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R R Alfano

Publications and source records attributed to R R Alfano.

At least 55 records · Page 3Linked to original sources
PubMed2000

Fluorescence spectroscopic imaging to detect changes in collagen and elastin following laser tissue welding.

OBJECTIVE: A study was performed to evaluate the use of native fluorescence imaging to detect in situ molecular changes. SUMMARY BACKGROUND DATA: There is no ideal noninvasive method to monitor molecular changes in a local region at a laser weld joint without removing a section of tissue for histological examination. METHODS: Two sections of animal skin were welded together border to border using a Ti:sapphire laser beam (800 nm). Fluorescence imaging was performed on the cross section of the welded site at specific emission wavelengths (lambda c) for collagen at 380 nm and for elastin at 450 nm using excitation wavelengths (lambda e) of 340 nm, and 380 nm, respectively. RESULTS: A reduction of the collagen and elastin emission was observed in the fluorescence images of the welded region. These results were confirmed with histology using picrosirius red F3BA under polarized light and orcein stains. CONCLUSION: Optical spectroscopic imaging offers a new noninvasive detecting method for microscopic evaluation of laser tissue welding.

Animals↗
PubMed1999

Subsurface tumor progression investigated by noninvasive optical second harmonic tomography.

Nonlinear optical imaging with femtosecond (10(-15)-second) laser technology was used to evaluate the subsurface tumor progression in control, dysplasia, and cancerous 7, 12-dimethylbenz[a]anthracene-treated hamster cheek pouch mucosa tissues. Two-dimensional images of hamster cheek pouch mucosa tissues were obtained by scanning the second harmonic signal at various sagittal and axial positions. The spatial mapping of the second harmonic signals showed depth differentiation between normal, dysplasia, and a more advanced cancerous state. This nonlinear optical method offers a noninvasive in situ imaging tool to the medical community.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Fluorescence spectroscopy of normal, SV40-transformed human keratinocytes, and carcinoma cells.

Native fluorescence emission and excitation spectra of SV40 infected human keratinocytes, A431 and SCC324 carcinoma cells, and normal human keratinocytes were measured and compared. A difference in the intracellular metabolic state of NADH was found between the normal cells and the cancer or virus-transformed cells. The observed difference, namely an increased proportion of bound, mitochondrial NADH in the cancer and virus-infected cells, manifests as a blue spectral shift in the emission spectra.

Carcinoma, Squamous Cell↗
PubMed1998

Time-resolved and nonlinear optical imaging for medical applications.

In this article, we have presented an overview of emerging novel techniques for early-light transillumination imaging as well as nonlinear optical tomography of body organs. The use of light for probing and imaging biomedical media offers the promise for development of safe, noninvasive, and inexpensive clinical imaging modalities with diagnostic ability. The strong scattering of light by biological tissues buries the shadowgram formed by forward-propatating image-bearing photons in the background noise of multiple-scattered light. Several methods for extraction of image-bearing light that capitalize on spatial, temporal and polarization characteristics of transmitted light are reviewed. More recently emerging nonlinear-optical histopathology methods for imaging subsurface structures of tissues in terms of its local spatial symmetry and molecular content are introduced. The progress made so far indicates that some of these techniques are apt to make a transition from laboratory to useful clinical modalities.

Animals↗
PubMed1998

In vivo native cellular fluorescence and histological characteristics of head and neck cancer.

Native cellular fluorescence (NCF) represents the innate capacity of tissues to absorb and emit light of a specified wavelength. The ability to define the relationship of in vivo NCF with biological characteristics of neoplastic disease may allow for an improved understanding of the clinical course of disease. Head and neck cancers from 35 patients were evaluated in vivo for NCF characteristics using a xenon lamp-based spectrometer coupled to a handheld fiberoptic probe. Spectral assessment was limited to lambda 450-nm emission characteristics, in which tissues were excited at various wavelengths, ranging from lambda 290 nm to lambda 415 nm, and the intensity of lambda 450 nm emission was recorded. Each cancer was subsequently biopsied and assessed for histological differentiation by a pathologist who was blinded to NCF analysis. Considerable variation in spectral characteristics between head and neck cancers was identified, which was determined, in part, by NCF characteristics of the normal mucosa from the same patient. Poorly differentiated tumors were more likely than well- or moderately differentiated tumors to have lower excitation maxima (P < 0.05 by ANOVA). Most significantly, the tumor differentiation status, as well as the probability of demonstrating recurrent disease, could also be related to the NCF characteristics of the patient's normal mucosa from the same site within the upper aerodigestive tract. NCF analysis may represent an effective tool to identify biological characteristics of head and neck tumors in vivo without the need for invasive biopsies. Results suggest the need to explore the determinants of NCF characteristics expressed by clinically normal mucosa.

Adult↗
PubMed1998

Native fluorescence spectroscopy of normal and malignant epithelial cells.

Native fluorescence spectroscopy of normal human oral and malignant epithelial cells was studied under uv excitation. Differences were observed in the excitation spectra between normal and malignant epithelial cells for 340 nm emission. The observed differences may be utilized for both discrimination and changes associated with the amino acid residues in the cellular proteins.

Carcinoma, Squamous Cell↗
PubMed1997

Advances in optical imaging of biomedical media.

In this article, we have presented an overview of fundamental issues involved in mediphotonic imaging, and reviewed some of the emerging techniques for early-light transillumination imaging of body organs. The results on human breast tissues presented here, together with the data accumulated and advances made by researchers around the globe, not only demonstrate the feasibility of optical imaging as a clinical procedure but indicate a road map to reach that goal. The milestones include evaluation of relative merits of available approaches for a particular imaging application; selection of diagnostic wavelengths, as well as sources to generate and detectors to monitor light at those wavelengths; accumulation of data on optical, spectroscopic, and transport properties of tissues and organs; in vivo testing; prototype instrumentation development; clinical trials; governmental approval; cost analysis and marketing; and finally system improvement based on feedback from end users. A new era of optical clinical imaging is at the door.

Animals↗
PubMed1997

Innate cellular fluorescence reflects alterations in cellular proliferation.

BACKGROUND AND OBJECTIVE: The objective of this study was to examine the question of whether unique spectral patterns were associated with cell proliferation and could be identified by comparing the fluorescence pattern of slow to rapid growing cells. STUDY DESIGN/MATERIALS AND METHODS: Three in vitro model systems, (A431 cells inhibited by EGF, serum-starved 3T3 fibroblasts, and normal oral epithelial cells exposed to TGF beta), were analyzed using fluorescence spectroscopy. Growth status was monitored by cell number, 3H-thymidine incorporation, and flow cytometry. RESULTS: The excitation spectra (lambda ex 240-430 nm, lambda em 450 nm) effectively distinguished slow and rapid growing cells in all three systems. Statistical analysis of the ratios of the main broad peak (320-350 nm) to a point on the down-slope of the curve at 370 nm was statistically significant. Ratios in the emission scan (lambda ex 340 nm, lambda em 360-660 nm) could separate slow and rapid growing A431 and oral epithelial cells (P = 0.0001 and P = 0.023, respectively), but not slow and fast growing 3T3 cells (P = 0.56). CONCLUSION: Innate cellular fluorescence has the potential to discriminate proliferating and nonproliferating cell populations.

Animals↗
PubMed1997

Polarization filter for biomedical tissue optical imaging.

A technique based on the degree that light is depolarized when propagating inside tissues is demonstrated for optical imaging in biomedical systems. The difference in the degree of polarization of the emerging light allows for the discrimination of different types of tissues. The technique was investigated in the transillumination and back-scattering geometry and in both cases the potential of this method to image and separate out different types of tissues is demonstrated.

Animals↗
PubMed1997

Native cellular fluorescence and its application to cancer prevention.

Native cellular fluorescence (NCF) represents the innate capacity of tissues to absorb and emit light of specified wavelengths. Recent advances in optical engineering and computer technology have provided the, opportunity to measure NCF characteristics of various tissues in vivo. This report will briefly review the current status of NCF analysis of various neoplastic tissues. The status of investigations involving the upper aerodigestive tract will be discussed. Though initial results demonstrate that neoplastic tissues can be discriminated from normal mucosa by NCF analysis, the biologic basis of this difference remains uncertain. This report will also emphasize that the ability to screen for cancer in aerodigestive mucosa may be enhanced through the assessment of multiple emission and excitation wavelengths. The true nature of the cellular fluorophores responsible for these mucosal spectral characteristics should be more fully defined in coming years.

Cell Differentiation↗
PubMed1996

Time-resolved optical diffusion tomographic image reconstruction in highly scattering turbid media.

The image of an object hidden in highly scattering media was reconstructed using a fast, noise-resistant algorithm newly applied to diffusion tomography. A pulsed light source producing scattered and transmitted light is examined at multiple times. Multiple source detector pairs around the medium are used to obtain data in many different directions. An inverse scattering algorithm with nonuniform regularization achieves rapid inversion convergence.

Journal Article↗
PubMed1996

Native cellular fluorescence identifies terminal squamous differentiation of normal oral epithelial cells in culture: a potential chemoprevention biomarker.

Native cellular fluorescence (NCF) is being investigated as an intermediate endpoint biomarker for chemoprevention. Oral epithelial cells were cultured under three conditions to identify a spectral pattern for epithelial differentiation: cells maintained in serum-free keratinocyte growth medium were the least differentiated (KGM cells); cells switched to DMEM/F12 plus 10% FCS were intermediate in differentiation (DMEM/F12/FCS cells); DMEM/F12/FCS cells switched to serum-free DMEM/F12 plus 0.8 M NaCl to induce cornified envelopes were the most differentiated (DMEM/F12/NaCl cells). The differentiation status was characterized using immunohistochemistry and electron microscopy. NCF analysis was able to distinguish terminally differentiated epithelial cells (DMEM/F12/NaCl) from those less differentiated cells (KGM, DMEM/F12/FCS) in several emission (lambda ex 340 nm, lambda em 360-660 nm; lambda ex 365 nm, lambda em 400-700 nm; lambda ex 420 nm, lambda em 440-800 nm) and excitation scans (lambda ex 200-360 nm; lambda em 380 nm, lambda ex 240-430 nm; lambda em 450 nm, lambda ex 250-460 nm, lambda em 480 nm; lambda ex 270-500 nm, lambda em 520 nm). The ability to discriminate terminal differentiation in this in vitro model supports the concept of using NCF as an intermediate biomarker to monitor in vivo mucosal differentiation.

Anticarcinogenic Agents↗
PubMed1995

Ultraviolet excitation fluorescence spectroscopy: a noninvasive method for the measurement of redox changes in ischemic myocutaneous flaps.

In this report, we discuss application of the noninvasive technology of ultraviolet fluorescence spectroscopy to the metabolic analysis of normal and compromised myocutaneous flaps. Acute changes in tissue redox states during ischemia and reperfusion were determined analysis of changes in the fluorescence spectrum of reduced nicotinomide adenine dinucleotide (NADH). Analysis of the system for NADH fluorescence showed good correlation between excitation spectra recorded at 450 nm from pure beta-NADH and those recorded from porcine rectus abdominis myocutaneous flaps. Sequential measurements of surface fluorescence were obtained from six flaps subjected to 6 hours of warm arterial ischemia and 4 hours of reperfusion. Results were compared with spectra obtained from six contralateral nonischemic control flaps. A significant mean increase in NADH fluorescence (49 percent; p < 0.05) was demonstrated within 30 minutes of vascular occlusion. Fluorescence intensity continued to increase throughout the ischemic period, reaching 320.5 percent of baseline values at 6 hours. Reperfusion resulted in the prompt return of fluorescence intensity to baseline levels. These results show that fluorescence spectroscopy of endogenous NADH is a sensitive and reliable indicator of vascular occlusion in experimental myocutaneous flaps.

Animals↗
PubMed1994

Detecting retinoic acid-induced biochemical alterations in squamous cell carcinoma using intrinsic fluorescence spectroscopy.

Intrinsic fluorescence spectroscopy offers a new method for diagnosing head and neck cancers. By establishing a unique spectral fingerprint for benign tissue, one can readily identify subtle changes in tissue based on altered spectral patterns. The authors applied this technology to a multicellular tumor spheroid (MTS) model and obtained baseline spectral data. A cohort of MTS was treated with the chemopreventive agent retinoic acid (RA) to determine its effect on tumor cells. Excitation and emission spectroscopy were performed on the samples. Spectroscopic scans demonstrated consistently that RA-treated MTS exhibit a decrease in the peak associated with reduced nicotinamide-adenine dinucleotide (NADH) and an increase in the peaks associated with flavins, tryptophan, and cytokeratins when compared to controls. These findings are suggestive of alterations in cellular electron transport, an increase in proteins incorporating tryptophan, and a decrease in adenosine triphosphate (ATP) in the RA-treated cells. A discussion of the potential clinical applications of intrinsic fluorescence spectroscopy is included.

Carcinoma, Squamous Cell↗
PubMed1993

Tissue autofluorescence as an intermediate endpoint in cancer chemoprevention trials.

Intermediate endpoints which reflect responsiveness to chemopreventive agents are needed in clinical trials. A potential problem in the assessment of these endpoints is their requirement for invasive biopsies. Secondly, their expression within the aerodigestive tract is doubtfully uniform. Without clinically definable disease, the potential for biopsy sampling error is significant. Our approach to this problem is the analysis of intrinsic tissue fluorescence. Various cellular components exist within tissues with the innate capacity to emit a characteristic spectral signature when excited at a particular wavelength of light. It can be postulated that cells in varying stages of progression towards malignancy will differ in both the qualitative and quantitative nature of these intrinsic cellular fluorophores which include folate derivatives and cytokeratins, as well as various vitamins and coenzymes. Using current bioptical technology, we have tested the applicability of tissue autofluorescence to chemoprevention studies through various model systems. In an N-nitroso-N-methylbenzylamine (NMBA)-induced rat esophageal cancer model, alteration of the 380 nm emission pattern corresponded to disease progression from normal mucosa through dysplasia to invasive cancer. In a multicellular tumor spheroid model, trans-retinoic acid (RA) altered autofluorescent profiles at multiple wavelengths including intensities at 340 nm, 450 nm, and 520 nm. Such RA-induced alterations corresponded to changes in the state of spheroid differentiation. In vivo human studies are in progress which suggest that aerodigestive mucosal neoplasias can be discriminated from normal mucosa by their autofluorescent profile. Because aerodigestive mucosa can be scanned without the need for invasive biopsies, the assessment of tissue autofluorescence as an intermediate endpoint may prove valuable.

Animals↗
PubMed1991

Ultrafast spectroscopy of the visual pigment rhodopsin.

We report on time-resolved absorption studies of the bovine visual pigment rhodopsin with subpicosecond resolution at room temperature. Our data show that bathorhodopsin, rhodopsin's early photoproduct, is photochemically formed in 3.0 +/- 0.7 ps. The data suggest that bathorhodopsin formation is kinetically preceded by two species along the rhodopsin-to-bathorhodopsin reaction coordinate. The first is identified with the vertically excited Franck-Condon state. This decays with an approximately 200-fs lifetime to an intermediate, which then decays to bathorhodopsin in 3.0 ps. We assign this intermediate to be an excited state transient near 90 degrees along the 11-12 torsional coordinate of rhodopsin's chromophore. Exchange of rhodopsin's exchangeable protons for deuterons does not affect the observed dynamics. These observations are both qualitatively and quantitatively consistent with molecular dynamics calculations, which model the rhodopsin to bathorhodopsin phototransition as a cis-trans isomerization along the 11-12 torsional coordinate of rhodopsin's chromophore.

Animals↗