The fundamental role of pirouettes in Caenorhabditis elegans chemotaxis.

To investigate the behavioral mechanism of chemotaxis in Caenorhabditis elegans, we recorded the instantaneous position, speed, and turning rate of single worms as a function of time during chemotaxis in gradients of the attractants ammonium chloride or biotin. Analysis of turning rate showed that each worm track could be divided into periods of smooth swimming (runs) and periods of frequent turning (pirouettes). The initiation of pirouettes was correlated with the rate of change of concentration (dC/dt) but not with absolute concentration. Pirouettes were most likely to occur when a worm was heading down the gradient (dC/dt < 0) and least likely to occur when a worm was heading up the gradient (dC/dt > 0). Further analysis revealed that the average direction of movement after a pirouette was up the gradient. These observations suggest that chemotaxis is produced by a series of pirouettes that reorient the animal to the gradient. We tested this idea by imposing the correlation between pirouettes and dC/dt on a stochastic point model of worm motion. The model exhibited chemotaxis behavior in a radial gradient and also in a novel planar gradient. Thus, the pirouette model of C. elegans chemotaxis is sufficient and general.

Hodgkin's cells express CD83, a dendritic cell lineage associated antigen.

Hodgkin's cells (HC) are considered to be the malignant cells of Hodgkin's disease (HD), but despite extensive studies, no conclusive evidence has emerged regarding their non-malignant counterpart and the ontogeny of these cells remains controversial. The analysis of a possible dendritic cell (DC) origin of HC has been hampered to date by the lack of a DC lineage specific marker. The expression of the two DC-associated antigens CD83 and CMRF-44, the B lymphocyte restricted molecule CD79, and the costimulator molecule CD86, was examined in lymph nodes from 23 HD patients using immunohistological techniques. The majority of HC expressed the CD83 (22/23) and CD86 antigens (20/23), whereas expression of the CMRF-44 antigen was variable (10/23) and usually only a subpopulation of HC stained. In contrast, the CD79 antigen was absent from most HC (17/23). The presence of the CD83 antigen on HC in the absence of the CD79 antigen supports a possible DC lineage origin for some HC. Regardless of its role in lineage assignment, CD83 may become a useful immunohistological marker for HD as the CD83 antigen was present on most HC.