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1.
Macroporous microcarriers entrap cells in a mesh network allowing growth to high densities and protect them from high shear
forces in stirred bioreactor cultures. We report the growth of Chinese hamster ovary (CHO) cells producing either recombinant
human beta-interferon (β-IFN) or recombinant human tissue-plasminogen activator (t-PA) in suspension or embedded in macroporous
microcarriers (Cytopore 1 or 2). The microcarriers enhanced the volumetric production of both β-IFN and t-PA by up to 2.5
fold compared to equivalent suspension cultures of CHO cells. Under each condition the cell specific productivity (Q
P) was determined as units of product/cell per day based upon immunological assays. Cells grown in Cytopore 1 microcarriers
showed an increase in Q
P with increasing cell densities up to a threshold of >1 × 108 cells/ml. At this point the specific productivity was 2.5 fold higher than equivalent cells grown in suspension but cell
densities above this threshold did not enhance Q
P any further. A positive linear correlation (r
2 = 0.93) was determined between the specific productivity of each recombinant protein and the corresponding cell density for
CHO cells grown in Cytopore 2 cultures. With a cell density range of 25 × 106 to 3 × 108 cells/ml within the microcarriers there was a proportional increase in the specific productivity. The highest specific productivity
measured from the microcarrier cultures was ×5 that of suspension cultures. The relationship between specific productivity
and cell density within the microcarriers leads to higher yields of recombinant proteins in this culture system. This could
be attributed to the environment within the microcarrier matrix that may influence the state of cells that could affect protein
synthesis or secretion. 相似文献
2.
Michael E. Horn Jack M. Widholm 《In vitro cellular & developmental biology. Plant》1992,28(4):161-166
A cell line ofDatura innoxia was selected in suspension culture to be resistant to 1% (vol/vol) ethanol (EtOHR). EtOHR cells were cross-resistant to 1% (vol/vol) methanol and 1% (vol/vol) 2-propanol but not 1% (vol/vol)n-propanol orn-butanol, whereas wild type (WT) cells were resistant only to methanol. Resistance in EtOHR cells is probably a result of a very low level of alcohol dehydrogenase (ADH) activity which was only 9 to 10% of that in
WT cells and was undetectable during much of the EtOHR growth cycle. In the absence of ethanol, EtOHR cells have a I50 for the toxic ethanol analog allyl alcohol, which is nearly 3 times higher than that in WT cells. In the presence of ethanol,
EtOHR cells have an I50 for allyl alcohol which is 12 times more than WT cells. This difference correlated well with the decrease in ADH activity
found in EtOHR cells grown on ethanol. When ethanol was removed from the suspension medium, ADH activity in EtOHR cells gradually increased to WT levels. When re-exposed to ethanol after 200 cell generations, ADH activity quickly decreased
and growth resumed after a 4- to 6-day lag period. Lipid analysis showed a 37% increase in total lipid in EtOHR cells, mostly in polar lipids, di- and triglycerides. The fatty acid composition of these lipid classes was shifted toward
the more polyunsaturated. These lipid changes were probably a reflection of the increased plastid number in the EtOHR cells and may be a result of growth in ethanol rather than a reason for resistance. EtOHR cells seem to be regulatory mutants able to quickly lower ADH activity in the presence of ethanol. 相似文献
3.
Kevin J. Gilligan Suzanne Littefild Allan P. Jarvis Jr. 《In vitro cellular & developmental biology. Plant》1988,24(1):35-41
Summary The cell growth and monoclonal antibody production characteristics of two rat x mouse heterohybridoma cell lines, designated
187.1 and M1/9.3, were investigated using a biocompatible microencapsulation technology. Both cell lines, derived from the
fusion of immunized rat spleen cells with either the NS1 or X63Ag8.653 myeloma cell lines, were found to reach a maximum intracapsular
cell density of 1.3 to 1.5×107 cells/ml during a 27-d culture period. During this period, rat monoclonal antibody accumulated in the intracapsular space
of both cultures to a final concentration of 2.0 to 2.8 mg/ml. Comparison of the concentration of rat monoclonal antibody
in the extracapsular vs. the intracapsular space of both cultures indicated that significantly less than 1% of the antibody
produced by the encapsulated hybridoma cells was capable of transiting the microcapsule membrane during the culture period.
Due to the partition of the rat monoclonal antibody within the intracapsular space, the initial purity of the antibody harvested
from 21-d microcapsule cultures of 187.1 and M1/9.3 cells was approximately 48 and 75% by weight, respectively. Analysis of
the intracapsular protein by sodium dodecyl sulfoxide gel electrophoresis at different times during the culture period demonstrated
that the principal contaminant associated with the unpurified antibody was bovine serum albumin. 相似文献
4.
T. Miyake K. Saigo T. Marunouchi T. Shiba 《In vitro cellular & developmental biology. Plant》1977,13(4):245-251
Summary To develop a method for culturing a large number of small-scale suspension cultures ofDrosophila melanogaster cells simultaneously, basic conditions were studied using a cell line GM2 and a gyratory shaker. Under gyration at more than 180 rpm, a majority (>80%) of the cells still remained as suspension and
grew normally. Lower speed of gyration caused adhesion of the cells to a substratum. Furthermore, size of the culture vessels
was found to affect the pattern of cell growth. Five- or 10-ml Erlenmeyer flasks gave satisfactory results, but the growth
curves in 30-ml flasks differed from flask to flask and the saturation level was lower. Besides, the growth curves in the
latter case were quite different depending on the volume of the medium. A preliminary experiment showed that the type of flask
might affect the pattern of a growth curve. Initial cell densities has to be more than 6×104 cells per ml. Lower densities resulted in the longer doubling time or no increase in the cell number. Therefore the following
conditions are recommended as a standard for gyration culture ofD. melanogaster cell, GM2: speed of gyration, 180 rpm; culture vessel, 5- or 10-ml Erlenmeyer flask of a certain type; initial cell density, 1 to 5×105 per ml. Both D20 and modified Schneider’s medium could be utilized as the medium. 相似文献
5.
Ricardo P. Baptista David A. Fluri Peter W. Zandstra 《Biotechnology and bioengineering》2013,110(2):648-655
Strategies for the production of pluripotent stem cells (PSCs) rely on serially dissociated adherent or aggregate‐based culture, consequently limiting robust scale‐up of cell production, on‐line control and optimization of culture conditions. We recently developed a method that enables continuous (non‐serially dissociated) suspension culture‐mediated reprogramming to pluripotency. Herein, we use this method to demonstrate the scalable production of PSCs and early derivatives using acoustic filter technology to enable continuous oxygen‐controlled perfusion culture. Cell densities of greater than 1 × 107 cells/mL were achieved after 7 days of expansion at a specific growth rate (µ) of 0.61 ± 0.1 day?1 with a perfusion rate (D) of 5.0 day?1. A twofold increase in maximum cell density (to greater than 2.5 × 107 cells/mL) was achieved when the medium dissolved oxygen was reduced (5% DO). Cell densities and viabilities >80% were maintained for extended production periods during which maintenance of pluripotency was confirmed by stable expression of pluripotency factors (SSEA‐1 and Nanog), as well as the capacity to differentiate into all three germ layers. This work establishes a versatile biotechnological platform for the production of pluripotent cells and derivatives in an integrated, scalable and intensified stirred suspension culture. Biotechnol. Bioeng. 2013; 110: 648–655. © 2012 Wiley Periodicals, Inc. 相似文献
6.
The UFL-AG-286 cell line, established from embryonic tissue of the lepidopteran insect Anticarsia gemmatalis, has been identified as a good candidate to be used as a cellular substrate in the development of a process for in vitro
production of the Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, a baculovirus widely used as bioinsecticide. In order to characterize the technological
properties of this cell line and evaluate its feasibility to use it for the large-scale production of Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, UFL-AG-286 cells were adapted to grow as agitated suspension cultures in spinner-flasks.
Batch suspension cultures of adapted cells in serum-supplemented TC-100 medium grew with a doubling time of about 29 h and
reached a maximum cell density higher than 3.5 × 106 viable cells ml−1. At the end of the growth period glucose was completely depleted from the culture medium, but l-lactate was not produced. Amino acids, with the exception of glutamine, were only negligibly consumed or produced. In contrast
to other insect cell lines, UFL-AG-286 cells appeared to be unable to synthesize alanine as a metabolic way to dispose the
by-product ammonia. The synchronous infection of suspension cultures with Anticarsia gemmatalis multicapsid nucleopolyhedrovirus in the early to medium exponential growth phase yielded high amounts of both viral progenies
per cell and reduced the specific demands of UFL-AG-286 cells for the main nutrients. 相似文献
7.
Summary A system to regenerate fertile rice (Oryza sativa L.) plants (both indica and japonica varieties) from protoplasts isolated from anther-derived embryogenic haploid suspension cultures has been established. Green plants were regenerated from protoplast-derived cell clusters five months after suspension culture initiation. Protoplast yields and subsequent growth of the protoplast-derived microcalli were enhanced by transferring suspension cells into AA medium (Muller et al. 1978) three to four days prior to protoplast isolation. Protoplasts were cultured initially in Kao medium (Kao et al. 1977) and in association with nurse cells for four weeks. Protoplast-derived microcalli were transferred onto N6 (Chu et al. 1975) or MS (Murashige and Skoog 1962) media for callus proliferation. Callus growth was more rapid and the calli were more enbryogenic when grown on N6 medium. The 2,4-D concentration used to develop the suspension culture was important. Cell cultures grown in medium containing 0.5 mg/l 2,4-D released protoplasts whose plating efficiency was higher than for protoplasts obtained from suspension cultures grown in 2.0 mg/l 2,4-D. However, suspension cells grown in 2.0 mg/l 2,4-D were superior with regard to the ability of protoplast-derived calli to regenerate green plants. Amongst several hormone treatments evaluated, a combination of 0.5 mg/l NAA + 5.0 mg/l BAP resulted in the largest number of green plants regenerated. There were no significant differences between BAP or kinetin regarding total number of plants regenerated. More than 200 green plants have been produced form six independently initiated suspension cell lines. The number of regenerated plants per 106 protoplats plated anged from 0.4 to 20.0, and the average seed fertility of single panicles of these RO plants was about 40%. 相似文献
8.
Summary Friable calli were obtained fromAchillea millefolium L. hypocotyls, in Gamborg B5 medium, supplemented with 1.5mg.1–1 2,4-D / 0.1mg.1–1 Kin, and used for the production of cell suspension cultures in the same liquid medium. The growth pattern of the cultures was determined in permanent light or dark conditions and with different inoculum densities, basal media, growth regulators and sucrose concentrations. Different sources and nitrogen amounts were assayed to study the effect on yarrow cell growth. The conditions found to be optimal for growth of yarrow cell suspension cultures were: 70g (f.w.).1–1 of initial inoculum in Gamborg B5 medium, supplemented with 1.5mg. 1–1 2,4-D / 0.1mg.1–1 Kin, NO3
–/NH4
+ (30/lmM), and 2% sucrose, in darkness. In these culture conditions the cell suspensions showed a doubling time of 35–40h.Abbreviations 2,4-D
dichlorophenoxyacetic acid
- NAA
naphtalenacetic acid
- BA
benzyladenine
- Kin
Kinetin 相似文献
9.
Here we present the TubeSpin bioreactor 50 (TubeSpins) as a simple and disposable culture system for Sf-9 insect cells in
suspension. Sf-9 cells had substantially better growth in TubeSpins than in spinner flasks. After inoculation with 106 cells/ml, maximal cell densities of 16 × 106 and 6 × 106 cells/ml were reached in TubeSpins and spinner flasks, respectively. In addition the cell viability in these batch cultures
remained above 90% for 10 days in TubeSpins but only for 4 days in spinner flasks. Inoculation at even higher cell densities
reduced the duration of the lag phase. After inoculation at 2.5 × 106 cells/ml, the culture reached the maximum cell density within 3 days instead of 7 days as observed for inoculation with 106 cells/ml. Infection of Sf-9 cells in TubeSpins or spinner flasks with a recombinant baculovirus coding for green fluorescent
protein (GFP) resulted in similar GFP-specific fluorescence levels. TubeSpins are thus an attractive option for the small-scale
cultivation of Sf-9 cells in suspension and for baculovirus-mediated recombinant protein production. 相似文献
10.
S. Jayasankar Richard E. Litz Dennis J. Gray Pamela A. Moon 《In vitro cellular & developmental biology. Plant》1999,35(6):475-479
Summary
Colletotrichum gloeosporioides Penz., the causal agent of mango anthracnose, produces a phytotoxin in vitro. The partially purified phytotoxin, presumably
colletotrichin, caused anthracnose-like symptoms on young mango leaves, was toxic to embryogenic suspension cultures of two
mango cultivars, ‘Hindi’ and ‘Carabao,’ and inhibited in vitro seed germination of two nonhosts, lettuce and tobacco. There
were linear relationships between concentration of the partially purified phytotoxin and mortality of mango embryogenic cultures.
Embryogenic cultures grown in the presence of the partially purified phytotoxin showed significantly lower growth rates than
the controls. Similarly, embryogenic cultures grown in the presence of 40% (vol/vol) fungal culture filtrate showed significantly
lower growth rates than unchallenged controls. Medium containing 40% (vol/vol) Czapek-Dox fungal broth did not reduce growth
of embryogenic cultures, indicating the production of phytotoxin in vitro. The results suggest that either fungal culture
filtrate or purified phytotoxin can be used as in vitro selection agents to screen for resistance to this fungus. 相似文献
11.
J. -J. Zhong T. Seki S. -I. Kinoshita T. Yoshida 《World journal of microbiology & biotechnology》1992,8(2):106-109
The effects of surfactants, adecanol LG-294 and silicone A, on anthocyanin accumulation and the growth ofPerilla frutescens cells in suspension cultures were studied. Production of the red pigment was remarkably reduced from about 1.9 g/l to 0.4 g/l by adecanol LG-294 at 0.06 ml/l but not by silicone A up to 0.4 ml/l. Several repeated shake-flask cultures also demonstrated no adverse effects of silicone A on the metabolite accumulation by the suspended cells. Furthermore, the addition of silicone A to a culture in a stirred bioreactor produced a three-fold higher growth rate and a seven-fold increase in anthocyanin compared with surfactant-free cultures. The improvement was due to the substantial reduction or prevention of foaming and of cell adhesion to the bioreactor wall. 相似文献
12.
Frank Maldarelli Mary Jane Yagi 《In vitro cellular & developmental biology. Plant》1986,22(9):542-548
Summary The MJY-alpha epithelial-like mammary tumor cell line was adapted for cultivation in suspension using a shaker culture technique.
Replication of suspension (MJY-beta) cells was more sensitive than monolayer cells to decreases in the concentration of serum
in the medium. Comparison of amino acid incoerporation and lactate production rates revealed additional differences between
monolayer and suspension cultures. In addition, growth in susfpension resulted in 10- to 400-fold increases in mouse mammary
tumor virus (MMTV) production by the mammary tumor cells. Incrases in MMTV yield were detected within 48 h of culture initiation
and MMTV production remained elevated throughout 20 cell passages in suspension. Exposure of MJY-beta cells to 14 μM hydrocorticone further increased MMTV yield two-to five-fold. The MJY-beta suspension cultures demonstrated that these epithelial-like
cells do not require attachment to a solid substrate for replication or for MMTV production. Loss of structural polarization
associated with growth as a monolayer resulted in stimulation of MMTV production greater than and independent of steroid exposure.
This work was supported by the T. J. Martell Foundation for Cancer and Leukemia Research and by USPHS grant 5P-30CA23102.
F. M. is a trainee on MSTP grant GM07280 from the National Institute of Health. This work was submitted in partial fullfillment
of the requirements for the Ph. D. degree (F. M.). 相似文献
13.
Zhao Dexiu Xing Jianming Li Maoyin Lu Dongping Zhao Qiao 《Plant Cell, Tissue and Organ Culture》2001,67(3):227-234
Calli cultures derived from the leaves of Saussurea medusa were selected on the basis of colour into three callus, A, B and C, which suggested different levels of metabolite accumulation. An improved reversed phase high performance liquid chromatographic method provided selective determination of the jaceosidin content of these samples. The jaceosidin concentration in callus B was higher than that of the callus A and C. By using 12-day old culture and 9-day old inoculum, jaceosidin yield of 72.91 mg l–1was obtained from cell line B in cell suspension cultures. The influence of some factors affecting jaceosidin formation, i.e. temperature, light, inoculum size, type of media, phytohormones, nitrogen and carbon source etc. were also examined. Light irradiation and combination of 3% (w/v) sucrose with 1% glucose brought about a marked increase of jaceosidin production. The effect of blue light on jaceosidin was markedly superior to other kinds of monochromatic light (red and far-red) or white light. Analysis of growth and jaceosidin content of callus cultures and cell suspension cultures demonstrated that the production of jaceosidin was growth-dependent in both cell solid culture and cell suspension culture. 相似文献
14.
Véronique Breguet Raphaël Gugerli Urs von Stockar Ian William Marison 《Cytotechnology》2007,53(1-3):81-93
Microencapsulation offers a unique potential for high cell density, high productivity mammalian cell cultures. However, for
successful exploitation there is the need for microcapsules of defined size, properties and mechanical stability. Four types
of alginate/poly-l-Lysine microcapsules, containing recombinant CHO cells, have been investigated: (a) 800 μm liquid core microcapsules, (b)
500 μm liquid core microcapsules, (c) 880 μm liquid core microcapsules with a double PLL membrane and (d) 740 μm semi-liquid
core microcapsules. With encapsulated cells a reduced growth rate was observed, however this was accompanied by a 2–3 fold
higher specific production rate of the recombinant protein. Interestingly, the maximal intracapsular cell concentration was
only 8.7 × 107 cell mL-1, corresponding to a colonization of 20% of the microcapsule volume. The low level of colonization is unlikely to be due to
diffusional limitations since reduction of microcapsule size had no effect. Measurement of cell leaching and mechanical properties
showed that liquid core microcapsules are not suitable for continuous long-term cultures (>1 month). By contrast semi-liquid
core microcapsules were stable over long periods with a constant level of cell colonization (ϕ = 3%). This indicates that
the alginate in the core plays a predominant role in determining the level of microcapsule colonization. This was confirmed
by experiments showing reduced growth rates of batch suspension cultures of CHO cells in medium containing dissolved alginate.
Removal of this alginate would therefore be expected to increase microcapsule colonization. 相似文献
15.
Scale-up of the adenovirus expression system for the production of recombinant protein in human 293S cells 总被引:6,自引:0,他引:6
Alain Garnier Johanne Côté Isabelle Nadeau Amine Kamen Bernard Massie 《Cytotechnology》1994,15(1-3):145-155
Human 293S cells, a cell line adapted to suspension culture, were grown to 5×106 cells/mL in batch with calcium-free DMEM. These cells, infected with new constructions of adenovirus vectors, yielded as much as 10 to 20% recombinant protein with respect to the total cellular protein content. Until recently, high specific productivity of recombinant protein was limited to low cell density infected cultures of no more than 5×105 cells/mL. In this paper, we show with a model protein, Protein Tyrosine Phosphatase 1C how high product yield can be maintained at high cell densities of 2×106 cells/mL by a medium replacement strategy. This allows the production of as much as 90 mg/L of active recombinant protein per culture volume. Analysis of key limiting/inhibiting medium components showed that glucose addition along with pH control can yield the same productivity as a medium replacement strategy at high cell density in calcium-free DMEM. Finally, the above results were reproduced in 3L bioreactor suspension culture thereby establishing the scalability of this expression system. The process we developed is used routinely with the same success for the production of various recombinant proteins and viruses.Abbreviations CFDMEM
calcium-free DMEM
- CS
bovine calf serum
- hpi
hours post-infection
- J+
enriched Joklik medium
- MLP
major late promoter
- MOI
multiplicity of infection (# of infectious viral particle/cell)
- q
specific consumption rate (mole/cell.h)
- pfu
plaque forming unit (# of infectious viral particle)
- Y
yield (g/E6 cells or mole/cell) 相似文献
16.
William R. Tolbert Joseph Peder Richard C. Kimes 《In vitro cellular & developmental biology. Plant》1981,17(10):885-890
Summary A system has been developed for growth and maintenance of mammalian cells in suspension culture at high density. In principle,
the maintenance of constant levels of required nutrients coupled with the removal of toxic cell byproducts can support much
higher suspension cell densities than may be obtained in conventional spinners. The system consisted of 4- or 40-liter reaction
vessels equipped with a vertically supported rotating cylindrical filter. Agitation was provided by the magnetically driven,
rotating filter. Fresh medium was supplied at a rate of 10 to 20 ml/h per 109 cells and the expended medium free of cells was withdrawn through the rotating filter. Both pH and dissolved O2 and CO2 were monitored and regulated. Walker 256 carcinosarcoma cells have been grown in these reactors to densities 10-to 30-fold
greater than that obtained in Bellco spinners. In addition to high cell densities, the yield of cells per liter of medium
used was 2- to 3-fold that obtained in the conventional systems. Both 4-and 40-liter versions of this reactor have been operated
without the use of antibiotics. The 40-liter reactor also has been modified for chemostat operation. In a single run, for
example, the Walker cell density was maintained between 6 and 10×106 cells/ml with a total yield of 8.7×1011 cells from 360 liters of medium. 相似文献
17.
The effects of constant osmolarity, between 300 and500 mOsm/kg, on the metabolism of Chinese HamsterOvary (CHO) cells producing tissue plasminogenactivator (tPA) were compared between adhesion andsuspension cultures. In both suspension and adhesionculture, the specific rates of glucose consumption(G), lactate production (qL), and tPAproduction (qtPA) increased as osmolarityincreased, while these rates decreased when osmolaritywas higher than the respective critical levels. However, specific growth rate () decreased withincrease in osmolarity and this slope grew steeper inthe osmolarity range higher than the critical level. The decrease in in the adhesion culture was morerapid than that in the suspension culture. Thecritical osmolarity for adhesion culture (400 mOsm/kg)was lower than that for suspension culture (450 mOsm/kg). These results indicated that the adhesionculture was more sensitive to increase of osmolaritythan the suspension culture, while the specific ratesobtained from the adhesion cultures were in general1.5- to 3-fold higher than those obtained from thesuspension cultures. Cell volume increased asosmolarity increased in both the suspension andadhesion cultures, as reported previously forsuspension culture of hybridoma cells, but there wasno morphological change in the suspension culture. Incontrast, cell height decreased and cell adhesion areamarkedly increased as osmolarity increased in theadhesion culture. This morphological change inadhesion cultures may be one reason for the highersensitivity of adherent cells to the increase ofosmolarity than suspended cells. 相似文献
18.
Relationship Between Substrate Concentration and Fermentation Product Ratios in Clostridium thermocellum Cultures 总被引:2,自引:1,他引:1
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Growth of Clostridium thermocellum in batch cultures was studied over a broad range of cellobiose concentrations. Cultures displayed important differences in their substrate metabolism as determined by the end product yields. Bacterial growth was severely limited when the initial cellobiose concentration was 0.2 (wt/vol), was maximal at substrate concentrations between 0.5 and 2.0%, and did not occur at 5.0% cellobiose. Ethanol accumulated maximally (38.3 μmol/109 cells) in cultures with an initial cellobiose concentration of 0.8%, whereas cultures in 2.0% cellobiose accumulated only 17.3 μmol, and substrate-limited cultures (0.2% cellobiose) accumulated little, if any, ethanol beyond that initially detected (8.3 μmol/109 cells). In a medium with 0.8% cellobiose, ethanol was produced at a constant rate of approximately 1.1 μmol/109 cells per h from late-logarithmic phase (16 h) of growth well into stationary phase (44 h). When ethanol was added exogenously at levels more than twice the maximum produced by the cultures themselves (0.5% [vol/vol]), neither the extent of growth (maximum Klett units, 150) nor the amounts of ethanol produced (~0.17%) by the culture was affected. The ratio of ethanol to acetate was highest (2.8) when cells were grown in 0.8% cellobiose and lowest (1.2) when cells were grown in 0.2% cellobiose. 相似文献
19.
R. S. PHILLIPS R. J. M. WILSON G. PASVOLS 《The Journal of eukaryotic microbiology》1978,25(3):394-398
SYNOPSIS. Gametocytes differentiated from ring-stage parasites in microcultures of human blood infected with Plasmodium falciparum. Immature gametocytes could be distinguished morphologically from late asexual trophozoites after ~ 40 h of culture. Differentiation into crescentic forms took several days and the incorporation of [3H]-isoleucine by developing gametocytes was demonstrated. About 1% of red cells contained gametocytes at the maximum densities attained. Differentiation of gametocytes occurred either directly from rings placed in culture or from the progeny of subsequent cycles of schizogony and invasion in vitro. The latter occurrence was confirmed by the development of gametocytes in marker fetal red cells added to cultures, although fetal red cells provide a less favorable environment than those with HbA for growth of the parasites. 相似文献
20.
Carbon dioxide (optimum concentration c. 1.0%) is essential to the initiation of the growth in suspension culture or on agar plates of cultured sycamore cells. By effective flushing of the cultures with CO2-free air it is possible to demonstrate this requirement with initial cell densities up to 50 × 103 cells ml?1. This growth-promoting activity of carbon dioxide is not related to any effect it may have on the pH of the culture medium. The cells fix applied carbon dioxide into organic and amino acids but attempts to replace the carbon dioxide requirement by non-toxic levels of organic or amino acids have not been successful. 相似文献