Tuesday, 4 December 2012

Alcohol, a brief description


In chemistry, an alcohol is an organic compound in which the hydroxyl functional group (-OH) is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms.
The most commonly used alcohol is ethanol, C2H5OH, with the ethane backbone. Ethanol has been produced and consumed by humans for millennia, in the form of fermented and distilled alcoholic beverages. It is a clear flammable liquid that boils at 78.4 °C, which is used as an industrial solvent, car fuel, and raw material in the chemical industry. Alcoholic beverages, typically containing 5% to 40% ethanol by volume, have been produced and consumed by humans since pre-historic times. A 50% v/v (by volume) solution of ethylene glycol in water is commonly used as an antifreeze.
Alcohol intoxication (also known as drunkenness or inebriation) refers to the physiological state induced by the consumption of alcohol, when it builds up in the bloodstream faster than it can be metabolized by the liver. Some effects of alcohol intoxication are central to alcohol's desirability as a beverage and its history as the world's most widespread recreational drug. Common effects are euphoria and lowered social inhibitions. Other effects are unpleasant or dangerous because alcohol affects many different areas of the body at once and may cause progressive, long-term harm when consumed in excess.
Common symptoms of alcohol intoxication include slurred speech, euphoria, impaired balance, loss of muscle coordination (ataxia), flushed face, dehydration, vomiting, reddened eyes, reduced inhibitions, and erratic behavior. Sufficiently high levels of blood-borne alcohol will cause coma and death from the depressive effects of alcohol upon the central nervous system.
Alcohol is metabolized by a normal liver at the rate of about one ounce (one two-ounce shot of spirits, a normal beer, a regular sized glass of wine) every 90 minutes. Ethanol's acute effects are largely due to its nature as a central nervous system depressant, and are dependent on blood alcohol concentrations:
  • 20–99 mg/dL - Impaired coordination and euphoria
  • 100–199 mg/dL - Ataxia, poor judgement, labile mood
  • 200–299 mg/dL - Marked ataxia, slurred speech, poor judgement, labile mood, nausea and vomiting
  • 300–399 mg/dL - Stage 1 anaesthesia, memory lapse, labile mood
  • 400+ mg/dL - Respiratory failure, coma
As drinking increases, people become sleepy, or fall into a stupor. After a very high level of consumption, the respiratory system becomes depressed and the person will stop breathing. The most important thing for people who witness someone "passing out" from too much alcohol is to get them emergency medical treatment. Comatose patients may aspirate their vomit (resulting in vomitus in the lungs, which may cause "drowning" and later pneumonia if survived). CNS depression and impaired motor co-ordination along with poor judgement increases the likelihood of accidental injury occurring. It is estimated that about one third of alcohol-related deaths are due to accidents (32%), and another 14% are from intentional injury.
The long term effects of alcohol range from possible health benefits for low levels of alcohol (ethanol) consumption to severe detrimental effects in cases of chronic alcohol abuse. Some experts argue that the benefits of moderate alcohol consumption may be outweighed by other increased risks, including those of injuries, violence, fetal damage, certain forms of cancer, liver disease and hypertension. As the apparent health benefits of moderate alcohol consumption are limited for populations at low risk of heart disease, other experts urge caution because of the possibility that recommending moderate alcohol consumption may lead to an increased risk of alcohol abuse.
Genetically speaking, an estimated one out of three people in East Asian countries have an alcohol flush reaction, colloquially known as "Asian Glow", a condition where the body cannot break down ingested alcohol completely because it lacks the genetically coded enzyme that performs this function in the bodies of drinkers with "European" tolerance levels. This syndrome has been associated with an increased risk of esophageal cancer in those who drink. It has also been associated with lower than average rates of alcoholism, possibly due to its association with adverse effects after drinking alcohol.
To the contrary, around 80% of Asian people (less common in Thailand and India) have a variant of the gene coding for the enzyme alcohol dehydrogenase called ADH1B, and almost all Chinese and Korean people have a variant of the gene called ADH1C. These genes result in an alcohol dehydrogenase enzyme which converts alcohol to acetaldehyde with a much higher efficiency than other gene variants (40 to 100-fold in case of ADH1B). In about 50% of Asians, the increased acetaldehyde accumulation is worsened by another gene variant, the mitochondrial ALDH2 allele, which results in an inhibited acetaldehyde dehydrogenase enzyme, responsible for the breakdown of acetaldehyde. The result is that affected people may be better at metabolizing alcohol, often not feeling the alcohol "buzz" to the same extent as others, but show far more acetaldehyde-based side effects while drinking.
 Family, twin and adoption studies have shown that alcoholism definitely has a genetic component. In 1990, Blum et al. proposed an association between the A1 allele of the DRD2 gene and alcoholism. The DRD2 gene is the first candidate gene that has shown promise of an association with alcoholism.
A protein which controls our urge to eat is involved in alcohol addiction, researchers from the Scripps Research Institute have found. Peptide ghrelin, which is known to stimulate eating, is said to play a major role in alcohol addiction. The discovery points to new possibilities for designing drugs to treat alcoholism and other addictions. The discovery was made while studying the amygdala region of the brain. Amygdala is thought to be a key region in the transition to alcohol dependence, that is, a biological change from experiencing a pleasant sensation upon consumption of alcohol to the need to consume alcohol to relieve unpleasant, negative feelings due to the lack of its consumption.
Peptide ghrelin is best known for stimulating eating through its action on a receptor known as GHSR1A in the hypothalamus region of the brain. But scientists have found that gene defects in both ghrelin and the GHSR1A receptor were associated with severe cases of alcoholism in animal models. Alcoholic patients have higher levels of ghrelin peptide circulating in their blood compared to non-alcoholic patients. And, the higher the ghrelin levels, the higher the patients' reported craving for alcohol.
After a week, researchers examined neurons from alcohol-addicted and control rats (which were not given alcohol), when both ghrelin and ethanol were added. First, the scientists added ghrelin followed by ethanol. This resulted in an even stronger increase in GABAergic responses in these neurons. GABAergic is a neurotransmitter that contributes to alcohol intoxication and it makes a person get addicted to alcohol.
Both shared and different mechanisms involved in the effects of ghrelin and ethanol in the central nucleus of the amygdala. Importantly, there is a tonic ghrelin signal that appears to interact with pathways activated by both acute and chronic ethanol exposure. Perhaps scientists could find a way to block ghrelin's activity in this region, they could theoretically dampen or even turn off the cravings felt by alcoholics.

Controversially researchers at the Norwegian University of Science and Technology analysed earlier studies on the drug between 1966 and 1970. Patients were all taking part in alcohol treatment programmes, but some were given a single dose of LSD of between 210 and 800 micrograms. For the group of patients taking LSD, 59% showed reduced levels of alcohol misuse compared with 38% in the other group. This effect was maintained six months after taking the hallucinogen, but it disappeared after a year. Those taking LSD also reported higher levels of abstinence.
Despite prohibition and other schemes for stopping the alcohol trade, it is still a popular social activity today. In many ways the process of temporarily losing ones inhibitions could give someone courage to talk to the opposite sex. Although some argue the process of finding a suitable mate at a bar might not give best results for long term compatibility. But however you define Alcohol, it is still a drug that will probably hang around society for a long time...



1 comment:

  1. maggie.danhakl@healthline.com24 September 2014 at 03:13

    Hi Simon,

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