If the cell had not passed through mitosis entirely, the cell would not be in the proper setup for the DNA to replicate correctly. Prophase, metaphase and the other steps in mitosis could still be going on, and the chromosomes would be in the middle of moving around and the DNA would not be accessible for replication because the chromosomes are condensed.
The JAK/Stat pathway is usually involved in cytokine signaling, cell migration, cell proliferation, apoptosis, hematopoiesis, and immune development. During the pathway, prolactin receptors dimerize, but they are not enzyme coupled receptors. On them, there are kinases called JAKs, but they are not receptor tyrosine kinases like in other pathways, they are non-receptor tyrosine kinases. When a signal comes in, the JAKs become activated through dimerization and they autophosphorylate each other. The JAKs then phosphorylate the prolactin receptor which allows downstream proteins called STATs to bind. After the STATs bind to the phosphorylated receptor, they are phosphorylated by the JAKs. The STATs dissociate and dimerize and enter the nucleus where they are able to activate transcription
Muscles can be stimulated really fast and then start to get tired when they reach maximum contraction, or the peak of what muscles are able to do. A good example of this is Lock Jaw, which is a symptom of tetanus. In other words, your muscles will reach a point of maximum tension and soon will not be able to produce any more force. The nervous system soon starts to lose control and stop working. In extreme forms, summation can lead to complete tetanus. Muscular stimulation comes in two forms; isotonic and isometric contraction. Isotonic contractions occur when the muscle is stimulated to the most sufficient level in order to move a required load. However, isometric contraction occurs when the muscle is stimulated below the necessary force that is needed to move the load.
Over the summer I read the book about Henrietta Lacks called The immortal Life of Henrietta Lacks. Recently I saw a movie trailer which will shine upon the life of Henrietta and is based on the book written about her. Henrietta was a tobacco farmer from Southern Virginia who was diagnosed with cervical cancer when she was 30 years old. Henrietta had cells removed from her cervix while at Johns Hopkins and they were sent to other scientists to grow tissues in cultures. Scientists previously had not been able to keep cells alive, but Henrietta’s cells have never died. This is why her cells are so important. They are the first immortal human cells to ever grow in culture. They were essential in the development of various vaccines and are still being used today to further medical research. Cloning, gene mapping an in vitro fertilization have all been successful with the help of these He(nrietta) La(cks) cells.
The book was one of the greatest books I have ever read and I am excited to see how the movie turns out. I think this story is really important because also her cells have made many medical improvements, there were a lot of ethical discrepancies that have been overlooked. If you are reading this blog post, I highly recommend reading the book to understand the full story about this remarkable woman.
The survival pathway in cells is to inhibit programmed cell death also known as apoptosis. When a receptor tyrosine kinase is activated and dimerized, it activates a kinases known as PI3. This interaction also has a SH2 domain which is where a target protein binds to a phosphorylated tyrosine on the receptor. Downstream proteins PDK1 and AKT bind to PIP3. The important kinase in this is the akt which is then phosphorylated by two protein kinases PK1 and PK2. Once phosphorylated, the AKT protein is released from PIP3 and enters the cytosol where it can then target BAD. BAD is a protein that sequesters Bcl2 which prevents Bcl2 from performing its function. Bcl2’s function is to prevent cell death so when BADis binding to bcl2, the cell is going to die. Akt phosphorylates BAD, Bcl2 is released and can do its function. BAD technically is inactive when phosphorylated because it can no longer perform its function of binding to bcl2 and sequestering its functional ability.
Only one flowering species of the three species tested experienced a treatment effect on pathogen load with bees foraging on more flowers receiving overall higher infections. The lack of a significant treatment effects on Penstemon digitalis and Lythrum salicaria make it unlikely that flower number alone is the causal trait impacting the transmission of pathogens to foraging B. impatiens among all flowering species. The significant difference observed in the Monarda didyma trials suggests that flower number may still play a part in determining the severity of infection of visitors even if it is not the ultimate determinant.
The significant difference in pathogen loads in Monarda didyma trials may be partly explained by the variation in flower range between species. On average, the upper range of Monarda “high” treatment trials had 25-30 flowers present while the lower range, 10-15 flowers, was similar to the “high” range of Penstemon digitalis trials (11-13 flowers). The Lythrum salicaria trials fell in between with a high range of 16-20 flowers. The greater number of flowers may have stimulated increased movement between individual flowers, resulting in a higher spread of inoculum and parasitic cells transported by the foraging worker. The total amount of inoculum was kept constant and the number of flowers probed was not a significant indicator of pathogen load, but the increase in available flowers and nectar may have affected the workers’ exposure to the pathogen.
A recent expedition into Madagascar has led to the discovery of a new species of gecko, geckolepis megalepis, which has a very unique trait; it has the ability to detach from its scales when attacked by a predator. All species of gecko in the geckolepis family are able to detach from their scales, however, the g megalepis has the largest scales of any gecko in this family by far. Some geckos captured by the researchers had scales measuring as long as 6 millimeters. It is believed that the large size of these scales may be benefical to lizards escaping predators as they are large enough to get stuck to teeth, actively giving the predator a mouthful of something without actually damaging the lizard. This proccess is believed to only be used in emergency situations, as it takes weeks for scales to grow back.
For many mammalian species the bends, or decompression sickness is a serious issue. This occurs when divers dive very deep and are under tremendous amounts of pressure by the water. If the diver comes to the surface or swims up too quickly it can cause decompression sickness. This happens due to a sudden change is pressure, much like when you open a soda can. The blood has been filled up with air, mainly nitrogen, and when the diver rises too quickly it causes the nitrogen to escape the blood and turn into bubbles. These bubbles will travel through your blood and essentially all your blood would start to fizz up like a soda. This can be extremely dangerous, even fatal in some cases. The bubbles will lodge themselves between bones, muscles, ligaments and cause extreme pain. This can cause permenant scarring on the bone if the condition worsens. In the worst case scenario the nitrogen will form a larger bubble that can travel to the lungs, heart or brain. the result of this is pulmenary edema, a stroke or cardiac arrest. We all know that humans are very suseptible to the bends can thus cannot dive very deep, but whales have also experienced the bends. If whales dive too deep and come up too quicly they too can get the bends. Granted whales have to dive much deeper, their bodies have mechanisms that help prevent the bends unlike humans.
The Beneski Museum of Natural History at Amherst College has an interesting display that shows the evolutionary history of the horse. The display has four skeletons that reveal how the horse has changed over the past 50 million years. The first case is of an ancient horse, about the size of a dog. The animal lived in a dense forest, where its diet consisted of leaves, berries, and parts of plants. As time passed, the environment began to change. The forests dried out and became grasslands, which also meant the horse’s diet had to change for its survival. Horses became grazers, eating mainly grass, and their teeth began to evolve to accommodate this diet. The crowns of their teeth became higher over time. Along with this change in dentition, was an increase in body size. One last significant change in the evolution of the horse is the development of the hooves. Bones fused, and the number of digits decreased, which optimized their ability to run. The four skeletons of this display show these changes in an ordered fashion, laying out just how the horse evolved over time.
A breakthrough in genetic engineering may now allow farmers to grow corn without the fear of a product tainted by fungus. This genetic engineering has resulted in a corn product that produces an RNA molecule that lies inactive until fungal spores are sensed. Once these spores are present, the RNA molecule begins a translational proccess that ultimately results in an inhibition of the fungus to produce a key protein, resulting in death of the fungus. This breakthrough in genetic engineering may allow for farmers to produce corn more efficently without fear of losing product or making consumers sick with a fungally contaminated product.