl-lysophosphatidylcholine - PC phosphatidylcholine This work was supported by grants from Stifteisen Svensk Oljeväxtforskning, Skanska Lantmännen Foundation, Swedish Farmers Foundation for Agricultural research, The Swedish Natural Science Research Council and The Swedish Council for Forestry and Agricultural Research. Nicki Engeseth was supported by the National Science Foundation under a grant award in 1992.     

Stereospecificity and electrogenicity of amino acid transport in Riccia fluitans

In the aquatic liverwort Riccia fluitans, membrane depolarization (_m), change in membrane conductance (g_m), and current-voltage (I-V) characteristics in the presence of different amino acids as well as the uptake of ¹⁴C-labeled amino acids were measured. L-isomers of the tested amino acids generate larger electrical effects (_m, g_m) than D-isomers, and the I-V characteristics show that the positive electrical inward-current of 20 mA m^-2 generated by 0.5 mM D-serine is only about 50% of the current generated by adding 0.5 mM L-serine. Whereas - and -amino acids rapidly depolarize the membrane to the same extend, with -aminobutyric acid (-AB) and dipeptides no significant electrical effects have been measured. The uptake kinetics of ¹⁴C-labeled amino acids display three components: (I) A saturable high-affinity component with K_s-values of 48 M D-alanine, 12 M -aminoisobutyric acid (AIB), 9 M L-alanine, 8 M L-proline, and 6 M L-serine, respectively; (2) an apparently linear low-affinity component, and (3) an also linear but unspecific component at concentrations >20 times the given K_s-value. Uptake of ¹⁴C-labeled AIB can be inhibited competitively by all tested neutral amino acids, the L-isomers being more effective than the D-isomers, as well as by ammonium or methylamine. Vice versa, AIB competitively inhibits uptake of L-serine and L-alanine. It is concluded that an uncharged stereospecific carrier for the investigated amino acids exists in the plasmalemma of Riccia fluitans. Accumulation ratios of about 50 suggest secondary active transport driven by a transmembrane electro-chemical gradient (mainly _m) which is generated by the electrogenic proton pump. It is suggested that this carrier binds to the amino group forming either a charged binary complex with positively charged amines (Felle 1980), or an uncharged complex with -AB or dipeptides, whereas electrogenic transport of - and -amino acids is mediated by a ternary carrier complex, probably charged by a proton.Symbols and Abbreviations _m membrane potential (mV) - E_co equilibrium potential (mV) of the transport system - g_m membrane (slope) conductance (Sm^-2) - g_m change in g_m - I-V curve current-voltage curve - AIB -aminoisobutytric acid - -AB -aminobutyric acid     

Sodium ions are necessary for growth and energy transduction in the marine cyanobacterium Oscillatoria brevis

The maximal growth rate of the marine cyanobacterium Oscillatoria brevis was reached at 200–400 mM NaCl and pH 9.0–9.6. NaCl was found (i) to stimulate the rate of the light-supported generation across the cytoplasmic membrane of the cells and (ii) to decrease the sensitivity of level and motility of the O. brevis trichomes to protonophorous uncouplers. The Na⁺/H⁺ antiporter, monensin, increased both and the uncoupler sensitivity of the cells. The data obtained agree with the assumption that O. brevis possesses a primary Na⁺ pump in its cytoplasmic membrane.Abbreviations ATP adenosine-5-triphosphate - TTFB tetrachlortrifluoromethylimidazol - CCCP carbonyl cyanide m-chlorophenylhydrazone - Na⁺ transmembrane electrochemical potential differences of Na⁺ - transmembrane electric potential difference - pNa transmembrane pNa difference     

Two novel isoneolacto-undecaglycosylceramides carrying Galα1→3Lewisx on the 6-linked antenna and N-acetylneuraminic acidα2→3 or Galactose α1→3 on the 3-linked antenna, expressed in porcine kidney

Three sialosylated and three neutral glycosphingolipids sharing a common iso-neolacto core were isolated from porcine kidney cortex. They were purified by preparative HPTLC, and were characterized by partial exoglycosidase hydrolysis followed by thin layer chromatography and immunostaining with anti-Gal13Gal, anti-type 2 lactosamine and anti-Lewisx antibodies, methylation analysis, MALDI-TOF mass spectrometry and 1H-NMR spectroscopy. Among neutral glycolipids, one was a known structure, VI3VI3(Gal)2-iso-nLc8Cer, and two were novel structures differing by the number of Gal3Lewisx determinants: VI3VI3(Gal)2V3Fuc-iso-nLc8, and VI3VI3(Gal)2 V3V3(Fuc)2-iso-nLc8. The single Gal3Lewis x determinant was found on the 6-linked antenna. Among sialosylated glycolipids, two had been previously found in other species and tissues, VI3VI3(NeuAc)2-iso-nLc8, and VI3NeuAcVI3Gal-iso-nLc8. A novel structure was discovered presenting a Gal3Lewisx determinant on the 6-linked antenna and a N-acetylneuraminic acid on the 3-linked antenna, VI3NeuAcVI3GalV3Fuc-iso-nLc8. These results indicate that, in vivo, the porcine kidney 3fucosyltransferase synthesizes the Gal3Lewisx determinant, acting on the 6-linked before the 3-linked Gal3neolactosamine, and appears unable to synthesize the sialosylated Lewisx determinant on neolactoseries glycolipids.     

Effect of L-triiodothyronine on liver microsomal Δ6 and Δ5 desaturase activity of male rats

The effect of different doses of L-triiodothyronine (T₃) on the activity of 6 and 5 desaturases and lipid fatty acid composition was studied in liver microsomes of male rats. The activity of 6 and 5 desaturases was decreased 24 and 28%, respectively, in animals administered a daily intraperitoneal dose of 1000g T₃/100g body wt. for 5 days, whereas with 500g T₃/100g body wt. only 6 desaturase activity was decreased. On the other hand, no enzyme activity changed at a shorter period of hormone treatment. Changes in microsomal fatty acid composition did not seem to be a direct consequence of desaturation activity, since after 1 and 5 days of T₃ treatment, the concentrations of 18:2 (n-6) and 20:3 (n-6) decreased and only after 1 day that of 20:4 (n-6) increased in spite of unchanged or decreased 6 and 5 desaturase activities. Other factors than desaturation activity must be involved in fatty acid composition of thyroid hormonetreated rats, such as diet, membrane lipid synthesis and degradation, fatty acid turn-over and oxidation. (Mol Cell Biochem121: 149–153, 1993)     

Theoretical stability diagram of solvent-containing black lipid films

Recently, we have developed an analytical, semi-microscopic theory for the macroscopic behavior of a solvent-containing black lipid film subjected to an electric cross film voltage, . Here we employ the theoretical expressions derived for the disjoining pressure, _D, the film elasticity, _F, and the film tension, _F, to construct the stability diagram of the film, in the _D-. Depending on its state (_D, ), the film is stable or is prone to squeezing or bending deformations. For a monooleate film we show how the destruction of the plane film due to a periodic thickness fluctuation (squeezing) is facilitated by two mechanisms: i) lowering of _D at fixed ; ii) lowering of at fixed _D, provided that the film is in a stable state characterized by _D<–7.03×10³ dyne/cm² and >0 mV. Bending of a low tension film (single interface tension _s 0.025 dyne/cm¹) can be achieved only for >170 mV and _D > –8.7 × 10⁴ dyne/cm². Finally, we demonstrate the existence of a marginal state ( _D ⁰ , ⁰) where the film is predicted to exhibit strong fluctuations both in the squeezing and in the bending mode.     

Effects of cannabinoids on the activities of mouse brain lipases

Cannabinoids were found to augment phospholipase activities and modify lipid levels of mouse brain synaptosomes, myelin and mitochondria. Delta-1-tetrahydrocannabinol (¹-THC) and several of its metabolites induced a dose-dependent (0.32–16 M) stimulation of phospholipase A₂ (PLA₂) activity resulting in the increased release of free arachidonic acid from exogenous [1-¹⁴C]phosphatidylcholine (PC). The potencies of the cannabinoids in modulating PLA₂ activity were approximately of the order: 7-OH-¹-THC > ¹-THC > 7-oxo-¹-THC > ¹-THC-7oic acid = 6 OH-¹-THC 6-OH-¹-THC. The hydrolysis of phosphatidylinositol (PI) by synaptosomal phospholipase C (PLC) was enhanced significantly by ¹-THC and promoted diacylglyceride levels by greater than 100 percent compared to control values. In contrast, arachidonate was the major product resulting from phospholipase activities of a 20,000g pellet. Synaptosomal diacylglyceride lipase activity was inhibited by ¹-THC. [1-¹⁴C]Arachidonic acid was readily incorporated into subcellular membrane phospholipids and after exposure to cannabinoids led to diminished phosphoglyceride levels and concomitant increases in released neutral lipid products. These data suggest that cannabinoids control phospholipid turnover and metabolism in mouse brain preparations by the activation of phospholipases and, through this mechanism, may exert some of their effects.     

Genetic analysis of carbon isotope discrimination and agronomic characters in a bread wheat cross

Carbon isotope discrimination () has been suggested as a selection criterion to improve transpiration efficiency (W) in bread wheat (Triticum aestivum L.). Cultivars Chinese Spring with low A (high W) and Yecora Rojo with high (low W) were crossed to develop F₁, F₂, BC₁, and BC₂ populations for genetic analysis of and other agronomic characters under well-watered (wet) and water-stressed (dry) field conditions. Significant variation was observed among the generations for only under the wet environment. Generation x irrigation interactions were not significant for . Generation means analysis indicated that additive gene action is of primary importance in the expression of under nonstress conditions. Dominance gene action was also detected for , and the direction of dominance was toward higher values of . The broad-sense and the narrow-sense heritabilities for were 61 % and 57% under the wet conditions, but were 48% and 12% under the draughted conditions, respectively. The narrow-sense heritabilities for grain yield, above-ground dry matter, and harvest index were 36%, 39%, and 60% under the wet conditions and 21%, 44%, and 20% under dry conditions, respectively. The significant additive genetic variation and moderate estimate of the narrow-sense heritability observed for indicated that selection under wet environments should be effective in changing in spring bread wheat.     

Relationship of the Donnan potential to the transmembrane pH gradient in tracheal apical membrane vesicles

Summary Experiments were performed to determine the factors which contribute to the transmembrane pH gradient (pH) and the potential gradient () in apical plasma membrane vesicles isolated from bovine tracheal epithelium. As indicated by the accumulation of¹⁴C-methylamine, the vesicles maintained a pH (inside acidic) which was dependent upon the external pH. The pH was also proportional to the ionic strength of the suspending medium, suggesting that the H⁺ distribution was dictated by a Donnan potential. Measurements of the distribution of⁸⁶Rb⁺ demonstrated an electrical potential gradient across the vesicle membrane, inside negative which was proportional to the medium ionic strength. pH changed in parallel with in response to a variety of imposed conditions. These results are compatible with the existence of a H⁺ conductance in the vesicle membrane. Thus the endogenous electrical and proton gradients may be manipulated and used as a general experimental tool to complement kinetic analysis in investigations of transport mechanism using isolated vesicle preparations.