As my time in the lab for the summer was coming to a close, my mentor and other members of the lab wanted to test my dissection and isolation skills by having me try isolating other arteries of interest to different groups in the lab. The artery of interest on one veteran stroke researcher: the middle cerebral artery (MCA). The MCA is a site in the brain where most of the stroke activity that she studies occurs. After successfully isolating pulmonary arteries all summer, I was ready for the next challenge, even if it was just explorative to see if the isolation and mount were possible for the lab to do. The lab had come to view me as their isolation expert, they trusted my judgment and abilities, an honor that I never expected to have, especially after such a short time. But despite their confidence in me, I was a little nervous about the MCA isolation; it was in a mouse and I had only ever worked in rats. Mice weigh about 20-30 grams and the rats that I had been using weighed about 280-500 grams.
As she removed the brain from the mouse, I was struck by how small it was, only about the size of a single peanut. Prior to the day of the MCA isolation attempt, I scoured the Internet for brain diagrams including the MCA and the other arteries in the brain. I wanted to prepare myself so that I would not be lost during the isolation, I was on my own, after all. Thanks to my preparation, I had no problem identifying the MCA, it and the other arteries were all on the surface of the brain. The biggest challenge of the isolation was the size of the artery, about the width of a hair, and the material of the brain which was nearly impossible to grasp onto. Grasping onto the brain tissue with micro-forceps was about equivalent to trying to grab jello, the forceps just went straight through the tissue. After becoming acquainted with the appearance and texture of the brain, I decided that the easiest way to remove the artery would be to simply peel it from the surface. I had to be careful not to grab the MCA with the forceps, as that would do damage to the artery, but to grab the branches and other material encasing the artery. After the artery was removed from the brain, I was left with peeling away the vein and connective tissue, leaving this:
Image through microscope lens with my cell phone’s camera. The measuring tape segment in the image is in millimeters. The artery is by the corner of the tape, curled into an uppercase “J” like shape. The top arm of the J is the anterior cerebral artery (ACA) and the body of the J is the MCA. I used the ACA as something to hold onto during the isolation and manipulation of the MCA.
This second image is of a mouse brain intravascular perfusion of carbon black to allow for visualization of the blood vessels with abbreviated names of each vessel. Image found on google images.
After the isolation was complete and I cut off the ACA, it was time to mount the artery on the pressure myograph. I switched to the smallest cannulas that we had available, which was a glass cannula (120-micron diameter). I was able to mount one end of the MCA on the cannula, but I was unable to mount the other due to the significant tapering in diameter. After attempting the mount in three different MCA isolations, I deemed the mouse MCA mount to be unattainable for me. The same segment in a rat would be very possible to mount since the size would be much larger. Even though the MCA mount was a bust, I was able to successfully isolate and mount the basilar artery (BA).
Doing the arterial isolations of the brain were a change of pace for me not only because I was exploring a new artery, but my mentor was also out of town. I normally have my mentor to refer to if I have a question or if an obstacle arises, but I was on my own. My mentor and I are the only ones in the lab who are experienced in isolations and the use of the pressure myograph. I always appreciate my mentor for his expertise, passion for the sciences, kindness, and patience but during the week of his absence, I gained an even greater appreciation for him. I know I will have other mentors throughout my education, but I will never find a mentor like this one again. Having a mentor that I am able to look up to makes my research experience that much better and I am fortunate to have been invited back for the upcoming fall and winter semesters.