Stereoselective total synthesis of ceramide Di-, Tri- and tetrahexosides of wheat flour

The first total synthesis of glycosphingolipids isolated from wheat flour has been achieved in a regio- and stereo-controlled manner.Abbreviations THF tetrahydrofuran - DMF dimethylformamide Part 53 in the series Synthetic Studies on Cell Surface Glycans     

Characterisation of Non-Uniform Photosynthesis Induced by Abscisic Acid in Leaves Having Different Mesophyll Anatomies

The effects of abscisic acid (ABA) on photosynthesis in leavesof Helianthus annuus L. were compared with those in leaves ofVicia faba L. After the ABA treatment, the response of photosyntheticCO₂ assimilation rate, A, to calculated intercellular partialpressure of CO₂, P_i, (A(p_i) relationship) was markedly depressedin H. annuus. A less marked depression was also observed inV.faba. However, when the abaxial epidermes were removed fromthese leaves, neither the maximum rate nor the CO₂ responseof photosynthetic oxygen evolution was affected by the applicationof ABA. Starch-iodine tests revealed that photosynthesis was not uniformover the leaves of H. annuus treated with ABA. The starch contentwas diffferent in each bundle sheath extension compartment (thesmallest subdivision of mesophyll by veins with bundle sheathextensions, having an area of ca. 0.25 mm² and ca. 50 stomata).In some compartments, no starch was detected. The distributionof open stomata, examined using the silicone rubber impressiontechniques, was similar to the pattern of starch accumulation.In V.faba leaves, which lack bundle sheath extensions, distributionof starch was more homogeneous. These results indicate that the apparent non-stomatal inhibitionof photosynthesis by ABA deduced from the depression of A(pⁱ)relationship is an artifact which can be attributed to the non-uniformdistribution of transpiration and photosynthesis over the leaf.Intercellular gaseous environment in the ABA-treated leavesis discussed in relation to mesophyll anatomy. ¹ Present address: Department of Botany, Duke University, Durham,NC 27706, U.S.A. (Received September 30, 1987; Accepted January 13, 1988)     

Exposure of Leaves of Cucumis sativus L. to Low Temperatures in the Light Causes Uncoupling of Thylakoids II. Non-Destructive Measurements with Intact Leaves

To examine the effects of chilling of leaves of cucumber (Cucumissativus L.) in moderate light on the coupling state of thylakoidsin situ, changes in fluorescence, changes in light scatteringand flash-induced changes in absorbance at 518 nm were examinedin intact leaves. After chilling of leaves at 5?C in the lightfor 5 h, the non-photochemical quenching of fluorescence, ameasure of energisation of thylakoids, was largely suppressed.The treatment also caused a suppression of light-induced changesin the light scattering by leaves, which depends on the formationof a pH gradient across thylakoid membranes. When thylakoidswere prepared by very gentle methods from the leaves chilledin the light, through a step of preparation of intact chloro-plasts,the transport of electrons from H₂O to ferricyanide was uncoupled,being insensitive to an uncoupler, methylamine. These data provide consistent evidence that the thylakoids areuncoupled in situ by the chilling of leaves in the light and,as a consequence of the uncoupling, the energisation of themembranes is suppressed. However, the decay of the flash-inducedchange in absorbance at 518 nm in leaves was not markedly acceleratedby the treatment. The thylakoids isolated from leaves chilledin the light, which were in the uncoupled state, also did notshow a rapid decay, unless an efficient uncoupler such as gramicidinwas added. These results suggest that even a considerable uncouplingof thylakoids, brought about by chilling of leaves in the light,is not sufficient to cause a marked acceleration of the decayof the flash-induced change in absorbance at 518 nm. Therefore,analysis at 518 nm is not always a sensitive method for assessingthe coupling state of thylakoids. (Received July 1, 1991; Accepted October 4, 1991)     

Effects of solute hydrophobicity and phospholipid composition on permeability of composite membranes containing phospholipids

Permeabilities of several solutes through the composite membranes containing phospholipids have been measured. They were inversely proportional to the content of the phospholipids in the membrane. Both the permeability of solutes and the degree of permeability change around the phase transition temperature of the phospholipids for the hydrophobic solutes such as n-butanol and salicylamide were larger than those for the hydrophilic solutes such as amino acids and pyridoxine. These results suggest thatthe permeation path of hydrophobic solutes is different from that of hydrophilic ones. The addition of phosphatidyl ethanolamine, phosphatidyl serine, or phosphatidic acid to the composite membrane influenced the solute permeability due to the introduced negative charge and/or the change in the molecular packing of phospholipid.     

Permeabilities of composite membranes containing phospholipids

Two types of artificial membranes containing a phospholipid were prepared and their permeabilities were measured around the phase-transition temperature of the phospholipid. The permeability of the membranes to a hydrophobic solute was higher than to a hydrophilic solute, and showed an abrupt change at the phase-transition temperature of the phospholipid, similar to that in biomembranes and liposomes, caused by the fluidity change of the phospholipid at this temperature.     

Proteolytic Activity against Model Peptides of the Cell Wall Lytic Enzyme from Chlamydomonas

A cell wall lytic enzyme (gamete wall-autolysin) from Chlamydomonasreinhardtii specifically cleaved several synthetic model peptides,-neo-endorphin, dynorphin (1–13), neurotensin and mastoparan,at the peptide bonds between consecutive hydrophobic amino-acidresidues. The cleavage was not significantly affected by high-saltconditions which are known to inhibit digestion of the cellwall. (Received December 14, 1989; Accepted April 5, 1990)     

Cause for dark, chilling-induced inactivation of photosynthetic oxygen-evolving system in cucumber leaves

Effects on oxygen evolution of the storage of detached cucumber (Cucumis sativus) leaves at 0°C in the dark were investigated with thylakoids and oxygen-evolving photosystem II membranes isolated from stored leaves. The cold and dark treatment of leaves selectively inactivated electron transport on the oxidizing side of photosystem II. Photosystem II membranes isolated from treated leaves were largely depleted of two proteins of 20 and 14 kilodaltons, which correspond to the extrinsic 23- and 17- kilodalton proteins of spinach functioning in oxygen evolution. The manganese content of photosystem II membranes was also markedly reduced by the treatment. Thus, the inactivation of oxygen evolution induced by the dark, chilling treatment is ascribed to solubilization of the 20- and 14-kilodalton proteins and extraction of manganese.     

Effect of testosterone on the susceptibility of C57BL/6 mice to infection with Brugia pahangi with reference to inflammatory cell response

Effects of testosterone on the susceptibility and inflammatory cell responses of C57BL/6 mice infected intraperitoneally with Brugia pahangi larvae were examined. On day 15 postinfection, female mice showed significantly greater resistance than did males, and peritoneal cell responses (lymphocytes, macrophages, and eosinophils) were great in females. Castration of highly susceptible male mice increased their resistance and peritoneal cell responses to the level of female mice; whereas, castration of female mice did not affect the susceptibility and cell responses. Furthermore, testosterone treatment at a physiological dose in the castrated male mice or a pharmacological dose in female mice suppressed resistance and inflammatory cell responses. These results suggest that male sex hormone, testosterone, but not female sex hormone has a regulatory role in the susceptibility and cellular response of C57BL/6 mice to infection with B. pahangi, and it causes differences between sexes in susceptibility.