Antioxidant- How does it help us

It is now a common saying that antioxidant is beneficial for health. But what is antioxidant and how does it help us? What are the sources of antioxidants? Before that we should know about oxidation better term autoxidation. In our daily life a continuous process called metabolism is going on in our body, by which we are getting energy from our foods. During this process of metabolism some chemical or elements ( called free radicals -highly reactive atoms or molecular species due to unpaired electrons) are produced in our body which cause some harm full effects on the cells of our body by a process called oxidation. Autoxidation is any oxidation that occurs in open air or in presence of oxygen and/or UV radiation. The process of autoxidation has enormous economic impact, since all foods, plastics, gasoline, oils, rubber, and other materials that must be exposed to air undergo continuous destructive reactions of this type. All good plastics and rubber and most processed foods should contain certain chemical (called antioxidant) to protect them against the attack of oxygen. The oxidation of food products involves the addition of an oxygen atom to or the removal of a hydrogen atom from the different chemical molecules found in food. Two principal types of oxidation that contribute to food deterioration are autoxidation of unsaturated fatty acids (i.e., those containing one or more double bonds between the carbon atoms of the hydrocarbon chain) and enzyme-catalyzed oxidation. The autoxidation of unsaturated fatty acids forms free radicals producing compounds that cause the off-flavours and off-odours characteristic of oxidative rancidity. Antioxidants that react with the free radicals (called free radical scavengers) can slow the rate of autoxidation. These antioxidants include the naturally occurring tocopherols (vitamin E derivatives) and the synthetic compounds butylated hydroxyanisole (BHA), hydroxytoluene (BHT), and tertiary butylhydroquinone (TBHQ). Specific enzymes may also carry out the oxidation of many food molecules. The products of these oxidation reactions may lead to quality changes in the food. For example, enzymes called phenolases catalyze the oxidation of certain molecules (e.g., the amino acid tyrosine) when fruits and vegetables, such as apples, bananas, and potatoes, are cut or bruised become brown in colour. The product of these oxidation reactions, collectively known as enzymatic browning, is a dark pigment called melanin. Antioxidants that inhibit these browning of fruits are reducing substances such as ascorbic acid (vitamin C), and agents that inactivate the enzymes, such as citric acid and sulfites. In human, free radical injury can be minimised by Antioxidants, which are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Free radical damage may lead to cancer. Antioxidants interact with and stabilize free radicals and may prevent some of the damage free radicals might otherwise cause. Examples of antioxidants include beta-carotene, lycopene , vitamins C, E, and A, and other substances.

Which foods are rich in antioxidants?

Antioxidants are abundant in fruits and vegetables, as well as in other foods including nuts, grains, and some meats, poultry, and fish. The list below describes food sources of common antioxidants.

Beta-carotene is found in many foods that are orange in color, including sweet potatoes, carrots, cantaloupe, squash, apricots, pumpkin, and mangoes. Some green, leafy vegetables, including collard greens, spinach, and kale, are also rich in beta-carotene.

Lutein, best known for its association with healthy eyes, is abundant in green, leafy vegetables such as collard greens, spinach, and kale.

Lycopene is a polymer of beta carotene and a potent antioxidant found in tomatoes, watermelon, guava ( red), papaya, apricots, pink grapefruit, pomegranate, blood oranges, and other foods.( not in strawberry or red berries). Lycopene is heat stable and is available in processed fruits containing natural lycopene e.g tomatoes sauch ( one tomato contain 3.5 mg lycopene but one cup of sauchcontain 28 mg lycopene)

Vitamin A is found in three main forms: retinol (Vitamin A1), 3,4-didehydroretinol (Vitamin A2), and 3-hydroxy-retinol (Vitamin A3). Foods rich in vitamin A include liver, sweet potatoes, carrots, milk, egg yolks, and mozzarella cheese.

Vitamin C is also called ascorbic acid, and can be found in high abundance in many fruits and vegetables and is also found in cereals, beef, poultry, and fish. Vitamin E, also known as alpha-tocopherol, is found in almonds, in many oils including wheat germ, safflower, corn, and soybean oils, and is also found in mangoes, nuts, broccoli, and other foods.

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Vewing without Spectckles in Hypermetropia

After 40 years of age it is physiological condition ( hypermetropia) that glasses are necessary for most people during their near vision. Suppose you incidentally left your glass at home. You have to read a telephone number in a visiting card. What will you do now? You will seek help from anybody nearby. He may be busy or illiterate. But don't be worry. You can do it yourself and its' easy. First curl your index finger on itself against thumb and so that a small hole is made. Now look through the hole with one eye in bright light to read anything that you can't read with naked eye ( the other eye must be closed). Smaller the size of the hole better will be the resolution of the image. Alternatively if time allowed make a small hole on a paper card ( e.g, visiting card) by a needle ( James clip or pin ) or tooth pic. Look through the hole and you can now read easily the smaller letters on a visiting card or news paper or on computer monitor for a considerable time.

How does it work:

Veiwing through fingers

Vewing through hole in card


Explanations:

1. Depth of focus of visual field and the size of aperture has a reciprocal relation in photography. In a manual camera it is possible to control this system. But our eye is like an automatic camera. Its size of aperture ( pupil) is controlled by the illumination of visual area. In hypermetropic people focusing power of eye is somewhat is impaired even in presence of high illumination of visual field. In this case if an additional diaphragm is used in front of iris with an aperture there will be increase in the depth of focus of the visual field. So in this way visual acuity is increased by increasing depth of focus by passing the light from a bright visual field through double apertures.


2. The air trapped in the hole in the card or between fingers behalves like a convex lens ( power approximately 0.75+). One can test it by a standard test for a convex lens by moving the card with the hole when the image behind it will move in opposite direction. It may be due effect of surface tension that may condense the trapped air in the hole which become a small convex lens.

Very High leucocytosis Interfere with colorimetric measurement of Hemoglobin

( Originally the article was published Northern Medical Journal, 2006; Vol-15 No-2, It has been modified for blog)-Helpful for laboratory practitioner
Hemoglobin estimation of a solution or a blood sample is commonly done in most cases by cyanmethhemoglobin method. But a less familiar method, which is also a photoelectric colorimetric methed,1developed by us, is followed in some areas of Bangladesh. The later method is a acid-hematin method and has found to have similar accuracy and stability. Unlike cyanmethhemoglobin method, it is very cheap and has a advantage that no biohazardous chemical have been used here2. Interestingly, during the development of the new method with a comparison to cyanmethhemoglobin method, it is observed that in both methods prepared fluid mixed with blood of high WBC count showed optical density resulting hemoglobin level that didn’t correspond with clinical condition of the patient. That means higher hemoglobin level was observed in a clinically anemic patient whose WBC count is very high e.g. in case leukemia. Moreover the blood mixed fluid, which is clear in other cases, was found to be hazy in these cases. To get rid from the problem we centrifuge the fluid and the clear supernatant fluid was used to measure the optical density and then the actual level of hemoglobin could be estimated which corresponded well with clinical condition of the patient. The deposit, after centrifugation, was examined under microscope and found plenty intact WBC. In normal cases, the deposits also shown WBC but were in very small number. Roughly it was estimated that hemoglobin level was increased by 1.2 to 1.4 gram% for 1,00,000WBC/cumm of blood. So, during estimation of hemoglobin in patient with very high WBC count (e.g leukemia) optical density should be taken from the supernatant fluid after centrifugation for few minutes (more than 3 minutes is satisfactory) of the prepared fluid.
Cyanmethaemoglobin method is followed in many countries for the last few decades, though potassium cyanide, which is used in this method, carries potential health hazard. Besides this, the limitation regarding high WBC count should be always considered. It can be easily proved in any laboratory by estimating hemoglobin of a patient having very high WBC count e.g. leukemia, by measuring absorbance before and after centrifuging the measuring fluid.

References:

1. Mujibur Rahman. A New Method for Measuring Hemoglobin. Laboratory Hematology;
2003, Vol 9, No 3: 179.
2. Barbara J Brain & Imelda Bates. Basic haematologic techniques. Dacie and Lewis Practical Haematology. Ninth Edition, Churchill Livingstone. 2001.19-46.

Why Solar Eclipse sometimes causes injury to Eye

It could be injurious to eye to look at the sun particularly several minutes before and after the full eclipse. At this time our pupil become larger in size because light intensity become slows down. Our eye reacts like an automatic camera . It opens in darker and closes in brighter light. In extreme light (looking at full sun) size of pupil can be 0.1 mm in diameter and in darkest light it can as large as 9 mm in diameter. During a solar eclipse size of pupil becomes 3 or 4 mm in diameter or like due to covering most part of the sun by the moon. But the light from exposed part of the sun will not loss its power of illumination and will enter our eye affecting the macula with a greater intensity of 30 to 40 times (0.1X30 or 40) than other time of normal days and it is sufficient to burn our macula causing blindness. It can be compared with looking at torch light at night or viewing television in dark room which eventually disturb our vision but not at day time. We should remember that in any time intensity of the sun never goes down or increases or there is no variation of UV light coming to the earth from the sun. Looking at sun in normal days for longer time may also causes burning our macula of eye.
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