An X-ray study of the pH property of frog sciatic nerve

Low-angle X-ray diffraction patterns have been recorded from frog sciatic nerve in pH solutions of 0.1–13.0. The normal X-ray pattern of frog sciatic nerve in Ringer's solution is maintained at pH 4.0–10.0. In acid pH, 2.5–4.0, and in alkaline pH, 10.0–11.0, the nerve myelin is in the partial swollen state. The partial swollen state and the normal state are reversible. Two physical states, the anomalous swollen state and the condensed state, at acid pH below 2.5 and the separated state at alkaline pH above 12.3 have been identified. These three physical states, the anomalous swollen state, the condensed state and the separated state, are reversible with each other on changing the pH solution but the normal state cannot be regained.     

An X ray diffraction study of frog sciatic nerve myelin in dimethyl sulfoxide.

Reversible structure modification of frog sciatic nerve myelin bathed in Ringer's solution containing dimethyl sulfoxide (DMSO) at a concentration of 33% has been studied by low-angle X-ray diffraction using a linear position-sensitive counter. Fourier images of native myelin layers, derived using low-order reflections measured at various stages of the DMSO treatment, reveal that the bilayer profile of native myelin membrane undergoes a specific asymmetric change prior to the phase transformation: The high-density peak on the extracellular side of the central lipid hydrocarbon layer decreases reversibly as the nerve is permeated by DMSO, while the internal peak and the central layer remain virtually unaltered. The dynamic process by which the contracted phase of myelin is derived from native myelin is speculated on the basis of the observed profile change.     

An X-ray study of the effect of enzymes on frog sciatic nerve myelin

Low-angle X-ray diffraction patterns have been recorded from frog sciatic nerve after digestion with trypsin and Pronase. Reproducible X-ray patterns were obtained by swelling the nerves in distilled water before treatment with enzymes. The X-ray patterns of enzyme-treated nerves are distinctly different from the X-ray pattern of normal (live) nerve. It would appear that the normal asymmetric nerve myelin membrane becomes symmetric about its center after treatment with enzymes as a result of proteolytic cleavage and a subsequent redistribution of protein components.     

Influence of the magnetic fields on frog sciatic nerve

The constant magnetic field (1000–7120 gauss) was applied to previously stimulated frog sciatic nerve. The following was observed : a) There is no instantaneous effect of either parallel or perpendicular magnetic field on compound action potential amplitude. b) Parallel magnetic field of 1000–7120 gauss does not change the amplitude of compound action potential significantly with time. c) When perpendicular magnetic field was applied to the nerve, an increase in the amplitude of compound action potential was observed, which can mean that the nerve exhibits some sort of magnetic anisotropy.     

Iontophoresis of lidocaine into frog sciatic nerve fibers

Iontophoresis applied to frog nerves with subthreshold concentration of lidocaine at the anode greatly facilitated inhibition of nerve action potential (NAP). Neither sodium chloride iontophoresis nor cathodal iontophoresis of lidocaine inhibited NAP. This experiment indicates that lidocaine entry into nerve fibers is facilitated by anodal iontophoresis.     

The internal structure of axons from rat sciatic nerve

Summary Sciatic nerves from rats were examined electron microscopically following fixation in 4 % tannic acid in 2.5 % glutaraldehyde, which allowed demonstration of a filamentous network between the usual intra-axonal organelles. The network appears to consist of longitudinal 10 nm in diameter filaments and cross-linking filaments of about 6 nm diameter. Exposure to cold caused disruption of microtubules, but not the filaments, and incubation at 37°C following cold exposure resulted in reformation of the microtubules which again showed linking with the filaments. Exposure of the nerves to cold in the presence of D₂O did not cause disruption of the microtubules but there did appear to be some loss of the fine filaments. These findings suggest that the finer cross-linking filaments are of a different nature than the longitudinal 10 nm filaments, and that there is a dynamic relationship between these filaments and microtubules since the cross-linkages reappear following microtubule disruption and reformation.     

Microtubules in myelinated and unmyelinated axons of rat sciatic nerve

Summary Tannic acid in glutaraldehyde was used to stain microtubules in myelinated and unmyelinated axons of rat sciatic nerve. In the majority of areas the tannic acid failed to penetrate the unmyelinated axons whilst penetrating neighbouring myelinated axons, suggesting a difference in the ability of the two types of nerves to exclude tannic acid. Where tannic acid had penetrated the unmyelinated axons the 13 protofilament substructure and size of the microtubules appeared identical to those seen in the myelinated axons.     

Effect of heat on frog sciatic nerve determined by X-ray diffraction

Low-angle X-ray diffraction patterns have been recorded from frog sciatic nerves in Ringer's solution after heat treatment from 20 to 80°C. The X-ray patterns were obtained from the heat treated specimens after cooling to room temperature. The normal X-ray pattern of frog sciatic nerve in Ringer's solution with $\text{d=171}\text{A}\text{?}$ was maintained from 20 to 58°C. Above 58°C, a new high temperature pattern based on a repeat period of $\text{d?435}\text{A}\text{?}$ was recorded from the nerve in Ringer's solution. The physical state of nerve myelin after heat teratment at a temperature ?58°C has been identified as the anomalous swollen state. Anomalous swelling takes place in units of four membranes.     

An intracellular opiate receptor

The adrenal medulla contains an intracellular opiate receptor associated with the chromaffin granule. This receptor may participate in regulation of the catecholamine content of the granule.     

AC impedance of the perineurium of the frog sciatic nerve

The AC impedance of the isolated perineurium of the frog sciatic nerve was examined at frequencies from 2 Hz to 100 kHz. A Nyquist plot of the imaginary and real components of the impedance demonstrated more than 1 capacitative element, and a DC resistance of 478 +/- 34 (SEM, n = 27) omega cm2. Transperineurial potential in the absence of externally applied current was 0.0 +/- 0.5 mV. The impedance data were fitted by nonlinear least squares to an equation representing the generalized impedance of four equivalent circuits each with two resistive and two capacitative elements. Only two of these circuits were consistent with perineurial morphology, however. In both, the perineurial cells were represented by a resistive and capacitative element in parallel, where capacitance was less than 0.1 microF/cm2. The extracellular matrix and intercellular junctions of the perineurium were represented as single resistive and capacitative elements in parallel or in series, where capacitance exceeded 2 microF/cm2. Immersion of the perineurium in low conductance Ringer's solution increased DC resistive elements as compared with their values in isotonic Ringer's solution, whereas treatment for 10 min with a hypertonic Ringer's solution (containing an additional 1.0 or 2.0 mol NaCl/liter of solution) reduced DC resistive elements, consistent with changes in perineurial permeability. The results indicate that (a) perineurial impedance contains two time constants and can be analyzed in terms of contributions from cellular and extracellular elements, and (b) transperineurial DC resistance, which is intermediate between DC resistance for leaky and nonleaky epithelia, represents intercellular resistance and can be experimentally modified by hypertonicity.