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Biomedical subjects

J L Rae

Publications and source records attributed to J L Rae.

At least 91 records · Page 5Linked to original sources
PubMed1983

Stereo scanning electron microscopy of the crystalline lens.

We have used an improved protocol to prepare human, human neonatal, rat and frog lenses for examination by stereo scanning electron microscopy. In this manner, complete and accurate images of the changes in lens cell shape, size and surface complexity are revealed as they differentiate and develop from cuboidal epithelial cells into elongate fiber cells. This method also shows that the apical ends of elongating fibers are variably expanded as they interface with the overlying lens epithelium. Apical ends are most expanded as they contact pre-germinative zone epithelial cells and least enlarged as they contact transitional zone cells. By examining the interlocking devices on opposed fibers in frog, rat and human lenses we determined that there are standard types and interlocking patterns in all lens species. Finally, stereo SEM reveals that the ridges previously reported on aged human nuclear fibers are also seen on human neonatal cortical fibers and that these ridges may actually be interlocked villous or fingerlike projections.

Adult↗
PubMed1982

A simple fluorescence technique for light microscopy of the crystalline lens.

Lenses fixed in formaldehyde or glutaraldehyde can be embedded in plastic, and sections as large as 3-4 mm across can be cut with glass knives on an ultramicrotome. When these sections are stained with 25% sodium fluorescein and allowed to bleach in a fluorescence microscope, high contrast images of essentially every cell in the section, including cells very near the lens center, can be seen. The method is effective with lenses from a number of species, and should be useful for a wide variety of morphological studies of normal and cataractous lenses.

Animals↗
PubMed1981

The lens as a nonuniform spherical syncytium.

The effective intracellular resistivity Ri of the ocular lens is a measure of the coupling between cells. Since degradation of coupling may accompany cataracts, measurements of Ri are of considerable interest. Experimental results show that the lens is a nonuniform syncytium in which Ri is much higher in the nuclear region than in the cortex. A theory describing the lens as a radially nonuniform spherical syncytium is proposed, solved, and described as a simple equivalent circuit. The impedance of the lens is measured with new circuitry which permits the accurate application and measurement of current and voltage over a wide bandwidth without arbitrary compensation of unstable capacitances. The fit of the nonuniform theory to experimental data is satisfactory and the parameters determined are consistent with theoretical assumptions. In the outer region (cortex) of the lens Ri = 2.4 k omega-cm, probably as a consequence of differences in coupling and cytoplasmic resistivity. The radial resistivity of the cortex is some five times the circumferential resistivity, demonstrating a marked anisotropy in the preparation, probably reflecting the anisotropy in the orientation of lens fibers and distribution of gap junctions. Current can flow in the circumferential direction without crossing from fiber to fiber; current can flow in the radial direction only by crossing from fiber to fiber.

Animals↗
PubMed1979

Electrical properties of structural components of the crystalline lens.

The electrical properties of the crystalline lens of the frog eye are measured with stochastic currents applied with a microelectrode near the center of the preparation and potential recorded just under the surface. The stochastic signals are decomposed by Fourier analysis into sinusoidal components, and the impedance is determined from the ratio of mean cross power to input power. The data are fit by an electrical model that includes two paths for current flow: one through the cytoplasm, gap junctions, and outer membrane; the other through inner membranes and the extracellular space between lens fibers. The electrical properties of the structures of the lens which appear as circuit components in the model are determined by the fit to the data. The resistivity of the extracellular space within the lens is comparable to the resistivity of Ringer. The outer membrane has a normal resistance of 5 kohm . cm(2) but large capacitance of 10 muF/cm(2), probably because it represents the properties of several layers of fibers. The inner membranes have properties reminiscent of artificial lipid bilayers: they have high membrane resistance, 2.2 megohm . cm(2), and low specific capacitance, 0.8 muF/cm(2). There is so much membrane within the lens, however, that the sum of the current flow across all the inner membranes is comparable to that across the outer surface.

Animals↗
PubMed1976

Current-voltage relationships in the crystalline lens.

1. Electrical coupling between the cells of the crystalline lens of the frog eye was studied using two intralenticular micro-electrodes, one to pass current and one to record potential. In most experiments, both electrodes were placed just inside the posterior surface of the lens at a depth of approximately 200 mum from the surface. Step functions of current were applied and the time course of the resulting change in voltage was measured at many different electrode separations. 2. The voltage change has both a fast component, which occurs only locally in the region close to the current passing micro-electrode, and a slow component, which is spatially uniform, independent of distance from the current micro-electrode. 3. This behaviour is predicted by an electrical model of a single large spherical cell, and so that model can be used to analyse our data. 4. The resistivity of the lens 'interior' (both cytoplasm and coupling resistivity) is 625 omega cm; the resistance of the lens 'membrane' is 2751 omega cm2. 5. The data and analysis help to reconcile discrepancies between previous measurements of the electrical properties of the lens and show clearly that there is substantial electrical coupling from cell to cell. The method should allow investigation of the role of electrical coupling in cataract formation in the crystalline lens.

Animals↗
PubMed1974

Nuclear magnetic resonance studies and water "ordering" in the crystalline lens.

Nuclear magnetic resonance studies of the relaxation times of the water in the crystalline lens show that, as in all interfacial systems, these parameters are markedly reduced from their values in pure water, that T(2) is less than T(1), and that both depend on water content. Determination of diffusion coefficients and studies on physiologically inert lenses indicate that reduced relaxation times do not provide direct evidence for ordering of the bulk of the cell water.

Animals↗