Most readers will probably be aware of how important stem cells are when it comes to medical research. As they have yet to differentiate they have the possibility of becoming any cell in the body if required, but this great variability comes with an inherent instability. The hematopoietic stem cells in the bone marrow, the cells from which the blood cells can be formed, have the potential to produce leukaemia and other blood cancers. There is also the risk of local tumours spreading their cells into the bone marrow which can result in cancer stem cells and rapid bone metastasis as the skeleton is invaded by the cancer. It is important to understand how the standard and malevolent stem cells interact with each other in the bone marrow so that these conditions can be counteracted and prevented.
A few months ago I wrote this post about using two photon fluorescence to study the capillary system. The basic idea being to use infrared light, which passes through flesh easily, to excite the fluorescent dye but to use the process of two photon absorption so that the remitted photon can be of greater frequency than infrared. Now although this can be done with a chemical dye, there is another option.
When people talk about organs the instant thoughts probably go to the heart, liver, stomach and kidneys. The liver is the largest of these internal organs but when it comes to largest organ overall it us outstripped by the skin which is often not thought of as an organ but does contribute to about 15% of a human’s body weight. The skin is, like almost everything else in the human body, made of a lot of water. 64% of the skin is in fact made of water.
Positron emission tomography (PET) is the process of injecting a radioactive dye into a human’s so that when it decays positrons (positive electrons) are emitted which can be used to learn about what might have gone wrong in the body. Often the dye is in fact glucose with the radioactive component attached so it will easily be absorbed into the blood and transferred around the body to the locations of interest. One of the other options is to use a metal ion as many of these are also required by the body and so accepted willingly. This study is looking primarily at copper (Cu) and the possibility of using it as the radioactive dye.
The blood brain barrier is an extremely selective semipermeable mmembrane which separates the blood that circulates in the body from the fluids that exist in the brain. Despite being excellent at preventing various neurotoxins and blood based diseases from infiltrating the brain, it manages to become a hindrance when it comes to administering drugs which want to directly effect the brain. This is one of the reasons that central nervous system diseases are so difficult to cure. One of the methods that has been employed for over fifteen years is to administer focused ultrasound which can work with induced microbubbles circulating in the body to increase the permeability of the blood brain barrier.
When an ion is produced by ionising radiation this is normally considered the end of the story at least from the perspective of the ion. The radiation goes flying off and the ion goes to destroy some DNA or something similar. In reality the situation is a bit more complicated than that. The ion, almost always positive, interacts with the electrons in whatever medium it’s found itself in leading to it losing energy. These interactions result in many electrons, called secondary electrons, gaining the energy to ionise the surroundings. This means that following the path of the primary radiation there is a cloud of secondary ionisations called the track structure as represented on the diagram:
Photodynamic therapy is a form of cancer treatment. It is another solution to the seemingly eternal problem of targeting cancer cells while minimising damage to the surroundings. By feeding a patient a drug, called a photosensitiser, the anticancer chemical can be administered in a non invasive way. The chemical itself is actually inactive until a certain frequency of light is applied resulting in absorbed photons and either the transfer of electrons to the surroundings or the production of the destructive reactive oxygen species. These events are only triggered when the accumulation in tumour cells is optimal compared to the surroundings dosage.