Experimental mouse leukemia L1210 cells were subjected to hyperthermia (43.0±0.05°C, waterbath) and photodynamic therapy (50μg/ml HpD, 630 ± 5nm at 0.1mW/cm2) for varying lengths of time and ...sequences. The results show that the two modalities intract in a manner which is more cytotoxic than the sum of the individual treatments, and the sequence of treatments is a determining factor in the degree of interaction of the HpD-uptake by the tumor cells. The most cytotoxic effect of photodynamic therapy is seen when the photodynamic therapy is treated after hyperthermia with HpD. When hyperthermia is done after HpD-uptake and photodynamic therapy, additive cytotoxic effect is obtained by analysis of dose-response curves. These data are supported on DNA damage (amount of single strand DNA) and RNA damage with analysing by flow cytometer to which the treated cells are stained with acridine orange (AO). Furthermore, an application to the clinical treatment, namely, the photodynamic therapy after the hyperthermia with HpD injection was able to propose as an useful combination therapy from the obtained finding in vitro experiments.
Flow cytometers with sequential measuring stations require alignment of event timing information to assure that multiparameter data for each cell are properly correlated. Information from the first ...detector must be delayed until signals are produced at the last detector, with adjustments to align them in time for simultaneous digitization after the last measurement is completed. By using an analog “pipeline” delay, the deadtime between the first and last measuring stations can be minimized. The described device is capable of acquiring and propagating many signals within the delay period, with good fidelity at high signal rates. An integrated circuit charge‐coupled device (CCD), which is an analog shift register, is shown to be useful as a signal delay in the time range from 22 μs to several milliseconds.
Thrombin‐induced stimulation of human platelets is accompanied by a dramatic increase in cytoplasmic calcium concentrations followed by a slow decrease. These changes are very rapid, are maximal by ...10‐5 s, and can be detected with probes such as Indo‐1. Suspension studies using spectrofluorometry, which reflect a value which is the average of 3 x 107 cells per ml, indicate a thrombin dosedependent increase in cytoplasmic calcium at doses up to 0.025 units per ml. We show here, using flow cytometry, that at less than halfsaturating thrombin doses only subpopulations of platelets rather than the entire sample are responding. The extent of these responses, however, still depends on thrombin concentration. When the thrombin doses are between half and fully saturating, one subpopulation responds fully (i.e., its extent of increase in cytoplasmic calcium concentration, Ca++in is 100% of that seen at saturating thrombin concentrations) while the remaining platelets respond partially or not at all. There is thus evidence of positive cooperativity leading to disproportionate thrombin receptor occupancy on different subpopulations when platelets are subjected to subsaturating doses of thrombin. The existence of responding subpopulations may explain how the reported multiple stimulations of the same suspension of platelets at low thrombin doses occur.
A device is described for simultaneous separate detection of the light scattering of cells at low and large scattering angles in an arc lamp‐based flow cytometer with epi‐illumination through an oil ...immersion microscope objective. Light scattering was measured in a dark field configuration that allows separate detection of light scattering greater than 2° and 15°, respectively. Dual parameter light scattering histograms of a blood cell suspension containing various types of leukocytes were closely similar to that obtained with a commercial laser‐based instrument with light scattering detection at forward and right angles. The sensitivity of the device was sufficient to measure polystyrene particles with 0.25‐μm diameter. A potential application may be differentiation of bacteria.
We describe an algorithm,
\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm V}_{{\rm out}} \, = \,{\rm Integer}\,\left\{ {\left{\frac{{2^{12} \, - \,1}}{{2^{12\lambda } \, - \,1}}} ...\right\,{\rm V}_{{\rm in}}^\lambda \, - \,1} \right\}\, + \,1;\,\lambda \, > \,0 $$\end{document}
based upon Box‐Cox transformations as an alternative to nonlinear electronic amplifiers to expand or compress high‐ or low‐amplitude flow cytometer‐derived signals. If the indexing parameter λ < 1, input channels in the high‐amplitude input range are compressed in the output range as occurs when an electronic logarithmic amplifier is used. However, if λ > 1, input channels in the low‐amplitude input range are compressed in the output range as occurs when an electronic power amplifier is used. Our modified Box‐Cox transform can be implemented either during data collection or off‐line for the transformation of previously collected raw data. The transform is the equivalent of an infinite class of nonlinear amplifiers. As the transform is implemented in software, it does not suffer from many of the disadvantages of nonlinear electronic amplifiers.
The effect of mitogens on the degree of polarization of the fluorescence from viable human lymphocytes, labeled with fluorescein, have been reported to be different in cells from subjects with ...malignant disease as compared with those from healthy donors. This has potential applications in the field of clinical diagnosis and a flow cytometer could be the instrument of choice for this purpose. We believe that such an instrument should be simple and easy to use and a flow cytometer was assembled with this in mind and with the object of gaining experience which would provide the basis for a future finalized design. The instrument is suitable for use in other biologic applications where polarization is of interest and also as a general purpose flow cytometer. Its main features, its characteristics and a preliminary performance report are presented here.
A routine is described that readily allows the rescaling of linear histographic data to a corresponding logarithmic histogram. This procedure significantly improves data display, particularly where a ...wide range in the measured parameter is encountered. The logarithmic scale displays peaks with band widths more proportional to their respective coefficients of variation than is the case in a linear display. Rescaling several linear histograms to a common logarithmic scale allows the combination of these linear data even though the linear ranges are different. This routine is presented as a program written in BASIC for execution on a microcomputer.
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