Isolation and characterization of microsatellite markers from the chestnut‐backed antbird,Myrmeciza exsul

We describe nine microsatellite loci from the chestnut‐backed antbird (Myrmeciza exsul), and one locus from the spotted antbird (Hylophylax naevioides) that cross‐amplifies in chestnut‐backed antbirds. The chestnut‐backed antbird is a common understorey insectivore in Neotropical lowland rain forests ranging from eastern Nicaragua to western Ecuador. Primers were developed in order to assess population structure in a fragmented landscape and to study dispersal at a local scale. Primers were tested on 60–62 individuals from a single population in the Sarapiquí Province of Costa Rica. Loci had varying degrees of polymorphism, ranging from two to 19 alleles.     

Free amino acids and nucleic acid content of cell nuclei isolated by a modification of Behrens' technique

1. Nuclei were prepared from frozen rat liver by a modification of the technique of Behrens, and were studied with regard to the content of free amino acids and nucleic acid. 2. Under rigorously controlled conditions, preparations of nuclei are obtained by the Behrens' method which form a gel in the presence of 5 or 10 per cent NaCl or of water plus a small amount of dilute alkali; whereas when conditions are less rigorously controlled, nuclei are obtained which form no such gel. The property of forming gels with alkali is probably characteristic of all cell nuclei which have not undergone autolysis. 3. Nuclei prepared by the Behrens' technique contain the enzymes arginase, catalase, and esterase in very appreciable concentrations. 4. The free amino acids of the isolated cell nuclei, as well as of other liver cell fractions, have been investigated using the technique of paper chromatography. 5. The chromatographic patterns of the free amino acids of whole cells, ground cytoplasm, and isolated cell nuclei were very similar or identical. A feature of interest in these chromatograms was the faintness or absence of the spots due to a number of the essential amino acids, as compared to the intensities of the spots due to glycine, alanine, and glutamic acid. Glutathione was present in the isolated nuclei as well as in the whole cells. 6. Chromatograms made from hydrolysates of nuclei showed high concentrations of the essential amino acids and were similar to chromatograms of hydrolysates of typical proteins.     

A Three-Dimensional Finite Element Analysis of Heat Transfer in the Forearm

Abstract

The finite element method was used to analyze heat transfer within a section of the forearm while exposed to different ambient conditions and with different metabolic states. The three-dimensional model accounts for the different material properties of bone, muscle and blood and incorporates a single artery-vein pair for counter-current heat exchange. The geometry of the model was developed from anatomical cross-sectional images of the forearm. The model was used to determine the effects or rest vs. exercise, free vs. forced surface convection and 0°C vs. — 20 °C external temperatures. The results of the model were compared to experimental data and the model exhibits qualitatively correct behaviour. This model can be used to study hyperthermia, burns and cryogenic freezing of tissue.     

From lynx spiders to cotton: Behaviourally mediated predator effects over four trophic levels

Food web studies often examine density and behaviourally mediated effects of predators on herbivores, but are less likely to assess the plant targeted by the herbivore. We conducted a study that incorporated four trophic levels examining the effect of two generalist predators (damsel bugs, Nabis kinbergii Reuter; and lynx spiders, Oxyopes molarius L. Koch) on damage to cotton bolls caused by green mirids (Creontiades dilutus (Stål)). First we tested whether lynx spiders and damsel bugs could control mirid numbers and cotton boll damage in field cages. We found that in cages containing mirids and only lynx spiders, lynx spiders reduced both mirid numbers and boll damage. However, in cages which contained mirids and both predators (lynx spiders and damsel bugs) only mirid numbers were reduced. To explain the negative effect of damsel bugs on boll damage, we examined the interactions between lynx spiders, damsel bugs and mirids. We found that lynx spiders were better mirid predators than damsel bugs, and that lynx spiders attacked damsel bugs, but not vice versa. Behaviourally, mirids responded to increasing predator pressure regardless of whether the predators were lynx spiders or damsel bugs. However, damsel bugs seemed to alter the behaviour of lynx spiders because in their presence, a higher proportion of lynx spiders moved to the top of the plant, towards the damsel bugs but away from the bolls found lower on the plant. These results suggest that the most likely explanation for the increase in boll damage in the presence of damsel bugs was that lynx spiders moved to the top of the plant in the presence of damsel bugs, which then exposed the bolls lower down on the plant to mirid attack. This work emphasizes the importance of behaviourally mediated effects in food webs extending over four trophic levels.     

Antibodies Blocking the Mating Reaction In Paramecium Multimicronucleatum Syngen 2

SYNOPSIS Antibodies induced in rabbits against Paramecium multimicronucleatum syngen 2 prevent sexually reactive cells from clumping, pairing, and forming cytoplasmic fusions. A biologic assay for the detection of these antibodies (designated blocking antibodies ) is described. the blocking antibodies, unlike the immobilization antibodies, are produced against breis of sexually reactive cells and nonreactive cells of 2 types, nonstarved and immature. Isolated cilia from reactive cells of either mating type are weak immunogens for blocking antibodies. No correlation between the mating type specificity (III or IV) and these antibodies has been detected. Blocking antibodies can be absorbed with living cells, of which sexually reactive ones are the most effective absorbers, while immature ones are the least effective.