Trypanosoma congolense: isolation and purification.

Yields of Trypanosoma congolense grown in rats may be increased by placing the rats in a 37 °C environment for 1 hr prior to sacrifice. A further increase in the number of parasites recovered per rat may be achieved by replacement of blood removed by a lactated Ringer's solution with 5% glucose as the rat is being bled from the abdominal aorta. The Ringer's solution serves to maintain intravascular volume during the bleeding procedure and thereby prevents premature cardiac arrest. Erythrocytes in infected blood may be then lysed by raising and rapidly lowering the osmolarity of the blood. This permits separation of the trypanosomes from 95% of the erythrocytes by differential centrifugation. The remaining blood cell contamination may then be removed on a small DEAE-cellulose column. The purified trypanosomes are motile, infective, and intact as judged by electron microscopy. More than 10¹⁰ purified T. congolense can be obtained from three adult rats by these methods.     

Prevalence of Toxoplasma gondii antibodies in nine populations of dairy goats: compared titers using modified direct agglutination and indirect hemagglutination

In a convenience survey of dairy goats on 9 farms in Tennessee, Kentucky, and Georgia, 54 of 99 females were positive for antibodies to Toxoplasma gondii as measured by the indirect hemagglutination test (IHA). Two of 9 males were also positive. Positive goats were found on all farms. The percentage of positive does increased from 55% to 65% when the sera were titered a second time by modified direct agglutination (MDAT). This difference was not statistically significant, indicating that both IHA and MDAT are reliable epidemiological tools.     

Biological Basis of Saki (Pithecia) Folk Species Recognized by the Matses Indians of Amazonian Perú

The Matses Indians of northeastern Perú recognize two linguistically labeled folk species of saki monkeys (Cebidae: Pithecia) that are said to be morphologically distinguishable, to prefer different habitats, and to be noninterbreeding. Because the systematic literature recognizes only one biological taxon of Pithecia in the area inhabited by the Matses, their folk taxonomy suggests either the presence of a previously undescribed species or a hitherto undocumented range extension. All known species of Pithecia are currently thought to be allopatric, so both possibilities are of interest. We obtained blood samples and anatomical voucher material from hunters' kills in order to test the biological basis for the Matses folk taxonomy of sakis. Molecular and morphological analyses of the collected material indicate that both Matses folk species correspond to one effectively panmictic population of Pithecia monachus. Overdifferentiation in folk classification systems, whereby one biological species is represented by two or more nonsynonymous folk species names, is a potentially widespread source of error that should be considered by researchers using local informants for primate field studies. In addition to resolving a folk-taxonomic enigma, our study provides the first quantitative analyses of local (within-population) morphological and molecular variation in this little-known platyrrhine genus.     

Laminin-11.

Laminins are a family of glycoproteins which are ubiquitous components of basement membranes and play key structural and functional roles. Eleven isoforms have been identified to date; each is an alpha beta gamma heterotrimer assembled from a repertoire of five alpha, three beta and two gamma chains. Studies of laminin-11 (alpha 5 beta 2 gamma 1) illustrate the unique expression patterns and distinct functions that can be displayed by laminin isoforms. Laminin-11 is found in the glomerular basement membrane in kidney, in the neuromuscular synaptic cleft in skeletal muscle and in other tissues such as placenta and lung. Mice lacking laminin-11 exhibit defective glomerular filtration and developmental defects in neuromuscular synapse formation, with Schwann cells invading the synaptic cleft. Consistent with these observations, both motoneurons and Schwann cells distinguish laminin-11 from other isoforms in vitro. These results suggest that laminin-11 is a structural component of the basement membrane which influences cell behavior in physiologically relevant ways. A greater understanding of laminin-11 assembly and basement membrane incorporation could provide a logical basis for therapy in merosin-deficient congenital muscular dystrophy.     

Learned changes in the complexity of movement organization during multijoint, standing pulls

 This paper tests the hypothesis that the central nervous system (CNS) learns to organize multijoint movements during a multijoint ‘bouncing pull’ task such that, after practice, motion of the anterior-posterior center of mass (CM_AP) more closely resembles that of a conservative, one degree of freedom (DF), inverted pendulum model. The task requires standing human subjects to produce precise peak pulling forces on a handle while maintaining balance – goals that can be easily accomplished if movement is organized as in the model. Ten freely standing subjects practiced making brief, bouncing pulls in the horizontal direction to target forces (20–80% of maximum) for 5 days. Pulling force, body kinematic and force plate data were recorded. An eight-segment analysis determined sagittal-plane CM motion. We compared the effects of practice on the regression-based fit between actual and model-simulated CM_AP trajectories, and on measures of CM_AP phase plane symmetry and parameter constancy that the model predicts. If the CNS learns to organize movements like the inverted pendulum model, then model fit should improve and all other measures should approach zero after practice. The fit between modeled and actual CM_AP motion did not improve significantly with practice, except for moderate force pulls. Nor did practice increase phase plane symmetry or parameter constancy. Specifically, practice did not decrease the differences between the pre-impact and rebound positions or speeds of the CM_AP, although speed difference increased with pulling force. CM_AP at the end of the movement was anterior to its initial position; the anterior shift increased after practice. Differences between the pre-pull and balance-recovery ankle torque (T _A) impulses were greater on day 5 and correlated with the anterior shift in CM_AP. These results suggest that practice separately influenced the force production and balance recovery phases. A modified model with damping could not explain the observed behaviors. A modified model using the actual time-varying T_A profiles improved fit at lower force levels, but did not explain the increased postural shift after practice. We conclude that the CNS does not learn to organize movements like the conservative, inverted pendulum model, but rather learned a more complex form of organization that capitalized on more time-varying controls and more intersegmental dynamics. We hypothesize that at least one additional DF and at least one time-varying parameter will be needed to explain fully how the CNS learns to organize multijoint, bouncing pulls made while standing. Received: 9 January 1997 / Accepted in revised form: 27 May 1997