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Biomedical subjects

F A Bettelheim

Publications and source records attributed to F A Bettelheim.

At least 37 records · Page 2Linked to original sources
PubMed1992

On the stability of bovine gamma II crystallin.

Bovine gamma II crystallin, undergoes structural changes when lyophilized. The lyophylized powder does not readily dissolve in buffer, although it can be taken up in distilled water. The lyophylized sample, as opposed to a sample concentrated by vacuum distillation at 30 degrees C, does exhibit different migration on isoelectric focusing gels. The hydration and denaturation properties of the two preparations are different. The lyophylized sample possesses a higher non-freezable water content as a function of concentration than its counterpart. The lyophylized sample also shows less denaturation in differential scanning calorimetry scans, up to 110 degrees C, than its counterpart. This indicates that lyophylization may induce a slight denaturation, due to structural-conformational change. On the other hand, the CD spectra of lyophylized and non-lyophylized gamma II crystallins do not differ significantly. This implies that the conformational changes upon lyophylization do not involve the secondary structure of gamma II crystallin.

Animals↗
PubMed1992

Water binding capacity of mixtures of lens crystallins.

The water binding capacity of mixtures of bovine lens crystallins were investigated by combined differential scanning calorimetry and thermogravimetric analysis techniques. Binary, ternary and quaternary mixtures of alpha, beta H, beta L, and lower molecular weight (LMW) crystallins were prepared in proportion of their natural abundance. The percentage of non-freezable water of the total water content was used as an index of the bound water in all these mixtures and it was obtained as a function of crystallin concentration. These experimental values were compared to theoretical values that were calculated from the water binding capacity of individual crystallins obtained previously [Bettelheim and Popdimitrova (1990) Exp. Eye Res. 50, 715-8]. The calculations were based on the assumption that the mixtures of crystallins have the same intermolecular interactions that exist in the individual crystallins. Thus, the difference between the experimental and theoretical curves is an indicator of the type of interactions that may exist among the different crystallins. In all mixtures the experimental bound water was higher than the theoretical, predicted value at physiological concentrations. The water binding capacity of the lyophilized thin lens sections, on the other hand, was lower than the theoretical, predicted value.

Animals↗
PubMed1992

Hyaluronic acid--syneretic glycosaminoglycan.

Hyaluronic acid from different sources, umbilical cord, vitreous, rooster comb and streptococcus, all exhibit a unique hydration behavior. Each hyaluronic acid and each different salt form has a maximum non-freezable water content at a set concentration beyond which the bound (non-freezable) water decreases. This type of behavior indicates a syneretic process simply due to concentration alone.

Animals↗
PubMed1991

Birefringence of actin.

The total strain birefringence of F-actin isolated from chicken gizzards was measured as a function of elongation in thin transparent films. Each film held at a certain elongation in a jig was allowed to swell in a penetrating but nondissolving liquid. Seven liquids with different refractive indices were employed. The thickness of the film in each swelling liquid was obtained once equilibrium was established. At each elongation, from 0 to 16%, a Wiener curve was obtained. The minima of the Wiener curves yielded the intrinsic birefringence of F-actin as a function of elongation. The intrinsic birefringence increases with elongation up to 16%, above which the thin films break. The form birefringence at a set refractive index also increases with elongation. The implication of the strain birefringence of F-actin is discussed as it affects the optical properties, mainly light scattering, of tissues such as the fiber cells of lens of the eye.

Actins↗
PubMed1991

Accessibility of crystallins to HCI gas.

Different crystallins (alpha, beta H, beta L and LMW) were isolated from bovine lenses. Lyophilized samples of single components (homoaggregates) and those of mixtures (heteroaggregates) were exposed to HCI vapor in a high vacuum vapor sorption apparatus. Lyophilized 5-microns sections of bovine lens were similarly exposed to HCI vapors. Sorption and desorption isotherms were obtained at two temperatures on all samples. Fourier transform infrared (FT IR) spectroscopy was conducted on solid samples of crystallin with and without irreversibly sorbed HCI gas. From the IR spectra the nature of interaction between HCI and protein were ascertained. From the sorption parameters, mainly from the irreversibly sorbed HCI, the accessibilities of homo and hetero aggregates were calculated. The accessibilities provided information on the preferential interactions among crystallins. One of the main conclusions derived from this and also from previous ammonia sorption studies is that the supramolecular organization in the lens fibers is not governed solely by the thermodynamically preferential interactions of crystallins, but also by other possibly cytoskeletal organizations of crystallins.

Animals↗
PubMed1991

The hydration of actin.

The hydration of actin was studied by differential scanning calorimetry between -30 degrees C and 30 degrees C and by thermogravimetric analysis. The differential scanning calorimetry provided the freezable water content of G- and F-actin as a function of concentration, and the thermogravimetric analysis measured the total water content. The difference between the two yielded the nonfreezable water content (bound water) as a function of concentration. The nonfreezable water content of G-actin was higher than the F-actin over the whole concentration range from 1-40% actin.

Actins↗
PubMed1990

Hydration properties of lens crystallins.

The water binding properties of bovine lens crystallins, alpha, beta H, beta L and low molecular weight (LMW), were investigated with different techniques. The water sorptive capacity was obtained in high vacuum sorption experiments volumetrically, and also gravimetrically in controlled atmosphere experiments. The two methods gave reproducible isotherms. The strongly sorbed water (bound water) was evaluated from the B.E.T. monolayer and from the values of isosteric heats. The bound water content of the crystallins were also measured by combined differential scanning calorimetry and thermogravimetric analysis. The non-freezable water contents calculated as % of the total water content and also as g g-1 crystallin, were used as an indicator for bound water. In all three different techniques, the following order was obtained: beta H greater than alpha greater than beta L = LMW.

Animals↗
PubMed1989

Second virial coefficient of alpha-crystallin.

Light scattering studies were performed on bovine alpha-crystallin measuring the scattering intensities as a function of scattering angle, concentration, and temperature. The data yielded the molecular weight, radius of gyration, and second virial coefficient of alpha-crystallin at different temperatures. The second virial coefficient increased with increasing temperature. Both the enthalpy and entropy of solution of alpha-crystallin are positive. The Flory theta temperature was found to be 271 K.

Animals↗
PubMed1989

Bound water content of bovine lens capsules.

The anterior parts of bovine lens capsules have been incubated in media with different glucose contents. The freezable water content of the lens capsule was obtained by differential scanning calorimetry and the total water content by thermogravimetric analysis. The bound (nonfreezable) water content was calculated as the difference between total and freezable water. The bound water as percent of the total water increases with the degree of glycosylation of the bovine lens capsules.

Animals↗
PubMed1989

Thermal denaturation of alpha-crystallin.

Low molecular weight alpha-crystallin, isolated from cow lenses, exhibit irreversible thermal denaturation in solution at 75 degrees C. The heat of denaturation was obtained from a differential scanning calorimetric endothermic peak. A second run on the denatured alpha-crystallin solution showed that the denaturation is irreversible. Viscosimetric study and ultraviolet absorption spectroscopy also indicated irreversible denaturation.

Animals↗
PubMed1988

Preferential interaction among lens proteins as evidenced from accessibility of crystallins to ammonia gas.

Different crystallins (alpha, beta H, beta L and low molecular weight--LMW) were isolated from bovine lenses. The study of accessibility of the lyophilized solid proteins to ammonia gas was conducted in a high-vacuum vapor sorption apparatus. The sorption and desorption isotherms obtained were used to calculate the sorptive capacity and retentive capacity (hysteresis and irreversibly sorbed ammonia gas) of the different proteins. Individual crystallins were used to study the accessibility of the self-aggregates. Protein mixtures (beta H + beta L; alpha + LMW, etc.) were employed to study the accessibility of binary, tertiary and finally quaternary systems to ammonia vapor. Finally lyophilized thin sections of the bovine lenses were exposed to ammonia vapor. Comparing the sorptive and retentive capacities of self- and hetero-aggregates gave an indication of the preferred interactions among lens proteins in free solution, and by inference in situ, in the lens fibers.

Absorption↗
PubMed1988

Distribution of total and non-freezable water contents of galactosemic rat lenses.

Galactosemic cataracts were induced in Sprague-Dawley rats by keeping them on a 50% galactose diet for 36 days. The galactosemic rat lenses as well as normal rat lenses were sliced into 0.50 mm sections and differential scanning calorimetric (DSC) and thermogravimetric (TGA) measurements were performed. The TGA measurements gave the total water content. This was much higher in cataractous lenses than in normal lenses. The total water content also showed different gradients in normal and cataractous lenses. In normal lenses the percentage of water decreases as one proceeds from cortex to nucleus. In galactosemic cataractous lenses the trend is the opposite. The non-freezable (bound) water content was obtained as the difference between the total and freezable (DSC measurements) water content. In both cataractous and normal lenses the non-freezable water content increases when one proceeds from cortex to nucleus. It seems that most of the water influx generated by the accumulation of galactitol ends up as free water in lakes and pools rather than water of hydration.

Animals↗
PubMed1988

Water gradients across bovine cornea.

Twenty-six bovine corneas, 30 micron thick, were sectioned perpendicular to the visual axis. Sections, weighing 10-20 mg, were analyzed for total water content by thermogravimetric analysis and for freezable water content by differential scanning calorimetry. The total water content as well as the free (freezable) water content increase, while the bound (nonfreezable) water content decreases in progressing from epithelium to endothelium. These results are correlated with the distribution of proteoglycans and their water sorptive and retentive capacity in bovine cornea.

Absorption↗
PubMed1987

Accessibility of low-molecular-weight crystallins to ammonia and hydrogen chloride gases.

Low-molecular-weight crystallin was isolated from bovine lenses. Its purity was established by high-pressure liquid chromatography (HPLC) and sodium dodecyl sulfate (SDS)-gel electrophoresis. The amino-acid composition, in general, and the total available acidic and basic sites, in particular, were obtained by amino-acid analysis. The accessibility of low-molecular-weight crystallins to ammonia and hydrogen chloride vapor was obtained by high vacuum vapor sorption. The sorption and desorption isotherms were analysed regarding the gas uptake at different vapor pressures. The amount of ammonia and hydrogen chloride irreversibly sorbed and retained as well as the hysteresis imply high accessibility of crystallins to the polar gases. The results indicate that molecular self aggregation of low-molecular-weight crystallins in solid state occurs mostly through hydrophobic domains.

Adsorption↗
PubMed1986

Distribution of the total and non-freezable water in rat lenses.

Twenty Sprague-Dawley rats of ages from 7 days to 29 weeks were studied. The cortical and nuclear samples from rat lenses were investigated by differential scanning calorimetry (freezable water content) and thermogravimetric analysis (total water content). Both cortical and nuclear regions showed a decrease in total water content with aging. Only the nuclear parts of the rat lenses showed a statistically significant increase in the non-freezable portion of the total water with aging. The cortical parts showed a slight but statistically non-significant increase in this parameter. It is concluded that in rat lenses aging is primarily an aggregation process and syneresis does not play a significant role.

Aging↗
PubMed1986

Topographic distribution of water in rhesus monkey vitreus.

The topographic distribution of total water content was measured by thermogravimetric analysis in 10 rhesus monkey vitreous bodies. The distribution of the freezable water content in the same vitreous bodies was obtained by differential scanning calorimetry. The nonfreezable water content (bound water) showed a decreasing gradient along the optic axis from lens to fovea; an opposite trend than that found in bovine vitreus. The nonfreezable water content is 25% lower in rhesus monkey than in bovine vitreus which is attributed to the syneresis existent in the rhesus monkey vitreus.

Animals↗
PubMed1986

Topographic correspondence between total and non-freezable water content and the appearance of cataract in human lenses.

Eight intracapsular and 18 extracapsular human surgical specimens were stereophotographed. Each lens was divided into 10 areas, separating those which appeared transparent from those that showed opacities. Samples weighing 6-12 mg from each area were investigated. The total water content was determined by thermogravimetric analysis; the freezable water content was measured by differential scanning calorimetry. The difference between the two provided the non-freezable water content. Graphic presentation illustrates the correspondence of high total water, low non-freezable water content with location of the turbidity in the lens. Pairwise, statistical comparison shows that in intracapsular human surgical specimens the non-freezable water content in the clear areas of both cortex and nucleus was significantly greater than in the opaque areas.

Body Water↗