Selection of microcarrier diameter for the cultivation of mammalian cells on microcarriers

The kinetics of mammalian cell growth in a microcarrier culture are affected by the distribution of cells on microcarriers. It has been shown previously that a critical cell number per microcarrier is required for the growth of FS-4 cells on microcarriers. It is advantageous to alter the cell distribution on microcarriers to allow for a larger fraction of microcarriers to acquire enough cells to initiate normal growth. This can be achieved by selecting the diameter of the microcarriers employed. It has also been shown previously that the critical cell number could be reduced by choosing a better culture medium to support low density growth. However, even if all cells inoculated into a culture are capable of growing to confluence, it is still necessary to select the microcarrier diameter ration ally to improve the growth kinetics. The method of selecting the microcarrier diameter is discussed. By employing a improved medium as well as using microcarriers of selected diameter, the multiplication ratio was in creased to 15- to 16-fold for FS-4 cells, as opposed to 3- to 4-fold typically obtained in a batch culture.     

Attachment and growth of mammalian cells on microcarriers with different ion exchange capacities

In the design of microcarriers for animal cell growth, the exchange capacity has been considered a critical factor. However, charge densities of microcarriers under culture conditions are not the same as the exchange capacities. Furthermore, the charge density requirement for optimum attachment is not necessarily the same as that required for optimum growth. We demonstrate that charge is not the sole factor affecting the attachment and growth of animal cells on microcarriers. We also show that supplemental serum in the growth medium has a negative effect on cell attachment to microcarriers.     

Expression of human lactotransferrin receptors in phytohemagglutinin-stimulated human peripheral blood lymphocytes. Isolation of the receptors by antiligand-affinity chromatography

In the resting rate, the human peripheral blood lymphocytes did not show detectable surface and intracellular receptors for human lactotransferrin. However, both types of lactotransferrin receptors were expressed during stimulation of lymphocytes with phytohemagglutinin. The appearance of receptors was time-dependent and the number of receptors reached a plateau after at least two days of mitogen stimulation. These results suggest that the presence of surface receptors on mitogen-stimulated lymphocytes is not consecutive to a modification of subcellular distribution but to an induction of biosynthesis of the receptors. As measured by incorporation of [3H]thymidine into DNA, addition of human lactotransferrin in a serum-free medium increased the proliferative activity of phytohemagglutinin-stimulated lymphocytes. Optimal enhancement of [3H]thymidine incorporation was obtained by adding 30% iron-saturated lactotransferrin at a concentration of 0.17 microM. Therefore, the role of lactotransferrin in the response of lymphocytes to mitogen stimulation appears to be similar to that previously described for serotransferrin. The lactotransferrin receptor was visualized using 125I-labeled lactotransferrin on nitrocellulose paper after electroblotting of the Triton X-100 extract of the phytohemagglutinin-stimulated lymphocytes as two protein bands of 100 and 110 kDa molecular mass. Purification of the lactotransferrin receptor from the Triton-X-100-soluble extract of stimulated lymphocytes was performed by antiligand-affinity chromatography. The binding of lactotransferrin to the purified receptors was reversible and dependent on concentration and pH.     

A differential scanning calorimetric study of the binding of sulfate ion and of Cibacron blue F3GA to yeast phosphoglycerate kinase

In continuation of earlier work [Hu, C. Q., & Sturtevant, J.M. (1987) Biochemistry 26, 178-182], differential scanning calorimetry has been employed in a study of the effects on the thermal denaturation of yeast phosphoglycerate kinase of two inhibitors of the enzyme, sulfate ion and the dye Cibracron blue F3GA. Sulfate ion, as is usual with ligands that dissociate during unfolding of the host protein, raises t1/2, the temperature of half-completion of the denaturation, has only a modest effect, stemming from the enthalpy of dissociation of the ligand, on the enthalpy of denaturation, and has little or no effect on the heat capacity change resulting from denaturation. In sharp contrast, Cibacron blue F3GA lowers t1/2 and drastically decreases both the enthalpy and heat capacity changes due to denaturation. The DSC results with sulfate ion are consistent with previous kinetic data [Scopes, R. K. (1978) Eur. J. Biochem. 91, 119-129; Khamis, M. H., & Larsson-Raznikiewicz, M. (1981) Biochim. Biophys. Acta 657, 190-194], which indicate two binding sites for sulfate ion at one of which the ligand acts as a competitive inhibitor. The results with Cibacron blue F3GA indicate that the dye induces a major destabilizing structural change in the enzyme in addition to rendering it enzymically inactive.     

抗阿特拉津转基因大豆植株后代的遗传分析

本试验用阿特拉津溶液涂抹、荧光诱导动力学检测、分子杂交等方法对抗阿特拉津转基因大豆植株的后代进行了鉴定,在第二代及第三代中检测到了抗性基因的存在,表明从龙葵中得到的此抗阿特拉津 psbA 基因不仅能导人大豆叶绿体基因组中获得表达,而且可以遗传到后代。     

The effect of carbamylcholine on CFU-s differentiation

The proportion of spleen colony-forming units (CFU-s) killed by hydroxyurea was greatly increased after bone marrow cells (BMCs) from LACA mice were exposed to carbamylcholine (Cach; 1 X 10(-13) to 1 X 10(-9) in vitro and there was a marked change in the proportion of spleen colony types. Following treatment with Cach, granulocytic and mixed erythroid-type colonies increased from 20 to 26.3% and 16.1 to 29.6% in 9-day colonies and from 8.3 to 28.2% and 21.7 to 39.4% in 13-day colonies, respectively. Single cell suspensions of spleen colonies were made for granulocyte-macrophage progenitor (CFU-gm) and late erythroid progenitor (CFU-e) assays. The number of CFU-gm from Cach-treated BMC was about twice that from control BMC for both day 9 and day 13 groups; the number of CFU-e decreased relatively. The results suggest that cholinergic receptors on CFU-s may increase the tendency to differentiate into the granulocytic/monocytic line.