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.
- Nasal TumoursA distinction is made between tumours of the external and of the internal nose. The former group mostly consist of skin tumours such as basalioma and squamous cell carcinoma. Within the nose, not only benign tumours such as polyps and chondromas* may occur, but also malignant tumours, such as squamous cell carcinoma or sarcoma.
- Nateglinidesee glinides
- Neck DissectionOperative clearing of the area of the neck, which may be on one or both sides. The regional lymph nodes from the base of the skull to the entry to the chest are removed, sometimes also parts of muscles, blood vessels and fat tissue. Neck dissection is indicated for malignant tumours in the head and neck area, accompanied by metastases in the lymph nodes in the back of the neck or lower jaw. The amount of tissue which is removed depends on the severity of the condition. Neck dissection may also be performed prophylactically if micrometastases or hidden metastases are suspected.
- negative feedbacka decrease in function in response to a stimulus ; serves to regulate various processes
- Neonatal JaundiceAlso icterus neonatorum.
Hepatitis (see Icterus) in the first week of life is normal. In the first days of life, bilirubin initially increases, with a maximum on days 3 to 5 of life, and then falls to normal values within 2 to 3 weeks. Higher values occur in premature babies and the jaundice is retained for a longer time. Phototherapy can be effective in cases of intermediate severity. Exchange transfusion of the whole blood must be considered in severe cases or when phototherapy does not bring improvement.
- Neonatal JaundiceSee Icterus neonatorum.
- NeoplasmNew growth of endogenous tissue which is due to the disturbance or loss of growth regulation in the tissue. Cf. Tumour.
- nephritisinflammation of the kidney
- nephronsmallest functional unit of the kidney
- NephrosclerosisDisease of the arterioles which lead to the kidneys, accompanied by high blood pressure (hypertension).
1.Primary malignant nephrosclerosis: arteriosclerosis; Causes: Hormonal contraception, virus infection, gestosis (diseases caused by pregnancy); 2. Secondary malignant nephrosclerosis: Thickening of the innermost vessel wall and necrosis of the arterial wall from high blood pressure; 3. Benign nephrosclerosis: Hyalinosis of the arterioles, a disease with deposition of substances in connective tissue. Occurs in metabolic syndrome, diabetic macroangiopathy, hypercholesterolaemia and primary hypertension.
Primary malignant nephrosclerosis: Acute kidney failure and transition to kidney failure. Secondary malignant and benign nephrosclerosis: Developing kidney insufficiency and high blood pressure.
- Neuraminidase InhibitorsInhibitors of the neuraminidase of the influenza virus types A and B. The release of newly formed viruses from the infected cell is blocked. Cf. virostatic drugs.
- NeuraminidasesEnzyme that occurs in certain viruses and bacteria, in plasma and in lysosomes (cell organelles). Neuraminidase is a surface antigen of the influenza virus. Mucoproteins are slime substances which are secreted by the skin and mucous membranes for protective purposes. The virus can attack these with the help of neuraminidase.
- NeuroblastomaA neuroblastoma is a highly malignant tumour which originates in the so-called sympathetic nervous tissue and which mostly occurs in small children. The most frequent site of the tumour is in the adrenals. In more than 50% of cases there are already metastases at the time of diagnosis. These are mostly in the bone.
Symptoms: The specific symptoms of the disease are predominantly related to the localisation of the tumour. There is generally pain, anaemia, fever, diarrhoea and weight loss.
Diagnosis: Ultrasound investigations (sonography), computer tomography, nuclear spin tomography and clinical chemistry tests are used for diagnosis. A genetic investigation of the tumour is possible and this can give indications about the prognosis.
Therapy: The treatment and the chances of a cure depend on the age of the patient, the stage of the tumour and the genetic characteristics. Spontaneous cure may occur in babies. Localised tumours are normally removed by operation and chemotherapy may be performed. The prognosis is favourable. The prognosis for very advanced tumours is poor, even with aggressive chemotherapy. Cf. Retinoblastoma.
- NeurofibromaNeurofibroma is a benign tumour which originates in the sheath cells of the nerve fibres. Neurofibromas are classified into so-called solitary tumours, with clear edges, and plexiform tumours, which spread randomly. Local spreading of the tumour can lead to pain and to loss of nerve function. In neurofibromatosis several neurofibromas occur simultaneously.
- NeurofibromatosisGenetically based disease in which tumours develop and there are changes in the blood vessels. It may be hereditary or arise spontaneously by mutation (gene changes) after fertilisation. The gene changes cause the loss or reduced function of specific proteins which hinders the development of tumours in healthy subjects.
The following forms are distinguished:
1. peripheral type (Recklinghausen disease): Symptoms: Benign tumours (neurofibromas) develop in the skin over all the body. There are also changes in the brown pigment of the skin, the so-called pigment anomalies. These include liver spots round the pits of the arms or the groin and large light brown skin patches, the so-called café-au-lait patches. There can also be changes in the bones and abnormalities in the eyes and nervous system. These may be combined with learning difficulties or hormonal abnormalities. Frequency: 1:3000 new born babies.
2. central type: symptoms: Tumours of the auditory nerve and the cerebral membranes, more rarely pigment anomalies and skin tumours.
Therapy: Possible surgical removal of the tumours, chemotherapy.
- Nicotinic acidsee lipid sinkers
- NIDDMAbbreviation for non-insulin-dependent diabetes mellitus, see type 2 diabetes
- Night SweatIntense sweating which occurs at night. Often occurs in acute leukaemia, tuberculosis and in AIDS.
- Nomaalso water cancer or gangrenous stotomatitis
Most severe form of progressive inflammation of the mucous membrane of the cheeks which destroys tissue. Occurs particularly in children with disturbed immune system after infectious diseases (measles, scarlet fever), in typhus, AIDS or in malnutrition and is caused by bacterial infection.
- Non-Hodgkin's LymphomaCollective term for a group of malignant lymphomas (malignant diseases of certain organs or cells in the immune system). Non-Hodgkins lymphomas include a large number of different types of cancer, which involve different types of cell (B-lymphocytes, T-lymphocytes) or which have different growth characteristics (slow growing, rapid growing, or of high or low malignancy). Most non-Hodgkins lymphomas are in lymph nodes, although some are in the bone marrow or in other organs of the immune system, such as bone marrow. Some forms of leukaemia (chronic lymphatic leukaemia) are included in non-Hodgkins lymphoma.
- NoradrenalineNoradrenaline is a substance with hormonal activity which is formed in the adrenal medulla and in the nervous system.
Like adrenaline, noradrenaline increases blood pressure and leads to constriction of the blood vessels. In contrast to adrenaline, noradrenaline lowers the heart rate. In addition, has a weaker effect than adrenaline on intestinal and bronchial smooth muscles and on metabolism
- Normal weightBody weight which is regarded as optimal for health. The body weight for adults is no longer estimated from the Broca formula, but calculated from the body-mass index.
- normochromicrefers to cells that have a normal concentration of hemoglobin
- normocytic anaemiaform of anaemia which is characterised by red blood cells of normal size
- Nuclear Spinsee Magnetic Resonance Tomography.
- Nuclear spin tomographyalso known as magnetic resonance tomography (abbreviation MRT)
Nuclear spin tomography is a computer-based imaging procedure which is based on the principle of magnetic resonance. In contrast to conventional X-ray diagnosis or computer tomography, no ionising radiation is used. A strong magnetic field is applied to the area to be examined. The spin of the nuclei in the sample are then excited by a short high frequency impulse. When the nuclei relax, electromagnetic waves are released and the energy of these is measured. If a field gradient is superimposed on a main homogenous magnetic field, measurements of magnetic resonance are possible which allow conclusions about the origin of the field-dependent signals. Layers of the body can be selected at will and with the help of the computer the signals from these can be assembled into two or three dimensional tomographic images. Superconducting magnets are suitable for the production of particularly stable magnetic field of high flux density. If these are used, very high contrast resolution and the imaging of small anatomical structures is possible, which is usually superior to computer tomography. Nuclear spin tomography is mostly used for diseases of nervous tissue (brain and spinal chord, multiple sclerosis), diagnosis of vertebral discs and imaging of joints and muscles.
- Nucleic acidsUnbranched long molecular chains of nucleotides, which are linked to each other by diphosphate links, either linearly or in a ring. These form the so-called genetic material. Depending on the sugar molecule involved, a distinction is made between deoxyribonucleic acids (DNA) and ribonucleic acids (RNA).
- NucleosidesMolecule consisting of sugar and base, i.e. of a pentose (sugar with 5 carbon atoms; D-ribose or D-deoxyribose) bound to a purine base (adenine or guanine) or pyrimidine base (uracil, thymine or cytosine). Cf. nucleotides.
- Nucleotidesalso known as nucleoside phosphate
A nucleotide is a molecule which consists of a base, a sugar and a phosphate residue. The sugar is a pentose, a sugar with 5 carbon atoms, normally D-ribose or D-deoxyribose. The base is either a purine base (adenine or guanine) or a pyrimidine base (uracil, thymine or cytosine). The biological significance of the nucleotides lies in their role as building blocks of nucleic acids. The nucleotides are classified as ribonucleotides (where the sugar is ribose) and deoxyribonucleotides (where the sugar is deoxyribose). Cf. DNA and RNA.
- nucleuscell nucleus, contains the genetic information
- Nutrition for diabeticsFood with low sugar content and/or the addition of saccharine, fructose or sweeteners
- Nutritional diseasesDiseases which are caused by undernutrition or false nutrition (e.g. protein or vitamin deficiency).
- Nutritional therapyNutritional therapy is the treatment of organic diseases or metabolic abnormalities by changes in nutrition, for instance reduction in food when there are digestive problems, regulated intake of carbohydrates in type 2 diabetes and type 1 diabetes, avoidance of certain foods when there is intolerance (food allergy) or adequate nutrition when the nutrition has been false or deficient (cf. civilization diseases).
- Nutritional valueValue of a food for both the formation and regeneration of body cells and as a fuel for the metabolic formation of energy (physiological combustion value). The chemical nutritional value is measured and evaluated in Joules (formerly in calories).
Glossary entries: Roche and Walter de Gruyter, Berlin