THE USE of FLOW CYTOMETRY FOR RAPID IDENTIFICATION of SALMONELLAE

Flow cell cytometry can be used in a sensitive fluorescent immunoassay to rapidly identify salmonellae of Groups D and E. Staphylococcal Protein A couples with the Fc region of many antibodies, especially immunoglobulin G. When a fluorescent marker, fluorescein isothiocyanate, is conjugated to Protein A, an antibody-antigen reaction can be visualized in a flow cell cytometer with an appropriate optical sensor after excitation. Ten thousand cells were individually analyzed in each cytometer run within a minute. the resultant data, presented as histograms and tables, indicated the number of cells in the suspension reacting positively with the antiserum by fluorescence, cell size, distribution and light scatter. This provides an in-depth analysis of the antibody-antigen reaction not possible with other types of immunoassays.     

Movement of Tritiated Water through Young Citrus Plants

Water movement through different organs of 1–2 year oldSour Orange seedlings was studied by using tritium as a tracerinjected into the nutrient solution. The activity of the leaftissue water of plants free to exchange water with the atmospherereached only 60–70% of the nutrient solution even afterlong periods exceeding 30 h, whereas in plants exposed to dryair the activity approached equilibrium with the solution. Turnoverof water was less rapid in the laminae than in the midveinsof the leaves, in both cases the rate being a function of theamount of foliage on the plant. A reduction in transpirationrate effected by plastic covering, silicone coating, or abscisicacid spray was clearly indicated by a lowered level of tritiumactivity in the plant tissue.