Evidence for a functional membrane barrier in the transition zone between the flagellum and cell body of Chlamydomonas eugametos gametes.

Evidence is presented which supports the concept of a functional membrane barrier in the transition zone at the base of each flagellum of Chlamydomonas eugametos gametes. This makes it unlikely that agglutination factors present on the surface of the cell body can diffuse or be transported to the flagellar membrane. The evidence is as follows: 1) The glycoprotein composition of the flagellar membrane is very different to that of the cell-body plasma membrane. 2) The flagella of gametes treated with cycloheximide, tunicamycin or α, α'-dipyridyl become non-agglutinable but the source of agglutination factors on the cell body is not affected. 3) Even under natural conditions when the flagella are non-agglutinable, for example in vis-à-vis pairs or in appropriate cell strains that are non-agglutinable in the dark, the cell bodies maintain the normal complement of active agglutinins. 4) When flagella of living cells are labeled with antibodies bound to fluorescein, the label does not diffuse onto the cell-body surface. 5) When gametes fuse to form vis-à-vis pairs, the original mating-type-specific antigenicity of each cell body is slowly lost (probably due to the antigens diffusing over both cell bodies), while the specific antigenicity of the flagellar surface is maintained. Even when the flagella of vis-à-vis pairs are regenerated from cell bodies with mixed antigenicity, the antigenicity of the flagella remains matingtype-specific. 6) Evidence is presented for the existence of a pool of agglutination factors within the cell bodies but not on the outer surface of the cells.

Ca2+ transport in erythrocytes from patients with Duchenne muscular dystrophy.

Erythrocyte membranes, isolated after step-wise hemolysis in buffered sucrose (Tris-sucrose membranes), showed higher Ca2+ Mg2+-ATPase activity than erythrocyte membranes obtained after hemolysis in Tris-HCl, and washing in EDTA (Tris-EDTA membranes). In Tris-sucrose membranes, the activity was not stimulated by the addition of monovalent cations, or calmodulin. Differences reported for the activity and properties of Ca2+ Mg2+-ATPase between Tris-EDTA membranes of Duchenne patients and controls, were not found in Tris-sucrose membranes. Also the activity and properties of the Ca2+-pump in resealed erythrocyte membranes were not changed.

Agglutination factor in the cell body of Chlamydomonas eugametos.

Chlamydomonas eugametos gametes agglutinate via the surfaces of their flagella. The mating-type minus (mt (-)) agglutination factor is a high-molecular-weight glycoprotein called PAS-1.2, present on the exterior surface of the flagellar membrane. During flagellar regeneration, mt (-) gametes were able to agglutinate as soon as the flagella protruded as short stumps. This was also observed when protein synthesis was blocked, indicating that gametes possess a pool of PAS-1.2. When the exterior surface of flagella-less gametes was extracted and the proteins were subjected to gel electrophoresis, large quantities of PAS-1.2 were detected. Using anti-PAS-1.2 serum, the presence of PAS-1.2-like material was visualized on the plasma membrane of mt (-) gamete cell bodies. By assaying the biological activity of extracts of the cell bodies and of isolated flagella, it was calculated that the plasma membrane of the cell bodies contains 25 times the activity present in the flagella and could, therefore, represent a large pool of mt (-) agglutination factor.

RNA synthesis in isolated yeast mitochondria.

Isolated yeast mitochondria incorporate added UTP into RNA. Amongst the products formed are the two rRNAs, 4S RNA and several components presumed to be mRNAs. In omega+ strains (containing an intervening sequence in the 21S rRNA gene) besides mature 21S rRNA a transcript could be detected still containing nucleotide sequences transcribed from this intervening sequence. In omega- strains (not containing this intervening sequence) also a longer form of the 21S rRNA could be observed. These results suggest that isolated yeast mitochondria are capable of carrying out RNA synthesis and processing, including splicing.