Time Course of Task Effects in the Processing of An Irrelevant Auditory Change: Electrophysiological Evidence

The physiological, biochemical, and ultrastructural aspects of the symbiotic relationship between the Chlorella-like algae and the hydra have been intensively investigated. Reciprocal cross-transfer of the Chlorellalike algae between different strains of green hydra provide a system for the study of cell recognition. However, our attempts to culture the algae free of the host hydra of the Florida strain, Hydra viridis, have been consistently unsuccessful. We were, therefore, prompted to examine the isolated algae at the ultrastructural level on a time course.

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Destruction of Actin Filaments by Osmium Tetroxide

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079772 ◽

1977 ◽

Vol 35 ◽

pp. 466-467

Author(s):

P. Maupin-Szamier ◽

T. D. Pollard

Keyword(s):

Actin Filaments ◽

Time Course ◽

Osmium Tetroxide ◽

Rabbit Muscle ◽

Muscle Actin ◽

Sodium Phosphate Buffer ◽

Transmission Electron ◽

The Difference ◽

Rates Of Decay ◽

Short Time

We have studied the destruction of rabbit muscle actin filaments by osmium tetroxide (OSO4) to develop methods which will preserve the structure of actin filaments during preparation for transmission electron microscopy.Negatively stained F-actin, which appears as smooth, gently curved filaments in control samples (Fig. 1a), acquire an angular, distorted profile and break into progressively shorter pieces after exposure to OSO4 (Fig. 1b,c). We followed the time course of the reaction with viscometry since it is a simple, quantitative method to assess filament integrity. The difference in rates of decay in viscosity of polymerized actin solutions after the addition of four concentrations of OSO4 is illustrated in Fig. 2. Viscometry indicated that the rate of actin filament destruction is also dependent upon temperature, buffer type, buffer concentration, and pH, and requires the continued presence of OSO4. The conditions most favorable to filament preservation are fixation in a low concentration of OSO4 for a short time at 0°C in 100mM sodium phosphate buffer, pH 6.0.

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The time course of calcium deposition in shells of the barnacle (Balanus amphititre amphititre) during cyprid-juvenile metamorphosis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168621 ◽

1994 ◽

Vol 52 ◽

pp. 178-179

Author(s):

Nancy R. Wallace ◽

Craig C. Freudenrich ◽

Karl Wilbur ◽

Peter Ingram ◽

Ann LeFurgey

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Time Course ◽

Vertical Plane ◽

Mantle Cavity ◽

Qualitative Assessment ◽

Calcium Deposition ◽

Free Swimming ◽

Freeze Dried ◽

Scanning Electron

The morphology of balanomorph barnacles during metamorphosis from the cyprid larval stage to the juvenile has been examined by light microscopy and scanning electron microscopy (SEM). The free-swimming cyprid attaches to a substrate, rotates 90° in the vertical plane, molts, and assumes the adult shape. The resulting metamorph is clad in soft cuticle and has an adult-like appearance with a mantle cavity, thorax with cirri, and incipient shell plates. At some time during the development from cyprid to juvenile, the barnacle begins to mineralize its shell, but it is not known whether calcification occurs before, during, or after ecdysis. To examine this issue, electron probe x-ray microanalysis (EPXMA) was used to detect calcium in cyprids and juveniles at various times during metamorphosis.Laboratory-raised, free-swimming cyprid larvae were allowed to settle on plastic coverslips in culture dishes of seawater. The cyprids were observed with a dissecting microscope, cryopreserved in liquid nitrogen-cooled liquid propane at various times (0-24 h) during metamorphosis, freeze dried, rotary carbon-coated, and examined with scanning electron microscopy (SEM). EPXMA dot maps were obtained in parallel for qualitative assessment of calcium and other elements in the carapace, wall, and opercular plates.

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