Temperature dependence of chlorophyll {alpha} fluorescence in lettuce and spinach chloroplasts at sub-zero temperatures

The temperature dependence of chlorophyll fluorescence wasmeasured in spinach and lettuce chloroplasts at sub-zero temperaturesin the presence of 50% ethylene glycol. In the presence of 5mM Mg²⁺, a fluorescence maximum appeared at –31?C in boththe spinach and lettuce chloroplasts, while in the presenceof only 5 mM Na⁺ as cations the maximum shifted to –20?Cin the spinach chloroplasts and to –11?C in the lettucechloroplasts. Since the occurrence of a maximum in the temperatureversus fluorescence curve is an indication for the transitionof the physical phase of thylakoid membrane lipids between theliquid crystalline and the phase-separation state (16, 18),these findings suggest that the (major) phase transition ofmembrane lipids occurs at these low temperatures in chloroplastsof higher plants and also that the phase transition temperatureis markedly lowered by the presence of divalent cations. Ethylene glycol at a concentration of 50% had almost no effecton the temperature dependence of chlorophyll fluorescence ina lamellar membrane preparation of Anabaena variabilis. In awater suspension of dimyristoylphosphatidylcholine, the additionof ethylene glycol to 50% did not alter the characteristic featureof the temperature dependence of fluorescence of 1-anilinonaphthalene-8-sulfonate.These findings suggest that 50% ethylene glycol does not affectthe temperature of the transition of the physical phase of membranelipids. ¹ C.I.W.-D.P.B. Publication No. 592. ² Present Address: Department of Biophysics and Biochemistry,Faculty of Science, University of Tokyo, Hongo 113, Tokyo, Japan. (Received June 22, 1977; )     

Degenerative changes and carotenoid uptake in the silk gland of the silkworm Bombyx mori

In the middle silk gland of the silkworm Bombyx mori, especially in the middle region, structural changes were studied in relation to absorbing activity, using a transplantation method. The physiologically active gland, which was prepared by the decapitation at the feeding stage of the fourth larval instar, maintained a normal structure when placed in the larval body cavity during the middle stage of the fourth instar or during the early stage of the fifth (last) larval instar. But, if the gland was placed there during the fourth larval-larval pharate stage, histolytic changes, e.g. invagination of tunica propria, its separation from the cell and contraction of the cell, took place in the tissue. These results suggest that, once activated, cells in the middle region of the middle silk gland undergo degenerative changes even in the presence of the corpus allatum hormone during the larval-larval pharate period.     

Bovine virus diarrhea-mucosal disease. II. Isolation and characterization of a cytopathogenic virus and experimental production of the disease.

A disease broke out in calves in the Tokachi district of Hokkaido. It induced pyrexia, respiratory symptoms, diarrhea, bloody feces, leukopenia, and sometimes erosion of the oral mucous membrane and muzzle. Its morbidity rate was 90% and its fatality rate 50%. Bovine virus diarrhea (BVD) virus was isolated from organs of dead calves and blood and feces of affected calves. It exhibited a cytopathic effect on calf kidney cell culture. Antisera against the Nose and the Oregon C24V strains of BVD virus showed an antibody titer of the same order against the homologous virus and the isolated strain. Antiserum against the isolated strain, however, showed much lower antibody titers against the Nose and the Oregon C24V strains than against the homologous virus. When inoculated with the isolated virus, two calves manifested acute symptoms, but recovered at any rate. One of them, however, suffered again from clinical infection and died eventually 37 days after inoculation. It presented pathological changes closely resembling those of the case of spontaneous infection. Virus was recovered from its principal organs, intestinal canal, and lymph nodes of various regions of the body.     

Analysis of dansyl amino acids by reverse-phase high-performance liquid chromatography

All 24 dansyl amino acids were separated by reverse-phase high-performance liquid chromatography on Develosil C8-5, using a linear gradient made from Tris-HCl buffer (pH 7.75) and methanol. A linear relationship between the amount of sample and peak area was found over the range of 6 to 300 ng (0.02–1 nmol) of dansyl derivatives. An application of this method to the NH₂-terminal analysis of lysozyme is described.     

Change in the intrinsic fluorescence of acetylcholine receptor purified from Narke japonica upon binding with cholinergic ligands

Effects of various cholinergic ligands on the intrinsic fluorescence of acetylcholine receptor purified from the electric organ of Narke japonica were investigated. Binding with acetylcholine decreased the fluorescence by 7–8%, and that with carbamylcholine by 4–5% at 20 °C. Decamethonium and d-tubocurarine did not affect significantly the fluorescence intensity, while hexamethonium enhanced it. These changes were completely inhibited by preincubation of the receptor with α-bungarotoxin, which indicated that the observed intrinsic fluorescence change was due to the specific binding of each ligand. Data of the quenching experiment using iodide ion as an extrinsic quencher suggested the occurrence of the conformational change in the receptor upon binding with various cholinergic ligands. Considering these results together with those on intrinsic fluorescence change, conformational change provoked by binding with acetylcholine or carbamylcholine seems to differ from that provoked by binding with other cholinergic ligands examined.     

Synthesis of a polymide containing a glucose unit in the main chain

A new type polyamide containing a glucose unit in the main chain has been synthesized by the polymerization of C₁, C₃, C₄ blocked C₆-carboxymethylglucosamine, prepared from chitin. The deblocking procedure gave the water-soluble polyamide, of MW 1.5 × 10⁴, which can be regarded as a model for the recognition site of lectin.     

Effect of dextran sulfate on the interaction between very low density lipoprotein and lipoprotein lipase

The effect of dextran sulfate on the interaction between very low density lipoprotein (VLDL) and purified bovine milk lipoprotein was studied. Dextran sulfate increased VLDL-triacylglycerol hydrolysis by lipoprotein lipase about 2-fold, but did not alter the Km value for triacylglycerol in VLDL. Strong association of dextran sulfate with the VLDL-lipoprotein lipase complex was demonstrated by gel filtration on BioGel A-5m, although dextran sulfate did not bind to VLDL and only very slightly to lipoprotein lipase. These findings suggest that dextran sulfate increases triacylglycerol hydrolysis in VLDL by binding to the VLDL-lipoprotein lipase complex.