Platelets | Health Dictionary

Blood platelets, or thrombocytes, are small spherical bodies in the BLOOD, which play an important part in the process of its COAGULATION. Normally, there are around 300,000 per cubic millimetre of blood.


Platelets | Health Dictionary

Keywords of this word: Platelets


Medical Dictionary

Sudden transitory impairment, or loss, of vision. It usually a?ects only one eye, and is commonly due to circulatory failure. In its simplest form it occurs in normal people on rising suddenly from the sitting or recumbent position, when it is due to the e?ects of gravity. It also occurs in migraine. A not uncommon cause, particularly in elderly people, is transient ocular ISCHAEMIA, resulting from blockage of the circulation to the retina (see EYE) by emboli (see EMBOLISM) from the common carotid artery or the heart. Treatment in this last group of cases consists of control of the blood pressure if this is raised, as it often is in such cases; and the administration of drugs that reduce the stickiness of blood platelets, such as aspirin. In some instances, removal of the part of the carotid artery from which the emboli are coming may be indicated.... Medical Dictionary

Medical Dictionary

Drugs which relieve or abolish PAIN. Unlike local anaesthetics, they are usually given systemically – a?ecting the whole body – and produce no SENSORY or MOTOR blockade stopping the activity in the sensory or motor nerves respectively that supply a part of the body. The many di?erent types of analgesics have varying modes of action. The choice of drug and method of administration will depend upon the type and severity of pain being treated.

Non-opioid analgesics include ASPIRIN, PARACETAMOL and NON-STEROIDAL ANTIINFLAMMATORY DRUGS (NSAIDS), which are used to treat mild or moderate pain such as headache (see also MIGRAINE), DYSMENORRHOEA, and transient musculoskeletal pain. Some analgesics – for example, aspirin and paracetamol – also reduce PYREXIA. A strong non-opioid analgesic is NEFOPAM HYDROCHLORIDE, which can be used for persistent pain or pain that fails to respond to other non-opioid analgesics, but does have troublesome side-e?ects. These non-opioid analgesics can be obtained without a doctor’s prescription – over the counter (OTC) – but the sale of some has to be supervised by a quali?ed pharmacist. A wide range of compound analgesic preparations is available, combining, say, aspirin or paracetamol and CODEINE, while the weak stimulant CAFFEINE is sometimes included in the preparations. Most of these are OTC drugs. NSAIDs are especially e?ective in treating patients with chronic diseases accompanied by pain and in?ammation. They, too, are sometimes combined with other analgesics.

Paracetamol acts within the central nervous system by inhibition of PROSTAGLANDINS. It is often combined with other analgesics – for example, aspirin or codeine; in proprietary compounds and in therapeutic doses it has few side-e?ects. Overdosage, however, can cause damage to the liver or kidneys (20–30 tablets are su?cient to do this). Paracetamol is often used by individuals attempting suicide. Even if there are no immediate symptoms, individuals suspected of having taken an overdose should be sent to hospital urgently for treatment.

The NSAIDs (including aspirin) inhibit prostaglandin synthesis. Prostaglandins are released by tissues that are in?amed, and may cause pain at peripheral pain sensors or sensitise nerve endings to painful stimuli: by inhibiting their production, pain and in?ammation are reduced. NSAIDs are particularly e?ective for pain produced by in?ammation – for example, ARTHRITIS. Side-e?ects include gastrointestinal bleeding (caused by mucosal erosions particularly in the stomach), inhibition of platelet aggregation (see PLATELETS), and potential for renal (kidney) damage.

Severe pain is often treated with opioid drugs. The original drugs were naturally occurring plant ALKALOIDS (e.g. MORPHINE), whilst newer drugs are man-made. They mimic the action of naturally occurring compounds (ENDORPHINS and ENCEPHALIN) which are found within the brain and spinal cord, and act on receptors to reduce the transmission of painful stimuli within the central nervous system (and possibly peripherally). They tend to produce side-e?ects of euphoria, respiratory depression, vomiting, constipation and itching. Chronic use or abuse of these drugs may give rise to addiction.... Medical Dictionary

Medical Dictionary

Anticoagulants are drugs which inhibit COAGULATION of the blood. They are used to prevent and treat abnormal clotting of the blood, to treat THROMBOSIS, and sometimes to prevent or treat STROKE or TRANSIENT ISCHAEMIC ATTACKS OR EPISODES (TIA, TIE). Anticoagulant drugs are also prescribed preventively in major surgery to stop abnormal clotting from occurring; HAEMODIALYSIS is another procedure during which these drugs are used. Anticoagulants are also prescribed to prevent thrombi (clots) forming on prosthetic heart valves after heart surgery.

The drugs are much more e?ective in the treatment and prevention of venous clotting – for example, deep vein thrombosis (DVT), see under VEINS, DISEASES OF – than in preventing thrombosis formation in arteries with their fast-?owing blood in which thrombi contain little ?brin (against which the anticoagulants work) and many PLATELETS.

The main anticoagulants now in use are the natural agent HEPARIN (a quick-acting variety and a low-molecular-weight long-acting type); synthetic oral anticoagulants such as WARFARIN and the less-often-used acenocoumarol and PHENINDIONE; and antiplatelet compounds such as ASPIRIN, clopidogrel dipyridamole and ticlopidines. Fondaparinux is an extract of heparin which can be given once daily by injection; ximelagatran, an inhibitor of thrombin, is being trialled as the ?rst new oral anticoagulant since heparin.

Patients taking anticoagulants need careful medical monitoring and they should carry an Anticoagulant Card with instructions about the use of whatever drug they may be receiving – essential information should the individual require treatment for other medical conditions as well as for thrombosis.... Medical Dictionary

Medical Dictionary

Blood consists of cellular components suspended in plasma. It circulates through the blood vessels, carrying oxygen and nutrients to the organs and removing carbon dioxide and other waste products for excretion. In addition, it is the vehicle by which hormones and other humoral transmitters reach their sites of action.

Composition The cellular components are red cells or corpuscles (ERYTHROCYTES), white cells (LEUCOCYTES and lymphocytes – see LYMPHOCYTE), and platelets.

The red cells are biconcave discs with a diameter of 7.5µm. They contain haemoglobin

– an iron-containing porphyrin compound, which takes up oxygen in the lungs and releases it to the tissue.

The white cells are of various types, named according to their appearance. They can leave the circulation to wander through the tissues. They are involved in combating infection, wound healing, and rejection of foreign bodies. Pus consists of the bodies of dead white cells.

Platelets are the smallest cellular components and play an important role in blood clotting (see COAGULATION).

Erythrocytes are produced by the bone marrow in adults and have a life span of about 120 days. White cells are produced by the bone

marrow and lymphoid tissue. Plasma consists of water, ELECTROLYTES and plasma proteins; it comprises 48–58 per cent of blood volume. Plasma proteins are produced mainly by the liver and by certain types of white cells. Blood volume and electrolyte composition are closely regulated by complex mechanisms involving the KIDNEYS, ADRENAL GLANDS and HYPOTHALAMUS.... Medical Dictionary

Medical Dictionary

A blood clot arises when blood comes into contact with a foreign surface – for example, damaged blood vessels – or when tissue factors are released from damaged tissue. An initial plug of PLATELETS is converted to a de?nitive clot by the deposition of FIBRIN, which is formed by the clotting cascade and erythrocytes. (See COAGULATION.)... Medical Dictionary

Medical Dictionary

Bone marrow is the soft substance occupying the interior of bones. It is the site of formation of ERYTHROCYTES, granular LEUCOCYTES and PLATELETS.... Medical Dictionary

Indian Medicinal Plants

Linn.

Synonym: Pyrethrum indicum L.

Family: Compositae; Asteraceae.

Habitat: Native to China and Japan. Cultivated as an ornamental.

English: Chrysanthemum.

Ayurvedic: Shatapatri.

Unani: Guldaaudi.

Siddha/Tamil: Samanthipoo, Akkarakkaram.

Action: Flowers—stomachic, aperient, anti-inflammatory. Leaves— prescribed in migraine (as circulatory stimulant). Uses same as those of chamomile.

The flowers contain daucosterol, cumambrin-A, glyceryl-l-monobehe- nate and palmitic acid. The flowers also contain chrysanthemol which showed strong anti-inflammatory activity in mice. The flavones, apigenin and lu- teolin, are reported to exhibit marked antitumour activity.

Flowers yield an essential oil containing camphor (16.0%), trans-cara- ne-trans-2-ol (15.0%), bornyl acetate (12.0%) and sabinene (7%).

A related species C. parthenium (Linn.) Berhh., Feverfew, synonym Tanacetum parthenium, used for the management of migraine in Western herbal, is found in Jammu and Kashmir. The plant extracts have a powerful and prostaglandin-independent inhibitory effect on the secretion of granule content by leucocytes and platelets. The inhibition of the agonist-induced serotonins release by platelets could be accounted for the benefit in migraine. The compound responsible for the anti-secretory activity has been identified as sesquiterpene alpha-methylene- gamma-lactone derivatives; partheno- lide being the main constituent of the lactones. (Two fresh or frozen leaves a day are chewed or capsules or pills containing 86 mg of the leaf material is taken for migraine. Fresh leaves may cause mouth sores.)... Indian Medicinal Plants

Medical Dictionary

Coagulation of the blood is the process whereby bleeding (or haemorrhage) is normally arrested in the body. Blood starts to clot as soon as the skin (or other tissue) has been cut. Coagulation is part of the process of HAEMOSTASIS which is the arrest of bleeding from an injured or diseased blood vessel. Haemostasis depends on the combined activities of vascular, platelet (see PLATELETS) and PLASMA elements which are o?set by processes to restrict the accumulation of platelets and FIBRIN to the damaged area.

The three-stage process of coagulation is complex, involving many di?erent substances. There are two cascading pathways of biochemical reactions for activating coagulation of blood. The extrinsic pathway is the main physiological mechanism, which is triggered when blood vessels are damaged, usually by trauma or surgery. The intrinsic pathway is activated by internal disruption of the wall of a blood vessel. The basic pattern is broadly the same for both and is summarised simply as follows:

prothrombin + calcium + thromboplastin

thrombin + ?brinogen

?brin

Prothrombin and calcium are normally present in the blood. Thromboplastin is an enzyme which is normally found in the blood platelets and in tissue cells. When bleeding occurs from a blood vessel, there is always some damage to tissue cells and to the blood platelets. As a result of this damage, thromboplastin is released and comes into contact with the prothrombin and calcium in the blood. In the presence of thromboplastin and calcium, prothrombin is converted into thrombin, which in turn interacts with ?brinogen – a protein always present in the blood – to form ?brin. Fibrin consists of needle-shaped crystals which, with the assistance of the blood platelets, form a ?ne network in which the blood corpuscles become enmeshed. This meshwork, or CLOT as it is known, gradually retracts until it forms a tight mass which, unless the tissue injury is very severe or a major artery has been damaged, prevents any further bleeding. It will thus be seen that clotting, or coagulation, does not occur in the healthy blood vessel because there is no thromboplastin present. There is now evidence suggesting that there is an anti-thrombin substance present in the blood in small amounts, and that this substance antagonises any small amounts of thrombin that may be formed as a result of small amounts of thromboplastin being released.

The clotting or coagulation time is the time taken for blood to clot and can be measured under controlled conditions to ensure that it is normal (3–8 minutes). In certain diseases – HAEMOPHILIA, for example – clotting time is greatly extended and the danger of serious haemorrhage enhanced.... Medical Dictionary

Tropical Medicinal Plants

Coleus spp.

Lamiaceae

The genus Coleus of the family Lamiaceae (Labiatae) comprises a number of herbaceous medicinal plants which are particularly employed in home remedies for various ailments. Three species are most popular and commonly cultivated. They are Coleus aromaticus, C. vettiveroides and C. forkoshlii.

1. Coleus aromaticus Benth. syn. C. amboinicus Lour., Plectranthus amboinicus (Lour.) Spreng.

Eng: Country borage, Indian borage;

San: Karpuravalli, Sugandhavalakam;

Hin: Patharchur;

Ben: Paterchur;

Mal: Panikkurkka, kannikkurkka;

Tam: Karpuravalli;

Kan: karpurahalli;

Tel: Sugandhavalkam.

It is found through out the tropics and cultivated in homestead gardens. It is a large succulent aromatic perennial herb with hispidly villous or tomentose fleshy stem. Leaves are simple, opposite, broadly ovate, crenate and fleshy. Flowers are pale purplish in dense whorls at distant intervals in a long slender raceme. Fruits are orbicular or ovoid nutlets. The leaves are useful in cephalagia, otalgia, anorexia, dyspepsia, flatulence, colic, diarrhoea, cholera, halitosis, convulsions, epilepsy, cough, asthma, hiccough, bronchitis, strangury, hepatopathy and malarial fever (Warrier et al,1995).

2. Coleus vettiveroides K.C. Jacob, syn. Plectranthus vettiveroides (Jacob) Singh & Sharma.

San: Valakam, Hriberam;

Hin: Valak;

Mal: Iruveli;

Tam: Karuver;

Tel: Karuveru,

It is seen in tropical countries and cultivated in gardens. It is a small profusely branched, succulent aromatic herb with quadrangular stems and branches and deep straw coloured aromatic roots. Leaves are glandular hairy, broadly ovate with dentate margins and prominent veins on the bark. Blue flowers are borne on terminal racemes. Fruits are nutlets. The whole plant is useful in hyperdipsia, vitiated conditions of pitta, burning sensation, strangury, leprosy, skin diseases, leucoderma, fever, vomiting, diarrhoea, ulcers and as hair tonic.

3. Coleus forskohlii Briq. syn. C. barbatus Benth.

Hin: Garmai

Kan: Maganiberu, Makandiberu

Guj: Maimul

It is a perennial aromatic herb grown under tropical to temperate conditions for its carrot-like tubers which are used as condiments in the preparation of pickles. Its tuberous roots are an exclusive source of a diterpenoid forskolin which has the unique property of activating almost all hormone sensitive adenylate cyclase enzymes in a biological system. It is useful in the treatment of congestive heart failure, glaucoma, asthma, cancer and in preventing immature greying of hair (Hegde,1997).

Agrotechnology: The Coleus group of plants grows in tropical to subtropical situations and in warm temperate climatic zone on mountains of India, Nepal, Burma, Sri Lanka, Thailand and Africa. It comes up well on the sun exposed dry hill slopes from 300m to 1800m altitude. A well drained medium fertile soil is suitable for its cultivation. it is propagated vegetatively through stem and root cuttings. Vine cuttings to a length of 10-15cm from the top portion are most ideal for planting. The land is ploughed or dug to a depth of 15-20cm and ridges are formed 30cm apart. Vine cuttings are planted on the ridges at 30cm spacing after incorporating basal manure. 10t of FYM and NPK at 50:50:50kg/ha are incorporated into the soil. Top dressing of N and K is also suggested for improved yields. Weeding and earthing up at 45 days after planting along with topdressing is highly beneficial. Bacterial wilt and root knot nematode are reported in the crop. Drenching the soil with fungicide, deep ploughing in the summer, burning of crop residues and crop rotation are helpful to tide over the disease and pest problem. The crop can be harvested after 5-6 months.

Properties and activity: The medicinal property of Coleus amboinicus is attributed to codeine, carvacrol, flavones, aromatic acids and tannins present in the plant. The essential oil from the plant contains carvacrol, ethyl salicylate, thymol, eugenol and chavicol. Leaves also contain cirsimaritin, -sitosterol- -D-glucoside and oxalacetic acid. Leaves are bitter, acrid, thermogenic, aromatic, anodyne, appetising, digestive, carminative, stomachic, anthelmintic, constipating, deodorant, expectorant, diuretic and liver tonic.

Coleus vettiveroides is bitter, cooling, diuretic, trichogenous and antipyretic.

Coleus forskohlii roots are rich in diterpenoids like forskolin, coleonols, coleons, barbatusin, cyclobutatusin, coleosol, coleol, coleonone, deoxycoleonol, 7-deacetylforskolin and 6-acetyl-7-deacetylforskolin. Its root is spasmolytic, CNS active, hypothermic and diuretic. Forskolin is bronchodialative and hypotensive (Hussain et al,1992). Forskolin is also useful in preventing the clotting of blood platelets, in reducing intraocular pressure in glaucoma and as an aid to nerve regeneration following trauma (Sharma, 1998)... Tropical Medicinal Plants

Medical Dictionary

An antiplatelet drug, best given under the supervision of a specialist. It inhibits the aggregation of PLATELETS in the blood that occurs in THROMBUS formation, and is used with HEPARIN and ASPIRIN to prevent early myocardial infarction (heart attack – see HEART, DISEASES OF) in patients with unstable ANGINA PECTORIS.... Medical Dictionary

Medical Dictionary

The formation of blood cells and PLATELETS – a continuous process throughout life. As ageing cells are removed from the circulation, new ones, generated in the BONE MARROW, replace them.... Medical Dictionary

Herbal Medical

The defense substance responsible for most inflammation. It is synthesized from the amino acid histidine and is secreted by mast cells, basophils, and blood platelets. It stimulates vasodilation, capillary permeability, muscle contraction of the bronchioles, secretions of a number of glands, and attracts eosinophils, the white blood cells that are capable of moderating the inflammation. Mast cell histamine release is what usually causes allergies.... Herbal Medical

Medical Dictionary

Sometimes described as thrombocytopenia, this is an autoimmune disorder in which blood PLATELETS are destroyed. This disturbs the blood’s coagulative properties (see COAGULATION) and spontaneous bleeding (PURPURA) occurs into the skin. The disease may be acute in children but most recover without treatment. Adults may develop a more serious, chronic variety which requires treatment with CORTICOSTEROIDS and sometimes SPLENECTOMY. Should the disease persist despite these treatments, intravenous immunoglobulin or immunosuppressive drugs (see IMMUNOSUPPRESSION) are worth trying. Should the bleeding be or become life-threatening, concentrates of platelets should be administered.... Medical Dictionary

Medicinal Plants Glossary

Leukaemia is an umbrella term for several malignant disorders of white blood cells in which they proliferate in a disorganised manner. The disease is also characterised by enlargement of the SPLEEN, changes in the BONE MARROW, and by enlargement of the LYMPH glands all over the body. The condition may be either acute or chronic.

According to the type of cells that predominate, leukaemia may be classi?ed as acute or chronic lymphoblastic leukaemia or myeloid leukaemia. Acute lymphoblastic leukaemia (ALL) is mostly a disease of childhood and is rare after the age of 25. Acute myeloid leukaemia is most common in children and young adults, but may occur at any age. Chronic lymphatic leukaemia occurs at any age between 35 and 80, most commonly in the 60s, and is twice as common in men as in women. Chronic myeloid leukaemia is rare before the age of 25, and most common between the ages of 30 and 65; men and women are equally a?ected. Around 2,500 patients with acute leukaemia are diagnosed in the United Kingdom, with a similar number annually diagnosed with chronic leukaemia.

Cause Both types of acute leukaemia seem to arise from a MUTATION in a single white cell. The genetically changed cell then goes through an uncontrolled succession of divisions resulting in many millions of abnormal white cells in the blood, bone marrow and other tissues. Possible causes are virus infection, chemical exposure, radiation and genetic background. The cause of chronic lymphocytic leukaemia is not known; the chronic myeloid version may have a genetic background.

Symptoms In acute cases the patient is pale due to anaemia, may have a purpuric rash due to lack of platelets, and may have enlarged lymphatic glands and spleen. The temperature is raised, and the condition may be mistaken for an acute infection (or may ?rst become apparent because the patient develops a severe infection due to a lack of normal white blood cells).

In the chronic type of the disease the onset is gradual, and the ?rst symptoms which occasion discomfort are either swelling of the abdomen and shortness of breath, due to painless enlargement of the spleen; or the enlargement of glands in the neck, armpits and elsewhere; or the pallor, palpitation, and other symptoms of anaemia which often accompany leukaemia. Occasional bleeding from the nose, stomach, gums or bowels may occur, and may be severe. Generally, there is a slight fever.

When the blood is examined microscopically, not only is there an enormous increase in the number of white cells, which may be multiplied 30- or 60-fold, but various immature forms are also found. In the lymphatic form of the disease, most white cells resemble lymphocytes, which, in healthy blood, are present only in small numbers. In the myeloid form, myelocytes, or large immature cells from the bone marrow, which are never present in healthy blood, appear in large numbers, and there may also be large numbers of immature, nucleated erythrocytes.

Treatment This varies according to the type of leukaemia and to the particular condition of the patient. Excellent results are being obtained in the control of ALL using blood transfusions, CHEMOTHERAPY, RADIOTHERAPY and bone-marrow TRANSPLANTATION. In the case of acute leukaemia, the drugs now being used include MERCAPTOPURINE, METHOTREXATE and CYCLOPHOSPHAMIDE. Blood transfusion and CORTICOSTEROIDS play an important part in controlling the condition during the period before a response to chemotherapy can be expected. Chemotherapy has almost completely replaced radiotherapy in the treatment of chronic leukaemia. For the myeloid form, BUSULFAN is the most widely used drug, replaced by hydroxyurea, mercaptopurine, or one of the nitrogen mustard (see NITROGEN MUSTARDS) derivatives in the later stages of the disease. For the lymphatic form, the drugs used are CHLORAMBUCIL, CYCLOPHOSPHAMIDE, and the nitrogen mustard derivatives.

Prognosis Although there is still no guaranteed cure, the outlook in both acute and chronic leukaemia has greatly improved – particularly for the acute form of the disease. Between 70 and 80 per cent of children with acute lymphoblastic leukaemia may be cured; between 20 and 50 per cent of those with acute myeloid leukaemia now have much-improved survival rates. Prognosis of patients with chronic lymphocytic leukaemia is often good, depending on early diagnosis.... Medicinal Plants Glossary

Medical Dictionary

A fall in the number of red ERYTHROCYTES and white LEUCOCYTES, as well as of platelets (see BLOOD – Composition). The condition is found in aplastic ANAEMIA, tumours of the BONE MARROW, enlarged SPLEEN, and other disorders.... Medical Dictionary

Herbal Medical

Platelets are the small, rather uniform fragments of large bone marrow cells that aid the blood in coagulation, hemostasis, inflammation, and thrombus formation. Mild subclotting and sticking is a common early condition that can lead to thrombosis, atherosclerosis, and strokes, and can be helped by an aspirin a day, better fat digestion, and Ceanothus.... Herbal Medical

Medical Dictionary

A rise in the amount of HAEMOGLOBIN in the blood. This may be caused by an excess in the number of ERYTHROCYTES produced in the BONE MARROW or to a fall in the total volume of PLASMA in the circulatory system. It may also be a response to reduced oxygen levels – for example, among people living at high altitudes – or to liver or kidney disease: this type is called secondary polycythaemia.

The disorder may, however, occur for no obvious reason and is then called polycythaemia vera. This type develops mainly in people over 40 and about 400 people develop the disorder every year in the United Kingdom. The blood thickens, the su?erer may develop high blood pressure, ?ushing, headaches, itching and an enlarged spleen. A stroke may occur later in the disease process. Treatment of polycythaemia vera is by regular removal of blood by VENESECTION, sometimes in combination with an anticancer drug. Secondary polycythaemia is treated by remedying the underlying cause.

Polycythaemia rubra vera A disorder in which the red blood cells increase in number along with an increase in the number of white blood cells and platelets. The cause is unknown. Severe cases may require treatment with CYTOTOXIC drugs or RADIOTHERAPY.... Medical Dictionary

Medical Dictionary

A prostaglandin (see PROSTAGLANDINS) produced by the endothelial lining of the blood vessels. It inhibits the aggregation of PLATELETS, and thereby reduces the likelihood of the blood clotting. It is also a strong vasodilator (see VASODILATORS).... Medical Dictionary

Medical Dictionary

A skin rash caused by bleeding into the skin from capillary blood vessels. The discrete purple spots of the rash are called purpuric spots or, if very small, petechiae. The disorder may be caused by capillary defects (nonthrombocytopenic purpura) or be due to a de?ciency of PLATELETS in the blood (thrombocytopenic purpura). Most worryingly, the rash may be due to a fulminant form of meningococcal SEPTICAEMIA called purpura fulminans. (See also HENOCH-SCHÖNLEIN PURPURA; IDIOPATHIC THROMBOCYTOPENIC PURPURA (ITP); THROMBOCYTOPENIA.).... Medical Dictionary

Medical Dictionary

Also known as 5-hydroxytryptamine, this is a substance widely distributed in the body tissue, but especially in the PLATELETS in the blood, the lining of the gastrointestinal tract, and the BRAIN. Serotonin is believed to have a similar function to that of HISTAMINE in INFLAMMATION. In the gut it inhibits gastric secretion and stimulates smooth (involuntary) muscle in the walls of the INTESTINE. Serotonin participates in the transmission of nerve impulses and may have a function in controlling mood and states of consciousness. (See also SELECTIVE SEROTONIN-REUPTAKE INHIBITORS (SSRIS).)... Medical Dictionary

Medical Dictionary

The ?uid which separates from blood, LYMPH, and other body ?uids when clotting occurs (see COAGULATION; HAEMORRHAGE). PLASMA is the ?uid of the blood, including FIBRIN, which carries the circulating blood cells and PLATELETS.

Serum is a clear, yellowish ?uid containing around 7 per cent proteins and globulins, small quantities of salts, fat, sugar, urea, and uric acid, and even smaller quantities of immunoglobulins, essential in the prevention of disease (see IMMUNITY; IMMUNOLOGY). The serum given in the commonly used vaccines is generally derived from horses’ blood, after they have been subjected to a long course of treatment.... Medical Dictionary

Medical Dictionary

An organ deeply placed in the abdomen and a major constituent of the RETICULOENDOTHELIAL SYSTEM.

Position and size The spleen lies behind the stomach, high up on the left side of the abdomen, and corresponds to the position of the ninth, tenth and 11th ribs, from which it is separated by the diaphragm. It is a soft, highly vascular, plum-coloured organ, and has a smooth surface. It is usually about 12·5–15 cm (5–6 inches) in length, and weighs about 170 grams or more. In diseased conditions the organ may reach a weight of 8–9 kg.

Structure The spleen is enveloped by peritoneal membrane beneath which is a strong elastic tunic, composed partly of ?brous tissue

containing many elastic ?bres, and partly of unstriped muscle. This elastic coat allows of the free expansion and contraction of the organ according to the varying amount of blood present in it. From the inner surface of the membrane, ?brous partitions known as trabeculae run down into the substance and form a network in which the dark spleen pulp is contained. The pulp consists of delicate connective-tissue ?bres passing between the various trabeculae, and of white and red blood cells lying in this meshwork. The spleen is very vascular and venous blood leaves by the splenic vein and then enters the portal vein from the liver. There are also numerous lymphatics in the organ, which run in the trabeculae or surround the veins.

Functions The organ produces lymphocytes (see LYMPHOCYTE) and acts as a reservoir of red blood cells for use in emergencies. It is also one of the sites for the manufacture of red blood cells in the fetus, but not after birth. Useless or worn-out red and white blood cells and blood PLATELETS are broken up by this organ. This results in the production of BILIRUBIN, which is conveyed to the liver, and of iron, which is used in the bone marrow for the production of new red blood cells.... Medical Dictionary

Medical Dictionary

For practical purposes a term interchangeable with splenitis, since neither will have the usual symptoms associated with inflammation. Splenomegaly is often associated with viral hepatitis, mononucleosis, typhoid fever and abnormally high levels of red blood cells or platelets.... Medical Dictionary

Medical Dictionary

Stroke, or cerebrovascular accident (CVA), is sudden damage to BRAIN tissue caused either by a lack of blood supply or rupture of a blood vessel (see ISCHAEMIC STROKE). The a?ected brain cells die and the parts of the body they control or receive sensory messages from cease to function.

Causes Blood supply to the brain may be interrupted by arteries furring up with ATHEROSCLEROSIS (which is accelerated by HYPERTENSION and DIABETES MELLITUS, both of which are associated with a higher incidence of strokes) or being occluded by blood clots arising from distant organs such as infected heart valves or larger clots in the heart (see BLOOD CLOT; THROMBOSIS). Hearts with an irregular rhythm are especially prone to develop clots. Patients with thick or viscous blood, clotting disorders or those with in?amed arteries – for example, in SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) – are particularly in danger of having strokes. Bleeding into the brain arises from areas of weakened blood vessels, many of which may be congenital.

Symptoms Minor episodes due to temporary lack of blood supply and oxygen (called TRANSIENT ISCHAEMIC ATTACKS OR EPISODES (TIA, TIE)) are manifested by short-lived weakness or numbness in an arm or leg and may precede a major stroke. Strokes cause sudden weakness or complete paralysis of the muscles controlled by the part of the brain a?ected, as well as sensory changes (e.g. numbness or tingling). In the worst cases these symptoms and signs may be accompanied by loss of consciousness. If the stroke a?ects the area of the brain controlling the larynx and throat, the patient may su?er slurring or loss of speech with di?culty in initiating swallowing. When the face is involved, the mouth may droop and the patient dribble. Strokes caused by haemorrhage may be preceded by headaches. Rarely, CVAs are complicated by epileptic ?ts (see EPILEPSY). If, on the other hand, numerous small clots develop in the brain rather than one major event, this may manifest itself as a gradual deterioration in the patient’s mental function, leading to DEMENTIA.

Investigations Tests on the heart or COMPUTED TOMOGRAPHY or ultrasonic scans (see ULTRASOUND) on arteries in the neck may indicate the original sites of distantly arising clots. Blood tests may show increased thickness or tendency to clotting, and the diagnosis of general medical conditions can explain the presence of in?amed arteries which are prone to block. Special brain X-rays show the position and size of the damaged brain tissue and can usually distinguish between a clot or infarct and a rupture of and haemorrhage from a blood vessel in the brain.

Management It is better to prevent a stroke than try to cure it. The control of a person’s diabetes or high blood pressure will reduce the risk of a stroke. Treatment with ANTICOAGULANTS prevents the formation of clots; regular small doses of aspirin stop platelets clumping together to form plugs in blood vessels. Both treatments reduce the likelihood of minor transient ischaemic episodes proceeding to a major stroke.

Once the latter has occurred, there is no e?ective treatment to reduce the damage to brain tissue. Function will return to the a?ected part of the body only if and when the brain recovers and messages are again sent down the appropriate nerves. Simple movements are more likely to recover than delicate ones, and sophisticated functions have the worst outlook. Thus, movement of the thigh may improve more easily than ?ne movements of ?ngers, and any speech impairment is more likely to be permanent. A rehabilitation team can help to compensate for any disabilities the subject may have. Physiotherapists maintain muscle tone and joint ?exibility, whilst waiting for power to return; occupational therapists advise about functional problems and supply equipment to help patients overcome their disabilities; and speech therapists help with di?culties in swallowing, improve the clarity of remaining speech or o?er alternative methods of communication. District nurses or home helps can provide support to those caring for victims of stroke at home. Advice about strokes may be obtained from the Stroke Association.... Medical Dictionary

Medical Dictionary

See PLATELETS.... Medical Dictionary

Medical Dictionary

A fall in the number of PLATELETS (thrombocytes) in the blood caused by failure of production or excessive destruction of platelets. The result is bleeding into the skin (PURPURA), serious bleeding after injury and spontaneous bruising. (See also IDIOPATHIC THROMBOCYTOPENIC PURPURA (ITP).)... Medical Dictionary

Medical Dictionary

The formation of a BLOOD CLOT within the vessels or heart during life. The process of clotting within the body depends upon the same factors as that of clotting of blood outside the body, involving the ?brinogen and calcium salts circulating in the blood, as well as blood PLATELETS. The indirect cause of thrombosis is usually some damage to the smooth lining of the blood vessels brought about by in?ammation, or the result of ATHEROMA, a chronic disease of the vessel walls. The blood is also specially prone to clot in certain general conditions such as ANAEMIA, the ill-health of wasting diseases like cancer, and in consequence of the poor circulation of old age.

Thrombosis may occur in the vessels of the brain and thus causes STROKE in people whose arteries are much diseased.

Thrombosis of a coronary artery of the heart is a very serious condition which a?ects, as a rule, middle-aged or elderly people.

(See also ARTERIES, DISEASES OF; COAGULATION; HEART, DISEASES OF – Coronary thrombosis; VEINS, DISEASES OF.)... Medical Dictionary

Medical Dictionary

A substance produced in the blood PLATELETS which induces aggregation of platelets and thereby THROMBOSIS. It is also a vasoconstrictor (a substance that causes the constriction of blood vessels).... Medical Dictionary

Medical Dictionary

A recently introduced antiplatelet drug, which decreases clumping of blood PLATELETS and thus inhibits the formation of clots (see BLOOD CLOT; THROMBUS). It is used to prevent episodes in patients with a history of symptomatic ischaemic disease such as STROKE and INTERMITTENT CLAUDICATION. The drug should be started under hospital supervision.... Medical Dictionary

Medical Dictionary

The administration of any ?uid into a person’s vein using a drip. This apparatus facilitates a continuous injection in which the ?uid ?ows by force of gravity from a suspended bottle, via a tube that is ?xed to a hollow needle inserted into a vein (usually in the front of the elbow). Saline solution, PLASMA and whole BLOOD (see below) are the most commonly administered ?uids. Saline is used to restore ?uid to a seriously dehydrated individual (see DEHYDRATION) and may be used as a temporary measure in SHOCK due to blood loss while the appropriate type of blood is being obtained for transfusion. Saline may also be useful as a way of administering a regular supply of a drug over a period of time. Plasma is normally used as a temporary measure in the treatment of shock until appropriately matched blood is available or if for any reason, such as for a patient with severe burns, plasma is preferable to blood.

Transfusion of blood is a technique that has been used since the 17th century – although, until the 20th century, with a subsequent high mortality rate. It was only when incompatibility of BLOOD GROUPS was considered as a potential cause of this high mortality that routine blood-testing became standard practice. Since the National Blood Transfusion Service was started in the United Kingdom (in 1946), blood for transfusion has been collected from voluntary, unpaid donors: this is screened for infections such as SYPHILIS, HIV, HEPATITIS and nvCJD (see CREUTZFELDT-JAKOB DISEASE (CJD)), sorted by group, and stored in blood-banks throughout the country.

In the UK in 2004, the National Blood Authority – today’s transfusion service – announced that it would no longer accept donations from anyone who had received a blood transfusion since 1980 – because of the remote possibility that they might have been infected with the PRION which causes nvCJD.

A standard transfusion bottle has been developed, and whole blood may be stored at 2–6 °C for three weeks before use. Transfusions may then be given of whole blood, plasma, blood cells, or PLATELETS, as appropriate. Stored in the dried form at 4–21 °C, away from direct sunlight, human plasma is stable for ?ve years and is easily reconstituted by adding sterile distilled water.

The National Blood Authority prepares several components from each donated unit of blood: whole blood is rarely used in adults. This permits each product, whether plasma or various red-cell concentrates, to be stored under ideal conditions and used in appropriate clinical circumstances – say, to restore blood loss or to treat haemostatic disorders.

Transfusion of blood products can cause complications. Around 5 per cent of transfused patients su?er from a reaction; most are mild, but they can be severe and occasionally fatal. It can be di?cult to distinguish a transfusion reaction from symptoms of the condition being treated, but the safe course is to stop the transfusion and start appropriate investigation.

In the developed world, clinicians can expect to have access to high-quality blood products, with the responsibility of providing blood resting with a specially organised transfusion service. The cause of most fatal haemolytic transfusion reactions is a clerical error due to faulty labelling and/or failure to identify the recipient correctly. Hospitals should have a strict protocol to prevent such errors.

Arti?cial blood Transfusion with blood from donors is facing increasing problems. Demand is rising; suitable blood donors are becoming harder to attract; the processes of taking, storing and cross-matching donor blood are time-consuming and expensive; the shelf-life is six weeks; and the risk of adverse reactions or infection from transfused blood, although small, is always present. Arti?cial blood would largely overcome these drawbacks. Several companies in North America are now preparing this: one product uses puri?ed HAEMOGLOBIN from humans and another from cows. These provide oxygen-carrying capacity, are unlikely to be infectious and do not provoke immunological rejections. Yet another product, called Oxygene®, does not contain any animal or human blood products; it comprises salt water and a substance called per?ubron, the molecules of which store oxygen and absorb carbon dioxide more e?ectively than does haemoglobin. Within 24 hours of being transfused into a person’s bloodstream, per?ubron evaporates and is harmlessly breathed out by the recipient. Arti?cial blood is especially valuable in that it contains no unwanted proteins that can provoke adverse immunological reactions. Furthermore, it is disease-free, lasts for up to three years and is no more expensive than donor blood. It could well take the place of donor blood within a few years.

Autologous transfusion is the use of an individual’s own blood, provided in advance, for transfusion during or after a surgical operation. This is a valuable procedure for operations that may require large transfusions or where a person has a rare blood group. Its use has increased for several reasons:

fear of infection such as HIV and hepatitis.

shortages of donor blood and the rising cost of units of blood.

substantial reduction of risk of incompatible transfusions. In practice, blood transfusion in the UK is

remarkably safe, but there is always room for improvement. So, in the 1990s, a UK inquiry on the Serious Hazards of Transfusion (SHOT) was launched. It established (1998) that of 169 recently reported serious hazards following blood transfusion, 81 had involved a blood component being given to the wrong patient, while only eight were the result of viral or bacterial infections.

There are three ways to use a patient’s own blood in transfusion:

(1) predeposit autologous donation (PAD) – taking blood from a patient before operation and transfusing this blood back into the patient as required during and after operation.

(2) acute normovalaemic haemodilution (ANH) – diluting previously withdrawn blood and thus increasing the volume before transfusion.

(3) perioperative cell salvage (PCS) – the use of centrifugal cell separation on blood saved during an operation, particularly spinal surgery where blood loss may be considerable.

The government has urged NHS trusts to consider the introduction of PCS as a possible adjunct or alternative to banked-blood transfusion. In one centre (Nottingham), PCS has been used in the form of continuous autologous transfusion for several years with success.

Exchange transfusion is the method of treatment in severe cases of HAEMOLYTIC DISEASE OF THE NEWBORN. It consists of replacing the whole of the baby’s blood with Rh-negative blood of the correct blood group for the baby.... Medical Dictionary

Medical Dictionary

Episodes of transient ISCHAEMIA of some part of the cerebral hemispheres or the brain stem (see BRAIN) lasting anything from a few minutes to several hours and followed by complete recovery. By de?nition, the ischaemic episode must be less than 24 hours. These episodes may be isolated or they may occur several times in a day. The cause is ATHEROMA of the carotid or vertebral arteries (see ARTERIES, DISEASES OF) and the embolisation (see EMBOLISM) of PLATELETS or CHOLESTEROL. These attacks present with strokes (see STROKE) that rapidly recover.... Medical Dictionary

Indian Medicinal Plants

Lam. (in part)

Family: Violaceae.

Habitat: Kashmir at 1,200-2,400 m.

English: Pale Wood Violet, Wood Violet.

Unani: Banafashaa (related species).

Action: Plant—pectoral, bechic; used in chest troubles. Stem, leaf and flower—applied to foul sores and wounds.

Habitat: Native to Europe; grown as an ornamental.

English: Heartsease, Wild Pansy.

Unani: Banafashaa (related species).

Action: Herb—anti-inflammatory, antiallergic, expectorant, diuretic, antirheumatic, alterative. Used for bronchitis, rheumatism, chronic skin disorders and for preventing capillary haemorrhage when under corticosteroid therapy. Root— antidysenteric; used as a substitute for Cephaelis ipecacuanha.

Key application: Externally in mild seborrheic skin diseases and milk scall in children. (German Commission E.) The British Herbal Pharmacopoeia recognizes the herb as an expectorant and dermatological agent.

The herb contains rutin, violin and salicylic acid. The flower contains rutin, quercetin, violanthin (6,8-digly- coside of apigenin), violaxanthin, p- hydroxycinnamic acid and delphini- din. A flavone C-glycoside-saponarin has also been obtained from flowers. Flowers, in addition, contain 15-cis- violaxanthin.

The herb exhibits anticoagulant property and diminishes the aggregation of platelets. It can be used as a preventive measure against thrombosis.

Habitat: Temperate Himalayas from Kashmir to Nepal between 1,200 and 2,700 m (a semiparasitic plant).

English: European Mistletoe.

Ayurvedic: Bandaaka, Suvarna- bandaaka. Vrikshaadani (substitute).

Unani: Kishmish Kaabuli.

Action: Vasodilator, cardiac depressant, tranquiliser, stimulates the vagus nerve which slows the pulse, anti-inflammatory, diuretic, immune enhancer, antineoplas- tic. Used for hypertension and tachycardia, as a nervine tonic.

The extract of leafy twigs is anti- inflammatory exerting an action upon capillary permeability and oedema. It stimulates granulation and the neoformation of connective tissue.

Key application: For treating degenerative inflammation of the joints by stimulating cuti- visceral reflexes following local inflammation brought about by intradermal injections; as palliative therapy for malignant tumour through non-specific stimulation. (German Commission E.)

Mistletoe contains glycoproteins; flavonoids, usually quercetin-derived (dependent on host tree to some extent); polypeptides; phenylcarboxylic acids; polysaccharides (including viscid acid); alkaloids; lignans.

Cardiotonic activity is due to the lig- nans. The polysaccharides stimulate the immune response. Antineoplas- tic activity is claimed to be responsible for prolongation of survival time in cancer patients. Polypeptides (visco- toxins) inhibit tumours and stimulate immune resistance. (For uses of lectin from Mistletoe in cancer, see Eur J cancer, 2001, Jan, 37(1), 23-31; Eur J Cancer 2001, 37 (15), 19101920.) (For application in hepatitis, see Fitoterapia, 70, 2001.)... Indian Medicinal Plants