Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalis

Abstract 1 Willows are frequently attacked and defoliated by adult leaf beetles (Phratora vulgatissima L.) early in the season and the plants are then attacked again when new larvae emerge. The native willow Salix cinerea has previously been shown to respond to adult grazing by producing new leaves with an increased trichome density. Subsequent larval feeding was reduced on new leaves. This type of induced plant response may reduce insect damage and could potentially be utilized for plant protection in agricultural systems. 2 Here, we investigated if the willow species most commonly used for biomass production in short rotation coppice, Salix viminalis, also responds to adult beetle grazing by increasing trichome density. Larval performance and feeding behaviour on plants previously exposed to adult beetles was compared with that on undefoliated control plants in a greenhouse. 3 We found an overall decrease in trichome density within all the plants (i.e. trichome density was lower on new leaves compared to that for older basal leaves on S. viminalis). However, leaves of beetle defoliated plants had a higher trichome density compared to control plants. Larval growth and feeding was not affected by this difference between treatments. Larvae appeared to remove trichomes when feeding on S. viminalis, a behaviour that might explain the lack of difference between treatments.     

The design and pharmacology of novel selective muscarinic agonists and antagonists

The muscarinic pharmacology of C1-methyl-substituted chiral compounds related to McN-A-343 and of (R)- and (S)-dimethindene has been studied. Among the McN-A-343 analogues, the (S)-enantiomers were more potent and had higher affinity than the (R)-isomers. The quaternary compound (S)-BN 228 was found to be the most potent M1-selective agonist known today (pEC50: M1/rabbit vas deferens = 7.83; M2/guinea-pig atria = 6.35; M3/guinea-pig ileum = 6.29). In both the atria and ileum the tertiary carbamate, (S)-4-F-MePyMcN, was a competitive antagonist (pA2 value = 7.39 and 6.82, respectively). In contrast, in rabbit vas deferens (S)-4-F-MePyMcN was a potent partial agonist (pEC50 = 7.22; apparent efficacy = 0.83). These results indicate that (S)-4-F-MePyMcN might be a useful tool to study M1 receptor-mediated effects involved in central cholinergic function. (S)-Dimethindene was a potent M2-selective antagonist (pA2 = 7.86/atria; pKi = 7.8/rat heart) with lower affinities for the M1 (pA2 = 6.36/rat duodenum; pKi = 7.1/NB-OK 1 cells), M3 (pA2 = 6.92/guinea-pig ileum; pKi = 6.7/rat pancreas) and M4 receptors (pKi = 7.0/rat striatum). It was more potent (up to 41-fold) than the (R)-isomer. In contrast, the stereoselectivity was inverse at ileal H1 receptors (pA2: (R)-isomer = 9.42; (S)-isomer = 7.48). Thus, (S)-dimethindene could be a valuable agent to test the hypothesis that M2 antagonists show beneficial effects in the treatment of cognitive disorders. It might also become the starting point for the development of diagnostic tools for quantifying M2 receptors in the CNS with PET imaging.     

Plastid development in germinating wheat (Triticum aestivum) is enhanced by gibberellic acid and delayed by gabaculine

Etioplast development and protochlorophyllide (Pchlide) accumulation was studied in wheat seedlings ( Triticum aestivum L. cv. Walde, Weibull) grown in darkness on gibberellic acid (GA₃), gabaculine (3-amino-2,3-dihydrobenzoic acid), or on a combination of the two. The results were compared with the features of seedlings grown on water only. GA₃ enhanced shoot growth and promoted etioplast development. A correlation was observed between the appearance of prolamellar bodies (PLBs) and of phototransformable Pchlide. Gabaculine, a known tetrapyrrole biosynthesis inhibitor, delayed growth, slowed down the rate of PLB formation and caused structural alterations of the etioplasts up to 48 h of germination. Gabaculine also delayed the formation of phototransformable Pchlide as well as overall Pchlide biosynthesis, as determined by low-temperature fluorescence emission in vivo. The spectral blue-shift of newly formed chlorophyllide (Chlide) was delayed in irradiated dark-grown gabaculine-grown seedlings, indicating an inhibited dissociation of Chlide and NADPH-Pchlide oxidoreductase (Pchlide reductase: EC 1.3.1.33). Thus there is a close correlation between accumulation of Pchlide and etioplast development, also under conditions when development is enhanced or delayed.     

The in vitro assembly of the NADPH-protochlorophyllide oxidoreductase in pea chloroplasts

The NADPH-protochlorophyllide oxidoreductase (pchlide reductase, EC 1.6.99.1) is the major protein in the prolamellar bodies (PLBs) of etioplasts, where it catalyzes the light-dependent reduction of protochlorophyllide to chlorophyllide during chlorophyll synthesis in higher plants. The suborganellar location in chloroplasts of light-grown plants is less clear. In vitro assays were performed to characterize the assembly process of the pchlide reductase protein in pea chloroplasts. Import reactions employing radiolabelled precursor protein of the pchlide reductase showed that the protein was efficiently imported into fully matured green chloroplasts of pea. Fractionation assays following an import reaction revealed that imported protein was targeted to the thylakoid membranes. No radiolabelled protein could be detected in the stromal or envelope compartments upon import. Assembly reactions performed in chloroplast lysates showed that maximum amount of radiolabelled protein was associated to the thylakoid membranes in a thermolysin-resistant conformation when the assays were performed in the presence of hydrolyzable ATP and NADPH, but not in the presence of NADH. Furthermore, membrane assembly was optimal at pH 7.5 and at 25°C. However, further treatment of the thylakoids with NaOH after an assembly reaction removed most of the membrane-associated protein. Assembly assays performed with the mature form of the pchlide reductase, lacking the transit peptide, showed that the pre-sequence was not required for membrane assembly. These results indicate that the pchlide reductase is a peripheral protein located on the stromal side of the membrane, and that both the precursor and the mature form of the protein can act as substrates for membrane assembly.     

Glycolytic flux is conditionally correlated with ATP concentration in Saccharomyces cerevisiae: a chemostat study under carbon- or nitrogen-limiting conditions.

Anaerobic and aerobic chemostat cultures of Saccharomyces cerevisiae were performed at a constant dilution rate of 0.10 h(-1). The glucose concentration was kept constant, whereas the nitrogen concentration was gradually decreasing; i.e., the conditions were changed from glucose and energy limitation to nitrogen limitation and energy excess. This experimental setup enabled the glycolytic rate to be separated from the growth rate. There was an extensive uncoupling between anabolic energy requirements and catabolic energy production when the energy source was present in excess both aerobically and anaerobically. To increase the catabolic activity even further, experiments were carried out in the presence of 5 mM acetic acid or benzoic acid. However, there was almost no effect with acetate addition, whereas both respiratory (aerobically) and fermentative activities were elevated in the presence of benzoic acid. There was a strong negative correlation between glycolytic flux and intracellular ATP content; i.e., the higher the ATP content, the lower the rate of glycolysis. No correlation could be found with the other nucleotides tested (ADP, GTP, and UTP) or with the ATP/ADP ratio. Furthermore, a higher rate of glycolysis was not accompanied by an increasing level of glycolytic enzymes. On the contrary, the glycolytic enzymes decreased with increasing flux. The most pronounced reduction was obtained for HXK2 and ENO1. There was also a correlation between the extent of carbohydrate accumulation and glycolytic flux. A high accumulation was obtained at low glycolytic rates under glucose limitation, whereas nitrogen limitation during conditions of excess carbon and energy resulted in more or less complete depletion of intracellular storage carbohydrates irrespective of anaerobic or aerobic conditions. However, there was one difference in that glycogen dominated anaerobically whereas under aerobic conditions, trehalose was the major carbohydrate accumulated. Possible mechanisms which may explain the strong correlation between glycolytic flux, storage carbohydrate accumulation, and ATP concentrations are discussed.     

EPR studies on the photosystem II donor side in salt-washed and reconstituted inside-out thylakoids

EPR measurements on inside-out thylakoids revealed that salt-washing, known to inhibit oxygen evolution and release a 23 and a 16 kDa protein, induced a Signal II_f and decreased the EPR signal from state S₂. Readdition of the released 23 kDa protein restored the oxygen evolution and decreased the Signal II_f, but did not relieve the decrease in the state S₂ signal. It is suggested that salt-washing inhibits the electron transfer from the oxygen-evolving site to Z, the physiological donor to P680. In inhibited photosystem II units lacking Signal II_f, Z⁺ is rapidly reduced, possibly by a modified S-cycle unable to evolve oxygen.     

Complete remission in a patient with acute myelogenous leukemia treated with leukocyte α-interferon and cimetidine

Summary A 76-year-old woman with acute myelogenous leukemia with approximately 65% myeloblasts on bone marrow examination was treated daily with a combination of 4 megaU of leukocyte interferon IM and 1,000 mg cimetidine PO. During therapy there was a gradual decrease of bone marrow myeloblasts down to 9% and a normalization of peripheral white blood cells. The treatment was discontinued after 6 weeks because of increasing fatigue and anorexia. The general condition improved greatly during the following weeks and the patient entered complete remission, which has continued for 6 months so far. In the course of therapy there was a gradual appearance of antibodies showing a selective binding capacity to autochthonous leukemic cells with no tendency to increased binding to remission cells. The aim of this report is to stimulate a further evaluation of this form of therapy in additional AML patients whenever this might be justified as an alternative to conventional chemotherapy.     

A comparison of models for sharpening of the frequency selectivity in the coachlea

The mechanical tuning of the basilar membrane has not been shown to be sharp enough to explain the very narrow tuning curves observed in primary auditory fibers. A mechanism for sharpening of the frequency selectivity or an unknown second filter is therefore assumed to exist in the cochlea. In the present paper, several theories for frequency selectivity sharpening in the cochlea are studied with the aid of a basilar membrane model. It is shown that the model proposed by Zwislocki (1974) for interaction between inner and outer hair cells results in the greatest increase in selectivity. It is also shown that nonlinear basilar membrane motion may very well explain the discrepancy between mechanical and neural tuning. Besides an increased selectivity at low sound intensities due to an increased low-frequency cut-off slope in the frequency transfer function, nonlinear basilar membrane motion also results in an increased high-frequency cut-off slope not present in other models for frequency selectivity sharpening.     

Periphytic and drifting microalgae in a tributary stream of Øvre Heimdalsvatn

Samples of drifting and periphytic microalgae were collected during 1972 from a fast-flowing, stony stream (Brurskardsbekken) in the Jotunheimen mountain area, central southern Norway. The predominant algal groups in the drift and the periphyton were diatoms and green algae, while only a few species were recorded in both communities. A considerable number of species from Chrysophyceae, Cryptophyceae and other algal classes were also recorded in the drift samples. The species composition was in good agreement with microalgal communities earlier described from mountain areas in Scandinavia, although species which probably are new to Norway, were also recorded. A quantitatively important fraction of planktonic species in the drift is interpreted as a contribution from lacustrine habitats in the watercourse. A general change in the periphyton during the summer, from green algae to diatoms, was observed, Altitudinal differences in the periphyton included a delayed green algal maximum at higher altitudes compared to lower. In the zone around the upper birch limit, a transition in species composition as one goes up stream, described in other investigations, was not observed.