Quantitative microscopy: I. A computer-assisted approach to the study of polymorphonuclear leukocyte (PMN) chemotaxis

Automated identification of axonal growth cones in time-lapse image sequences

The isolation and purification of axon guidance molecules has enabled in vitro studies of the effects of axon guidance molecule gradients on numerous neuronal cell types. In a typical experiment, cultured neurons are exposed to a chemotactic gradient and their growth is recorded by manual identification of the axon tip position from two or more micrographs. Detailed and statistically valid quantification of axon growth requires evaluation of a large number of neurons at closely spaced time points (e.g. using a time-lapse microscopy setup). However, manual tracing becomes increasingly impractical for recording axon growth as the number of time points and/or neurons increases. We present a software tool that automatically identifies and records the axon tip position in each phase-contrast image of a time-lapse series with minimal user involvement. The software outputs several quantitative measures of axon growth, and allows users to develop custom measurements. For, example analysis of growth velocity for a dissociated E13 mouse cortical neuron revealed frequent extension and retraction events with an average growth velocity of 0.05 +/- 0.14 microm/min. Comparison of software-identified axon tip positions with manually identified axon tip positions shows that the software's performance is indistinguishable from that of skilled human users.

Quantifying the soft tissue response to implanted materials

As the diversity of biomaterials increases, new developments are aimed at these materials becoming interactive rather than passive with respect to the environment they are placed in. The need accurately and reproducibly to assess the response of the body to these materials increases. Historically, quantification of tissue responses has taken many forms but with the continuing development of powerful computers, our ability to quantify the tissue response to implanted materials has become a reality. Computer systems can now analyse sections automatically and then go on to sort the huge quantities of data created, into in depth patterns and cross comparisons so that subtle changes in tissue responses can be detected and understood.

Human neutrophil motility: time-dependent three-dimensional shape and granule diffusion

The locomotion of human polymorphonuclear leukocytes (PMNs) was studied with two complementary methods: Three-dimensional shapes were reconstructed from time series of optical sectioning microscopy using differential interference contrast (DIC) optics, and the diffusion of cytoplasm granules within individual cells was measured using quasielastic laser light scattering (QELS). The three-dimensional cell edges outlined in the optical sections were analyzed qualitatively in time-lapse film strips and quantitatively from morphometry. The fastest locomotion occurred in chemotactic gradient with cell velocity that oscillated between 10 and 30 microns/min with a period of 50-55 seconds. Within the periodic bursts of speed, a fibroblast-like locomotory cycle was observed, with leading lamella extended and contacts formed with the substrate surface, followed by rapid motion of the cell body and nucleus over the immobile contacts. Consistent with this apparent staged motion, correlation analysis revealed a phase lag of 2-3 seconds in velocities between the bottom (ventral) and the top layers of the cell. In addition there was a tendency to a lower cell profile at times of higher velocity. The diffusion of natural cytoplasmic granules within resting PMNs was not affected by cytoskeleton disrupting drugs. During the stage of most rapid motion, when cytoplasmic streaming could be seen, diffusion of the granules decreased two- to 2.5-fold, and then returned to resting levels. These observations suggest that PMN locomotion consists of extensions near the surface to form forward contacts and then stiffening or possibly contraction of the cytoskeleton when the body of the cell is moved forward. Three-dimensional movies of PMN cells are included in the video supplement.

An image processing workstation for automatic evaluation of human granulocyte motility

Polymorphonuclear (PMN) motility is currently determined by a method using chemotactic chambers with micropore filters. PMN locomotive capacity is measured by evaluating the maximum distance travelled by the cells, or by counting the number of cells which have moved through the filter. Although in recent years some attempts to improve the analysis of chemotaxis data by computer-assisted systems have been made no technique has been shown capable of both measurement and correlation of these parameters in real time. In the present paper we describe an automated technique, based on a workstation capable of exploring microporous filters employed in chemotactic chambers and of measuring PMN motility in a reliable, reproducible, rapid manner, independent of the subjectivity of the operator. The measurement is carried out by custom software capable of undertaking computerized image analysis of microscopic fields acquired by a TV camera and of driving the motorized microscopic table. Depth of migration, cell distribution at each plane, correlation index of the random behaviour with the model described by a gaussian distribution and data about the patient or assay under study, are computed, displayed, stored in a data base and printed in real time.