Coupling of fructose-1,6-P2 to aminated agarose by Schiff base reduction. Affinity chromatography of yeast aldolase.

Fructose-1,6-P2 was immobilized by sodium borohydride reduction of the Schiff base formed with aminated agarose (AH-Sepharose 4B). The coupling occurs with high yield (25 mumoles immobilized fructose-1,6-P2 per ml packed gel) at neutral pH and room temperature. Schiff base reduction thus provides a convenient and mild coupling prodecure for sugar phosphates preserving their labile phospho ester bonds. As exemplified by a new isolation procedure for fructose-1,6-P2 aldolase from yeast, sugar phosphates insolubilized in this manner may be used for affinity chromatography of the corresponding enzymes, provided that contaminating unspecific phosphatases are removed in a preceding fractionation step.     

Negative adsorption of anions by suspensions of bentonites

Résumé Nous avons étudié l'adsorption négative des anions I*O ₃ ^– et Cr*O ₄ ^–– à différents bentonites en fonction d'électrolytes additionnés. Pour les électrolytes NaCl et Na₂SO₄ les résultats sont en bon accord avec ceux deSchofield etMattson; nous avons étudié aussi l'effet de l'addition de solutions de CaCl₂; celles-ci produisent le même effet à des dilutions 20 fois plus grandes que les solutions de NaCl. Comme ceci ne peut pas être expliqué sur la base de la théorie deDebye-Hückel, nous avons appliqué la théorie exacte de la couche double; le facteur 20 mentionné plus haut mène à une valeur de=–75 mV. En introduisant cette valeur de, une représentation graphiques–1/c pour les résultats des expériences au Na-bentonite + solutions de NaCl, donne une surface spécifique de 1110 m²/g.     

Sul meccanismo della eptoformazione non ossidativa nel muscolo scheletrico

Summary F-1,6-P has been shown to increase the rate of non-oxydative heptoformation from glucose-6-phosphate and fructose-6-phosphate in enzymatic preparations of rat skeletal muscle. The mechanism of this increase — probably due to triose-phosphate, formed by aldolase action on F-1,6-P — is discussed.     

Effect of acute administration of Δ1-tetrahydrocannabinol on β-endorphin levels in plasma and brain tissue of the rat

Summary Acute treatment with ¹-tetrahydrocannabinol (¹-THC) elevated the concentration of -endorphin-like immunoreactivity (-ELIR) in plasma and in the hypothalamus, but not in the hippocampus of rats habituated to the injection procedure. These effects were not obtained with the psychotropically inert analog of (¹-THC), cannabidiol. In animals that had not been habituated to the injection procedure, placebo treatment induced a decrease in hippocampal -ELIR.The authors acknowledge the skillful technical assistance of Mrs Willeke Logtenberg.     

The isolation and structure of trichosiderin B

Riassunto Un nuovo pigmento feomelanico, denominato tricosiderina B, è stato isolato dalle piume di pollo di razza New Hampshire. Sulla base delle proprietà chimiche e spettrali a tale pigmento, C₂₃H₂₀N₄O₉S₂, è stata assegnata la struttura ^2,2-bibenzotiazinica IV.

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This work was supported by a grant from Laboratorio per la Chimica e Fisica di Molecole di Interesse Biologico del C.N.R., Napoli.     

The isolation and structure of trichosiderin B

Riassunto Un nuovo pigmento feomelanico, denominato tricosiderina B, è stato isolato dalle piume di pollo di razza New Hampshire. Sulla base delle proprietà chimiche e spettrali a tale pigmento, C₂₃H₂₀N₄O₉S₂, è stata assegnata la struttura ^2,2-bibenzotiazinica IV.

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This work was supported by a grant from Laboratorio per la Chimica e Fisica di Molecole di Interesse Biologico del C.N.R., Napoli.     

Pathways of proton transfer in the light-driven pump bacteriorhodopsin

The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood. Light causes the all-trans to 13-cis isomerization of the retinal chromophore. This sets off a sequential and directed series of transient decreases in the pK_a's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96. The timing of these pK changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.     

Endogenous gibberellins and amylase activity in tall and dwarf strains of rice (Oryza sativa)

Summary 2 tall and 7 dwarf strains of rice were sprayed with 0 or 40 g ml^–1 GA₃, 4 dwarf strains responded to exogenous GA₃, and showed a markedly lower endogenous gibberellin content than the tall strains, while 2 dwarf strains did not respond to GA₃ application and had considerably higher endogenous gibberellin levels than the tall ones. Amylase activity in germinating seeds showed a significant negative correlation with the endogenous gibberellin content.     

Soybean photosynthesis: simultaneous14CO2 and O2 estimates

Summary A method of estimating the photosynthetic rate of soybean leaves using an oxygen electrode is presented. The procedure is rapid, requires small samples and compares favourably with estimates by other techniques. Light saturation occurs at 1200 E·m^–2·sec^–1. The apparent K_m for HCO ₃ ^– is 3.2 mM at pH 7.6.     

Biosynthesis of 1-aminocyclopropanecarboxylic acid: Steric course of the reaction at the C-4 position

Summary Under the action of the appropriate synthase from ripe tomatoes a 11 mixture of (3S, 4R)-[3,4-²H₂] and (3R, 4S)-[3,4-²H₂]-(2S)-adenosylmethionine is transformed into a 11 mixture of the two meso forms of [²H₂]-1-aminocyclopropanecarboxylic acid, a result which proves the operation of an inversion mechanism and which is consistent with direct nucleophilic displacement of the leaving group in the substrate.     

Evidence for suppression of Na-dependent Ca2+ efflux from rat brain synaptosomes by ovarian steroids in vivo

Summary The possibility that intracellular Ca²⁺, which mediates neurotransmitter release, regulation of membrane permeability, microtubule polymerization and axonal transport, is influenced by gonadal steroids via a Na–Ca exchange mechanism was examined. The resting Ca²⁺ uptake into synaptosomes was measured using crude synaptosomal pellets (P₂ fraction), isolated from the brain stem, mesencephalic reticular formation (MRF), nucleus caudatus (NC) and the hippocampus of intact, long-term ovariectomized (OVX) and OVX plus progesterone (P) or estradiol-17 benzoate (EB) treated adult female rats. Irrespective of the brain structure investigated, the uptake was 1) markedly increased in synaptosomes from OVX animals in comparison to intact controls, and 2) reduced to near control values in synaptosomes from OVX rats treated s.c. with a single dose of 2 mg P or 5 g EB. Since Ca²⁺ influx into synaptosomes was shown earlier to depend on external sodium concentration, which was the same in all experiments described in this work, the results obtained indicate that ovarian steroids modulate basal synaptic activity in the rat brain by suppressing Na-dependent Ca²⁺ efflux from the nerve cell.     

Influence of environmental conditions on the amount of N2O released from activated sludge in a domestic waste water treatment plant

Waste water purification is characterized by intensive mineralization and nitrification processes. Because of the high O₂ demand, temporarily anaerobic conditions may be produced, and denitrification by nitrifying organisms as well as heterotropic denitrification may contribute to N₂O release. In situ measurements (1993–1994) suggest that N₂O is released from activated sludge in a domestic waste water treatment plant at an average rate of 1040 g m^–2h^–1 with a range between zero and 6198 g m^–2h^–1. The production of N₂O seems to be related to the concentration of NO ₂ ^– and NO ₃ ^– as well as to the pH. In the waste water about 75–200 g N₂O l^–1 is dissolved. This N₂O is released after discharge into the receiving waters. The N₂O is produced essentially by nitrification rather than by heterotropic denitrification. On a long-term scale the increasing use of mechanical-biological waste water purification plants world-wide may add increasingly to the anthropogenic production of N₂O, although the present amount of N₂O produced is negligible compared to its global terrestrial production.     

Presence of specific binding sites for [3H]sarcophytol-A in cultured human skin fibroblasts

Summary The presence of specific binding sites for [³H]sarcophytol-A in human skin fibroblasts was examined using biochemical and morphological methods. The displacement studies clearly revealed that high (K_D=31.0 nM) and low (K_D=6.05 M) affinity sites were present in the intact cells. Moreover, autoradiographic studies using light microscopy revealed that the specific binding sites may exist in boththe cytoplasm and the nuclei.     

Ginkgo biloba extract inhibits oxygen species production generated by phorbol myristate acetate stimulated human leukocytes

Summary A Ginkgo biloba extract (Gbe) containing flavonoids, among other compounds, was tested for the release of activated oxygen species ( , H₂O₂, OH^.) during the stimulation of human neutrophils (PMNs) by a soluble agonist. The extract slows down O₂-consumption (respiratory burst) of stimulated cells by its inhibitory action on NADPH-oxidase, the enzyme responsible for the reduction of O₂ to . Consequently, superoxide anion ( ) and hydrogen peroxide (H₂O₂) production is significantly decreased when the PMNs stimulation is done in the presence of the extract at concentrations of 500, 250 and 125 g/ml. Moreover, the hydroxyl radical generation (OH^.) is very much decreased at concentrations as low as 15.6 g Gbe/ml, which indicates that the extract also has free radical scavenging activity. Gbe is able at least to reduce very severel the activity of myeloperoxidase contained in neutrophils. This enzyme, secreted into the intra and extracellular medium, catalyzes the oxidation of chloride (Cl^–) by H₂O₂ to yield strong oxidants (HOCl, chloramines) which are implicated in inflammatory processes     

Dynamic laser light scattering studies of the effects of pyrophosphate on cyclic motions of cross-bridges in isolated thick myofilaments fromLimulus striated muscle

Pyrophosphate (PP_i) is a non-hydrolyzable ATP analogue known to affect the binding between myosin heads and actin. By using a dynamic laser light scattering method, we have shown that 1–2 mM PP_i enhances the increase in values induced by Ca²⁺ in isolated thick myofilaments fromLimulus striated muscle. However, similar treatment has no effect on the values of filaments suspended in either relaxing solution or ATP-free solution. is the average linewidth of the photoelectron count autocorrelation function of the light scattered. PP_i had no effect on the increase of values by Sr²⁺ but it substantially increased the values of the thick myofilaments suspended in Ba²⁺-substituted Ca²⁺ activating solution. The results show that PP_i also affects the energy-requiring cyclic cross-bridge motions.     

Deciduogenic effects of mediators of the polyphosphatidylinositol pathway in pseudopregnant mice

Intraluminal injections (15 l) of either concanavalin A (125 g) or ionophore A 23187 (0.01 mol) induced a decidual cell reaction (DCR) in the uterus of day 4.5 pseudopregnant mice. However, when these agents were administered in different combinations with each other or with CaCl₂ (15 mol) and phorbol-12-myristate-13-acetate (1.6 nmol), interacting effects occurred to either enhance or inhibit each of the others' independent deciduogenic capacities. The results suggest that the polyphosphatidylinositol pathway and Ca²⁺ are involved in the induction of the DCR in mice with complex interactions occurring between the active components of the pathway to modulate the outcome of the transformation process.     

Vorgänge bei pH-Änderung und bei Belichtung eines Anthocyanidins

Summary The anthocyanidin investigated here exists below pH 4 as a cationAH ₂ ⁺ (wave length of absorption maximum _max=459 mµ), between pH 5 and 7 in the neutral formAH ( _max=492 mµ) and above pH 8 as an anionA ^– ( _max=537 mµ). At pH 5 the freshly dissolved substance is partially converted into a colourless formBH ( _max=372 mµ) and a chemical equilibrium betweenAH andBH is reached within 1 h. A kinetic study of the process of formation ofBH shows that an intermediate productZ is formed. This process can be reversed by light exposure. It can be concluded from a kinetic investigation by using flash light thatBH is transformed by the absorbing light into a new substanceL ( _max 275 mµ and 225 mµ), andL changes partially intoBH, partially intoZ, which itself is transformed partially intoAH ₂ ⁺ ,AH,A ^–, partially intoBH. The reactionZ AH,AH ₂ ⁺ ,A ^– is proportional to the concentration of protons [H ⁺], the reactionZ BH independent of [H ⁺]. Thus a photochemical production ofAH ₂ ⁺ ,AH,A ^– fromBH is readily obtained in the presence ofH ⁺ and not obtained in the absence ofH ⁺.     

The effect of ligand on the kinetics of the reaction of the sulfhydryl groups of human hemoglobin with p-mercuribenzoate

Summary The rate of reaction of PMB with the masked sulfhydryls of human hemoglobin derivatives correlates well with the extent of dissociation for various ligands. It is suggested that the ₁₂ dimer of hemoglobin participates in the slow step of the reaction with PMB.     

Nitrogenase activity in a transfilter culture of rhizobia with a non-leguminous plant callus culture: Transfer of fixed15N2 from bacteria toPortulaca callus

Summary A transfilter culture of the non-leguminous plantPortulaca grandiflora var. JR andRhizobium sp. cowpea 32H1 was established. Using¹⁵N₂-analysis we demonstrated that¹⁵N-containing substances produced by the bacteria passed through the membrane and¹⁵N was enriched in the plant cells.Acknowledgment. The authors wish to express their gratitude to Prof. H. Marschner and Dr G. Hentschel for the determination of the nitrogen-content of our samples by the Dumasmethod and for advice on the optic emission method. Drs J. Burton, Milwaukee, Wisc., and Tjepkema, Oregon State University, are thanked for generous gifts ofRhizobium sp. cowpea 32H1. This work was supported by the DFG.     

Effects of scavengers of superoxide radicals,hydrogen peroxide,singlet oxygen and hydroxyl radicals on malondialdehyde generation from arachidonic acid by bovine seminal vesicle microsomes

Summary Superoxide dismutase, catalase and sodium formate did not inhibit the formation of malondialdehyde (MDA) from arachidonic acid, suggesting that O ₂ , H₂O₂ and OH^. are not involved in the enzymatical oxidation of arachidonic acid. Sodium azide was found to be an inhibitor of MDA production.