Things You Need to Know About Dopamine Agonists
Dopamine agonists are drugs that increase the activity of a neurotransmitter called dopamine by binding to its receptors. This Buzzle write-up presents information on things you need to know about dopamine agonists.
Fact about dopamine agonists
Dopamine agonists must not be confused with dopamine precursors, such as levodopa and carbidopa, which are central nervous system agents that get converted to dopamine before binding to the dopamine receptors.
The term 'neurotransmitter' refers to a chemical that transmits nerve impulses across a synapse. Dopamine is one such chemical act that is both excitatory and inhibitory in nature, which means that it can determine the probability of the neuron firing or not firing an action potential (message that is transmitted). Thus, the activation of the receptors can promote or suppress the generation of action potential. Out of the 10 billion cells in the cerebral cortex, only one million dopaminergic cells are present in the brain. Though the number of dopaminergic neurotransmitter is less, dopamine plays a vital role in the proper functioning of the human body. It controls the cognitive function (memory, attention, and problem solving), movements, and emotional behavior.
Moreover, it also controls the reward and pleasure centers of the brain. When the link between dopaminergic cells that are present in a part of midbrain called substantia nigra and the corpus striatum (mass of white and gray matter located in front of the thalamus in both cerebral hemispheres in the brain) is adversely affected, it results in a dopamine deficiency. Such a deficiency is bound to give rise to impaired movement and a host of untoward symptoms. Under such circumstances, medicines belonging to a class of drugs called dopamine agonists are prescribed. These drugs mimic the action of dopamine and activate its receptors in the brain, even in the absence of dopamine.
Types of Dopamine Agonists
Dopamine agonists can be classified into ergoline and non-ergoline agonists. Drugs belonging to these subclasses work by targeting dopamine D2 receptors. Drugs belonging to ergoline dopamine agonists include:
➠ Bromocriptine
➠ Pergolide
➠ Lisuride
➠ Cabergoline/Cabaser
The drugs belonging to non-ergoline agonists include:
➠ Ropinirole
➠ Pramipexole
Uses of Dopamine Agonists
Deficiency of dopamine is a major reason behind the development of Parkinson's disease, which is why some of the aforementioned drugs are prescribed for the treatment of this medical condition.
Parkinson's Disease
Parkinson's disease is characterized by symptoms such as tremors, rigidity, speech changes, difficulty in writing, bent posture, loss of automatic movements, and slowness of movement. Subcutaneous administration of a drug called apomorphine also helps in the treatment of Parkinson's disease. This drug works by targeting both D1 and D2 receptors. Another drug from the non-ergoline class of medications called Neupro (Rotigotine) is available in the form of a patch. It is approved by the FDA for alleviating the early signs of Parkinson's disease and restless legs syndrome.
It must be noted that Bromocriptine and Pergolide are no longer used for the treatment of Parkinson's disease in the United States due to the increased risk of pulmonary fibrosis and valvular heart disease, respectively. Lisuride (low strength lisuride is classified as N02CA, an ergot alkaloid) is not used in the United States, as it was less successful in comparison to other dopamine receptor agonists. Amongst the ergoline derivates, Cabergoline and Cabaser are commonly prescribed for individuals affected by hyperprolactinemia and early stages of young-onset Parkinson's disease, respectively, which occur due to the deficiency of dopamine. Here is a list of common dopamine agonist drugs that have been approved by the FDA:
➠ Pramipexole (Mirapex®) is believed to be effective in the early treatment of the motor symptoms of Parkinson's Disease. It helps control the motor fluctuations.
➠ Ropinirole (Requip®) also helps control the motor symptoms of Parkinson's Disease.
➠ Rotigotine (Neupro® patch) is a transdermal patch that is changed every 24 hours.
➠ First used in the treatment of Parkinson's disease in 1950, concerns were raised about Apomorphine (Apokyn®) due to its side effects. In 1990s, it was released in an injectable form. These days, it is only prescribed in severe cases, especially during the 'off periods' as a rescue drug. It is believed that it might delay the onset of the 'on-off' phenomena. In people affected by Parkinson's disease, the 'on' period is the time when the patient feels that their medication is able to control the symptoms. On the other hand, the 'off' period refers to the period when the patient feels that the medication is not providing the desired effects. Thus, the on-off phenomenon describes the sudden onset of the motor symptoms (stiffness, slowness or tremor) or non-motor symptoms (anxiety, nausea, depression).
While dopamine receptor agonists can be taken alone in the early stages of Parkinson's disease, it can be safely used with a dopamine precursor (Levodopa/Carbidopa) later. These can be safely taken, as they only mimic the action of dopamine in its absence, and don't affect the production, transport, or release of real dopamine.
Hyperprolactinemia
Thus, the uses of dopamine agonists are not restricted to the treatment of Parkinson's disease, they also act as prolactin-inhibiting factors, which is why it is prescribed for the treatment of elevated levels of prolactin in the blood. It reduces the production of prolactin from the pituitary gland. More often than not, the use of a long-acting dopamine receptor agonist called cabergoline is suggested for the treatment of hyperprolactinemia. It works by activating the D2 receptors that are found in the pituitary gland, which in turn reduce the amount of prolactin secreted by the pituitary gland. Low strength bromocriptine, low strength cabergoline tablets, and high strength lisuride are classified as G02CB (Prolactin inhibitors).
Dopamine agonists are also prescribed for the treatment of conditions such as Attention Deficit/Hyperactivity Disorder (ADHD), restless legs syndrome, pituitary tumors, etc. FDA has approved drugs called Requip (Ropinirole) and Mirapex (Pramipexole) for treating restless legs syndrome.
Side Effects of Dopamine Agonists
One of the major side effects of these drugs is impulse control disorder. In fact, these drugs put the patient at a greater risk of impulse control disorder (Compulsive behavior such as gambling, uncontrolled shopping, binge eating, sexual urges, etc.) in comparison to dopamine precursors such as levodopa. Other adverse effects that are associated with dopamine agonist use include:
➠ Excessive daytime sleepiness
➠ Nausea
➠ Extreme weakness or fatigue
➠ Orthostatic hypotension
➠ Dizziness
➠ Lightheadedness
➠ Fainting
➠ Visual hallucinations/psychosis/euphoria
➠ Confusion
➠ Skin irritation in case of transdermal delivery
➠ Ankle edema
➠ Difficulty in performing voluntary muscle movements (in some cases)
Most of the aforementioned side effects can be alleviated by changing the dosage, depending on the patient's response to the drug. More often than not, the side effects occur with large doses, which is why, very small doses are given initially, gradually building up to an effective dose over weeks or months. In order to avoid adverse drug interactions, inform your healthcare provider about all the drugs that you are taking. Comply with the doctor's directions regarding the dosage schedule and diet. Don't change the dose or double it in case of a missed dose. Don't stop taking the drug, as sudden discontinuation of these drugs can cause the symptoms to worsen.
Though dopamine receptor agonists are quite effective in the treatment of hyperprolactinemia and the early stages of Parkinson's disease, they can cause impulse control issues or compulsive behavior. The risk is higher, if the patient is taking a dopamine agonist with levodopa. Thus, medical assistance must be immediately sought, if the patient exhibits such behavior.
Blood Pressure Chart by Age
Various diseases and disorders can lead to abnormal blood pressure levels not only in adults, but also in children. Take a look at the blood pressure chart by age that is presented in this Buzzle article. Also, know the normal, high, and low blood pressure levels.
Various diseases and disorders can lead to abnormal blood pressure levels not only in adults, but also in children. Take a look at the blood pressure chart by age that is presented in this Buzzle article. Also, know the normal, high, and low blood pressure levels.
The force exerted by blood on the walls of the blood vessels is
known as blood pressure (BP). The pressure measured when the heart
contracts and pumps the blood into the vessels is called systolic blood
pressure, and the pressure measured when the heart relaxes and fills up
with blood is called diastolic blood pressure.
The unit of BP is millimeters of mercury (mmHg). The normal blood pressure range for adults is 120-80 mmHg (systolic should be below 120, while diastolic should be below 80). The ideal blood pressure for men and women (even for women over 40 and for women over 50) can be slightly different. It is a scaring fact that more and more children are diagnosed with high blood pressure every year.
Hypertension and Hypotension
BP higher than the normal levels is referred to as high BP (HBP) or hypertension. It causes extra strain on the heart and arteries. It indicates that more force is required by the heart to pump certain quantity of blood within certain time. In hypotension, the condition is exactly opposite. The condition wherein lower than normal levels of BP are experienced is termed as hypotension. It usually results in dizziness. Aging results in higher levels of BP. The official blood pressure percentile charts, prepared using height, weight, and Body Mass Index (BMI) data of certain groups of children and adults are available in all clinics.
Prehypertension
According to the U.S. Department of Health and Human Services, people are said to have "prehypertension" when their blood pressure levels are slightly higher than normal. The systolic BP can be in between 120 and 139 and the diastolic BP can be between 80 and 89. The person diagnosed with prehypertension is at a higher risk for developing hypertension. But at this stage, simple dietary and lifestyle changes can help lower the blood pressure.
Factors that Affect Blood Pressure
Blood pressure levels keep on changing every minute. They vary according to the age, gender, height, weight, and overall health of the person. They are seriously affected by:
Physical or emotional stress
Wrong diet
Excess intake of common salt
Sedentary lifestyle
Smoking
Excessive intake of alcohol
Overconsumption of caffeine
Excessive consumption of nicotine
Excessive use of birth control pills
Genetic disposition
Family history
Excess weight
Obesity
Pregnancy
Menopause, when the estrogen (the hormone that helps regulate BP) levels drop down significantly
Chart by Age for Children and Adults
Group Age Systolic BP Diastolic BP
Kids 3-6 years 116 76
Kids 7-10 years 122 78
Kids 11-13 years 126 82
Teens 14-16 years 136 86
Optimal Level for Young Adults 17-19 years less than or equal to 120 less than or equal to 85
Adults 20-24 years 120 79
Adults 25-29 years 121 80
Adults 30-34 years 122 81
Adults 35-39 years 123 82
Adults 40-44 years 125 83
Adults 45-49 years 127 84
Adults 50-54 years 129 85
Adults 55-59 years 131 86
Adults 60 years and above 134 87
BP Chart by Gender for Children
Age Male (mmHg) Female (mmHg)
1 to 3 80/34 to 120/75 83/38 to 117/76
4 to 6 88/47 to 128/84 88/50 to 122/83
7 to 10 92/53 to 130/90 93/55 to 129/88
Babies born earlier than usual (before 37 weeks pregnancy) or babies born with heart/kidney problems may exhibit the symptoms of high BP.
Researches show that obesity and excessive consumption of salt are the main contributing factors for elevated blood pressure in children aged 8-17. A family history of hypertension and an unhealthy lifestyle are some of the main risk factors. Excessive consumption of junk food, lack of essential nutrients in diet, stress, insufficient physical activity, higher body mass, and a larger waistline can result in high BP in teenagers.
Normal, High, and Low Blood Pressure
Pressure Level Systolic (mmHg) Diastolic (mmHg)
Low Blood Pressure (Hypotension) 50 - 90 35 - 60
Mild Low Blood Pressure 90 - 100 60 - 70
Normal Blood Pressure 100 - 130 70 - 85
Mild High Blood Pressure 130 - 140 85 - 90
Moderately High Blood Pressure 140 - 160 90 - 110
Severely High Blood Pressure (Hypertension) 160 - 230 110 - 135
Necessary Changes in Diet and Lifestyle
Reduce your salt intake. Studies show that store-bought foods and foods from restaurants are high in salt. It has been observed that the daily salt intake by Americans is almost double than the one that is recommended by the American Heart Association.
A healthy diet is essential for an uninterrupted blood flow.
Increase your intake of potassium, calcium, and magnesium.
Regular exercise helps increase the capacity of the heart.
Try to maintain your weight within the range of normal weight for your height.
Incorporate fruits, vegetables, and low-fat dairy products in your diet.
Lowering the stress helps lower BP.
Opting for a less demanding job, or doing things of your own interest help relieve stress.
Avoid smoking.
Avoid excessive intake of alcohol.
Avoid excessive intake of medicines and supplements.
The unit of BP is millimeters of mercury (mmHg). The normal blood pressure range for adults is 120-80 mmHg (systolic should be below 120, while diastolic should be below 80). The ideal blood pressure for men and women (even for women over 40 and for women over 50) can be slightly different. It is a scaring fact that more and more children are diagnosed with high blood pressure every year.
Hypertension and Hypotension
BP higher than the normal levels is referred to as high BP (HBP) or hypertension. It causes extra strain on the heart and arteries. It indicates that more force is required by the heart to pump certain quantity of blood within certain time. In hypotension, the condition is exactly opposite. The condition wherein lower than normal levels of BP are experienced is termed as hypotension. It usually results in dizziness. Aging results in higher levels of BP. The official blood pressure percentile charts, prepared using height, weight, and Body Mass Index (BMI) data of certain groups of children and adults are available in all clinics.
Prehypertension
According to the U.S. Department of Health and Human Services, people are said to have "prehypertension" when their blood pressure levels are slightly higher than normal. The systolic BP can be in between 120 and 139 and the diastolic BP can be between 80 and 89. The person diagnosed with prehypertension is at a higher risk for developing hypertension. But at this stage, simple dietary and lifestyle changes can help lower the blood pressure.
Factors that Affect Blood Pressure
Blood pressure levels keep on changing every minute. They vary according to the age, gender, height, weight, and overall health of the person. They are seriously affected by:
Physical or emotional stress
Wrong diet
Excess intake of common salt
Sedentary lifestyle
Smoking
Excessive intake of alcohol
Overconsumption of caffeine
Excessive consumption of nicotine
Excessive use of birth control pills
Genetic disposition
Family history
Excess weight
Obesity
Pregnancy
Menopause, when the estrogen (the hormone that helps regulate BP) levels drop down significantly
Chart by Age for Children and Adults
Group Age Systolic BP Diastolic BP
Kids 3-6 years 116 76
Kids 7-10 years 122 78
Kids 11-13 years 126 82
Teens 14-16 years 136 86
Optimal Level for Young Adults 17-19 years less than or equal to 120 less than or equal to 85
Adults 20-24 years 120 79
Adults 25-29 years 121 80
Adults 30-34 years 122 81
Adults 35-39 years 123 82
Adults 40-44 years 125 83
Adults 45-49 years 127 84
Adults 50-54 years 129 85
Adults 55-59 years 131 86
Adults 60 years and above 134 87
BP Chart by Gender for Children
Age Male (mmHg) Female (mmHg)
1 to 3 80/34 to 120/75 83/38 to 117/76
4 to 6 88/47 to 128/84 88/50 to 122/83
7 to 10 92/53 to 130/90 93/55 to 129/88
Babies born earlier than usual (before 37 weeks pregnancy) or babies born with heart/kidney problems may exhibit the symptoms of high BP.
Researches show that obesity and excessive consumption of salt are the main contributing factors for elevated blood pressure in children aged 8-17. A family history of hypertension and an unhealthy lifestyle are some of the main risk factors. Excessive consumption of junk food, lack of essential nutrients in diet, stress, insufficient physical activity, higher body mass, and a larger waistline can result in high BP in teenagers.
Normal, High, and Low Blood Pressure
Pressure Level Systolic (mmHg) Diastolic (mmHg)
Low Blood Pressure (Hypotension) 50 - 90 35 - 60
Mild Low Blood Pressure 90 - 100 60 - 70
Normal Blood Pressure 100 - 130 70 - 85
Mild High Blood Pressure 130 - 140 85 - 90
Moderately High Blood Pressure 140 - 160 90 - 110
Severely High Blood Pressure (Hypertension) 160 - 230 110 - 135
Necessary Changes in Diet and Lifestyle
Reduce your salt intake. Studies show that store-bought foods and foods from restaurants are high in salt. It has been observed that the daily salt intake by Americans is almost double than the one that is recommended by the American Heart Association.
A healthy diet is essential for an uninterrupted blood flow.
Increase your intake of potassium, calcium, and magnesium.
Regular exercise helps increase the capacity of the heart.
Try to maintain your weight within the range of normal weight for your height.
Incorporate fruits, vegetables, and low-fat dairy products in your diet.
Lowering the stress helps lower BP.
Opting for a less demanding job, or doing things of your own interest help relieve stress.
Avoid smoking.
Avoid excessive intake of alcohol.
Avoid excessive intake of medicines and supplements.
Advantages and Disadvantages of Ballistic Stretching
Ballistic stretching is helpful in improving dynamic flexibility, but as it pushes the muscles beyond their healthy range of motion, the possibility of injury is pretty high. The following Buzzle article elaborates more on the pros and cons of ballistic stretching.
Ballistic stretching is helpful in improving dynamic flexibility, but as it pushes the muscles beyond their healthy range of motion, the possibility of injury is pretty high. The following Buzzle article elaborates more on the pros and cons of ballistic stretching.
Ballistic stretching involves a set of stretching exercises that
pushes your muscles past their normal range of motion. It involves
repeatedly moving a part of the body in a jerky or bouncing fashion in
an attempt to stretch the associated muscles beyond their normal limits.
The sitting toe stretch, shoulder rotations for baseball pitchers, and
stretch kicks for martial artists are some examples of ballistic
stretching.
Cell-mediated Immunity Vs. Humoral Immunity
The human immune system employs physical, chemical, and cellular defenses to counter the attack by pathogens or anything that the immune system deems to be a threat. This Buzzle write-up provides information on the immune response, with the main focus on the difference between cell-mediated immunity and humoral immunity.
A healthy immune system is essential for our survival, as we are
constantly exposed to pathogens or disease-causing agents. The skin and
the mucous membranes serve as the first line of defense, whereas
phagocytes, macrophages, non-phagocytic leukocytes, complementary
proteins, chemokines, etc., come to the rescue when the pathogens make
it past the physical barriers such as the skin or the mucous membranes.
However, these are responsible for generalized response to infections,
and are a part of the non-specific or innate immune system. The
specific/adaptive immune system is the third line of defense, which
caters to the infections or threats that cannot be handled by the innate
immune system. Only vertebrates have specific immune responses, which
are characterized by a targeted response against a specific pathogen.
The specific immunity facilitates a targeted response against a specific pathogen. Together, innate immunity and adaptive immunity are responsible for immune responses that protect the body from dangerous cells (cancerous cells), allergens, foreign bodies, pathogens (bacteria, viruses, fungi, parasites), etc. The adaptive immune system includes immune responses called 'cell-mediated immunity' and 'humoral immunity', which recognize specific antigens. The term 'antigens' is derived from the term 'antibody generator', and refers to substances which trigger an immune response or the production of antibodies by the immune system. An interesting feature of the adaptive immunity is that after neutralizing the foreign invader or pathogen, a few B cells or T cells stay in the body as memory cells. If the same pathogen attacks in the future, these recognize the pathogen, and mount an attack.
Cell-mediated Immunity vs. Humoral Immunity
In order to understand the difference between cell-mediated and humoral immunity, we need to understand the function and nature of B cells and T cells, which are an integral part of the adaptive immune system. T cells, as well as the B cells are lymphocytes, which in turn, are a type of leukocyte (white blood cell). These are dedicated cells that are triggered in the presence of an antigen. These are essential for the targeted response against a specific disease-causing agent. Humoral immunity refers to the immune response that involves the use of antibodies produced by B cells for attacking a foreign invader. Therefore, this type of immune response is also referred to as antibody-mediated immunity.
The use of the term 'humoral' is also due to the fact that the antibodies which bind to the antigen and trigger a response are dissolved in the humor (bodily fluids such as blood, lymph). On the other hand, the cell-mediated immunity involves the destruction of cells that are damaged by mutations or infected by viruses with the help of Helper T cells (CD4+) and cytotoxic T cells (CD8+). The T cells bind to the surface of other antigen presenting cells (cells that display the antigen), thereby triggering a response. Other types of T cells that are present include NK (Natural Killer) cells, regulatory T cells, etc.
T-cells and Cell-mediated Immunity
The T cells, which are produced in the bone marrow and mature in the thymus, play a vital role in the immune response, as these attack the cells that have been infected by pathogens, or the cells that have become cancerous due to the abnormal and uncontrolled cell division. When the immune system identifies a threat, specialized immune cells called macrophages, granulocytes, and dendritic cells, respond to the threat by engulfing and digesting pathogens. Macrophages keep parts of the cell markers of the pathogen or invader and display them on the surface of their own membrane. This process is called antigen presentation. The macrophages also help activate the rest of the immune system by traveling to the nearest lymph node, where they present an antigen fragment from the pathogen.
Cell-mediated immunity
T cells get activated when the receptor of a Helper T cell identifies the antigen and binds to it. Once activated, Helper T cells divide and produce cytokines (cell-signaling protein molecule). The cytokines help activate both B cells and T cells. They increase phagocytotic activity (digestion of pathogens by the phagocytes), and give rise to T cell proliferation, T cell differentiation, and increased cytokine secretion. They can also direct the infected body cells to self-destruct, so as to destroy the pathogen. T cells can also secrete a substance called perforin, which penetrates through membranes and destroys those cells.
Immune response of Helper T cells
Molecular receptors on the surface of T cells (T cell receptors) can recognize protein antigens and bind to their cognate antigens. The main difference between the T cells and B cells is that T cell receptors remain on the surface of the cell, whereas B cells can release the receptors as antibodies. Moreover, B cell antibodies can recognize any organic molecule. Once the receptors of T cells are activated by a specific antigen, they replicate to create clones of T cells that are specifically programmed to counter that particular antigen.
As mentioned earlier, Major Histocompatibility Complex is the specific marker that helps the immune system differentiate between the invader and body's cells. While MHC-I markers are on every cell, MHC-II are present only on the antigen-presenting cells (APCs) and lymphocytes. In short, the steps of cell-mediated response include:
➠ Self-cells or APCs that present antigens bind to T cells.
➠ Cytokines or interleukins (secreted by APCs or helper T cells) trigger the activation of T cells.
➠ If MHC‐I and endogenous antigens are displayed on the plasma membrane, T cells proliferate, producing cytotoxic T cells. Cytotoxic T cells destroy cells that display the antigens.
➠ If MHC‐II and exogenous antigens are displayed on the plasma membrane, T cells proliferate, thereby stimulating the production of Helper T cells. Helper T cells release interleukins (and other cytokines), which in turn stimulate B cells to produce antibodies that bind to the antigens. These also induce NK cells and macrophages to destroy the antigens.
Cytotoxic T cell
If the virus or pathogen enters the cell, it can replicate at a rapid rate and emerge through the cell walls, thereby infecting the surrounding cells. Under such circumstances, the T cells come to the rescue. The cell-mediated immunity involves the activation of NK cells, T lymphocytes, macrophages, and cytokines in response to an antigen. The T cells are also instrumental in activating B cells to divide into plasma cells. They also activate phagocytes to destroy microbes, and activate killer T cells that identify and destroy the infected body cells. On the other hand, regulatory T cells (suppressor T cells) signal to put an end to the immune response or attack, once the situation in under control. Moreover, lymphocytes called the memory T cells can identify the antigen, previous vaccination, or a cancer cell, if there's another attack in the future.
B Cells and Humoral Immunity
B cells are produced from the stem cells in the bone marrow. They perform the vital task of the synthesis of antibodies (Y-shaped protein molecules that are produced in response to an antigen) that launch an attack on the disease-causing agents. Numerous receptors lie on the surface of a B cell. The B cells get activated after receiving an interleukin signal from a helper T cell, which in turn has been activated by a macrophage with a MHC-antigen complex. Once the B cell receptors (BCRs) identify a matching (or cognate) antigen, they bind to the antigen. Thereafter, the B cells divide or proliferate rapidly into plasma cells (effector cells) and memory cells. They double every six hours for a period of 7 days. Once they reach a count of around 20,000, about 2,000 antibodies are released every second.
Humoral immunity
While the effector cells produce a large number of antibodies, the memory cells are responsible for the immune system's ability to remember an antigen and properly respond to it. So, the next time that pathogen attacks the body, the immune system gets activated immediately and destroys the pathogen before it is able to cause an infection.
In short, the steps of antibody-mediated immune response include:
➠ Antigens bind to B cells.
➠ Helper T cells or interleukins activate B cells. In most cases, both an antigen and a co-stimulator are required to activate a B cell and induce B cell proliferation.
➠ B cells replicate, thereby producing effector cells. The plasma cells bear antibodies that are specific to that antigen on the activated B cells. This is followed by the release of antibodies, which then bind to the antigens.
➠ B cells produce memory cells, which help activate the immune system if the same pathogen attacks in the future.
The specific immunity facilitates a targeted response against a specific pathogen. Together, innate immunity and adaptive immunity are responsible for immune responses that protect the body from dangerous cells (cancerous cells), allergens, foreign bodies, pathogens (bacteria, viruses, fungi, parasites), etc. The adaptive immune system includes immune responses called 'cell-mediated immunity' and 'humoral immunity', which recognize specific antigens. The term 'antigens' is derived from the term 'antibody generator', and refers to substances which trigger an immune response or the production of antibodies by the immune system. An interesting feature of the adaptive immunity is that after neutralizing the foreign invader or pathogen, a few B cells or T cells stay in the body as memory cells. If the same pathogen attacks in the future, these recognize the pathogen, and mount an attack.
Cell-mediated Immunity vs. Humoral Immunity
In order to understand the difference between cell-mediated and humoral immunity, we need to understand the function and nature of B cells and T cells, which are an integral part of the adaptive immune system. T cells, as well as the B cells are lymphocytes, which in turn, are a type of leukocyte (white blood cell). These are dedicated cells that are triggered in the presence of an antigen. These are essential for the targeted response against a specific disease-causing agent. Humoral immunity refers to the immune response that involves the use of antibodies produced by B cells for attacking a foreign invader. Therefore, this type of immune response is also referred to as antibody-mediated immunity.
The use of the term 'humoral' is also due to the fact that the antibodies which bind to the antigen and trigger a response are dissolved in the humor (bodily fluids such as blood, lymph). On the other hand, the cell-mediated immunity involves the destruction of cells that are damaged by mutations or infected by viruses with the help of Helper T cells (CD4+) and cytotoxic T cells (CD8+). The T cells bind to the surface of other antigen presenting cells (cells that display the antigen), thereby triggering a response. Other types of T cells that are present include NK (Natural Killer) cells, regulatory T cells, etc.
T-cells and Cell-mediated Immunity
The T cells, which are produced in the bone marrow and mature in the thymus, play a vital role in the immune response, as these attack the cells that have been infected by pathogens, or the cells that have become cancerous due to the abnormal and uncontrolled cell division. When the immune system identifies a threat, specialized immune cells called macrophages, granulocytes, and dendritic cells, respond to the threat by engulfing and digesting pathogens. Macrophages keep parts of the cell markers of the pathogen or invader and display them on the surface of their own membrane. This process is called antigen presentation. The macrophages also help activate the rest of the immune system by traveling to the nearest lymph node, where they present an antigen fragment from the pathogen.
Cell-mediated immunity
T cells get activated when the receptor of a Helper T cell identifies the antigen and binds to it. Once activated, Helper T cells divide and produce cytokines (cell-signaling protein molecule). The cytokines help activate both B cells and T cells. They increase phagocytotic activity (digestion of pathogens by the phagocytes), and give rise to T cell proliferation, T cell differentiation, and increased cytokine secretion. They can also direct the infected body cells to self-destruct, so as to destroy the pathogen. T cells can also secrete a substance called perforin, which penetrates through membranes and destroys those cells.
Immune response of Helper T cells
Molecular receptors on the surface of T cells (T cell receptors) can recognize protein antigens and bind to their cognate antigens. The main difference between the T cells and B cells is that T cell receptors remain on the surface of the cell, whereas B cells can release the receptors as antibodies. Moreover, B cell antibodies can recognize any organic molecule. Once the receptors of T cells are activated by a specific antigen, they replicate to create clones of T cells that are specifically programmed to counter that particular antigen.
As mentioned earlier, Major Histocompatibility Complex is the specific marker that helps the immune system differentiate between the invader and body's cells. While MHC-I markers are on every cell, MHC-II are present only on the antigen-presenting cells (APCs) and lymphocytes. In short, the steps of cell-mediated response include:
➠ Self-cells or APCs that present antigens bind to T cells.
➠ Cytokines or interleukins (secreted by APCs or helper T cells) trigger the activation of T cells.
➠ If MHC‐I and endogenous antigens are displayed on the plasma membrane, T cells proliferate, producing cytotoxic T cells. Cytotoxic T cells destroy cells that display the antigens.
➠ If MHC‐II and exogenous antigens are displayed on the plasma membrane, T cells proliferate, thereby stimulating the production of Helper T cells. Helper T cells release interleukins (and other cytokines), which in turn stimulate B cells to produce antibodies that bind to the antigens. These also induce NK cells and macrophages to destroy the antigens.
Cytotoxic T cell
If the virus or pathogen enters the cell, it can replicate at a rapid rate and emerge through the cell walls, thereby infecting the surrounding cells. Under such circumstances, the T cells come to the rescue. The cell-mediated immunity involves the activation of NK cells, T lymphocytes, macrophages, and cytokines in response to an antigen. The T cells are also instrumental in activating B cells to divide into plasma cells. They also activate phagocytes to destroy microbes, and activate killer T cells that identify and destroy the infected body cells. On the other hand, regulatory T cells (suppressor T cells) signal to put an end to the immune response or attack, once the situation in under control. Moreover, lymphocytes called the memory T cells can identify the antigen, previous vaccination, or a cancer cell, if there's another attack in the future.
B Cells and Humoral Immunity
B cells are produced from the stem cells in the bone marrow. They perform the vital task of the synthesis of antibodies (Y-shaped protein molecules that are produced in response to an antigen) that launch an attack on the disease-causing agents. Numerous receptors lie on the surface of a B cell. The B cells get activated after receiving an interleukin signal from a helper T cell, which in turn has been activated by a macrophage with a MHC-antigen complex. Once the B cell receptors (BCRs) identify a matching (or cognate) antigen, they bind to the antigen. Thereafter, the B cells divide or proliferate rapidly into plasma cells (effector cells) and memory cells. They double every six hours for a period of 7 days. Once they reach a count of around 20,000, about 2,000 antibodies are released every second.
Humoral immunity
While the effector cells produce a large number of antibodies, the memory cells are responsible for the immune system's ability to remember an antigen and properly respond to it. So, the next time that pathogen attacks the body, the immune system gets activated immediately and destroys the pathogen before it is able to cause an infection.
In short, the steps of antibody-mediated immune response include:
➠ Antigens bind to B cells.
➠ Helper T cells or interleukins activate B cells. In most cases, both an antigen and a co-stimulator are required to activate a B cell and induce B cell proliferation.
➠ B cells replicate, thereby producing effector cells. The plasma cells bear antibodies that are specific to that antigen on the activated B cells. This is followed by the release of antibodies, which then bind to the antigens.
➠ B cells produce memory cells, which help activate the immune system if the same pathogen attacks in the future.
Causes of Absent Red Reflex in Newborns
The term 'red reflex' refers to the reddish-orange glow or the reflection of light that is observed from the eye's retina during direct ophthalmoscopy. This Buzzle write-up provides information on the causes of the absence of red reflex in newborns.
One of the main vision-related tests―the red reflex test―is a
screening test that must be conducted for the early detection of vision
problems in newborns. This test involves the use of an ophthalmoscope,
which is a lighted instrument that is used by ophthalmologists to
examine the inside of the eye, including the retina and the optic nerve.
The test is conducted in a dimly-lit room, and the ophthalmoscope is held at a distance of 12 to 18 inches. During this test, light that is transmitted from an ophthalmoscope passes through the tear film, cornea, aqueous humor, crystalline lens, and vitreous humor (transparent parts of the human eye). As this light reflects off the fundus (back of the eye) and is transmitted back through a tiny opening in the ophthalmoscope, the ophthalmologist can see a magnified image of the structures at the back of the eye, which include the optic disc, retina, retinal blood vessels, macula, and choroid.
In case of healthy eyes where there is no obstruction in the optical pathway, red reflex is present, which means that a reddish-orange reflection of light from the retina would be observed. Absence of red reflex is indicative of certain serious eye conditions, which is why, this test is conducted in newborns to rule out vision-related problems.
Ophthalmoscopic Examination for Red Reflex
Red reflex is considered to be an effective test for the detection of abnormalities or opacities in the back of the eye or the visual axis. For accurate results, a direct ophthalmoscope that has a large-sized aperture should be used, as that would allow the doctor to focus on the face clearly and check and compare the reflection in both eyes simultaneously.
Ophthalmoscopic examination
Ophthalmoscope
Normal Red Reflex
The test will be considered normal under the following circumstances:
➠ The red or orange glow must be observed in both the eyes.
➠ The reflection should be symmetrical in terms of color, intensity, and clarity.
Red reflex
The pediatrician should make a referral to an ophthalmologist in the following cases:
➠ Opacities or white spots (leukocoria) are observed within the area of red reflex in one or both eyes
➠ Dark spots are present in the region of red reflex
➠ Red reflex is blunted on one side
➠ Red reflex is absent
➠ White reflex is present (retinal reflection)
The test must be conducted properly, as the pupils in infants can sometimes be small. Moreover, the infant might not keep the eyes open. In such cases, pupils might have to be dilated, provided the infant is older than 2 weeks. While observing the change in the color, the change in the level of pigmentation of the fundus in children from different ethnic groups should be considered. In case the reflection is abnormal or absent, and there is family history of retinoblastoma or cataract, the child should be taken to an ophthalmologist at the earliest.
Absent/Abnormal Red Reflex in Newborns
If the reddish-orange reflection of the light is not observed in one or both eyes, it implies that the red reflex is absent. This indicates the presence of an obstruction or abnormalities in the structures located at the back of the eye. In some cases, lack of symmetry in the red reflex might be indicative of unequal or high refractive errors. The contributing factors for an absent red reflex might include:
Cataract
Cataract is an eye condition that is characterized by the clouding of the natural lens of the eye. It can affect one or both eyes. The natural lens is a clear part of the eye, which helps focus light or an image on the retina. Under normal circumstances, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.
Human eye
Cataract
The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image would be blurred. This condition can also be present at birth. However, the cataract in newborns might be so small that it might not affect the vision. Thus, checking red reflex is extremely important to rule out cataract.
Retinal Abnormalities
Retinoblastoma refers to a rare type of eye cancer that might affect children before the age of 5 years. The cancer affects the retina, which is the specialized light-sensitive membrane at the back of the eye. Leukocoria, which refers to the whiteness in the pupil, is one of the most early signs of retinoblastoma. This can be detected through the red reflex test, or even observed in photographs that have been taken with a flash. It is believed that retinal detachment (detachment of retina from the underlying tissue layer) could be responsible for the absence of red reflex.
Damaged optic nerve and retinal detachment
Retinal detachment could occur in individuals affected by Coat's disease, where dilated and abnormally twisted blood vessels in the eye hamper the normal flow of blood. Leakage of fluid from the blood vessels might give rise to a buildup of fatty material into the retina. Retinal detachment can occur when there is a large buildup of fatty material. In children affected by Coat's disease, a yellowish glow is observed during direct ophthalmoscopy.
Refractive Errors
For us to be able to see properly, light rays are bent (refracted) while they pass through the cornea and the lens. Thereafter, the light is focused on the retina, which is a light-sensitive membrane covering the back wall of the eyeball that is continuous with the optic nerve. The retina converts the images into electric signals, and sends them to the brain through the optic nerve. The brain then interprets these messages into the images we see. Refractive errors occur when one has a problem in focusing due to the irregular shape of the cornea or the length of the eyeball. High refractive errors could sometimes cause an asymmetrical red reflex. Sometimes, both eyes might have a red reflex; however, there might be difference in the level of brightness. This could be indicative of anisometropic amblyopia that occurs due to different refractions.
Strabismus
Strabismus, which is commonly referred to as crossed eyes, is an eye condition that is characterized by abnormal alignment of one or both eyes. This condition could occur in the event of problems related to eye muscles, control center in the brain that is involved with movements of the eyes, or the nerves that transmit information to the muscles. The cause of congenital strabismus, which means strabismus that occurs at or shortly after birth, is not known. It is believed that family history could put one at a risk. Conditions such as retinoblastoma, retinopathy of prematurity, cerebral palsy, etc., could be associated with strabismus in children.
The test is conducted in a dimly-lit room, and the ophthalmoscope is held at a distance of 12 to 18 inches. During this test, light that is transmitted from an ophthalmoscope passes through the tear film, cornea, aqueous humor, crystalline lens, and vitreous humor (transparent parts of the human eye). As this light reflects off the fundus (back of the eye) and is transmitted back through a tiny opening in the ophthalmoscope, the ophthalmologist can see a magnified image of the structures at the back of the eye, which include the optic disc, retina, retinal blood vessels, macula, and choroid.
In case of healthy eyes where there is no obstruction in the optical pathway, red reflex is present, which means that a reddish-orange reflection of light from the retina would be observed. Absence of red reflex is indicative of certain serious eye conditions, which is why, this test is conducted in newborns to rule out vision-related problems.
Ophthalmoscopic Examination for Red Reflex
Red reflex is considered to be an effective test for the detection of abnormalities or opacities in the back of the eye or the visual axis. For accurate results, a direct ophthalmoscope that has a large-sized aperture should be used, as that would allow the doctor to focus on the face clearly and check and compare the reflection in both eyes simultaneously.
Ophthalmoscopic examination
Ophthalmoscope
Normal Red Reflex
The test will be considered normal under the following circumstances:
➠ The red or orange glow must be observed in both the eyes.
➠ The reflection should be symmetrical in terms of color, intensity, and clarity.
Red reflex
The pediatrician should make a referral to an ophthalmologist in the following cases:
➠ Opacities or white spots (leukocoria) are observed within the area of red reflex in one or both eyes
➠ Dark spots are present in the region of red reflex
➠ Red reflex is blunted on one side
➠ Red reflex is absent
➠ White reflex is present (retinal reflection)
The test must be conducted properly, as the pupils in infants can sometimes be small. Moreover, the infant might not keep the eyes open. In such cases, pupils might have to be dilated, provided the infant is older than 2 weeks. While observing the change in the color, the change in the level of pigmentation of the fundus in children from different ethnic groups should be considered. In case the reflection is abnormal or absent, and there is family history of retinoblastoma or cataract, the child should be taken to an ophthalmologist at the earliest.
Absent/Abnormal Red Reflex in Newborns
If the reddish-orange reflection of the light is not observed in one or both eyes, it implies that the red reflex is absent. This indicates the presence of an obstruction or abnormalities in the structures located at the back of the eye. In some cases, lack of symmetry in the red reflex might be indicative of unequal or high refractive errors. The contributing factors for an absent red reflex might include:
Cataract
Cataract is an eye condition that is characterized by the clouding of the natural lens of the eye. It can affect one or both eyes. The natural lens is a clear part of the eye, which helps focus light or an image on the retina. Under normal circumstances, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.
Human eye
Cataract
The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image would be blurred. This condition can also be present at birth. However, the cataract in newborns might be so small that it might not affect the vision. Thus, checking red reflex is extremely important to rule out cataract.
Retinal Abnormalities
Retinoblastoma refers to a rare type of eye cancer that might affect children before the age of 5 years. The cancer affects the retina, which is the specialized light-sensitive membrane at the back of the eye. Leukocoria, which refers to the whiteness in the pupil, is one of the most early signs of retinoblastoma. This can be detected through the red reflex test, or even observed in photographs that have been taken with a flash. It is believed that retinal detachment (detachment of retina from the underlying tissue layer) could be responsible for the absence of red reflex.
Damaged optic nerve and retinal detachment
Retinal detachment could occur in individuals affected by Coat's disease, where dilated and abnormally twisted blood vessels in the eye hamper the normal flow of blood. Leakage of fluid from the blood vessels might give rise to a buildup of fatty material into the retina. Retinal detachment can occur when there is a large buildup of fatty material. In children affected by Coat's disease, a yellowish glow is observed during direct ophthalmoscopy.
Refractive Errors
For us to be able to see properly, light rays are bent (refracted) while they pass through the cornea and the lens. Thereafter, the light is focused on the retina, which is a light-sensitive membrane covering the back wall of the eyeball that is continuous with the optic nerve. The retina converts the images into electric signals, and sends them to the brain through the optic nerve. The brain then interprets these messages into the images we see. Refractive errors occur when one has a problem in focusing due to the irregular shape of the cornea or the length of the eyeball. High refractive errors could sometimes cause an asymmetrical red reflex. Sometimes, both eyes might have a red reflex; however, there might be difference in the level of brightness. This could be indicative of anisometropic amblyopia that occurs due to different refractions.
Strabismus
Strabismus, which is commonly referred to as crossed eyes, is an eye condition that is characterized by abnormal alignment of one or both eyes. This condition could occur in the event of problems related to eye muscles, control center in the brain that is involved with movements of the eyes, or the nerves that transmit information to the muscles. The cause of congenital strabismus, which means strabismus that occurs at or shortly after birth, is not known. It is believed that family history could put one at a risk. Conditions such as retinoblastoma, retinopathy of prematurity, cerebral palsy, etc., could be associated with strabismus in children.
How to Keep Your Skin from Thinning
Eating skin-friendly foods, avoiding unhealthy habits, such as smoking, and using appropriate moisturizers are some of the ways to prevent thinning of skin. Read the following Buzzle article to know more about ways to keep skin healthy.
Eating skin-friendly foods, avoiding unhealthy habits, such as smoking, and using appropriate moisturizers are some of the ways to prevent thinning of skin. Read the following Buzzle article to know more about ways to keep skin healthy.
Aging of the body and its organs, which includes the skin, is
inevitable and inescapable, but one can always delay this process by
leading a healthier lifestyle. With age, the top layer of the skin loses
its natural texture and eventually becomes thin, saggy, followed by
formation of fine lines and wrinkles.
However, even during old age, you can still maintain the natural glow on the skin, provided you take proper care of your skin. So, to ensure that the beauty of the skin does not diminish with age, here's what you can do.
Eat Skin-Friendly Foods
Our diet or the type of food we consume can have a negative or positive influence on our skin. Eating junk food daily will surely rob your skin of its healthy texture. These foods predispose your skin to a wide range of skin problems as well as accelerate aging of the skin. Therefore, discard processed foods and prefer natural, freshly-cooked foods. Including skin-friendly foods in the diet can go a long way in maintaining the beauty of the skin and prevent it from thinning.
Use Appropriate Moisturizers
Ignoring proper skin care routine can also lead to premature thinning of the skin. Our skin loses its moisture daily, making it dry and dull. The skin may crack and peel. Eventually the skin loses its elasticity, leading to thinning and formation of wrinkles. No matter what type of skin you have, make moisturizing an integral part of your skin care regimen. This will certainly help to preserve the natural moisture of the skin. Apply an appropriate moisturizer daily, to keep your skin from thinning. This works to keep the skin well-hydrated, soft, and supple.
Quit Smoking
If you diligently follow a healthy diet but puff cigarettes without fail, then all your efforts to maintain skin health will draw to a naught. The point is, smoking produces damaging effects on the skin. Smoking decreases blood circulation in the skin by constricting the blood vessels. As a result, oxygen and nutrient supply to the skin chronically drops, which changes the appearance of the skin significantly. No wonder, thin old-looking skin is one of the major side effects of smoking. So, for a healthy, supple, radiant skin that everyone dreams of, it is necessary to quit smoking.
Exercise Daily
Leading a sedentary life will not only cause a decline in cardiovascular health, but it can also have repercussions on your skin. Any form of physical activity, be it brisk walking, running or any other workout, is beneficial to the skin. As we all know, exercise increases blood circulation throughout the body including the skin. The increased blood flow supplies much-needed nutrients to the skin cells, in turn keeping the skin healthy. Moreover, a regular exercise routine ensures that your muscles are firm and the skin is tight.
Drink Plenty of Water
Water is a vital 'nutrient' for healthy skin. Adequate water intake ensures that nutrients from ingested food reach the skin cells, which help to nourish the skin. Also, water acts as a natural moisturizer for the skin, thereby keeping its texture and appearance youthful. Moreover, adequate water intake helps to get rid of toxins, which also contributes in improving skin health So, drink at least 7 to 8 glasses of water everyday for a clear, healthy complexion.
Reduce Sun Exposure
Overexposure to the sun is one of the primary factors that can accelerate thinning of the skin. It is a known fact that long-term exposure to UV rays damages the vital structures of the skin. For instance, it leads to the breakdown of collagen―a protein structure that imparts elasticity and firmness to the skin. No wonder, sun-damaged skin loses its elasticity and appears dull and thin. To protect the skin from harmful UV rays of the sun, apply sunscreens with an SPF of 15, particularly to frequently exposed areas of the skin such as the arms.
Wear Sun-protective Clothing
In case you are not comfortable wearing sunscreens, considering that they may contain harmful ingredients, don't forget to wear sun-protective clothing, such as long-sleeved shirt, pants, wide-brimmed hats, and sunglasses, before moving out in the hot sun.
However, even during old age, you can still maintain the natural glow on the skin, provided you take proper care of your skin. So, to ensure that the beauty of the skin does not diminish with age, here's what you can do.
Eat Skin-Friendly Foods
Our diet or the type of food we consume can have a negative or positive influence on our skin. Eating junk food daily will surely rob your skin of its healthy texture. These foods predispose your skin to a wide range of skin problems as well as accelerate aging of the skin. Therefore, discard processed foods and prefer natural, freshly-cooked foods. Including skin-friendly foods in the diet can go a long way in maintaining the beauty of the skin and prevent it from thinning.
Use Appropriate Moisturizers
Ignoring proper skin care routine can also lead to premature thinning of the skin. Our skin loses its moisture daily, making it dry and dull. The skin may crack and peel. Eventually the skin loses its elasticity, leading to thinning and formation of wrinkles. No matter what type of skin you have, make moisturizing an integral part of your skin care regimen. This will certainly help to preserve the natural moisture of the skin. Apply an appropriate moisturizer daily, to keep your skin from thinning. This works to keep the skin well-hydrated, soft, and supple.
Quit Smoking
If you diligently follow a healthy diet but puff cigarettes without fail, then all your efforts to maintain skin health will draw to a naught. The point is, smoking produces damaging effects on the skin. Smoking decreases blood circulation in the skin by constricting the blood vessels. As a result, oxygen and nutrient supply to the skin chronically drops, which changes the appearance of the skin significantly. No wonder, thin old-looking skin is one of the major side effects of smoking. So, for a healthy, supple, radiant skin that everyone dreams of, it is necessary to quit smoking.
Exercise Daily
Leading a sedentary life will not only cause a decline in cardiovascular health, but it can also have repercussions on your skin. Any form of physical activity, be it brisk walking, running or any other workout, is beneficial to the skin. As we all know, exercise increases blood circulation throughout the body including the skin. The increased blood flow supplies much-needed nutrients to the skin cells, in turn keeping the skin healthy. Moreover, a regular exercise routine ensures that your muscles are firm and the skin is tight.
Drink Plenty of Water
Water is a vital 'nutrient' for healthy skin. Adequate water intake ensures that nutrients from ingested food reach the skin cells, which help to nourish the skin. Also, water acts as a natural moisturizer for the skin, thereby keeping its texture and appearance youthful. Moreover, adequate water intake helps to get rid of toxins, which also contributes in improving skin health So, drink at least 7 to 8 glasses of water everyday for a clear, healthy complexion.
Reduce Sun Exposure
Overexposure to the sun is one of the primary factors that can accelerate thinning of the skin. It is a known fact that long-term exposure to UV rays damages the vital structures of the skin. For instance, it leads to the breakdown of collagen―a protein structure that imparts elasticity and firmness to the skin. No wonder, sun-damaged skin loses its elasticity and appears dull and thin. To protect the skin from harmful UV rays of the sun, apply sunscreens with an SPF of 15, particularly to frequently exposed areas of the skin such as the arms.
Wear Sun-protective Clothing
In case you are not comfortable wearing sunscreens, considering that they may contain harmful ingredients, don't forget to wear sun-protective clothing, such as long-sleeved shirt, pants, wide-brimmed hats, and sunglasses, before moving out in the hot sun.
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