damianszyk's blog

Studies have been done where researchers alter thyroid hormone levels by treating adult rats with T4, the same drug we will treat our zebrafish with. In these studies, they have found that neural stem cell proliferation decreases in T4 treated rats. The differences in our experiment is that we are using zebrafish as a model organism, the zebrafish are 5 days post fertilization, and the dosage of TL4 that we are using can be different since we do not know how much was used in the study on adult rats.

Over the past decade or two, scientists have been trying to study the effects of PTU on fish. Studies on amphibians and mammalians have been much more popular during the course of this time period. Mentioned in one of the excerpts, researchers have been able to figure out that low thyroid hormone levels prior to the development of the hypothalamus-pituitary-thyroid (HPT) axis leads to brain damage and impairments in humans and rodents. Due to the fact that the HPT axis does not form right away in zebrafish offspring, the levels of thyroid hormone comes directly from the maternal egg yolk. After about 60-72 hours post fertilization, the HPT axis is formed and the zebrafish can now produce their own thyroid hormones.  Altering thyroid hormone levels is one of the major factors involved in neuronal and oligodendrocyte balance in the development of the zebrafish brain.

Today, in my neurobiology and physiology lab, we dissected zebrafish brains that were treated with 0.5 mM PTU and 300 nM T4. Drug treatment with PTU induces hypothyroidism, while treatment with T4 induces hyperproliferation. We are measuring how the different levels of thyroid hormone affects neural stem cell proliferaation. After dissection of the brain, we will mount themn and look under a fluorescent microscope to count indivial cells in the posterior recess and later recess. These two regions make up the hypothalamus which is where neural cell proliferation occurs. 

There are many hormones plants release to stimulate growth, defense and other mechanisms needed for a plant to survive and reproduce. The main hormone resposible for growth is gibberllin. This hormone is produced in the plant cells plastids, where they are then transported to the endoplasmic reticulum. The receptor responsible for recognizing this hormone to be able to transport it into the endoplasmic reticulum is DELLA. With gibberellin located in the endoplasmic reticulum, this allows for gene transcription to be turned on, resulting in the elongation of a plant. The gibberellin hormone was important during the green revolution which is thought to have saved over a billion lives worldwide. 

Today in my neurobiology and physiology lab, we drug treated 5 days post fertilization zebrafish with 0.5 mM PTU and 300 nM T4 to manipulate the levels of thyroid hormones in the zebrafish. Also, we drug treated 7 days post fertilization zebrafish with 1X EdU for three hours in a 28 degress Celsius incubator. During the three hour wait, we were lectured on the hypothalamus-pituitary thyroid axis and the Notch signaling pathway to help us better understand the whole process when formulating our hypothesis. Along with this information and additonal readings, we will have to formulate our own hypothesis and test for it in the upcoming weeks.

Review Article: Link, G. K. K. Botanical Gazette, vol. 86, no. 2, 1928, pp. 243–243. JSTOR, www.jstor.org/stable/2470664.

Journal Article: Faeth, Stanley H. “Host Leaf Selection by Leaf Miners: Interactions among Three Trophic Levels.” Ecology, vol. 66, no. 3, 1985, pp. 870–875. JSTOR, www.jstor.org/stable/1940549.

The control of the thyroid hormone levels in the blood is maintained by the HPT axis. The HPT axis is known as the hypothalamic-piutuitary-thyroid axis and it depends on three things: the hypothalamus, the pituitary, and the thyroid gland. Low levels of thyroid hormone cause the hypothalamus to release TRH, thyrotropin-releasing hormone. This then causes the pituitary to secrete TSH, thyroid-stimulating hormone. This then signals for the thyroid gland to secrete both T3 and T4, which are both types of thyroid hormones. Both T3 and T4 act as a negative feedback loop on both the hypothalamus and the pituitary. This means that a high level of thyroid hormone in the blood will not cause the hypothalamus and pituitary to release TRH and TSH, respectively. The whole system together acts to maintain the balance of thyroid hormone in the blood of an organism.

In plants, actin dynamics are regulated by actin-associated proteins. There are multiple processes in the plants that are carried out due to these proteins. Some of the processes include growing filaments, capping the filaments at either end so new monomers cannot be added or removed, severing actin filaments, and budnling together several actin filaments. Myosin are motors that are able to walk along the actin filaments towards the plus end promoting growth of the filament. Dyneins are able to walk towards the minus ends, but this motor protein only appears in animals cells, not plant cells.

Major crops cultivated today diversed from many different regions across the world. From Southern Mexico and Middle America came maize. Tomatos diversified from South American countries such as Bolivia, Peru, and Southern Chile. Peas and olives came from the Mediterranean Sea and other coastal regions. From the Middle East came the pear. The center of diversity for hemp and carrots were Central Asia countries such as Afghanistan. Rice and orange diversified from India. The main crops to diversify from China were rice and soybean. It is very interesting to know that there were many centers of diversity for crops to diversify from.

Today, I had two classes. One in the morning and the other during early afternoon. After class today, I studied for my plant biology exam that is tomorrow during class. The exam covers the first eight lectures that we had in class and covers the topics of photosynthesis, different light receptors, plant pathogens and their defense sytem, and crop diversity. An interesting yet shocking fact I learned during one of the lectures is that undernutrition contributes to nearly half of all deaths in children under 5 and is widespread in Asia and Africa. Knowing that many children are dying from undernutrition is an important reason for studying the plants and crops that are produced to feed a population. Knowing how to effectively speed up the process of growing crops to feed a population who are being underfed can lead to a lower percentage of children under 5 being affected by undernutrition.