Electron Microscopic Localization of ATPase Activity in the Cytopharyngeal Basket of the Ciliate Pseudomicrothorax dubius

The cytopharyngeal basket of Pseudomicrothorax dubius is used to ingest filamentous blue-green algae. The basket has three main components: a sheath of microfilaments, bundles of microtubules (the nemadesmata), and ribbons of microtubules. The ribbons of microtubules (nemadesmal lamellae) are adpressed to the food vacuole during ingestion. Cytochemical techniques show that both the lamellae and the microfilamentous sheath possess ATPase activity, but the reaction product appears under different conditions in the two cases. The presence of ATPase activity within the microtubular lattices of the feeding organelle suggests the capacity for active motility. Consequently the basket seems to have two motile systems, one may be used to constrict and dilate the cytopharynx while the other is used in the inward propulsion of the forming food vacuole.     

Commons + Borderlands: Working Papers on Interdisciplinarity, Accountability and the Flow of Knowledge

Commons + Borderlands: Working Papers on Interdisciplinarity, Accountability and the Flow of Knowledge . Marilyn Strathern. Wantage, Oxfordshire: Sean Kingston Publishing, 2004. 102 pp.     

Fence-Line Contact Between Wild and Farmed Cervids in Colorado: Potential for Disease Transmission

Abstract: Direct and indirect contact between wild and farmed cervids along perimeter fences may play a role in transmission of diseases like chronic wasting disease (CWD), but no studies have quantified such interactions. At 9 high-fenced commercial elk (Cervus elaphus) farms in Colorado, USA, during October 2003 to January 2005, we used animal-activated video to estimate rates of fence-line use by wild cervids, rates of direct contact between farmed and wild cervids, and probability of direct contact when wild cervids were present. We recorded 8-fold-more wild elk per unit time than mule deer (Odocoileus hemionus) at fence lines. Depending on site, we recorded 0.66 to 46.90 wild elk per 1,000 hours of camera monitoring. We documented 77 interactions between wild and farmed elk involving naso-oral contact and no contact between wild mule deer and farmed elk. Rate of direct contact ranged from 0.00 to 1.92 direct contacts per 1,000 hours of camera monitoring among sites. Given recorded presence of wild elk, estimated probability of observing direct contact during a 2-minute video recording ranged from 0.00 to 0.11 among sites. Risk of direct contact was about 3.5 times greater for single woven-wire fence compared with offset electric fence attached to a single woven-wire fence. We observed no direct contact through double woven-wire fences. Because little is currently known about infection rates associated with infection mechanisms, we cannot infer a level of CWD infection risk from our results, but some form of double fencing should reduce potential for direct and indirect transmission of disease into or out of elk farms.     

Transmission Electron Microscopical Observations on Stomatogenesis during Metamorphosis of Eufolliculina uhligi (Ciliophora: Heterotrichida)1

Stomatogenesis during metamorphosis of the marine loricate ciliate, Eufolliculina uhligi, was observed by transmission electron microscopy. Kinetosome proliferation in the stomatogenic territory leads to the formation of an anarchic field. This separates into the left adoral and the right paroral primordia. Both primordia consist of pairs of kinetosomes. One kinetosome of a pair is associated with one transverse and two postciliary microtubules; the other has one transverse microtubule. The postciliary microtubules of the adoral kinetosomes become divergent; those of the paroral kinetosomes become convergent. The adoral kinetosomes arrange in promembranelles. Then a third row of kinetosomes is produced anteriorly to each promembranelle. This third row is short at the peristome but longer in the buccal area. The paroral kinetosomes form a stichodyad. The buccal part of the paroral primordium is resorbed during formation of the buccal cavity. Stomatogenesis ends with the development of a functioning cytostome. During this process, the postciliary microtubules of the buccal adoral membranelles elongate and become associated with cytopharyngeal vesicles. Fusion of these vesicles with the cytostome has been observed some time after the completion of the oral structures.     

The Nuclear Apparatus of the Ditransversal Ciliate Homalozoon Vermiculare (Ciliophora, Rhabdophora) During Interphase and Division Ii. the Micronuclei and Some Observations On Conjugation

ABSTRACT. The nuclear apparatus of H. vermiculare consists of a single moniliform macronucleus and about 25 micronuclei. the micronuclei are about 3 μm in diameter and characterized by a meshwork of thick condensed chromatin. Mitosis is intranuclear and acentric as in all other ciliates. In metaphase, interpolar and chromosomal microtubules are abundant and the length of the micronuclei increases to about 5 μm. In late anaphase, interzonal microtubules become prominent and the spindle elongates to about 50 μ. In meta- and anaphase, the microtubules of the spindle are attached to the polar vesicles, and in anaphase, chromosomes become attached to it. In contrast to most other eukaryotes, micronuclear mitosis is not strictly bound to cell division in H. vermiculare. While most of the micronuclei divide prior to cytokinesis, others retain their interphasic shape or degenerate. In addition, some micronuclei divide in the interdivision period, i.e. between two successive divisions of the cell and macronucleus. Mating cells of H. vermiculare become joined to each other in the cilia-free region covering the cytostome. In the course of conjugation, the cell membranes and the underlying oral filamentous sheaths of both cells fuse, thus uniting the endoplasm of both cells in the mouth region. Synaptonemal complexes in the meiotic chromosomes are more distinct in H. vermiculare than in most other dilates. the micrographs presented here depict dearly the central filament, transverse elements, and other substructures.