Effect of increased potassium concentrations on particle motion within a neurosecretory structure.

Abstract

Intensity fluctuation spectroscopy was used to detect particle motion within the pericardial organ of the crab Carcinus while it was perfused with media with increased potassium concentrations. Replacement of some or all of the sodium ions of the normal medium with potassium ions caused a graded increase in motion. Evidence is presented which indicates that this effect is not a consequence of membrane depolarization or calcium ion influx, but is due to the flux of potassium chloride and water into the cytoplasm of the cells. The observation of Shaw and Newby has been confirmed and extended by Piddington and Sattelle (5). They found, however, that omission of calcium ions from the medium had no effect on the potassium response (6). Despite this, they nevertheless attributed the scattering change to calcium entry.We have investigated this phenomenon to determine whether it has any relevance to the mechanism of neurotransmitter release. The pericardial organ of the crab Carcinus was used. This is a specialized neurosecretory structure, the cortex of which is packed tightly with neurosecretory endings containing a variety of granules and vesicles (7). It usually has a bluish color when viewed under a dissecting lamp, probably due to light scattering by the granular inclusions of the nerve endings (8). METHODSSpecimens of Carcinus were obtained from the Marine Biological Laboratory at Woods Hole and kept in a tank of artificial sea water at about 15'C. The pericardial organ was dissected from an animal in artificial sea water and transferred to a microscope slide to which it was fastened with Vaseline. The microscope slide formed the bottom of a perfusion chamber which could be covered and sealed with a cover slip. This chamber was then mounted on the stage of a specially modified Zeiss WL microscope (Fig. 1).This microscope permits observation of preparations with the incandescent illuminator of the microscope as well as with laser light. The beam of a 4-mW He/Ne laser (Coherent Radiation model 80) passes through a lens and is reflected from a half-silvered mirror and focused onto the back focal plane of the microscope condenser (numerical aperture = 1.4). The beam then passes through the preparation at an angle determined by the lateral displacement of the beam off the optical axis of the microscope (9). This angle can be adjusted between 0°and almost 90°by means of the micrometer drive on the lens-mirror assembly.An iris diaphragm in the image plane of the microscope can limit the field to an area 27 gam in diameter (using a 40X objective). This diaphragm and the image of the preparation can be observed through an ocular or, by removing a mirror from the system, the light scattered from the preparation can be passed through a pair of lenses that bring the back focal plane of the microscope objective (40X, numerical aperture = 0.65) to focus on an aperture in front of the cathode of a photomultiplier tube. The position of this aperture in the back focal plane determines the angle at which light is collected...

Noninvasive detection of functional brain activity with near-infrared diffusing-wave spectroscopy

“…56 Similar to the situation at rest, cortical diffusion coefficients measured during activation could be increased not only due to enhanced blood flow rate, but also due to increased mobility of synaptic vesicles associated with primary neural signals. [57][58][59] While for the current motor protocol and data † We use = ͐ =200 ns =3.1 s d͓g ͑2͒ ͑r , ͒ −1͔ / ␤ coh . ‡ This value of ␤ coh results from a combination of the optics of the receiver fiber guiding six transverse modes, and the presence of about two longitudinal laser modes of unequal amplitude, yielding an effective mode number of 2 ϫ 6=12Ϸ 1/␤ coh .…”

Large and rapid changes in light scattering accompany secretion by nerve terminals in the mammalian neurohypophysis.

“…The intrinsic optical signal, resulting from the train of stimuli shown here, corresponds to a fractional change in intensity of ^-0 .2% . Single a thoracic ganglion of a locust (Schistocerca gregaria) by monitoring the power spectrum of "twinkling" (light beating) produced by scattered laser light (see also Piddington and Sattelle, 1975 ;Englert and Edwards, 1977) . These preliminary reports, however, have not been pursued.…”

A study of the dynamic properties of the human red blood cell membrane using quasi-elastic light-scattering spectroscopy

“…Many previous QELS studies of individual cells have focused on studying motion of cytoplasmic inclusions or intrinsic properties of the cytoplasm (Shaw and Newby, 1972;Englert, 1980;Englert and Edwards, 1977;Piddington and Satelle, 1975;Satelle and Piddington, 1975;Nishio et al, 1983, Peetermans et al, 1986. The present work demonstrates that membrane motion may make a contribution in studies of cytoplasmic inclusions or diffusive processes and that these contributions must be considered in the analysis of QELS data from single cells.…”