Nitrogen cycling in the seasonally dry forest zone of Belize,Central America

Two forest associations, cohune palm (Cohune Ridge) and mixed tropical hardwood (High Bush), were assessed on the basis of nutrient movement and storage for their suitability for agriculture. Continuous monitoring of soil nitrogen and leaf litterfall over a one-year period provided information on soil building processes in the forest fallow. Destructive cuts revealed the storage of 690 kg N ha^–1 in the standing biomass of the Cohune forest versus 203 kg N ha^–1 in the High Bush. Litter biomass was exceptionally high in the Cohune Ridge (497 kg ha^–1 dry matter) as compared to the High Bush (65 kg ha^–1 dry matter) and other tropical forests. This is probably because of a low rate of decomposition in the Cohune Ridge palm forest. A substantial reserve of nitrogen is present in both forests' fallows, and this can in part be harvested by the small farmer for crop production.

---

Ciclo de nitrógeno en la zona de bosque seco estacional de Belize, América Central

Resumen Dos asociaciones boscosas (Palma Cohune y Matorral Alto) se estudiaron en relación a sus reservas y flujos de nutrimentos y sus posibilidades de aprovechamiento agricola. Se siguió la evolución del nitrógeno en el suelo y en la caida de hojarasca durante un año obteniéndose asi información sobre los procesos pedogenéticos en el barbecho del bosque.A través de muestreos destructivos se encontró que en la biomasa del bosque de Palma Cohune habían 690 kg N ha^–1 y en el Matorral Alto solo 203 kg N ha^–1. La biomasa de hojarasca era excepcionalmente alta en Palma Cohune alcanzando un valor de 497 kg materia seca ha^–1; en el bosque de Matorral Alto la hojarasca era de 65 kg materia seca ha^–1. Esto probablemente se deba a la baja velocidad de descomposición en el caso de la palma.Las reservas sustanciales encontradas en ambos barbechos para el nitrógeno podrían ser parcialmente utilizadas para la producción agrícola campesina.

     

Effect of temperature on stability of marker constituents in Echinacea purpurea root formulations.

Stability of an alkamide and a phenolic phytochemical marker in a hydro-alcoholic extract of Echinacea purpurea root and a dried powder prepared by evaporation of the extract was assessed in storage for 7 months at three temperature regimes: -20, 25 and 40 degrees Celsius. In the extract, the major alkamide, dodeca-2E, 4E, 8Z, 10E/Z-tetraenoic acid isobutyl amide, was not significantly affected by storage at any of the temperatures, but cichoric acid content declined as significantly (P = 0.05) at both 25 degrees C and 40 degrees C as compared to low-temperature storage. In the powder, the major alkamide showed a significantly reduced level at 25 degrees C and 40 degrees C while cichoric acid did not decline significantly. These results suggest that more attention should be given to the effect of formulation and temperature on storage of Echinacea products.     

Estimation of age-specific breeding probabilities from capture-recapture data

We provide a new method for estimating the age-specific breeding probabilities from recaptures or resightings of animals marked as young. Our method is more direct than previous methods and allows the modeler to fit and compare models where the age-specific breeding proportions are equal over different cohorts or are a function of external covariates.     

Design and expression of polymeric immunoglobulin fusion proteins: a strategy for targeting low-affinity Fcgamma receptors

We have developed a family of cloning vectors that direct expression of fusion proteins that mimic aggregated immunoglobulin (IgG) (AIG) and immune complex function with respect to their interactions with FcgammaR and that allow for the inclusion and targeting of a second protein domain to cells expressing FcgammaR. This was accomplished by expressing multiple linear copies of the hinge and CH2 domains (HCH2) of human IgG(1) fused to the framework region of human IgG(1). Convenient restriction sites allow for the facile introduction of additional amino-terminal domains. The resulting molecule is tripartite. The carboxyl-IgG(1) framework domain provides stability and permits dimerization, and the intervening polymer provides increased effector function and targeting to FcgammaR while the amino-terminal domain can deliver an additional signal to cells expressing FcgammaR. To demonstrate the utility of the vectors, the extracellular domain of human CD8alpha was expressed as a HCH2 polymer fusion protein. The fusion proteins were secreted in useful amounts from polyclonal cell lines established in Sf9 cells following transfection and selection with G418. The biological activity of the recombinant CD8alpha-HCH2 polymers was determined and compared to those of AIG and an anti-CD16 monoclonal antibody using an in vitro assay. The activity of the fusion proteins positively correlates to the number of HCH2 units. The largest polymer tested was severalfold more potent than AIG at similar concentrations. The HCH2 polymers described here represent a new strategy in the design of recombinant proteins for the therapeutic targeting of FcgammaR in autoimmune disorders.     

Elimination of Mange Mites <Emphasis Type="Italic">Sarcoptes scabiei</Emphasis> var. <Emphasis Type="Italic">suis</Emphasis>from Two Naturally Infested Danish Sow Herds Using a Single Injection Regime with Doramectin

Attempts to eliminate Sarcoptes scabiei var. suis were made in 2 naturally infested sow herds, by intramuscular (IM) injection of doramectin (Dectomax^®, Pfizer, New York, USA). A single injection strategy was used. In one of the herds, the environment was treated with an acaricide following dry cleaning of floors, walls and equipment. In the second herd, no environmental treatment was performed. Results were measured by skin lesion scoring, ear scrapings to show Sarcoptes scabiei var. suis, and calculating rubbing index throughout the observation period of 20 months following treatment. Skin lesion scores decreased and stayed low following treatment for the entire observation period. Live Sarcoptes scabiei var. suis mites were isolated prior to treatment from both herds, but not following treatment. Rubbing index decreased following treatment, but was occasionally at or above 0.4. The results of these studies indicate that elimination of Sarcoptes scabiei var. suis from 2 naturally infested herds was successful, using doramectin in a single injection strategy. Precautions must be taken to ensure adequate dosing of every pig, and to avoid reinfestation due to poor biosecurity.     

Growth and chemical defense in relation to resource availability: tradeoffs or common responses to environmental stress?

One aspect of plant defense is the production of constitutive secondary compounds that confer toxicity on herbivores and pathogens. The purpose of this study was to compare patterns of plant tissue toxicity across gradients of irradiance and nutrient content. We measured the potential toxicity (1/LC50) of extracts of six species of herbaceous Asteraceae grown under controlled conditions of temperature (25 degrees C), humidity (80%), photoperiod (16 h/day), in a range of concentrations of a modified Hoagland hydroponic solution (full-strength, 1/5 dilute, 1/10 dilute, and 1/50 dilute) and under two different light intensities (250 and 125 micromol/m2/s). The plants grew from seed for 42 days post-germination, and randomly chosen plants were harvested each 7 days. We did a general measure of potential phytochemical toxicity using an alcohol extraction of secondary compounds followed by brine shrimp (Artemia sp.) bioassay. Contrary to the carbon/nutrient balance hypothesis, tissue toxicity generally increased with decreasing irradiance and nutrient levels, so that plants whose growth was most restricted had tissues that were most toxic, although there were species-specific differences in this trend.     

Platelet activating factor-induced neuronal apoptosis is initiated independently of its G-protein coupled PAF receptor and is inhibited by the benzoate orsellinic acid

The bioactive lipid mediator platelet activating factor (PAF) is recognized as a key effecter of neuronal apoptosis, yet it is not clear whether its G-protein coupled receptor (PAFR) initiates or prevents PAF neurotoxicity. Using PAFR-/- and congenic wild-type mice, we show that PAF triggers caspase-3/7 activity and neuronal death in PAFR-/- but not PAFR+/+ cerebellar granule neurons. Restoring receptor expression by recombinant adenoviral infection protected cells from PAF challenge. Neuronal death was not mediated by nitric oxide or N-methyl-d-aspartate receptor signaling given that N-nitro-l-arginine methyl ester and MK-801 did not inhibit PAF-induced neuronal loss in PAFR-/- neurons. To intervene in PAFR-independent neurotoxicity, the anti-apoptotic actions of three structurally distinct PAF antagonists were compared to a panel of plant and fungal benzoic acid derivatives. We found that the PAF antagonist BN 52021 but not FR 49175 or CV 3988 inhibited PAFR-independent neurotoxicity. Orsellinic acid, a fungal-derived benzoic acid, blocked PAF-mediated neuronal apoptosis without affecting PAFR-mediated neuroprotection. These findings demonstrate that PAF can transduce apoptotic death in primary neurons independently of its G-protein coupled receptor, that PAFR activation is neuroprotective, and that orsellinic acid effectively attenuates PAFR-independent neuronal apoptosis.     

Ethnobotany of Immunomodulatory Treatments Used by the Q’eqchi’ Maya of Belize

Using a quantitative ethnobotanical methodology, we identified 107 plant species belonging to 49 families used by Q’eqchi’ Maya healers in the treatment of symptoms from 14 usage categories related to inflammation. The families with the largest number of medicinal species were Piperaceae, Araceae, Asteraceae, Fabaceae, and Adiantaceae with five or more medicinal species. Healer consensus for plant species was high, with 56 species (52%) being used by all the healers, and consensus for usage categories was also high, as informant consensus factor (FIC) values for each category were greater than 0.4.