Donald Lee

The effect of dimethylsulphoxide on the permeability of the lysosomal membrane

Abstract The latency of acid phosphatase in sucrose homogenates of rat liver and Tetrahymena pyriformis was found to decrease progressively on exposure to concentrations of dimethylsulphoxide between 5 and 25% (v/v). A progressive decrease in latency was also found in homogenates of rat liver prepared with potassium gluconate although, in this instance, the extent of the decrease was much less than with homogenates prepared in sucrose. With homogenates of rat liver prepared in s-glycerophosphate, dimethylsulphoxide in concentrations up to 10% had little effect on the latency of acid phosphatase, although it decreased on exposure to higher concentrations.

The Effect of Temperature on the Synthesis of Rhinovirus Type 2 RNA

The reduced yields of rhinovirus type 2 at temperatures above 37 degrees C were shown to result from the degradation of virus-induced RNA, leaving little RNA available for inclusion into mature infectious virions. The degradation occurred about 6 h p.i., and appeared to be selectively effecting the single-stranded species. Lysosomal nucleases do not appear to have a role in this supra-optimal degradation.

The relative permeability of lysosomes from Tetrahymena pyriformis to carbohydrates, lactate and the cryoprotective nonelectrolytes glycerol and dimethylsulphoxide

Lysosomes in homogenates of Tetrahymena pyriformis have been shown to be permeable to the cryoprotective nonelectrolytes glycerol and dimethylsulphoxide, to the hexoses glucose, galactose and α-methylglucose and to the hexitols mannitol, sorbitol and inositol. They are impermeable to the disaccharides sucrose, maltose and melibiose and to the trisaccharide raffinose. The presence of a charge group has a great influence on permeability, the lysosomes being impermeable to the gluconate and glucuronate anions and only slightly permeable to the lactate anion and the glucosaminium cation.

Effect of increasing concentrations of salt on the lysosomes of rat liver and Tetrrahymena pyriformis

Abstract When cells are cooled below their freezing point there will be an increase in the concentration of solutes surrounding the subcellular organelles and, for that reason, we have studied the effect of different concentrations of a model solute, KCl, on the lysosomes of rat liver and Tetrahymena pyriformis . The latency of acid phosphatase and β-glucuronidase in homogenates of rat liver fell progressively after exposure to increasing concentrations of KCl and, although the sedimentable acid phosphatase also declined, the decrease was less marked. After exposure of homogenates of T. pyriformis to increasing concentrations of KCl, there was no decrease in the sedimentability of acid phosphatase although a progressive decline in the latency of the enzyme was demonstrated. The rat liver lysosomal membrane was shown to be only slighly permeable to KCl although the lysosomes of T. pyriformis were much more permeable to this salt. It seems possible that the disruptive effect of high concentrations of KCl is due to transiet osmotic pressure gradients which may arise when the concentration is reduced by dilution.

The relative permeability of lysosomes from Tetrahymena pyriformis to some amino acids and dipeptides.

Abstract It has been shown that lysosomes in homogenates of Tetrahymena pyriformis are permeable to the amino acids glycine, l -alanine, d -alanine and l -valine (probably by means of a simple diffusion process). These lysosomes are impermeable to the dipeptides glycylglycine, glycyl- l -alanine, l -alanylglycine, l -valyl- l -leucine and l -leucylglycine although they are permeable to glycyl- l -leucine. The reason for the behaviour of glycylleucine is not understood.

The effect of glycerol, ethanol and dimethylsulphoxide on rat liver lysosomes

Abstract Homogenates of rat liver prepared in either sucrose or β-glycerophosphate were exposed, for 30 min at 0°, to concentrations of glycerol between 5 and 28 % (v/v). After this treatment, and in spite of the fact that the concentration of sucrose or β-glycerophosphate was always maintained at 0.25 M, the latency of β-glucuronidase was shown to have fallen progressively as the concentration of glycerol increased. The latency of this enzyme also decreased when homogenates prepared in sucrose were exposed to increasing concentrations of dimethylsulphoxide. However, when the homogenates were prepared in β-glycerophosphate, the latency of β-glucuronidase showed only a slight fall on exposure to 10 % dimethylsulphoxide but a progressive decrease at higher concentrations. On exposure to concentrations of ethanol between 5 and 25 % (v/v), the latency of β-glucuronidase did not decrease until the concentration of ethanol was greater than about 15 %. The rat liver lysosomal membrane was found to be freely permeable to dimethylsulphoxide and ethanol. However, glycerol penetrated the membrane much less readily and it is possible that rat liver lysosomes are disrupted after exposure to glycerol as a result of the transient osmotic pressure gradients which occur when the concentration of glycerol outside the lysosomes is reduced.

Studies on the lysosomes of L132 cells infected with either rhinovirus type 2 or poliovirus type 1.

Summary Samples taken from either rhinovirus- or poliovirus-infected suspensions of L132 cells at various times during the growth cycle were assayed for intra- and extracellular virus infectivity, trypan blue uptake and release of acid phosphatase from lysosomes. At similar times infected L132 cell monolayers were observed for cell rounding (virus c.p.e.). At 16 h after infection with rhinovirus 2, cells showed no change in the distribution of acid phosphatase activity but had undergone extreme cytopathogenic changes; at this time 99% of the virus was intracellular and few cells took up trypan blue. Poliovirus-infected cells showed no change in the distribution of acid phosphatase at 6 h after infection when cytopathogenic changes were extreme, but 2 h later when cells began to take up trypan blue and release virus, acid phosphatase was released from the lysosomes. It is suggested that lysosomal enzymes have no role in the induction of virus c.p.e. but are involved at a later stage of degeneration of the cell.