Use of ferro-electric liquid crystal shutters for time-resolved fluorescence microscopy.

A technique is described to modify a standard fluorescence microscope for time-resolved visualization of delayed luminescing substances with decay times from 50 microseconds to several milliseconds. The modification consists of synchronized operation of a mechanical shutter, positioned in an aperture plane in the excitation pathway, simultaneously with a ferro-electric liquid crystal (FLC) shutter on the emission side. Operation of the microscope is through a microprocessor interfaced keypad by which all timing parameters can be adjusted for optimal suppression of fast decaying luminescence. Accuracy of the timing was within 1 microsecond. Prompt fluorescence was suppressed up to 10(6) times, as determined for bright prompt fluorescing microspheres. The use of the FLC shutter resulted in a reduction in emission intensity by a factor of 8 (due to the use of polarizers, the lower transmission of the FLC devices, and IR blocking filters). No significant image degradation due to shutter operations was observed. The modified microscope was successfully used for the visualization of delayed luminescing immunolabels, such as inorganic phosphor particles and lanthanide chelates, as well as naturally phosphorescing materials.

The automation of culturing and harvesting of human chromosome specimens.

This paper describes the development of a machine for the automated culturing and harvesting of human chromosome specimens. The machine is capable of handling different preparation methods simultaneously, such as standard blood cell, blast cell and bone marrow cultures, and can be programmed to perform the prophase synchronization techniques. It is composed of a culture tray, centrifuge, mixer, input and output station and a head assembly capable of transporting samples between the various stations and which is equipped with an aspirator needle to suck off the supernatant and fluid dispensers for the dosing of the various chemicals. A microprocessor system controls all hardware functions and schedules the manipulations of all samples thereby preventing, that more than one sample requires servicing at the same time. The samples (up to a maximum of 255) are processed by the machine in small batches of maximal 16, which can be activated at any time according to one of 16 culture procedures. The cytogeneticist can modify these procedures using a simple interpretive language specifying both the types of manipulations, such as centrifugation, addition of chemicals, sucking of supernatant and the minimal and maximal variation in time, which is allowed between two sequential manipulations. Besides the hardware setup and software organization of the machine, the first preliminary results and future prospects for the machine are presented.