A Spatially Explicit Model of Synchronization in Fiddler Crab Waving Displays

Fiddler crabs (Uca spp., Decapoda: Ocypodidae) are commonly found forming large aggregations in intertidal zones, where they perform rhythmic waving displays with their greatly enlarged claws. While performing these displays, fiddler crabs often synchronize their behavior with neighboring males, forming the only known synchronized visual courtship displays involving reflected light and moving body parts. Despite being one of the most conspicuous aspects of fiddler crab behavior, little is known about the mechanisms underlying synchronization of male displays. In this study we develop a spatially explicit model of fiddler crab waving displays using coupled logistic map equations. We explored two alternative models in which males either direct their attention at random angles or preferentially toward neighbors. Our results indicate that synchronization is possible over a fairly large region of parameter space. Moreover, our model was capable of generating local synchronization neighborhoods, as commonly observed in fiddler crabs under natural conditions.     

Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

Sterilization of Plants for Phytoremediation Studies by Bleach Treatment

Bleach treatment of plants was studied as a simple alternative to axenic tissue cultures for demonstrating phytodegradation of aqueous and gas-phase environmental contaminants. Parrotfeather (Myriophyllum aquaticum), spinach (Spinacia oleracea), and wheat (Triticum aestivum) were exposed to 0.525% NaC10 solutions for 15 s, then rinsed in deionized water. Plate counts indicated that 97 to 100% of viable bacteria were removed from parrotfeather and spinach. Transformation rates for 2,4,6-trinitrotoluene (TNT) by bleached and untreated parrotfeather were virtually identical. Similarly, treated and untreated spinach, wheat heads, and wheat leaves removed methyl bromide (MeBr) from air at the same rates. However, wheat root with attendant adhering soil was rendered inactive by bleach treatment. Parrotfeather roots examined by dissecting microscope and by electron microscope showed no significant damage caused by bleach treatment.     

Isolation and characterization of microsatellites in Pacific white shrimp Penaeus (Litopenaeus) vannamei

Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)₁₀ and (GT)₁₀ probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies.     

Lipid quantitation in formalin-fixed liver sections

We describe a simple, sensitive, and quantitative procedure for measurement of triglycerides and protein contents in formalin-fixed liver sections. The method can detect as little as 0.27 microgram of triglycerides per mg of protein. It is based on selective binding of Sudan IV and Fast Green FCF to fat and total proteins, respectively, and their sequential elution with solvents. Sudan IV is eluted readily with acetone and Fast Green with NaOH-methanol, and the absorbances obtained at 500 and 610 nm can be used to determine the amount of triglycerides and total protein. The color equivalence for Fast Green was obtained after destaining the sections and measuring the protein contents by micro-Kjeldahl analysis. The color equivalence of Sudan IV was estimated by determining the triglyceride content in liver homogenates by an enzymatic procedure and then measuring the amount of dye bound to multiple fixed sections. There was a strong linear correlation between the triglyceride content as determined chemically and that obtained using the equivalence colors (r2 = 0.98). This method is useful to measure fat content in tissue samples and could be applied to evaluate the progression of liver disease.     

Mutants of the Rous sarcoma virus envelope glycoprotein that lack the transmembrane anchor and cytoplasmic domains: analysis of intracellular transport and assembly into virions.

The envelope glycoprotein complex of Rous sarcoma virus consists of a knoblike, receptor-binding gp85 polypeptide that is linked through disulfide bonds to a membrane-spanning gp37 spike. We used oligonucleotide-directed mutagenesis to assess the role of the hydrophobic transmembrane region and hydrophilic cytoplasmic domain of gp37 in intracellular transport and assembly into virions. Early termination codons were introduced on either side of the hydrophobic transmembrane region, and the mutated env genes were expressed from the late promoter of simian virus 40. This resulted in the synthesis of glycoprotein complexes composed of a normal gp85 and a truncated gp37 molecule that lacked the cytoplasmic domain alone or both the cytoplasmic and transmembrane domains. The biosynthesis and intracellular transport of the truncated proteins were not significantly different from those of the wild-type glycoproteins, suggesting that any protein signals for biosynthesis and intracellular transport of this viral glycoprotein complex must reside in its extracellular domain. The glycoprotein complex lacking the cytoplasmic domain of gp37 is stably expressed on the cell surface in a manner similar to that of the wild type. In contrast, the complex lacking both the transmembrane and cytoplasmic domains is secreted as a soluble molecule into the media. It can be concluded, therefore, that the transmembrane domain alone is essential for anchoring the RSV env complex in the cell membrane and that the cytoplasmic domain is not required for anchor function. Insertion of the mutated genes into an infectious proviral genome allowed us to assess the ability of the truncated gene products to be assembled into virions and to determine whether such virions were infectious. Viral genomes encoding the secreted glycoprotein were noninfectious, whereas those encoding a glycoprotein complex lacking only the cytoplasmic domain of gp37 were infectious. Virions produced from these mutant-infected cells contained normal levels of glycoprotein. The cytoplasmic tail of gp37 is thus not required for the assembly of envelope glycoproteins into virions. It is unlikely, therefore, that this region of gp37 interacts with viral core proteins during the selective incorporation of viral glycoproteins into the viral envelope.     

Specific inhibitor of complement (C5)-derived chemotactic activity in systemic lupus erythematosus related antigenically to the Bb fragment of human factor B

Serum and plasma from patients with active systemic lupus erythematosus contain a specific inhibitor of complement (C5)-derived chemotactic activity. We found that the inhibitor is antigenically related to the Bb fragment of complement factor B. Lupus plasma and purified inhibitor significantly reduced the chemotactic activity of zymosan-treated normal serum, an effect that was abolished by antibodies to factor B. Similar results were obtained when purified Bb was used. Neither purified inhibitor nor Bb inhibited the chemotactic activity of purified human C5a or C5a des Arg. As reported previously, the chemotactic activity of C5a des Arg was enhanced significantly by the addition of an anionic polypeptide (cochemotaxin) present in normal serum and plasma. Interestingly, both purified lupus inhibitor and Bb inhibited the chemotactic activity exhibited by mixtures of C5a des Arg and its cochemotaxin. This effect was due, most likely, to their ability to neutralize the enhancing effect of the cochemotaxin on the chemotactic activity of C5a des Arg. Immunoelectrophoresis and western blots revealed that the purified inhibitor reacted with anti-factor B and exhibited a similar charge and molecular weight as purified Bb.