We hypothesized that generation of nitric oxide (NO) was associated with persistent hemodynamic abnormalities observed in the rat cortex exposed to a shock wave. To examine this speculation, we performed in vivo imaging of NO in the rat cortex exposed to a laser-induced shock wave (LISW). An NO sensitive fluoroprobe (DAF-2 DA) was applied to the cortical surface, and NO-originating fluorescence was observed under the stereoscopic fluorescence microscope. We observed that the fluorescence intensity in perivascular spaces as well as in parenchyma was drastically increased after LISW application. Intense fluorescence spots in the parenchyma probably indicate NO generation from neurons.
We investigated a rapid imaging method to monitor the spatial distribution of total hemoglobin concentration (CHbT), the tissue oxygen saturation (StO2), and the scattering power b in the expression of musp=a(lambda)^-b as the scattering parameters in cerebral cortex using a digital red-green-blue camera. In the method, Monte Carlo simulation (MCS) for light transport in brain tissue is used to specify a relation among the RGB-values and the concentration of oxygenated hemoglobin (CHbO), that of deoxygenated hemoglobin (CHbR), and the scattering power b. In the present study, we performed sequential recordings of RGB images of in vivo exposed brain of rats before, during, and after hindlimb electrical stimulation. The remarkable increases in CHbO, CHbT, and StO2 were induced by hindlimb electrical stimulation whereas significant decreases in the scattering power b and CHbR were observed after the onset of stimulation. It has been reported that cerebral blood flow (CBF) and blood oxygen level-dependent (BOLD) signal responses show better correlation with post-synaptic local field potentials than with spiking activity. Positive CBF and BOLD responses during stimulation are associated with an increase in neuronal activity and decrease in deoxyhemoglobin content. Therefore, the decrease in the scattering power b of somatosensory cortex after hindlimb electrical stimulation is indicative of slow post-synaptic potential change. The results in this study indicate potential of RGB camera-based imaging to evaluate both hemodynamics and synaptic activity in brain tissue.
Due to the frequent attacks using improvised explosive devices (IEDs), the number of patients suffering from blast-induced traumatic brain injury (bTBI) has been growing. Although most of the patients have been diagnosed as having mild bTBI, many of them show higher brain dysfunction in the chronic phase. However, the mechanisms of bTBI are unclear, and methods of prevention, diagnosis and treatment have therefore not been established. In our previous study, we applied a laser-induced shock wave (LISW) to the rat brain, for which real-time measurements of cerebral hemodynamics were conducted based on diffuse reflectance spectroscopy. We found that LISW application caused spreading depolarization (SD) and transient hyperemia/hyperoxemia, which was followed by persistent oligemia/hypoxemia in the cortex. We hypothesized that nitric oxide (NO) may be involved in these abnormal hemodynamic changes. In this study, we investigated our hypotheses using an inhibitor of NO synthesis. We observed that by inhibiting NO synthesis with LNAME, transient hyperemia and persistent oligemia/hypoxemia were reduced, suggesting that NO generation is activated by shock wave exposure and causes the abnormal hemodynamic changes in the rat brain.
Due to the topographical location and extensive size, skin encounters high dose of clastogen those cause cancer which can be cured, if diagnosed at the early stage. While visual inspection, histopathological study, bio-sensing, dermoscopy exhibit some limitations, noninvasive optical methods cater comfortable, early and precise diagnosis. In this research, we investigated a multispectral imaging method based on the diffuse reflectance spectroscopy (DRS) to estimate spatiotemporal changes in the light scattering and hemodynamic parameters in mice during cutaneous two-stage chemical carcinogenesis. In this method, Monte Carlo simulation-based empirical formulas assisted in the extraction of the light scattering power b, total hemoglobin concentration Cth, and tissue oxygen saturation StO2 in the skin. In laboratory environment, we induced mice skin cancer by 7,12-dimethylbenz[a]anthracene (DMBA) and 12-Otetradecanoylphorbol-13-acetate (TPA) and monitored the changes in the cutaneous tissue at a particular interval through capturing multispectral diffuse reflectance images and analyzing over the period of initiation, promotion and progression. The results displayed the decrease in b and increases in both Cth and StO2 in tumor regions. Significantly, we found that the inception of rapid changes in the scattering parameter is about one to two week(s) earlier than the hemoglobin concentration. On the other hand, at the advanced stage, we also found the blackish discoloration of the skin in the tip of the papilloma when it experienced necrosis, which corresponds to the regional decrease in StO2 of some large papilloma.
The pathophysiology and mechanism of primary blast-induced traumatic brain injury (bTBI) have not yet been elucidated. We previously observed the occurrence of spreading depolarization (SD) and transient hyperemia/hyperoxemia followed by persistent oligemia/hypoxemia in the cortex of the rat brain exposed to a laserinduced shock wave (LISW). However, the mechanism of such hemodynamic abnormalities is not clear. In this study, we investigated the involvement of nitric oxide (NO), which is known as an endothelium-derived relaxing factor (EDRF) and also as a substance associated with vasoconstriction. By the inhibition of NO synthesis, we found that the transient hyperemia/hyperoxemia immediately after LISW application was diminished and the level of persistent oligemia/hypoxemia was mitigated even when SD occurred. The results suggest that hemodynamic abnormalities caused by an LISW in the rat cortex was associated with an increased NO production and its vasodilatory/vasoconstrictory effects.
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