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981.
We have used phase-contrast microscopy to determine a necrotic end point of the order of minutes in primary hepatocytes exposed to oxyradicals generated with xanthine oxidase plus hypoxanthine. This study examines whether the morphologic end point thus determined agrees with other criteria of cell necrosis. When 95-100% of the cells were shown to be necrotic by our morphologic assay, transmission electron microscopy confirmed definitive subcellular evidence of cell death, trypan blue exclusion revealed a 92% loss in the ability of cells to exclude the dye, and there was a 47% specific release of 51Cr (versus a 50% theoretical value). In contrast, the appearance of extracellular aspartate aminotransferase activity was relatively slow and did not corroborate the morphologic end point. In summary, we have validated the morphologic end point in our cell-based assay of oxyradical damage. 相似文献
982.
J M Shipley R D Miller B M Wu J H Grubb S G Christensen J W Kyle W S Sly 《Genomics》1991,10(4):1009-1018
983.
984.
Perin L. Donnini M. Diomede L. Romano M. Tacconi M. T. Luisetti M. Salmona M. 《Cytotechnology》1991,7(1):25-32
An expression vector for G-CSF, pASLB3-3, was constructed and introduced into Namalwa KJM-1 cells (Hosoi et al., 1988), and cells resistant to 100 nM of methotrexate (MTX) were obtained. Among them, the highest producer, clone SC57, was selected and the productivity of this clone was further characterized. The maximal production of G-CSF was at the most 1.8 g/ml/day using a 25 cm2 tissue culture flask, even though the cell number was above 7×105 cells/ml. The limiting factors at high density were analyzed as the deficiency of nutrients, such as glucose, cysteine and serine, and pH control. The depression of specific G-CSF productivity per cell under the batch culture conditions was overcome by using a perfusion culture system, BiofermenterTM (Sato, 1983) with modifications of nutrients supplementation by a dialysis membrane and/or dissolved oxygen (DO) supplementation by microsilicone fibers. ITPSGF medium was modified to elevate concentrations of amino acids and glucose by 2.0- and 2.5-times, respectively. Under the control of pH at 7.4 and DO at 3 ppm, the specific G-CSF productivity was not depressed even at high cell density (above 1×107 cells/ml), and the amount of G-CSF reached 41 g/ml. These results indicated the possibility of finding the optimum culture conditions for the production of recombinant proteins by Namalwa KJM-1 cells.Abbreviations ABTS
2,2-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
- BSA
Bovine Serum Albumin
- BSA-PBS
Phosphate-buffered Saline without Ca2+ and Mg2+ containing Bovine Serum Albumin
- dhfr
Dihydrofolate Reductase
- DO
Dissolved Oxygen
- G-CSF
Granulocyte Colony-stimulating Factor
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethansulfonic Acid
- IFN
Interferon
- MTX
Methotrexate
- PBS(-)
Phosphate-buffered saline without Ca2+ and Mg2+
- Tween-PBS
Phosphate-buffered saline without Ca2+ and Mg2+ containing 0.05% of Tween 20 相似文献
985.
The establishment of a cell culture system promoting chondrocyte differentiation has been utilized to better characterize phenotypic stages of chondrogenesis at the cellular level. Although the expression of the type II collagen gene has been studied during “in vitro” chondrocyte differentiation, little is known about the expression of the gene coding for its receptor: anchorin CII. The modulation of the anchorin mRNA steady state level in chick embryo chondrocytes at different developmental stages is described here.The anchorin mRNA level was low in dedifferentiated chondrocytes, progressively increased after the cell transfer into suspension (a condition promoting differentiation), reached its maximal value after 4 weeks and decreased after 5 weeks.Therefore anchorin CII mRNA reaches its maximum level in hypertrophic stage II chondrocytes. 相似文献
986.
Summary An Enzyme Linked Immuno Sorbent Assays (ELISA) and an Electro-chemiluminescent Immuno Assay (CIA) are compared for the purpose of monitoring product formation in mammalian cell bioreactors. The ELISA had a relative standard deviation of 10%, compared to 8% for the CIA . The CIA was found to be a fast and accurate alternative to the ELISA. The use of more than one immuno assay format was also shown to provide additional insight into process performance. 相似文献
987.
988.
989.
990.
Cultivation of Brevibacterium divaricatum for glutamic acid production in an airlift reactor with net draft tube was developed. Cell concentration gave an index for adding penicillin G. On-line estimation of total sugar concentration yielded an identified model which was used for determination of the substrate addition. Fermentation for glutamic acid production requires high oxygen concentration in the broth. The proposed reactor has the capability to provide sufficient oxygen for the fermentation. Since the reactor is suitable for fed-batch culture, the cultivation of B. divaricatum for glutamic acid production in the proposed reactor is successfully carried out.List of Symbols
a
system parameter
-
b
system parameter
-
C
c,in
mole fraction carbon dioxide in the gas inlet
-
C
c,out
mole fraction carbon dioxide in the gas outlet
-
C
L
mole/dm3
oxygen concentration in liquid phase
-
C
L
*
mole/dm3
saturated oxygen concentration in liquid phase
-
C
0,in
mole fraction of oxygen in the gas inlet
-
C
0,out
mole fraction of oxygen in the gas outlet
-
CPR mole/h/dm3
carbon dioxide production rate based on total broth
-
E(t)
error signal
-
F
in
mole/h
inlet gas flow rate
-
k
1
constant defined by Eq. (4)
-
k
2
constant defined by Eq. (5)
-
k
L
a 1/h
volumetric mass transfer coefficient of gas-liquid phase
-
OUR mole/h/dm3
oxygen uptake rate based on total broth
-
P atm
pressure in the reactor
-
t h
time
-
TS
c
g
total sugar consumption
-
TS
s
g/dm3
set point of total sugar concentration
-
TS
*
g/dm3
reference value of total sugar concentration
-
TS(t) g/dm3
total sugar concentration in the broth at timet
-
u(t) cm3/min
feed rate at timet
-
V dm3
total broth volume
-
VVM (dm3/min)/dm3
flow rate per unit liquid volume
-
a negative constant defined by Eq. (7) 相似文献