Confocal imaging of flows in artificial venular bifurcations.

We describe a new experimental methodology for visualizing three-dimensional structures in microscopic tubes under flow conditions. Through the use of microfabrication techniques, artificial venular bifurcations are constructed from glass tubes with semicircular cross sections (radius = 50 mu). Aqueous fluorescent solutions are infused into the tubes at flow rates of about 1 microliter/min, a value comparable to blood flow in the microcirculation. The flow is imaged using a combination of confocal microscopy and three-dimensional image reconstruction software techniques. The quantitative accuracy of the experimental method is evaluated by measuring the "separation surface," a formation resulting from converging flows at a bifurcation. Details of the fabrication process, fluidics, confocal microscopy, image reconstructions, optical effects, and computations are described. We show the first three-dimensional visualization of a microscopic flow structure using confocal microscopy, and within certain limitations, quantitative agreement between the measured and computed positions of the separation surface.

A new method for blood velocimetry in the microcirculation.

We describe a simple new method for computing two-dimensional velocity vector fields of blood flows in microvascular networks. This method, known as optical flow, requires a time sequence of two or more images obtained by a process such as conventional videomicroscopy. There is no need to distinguish individual cells provided clear variations in the light intensity levels are present in the images. The result of the computation reveals the velocity distribution in the microvascular network and the geometry of the blood vessels. Although various implementations of the optical flow technique exist, we have found that the spatial correlation algorithm of Anandan performs best for microcirculatory flows. This report is an introduction to the application of optical flow to the microcirculation and provides instructions on how to obtain and run the codes.

Teaching coin summation to the mentally retarded.

A procedure to teach four mild and moderately retarded persons to sum the value of coin combinations was tested. Subjects were first taught to count a single target coin, and then to sum that coin in combination with coins previously trained. Five American coins and various combinations were trained. Modelling, modelling with subject participation, and independent counting by the subject constituted the training sequence. The subjects improved from a mean pretest score of 29% to 92% correct at posttest. A four-week followup score showed a mean of 79% correct. A multiple-baseline design suggested that improvement in coin-counting performance occurred only after the coin was trained. The results indicate that this procedure has potential for teaching the retarded to sum combinations of coinds in 5 to 6 hr of instruction.

Improved method for euglobulin clot lysis time.

1. The use of Evans Blue dye to facilitate endpoint determination the elimination of 4 degrees, assay conditions are technical improvements in the euglobulin clot lysis test. 2. Plasma samples have limited stability at 30 degrees or 4 degrees, but are stable for prolonged periods at minus 20 degrees. Samples with accelerated clot lysis are much less stable than normal samples at 30 degrees. 3. The normal range is determined as greater than 70 minutes for citrated plasma and greater than 50 minutes for oxalated plasma. There is no sex difference in the normal range.