Laser beam coupling into nerve fiber myelin allows one to assess its structural membrane properties

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10-5 maintains the average input power on the order of 10 mW, only slightly greater than the power normally used in confocal microscopy.

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Mast cell-nerve fiber interaction: Ultrastructural studies

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159680 ◽

1990 ◽

Vol 48 (3) ◽

pp. 428-429

Author(s):

E.Y. Chi ◽

M.L. Su ◽

Y.T. Tien ◽

W.R. Henderson

Keyword(s):

Mast Cell ◽

Mast Cells ◽

Substance P ◽

Nerve Fiber ◽

Sensory Nerves ◽

Ultrastructural Studies ◽

Morphological Studies ◽

Granulocyte Infiltration ◽

Intracutaneous Injection ◽

Recent Attention

Recent attention has been directed to the interaction of the nerve and immune systems. The neuropeptide substance P, a tachykinnin which is a neurotransmitter in the central and peripheral nervous systems produces tissue swelling, augemntation of intersitial fibrin deposition and leukocyte infiltration after intracutaneous injection. There is a direct correlation reported between the extent of mast cell degranulation at the sites of injection and the tissue swelling or granulocyte infiltration. It has previously been demonstrated that antidromic electrical stimulation of sensory nerves induces degranulation of cutaneous mast cells, cutaneous vasodilation and augmented vascular permeability. Morphological studies have documented a close anatiomical association between mast cells and nonmyelinated nerves, that contain substance P and other neuropeptides. However, the presence of mast cells within nerve fasicles has not been previously examined ultrastructurally. In this study, we examined ultrastructurally the distribution of mast cells in the nerve fiber bundles located in the muscular connective tissue of rat tongues (n=20).

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The atomic-force microscope and its future in biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149350 ◽

1993 ◽

Vol 51 ◽

pp. 704-705

Author(s):

Jean-Paul Revel

Keyword(s):

Silicon Nitride ◽

Laser Beam ◽

Atomic Force Microscope ◽

Scanning Tunneling Microscope ◽

Point Of View ◽

Scanning Tunneling ◽

Close Relative ◽

Tunneling Microscope ◽

Atomic Force ◽

Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

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