Growth Of Animal Cells Research Articles

A new perspective on ornithine decarboxylase regulation: Prevention of polyamine toxicity is the overriding theme

The polyamines are essential cellular components for growth. Control of a key regulated enzyme of polyamine biosynthesis, ornithine decarboxylase (ODC), as a function of growth, is an area of intense interest. A unique regulatory property of ODC is the short half-life of the protein, which has been suggested to be an important factor in rapid activation of polyamine biosynthesis after cells are mitogenically stimulated. In this paper, it is argued that the biological significance of the short half-life of ODC is unrelated to the rate of its induction to a new steady state by growth factors, which is in fact limited by the relatively long half-life of the ODC mRNA. Instead, I suggest that the rapid turnover of ODC protein becomes of significance when cells cease growth and expeditious downregulation of the enzyme is important in preventing polyamine overproduction, which would result in cytotoxicity in the arrested cells. Although mitogenic activation of ODC expression has been studied extensively, there is very little known about the mechanisms controlling downregulation of polyamine biosynthesis during the arrest of animal cell growth. These considerations suggest that this would be a fertile area of future inquiry.

Animal cell bioreactors — recent advances and challenges to scale‐up

AbstractThe demand for animal cell derived products has stimulated the development of bioreactors in the last decade. Most of those developments allow a higher cell concentration to be achieved in the bioreactor than in the past, primarily by means of the continuous flow of culture medium and a mechanism of cell retention. The advantages and technological challenges of some of these developments are discussed. Lagging behind the bioreactor developments is the strategy for culture operation and optimization. The need for suitable kinetic models to describe animal cell growth is emphasized.

The adhesiveness and growth of anchorage-dependent animal cells on biocompatible ceramic culture carriers

The growth of anchorage-dependent animal cells was significantly affected by the adhesiveness on carrier materials. The relationship between the cell division rate and adhesiveness was quantitatively studied by use of ceramic carriers whose chemical compositions were regulated stepwise. An apparatus using a spinner flask was designed to estimate numerically the adhesive strength of cells to ceramic carriers. Using this apparatus, the adhesive strength of cells to ceramic sinters made by mixtures of synthesized hydroxyapatite (HAP) and tricalcium phosphate (TCP), a polystyrene dish (LUX), a glass dish, and a ZrO 2 ceramic plate were measured. The adhesiveness was comparably analyzed by trypsination method. Both measurements showed that the adhesiveness of L929 cells to calcium-phosphate sinters was considerably weaker than to LUX. Kinetic analyses of cell division and the adhesiveness to various carriers showed that a certain degree of weak adhesiveness was apparently advantageous for accelerating cell division. Another noteworthy and compatible correlation was obtained by the numerical analysis of growth phase dependent changes of these physiological parameters. The relationship between the cell division rate and adhesiveness based on the quantitative analysis was applicable for all the ceramic carriers used in this study. Measurement of the contact angle of the ceramic carrier with water suggested that the hydrophobicity of the carrier material was the dominant factor in determining the adhesiveness at the cell-carrier interface. The calcium-phosphate ceramic sinters had contact angle values from 42° to 56°. On the other hand, LUX, glass and ZrO 2 carriers had more hydrophobic surfaces as the values were around 65°. The most favored carrier for cell division had weak hydrophobicity with an angle of 51°.

In Vivo Effects of an Osteogenic Bone Extract on Cartilage of the Chick Embryo

Growth and differentiation of animal cells are influenced by a number of interacting local and circulating protein factors. Several such growth factors, or morphogenetic proteins, that affect hard tissue regeneration and repair have been isolated from bone [1–3]. Bone matrix is a complex milieu consisting of serum, cell, and hydroxyapatite binding proteins, bioactive agents, and other proteins whose functions are not yet known. Most of the growth factors can be dissociated from the decalcified collagen matrix only by using chaotropic solvents such as guanidine hydrochloride or urea [4].This extraction removes virtually all noncollagenous proteins from the matrix, producing a nonselective portfolio of proteins, of which growth factors are only a small percentage. A series of chromatographic separations are then required to isolate the morphogenetic proteins from the mixture [5]. Recently, a process has been developed that permits selective extraction of certain growth factors from demineralized bone and produces a water-soluble extract of collagenous and noncollagenous proteins. When placed in an orthotopic site in the rat, the extract exhibits pronounced osteogenic activity and has a surface-adherent property that may be exploited in the coating of allograft bone or osteoprosthetic implants to facilitate osseointegration. The objective of this study is to observe the in vivo effects of this extract on proliferation and synthetic activity of cartilage cells of the chick embryo.

Microcalorimetric measurement of aerobic cell metabolism in unstirred cell cultures

Studies of cell metabolism in small-volume, unstirred calorimeters has been limited by the problem of oxygen diffusion to the cells. Many cell types settle to the bottom of the sample container and become essentially anaerobic. Cells subjected to these conditions generally die, or when capable, alter metabolism to anaerobic pathways. Metabolic heat measurements in such conditions do not reflect normal metabolism and provide little information about normal metabolic rates. To avert this problem, the densities of the media supporting growth of animal and plant cells were increased by addition of sterile solutions of Percoll, causing cells to float at the surface of the media where they could readily absorb oxygen. Under these conditions, a wide range of cell types were studied. Plant, microbial, and animal cells could be analyzed for responses to metabolic effectors or environmental factors which influence growth.

Strobilurin D and Strobilurin F: Two New Cytostatic and Antifungal (E)-β-Methoxyacrylate Antibiotics fromCyphellopsis anomala

Strobilurin D and strobilurin F, two new cytostatic and antifungal antibiotics of the (E)-beta-methoxyacrylate class, have been isolated from mycelial cultures of the basidiomycete Cyphellopsis anomala (Pers. ex Fr.) Sing. The structures were elucidated by spectroscopic methods. The antibiotics inhibit the growth of human and animal cells and a wide variety of fungi. Like strobilurins A and B, the new metabolites are potent inhibitors of respiration.

Nutritional aspects of the growth of animal cells in culture

Mise au point sur les besoins nutritifs de cellules animales mises en culture: source d'energie, acides amines, lipides, inhibiteurs de croissance, besoins en oxygene, supplementation en serum. La culture a grande echelle dans un bioreacteur permettant d'obtenir des produits commerciaux, l'optimisation des rendements de ces productions est indispensable, d'ou la necessite de bien connaitre les besoins des cultures cellulaires

Modeling of contact‐inhibited animal cell growth on flat surfaces and spheres

A model of contact-inhibited growth of cells on flat and spherical surfaces is presented. It shows that contact inhibition does not significantly affect the calculated growth rate of cells unless they are allowed to multiply a large amount from the original seeding density. Microcarriers seeded at low densities require long times to reach confluence because contact inhibition becomes important. In systems with both growth and separate cell death, the equilibrium fraction of holes in the confluent monolayer is below 8% if the death rate is less than half the growth rate, but increases rapidly as the death rate increases from that value.

Measurement of viable animal cell concentration based on fluorometry.

In viable animal cells, fluorescein diacetate is hydrolyzed to fluorescein (a fluorescent compound) which is retained in the cells. Fluorescein was effectively extracted from the cells by treatment with hypotonic phosphate buffer (1 mmol·dm–3, pH 7.4) and the extract showed a fluorescent peak at excitation and emission wavelengths of 496.5 and 515 nm, respectively. A linear relationship was confirmed between the viable cell concentrations based on fluorometry and microscopy. Animal cell growth could be successfully monitored based on fluorometry for suspension and microcarrier cultures of animal cells.

Formation of effective channels in alginate gel for immobilization of anchorage-dependent animal cells

The conditions for formation of effective channels in alginate gels for growth of anchorage-dependent animal cells were examined. Many channels were formed in the gels by adding a low concentration solution of a high molecular weight polymer of alginate to a high concentration solution of divalent cations. It is recommended that an alginate with a high molecular weight and a low mannuronic acid/guluronic acid ratio be gelled by contact with strontium ions for the cultivation of immobilized anchorage-dependent cells because the gels produced have many channels and are mechanically strong.

The growth and productivity of recombinant animal cells in a bubble-free aeration system

The cultivation of animal cells at high densities requires reasonably high rates of gas transfer. Although these can be achieved using various reactor configurations, problems of either excessive shear or foam formation can result. Bubble-free aeration may provide a solution.

Regulation of c-myc and c-fos proto-oncogene expression by animal cell growth factors.

Animal cell growth factors stimulate expression of the proto-oncogenes c-myc and c-fos. The products of these genes seem to act as intracellular mediators of the mitogenic response to growth factors. Phosphatidyl inositol breakdown products function as cytoplasmic second messengers to induce transcription of c-myc and c-fos although they may not play an exclusive role in this regard. Post-transcriptional events may contribute to the modulation of c-myc gene expression. Following induction, the c-myc and c-fos mRNAs are selectively degraded within the cell.

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.

Growth of animal cells on microbeads. II. Estimation of biomass in situ and observation of cytopathic effects after infection of McCoy cells with Chlamydia trachomatis

The Channelyzer C256 together with the ZB Coulter Counter have been used to study in situ the growth kinetics of McCoy cells attached on Cytodex 3 microbeads. The number of cells per microbead varied linearly with the average size of the covered microbeads, showing that electronic particle sizing can be used to measure biomass or cell numbers. As the cells became confluent, an increase in cell volume with little accompanying increase in cell number was detected. The technique also enables the experimenter to follow in situ the development of cytopathic effects resulting from the infection by pathogens such as Chlamydia trachomatis serotype L1.

Growth limitations in microcarrier cultures.

The use of various commercially avaiable microcarriers is considered for the large-scale growth of anchorage-dependent animal cells. Cell productivity in such cultures can be maximised by an analysis of various kinetic aspects of growth. Such parameters as the critical cell to bead ratio at inoculation is particularly important in this respect.The full theoretical capacity of microcarriers to support cell growth can only be realised by an understanding of the interaction of the cell with is micro-environment. The final cell yield in culture may be limited by the supply of nutrients or by the accumulation of inhibitory metabolites. Glucose and glutamine are widely used as the major energy sources for cell growth and their relative concentrations in the media can influence cellular metabolism. The products of such metabolism — lactic acid and ammonia — may be inhibitory and methods to reduce their accumulation should be considered. The requirements for other essential metabolites such as amino acids vary but their supply should reflect the needs of each specific cell type. The advantages of serum-free media and the problems of oxygen supply particularly in large-scale microcarrier cultures are reviewed.Full investigation of these parameters that affect cell productivity will result in an increased ability to control the culture of anchorage-dependent animal cells on microcarriers. This will lead to considerable benefits for the production of an expanding list of useful cell products.

Growth of animal cells on microbeads. I. In situ estimation of numbers

Evaluation of the number of anchorage-dependent cells growing on the surface of microbeads kept in suspension in a bioreactor is a tedious procedure fraught with many difficulties. Using the Coulter counter as a biomass probe, this article shows that the number of cells adhering to microbeads can be determined while the cells are still attached.

Effect of bovine milk on growth of animal cells in culture

Effect of bovine milk on growth of animal cells in culture

Monoclonal antibodies NORM-1 and NORM-2 induce more normal behavior of tumor cells in vitro and reduce tumor growth in vivo

In this study, large numbers of hybridomas (produced by syngeneic immunization with B16 mouse melanoma and fusion with NS-1 myeloma cells) were screened for the production of antibodies that affected morphology and growth of animal and human tumor cells in vitro. Two such antibodies, NORM-1 and NORM-2 (both IgG2a), inhibited the growth of B16 melanoma cells in soft agar and increased the serum requirements of tumor cells in tissue culture. Antibody NORM-2 also inhibited the growth of SV40-transformed 3T3 cells in agar and caused them to deposit more fibronectin into extracellular matrix. These antibodies thus seem to induce a more normal behavior of tumor cells in vitro. In vivo both antibodies reduced the number of growing lung tumors of B16 melanoma in C57BL/6 mice by 70%–90% when injected 3 days after the tumor cells. By immunoprecipitation of 35S-methionine-labeled cell extracts, NORM-2 antibody recognized a 59 kd protein in B16 mouse and in A375 human melanoma cells but not in 3T3 fibroblasts.

Adhesion, spreading and growth of animal cells on the surface of glass ceramic Ap40 — a contribution to the cell compatibility of dental permanent hard tissue implants

Cells of different cell lines on the surface of glass ceramic Ap40 responded in the manner of reversible vacuolization in the cytoplasm. Whereas the eluate of bulk glass ceramic did not produce toxic effect on cell populations in vitro, the eluate of pulverized glass ceramic Ap40 caused a toxic reaction, the effect being dependent on concentration and incubation time. Although cell attachment, spreading and proliferation of fibroblast-like and epithel-like cells on glass ceramic surfaces are delayed when compared to glass and polystyrene the cells are adhering to a confluent monolayer.

On the contribution of the mitochondrial genome to the growth of Chinese hamster embryo cells in culture.

The present results demonstrate that Chinese hamster embryo cell populations in culture can be adapted to grow in the presence of chloramphenicol. It is shown that tryptose phosphate broth and uridine, one of its components, prevent the growth inhibitory effect of the drug. Study of some respiratory parameters (cytochrome c oxidase, cytochrome spectra, oxygen consumption) indicated that neither the broth nor uridine prevented the inhibitory effect of chloramphenicol on mitoribosomal protein synthesis. The cells grew with mitochondria devoid of a functional respiratory chain. Auxotrophy for pyrimidines appeared to result from the absence of dihydroorotate dehydrogenase, a respiratory chain-linked enzyme that catalyzes the fourth step of de novo pyrimidine biosynthesis. These and other results suggest that the synthesis of orotic acid may be considered as one of the main contributions of mitochondria to the growth of animal cells in culture.