Half Fold Increase Research Articles

Enhancement of rat ACT-1 tumor clonogenicity by xenogeneic mouse macrophages

In vitro growth of rat atriocaval epithelial tumor cells (ACT-1) was enhanced by the inclusion of xenogeneic mouse adherent peritoneal exudate cells (PECs) in a two-layer soft agar system. A linear relationship was found between the number of cells plated and the number of colonies when ACT-1 tumor cells were plated at plating densities of between 1 and 5 X 10(5) cell/60 mm plate (r = 0.9, P less than 0.001). Inclusion of irradiated PECs in the bioassay for tumor stem cells resulted in a two and a half-fold increase in colony formation in three separate experiments (P less than 0.001).

Enrichment of the Murine Natural Killer (NK) and Mitogen Induced Cellular Cytotoxicity (MICC) Cells Using Preparative Free-Flow High Voltage Electrophoresis

A procedure using preparative free-flow high voltage electrophoresis is described for the fractionation of murine spleen and bone marrow cells so as to obtain cell subpopulations that are either enriched in or depleted of "natural killer" (NK) cells and "mitogen-induced cellular cytotoxicity" (MICC) effector cells. A nearly three fold enrichment in the NK and MICC activities of spleen cells was achieved. The enrichment in these cells could be further increased if the phagocytic cells were removed prior to electrophoresis. When bone marrow cells were fractionated a two and a half fold increase of NK activity, and a one and a half fold enrichment of MICC activity was achieved. In both cases, other fractions were nearly devoid of NK and MICC activity. The cell recovery after electrophoresis averages 70% of the cells applied, and at least 90% of these cells were viable. MICC and NK effector cells could not be separated to a useful extent electrophoretically but were found to be separable using Sephadex C-10 gel filtration columns. The MICC but not the NK cells were retained on these columns.

Primary Production and Nutrients in Ogac Lake, a Landlocked Fiord on Baffin Island

Primary production was about 12 g/m2 in the middle basin of Ogac Lake during 1962. Production was limited by available N, probably largely by amount of nitrate available at the end of winter. Production was largely concentrated in narrow strata — one descending from near the surface in June to occupy nutrient-rich deep water in summer, and another developing at the halocline in summer, possibly sustained by nutrients from freshwater kill of the littoral biota in 1962.Polyethylene columns, 1 m in diameter and 30.5 m long, were set between the fresh surface and anoxic depth of the middle basin in 1962. A four-fold increase of nitrate and a two and a half-fold increase of phosphate led to a parallel uptake of the two nutrients in the columns, and to an approximately five-fold increase in mean amount of chlorophyll and a seven-fold increase in primary production compared with the lake during the period of the fertilization experiment.

Role of micronutrient elements in the metabolism of higher plants. I. Changes in oxidative enzyme constitution of tomato leaves deficient in micronutrient elements

Cell-free extracts of tomato leaves from plants grown on media individually deficient in each of the micronutrient elements showed marked changes in enzymatic constitution. Each deficiency caused an alteration in the over-all enzyme pattern which was characteristic of the micronutrient element in question. The metallo-enzymes such as polyphenol oxidase, ascorbic acid oxidase, and peroxidase lost approximately half their activity in plants deficient in the specific metal concerned. In the cases of all other metal deficiencies, however, polyphenol oxidase and peroxidase were elevated in concentration at least two to six times that of the control. Ascorbic acid oxidase was doubled in zinc- and manganese-deficient material. Glycolic acid dehydrogenase and lactic acid dehydrogenase showed smaller parallel rises averaging a one and a half fold increase in content in zinc- and manganese-deficient plants. Reduced diphosphopyridine nucleotide diaphorase was doubled by copper and manganese deficiencies and was increased to almost one and a half fold by zinc deficiency. Endogenous oxygen uptake in boron-deficient, copper-deficient, and manganese-deficient leaf homogenates was increased, and almost lacking in molybdenum-deficient material. Addition of the metals to the corresponding deficient extracts elicited no change in enzyme activities. Addition of missing ions to corresponding nutrient solutions resulted in varied responses of the already modified enzyme patterns. The results are discussed in relationship to the role of micronutrient elements in the activity and metabolism of catalytic proteins.