Frederick A. Bettelheim

The hydration of proteoglycans of bovine cornea

The water sorptive and retentive capacities of three corneal proteoglycans with different keratan sulfate/chondroitin-4-sulfate compositions were investigated. The calcium salt of a predominantly keratan sulfate containing proteoglycan had hydration properties similar to that of calcium keratan sulfate. The proteoglycan containing predominantly calcium chondroitin-4-sulfate side chains sorbed water to a greater extent than pure calcium chondroitin-4-sulfate but its retentive power was somewhat less. The proteoglycan containing about twice as much keratan sulfate as chondroitin-4-sulfate, on a dissaccharidic molar basis and had hydration properties which were closer to the behavior of chondroitin-4-sulfate than keratan sulfate. The results are discussed in terms of structure and polymer interaction in the proteoglycan matrices.

Effect of change in concentration upon lens turbidity as predicted by the random fluctuation theory

Theoretical calculations were performed to predict how the light scattering intensity would change with changes in concentration in the gel state. The theory of light scattering was applied to a random distribution of hard spheres. The spherical particles with constant diameter were embedded in a medium having a different refractive index. The light-scattering intensities obtained as a function of concentration showed that in dilute solutions the scattered light intensity increases with concentration. However, in concentrated solution greater than 0.1 or 0.2 volume fraction, the light-scattering intensity decreases with increase in concentration.

Syneresis and its possible role in cataractogenesis.

Abstract Theoretical calculations were performed to assess the relative contribution to turbidity of changes in the refractive index as compared to changes in the aggregate size. It was found that while the size contribution depends on the physical model adopted, the contribution of refractive index fluctuation amplitude is model independent. From theoretical consideration as well as on the basis of experimental evidences it was shown that a syneretic process in the lens can be an important contributor to cataractogenesis. Syneresis that starts with changes in the local hydration of lens protein can proceed to vacuole and lake formations, in extreme. Therefore, it is proposed that syneresis with or without an accompanying aggregation process can account for a large part of opacification.

On the optical anisotropy of lens fiber cells

Abstract The birefringence of bovine lens was found to be very small, of the order of 10 −6 –10 −7 . It is proposed that this optical isotropy, that enhances transparency, is due to the fact that the form birefringence and the intrinsic birefringence cancels each other. Calculated values of form and intrinsic birefringence indicate a range from 10 −3 –10 −5 . The order of magnitude of such intrinsic birefringence means a special organization of optically anisotropic macromolecules into aggregates.

Light-scattering studies of bovine submaxillary mucin

Light-scattering measurements of bovine submaxillary mucin yield molecular weights of 4·106 in water and aqueous NaCl solutions. The shape of the molecule was that of a rigid rod and the length of the rod was evaluated. The contribution of the mucin molecule to the viscosity of solution was calculated on the basis of the molecular parameters and found to be in good agreement with the experimental value. The mucin was found to be a polydisperse system as indicated by the comparison of the number and weight average molecular weights.

Molecular parameters of submaxillary mucins

Abstract Light scattering, refractive index increment, viscometric and apparent specific volume measurements were performed on bovine and porcine submaxillary mucins and on the mild acid hydrolysis products of the same. The molecular parameters thus obtained indicated that both mucins are highly anisotropic stiff rods. The stiffness of the bovine submaxillary mucin is derived mainly from the electrostatic repulsion of the frequent side chains ending in sialic acid moieties. The anisotropy of the porcine submaxillary mucin resides more in the intrinsic anisotropic structure of its protein core.

Light scattering of normal human lens III. Relationship between forward and back scatter of whole excised lenses

Twenty-three human lenses from age 3-76 years were studied. Lenses obtained 24-36 post-mortem were exposed to monochromatic light (435.8 and 546.1 nm) in the I parallel and I+ modes and to white (tungsten lamp) unpolarized radiation. The light scattering intensities were obtained as a function of scattering angles from 0 to 135 degrees. The scattering intensities in the forward directions are greater than in the back scatter in all modes of illuminations. The age dependence of a number of light scattering parameters such as percent transmission; I theta/Io; dissymmetry and depolarization were obtained using regression analysis. These parameters may serve as standards of normal lenses to which similar parameters of cataractous lenses can be compared. Relationships between back scatter and forward scatter have been established using the regression coefficients. Thus, the light scattering intensity observed in the slit lamp (at 135 degrees back scatter) can be quantitatively related to the light reaching the retina at different angular displacements.

Dynamic viscoelastic properties of bovine vitreous

Abstract The loss tangent, tan δ, the dynamic storage modulus E′ and the dynamic loss modulus E″ were obtained for intact bovine vitreous. All three quantities were temperature independent within the observation range, 10–40°C. The greatest frequency dependence was demonstrated by the loss moduli. The direction of compression made a slight difference: the frequency dependence of the loss tangent and the two moduli was most accentuated when the sinusoidal compression was along the direction of the Cloquets canal.

Light scattering of normal human lens. II. Age dependence of the light scattering parameters.

Fifteen human lenses from age 2 to 81 years were investigated. Six to eight thin sections (20 μm)were cut perpendicular to the visual axis from each lens. The light scattering intensities of the thin sections were obtained as a function of scattering angles. The data were analyzed using random density and orientation fluctuation theories. The structural parameters, such as the size of protein aggregates, their separation distance, their concentration, etc. were plotted as a function of position within the lens as well as a function of age. The data indicate that the parameter that changes most with aging is the refractive index difference between protein aggregates and their surrounding. This implies that in aging syneresis is the most important process, namely a gradual loss of water of hydration from the protein aggregates.

Packing and orientation of fiber cells

Sections of bovine lenses were exposed to a continuous He-Ne gas laser and the low-angle scattering was studied. Diffraction patterns resulted and repeat distances were calculated for various parts of the lens. The repeat distance decreased as one proceeded from the cortex into the nucleus. Experimental evidence indicates that the fiber cells are well aligned and organized throughout the lens.