CELL CYCLE AND MEMBRANE: 1. DESEASE: Cell membrane alteration. Origin, causes and consequences. Treatment. Social impact. Reflection. References.
CELL ... THE ORIGIN OF EVERYTHING
2. INTERVIEWS
Published by: SEBASTIÁN PARRA CADENA 7-39 10/02/18
CYSTIC FIBROSIS
CELL MEMBRANE ALTERATION
Figure 1. Chromosome 7, CFTR gene. (http://learn.genetics.utah.edu/content/disorders/singlegene/).
Cystic fibrosis is a genetic disorder that affects the respiratory and digestive systems. People with cystic fibrosis inherit a defective gene on chromosome 7 called CFTR (cystic fibrosis transmembrane conductance regulator). The protein produced by this gene normally helps salt (sodium chloride) move in and out of cells. If the protein doesn't work correctly, that movement is blocked and an abnormally thick sticky mucus is produced on the outside of the cell. The cells most seriously affected by this are the lung cells. The thick mucus also blocks ducts in the pancreas, so digestive enzymes can't get into the intestines. Without these enzymes, the intestines cannot properly digest food. Finally, cystic fibrosis affects the sweat glands. Too much salt is lost through sweat, which can disrupt the delicate balance of minerals in the body.
Figure 2. Cell membrane alteration. (http://learn.genetics.utah.edu/content/disorders/singlegene/).
HOW DO PEOPLE GET CYSTIC FIBROSIS? Cystic fibrosis is a recessive disorder, which means that both parents must pass on the defective gene for any of their children to get the disease.
Figure 3. Recessive disorder. (http://learn.genetics.utah.edu/content/disorders/singlegene/).
SYMPTOMS
Figure 4. Organs Affected By Cystic Fibrosis. (http://learn.genetics.utah.edu/content/disorders/singlegene/).
Cystic fibrosis signs and symptoms vary, depending on the severity of the disease. Some people may not experience symptoms until adolescence or adulthood. People with cystic fibrosis have a higher than normal level of salt in their sweat.
Respiratory signs and symptoms The thick and sticky mucus associated with cystic fibrosis clogs the tubes that carry air in and out of your lungs. This can cause signs and symptoms such as: A persistent cough that produces thick mucus (sputum) Wheezing Breathlessness Exercise intolerance Repeated lung infections Inflamed nasal passages or a stuffy nose Digestive signs and symptoms
The thick mucus can also block tubes that carry digestive enzymes from your pancreas to your small intestine. Without these digestive enzymes, your intestines aren't able to completely absorb the nutrients in the food you eat. The result is often: Foul-smelling, greasy stools Poor weight gain and growth Intestinal blockage, particularly in newborns (meconium ileus) Severe constipation
RISK FACTORS Family history. Because cystic fibrosis is an inherited disorder, it runs in families. Race. Although cystic fibrosis occurs in all races, it is most common in white people of Northern European ancestry.
COMPLICATIONS Respiratory system complications Damaged airways (bronchiectasis). Chronic infections. Growths in the nose (nasal polyps). Coughing up blood (hemoptysis). Pneumothorax. Respiratory failure. Acute exacerbations.
Digestive system complications Nutritional deficiencies. Diabetes. Blocked bile duct. Intestinal obstruction. Distal intestinal obstruction syndrome (DIOS). Reproductive system complications infertile Other complications Thinning of the bones (osteoporosis). Electrolyte imbalances and dehydration.
TREATMENT Although there is no cure for cystic fibrosis, new treatments are helping people with the disease live longer than before. Most treatments work by clearing mucus from the lungs and preventing lung infections. Common treatments include:
Chest physical therapy, in which the patient is repeatedly clapped on the back to free
up mucus in the chest. Inhaled antibiotics to kill the bacteria that cause lung infections. Bronchodilators (also used by people with asthma) that help keep the airways open. Pancreatic enzyme replacement therapy to allow proper food digestión. Gene therapy (a treatment currently in clinical trials), in which the healthy CFTR gene is inserted into the lung cells of a patient to correct the defective gene.
PREVENTION If you or your partner has close relatives with cystic fibrosis, you both may want to undergo genetic testing before having children.
SOCIAL IMPACT: This disease not only affects the physical condition, but also the mental and social health of the patient and his family, generating different emotions that include the feeling of guilt, impotence and fear. The economic cost to the family is very high, which can generate tensions for family members. They are people who do not have a good quality of life and possibly require the support of others in their daily activities. Children can be ignored and rejected by other people, these patients may have high school absenteeism. The costs for care of these people are very high for health services.
REFLECTION: It is a deadly disease and has no cure and people die very young; in previous times, children who had this disease could not live long, but thanks to technological, scientists and medical advances, now people live longer and with a better quality of life. If couples want to have children, it is very important to have blood tests to determine if they are carriers of the disease and thus reduce the probability of having children with cystic fibrosis.
BIBLIOGRAPHY Genetic Science Learning Center. (2014, February 15). Single Gene Disorders. Retrieved February 09, 2018. From http://learn.genetics.utah.edu/content/disorders/singlegene/
Mayo Clinic Staff. 1998-2018 Mayo Foundation for Medical Education and Research (MFMER). Cystic fibrosis. From https://www.mayoclinic.org/diseases-conditions/cysticfibrosis/symptoms-causes/syc-20353700
MYASTHENIA GRAVIS
CELL MEMBRANE ALTERATION Myasthenia gravis is caused by an error in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.
Neurotransmitters are chemicals that neurons, or brain cells, use to communicate information. Normally when electrical signals or impulses travel down a motor nerve, the nerve endings release a neurotransmitter called acetylcholine. Acetylcholine travels from the nerve ending and binds to acetylcholine receptors on the muscle. The binding of acetylcholine to its receptor activates the muscle and causes a muscle contraction.
In myasthenia gravis, antibodies (immune proteins) block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents the muscle from contracting. In most individuals with myasthenia gravis, this is caused by antibodies to the acetylcholine receptor itself. However, antibodies to other proteins, such as MuSK (Muscle-Specific Kinase) protein, can also lead to impaired transmission at the neuromuscular junction. These antibodies are produced by the body's own immune system. Myasthenia gravis is an autoimmune disease because the immune system—which normally protects the body from foreign organisms—mistakenly attacks itself.
Figure 5: Receptors: Chemicals messengers, called neurotransmitters, fit precisely into receptor sites on your muscle cells. In myasthenia gravis, certain receptor sites are blocked or destroyed, causing muscle weakness. (Mayo fundation for medical education and research. (https://www.mayoclinic.org/diseases-conditions/myastheniagravis/symptoms-causes/syc-20352036)
SYMPTOMS Although myasthenia gravis may affect any skeletal muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The onset of the disorder may be sudden and symptoms often are not immediately recognized as myasthenia gravis. Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Because symptoms usually improve with rest, your muscle weakness may come and go. However, myasthenia gravis symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease. Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others.
Eye muscles In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as: Drooping of one or both eyelids (ptosis). Double vision (diplopia), which may be horizontal or vertical, and improves or resolves when one eye is closed. Face and throat muscles In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause: Altered speaking. Your speech may sound very soft or nasal, depending upon which muscles have been affected. Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you're trying to swallow may come out your nose. Problems chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you've been eating something hard to chew, such as steak. Limited facial expressions. Your family members may comment that you've "lost your smile" if the muscles that control your facial expressions have been affected. Neck and limb muscles Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along with muscle weakness in other parts of your body, such as your eyes, face or throat. The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold up your head.
When to see a doctor: Talk to your doctor if you have difficulty: Breathing Seeing Swallowing Chewing Walking Using your arms or hands Holding up your head
COMPLICATIONS Complications of myasthenia gravis are treatable, but some can be life-threatening. Myasthenic crisis Myasthenic crisis is a life-threatening condition that occurs when the muscles that control breathing become too weak to do their jobs. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people to again breathe on their own. Thymus tumors About 15 percent of people with myasthenia gravis have a tumor in their thymus, a gland under the breastbone that is involved with the immune system. Most of these tumors, called thymomas, aren't cancerous (malignant). Other disorders People with myasthenia gravis are more likely to have the following conditions:
Underactive or overactive thyroid. The thyroid gland, which is in the neck, secretes hormones that regulate your metabolism. If your thyroid is underactive, you may have difficulties dealing with cold, weight gain and other issues. An overactive thyroid can cause difficulties dealing with heat, weight loss and other issues. Autoimmune conditions. People with myasthenia gravis may be more likely to have autoimmune conditions, such as rheumatoid arthritis or lupus.
DIAGNOSIS To diagnose your condition, your doctor will review your symptoms and your medical history and conduct a physical examination. Your doctor may conduct several tests, including: Neurological examination Your doctor may check your neurological health by testing your: Reflexes Muscle strength Muscle tone Senses of touch and sight Coordination Balance The key sign that points to the possibility of myasthenia gravis is muscle weakness that improves with rest. Tests to help confirm the diagnosis may include: Edrophonium test Ice pack test Blood analysis
Repetitive nerve stimulation Electromyography (EMG) Imaging scans Pulmonary function tests
TREATMENT Today, myasthenia gravis can generally be controlled. There are several therapies available to help reduce and improve muscle weakness. Medications Cholinesterase inhibitors. Medications such as pyridostigmine (Mestinon) enhance communication between nerves and muscles. These medications don't cure the underlying condition, but they may improve muscle contraction and muscle strength. Possible side effects may include gastrointestinal upset, nausea, and excessive salivation and sweating. Corticosteroids. Corticosteroids such as prednisone inhibit the immune system, limiting antibody production. Prolonged use of corticosteroids, however, can lead to serious side effects, such as bone thinning, weight gain, diabetes and increased risk of some infections. Immunosuppressants. Your doctor may also prescribe other medications that alter your immune system, such as azathioprine (Imuran), mycophenolate mofetil (CellCept), cyclosporine (Sandimmune, Neoral), methotrexate (Trexall) or tacrolimus (Prograf). Side effects of immunosuppressants can be serious and may include nausea, vomiting, gastrointestinal upset, increased risk of infection, liver damage and kidney damage.
Intravenous therapy Plasmapheresis (plaz-muh-fuh-REE-sis). This procedure uses a filtering process similar to dialysis. Your blood is routed through a machine that removes the antibodies that block transmission of signals from your nerve endings to your muscles' receptor sites. However, the beneficial effects usually last only a few weeks. Intravenous immunoglobulin (IVIg). This therapy provides your body with normal antibodies, which alters your immune system response. Monoclonal antibody. Rituximab (Rituxan) is an intravenous medication that is used in some cases of myasthenia gravis. This drug depletes certain white blood cells, altering the immune system and improving myasthenia gravis. Surgery About 15 percent of the people with myasthenia gravis have a tumor in their thymus gland, a gland under the breastbone that is involved with the immune system. If you have a tumor, called a thymoma, doctors will conduct surgery to remove your thymus gland (thymectomy). If you don't have a tumor in the thymus gland, surgery to remove the thymus gland may improve your myasthenia gravis symptoms. It may eliminate your symptoms, and you may be able to stop taking medications for your condition. However, you may not notice the benefits of a thymectomy for several years, if at all.
SOCIAL IMPACT It is a debilitating disease that can generate dependence. Patients with the disease may need help to perform some activities in their daily lives. The family must understand how the person feels as he adapts to the illness.
For people with myasthenia gravis and their family members, coping with the disease may be difficult. For the diagnosis different tests are used and different treatments are employed that can generate high costs for the health system. With treatment, most individuals with myasthenia can significantly improve their muscle weakness and lead normal or nearly normal lives. Sometimes the severe weakness of myasthenia gravis may cause respiratory failure, which requires immediate emergency medical care. Some cases of myasthenia gravis may go into remission—either temporarily or permanently —and muscle weakness may disappear completely so that medications can be discontinued.
BIBLIOGRAPHY By Mayo Clinic Staff. https://www.mayoclinic.org/diseases-conditions/myastheniagravis/diagnosis-treatment/drc-20352040
"Myasthenia Gravis Fact Sheet", NINDS, Publication date May 2017. NIH Publication No. 17-768. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/FactSheets/Myasthenia-Gravis-Fact-Sheet