Biomedical subjects

G J Morris

Publications and source records attributed to G J Morris.

At least 37 records · Page 2Linked to original sources

PubMed1978

The cryopreservation of Chlorella. 4. Accumulation of lipid as a protective factor.

Following growth under sub-optimal concentrations of nutrients, cells of Chlorella emersonii accumulated lipid and became more resistant to the damage caused by freezing and thawing. These results suggest that the factor responsible for the cold hardening of some Chlorella spp is not the effect of low temperatures per se but simply that of the reduced metabolic rate. Evidence is given that the post-thaw injury observed following rapid rates of cooling is associated with the vacuole.

Chlorella↗

PubMed1977

Structural and functional aspects of biological freezing techniques.

The cooling procedures used to prepare samples for ultrastructural examination at low temperatures often differ markedly from those used to recover optimal function of cells on thawing. The implications of these differences are reviewed. Damage and alteration to the structure and function of the cells may be caused by the high concentrations of cryoprotective agents such as glycerol or dimethyl sulphoxide (DMSO) often added to reduce ice crystal artefacts. Under the rapid cooling conditions commonly employed for structural studies, these additives are not cryoprotective; low rates of cooling are necessary for them to be effective. Rapidly cooled cells that contain intracellular ice are only injured during rewarming so their structure may be as yet unaltered by any damaging effects at low temperatures. Most cells able to recover on thawing are grossly shrunken at low temperatures but since they are potentially functional they are of interest structurally. These cryobiological principles are illustrated with freeze-fracture, freeze substitution and functional assays. The cell types chosen were Chlorella sp. and mammalian tissue culture cells.

Animals↗

PubMed1976

The cryopreservation of Chlorella. 2. Effect of growth temperature on freezing tolerance.

The temperature at which Chlorella 211/8h was grown determined the response to a subsequent stress of freezing to and thawing from-196 degrees C. Cells cultured at 20 degrees C were the most sensitive to freezing injury; at both higher and lower growth temperatures resistance to damage induced by freezing developed. At all culture temperatures examined the freezing tolerance varied with the age of culture.

Cell Membrane Permeability↗

PubMed1976

The cryopreservation of Chlorella. 1. Interactions of rate of cooling, protective additive and warming rate.

The cryoprotective additives glycerol and dimethylsulphoxide were found to be toxic to Chlorella cells at concentrations greater then 2.5% w/v. Polyvinylpyrrolidone, was not damaging up to a concentration of 15%w/v. Chlorella 211/7a had a recovery rate greater than 95% at all rates of cooling studied. With Chlorella 211/8h the survival was lower than 0.1% at all rates examined. The addition of dimethylsulphoxide (5% w/v) to Chlorella 211/8h increased the recovery, particularly at the faster rates of cooling; with polyvinylpyrrolidone (10% w/v) there was an optimum range of cooling rate. Cells of Chlorella 211/7a from the exponential phase of growth were found to be damaged both by a temperature reduction from 25 degrees C to 0 degrees C (thermal shock) and by freezing and thawing. In contrast cells from the stationary phase of growth were resistant to these stresses.

Cell Division↗

PubMed1976

Effect of growth temperature on the cryopreservation of prototheca.

The temperature at which Prototheca spp. were grown determined their response to freezing to -196 degrees C and subsequent thawing. Cells cultured at 35 degrees C were the most sensitive to freezing injury; at lower growth temperatures, resistance to freezing damage was seen. At all culture temperatures examined, the freezing tolerance varied with the age of the culture.

Eukaryota↗

PubMed1975