"In 2005, high blood pressure was responsible for one in six death in the United states," says a new report from experts at the Institute of Medicine. Too much intake of sodium in our diets often leads to high blood pressure. Hypertension can lead to heart attacks, strokes, and other cardiovascular events that may ultimately result in death. To have hypertension means that one's blood pressure reads above 140 over 90. Unfortunately, people are at risk for cardiovascular disease at pre-hypertension, which is between a blood pressure reading of 'normal' and 'high.' Of the 42 million Americans who have uncontrolled hypertension, 27% are unaware of it, 11% are not being treated, and 26% are being treated but their blood pressure has not significantly decreased. There are no symptoms to hypertension, which is why so many people neglect the possibility of having it. Hypertension is a serious issue in our society because there is so much exposure to excess sodium in the foods that we eat, whether it is at the restaurant or packaged at the grocery store to be cooked at home. Because so much of the sodium in our bodies comes from the foods that we eat, the best way to save lives is to cut down on dietary sodium intake.
In plants, there stem cells are located in the shoot meristem where WUSCHEL (WUS) homeobox genes and CLAVATA 3 (CLV3) genes are constantly being expressed through negative feedback loops. When plants want to grow, the shoot meristem WUS, a transcription factor, specifies stem cell identity for growth when it is expressed. WUS also turns on its own repressor CLV3 as well that in turn regulates shoot meristem size. This negative feedback loop is important in plant growth and regulation. CLV3 is a signal peptide that binds to CLV1 a receptor complex however the exact pathway for modifying CLV3 and its applicability for CLV signaling are unknown.
In the experimet exploring environmental effects on planarian motility, a low concentration of sucrose was associated with increased average velocity. However, high concentrations of sucrose were associated with decreased planarian motility and a slower average velocity. Some of the planarians in the high-concentration sucrose environments were unable to survive. Based on this finding, we expect that the lowest concentration of splenda may have a positive effect on head regeneration. However, higher concentrations of Splenda may cause reduced regeneration rate. The planarians in highest concentration Splenda may lose their ability to regenerate altogether.
In this same experiement, the planarians that were placed in energy drink were unable to survive. Because caffeine is the major ingredient in energy drinks, this finding leads us to predict that the caffeine environments in our experiment will have a negative effect the planarian's ability to regeneration. Since our concentration of caffeein will be low, the planarians will hopefully still be able to survive in the caffeinated environment. However, if able to survive, we predict that the planarian's regeneration rate will be slowed or reduced completely.
Because brown planarians are a freshwater species, we expect that the salt environments will have a negative effect on their ability to regenerate. This species of planarians are not evolved or adapted to saltwater environments so we expect they will be unable to complete their basic life functions as efficiently when placed salt. They may regenerate at a slower rate, or be completely unable to regenerate.
Planarians have a nervous system composed of two main nerve chords running from their head to their tail, and connected by transverse nerves. Although basic, planarians have been shown to exhibit decision making behavior by processing external stimuli. Planarians are able to process external stimuli by their sensory organs, eye spots and auricles. The eyespots are located on the head of the planarians and are used to detect light. The behavior in response to the change in light is called phototaxis. Planarians exhibit negative phototaxis, moving away from the light source. Auricles are on the side of the planarians head, and contribute to its triangular shape. The auricles contain chemoreceptors which respond to chemical stimuli. The auricles can play a role in finding food or the detection of changes in habitat. Both their photoreceptors and auricles help them make decisions about their environment.
Planarians are flatworms that are mostly found in freshwater. The length of their bodies on average are 3-15 mm ( Britannica Encyclopedia). Their bodies can be described as soft and leaf shaped. Planarians are generally carnivorous and feed on protozoans, worms, and tiny snails. Planarians are one of the first species with a central nervous system. While researching planarians one thing that I found interesting is that they are often used as a model for preference for humans. This led me to wonder how planarians preference different substances The specific aim of this study is to observe how planarians preference 3 different forms of sweetener and see if they are more attracted to a specific sweetener, thus indicating which of these three could potentially be more highly preferred in humans. The three forms of sweetener observed are pure sucrose, pure brown sugar, and pure saccharin.
Biewener’s experiment was a very well organized experiment that tested a well thought out hypothesis that answered how large animals bodies were able to function without being near their skeletal limit. This finding is a very important one because it answers how large mammals are able to function. One thing I personally disliked about this paper was the format was tougher to follow and understand when compared to a normal formatted research paper. The formatting distracted me from the actual science and caused me to spend more time trying to just understand the format. One thing Biewener should have discussed in greater detail was how the mechanical advantage of the extensor muscle groups was calculated instead of just stating that radiographs and anatomic dissection determined it. This also leads to the question whether radiographs and anatomic dissection could be used to both find the same mechanical advantage or if there is a slight variation between the two. Overall, I believe this was a good paper and good research that helped prove Biewener’s theory that larger species would develop a more upright position to achieve similar stresses as smaller mammals.
Epigenetics is the study of changes in gene function that are not caused by changes in the DNA sequence. This is a quite interesting and rapidly growing field of genetics. Epigenetics describes phenomena in which genetically identical cells may express their genomes differently, which will cause phenotypic, or observable, differences. The driving forces of epigenetic differences are mainly environmental effects. The two main components of epigenetic code are DNA methylation and histone modification. DNA methylation is when methyl marks are added to certain bases of the DNA. This can repress gene activity of the methylated DNA. Histone modification is the process by which a combination of different molecules may attach to the end of a histone's "tails". This may alter the gene activity of the entire strand of DNA wrapped around the histone.
Although planaria may be able to retain information to go in a certain direction using a negative stimulus, it seems that after the negative stimulus is removed for a short period, they revert back to random directional selection (Abbott 2008). The experimental trials done by Abbott and Wong (2008) showed that they do not have a directional bias since after the nine days of trials, 96% of the planaria were non-bias (Abbott 2008); however, after conditioning using electrical shock in response to an undesired directional bias (Abbott 2008), they can be trained to go in a certain direction for a short duration. This leads to the possibility of using a different stimulus such as food that may be more effective toward having them remember.
In a monoculture stand of plants, the number and size of seedlings can change over time. Individual plant sizes are generally extremely uneven. Usually, a few large individuals dominate an available area given, while most individuals remain very small. This unevenness is highly unequal in size distribution, which is characterized by size hierarchies that can be attributed to asymmetric competition – larger individuals have negative effects on smaller neighboring individuals. For example, starting with a population that is relatively homogeneous, as time goes on, the distribution becomes increasingly unequal with the proportion of smaller plants increasing and smaller number of large plants. Eventually, self-thinning occurs, which is when death removes the smallest individuals from the population, in this case, so that the population is less unequal as time goes on. This shows that plant sizes vary in a cycle from having more plants of one size over the other. Also, as a population increases in size, it can reach a maximum capacity, which then individuals start dying due to reduced resources.
The authors used two different systems in this experiment: mice and rats. The main reason that mice were used was due to their transgenic nature. It was relatively easy and cost efficient for the researchers to insert their gene of interest into these mice's DNA and observe what the results were. Mice are one of the few model organisms in which this would have been effective due to the nature of this gene. They are also small and relatively easy to breed. Rats were used perhaps because the researchers were more experienced in handling them. Or, maybe they were chosen for their larger size, but also because they are still comparable to the mice, which were used initially. Thus, the authors chose to uilize mice and rats to perform their experiments on.