Assessment of the metabolism and morphology of the porcine cornea, lens and retina by 2-photon imaging

Two-photon imaging is a noninvasive imaging technique with increasing importance in the biological and medical fields since it allows intratissue cell imaging with high resolution. We demonstrate the feasibility of using a single 2-photon instrument to evaluate the cornea, the crystalline lens and the retina based on their autofluorescence (AF). Image acquisition was performed using a custom-built 2-photon microscope for 5-dimensional microscopy with a near infrared broadband sub-15 femtosecond laser centered at 800 nanometers. Signals were detected using a spectral photomultiplier tube. The spectral ranges for the analysis of each tissue/layer AF were determined based on the spectra of each tissue as well as of pure endogenous fluorophores. The cornea, lens and retina are characterized at multiple depths with subcellular resolution based on their morphology and AF lifetime. Additionally, the AF lifetime of NAD(P)H was used to assess the metabolic activity of the cornea epithelium, endothelium and keratocytes. The feasibility to evaluate the metabolic activity of lens epithelial cells was also demonstrated, which may be used to further investigate the pathogenesis of cataracts. The results illustrate the potential of multimodal multiphoton imaging as a novel ophthalmologic technique as well as its potential as a diagnostic tool.

Low-level laser therapy on skeletal muscle inflammation: evaluation of irradiation parameters

We evaluated the effect of different irradiation parameters in low-level laser therapy (LLLT) for treating inflammation induced in the gastrocnemius muscle of rats through cytokines concentration in systemic blood and analysis of muscle tissue. We used continuous (830 and 980 nm) and pulsed illuminations (830 nm). Animals were divided into five groups per wavelength (10, 20, 30, 40, and 50 mW), and a control group. LLLT was applied during 5 days with a constant irradiation time and area. TNF-α, IL-1β, IL-2, and IL-6 cytokines were quantified by ELISA. Inflammatory cells were counted using microscopy. Identical methodology was used with pulsed illumination. Average power (40 mW) and duty cycle were kept constant (80%) at five frequencies (5, 25, 50, 100, and 200 Hz). For continuous irradiation, treatment effects occurred for all doses, with a reduction of TNF-α, IL-1β, and IL-6 cytokines and inflammatory cells. Continuous irradiation at 830 nm was more effective, a result explained by the action spectrum of cytochrome c oxidase (CCO). Best results were obtained for 40 mW, with data suggesting a biphasic dose response. Pulsed wave irradiation was only effective for higher frequencies, a result that might be related to the rate constants of the CCO internal electron transfer process.

Evaluation of a non-invasive fluorescence technique as a marker for diabetic lenses in vivo

BACKGROUND

A fluorescence spectrometer has been constructed to study in vitro and in vivo fluorescence of human lenses. This instrument can measure fluorescence emission spectra, which can be useful in the characterisation of the lens endogenous fluorophores and evaluation of the feasibility of fluorescence measurement as a non-invasive marker for diabetes. The spectrometer allows determination of the optimum excitation and emission wavelengths, which can be used in simpler instrumentation for monitoring purposes.

METHODS

To est the application in such studies a homogeneous group of type II diabetic subjects and normal controls was studied. For each subject the fluorescence emission spectra was measured using a spectrometer prototype consisting of a modified slit lamp coupled to a optical multichannel analyser (OMA). The incorporation of narrow-band filters allows the selection of three different excitation wavelengths: 404 nm, 436 nm and 485 nm.

RESULTS

With both in vitro and in vivo measurements, no significant differences were found between diabetic and normal lenses concerning the wavelength of maximum emission of fluorescence. However, the spectra (lambda(exc)=436 nm) between 480 and 550 nm were better defined with diabetic lenses. Using ratios of fluorescence intensity at two different wavelengths (490/610, 510/610, and 550/610) allows for good discrimination between normal controls and diabetic patients. The use of ratios largely removes the effects due to attenuation of excitation light and emitted fluorescence.

CONCLUSIONS

The non-invasive evaluation of lens fluorescence is proposed as early indicator of ocular complications associated with diabetes.