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

The effect of ions and ionophores on cystine egress from human leucocyte lysosome-rich granular fraction

This paper describes the stimulation of exodus of cystine from lysosome-rich granular fractions by potassium. Potassium permeability into lysosomes is low, but in the presence of an ionophore or permeable anion, the movement of K+ into lysosomes caused a large stimulation of cystine exodus. Lysosomal preparations from leucocytes of cystinotic patients, which lack carrier-mediated cystine transport, also manifested stimulation of cystine egress by valinomycin and K+. This suggests that potassium-dependent cystine egress involves a carrier different from that defective in cystinosis, or occurs through a non-carrier-mediated mechanism.

[Studies on lysine availability with Tetrahymena pyriformis as the test organism]

A series of experiments was performed to verify the suitability of the protozoon Tetrahymena pyriformis (T.P.) for determining the lysine availability of feeds. The multiplication rate was estimated with the aid of organism counting, turbidimetry and reduction of triphenyltetrazolium chloride. The volume of T.P. was calculated on the basis of length and breadth measurements, Within higher rates of multiplication, there was connected a tendency towards larger organism volumes. A comparison of the growth tests showed that only turbidimetry is able to reflect, under certain conditions, the efficiency of the test organism in protein synthesis. The values for lysine availability varied widely according to the kind and pretreatment of the feedstuff, but did in no case attain those obtained with animal experiments. T.P. is, therefore, scarcely suited as a test organism for determining the protein quality and amino-acid availability of feedstuffs.

Progesterone-induced lysis of rat kidney lysosomes as studied by changes in light-absorbance

1. A rat kidney lysosomal fraction was prepared by the method of Maunsbach (1966) and characterized by its content of representative marker enzymes for lysosomes, mitochondria, peroxisomes and endoplasmic reticulum. 2. It was shown that both pH-dependent and progesterone-induced lysis lead to a decrease in the E(520) of suspensions of this preparation. This decrease parallels quantitatively and temporally the release of soluble acid phosphatase. 3. It is suggested that E(520) measurements are a valid method for the continuous measurement of changes in lysosomal integrity. 4. As an example, results are included which demonstrate the ability of Zn(2+) to stabilize lysosomes against spontaneous and progesterone-induced lysis.