Spatial and temporal factors associated with nest survival of Gray Flycatchers in managed ponderosa pine forests

Gray Flycatchers (Empidonax wrightii) breed in a variety of habitats in the arid and semi‐arid regions of the western United States, but little is known about their breeding biology, especially in the northern portion of their range where they nest in ponderosa pine (Pinus ponderosa) forests. From May to July 2014 and 2015, we conducted surveys for singing male Gray Flycatchers along the eastern slope of the Cascade Range in Washington, U.S.A, monitored flycatcher nests, and quantified nest‐site vegetation. We used a logistic‐exposure model fit within a Bayesian framework to model the daily survival probability of flycatcher nests. During the 2 yr of our study, we monitored 141 nests, with 93% in ponderosa pines. Mean clutch size was 3.6 eggs and the mean number of young fledged per nest was 3.2. Predation accounted for 90% of failed nests. We found a positive association between daily nest survival and both nest height and distance of nest substrates from the nearest tree. Flycatchers that locate their nests higher above the ground and further from adjacent trees may be choosing the safest alternative because higher nests may be less exposed to terrestrial predators and nests in trees that are farther from other trees may be less exposed to arboreal predators such as jays (Corvidae) that may forage in patches with connected canopies. Nests in trees farther from other trees may also allow earlier detection of approaching predators and thus aid in nest defense.     

Glycosylation of high-affinity thrombin receptors appears necessary for thrombin binding.

Monosaccharide binding competition, lectin affinity chromatography, and glycosylation inhibitors have been used to determine if glycosylation plays a role in thrombin-receptor interactions. Mannose appeared to specifically inhibit thrombin binding to mouse embryo (ME) and hamster fibroblasts. Concanavalin A bound to antibody-purified receptor fractions, and was used as an affinity ligand to purify receptor fractions that retained thrombin binding activity. Cells treated with tunicamycin (6.25 ng/ml) for 24 h lost approximately 35% of their high-affinity thrombin binding sites, yet binding of receptor monoclonal antibody TR-9 was not affected, indicating that the receptor was present in the membrane, but unable to bind thrombin. Thus thrombin receptor glycosylation may be directly involved in thrombin binding.     

Eye movements in Daphnia pulex (De Geer).

1. The various types of eye movement exhibited by the cyclopean eye of Daphnia pulex were studied using high speed motion photography. 2. This rudimentary eye, which consists of only 22 ommatidia, can move through approximately 150 degrees in the sagittal plane and 60 degrees in the horizontal plane. 3. Four classes of eye movement were found: (1) a high speed tremor at 16 Hz with an amplitude of 3-4 degrees, which resembles physiological nystagmus, (2) a slow rhythmic scanning movement at 4 Hz, and 5-6 degrees amplitude, (3) large fast eye movements similar to saccadic eye movements and (4) optokinetic nystagmus produced by moving striped patterns. 4. Where the fast tremor occurred concurrently with the slow rhythmic scan, a Fourier analysis revealed that the former was the fourth harmonic of the latter.     

A quantitative method for the detection and localization of quantum-limited events from radionuclides in cells and tissue sections by computer-enhanced video microscopy

Cellular dynamics often involve extremely low concentrations of biologically active substances, which can be radiolabeled and detected, localized and quantitated by autoradiography. The latter may require exposures from a few days to many months. The objective of this research was to demonstrate the feasibility of reducing this long period of data collection by one to two orders of magnitude, while maintaining or improving the spatial resolution and localization in tissues and the quantitative characteristics inherent in autoradiography. A mathematical model describing the complete system was generated using energy partition calculations to estimate photon production via scintillant per H3 beta particle emission and to estimate the subsequent photon capture based upon imaging system parameters and microscope geometry. Calculations showed that, typically, a single tritium beta particle produces a maximum of 5.8 X 10(3) photons. A photon-limited camera and microscope imaging system were selected and optimized in conjunction with a specially developed physical scintillation model. Results showed that the number of detected photoevents increases monotonically with both signal integration time and, independently, with the concentration of the radionuclide. Consequently, this work demonstrates that video microscopy imaging methods can spatially and temporally quantify very low concentrations of radiolabeled substances and can reduce data acquisition times.     

Effects of exogenous guanosine on chromatophore differentiation in the axolotl

Guanosine is shown to dramatically alter the pigment phenotype of axolotls by suppressing melanization and enhancing the biosynthesis and deposition of purine-derived pigments. Phenotypic changes caused by guanosine are manifested by altered chromatophore differentiation patterns such that few black pigment cells (melanophores) differentiate (and those that do are punctate and necrotic in appearance), whereas the development of yellow (xanthophore) and reflecting (iridophore) pigment cells is enhanced. Mechanisms for changes in chromatophore differentiation, and thus pattern formation, are discussed, including the possibility that pigment cells may undergo transdifferentiation in vivo.     

Sperm-macrophage interaction in the mouse: a quantitative assay in vitro using 111indium oxine-labeled sperm

The role of reproductive tract macrophages in contraception and reproductive failure has become widely recognized. However, in vitro analysis of sperm phagocytosis by macrophages has relied upon a semi-quantitative method of sperm counting that is of limited accuracy and reproducibility. We have developed an assay using murine sperm labeled with 111indium oxine, and results indicate the labeling to be rapid and efficient. Incorporation of 111indium into sperm increased the dose and sperm concentration and reached 90% maximal uptake after 15 min incubation, with maximal uptake occurring at 30 min. No decrease in sperm motility was noted with levels of oxine in excess of those required for significant labeling. Maximal labeling efficiency occurred in phosphate-buffered saline (PBS), with Dulbecco's modified Eagle's medium (DMEM) + 10% adult bovine serum (ABS) producing significantly less uptake. Label dissociation was detectable in PBS at room temperature, but at 37 degrees C in DMEM + 10% ABS, loss of label occurred at a rate of 23.5%/h. Addition of labeled sperm to murine macrophage monolayers under optimal conditions resulted in uptake of 111indium by macrophages, while free label was unincorporated. Results indicated assay specificity for macrophage-limited uptake, with insignificant label uptake by nonphagocytic murine fibroblasts and better sensitivity than sperm counting. Macrophages from Bacillus Calmette-Guerin (BCG)-infected mice resulted in a decrease in sperm uptake. Female macrophages showed greater capacity for sperm uptake than those of the male mouse. These initial studies demonstrated the utility of this model system in enhancing the understanding of sperm-macrophage interaction in the female reproductive tract.     

Predator-induced diet vertical migration in a planktonic copepod

Predator evasion is the most commonly hypothesized reason fordiel vertical migrations undertaken by a wide variety of planktonicorganisms in lakes and seas, yet direct evidence remains elusive.We tested the predation hypothesis by exposing enclosed populationsof a marine copepod Acartia hudsonica to caged or free-rangingindividuals of their natural predator, the planktivorous fishGasterosteus aculeatus. After little more than a week, adultcopepods changed their vertical distribution and migration behaviordepending on the presence or absence of predation. Only free-rangingfish induced vertical migration in the copepod population. Cagedfish had no effect, indicating that vertical migration was nota simple chemically mediated response of copepods to the predator.Rather, copepods seemed to react to the presence of predatorsby other means, perhaps visual or mechanical stimuli, and toexhibit a downward escape response which, because encounterswith visually orienting fish occur chiefly in the daytime, effectivelylimited the copepods' occurrence in the upper water column tothe night-time hours. Alternatively, because fish imposed heavymortality on copepods, it is possible that selective predationaltered the proportions of individuals with fixed, geneticallydetermined migration behaviors. We suggest experiments to distinguishthese alternatives.