Effects of enzyme isolation on the basal lamina of developing avian limb bud epithelia

Summary The developing avian limb bud is a classic example of an epithelial-mesenchymal interaction. Numerous attempts at maintenance of the epithelia in culture have been predominantly unsuccessful. The fate of the isolated epithelial sheet of the limb bud [including the apical ectodermal ridge (AER)] in culture may depend at least in part on the integrity of its basal lamina following isolation. In this study the distal epithelium of the stage 23 limb bud was isolated utilizing trypsin and Dispase II in a variety of procedures. The integrity of the basal lamina of limb epithelium immediately upon isolation and after 2 h in culture was determined by immunofluorescent staining for laminin, and electron microscopy. In epithelial sheets isolated with Dispase II a direct relationship was observed between maintenance of the extracellular matrix at isolation and the preservation of the tissue structure and cytoarchitecture following 2 h in culture. In contrast, there was an accelerated deterioration during incubation of the tissue isolated with trypsin, independent of isolation conditions and integrity of basal lamina after isolation. Short-term maintenance of limb bud epithelial structure and cytoarchitecture after enzymatic isolation seems correlative to the maintenance of extracellular matrix at the epithelial basal surface.     

Applying GPS to the study of primate ecology: A useful tool?

Data on the spatiotemporal distribution of resources can be collected and plotted using GPS (global positioning system) and GIS (geographical information system) technologies. By combining such data with information on foraging and ranging behavior of nonhuman primates, one can analyze the influence of resource distribution on social organization and group cohesion. We investigated the abilities of a three-channel GPS receiver to collect location data under varying canopy densities in both temperate and tropical forests. Eighty randomly selected points were sampled in a beech–maple forest in northeast Ohio, USA; 65 points also were sampled at several tropical forests in Costa Rica and Trinidad. At each point we attempted to obtain a GPS position fix; we also determined the speed of satellite acquisition and measured canopy density using a spherical densiometer. The ability to obtain a reading differed greatly between the two forest types (χ² = 53.79, P < 0.001). Ninety-seven percent of all attempts were successful in the temperate forest, whereas only a 34% acquisition rate was obtained in the tropical forests. Logistic regression showed that the probability of obtaining a reading in Neotropical forests was 75% but only when canopy cover was less than 20%. Thus, these minimal-channel GPS units may be of limited utility for behavioral ecologists working in closed-canopy Neotropical forests. Am. J. Primatol. 46:167–172, 1998. © 1998 Wiley-Liss, Inc.     

Transgene excision in pollen using a codon optimized serine resolvase CinH-<Emphasis Type="Italic">RS2</Emphasis> site-specific recombination system

Transgene escape, a major environmental and regulatory concern in transgenic crop cultivation, could be alleviated by removing transgenes from pollen, the most frequent vector for transgene flow. A transgene excision vector containing a codon optimized serine resolvase CinH recombinase (CinH) and its recognition sites RS2 were constructed and transformed into tobacco (Nicotiana tabacum cv. Xanthi). CinH recombinase recognized 119 bp of nucleic acid sequences, RS2, in pollen and excised the transgene flanked by the RS2 sites. In this system, the pollen-specific LAT52 promoter from tomato was employed to control the expression of CinH recombinase. Loss of expression of a green fluorescent protein (GFP) gene under the control of the LAT59 promoter from tomato was used as an indicator of transgene excision. Efficiency of transgene excision from pollen was determined by flow cytometry (FCM)-based pollen screening. While a transgenic event in the absence of CinH recombinase contained about 70% of GFP-synthesizing pollen, three single-copy transgene events contained less than 1% of GFP-synthesizing pollen based on 30,000 pollen grains analyzed per event. This suggests that CinH-RS2 recombination system could be effectively utilized for transgene biocontainment.     

An improved medium for growing Staphylococcus aureus biofilm

A medium (Brain Heart Infusion plus 10% human plasma) was developed, tested, and validated for growing Staphylococcus aureus biofilm in vitro. With this medium, S. aureus forms reproducible and robust biofilms in flow chambers under controlled shear flow and with increased viability recovery in static well plates.