Friday, September 20, 2019
Sickle Cell Anemia And Hemophilia Biology Essay
Sickle Cell Anemia And Hemophilia Biology Essay Abstract In the following paper, sickle cell anemia and hemophilia disorders were studied extensively. Sickle cell anemia was found to be the disorder where the red blood cells develop into sickle shaped cells due to a mutation of the hemoglobin protein. When the cell becomes sickle shaped, they also become sticky and will clump with other cells in the blood vessel. This can lead to decrease blood flow in that blood vessel which will lead to various effects. Sickle cell anemia is a hereditary disease in that it is passed down generations genetically. The main effect of sickle cell anemia is the decrease in number of red blood cells in the blood and lack of oxygen transport to certain areas of the body. Though are many drugs to help with the pain caused by sickle cell anemia, there is no definitive cure to the disorder. However, the main type of treatment is bone marrow transplant. However this procedure is very risky and not advised unless the symptoms of sickle cell anemia are severe. There is much research being done on sickle cell anemia, but no definitive cure has been found. The life expectancy of patients with sickle cell anemia is from 40 -60 years old and majority of the patients are African descent. Hemophilia is the disorder that prevents the body to stop bleeding. If a person is cut, the body will not form clots to stop the bleeding because people with hemophilia lack a clotting factor. This is also a genetic disorder and is found only on the X chromosome. Hemophilia can be divided into two categories: hemophilia A (lacks clotting factor 8) and hemophilia B (lacks clotting factor 9). About 9 out of 10 people who have hemophilia have type A. Rarely, hemophilia can be acquired. This means that you can develop it during your lifetime. About 18,000 people in the United States have hemophilia. Each year, about 400 babies are born with the disorder. Hemophilia usually occurs only in males (with very rare exceptions). The major signs and symptoms of hemophilia are excessive bleeding and easy bruising. The main treatment for hemophilia is called replacement therapy. Concentrates of clotting factor 8 or clotting factor 9 are slowly dripped in or injected into a vein. These infusions he lp replace the clotting factor thats missing or low. Hemophilia treatment centers are located in many areas of the United States. These centers can provide treatment, education, and support to hemophilia patients, their families, and their health care providers. Sickle Cell Anemia What is Sickle Cell Anemia? Sickle Cell Anemia or sickle cell disease is a blood disorder that is genetic. This disorder affects the red blood cells of the human body and can cause much damage to the body. It causes the red blood cells of the body to become an abnormal shape, usually in the shape of a sickle or crescent. Red blood cells are cells that carry nutrients and oxygen to different organs in the body and carry carbon dioxide back to the lungs. However, Sickle Cell Anemia basically does not allow for the red blood cells to act normally. The way a red blood cell is able to carry the oxygen molecules to the organs is by a protein molecule located on the cell called hemoglobin. This molecule is able to carry oxygen from the lungs to the bodys tissues and return carbon dioxide to the lungs. A defect of this molecule can affect every part of the body that is supplied oxygen by red blood cells which is everything. In Sickle Cell Anemia, the regular hemoglobin is mutated and changes from the normal hemoglobin A to hemoglobin S. the ability for a protein to be mutated that is located on the red blood cells means that this mutation can will be passed down to the persons child, making this disease hereditary. The mutated hemoglobin causes the entire normal red blood cell to become sickle shaped and stickier. The abnormal cells begin to clump together and have a difficult time being transported throughout the body through the blood vessels. When the blood vessels become obstructed by the sickle cells, blood flow decreases in that part of the body. This will cause a lack of oxygen in those areas which, ultimately, leads to those cells death. Another characteristic of Sickle Cell Anemia is that the abnormal red blood cells have a shorter life expectancy. Normal red blood cells usually live up to 120 days and through a process called phagocytosis they are removed from circulation. However, the red blood cells infected with the sickle cell disease live only about 10 to 20 days. This means that the body needs to produce ten times as many red blood cells if the person has Sickle Cell Anemia than a normal person. However, the body cannot produce that many red blood cells that fast. Red blood cells are produced in bone marrow, located in the inner hollow interior portion of bones, by a process called erythropoiesis. The bone marrow cannot produce red blood cells fast enough to replace the dying ones. This will lead to decreased number of red blood cells which can lead to many side effects. Causes of Sickle Cell Anemia Sickle Cell Anemia is a type of disease that someone cannot get unless if they were born with it. This disease is an inherited blood disorder that one is born with. A person is born with genes that give him/her distinctive appearance and personality. They get these genes from their parents, half from each. In Sickle Cell Anemia, there is a specific gene that can be passed down generation which will cause the disorder. This gene, sickle cell gene (HbAS), is a recessive type of gene which means that unless there is another one of it, it will not be expressed. However, that gene will be part of them forever and there will be a 50% chance that their child will have that gene. However, if two people with the sickle cell gene have a child, then there will be a 25 % chance that there child will have the disorder, 50% chance that their child will have only sickle cell gene, and 25% their child will have zero copies of the sickle cell gene. This gene which represents a specific trait will cause the Sickle Cell Anemia. Once the person has the trait, then it will begin to cause the body to make abnormal proteins on the red blood cells called hemoglobin. As discussed earlier, the mutated form of hemoglobin causes the cell to become sickle shaped and cause all sorts of havoc in the body. In addition, a distinctive trait about Sickle Cell Anemia is that once someone gets it, there is no way to get rid of it. Also since this is a genetic disease, there can be different variations of the disease. If a person inherits one sickle cell trait and if the person has the abnormal hemoglobin C (not hemoglobin S which is present in Sickle Cell Anemia), then the person will develop a milder form of the Sickle Cell Anemia disease called HbSC. If a person inherits one sickle cell gene and one gene for beta thalassemia (another type of anemia) which can be 0 or + then the person will either severe case of Sickle Cell Anemia (if HbS Beta 0- thalassemia) or a milder case of it (if HbS beta +-thalassemia). Symptoms of Sickle Cell Anemia Even though that people are born with Sickle Cell Anemia, the symptoms do not appear until after 4 months of age. The symptoms of Sickle Cell Anemia can be divided into three categories: symptoms related to anemia, symptoms related to pain, and symptoms that arise due to disorder. The first category deals with how the lack of red blood cells can affect the body. The most common symptom is fatigue because in order for the body to function and stay alert, it needs oxygen which is what anemia decreases. In addition, anemia causes dizziness, headaches, pale skin, chest pain, coldness in the hands and feet, and shortness of breath. These are all caused by the lack of oxygen reaching certain areas of the body. The second category deals with symptoms that are related to pain. A person with Sickle Cell Anemia is likely to express pain throughout their body which is called sickle cell crisis. This occurs when there is a mass of sickle cells in the blood vessels. With decreased blood flow to organs and limbs, there is usually sharp pain and organ damage. This crisis also has a range on how painful the pain is. If it is an acute pain, then the pain will be mild to severe and may last from hours to days. On the other hand, chronic pain will last for a lot longer period of time and will be hard to bear and mentally draining. This pain may severely limit your daily activities. The final category deals with the complications of Sickle Cell Anemia. This category examines certain complications that arise in certain areas of the body due to the Sickle Cell Anemia. The first complication is called Hand-Foot Syndrome. This occurs when the mass of sickle cells block a blood vessel in the limbs of the body. This will cause there to be pain, swelling, and/or fever. This is syndrome is one of the first signs an infant may have Sickle Cell Anemia. The next complication arises in the spleen. The spleen filters out abnormal red blood cells and helps fight infections. If a person has Sickle Cell Anemia, the spleen may become enlarged due to all of the sickle cells getting stuck in the spleen. If the spleen becomes enlarged, then the person will feel weak, have pale lips, higher respiration rate, extreme thirst, and abdominal pain. To treat the enlarged spleen, the patient should get a blood transfusion. Another complication that can occur is infections. Since Sickle Cell Anemia affects the immune fighting organ, the spleen, both young and old patients will have a hard time fighting infections. Young children who have a damaged spleen will most likely die in a few days due to the infections. Some common infections a child may get are pneumonia, meningitis, influenza, and hepatitis. Another life threatening complication due to Sickle Cell Anemia is acute chest syndrome. This occurs when there is sickle cells trapped in the lungs which may lead to the patient developing pulmonary arterial hypertension. This is when the lungs are damaged which make it hard for the heart to pump blood through the lungs. This will lead to elevated heart rate and pressure. A complication that is common with children is their delayed growth and puberty. This is caused by the shortage of red blood cells in the body. Young children will grow slower and reach puberty later than normal children. Adults will be thinner and smaller than normal adults. A more serious complication that can arise in adults however, is a stroke. Sickle Cell Anemia can cause both types of strokes in adults: a blood vessel in the brain is blocked or a blood vessel bursts. Both types of strokes lead to learning disabilities, brain damage, paralysis, or even death. Sickle Cell Anemia can also lead to priapism. This is when a male Sickle Cell Anemia patient will have painful unwelcomed erections. This will occur because the sickle cells block the blood flow out of an erect penis. Since sickle cells have a shorted life span, they break down too fast for the body to remove them from the body. When a red blood cell dies, it will release the hemoglobin protein in the form of bilirubin. The bilirubin will form stones in the gallbladder called gallstones. This will cause the patient to feel pain, nausea, vomiting, fever, sweating, chills, clay-colored stools, or jaundice. Jaundice is when the skin color of a patient turns to a yellowish color because of elevated bilirubin level in the blood. A more severe symptom of Sickle Cell Anemia are ulcers or sores that begin as small, raised, crusted sores on the lower third of the leg. Leg sores occur more often in males than in females. These sores usually appear between the ages of 10 and 50. The cause of sickle cell ulcers isnt clear. The number of ulcers can vary from one to many. Some heal quickly, but others persist for years or come back after healing. The last major complication of Sickle Cell Anemia is multiple organ failures. This may be one of the more rare complications but is one of the most dangerous. If too many of your organs fail, then there is a high probability that you will die. Though only a few of the symptoms of Sickle Cell Anemia have been presented, there are many more which can lead to serious damage to the body if gone unattended. Demographics Though Sickle Cell Anemia is a worldwide disease, it is most common in people who come from Africa, South America, Central America, specifically panama, the Caribbean islands, Turkey, Greece, Italy, other Mediterranean countries, India, and Saudi Arabia. Statistically, 1 in every 500 African American births has the sickle cell disease and about 1 in every 1,000 Hispanic Americans have the disease. About 2 million people carry the sickle cell trait in America and about 1 in 12 African Americans carry the trait in America. There have been close to 72,000 cases of Sickle Cell Anemia in America and the prevalence rate in America is 0.10% or 272,000 people. The deaths from Sickle Cell Anemia are close to 500 deaths per year. Diagnosis One way someone can find out if they have Sickle Cell Anemia is by a simple blood test. When a baby is born, he/she will go through a series of newborn screening exams which test for diseases or disorders the baby may have. A blood test will show if the baby has the disease or if he/she has only the trait. Once the tests are conformed by a second test, the baby will be sent to a hematologist who is a specialist in blood diseases and disorders for further guidance. There is also a way for a parent to know if their child will have sickle cell anemia before he/she is born. Doctors do this by taking a sample of amniotic fluid or tissue from the placenta and testing it for sickle cell anemia gene instead of the hemoglobin the gene makes. Treatment Treatment for sickle cell anemia can be divided in to the three categories that were created for the different types of symptoms. The first category was the pain category. To treat the pain caused by sickle cell anemia, pain killers and fluids are used. To treat the pain, fluids and pain killers are used because the fluids will prevent dehydration which is caused by the disease. The pain killers that doctors prescribe can include acetaminophen, nonsteroidal anti-inflammatory drugs, and narcotics which include meperidine, morphine, oxycodone and others. Another drug that doctors use for sickle cell anemia is hydroxyurea. This drug will reduce the number of pain crises the patient experiences. This drug does not treat the pain crises when they occur but prevents them from occurring at all. Also research has found that this drug will reduce organ damage and improve growth of children. The treatment discussed in the next category, symptoms that deal with Anemia, can help treat anemia. The treatment is called blood transfusion and is used to treat severe cases of anemia. Blood transfusion is a procedure where blood is given to the patient by an intravenous line. This is done to replace the dead red blood cells that were a result of the disease. The last category dealt with complications that arise due to sickle cell anemia. One complication that can be treated is an infection. Due to the reduced number of red blood cells, the human immune system is weakened and children will be at risk for harmful infections. One infection that usually kills children is pneumonia. To treat pneumonia, children should take vaccines regularly. Also to treat other infections, antibiotic medicines and blood transfusion may be used. To treat the acute chest syndrome that arises from sickle cell anemia, the patient must get treated with oxygen, blood transfusions, and antibiotics. The main medication for this complication is the same one that reduces the number of pain crises, hydroxyurea. To prevent and treat patients with sickle cell anemia that experience strokes, the patient should get ultrasound scans of their heads. This will allow the doctor measure the blood flow to the brain see if there are any complications due to the sickle cell disease. The ulcers in the leg can be treated with pain killers, cleansing solutions, creams or ointments, and skin grafts (for severe ulcers). And lastly, to treat the gallstones, surgery may be needed to remove them from the gallbladder. Surgery can also be used to help patients that have priapism. Since the discovery of sickle cell anemia, doctors have been working hard to find new treatments for the disease. In recent years, there have been new and experimental treatments that help patients with the disease. One of these treatments is bone marrow transplant. Since the sickle cell anemia affects the red blood cell production, it was thought that replacing the material the produces the cells may help people with the disease. After numerous trials, it has been shown that bone marrow transplant is somewhat of a cure. However, the procedure is very dangerous and lead to serious side effects or even death. Due to this risk, only young patients and people with significant symptoms or problems get the treatment. The procedure is still being researched. Another experimental treatment is gene therapy. Gene therapy is when researchers insert the normal gene for hemoglobin creation into the bone marrow of infected patients. Researchers hope that the normal genes will begin to produce the correct hemoglobin or if they can cancel the sickle cell gene by turning it off in babies. In addition, researchers are producing new drugs that may help patients. On drug has butyric acid in it which can increase the amount of normal hemoglobin in the blood. Another drug has nitric oxide in it which makes the actual sickle cells less sticky which will lead to less blocked blood vessels. The final drug contains decitadine. This will increase the amount of certain hemoglobin protein that carries more oxygen. Though there are many drugs that seem that they will work, there still more research to be done. Research Due to the severity of sickle cell anemia, there are many doctors working hard to find a definitive cure. One research that may help with finding a cure dealt with the prevalence of pulmonary hypertension in adults with sickle cell disease. The research group studied the mechanism of its development, and its prospective prognostic significances. They performed Doppler echocardiographic assessments of pulmonary-artery systolic pressure in 195 consecutive patients (82 men and 113 women with the average age of 36). The pulmonary hypertension was prospectively defined as a tricuspid regurgitant jet velocity of at least 2.5 m per second. Patients were followed for a mean of 18 months, and data were censored at the time of death or loss to follow-up. The group reached the following results. They determined that the Doppler-defined pulmonary hypertension occurred in 32 percent of patients. Multiple logistic-regression analysis, with the use of the dichotomous variable of a tricuspid regurgitant jet velocity of less than 2.5 m per second or 2.5 m per second or more, identified a self-reported history of cardiovascular or renal complications, increased systolic blood pressure, high lactate dehydrogenase levels (a marker of hemolysis), high levels of alkaline phosphatase, and low transferrin levels as significant independent correlates of pulmonary hypertension. The fetal hemoglobin level, white-cell count, and platelet count and the use of hydroxyurea therapy were unrelated to pulmonary hypertension. A tricuspid regurgitant jet velocity of at least 2.5 m per second, as compared with a velocity of less than 2.5 m per second, was strongly associated with an increased risk of death and remained so after adjustment for other possible ri sk factors in a proportional-hazards regression model. They came to the following conclusions. They believed that the pulmonary hypertension, diagnosed by Doppler echocardiography, is common in adults with sickle cell disease. It appears to be a complication of chronic hemolysis, is resistant to hydroxyurea therapy, and confers a high risk of death. Social Impact Though many believe that living with sickle cell anemia is impossible, that is not true. The infected people can live like any other person with just a few deviations. The only negative thing about living with sickle cell anemia is that the life expectancy is between 40 and 60 years old. However a person can live longer if they maintain a healthy lifestyle, control the complications that arise from the disease, and if they learn the correct ways to cope with the pain. A healthy life style means you eat healthy foods or foods that contain certain vitamins that may help your body cope with the disease. An example of a vitamin would be folic acid. Also doctors advise patients to drink plenty of water so he/she wont become dehydrated. To help prevent and control the complications of sickle cell anemia, the patient needs to follow certain instructions and warnings. Some of these instructions and warnings include avoiding decongestants and drugs that tighten blood vessels. Also the patient should avoid living in extreme hot and cold areas or in low oxygen level areas (well above sea level cities). Also doctors recommend that the patient avoid or reduce stress in their life and to avoid jobs that require a lot of physical labor. In addition, the patient should get all of the vaccines and flu shots that are available. Though following doctors recommendations will help a patient, learning and studying different treatments and lifestyle choices on their own can help them a lot. If a patient reads about sickle cell anemia, they will be better equipped to deal with symptoms and complications that may arise. If you or someone in your family has sickle cell anemia, you may want help with the stresses of this lifelong disease. Sickle cell centers and clinics can provide information and counseling. Ask your doctor or the staff at a sickle cell center if there are support groups for families in your area. Talking with others who are facing the same challenges you are can be helpful. Its especially important to find ways to control and cope with pain. Different techniques work for different people, but it might be worth trying heating pads, hot baths, massages or physical therapy. Prayer, family and friends also can be sources of support. If you have a child with sickle cell anemia, learn as much as you c an about the disease and make sure your child gets the best health care possible. A child with sickle cell disease has special needs and requires regular medical care. Your doctor can explain how often to bring your child for medical care and what you can do if he or she becomes ill. Conclusion Sickle cell anemia is a significant disease that must be addressed immediately. The number of people that know about sickle cell anemia is alarmingly low and that must change. People must become aware of the dangers of this disease and must do everything in their power to help prevent it from spreading. This disease can lead to death in infants, children, teens, and adults. It is also a worldwide disorder that needs more attention. This disease, which is genetically passed down to people, needs more people researching it and trying to find cures to. Though there are many doctors hard at work to find a cure, there can be so much more that can be done. Though there is a group of people unaware of this disease, it does not mean the work already done should be neglect. Through the hard work of doctors, we have been able to find almost every symptom of sickle cell anemia and how to treat most of the symptoms. To find a cure for sickle cell anemia, everyone must do their part and help in some way. Hemophilia What is Hemophilia? Hemophilia is a blood disorder that prevents your blood to clot normally. When the body experiences an injury where the person begins to bleed, the body reacts in a very unique manner. Blood is a liquid membrane that is composed red blood cells, white blood cells, and platelets. The purpose of the blood is to transport nutrients and oxygen from the lungs to different areas of the body and to transport carbon dioxide and waste from those areas back to the lungs. Blood also serves as a transport system for white blood cells which are part of the immune system and fighters of the immune system. However, blood also serves as a clotting mechanism. In order for the body to clot an injury, platelets must be able to stick together at the injury site. This stickiness is called the blood clotting factor. Hemophilia is a disorder that causes people to have little to none clotting factor. Hemophilia is usually an inherited disease which does not allow your blood to clot externally or internally. People with hemophilia will have a gene that will cause the clotting factor, a protein, to not work properly which will cause the patient to keep bleeding. The clotting factor is needed to form clots with platelets. Hemophilia can be divided into two major types: hemophilia A or hemophilia B. about 9 out of 10 people who have hemophilia will have type A hemophilia which means the body is missing or has low levels of clotting factor 8. If the person has type B, then they are missing or have low levels of clotting factor 9. In addition, hemophilia is usually genetically acquired but some can develop hemophilia during their lifetime. This can happen if your body forms antibodies (proteins) to the clotting factors in your bloodstream. The antibodies can prevent the clotting factors from working. Causes of Hemophilia A person usually inherits hemophilia but as discussed earlier, they can develop hemophilia during their lifetime. If a disease is inherited, then that means the parents of the patient will also have the gene for the disease. In the case of hemophilia, the gene for hemophilia is located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. Only the X chromosome carries the genes related to clotting factors. A male who has the abnormal gene on his X chromosome will have hemophilia. A female must have the abnormal gene on both of her X chromosomes to have hemophilia; this is very rare. A female is a carrier of hemophilia if she has the abnormal gene on one of her X chromosomes. Even though she doesnt have the condition, she can pass the gene on to her children. If a father does not have the hemophilia trait but the mother does have only one copy of the gene and they have 2 daughters and 2 sons, then each daughter has a 50 percent chance of inheriting the abnormal gene from her mother and being a carrier. Each son has a 50 percent chance of inheriting the abnormal gene from his mother and having hemophilia. However if the father has hemophilia and the mother has neither hemophilia or the hemophilia trait and they have 2 daughters and 2 sons, then each daughter will inherit the abnormal gene from her father and be a carrier. None of the sons will inherit the abnormal gene from their father, and, therefore, none will have hemophilia. Very rarely, a girl is born with hemophilia. This can happen if her father has hemophilia and her mother is a carrier. In addition to the genes that cause hemophilia, there are other factors that may cause it. One factor is the type of clotting factor that the person is missing. If the person has hemophilia A, then the person lacks clotting factor 8. If the person has hemophilia B, then the person lacks the clotting factor 9. Finally, if the person has Hemophilia C which is rare in the United States, then person has a different inheritance pattern and lacks clotting factor 9. Symptoms of Hemophilia The main symptom of hemophilia is excessive bleeding externally and internally. The extent of bleeding depends on the type and severity of the hemophilia. Children who have mild hemophilia may not have symptoms unless they have excessive bleeding from a dental procedure, an accident, or surgery. In addition, the symptoms of hemophilia vary depending on how deficient your clotting factors are. If levels of your deficient clotting factor are very low, you may experience spontaneous bleeding. If levels of your deficient clotting factor are slightly to moderately low, you may bleed only after surgery or trauma. If you bleed spontaneously then you have the following symptoms: many large or deep bruises, joint pain and swelling caused by internal bleeding, unexplained bleeding or bruising, blood in your urine or stool, and prolonged bleeding from cuts or injuries, or after surgery or tooth extraction. Bleeding in the knees, elbows, or other joints is another common form of internal bleeding in people who have hemophilia. This bleeding can occur without obvious injury. At first, the bleeding causes tightness in the joint with no real pain or any visible signs of bleeding. The joint then becomes swollen, hot to touch, and painful to bend. Swelling continues as bleeding continues. Eventually, movement in the joint is temporarily lost. Pain can be severe. Joint bleeding that isnt quickly treated can permanently damage the joint. Internal bleeding in the brain is a very serious complication of hemophilia that can happen after a simple bump on the head or a more serious injury. The signs and symptoms of bleeding in the brain include long-lasting, painful headaches or neck pain or stiffness or convulsions or seizures. Demographics Hemophilia affects 1 in 5,000 male births. About 400 babies are born with hemophilia each year. The exact number of people living with hemophilia in the United States is not known. Currently, the number of people with hemophilia in the United States is estimated to be about 20,000. In the United States, most people with hemophilia are diagnosed at a very young age. Based on CDC data, the median age at diagnosis is 36 months for people with mild hemophilia, 8 months for those with moderate hemophilia, and 1 month for those with severe hemophilia. In about two thirds of cases, there is a family history of hemophilia. The diagnosis of hemophilia is made using a special blood test and most babies can be tested soon after birth. Sometimes prenatal genetic testing is done to diagnose hemophilia before birth. Treatment Though, like sickle cell anemia, there is no definitive cure for hemophilia, there are many treatments that help people cope with the disease. However, the treatments people get is based on the severity of the disease. However there is main treatment for hemophilia; it is called replacement therapy. In this therapy, the missing clotting factor is injected into the body intravenously to replace the clotting factor. Though this treatment sounds good, there is a drawback, the patient has to continuously take injections of the therapy to prevent bleeding. Antifibrinolytic medicines (including tranexamic acid and aminocaproic acid) may be used with replacement therapy. Theyre usually given as a pill, and they help keep blood clots from breaking down. Another complication to this treatment is that the body may develop antibodies that act against the new clotting factor or there might be damage to joints, muscles, or other parts of the body resulting from delays in treatment. Antibodies can destroy the clotting factor before it has a chance to work. This is a very serious problem. It prevents the main treatment for hemophilia (replacement therapy) from working. Antibodies to clotting factor, also called inhibitors, develop in about 20 percent of people who have severe hemophilia A and 1 percent of people who have hemophilia B. When antibodies develop, doctors may use larger doses of clotting factor or try different clotting factor sources. Sometimes, the antibodies go away. Desmopressin (DDAVP) is a man-made hormone used to treat people who have mild to moderate hemophilia A. DDAVP isn
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.