Name: simultaneous evaluation of cerebral hemodynamics and light scattering properties of the in vivo rat brain using multispectral diffuse reflectance imaging
Uploaded: 2017-05-07T15:00:00
Description: Watch this Scientific Journal Video about Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging at J

Part of this work was supported by a Grant-in-Aid for Scientific Research (C) from the Japanese Society for the Promotion of Science (25350520, 22500401, 15K06105) and the US-ARMY ITC-PAC Research and Development Project (FA5209-15-P-0175).

Animal care, preparation, and experimental protocols were approved by the Animal Research Committee of Tokyo University of Agriculture and Technology. For this methodology, the rat is housed in a controlled environment (24 &#176;C, 12 h light/dark cycle), with food and water available ad libitum.
1. Construction of a Conventional Multispectral Diffuse Reflectance Imaging System
<ol>
	<li>Mount nine narrowband optical interference filters with center wavelengths of 500, 520, 540, 560...

<ol>
	<li>Bonhoeffer, T., Grinvald, A., Toga, A. W., Mazziotta, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+Imaging+based+on+intrinsic+signals:+the+methodology.">Optical Imaging based on intrinsic signals: the methodology.</a> Brain mapping; the methods. , 55-97 (1996).</li><li>Mourant, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+light+scattering+from+biological+cells+relevant+to+noninvasive+optical-tissue+diagnostics.">Mechanisms of light scattering from biological cells relevant to noninvasive optical-tissue diagnostics.</a> Appl. Opt. 37 (16), 3586-3593 (1998).</li><li>Abookasis, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+cortical+absorption,+scattering,+and+hemodynamic+response+during+ischemic+stroke+using+spatially+modulated+near-infrared+illumination.">Imaging cortical absorption, scattering, and hemodynamic response during ischemic stroke using spatially modulated near-infrared illumination.</a> J. Biomed. Opt. 14 (2), 024033 (2009).</li><li>Lipton, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ischemic+cell+death+in+brain+neuron.">Ischemic cell death in brain neuron.</a> Physiol. Rev. 79 (4), 1432-1568 (1999).</li><li>Jarvis, C. R., Anderson, T. R., Andrew, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anoxic+depolarization+mediates+acute+damage+independent+of+glutamate+in+neocortical+brain+slices.">Anoxic depolarization mediates acute damage independent of glutamate in neocortical brain slices.</a> Cereb. Cortex. 11 (3), 249-259 (2001).</li><li>Joshi, I., Andrew, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+anoxic+depolarization+during+ischemia-like+conditions+in+the+mouse+hemi-brain+slice.">Imaging anoxic depolarization during ischemia-like conditions in the mouse hemi-brain slice.</a> J. Neurophysiol. 85 (1), 414-424 (2001).</li><li>Polischuk, T. M., Jarvis, C. R., Andrew, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrinsic+optical+signaling+denoting+neuronal+damage+in+response+to+acute+excitotoxic+insult+in+the+hippocampal+slice.">Intrinsic optical signaling denoting neuronal damage in response to acute excitotoxic insult in the hippocampal slice.</a> Neurobiol. Dis. 4 (6), 423-437 (1998).</li><li>Jarvis, C. R., Lilge, L., Vipond, G. J., Andrew, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interpretation+of+intrinsic+optical+signals+and+calcein+fluorescence+during+acute+excitotoxic+insult+in+the+hippocampal+slice.">Interpretation of intrinsic optical signals and calcein fluorescence during acute excitotoxic insult in the hippocampal slice.</a> NeuroImage. 10 (4), 357-372 (1999).</li><li>Obeidat, A. S., Jarvis, C. R., Andrew, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glutamate+does+not+mediate+acute+neuronal+damage+after+spreading+depression+induced+by+O2/glucose+deprivation+in+the+hippocampal+slice.">Glutamate does not mediate acute neuronal damage after spreading depression induced by O2/glucose deprivation in the hippocampal slice.</a> J. Cereb. Blood Flow Metab. 20 (2), 412-422 (2000).</li><li>Dunn, A. K., Devor, A., Dale, A. M., Boas, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+extent+of+oxygen+metabolism+and+hemodynamic+changes+during+functional+activation+of+the+rat+somatosensory+cortex.">Spatial extent of oxygen metabolism and hemodynamic changes during functional activation of the rat somatosensory cortex.</a> Neuroimage. 27 (2), 279-290 (2005).</li><li>Jones, M., Berwick, J., Johnston, D., Mayhew, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concurrent+optical+imaging+spectroscopy+and+laser-Doppler+flowmetry:+the+relationship+between+blood+flow,+oxygenation,+and+volume+in+rodent+barrel+cortex.">Concurrent optical imaging spectroscopy and laser-Doppler flowmetry: the relationship between blood flow, oxygenation, and volume in rodent barrel cortex.</a> Neuroimage. 13 (6), 1002-1015 (2001).</li><li>Jones, M., Berwick, J., Mayhew, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+blood+flow,+oxygenation,+and+volume+following+extended+stimulation+of+rodent+barrel+cortex.">Changes in blood flow, oxygenation, and volume following extended stimulation of rodent barrel cortex.</a> Neuroimage. 15 (3), 474-487 (2002).</li><li>Zhou, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffuse+optical+correlation+tomography+of+cerebral+blood+flow+during+cortical+spreading+depression+in+rat+brain.">Diffuse optical correlation tomography of cerebral blood flow during cortical spreading depression in rat brain.</a> Opt. Express. 14 (3), 1125-1144 (2006).</li><li>Bouchard, M. B., Chen, B. R., Burgess, S. A., Hillman, E. M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-fast+multispectral+optical+imaging+of+cortical+oxygenation,+blood+flow,+and+intracellular+calcium+dynamics.">Ultra-fast multispectral optical imaging of cortical oxygenation, blood flow, and intracellular calcium dynamics.</a> Opt. Express. 17 (18), 15670-15678 (2009).</li><li>Jones, P. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+multispectral+reflectance+imaging+and+laser+speckle+flowmetry+of+cerebral+blood+flow+and+oxygen+metabolism+in+focal+cerebral+ischemia.">Simultaneous multispectral reflectance imaging and laser speckle flowmetry of cerebral blood flow and oxygen metabolism in focal cerebral ischemia.</a> J. Biomed. Opt. 13 (4), 044007 (2008).</li><li>Kawauchi, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffuse+light+reflectance+signals+as+potential+indicators+of+loss+of+viability+in+brain+tissue+due+to+hypoxia:+charge-coupled-device-based+imaging+and+fiber-based+measurement.">Diffuse light reflectance signals as potential indicators of loss of viability in brain tissue due to hypoxia: charge-coupled-device-based imaging and fiber-based measurement.</a> J. Biomed. Opt. 18 (1), 015003 (2013).</li><li>Yoshida, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multispectral+imaging+of+absorption+and+scattering+properties+of+in+vivo+exposed+rat+brain+using+a+digital+red-green-blue+camera.">Multispectral imaging of absorption and scattering properties of in vivo exposed rat brain using a digital red-green-blue camera.</a> J. Biomed. Opt. 20 (5), 051026 (2015).</li><li>Nishidate, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+Cerebral+Hemodynamics+and+Tissue+Morphology+of+In+Vivo+Rat+Brain+Using+Spectral+Diffuse+Reflectance+Imaging.">Evaluation of Cerebral Hemodynamics and Tissue Morphology of In Vivo Rat Brain Using Spectral Diffuse Reflectance Imaging.</a> Appl. Spectrosc. , (2016).</li><li>Wang, L. -. H., Jacques, S. L., Zheng, L. -. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MCML-Monte+Carlo+modeling+of+photon+transport+in+multi-layered+tissues.">MCML-Monte Carlo modeling of photon transport in multi-layered tissues.</a> Comput. Methods Programs Biomed. 47 (2), 131-146 (1995).</li><li>Tsytsarev, V., Premachandra, K., Takeshita, D., Bahar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+cortical+electrical+stimulation+in+vivo:+Fast+intrinsic+optical+signal+versus+voltage-sensitive+dyes.">Imaging cortical electrical stimulation in vivo: Fast intrinsic optical signal versus voltage-sensitive dyes.</a> Opt. Lett. 33 (9), 1032-1034 (2008).</li><li>Arnold, T., Biasio, M. D., Leitner, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyper-spectral+video+endoscope+for+intra-surgery+tissue+classification+using+auto-fluorescence+and+reflectance+spectroscopy.">Hyper-spectral video endoscope for intra-surgery tissue classification using auto-fluorescence and reflectance spectroscopy.</a> Proc. SPIE. 8087, 808711 (2011).</li><li>Basiri, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+a+multi-spectral+camera+in+the+characterization+of+skin+wounds.">Use of a multi-spectral camera in the characterization of skin wounds.</a> Opt. Express. 18 (4), 3244-3257 (2010).</li><li>Nishidate, I., Maeda, T., Niizeki, K., Aizu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimation+of+melanin+and+hemoglobin+using+spectral+reflectance+images+reconstructed+from+a+digital+RGB+image+by+the+Wiener+estimation+method.">Estimation of melanin and hemoglobin using spectral reflectance images reconstructed from a digital RGB image by the Wiener estimation method.</a> Sensors. 13 (6), 7902-7915 (2013).</li></ol>

The most critical step in this protocol is the removal of the thinned skull region to make the cranial window; this should be performed carefully to avoid unexpected bleeding. This step is important for obtaining high-quality multispectral diffuse reflectance images with high accuracy. The use of a stereomicroscope is recommended for the surgical procedure if possible. Small pieces of gelatin sponge are useful for hemostasis.
The optical system described in this article passes a monochromatic ...

Multispectral diffuse reflectance imaging is the most common technique for obtaining a spatial map of intrinsic optical signals (IOSs) in cortical tissue. IOSs observed in the in vivo brain are mainly attributed to three phenomena: variations in light absorption and scattering properties due to cortical hemodynamics, variation in absorption depending on the reduction or oxidization of cytochromes in mitochondria, and variations in light scattering properties induced by morphological alterations1.
Light in the visible (VIS) to near-infrared (NIR) spectral range is effectively absorbed and scattered by biological tissue. The diffuse reflectance spectrum of the in vivo brain is characterized by absorption and scattering spectra. The reduced scattering coefficients &#956;s&#39; of brain tissue in the VIS-to-NIR wavelength range result in a monotonous scattering spectrum exhibiting smaller magnitudes at longer wavelengths. The reduced scattering coefficient spectrum &#956;s&#39;(&#955;) can be approximated to be in the form of the power law function2,3 as &#956;s&#39;(&#955;) = a &#215; &#955;-b. The scattering power b is related to the size of biological scatterers in living tissue2,3. Morphological alterations of the tissue and reduction of the viability of living cortical tissue can affect the size of the biological scatterers4,5,6,7,8,9.
An optical system for multispectral diffuse reflectance imaging can be easily constructed from an incandescent light source, simple optical components, and a monochromatic charged-coupled device (CCD). Therefore, various algorithms and optical systems for multispectral diffuse reflectance imaging have been used to evaluate cortical hemodynamics and/or tissue morphology10,11,12,13,14,15,16,17,18.
The method described in this article is used to visualize both the hemodynamics and light scattering properties of rat cerebral tissue in vivo using a conventional multispectral diffuse reflectance imaging system. The advantages of this method over alternative techniques are the ability to evaluate spatiotemporal changes in both cerebral hemodynamics and cortical tissue morphology, as well as its applicability to various brain dysfunction animal models. Therefore, the method will be appropriate for investigations of traumatic brain injury, epileptic seizure, stroke, and ischemia.

<table border="0" cellpadding="0" cellspacing="0" width="856">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="36">
			<td height="36" style="height:36px;width:289px;">150-W halogen-lamp light source</td>
			<td style="width:281px;">Hayashi Watch Works Co., Ltd, Tokyo, Japan</td>
			<td style="width:119px;">LA-150SAE</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="36">
			<td height="36" style="height:36px;">Light guide</td>
			<td style="width:281px;">Hayashi Watch Works Co., Ltd, Tokyo, Japan</td>
			<td>LGC1-5L1000</td>
			<td></td>
		</tr>
		<tr height="36">
			<td height="36" style="height:36px;">Collecting lens</td>
			<td style="width:281px;">Hayashi Watch Works Co., Ltd, Tokyo, Japan</td>
			<td>SH-F16</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@500nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65088</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@520nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65093</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@540nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65096</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@560nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#67766</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@570nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#67767</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@580nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65646</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@600nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@730nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#65115</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interference filters l@760nm</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>#67777</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Motorized filter wheel&#160;</td>
			<td>Andover Corporation, NH, USA</td>
			<td>FW-MOT-12.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">16-bit cooled CCD camera</td>
			<td>Bitran, Japan</td>
			<td>BS-40</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;">Video zoom lens</td>
			<td>Edmund Optics Japan Ltd, Tokyo, Japan</td>
			<td>VZMTM300i</td>
			<td></td>
		</tr>
		<tr height="36">
			<td height="36" style="height:36px;width:289px;">Spectralon white standard with 99% diffuse reflectance</td>
			<td>Labsphere Incorporated, North Sutton, NH, USA</td>
			<td>SRS-99-020</td>
			<td></td>
		</tr>
	</tbody>
</table>

simultaneous evaluation of cerebral hemodynamics and light scattering properties of the in vivo rat brain using multispectral diffuse reflectance imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system. This system is constructed from a broadband white light source, a motorized filter wheel with a set of narrowband interference filters, a light guide, a collecting lens, a video zoom lens, and a monochromatic charged-coupled device (CCD) camera. An ellipsoidal cranial window is made in the skull bone of a rat under isoflurane anesthesia to capture in vivo multispectral diffuse reflectance images of the cortical surface. Regulation of the fraction of inspired oxygen using a gas mixture device enables the induction of different respiratory states such as normoxia, hyperoxia, and anoxia. A Monte Carlo simulation-based multiple regression analysis for the measured multispectral diffuse reflectance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) is then performed to visualize the two-dimensional maps of hemodynamics and the light scattering properties of the in vivo rat brain.

Representative spectral images of diffuse reflectance acquired from in vivo rat brains are shown in Figure 3. The images at 500, 520, 540, 560, 570, and 580 nm clearly visualize a dense network of blood vessels in the cerebral cortex. The deterioration of contrast between blood vessels and the surrounding tissue observed in the images at 600, 730, and 760 nm reflects the lower absorption of light by hemoglobin at longer and NIR wavelengths.
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Watch this Scientific Journal Video about Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging at J

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system.

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional ...

The overall goal of this procedure is to visualize the hemodynamics and light-scattering property of in vivo brain tissue. This method can help answer key questions in the field of biomedical optics through the use of imaging for intrinsic optical signals in rat brain tissues. The main advantage of this technique is that special temporal changes in post cerebral hemodynamics and cortical tissue morphology can be evaluated.The implications of this technique extend throughout monitoring brain functions and viability for various brain disorder models because experiments with those animal models are often performed through the cranial window. So this method can provide insight into the intrinsic optical signals. It can also be applied to other spectral imaging techniques.Begin by affixing the rat head in a stereotaxic frame. After anesthetizing, shave the head region beyond the prospective incision site using hair clippers until the skin surface appears. Then make a longitudinal incision approximately 20 millimeters long along the midline of the head using a surgical scalpel.And expose the subcutaneous connective tissues. Remove the subcutaneous connective tissues using a sharp curette, and pull it to both sides of the head to expose the skull bone. Next use a high speed drill to dig an ellipsoidal ditch on the skull bone inside the cranial sutures.Then slowly and homogeneously excavate the skull bone inside the ditch. Next press lightly on the surface of the thinned skull with the tip of the pincer to estimate the bone thickness and strength after a cerebral blood vessel appears. Then use the tip of the pincer to cut the ellipsoidal border line of the thinned skull piecemeal.And slowly remove the thinned skull from the brain's surface. Finally gently bathe the cranial window with physiological saline and cover it with a transparent glass plate approximately 0.1 millimeters thick. Begin by using a tube to connect the first port of a Y shaped tube called connector one to the first port of another Y shaped tube called connector two.Then connect the inlet port of the mouthpiece to the second port of tube connector one. Next use a tube to connect the third port of tube connector one to an oxygen concentration monitor device. Similarly, use a tube to connect the second port of tube connector two to the outlet port of an anesthesia machine, and use another tube to connect the third port of tube connector two to the outlet port of a gas mixture device.Next use a tube to connect one inlet port of the gas mixture device to a high pressure 95%o2 5%co2 gas cylinder. Likewise connect the other inlet port of the gas mixture device to a high pressure 95%n2 5%co2 gas cylinder using a tube. Then use the rotary knobs on the gas mixture device to change the gas flow rates of o2 and n2.Finally check and regulate the fraction of inspired oxygen or fio2 using the oxygen concentration monitor device. Begin by gently placing the rat on the stage and slowly adjust the STage level so that the camera can focus on the surface of the rat brain. Within the image acquisition software, select the save command from the file menu to save an image to a file, naming it according to the sample and wavelength.Then change the filter location by rotating the filter wheel. Repeat the image acquisition at each of the nine wavelengths. Next turn off the halogen lamp light source.Block the light path to the monochromatic charge coupled device camera system using a shielding plate. Finally select the save command from the file menu and choose a file name that identifies the sample. The estimated images of hemoglobin concentration, oxygenation state, and scattering power for in vivo exposed rat brain are shown here.The oxygenated hemoglobin concentration and regional oxygen saturation in arteriole are higher than those in venules. Here images of an exposed rat brain during changes in fio2 for the light scattering power B are shown here. The value of B was slightly increased during the period from the onset of anoxia until respiratory arrest, whereas it continuously decreased during the period from five minutes to 30 minutes after the onset of anoxia.Once mastered, this technique can be completed in three hours if it is performed properly. While measuring the spectral images, it's important to remember to maintain the arrangement of the optical components. Following this procedure, other methods like rapid multispectral imaging can be performed in order to answer additional questions about post optical intrinsic signals.After watching this video, you should have a good understanding of how to visualize hemodynamics and light scattering properties of in vivo exposed rat brains. Don't forget that working with isoflurane can be hazardous and anesthesia gas rates should be controlled with an anesthetic gas scavenging theater.

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Neuroscience

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal models, including monkeys, ferrets, bats, rodents, and cats. In order to draw suitable parallels between human and animal models of auditory function, it is important to establish a bridge between human functional imaging studies and animal electrophysiological studies. Functional magnetic resonance imaging (fMRI) is an established, minimally invasive method of measuring broad patterns of hemodynamic activity across different regions of the cerebral cortex. This technique is widely used to probe sensory function in the human brain, is a useful tool in linking studies of auditory processing in both humans and animals and has been successfully used to investigate auditory function in monkeys and rodents. The following protocol describes an experimental procedure for investigating auditory function in anesthetized adult cats by measuring stimulus-evoked hemodynamic changes in auditory cortex using fMRI. This method facilitates comparison of the hemodynamic responses across different models of auditory function thus leading to a better understanding of species-independent features of the mammalian auditory cortex.

Functional studies of the auditory system in mammals have traditionally been conducted using spatially-focused techniques such as electrophysiological recordings. The following protocol describes a method of visualizing large-scale patterns of evoked hemodynamic activity in the cat auditory cortex using functional magnetic resonance imaging.

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal ...

Deep Brain Stimulation with Simultaneous fMRI in Rodents

In order to visualize the global and downstream neuronal responses to deep brain stimulation (DBS) at various targets, we have developed a protocol for using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) to image rodents with simultaneous DBS. DBS fMRI presents a number of technical challenges, including accuracy of electrode implantation, MR artifacts created by the electrode, choice of anesthesia and paralytic to minimize any neuronal effects while simultaneously eliminating animal motion, and maintenance of physiological parameters, deviation from which can confound the BOLD signal.&#160;Our laboratory has developed a set of procedures that are capable of overcoming most of these possible issues. For electrical stimulation, a homemade tungsten bipolar microelectrode is used, inserted stereotactically at the stimulation site in the anesthetized subject. In preparation for imaging, rodents are fixed on a plastic headpiece and transferred to the magnet bore. For sedation and paralysis during scanning, a cocktail of dexmedetomidine and pancuronium is continuously infused, along with a minimal dose of isoflurane; this preparation minimizes the BOLD ceiling effect of volatile anesthetics. In this example experiment, stimulation of the subthalamic nucleus (STN) produces BOLD responses which are observed primarily in ipsilateral cortical regions, centered in motor cortex. Simultaneous DBS and fMRI allows the unambiguous modulation of neural circuits dependent on stimulation location and stimulation parameters, and permits observation of neuronal modulations free of regional bias. This technique may be used to explore the downstream effects of modulating neural circuitry at nearly any brain region, with implications for both experimental and clinical DBS.

This protocol describes a standard method for simultaneous functional magnetic resonance imaging and deep brain stimulation in the rodent. The combined use of these experimental tools allows for the exploration of global downstream activity in response to electrical stimulation at virtually any brain target.

In order to visualize the global and downstream neuronal responses to deep brain stimulation (DBS) at various targets, we have developed a protocol for ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in the mouse retrosplenial cortex (RSC) using in vivo two-photon microscopy in Thy1-GFP transgenic mouse line. This approach creates a possibility to investigate the correlation of behavioural manipulations with changes in neuronal morphology in vivo.
The cranial window implantation procedure was considered to be limited only to the easily accessible cortex regions such as the barrel field. Our approach allows visualization of neurons in the highly vascularized RSC. RSC is an important element of the brain circuit responsible for spatial memory, previously deemed to be problematic for in vivo two-photon imaging.
The cranial window implantation over the RSC is combined with an injection of mCherry-expressing recombinant adeno-associated virus (rAAVmCherry) into the dorsal hippocampus. The expressed mCherry spreads out to axonal projections from the hippocampus to RSC, enabling the visualization of changes in both presynaptic axonal boutons and postsynaptic dendritic spines in the cortex. 
This technique allows long-term monitoring of experience-dependent structural plasticity in RSC.

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in mouse retrosplenial cortex using in vivo two photon microscopy in Thy1-GFP transgenic line. This approach is combined with injection of mCherry-expressing adeno-associated virus into dorsal hippocampus. These techniques allow long-term monitoring of experience-dependent structural plasticity in RSC.

This video shows the craniotomy procedure that allows chronic imaging of neurons in the mouse retrosplenial cortex (RSC) using in vivo two-photon ...

Evaluation of Bioenergetic Function in Cerebral Vascular Endothelial Cells

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types that comprise the BBB; these cells have a very high-energy demand, which requires optimal mitochondrial function. In the case of disease or injury, the mitochondrial function in these cells can be altered, resulting in disease or&#160;the opening of the BBB. In this manuscript, we introduce a method to measure mitochondrial function in CVE cells by using whole, intact cells and a bioanalyzer. A mito-stress assay is used to challenge the cells that have been perturbed, either physically or chemically, and evaluate their bioenergetic function. Additionally, this method also provides a useful way to screen new therapeutics that have direct effects on mitochondrial function. We have optimized the cell density necessary to yield oxygen consumption rates that allow for the calculation of a variety of mitochondrial parameters, including ATP production, maximal respiration, and spare capacity. We also show the sensitivity of the assay by demonstrating that the introduction of the&#160;microRNA, miR-34a, leads to a pronounced and detectable decrease in mitochondrial activity. While the data shown in this paper is optimized for the bEnd.3 cell line, we have also optimized the protocol for primary CVE cells, further suggesting the utility in preclinical and clinical models.

Endothelial cell mitochondria are critical to maintain blood-brain-barrier integrity. We introduce a protocol to measure bioenergetic function in cerebral vascular endothelial cells.

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types ...

Live Imaging of Primary Cerebral Cortex Cells Using a 2D Culture System

During cerebral cortex development, progenitor cells undergo several rounds of symmetric and asymmetric cell divisions to generate new progenitors or postmitotic neurons. Later, some progenitors switch to a gliogenic fate, adding to the astrocyte and oligodendrocyte populations. Using time-lapse video-microscopy of primary cerebral cortex cell cultures, it is possible to study the cellular and molecular mechanisms controlling the mode of cell division and cell cycle parameters of progenitor cells. Similarly, the fate of postmitotic cells can be examined using cell-specific fluorescent reporter proteins or post-imaging immunocytochemistry. More importantly, all these features can be analyzed at the single-cell level, allowing the identification of progenitors committed to the generation of specific cell types. Manipulation of gene expression can also be performed using viral-mediated transfection, allowing the study of cell-autonomous and non-cell-autonomous phenomena. Finally, the use of fusion fluorescent proteins allows the study of symmetric and asymmetric distribution of selected proteins during division and the correlation with daughter cells fate. Here, we describe the time-lapse video-microscopy method to image primary cerebral cortex murine cells for up to several days and analyze the mode of cell division, cell cycle length and fate of newly generated cells. We also describe a simple method to transfect progenitor cells, which can be applied to manipulate genes of interest or simply label cells with reporter proteins.

Live imaging is a powerful tool to study cellular behaviors in real time. Here, we describe a protocol for time-lapse video-microscopy of primary cerebral cortex cells that allows a detailed examination of the phases enacted during the lineage progression from primary neural stem cells to differentiated neurons and glia.

During cerebral cortex development, progenitor cells undergo several rounds of symmetric and asymmetric cell divisions to generate new progenitors or ...

Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One's Thumb

The capillary refill test was introduced in 1947 to help estimate circulatory status in critically ill patients. Guidelines commonly state that refill should occur within 2 s after releasing 5 s of firm pressure (e.g., by the physician&#39;s finger) in the normal healthy supine patient. A slower refill time indicates poor skin perfusion, which can be caused by conditions including sepsis, blood loss, hypoperfusion, and hypothermia. Since its introduction, the clinical usefulness of the test has been debated. Advocates point out its feasibility and simplicity and claim that it can indicate changes in vascular status earlier than changes in vital signs such as heart rate. Critics, on the other hand, stress that the lack of standardization in how the test is performed and the highly subjective nature of the naked eye assessment, as well as the test&#39;s susceptibility to ambient factors, markedly lowers the clinical value. The aim of the present work is to describe in detail the course of the refill event and to suggest potentially more objective and exact endpoint values for the capillary refill test using diffuse polarization spectroscopy.

Diffuse Reflectance Spectroscopy: Getting the Capillary Refill Test Under One&#039;s Thumb

This protocol describes how the use of diffuse polarization spectroscopy can improve the clinical usefulness of the capillary refill test. We suggest a more detailed analysis of the course of the capillary refill in healthy volunteers using diffuse reflectance spectroscopy videos and new informatic endpoints.

The capillary refill test was introduced in 1947 to help estimate circulatory status in critically ill patients. Guidelines commonly state that refill ...

Induction of Diffuse Axonal Brain Injury in Rats Based on Rotational Acceleration

Traumatic brain injury (TBI) is a major cause of death and disability. Diffuse axonal injury (DAI) is the predominant mechanism of injury in a large percentage of TBI patients requiring hospitalization. DAI involves widespread axonal damage from shaking, rotation or blast injury, leading to rapid axonal stretch injury and secondary axonal changes that are associated with a long-lasting impact on functional recovery. Historically, experimental models of DAI without focal injury have been difficult to design. Here we validate a simple, reproducible and reliable rodent model of DAI that causes widespread white matter damage without skull fractures or contusions.

This protocol validates a reliable, easy-to-perform and reproducible rodent model of brain diffuse axonal injury (DAI) that induces widespread white matter damage without skull fractures or contusions.

Traumatic brain injury (TBI) is a major cause of death and disability. Diffuse axonal injury (DAI) is the predominant mechanism of injury in a large ...

Whole-Brain Single-Cell Imaging and Analysis of Intact Neonatal Mouse Brains Using MRI, Tissue Clearing, and Light-Sheet Microscopy

Tissue clearing followed by light-sheet microscopy (LSFM) enables cellular-resolution imaging of intact brain structure, allowing quantitative analysis of structural changes caused by genetic or environmental perturbations. Whole-brain imaging results in more accurate quantification of cells and the study of region-specific differences that may be missed with commonly used microscopy of physically sectioned tissue. Using light-sheet microscopy to image cleared brains greatly increases acquisition speed as compared to confocal microscopy. Although these images produce very large amounts of brain structural data, most computational tools that perform feature quantification in images of cleared tissue are limited to counting sparse cell populations, rather than all nuclei.
Here, we demonstrate NuMorph (Nuclear-Based Morphometry), a group of analysis tools, to quantify all nuclei and nuclear markers within annotated regions of a postnatal day 4 (P4) mouse brain after clearing and imaging on a light-sheet microscope. We describe magnetic resonance imaging (MRI) to measure brain volume prior to shrinkage caused by tissue clearing dehydration steps, tissue clearing using the iDISCO+ method, including immunolabeling, followed by light-sheet microscopy using a commercially available platform to image mouse brains at cellular resolution. We then demonstrate this image analysis pipeline using NuMorph, which is used to correct intensity differences, stitch image tiles, align multiple channels, count nuclei, and annotate brain regions through registration to publicly available atlases.
We designed this approach using publicly available protocols and software, allowing any researcher with the necessary microscope and computational resources to perform these techniques. These tissue clearing, imaging, and computational tools allow measurement and quantification of the three-dimensional (3D) organization of cell-types in the cortex and should be widely applicable to any wild-type/knockout mouse study design.

This protocol describes methods for conducting magnetic resonance imaging, clearing, and immunolabeling of intact mouse brains using iDISCO+, followed by a detailed description of imaging using light-sheet microscopy, and downstream analyses using NuMorph.

Tissue clearing followed by light-sheet microscopy (LSFM) enables cellular-resolution imaging of intact brain structure, allowing quantitative analysis of ...