Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ANNELIDA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed1965

ERYTHROCRUORIN OF MARPHYSA SANGUINEA.

1. The polychaete worm Marphysa sanguinea has a circulating erythrocruorin of mol.wt. about 2.4x10(6) (S(0) (20,w) 58.2s, D(20,w) 2.06x10(-7) cm.(2)/sec). This is the predominant form existing at pH 6-8 and (non-protein) I 0.10-0.21, and also at approx. pH 6.7 and I 0.15-3.00. 2. The pigment contains 2.24% of protohaem. 3. The 58s protein has an electrophoretic mobility of 8.08x10(-5) cm.(2)/v/sec. at pH 8.12, I 0.21 and 0 degrees . The isoelectric point of suspended particles is 4.63 at I 0.16 and 21.5 degrees . 4. At very low ionic strength and pH 6.7 (unbuffered) the 58s pigment associates reversibly to 97s and 150s forms, which are probably dimer and tetramer species. 5. At pH 10.0 and I 0.025, it dissociates irreversibly to give a small amount of 2-4s non-haem-containing protein and much 9s haem-enriched protein. These and the 58s pigment may correspond to structures found in Levin's (1963) electron-microscope studies of other erythrocruorins. 6. Absorption spectra of the 58s oxygenated erythrocruorin and the deoxygenated and carbon monoxide derivatives have been obtained.

Animals↗
PubMed1963

SOLUBLE EARTHWORM CUTICLE COLLAGEN: A POSSIBLE DIMER OF TROPOCOLLAGEN.

When soluble earthworm cuticle collagen molecules are subjected to the shearing forces of a flow birefringence instrument, they are broken into particles approximately half the original size. The broken particles resemble vertebrate tropocollagen molecules in their hydrodynamic properties, in levorotatory powers, and in their appearance in the electron microscope. Most significantly, the broken earthworm particles form ordered aggregates similar to the segmented-long-spacing aggregations formed by vertebrate tropocollagen. These phenomena are explained by the suggestion that earthworm collagen molecules are dimers of tropocollagen-like particles. On this basis, an explanation is presented for the lack of striations in the gross collagen fibrils of earthworm cuticle.

Animals↗
PubMed1963

ROLE OF THE GAMETE MEMBRANES IN FERTILIZATION IN SACCOGLOSSUS KOWALEVSKII (ENTEROPNEUSTA). I. THE ACROSOMAL REGION AND ITS CHANGES IN EARLY STAGES OF FERTILIZATION.

Previous electron microscope studies of sperm-egg association in the annelid Hydroides revealed novel aspects with respect to the acrosomal region. To determine whether these aspects were unique, a comparable study was made of a species belonging to a widely separated phylum, Hemichordata. Osmium tetroxide-fixed polyspermic material of the enteropneust, Saccoglossus, was used. The acrosomal region includes the membrane-bounded acrosome, with its large acrosomal granule and shallow adnuclear invagination, and the periacrosomal material which surrounds the acrosome except at the apex; here, the acrosomal membrane lies very close to the enclosing sperm plasma membrane. After reaching the egg envelope, the spermatozoon is activated and undergoes a series of changes: the apex dehisces and around the resulting orifice the acrosomal and sperm plasma membranes form a continuous mosaic membrane. The acrosomal granule disappears. Within 7 seconds the invagination becomes the acrosomal tubule, spans the egg envelopes, and meets the egg plasma membrane. The rest of the acrosomal vesicle everts. The periacrosomal mass changes profoundly: part becomes a fibrous core (possibly equivalent to a perforatorium); part remains as a peripheral ring. The basic pattern of structure and sperm-egg association in Saccoglossus is the same as in Hydroides. Previous evidence from four other phyla as interpreted here also indicates conformity to this pattern. The major role of the acrosome is apparently to deliver the sperm plasma membrane to the egg plasma membrane.

Animals↗
PubMed1964

A STUDY OF THE STRUCTURE AND DISTRIBUTION OF THE NEXUS.

Nexuses, that is, fusions of plasma membranes of adjacent cells, are described in mammalian smooth and cardiac muscle, median giant axon of earthworm, frog skin, and rat submandibular gland. In smooth muscle they usually occur where a process from one cell either meets a process of, or projects into a neighboring cell. On the other hand, in mammalian heart muscle and in earthworm giant axon the nexuses occur along the intercalated disc and intercellular segmental septa, respectively. Their occurrence between these excitable cells is correlated with propagation of action potentials by an electrical rather than chemical mechanism. Since the nexuses may offer pathways for electric current between cell interiors, it seems possible that they constitute a link in the structural basis for electrical transmission in these systems. In epithelia, nexuses usually appear as part of a terminal bar complex. This is true in the rat salivary gland studied here. In the epidermis of frog skin, nexuses are less numerous between the basilar columnar cells than between the subjacent squamous cells. The nexuses which occur in epithelia in frog skin and rat salivary gland are distributed as though to provide seals against electrochemical backleaks and sites of chemical exchange between cell interiors.

Animals↗
PubMed1965

THE ACROSOME REACTION IN MYTILUS EDULIS. I. FINE STRUCTURE OF THE INTACT ACROSOME.

The intact acrosome of the Mytilus edulis spermatozoon consists of a conical vesicle, the basal side of which is deeply invaginated so that the whole vesicle forms a sheath around a very slender axial rod, about 2.7 micro long, inserted in a tube passing through the nucleus. The annular base of the acrosomal vesical is filled with a homogeneous substance; the outer wall of the vesicle is lined with a somewhat irregular layer of a particulate substance interspersed with very fine tubular elements, and its lumen is nearly filled by a strand of material which extends from the inner tip of the invagination to the apex of the acrosome. The lumen of the invagination appears empty except for the rod and a delicate sleeve-like structure which surrounds it. The plasma membrane of the sperm cell lies in immediate contact with the acrosomal membrane over its whole outer surface. In its general organization, this molluscan acrosome shows a rather close homology with that of the annelid Hydroides.

Acrosome↗