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Biomedical subjects

J S Walker

Publications and source records attributed to J S Walker.

At least 145 records · Page 8Linked to original sources
PubMed1972

Human leucocyte antigens in Crohn's disease and ulcerative colitis.

The frequency of occurrence of 15 of the commoner human leucocyte antigens was determined in 18 patients with Crohn's disease and in 16 patients with ulcerative colitis, using an in-vitro lymphocyte cytotoxicity test (Harris, Wentzel, Cocking, Dodsworth, and Ukaejiofo, 1970). The overall results showed that, with the exception of human leucocyte antigen 3 in patients with Crohn's disease, in neither disease was there any major difference in any of the other antigen frequencies compared with a panel of 50 healthy controls. Nor was there an excess frequency of any particular antigen occurring in both Crohn's disease and colitis.

Antigens↗
PubMed1970

Evaluation of methods for reestablishment of L-cell suspension cultures directly from liquid nitrogen stored stocks.

Methods were developed and evaluated for the preservation of tissue cells grown in suspension culture and the reestablishment of suspension cultures directly from inoculum stored at -175 C. The factors investigated were processing pH, temperature of processing, freezing medium, and method of inoculation of the starter suspension cultures from the frozen stock (-175 C). Three parameters, cell viability, cell size, and growth potential in suspension culture after freezing, were used to evaluate the various factors. The results indicate that cells processed at 4 C, frozen at 1 C per min to -50 C in a medium containing 5% dimethyl sulfoxide plus 10% bovine serum at concentrations of 2 x 10(7) to 4 x 10(7) cells/ml, and stored at -175 C will reestablish suspension cultures directly from frozen seed. A 1-ml amount of frozen stock inoculated into 99 ml of medium routinely produced 2 x 10(6) to 3 x 10(6) viable cells/ml (2 x 10(8) to 3 x 10(8) total cells) in suspension culture in 4 to 5 days. Inoculum preserved by this procedure grew equally well in either serum-free or serum-containing growth medium.

Animals↗
PubMed1969

Interacting factors that influence long-term storage of live Pasteurella tularensis vaccine and Rift Valley fever virus.

Studies were conducted on the interaction of various parameters which affect the storage stability and growth potential of liquid cultures of Pasteurella tularensis live vaccine strain (LVS) and Rift Valley fever virus Van Wyk strain (RVFV). Storage variables studied with LVS included four storage temperatures (4, -20, -65, -175 C), single and multiple freeze-thaw cycles, two freezing and two thawing rates (slow and fast), various inoculum levels (1, 3, 5, and 10%) for the determination of growth potential, and the retention of immunizing potential (mice and guinea pig) after storage. Neither the freezing rate nor the number of freeze-thaw cycles seriously affected the growth of LVS after storage at -175C; however, the slow rate of thaw proved deleterious as were all temperatures of storage except -175 C after 1 year of storage, as shown by both criteria of evaluation. RVFV produced in two combinations of cell lines and media (LM cell line-199 peptone medium and LDR cell line-Eagle's minimum essential medium) was stored at three serum levels (10, 20, 40%), three pH values (6.2., 7.0, 7.8), and three temperatures (-20, -65, -175 C). These studies indicated: (i) virus produced in the LDR cell line and Eagle's medium was more stable than that produced in the LM cell line and 199 peptone medium for either short- or long-term storage; (ii) serum levels did not affect stability; and (iii) low pH resulted in losses during long-term storage under all conditions tested. Thus, cryogenic storage is advantageous for stock culture maintenance of bacteria and viruses and for other similar applications.

Animals↗
PubMed1969

Evaluation of factors related to growth of Rift Valley fever virus in suspended cell cultures.

The effect of several controlled variables on the peak titer and fold increase of Rift Valley fever virus grown in suspension culture on two variants of Earle's L cell, L-DR and L-MA clone 1-1, was studied. No significant amount of cell-associated virus was found at 24 hr, indicating a release of virus soon after its formation. Mild sonic treatment of the virus produced in serum-free medium increased the infective titer about 10x. This difference was not observed with virus produced in medium supplemented with serum. Peak titer was not affected by medium used during the infection period, by multiplicity of inoculum (MOI), or by initial cell concentration within the test range of 10(4) to 2 x 10(6) cell/ml. Cell strain employed influenced titer, because the L-DR cell did not produce virus efficiently at low MOI and low initial cell concentration. The time of peak titer and fold replication was dependent on MOI and initial cell concentration. Differences in virus propagation in monolayer and suspension systems are discussed.

Animals↗
PubMed1968

A precise method for replicating suspension cultures of mammalian cells.

A simple, readily assembled shaker-culture system for the cultivation of mammalian cells is described. No specialized glassware and equipment were used in this system, which consists of an Erlenmeyer flask fitted with a breather-sampling assembly. This unit was employed to quantitate the effects of several variables, including medium ingredients, serial transfers, and freezing and storage on two variants of the L-cell line. This system is reproducible and precise and allows for growth of cells in suspension for extended periods of time. Large numbers of cells can be mass-produced. Many replicates can be run simultaneously to yield data for statistical analysis.

Culture Media↗