lgorman's blog

Heart disease is one of the leading causes of death in america. Valvular heart disease is a type of heart disease that revolves around the valves in the heart. These valves play a major role in controlling the flow of blood, and preventing backflow between the separate chambers. Although some heart valve issues can be fixed via drugs and therapies, sometimes patients have to get their valves replaced.  When a patient is considering this option, they can either get a mechanical valve or a bioprosthetic heart valve (BHV). Each option has its pros and cons, however BHVs offer more pros than the mechanical option. The main issue with BHVs is that they come from another animal, usually from cattle or pigs, and this triggers an immune response in the human body. This immune response leads to calcification of of the heart valve and severely reduces the shelf life of the prosthetic.

1. After what step are the carbons of a fatty acid completely oxidized? (Lecture 22-Slide 11)

2. This question is testing the students knowledge on the oxidation of fatty acids. More specifically, it asks the student to recall the steps of the oxidation, and know determine which step is completely oxidized.

3. New Question: What step produces the most reduced electron carriers, and how many does it make for a (18:0) fatty acid?

   1. Acyl-CoA transport , 4 reduced electron carriers

   2. Beta oxidation, 36 reduced electron carriers

   3. Citric Acid Cycle, 36 reduced electron carriers (CORRECT)

   4. Citric Acid Cycle, 32 reduced electron carriers

4. Why each answer is wrong/right:

   1. A is incorrect, because Acyl-CoA transport produces no reduced electron carriers, and 4 is the incorrect number.

   2. B is incorrect, because Beta oxidation does not produce the most reduced electron carriers, however 36 is the correct number.

   3. C is correct, because Citric Acid cycle step produces the most electron carriers, and 36 reduced electron carriers is the correct number.

   4. D is incorrect, while Citric acid cycle is the correct answer, 32 reduced electron carriers is the incorrect number.

The stems that were being rotated were unable to feel a constant directional effect of gravity, while the non rotated stems did, which means that gravity had a 14.4° change on the root angle. Additionally, they placed one stem section upright and another stem section upside down in a beaker. After the roots were allowed to grow, they found that the stem grown upside down changed the root angle by 22.1°. This was because the plant was experiencing gravity from the opposite direction. Plants sense gravity using statoliths in their roots. By cutting a cross section of the root and staining them, the researchers found that statoliths are present in adventitious root nodes no matter the age of the node. Ultimately, gravity was found to have a moderate effect on the growth of the adventitious roots.

In conclusion, they discovered that mechanisms rice plants use to grow adventitious roots mostly involve light signals to stimulate growth, while gravity was a small factor. They found the root growth had a dosage dependent relationship with all colors of light, with red light having the most efficient effect. These plants use light as the most important signal because when there is less light, the plant is probably submerged and it needs to obtain more oxygen. Using this discovery, they proposed that plants monitor oxygen availability by sensing light.

The effects of different colored light was also a topic that they researched. To begin, they tested the root growth on stems when exposed to red light and far red light. In darkness, the stems had root penetration of 84.8%. When the stem was exposed to a high fluence rate of far-red light, the root penetration decreased to 19.1%. This was found to be a gradual decline; as the fluence rate of thel light increased, the root penetration decreased. Red light had a similar effect, causing root penetration to decrease to 18.4%. However, red light was discovered to have a stronger effect on root penetration than far-red light.  In addition to red light, they tested the effects of blue light on the plants.

Plants sense gravity using statoliths in their roots. By cutting a cross section of the root and staining them, the researchers found that statoliths are present in adventitious root nodes no matter the age of the node. In order to study the variable of gravity when it came to the adventitious root growth, they used different experiments. First, they used a clinostat experiment, where the plants were planted and mounted and rotated for three days. After the rotation, the rotated stems had a root angle of 106°, as opposed non rotated stems which had an angle of 120.4°. The stems that were being rotated were unable to feel a constant directional effect of gravity, while the non rotated stems did, which means that gravity had a 14.4° change on the root angle.

Interestingly, a plant that was exposed to white light and ethylene for two days and then grew in darkness for two days. In the case of this plant, its roots initially grew downwards for the first two days, and then they grew upwards for the next two days, giving the roots a kinked shape by the end of the four days. Similar to that, a plant grown in darkness for two days and then white light for two days grew upwards for the first two days and downwards for the final two days. This created a kinked shape in the roots, however it was in the opposite direction. Upon researching the effects of gravity on the growth of the roots, they found that gravity affected the root growth in a less impactful way.

In addition to red light, they tested the effects of blue light on the plants. Blue light is received by phototropins in plants. Phototropins are in control of stomatal opening and chloroplast movement. When the rice stems were exposed to the blue light, it had a dosage dependent pattern. At a low fluence rate of blue light, the rice stems had similar root growth and angle to rice stems that were grown in the dark. In comparison, at a high fluence rate of blue light, the rice stems had similar root growth and angle to stems that were grown in white light. The direction of rice roots growth in response to white light was found to be reversible. They studied four different rice plants in different setups; one plant was exposed to white light and ethylene for four days, and it grew roots that went downwards. The next plant was grown in darkness, and its roots grew upwards.

However, the roots that penetrated in the light grew at a 45° angle, while the roots that penetrated in the dark grew at a 119°. This difference exhibited the fact that light is the major contributor of which direction the adventitious roots will grow. The plants that were not submerged underwater in this experiment did not grow any adventitious roots. This can be attributed to the the ethylene levels not being able to reach a high enough level in the three days the experiment was conducted, while the ethylene could get trapped and reach a high enough level in the submerged plants. An important note to make is that the adventitious roots grow in the same patterns in different media: water, soil, and styrofoam beads. This is indicative that the growth patterns are independent of the medium.  

Initially, they studied the rice plants root growth in response to white light and total darkness. Over five days, one batch of excised rice stems was grown in a light environment and another was grown in a dark environment. At the end of the growth period, the stems that had grown in the dark had sprouted roots, while the stems grown in the light did not. The root angle of the dark grown stems stayed consistent throughout the time period at an average of 119°, and the roots grew at a consistent rate. This experiment showed that darkness is a stimulus for the plant to increase root penetration in order to find more nutrients, which is how the plants know when to grow adventitious roots underwater.  When full plants were grown in light and dark while submerged, the plants grown in the light grew adventitious roots.