trajr: An R package for characterisation of animal trajectories

Quantitative characterisation of the trajectories of moving animals is an important component of many behavioural and ecological studies, however methods are complicated and varied, and sometimes require well‐developed programming skills to implement. Here, we introduce trajr, an R package that serves to analyse animal paths, from unicellular organisms, through insects to whales. It makes a variety of statistical characterisations of trajectories, such as tortuosity, speed and changes in direction, available to biologists who may not have a background in programming. We discuss a range of indices that have been used by researchers, describe the package in detail, then use movement observations of whales and clearwing moths to demonstrate some of the capabilities of trajr. As an open‐source R package, trajr encourages open and reproducible research. It supports the implementation of additional methods by providing access to trajectory analysis “building blocks,” allows the full suite of R statistical analysis tools to be applied to trajectory analysis, and the source code can be independently validated.     

Colchicine-binding activity and neurotubule integrity in a rat sympathetic ganglion

The colchicine-binding activity of rat superior cervical ganglia was examined. Ganglia were cooled and re-warmed in the presence of either Cu²⁺ or of metabolic inhibitors. Electronmicroscopy showed that these treatments depolymerized the neurotubules. This depolymerization of neurotubules did not affect the colchicine-binding activity of ganglion homogenates but caused a two-fold increase in colchicine-binding by whole ganglia. This suggests that colchicine binds only to depolymerized neurotubule subunits and that colchicine-binding by whole ganglia can be used as a measure of polymerization of the neurotubule protein.The major part of the colchicine-binding activity of ganglion homogenates was found in the soluble fraction and was unstable. In the absence of divalent cations, 10⁻⁴ M vinblastine stabilised the soluble colchicine-binding activity.     

Epizootic vesicular stomatitis in Colorado, 1982: some observations on the possible role of wildlife populations in an enzootic maintenance cycle

Sera obtained from wild ungulates, carnivores, and rodents in Colorado were tested for neutralizing (N) antibody against vesicular stomatitis, New Jersey serotype (VSNJ), virus to determine their involvement in the 1982 Colorado VSNJ epizootic in domestic animals. Viremic and N antibody responses of two local rodent species to a 1982 Colorado isolate of VSNJ were determined in the laboratory. The rodents produced only weak viremias, but all developed N antibody. N antibody prevalences for VSNJ in sera from wild ungulates was sufficiently high to indicate their involvement during the epizootic. In addition, the demonstration of N antibody in elk (Cervus elaphus) and mule deer (Odocoileus hemionus) prior to the epizootic in cattle and horses suggests that an enzootic cycle may exist in Colorado.     

Retention of fully differentiated electrophysiological properties of chick embryonic heart cells in culture.

Many cultured cells in spherical reaggregates (100–1000 μm diameter), prepared using cells isolated from embryonic chick ventricles (16 days in ovo), retain great sensitivity to tetrodotoxin (TTX; 0.1 μg/ml), rapidly rising action potentials (up to 200 V/sec), high resting potentials (up to ?90 mV), and they lack automaticity. The Na⁺ channels generating the action potential upstroke inactivate totally at about ?50 mV. The chronaxie (hence, excitability), the ratio of $\text{P}{}_{\mathrm{<mtext>Na</mtext>}}\text{P}{}_{\mathrm{<mtext>K</mtext>}}$, and the intracellular K⁺ concentration are about the same as in adult cells. Following blockade of the Na⁺ channels with TTX, norepinephrine produces slowly rising overshooting responses, indicating the presence of functional beta-adrenergic receptors. Thus, trypsin-dispersed myocardial cells can be made to retain highly differentiated membrane properties in vitro.