What is one result of decreasing blood flow to the heart or brain?

Depends upon whats the level of restriction

If there is a little decrease in blood flow in the brain,it leads to  headaches ,dizziness , confusion  

If there is little decrease in blood flow in the heart it can cause chest pain or what we call angina

But if there is clogged vessel of the brain ,it can cause stroke because the part of the brain the vessel is supplying will become ischemic or deprived of the oxygen and nutrients

Similarly if the artery supplying the heart gets clogged ,it leads to heart attack ,the reason being the same that the tissue of the heart become ischemic .

to prevent people from getting the ebola virus, countries around the world paid to doctors develop a new vaccine. now that the vaccine has been made, doctors will need to experiment on a large number of people to find out if it works safely.

what is the greatest limitation that scientists are dealing with as they try to figure out how to experiment with the ebola vaccine?

meditation is a practice of sitting still and quiet for minutes or even hours. it has been practiced for thousands of years and is even a part of religious practices for some people. carefully controlled, repeated measurements of brain activity have shown that meditation does increase certain chemicals in the brain and even grows the part of the brain that people connect with their current surroundings and activities.

are claims about the effects of meditation most likely scientific or pseudoscientific?

not pseudoscientific, because people have made claims about it but scientific observations have not been made