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Articles 10321 - 10327 of 10327
Full-Text Articles in Entire DC Network
The Fine Structure Of Haematolœchus Spermatozoan Tail, J. E. Shapiro, B. R. Hershenov, G. S. Tulloch
The Fine Structure Of Haematolœchus Spermatozoan Tail, J. E. Shapiro, B. R. Hershenov, G. S. Tulloch
Publications and Research
No abstract provided.
Egg Membrane Lytic Activity Of Sperm Extract And Its Significance In Relation To Sperm Entry In Hydroides Hexagonus (Annelida), Arthur L. Colwin, Laura Hunter Colwin
Egg Membrane Lytic Activity Of Sperm Extract And Its Significance In Relation To Sperm Entry In Hydroides Hexagonus (Annelida), Arthur L. Colwin, Laura Hunter Colwin
Publications and Research
Previous electron microscope studies indicated that the individual spermatozoön of Hydroides hexagonus forms a hole in the vitelline membrane by means of lysis. Other observations established that the hole is real, being visible in living material during sperm entry. During the present investigation sea water extracts from frozen-thawed sperm were tested for lytic effect on the membrane. In normal living eggs the membrane appears as a single thick envelope, but in electron micrographs of sections it is seen to consist of a narrow outer border layer, a wide principal or middle layer, and a narrow inner border layer. After immersion …
Formation Of Sperm Entry Holes In The Vitelline Membrane Of Hydroides Hexagonus (Annelida) And Evidence Of Their Lytic Origin, Laura Hunter Colwin, Arthur L. Colwin
Formation Of Sperm Entry Holes In The Vitelline Membrane Of Hydroides Hexagonus (Annelida) And Evidence Of Their Lytic Origin, Laura Hunter Colwin, Arthur L. Colwin
Publications and Research
Electron micrographs of inseminated eggs of Hydroides hexagonus previously had shown that in the immediate vicinity of the penetrating spermatozoön a small portion of the vitelline membrane regularly was absent, and it had been suggested that this area was a hole made by lytic activity of the individual spermatozoön during the course of its passage through the membrane. This deduction would receive support if it could be established that a sperm entry hole does form in living material. During the present study a hole repeatedly observed and photographed in the membrane of living eggs was found to arise as the …
The Effect Of Ions Upon The Response Of Smooth Muscle To Cooling, Rita Guttman, Samuel M. Ross
The Effect Of Ions Upon The Response Of Smooth Muscle To Cooling, Rita Guttman, Samuel M. Ross
Publications and Research
The slow tonic responses of the anterior byssus retractor of Mytilus edulis to rapid cooling were investigated by simultaneously recording tension and resting potential changes after soaking the muscle in banthine, a powerful neuromuscular blocking agent. The quantitative relations between the amount of cooling and the amount of associated depolarization necessary for contraction at various concentrations of potentiating potassium can be expressed in a family of curves. The plateaus of the curves for sea water and for potassium-free sea water were beneath the depolarization value necessary for contraction, so that it is clear that no amount of cooling with sea …
Electron Microscope Studies Of Early Stages Of Sperm Penetration In Hydroides Hexagonus (Annelida) And Saccoglossus Kowalevskii (Enteropneusta), Arthur L. Colwin, Laura Hunter Colwin, Delbert E. Philpott
Electron Microscope Studies Of Early Stages Of Sperm Penetration In Hydroides Hexagonus (Annelida) And Saccoglossus Kowalevskii (Enteropneusta), Arthur L. Colwin, Laura Hunter Colwin, Delbert E. Philpott
Publications and Research
1. The early events of sperm entry in Saccoglossus and Hydroides are described and examined in relation to present knowledge of the acrosome reaction and of egg membrane lysins. In Saccoglossus and several other species these events occur in two phases. First. The acrosome filament of the spermatozoön spans the egg membrane barriers, reaches the reactive egg protoplasm, and causes the egg to begin its fertilization reaction. Second. The filament and its connected sperm head move through the egg membrane barriers and enter the egg proper. The first phase is completed in a matter of seconds but the second phase …
Life Insurance?, William (Bill) H. Williams
Life Insurance?, William (Bill) H. Williams
Publications and Research
Should a student buy whole life insurance or term insurance?
Action Of Potassium And Narcotics On Rectification In Nerve And Muscle, Rita Guttman
Action Of Potassium And Narcotics On Rectification In Nerve And Muscle, Rita Guttman
Publications and Research
Electrical rectification was demonstrated in whole sartorius muscle and sciatic nerve of Rana pipiens and also in the single giant nerve fiber of the northern squid, Ommastrephes illecibrossus. It is probably a property of the plasma membrane. Rectification decreases reversibly under the influence of increased concentrations of the potassium ion and with chloroform, veratrine sulfate and isoamyl carbamate. No effect was found with lack of calcium, excess calcium, or barium chloride. Decrease in rectification is invariably accompanied by simultaneous decrease in resting potential. A proposed explanation of the mechanism of rectification is discussed. Rectification in a living membrane, viz. a …