My Science School

Pulse and heart beat are checked primarily to have a simple and quick assessment of the condition of the heart and other system of the body. By checking the pulse the doctor can know the rate, rhythm and wave pattern of the arterial pulse. The normal arterial pulse will have certain characteristic features and any deviation from this pattern suggests an underlying problem.

For example normal, adult resting person's pulse rate/heart rate is around 72 beats per minute. Here the words normal, adult resting all have significance as children's heart rate is more compared to adults and a person who did some exercise like running, cycling and swimming will have a higher pulse/heart rate compared to other persons at rest. These are all physiological variations.

 Even at rest if a person's pulse rate grossly deviates from the beat it signifies some underlying problem. In the same way if the rate of the rhythm or wave pattern of the pulse deviates from the normal it also denotes some underlying problem. Normal heartbeat consists of two heart sounds. In addition if any other sounds or murmurs (peculiar noises heard in between or along with the heart sounds) are heard, it also signifies some problem in the heart.

The arterial pulse can be felt at several places viz near the wrist, elbow, armpit, neck, groin, popletial fossa (area behind the knee joint) and foot. The wrist and neck are the most easily accessible places for the doctor to check the pulse with little discomfort to the patient. Hence these regions are usually preferred. In certain special conditions or diseases the pulse at the other regions are also checked. 

            There is no one reason why we get more colds and flu in winter. The rhinovirus, which is responsible for up to 40 per cent of colds, cultures better at a temperature of 32 degrees C rather than the normal body temperature of 37 degrees C. However, 32 degrees C is the normal temperature of the lining of the nose, which is good news for the virus.

We do tend to be indoors more often in poorly ventilated areas during the winter and this aids the airborne transmission of the virus. Similarly, ultraviolet rays will kill viruses and this may be another factor as there is obviously much less sunlight in winter. However, it is believed that one of the biggest factors for the great increase in colds that occurs in early autumn and just after Christmas is the return of school children and students to schools and colleges.

Children and teenagers are far more susceptible to infection as their immune system learns how to combat more infections as they get older and have been exposed to more of the 200 or so viruses responsible for the common cold. Densely packed nurseries, schools and colleges provide an ideal breeding ground for viruses which then spread out into the community, aided by the cold damp weather. 

Dandruff is thought to be caused by overgrowth of yeast such as Pityrosporum ovale which live on normal skin. This overgrowth causes local irritation resulting in hyper proliferation of the cells (keratinocytes) forming the outer layer of the skin. These form scales which accumulate and are shed as dandruff flakes.

Dandruff is a condition of excessive scaliness of the scalp. There are two varieties – dry and greasy. In the dry variety, the scales are fine, thin, white or grayish, and dry or slightly greasy. Such type of hair lacks lusture. People with this type of hair will have mild to moderate itching. The scales will fall freely on the shoulders.

This dandruff will be more common in winter than in summer. It signifies exaggeration of normal exfoliation of the horny layer of the epidermis. It usually affects people with dry integument and scalp. Such people are rather reluctant to use oil, on their scalp. In the greasy variety both the scalp and the integument are oily. It diffuses all over the scalp. Later the condition also extends to other hairy regions. It may extend typically to the eyebrows, eyelids, beard and other regions. The basic defect in this case is over production and/or change in composition of the sebaceous secretion. Dandruff is common at puberty and it occurs due to endocrine disorders, familial predisposition, unbalanced diet and constipation. Effective treatments for these conditions are prescribed, in Siddha medicine, based on commonly available plant products.

Cramp is a sudden, painful, involuntary contraction of a muscle. It generally affects the legs and hands. It can occur due to various reasons such as metabolic abnormality, sever cold, lack of blood flow and mineral deficiency. All these elicit pain or other types of sensory impulses that are transmitted from the muscle to the spinal cord, thus causing reflex muscle contraction. Thus, a positive feedback mechanism occurs so that a small amount of initial irritation leads to more and more contraction until a full-blown muscle cramp ensues.

Massage helps to overcome cramp mainly by stretching the cramped muscle. In other words, it elicits what can be termed as ‘reciprocal inhibition’ of the muscle. This can at times relieve the cramp.

Cramp can occur due to localized muscle spasm. The pain or uneasiness is caused by nervous irritation due to accumulation of some ‘metabolites; or chemicals’ in that area. Massage, external compression of muscle, improves blood supply.  Helps in washing away these metabolites and thus relives the cramp. However, not all cramps can be relieved by massage. 

Myopia is defined as an eye defect where the image of the object falls before the retina of the eye. The person affected with myopia cannot see distant objects clearly, but can see objects that are close to him. Myopia is also known as short sight. It may be caused due to: Increased Anterio Posterior length of the eyeball, Increased curvature of cornea or lens, Increased refractive index of the media particularly of lens sclerosis (early cataract).

Myopia can be broadly classified into three main types: Congenital myopia: It is present since birth and may be unilateral or bilateral. Simple or developmental myopia is common type where the defect increases usually as age advances,

Pathological myopia or degenerative myopia was the condition rapidly increases and there may be high myopia up to 20 D or more. Degenerative changes occur in post segment and fundus like myopic crescent choroidal sclerosis, post staphyloma due to stretching or sclera, vitreous degeneration retinal detachment and development of nuclear cataract seen.

 Latest technologies that are available for the treatment of myopia are: Radial Keratectomy, where the problem is corrected by making a series of radial cuts around outer edges of the cornea by a handheld small blade thereby reducing corneal curvature and reduction of myopia.

Photorefractive Keratectomy, where laser rays are used to correct the defect by gently removing corneal tissues from the central area of the cornea thereby reducing the corned curvature

 Lasik procedure combined with laser where small layer of the cornea are removed microscopically and then laser rays are applied to correct the defect. 

Our eyes are lubricated by tears that are produced by glands around the eye.

There are two types of tears: moisturizing tears and reflex tears. Moisturizing tears are produced continuously

Continue reading "What is dry eye syndrome? Would it help to have an air purifier in the house?"

Most cough syrups contain menthol and natural extracts, for carminative and antitussive actions. These substances are water-insoluble and so alcohol is used as a solvent.

Alcohol is miscible in all proportions with many of the syrups and so is the solvent of choice for many preparations. This property is rendered by its R-OH (hydroxyl) group which increases miscibility via inter molecular hydrogen bonding with solute particles. This enables the syrup to be absorbed easily by the body. It is used as a preservative in pharmaceutical preparations to prevent microbial growth. In addition syrups are mainly made of gels which in turn contain a liquid (as dispersed phase) and a solid (as dispersion medium). In them, alcohols play the role of stabilizers by preventing coagulation of solute particles during storage.

Sucrose is used as a vehicle in most of the medicated syrups. If the syrup is completely saturated with sucrose, under cool storage conditions some sucrose might crystallize from the esolution and, by acting as nuclei, initiate a type of chain reaction that would result in the separation of an amount of sucrose disproportionate to its solubility at the storage temperature. The syrup would then be very much unsaturated and probably support microbial growth. Many of them are not intended to be as nearly saturated as simple syrup (85g of sucrose is dissolved in 100 ml of purified water) and therefore need preservatives to ensure their stability   during storage. Sucrose may be substituted in whole e or in part by other agents in the preparation of medicated syrups. Polyols like sorbitol or a mixture of polyols like sorbitol and glycerin are commonly used. Here, alcohol serves as a preservative and stabilizer.

Alcohols are good sedatives and hypnotics as they depress the activity of the central not nervous system and lead to sleep. As a result they reduce the irritation in the throat and also reduce coughing.

Hypnotic property of alcohols increase with increase in molecular weight. Heavy doses of some of these alcohols can lead to anesthesia and coma.

The air we exhale on a cold day is visible because of the formation of dew. Actually, the main constituents of the air exhaled from the lungs, are water vapour and carbon dioxide. The temperature of this air is about 40 degrees Centigrade while that of the outside atmosphere is about 10 degrees Centigrade or less. Cold air cannot hold as much water vapour as warm air. Dew is formed when air is cooled to the point where it cannot hold all its water vapour, so the moisture in it begins to condense forming tiny water droplets. The temperature at which the moisture in the air begins to condense is called dew point. If relative humidity is100 per cent, then dew point is nearly equal to the atmospheric temperature.

On a cold day when we breathe out air with water vapour, it is cooled from 40 degrees Centigrade to less than 10 degrees Centigrade. That is, it is cooled to below the dew point but above its freezing point. Hence the tiny water droplets float in the air and are visible.

Humans can survive only for a few minutes without oxygen. This is because of the susceptibility of the brain is only about 2 percent of the body’s weight, it consumes about 20 per cent of the oxygen we breath in.

Hence if oxygen supplied (by the blood) is stopped for a few minutes, the brain ceases its function resulting in death. We will lose consciousness in 8-10 seconds after the blood supply to the brain is cut.

Brain cells can survive for long periods without oxygen at very low temperatures, as oxygen consumption is reduced. This technique, induced hypothermia, is made use of during major surgeries. Other tissues can survive for long periods without oxygen and that is why it is possible to remove organs, from brain dead persons, for transplantation.

The classification of blood types is based on the different types of antigens present on the surface of the red blood cells (RBC).

The human blood group is broadly classified into four groups called A, B, AB and O. The letters stand for the type of antigen present on the red blood cells.

The corresponding antibodies are carried in the plasma and if the person has a particular antigen in his red cells, he cannot have the corresponding antibody, since agglutination would occur. Thus group A contains antigen A and antibody anti-B.

Similarly group B contains antigen B and antibody anti-A. Group AB contains antigens A and B and no antibodies of either type. Group O has no antigens and antibodies anti-A and anti-B.

There is another factor behind blood grouping. It is a type of blood protein, first discovered in the blood of the Rhesus monkey.

Later it was discovered that some human beings also posses this factor in their blood.

If this factor is present in the blood cells, then the blood cells are called Rh positive and if they are absent it is called Rh negative.

Human blood consists of red blood corpuscles (RBCs) as a constituent which gives it is red colour. On the surfaces of these red cells are present one or both of two types of antigens (proteins), designated as A and B. Other than these, two antibodies, designated as antibody-A and antibody-B, present in the serum, are also involved in the classification of human blood. (Serum, a constituent of blood, is a straw-coloured liquid that can be seen after removing all the other blood cells from a sample).

 Antibodies have the property of clumping red cells. When antigen-A is present on the red cells, the serum contains only antibody-B that will clump red cells having antigen -B on their surface. Then the blood is classified as group A. When antigen-B is present on the red cells, the serum contains only antibody-A that will clump red cells having antigen-A. As a result the blood is classified as group B.

In some people, both the antigens A and B are present on all the red cells and so their serum does not contain any of the antibodies. They belong to the AB group. As a result, their blood cells do not clump whether they receive A group or B group blood. That is A and B are compatible with the AB group. The fourth type, O, has neither of the antigens on its red cells, but has both antibodies in the serum.

In order to prevent clumping of red cells, A group can get blood only from A and O, and B group only from B and O. But the AB group can get blood from any of the groups. Hence it is called universal recipient. On the other hand, an O group person can receive only O blood, but can donate blood to anybody else. Hence 0 is termed a universal donor this system of classification is known as ABO system. Blood groups are also classified by the Rhesus system (Rh). The Rh factor leads to one type in which the Rh factor is present (Rhesus positive) and the other in which it is not (Rhesus negative).

One of the remarkable properties of blood is its ability to clot, or coagulate, when it is withdrawn from the body. Inside the body, a clot is formed in response to tissue injury, such as muscle tear, a cut, or a sharp blow. In the blood vessels, the blood remains in a fluid condition: shortly after being withdrawn it becomes viscid and gelatinous and sets into a firm, jelly-like mass. This mass then separates into two positions, a firm red clot floating free in a transparent, straw-coloured fluid called serum.

A clot consists almost entirely of red corpuscles entangled in a network of fine fibrils or threads, composed of a substance called fibrin. It also contains platelets and plasma.

Certain substances promote coagulation (procoagulants) and others inhibit coagulation (anticoagulants). Clotting depends on the balance between procoagulants and anticoagulants in the blood. While the anticoagulants normally predominate the procoagulants get activated and cause clotting when a blood vessel is ruptured. Injury to a blood vessel causes a complex cascade of reactions leading to the formation of a clot.  This is term as hemostasis. A temporary hemostatic platelet plug occurs after the initial event of constriction of the vessel and it is mediated by serotonin and other vasoconstrictors liberated from the platelets that adhere to the walls of damaged vessels.

This occurs when the platelets swell, become sticky and get aggregated, bind to the collagen and plug the hole. The loose aggregation of platelets in the temporary plug is bound together and converted into a definite clot by fibrin. This is the fundamental reaction in clotting which involves conversion of soluble plasma protein fibrinogen to insoluble fibrin.

The blood clotting factors are the inactive forms of proteolytic enzymes called serine dependent proteases. When activated they collectively form prothrombin activator via two pathways. This in the presence of calcium ions, converts prothrombin to thrombin which in turn causes the polymerization of fibrinogen to fibrin fibres within 10-15 seconds. They enmesh the platelets, blood cells and plasma forming clot. Thus, the rate limiting factor in blood coagulation is the formation of prothrombin activator. The clot begins to contract and express serum within 20-40 minutes. This process is called clot retraction. As the clot retracts the edges of a broken vessel are pulled together thus contributing to ultimate hemostasis. Addition of sodium citrate removes calcium ions from the blood and thus prevents clot. Lack of vitamin K makes impossible the maintenance of the proper amount of prothrombin in the blood. Certain diseases may lower the concentration of the various clotting proteins or of the platelets of the blood. But blood does not clot in blood vessels due to presence of anticoagulant 'heparin’ secreted by the liver.

 A deficiency in any of the factors necessary for blood coagulation leads to excessive bleeding. A decrease in platelets is known as thrombocytopenia; a decrease in clotting factor VIII results in hemophilia A (classic hemophilia); a decrease in clotting factor IX results in hemophilia B, commonly known as Christmas disease. Several of the hemorrhagic diseases, such as hemophilia, are hereditary. A genetic engineering technique for making VIII, a blood-clotting factor of vital importance for victims of the most common form of hemophilia, has been developed recently. Although clot formation is a normal process, it sometimes occurs inappropriately and constitutes a threat to life. In patients hospitalized for a long time, for example, clots form in the large vein of the legs. If these clots or thrombi travel to the lungs they can cause death.

 Anticoagulants include the natural compound heparin, prepared from the lungs and livers of animals, and the synthetic chemicals dicumarol warfarin. Introduction of thrombocytes with the fatty deposits found in atherosclerotic heart disease is thought to contribute to heart attacks. Compounds such as aspirin and sulfinpyrazone, which inhibit platelet activity, may decrease heart attacks in person with atherosclerotic disease.

 

           

 

 

 

 

 

 

 

 

Artificial blood is an emulsion of an oxygen carrying compound, a colloidal substance, plasma expander, electrolytes and a few other buffer compounds.

The huge demand for human blood for patient care has led researchers to develop artificial blood. The research (which dates back to the Fifties) is focused on human recombinant haemoglobin and per fluorocarbons. The artificial haemoglobin rHb 1.1 has oxygen binding characteristics similar to that of HbA in red blood cells.

Using recombinant DNA technology rHb 1.1 can be produced in required quantities. Per fluorocarbons also dissolve a greater amount of oxygen than RBCs. Its solubility for carbon dioxide is three times that for oxygen. These blood substitutes have different boiling points, molecular structures and gas solubilities. Once they are used up, they form colourless, odourless and stable compounds which can be safely expelled.

The fear of contracting dreadful diseases through human blood transfusion has led doctors to opt for artificial blood.

Based on decades of research, scientists have come out with an alternative to human blood in the form of genetically engineered synthetic haemoglobin named as rHb 1.1.

It can be produced by fermentation and purification by cultivating genetically engineering E. Coli bacteria. The genes for rHb 1.1 are cultivated in the bacterial cells placed in a container called vat. The cells are then multiplied by fermentation – within 24 hours they become blood red.

The E. Coli cells are then broken up to extract the artificial haemoglobin which is purified to remove endoxins, bacterial protein and DNA. (The artificial blood may provoke harmful physiological reactions if not properly purified).

The rHb 1.1 30 per cent more effective than natural blood in supplying oxygen from the lungs to tissues. It eliminates the risks associated with transmission of dreadful disease and offer universal compatibility regardless of blood group in contrast to human blood which requires grouping and cross matching. It has long storage life (42 days currently recommended for human blood).

The function of an incubator is to help sustain the life of prematurely born babies who, because of their low weight and weak general constitution, have diminished viability. For such babies, weighing Perhaps as little as a kilogram, at birth, the incubator provides an ideal life environment, capable of being varied to suit specific requirement, characterized by: sterility (freedom from germs), temperature (up to 37 degrees Centigrade), relative atmospheric humidity (up to 100 per cent), an oxygen concentration (40 per cent) which is about twice the normal oxygen content in the atmosphere.

From the technical point of view, the incubator is a special air-conditioned chamber with its own climate-control system. A built-in motor draws in fresh air, which is freed from germs by passing through a bacterial filter and then flows through a thermostatically controlled heating system and a water evaporator. If necessary, oxygen is added. Because of the continuous inflow of air - at a rate of about 6 litres per minute - a slight excess pressure in relation to the surrounding atmosphere is maintained in the incubator. This ensures that the airflow is always directed outwards and the exhaled carbon dioxide is carried away and no external air can penetrate through any small leaks that may be present in the enclosure.

Normally, the prematurely born baby is kept continuously in the incubator for the first few weeks of its life. All nursing manipulations are done by means of special holes through which the nurse inserts her arms and which are provided with sealing devices that fit closely around the arms.

 The baby is fed, weighed. (By means of built-in scales) cleaned and medically treated inside the incubator. Minor operations, transfusions and x-ray photography can likewise be done without having to remove the baby from the incubator.

 The incubator is equipped with various safety devices which sound a warning and/or take preventive action in the event of a failure in the electric power, water or oxygen supply, or if the temperature in the incubator should become too high or low, or if the oxygen concentration becomes too high.