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Saturday, 22 February 2014

Blood Pressure

Blood pressure (BP), sometimes referred to as arterial blood pressure, is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.The blood pressure in the circulation is principally due to the pumping action of the heart. Differences in mean blood pressure are responsible for blood flow from one location to another in the circulation. The rate of mean blood flow depends on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as the circulating blood moves away from the heart through arteries and capillaries due to viscous losses of energy. Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries and arterioles. Gravity affects blood pressure via hydrostatic forces (e.g., during standing), and valves in veins, breathing, and pumping from contraction of skeletal muscles also influence blood pressure in veins.

Blood pressure without further specification usually refers to the systemic arterial pressure measured at a person's upper arm and is a measure of the pressure in the brachial artery, the major artery in the upper arm. A person’s blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimetres of mercury (mmHg), for example 120/80. It is also expressed as the amount over normal atmospheric pressure (760 mmHg), so a blood pressure of 120 mmHg would actually be 880 mmHg of true pressure.

Blood pressure varies in healthy people and animals, but its variation is under control by the nervous and endocrine systems. Blood pressure that is pathologically low is called hypotension, and that which is pathologically high is hypertension. Both have many causes and can range from mild to severe.


Monday, 17 February 2014

Anesthetics

Because diethyl ether ( commonly known simply as ether ) is a short-lived muscle relaxant, it has been widely used as an inhalation anesthetic. However, because it takes effect slowly and has a slow and unpleasant recovery period, other compounds, such as enflurane, isoflurane, and halothane, have replaced ether as an anesthetic. Diethyl ether is still used where there is a lack of trained anesthesiologists, because it is the safest anesthetic to administer by untrained hands. Anesthetics interact with the nonpolar molecules of cell membranes, causing the membranes to swell, which interferes with their permeability.

sodium pentothal ( also called thiopental sodium ) is commonly used as aintravenous anesthetic. The onset of anesthesia and the loss of consciousness occur within seconds of its administration. Care must be taken when administrating sodium pentothal because the dose for effective anesthesia is 75% of the lethal dose. Because of its toxicity, it cannot be used as fore an inhalation anesthetic is administered. Propofol is an anesthetic that has all the properties of the "perfect anesthetic ": It can be used as the sole anesthetic by intravenous drip, it has a rapid and pleasant induction period and a wide margin of safety, and recovery from the drug also is rapid and pleasant.

Friday, 14 February 2014

Lead Compound

The goal of the medicinal chemist is to find compounds that have potent effects on given diseases with minimum side effects. In other words, a drug must react selectively with its target and have minimal negative effects. A drug must get to the right place in the body, at the right concentration, and at the right time. Therefore, a drug must have the appropriate solubility to allow it to be transported to the target cell. If it is taken orally, the drug must be insensitive to the acid conditions of the stomach, and it also must resist enzymatic degradation by the liver before it reaches its target. Finally, it must eventually be either excreted as is or degraded to harmless compounds that can be excreted.

Medicinal agents used by humans since ancient Times provided the starting point for the development of our current arsenal of drugs . The active ingredients were isolated from herbs , berries, roots, and bark used in traditional medicine. Foxglove, for instance, furnished digitoxin, a cardiac stimulant. The bark of the cinchona tree yielded quinine for relief from malaria. Willow bark contains salicylates used to control fever and pain. The sticky juice of the oriental opium poppy provided morphine for severe pain and codeine for the control of a couch. By 1882, more than 50 different herbs were commonly used to make medicines. Many of these herbs wrere grown in the gardens of religious establishments that treated the sick.


Scientists still search the world for plants and berries and the oceans for flora and fauna that might yield new medicinal compounds . Taxol, a compound isolated from the bark of the Pacific yew tree, is a relatively recently recognized anticancer agent.
Once a naturally occurring drug is isolated and its structure determined, it can serve as a prototype in a search for other biologically active compounds . The prototype is called a lead compound ( i.e., a compound that plays a leading role in the search ). Analogs of the lead compound are synthesized in order to find one that might have improved therapeutic properties or fewer side effects. The analog may have a different substituent than the lead compound , a branched chain instead of a straight chain , or a different ring system. Changing the structure of the lead compound is called molecular modification.

Sunday, 9 February 2014

Vitamin B1

Christiaan Eijkman (1858-1930) was a member of a medical team that was sent to the East Indies to study beriberi in 1886. At that time , all diseases are thought to be caused by microorganisms. When microorganisms that caused beriberi could not be found, the team left the East Indies .

Eijkman stayed behind to become the director of a new bacteriological laboratory. In 1896, Eijkman accidentally discovered the cause of beriberi when he noticed that the chickens used in the laboratory had developed symptoms characteristic of the disease. He found that the symptoms had developed when a cook had started feeding the chickens rice meant for hospital patients. The symptoms disappeared when a new cook resumed feeding chicken feed to the chickens.

Later it was recognized that thiamine ( vitamin B1) is present in rice hulls but not in polished rice. For this work, Eijkman shared the Nobel Prize in physiology or medicine with Frederick Hopkins.



Saturday, 8 February 2014

VITAMIN C

Vitamin C is an antioxidant because it prevents oxidation reactions by radicals. We have seen that vitamin C traps radicals formed in aqueous environments. Not all the physiological functions of vitamin C are known. What is known, though, is that vitamin C is required for the synthesis of collagen, which is the structural protein of skin , tendons, connective tissue, and bone. If vitamin C is not present in the diet ( it is abundant in citrus fruits and tomatoes ), lesions appear on the skin , severe bleeding occurs about the gums , in the joints, and under the skin , and wounds heal slowly. The disease caused by a deficiency of vitamin C is known as scurvy. British sailors who shipped out to sea after the late 1700s were required to eat limes to prevent scurvy. This is how they came to be called "limeys" . Scurvy was the first disease to be treated by adjusting the diet. Scorbutus is Latin for "scurvy" ; ascorbic, therefore, means"no scurvy".

Thursday, 6 February 2014

Plastic Polymers and Food Safety

When plastics are recycled, the various types must be separated from one another. To aid in the separation, many states require manufacturers to include a recycling symbol on their products to indicate the type of plastic. 

You are probably familiar with these symbols, wich are found on the bottom of plastic containers. The symbols consist of three arrows around one of seven numbers; an abbreviation below the symbol indicates the type of polymer from wich the container is made. 


The lower the number in the middle of the symbol,the greater is the ease with wich the material can be recycled: 1 (PET) stands for poly ( ethylene terephthalate), 2(HDPE) for high-density polyethylene, 3(V) for poly ( vinyl chloride ), 4 (LDPE) for low-density polyethylene, 5 (PP) for polypropylene, 6 (PS) for polystyrene, and 7 for all other plastics.


Plastic Container Symbols for Food Grade Plastics

Types of Plastics and Food Safety By Plastic Number
Please reference Graphics for Quick View of Numbers to look for embedded into plastic products to help determine their safety.
1. PETE: Polyethylene terephthalate ethylene, used forsoft drink, juice, water, detergent, cleaner and peanutbutter containers.
2. HDPE: High density polyethylene, used in opaque plastic milk and water jugs, bleach, detergent and shampoo bottles, and some plastic bags.
3. PVC or V: Polyvinyl chloride, used for cling wrap, plastic squeeze bottles, cooking oil and peanut butter containers, and detergent and window cleaner bottles.
4. LDPE: Low density polyethylene, used in grocery store bags, most plastic wraps, Ziplock bags and some bottles.
5. PP: Polypropylene, used in most Rubbermaid, deli soup, syrup and yogurt containers, straws and other clouded plastic containers, including baby bottles.
6. PS: Polystyrene, used in styrofoam food trays, egg cartons, disposable cups and bowls, carry-out containers and opaque plastic cutlery.
7. Other: This is a catch-all category for plastics that don’t fit into the #1-6 categories. It includes polycarbonate, bio-based plastics, co-polyester, acrylic, polyamide and plastic mixtures like styrene-acrylonitrile resin (SAN). Number 7 plastics are used for a variety of products like baby bottles and “sippy” cups, baby food jars, 5-gallon water bottles, “sport” water bottles, plastic dinnerware and clear plastic cutlery.

What to look for on Plastic Containers
Here are some things to keep in mind when using the microwave:
  • Most takeout containers, water bottles, and plastic tubs or jars made to hold margarine, yogurt, whipped topping, and foods such as cream cheese, mayonnaise, and mustard are not microwave-safe.
  • Microwavable takeout dinner trays are formulated for one-time use only and will say so on the package.
  • Don’t microwave plastic storage bags or plastic bags from the grocery store.
  • Before microwaving food, be sure to vent the container: Leave the lid ajar, or lift the edge of the cover.
  • Don’t allow plastic wrap to touch food during microwaving because it may melt. Wax paper, kitchen parchment paper, or white paper towels are alternatives.
  • If you’re concerned about plastic wraps or containers in the microwave, transfer food to glass or ceramic containers labeled for microwave oven use.



Our homes are full of plastic, and the kitchen is no exception. The problem: Chemicals in plastic containers and other kitchenware may leach into the foods or drinks that they’re holding. Scientific evidence suggests that some of these chemicals may be harmful to people, especially infants and children.
The two best-studied offenders are bisphenol A (BPA) and phthalates. BPA mimics estrogen and has been shown to disrupt hormone and reproductive system function in animals. Research by the National Toxicology Program found a moderate level of concern about its “effects on the brain, behavior and prostate gland in fetuses, infants and children.” Phthalates have been shown to disrupt the endocrine system and have led to malformations in the male reproductive system in animals. Studies in humans have found associations between high phthalate exposure and a variety of health concerns including low sperm quality, high waist circumference and insulin resistance.
Researchers are still debating whether phthalates and BPA actually cause these health problems and, if so, how much exposure is necessary to trigger them. While these issues are being figured out, some experts recommend taking a preventive approach: “Minimize contact of food with problematic plastics as a precautionary measure to protect your health,” suggests Rolf Halden, PhD, adjunct associate professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. Here are six simple tips for reducing your exposure to the potentially harmful chemicals in plastics.
1. Know the code. Look on the bottom of your plastic to find the recycling symbol (a number between 1 and 7 enclosed in a triangle of arrows). The code indicates the type of plastic you are using and can give you important clues about safety. “We generally say 1, 2, 4 and 5 are considered to be the safest,” says Sonya Lunder, senior analyst at the Environmental Working Group. Try to avoid using plastics with 3 or 6, as these leach chemicals that may be harmful. Number 7 is an “other” category that includes BPA-containing plastics called polycarbonates. These plastics, which you should avoid, will have the letters PC printed underneath the 7.
2. Reconsider the microwave. Heat can increase the rate at which chemicals like BPA leach from plastic. Containers labeled “microwave safe” have been tested by the Food and Drug Administration (FDA) and found to leach extremely small amounts, which the FDA has determined to be safe. However, some experts advise people to keep plastic out of the microwave altogether. “I don’t microwave anything in plastic,” says Lunder. “It’s really easy and fast to put my food into a ceramic or glass container and heat it that way.” And never put plastic wrap on top of your food in the microwave, since it can melt. Use wax paper or a paper towel instead.
3. Use it for its intended purpose. Plastics that are designed for single use should only be used once. “Plastic breaks down over time,” Lunder explains. “Some aren’t designed to withstand heating and cooling.” Most plastics with recycling code number 1 are intended for single use, such as disposable water bottles. And that takeout container from six months ago? Toss it. In general they’re fine for refrigerating leftovers, but aren’t designed for heat exposure or long-term use.
4. Wash by hand. Only put plastics into the dishwasher if they have a dishwasher safe label. If you want to be extra-cautious, wash all plastics by hand or use only glass and ceramic plates and dishes. In the dishwasher, plastics are exposed to detergents and heat, which may accelerate the leaching of BPA from food containers.
5. Do not freeze. Only put plastics in the freezer if they have a freezer-safe label. Freezer temperatures can cause plastics to deteriorate, which increases the leaching of chemicals into the food when you take containers out of the freezer to thaw or reheat.
6. Don’t panic. Cutting down on exposure to potentially harmful chemicals in plastics can benefit your health. But as Dr. Halden reminds us, “Many things in your life pose a much higher risk than exposure to plastics, such as smoking, poor diet and even driving a car.”

Ref; 
Essentia Organic Chemistry, Paula Y. Bruice 

Cancer Chemotherapy ; 5-fluorouracil

Cancer is associated with rapidly growing and proliferating cells . Because cells cannot multiply if they cannot synthesize DNA, several cancer chemotherapeutic agents have been developed to inhibit thymidylate synthase. If a cell cannot make thymidine( T ), it cannot synthesize DNA.

A common anticancer drug that inhibits thymidylate synthase is 5-fluorouracil. The enzyme reacts with 5-fluorouracil the same way it reacts with uracil. However, the fluorine substituent causes 5-fluorouracil to become permanently attached to the enzyme (because the base cannot remove a F+ in an elimination reaction) , blocking the active site of the enzyme so it can no longer bind uracil. Therefore, thymidine can on longer be synthesized , and without thymidine, DNA cannot be synthesized.

Unfortunately, most anticancer drugs cannot discriminate between diseased and normal cells. As a result, cancer chemotherapy is accompanied by terrible side affects. However, cancer cells undergo uncontrolled cell division; thus, because they are dividing more rapidly than normal cells, they are harder hit by cancer-fighting chemotheraputic agents.




Ref; Essentia Organic Chemistry, Paula Y. Bruice
 

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