PubMed Health⌕ Search

Biomedical subjects

F A Bettelheim

Publications and source records attributed to F A Bettelheim.

86 records · Page 5Linked to original sources
PubMed1972

Dynamic rheooptical behavior of isolated bovine cornea.

The dynamic Young's modulus E' and loss modulus E'' were obtained for isolated bovine cornea using a direct-reading dynamic viscoelastometer. Within the temperature range (0-60 degrees C) and frequency range (3.5-110 Hz) studied, both moduli were temperature and frequency independent. The dynamic birefringence of the cornea was measured in a special apparatus designed for this purpose in conjunction with the dynamic viscoelastometer. The stress-optical and strain-optical coefficients as well as the corresponding phase angles were evaluated as a function of temperature and frequency. The strain- and stress-optical coefficients were both temperature and frequency dependent.

Animals↗
PubMedDate not supplied

Thermodynamic stability of bovine alpha-crystallin in its interactions with other bovine crystallins.

Light scattering measurements were performed on dilute solutions of alpha-crystallin mixed with different combinations of beta H, beta L and gamma-fractions of bovine lens crystallins. Light scattering intensities were obtained as a function of scattering angle, concentration and temperature. The temperature dependence of the second virial coefficients was used to obtain partial molar enthalpy and end entropy of solutions. The difference between the thermodynamic parameters of the crystallin mixtures and those of the weighted averages of the individual components yielded the excess enthalpy and entropy functions of the solutions. Both the excess enthalpy and entropy functions indicated that thermodynamic stability of alpha-crystallin is progressively enhanced by its interactions with gamma [symbol: see text] (beta H + gamma) [symbol: see text] (beta H + beta L + gamma) crystallins. The last two combinations showed negative values both for excess enthalpy as well for excess entropy of solutions. Other combinations demonstrated increasing positive values. This implies that the combination of all four crystallins in the vertebrate lens enables the best solvation property as well as the best packing as opposed to any other single or combinatorial arrangements of crystallins. Similar conclusions have been obtained in the past from water and other vapor sorption studies.

Animals↗
PubMedDate not supplied

Differential scanning calorimetric measurements on human lenses.

Differential scanning calorimetric measurements were performed between - 30 degrees C and 15 degrees C. The cortical sections of normal human lenses usually show one endotherm at the melting point, while the nucleus indicates a composite endotherm that can be separated into two endotherms with two melting points. Cataractous human lenses usually have composite endotherms from the cortical, intermediate as well as nuclear regions. We interpret the different endotherms as representing different kinds of freezable water contents: free water and partially bound water. Both in normal and cataractous human lenses, there is an appreciable amount of non-freezable water. The amount of non-freezable water is less in cataractous lenses than in normal lenses, indicating a syneretic process as a cause of cataract formation.

Body Water↗