Chinese hamster ovary cell production of recombinant tissue‐type plasminogen activator (t‐PA) was increased by amplification of cotransfected dihydrofolate reeducates cDNA using stepwise adaptation to increasing methotrexate (MTX) concentrations. The highest producing clones were isolated at 5 μM MTX and yielded 26,000 U/106 cells/day t‐PA (43 μg/106 cells/day). Above 25 μM MTX, cell specific t‐PA production rates became increasingly variable and the cDNA copynumbers decreased. No apparent correlation between the cell specific t‐PA production rate and the growth rate was observed upon sub cloning of the amplified cells. When MTX selection was removed, the t‐PA production rate decreased up to tenfold within 40 days; this was accompanied by an up to 60% drop in cDNA copynumber. Subclones isolated after 108 days of culture in the absence of MTX were, on average, sixfold more stable than their parental cells. In culture without MTX, the maximum stable t‐PA production rate obtained (over 250 days) was 7000 ± 750 U/106cells/day (∼12 μg/106 cells/day), approximately threefold lower than the maximum unstable levels of production reached under selective pressure. Taken together, these results define a wide range of the highest t‐PA expression rates obtained under MTX selection, for which stable expression without selection has not been reported
Answer:
The smallest cell in humans is a sperm cell and the largest cell is the egg cell.
Explanation:
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To collect the water and mineral nutrients.
Answer:
c. dilated, constricted
Explanation:
During exercise, more energy is required by skeletal muscles. Oxygen is an important component required for energy production hence supply of oxygen is also increased to skeletal muscles. This is done by increasing the blood flow to skeletal muscles since red blood cells carry oxygen. To increase the blood flow, blood vessels in skeletal muscles are dilated so that more blood can reach them.
Blood vessels of digestive system are constricted because during exercise digestion process is not the priority. More blood should reach skeletal muscles than digestive system.
I’m assuming that the answer it a) it altered the composition of the soil in that area, but I’m not 100% sure. Hope that helped you some!
