radiotracer

Days 23-26: July 5-8: Nuclear Medicine Week

Nuclear Medicine Week. 75% of the students in this program will shudder at the very mention of this name. But, because I cater to those who want to learn and share in my experiences, I will recount my survival of Medicine Week for those readers who might be interested in the material. Who I commend for their bravery and dedication to such a ridiculous (but very important) science.

Tuesday: Dr. Cathy Cutler from Washington University in Missouri and Dr. Henry Van Brocklin from University of California-San Francisco were our guest lecturers for the week. Dr. Cutler also works at the University of Missouri Research Reactor (MURR.) I had the hardest time staying awake for all 6 hours of lecture this day. But I took some notes on some interesting things so bear with me:

  • Radiotracers are very small amounts of a radioactive isotope that are injected into the body that participate in biological processes but do not perturb the processes. It can be used either for treatment or diagnosis of diseases. 
  • The Magic Bullet was Paul Ehrlich’s idea to use a drug that would seek out and attack the ‘parasitic invader’ but not harm the host. This resulted in the cure for syphilis in 1909. He also attached toxins to antibodies so that the body could naturally transport the drug to the diseased site. This paved the way for the development of immunotoxins.
  • Technetium-99m is a very important isotope that is used extensively in radiopharmacy. We’ll come back to all the cool things it does.
  • Imaging! I’m sure most of you have heard of one of the following: MRI (Magnetic Resonance Imaging), SPECT (Single-Photon Emission Computed Tomography), or PET (Positron-Emission Tomography) scans. I’ll go into detail about them later.
  • Radiolabeled Probes/Drugs: there were a couple stories in here about how iodine-123 is used for treatment of the thyroid (maybe for cancer?? I don’t know, my notes started to suck at this point) and strontium-90 is used to treat bone cancer. Also, it is difficult to get the isotope to go exactly where you want it to in the body, so that is a current challenge. Other challenges to consider when using radioisotopes in medicine are production capacity (can we make enough of it for efficient use?) and the economy (can we afford to regularly make the drug with this isotope?) Something to keep in mind is that every radioisotope used in medicine has to have a fairly short half life so that it decays away quickly and the patient doesn’t receive an excess dose of radiation. That means the production of the drug needs to be fast, and the process of administration to the patient needs to be fast. 
  • George de Hevesy did research with radioactive isotopes of lead-210 (which he thought were forms of radium, called “radium-D”) in Ernest Rutherford’s lab in his earlier career, won the 1943 Nobel Prize in chemistry for his studies of radiotracers in plants, animals, and humans, developed the technique of neutron activation analysis (NAA - you’ll hear about this technique later) and discovered element # 72, Hafnium. He was an accomplished man, but throughout the course of Medicine Week we heard this famous landlady story about his first radiotracer 'investigation’ a billion times: While at boarding school in Manchester, England, he suspected that the landlady was recycling their food scraps from each meal after he began having chronic upset stomach. To test his hypothesis, he placed trace amounts of radioactive material in the Sunday meal, then tested the meal served a few days later, confirming the presence of radioactivity in the food and confronting a bewildered landlady. Cheeky Bastard.

Wednesday: I came to class prepared with an energy drink the size of my quad that day. I definitely enjoyed today’s lecture the best (maybe because I was awake for all of it??) Dr. Cutler talked about radionuclide generators because we did a lab that afternoon using one. Basically a generator is a device that produces a useful short-lived supply of a medical radionuclide (called the “daughter” in nuke chem) from a non-medical long-lived radionuclide (called the “parent.”) [Note: the reaction is the parent with the long half-life decays into the daughter with the short half-life.] Here’s a summary of the lab we did, which includes the concepts that complemented it from lecture:

  1. Prepared Technetium-99m PnAO (the “m” means “meta-stable,” so a very short half-life) by directly combining 99mTcO4-, PnAO, Sn2+ and NaHCO3.
  2. Prepared it again using a Glucoscan kit as an exchange ligand. The kit contains glucoheptonate, Sn2+ and some other stabilizers.
  3. Executed paper chromatography using the Technetium-99m PnAO produced using both the above methods with ether, acetone, and saline as the chromatography solvents.
  4. Executed a solvent extraction on both types of Technetium-99m PnAO solutions, separating the 99mTcPnAO from the pertechnetate anion and the 99mTc-GH in ether and saline. The former compound partitioned into the organic ether layer, while the latter two sank into the aqueous saline layer.
  5. Both the Chromatography and Solvent Extraction methods were used to illustrate the concept of Quality Control. QC just checks on the purity of the compounds used in the generator, to make sure you are synthesizing exactly what you need and the amount of that product you need without the presence of by-products (radiochemical purity) or other unwanted isotopes (radionuclidic purity.)

I’m convinced that the write-up instructions for this lab were sent to us directly from Hell. I even received an email from Dr. Van Brocklin asking if I sent him the entire report or if the last few pages got lost in cyberspace… I had to assure him that what I sent him was my report in its entirety :P But in happier news, all the suffering I endured last Fall semester in Biochemistry I paid off… I understood quite a bit of the chemistry between the radionuclides and the body! Yay for retention! Also, for all you biochem kids out there, when Dr. Cutler starting talking about 'current Good Manufacturing Practice,’ or 'cGMP,’ all I could think about was cyclic guanosine monophosphate! Hahaha

Thursday: Dr. Van Brocklin lectured for a RIDICULOUS AMOUNT OF TIME about PET scans. No one should know that much about PET, let alone choose to teach it to a group of nuclear chemistry students who would rather play with accelerator beams and fission reactions than even utter the words “molecular imaging.” However, we sally forth. Dr. Cutler talked about MURR and the research she does over there with medical radioisotope production. The MURR, as the name suggests, is home to a nuclear reactor that uses a flux of neutrons generated in the cyclotron to produce molybdenum-99 (which decays to the famous technetium-99 isotope) as well as many other medical radionuclides.

Friday: **TO BE CONTINUED**

the yellow yaois are back in town? what a great time to celebrate by injecting radiation directly into my heart and soul

Sewage sludge could be used as sustainable fertiliser

Antananarivo, Aug 16 (IANS) Researchers have found that thermally conditioned sewage sludge improves soil properties and could be used as a sustainable alternative to commercial fertilisers.


Use of sewage sludge enables sustainable re-use of essential and finite phosphorus resources, the researchers said.

Without phosphorus, there can be no food production and as the source of phosphorus is non-renewable phosphate rocks, there is a strong need for increased recycling to ensure phosphorus security.

“Sewage sludge is a non-limited continuously available and sustainable fertiliser source,” said one of the researchers Andry Andriamananjara from the University of Antananarivo in Madagascar.

To assess its effectiveness, the researchers used a phosphorus radiotracer technique to measure the availability of phosphorus for plants in thermally conditioned sewage sludge.

They grew ryegrass in pots filled with soil added with either no fertiliser, thermally conditioned sewage sludge as fertiliser, or commercial triple superphosphate fertiliser.

The addition of fertiliser increased phosphorus uptake by the plants, showed the study published in the journal Frontiers in Nutrition.

This was not only because the fertiliser offered an additional phosphorus source, but also because the plants increased their soil exploitation.

However, total phosphorus uptake from thermally conditioned sewage sludge was lower than that from the commercial fertiliser.

This could be explained by the fact that the phosphorus in the water-soluble commercial fertiliser is immediately available for plant uptake after application, whereas the phosphorus in thermally conditioned sewage sludge is present in a lower available form.

Moreover, the other nutrients present in the sludge stimulated the microbial activity, thereby inducing competition between microorganisms and the plant roots for phosphorus uptake.

However, the researchers still recommend the usage of sewage sludge as fertiliser.

“It was shown to have a higher agronomic effectiveness in comparison with commercial fertiliser,” Andriamananjara said.

“Although on the short term it enhanced the microbial biomass and therefore phosphorus immobilisation, on the longer term the phosphorus captured by this microbial biomass can again become available for the plants,” he noted.

–IANS

gb/vt