Larger adenylate energy charge and ATP/ADP ratios in aerenchymatous roots of Zea mays in anaerobic media as a consequence of improved internal oxygen transport

Internal transport of O₂ from the aerial tissues along the adventitious roots of intact maize plants was estimated by measuring the concentrations of adenine nucleotides in various zones along the root under an oxygen-free atmosphere. Young maize plants were grown in nutrient solution under conditions that either stimulated or prevented the formation of a lysigenous aerenchyma, and the roots (up to 210 mm long) were then exposed to an anaerobic (oxygen-free) nutrient solution. Aerenchymatous roots showed higher values than non-aerenchymatous ones for ATP content, adenylate energy charge and ATP/ADP ratios. We conclude that the lysigenous cortical gas spaces help maintain a high respiration rate in the tissues along the root, and in the apical zone, by improving internal transport of oxygen over distances of at least 210 mm. This contrasted sharply with the low energy status (poor O₂ transport) in non-aerenchymatous roots.Abbreviation AEC adenylate energy charge     

Chloroplast movement in Mougeotia induced by blue light pulses

The profile-to-face chloroplast movement in the green alga Mougeotia has been induced by strong blue and near-ultraviolet light pulses (6 J m^-2). Simultaneously, strong red or far-red light (10 W m^-2) was applied perpendicularly to the inducing beam. The response was measured photometrically. Against the far-red background the reciprocity law was found to hold for pulse durations varying two orders of magnitude. The action spectrum exhibited a maximum near 450 nm and a distinct increase in near-ultraviolet. The time-course and the spectral dependence of pulse responses of chloroplasts in Mougeotia were similar to those recorded for other plants which are sensitive only to blue. This points to an alternative sensor system active in the short-wavelength region in addition to the phytochrome system.Abbreviations FR far-red light - Pr red absorbing form of phytochrome - Pfr far-red absorbing form of phytochrome - R red light This paper is dedicated to the memory of Professor Jan Zurzycki     

The nutrition of stomachless phytoplanktivorous fish in comparison with Tilapia

The contents of alimentary tracts of stomachless phytoplanktivorous fish, including silvercarp (Hypophthalmichthys molitrix), Esomus danrica thermoicos, and Amblypharyngodon meletinus were investigated microscopically and compared with those of Tilapia (Oreochromis mossambicus, a fish with stomach).The predominance of detritus in the food and the low efficiency with which phytoplankton is utilized prove, that stomachless fish are not primarily herbivorous. The possibility of omnivorous feeding as an alternative is discussed. These results may contribute to our understanding of the role of filterfeeders in aquaculture and ecosystems.     

Impact de l'échantillonnage sur la mésure des nucléotides adényliques (ATP,ADP, AMP) du microplancton

The influence of sampling and sample treatment upon adenylic nucleotide (ATP, ADP, AMP) content of microplankton is studied. Changes in light conditions during nigh-sampling and extracting do not induce significant variations, in the adenylic nucleotide content of microplankton or in energy charge values.The contribution of zooplankton (size up to 200 µm) to microplankton adenosine values can be neglected for inshore surface waters and traditional sample volumes (about one liter). This result can been explained by the low density of zooplankton in such a small sample volume and by differences in efficiency of the extracting method used.

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Impact de l'échantillonnage sur la mésure des nucléotides adényliques (ATP, ADP, AMP) du microplancton

     

Interaction of Opiates with Opioid Binding Sites in the Bovine Adrenal Medulla: I. Interaction with δ and μ Sites

In the present study we examined the interaction of opiates with the delta and mu opioid binding sites in the bovine adrenal medulla. [3H][D-Ala2, D-Leu5]-enkephalin ( [3H]DADLE) in the presence of saturating concentrations of morphiceptin was used to analyze delta site interactions, whereas either [3H]DADLE in the presence of saturation concentrations of [D-Ser2, Leu5]-enkephalin-Thr6 (DSLET) or [3H][D-Ala2, Me-Phe4, Gly5-ol]-enkephalin ( [3H]DAGO) was used for the determination of mu sites. Both binding sites were found to interact stereoselectively with opiates. The binding was affected differentially by proteolytic enzymes (trypsin, alpha-chymotrypsin, pepsin), N-ethylmaleimide, and A2-phospholipase. Kinetic and equilibrium binding studies revealed that in each case radiolabeled opiates interact with one class of binding sites, following simple second-order bimolecular kinetics. Competition for binding by opiates and opioid peptides confirmed the delta and mu selectivity of these sites. Monovalent (Na+, Li+, K+) and divalent (Mg2+, Mn2+, Ca2+) ions interacted differentially with these two binding sites: In general, monovalent cations affected preferentially the apparent number of binding sites, whereas divalent ions modified the equilibrium dissociation constant. Furthermore, positive or negative cooperativity and an apparent heterogeneity of binding sites were detected under some ionic conditions.     

Drug Potencies on Partially Purified Brain D2 Dopamine Receptors

To examine the sensitivities of partially purified dopamine receptors to various dopaminergic agonists and antagonists, canine brain striatum dopamine receptors were enriched by isoelectric focusing. The digitonin-solubilized receptors were prelabelled with [3H]spiperone and focused for two time periods. After 5 h (incomplete focusing), radioactive peaks were detected at pH 6 and 9-11. Only the pH 6 peak revealed drug sensitivities expected of D2 receptors. Receptor recovery of the pH 6 peak was 79% with purification being sevenfold. After focusing overnight to equilibrium, the pH 6 peak further separated into peaks at pH 4.6 and 6.8. The receptor was identified only in the pH 4.6 fraction. The recovery of receptors in the pH 4.6 peak was low (10%), indicating little enrichment of the receptor. The rank order of binding of neuroleptics and dopamine agonists to the purified material was similar to that of the original preparation of soluble receptors. Dopamine did not bind to the purified pH 4.6 fraction unless the phosphate buffer (used during focusing) was replaced with Tris buffer. The absence of receptors in the pH 6.8 and pH 10 fractions, although both contained prelabeled [3H]spiperone, indicates the importance of testing agonists and antagonists on each fraction at each step in purification.     

Measurement of Substance P Metabolites in Rat CNS

A procedure based on ion-exchange chromatography for chemical separation and radioimmunoassays for quantitation of substance P (SP), the SP(1-7), and C-terminal fragments, respectively, has been developed. The procedure allows the determination of these fragments in the presence of large (i.e., 50- to 100-fold) excess of parent compound. The chemical identity of isolated SP and fragments was studied with preparative electrophoresis on dilute agarose gel and with HPLC. The activity identified as SP(1-7) comigrated with the authentic standard whereas practically all activity isolated as C-terminal fragments comigrated with SP(5-11). The levels of C-terminal fragments in rat brain areas rich in SP and in spinal cord were 1-2% of those of parent compound. The levels of SP(1-7) were always higher, in the spinal cord markedly higher (three to five times). Postmortem storage of samples from brain and spinal cord indicated that SP(1-7) levels fell more rapidly than those of SP or C-terminal fragments.     

Deamination of Aliphatic Amines by Monoamine Oxidase A and B Studied Using a Bioluminescence Technique

Deamination of n-octylamine and n-decylamine has been studied in various tissues using a new bioluminescence technique. Selectivity of n-octylamine and n-decylamine as substrates for monoamine oxidase (MAO) A or B has been determined using both clorgyline and (-)-deprenyl inhibition curves and kinetic parameters. Homogenates of rat brain, liver and heart containing predominantly MAO-A or -B were prepared by preincubation for 60 min with (-)-deprenyl or clorgyline (30 nM), respectively. Human placenta (MAO-A) and platelet (MAO-B) were used as reference tissues containing only one MAO form. In tissues (rat liver, brain) containing both MAO forms in equal proportion, inhibition curve studies showed a preference of both substrates for the B form of the enzyme; however, where MAO-A was the major form (rat heart, human placenta), clorgyline was the more effective inhibitor. In the beef brain cortex n-octylamine showed marked preference for MAO-B, whereas n-decylamine was selective toward-MAO-A. Kinetic studies in general supported the picture of greater selectivity of the aliphatic amine substrates for deamination by MAO-B, as reflected by lower Km values for this enzyme type. However, n-octylamine was more selective for MAO-B than n-decylamine in both kinetic and inhibition curve studies. The deamination of these aliphatic amine substrates cannot be explained only by reference to the binary classification of MAO into types A and B.     

k-Binding and Degradation of [3H]Dynorphin A (1–8) and [3H]Dynorphin A (1–9) in Suspensions of Guinea Pig Brain Membranes

Following incubation of [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9) with suspensions of guinea pig brain membranes, analysis of the supernatants by HPLC has shown that both peptides are degraded at 25 degrees C and at 0 degrees C. Bestatin and captopril reduce degradation at 0 degrees C but for a similar degree of protection at 25 degrees C arginine-containing dipeptides are also required. The effects of these peptidase inhibitors on the degradation profiles indicate that [3H]dynorphin A (1-8) has three main sites of cleavage: the Tyr1-Gly2, Arg6-Arg7, and Leu5-Arg6 bonds. With [3H]dynorphin A (1-9) as substrate the Arg7-Ile8 and Ile8-Arg9 bonds are also liable to cleavage. In binding assays, in contrast to the effects of peptidase inhibitors on the degradation of unbound [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9), bestatin and captopril have little effect on the binding characteristics of the tritiated dynorphin A fragments at the kappa-site at 0 degrees C. However, at 25 degrees C binding is low in the absence of peptidase inhibitors. When binding at mu- and delta-sites is prevented, the maximal binding capacities of [3H]dynorphin A (1-8), [3H]dynorphin A (1-9), and [3H](-)-bremazocine at the kappa-site are similar; [3H]dynorphin A (1-9) has 5-10 times higher affinity for the kappa-site than [3H]dynorphin A (1-8). Comparison of the effects of peptidase inhibitors on unbound dynorphin A fragments with their effects in binding assays suggests that the bound peptides are protected from the action of peptidases.     

Massive ribonucleoprotein bodies in gametophyte vegetative cells of the mossTimmiella barbuloides (Brid.) Moenk

Summary Vegetative cells of the gametophyte phase of the mossTimmiella barbuloides (Pottiales) are characterized by large cytoplasmic bodies of spherical shape (SBs) whose ribonucleoprotein composition is cytochemically demonstrated. SBs seem to be derived from massive aggregation of cytoplasmic ribosomes, with possible participation by rough endoplasmic reticulum elements. SBs have been found in stereids, parenchymatous cells and young hydroids of the gametophyte stem, and in euricysts of the leaf nerve. The SBs develop early in the course of cell differentiation and, once formed, persist until advanced stages of cell senescence.