DNA replication in X-irradiated human lymphocytes

Human peripheral blood lymphocytes are well-differentiated cells. Ordinarily, they do not divide and are considered to be in the G0 stage of the cell cycle. These cells can be stimulated to undergo DNA replication in culture by mitogens such as phytohemagglutinin. In the present study, we have examined cellular and biochemical events that occur after exposure of lymphocytes to X-irradiation. Irradiation with up to 100 rads, prior to stimulation with phytohemagglutinin, did not interfere with DNA replication. At later periods, DNA replication was inhibited proportionally to the amount of radiation. In comparison to DNA synthesis, the effect of X-irradiation on RNA and protein synthesis in phytohemagglutinin-stimulated lymphocytes was less marked. Furthermore, X-rays did not inhibit either the induction or the continual synthesis of DNA polymerase-α or -β in response to phytohemagglutinin. Kinetic studies with different nucleotide substrates suggest that cellular pools of nucleotides are not significantly altered by χ -irradiation. Thus, the inhibition of DNA synthesis in irradiated cells is likely to be due to damage to the cellular DNA template. The inhibition of DNA synthesis was accompanied by accumulation of cells in the G2 and M stages of the cell cycle, suggesting that inhibition of DNA replication by X -irradiation is a postmitotic event

Forage Production Potential and Nitrate Nitrogen in Napier Bajra Hybrid as Influenced by Nitrogen Dose under Shaded and Un-Shaded Environments

Dairy farming is an important and prevalent subsidiary occupation along with agriculture in the state of Punjab. But because of declining land holding, the pressure on land is so high that there is little scope of expanding the area under forage crops. Crop intensification either in space (intercropping) or in time (sequential cropping) or both is the feasible option left to the farmers for enhancing the fodder production. The green fodder is deficit by about 25% in the state and there is around 65,000 ha area under Agroforestry. There is a need to explore possibility of growing fodder crops under shade of trees, as light intensity is one of the major growth resources that determine the productivity of a particular crop (Dodd et al., 2005). Data are also lacking about how fodder crops will respond to different amounts of N fertilization under shade conditions. Napier Bajra is an inter-specific hybrid between bajra (Pennisetum glaucum) and napier grass (P. purpureum) and combines high quality and faster growth of bajra with the deep root system of napier grass. It is photosensitive and flowers only in winter. Due to this characteristic, it remains in the vegetative stage throughout the year, except in winter, when it is dormant. With these points in mind, the present study was planned to find out the influence of shading in comparison with normal conditions on forage productivity and quality under varying nitrogen levels

NASA/American Cancer Society high‐resolution flow cytometry project – III. Multiparametric analysis of DNA content and electronic nuclear volume in human solid tumors

BackgroundThe NASA/American Cancer Society (ACS) flow cytometer can simultaneously measure electronic nuclear volume (ENV) and DNA content of nuclei. The preceding articles in this volume (“NASA/American Cancer Society High‐Resolution Flow Cytometer Project‐I”) described the schematics, performance, and procedures used for the preparation of nuclei for analysis on this unit. In the present article, we describe the analysis of selected human tumors using the ratio of ENV/DNA content (nuclear packing efficiency [NPE]).MethodsTumor specimens (frozen) were minced with scalpels and stained with 1–10 μg/ml of 4',6‐diamidino‐2‐phenylindole (DAPI) dihydrochloride at pH 6.0–7.2. Trout erythrocytes were used as internal standards. Data on ENV and DNA content were collected in list mode files. Propidium iodide‐stained nuclei, analyzed on a Coulter XL cytometer, were used for comparison.ResultsSimultaneous measurement of ENV and DNA makes it possible to discriminate between hypodiploid or hyperdiploid tumor cells, as well as to differentiate between near‐diploid aneuploid and diploid cells on the basis of their increased ENV. The NPE ratio is a valuable parameter for the detection of small quantities of tumor cells, separating overlapping diploid and aneuploid populations for cell cycle analysis and characterizing the level of differentiation in some tumors.ConclusionNPE analysis provides unique measuring capabilities for the study of human solid tumors by flow cytometry. Cytometry 43:16–22, 2001. © 2001 Wiley‐Liss, Inc