Globule Complex Research Articles

Fragmentation of Globules in HiiRegions:Hubble Space TelescopeImages of Thackeray's Globules

We present Hubble Space Telescope WFPC2 images through an Hα filter of Thackeray's globules in the southern H II region IC 2944. The images document the state of the globule complex during its current highly dynamical phase of breakup. A population of very small and short-lived splinters suggests that continuous fragmentation must play an important role in increasing the surface-to-mass ratio of the neutral gas, thus accelerating the processes of photoevaporation and photoablation. We are not able to single out which of various theoretical mechanisms for breakup is operating in the globule complex.

THALASSOCHYTRIUM GRACILARIOPSIDIS (CHYTRIDIOMYCOTA), GEN. ET SP. NOV., ENDOSYMBIOTIC IN GRACILARIOPSIS SP. (RHODOPHYCEAE)

Thalassochytrium gracilariopsidis gen. et sp. nov. is an endosymbiotic, polycentric, zoosporic fungus that infected cultures of the red alga Gracilariopsis sp. Based on the posteriorly uniflagellate zoospore and the platelike cristae of the mitochondria, the fungus is placed in the Chytridiomycota. Ultrastructurally, the fungal zoospore is distinguished by the anterior position of the kinetosome, a unique microbody‐lipid globule complex, an electron‐opaque helix associated with the kinetosome and lipid globules, and a beaked nucleus. Zoospores are positively phototactic, and the unusual helix might constitute part of the photosensory apparatus. Zoospores lack certain taxonomically important structures, such as a rumposome, props, a nonflagellated kinetosome, and flagellar roots. The organism does not fit into any described genus, and the features of its zoospore differ from those of any described order. The fungal thallus is polycentric with multinucleate, septate hyphae. Haustoria form within the algal cells. The fungus does not appear to cause major harm to its host and seems to be host specific. However, during intense sporulation of the fungus, degradation of host chloroplasts was observed in medullary cells.

ZOOSPORE STRUCTURE OF THE MYCOPARASITIC CHYTRID CAULOCHYTRIUM PROTOSTELIOIDES OLIVE

The subcellular organization of zoospores released from sessile, parasitic sporangia of Caulochytrium protostelioides was studied with light and electron microscopy. A single flagellum is posteriorly directed but laterally inserted into the cylindrical motile zoospore. A striated rhizoplast attaches the proximal end of the kinetosome to a specialized region of the nuclear envelope. A system of rough endoplasmic reticulum, smooth endoplasmic reticulum, dictyosomes and bristle‐coated vesicles are associated with the one to several pulsating vacuoles typically located near the flagellar apparatus. The microbody‐lipid globule complex (MLC) comprises one to many lipid globules. An extensive microbody branches around each lipid globule and encloses a portion of the rhizoplast. A reticulum of smooth surfaced cisternae interdigitates among the branches of the complex microbody, and cisternae are opposed to the surface of lipid globules opposite the microbodies. Mitochondria with predominantly circular profiles are scattered throughout the zoospore body, but several are always adjacent to the microbody, and hence, are also part of the MLC. Ribosomes are uniformly distributed throughout the zoospore, and one to several cisternae of rough endoplasmic reticulum are adjacent to the nuclear envelope. Zoospores of C. protostelioides are similar to several other chytrid zoospores, which also have the same type of microbody‐lipid globule complex, but yet are structurally distinct from any other chytrid zoospore.

H I self-absorption in the Southern Coalsack dust complex

view Abstract Citations (18) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H I self-absorption in the Southern Coalsack dust complex. Bowers, P. F. ; Kerr, F. J. ; Hawarden, T. G. Abstract A search for H I self-absorption features toward 23 globules or dark regions in the Southern Coalsack dust complex has resulted in the detection of a cold H I cloud surrounding three globules. The H I distribution is less clumpy and more extended than the OH and H2CO distributions associated with the globule complex, but it generally agrees with the dust distribution except at the positions of the globules. There is no evidence that the H I distribution is strongly peaked at the positions of the globules; rather, the globules appear to be embedded in the relatively uniform density H I cloud. At the position of one of the globules (globule 2) where sufficient data exist for comparison, the H I, OH, H2CO, and CO velocities agree to within their relative uncertainties. Elsewhere there appears to be a velocity gradient observable for H I but not for OH; the difference between these velocity distributions is not understood. Publication: The Astrophysical Journal Pub Date: October 1980 DOI: 10.1086/158330 Bibcode: 1980ApJ...241..183B Keywords: Cosmic Dust; Hydrogen Clouds; Radio Sources (Astronomy); Self Absorption; Astronomical Catalogs; Astronomical Maps; Centimeter Waves; Optical Thickness; Velocity Distribution; Astrophysics; Globules:Neutral Hydrogen full text sources ADS |