Employing a newly developed computer-assisted system for visualizing and quantitating cell motility in three dimensions, we have examined the 3-dimensional changes in cell shape and the dynamics of pseudopod extension during translocation of Dictyostelium amoebae. Amoebae exhibit a 3-dimensional behavior cycle with an average period of 1.5 min. The cycle includes a transient pseudopod extension phase in the x,y axis followed by a z-axis expansion phase. Anterior pseudopod extension in the x,y axis is accompanied by a decrease in height, not by uropod retraction. The increase in height is accompanied by uropod retraction. In the pseudopod extension phase in the x,y axes, pseudopods form either anteriorly or laterally, and either on or above the substratum. Pseudopods which initially form on the substratum in almost all cases continue to expand as the anterior end of the cell. In the case of lateral pseudopods, anteriorization leads to a turn. Approximately half of anterior pseudopod and two-thirds of lateral pseudopods which initially form above the substratum are retracted. These results suggest that pseudopod-substratum interaction plays a fundamental role in the regulation of directionality and turning in the translocation phase of the 3-dimensional behavior cycle.

Colony phenotype and genetic similarity were assessed within and between groups of commensal and pathogenic strains of Candida albicans collected from the oral cavities of individuals in a single geographical locale. Thirty-eight percent of pathogenic isolates contained predominant or minor variant colony morphologies (other than smooth) when samples from the sites of infection were cultured on plates, while 16% of commensal isolates contained minor variant colony morphologies when samples from the sites of carriage were cultured. The genetic similarities of isolates within and between groups were assessed by DNA fingerprinting by using Southern blot hybridization with the fingerprinting probe Ca3 and analysis with the computerassisted, automated Dendron system. Both the commensal and the pathogenic groups contained a major cluster of genetically similar C. albicans isolates representing 31 and 33% of the strains in the respective groups. When a combined dendrogram of both commensal and pathogenic isolates was generated, the major clusters of genetically similar isolates in each group mixed into one large cluster.

A 3-dimensional dynamic image analyzing system (3D-DIAS) has been developed in which a translocating cell is optically sectioned in the z-axis within a 2 sec period; the perimeter of the cell in each section is digitized into the 3D-DIAS data file, and the digitized perimeters are wrapped in order to reconstruct the cell image in three dimensions. Using 3D-DIAS, we have obtained the first dynamic 3-dimensional description of human polymorphonuclear leukocytes (PMN) translocating on a glass surface. A general behavior cycle has emerged which includes two phases. In the first, an ellipsoidal PMN with significant z-axis extends anteriorly and descends to the substratum. When the ventral surface of the anterior end contacts the substratum, there is rapid anterior expansion, which correlates with velocity peaks. In the second phase, the elongate PMN stops translocating along the substratum, the anterior end lifts off of the substratum, sometimes to heights greater than the length of the PMN at the substratum, and finally the PMN retracts into an ellipsoidal morphology still capable of random protrusions. During this second phase, which correlates with velocity troughs, turning usually occurs. The degree of turning is restricted by the continuous integrity of the posterior uropod. The period of the behavior cycle varies from roughly 0.5 to 2 min between PMNs, but is relatively constant within each individual PMN.