Structure-function relationships of the flexor carpi radialis muscle compared among four species of mammals

Investigations of the structure and function of the flexor carpi radialis muscle (FCR) in the cat have led to the hypothesis that the compartmentalized (nonuniform) distribution of fiber types within the muscle relate to the complex motor skills of the cat. To test this hypothesis a study was undertaken to compare the FCR in four mammalian species of similar body size but with different forelimb motor tasks. The species chosen were: dog, opossum, armadillo, and cat. Comparisons were made among species with regard to general muscle morphology, fiber types and sizes, fiber proportions, and fiber distriburtions. The FCR of all species was morphologically similar and contained three muscle fiber types (SO, FOG, and FG). The mean area of muscle fibers was largest in opossum, while the FCR fibers of dogs were smallest. The percentage of SO fibers in the dog FCR was greater than in the other species studied. The opossum FCR also contained a high percentage of SO fibers. The armadillo FCR consisted of a high percentage of FG fibers. In the cat FCR the percentages of all three fiber types were similar. For each species, individual fiber proportions were in agreement with the results for fiber percentages. Compartmentalized distribution of fiber types existed in each species with the dog having the most compartmentalized fiber type distribution and the cat the least compartmentalized distribution. Therefore it seems that the compartmentalized organization of the FCR is not related to any specialized motor task, but may be a generalized pattern associated with motor patterns shared among all species studied.     

Modelling the spread of pollen from Lolium perenne. The implications for the release of wind-pollinated transgenics

The dispersal of pollen from a Lolium perenne source has previously been described using various Gaussian plume models which take distance and wind direction into account. One of these models is used here to calculate, using integration, possible pollen deposition onto small conspecific populations a kilometer from the source. The percentage of immigrant pollen is compared for six different sets of parameter values previously estimated from pollen-dispersal experiments. The source size is then scaled up to simulate what might happen if transgenic ryegrass was grown on a large scale. In this case it is seen that small conspecific populations might, in some conditions, be swamped by immigrant pollen, even if they are not directly downwind of the source. The implications of this are discussed in terms of assessing and managing the risks of releasing wind-pollinated transgenic crops. Received: 10 July 1999 / Accepted: 27 August 1999     

High incidence of selenite-resistant bacteria from a site polluted with selenium

The level of selenium-resistant bacteria in water, algal mats, and sediment from Kesterson reservoir, Calif., a site with known selenium pollution, was compared with that in nearby Volta reservoir, a site with low selenium levels. A high percentage (greater than 50%) of all isolates from the Kesterson samples were resistant to 10 mM selenite. In contrast, only a small percentage of the Volta isolates were resistant to this level of selenite. The identity of some selenite-resistant isolates and MICs of selenite, selenate, arsenate, tellurite, and tellurate were determined.