Starting with A for "ACE inhibitor" and continuing through to Y for "Yolk Sac Tumour", we give you succinct explanations for scientific and medical terms in clear and simple words.
- Radiationsee Radiotherapy.
- RadiationParticularly X-radiation; see radiotherapy.
- RadiologyScience and discipline of the medical use of certain sorts of radiation in diagnosis and treatment. Diagnostic radiology is a broad expression which includes X-ray diagnosis and other imaging techniques, such as ultrasound diagnosis and nuclear spin tomography.
- RadiotherapyIn the restricted sense this is the use of specific radiation (ionising radiation) for the treatment of malignant (rarely benign) tumours. Radiotherapy can either be used to cure the disease or to stop its progression. Radiotherapy can be used alone or in combination with surgery or chemotherapy. The aim is to maximise the damage to the tumour tissue with the radiation, while sparing the surrounding healthy tissue to the maximum extent. For this to be possible, either the tumour must be more sensitive to the radiation than the surrounding tissue or the dose of radiation is deliberatively made greater in the area of the tumour. Possible approaches include the choice of radiation with a suitable wavelength for it to be able to penetrate properly or the introduction of radiation sources into the body. Either high energy electromagnetic waves are used, such as UV-, X- or gamma-radiation, or corpuscular radiation, such as helium nuclei (alpha-rays), electrons (beta-rays), protons or neutrons.
In a less restricted sense, radiotherapy means any use of electromagnetic radiation for therapeutic purposes, for example, microwaves, infrared radiation, visible light.
- Randle cyclealso known as the glucose fatty acid cycle
Mutual influence of the metabolism of free fatty acids and glucose. This results in both inhibition of the release of fatty acids by high blood glucose concentrations (e.g. after a meal) and inhibition of glucose metabolism by high concentrations of free fatty acids.
- ReagentTest substance; Substance which makes the presence of another substance recognisable by its chemical effect.
- ReceptorsThe system in an organism to detect or receive specific stimulation; !. Cells with specific structures to detect stimulation (the so-called sensory cells), e.g. mechanoreceptors (touch sensitive) and pressoreceptors (pressure), thermoreceptors (sensitive to warmth or cold), photoreceptors (in the retina of the eye to sense light), chemoreceptors (smell, taste, regulation of body functions such as breathing) and osmoreceptors (water balance); 2. Receptors in the cell or on the cell membrane to receive specific signals which are mediated by nerve transmitters, hormones, antibodies, antigens or drugs.
- Recklinghausen-Applebaum diseasesee osteodystrophia fibrosa generalisata
- recombinant DNA technologytechniques by which genetic material from one organism is inserted into a foreign cell in order to mass produce the protein encoded by the inserted genes; also referred to as genetic engineering
- RecombinationFormation of a new gene combination from genetically different genomes (total genetic material in a cell or organisms).
- Rectal CarcinomaSee Colorectal Carcinoma.
- red blood cell indicestests that provide information about the size, weight and hemoglobin concentration of red blood cells (corpuscles); indices include mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC); these tests are useful in diagnosing and classifying the different types of anemia
- Reduction dietDiet to reduce weight; cf. overweight. A reduction diet consumes more energy than is added. The energy added depends on the degree of overweight and the activity of the overweight person. Food which is rich in fat or sugar and alcohol must be reduced. Fruit, vegetables, wholemeal, mineral water and tea should be favoured.
- registration triala study used to support the regulatory approval of a drug
- Regulation of blood pressureComplex system in the body to regulate and adjust arterial blood pressure. Acute changes, such as when the body is no longer horizontal but vertical, are detected by the so-called pressoreceptors in the wall of the aorta and jugular arteries (see receptors), which are activated by stretching of the vessel wall. The information is then transmitted to circulation centres in the extended spinal column. If the measured pressure deviates from the target value, these centres influence the tension of the resistance vessels, the heart rate and the strength of contraction through nervous impulses, so that the arterial pressure is appropriately adjusted by changes in the peripheral resistance and cardiac output per minute. Other regulatory mechanisms, such as the renin-angiotensin-aldosterone system are superimposed on this.
- Regulations for VisitorsSome countries have regulations, such as inoculations, for visitors, before they are allowed to enter. For some diseases there are severe restrictions on travel. For example, certain countries forbid HIV-infected individuals from entering. Short term entry as a tourist is usually possible, although a medical certificate can be demanded for a longer term stay and HIV-positive individuals are not given a visa (e.g. Argentine, China, Russia, Cyprus).
- RelapseAlso recurrence.
Recurrence of a disease after an apparent cure; e.g. recurrence of an infection (re-infection), recurrence of a tumour (tumour of the same sort recurs at the same site or in the same organ after previous radical treatment).Cf. Late Relapse.
- renalrelating to the kidney
- renal anemiaAnemia is a frequent complication in patients with chronic kidney disease, which gains in importance in the treatment of patients with renal disease. The main cause of renal anemia is the inadequately low production of endogenous erythropoietin. Often the patients develop an additional absolute or functional iron deficiency, which complicates the diagnostic and therapeutic procedures. Substitution of recombinant human erythropoietin (r-HuEPO) is the most effective therapy. The goal is a stable hemoglobin level >11 g/dl. An often additional existing iron deficiency should be balanced adequately according to the guidelines. With resolute and early treatment, morbidity, mortality and quality of life can be effectively improved.
- Renal arterial stenosisNarrowing of one or both kidney arteries (Arteriae renales). Chronically poor perfusion leads to sclerotic kidneys and renal underfunction or false function and to release of renin, with resulting high blood pressure (hypertension).
1. Arteriosclerotic renal stenosis (cf. arteriosclerosis): occurs most frequently in the fifth and sixth decades of life; isolated narrowing of the exit of the artery with widening behind this. 2. Fibromuscular renal arterial stenosis (with proliferation of muscular tissue and connective tissue in the arterial wall): occurs particularly in women in their third decade.
Widening of the narrowed renal arteries, mostly with the balloon catheter (angioplasty) or introduction of an aortorenal bypass by vascular surgery.
- renal artery stenosisnarrowing of the artery supplying blood to the kidneys; complications of renal artery stenosis include hypertension
- Renal CarcinomaAlso Renal Cell Carcinoma, Hypernephroid Carcinoma, Hypernephroma, Grawitz Tumour.
Malignant tumour of the kidneys which most often occurs between 45 and 75 years of age and particularly in men (men : women 2:1). Metastases may occur in the lungs, skeleton, brain, the other kidney, the adrenals or in the lymph nodes.
Symptoms: Blood in the urine, anaemia, fever, possibly pain in the kidneys, sensitivity to pressure round the kidneys, swelling in the area of the kidneys, loss of weight.
Diagnosis: Ultrasound investigation of the kidney, X-ray investigation of the urinary organs (kidney, renal pelvis, urethra, bladder, ureter), computer tomography, X-ray investigation of the blood vessels in the kidney by renovasography, other investigations to look for metastases (X-ray investigation of bones and lungs).
Therapy: Removal of the kidney and neighbouring lymph nodes by operation, possibly in combination with radiotherapy or treatment with interleukin-2.
Prognosis: Dependent on tumour stage. If there are no metastases, the 5-year survival rate is about 50%.
- renal cell carcinomathe most common type of kidney cancer; a malignant tumour that originates in the epithelial cells of the kidney
- renal corpusclepart of a nephron that consists of the glomerulus and Bowmans capsule
- Renal dysfunctionRenal dysfunction indicative of renal failure:
Severe renal dysfunction with retention of substances normally excreted in the urine, altered fluid and electrolyte balance, and altered acid-base balance. Global renal failure always involves a decrease in the glomerular filtration rate and – depending on the cause – impairment of tubule function. In partial renal failure (a partial reduction in renal function), substances normally excreted in the urine are not retained, despite some loss of tubule function.
- Renal embolismPartial or total occlusion of one or both renal arteries
Embolism, particularly from thrombosis in the heart (when there is inflammation of the inner surface of the heart or atrial fibrillation) or from the aorta in arteriosclerosis. May also be caused by the activity of the physician, e.g. angiography (X-ray imaging with contrast medium) or angioplasty (stretching the vessel with a balloon catheter).
Pain round the kidneys or abdomen, acute increase in blood pressure, blood in urine and increased urinary excretion of albumin. The kidney is irreversibly damaged within a few hours if the arterial occlusion is total.
Dissolution of the blood clot by drug action (fibrinolysis)
- Renal hypertensionHigh blood pressure (hypertension) caused by disease to the kidneys or renal arteries (particularly stenosis of the renal arteries)
- renal osteodystrophybone disease that results from mineral and hormonal abnormalities associated with chronic kidney disease
- renal replacement therapydialysis or kidney transplantation used to compensate for the loss of kidney function in kidney failure; also referred to as kidney replacement therapy
- renal sarcomaa rare type of malignant tumour (accounting for less than 1% of kidney tumours) that arises in the connective tissue of the kidney and spreads by extension into neighbouring tissue or by way of the bloodstream
- Renal thresholdMaximal capacity of the kidney to reabsorb a substance into the blood stream after initial filtration. If the concentration in the blood is above a certain level, it is excreted in the urine, as it cannot be reabsorbed. The renal threshold is the blood concentration corresponding to the maximum tubular transport and at which a substance is detectable in final urine. The renal threshold is, for example, 10 mmol/l or 180 mg/dl for glucose and 25 mmol/l for bicarbonate. Cf. glucosuria, glucose threshold.
- renal tubulepart of a nephron that protrudes from the renal corpuscle
- Renal TumoursBenign or malignant tumours of the kidney.
The following forms are distinguished:
Benign tumours: Tumours of connective tissue or of some glands; rare
Malignant tumours: a) Renal carcinoma; most frequent renal tumour in adults (about 85% of renal tumours) ; b) Wilms Tumour, most frequent renal tumour in children ; c) Metastases from malignant tumours in other organs, e.g. lung cancer, colon cancer (Carcinoma, colorectal).
Symptoms: Blood in the urine.
- ReninThis is an enzyme which is mostly formed in the kidney and which is released in low concentrations into the blood and lymph. Apart from the kidney, renin is also formed in the womb, liver and vessel walls. In various kidney diseases there is an increased concentration of renin in blood plasma and this is important in hypertension which is caused by disturbed renal function.
In plasma renin splits angiotensinogen, giving angiotensin I. This is then converted by angiotensin converting enzyme to angiotensin II, which raises blood pressure ( cf. renin-angiotensin-aldosterone system).
Renin release is stimulated by: 1. Low renal perfusion, e.g. after acute drop in blood pressure or of the circulating volume of blood plasma or as a result of constriction of the renal arteries; 2. As a result of the composition (particularly of dissolved salt) of the fluid produced in the kidney at the end of passage through the kidney, reduced excretion of dissolved salt (sodium chloride) from a decrease in renal perfusion; 3. Through beta-2-receptors, which react to circulating adrenalin and to the sympathetic nerves in the kidney; 4. When there are low blood concentrations of potassium. Renin release is inhibited largely by angiotensin II, the hormone aldosterone which this releases and certain drugs (beta-receptor blockers).
- reninan enzyme produced by the kidneys in response to changes in blood pressure; renin is a component of the renin-angiotensin-aldosterone system, a biochemical mechanism involved in the regulation of blood pressure
- Renin-angiotensin-aldosterone systemAbbreviation RAAS
Complex multiple feedback regulation system for the maintenance of plasma volume, plasma osmolarity and blood pressure, in which the enzyme renin plays a particularly important role, as do the hormones angiotensin II and aldosterone, which it directly releases. Angiotensin II constricts blood vessels more than any other hormone. This results in a reduction in renal perfusion, followed by a decrease in the production of primary urine. Aldosterone intensifies this effect by increasing sodium re-absorption and decreasing water excretion. One of the ways in which the RAAS is activated is when there is a drop in circulating blood volume (e.g. from blood loss of shock) or in blood pressure. After salt reduction and in certain forms of high blood pressure (malignant, renovascular, perhaps primary hypertension), the RAAS helps to regulate blood pressure by directly constricting blood vessels and by interacting with the sympathetic nervous system. Drugs which reduce blood pressure (antihypertensives, see ACE inhibitors) inhibit the RAAS.
- renin-angiotensin-aldosterone systema series of reactions for regulating blood pressure
- Repaglinidesee glinide
- ReplicationIdentical duplication of genetic material (DNA or RNA); with double-stranded DNA, replication usually occurs before cell division. A daughter strand is formed on each of the two original strands, which serve as matrixes. This leads to two identical double strands.
- ResistanceThe resistance of infective agents to drugs is of particular importance in medicine. The infective agent may gradually become resistant to a drug or this may happen suddenly as a result of mutation. HIV is known to develop resistance rapidly to drugs which have been used against it.
- Resistance hypertensionsee hypertension
- Respiratory chainCellular system which uses various redox systems with many enzymes and which consumes oxygen, producing energy in the form of the molecule ATP (adenosine triphosphate) and heat. The respiratory chain consists of many different steps in series. It is closely connected to the citrate cycle, some of the products of which pass into the respiratory chain. The transfer of reductive equivalents and electrons to oxygen is coupled to energy extraction and the production of carbon dioxide and water.
- Respiratory TractThe upper sections of the respiratory tract include the nasal cavity with its sinuses and the throat, where the respiratory tract crosses the digestive tract. The lower respiratory tract begins with the larynx. After this comes the trachea (windpipe) and all the branches of the bronchial tree (bronchus, bronchioles), up to the air sacs (alveoli).
- reticulocytean immature red blood cell
- reticulocyte counta measure of the number of reticulocytes, or immature red blood cells, in the circulation
- RetinoblastomaMalignant tumour of the retina which occurs in children and (more rarely) in adolescents. It grows into the optic nerves and cerebral membranes and form metastases in the lungs, bones and brain by transfer through the blood vessels.
Causes: In 85% of cases there is no recognisable cause for retinoblastoma. In 15% of cases there is a hereditary genetic change.
Symptoms: If the pupil is directly illuminated, the background (fundus) of the eye shines yellow instead of red. This is often striking when children are photographed by flash, as one eye is then red and the other yellow. Many children squint; the ball of the eye appears enlarged and pain and loss of vision may develop.
Diagnosis: Mirror examination of the background of the eye, ultrasound investigation.
Therapy: Radiotherapy, Irradiation of the tumour with intense light (photocoagulation), possibly together with chemotherapy. In advanced cases the whole eye ball must be removed. When only one eye is affected, the other must be examined regularly after the therapy, as the risk of a second retinoblastoma is increased.
- retrospective studya study based on the medical records of patients, looking back at events that happened in the past
- RetroviridaeViruses which used to be known as retroviruses, oncoviruses, oncornaviruses and leukoviruses are now known as retroviridae. This is a group of spherical RNA viruses, which are the only RNA viruses which are capable of triggering cancer. The agent for AIDS also belongs to the retroviridae. See Transcriptase, Reverse.
- Reverse Transcriptase, InhibitorDrugs which fight a virus infection by inhibiting the enzyme which catalyses the conversion of virus RNA into DNA (reverse transcriptase). This makes it impossible for the virus hereditary material to be incorporated into the hereditary material of the cell and which then protects new cells from infection. There are now three groups of drugs which inhibit reverse transcriptase in various ways: 1. Nucleoside analogues, 2. Nucleotide analogues and 3. Non-nucleoside analogues
- RhinitisAlso known as coryza or nasal catarrh
Superficial inflammation of the nasal mucous membrane, which often occurs without the temperature being raised. Acute rhinitis is often the first symptom of other infectious diseases such as influenza and whooping cough. "Chronic rhinitis" means chronic inflammation of the nasal mucous membrane, which leads to an increase in the volume of the mucous membrane, particularly in the area of the nasal muscles, which can hinder breathing through the nose. Possible cause for this include recurrent inflammation, chemical or physical irritation or hormonal disturbance.
Cause of the disease (pathogens)
Mostly rhinoviruses, but also numerous other viruses.
There is a dry first stage with a general feeling of illness, burning and tickling in the nose and throat and the urge to sneeze. This is followed by acute rhinitis, with watery secretion, which then becomes viscous and contains pus.
Catarrh drops or sprays, which reduce the swelling in the nasal mucous membrane.
Nose drops should never be used for more than 14 days, because of the danger of excessive perfusion of the blood vessels of the nasal mucous membrane, with chronic rhinopathy (narrowing of the nose, which hinders breathing, damage to the mucous membrane, disturbances in smelling, calcification of the blood vessels).
- RhinovirusGenus of small RNA viruses from the family of the Picornaviridae; up to now more than 115 serotypes have been recognised. These are classified as belonging to the Rhinovirus major group or the Rhinovirus minor group, depending on the cellular receptor. Rhinoviruses mostly occur in the nasopharynx and are the most frequent cause of rhinitis. Cf. colds.
- RhodococciRhodococci are a type of bacterium which can cause inflammation of the lungs and heart, particularly in patients with depression of the immune system.
- RIBAAbb. for recombinant immunoblot assay
Laboratory and diagnostic method for the detection of specific molecules which is based on the natural reaction between antigen and antibody. RIBA serves as the basic diagnostic method for hepatitis C infection. cf. ELISA.
- Ribonucleic Acidsee RNA
- RicketsAlso known as vitamin D rickets or English disease
Diet-related disturbance in calcium and phosphate metabolism in small children, rare in older children. Changes in the skeleton as a result of inadequate calcification of the bone ground substance (a form of secondary disturbance in ossification) are characteristic.
Inadequate photochemical conversion of vitamin D precursors in the skin to vitamin D, as a result of inadequate irradiation with ultraviolet light or inadequate intake or disturbed absorption of vitamin D in the intestine. Without adequate intake of vitamin D, vitamin D deficiency particularly develops in the winter months. This decreases the intestinal absorption of calcium, the re-absorption of phosphate in the kidneys and the exchange of calcium between the skeleton and blood. As a result of excessively low levels of calcium in the blood, secondary hyperparathyroidism develops, with increased release of calcium from the bones and increased excretion of phosphate in the kidneys.
The first symptoms mostly occur in the second to third months of life: restlessness, nervousness, sweating (particularly on the head or bald spot at the back of the head). In the third to fourth months, there is reduced muscular tension, a flabby surface to the stomach (so-called frog's stomach), constipation, sometimes muscular spasm and usually abnormal softness of the bones of the skull. Later symptoms include flattening of the back of the head and the formation of bulges to the bones of the skull, distension of the growth zones and beaker-shaped expansion of the ends of the long bones which are distal to the trunk (as a result of disturbances in cartilage breakdown and the deposition of non-calcified bone ground substance). In the rest of the skeleton, there are bone deformations, including deformation of the pelvis, dorsad curvature of the spinal column, pigeon chest and shortening of the legs. Eruption of the milk teeth is delayed and these teeth exhibit defects in the enamel.
Typical results of the X-ray investigation are osteopenia, delayed maturation and calcification of the ossification centres, beaker-shaped distension of the growth zones of the long bones, band-shaped Looser transformation zones in the growth zones and in the area round the ends of the joints of the long bones. Typical results of the laboratory measurements are: raised alkaline phosphatase, serum calcium concentration in the low normal range (lowered in the later stages), serum phosphate concentration at first normal or raised, later lowered.
Cholecalciferol (vitamin D3, generally oral intake, intravenous only when intestinal absorption is disturbed), X-rays and clinical chemistry checked.
Treatment with calciferol, at increasing doses, from the second week of life (hindered by rickets due to vitamin D deficiency). Uncontrolled treatment with calciferol may lead to intoxication (renal calcification).
- Risk factorsConditions which have been statistically demonstrated to further the development of certain diseases. Psychosocial risk factors for chronic cardiovascular diseases are believed to include high blood pressure, high blood concentrations of cholesterol (hypercholesterolaemia), type 2 diabetes, type 1 diabetes, nicotine consumption, overweight, low physical activity and certain professions. The risk factors may interact and their contribution to the origin of chronic diseases is controversial.
- RNAAbbreviation for ribonucleic acid
The structure of RNA is similar to that of DNA. RNA too is a polynucleotide, which is built up from ribose-containing nucleotides with the bases adenine, guanine, cytosine and uracil (instead of thymine in DNA). The sugar component of RNA is always RNA, whereas that of DNA is deoxyribose. RNA is mostly present as a single-stranded molecule, unlike DNA which is two-stranded. RNA has however spatial structure, as certain intramolecular sections bind together to form shorter sections, while the unpaired sequences form loops. Different forms of RNA are used in the transfer of genetic information from the cell nucleus to the sites of protein biosynthesis or for the protein synthesis itself.
- RoughageGeneral term for carbohydrates which are indigestible to man and which occur in plants as supportive and structural elements (e.g. cellulose).
1. The fibrous structure of the roughage requires long and intensive chewing, which supports the retention of teeth and the predigestion of food. 2. The ability of roughage to bind water and the resulting increase in volume support normal intestinal function. Intestinal activity is stimulated and the passage time in the intestine is shortened. Roughage supports the maintenance of healthy intestinal flora and prevents the development of intestinal cancer. 3. The concentration of cholesterol is decreased. 4. A reduction in the blood concentrations of insulinand glucose is observed after meals, for both diabetics and healthy subjects.
Particularly in full corn cereals, vegetables (particular legumes), potatoes and fruit.
For adults, the requirement of roughage is at least 30 g/day. Inadequate intake favours the development of constipation, colonic cancer, gall stones, disturbances in lipid metabolism and diabetes mellitus.
- Rubeosis facieiPermanently reddening of the face, often only the forehead or cheeks. Possible causes include an increase in the count of red blood cells, high blood pressure (hypertension), acute pancreatic inflammation (pancreatitis), type 2 diabetes, type 1 diabetes and long-term use of ointments which contain cortisone. The development of the condition depends on the individual constitution.
Glossary entries: Roche and Walter de Gruyter, Berlin