Pigment dynamics and autumn leaf senescence in a New England deciduous forest,eastern USA

The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing chloroplasts. In nine red-senescing species, anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence, with less than 20µg cm^–2 of chlorophyll remaining. Xanthophyll concentrations declined in relation to chlorophyll to the same extent in both yellow- and red-leaved taxa. Declines in the maximum photosystemII quantum yield of leaves collected prior to dawn were only slightly less in the red-senescing species, indicating no long-term protective activity. Red-leaved species had significantly greater mass/area and lower chlorophylla/b ratios during senescence. Nitrogen tissue concentrations in mature and senescent leaves negatively correlated to anthocyanin concentrations in senescent leaves, weak evidence for more efficient nitrogen resorption in anthocyanic species. Shading retarded both chlorophyll loss and anthocyanin production in Cornus alternifolia, Acer rubrum, Acer saccharum, Quercus rubra and Viburnum alnifolium. It promoted chlorophyll loss in yellow-senescing Fagus grandifolia. A reduced red:far-red ratio did not affect this process. Anthocyanins did not increase leaf temperatures in Q.rubra and Vaccinium corymbosum on cold and sunny days. The timing of leaf-fall was remarkably constant from year to year, and the order of senescence of individual species was consistent.     

The multiple complexes formed by the interaction of platelet factor 4 with heparin.

The anisotropy of the fluorescence of dansyl (5-dimethylaminonaphthalene-1- sulphonyl) groups covalently attached to human platelet factor 4 was used to detect the macromolecular compounds formed when the factor was mixed with heparin. At low heparin/protein ratios a very-high-molecular-weight compound (1) was formed that dissociated to give a smaller compound (2) when excess heparin was added. 2. A large complex was also detected as a precipitate that formed at high protein concentrations in chloride buffer. It contained 15.7% (w/w) polysaccharide, equivalent to four or five heparin tetrasaccharide units per protein tetramer. In this complex, more than one molecule of protein binds to each heparin molecule of molecular weight greater than about 6 X 10(3).3. The stability of these complexes varied with pH, salt concentration and the chain length of the heparin. The limit complexes found in excess of the larger heparins consisted of only one heparin molecule per protein tetramer, and the failure to observe complexes with four heparin molecules/protein tetramer is discussed.     

Fine needle aspiration cytology of neuroblastoma, including peripheral neuroectodermal tumor, with immunocytochemical and ultrastructural confirmation

Eleven fine needle aspiration (FNA) biopsies were performed on seven children with neuroblastoma, including one patient with a congenital neuroblastoma and another with a peripheral neuroblastoma of the thoracopulmonary region. FNA cytology made the primary diagnosis of neuroblastoma in four of the seven cases. The other biopsies documented local recurrences and metastases to liver, lymph nodes, orbit and breast. The cytologic features included varying numbers of small primitive cells with scanty cytoplasm, poorly to well-formed pseudorosettes, cell processes, a fibrillary matrix and multinucleated ganglion cells. Five of the seven patients had electron microscopic (EM) examination of the FNA specimen, which in all cases confirmed the diagnosis. Batteries of immunoperoxidase stains were performed on all 11 aspirates with variable results. Staining for neuron-specific enolase was positive in four of the five neoplasms tested, although strongly positive in only three of the cases. Staining for neurofilament markers was positive in only two of five tumors. Studies for cytokeratin markers (AE1/3), low-molecular-weight cytokeratin (35BH11), hematopoietic markers (T29/33), immunoglobulin light chains and myoglobin were negative. One case was positive for vimentin. This study attests to the value of FNA cytology in suggesting a correct diagnosis of either primary, recurrent or metastatic neuroblastoma in children. Selective use of immunoperoxidase stains and EM on the aspirates may be of value.     

Differential inhibition of inducible T cell cytokine secretion by potent iron chelators

Effector functions and proliferation of T helper (Th) cells are influenced by cytokines in the environment. Th1 cells respond to a synergistic effect of interleukin-12 (IL-12) and interleukin-18 (IL-18) to secrete interferon-gamma (IFN-gamma). In contrast, Th2 cells respond to interleukin-4 (IL-4) to secrete IL-4, interleukin-13 (IL-13), interleukin-5 (IL-5), and interleukin-10 (IL-10). The authors were interested in identifying nonpeptide inhibitors of the Th1 response selective for the IL-12/IL-18-mediated secretion of IFN-gamma while leaving the IL-4-mediated Th2 cytokine secretion relatively intact. The authors established a screening protocol using human peripheral blood mononuclear cells (PBMCs) and identified the hydrazino anthranilate compound 1 as a potent inhibitor of IL-12/IL-18-mediated IFN-gamma secretion from CD3(+) cells with an IC(50) around 200 nM. The inhibitor was specific because it had virtually no effect on IL-4-mediated IL-13 release from the same population of cells. Further work established that compound 1 was a potent intracellular iron chelator that inhibited both IL-12/IL-18- and IL-4-mediated T cell proliferation. Iron chelation affects multiple cellular pathways in T cells. Thus, the IL-12/IL-18-mediated proliferation and IFN-gamma secretion are very sensitive to intracellular iron concentration. However, the IL-4-mediated IL-13 secretion does not correlate with proliferation and is partially resistant to potent iron chelation.     

Degradation of 2-carboxyarabinitol 1-phosphate by a specific chloroplast phosphatase

The catalytic degradation of 2-carboxyarabinitol 1-phosphate (CA 1-P), a naturally occurring inhibitor of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), was investigated by chromatographic and spectroscopic analyses of the reaction products. Carboxy-labeled [¹⁴C]CA 1-P was incubated with a partially purified tobacco (Nicotiana rustica) chloroplast protein that has been shown previously to catalyze metabolism of CA 1-P to a form incapable of inhibiting Rubisco (ME Salvucci, GP Holbrook, JC Anderson, and G Bowes [1988] FEBS Lett 231: 197-201). In the presence and absence of NADPH, ion-exchange chromatography showed a progressive conversion of [2′-¹⁴C]CA 1-P to a labeled compound which coeluted with authentic carboxyarabinitol. Parallel assays with unlabeled CA 1-P showed a concomitant decrease in the ability of reaction samples to inhibit Rubisco activity. In separate experiments, a 1:1 stoichiometry was found between the release of inorganic phosphate from [2′-¹⁴C]CA 1-P and accumulation of the ¹⁴C-labeled product. Liberation of inorganic phosphate was not observed when the tobacco enzyme was incubated with ribulose-1,5-bisphosphate, fructose-1,6-bisphosphate, glucose-1-phosphate, glucose-6-phosphate, or 6-phosphogluconate. Proton nuclear magnetic resonance spectroscopy of the labeled CA 1-P reaction product established its identity as carboxyarabinitol. We therefore propose that light-stimulated degradation of CA 1-P is catalyzed in vivo by a specific phosphatase, 2-carboxyarabinitol 1-phosphatase. Carboxyarabinitol 1-phosphatase activity was detected in the absence of NADPH, but increased threefold when 2 millimolar NADPH was present. Thus, while not required for the reaction, NADPH may play an important role in the regulation of CA 1-P degradation.     

Tolerization as a tool for generating novel monoclonal antibodies

Standard hybridoma production involves the fusion of spleen cells from an immunized mouse with a non-secretory murine myeloma cell line. While this technology has provided numerous reagents that are highly valuable, demand is now increasing for monoclonal antibodies which can distinguish between closely related antigens. Induction of tolerance towards common antigens enables the recovery of high-specificity reagents that have previously proved elusive. This review details a number of strategies using either complex protein mixtures or purified proteins as tolerogens and subsequent immunization with a closely related immunogen.     

Species traits and climate velocity explain geographic range shifts in an ocean‐warming hotspot

Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean‐warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small‐ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances.     

The role of freezing in setting the latitudinal limits of mangrove forests

Mangrove trees dominate coastal vegetation in tropical regions, but are completely replaced by herbaceous salt marshes at latitudes above 32 degrees N and 40 degrees S. Because water deficit can increase damage caused by freezing, we hypothesized that mangroves, which experience large deficits as a result of saline substrates, would suffer freeze-induced xylem failure. Vulnerability to freeze-induced xylem embolism was examined in the most poleward mangrove species in North America, in an area where freezing is rare but severe, and in Australia, in an area where freezing is frequent but mild. Percentage loss in hydraulic conductivity was measured following manipulations of xylem tension; xylem sap ion concentration was determined using X-ray microanalysis. Species with wider vessels suffered 60-100% loss of hydraulic conductivity after freezing and thawing under tension, while species with narrower vessels lost as little as 13-40% of conductivity. These results indicate that freeze-induced embolism may play a role in setting the latitudinal limits of distribution in mangroves, either through massive embolism following freezing, or through constraints on water transport as a result of vessel size.     

A biomechanical perspective on the role of large stem volume and high water content in baobab trees (Adansonia spp.; Bombacaceae)

The stems of large trees serve in transport, storage, and support; however, the degree to which these roles are reflected in their morphology is not always apparent. The large, water-filled stems of baobab trees (Adansonia spp.) are generally assumed to serve a water storage function, yet recent studies indicate limited use of stored water. Through an analysis of wood structure and composition, we examined whether baobab morphology reflects biomechanical constraints rather than water storage capacity in the six Madagascar baobab species. Baobab wood has a high water content (up to 79%), low wood density (0.09-0.17 g · cm(-3)), high parenchyma content (69-88%), and living cells beyond 35 cm into the xylem from the cambium. Volumetric construction cost of the wood is several times lower than in more typical trees, and the elastic modulus approaches that of parenchyma tissue. Safety factors calculated from estimated elastic buckling heights were low, indicating that baobabs are not more overbuilt than other temperate and tropical trees, yet the energy investment in stem material is comparable to that in temperate deciduous trees. Furthermore, the elastic modulus of the wood decreases with water content, such that excessive water withdrawal from the stem could affect mechanical stability.     

An integrated genetic linkage map of cultivated peanut (Arachis hypogaea L.) constructed from two RIL populations

Construction and improvement of a genetic map for peanut (Arachis hypogaea L.) continues to be an important task in order to facilitate quantitative trait locus (QTL) analysis and the development of tools for marker-assisted breeding. The objective of this study was to develop a comparative integrated map from two cultivated × cultivated recombinant inbred line (RIL) mapping populations and to apply in mapping Tomato spotted wilt virus (TSWV) resistance trait in peanut. A total of 4,576 simple sequence repeat (SSR) markers from three sources: published SSR markers, newly developed SSR markers from expressed sequence tags (EST) and from bacterial artificial chromosome end-sequences were used for screening polymorphisms. Two cleaved amplified polymorphic sequence markers were also included to differentiate ahFAD2A alleles and ahFAD2B alleles. A total of 324 markers were anchored on this integrated map covering 1,352.1 cM with 21 linkage groups (LGs). Combining information from duplicated loci between LGs and comparing with published diploid maps, seven homoeologous groups were defined and 17 LGs (A1-A10, B1-B4, B7, B8, and B9) were aligned to corresponding A-subgenome or B-subgenome of diploid progenitors. One reciprocal translocation was confirmed in the tetraploid-cultivated peanut genome. Several chromosomal rearrangements were observed by comparing with published cultivated peanut maps. High consistency with cultivated peanut maps derived from different populations may support this integrated map as a reliable reference map for peanut whole genome sequencing assembling. Further two major QTLs for TSWV resistance were identified for each RILs, which illustrated the application of this map.