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Biomedical subjects

L S Cram

Publications and source records attributed to L S Cram.

64 records · Page 4Linked to original sources
PubMed1977

Differential fluorochromasia of human lymphocytes as measured by flow cytometry.

Peripheral human lymphocytes reacted with fluorescein diacetate and analyzed by flow cytometry produced a bimodal fluorescence distribution that was shown to be attributable to the differential staining of T and B lymphocytes. Lymphocytes were fractionated into rosetting (T cell) and nonrosetting (B cell) populations. Both subfractions were reacted with fluorescein diacetate and analyzed by flow cytometry. The rosetting fraction was more fluorescent than the nonrosetting fraction, and the analysis of an appropriate mixture of the subfractionated populations produced a fluorescence distribution very similar to that obtained with unfractionated lymphocytes.

B-Lymphocytes↗
PubMed1976

Flow microfluorometric quantitation of the blastogenic response of lymphocytes.

A method for quantitating the specific stimulation of peripheral lymphocytes has been developed using the techniques of flow microfluorometry. Peripheral bovine lymphocytes were collected and specifically stained for deoxyribonucleic acid (DNA) content using a low-salt propidium iodide procedure. Flow microfluorometry was used to determine, on the basis of DNA content, the percentage of cells in a population that was stimulated. Extremely uniform staining of the lymphocytes (coefficient of variation of less than 2%) provides a high resolution between proliferating and nonproliferating cells. The method provides a rapid, highly repoducible technique for determing the fraction of lymphocytes stimulated in response to tuberculin antigens based on an increase in cellular DNA content. Specific and nonspecific stimulation by a defined antigen can be measured and resolved.

Animals↗
PubMed1976

Microfluoremetric analysis of DNA content changes in murine teratocarcinoma.

The multipotential stem cell of the murine tetratocarcinoma, embryonal carcinoma (EC), is capable of differentiation in vivo and in vitro to nonneoplastic progeny. Undifferentiated EC cells, spontaneously differentiating tetratocarcinoma cells, and differentiated cells derived from EC cells were analyzed for DNA content and chromosome number distributions. Flow microfluorometric and fluorescence cytophotometric analysis of DNA content showed that EC cells had a characteristic diploid (2c) distribution, whereas several differentiated cell lines derived from EC cells had 4c DNA distributions. The tetraploid cell populations studied were capable of cell division but had restricted differentiative potential and were either of low tumorigenicity or non-tumorigenic. In vivo teratocarcinomas, comprised of both EC cells and differentiated cell types, contained diploid and tetraploid populations. Chromosomally, EC cells were neardiploid (39 chromosomes) and differentiated cells were near-tetraploid (62 to 76 chromosomes). The teratocarcinoma provides a model for studying the basic mechanisms that control the growth dynamics of the rapidly and slowly proliferating cell populations present in many tumors.

Cell Differentiation↗
PubMed1970

Ultraviolet inactivation dichroic ratio of oriented fd bacteriophage.

Polarized UV light irradiation of flow-oriented fd bacteriophage indicates that the degree of damage (inactivation) depends on the relative orientation of the light polarization vector and the plane of the DNA bases. The technique of anisotropic UV inactivation was evaluated, and further information on the orientation in this virus was gained. The fd bacteriophage were aligned and irradiated with plane-polarized monochromatic UV light either parallel or perpendicular to the virus axis. Variation of the inactivation dichroic ratio with wavelength implicated virus inactivation by light absorbed in both the DNA and protein. Analysis of the wavelength variation of inactivation dichroic ratios gave molecular dichroic ratios of 0.76 and 1.48 for the DNA and protein components, respectively. On the basis of these anisotropic inactivation studies, the average angle of DNA base tilt in fd was calculated to be 29-32 degrees , a value in agreement with the absorption dichroism studies of Bendet and Mayfield.

Coliphages↗