Artificial Bending Research Articles

An experiment on needle-fall and die back of young Todo-fir (Abies sachalinensis MAST.) by artificial bending

An experiment on needle-fall and die back of young Todo-fir (Abies sachalinensis MAST.) by artificial bending

A vibration-sensitive descending statocyst interneurone in the crayfish Procambarus Clarkii

ABSTRACT An interneurone specifically sensitive to substratum vibration was identified in the crayfish circumoesophageal connective. The interneurone, called B1 in this paper, received excitatory input from the statocysts on both sides. Electrical stimulation of the statocyst nerve elicited several spikes in the interneurone with latencies that depended on which side was stimulated. B1 responded phasically to artificial bending of the statocyst sensory hairs. The response was similar to that of the phasic-type receptor in the statocyst. The morphology of B1 was studied by an intracellular staining technique using nickel chloride and subsequent silver intensification. The interneurone projects its neurite arborization to the dorsal part of the deutocerebrum and parolfactory lobe on both sides, where the statocyst primary afferents also project. The overlapping of central projections, together with the properties of the response of B1; suggests that the interneurone receives excitatory input from the phasic-type receptors and transmits information about phasic body movement, but not static positional information, to the posterior ganglia. Branches of B1 also project to the antennal and tegumentary lobes ipsilateral to the axon. B1 may receive additional mechanosensory information from the cuticular sensory hairs on the antennae and the cephalic body surface.

Morphology of descending statocyst interneurons in the crayfish Procambarus clarkii Girard

The morphological features of descending interneurons that responded to the artificial bending of statolith hairs were assessed with intracellular recording and staining techniques. Seven statocyst interneurons were identified on the basis of their structure and response characteristics and designated as interneurons S1 to S7. All seven identified interneurons project to the optic lobe, where the optic nerve also projects, and to the dorsal part of the tritocerebrum, where the eyestalk motoneurons originate. All except interneuron S6 also extend their major branches to other neuropilar regions. S2 projects to the dorsal part of the deutocerebrum, where the statocyst nerve terminates, and S3 to the dorsal part of deutocerebrum and the antennal lobe. Four other interneurons (S1, S4, S5, S7) also extend their branches to the parolfactory lobe to which the statocyst nerve projects as well as to the deutocerebrum and antennal lobe. The extensive dendritic projections of S1–S7 suggest that they are complex multimodal interneurons rather than simple relay interneurons, receiving at least visual and statocyst sensory information. The function of the antennal lobe branches, however, has yet to be determined since the functional role of antennal input in equilibrium control is unknown.

The application of TMV particles as an internal magnification standard for determining virus particle sizes with the electron microscope

At various sites on three grids with crude-sap preparations of tobacco mosaic virus (TMV), electron micrographs were made and per photograph 50–200 particles were measured. Calculated average lengths turned out to differ up to 4% according to the site photographed. Calculated lengths appeared to depend on potentiometer settings required for focussing. This is due to the effect of preparation height or object position along the optical axis of the electron microscope on image magnification. This is further supported by the effect of additional rings underneath the grid and of artificial bending of the grid. Because it is hard to reproduce exactly electron microscope magnification, and at given potentiometer settings per photograph calculated average lengths may still vary up to c. 4%, the application of internal standards is essential for determining the size of unknown viruses. With TMV only relative particle sizes can be determined, and even with more accurate non-biological standards no absolute virus sizes will be found.