Biomedical subjects

M Z Cai

Publications and source records attributed to M Z Cai.

3 recordsLinked to original sources

PubMed1991

Resonance Raman detection of a carotenoid in the lens of the deep-sea hatchetfish.

A laser scanning micro-probe has been used to elicit resonance Raman signals from frozen sections of the lens of the deep-sea hatchetfish, Argyropelecus affinis. The signals demonstrate with certainty the presence of a carotenoid and its distribution in the lens. The carotenoid exhibits characteristic resonance Raman vibrational modes at 1551 cm-1 (C = C stretch, v1), 1147 cm-1 (C-C stretch with C-H bend, v2), 2285 cm-1 (2v2) and 2681 cm-1 (v1 + v2), upon excitation at 441.6 nm. Unlike glycogen in the nucleus of dove lens, the carotenoid in the lens of A. affinis occurs at a higher concentration in the cortex, although its presence in the nucleus is established. A study of lenses of varying age showed that carotenoid incorporation is accelerated as the fish grows older and hence its concentration is highest in the cortex. Because of the extremely low concentration of the carotenoid in the nucleus, it was detectable only by the very sensitive resonance Raman technique.

Aging↗

PubMed1989

Galactose-induced cataract in rat: Raman detection of sulfhydryl decrease and water increase along an equatorial diameter.

Raman spectroscopy shows that maturation of galactose cataract greatly increases the water signal (at 3417 cm-1) which is correlated with the inbibition of water in the lens. The maximum water: protein ratio (expressed as Raman intensity ratio I3417:I2936) occurs at the peripheral cortex (i.e. approximately 4.7), which is much higher than the ratios found in Emory cataract (approximately 0.3) and in cac-strain mouse cataract (approximately 0.5). It is demonstrated that Raman measurement of the intensity ratio I3417:I2936 is a more sensitive way to reflect increase of water in cataract, compared to water concentration (percentage of wet weight of the lens). The small decrease in the sulfhydryl profile along an equatorial diameter is attributed to the concentration decrease in glutathione. There is no spectroscopic evidence for extensive disulfide bond formation associated with galactosemic cataractogenesis in rat. There is an increase in the tyrosine I832:I858 ratio (normal 1.74; cataract 3.43), indicating a strengthening of the phenolic hydrogen bond, a change which has been found in Raman spectra of all cataracts studied. A comparison of the Raman spectra of normal lenses and mature cataracts reveals no change in conformation of the protein backbone.

Animals↗

PubMed1988

Automated laser-scanning-microbeam fluorescence/Raman image analysis of human lens with multichannel detection: evidence for metabolic production of a green fluorophor.

A laser-microprobe fluorescence/Raman spectrometer with a 700-channel detector has been constructed and applied to the collection of data on the distribution of a green fluorophor throughout the exposed area of a human lens sectioned along the visual axis. The area (approximately 6.5 X 9.5 mm) covering the lens section was scanned automatically by the microprobe programmed to measure the fluorescence intensity at 1200 data points. The spectrometer output was accumulated in a microcomputer and displayed as a three-dimensional perspective view showing the fluorescence intensity at each point on the grid. The method permits the precise and detailed mapping at high resolution of the spatial distribution of a fluorophor or Raman-emissive constituent in a plane of the frozen lens to give results not obtainable by any other feasible procedure. The green fluorophor (441.6 nm, excitation wavelength; 520 nm, peak emission wavelength) has a distribution indicating a metabolic rather than a photochemical mode of production. Moreover, the lower level of fluorophor in the anterior segment suggests the existence of mechanisms in the anterior cortex (including the epithelium) that reduce significantly the accumulation of fluorophor. Such distribution studies are invaluable in clarifying metabolic interrelationships among the different zones of the lens, including especially photochemical reactions postulated to involve the effect of daylight on the lens in human subjects.

Aged↗