Kinds Of Organelles Research Articles

Structure and mode of function of the organelles associated with nutrition of the macrogametes of Eimeria acervulina.

The macrogamete of Eimeria acervulina, lay and developed within the host cell in a parasitophorous vacuole. The cytoplasmic membrane of the host cell bordering the vacuole was not smooth, but it had numerous folds extending into the vacuole. These "intravacuolar folds" varied in depth and number in different sections. In some, the majority of the folds were disconnected from the host cell. Once disconnected, they evidently disintegrated forming the amorphous, particulate material present in the parasitophorous vacuole. The pellicle of the young macrogamete consisted of a single unit membrane with an osmiophilic material representing the second membrane. Two unit membranes were apparent at a later stage of development when the wall-forming bodies had been formed and amylopectin granules deposited. Two kinds of organelles were present on the surface of the macrogamete, typical micropores and invaginations of the pellicle. The micropores arose from an invagination of the outer membrane, which continued through the invagination without interruption. Irrespective of whether an inner membrane was present in the pellicle or not, a thickened cylindrical wall around the inner portion of the invagination was always present. Micropores appeared in large numbers in both micro- and macrogametocytes. As many as three micropores were seen in a surface area of 2 mu2. Invaginations arose in a similar manner by infolding of the pellicle. They differed from micropores in that the thickened cylindrical wall present around the inner portion of the micropore was absent, and also in that invaginations had no uniform appearance. They were of varying shapes, and lengths, varying from very short V-shaped to long and narrow. Micropores and invaginations take in nutrients in the form of particulate matter present in the parasitophorous vacuole, this material having been derived from the host-cell membranous "intravacuolar folds". The micropores function as cytostomes and the invaginations take in material by means of pinocytosis. Large numbers of intravacuolar tubules were seen at the surface of the macrogamete. They were present only at certain areas of the macrogamete and in groups and were connecting the parasite with the host cell. They were about 80-110 nm in diameter, and were seen to attain a length of up to 6 mu. Evidence was obtained indicating that the tubules transport free ribosomes from the host cell to the parasite. The ribosomes were seen to accumulate in "pockets" within the cytoplasm of the host cell, at the area where the tubules were connected.

An ultrastructural analysis of fertilization in the surf clam, Spisula solidissima. I. Polar body formation and development of the female pronucleus

Breakdown of the germinal vesicle in inseminated eggs of the surf clam, Spisula solidissima, consists of a vesiculation of its nuclear envelope and the condensation of its chromatin. Adjacent to the disrupting germinal vesicle, two asters develop, move to either side of the chromosomes, and form the first meiotic apparatus. The meiotic apparatus moves to one side of the zygote so that one aster is located at the cortex (peripheral aster) while the other is situated medially (inner aster). At anaphase the dyads separate and those that are attached to the peripheral aster move into a cytoplasmic protrusion, which will become the first polar body. Subsequently, the chromosomes remaining in the zygote are realigned on the metaphase plate of the second meiotic apparatus. Other than its chromatin content, the second meiotic apparatus appears to be morphologically equivalent to the first. The second polar body is formed in a manner similar to that observed in the production of the first; however, the second remains attached to the zygote via a cytoplasmic bridge at least until the time of the first cleavage. Both polar bodies appear to contain the same number and kinds of organelles and inclusions, although only the second polar body has its chromatin limited by a nuclear envelope. The maternal chromatin remaining in the zygote after the formation of the second polar body is reorganized into chromosome containing vesicles which later fuse and form the female pronucleus.

Cytochemical localization of catalase activity in yeast peroxisomes.

Diaminobenzidine oxidation product occurred in peroxisomes and in the intracristate spaces of mitochondria. The reaction was inhibited only in peroxisomes when 3-amino-1,2,4-triazole was present, but cyanide and azide inhibited deposition in both kinds of organelles.