The relationship between rubella hemagglutination inhibition antibody (HIA) and rubella induced in vitro lymphocyte tritiated thymidine incorporation

The parameters of lymphocyte, rubella virus interaction were studied by means of tritiated thymidine incorporation and compared with the rubella HIA level. Stimulation of lymphocyte DNA synthesis was found to depend on antigen concentration and to be independent of the presence of viable virus. When compared to HIA titer, lymphocyte transformation was found to be detectable in the absence of antibody. It is suggested that lymphocyte transformation is a sensitive method to detect both prior exposure and cellular immune reactivity to rubella virus.     

Measurement of bacterial growth rates in subsurface sediments using the incorporation of tritiated thymidine into DNA

Microbial growth rates in subsurface sediment from three sites were measured using incorporation of tritiated thymidine into DNA. Sampling sites included Lula, Oklahoma, Traverse City, Michigan, and Summit Lake, Wisconsin. Application of the thymidine method to subsurface sediments required (1) thymidine concentrations greater than 125 nM, (2) incubation periods of less than 4 hours, (3) addition of SDS and EDTA for optimum macromolecular extraction, and (4) DNA purification, in order to accurately measure the rate of thymidine incorporation into DNA. Macromolecule extraction recoveries, as well as the percentage of tritium label incorporated into the DNA fraction, were variable and largely dependent upon sediment composition. In general, sandy sediments yielded higher extraction recoveries and demonstrated a larger percentage of label incorporated into DNA than sediments that contained a high silt-clay component. Reported results also indicate that the acid-base hydrolysis procedure routinely used for macromolecular fractionation in water samples may not be routinely applicable to the modified sediment procedure where addition of SDS and EDTA are required for macromolecule extraction. Growth rates exhibited by subsurface communities are relatively slow, ranging from 5.1 to 10.2×10⁵ cells g^–1 day^–1. These rates are 2–1,000-fold lower than growth rates measured in surface sediments. These data lend support to the supposition that subsurface microbial communities are nutritionally stressed.     

Autoradiographic investigation of sperm transit through the male mouse genital tract after tritiated thymidine incorporation

The transit of spermatozoa in the genital tract of the male mouse was investigated by quantitative light microscopic autoradiography after intraperitoneal injection of tritiated thymidine. Transit duration in the caput and the corpus of the epididymis was shown to be 3 days; the total duration of transit in the genital tract was 5 days. These findings indicate that the time required for the transit of spermatozoa in the epididymal caput and corpus was comparable to that calculated in other mammals studied. However, the duration of sperm storage in the epididymal cauda appeared to be shorter than that previously reported for rodents.     

Cell-associated immunity to measles (rubeola): The demonstration of in vitro lymphocyte tritiated thymidine incorporation in response to measles complement fixation antigen

Lack of a reliable in vitro assay for lymphocyte responsiveness to measles (rubeola) has hampered our understanding of the cell-associated response in diseases caused by, or related to, the measles virus. We report a reliable and reproducible system for demonstrating specific lymphocyte incorporation of ³H-thymidine in response to measles complement fixation antigen (CFA). Seventeen patients with positive histories of measles as children demonstrated a dose-response curve that varied between individuals but was constant for each individual. Kinetic data disclosed maximal responsiveness on day 7, and viral inactivation experiments disclosed that live virus was neither necessary for nor inhibitory to the reaction. The implications of this assay in terms of our understanding of the cell-associated response to measles virus in clinical measles and SSPE are discussed. The concept is explored that membrane-associated antigen is crucial in demonstrating the host's cellular immune response to viruses that can grow by cell-to-contiguous cell spread.     

Low level incorporation of tritiated thymidine into the nuclear DNA of Purkinje neurons of adult mice.

Adult mice were pulse labeled with tritiated thymidine [3H]TdR and killed 9 hr later. A low level incorporation of [3H]TdT into the nuclear DNA of Purkinje neurons was found in autoradiographs. Enzymatic digestions with DNase and with RNase in combination with autoradiographic grain counts indicate that a portion of nuclear DNA is not stable in the Purkinje nucleus. These results are discussed in light of reports of the stable nature of DNA in Purkinje neurons of adult mice.     

Relationship between release of LH and incorporation of tritiated thymidine in the anterior pituitary gland of the castrated female rat

Castration of female rats during diestrus increases the concentration of circulating LH from days 3 and the incorporation of 3H thymidine into pituitary DNA from day 5. Both effects are completely abolished by the administration of dihydrotestosterone. Although the i.v. injection of LHRH markedly enhances the concentration of LH in serum, it does not modify the incorporation of 3H thymidine into pituitary DNA. Castration might produce a maximal stimulation in 3H thymidine incorporation and a further stimulation of LH release with LHRH is unable to enhance the incorporation of the radioactive precursor. The results suggest a relationship between LH secretion and DNA synthesis in the pituitary gland of the rat.     

Failure of tritiated thymidine incorporation into DNA to reflect the autoradiographically demonstrable calcium-induced increase in thymic lymphoblast DNA synthesis

Increasing the extracellular calcium concentration in thymic lymphocyte suspension from 0.6 to 1.8 mM stimulated the proliferation of the lymphoblast subpopulation as measured by increases in the proportion of cells autoradiographically labeled with ³H-TdR and in mitotic activity. However it was not possible to show this increased DNA synthesis by scintillometric measurement of the amount of ³H-TdR incorporated into extracted DNA. On the other hand, calcium did raise the incorporation of ¹⁴C-formate into the thymine residues of DNA, and increased the activity of isolated thymocyte thymidylate synthetase. In contrast to the mitogenic calcium ion, a thymidylate synthetase inhibitor, methotrexate, actually increased the incorporation of ³H-TdR into DNA. It is concluded that calcium increases the endogenous synthesis of thymidylate which in turn prevents the amount of incorporation of exogenous ³H-TdR from accurately reflecting the true level of DNA synthesis.