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PubMed1992

Subcellular fractionation of the two organelle DNAs of malaria parasites.

Malaria parasites contain two extrachromosomal DNAs, a 6 kb repetitive linear molecule which is assigned on the basis of its genetic content to the mitochondria, and a 35 kb transcriptionally active circular molecule whose intracellular location is not known. We used the polymerase chain reaction to detect and estimate the numbers of both molecules in sub-cellular fractions derived from the rodent parasite Plasmodium yoelii. The two DNA molecules were not coordinately partitioned by the fractionation process, the 6 kb molecule being more abundant, relative to the 35 kb circle, in a fraction enriched for mitochondria, the converse being true for a less dense fraction of unknown identity. This implies that the two molecules are located in different cellular compartments, and is consistent with other evidence suggesting they have different evolutionary origins.

Animals↗
PubMed1980

Effects of the ionophores X537A and A23187 on GABA, glycine, and taurine release from chick retinal subcellular fractions.

The ionophore X537A at concentrations of 5--20 microM stimulated the release of [3H]GABA and [35S]taurine from retinal subcellular crude nuclear (P1) and crude synaptosomal (P2) fractions. The release of [3H]GABA increased 114% and 136% over control values in P1 and P2 fractions, respectively. The efflux of [35S]taurine from P1 was increased by 45% and that from P2 by 21%. X537A increased 45Ca2+ uptake in the P2 fraction but not in the P1 fraction. The effect of X537A on the amino acid release was not dependent on the presence of exogenous calcium. X537A did not affect [3H]GABA or [35S]taurine uptake by the retinal fractions. A23187 enhanced [3H]GABA release from P1 and P2 by 52% and 105%, respectively. The ionophore also increased [14C]glycine liberation in both P1 (35%) and P2 (50%) but failed to stimulate [35S]taurine release. A23187 produced a transient increase of 45Ca2+ uptake of 38% in P1 and 30% in P2. The effects of A23187 on the release of amino acids were calcium dependent. The amino acid uptake was not affected by the ionophore. These results are consistent with the suggested neurotransmitter role for GABA at the outer synaptic layer and for GABA and glycine at the inner synaptic layer of the retina. A neurotransmitter role for taurine is not supported by the present results.

Animals↗
PubMed1985

Subcellular fractionation of a hypercellulolytic mutant, Trichoderma reesei Rut-C30: localization of endoglucanase in microsomal fraction.

The growing mycelia of Trichoderma reesei Rut-C30 are richly endowed with endoplasmic reticula and a variety of pleomorphic subcellular bodies. Mycelia of the culture growing in presence of avicel pH101 was fractionated in sucrose density gradients, and several morphologically and biochemically distinct fractions were isolated. Mycelia were homogenized in a Bead Beater, and the homogenate was freed of nucleus and wall fragments by low-speed centrifugation before fractionation. Organelle-free cytosol, which did not penetrate the gradient, contained (of the total) 72% of the vanadate-sensitive ATPase, 26% of carboxymethyl cellulase (CMCase), 2% of cytochrome c reductase, and 13% of the protein. Significant fractions separated on a gradient were light vesicles containing heavily stained material inside and ribosomes attached to the outside surface, intact vesicles resembling condensing vacuoles, large vesicles derived from the plasma membrane, and heavy vesicles containing crystalline material. The light-vesicle fraction contained a large portion of the cell-bound CMCase activity. The particle-bound ATPase and cytochrome c reductase activities were concentrated in heavy fractions. The fractionation in the presence of MgCl2 improved the preservation of subcellular bodies derived from the endoplasmic reticula. Although the CMCase activity of the light-vesicle fraction was 4 times higher than the activity in the heavy-vesicle fraction, the CMCase antibody-binding capacities of both fractions were about the same. This discrepancy between the catalytic activity and the antibody-binding capacity suggests that the heavy vesicles might have contained considerable amount of inactive CMCase compared with that present in the light vesicles.

Cell Fractionation↗