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Cheek Pouch (cheek + pouch)
Kinds of Cheek Pouch Selected AbstractsDual-mode reflectance and fluorescence near-video-rate confocal microscope for architectural, morphological and molecular imaging of tissueJOURNAL OF MICROSCOPY, Issue 1 2007ALICIA L. CARLSON Summary We have developed a near-video-rate dual-mode reflectance and fluorescence confocal microscope for the purpose of imaging ex vivo human specimens and in vivo animal models. The dual-mode confocal microscope (DCM) has light sources at 488, 664 and 784 nm, a frame rate of 15 frames per second, a maximum field of view of 300 × 250 ,m and a resolution limit of 0.31 ,m laterally and 1.37 ,m axially. The DCM can image tissue architecture and cellular morphology, as well as molecular properties of tissue, using reflective and fluorescent molecular-specific optical contrast agents. Images acquired with the DCM demonstrate that the system has the sub-cellular resolution needed to visualize the morphological and molecular changes associated with cancer progression and has the capability to image animal models of disease in vivo. In the hamster cheek pouch model of oral carcinogenesis, the DCM was used to image the epithelium and stroma of the cheek pouch; blood flow was visible and areas of dysplasia could be distinguished from normal epithelium using 6% acetic acid contrast. In human oral cavity tissue slices, DCM reflectance images showed an increase in the nuclear-to-cytoplasmic ratio and density of nuclei in neoplastic tissues as compared to normal tissue. After labelling tissue slices with fluorescent contrast agents targeting the epidermal growth factor receptor, an increase in epidermal growth factor receptor expression was detected in cancerous tissue as compared to normal tissue. The combination of reflectance and fluorescence imaging in a single system allowed imaging of two different parameters involved in neoplastic progression, providing information about both the morphological and molecular expression changes that occur with cancer progression. The dual-mode imaging capabilities of the DCM allow investigation of both morphological changes as well as molecular changes that occur in disease processes. Analyzing both factors simultaneously may be advantageous when trying to detect and diagnose disease. The DCM's high resolution and near-video-rate image acquisition and the growing inventory of molecular-specific contrast agents and disease-specific molecular markers holds significant promise for in vivo studies of disease processes such as carcinogenesis. [source] Optimal methods for fluorescence and diffuse reflectance measurements of tissue biopsy samplesLASERS IN SURGERY AND MEDICINE, Issue 3 2002Gregory M. Palmer BS Abstract Background and Objective In developing fluorescence spectroscopy systems for the in vivo detection of pre-cancer and cancer, it is often necessary to perform preliminary testing on tissue biopsies. Current standard protocols call for the tissue to be immediately frozen after biopsy and later thawed for spectroscopic analysis, but this process can have profound effects on the spectroscopic properties of tissue. This study investigates the optimal tissue handling methods for in vitro fluorescence spectroscopy studies. Study Design/Materials and Methods The epithelial tissue of the Golden Syrian hamster cheek pouch was used in this study. Three specific experiments were carried out. First, the fluorescence properties of tissues in vivo and of frozen and thawed tissue biopsies were characterized at multiple excitation wavelengths spanning the ultraviolet-visible (UV-VIS) spectrum. Next, comparison of tissue fluorescence emission spectra in vivo, ex vivo (immediately after biopsy), and after the freeze and thaw process were systematically carried out at the excitation wavelengths corresponding to the previously identified fluorescence peaks. Lastly, intensities at the excitation and emission wavelength pairs corresponding to the fluorescence peaks were measured as a function of time after biopsy. Diffuse reflectance measurements over the UV-VIS spectrum were also made to evaluate the effects of oxygenation, blood volume, and scattering on the tissue fluorescence at these different excitation,emission wavelengths. Results This study indicates that the freezing and thawing process produces a significant deviation in intensity and lineshape relative to the in vivo fluorescence emission spectral data over the entire UV-VIS range between 300 and 700 nm. By contrast, examination of ex vivo emission spectra reveals that it closely preserves both the intensity and lineshape of the in vivo emission spectra except between 500 and 700 nm. The observed deviations can be explained by the diffuse reflectance measurements, which suggest increased hemoglobin deoxygenation and wavelength dependent changes in scattering in ex vivo tissues, and increased total hemoglobin absorption in the frozen and thawed samples. Furthermore, it was found that over a time window of 1.5 hours, spectroscopic changes brought about by degradation of the tissue due to biopsy or other factors are significantly smaller (10,30% variations in intensity) than those associated with the freezing and thawing process (50,70% decrease in intensity). Conclusions It was found that the effects of freezing and thawing on the fluorescence properties of tissue are greater than any changes brought about by degradation of tissue over a time frame of 90 minutes after biopsy. Performing ex vivo fluorescence measurements within a reasonable time window has the advantage of more accurately reproducing the clinically relevant in vivo conditions in the case of the hamster cheek pouch tissue. Therefore, in tissue biopsy studies, the tissue sample should ideally be maintained in an unfrozen state prior to measurement. Lasers Surg. Med. 30:191-200, 2002. © 2002 Wiley-Liss, Inc. [source] Independent Regulation of Periarteriolar and Perivenular Nitric Oxide Mechanisms in the In Vivo Hamster Cheek Pouch MicrovasculatureMICROCIRCULATION, Issue 4 2009DAVID D. KIM ABSTRACT Objective: We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre- and postcapillary segments of the microcirculation in the hamster cheek pouch. Materials and Methods: We applied acetylcholine (ACh) or platelet-activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO-sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF. Results: ACh increased periarteriolar [NO] significantly in a dose-dependent manner. ACh at 1 ,M increased [NO] from 438.1±43.4 nM at baseline to 647.9±66.3 nM, while 10 ,M of ACh increased [NO] from baseline to 1,035.0±59.2 nM (P<0.05). Neither 1 nor 10 ,M of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.6±50.8 to 622.8±41.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.6±2.1 to 455.5±19.9 in CVEC, while ACh had no effect. Conclusions: We conclude that NO production can be stimulated in a differential manner in pre- and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules. [source] Longitudinal and Radial Gradients of PO2 in the Hamster Cheek Pouch MicrocirculationMICROCIRCULATION, Issue 3 2008Helena Carvalho ABSTRACT Objectives: The aim of this study was to determine longitudinal and radial gradients in oxygen tension (PO2) in microvessels of the hamster cheek pouch. Methods: We measured PO2 using the phosphorescence-quenching method in two orders of arterioles (45.8 ± 5.5 and 19.9 ± 1.8 , m diameter), capillaries, and two orders of venules (50.5 ± 3.4 and 21.4 ± 2.0 , m diameter) in order to determine the longitudinal PO2 gradient. At the arteriolar and venular sites, we also measured PO2 at four different sites for an analysis of radial PO2 gradients: centerline, inside wall (larger arteriole and venule only), outside wall, and interstitium. We used 10 hamsters weighing 115 ± 27 g anesthetized with pentobarbital intraperitoneally and maintained with alpha-chloralose intravenously. The cheek pouch was everted and a single-layered preparation was studied by intravital microscopy. Albumin-bound Pd-porphyrin was infused into the circulation and excited by flash illumination at 10 Hz, with a rectangular diaphragm limiting the excitation field to 5 × 25 , m. Results: In the longitudinal direction, intravascular PO2 decreased significantly (P < 0.01) from large arterioles (39.5 ± 2.3 mmHg) to small arterioles (32.2 ± 0.3 mmHg), then to capillaries (30.2 ± 1.8 mmHg), and on to small venules (27.3 ± 2.1 mmHg) and large venules (25.5 ± 2.2 mmHg). In the radial direction, PO2 decreased significantly (P < 0.01) in and around larger arterioles, and to a lesser extent, around the smaller ones (P < 0.05). There was no significant PO2 gradient, longitudinal or radial, associated with venules. The PO2 difference from the centerline to the outside wall in large arterioles was 8.3 ± 1.4 mmHg, and most of the decline in PO2 in the radial direction was contributed by the intravascular difference (4.7 ± 2.1 mmHg) and only about 1.0 ± 2.7 mmHg by the transmural difference. Conclusions: Our data show that there are large intra-arteriolar radial PO2 gradients, but no large transmural PO2 differences, suggesting that the oxygen consumption of the microvessel wall is not exceptionally high. [source] Microvessels Promote Motor Nerve Survival and Regeneration Through Local VEGF Release Following Ectopic ReattachmentMICROCIRCULATION, Issue 8 2004SHAWN E. BEARDEN ABSTRACT Objectives: Nerves and blood vessels form a close association during embryogenesis. Growth and guidance factors initially attributed to either nerves or vessels are now known to affect both tissues; prominent among these is vascular endothelial growth factor (VEGF). The authors investigated whether axons would associate with blood vessels in a regenerating system and questioned whether VEGF is integral to neurotization following axotomy. Methods: In hamsters 8,12 weeks of age, the accessory nerve (CN XI) to the retractor muscle of the cheek pouch was cut and the proximal stump was reattached ectopically onto the muscle. Vascular casting and immunolabeling were used to quantify the extent of neurovascular association during regeneration. A role for VEGF was investigated using immunolocalization of VEGF and its receptor (sVEGFR2) as well as local sequestration of VEGF with soluble receptor (sVEGFR1). Results: Regenerating axons aligned with microvessels of the vasa nervorum along a "chaperone" region during outgrowth from the reattachment site and while entering the muscle. In this ,1-mm region, VEGF protein was expressed by growing microvessels despite a ,50% reduction (p < .05) in total muscle VEGF concentration. VEGFR2 was expressed by regenerating axons and growth cones. Sequestration of VEGF by sVEGFR1 impaired neurotization by ,40% (p < .05). The chaperone region ended where regenerating microvessels anastomosed with the native microcirculation and their expression of VEGF protein diminished. Conclusions: Regenerating axons and blood vessels align during outgrowth from ectopic reattachment. This interaction dissipates as vascular anastomoses form with established microvessels and axons target muscle fibers. Local production of VEGF by growing microvessels supports motor nerve survival and regeneration. [source] Volumetric flow mapping for microvascular networks by bimodality imaging with light microscope and laser doppler imagerMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2004Ying Sun Abstract A method was developed to produce a composite image of microvascular networks with grayscales proportional to volumetric flows. Velocities in arterioles and venules were assessed with a high-resolution laser Doppler imager (LDI). The vascular structures were quantified from the micrograph with a computerized vessel detection algorithm. After registering the detected vascular network with the LDI scan, volumetric flows were calculated along the centerlines of the vessels. In vivo data were obtained from the hamster cheek pouch in 6 studies. Flow continuity of the flow map was evaluated by comparing the main flow (Q) with the sum of branch flows (Qs), averaging over the respective vessel segments incident to each bifurcation. The method was reproducible across the 6 studies with the correlation coefficient (r) between Qs and Q ranging from 0.913 to 0.986. In all, over 20,000 flow estimates from 360 vessel segments (24,160 ,m in diameter) at 166 bifurcations were analyzed. With flow normalized between 0 and 1, the linear regression yielded: Qs = 1.03 Q + 0.006; r = 0.952, n = 166, P < 0.0005. The bimodality imaging method exploits a large amount of velocity and diameter data, and therefore should be useful for studying heterogeneous flows in the microvasculature. Microsc. Res. Tech. 65:130,138, 2004. © 2004 Wiley-Liss, Inc. [source] Evaluation of the Photosensitizer Tookad® for Photodynamic Therapy on the Syrian Golden Hamster Cheek Pouch Model: Light Dose, Drug Dose and Drug,light Interval Effects,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2003François Borle ABSTRACT We have evaluated the efficacy of the new photosensitizer (PS) Tookad® in photodynamic therapy (PDT) in vivo. This PS is a palladium-bacteriopheophorbide presenting absorption peaks at 762 and 538 nm. The light dose, drug dose and drug injection,light irradiation interval (DLI), ranging between 100 and 300 J/cm2, 1 and 5 mg/kg and from 10 to 240 min, respectively, were varied, and the response to PDT was analyzed by staging the macroscopic response and by the histological examination of the sections of the irradiated cheek pouch. The level of PDT response, macroscopically and histologically, shows a strong dependence on the DLI, light dose and drug dose at the applied conditions in the normal hamster cheek pouch. A decay of the tissular response with increasing DLI is observed corresponding to a time of half-maximum response ranging from 10 to 120 min, depending on drug dose and light dose. The tissues affected at the lowest doses are predominantly the vascularized diffuse connective tissue situated between the inner and outer striated muscle (SM) layers as well as these muscle layers themselves. The highest response at the shortest DLI and the absence of a measurable response at DLI longer than 240 min at 300 J/cm2 and drug dose of 5 mg/kg are characteristics of a predominantly vascular effect of this PS. This observation suggests that Tookad® could be effective in PDT of vascularized lesions or pathologies associated with the proliferation of neovessels. [source] Characterization of adenosine receptors mediating the vasodilator effects of adenosine receptor agonists in the microvasculature of the hamster cheek pouch in vivoAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2002J. Nicholls Summary 1 The aim of this study was to characterize the adenosine receptor mediating vasodilation in the microvasculature of the hamster cheek pouch in vivo. A range of adenosine agonists was used including N6 -cyclopentyladenosine (CPA) (A1 agonist), 5,- N -ethylcarboxamidoadenosine (NECA) (non-selective), 2-chloroadenosine (2CADO) (non-selective), 2- p -(2-carboxyethyl)-phenethylamino-5,- N -ethylcarboxamidoadenosine (CGS 21680) (A2A agonist), N6 -(3-iodobenzyl)-adenosine-5,- N -methyluronamide (IBMECA) (A3 agonist) and adenosine, as well as the adenosine antagonists 8-sulphophenyltheophylline (8-SPT) (A1/A2 antagonist), 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (A1 antagonist) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) (A2A antagonist). 2 All the adenosine analogues used induced vasodilation at concentrations between 10 nm and 1 ,m, and the potency order was NECA > CGS 21680 > 2CADO > CPA=IBMECA >> adenosine, indicating an action at A2A receptors. 8-SPT (50 ,m) antagonized vasodilator responses to NECA with an apparent pKB of 5.4, consistent with an action at A1 or A2 receptors and confirming that A3 receptors are not involved in this response. 3 DPCPX (10 nm) had no effect on vasodilation evoked by NECA, suggesting that this response was not mediated via A1 receptors, while ZM 241385 (10 nm) antagonized dilator responses to NECA with an apparent pKB of 8.9 consistent with an action via A2A receptors. 4 Overall these results suggest that adenosine A2A receptors mediate vasodilation in the hamster cheek pouch in vivo. [source] Chemopreventive Effect of Celecoxib in Oral Precancers and Cancers,THE LARYNGOSCOPE, Issue 10 2006Lining Feng PhD Abstract Objectives: Oral cancer has become an important health care problem in many countries. Because this disease develops slowly, early detection and intervention can greatly affect ultimate outcome. Celecoxib is a cyclooxygenase-2 inhibitor with significantly less toxicity. This study investigated the possibility of using it for chemoprevention of oral cancer at the early stages. Study Design: Randomized animal study. Methods: Dysplastic lesions were induced in the buccal pouches of 47 hamsters by a 5 week painting of 9,10-dimethl-1,2-benzanthrancene (DMBA). Basal diets or diets containing 500 or 1,500 ppm of Celecoxib were orally given for 7 weeks. The T50 (50% incidence; i.e., the time to appearance of tumors in 50% of the hamsters) was observed, and volume of tumors was measured on day 1, 9, 19, 28, 35, and 48 with the Celecoxib treatment. Results: The T50 was 9, 19, and 28 days with the treatment in the control group, in the 500 ppm group, and in the 1,500 ppm group, respectively. It indicated that the Celecoxib treatment could delay progression of early lesion. The tumor measurement showed that this treatment was also effective in delaying tumor growth in both treatment groups. There was a difference in the treatment efficacy between the 500 ppm and 1,500 ppm of Celecoxib, indicating a dose-dependent efficacy. Conclusions: Celecoxib is effective in delaying onset of early lesions induced by DMBA and in slowing growth of the tumors in hamster cheek pouches during the postinitiation stage. Its treatment efficacy appears to be dose dependent. [source] | ||||||||||