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Alginic acid (algine, alginate) is a viscous gum that is abundant in the cell walls of brown algae. more...

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Structure

Chemically, it is a linear copolymer with homopolymeric blocks of (1-4)-linked ß-D-mannuronate (M) and its C-5 epimer α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.

The monomers can appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks), alternating M and G-residues (MG-blocks) or randomly organized blocks. The relative amount of each block type varies both with the origin of the alginate. Alternating blocks form the most flexible chains and are more soluble at lower pH than the other blocks. G-blocks form stiff chain elements, and two G-blocks of more than 6 residues each form stable cross-linked junctions with divalent cations (e.g. Ca2+, Ba2+, Sr2+ among others) leading to a three-dimensional gel network. At low pH, protonized alginates will form acidic gels. In these gels, it is mostly the homopolymeric blocks that form the junctions, where the stability of the gel is determined by the relative content of G-blocks.

Forms

Commercial varieties of alginate are extracted from seaweed, including the giant kelp Macrocystis pyrifera, Ascophyllum Nodosum and various types of Laminaria.

Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles. It is also used for waterproofing and fireproofing fabrics, for thickening drinks, ice cream and cosmetics, and as a detoxifier that can absorb poisonous metals from the blood. Alginate is also produced by certain bacteria, notably Azotobacter species. Attempts to produce bacterial alginate have not yet been commercially successful.

Alginate ranges from white to yellowish brown, and takes filamentous, grainy, granular, and powdered forms. It is insoluble in water and organic solvents, and dissolves slowly in basic solutions of sodium carbonate, sodium hydroxide and trisodium phosphate.

Uses

Purified forms of alginate are used in antacid preparations such as Gaviscon®, Bisodol®, Asilone®, and Boots Own® tablets. Alginate is used extensivly as a mold-making material in dentistry and prosthetics, and in textiles. It is also used in the food industry, for thickening soups and jellies. Calcium alginate is used in burn dressings that promote healing and can be removed painlessly.

Read more at Wikipedia.org


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Heartburn: How to Extinguish the Fire
From Vibrant Life, 7/1/01 by Richard G. Edison

It's called gastroesophageal reflux disease. And it's no fun. Here's what to do if your heart's on fire.

It had been a particularly rough day at work. Jim's boss had been on his case all morning because sales were down in his division. In the afternoon his biggest client screamed at Jim for a half hour because his order was late. On the ride home the airconditioner in the car quit, leaving him sweltering in the middle of a traffic jam.

When he finally made it home, all Jim wanted to do was relax. Settling down in his favorite chair with a bowl of hot chili, he popped open a cola and flicked on the television. Later Jim treated himself to some chocolate ice cream--his favorite. He thought about going for a walk, but then his favorite show came on, and he decided exercise could wait. Tonight he was just going to take it easy.

It started while he was watching the 11:00 news. At first there was just a vague discomfort in his upper abdomen, but within moments Jim's chest felt like it was on fire. He'd been having occasional mild heartburn for the last couple months, but it had never been this intense before. The sensation seemed to come in waves, and he was a little short of breath. Jim felt a need to burp, but when he did sour acid filled the back of his throat. He tried lying down on the couch, but this seemed to make things worse.

His symptoms finally resolved after he took an antacid tablet, but the episode concerned Jim enough that he called his family physician the next day. After explaining what had happened, Jim asked, "What was happening to me, Doc? Was I having a heart attack or just an anxiety attack?"

"It was probably neither," his doctor replied. "I'll need to ask you a few more questions and run an electrocardiogram, just to be sure this wasn't heart-related, but I'm pretty sure what you were experiencing was gastroesophageal reflux disease, or GERD. It's pretty common and usually responds well to treatment. But you may have to make some changes in your lifestyle. Now, tell me about your diet ..."

Gastroesophageal reflux disease affects millions of people in the United States and is a major cause of emergency room visits for chest pain. It costs Americans millions of dollars each year in medical expenses and lost time from work. But for many people it remains a misunderstood and undertreated disease and a cause of unnecessary anxiety and discomfort.

Gastroesophageal reflux occurs when stomach acid flows backward into the stomach. Everybody experiences this to some extent. However, for about 25 to 35 percent of the people in the United States, this normal process becomes a chronic condition that can impact their enjoyment of life.

For most people GERD is caused by a decrease in lower esophageal sphincter tone, increased stomach pressure, or a combination of these two conditions.

The lower esophageal sphincter is a band of smooth muscle that acts as a valve to prevent backflow of stomach contents into the esophagus. In people with GERD this muscle may relax abnormally, allowing reflux to occur.

Increased stomach pressure also can cause reflux. People often experience this after eating a big meal and then lying down.

GERD is often described as a burning sensation in the chest or "heartburn." This was what Jim was experiencing. However, GERD can manifest itself in many other ways. The most common is a sour taste in the mouth. Other symptoms are trouble breathing while sleeping, a sore throat, a choking sensation when lying down, trouble swallowing, or a chronic cough. It has even been associated with an increase in asthma symptoms.

Complications can occur with GERD if it is not adequately treated. One of the most serious is Barrett's esophagus, when the esophageal lining becomes so irritated that it forms a new layer of tissue that is more resistant to stomach acid. Recent studies have noted an increased risk of esophageal cancer in patients with Barrett's esophagus. Other complications include insomnia, fatigue, asthma, strictures, and ulcerations.

Your doctor can often make the diagnosis of GERD from your history and symptoms, but they may also order tests such as a UGI, endoscopy, or ambulatory pH monitoring.

A UGI is a special X-ray that uses a substance called barium, which the patient drinks, to outline the upper gastrointestinal tract. This test is useful for revealing other causes of GI symptoms, such as peptic ulcers or strictures.

In endoscopy a physician runs a small tube into the esophagus. A miniature video camera mounted on the end allows the examiner to visualize inflammation of the tissue lining, which would indicate the presence of esophagitis, a complication of GERD. If inflammation is present, a biopsy may be taken of the esophageal lining. This test is most often reserved for people whose reflux is responding poorly to lifestyle changes and medication.

Ambulatory pH monitoring allows the physician to measure the acid levels in the esophagus through a 24-hour period. This may show an association between a patient's symptoms and meal intake, physical activity, or position changes.

Unfortunately, at the present time there is no cure for GERD. However, in most cases it is fairly easy to control the symptoms with proper medical evaluation and treatment. But it is not a simple matter of taking a pill. As Jim's doctor mentioned to him, people suffering from reflux have to make changes in their lifestyle and diet. This is often the hardest thing for them to do, especially when it involves giving up something they enjoy, such as chocolate. However, in the long run it is worth it.

Soft drinks, chocolate, peppermint, and peanut butter all tend to relax the lower esophageal sphincter muscle, causing reflux. Foods such as citrus juices, tomato sauces, and peppers can irritate the esophageal lining and increase symptoms. Alcohol, coffee, and cigarette smoking have similar effects and should also be avoided.

It may also be necessary to avoid large, fatty meals, especially less than three hours before bedtime. Your physician may recommend losing weight, because overweight people are more likely to have GERD. Reflux is often increased by lying flat, so elevating the head of your bed on six-inch blocks will allow gravity to help keep stomach acid down where it belongs. Regular exercise is also helpful for reducing stress, which can cause increased acid secretion in the stomach.

If lifestyle changes don't give adequate symptom relief, medications become necessary. For people who have only occasional reflux symptoms, over-the-counter antacids usually give adequate relief. They all work basically the same by neutralizing stomach acid, but some people find an antacid combined with alginic acid, such as in Gaviscon, gives improved relief. Your pharmacist can provide helpful information about the differences between these medications.

For years the primary medications used in treatment of gastrointestinal symptoms, including GERD, were the [H.sub.2] blockers. Examples of this class are cimetidine (Tagamet), ranitidine (Zantac), and famotidine (Pepcid). These drugs remain highly effective for treatment of chronic reflux and are now available over the counter in nonprescription strength.

A newer group of drugs that are showing excellent results are the proton pump inhibitors, such as omeprazole (Prilosec), lansoprazole (Prevacid), rabeprazole (Aciphex), or pantoprazole (Protonix). Available only by prescription, these medications work by blocking an enzyme required for acid secretion in the stomach. They are often effective when the [H.sub.2] blockers fail.

Other prescription medications that have been used to treat GERD are motility drugs, which increase gastric emptying and lower esophageal sphincter pressure. Metoclopramide (Reglan) is an example of this class of medication. Cisapride (Propulsid) was a highly effective motility medication, but it has recently been pulled from the market because it was found to cause serious heart rhythm changes.

In spite of lifestyle changes and medication, a small percentage of people remains symptomatic or develops complications, such as severe esophagitis or Barrett's esophagus. For them surgery may be necessary. A procedure called fundoplication has been showing excellent results, with up to 90 percent of people reporting good relief of symptoms. This surgery involves wrapping part of the stomach around the lower esophagus to form a valve mechanism.

Almost everyone, at some point during their childhood, was told, "Don't play with fire." In the case of gastroesophageal reflux disease this is especially good advice. GERD can have devastating effects on your personal feeling of well-being and may put you at risk for more serious health problems such as asthma or even cancer. Don't let it reach that point. If you are experiencing symptoms of GERD, make an appointment to see your doctor. Don't put up with heartburn--put the fire out.

RELATED ARTICLE: Heartburn Versus Heart Attack--Can You Tell the Difference?

That vague burning sensation in your chest--is it a heart attack or "heartburn"? Anyone who's ever felt chest discomfort has asked themselves similar questions. Is there any way for you to tell the difference between a heart attack and "heartburn" without going to the doctor?

The short answer to that question is "No." The only way to safely rule out a heart attack is to be seen by a doctor as soon as possible and allow them to run diagnostic tests. Passing off chest pain as indigestion or reflux is a recipe for disaster. The severe crushing pain people imagine when they think of a heart attack is not always present. Sometimes, especially in women and the elderly, there may be no pain at all or just a feeling of indigestion, shortness of breath, or fatigue.

So how can you know when to go to the emergency room? Here are some things to look for:

* If the pain is relieved by movement or by antacids, you are probably not having a heart attack. Reflux, indigestion, or muscle spasms are more likely causes of the pain. However, see your doctor as soon as possible for a full evaluation of these symptoms.

* If the discomfort lasts less than five minutes it may be only muscle spasms or reflux, but it could be angina pectoris. Angina occurs when a portion of the heart is not getting enough blood. It is a sign of coronary heart disease or "hardening of the arteries." See your doctor as soon as possible for evaluation and treatment.

* Squeezing pain in the chest, a feeling of fullness, or pressure that lasts for several minutes are symptoms commonly associated with a heart attack. These signs may be accompanied by lightheadedness, shortness of breath, sweating, or nausea. The pain may radiate to either shoulder, the back, the neck, or the jaw. If you experience any of these symptoms, it is important to call 911 immediately, take an aspirin (unless you have an allergy to aspirin or have been told not to take it by your doctor), and go to the emergency room by ambulance. Do not attempt to drive yourself.

The most important thing to remember when dealing with chest discomfort is this--every moment counts. If your pain is caused by a heart attack, the longer you wait to seek treatment the more severe the damage to your heart. Don't fool around with chest pain. Your life could be at stake.

Richard G. Edison is a writer living in Cayuga, New York.

COPYRIGHT 2001 Review and Herald Publishing Association
COPYRIGHT 2001 Gale Group

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