D-Amino-acid-stimulated ethylene production in seed tissues

Ethylene production by axial and cotyledonary tissues excised from Xanthium pennsylvanicum Wallr. seeds was markedly (up to 5-fold) stimulated by the D-isomers of phenylalanine, valine, leucine, threonine, methionine and eithionine while the L-isomers caused no such effect. Responsiveness of these seed tissues to D-methionine appeared soon after the beginning of imbibition, reached a maximum after 6–12 and 12–24 h for the axial and cotyledonary tissues, respectively, and then decreased sharply. D-Phenylalanine and D-methionine also stimulated ethylene production in seed tissues of X. canadense Mill. and in cotyledonary segments from seeds of Helianthus annuus L., Cucurbita moschata Duch. and Vigna radiata (L.) Wilczek. The endogeneous ethylene production and the D-amino-acid-stimulated ethylene production by the seed segments was strongly inhibited by aminoethoxyvinyl glycine, a potent inhibitor of ethylene synthesis from L-methionine.     

Effect of disulfiram on turnover of 5-hydroxytryptamine in rat brain.

Effect of disulfiram on 5-hydroxytryptamine (5-HT) turnover was studied. Treatment with disulfiram caused increases in 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in rat brain. Under the same condition, activity of brain mitochondrial aldehyde dehydrogenase was reduced, however, supernatant aldehyde dehydrogenase and monoamine oxidase activities remained unchanged. Disulfiram had no effect on synthesis rate of 5-HT, but decreased metabolism of 5-HT. Moreover, disulfiram impaired transport of 5-HIAA from brain tissue.     

Ultrastructural localization of acid phosphatase activity in the small intestinal absorptive cells of postnatal rats

Summary The ultrastructural localization of acid phosphatase activity was investigated in ultrathin (0.05 m) and semithin (0.5 m) sections of the small intestinal epithelial cells of postnatal rats. Until around the 15th day of neonatal life acid phosphatase activity in the duodenal and jejunal epithelial cells was observed on the microvillous membrane, the membrane of the tubulo-vacuolar system, the lateral cell membrane, the lysosomes, the Golgi apparatus and the GERL of Novikoff (1963). After about the 15th neonatal day, the tubulo-vacuolar system enzyme disappeared from both cells. Acid phosphatase activity then became localized on the microvillous membrane, the lateral cell membrane, the lysosomes, the Golgi apparatus, and the GERL, as in adult rats. During the suckling period, acid phosphatase in the ileal cells could be seen on the microvillous membrane, the lateral cell membrane, the Golgi apparatus, the GERL, the membrane of tubulo-vacuolar system and the supranuclear vacuole. At weaning, however, the tubulovacuolar system and the supranuclear vacuole enzyme disappeared, and only the lysosomes and the GERL of these cells showed acid phosphatase activity, as in the adult rat. It was concluded that the acid-phosphatase-containing tubulo-vacuolar system and the supranuclear vacuole in the epithelial cells of the distal intestine of suckling rats may possess a strong phagolysosomal function as well as having an absorptive capacity.     

Dependence on ionic strength of charge-induced coil-helix transition of sodium poly(L-glutamate) in aqueous solution

Helix contents of sodium poly(L-glutamate) in aqueous NaCl solutions were estimated as functions of the degree of ionizalion, alpha. and the salt concentration by CD measurement. The helix content increases with increasing salt concentration but this helix stabilization decreases with decreasing alpha and at alpha<0.25 the helix conformation is destabilized by salt addition. The alpha dependence of the helix stabilization was qualitatively interpreted by Manning's theory in which electrostatic interactions between charges on alternatively arrayed coil and helix segments in a simplified polymer model were incorporated.     

Photosynthetic activities of a thermophilic blue-green alga

Photosynthetic activities of a thermophilic blue-green alga,a species of Synechococcus, were studied with special referenceto its growth at high temperatures. A rapid algal growth occurredin the temperature range between 50 and 60?C, showing the maximumrate, six doublings per day, at about 57?C. Photosynthetic oxygenevolution and methyl viologen photoreduction in the cells werealso active at high temperatures and the optimum temperaturesfor these activities agreed with that of the algal growth. Thegrowth and photosynthetic activities were very low at room temperatureand irreversibly inactivated at temperatures above 60?C. The thylakoid membranes isolated from the alga were also photochemicallyactive at high temperatures. The membranes mediated ferricyanidephotoreduction coupled with a stoichiometric oxygen evolutionat a rate comparable to that of photosynthetic oxygen evolutionin the cells. The optimum temperature for the reaction was ashigh as 50?C. The membranes also showed a photosystem I-mediatedreaction at high temperatures. These observations indicate thatthe thylakoid membranes are intrinsically thermophilic in thisorganism. Thus the growth of the alga at high temperatures canbe well correlated to thermophilic properties of the photosyntheticapparatus. (Received February 20, 1978; )     

Effects of dibromothymoquinone and bathophenanthroline on flash-induced cytochrome f oxidation in spinach chloroplasts

The effects of several electron transport inhibitors on themagnitude and kinetics of cytochrome f oxidation induced byflash illumination were studied in the - and -band regions.On the flash excitation only a fraction of cytochrome f presentin the chloroplasts was oxidized with a half time of 0.1 to0.3 msec and then reduced with a half time of 10 to 25 msec. Dibromothymoquinone (DBMIB) at concentrations which severelysuppressed the reduction of cytochrome f approximately doubledthe magnitude of cytochrome f oxidation caused by a flash, mainlyby inducing an additional slow oxidation of cytochrome f witha half time longer than 1 msec. Enhancement of the cytochromef oxidation was also observed in the presence of bathophenanthroline.Such enhanced oxidation in duced by the two inhibitors was largelydiminished with the addition of reduced 2,6-dichlorophenolindophenolwhich accelerated cytochrome f reduction. In contrast, the inhibitionof cytochrome f reduction by 3-(3,4-dichlorophenyl)-1,1-dimethylurea(DCMU) was not associated with an increase in the magnitudeof cytochrome f oxidation. However, addition of DBMIB to theDCMU-poisoned chloroplasts enhanced cytochrome f oxidation,suggesting that this is related to a block of the electron transportbetween plastoquinone and cytochrome f. The results are explainedby assuming the occurrence of an electron carrier between plastoquinoneand cytochrome f. (Received May 10, 1978; )     

Low temperature spectral properties of subchloroplast fractions purified from spinach

Spinach (Spinacia oleracea L.) chloroplasts solubilized by digitonin were separated into five fractions by sucrose density gradient centrifugation. Three of the fractions, F_I, F_II, and F_III, corresponding to photosystem I, photosystem II, and the chlorophyll a/b complex, were purified further by two steps of diethylaminoethyl-cellulose chromatography followed by electrofocusing on an Ampholine column. The polypeptide patterns of the fractions were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the spectral properties of the fractions at −196 C determined by absorption spectra, fourth derivative curves of the absorption spectra, fluorescence emission spectra, and fluorescence excitation spectra. The activity of purified F_II (photosystem II) was also assayed by the photoreduction of dichlorophenol-indophenol at room temperature using 1,5-diphenylcarbohydrazine as the electron donor and by the photoreduction of C-550 at −196 C. The different fractions showed unique polypeptide patterns and unique sets of low temperature-absorbing forms of chlorophyll. The fluorescence emission spectra of F_I, F_II, and F_III at −196 C were also unique with maxima at 734, 685 and 681 nm, respectively. F_I showed negligible emission at wavelengths shorter than 700 nm and the long wavelength tails of F_II and F_III in the 730 nm region were relatively small (approximately 10% of emission of their wavelength maxima). Addition of 0.1% Triton to F_I and F_II caused the longer wavelength absorbing forms of chlorophyll to shift to 670 nm and the fluorescence emission maxima (of both fractions) to shift to 679 nm at −196 C with an increase in the yield of fluorescence especially in the case of F_I.     

Cytochemical and electron microscopic demonstration of organelle translocation and the inhibition of such translocation by colchicine during the mitosis of rat hepatocytes

Hepatocyte lysosomes, mitochondria, and peroxisomes show a dramatic translocation during mitosis induced by partial hepatectomy. During prophase, all three organelles move to the perinuclear cytoplasm. In metaphase, they become concentrated in the polar regions. During telophase, these organelles form clusters in the juxtanuclear regions. This organelle translocation is inhibited by the administration of a low concentration of colchicine, suggesting an involvement of microtubules in their movement.     

Determination of enzyme activities of energy metabolism in the maturing rat oocyte.

Enzyme activities were determined quantitatively in individual rat oocytes to study their energy metabolism during maturation. Low hexokinase activity and high activities of lactate dehydrogenase and enzymes in the phosphate pathway, i.e., glucose 6-P and 6-P gluconate dehydrogenases, were characteristic of immature oocytes. Hexokinase may be a rate-limiting enzyme that enables oocytes to use glucose as an energy source. During maturation, the activities of hexokinase, phosphofructokinase, and malate dehydrogenase increased significantly, suggesting that the glycolytic pathway, as well as the tricarboxylic acid cycle, developed as the first meiotic division proceeded. In contrast, the activities of glucose 6-P and 6-P gluconate dehydrogenases decreased in maturing oocytes. The observation that the enzyme pattern in mature oocytes resembles more closely that in somatic cells appears to be significant, especially in light of previous studies showing this developmental trend in preimplantation embryos.     

Expression of cDNA for batroxobin, a thrombin-like snake venom enzyme

The cloned cDNA for batroxobin has been expressed in E. coli. Batroxobin could only be obtained as intracellular aggregates of fusion proteins, fused with a small peptide. To obtain the mature batroxobin, the recognition sequence for thrombin was inserted between the peptide and the mature batroxobin. This fusion protein accumulated in an insoluble form and could easily be purified. After site-specific cleavage of the fusion protein with thrombin, recombinant batroxobin was isolated by preparative electrophoresis. Batroxobin with enzymatic activity was obtained by the refolding of recombinant batroxobin.