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January 2016 - Issue

 Q1. How melatonin hormone works on our 24 hours daily rhythm?
Ans. Melatonin is an endocrine hormone produced by the pineal gland and sends a signal to regulate the sleep-wake cycle in the sleep center of the brain. Interestingly, melatonin is also produced in the retina, the skin, and the GI tract, but this is not the melatonin that affects our biological sleep clock. Melatonin is a sleep and body clock regulator, but not a sleep initiator. It regulates night and day cycles or sleep-wake cycles. It works with our biological clock by telling the brain when it is time to sleep. Melatonin does not increase the sleep drive or need for sleep.
 
Melatonin is called the “Vampire Hormone” because it is produced primarily in darkness and is inhibited by light. Darkness causes the body to produce more melatonin, which signals the body to prepare for sleep. Light decreases melatonin production and signals the body to prepare for being awake. The levels of melatonin in the body increase in the middle of the night and gradually fall as the night turns to morning, so exposure to light before bed can push your biological clock in the wrong direction, making melatonin ineffective. In humans and most diurnal mammals, melatonin is secreted at night with a robust circadian rhythm and maximum plasma levels occur around 3 to 4 AM. The daily rise of melatonin secretion correlates with a subsequent increase in sleep propensity about 2 hours before the person’s regular bedtime. The time before this secretion is the least likely for sleep to occur, and when it starts, the propensity for sleep increases greatly as the “sleep gate” opens. The rhythmic release of melatonin is regulated by the central circadian rhythm generator—the suprachiasmatic nucleus (SCN) of the anterior hypothalamus.
 
 
 Q2. Why women are more prone to gall bladder stones than men?
Ans. Gall bladder is a digestive organ and its normal function is to store bile produced by the liver, and to aid in the digestion and absorption of fats in the duodenum (the first portion of the small intestine). Imbalance in the substances that make up bile cause gallstone. It comprises of a solid formation of cholesterol or bile salts. 80% of gallstones are made up of cholesterol known as cholesterol stones and the remaining 20% condition is due to pigment stones which are made up of calcium mixed with bilirubin. The gall bladder can develop a single large gallstone, hundreds of tiny stones, or both small and large stones. Gallstones can range in size from a grain of sand to a golf ball. It can cause sudden pain in the upper right abdomen.
 
This pain, called a gall bladder attack or biliary colic, occurs when gallstones block the ducts of the biliary tract (consists of gall bladder and bile ducts). This is one of the most common and costly digestive diseases. For reasons that are still unclear, women are two times more likely than men to be afflicted. Risk factors which can lead to increased incidence of gallstones in women are multiple pregnancies, obesity and rapid weight loss. Pregnant women and women who have higher body fat percentages and live less active lives than males, are at greater risk for gallstones. Gallstones tend to form in women during pregnancy because of increased hormone levels. Extra estrogen in women increases risk of gallstones as it can increase cholesterol levels in bile by stimulating the liver to remove more cholesterol from blood and diverting it into the bile. Estrogen also decrease gall bladder contractions, which may cause gallstones to form. Women may have extra estrogen due to pregnancy, hormone replacement therapy or birth control pills.

 

February 2016 - Issue

 Q1. What will be the immediate effect if all chordae tendineae are weakened or removed? – Souvik Seth, West Bengal
Ans. Chordae tendineae are special fibrous cords that are attached to the flaps of bicuspid and tricuspid valves. These cords are joined to other ends with special muscles of ventricular wall, the papillary muscles.
The main function of chordae tendineae is to prevent the bicuspid and tricuspid valve from collapsing back into atria during ventricular contractions. When the ventricular walls contract, papillary muscles also contract. They pull the vanes of the valves inward towards the ventricles to prevent their bulging backwards toward the atria (due to force of ventricular contraction). If the chordae tendineae are weakened or ruptured, then the valve bulges far backward into atria during ventricular contractions, sometimes so far that it leaks severely and results in severe or even lethal cardiac incapacity.
 
 
 Q2. Which enzyme is called Kornberg’s enzyme? – Saswata Guchhait, West Bengal
Ans. The enzyme DNA-polymerase I, is known as Kornberg’s enzyme. It is called so, because it was isolated for the first time by Arthur Kornberg and his colleagues from E. coli. It was also able to direct DNA synthesis in a cell-free (in vitro) system. It is an important repair enzyme, and plays a major role in proofreading and repairing the damaged DNA.
 
 
 Q3. What is a knockout mouse? – Saswata Guchhait, West Bengal
Ans. A knockout mouse is a laboratory mouse in which researchers have inactivated or ‘knocked out’ an existing gene by replacing it or disrupting it with an artificial piece of DNA. The loss of gene activity often cause changes in a mouse’s phenotype, which include appearance, behaviour and other observable physical and biochemical characteristics. Many of the knockout mouse models are named after the gene that has been inactivated. For example, the p53 knockout mouse is named after the p53 gene.
Knockout mouse are important animal models for studying the role of genes which have been sequenced but whose functions have not been yet determined. By causing a specific gene to be inactive in the mouse, and observing any differences from normal behaviour or physiology, researchers can infer its probable function. Knockout mice have been very useful in studying and modeling different types of cancer, obesity, heart diseases, diabetes, arthritis and Parkinson disease.
 
 

March 2016 - Issue

 Q1. Why lemon tastes even more bitter on hitting the ground when dropped down from a height? – Bishal Modak, West Bengal   
Ans. The lemon peel consists of two parts : zest and pith. Lemon zest has an intense lemon flavour with little bitterness but the pith which is a white part is very bitter in taste as it contains a compound hesperidin which is a glucoside. Hesperidin is a flavanone glycoside consisting of the flavone hesperitin bound to the disaccharide rutinose. This sugar causes hesperidin to be more soluble than hesperitin. Glucoside hesperidin is bitter in taste. When the lemon is dropped down from a height then on hitting the ground, there may be chances of diffusion of hesperidin from peel to the pulp which makes lemon taste more bitter. Although there is no factual evidence regarding the same.
 
 
 Q2. Why Japanese are more sensitive to alcohol than Caucasians? – Amir Hira, West Bengal
Ans. Genetic variability is one of the major contributors to drug and chemical sensitivity. It exists between all individuals to one degree or another. The source of this variation occurs as DNA in ovum and sperm cells, mutates, recombines and is passed down to our offsprings. Some mutations impart the ability to fight diseases while others put us at a disadvantage and others yet seem to impact no obvious changes at all. The passing of genes over thousands of generations results in genetic traits that reach beyond the immediate family and may extend throughout a nation or race of people. Individual and racial differences in alcohol intoxication have been reported by many investigators. Alcohol-sensitive persons, exhibit rapid facial flushing, elevation of skin temperature and an increase in pulse rate when they drink more than 0.2 mL of alcohol per kg of body weight. Such sensitivity is far more commonly observed in individuals of Oriental origin, such as the Japanese, Korean and American Indian than in Caucasians.
 
Ethanol, found in alcoholic beverages is broken down into water and acetic acid by a two step process:
Firstly, alcohol is converted into acetaldehyde by an enzyme called alcohol dehydrogenase (ADH). This enzyme consists of two subunits which are encoded at five different gene locations (a, b, c, d and e). ADH may consists of any two subunits from any of these two locations termed as ‘isozymes’ of ADH. There is unusually high rate of enzyme activity when the isozymes contains atleast one subunit from location ‘b’. This is one basis for variation in ethanol metabolism among genetically diverse people.
Secondly, acetaldehyde is broken down to acetic acid and water by an enzyme called acetaldehyde dehydrogenase 2 (ALDH 2). It has high affinity for acetaldehyde and will rapidly convert it.
Japanese (belonging to Orientals) have unique alleles of ethanol metabolising enzyme genes, such as *2 allele of alcohol dehydrogenase-2 (ADH2*2) and *2 allele of aldehyde dehydrogenase-2 (ALDH2*2). These alleles are quite rare or almost absent in Caucasians. Japanese are deficient in ALDH2 activity due to a point mutation; the replacement of one amino acid for another (GLU487 to LYS487). This deficit in the activity of ALDH2, which converts acetaldehyde into acetic acid due to the ALDH2*2 allele exerts a strong influence on drinking behaviour in Orientals. The ALDH2*2 allele encodes an inactive subunit protein of the enzyme. The enzyme of ALDH2 consists of four subunit proteins and show loss of the activity when even one inactive subunit protein is included. People homozygous for ALDH2*2 allele (ALDH2*2/2) thus do not have any activity at all.
One half of Japanese have the ALDH2*2 allele and cannot convert acetaldehyde into acetic acid rapidly. So, the rapid conversion of alcohol to acetaldehyde coupled with the slow conversion of acetaldehyde to acetic acid can cause a build up of acetaldehyde in the blood. This results in uncomfortable symptoms of facial flushing, palpitation, blood vessels dilation and headache even when a small amount of alcohol is consumed.
Differences in body size and in lifestyle (food, use of medication) may further influence the kinetics of alcohol. Hence, Japanese are more sensitive to alcohol than Caucasians.

 

April 2016 - Issue

 Q1. Memory is stored in brain and reflex actions reach only till spine, then how do we remember our reflex actions? - Supriya landge
Ans. Reflex actions are sudden reactions which do not involve thinking. Spinal cord controls the reflex actions, though signals are also sent to brain by nerves for analysing them.
Two types of memory stored in our brain are:
(i) Short-term memory or sensory memory: It remains for few seconds or a minute.
(ii) Long-term memory or lifetime memory: Day to day work experience is not converted into long-term memory. The avoidable reflexes save as sensory or short-term memory and are filtered out. If they have survival value they get converted into long-term memory by memory consolidation and unnecessary memories are erased from brain.
 
Reflex actions have survival value. Reflex actions (involuntary, automatic and nearly instantaneous response to a stimulus) are mediated via reflex arc. It is a neural pathway that mediates the reflex action. Reflexes are of two types:
(i) Simple or unconditional : Reflex in which brain is not involved. The receptor is stimulated which is conducted to the spinal cord by the effector. The effector neuron from the spinal cord conducts a response to the muscle or the gland. This causes an immediate reaction and does not involve any thinking or reasoning. Simple reflex is of two types— In the first type, only sensory and motor neurons of spinal nerves are involved. In second type, interneurons present in spinal cord are also involved.
(ii) Complex or conditional : This type of reflex involves the brain and is as fast as the simple reflex, for example we salivate on smelling our favourite food. The individual recognises the particular smell and based on a previous experience the response (salivation) occurs. The recognisation of the previous experience involves the association centers of the brain.
 
 Q2. Explain about the disease myotonic dystrophy and why it is considered an autosomal dominant disease? – Akanksha deshmukh
Ans. Myotonic dystrophy is a part of group of inherited disorders called muscular dystrophies. Myotonic dystrophy is characterised by progressive muscle wasting and weakness. People with this disorder often have prolonged muscle contractions (myotonia) and are not able to relax certain muscles after use. For example, a person may have difficulty releasing their grip on a doorknob or handle. Also, affected people may have slurred speech or temporary locking of their jaw.
Myotonic dystrophy is often abbreviated as DM after its Latin name dystrophia myotonica. There are two forms of myotonic dystrophy, usually referred to as type 1 or DM1 and the rarer type 2 or DM2. Both are genetic disorders but each affects a different gene.
The systems affected, the severity of symptoms, and the age of onset of those symptoms vary greatly between individuals, even in the same family. In general, the younger an individual is when symptoms first appear, the more severe symptoms are likely to be. There are two well-defined types of the disease (DM1 and DM2) which have distinct but overlapping symptoms. Both DM1 and DM2 are characterised by muscle weakness and myotonia, heart abnormalities, cataracts and insulin resistance. In general, DM2 is less severe than DM1: fewer systems are affected, patients develop the disease only as adults, and the disorder’s impact on everyday life is relatively less disruptive. In contrast, DM1 can occur from birth to old age. Symptoms vary greatly among patients, from minor muscle pain to serious respiratory and cardiac issues. The congenital form of DM1 is the most severe version and has distinct symptoms that can be life-threatening.
Myotonic dystrophy is an inherited disease where a change, called a mutation, has occurred in a gene required for normal muscle function. The mutation prevents the gene from carrying out its function properly. The change is an autosomal dominant mutation, which means one copy of the altered gene is sufficient to cause the disorder. As a result, affected individuals have a 50% chance of passing on the mutated gene to their children. A child is equally likely to have inherited the mutated gene from either parent. If both parents do not have the disease, their children cannot inherit it. The congenital form of DM1 is inherited differently from the other types of myotonic dystrophy. Children with congenital myotonic dystrophy almost always inherit the disease from an affected mother.
Myotonic dystrophy type 1 is caused by mutations in the DMPK gene, while type 2 results from mutations in the CNBP gene (also called ZNF9 gene). The specific functions of these genes are unclear. The protein produced from the DMPK gene may play a role in communication within cells. It appears to be important for the correct functioning of cells in the heart, brain, and skeletal muscles (which are used for movement). The protein produced from the CNBP gene is found primarily in the heart and in skeletal muscles, where it probably helps to regulate the function of other genes.
Similar changes in the structure of the DMPK and CNBP genes cause the two forms of myotonic dystrophy. In each case, a segment of DNA is abnormally repeated many times, forming an unstable region in the gene. The mutated gene produces an expanded version of messenger RNA, which is a molecular blueprint of the gene that is normally used to guide the production of proteins. The abnormally long messenger RNA forms clumps inside the cell that interfere with the production of many other proteins. These changes prevent muscle cells and cells in other tissues from functioning normally, which leads to the signs and symptoms of myotonic dystrophy.

 

May 2016 - Issue

 Ques. How does brain know that it is male body or female body to decide the release of hormones? - Supriya landge
Ans. The brain structure differences that result from the interaction between hormones and developing brain cells are thought to be the basis of sex differences in a wide spectrum of behaviors, such as gender role (behaving as a man or a woman in society), gender identity (the conviction of belonging to the male or female gender), sexual orientation (heterosexuality, homosexuality or bisexuality), and sex differences regarding cognition, aggressive behavior and language organisation. Factors that interfere with the interactions between hormones and the developing brain systems during development in the womb may permanently influence the behavior.
 
As sexual differentiation of the genitals takes place much earlier in development (i.e. in the first two months of pregnancy) than sexual differentiation of the brain, which starts in the second half of pregnancy and becomes overt upon reaching adulthood, these two processes may be influenced independently of each other. In rare cases, this may result in transsexuality, i.e. people with male sexual organs who feel female or vice versa. It also means that in the event of an ambiguous sex at birth, the degree of masculinisation of the genitals may not always reflect the degree of masculinisation of the brain. In addition, gender identity may be determined by prenatal hormonal influences, even though the prenatal hormonal milieu might be inadequate for full genital differentiation.
 
The testicles and ovaries develop in the sixth week of pregnancy. This occurs under the influence of a cascade of genes, starting with the sex-determining gene on the Y chromosome (SRY). The production of testosterone by a boy’s testes is necessary for sexual differentiation of the sexual organs between 6th and 12th weeks of pregnancy. The peripheral conversion of testosterone into dihydrotestosterone is essential for the formation of a boy’s penis, prostate and scrotum. Instead, the development of the female sexual organs in the womb is based primarily on the absence of androgens.
 
Once the differentiation of the sexual organs into male or female is settled, the next thing that is differentiated is the brain, under the influence, mainly, of sex hormones on the developing brain cells. The changes (permanent) brought about in this stage have organising effects; later, during puberty, the brain circuits that developed in the womb are activated by sex hormones.
 
During fetal development, the brain is influenced by sex hormones such as testosterone, estrogens and progesterone. From the earliest stages of fetal brain development, many neurons throughout the entire nervous system already have receptors for these hormones. The early development of boys shows two periods during which testosterone levels are known to be high. The first surge occurs during pregnancy, testosterone levels peak in the fetal serum between weeks 12th and 18th of pregnancy and in weeks 34-41 of pregnancy the testosterone levels of boys are ten times higher than those of girls. The second surge takes place in the first three months after birth. At the end of pregnancy, when the -fetoprotein level declines, the fetus is more exposed to estrogens from the placenta, this exposure inhibiting the hypothalamus-hypophysial-gonadal axis of the developing child. Loss of this inhibition once the child is born causes a peak in testosterone in boys and a peak in estrogens in girls. The testosterone level in boys at this time is as high as it will be in adulthood, although a large part of the hormone circulates. During these two periods, girls do not show high levels of testosterone. These fetal and neonatal peaks of testosterone, together with the functional steroid receptor activity, are thought to fix the development of structures and circuits in the brain for the rest of a boy’s life (producing “programming” or “organising” effects). Later, the rising hormone levels that occur during puberty “activate” circuits and behavioral patterns that were built during development, in a masculinised and de-feminised direction for male brain or in a feminised and de-masculinised direction for female brain.

 

June 2016 - Issue

 Q1. Why the cry of a new born baby is so important after parturition? - Biraja Prasad Dalai
Ans. Crying is a normal event in the lives of all babies. When a baby comes out of the womb the first thing a baby do is crying. During gestation period, baby’s lungs are not used to exchange oxygen and carbon dioxide, and need less blood supply. The baby depends on placenta for oxygen and nutrition, as it is the umbilical cord which provides fresh oxygen and takes away carbon dioxide from their blood stream.
When a baby is born, he/she has to breathe on its own. As he/she begins to breathe air, the change in pressure in the lungs helps to close the fetal connections and redirect the blood flow. Now blood is pumped to the lungs to help with the exchange of oxygen and carbon dioxide.
The lungs are filled with mucus, amniotic fluid and other secretions which are cleared by baby’s first cry. Crying is a reflex action of newborn baby which helps to open up his/her lungs more efficiently and fill them with air by removing the fluid. It is quite amazing that fetus does not make use of lungs for breathing instead they use blood. All air that is required by the fetus comes through blood.
During delivery, the baby gets tired and hungry which can also be another reason of crying.
 
 Q2. Why the blood clotting is disturbed in diabetic patients? – Jagadish Rana
Ans. In a normal person, a small wound usually takes minutes to reach blood clot stage. However, when a person is diabetic or is suspected to be diabetic, this might take a quite longer period.
Diabetic persons possess high levels of blood sugar which may affect proper blood circulation. High level of blood sugar affects certain nerves and causes blood flow in blood vessels to slow down. As a consequence, when an area is wounded, it is hard for the blood vessels to transport blood through the wounded area and produce coagulant to make the blood clot.
Due to high blood sugar level arterial walls get thicken and become stiff. Narrow blood vessels limit the blood circulation and oxygen supply, required by white blood cells to produce antibodies for fighting any infection. Limited blood flow also makes it difficult for the skin to produce new cells which is needed for skin repairs.

 

July 2016 - Issue

 Q1. What is chimerism? - Arka Ghosh
Ans. Chimerism is a condition whereby a person has not one but two complete genomes (sets of DNA) in their body. One genome is found in one region or organ(s), while the other genome can be predominant in other organs or tissues. So, a DNA test result would be entirely different depending on where the sample was originally from (blood, saliva, nail clippings or hair, etc). A genetic chimerism or chimera is a single organism composed of cells from different zygotes i.e. a person composed of two genetically distinct types of cells. This can result in male and female organs, two blood types, or subtle variations in form. Animal chimeras are produced by the merging of multiple fertilised eggs.
 
The most common cause of chimerism is a twin pregnancy that naturally reduces to a single baby. In this condition, one embryo does not survive and the embryo’s cells are absorbed by its twin and the mother. The remaining embryo incorporates the disappearing twin’s cells into various tissues and develops to a healthy baby. Human chimeras were first discovered with the advent of blood typing when it was found that some people had more than one blood type. Most of them proved to be “blood chimeras” – non-identical twins who shared a blood supply in the uterus. Those who were not twins are thought to have blood cells from a twin that died early in gestation. Twin embryos often share a blood supply in the placenta, allowing blood stem cells to pass from one and settle in the bone marrow of the other. Some common symptoms of chimerism include different coloured eyes, patches of different skin tones, different coloured sections of hair, and sometimes disorders of sexual differentiation (hermaphroditism). Some chimeras have autoimmune diseases because the body recognises the twin’s genome as a foreign substance but this does not suggest that anyone who has different coloured eyes or skin, or an autoimmune condition has chimerism.
 
 Q2. Why do snakes have two penises? – Supriya Landge
Ans. Snakes do have two penises together, called hemipenes, and each individually is hemipenis. The development of the penis is controlled by the cloaca - a cavity at the end of the digestive tract that serves as the bodily exit for an animal’s digestive, urinary, and reproductive systems. During development, the cloaca sends out molecular signals to the surrounding tissue to turn into genitals (penis). In reptiles the cloaca is near their legs. Snakes having paired limbs, develop two penises (even though only one is used for mating). In mammals, the cloaca is nearer the tail bud, so only one penis develops.
 
Each testis is dedicated to a single hemipenis, an alternating pattern of hemipenis use would allow a male a second chance to transfer a fresh batch of sperm if he has just mated recently.
 
Unlikely in humans and most other mammals, sperms from both testes are mixed together prior to ejaculation, so these species have just one chance to inseminate before they enter a refractory period.

 

August 2016 - Issue

 Q1. What is the actual function of SGOT and SGPT? - Pritam Modak, Kolkata
Ans. The alanine aminotransferase (ALT) or Serum Glutamic Pyruvic Transaminase (SGPT) and aspartate aminotransferase (AST) or Serum Glutamic Oxaloacetic Transaminase (SGOT) are two commonly measured aminotransferases, the liver enzymes sensitive to liver abnormalities. Liver function tests are the blood tests that are most commonly performed to assess the function of the liver or injury caused to the liver by determining the level of various liver enzymes present in the blood. The aminotransferases catalyse the chemical reactions involving the amino acids, where an amino group is transferred from the donor amino acid to the recipient molecule. Aminotransferases are also referred to as transaminases. These liver enzymes form a major constituent of the liver cells. They are present in lesser concentration in the muscle cells. When the liver cells get damaged or injured, these enzymes seep into the blood stream, raising their blood levels. Hence raised blood levels of SGOT and SGPT signifies liver disease or injury. SGOT is normally present in a number of tissues such as heart, liver, muscle, brain and kidney. It is released into the blood stream whenever any of these tissues get damaged. For instance, blood AST or SGOT level is increased in conditions of muscle injury and heart attacks. Hence, it is not highly specific liver tissue damage indicator as it can be elevated in conditions other than liver damage. In contrast, SGPT is normally present in large concentrations in the liver. Hence, due to liver damage its level in the blood rises, thereby, serving as a specific indicator for liver injury. To regard SGOT and SGPT as liver function tests is a misnomer that is commonly prevalent in the medical community as they do not reflect functioning of the liver. They only detect type of liver injury or damage done to the liver due to any kind of infection and inflammatory changes. The liver may keep functioning normally even in cases when both of these enzymes are highly raised. The normal levels of SGOT ranges between 5 and 40 units per litre of serum and the normal levels of SGPT is in between 7 and 56 units per litre of serum. Additionally, the precise level of these enzymes and the intensity of liver disease and its prognosis do not correlate well. Hence, the precise blood levels of these enzymes cannot be utilised to determine the intensity or degree of liver illness. For instance, SGOT and SGPT are raised to high levels in individuals suffering from viral hepatitis A, they sometimes reach in the range of thousands of units/litre. However, most cases of acute viral hepatitis A recover completely with no signs of residual liver illness. Conversely, individuals developing chronic hepatitis C infection have minor elevations in their SGOT and SGPT levels, whereas, their liver is injured or damaged substantially by the infection even leading to scarring (cirrhosis) from ongoing liver infection and inflammation.
 
 Q2. Valves are generally absent in arteries, but pulmonary artery has valves. Why? – Mohana Sai Bios, Telangana
Ans. Blood in veins flow slowly and is under much lower pressure as it is returning to the heart from the various organs and tissues and so has a risk of back flow if the valves are not present to prevent it. Thus, veins have valves to prevent backflow of blood, but arteries do not have valves because they take blood away from the heart which provide necessary pressure to pump blood to other parts of the body. If there were valves in arteries, they might burst. The only exception to this are aortic valve, where aorta leaves the left ventricle of heart and pulmonary valve where pulmonary artery leaves right ventricle. Aorta carries blood to all body tissues and pulmonary artery carries deoxygenated blood to lungs for oxygenation. The pulmonary valve is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. The pulmonic valve is the valve that allows blood to leave the heart via arteries. It is a one way valve, meaning that blood cannot flow back into the heart through it. The pulmonary valve opens in ventricular systole, when the pressure of the blood in the right ventricle rises above the pressure in the pulmonary artery pushing the blood out of the heart and into the artery. At the end of ventricular systole, when the pressure in the right ventricle falls rapidly, the pressure in the pulmonary artery will close the pulmonary valve.

 

September 2016 - Issue

 Q1. How pineapples can flush out nicotine stored in body by smoking cigarette? – Bishal Modak, West Bengal
Ans. When a person smokes a cigarette, nicotine circulating in the bloodstream gives a kind of high. On an average, nicotine from a single cigarette lasts for 6-8 hours. Most of that nicotine will get eliminated in the urine. The stored nicotine takes 48-72 hours to get metabolised and leave the body. The nicotine by-product cotinine can continue to circulate in the bloodstream for 20-30 days. Vitamin C is the best known substance for flushing nicotine from the bloodstream as it increases metabolism.
Many experts recommend doing a pineapple cleanse to promote healthy lung functioning. For the cleanse, one needs frozen castor oil capsules, crushed pineapples, figs, herbal teas, pineapple juices, pumpkin seeds, raw almonds, and a laxative tea. This can be done for upto ten days but for a minimum of three days is required to get any results. Fresh pineapples can be taken at any time during the cleanse. Cleanse would include all citrus fruits such as oranges, sweet limes, lemons, grapefruit, mandarins, pomelos and tangerines. One must make it a point to eat at least two pineapples per day, as they will help to fight the addictive effects of nicotine in body. Pineapples neutralise the working of nicotine in the body. Kiwi is another fruit that will help to destroy nicotine stored in the far reaching cracks and crevices of the body and lungs. Although this may sound too simple to be true, every time a person feel the urge to smoke, he should drink a whole glass of water. This will generally take away the desire to smoke, and he will also be able to detoxify his system with drinking too much water. Pineapple is an excellent source of vitamin C and manganese. It is also a very good source of copper and a good source of vitamin B1, vitamin B6, dietary fiber, folate and pantothenic acid.
Pineapple juice contains antioxidants which are beneficial for the respiratory system. It boosts immune system because of the presence of vitamin A and C and selenium, and are also beneficial in curing of sore throat and bronchitis. The astringent property of the pineapple is supposed to loose and eliminate toxins and mucus that have built up in the lungs letting them function better. Lungs help to deliver oxygen throughout the body and proper functioning is essential for overall health.
 
 Q2. All amino acids based hormone require extracellular receptor for carrying out their activities except the hormones of thyroid gland. Why so? – Priyanka Soren
Ans. Thyroid hormones; thyroxine (T4) and triiodothyronine (T3) are lipid soluble hormones and they can easily pass through the plasma membrane (cell membrane) of a target cell into the cytoplasm. In the cytoplasm, they bind to specific intracellular receptor proteins forming a hormone receptor complex that enters the nucleus. In the nucleus, hormones which interact with intracellular receptors regulate gene expression. The hormone receptor complex binds to specific regulatory sites on the chromosomes and activates certain genes (DNA). The activated gene transcribes mRNA which directs the synthesis of proteins and usually enzymes in the cytoplasm. The enzymes promote the metabolic reactions in the cell. The actions of lipid soluble hormones are slower and last longer than water soluble hormones. Thyroid hormone receptors regulate gene expression by binding to hormone response elements in DNA.

 

October 2016 - Issue

 Q1. Describe the digestive system in a typical bird. – Shibankur Bhattacherjee, Hooghly
Ans.Class Aves include birds. Birds are unique in having a coat of feathers and they rest on the hindlimbs only. Birds show great variety of colours and behaviour such as courtship, nest building, parental care and migration. The avian digestive system is made up of digestive tract and the glands (arising from its epithelial wall). The digestive tract comprise mouth, buccal cavity, pharynx, oesophagus and crop, stomach, small intestine and large intestine. Digestive glands include buccal glands, salivary glands, gastric glands, liver, pancreas, intestinal glands, tubular glands and caecal glands.
Food is picked up by the mouth, which has horny beak without teeth. Mouth opens into buccal cavity which bears numerous glands. These glands secrete saliva, which lubricates the food to make it easier to swallow. Also, the saliva contains enzymes, such as amylase, that starts the digestion process. Buccal cavity leads into pharynx which posteriorly lead into oesophagus. Oesophagus, at the level of sternum, expand to form crop which function as food reservoir. It carries food from the mouth to the crop and from the crop to the proventriculus. Swallowed food and water are stored in the crop until they are passed to the rest of the digestive tract. When the crop is empty or nearly empty, it sends hunger signals to the brain. Very little digestion takes place in the crop. It is simply a temporary storage pouch. The oesophagus continues past the crop, connecting the crop to the proventriculus. The proventriculus (also known as the true stomach) is the glandular stomach where digestion primarily begins. Hydrochloric acid and digestive enzymes, such as pepsin, are added to the food here and it begins to break more significantly than the enzymes secreted by the salivary glands. The ventriculus, or gizzard, is a part of the digestive tract of birds, reptiles, earthworms and fish. Often referred to as the mechanical stomach, the gizzard is made up of two sets of strong muscles that act as the bird’s teeth and has a thick lining that protects those muscles. Consumed food and digestive juices from the salivary glands and proventriculus pass into the gizzard for grinding, mixing and mashing. The small intestine is made up of the anterior duodenum (also referred to as the duodenal loop) and posterior ileum. The remainder of the digestion occurs in the duodenum and the released nutrients are absorbed mainly in the jejunum and ileum. Jejunum and ileum are poorly differentiated in birds. The duodenum receives, digestive enzymes and bicarbonate (to counter the hydrochloric acid from the proventriculus) from the pancreas and bile from the liver (via the gall bladder). The digestive juices produced by the pancreas are involved primarily in protein digestion. Bile is important in the digestion of lipids and the absorption of fat-soluble vitamins A, D, E and K.
The Meckel’s diverticulum marks the end of the jejunum and the start of the ileum. The ceca (plural form cecum) are two blind pouches located where the small and large intestines join. Some of the water remaining in the digested material is reabsorbed here. Another important function of the ceca is fermentation of any remaining coarse materials. During this fermentation, the ceca produce several fatty acids and vitamin B (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid and vitamin B12). Next part is large intestine which is actually shorter than the small intestine. It is differentiated into rectum and cloaca. Water reabsorption occurs in this part. In the cloaca, the digestive wastes mix with wastes from urinary system (urates). Birds usually void faecal material as digestive waste with uric acid crystals.
 
 Q2. Why are most of human beings right handed? – Damanpreet Singh
Ans. Handedness is an idea that one hand is better able to perform certain tasks than the other. It is estimated that 70-90% of the human population is right-handed, and this leaves left-handed individuals vastly outnumbered. But exactly why humans favour different hands, or why most people tend to be right-handed, remains mysterious. Our dominant hand is determined by genetics, brain or parental/societal pressures. Handedness is determined by the structure of our brains, which are divided into two hemispheres. Most neural activities are shared between the hemispheres to some extent, but we can definitely say that many functions are primarily handled by one hemisphere as opposed to another. This is known as brain lateralisation.
Two of the most energy-intensive human activities are language and the use of our hands. One theory suggests that it’s more efficient for the brain to cluster control of these two major tasks in one hemisphere rather than having it spread throughout the brain. Since, the majority of people have their language functions centered in the left hemisphere, it follows that most people’s fine motor skills would be controlled by the left hemisphere too. Each hemisphere generally controls the opposite side of the body, so the result is that most people are right-handed. However, the opposite does not hold true, being left-handed does not mean that the language centers are located in the right hemisphere, which is fairly rare. Certainly, lefties are more likely than righties to have their right hemisphere responsible for language, but it’s still not a common arrangement. Between 61 and 73% of lefties have their language centers in the left hemisphere, compared to over 90% of right-handed people.
After all, if the energy intensive language centers happened to evolve so that they were usually in the right hemisphere, then most people would probably be left-handed instead. To that point, there’s no reason why our brains could not have evolved that way - it’s simply a historical fact that they did not. The root of handedness quite possibly is a random genetic mutation that pushed the language centers to the left hemisphere as the ancient human brain became more specialised. Without this particular genetic mutation, our brains still might have evolved to their present levels of sophistication, but our language hemispheres would be chosen at random, meaning handedness would be more evenly split.
In fact, a second major gene mutation might have had precisely that effect, at least in a subset of the population. University College London neuropsychologist Chris McManus suggests that sometime between 20,000 and 100,000 years ago, a second mutation entered the human gene pool that cancelled out the brain’s natural bias towards right-handedness, allowing for the emergence of more left-handers.

 

November 2016 - Issue

 Q1. Why only one side of nose is blocked during cold? – Priyanka Soren, Jharkhand
Ans.You may not have paid attention to it unless you are sick, but you are always breathing more heavily from one nostril than the other. During the day, the sides switch and the other nostril goes into ‘work mode’. This process is automated by autonomic nervous system, it is the same system that controls many processes such as digestion and heart rate. For your nose, this system also controls your ‘nasal cycle’, so that each nostril operates effectively. This nasal cycle occurs several times during the day, and gets attention only when your nose is clogged up more than usual. In order to open one side of your nose and close the other, your body inflates tissue with blood. Increased blood flow causes congestion in one nostril for about 3 to 6 hours before switching to the other side. There is also increased congestion when one is lying down, which can be especially noticeable if the head is turned to one side. It is believed that this cycle helps improve our sense of smell as some smells are better picked up by fast moving air through your nose, while others take more time and are detected better with slow-moving air. Even more interesting fact is that depending on the nostril, one is predominantly breathing at any given moment, it seems to greatly affect your body and brain. A study shows that breathing through right nostril significantly increases blood glucose levels, while breathing through left nostril has the opposite effect. In an another study, it is shown that when you are breathing through your left nostril, the right hemisphere of your brain will be more active or dominant and vice-versa when you are breathing through your right nostril.
This process also gives each side of your nose a break, since a constant stream of heavily flowing air can dry it out and kill off the small hairs that protect you from foreign contaminants.
When you get cough and cold, the whole process becomes unbearable, because the one nostril gets more clogged than the other. The clogged-up feeling is just amplified by the cold. So the next time you feel like you are only breathing from one side of your nose, remember that it is a natural, automatic system working to keep you smelling properly, and to make sure your nose does not get dried out by a constant onslaught of dirty air.
 
 Q2. Why different flowers have different smell?– Debanjan Ghosh, West Bengal
Ans. When we think or talk about flowers, we immediately think of pleasant scents. But, this is not always true because all flowers do not smell pleasantly, e.g., Titan arum, a huge flower smells like a rotting carcass. Flowers have unique smells because they attract different pollinators. For example, bees, moths and butterflies tend to be drawn to sweet smelling flowers, like roses, whereas insects like dung flies are attracted to flowers that smell like rotten meat. Bats prefer flowers with musty odours and some beetles are attracted to strong, fruity fragrances.
The chemicals responsible for these various floral scents are essential oils, which are produced in the petals of flowers. Combinations of these oils are responsible for the distinctive smells of flowers.
The odour of flowers is typically due to a complex mixture of low molecular weight volatile compounds emitted by flowers into the atmosphere and its odour acts as critical factor in attracting pollinators. Terpenes and esters constitute floral fragrance where as foul smelling flowers contains sulphur, phenols, etc. Flowers can be identical in their colour or shape, but there are no two floral scents (odour) that are exactly the same because of the large diversity of volatile compounds and their relative abundances and interactions. Pollinators are rewarded with sweet nectar for their reproductive assistance. Volatiles emitted from flowers function as both long and short distance attractants and play a prominent role in the localisation and selection of flowers by insects, especially moth-pollinated flowers.
Though little is known about how insects respond to individual components found within floral scents, but it is clear that they are capable of distinguishing among complex scent mixtures. In addition to attracting insects to flowers and guiding them to food resources within the flower, floral volatiles are essential in allowing insects to discriminate among plant species and even among individual flowers of a single species. For example, closely related plant species that rely on different types of insects for pollination produce different odours, reflecting the olfactory sensitivities or preferences of the pollinators. By providing species-specific signals, flower fragrances facilitate an insect’s ability to learn particular food sources.
Plants tend to have their scent output at maximal levels only when the flowers are ready for pollination and when its potential pollinators are active as well. Plants that maximise their output during the day are primarily pollinated by bees or butterflies, whereas those that release their fragrance mostly at night are pollinated by moth and bats. During flower development, newly opened and young flowers, which are not ready to function as pollen donors, produce fewer odours and are less attractive to pollinators than are older flowers.

 

December 2016 - Issue

 Q1. The eyes of my father are brown whereas those of my mother are green but I have blue eyes. How is this possible? – Rohan Pandey, Maharashtra
Ans.Human eye colour is a polygenic trait. Human eyes may be brown, green or blue in colour. Usually each gene has two alleles for a particular trait but the genes that determine eye colour has total 4 alleles B, b, G, g.
The B allele (brown) is always dominant over the G allele (green), while the blue eye trait is always recessive. Even the presence of single B allele contributes to brown eye colour while the presence of G allele in absence of B allele contributes to green eye colour.
 
Following table represents genotype and phenotype of human eye colour:

BBGG

Brown

BbGG

Brown

BBGg

Brown

BbGg

Brown

BBgg

Brown

Bbgg

Brown

bbGg

Green

bbGG

Green

bbgg

Blue

 
Therefore, B allele will always make brown eyes regardless of what allele is present at other locus, as B is dominant over G. Individual homozygous for B alleles have darker brown eyes than heterozygous individual and if person is homozygous for G allele, then the eyes will be darker green than a person heterozygous for G allele (in absence of B). Absence of any dominant allele - B or G or all recessive alleles with genotype bbgg gives true blue eyes.
 
 Q2. How do the emotions and motivated behaviour originate in us?– Shruti Talwar, Rajasthan
Ans. Emotions are difficult to define and describe but they do arise and are classified as anger, aggression, fear, pleasure, contentment, happiness, grief, etc. They arise in different parts of brain but can’t be voluntarily turned on or off. Emotions and motivation are two aspects of brain function that probably represent an overlap of behavioral state system and cognitive system. Emotions are believed to be generated from part of the brain known as limbic system which is made up of several structures located in the cerebral cortex.
 
Various sensory stimuli feeding into the cerebral cortex associate in the brain to create a perception of surroundings or world. This information after being integrated by association areas is passed to limbic system, which gives feedback to cerebral cortex, creating awareness of the emotion. The pathways descending to the hypothalamus, initiate voluntary behaviours and unconscious responses mediated by autonomic, endocrine, immune and somatic motor systems. As a result, the physical effect of emotions can be dramatic as well e.g., development of fast or irregular heartbeat.
 
The internal signals that shape voluntary behaviours can be referred to as motivation. Some of them e.g., eating and drinking are related to survival while others are linked to emotions. Some motivational states are known to create an increased state of CNS arousal (alertness), goal oriented behaviour and coordinating disparate behaviours to achieve a particular goal. Such states are known as drives. Some drives can be activated by internal stimuli, that may not be obvious to the individual where it originates. Many motivated behaviours may stop when one has reached a certain level of satisfaction. Pleasure is also an example of motivational state.
 
Motivated behaviours work in parallel with autonomic and endocrine responses in the body i.e., one stimulus triggers both motivated behaviour and homeostatic endocrine response.

 

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