Net nitrogen mineralization in soils under six indigenous tree species,an abandoned pasture and a secondary forest in the atlantic lowlands of costa rica

Nitrogen mineralization, nitrification potentials, pH, total N, C, extractable P and cations were measured in soils under 4-year-old, mono-specific stands of six fast-growing, native tree species, an abandoned pasture, and a 20-year-old secondary forest, as part of a study on the use of indigenous tree species for rehabilitation of soil fertility on degraded pastures at the La Selva Biological Station in the Atlantic humid lowlands of Costa Rica. Soil net nitrification potential rates were higher under two N-fixing, leguminous species,Stryphnodendron microstachyum Poepp. et Endl. (1.1–1.9 mg kg^–1 day^–1) andDalbergia tucurensis Donn. Smith (0.7–1.5 mg kg^–1 day^–1), than under the non-N-fixing trees in the plantation,Vochysia guatemalesis Don. Sm.,Vochysia ferruginea Mart,Dipteryx panamensis (Pittier) Record and Mell andHyeronima alchorneoides Fr. Allemao (0.2–0.8 mg kg^–1 day^–1). Values under the N-fixing trees were comparable to those found in secondary forest. There were no statistically significant differences in soil total N or in other nurtients between the species. Results of pH measurements done before and after incubation did not show any clear evidence of a pH drop attributable to nitrification.     

Vesicular-arbuscular mycorrhizal inoculum potential affects the growth of Stryphnodendron microstachyum seedlings in a Costa Rican human tropical lowland

This study used a plant bioassay to investigate the vesicular-arbuscular mycorrhizal (VAM) inoculum potential of soil from three vegetation types (fern, secondary forest, and grass) in an abandoned pasture in the tropical humid lowlands at La Selva, in northeastern Costa Rica. Growth, measured as seedling height, number of leaves, and total (above- and belowground) biomass, of Stryphnodendron microstachyum Poepp. et Endl. (Synon. S. excelsum Harms) seedlings was significantly lower when grown in soil inoculum from the fern areas than in soil inoculum from the forest and grass areas. However, S. microstachyum seedlings grown in the fern inoculum had significantly greater VAM colonization than seedlings grown in the forest and grass inoculum. In addition, roots collected from a dominant plant species from each of the three vegetation types showed that the fern (Nephrolepsis biserrata) had significantly greater mycorrhizal colonization than the tree (Pentaclethra macroloba (Willd.) Kuntze or the grass (Brachiaria spp.). The results of this study suggest that differences in mycorrhizal inoculum potential among vegetation types and its effects on seedling growth may have important implications for the restoration and management of degraded lands.     

The nitrogen cycle in a ‘Terra Firme’ rainforest on oxisol in the Amazon territory of Venezuela

Standing stocks and fluxes of nitrogen, including nitrogen fixation and denitrification, were measured in a tropical rainforest on Oxisol in the Amazon Territory of Venezuela. The standing stock of nitrogen was comparable to that of temperate forests, but was higher than that in an adjacent forest on Spodosol. Fluxes were higher than in forests in the temperate zone, but lower than in another tropical forest on more fertile soil. Even though nitrogen was abundant, this does not mean that nitrogen could not be limiting to agriculture if the forest is cleared and the land cultivated. The nitrogen fixing and nitrogen conserving mechanisms are dependent upon the structure of the undisturbed forest, and destruction of the forest would eventually decrease the input of nitrogen to the soil.     

The expression of the dodecameric ferritin in Listeria spp. is induced by iron limitation and stationary growth phase

The new discipline of Evolutionary Developmental Biology (Evo-Devo) is facing the fascinating paradox of explaining morphological evolution using conserved pieces or genes to build divergent animals. The cephalochordate amphioxus is the closest living relative to the vertebrates, with a simple, chordate body plan, and a genome directly descended from the ancestor prior to the genome-wide duplications that occurred close to the origin of vertebrates. Amphioxus morphology may have remained relatively invariant since the divergence from the vertebrate lineage, but the amphioxus genome has not escaped evolution. We report the isolation of a second Emx gene (AmphiEmxB) arising from an independent duplication in the amphioxus genome. We also argue that a tandem duplication probably occurred in the Posterior part of the Hox cluster in amphioxus, giving rise to AmphiHox14, and discuss the structure of the chordate and vertebrate ancestral clusters. Also, a tandem duplication of Evx in the amphioxus lineage produced a prototypical Evx gene (AmphiEvxA) and a divergent gene (AmphiEvxB), no longer involved in typical Evx functions. These examples of specific gene duplications in amphioxus, and other previously reported duplications summarized here, emphasize the fact that amphioxus is not the ancestor of the vertebrates but 'only' the closest living relative to the ancestor, with a mix of prototypical and amphioxus-specific features in its genome.     

Seed Rain and Seed Dispersal Agents in Pure and Mixed Plantations of Native Trees and Abandoned Pastures at La Selva Biological Station, Costa Rica

Lack of seed dispersal can be an important obstacle to natural regeneration (NR) of degraded pastures in the humid tropics. Tree plantations can facilitate secondary forest succession by attracting seed dispersal agents from nearby forests. We studied seed rain and seed dispersal agents in 12–13 years old pure and mixed native tree plantations at La Selva Biological Station, Costa Rica from July to December 2004. Plantations of Balizia elegans (5,522), Dipteryx panamensis (2,263), and Jacaranda copaia (2,091) had the greatest total seed abundance; treatments with the least total seed abundance were Calophyllum brasiliense (56), nonplanted abandoned pasture control 2 (353), Mixed Species 2 (389), and control 1 (836). Plantations of J. copaia and Hyeronima alchorneoides had the greatest seed species richness density, whereas the lowest seed species richness was found in the control treatments. The NR plots had more seeds dispersed by wind, whereas in the plantations, the most important dispersal agents were birds and mammals. The most abundant seeds were those of Miconia spp. (14,492), Psychotria bracheata (2,252), and the Poaceae family (1,346), all species from early successional stages. Plantations of native species are effective in attracting seed dispersal agents and thus facilitating regeneration of degraded pasturelands in the region.     

Bayesian modeling of dynamic motion integration

The quality of the representation of an object's motion is limited by the noise in the sensory input as well as by an intrinsic ambiguity due to the spatial limitation of the visual motion analyzers (aperture problem). Perceptual and oculomotor data demonstrate that motion processing of extended objects is initially dominated by the local 1D motion cues, related to the object's edges and orthogonal to them, whereas 2D information, related to terminators (or edge-endings), takes progressively over and leads to the final correct representation of global motion. A Bayesian framework accounting for the sensory noise and general expectancies for object velocities has proven successful in explaining several experimental findings concerning early motion processing [Weiss, Y., Adelson, E., 1998. Slow and smooth: a Bayesian theory for the combination of local motion signals in human vision. MIT Technical report, A.I. Memo 1624]. In particular, these models provide a qualitative account for the initial bias induced by the 1D motion cue. However, a complete functional model, encompassing the dynamical evolution of object motion perception, including the integration of different motion cues, is still lacking. Here we outline several experimental observations concerning human smooth pursuit of moving objects and more particularly the time course of its initiation phase, which reflects the ongoing motion integration process. In addition, we propose a recursive extension of the Bayesian model, motivated and constrained by our oculomotor data, to describe the dynamical integration of 1D and 2D motion information. We compare the model predictions for object motion tracking with human oculomotor recordings.     

Reduced variability of ongoing and evoked cortical activity leads to improved behavioral performance

Sensory responses of the brain are known to be highly variable, but the origin and functional relevance of this variability have long remained enigmatic. Using the variable foreperiod of a visual discrimination task to assess variability in the primate cerebral cortex, we report that visual evoked response variability is not only tied to variability in ongoing cortical activity, but also predicts mean response time. We used cortical local field potentials, simultaneously recorded from widespread cortical areas, to gauge both ongoing and visually evoked activity. Trial-to-trial variability of sensory evoked responses was strongly modulated by foreperiod duration and correlated both with the cortical variability before stimulus onset as well as with response times. In a separate set of experiments we probed the relation between small saccadic eye movements, foreperiod duration and manual response times. The rate of eye movements was modulated by foreperiod duration and eye position variability was positively correlated with response times. Our results indicate that when the time of a sensory stimulus is predictable, reduction in cortical variability before the stimulus can improve normal behavioral function that depends on the stimulus.     

Early Woody Invasion Under Tree Plantations in Costa Rica: Implications for Forest Restoration

The role of tree plantations as facilitators of tropical forest restoration in degraded lands has been explored recently, but there are few data on the effect of different tree species on invasion of the plant understory. We evaluated early patterns of understory composition in three-year-old native tree plantations in lowland Costa Rica using two pure-species treatment (Jacaranda copaia and Vochysia guatemalensis) and one mixed-species treatment (J. copaia, V. guatemalensis, Stryphnodendron microstachyum, and Calophyllum brasiliense). We also monitored woody invasion in unplanted control areas dominated by grasses. The understory of the different plantation treatments differed in light environment, woody-plant growth and recruitment, and quantity and quality of woody regeneration. Forest tree invasion appeared to be enhanced under Vochysia, while shrubs were more abundant under the Jacaranda and mixed-species treatments. Woody plant growth, herbaceous cover, and understory light availability were highest under Jacaranda, intermediate under mixed species, and lowest under Vochysia. Soil-stored seeds seemed an important source for woody plant recruitment in Jacaranda and mixed species and of minimal importance under Vochysia, probably due to light suppression. It appears that competition from grasses is a major factor influencing early woody invasion in our study area. We found no woody recruitment after one year in the unplanted controls. We suggest that to promote the use of plantations as tools of forest restoration, there is a need to gather basic ecological information on how different tree species may influence patterns of plant understory colonization.     

Presence of cancer cells in gastric lavage of gastric cancer patients as an indicator of advanced disease,predictor of tumour aggressive phenotype and independent prognostic factor for poor survival: The endoluminal metastatic pathway of gastric cancer and GL0/GL1 classification

Objective

As of 2017, the pathobiology of gastric cancer (GC) is far from fully understood; consequently, new methods of basic and advanced research have been proposed and tested. The presence (GL1) vs absence (GL0) of malignant cells exfoliated in gastric lavage (GL) of GC patients was formerly evaluated with diagnostic intent but not for staging or prognostic assessment. We investigated this hitherto unreported application of cytopathology.

Methods

GL was preoperatively and prospectively collected from 80 GC patients and cytologically analysed. The results were compared with the classic clinicopathological features of GC and related to survival. The prognostic value of GL1 was assessed through univariate and multivariate analyses.

Results

GL1 was detected in 36 samples (45%) and correlated with advanced tumour depth (T3‐T4), lymphatic metastasis (N+), distant metastasis (M1) and lymphovascular invasion (LVI1; P=.0317, .0024, .003 and .0028, respectively). Overall survival (OS) was significantly shorter for GL1 (23 months) vs GL0 patients (42 months; P=.005) and GL1 vs GL0 T1 subjects (12.6 vs 47.8 months, P=.0029). Univariate analysis revealed that GL1, N+, M1, LVI1 and advanced stage were significantly associated with OS. Multivariate analysis assessed GL1 as the only independent prognostic factor for worse OS and progression‐free survival (P=.0013 and .0107).

Conclusions

In the present study, GL1 was correlated with advanced disease, aggressive tumour behaviour and poor prognosis. Although additional studies are needed to confirm these findings, the GL0/GL1 classification can be applied to GC patients to achieve higher accuracy in staging, prognostic stratification and treatment selection.     

Nitrification potentials in early successional black locust and in mixed hardwood forest stands in the southern Appalachians,USA

Soil nitrogen mineralisation and nitrification potentials, and soil solution chemistry were measured in black locust (Robinia pseudo-acacia L.), in pine-mixed hardwood stands on an early successional watershed (WS6), and in an older growth oak-hickory forest located on an adjacent, mixed hardwood watershed (WS14) at Coweeta Hydrologic laboratory, in the southern Appalachian mountains, U.S.A. Nitrification potentials were higher in black locust and pine-mixed hardwood early successional stands than in the oak-hickory forest of the older growth watershed. Ammonification rates were the main factor controlling nitrification in the early successional stands. There was no evidence of inhibition of nitrification in soils from the older growth oak-hickory forest site.Within the early successional watershed, black locust sites had net mineralisation and nitrification rates at least twice as high as those in the pine mixed-hardwood stands. Concentrations of exchangeable nitrate in the soil of black locust stands were higher than in pine-mixed hardwoods at 0–15 cm in March and they were also higher at 0–15, 16–30 and 31–45 cm depth in the black locust dominated sites in July. Soil solution nitrate concentrations were higher under black locust than under pine-mixed hardwoods. Areas dominated by the nitrogen fixing black locust had greater nitrogen mineralisation and nitrification rates, resulting in higher potential for leaching losses of nitrate from the soil column in the early successional watershed.