Biomedical subjects

S Vaezy

Publications and source records attributed to S Vaezy.

23 records · Page 2Linked to original sources

PubMed1995

Two-dimensional fourier analysis of electron micrographs of human skin for quantification of the collagen fiber organization in the dermis.

Two-dimensional (2-D) Fourier analysis was used to quantify the structural organization of collagen fibers in the dermis of the human skin. The 2-D Fourier spectra of electron micrographs of collagen fibers contained large amplitude Fourier components (1 fundamental and 3 harmonic peaks), representing the predominant structural parameter of the fibers, the center-to-center spacing of collagen fibrils. The average center-to-center spacing of the collagen fibrils was found from the position of the peaks. For a normal fiber of reticular dermis, this spacing was 116 nm. The fibril diameter appeared to modulate the peak heights.

Collagen↗

PubMed1994

Quantitative analysis of the microstructure of the human cornea and sclera using 2-D Fourier methods.

A two-dimensional (2-D) Fourier analysis was used to characterize the microstructure of the human cornea and sclera. The average centre-to-centre spacing of collagen fibrils was found to be 59 nm for the cornea and 285 nm for the sclera. These results agreed with those obtained by direct measurement using the electron micrographs, and those reported in the literature. The spatial order in the microstructure of the cornea was much greater when compared with that of the sclera. The results of the 2-D Fourier analysis were consistent with the theory of transparency of the eye. The 2-D Fourier analysis will be useful in quantitative characterization and analysis of the complex microstructure of biological cells and tissues in normal development and abnormal pathogenesis.

Cornea↗

PubMed1991

A quantitative evaluation of Fourier components in transparent and opaque calf cornea.

Fourier transform methods were applied to STEM (scanning transmission electron microscopy) images to detect and quantify the subtle differences between the structure of normal transparent calf cornea and opaque calf cornea. In order for a tissue to be transparent, it can scatter or absorb only a small amount of light. Light scattering is minimized when the principal Fourier components of the spatial fluctuations in the index of refraction have wavelengths which are small relative to the wavelength of light (Benedek, 1971). Corneal opacity was produced as a result of high intraocular pressure (100-150 mmHg) when liquid was injected into calf eyes (0-2 weeks old). Pressurization created large structural defects and slight disruptions in the organization of the collagen fibers. Although the fiber organization appeared similar in the micrographs of both opaque and transparent corneas, Fourier analysis of STEM images collected at 50K magnification identified statistically significant differences. Far fewer Fourier components with wavelengths in the light scattering range (200-1100 nm) were observed in the transparent corneas than in the pressurized corneas as predicted by Benedek's theory. It was of interest that corneas treated with 100% glycerol prior to pressurization remained transparent at high intraocular pressures, possibly because glycerol stabilized the structure of the corneas and maintained a uniform index of refraction across the corneal stroma. The results demonstrate the effectiveness of Fourier analysis in detection and quantification of slight changes in structure at the electron microscopic level.

Animals↗

PubMed1991

A quantitative analysis of transparency in the human sclera and cornea using Fourier methods.

Cellular microstructure observed by scanning transmission electron microscopy (STEM) was analysed using Fourier methods. Fourier components of the density fluctuations in the sclera and the cornea of the human eye were quantified. The results show that the Fourier components responsible for the opacity of the sclera have sizes of the order of the wavelength of visible light. In the sclera, approximately 54% of the spectral energy of the density fluctuation falls in the range of 200-1100 nm (scattering range). In the cornea, approximately 24% of the total spectral energy falls in this range. The predominant Fourier components of the density fluctuations in the opaque sclera are approximately 300 nm in wavelength, whereas those of the transparent cornea are approximately 80 nm in wavelength. This method will be useful in quantitative analysis of microstructural changes accompanying biological phenomena such as normal development of transparency in the human lens, and abnormal loss of transparency during cataract formation.

Cornea↗

PubMedDate not supplied

Characterization of the cellular microstructure of ocular lens using 2D power law analysis.

Power law analysis provides a quantitative method for characterization of spatial fluctuations in the cellular microstructure of the ocular lens. In the power law analysis, Fourier components of the spatial fluctuations are computed, and the relationship between the amplitude, A, and spatial frequency, f, of the components is defined by a power law function: [formula, see text]. The exponent of the function, beta, defines the scaling of the amplitude of the Fourier components as a function of spatial frequency. We performed two-dimensional power law analysis on electron micrographs of lens cells ranging from transparent to opaque. We identified two values of power law exponent, beta, for the spatial fluctuations of all lens cells, one for low- and a second for high-spatial frequencies. In the low-spatial frequency region, the value of beta was in the range of 0.53 to 1.33, for transparent and opaque cells. In the high-spatial frequency region, the value of beta increased from 2.78 for transparent lens cells to 3.60 for opaque lens cells. The power law analysis provides a new method for quantitative characterization of the spatial fluctuations in the microstructure of transparent and opaque lens cells.

Animals↗