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Gold nanostars: surfactant-free synthesis, 3D modelling, and two-photon photoluminescence imaging

Understanding the control of the optical and plasmonic properties of unique nanosystems—gold nanostars—both experimentally and theoretically permits superior design and fabrication for biomedical applications. Here, we present a new, surfactant-free synthesis method of biocompatible gold nanostars with adjustable geometry such that the plasmon band can be tuned into the near-infrared region ‘tissue diagnostic window’, which is most suitable for in vivo imaging. Theoretical modelling was performed for multiple-branched 3D nanostars and yielded absorption spectra in good agreement with experimental results. The plasmon band shift was attributed to variations in branch aspect ratio, and the plasmon band intensifies with increasing branch number, branch length, and overall star size. Nanostars showed an extremely strong two-photon photoluminescence (TPL) process. The TPL imaging of wheat-germ agglutinin (WGA) functionalized nanostars on BT549 breast cancer cells and of PEGylated nanostars circulating in the vasculature, examined through a dorsal window chamber in vivo in laboratory mouse studies, demonstrated that gold nanostars can serve as an efficient contrast agent for biological imaging applications.

Biological control of sclerotial blight of tea using arbuscular mycorrhizal fungus and plant growth promoting rhizobacterium.

Glomus fasciculatum , one of the dominant arbuscular mycorrhizal fungus (AMF) associated with tea root colonization, was selected and maintained in maize plants. Besides AMF, Bacillus amyloliquefaciens TRS6 isolated from tea rhizosphere, which showed in vitro antagonism to a number of tea root rot pathogens as well as siderophore-producing and phosphate-solubilizing activities, was selected for utilization as bioinoculants in tea plants for improvement of health status. The bacterium was applied to the soil as aqueous suspensions, and in case of G. fasciculatum , soil was inoculated with its spores and in joint inoculations, the AMF was inoculated prior to the bacterium. Inoculation of rhizosphere of tea plants of six different varieties (TV-18, T-17, AV-2, T-78, UP-3 and UP-26) with any of two microorganisms increased growth of plants, but the most significant increase was obtained in dual application. Plant growth was measured in terms of increase in height, increase in number of branches and leaves. Similarly, sclerotial blight of tea, caused by Sclerotium rolfsu , was suppressed to certain extent by G. fasciculatum or B. amyloliquefaciens , but significant suppression occurred when G. fasciculatum and B. amyloliquefaciens were applied jointly. Polyphenolics and four major defense enzymes showed enhanced activities during disease suppression. Western blot of the enzjone extracts from control and all treated plants using PAb raised against chitinase revealed strong reaction when disease suppression was evident. Population of S. rolfsu in soil was also determined following immunological techniques using PAb raised against the pathogen. Results of ELISA and dot-blot revealed that application of G. fasciculatum and B. amyloliquefaciens significantly reduced S. rolfsu population.

Symmetrical and unsymmetrical multibranched D–π–A molecules based on 1,3,5-triazine unit: synthesis and photophysical properties

A series of V-shaped (D–π–A–π–D) and star-shaped ((D–π–)3A) molecules based on the electron acceptor 1,3,5-triazine core (A) connected to different electron donor groups (D) by a carbon–carbon triple bond as a conjugation bridge (π) has been synthesized. The studied molecules can be separated into symmetrically and unsymmetrically substituted molecules depending on the combination of the electron donating branches connected to the triazine core. Their photophysical properties are characterized experimentally and the structure–properties relationship is analysed with the aid of theoretical calculations. The symmetrically branched 1,3,5-triazine-based molecules exhibit similar UV-vis absorption to the corresponding linear molecules, but an obvious blue-shift in the emission is observed with increasing dimensionality. The absorption of the unsymmetrically branched 1,3,5-triazine-based molecules is clearly localized on a specific branch, suggesting a weak interbranch conjugation in the ground state. Emission is mainly controlled by the branch with the lowest energy excited state, which corresponds to the one with the largest intramolecular charge transfer (ICT) effect. The two-photon absorption properties of selected molecules are studied. They exhibit strong two-photon absorption activities and a modest interbranch conjugation effect, enhancing the TPA cross-section beyond the additive effect of increasing branch number.

Transgenic poplar expressing Arabidopsis NDPK2 enhances growth as well as oxidative stress tolerance

Nucleoside diphosphate kinase 2 (NDPK2) is known to regulate the expression of antioxidant genes in plants. Previously, we reported that overexpression of Arabidopsis NDPK2 (AtNDPK2) under the control of an oxidative stress-inducible SWPA2 promoter in transgenic potato and sweetpotato plants enhanced tolerance to various abiotic stresses. In this study, transgenic poplar (Populus alba × Poplus glandulosa) expressing the AtNDPK2 gene under the control of a SWPA2 promoter (referred to as SN) was generated to develop plants with enhanced tolerance to oxidative stress. The level of AtNDPK2 expression and NDPK activity in SN plants following methyl viologen (MV) treatment was positively correlated with the plant's tolerance to MV-mediated oxidative stress. We also observed that antioxidant enzyme activities such as ascorbate peroxidase, catalase and peroxidase were increased in MV-treated leaf discs of SN plants. The growth of SN plants was substantially increased under field conditions including increased branch number and stem diameter. SN plants exhibited higher transcript levels of the auxin-response genes IAA2 and IAA5. These results suggest that enhanced AtNDPK2 expression affects oxidative stress tolerance leading to improved plant growth in transgenic poplar.

Kinetic Analyses of Bindings of Shiga-like Toxin to Clustered and Dispersed Gb3 Glyco-Arrays on a Quartz-Crystal Microbalance

One-, two-, four-, and eight-branched globotriaosyl saccharides (Gb(3): Gal-alpha1,4-Gal-beta1,4-Glc), whose reducing ends were biotinylated, were prepared (1Gb(3)-bio, 2Gb(3)-bio, 4Gb(3)-bio, and 8Gb(3)-bio, respectively). They are dispersively immobilized as a glyco-array in the matrix of biotinylated maltotriose (Glc(3)-bio) on a streptavidin-covered 27 MHz quartz-crystal microbalance (QCM). The binding kinetics of the verotoxin B subunit (VTB) to various branched Gb(3)-bio ligands in the Glc(3)-bio matrix could be obtained from frequency decreases (mass increases) of the QCM. VTB can recognize the Gb(3) unit but not the Glc(3) unit, where VTB is a pentamer having five binding sites for one Gb(3) unit per each B subunit (having a total of 15 binding sites for Gb(3)). By changing the Gb(3) multivalency, the Gb(3) packing density, and the Gb(3) cluster size in the Glc(3) matrix, association constants (K(a)), maximum amounts bound (Delta m(max)), and binding and dissociation rate constants (k(on) and k(off)) were obtained. When 15 sites of VTB were recognized by 16 Gb(3) units, K(a) was 100 times larger than that when 15 sites of VTB were recognized by only 2 Gb(3) units, with a 6-fold-larger k(on) and a 25-fold-smaller k(off). When the Gb(3) multivalency was changed by covering with two 1Gb(3)-bio, 2Gb(3)-bio, 4Gb(3)-bio, or 8Gb(3)-bio ligands on two pockets of one streptavidin, the K(a) values increased with increasing branch number from one to eight. When the Gb(3) cluster size was changed from eight 1Gb(3)-bio units to one 8Gb(3)-bio unit in the matrix, the K(a) values increased but the Delta m(max) values decreased with increasing cluster size from eight 1Gb(3)-bio units to one 8Gb(3)-bio unit. This is the first example of systematically obtaining all kinetic parameters of sugar-binding proteins to sugars on a glyco-array by changing the sugar multivalency, the sugar packing density, and the sugar cluster size in the matrix.

Netrin Participates in the Development of Retinotectal Synaptic Connectivity by Modulating Axon Arborization and Synapse Formation in the Developing Brain

Netrin has been implicated in retinal ganglion cell (RGC) axon pathfinding in a number of species. In Xenopus laevis, RGC axons reaching their target in the optic tectum can be repelled by a netrin-1 gradient in vitro, suggesting that netrin may also function in wiring events that follow successful axon pathfinding. Here, we examined the contribution of netrin to RGC axon arborization and synapse formation at the target. Time-lapse confocal microscopy imaging of individual RGC axons coexpressing GFP-synaptobrevin and DsRed in the intact Xenopus brain demonstrated a role for deleted in colorectal cancer (DCC)-mediated netrin signaling. Microinjection of netrin-1 into the tectum induced a rapid and transient increase in presynaptic site addition that resulted in higher presynaptic site density over a 24 h observation period. Moreover, netrin induced dynamic axon branching, increasing branch addition and retraction; a behavior that ultimately increased total branch number. In contrast, microinjection of DCC function-blocking antibodies prevented the increase in presynaptic site number normally observed in control axons as well as the associated increase in branch number and axon arbor growth. Dynamic analysis of axon arbors demonstrated that the effects of anti-DCC on axon morphology and presynaptic connectivity were attributable to a specific decrease in new synapse and branch additions, without affecting the stability of existing synapses and branches. Together, these results indicate that, in the absence of DCC signaling, RGC axons fail to branch and differentiate, and support a novel role for netrin in later phases of retinotectal development.

Over‐expression of the rice LRK1 gene improves quantitative yield components

In rice (Oryza sativa L.), the number of panicles, spikelets per panicle and grain weight are important components of grain yield. These characteristics are controlled by quantitative trait loci (QTLs) and are derived from variation inherent in crops. As a result of the complex genetic basis of these traits, only a few genes involved in their control have been cloned and characterized. We have previously map-cloned a gene cluster including eight leucine-rich repeat receptor-like kinase (LRK) genes in Dongxiang wild rice (Oryza rufipogon Griff.), which increased the grain yield by 16%. In the present study, we characterized the LRK1 gene, which was contained in the donor parent (Dongxiang wild rice) genome and absent from the recurrent parent genome (Guichao2, Oryza sativa L. ssp. indica). Our data showed that rice LRK1 is a plasma membrane protein expressed constitutively in leaves, young panicles, roots and culms. The over-expression of rice LRK1 results in increased panicles, spikelets per panicle, weight per grain and enhanced cellular proliferation, leading to a 27.09% increase in total grain yield per plant. The increased number of panicles and spikelets per panicle are associated with increased branch number. Our data suggest that rice LRK1 regulates rice branch number by enhancing cellular proliferation. The functional characterization of rice LRK1 facilitates an understanding of the mechanisms involved in cereal crop yield, and may have utility in improving grain yield in cereal crops.

Evidence for elevated nicotine-induced structural plasticity in nucleus accumbens of adolescent rats

Male Long–Evans rats were administered nicotine bitartrate or sodium tartrate either during adolescence (p29–43) or adulthood (p80–94). Route of administration was via subcutaneously implanted osmotic pump (initial dose 2.0 mg/kg/day, free base). Five weeks following nicotine administration, brains were processed for Golgi–Cox staining. Medium spiny neurons from nucleus accumbens (NAc) shell were digitally reconstructed for morphometric analysis. Total dendritic length and branch number were greater in medium spiny neurons from animals pretreated with nicotine during adolescence. A branch order analysis indicated that increased branch number was specific to higher order branches. Mean branch lengths did not differ with respect to treatment as a function of branch order. Thus, nicotine-induced increases in total dendritic length were a function of greater numbers of branches, not increased segment length. In contrast, adult nicotine exposure did not significantly alter total dendritic length or branch number of medium spiny neurons. Total dendritic length and branch number of a second morphological type, the large aspiny neuron, did not differ following either adolescent or adult pretreatment. The age-dependent alteration of accumbal structure was associated with qualitatively different behavioral responses to drug challenge. These data provide evidence that drug-induced structural plasticity in nucleus accumbens is considerably more pronounced during adolescence.

EFFECT OF COMPOST, BIO-FERTILIZER AND ACTIVE DRY YEAST ON ORIGANUM SYRIACUM, L. PLANTS UNDER SINAI CONDITIONS

This experiment was conducted at El-Maghara Research Station (North Sinai), Desert Research Center, during the two successive seasons of 2004 and 2005 to study the effect of compost, bio-fertilizer and yeast on growth , oil production and chemical composition of Origanum syriacum L. cv. Sinaicum (Boiss). The plants were fertilized with compost at the rates 5, 10 and 20 m3/feddan, bio-fertilizer (Azotobacter chroococcum, Azospirillum sp., Bacillus cirulans and Bacillus megaterium var. phosphaticum) and active dry yeast at the concentrations of 0, 5 and 10 g /L. The results showed that compost application at 10 and 20 m3/feddan enhanced number of branches, herb fresh and dry weights, oil percentage, oil yield / plant and chemical composition (N, P, K and total carbohydrates percentage ) of oregano plants. Compost at 10 m3/feddan was the most effective treatment followed by 20m3/ feddan. Active dry yeast, at 5 or 10 g /L led to a significant increment in vegetative growth parameters, oil percentage and oil yield / plant, as well as chemical composition ( N, P , K and total carbohydrates percentage) . Yeast at 5 g /L was the most effective treatment in most cases. Whereas Yeast at 10 g / L was the most effective treatment on oil percentage. Bio-fertilizer led to a significant increase in number of branches, fresh and dry weights / plant, oil percentage, oil yield/ plant, and chemical composition (N, P, K and total carbohydrates percentages) in both two seasons. Interaction had a significant effect on all parameters. Compost at 10 or 20 m3 / feddan plus bio-fertilizer plus active dry yeast at 5 or 10 g /L gave the highest values of vegetative growth parameters, oil percentage, oil yield / plant and N, P , K and total carbohydrates percentage. Keywords: .

Luminescent amphiphilic dendrimers with oligo(p-phenylene vinylene) core branches and oligo(ethylene oxide) terminal chains: syntheses and stimuli-responsive properties

A class of new dendrimers consisting of hydrophobic oligo(p-phenylene vinylene) core branches and hydrophilic oligo(ethylene oxide) terminal chains was synthesized. These amphiphilic dendritic molecules are highly luminescent and exhibit critical micellization behaviors. They also show a lower critical solution temperature (LCST) in an aqueous medium. Both the critical micelle concentration (CMC) and LCST increased with increasing branch number and the ratio of the hydrophilic oligo(ethylene oxide) to hydrophobic oligo(p-phenylene vinylene) moieties. Besides, a temperature-dependent phase transition from a clear to cloudy aqueous solution was observed. The temperature-induced phase transition was also reflected by fluorescence quenching, 1H NMR resonance peak broadening, and UV–vis absorption shift arising from the hydrophobic conjugated core. These changes in the phase structure and photophysical properties were demonstrated to be highly reversible, indicating some interesting stimuli-responsive behaviors.

The Integrated Control of Armillaria mellea 2. Field Experiments

ABSTRACT Several isolates of Trichoderma harzianum, T. viride and T. hamatum, and an isolate each of Dactylium dendroides and Chaetomium olivaceum, found antagonistic in vitro and under glasshouse conditions against several isolates of the root rot pathogen, Armillaria mellea, were evaluated for their ability to suppress root rot of young apple trees under field conditions. Some of these antagonists were selected for integration with two systemic fungicides, fosetyl-Al and fenpropidin. The antagonists were applied on mushroom compost with dead mycelia of Agaricus bisporus either before or after a 2000 mg 1−1 dose of the fungicides, with a time interval of 40 days. Some isolates of the Trichoderma spp. and D. dendroides reduced the extent of infection as compared with that on control plants inoculated only with A. mellea. A significant interaction was found between the antagonists, fungicides and their sequence of application. D. dendroides was significantly (p < 0.05) more effective in reducing the rot when applied 40 days before fosetyl- Al. Conversely, T. harzianum isolate Th23 showed greater efficacy when introduced 40 days after fenpropidin. T. hamatum isolate Tham 1, however, exhibited a greater effect when applied before fenpropidin. Changing sequence of application of the other antagonists with either of the two fungicides had no significant effect on the extent of the root rot. Trees treated with Trichoderma viride isolate Tv3 and fenpropidin had a greater increase in number of branches > 30 cm, but Chaetomium olivaceum caused a greater increase with fosetyl-Al than with fenpropidin. Similarly, increase in branches > 30 cm was significantly greater on trees treated with fosetyl-Al only, compared with those treated with fenpropidin only. Whereas dose rates of fosetyl-Al did not cause significant differences, a dose rate of 8000 mg 1−1 of fenpropidin resulted in significantly fewer branches < 30 cm, compared with the lower dose rates of 2000 and 4000 mg 1−1.

Overcompensation and adaptive plasticity of apical dominance in Erysimum strictum (Brassicaceae) in response to simulated browsing and resource availability

In the cases where overcompensation has been observed in monocarpic herbs, overcompensation is associated with an apically dominant shoot architecture of intact plants, increased lateral branching following herbivory, and increased reproductive success as a consequence of damage. The compensatory continuum hypothesis expects overcompensation to be more prevalent in resource rich environments compared to poor environments. This is paradoxical since in resource rich conditions the intact plants should branch most vigorously and hence any further increase in branch number should lead to lower seed yield. An explanation could be that apical dominance is rather insensitive to changes in resource availability, and that overcompensation is possible in conditions where plants experience meristem limitation (due to apical dominance) in relation to available resources.We explored the branching patterns and fitness responses of tall wormseed mustard (Erysimum strictum) to simulated browsing, soil nutrients, and competition in common garden. Competition increased apical dominance and reduced plant fitness whereas fertilization had the reverse effects. Simulated browsing increased lateral branching and had little impact on plant fitness. Fitness overcompensation was observed only among plants grown in competition and in the absence of fertilization – the most resource poor treatment combination in the experiment. The results contradict both with the compensation continuum and the assumption that apical dominance shows no or very little plasticity in relation to growing conditions. Because directional selection gradients on branch number were invariantly positive irrespective of growing conditions, we propose that, in spite of phenotypic plasticity of apical dominance, the plants appear to be meristem rather than resource limited, and that meristem limitation is strongest in conditions where intact plants produce fewest lateral branches. Our results deviate from the compensation continuum because resource availability affected compensation ability more strongly through phenotypic plasticity of shoot architecture rather than via changes in resource availability per se.

Highly Fluorescent Naphthalimide Derivatives for Two-photon Absorption Materials

Abstract Novel multi-branched naphthalimide derivatives (TPA-NA1, TPA-NA2, and TPA-NA3) were synthesized by the Sonogashira reaction of N-butyl-4-bromo-1,8-naphthalimide with mono-, di-, and tri-ethynylated triphenylamine. The fluorescence increases with the increase of branch number and the quantum yield is as high as 0.87 for TPA-NA3 in toluene. Two-photon absorption cross sections of TPA-NA1, TPA-NA2, and TPA-NA3 were determined to be 0.42 × 10−20 cm4/GW, 1.4 × 10−20 cm4/GW and 1.0 × 10−20 cm4/GW (open aperture Z-scan, 120 fs, 780 nm), respectively.

Micropropagation of Hagenia abyssinica: a multipurpose tree

An in vitro propagation protocol has been developed for Hagenia abyssinica using original material from both juvenile and mature trees. Juvenile explants were obtained from seedlings, as well as shoots and meristems from 5 to 7-month-old greenhouse grown plants. Shoots collected from stem bases of five genotypes were used to establish cultures from mature trees. Explants of seedling origin were used to optimize the multiplication medium and growth regulators concentration. The best result was obtained from shoots subcultured on either MS or WPM medium supplemented with 4.4 μM BAP and 0.49 μM IBA. The initiated shoots from all the different explants were multiplied on these media. Rooting of shoots was achieved using MS medium containing macronutrients at one-third strength supplemented with 4.9 μM IBA. The shoots were kept in the dark for 4 days and transferred to medium of the same composition but containing 0.3% activated charcoal without growth regulators. Up to 100% rooting was achieved depending on genotype. Shoots multiplied on MS medium rooted better than those multiplied on WPM. Plantlets were transferred to pots containing a mixture of soil and perlite in a 2:1 ratio, respectively, and were maintained in the greenhouse. Increased irradiance reduced stem and leaf lengths and increased branch number of micropropagated plants.

Interactive Effects of Sodium Chloride and Nitrogen on Growth and Ion Accumulation of a Halophyte

A sand culture experiment was conducted with a total of 20 treatments including 5 sodium chloride (NaCl) levels (0, 50, 100, 200, and 500 mM) and 4 nitrogen (N) levels (0, 3, 7.5, and 15 mM) to evaluate the interactive effects of NaCl and N on the growth and ion accumulation of the halophyte Suaeda salsa. Under 0 mM N condition, NaCl did not affect plant height significantly, while it increased branch number and root dry weight. Addition of N increased plant growth significantly; this increase was greatest at moderate level and further increase of N concentration did not increase growth significantly. Sodium chloride concentration 50 mM stimulated plant growth in moderate levels of N. Plant growth was significantly inhibited by 500 mM NaCl. Sodium uptake increased with increases of NaCl concentrations, while uptake of potassium (K), calcium (Ca), and magnesium (Mg) decreased. Addition of N increased Na uptake, and decreased K, Ca, and Mg uptake compared with no N treatment. Potassium/Na ratio in plants decreased with addition of 3 mM N, but was unaffected by further increasing N concentration. Ca/Mg ratio in plants increased by addition of moderate N and then decreased by further addition.

Bmp7 regulates branching morphogenesis of the lacrimal gland by promoting mesenchymal proliferation and condensation.

The lacrimal gland provides an excellent model with which to study the epithelial-mesenchymal interactions that are crucial to the process of branching morphogenesis. In the current study, we show that bone morphogenetic protein 7 (Bmp7) is expressed with a complex pattern in the developing gland and has an important role in regulating branching. In loss-of-function analyses, we find that Bmp7-null mice have distinctive reductions in lacrimal gland branch number, and that inhibition of Bmp activity in gland explant cultures has a very similar consequence. Consistent with this, exposure of whole-gland explants to recombinant Bmp7 results in increased branch number. In determining which cells of the gland respond directly to Bmp7, we have tested isolated mesenchyme and epithelium. We find that, as expected, Bmp4 can suppress bud extension in isolated epithelium stimulated by Fgf10, but interestingly, Bmp7 has no discernible effect. Bmp7 does, however, stimulate a distinct response in mesenchymal cells. This manifests as a promotion of cell division and formation of aggregates, and upregulation of cadherin adhesion molecules, the junctional protein connexin 43 and of alpha-smooth muscle actin. These data suggest that in this branching system, mesenchyme is the primary target of Bmp7 and that formation of mesenchymal condensations characteristic of signaling centers may be enhanced by Bmp7. Based on the activity of Bmp7 in promoting branching, we also propose a model suggesting that a discrete region of Bmp7-expressing head mesenchyme may be crucial in determining the location of the exorbital lobe of the gland.

Activation of cAMP signaling facilitates the morphological maturation of newborn neurons in adult hippocampus.

Previous studies have demonstrated that activation of the cAMP cascade, including the cAMP response element-binding protein (CREB), increases the proliferation and survival of newborn neurons in adult mouse hippocampus. In the present study, we determined whether the cAMP-CREB cascade also influences the morphological maturation of newborn neurons in the subgranular zone of the hippocampus. Rolipram, a selective inhibitor of the cAMP-specific phosphodiesterase type 4, was administered to activate the cAMP cascade, and neuronal morphology was determined by analysis of Golgi-impregnated neurons in the subgranular zone of hippocampus. Rolipram administration significantly increased the number of branch points and length of dendrites relative to vehicle treatment. Increased branch number and length were accompanied by increased levels of phosphorylated CREB, the active form of this transcription factor, in immature neurons. In contrast, the morphology of Golgi-impregnated neurons was not significantly influenced by rolipram treatment in inducible transgenic mice expressing a dominant-negative mutant of CREB in hippocampus. We also tested the influence of cAMP analogs in primary hippocampal cultures and found that activation of the cAMP pathway increased and inhibition of the cAMP cascade decreased the number of branches and length of processes as observed in vivo. These findings indicate that the cAMP-CREB cascade plays an important role in the differentiation and maturation of newborn neurons in hippocampus.

Physiological basis of spacing effects on tree growth and form in Eucalyptus globulus

We examine the effects of spacing and layout on the growth and form of 3- to 4-year-old Eucalyptus globulus in a farm forestry context. Four planting layouts were chosen. These represented the range commonly in use in farm forestry: block plantings (2×4 m), triple rows (2×4 m) at 10-m intervals, single rows (2×10 m) and isolated trees (10×10 m). The physiological significance of key results is interpreted in terms of changes in the parameters of a simple plantation growth model. Under conditions where levels of direct light are high, for example during summer, block-planted trees intercepted only 38% of the light intercepted by isolated trees. On a stand basis, however, the combination of incident radiation and ground coverage declined with lower stand densities. While stand leaf area index declined from around 6 to 1 with increased spacing, individual tree leaf areas rose from around 50 m2 in block plantings to 150 m2 in isolated trees. The proportion of above-ground biomass found in stems declined with increasing spacing as the mass in foliage and branches increased. Stems accounted for 65% of above-ground biomass in block-planted trees but only 35% in isolated trees. The contributions of leaves and branches correspondingly rose from 19% to 35% and from 16% to 29%, respectively. Changes in biomass distribution were accompanied by increasing branch number, branch thickness, flatter branch angles and the longer retention of lower branches with greater spacing. These changes have implications for the merchantability of the timber. The efficiency of above-ground radiation conversion was constant at 0.67 g MJ–1 irrespective of spacing. We estimated that foliar maintenance respiration (R m) accounted for about 90% of above-ground R m. On a stand basis R m costs block plantings 23.90 t DM ha–1 year–1 (50% annual above-ground photosynthetic production) compared with 6.22 t DM ha–1 year–1 (40% annual above-ground photosynthetic production) in stands of isolated trees.

Properties of Branched and NetworkPoly(vinyl alcohols) Prepared withPoly(vinyl alcohol) Having AldehydeGroups at the Chain Ends

Branched and network poly(vinyl alcohols) (PVAs) were prepared with inter-acetalization of the PVA with aldehyde groups at the chain ends which was prepared by the cleavage of 1,2 glycol bonds in commercial PVA. The numbers of branches estimated from molecular weights were compared with those estimated by theory. Huggins' constant and crystallinity decreased with increasing branch number. Dissolution of branched PVAs into dimethylsulphoxide was not so easy compared with commercial PVA. The colour of branched PVA–iodine complex decreased rapidly with standing while that of commercial PVA decreased gradually. Network PVAs with Young's modulus of 1–8 MPa were prepared.

Morphology of individual axons in crossed corticorubral projections in developing cats and effects of partial denervation.

Ordered neuronal connections in mature brains are thought to be sculpted from initially diffuse projections by elimination of inappropriate projections and strengthening of appropriate ones. Although evidence suggests that neuronal activity plays a role in these processes, the mechanism behind the modification of neuronal connections remains obscure. To gain insight into the mechanisms of axonal elimination and projection strengthening, we examined the morphology of individual axons that were to be eliminated as well as the consequences of partial denervation. While corticorubral projections in adult cats are thought to be uncrossed, early in postnatal development and after early unilateral lesions to the sensorimotor cortex, however, a significant amount of crossed corticorubral projections occurs. We examined the morphology of individual corticorubral axons in fetal cats and kittens from embryonic day 59 to postnatal day 48 and those that had received early unilateral lesions to the cortex, by serial reconstruction of Phaseolus-vulgaris-leucoagglutinin- or biocytin-labeled axons. For about 2 weeks during pre- and postnatal development, crossed axons remained simple in morphology, with few branches. Thereafter, they showed an increase in branch number, but then began to show fewer branches again. Axons and their collaterals were found in nonrestricted areas of the red nucleus (RN) throughout the period of observation, indicating that axons can sit at an inappropriate target for weeks but fail to ramify. In contrast, crossed corticorubral axons in kittens with cortical lesions showed terminal-arbor-like structures in the RN region that are in mirror symmetry to topographically appropriate areas in the ipsilateral RN, although some showed simple morphology without arbors. These complicated forms of morphology of individual axons during development and after partial denervation may not be explained by a simple activity-dependent mechanism.