Plant science in forest canopies--the first 30 years of advances and challenges (1980-2010)

As an emerging subdiscipline of forest biology, canopy science has undergone a transition from observational, 'oh-wow' exploration to a more hypothesis-driven, experimental arena for rigorous field biology. Although efforts to explore forest canopies have occurred for a century, the new tools to access the treetops during the past 30 yr facilitated not only widespread exploration but also new discoveries about the complexity and global effects of this so-called 'eighth continent of the planet'. The forest canopy is the engine that fixes solar energy in carbohydrates to power interactions among forest components that, in turn, affect regional and global climate, biogeochemical cycling and ecosystem services. Climate change, biodiversity conservation, fresh water conservation, ecosystem productivity, and carbon sequestration represent important components of forest research that benefit from access to the canopy for rigorous study. Although some canopy variables can be observed or measured from the ground, vertical and horizontal variation in environmental conditions and processes within the canopy that determine canopy-atmosphere and canopy-forest floor interactions are best measured within the canopy. Canopy science has matured into a cutting-edge subset of forest research, and the treetops also serve as social and economic drivers for sustainable communities, fostering science education and ecotourism. This interdisciplinary context of forest canopy science has inspired innovative new approaches to environmental stewardship, involving diverse stakeholders.     

ABDOMINAL FASCIAL TRANSPLANTS—Physiological and Psychological Benefits

Even when they cannot restore the ability of a paralyzed patient to walk, fascial transplanting operations to stabilize the trunk, to give firmness to the abdominal wall and to improve the posture can be of great benefit. Well designed and well executed operations can greatly improve respiratory, circulatory and eliminatory function. Often the ability to talk or even to sing is restored. Even the ability to cough effectively can sometimes be a boon.The rewards in improved physical health and in morale can make the pain and the expense of operation well worth while to the patient.     

p53 Promotes Cancer Cell Adaptation to Glutamine Deprivation by Upregulating Slc7a3 to Increase Arginine Uptake

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The proapoptotic function of Noxa in human leukemia cells is regulated by the kinase Cdk5 and by glucose

The BH3-only protein, Noxa, is induced in response to apoptotic stimuli, such as DNA damage, hypoxia, and proteasome inhibition in most human cells. Noxa is constitutively expressed in proliferating cells of hematopoietic lineage and required for apoptosis in response to glucose stress. We show that Noxa is phosphorylated on a serine residue (S(13)) in the presence of glucose. Phosphorylation promotes its cytosolic sequestration and suppresses its apoptotic function. We identify Cdk5 as the Noxa kinase and show that Cdk5 knockdown or expression of a Noxa S(13) to A mutant increases sensitivity to glucose starvation, confirming that the phosphorylation is protective. Both glucose deprivation and Cdk5 inhibition promote apoptosis by dephosphorylating Noxa. Paradoxically, Noxa stimulates glucose consumption and may enhance glucose turnover via the pentose phosphate pathway rather than through glycolysis. We propose that Noxa plays both growth-promoting and proapoptotic roles in hematopoietic cancers with phospho-S(13) as the glucose-sensitive toggle switch controlling these opposing functions.     

Maternal Genes and Facial Clefts in Offspring: A Comprehensive Search for Genetic Associations in Two Population-Based Cleft Studies from Scandinavia

Background

Fetal conditions can in principle be affected by the mother''s genotype working through the prenatal environment.

Methodology/Principal Findings

Genotypes for 1536 SNPs in 357 cleft candidate genes were available from a previous analysis in which we focused on fetal gene effects [1]. After data-cleaning, genotypes for 1315 SNPs in 334 autosomal genes were available for the current analysis of maternal gene effects. Two complementary statistical methods, TRIMM and HAPLIN, were used to detect multi-marker effects in population-based samples from Norway (562 case-parent and 592 control-parent triads) and Denmark (235 case-parent triads). We analyzed isolated cleft lip with or without cleft palate (iCL/P) and isolated cleft palate only (iCP) separately and assessed replication by looking for genes detected in both populations by both methods. In iCL/P, neither TRIMM nor HAPLIN detected more genes than expected by chance alone; furthermore, the selected genes were not replicated across the two methods. In iCP, however, FLNB was identified by both methods in both populations. Although HIC1 and ZNF189 did not fully satisfy our stringency criterion for replication, they were strongly associated with iCP in TRIMM analyses of the Norwegian triads.

Conclusion/Significance

Except for FLNB, HIC1 and ZNF189, maternal genes did not appear to influence the risk of clefting in our data. This is consistent with recent epidemiological findings showing no apparent difference between mother-to-offspring and father-to-offspring recurrence of clefts in these two populations. It is likely that fetal genes make the major genetic contribution to clefting risk in these populations, but we cannot rule out the possibility that maternal genes can affect risk through interactions with specific teratogens or fetal genes.     

Human skin mast cells: their dispersion, purification, and secretory characterization

Digestion of human foreskin with collagenase and hyaluronidase disperses approximately 3.4 X 10(7) nucleated cells per gram of tissue, of which mast cells constitute 4.7%. These may be purified to 80% by use of density gradient centrifugation. The majority of mast cells (79%) measured between 9 and 13 micron in diameter, and the mean histamine content was 4.6 pg/cell. Viability was demonstrated by trypan blue exclusion by 93% of the cells and the low spontaneous histamine secretion of less than 7% in functional studies. Anti-IgE released up to 17.5% of cell-associated histamine within 5 to 7 min. Calcium ionophore-induced release was optimal with 0.3 microM A23187 when 28.6% histamine was released. Unlike human lung mast cells, skin mast cells released histamine in response to compound 48/80 and poly-L-lysine. This release, which was complete within 20 sec, was totally dependent on intact glycolysis and oxidative phosphorylation and partially dependent on extracellular calcium. The same characteristics were observed with secretion induced by substance P and morphine. The weak activity of eledoisin and physalaemin suggests that the substance P receptor, like that of the rat mast cell, is not of the classical types described for smooth muscle. Morphine-induced secretion was partially blocked by naloxone in a manner not compatible with competitive antagonism at a classical opioid receptor. The sensitivity of skin mast cells to nonimmunologic stimulation clearly distinguishes them from mast cells of the lung and lymphoid tissues and provides evidence of functional heterogeneity within human mast cells.     

On the recognition of helical RNA by cobra venom V1 nuclease

The V1 nuclease from cobra venom preferentially hydrolyzes double helical RNA and has been used extensively for detecting RNA secondary structure. To increase the utility of this enzyme as an RNA structure probe, we have investigated its properties and substrate specificity, using assays for polynucleotide hydrolysis based on fluorescent polynucleotide derivatives. Enzymatic activity requires both Na+ and Mg2+, with optima at 100 and 0.3 mM, respectively. From the sharp decrease in enzyme activity above 100 mM Na+ we estimate that 3-4 ionic interactions between the protein and polynucleotide phosphates take place. Analysis of products remaining after extensive V1 digestion also shows that the minimum size substrate is 4-6 nucleotides long. Helical RNAs and DNAs have Michaelis constants a factor of 3-10 times lower than most single-stranded RNAs. However, poly(epsilon A) has a Michaelis constant equal to the best synthetic double helices tested and is hydrolyzed at a rate comparable to helical RNA. The major V1 cutting sites in yeast tRNAPhe have Michaelis constants lower than any synthetic polymers. These data suggest that V1 nuclease recognizes any 4-6-nucleotide segment of polynucleotide backbone with an approximately helical conformation, but does not require that the bases be paired in a helix. A few single-stranded V1 cleavage sites are known in tRNA and rRNA, and their structures are consistent with the suggested V1 recognition site.     

Plants in the forest canopy: some reflections on current research and future direction

Plants are one of the sessile components of the forest canopy, and consequently quantitative studies of plant components are more widely available than for some of their mobile counterparts. From a global perspective, several exciting and innovative canopy access tools have been designed over the past few decades that have facilitated the expansion our understanding of canopy plants. These include a network of canopy cranes, the development of the French luge (or sled), and the construction of walkways and platforms for access into different levels of the canopy on a permanent basis. At the recent international forest canopy conference in Sarasota, Florida (Forest Canopies 1998: Global Perspectives, November 4–8, 1998), many canopy plant studies were presented that illustrated the achievements in this field. As co-chair at this event, I present here some reflections based on my observations of the development of canopy research between the first and second international conferences. A selection of case studies from the conference presentations are cited in this review, including: tree crown respiration studies from the crane in Panama; epiphyte ecology from walkways in Peru; insect-plant relationships in tree crowns of the USA using platforms; experimental studies of epiphytes in cloud forests using single rope techniques; and epiphyte diversity surveys in Africa. Ideas for the future are also mentioned such as the novel concept of canopy farming of orchids in Costa Rica, the linking of canopy processes to forest floor activities, and the construction of canopy walkways to provide a sustainable forest economy instead of the conventional practice of logging. The integration of research with sustainable use of forests provides a conservation theme for future canopy studies. Such new approaches to studies of canopy plants are important, as scientists increasingly play a role in global conservation policies.