Topics in Plant Bio Notes - Cell Expansion and Walls III

Submitted by samihaalam on Thu, 11/23/2017 - 13:43

As well as having a great eccet on waer intake in the cell, turgor pressure can also mediate rapid movements in the cell. For example, there is one plant where if it is touched, all of the leaves very rapidly close up and shrink back. This is caused by changes in turgor pressure. When the leaf is normal wih nothing touching it, the flexor cells and the extensor cells are both extended and turgid. But, after the plant has been touched, the flexor cells become stretched and the extensor ccells become flaccid. In the turgid state, the cell is completely filled with water. But as the cell is touched and begins to shrink, H+ ions enter the cell, while Cl-, K+, and some water leave the cell. This leaves the cell in its flaccid state, where there is still some water, but it is in pockets, and the overall size of the cell is smaller, as previously described. There is low turgor pressure in this state. Then, after a while, the cells begin to sweel to their turgid state, and H2-, K+, and Cl- enter the cell, while H+ leaves the cell. This allows the cell to completely filll up with water so that there is high turgor pressure in the cell.

Turgor pressure is also very important in sunflower movement. Sunflowers move in response to the sunn and follow it though the day. At night, the sunflowers still move to face the east even though there is no sunlight, so that they can be in the optimal position when the sun rises. This is due to their intrinsic circadian rhythms. However, this movemen of following the sun is due to changes in turgor pressure in the cells at the base of the moving organ in the sunflower.

The primary cell wall contains cellulose microfibrils that are a part of a polysaccharide matrix. The matrix has pectins, which are polysaccharides that can create a hydrated gel phase, and hemicellulose, which are flexible polysaccharides that like cellulose. The primary cell wall is about 25% cellulose, 25% hemicellulose, 35% pectin, and 1-8% structural proteins, but these numbers can be highly variable depending on the tested structure. These are the parts in the priamry cell wall that are involved in expanding the cell. 

Neurobio Paper 3 Draft 2

Submitted by samihaalam on Wed, 11/22/2017 - 23:45

4. What methodological approach has been used?

The researchers inserted electrodes into the thalamus. They tapped on and around a pateint' s stump and, using the electrode, recorded which neurons were activated in response to the tapping. This was teh receptive field. Then, again using the electrode, the researchers inserted the electrode into the thalamus at different depths corresponding to the depths in which the neurons in the receptive field were. They then added current to the electrode to electrically stimulate that particular depth. The patient was fully awak for this, and thus the patient responded where they felt pain or a sensation after being electrically stimulated in certain parts of their receptive field. This was called the projective field.

5. What were the results of their experiments?

One would normally expect that the receptive field and the projective field to line up perectly, since if a neuron or brain region is stimulated by a certain body part, then that neuron should then map back to that body part and stimulate the same body part. However, the researchers found different results. In general, some of the neurons or depths that were stimulated by the stump in the receptive field projected to a projective field in the phantom limb. In some cases, some depths did not have a receptive field, but when stimulated, they led to pain or unpleasant sensation in the phantom limb, indicating that the thalamus still has a representation of the limb even though it is no longer there. One would normally expect the brain to re-wire itself, so that there would be no representation of something that wasn’t there, but that does not seem to be the case.

6. What are the strengths of this study?

One strength of this study was that it was a good use of an opportunistic study. Another strength was that it was a good simple, straightforward study. There was also good, clear concise writing and diagrams. They were also able to clearly map ou precisely both the receptive and projective field. 

polypterus

Submitted by msgordon on Wed, 11/22/2017 - 18:49

First fossil record of Actinops was found in the Silurian period. Historically, Polypterus have been found in SA and Africa, however the 2 extant genera. of the family are only found in Africa. Species of Polyperterus have ganoine covered rhombic scales, and they respire through elastic recoil. Spiracles atop their head are used to inhale extra air - primitive lungs are used instead of a swim bladder.

Discussion

Submitted by dalon on Wed, 11/22/2017 - 08:51

N-propyl propionate was synthesized via Fischer esterification using sulfuric acid as a catalyst with a 32.9% yield. The product was identified using an IR test. The IR test was used to measure bond vibrations and the absorption of IR radiation in order to determine which bonds were present in the compound via wavelength, thus indicating if the ester bond was present. The accepted IR reading for the C=O bonds present in an ester is 1740 1/cm. As demonstrated by the IR graph attached, there was one sharp peak observed at 1741 1/cm, indicating the presence of the C=O ester bond; however, there were also two peaks observed at 2,972 and 2,883 1/cm. These fit in the range of carboxylic acid –OH presence, which has a range of 3,400-2,400 1/cm, indicating that some of the alcohol was left behind and therefore the mixture was not a pure ester. In addition, when the odor was observed the smell of alcohol was still present in addition to the sweetness of the ester, indicating that the ester was not pure. To improve the experiment, in the future there should be more steps separating the aqueous and organic layers through mixing and drying, yielding more of a purer product. The purity of the product was assessed and was deemed to be impure due to the IR spectroscopy reading and odor observation results.

Neurobio Paper 3 Draft 1 - Phantom Limb Stuff

Submitted by samihaalam on Wed, 11/22/2017 - 06:04

1. What is the objective/hypothesis/question of this study?

The objective of this study was to explore the causes of phantom limbs. It was already known that there was a representation in the thalamus of the missing limb, but this was done to see if there was any sort of connection between this representation and phantom sensatoins/pain.

2. What is the rationale/relevance of this question?

As stated before, it was previously estabished that even though a limb had been amputated, there was still a representation of that limb in the thalamus. It is important to study the causes of this sensation to understan and come up with new therapeuic studies to help people suffering from phantom sensations. 55-85% of amputees experience phantom pains or phantom sensations, so it is a widespread issue that affects a majority of people who have had limbs amputated. This study was done on the preface of performing a new therapy - the experimenters inserted something ino the brains of these patients at the site in the thalamus where the pain from the missing limb is coming from. If there is any phantom pain or stub pain, the pateitn could then stimulate the thing in their brain, which would stimulate the area in a way to alleviate the pain sensation. Along the way, the researchers mapped out patients' receptive and projective fields for around the stump.

This is a last ditch effort, opprotunistic kind of study. This is because these surgeries were performed on people who normal drugs and therapies didn't work on. In one case, a patient had been experiencing phantom pains for years before this study came along. Therefore, the researchers had to wait for patients to volunteer for this study in a way, and thus the rationale for this study was really to help people who had tried every other option, and were still not getting the results they wanted in their pain management.

3. What system are the authors using to answer this question? Why?

The authors are using human patients in this study. This is because this is a problem that affects humans, and they'd designed a study in which it was possible and feasible to test their theories on humans, so it would make the most sense to do this on humans. Another reason they used humans was because it would have been difficult to use mice or rats for this study due to the nature of this study. The researchers could have easily identified the rats recceptive field, but it would have been a challenge to map out the projective field. This is becuse the projective field was determined by researchers stimulating certain neurons in the brain, and then having the patients describe where they feel pain or tingling sensations. Mice or rats would not be able to commnicate clearly where they wer feeling pain or anything. On the other han, it would be easy to determine the receptive fields on rodents because that was easily determined by tapping different areas around or near the stump, and then recording which neurons or which part of the brain was active in response to the tapping. It also would have been difficult for researchers to determine if the rodents were feelign phantom sensations at all in the irst place. 

ester synthesis

Submitted by msgordon on Wed, 11/22/2017 - 00:49

Acetic acid (0.74 mL, 13 mmol) and 3-methyl-1-butanol (1.2 mL, 11 mmol) was added to a round bottom flask containing several boiling chips. Sulfuric acid (4 drops) was added to the flask and the contents were mixed via expelling with a pipet. The mixture was refluxed for a total of 45 minutes using a reflux assembly with a side arm. Every fifteen minutes, the top layer consisting of organic product that was collected in the side arm was tilted back into the flask. After the last 15 minute block, the mixture was allowed to cool and the entire contents of the side arm was tilted back into the flask. Following this, the cooled mixture was transferred to a centrifuge tube containing water (1 mL) and the aqueous layer was extracted. The extraction of the aqueous layer was repeated twice following the addition of sodium bicarbonate (1 mL) and again with the addition of sodium chloride (1 mL). The product (1.09 g, 76.3%) was then dried with anhydrous calcium chloride and subsequently weighed before undergoing analysis by infrared spectroscopy.

 

Neurobio Notes L11

Submitted by samihaalam on Tue, 11/21/2017 - 22:34

The nervous system is useful to sense the environment around us and thus move in accordance to the environment. The spinal cord plays a huge part in movement; information is passed between the brain and the muscles via the spinal cord. However, the spinal cord also has a certain amount of autonomy from the brain.

One very well known example of the spinal cord having autonomy from the brain is in the case of Lloyd Olsen and his headless chicken, Mike. Mike was born in April 1945, and on September 10, 1945, Lloyd chopped Mike's head off. Mike continued to walk around after this happened, as well as preening, pecking for food, and attempting to crow. He then took Mike and went around for two years showing off his headless chicken. This isn't a perfect example of spinal cord autonomy as one ear and most of the brain stem was still intact on Mike, but it is still a remarkable example of how the spinal cord can mostly function, even without being connected to a brain. It also is probably where the phrase "running around like a chicken without its head" come from. The town in Colorado where Lloyd and Mike come from still celebrate them today.

There are two types of muscle: smooth and striated mucles. Of the striated muscle, there is also two types of that: cardiac and skeletal. In the somatic motor system, muscles pull, and never push against each other. Motor neurons are in the ventral horns of the spinal cord, while sensory information enters through the dorsal horns of the spinal cord. To control the force of a muscle contraction, either the number of active motor units can be changed or the rate of motor unit firing can be changed. Amyotrophic Lateral Scelrosis (ALS) is a very serious degenarative disease in which a person's alpha motor units start degenerating. It is not very well understood why only the alpha motor units degenerate in this disease. 

Devo intro

Submitted by daniellam on Tue, 11/21/2017 - 19:45

What makes each of our limbs different and how do they form? Limb development occurs at the limb bud and contains so much diversity and that diversity is provided by morphogen gradients. Morphogens are chemicals that change a type of cell depending on how much of that chemical is present at certain times. High amounts are found where these chemicals are made. For instance, if Chemical A is made on Side 1 and Chemical B was made on Side 2, the amount of Chemical A is greater on Side 1 than Side 2. Different amounts of the chemical make different types of cells. A large amount of the molecule forms a different identity for the area than a low amount of that molecule. There are intermediate amounts that also form different identities.

Shh and finger formation

More specifically, Shh is one of these chemicals and it forms your different fingers by using this gradient model. A high amount of Shh makes the pinky, while no Shh makes the thumb. Amounts of Shh in between make the middle three fingers. High amounts of Shh generally occur on the posterior (bottom) side of the limb bud. Implanting Shh to the other side of the limb bud showed the formation of a mirror imaged limb; this is the equivalent of having a pinky on both sides of a hand (Bartlett 2017).

Developmental Biology Assignment

Submitted by hamacdonald on Tue, 11/21/2017 - 16:19

Hailey MacDonald November 19th 2017 Writing Assignment 4

Mittens or Gloves?
There is no denying the appreciation and usefulness humans have for digits, fingers. It is

a main separating factor between humans and other mammals. What we might not think about is how important the timing of the production of digits are. Although it is a complex process, in theory has been explained more simply by Alan Turings using his mathematical model, A Turing- Type Mechanism.

The basic idea behind this model is there are two chemicals. One of the two chemicals is called the activator meaning it turns things on. Specifically, the activator found in mice embryos is fgf. The other of the two chemicals is the inhibitor known as Gli3 in mice, which turns things off. In this case, it stops the production of digits. At first, these two chemicals fluctuate randomly at similar levels. The activator is turned on, it then turns on the inhibitor which quickly turns the activator off. As seen in the figure below, the activator builds up which also causes the inhibitor to build up. Eventually the inhibitor has a high enough concentration to severely limits the amount of activator and turning digit development off. The two chemicals together work to create a wave like pattern. This pattern is what gives us the spaces in-between our fingers. The activator triggers digit development, and the inhibitor is what gives us these negative spaces

between each finger.

What controls this pattern is the Hox genes, or more specifically the distal Hox genes (distal meaning far away, our digits are furthest away from our bodies). Hox genes are what control the body plan of the embryo on the anterior-posterior (head- tail) axis. The amount of distal hox genes being expressed controls the digit formation by starting the self-regulating loop between the activator and inhibitor.

In order to determine what controls the normal digit formation, mutants, or mice with more and skinner fingers than normal mice were observed. This is known as polydactyl. Something went wrong in the timing or development of the digits causing an abnormal amount of digits to form.

The mutants in which the inhibitor, Gli3 was not expressed showed increased number of digits until the digits began to fuse together in a

mitten- like structure. This can be seen in the figure to the left. The less Gli3 that inhibits the activator that produces digit development, the more digits form and the skinner these digits are

Reference:

K. (2011, January 13). Alan Turing’s Reaction-Diffusion Model – Simplification of the

Complex. Retrieved November 19, 2017, from

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