Prevalence of Tree Regeneration by Sprouting and Seeding Along a Rainfall Gradient in Hawai'i

Drought stress in tropical dry forests is thought to result in greater asexual regeneration via vegetative sprouting ( e.g ., basal, root, and branch layering) than occurs in moister tropical forests. We tested this hypothesis by examining the prevalence of tree sprouting and seeding in tropical forests located along a rainfall gradient on the island of Hawai'i. Additionally, we examined the potential for novel disturbance, feral pig Sus scrofa rooting and trampling, to alter patterns in tree regeneration mode. We found greater sprouting (in terms of relative density and basal area) in dry forests than in mesic and wet forests, supporting the hypothesis. We also found that feral pig disturbance is negatively correlated with the relative density and basal area of seedlings in wet forests, but is positively correlated with the relative importance of sprouting, and the richness and diversity of sprouting species. Our results suggest rainfall regimes may be an important factor controlling broad-scale patterns in tree regeneration mode, and that exotic ungulates can significantly modify such patterns with potential consequences for the structure and dynamics of tree populations and communities.     

The above-ground coarse wood productivity of 104 Neotropical forest plots

The net primary production of tropical forests and its partitioning between long‐lived carbon pools (wood) and shorter‐lived pools (leaves, fine roots) are of considerable importance in the global carbon cycle. However, these terms have only been studied at a handful of field sites, and with no consistent calculation methodology. Here we calculate above‐ground coarse wood carbon productivity for 104 forest plots in lowland New World humid tropical forests, using a consistent calculation methodology that incorporates corrections for spatial variations in tree‐size distributions and wood density, and for census interval length. Mean wood density is found to be lower in more productive forests. We estimate that above‐ground coarse wood productivity varies by more than a factor of three (between 1.5 and 5.5 Mg C ha^?1 a^?1) across the Neotropical plots, with a mean value of 3.1 Mg C ha^?1 a^?1. There appear to be no obvious relationships between wood productivity and rainfall, dry season length or sunshine, but there is some hint of increased productivity at lower temperatures. There is, however, also strong evidence for a positive relationship between wood productivity and soil fertility. Fertile soils tend to become more common towards the Andes and at slightly higher than average elevations, so the apparent temperature/productivity relationship is probably not a direct one. Coarse wood productivity accounts for only a fraction of overall tropical forest net primary productivity, but the available data indicate that it is approximately proportional to total above‐ground productivity. We speculate that the large variation in wood productivity is unlikely to directly imply an equivalent variation in gross primary production. Instead a shifting balance in carbon allocation between respiration, wood carbon and fine root production seems the more likely explanation.     

Hepatitis B surface antigen immunopurification using a plant-derived specific antibody produced in large scale

This paper provides an evaluation of a plant-derived HBsAg-specific antibody in the immunopurification of the recombinant HBsAg for vaccine purposes. This plant-derived antibody was obtained from different batches of 100-200kg of tobacco leaves and coupled to Sepharose CL-4B with high efficiency. The plant-derived antibody immunoaffinity matrix purification behavior (elution capacity, antigen purity, purification cycles, and ligand leakage) was comparable to that of its mouse-derived monoclonal antibody homolog. This result supports the feasibility of using this plant-derived antibody for the immunopurification of the Hepatitis B surface antigen for human use, opening a new possibility to overcome the constrain of monoclonal antibody production in mice.     

Neurocircuitry of the basal ganglia studied by monitoring neurotransmitter release

The neurocircuitries of the basal ganglia are studied with in vivo microdialysis, with special consideration to dopamine transmission and its interaction with other neurotransmitter systems. The aim is to develop experimental models to study the pathophysiology and therapy of neurodegenerative disorders of the basal ganglia, as well as to develop models to study the short- and long-term consequences of perinatal asphyctic lesions. A main goal of these studies is to find and to characterize new treatments for these disorders.     

Post‐dispersal seed recovery by animals: is it a plant‐ or an animal‐driven process?

The ability of animals to find and consume hoarded seeds (i.e. seed recovery) is a key stage within the seed dispersal process. However, the ecology of seed recovery is still poorly understood. Here, we analyze the factors controlling seed recovery by scatter‐hoarding rodents in an oak‐dominated temperate forest. We examined the relative importance of intrinsic seed traits (i.e. plant‐driven) and extrinsic seed factors (i.e. animal‐driven) on the probability of seed recovery. We found that seed recovery is mainly driven by extrinsic seed factors, mostly related to animal behavior (pilfering frequency, microsite preference, predation risk, burial depth and cache size). Important intrinsic traits such as seed size, seed quality and seed‐drop timing were, on average, of lower significance in the probability of seed recovery (2.8‐times less important than extrinsic factors); only seed quality was an important intrinsic trait. On the other hand, larger and nutritionally more valuable seeds showed a removal–recovery tradeoff as they enhance seed removal and hoarding (increasing dispersal quality) but also favour seed recovery (increasing predation). We find that other mechanisms beyond seed traits (e.g. masting) are needed to decrease seed recovery and, thus, increase seed survival. We conclude that, as seed recovery is mostly driven by animal behavioural factors, it substantially differs from other previous stages of the seed dispersal process that are more dependent on seed traits. We argue that seed recovery needs further attention to advance our understanding of the ecology of seed dispersal and the role of secondary dispersers as a selective force for seeds.     

Thymulin and the neuroendocrine system

Thymulin is a thymic hormone exclusively produced by the thymic epithelial cells. It consists of a nonapeptide component coupled to the ion zinc, which confers biological activity to this molecule. After its discovery in the early 1970, thymulin was characterized as a thymic hormone involved in several aspects of intra- and extrathymic T-cell differentiation. Subsequently, it was demonstrated that thymulin production and secretion is strongly influenced by the neuroendocrine system. Conversely, an emerging core of information points to thymulin as a hypophysotropic peptide. Here we review the evidence supporting the hypothesis that thymulin is an important player in the hypophyso-thymic axis.     

<Emphasis Type="Italic">Rhodospirillum rubrum</Emphasis> has a family I pyrophosphatase: purification,cloning, and sequencing

The cytoplasmic pyrophosphatase of the photosynthetic bacterium Rhodospirillum rubrum was purified to electrophoretic homogeneity. The enzyme is a homohexamer of 20-kDa monomers. The gene was cloned and sequenced. Alignment of the deduced 179-amino-acid protein with known bacterial pyrophosphatases revealed conservation of all residues in the active site. Attempts to obtain an insertion mutant of the cytoplasmic pyrophosphatase gene did not yield any cell completely devoid of cytoplasmic pyrophosphatase activity. The mutants obtained showed 50% of the enzymatic activity and grew in twice the generation time of wild-type cells. This suggests that the membrane-bound pyrophosphatase of Rsp. rubrum is not sufficient for a normal growth rate, whereas the cytoplasmic enzyme is essential for growth. The characteristics of the gene and the encoded protein fit those of prokaryotic family I pyrophosphatases.