PubMed Health⌕ Search

Biomedical subjects

F A Bettelheim

Publications and source records attributed to F A Bettelheim.

At least 55 records · Page 3Linked to original sources
PubMed1986

Freezable and non-freezable water content of cataractous human lenses.

Twenty-nine cataractous human lenses between the ages of 36 and 93 were investigated. The total water content of cortex and nucleus were obtained by vacuum dehydration. The freezable water content was measured by differential scanning calorimetry. The non-freezable water content was obtained by difference. To measure the extent that syneresis contributes to cataract formation, an excess function was designed. The excess function represents the changes that occur, for example, in non-freezable water content due to cataractogenesis. It is calculated as the difference between the non-freezable water content of a normal lens and that of a cataractous lens of the same age. On the average, there is 7% less non-freezable water in the cortex of a cataractous lens than in the cortex of a normal lens. The corresponding number for the nucleus is 9%. This represents 29 and 36% changes, respectively, in the cortex and nucleus due to syneresis during cataractogenesis.

Adult↗
PubMed1985

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.

Adolescent↗
PubMed1985

Light scattering of whole excised human cataractous lenses. Relationships between different light scattering parameters.

The light scattering intensities of 27 cataractous human lenses were obtained as a function of scattering angle. Unpolarized white light (tungsten) and polarized light of Hg lamp at 435.8 and 546.1 nm were used in the I parallel and I+ modes. Selected light scattering parameters such as relative scattering intensities (I45/I0), dissymmetry ratio (I135/I45) and depolarization ratios (I45/I0)+/(I45/I0) parallel were correlated with the age of lens with percent transmission using regression analysis. Excess scattering functions were calculated that quantitatively describe the quality of lens. These excess functions were also correlated with other scattering parameters. A method which can be used to estimate the light intensity that reaches the retina at different scattering angles for a cataractous lens once the back scatter intensity (slit lamp examination) is known is given.

Adult↗
PubMed1985

Age dependence of freezable and nonfreezable water content of normal human lenses.

The cortex, intermediate zone, and nucleus of 19 normal human lenses between the ages of 3 and 77 yr were investigated. The freezable water content of the lenses was obtained by differential scanning calorimetry. The total water content was measured by vacuum dehydration. The nonfreezable water content was calculated from these two measurements. The total water content of the nucleus and intermediate layers decrease with age, while that of the cortex does not vary appreciably. The nonfreezable water content of all three regions of normal human lenses decreases with age.

Adolescent↗
PubMed1984

Distribution of freezable and non-freezable water in bovine vitreous.

The viscoelastic behavior of and the transport of molecules in the vitreous is influenced by the binding of water to the macromolecular components. The macromolecular components are unevenly distributed in the vitreous. Therefore, it is of interest if the bound water, which can be identified with the non-freezable water content, is also unevenly distributed in the vitreous. Differential scanning calorimetric measurements between -30 degrees C and 15 degrees C were performed on samples from different regions of bovine vitreous body. From the endotherms the amount of freezable water content was calculated. The total water content of the vitreous was measured by vacuum dehydration. There is a slight increase in the non-freezable water content when one proceeds from the lens to the retina along the optic axis. The average amount of non-freezable (bound) water content of the vitreous is high, approximately 20% of the total water content.

Animals↗
PubMed1983

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.

Animals↗
PubMed1983

The effect of freezing on human cortical cataracts.

To ascertain a direct relationship between the light scattering intensity and the particle scattering the light, thin (6-20 micrometers) sections were cut from frozen human cataracts. Freezing for 15 min (-10 C) and then thawing had no effect on the clarity or light scattering properties of nuclear cataracts. Cortical cataracts treated in the same manner appeared to be much clearer than they were prior to freeze-thawing. Light scattering measurements were obtained as a function of scattering angle, both in the I parallel and I perpendicular mode; a He-Ne laser was used. Results showed a reduction in the light scattering intensity in the I parallel and I perpendicular modes with repeated cyclical freezing and thawing and that this decrease was most pronounced at higher scattering angles. Morphologic data showed that much of the anatomical heterogeneity present in the human cortical and rat lens osmotic cataract disappeared upon freeze-thawing. However, even though the anatomical heterogeneity was less, there was persistence of serious cellular anatomical disorganization in grossly transparent parts of the cortex. This suggests that transparency is not dependent upon the presence of intact fiber cells. The importance of these findings to studies of light scattering, cataract classification and analysis of cryoextracted human lenses is discussed.

Animals↗
PubMed1981

Studies on human cataracts. I. Evaluation of techniques of human cataract preservation after extraction.

The effects of several media and temperatures on the features (i.e. classification) of human cataracts have been studied with the aim of defining those storage conditions that least alter the appearance of the cataract after extraction. It was found that distilled water, normal saline, TC 199 medium with extra bicarbonate and 5.5 mM glucose, and silicone oil at 4 degrees, 36 degrees, and 37 degrees C are all unsatisfactory for preserving cataracts for more than 1 hr. Normal saline and TC 199 medium with bicarbonate and glucose are satisfactory for period not exceeding 30 to 60 min at 4 degrees C. The best set of conditions, one that leads to no significant change in the appearance of the cataract, is storage in a small covered glass vial at 4 degrees C with no added fluid. In this moist chamber, no significant changes in cataract classification occurred during a 4 hr period. The effect of -20 degrees C for 15 min on the appearance of a nuclear cataract was negligible, and it was concluded that lenses so treated could be used for a correlation between the nuclear cataract's CCRG classification and its light scattering properties, as studied in Parts II and III.

Cataract↗
PubMed1981

Studies on human cataracts. II. Correlation between the clinical description and the light-scattering parameters of human cataracts.

Eight lenses with nuclear cataracts have been classified. The light-scattering properties of the eight lenses were obtained with thin sections cut perpendicularly to the posterior-anterior axis. Analysis of the light scattering envelop in the I and I+ models yielded eight structural parameters that describe the density and orientation fluctuations. The variation of these parameters within each less corresponded well to the clinical description obtained from the stereoscopic photos.

Cataract↗
PubMed1981

Studies on human cataracts. III. Structural elements in nuclear cataracts and their contribution to the turbidity.

Gross correlation coefficient between light-scattering intensity and the optical parameters obtained for 48 sections of eight lenses with nuclear cataracts were evaluated. On the basis of these and other data in the literature, the structural elements, within the lens fiber are identified. These give rise to the optical parameters. It is proposed that three processes contribute to nuclear cataractogenesis: (1) syneretic process, (2) increase in the concentration but not in the size of protein aggregates, and (3) association (entanglement) between aggregates and optically anisotropic cytoskeleton or membrane components that leads to a decrease in structural bire-fringence.

Cataract↗
PubMed1979

Light scattering of normal human lens I. Application of random density and orientation fluctuation theory.

Light-scattering intensities in the I parallel and I+ mode were obtained on thin sections of three human lenses. Random density and orientation fluctuation theory, without cross correlation, was employed to evaluate light-scattering parameters. Both the density correlation distances, as well as the orientation correlation distances, were related to structural elements in the lens fiber cell that have been observed by other investigators with different techniques. The magnitude of these fluctuations were evaluated, and it was demonstrated that the density fluctuations are the main contributors to light scattering in normal human lenses. Changes in the light-scattering parameters were evaluated as a function of position within the lens. The changes observed agree with the biochemical data in the literature that reflects that an aging process occurs when one proceeds from the periphery of the lens toward the center.

Adult↗
PubMed1978

Small-angle light scattering studies on xylose cataract formation in bovine lenses.

Using polarized light scattered in the I'' and I+ modes, we determined the relative contributions of density and orientation fluctuation to the opacity of bovine lenses. In both the cortex and the nucleus of bovine lenses cultured in xylose column, we found that the increase in hydration effects the optical anisotropy (birefringence) first, before the lake formation will contribute heavily to the density fluctuation.

Animals↗