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Biomedical subjects

J B Griffiths

Publications and source records attributed to J B Griffiths.

At least 37 records · Page 2Linked to original sources
PubMed1987

A comparison of unit process systems for anchorage dependent cells.

The performance of three unit process systems for anchorage-dependent cells, namely the APV plate heat exchanger, glass bead reactor and microcarrier culture are reviewed. All three systems have been used for the production of various viruses and protein products and their use in a production process is related to various scaling-up parameters.

Animals↗
PubMed1987

Amplification of tissue plasminogen activator expression from epithelial cell lines.

Two established non-malignant epithelial cell lines, one derived from human breast tissue (BEB), the other from guinea pig ear keratocytes (GPK), have been shown to secrete a tissue plasminogen activator (tPA). The protein yield of this epithelial enzyme is similar to that from the malignant cell line, Bowes melanoma, but as the specific activity is approximately 10-20 fold lower, means of potentiating the yield are being sought. The enzyme is mainly expressed during the cell growth phase rather than from stationary culture cells. Also, production has to be a 2-step operation with initial growth to about 70% confluency in the presence of serum followed by a change to serum-free conditions for the final period of growth after which the enzyme is harvested. To increase the enzyme yield, means of amplifying enzyme expression, of establishing a serum-free medium so that the enzyme can be continuously harvested, and stimulation of stationary-phase cells have been studied. Of the many regulatory agents studied only the hypomethylating agent 5-azacytidine brought about significant increases (3-5 fold) in enzyme secretion. The effect of a number of mitogenic lectins was also investigated and resulted in further increases of enzyme yield (15-20 fold). Concanavalin A considerably extended the culture period in which enzyme secretion occurred and the reasons for this were investigated using tritiated thymidine.

Animals↗
PubMed1987

Serum and growth factors in cell culture media--an introductory review.

Amongst this bewildering array of growth factors, serum replacements and serum-free media is there a system which works well for most cell types used in biotechnology? If so is there a short-cut for novices in the field to be able quickly to select the right formulation. I hope the following discussion will enable those with experience in this field to share that experience so that we can get an indication of which compound works for which cell under which conditions. Also the cost in both yield and monetary terms needs to be kept in perspective as one option is to produce these very expensive factors from genetically engineered bacteria. Discussion points should include the question of why so many medium formulations still include serum at 0.1 or 0.5% i.e. what does this small quantity of serum provide and does it mean that in fact we cannot have a completely protein-free media to achieve optimal growth? In which case, what is the minimal acceptable level? An adaptation procedure to low-serum media is accepted as essential but in fact the time-scale for this varies enormously from laboratory to laboratory and the question must be asked "is this based on quantitative or empirical investigation"? I hope the following panel discussion will answer these questions as the correct use of growth factors is of vital importance to the future development of cell product technology. It is probably true to say that with the correct blend of these compounds all cell types can be grown in culture as successfully as the ubiquitous fibroblast.

Animals↗
PubMed1985

The production and properties of a tissue plasminogen activator from normal epithelial cells grown in microcarrier culture.

A plasminogen activator with different biochemical and physical properties to the one obtained from Bowes melanoma cells has been isolated from a normal epithelial cell line derived from guinea-pig keratocytes (GPK). Cell growth and enzyme production is carried out in microcarrier cultures using up to 15 g Cytodex 3 per litre. Cells are maintained in optimum conditions by the use of a closed perfusion loop and the system has been scaled up to 20 litres. Initially enzyme production was in serum-free medium following a growth phase in serum supplemented medium. However, the discovery that the cells produce the enzyme mainly during the replicative phase has led to investigating the use of serum-substitutes and growth factors on cell growth and enzyme production. The aim is to harvest the enzyme after the growth phase which precludes the use of high (greater than 1%) serum concentrations. The biochemical and biophysical properties of the enzyme are described.

Animals↗
PubMed1983

Hepatitis B vaccines.

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Acquired Immunodeficiency Syndrome↗
PubMed1981

The development and use of microcarrier and glass sphere culture techniques for the production of herpes simplex viruses.

Two high productivity monolayer culture methods, the microcarrier and glass sphere culture, were compared for their capacity to support the growth of MRC-5 and Vero cells, and Herpes simplex type 2 virus. Cell growth was similar in both systems giving yields of 14 X 10(5)/cm2 in microcarrier and 18 X 10(5)/cm2 in glass sphere cultures with yields of Vero cells being marginally better than MRC-5 cells. Virus yields were only slightly lower in these cultures than in small scale stationary cultures and confirmed the fact that MRC-5 cells produce twice as much HSV-2 as Vero cells, thus neutralising the growth advantage of these cells. Techniques for harvesting the virus in small volumes need to be improved in order to get a high titre suspension from the high capacity cultures.

Animals↗
PubMed1981

Herpes simplex vaccine using cell membrane associated antigen in an animal model.

Vesicles of plasma membrane, containing no detectable live virus, were prepared by treatment of Herpes simplex virus type 2 (HSV-2) infected Vero cells with dithiothreitol and formaldehyde. These preparations proved to be antigenic on injection into guinea-pigs and also protected these animals against intravaginal challenge with HSV-2.

Animals↗