Conservapedia - User contributions [en]

Muscle

2012-03-24T02:53:04Z

JamesRi:

[[Image:muscle1.jpg|left]]
A '''muscle''' is made of a bundle of muscle fibers. These fibers can be extremely long, up to about 14 inches in the leg, or very short, fractions of an inch. Within the muscle fiber are thousands of parallel structures called myofibrils. The myofibrils contain two types of filaments ([[actin]] and myosin) that cause the contractions of the muscle. These interlocking filaments can shorten by grabbing on to each other and pulling together; this is a muscle contraction.
[[Image:Illu muscle tissues.jpg|right|thumb|300px|3 types of muscle tissues.]]
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==Difference in Muscle Cells==
Depending on the type of myosin in the mycofibril, a muscle can be either fast-twitch or slow-twitch. The slow-twitch or ''type I'' fibers use energy much more efficiently, but cannot contract as quickly. The fast-twitch or ''type II'' fibers use energy less efficiently, but contract up to ten times faster than the type I fibers. Both types of muscle fiber contract with about the same amount of force.

==Variation in Fiber Composition==
{| class="wikitable"
|-
! Type of Person
! Fast-twitch percent
! Slow-twitch percent
|-
| Olympic Sprinter
| 80%
| 20%
|-
| Couch Potato
| 60%
| 40%
|-
| Weekend Warrior
| 50%
| 50%
|-
| Olympic Marathoner
| 15%
| 85%
|}

== See also ==

*[[Bone]]
*[[Fat]]
*[[Bodybuilding]]
[[Category:Anatomy]]

Aspirin

2010-10-02T23:28:09Z

JamesRi: added a mechanism of action and linked that to the effects and side effects

'''Aspirin''' originated as a [[herbal]] remedy, a bitter powder now called [[salicin]] which was extracted from the bark of the [[willow]] tree in ancient Greek times. This raw form often induced extreme stomach pains as a side effect. <ref>[http://www.howstuffworks.com/aspirin.htm ''HowStuffWorks.com'']</ref> First synthesized as acetylsalicylic acid in 1899, this drug is widely used to treat pain, fever, and inflammation.

Aspirin acts by irreversible inhibition of the enzyme cyclooxygenase. This limits the production of the thromboxanes and prostaglandins. The reduction in thromboxanes, which are responsible for platelet adhesion gives the drug its anticlotting properties. The reduction in prostaglandins alleviates pain and is also responsible for the side effect of ulceration of the gastric mucosa as prostaglandins are stimulators of mucous production in and blood flow to the gastric mucosa.

Because of the anticlotting effect, aspirin is prescribed in low doses—typically 81 mg daily—to help prevent [[heart attack]]s, strokes, and blood clot formation in people at high risk for developing blood clots. Research has also shown that aspirin given immediately after a [[heart attack]] can significantly increase one's chance of survival.<ref>[http://www.americanheart.org/presenter.jhtml?identifier=4456 American Heart Association]</ref>

Aspirin has a number of potential side effects including: ulceration of the stomach lining, easy bruising and bleeding, nausea, and allergic reaction. Overdose of aspirin can result in death. Aspirin use in children with some viral illnesses is linked to the development of [[Reye's syndrome]].

==References==
{{reflist}}

[[Category:Drugs]]

Celiac disease

2010-10-02T23:16:58Z

JamesRi: minor correction - HIV is a disease of the immune system, but I've never heard it characterised as autoimmune.

'''Celiac disease''' is a disease in which eating foods containing [[gluten]] causes the [[immune system]] to respond by damaging the [[small intestine]]. Gluten is a protein in wheat, rye and barley. It is found mainly in foods but may also be in other products like medicines, [[vitamin]]s and even the glue on stamps and envelopes.

Celiac disease affects each person differently. Symptoms may occur in the digestive system or in other parts of the body. One person might have diarrhea and abdominal pain, while another person may be irritable or depressed. Irritability is one of the most common symptoms in children. Some people have no symptoms.

Celiac disease is [[genetic]]. The only treatment is a diet free of gluten.<ref>[http://www.nlm.nih.gov/medlineplus/celiacdisease.html National Library of Medicine]</ref>

Celiac Disease, also known as Coeliac Disease, is often mistaken for other conditions due to its various symptoms. The intestinal tract, regardless of other symptoms, is affected by this disease. Celiac Disease is an autoimmune disease, putting it in the same family of diseases as lupus and Goodpasture's syndrome. When gluten is ingested, the immune system of the sufferer reacts, sending white blood cells to 'attack' the offending food particles.
Over time, the intestinal tract gradually loses its ability to ingest any food whatsoever if gluten remains a part of the celiac's diet. Because of the proximity of the area of the intestinal tract that digests lactose, lactose intolerance is a common symptom of the celiac. If the disease is allowed to progress, the body of the celiac will exhibit symptoms common to anorexia, despite the sometimes vast quantities of food that the celiac may ingest. Accompanied by this gradual descent is muscle loss (sometimes accompanied by inflammation of the tissue) as it is digested in the body's attempt to survive. Another common symptom deals with outbreaks on the skin.

Gluten exists in many common foods, such as wheat, barley, rye, malt (unless it is specified as corn, rice, or some other gluten-free grain), and oats. Oat is a questionable substance, with many pointing out that it does not specifically contain gluten. However, oats are not usually processed in dedicated facilities, so more often than not they are processed directly with gluten-containing grains.

[[category:Diseases]]

==References==
{{reflist}}
==External Links==
[http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/ National Digestive Diseases Information Clearinghouse (NDDIC)]

Cancer

2010-02-14T16:34:22Z

JamesRi: removed non scientific, unsupported claims reminscent of some the more bizarre conspiracy theories heard.

The term '''cancer''' refers to many different diseases. They all have in common uncontrolled ''cell [[proliferation]]'' (growth and division). Cancers are usually named for the organ or cell type that is originally involved. After beginning at one site, cancer may ''metastasize'' (spread) to other organs. The cancer is still named by its place of origin.

==Types of Cancer==
[[Image:Cancerxray.jpg|200px|right|thumb|X-Ray of patient with tumor cancer in right lung]]
[[Image:LUNG069.jpg|200px|right|thumb|Lung tumor]]
''Data are for USA''

*Most common cancers in men:
#[[Prostate cancer|Prostate]]
#[[Lung cancer|Lung]]
#[[Colon cancer|Colorectal]]

*Deadliest cancers in men:
#Lung
#[[Prostate cancer|Prostate]]
#Colon
#Pancreatic
#Leukemia
#[[Liver cancer|Liver]]
#Stomach
*Most common cancers in women
#[[Breast cancer|Breast]]
#Lung
#Colorectal

*Deadliest cancers in women
#Lung
#Breast
#Colorectal
#Pancreatic
#Uterus
#Stomach

see [[Mortality]]

==Prevention and Screening==
''Preventative strategies are continuously being revised. Please see references below for up to date information.''
*[[Breast cancer]]: In women without a family history of breast cancer, mammograms should be done yearly. Clinical breast exam by a medical professional should also be done yearly. Women who have had abortions are significantly more likely to contract breast cancer.
*[[Lung cancer]]: There are no currently accepted preventative guidelines
*[[Prostate cancer]]: evidence is inconclusive, but most doctors recommend yearly PSA blood test and digital rectal exam
*[[Colon cancer]]: in people without a family history of colon cancer, most sources recommend a colonoscopy at age 50, with further studies based on the results. Fecal occult blood testing should also be conducted yearly.
*[[Cervical cancer]]: yearly Pap smears should be done on all women who have been sexually active and have not had a [[hysterectomy]]. Over age 65, women in monogamous relationships and recent normal Pap smears probably do not need to be screened as frequently.
*[[Testicular cancer]]: the evidence is unclear, however most physicians recommend routine testicular exams in young men.
*[[Skin cancer]]: keep skin protected from sunlight by use of clothing and sunscreen, and watch you skin for new moles, or changes in existing moles.

==Treatment of cancer==

===Chemotherapy===
[[Chemotherapy]] is the use of drugs that kill [[tumor]] cells. Conventionally, the drugs that are used are those that target cells which are rapidly undergoing [[mitosis]]; this approach is effective but is limited by side effects, which occur because these drugs have an adverse effect on normal tissues that contain rapidly-dividing cells. Research is under way to find drugs with a wider [[therapeutic index]]. One approach is to study specific molecular markers that may be used to identify cancer cells, and to develop drugs that preferentially kill cells that exhibit those markers.

===Radiation therapy===
Radiation therapy involves the use of precisely-targeted [[radiation]] to destroy cancer cells. Because radiation damages [[DNA]] and thus has the ability both to treat and to cause cancer, this method of treatment must be administered by physicians highly-skilled in [[physics]].

===Surgery===
The goal of cancer surgery is to physically remove the abnormal cells. This becomes more difficult after the cancer spreads. Often, chemotherapy is used either before or after surgery to kill cancer cells that have [[metastasis|metastasized]].

===Immunotherapy===
The immune system contains a number of cell types, such as [[NK cells]] and [[cytotoxic T cell|killer T cells]] that have the capability to destroy other cells that have become infected with viruses or have become cancerous. [[Immunotherapy]] involves the enhancement or potentiation of these natural defenses against tumor cells. A common procedure is to remove immature immune cells from the patient's [[bone marrow]], purify the T-cells and expose them to [[antigen]]s from the tumor. The activated cells are then re-injected, allowing them to seek out cancerous tissues.

== See also ==

*[[Mortality]]
*[[Mobile phones and brain tumor risk]]

==References==
*http://www.cdc.gov
*[http://www.cancer.org/docroot/stt/stt_0.asp American Cancer Society: Cancer statistics for 2007]
*[http://www.cancer.org/docroot/ETO/content/ETO_1_4X_What_Is_Chemotherapy.asp?sitearea=ETO American Cancer Society: What is chemotherapy?]
*[http://www.cancer.org/docroot/ETO/content/ETO_1_4X_How_Does_Chemotherapy_Work.asp?sitearea=ETO American Cancer Society: How does chemotherapy Work?]
*[http://www.cancer.org/docroot/ETO/content/ETO_1_4X_Whats_New_in_Chemotherapy_Research.asp?sitearea=ETO American Cancer Society: What's new in chemotherapy research?]
*[http://www.ahrq.gov/clinic/pocketgd.htm Agency for Healthcare Research and Quality: Guide to Clinical Preventive Services]
*[http://www.mayoclinic.com/print/chemotherapy/CA00029/METHOD=print Mayo Clinic: Chemotherapy: Drug treatment uses chemicals to kill cancer cells]
*[http://women.webmd.com/guide/health-myths-know-truth?page=2 Myth: Cancer cannot be prevented]

[[Category:Diseases]]
[[Category:Demography]]
[[Category:Cancer| ]]

Cell Wall

2010-02-14T16:24:44Z

JamesRi: Added more detail, will probably create page on pectins as they are of major importance at some point.

{{merge|Cell wall}}
A '''cell wall''' is a structure formed largely of [[cellulose]] that surrounds plant cells. Other components include cross linking glycans and pectins. Many proteins are found, largely those which act to remodel the cell wall polysaccharides, however highly glycosylated proline rich proteins are also found which are not enzymatically active. Plant cell walls are classified as primary and secondary. The primary cell wall is ellucidated below and is found in all plant cells. The secondary cell wall is found in tissues that require extra rigidity such as the stem, trunk, xylem or other specialised tissue. This secondary cell wall may consist of simply thicker cellulose microfibrils with more cross linking, or the deposition of lignin that makes up wood in the case of the xylem.

Cellulose microfibrils are initially synthesised by the cellulose synthase complex, a set of enzymes embedded in the cell membrane. The cellulose molecule is initially about 500 glucose molecules long. Neighbouring cellulose molecules interact via hydrogen bonding to form parallel, overlapping aggregates of around 40 molecules. These are referred to as a microfibril. These are then arranged in layers referred to as lamellae and bound together by cross linking glycans.

Cross linking glycans are highly branched polysaccharides that interact via hydrogen bonding with the cellulose microfibrils. These are composed of a backbone, usually glucose but also xylose or mannose with many side chains. These vary greatly between species.

Pectins are branched polysaccharides, typified by the huge numbers of negatively charged galacturonic acid residues. Owing to this negative charge, the addition of divalent cations, such as calcium allows these chains to be cross linked by the positive ions.

== References ==
*Alberts B, et al.(2002). ''Molecular Biology of the Cell, 4th ed.'' Garland Science, pp. 1120-1124. ISBN 0-8153-3218-1.

[[Category:Biology]]

Cell wall

2010-02-14T15:50:05Z

JamesRi: fungi forgotten

A '''cell wall''' is a rigid substance on the outside of certain [[cell|cells]], usually [[plant]], fungi and [[bacteria]] cells.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref>

==References==
<references/>

[[Category:Cellular Biology]]