Shade tolerance of <Emphasis Type="Italic">Ailanthus altissima</Emphasis> revisited: novel insights from southern Switzerland

The tree of heaven (Ailanthus altissima (Mill.) Swingle) is considered to be an early-successional, gap-obligate pioneer species with vigorous height growth, low shade tolerance, early fecundity and large seed production. It is a highly invasive species in many temperate and Mediterranean ecosystems outside its natural range, especially after disturbance. Due to its low shade tolerance, the potential of A. altissima to colonise undisturbed forests is thought to be low. In this study we analysed the potential of juvenile A. altissima to grow and survive in sweet chestnut (Castanea sativa Mill.) forests in southern Switzerland. We used hemispherical photography to assess the light conditions of 204 individuals of A. altissima (31 % generative, 69 % vegetative) aged between 1 and 7 years (median: 3 years) in six sites. Generative (seed-borne) and vegetative (clonal ramet) offspring of A. altissima are able to grow in light conditions well below the requirements of shade-intolerant tree species such as European larch (Larix decidua Mill.) and Scots pine (Pinus sylvestris L.). The relatively low light conditions found to be sufficient for the growth and survival of generative regeneration of A. altissima suggest a higher shade tolerance for this species than previously stated, at least for early regeneration. Consequently, the colonisation frontier of A. altissima should be intensively monitored in both forest openings but also in closed canopy forests in the vicinity of seed-bearing A. altissima.     

Bio-cultural effects in medieval populations

Male skeletons from medieval archaeological sites are analysed to assess differences in stature and body proportions related to the bio-cultural environment, such as social, economic, and health factors. Environmental factors, such as climate change in the course of the Middle Ages, did not have statistically significant effect on body proportions in these samples. The results show a relationship between bio-cultural factors and physique in the analysed populations that indicate stunted growth in height and weight in a leprosarium population with a low socio-economic and health status. A high-status monastic population is characterised by a stocky build, i.e., increased weight for height and relatively shorter limbs, while a medieval parish population has a linear build, i.e., relatively long limbs for height and decreased weight for height. These characteristics, relative weight for height and relative limb length, changed during the course of the Middle Ages, as did stature.     

Tolerance and Metabolic Response of Acetogenic Bacteria toward Oxygen

The acetogens Sporomusa silvacetica, Moorella thermoacetica, Clostridium magnum, Acetobacterium woodii, and Thermoanaerobacter kivui (i) grew in both semisolid and liquid cultivation media containing O₂ and (ii) consumed small amounts of O₂. Low concentrations of O₂ caused a lag phase in growth but did not alter the ability of these acetogens to synthesize acetate via the acetyl coenzyme A pathway. Cell extracts of S. silvacetica, M. thermoacetica, and C. magnum contained peroxidase and NADH oxidase activities; catalase and superoxide dismutase activities were not detected.     

Novel pseudosymmetric inhibitors of HIV-1 protease

Compounds containing the easily accessible Phe[CH(OH)CH₂N(NH)Phe dipeptide isostere as a non-hydrolyzable replacement of the scissile amide bond in the natural substrate are potent inhibitors of HIV-1 protease. The expected symmetric binding pattern of the most potent inhibitor in this series (CGP 53280, IC₅₀ = 9 nM) is illustrated by the X-ray analysis performed with the corresponding enzyme-inhibitor complex.     

Isolation of early viral proteins from poxvirus-infected chick embryo fibroblasts by DNA-cellulose chromatography and inhibition of their synthesis by chicken interferon

Up to seven early poxvirus-specific proteins have been isolated from vaccinia-WR-infected and cowpox-virus-infected chick embryo fibroblasts by affinity chromatography on native DNA-cellulose columns. The proteins have been characterized by one-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis and by nonequilibrium pH-gradient electrophoresis. The molecular weights of the viral proteins were determined by comparison with proteins of known molecular weight and are comparable to several of the vaccinia-WR-specific DNA-binding proteins isolated previously from infected L-929 cells by Solosky J. M., Esteban M. and Holowczak J.A. [J. Virol. 25, 263-273 (1978)]. The viral proteins binding reversibly to native DNA have been classified as immediate early viral gene products. Synthesis of cowpox-virus-induced early DNA-binding proteins is inhibited in chick cells pretreated with homologous interferon at a concentration of 500--1000 units/ml.     

K-252b Is a Selective and Nontoxic Inhibitor of Nerve Growth Factor Action on Cultured Brain Neurons

K-252b is a kinase inhibitor structurally related to K-252a, which is known to abolish selectively the effects of nerve growth factor (NGF) on PC12 cells and PNS neurons. We tested whether K-252b, K-252a, and staurosporine, another related compound, are effective and selective inhibitors of NGF actions on CNS neurons. All three compounds, at appropriate concentrations, completely and selectively prevented the NGF-mediated activity increase of the cholinergic marker enzyme choline acetyltransferase in cultures of rat basal forebrain cells. The stimulatory effects of basic fibroblast growth factor and insulin on choline acetyltransferase in these cultures and on dopamine uptake in cultures of dissociated ventral mesencephalon were not affected. No signs of toxicity were observed in cultures treated with K-252b. In contrast, K-252a and staurosporine, at concentrations required to block the NGF actions on cholinergic cells, were cytotoxic and produced cell loss. In addition, K-252a, at higher concentrations and in the absence of growth factors, increased cell numbers. Our study suggests that K-252b is a selective and nontoxic inhibitor of NGF actions in the brain and may become a useful tool to study these actions in vivo.     

Immunohistochemical localization of β-glucosidases in lignin and isoflavone metabolism in Cicer arietinum L. seedlings

Coniferin specific- and isoflavone 7-glucoside specific -glucosidases have been localized in stem and root sections of chick pea (Cicer arietinum L.) seedlings by the indirect immunofluorometrical method. The coniferin specific -glucosidase has been found in the cell walls of the tracheary elements and of the endo-, epi-, and exodermis. All these tissues are known to contain either lignin or polymers, like suberin and cutin, which consist partially of phenylpropanoid elements. The localization of this -glucosidase is therefore in agreement with its postulated relationship to the phenylpropanoid metabolism. The isoflavone 7-glucoside specific -glucosidase, on the other hand, is predominantly located in the parenchymatic cortex cells, and obviously in the cytoplasm. These cells are known to contain the isoflavone formononetin, which has been shown to undergo turnover in chick pea seedlings. We therefore have good reason to assume that this -glucosidase is involved in the metabolism of the 7-glucoside of this isoflavone.Abbreviations SDS sodium dodecylsulfate - PBS physiological phosphate saline The results are part of the thesis of Gerd Burmeister, 1980, University of Münster     

Beta-Glucosidases from Cicer arietinum L. Purification and Properties of isoflavone-7-O-glucoside-specific beta-glucosidases.

Beta-Glucosidases specific for isoflavone 7-O-glucosides have been isolated from garbanzo plants, Cicer arietinum L. These aryl-beta-glucohydrolases occur in the different organs of the plant as multiple molecular forms. The major isoenzymes of the roots, the leaves and the hypocotyl were purified to electrophoretic homogeneity. When subjected to isoelectric focussing in polyac rylamide gels the electrophoretically homogeneous glucohydrolases were found to consist of one or two major and several minor enzymically active molecular species. In roots the beta-glucohydrolase isoenzymes constitute a considerable portion of the extractable protein, so that purification to an electrophoretically homogeneous form is easily attainable. All beta-glucosidases analyzed possess molecular weights in the range of 125 000 (ultracentrifugation) to 135 000 (Sephadex G-200) and contain two subunits of molecular weight near 68 000. The pH optimum for enzymic activity is 7--7.5 with a second optimum of 4.5--5. The isoelectric points of the various species range between pH 5.9 AND 7.1. Staining for glycoprotein was positive. Kinetic analysis demonstrated a pronounced specificity of the enzymes for aromatic substrates with glucose as the sugar moiety. alpha-Glucosides as well as disaccharides were not hydrolyzed at all. Isoflavone 7-O-glucosides are the most favoured substrates with a Km of 2 x 10(-5) M, while the Km with aromatic glucosides (i.e. salicin, 4-nitrophenyl glucoside) are 100 times larger. In addition the beta-glucosidases show a pronounced specificity for glucose in the 7-position of the flavonoid nucleus. Using isoflavone aglycones as substrates glucose transferase activity was also demonstrable. The beta-glucohydrolase activity is strongly inhibited by Hg2plus. This inhibition is partially reversible and preferentially influences the Km values of the enzymes compared to V. Agplus, glucono-1,5-lactone, ethyleneglycol monomethyl ether and glycerol are only weakly inhibitory, while glucose, p-chloromercuribenzoate and Cu2plus are without effect.     

Ueber den abbau von flavonolen durch pflanzliche peroxidasen

Peroxidases have been shown to catalyse the degradation of flavonols via 2,3-dihydroxyflavanones to benzoic acids. Incubation of (U-¹⁴C)-kaempferol with pure horseradish peroxidase leads to the same reaction products (2,3,4,5,7,4′-pentahydroxyflavanone, p-hydroxybenzoic acid, ¹⁴CO₂, several polar, water soluble catabolites as given by enzyme preparations from various plant species. Further reactions of flavonols and their glycosides with peroxidases are discussed. All peroxidase isoenzymes of Sinapis alba and Cicer arietinum, obtained by isoelectric focusing, have been shown to degrade flavonols at the same rate. The peroxidase catalysed degradation of polyphenols is discussed in relation to IAA oxidase.