16, 16 Dimethyl prostaglandin E2 reduces histamine release from the stomach and protects the gastric mucosal barrier altered by ethanol in neutral solution

Damage to the gastric mucosal barrier results in histamine release from intramucosal stores. Previous reports have shown that 16, 16 dimethyl prostaglandin E₂ (dm PGE₂) protects the stomach from injury by various damaging agents in either acidic or neutral solution. Furthermore histamine released in response to a damaging drug in an acidic medium was reduced by dm PGE₂. Using the Heidenhain pouch dog preparation, the present study examined the action of dm PGE₂ on ethanol-induced barrier breaking and histamine release in neutral solution. Topical ethanol treatment (15% w/v) damaged the gastric mucosal barrier as evidenced by increased net fluxes of Na+ and K+ and an increase in the histamine content of the fluid irrigating the Heidenhain pouch. Intravenous injection of dm PGE₂ in the doses of 0.01, 0.10 and 1.00 μg/kg one-half hour before ethanol administration significantly reduced the appearance of Na+, K+ and histamine. It is concluded that dm PGE₂ effectively protects the canine gastric mucosa from damaging agents in neutral solution as evidenced by a reduction in the luminal appearance of Na+, K+ and histamine.     

Entomophthora bullata as a pathogen of Sarcophaga aldrichi

Adults of Sarcophaga aldrichi killed by Entomophthora bullata were found in the field 7 days after emergence. Resting spores were not found until 6 days later, although conidia were formed from the first incidence of mortality. It is suggested that the life cycle of the fungus involves alternating generations of conidia and thick-walled overwintering resting spores.     

Micromachining in plastics using X-ray lithography for the fabrication of microelectrophoresis devices

Micromachining was performed in polymethylmethacrylate (PMMA) using X-ray lithography for the fabrication of miniaturized devices (microchips) for potential applications in chemical and genetic analyses. The devices were fabricated using two different techniques: transfer mask technology and a Kapton mask. For both processes, the channel topography was transferred (1:1) to the appropriate substrate via the use of an optical mask. In the case of the transfer mask technique, the PMMA substrate was coated with a positive photoresist and a thin Au/Cr plating base. Following UV exposure, the resist was developed and a thick overlayer (approximately 3 microns) of Au electroplated onto the PMMA substrate only where the resist was removed, which acted as an absorber of the X-rays. In the other technique, a Kapton film was used as the X-ray mask. In this case, the Kapton film was UV exposed using the optical mask to define the channel topography and following development of the resist, a thick Au overlayer (8 microns) was electrodeposited onto the Kapton sheet. The PMMA wafer during X-ray exposure was situated directly underneath the Kapton mask. In both cases, the PMMA wafer was exposed to soft X-rays and developed to remove the exposed PMMA. The resulting channels were found to be 20 microns in width (determined by optical mask) with channel depths of approximately 50 microns (determined by x-ray exposure time). In order to demonstrate the utility of this micromachining process, several components were fabricated in PMMA including capillary/chip connectors, injectors for fixed-volume sample introduction, separation channels for electrophoresis and integrated fiber optic fluorescence detectors. These components could be integrated into a single device to assemble a system appropriate for the rapid analysis of various targets.     

Synthesis and evaluation of unsaturated caprolactams as interleukin-1beta converting enzyme (ICE) inhibitors

Peptidomimetic compounds possessing a caprolactam ring constraint were prepared and evaluated as interleukin-1beta converting enzyme (ICE) inhibitors. The caprolactam ring was used to constrain the P3 region of our inhibitors. This strategy proved to be effective for the synthesis of ICE inhibitors, maintaining key hydrogen bond interactions with the enzyme and invoking a preferred conformation for binding. Several compounds exhibited IC(50) values less than 10nM in a caspase-1 enzyme assay and less than 100nM in a THP-1 whole cell assay measuring IL-1beta production. Two compounds, 13c and 13j, were found to have good oral bioavailability (>50%) in rats when administered as prodrugs.     

Toward a fine-scale population health monitoring system

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Media suitable for industrial production of Entomophthora virulenta zygospores

Entomophthora virulenta has been grown using inexpensive, commercial grade nutrient sources in order to produce a resting spore formulation available to agriculture. Solid media and liquid media in shake flasks and fermentors were examined. The best carbon sources for sporulation were dextrose and corn syrup, while the best nitrogen sources were yeast extract, soybean, and cottonseed flours. The optimal nutrient concentration (12%) produced 3 × 10⁶spores/ml with a 70% germination rate within five days.     

Leaf litter inputs reinforce islands of nitrogen fertility in a lowland tropical forest

The role of lowland tropical forest tree communities in shaping soil nutrient cycling has been challenging to elucidate in the face of high species diversity. Previously, we showed that differences in tree species composition and canopy foliar nitrogen (N) concentrations correlated with differences in soil N availability in a mature Costa Rican rainforest. Here, we investigate potential mechanisms explaining this correlation. We used imaging spectroscopy to identify study plots containing 10–20 canopy trees with either high or low mean canopy N relative to the landscape mean. Plots were restricted to an uplifted terrace with relatively uniform parent material and climate. In order to assess whether canopy and soil N could be linked by litterfall inputs, we tracked litter production in the plots and measured rates of litter decay and the carbon and N content of leaf litter and leaf litter leachate. We also compared the abundance of putative N fixing trees and rates of free-living N fixation as well as soil pH, texture, cation exchange capacity, and topographic curvature to assess whether biological N fixation and/or soil properties could account for differences in soil N that were, in turn, imprinted on the canopy. We found no evidence of differences in legume communities, free-living N fixation, or abiotic properties. However, soils beneath high canopy N assemblages received ~ 60% more N via leaf litterfall due to variability in litter N content between plot types. The correlation of N in canopy leaves, leaf litter, and soil suggests that, under similar abiotic conditions, litterfall-mediated feedbacks can help maintain soil N differences among tropical tree assemblages in this diverse tropical forest.