Confocal microscopy Health Dictionary

The study of the minute structure of the tissues using special staining processes which are combined with electron and light microscopy. The specialty is sta?ed by medically quali?ed pathologists (histologists) and scienti?cally quali?ed technicians.... histology

(artefact) n. 1. (in radiography) an appearance on an image that is not a true representation of the patient’s body part. The cause may be a problem with the radiographic technique or something more straightforward. For example, a movement artifact is blurring of the image due to movement of the patient or organ during the exposure. All imaging techniques, including CT and MRI, are susceptible to a range of artifacts. See also partial volume artifact. 2. (in microscopy) a structure seen in a tissue under a microscope that is not present in the living tissue. Artifacts, which are produced by faulty *fixation or staining of the tissue, may give a false impression that disease or abnormality is present in the tissue when it is not.... artifact

(glomerular nephritis, GN) n. inflammation of the glomeruli, although in practice the term is used for a number of glomerular conditions lacking microscopical signs of inflammation. For instance, *membranous nephropathy is often referred to as membranous glomerulonephritis. GN may be a primary disease, restricted in its clinical manifestations to the kidney, or part of a multisystem disorder, such as systemic *lupus erythematosus or *vasculitis. Its presentation may be acute, with a *nephritic or *nephrotic syndrome; subacute, with rapidly declining renal function over a period of days or weeks; or chronic, with signs of the disease picked up on routine medical examination. Abnormalities of urine analysis are to be expected, with blood, protein, and casts present in variable amounts. Arterial hypertension is a common associated finding. GN is classified according to the different patterns of histological injury seen on renal biopsy specimens; these are examined by light and electron microscopy and by immunofluorescent studies.... glomerulonephritis

n. the passage of blood in the urine. This may be seen by the naked eye (frank, macroscopic, or visible haematuria) or detected by urine microscopy or urine dipstick (microscopic or nonvisible haematuria) The latter is subclassified into symptomatic nonvisible or asymptomatic nonvisible haematuria. Haematuria is a very important symptom because it is associated with *transitional cell carcinoma, most commonly in the bladder, and kidney cancer. It may also be due to urinary-tract infections, stone disease, or some forms of *glomerulonephritis.... haematuria

n. the study of the identification and distribution of chemical compounds within and between cells, by means of stains, indicators, and light and electron microscopy. —histochemical adj.... histochemistry

n. a genus of spirochaete bacteria, commonly bearing hooked ends. They are not visible with ordinary light microscopy and are best seen using dark-ground microscopy. The parasitic species L. icterohaemorrhagiae is the main causative agent of Weil’s disease (see leptospirosis), but many closely related species cause similar symptoms.... leptospira

a frequent and serious complication of systemic *lupus erythematosus (SLE). The 2002 WHO/ISN/RPS classification of lupus nephritis recognizes six classes: class I is the presence of mesangial deposits (see juxtaglomerular apparatus) seen on immunofluorescence and/or electron microscopy; class II is the presence of mesangial deposits and mesangial hypercellularity; class III is focal and segmental *glomerulonephritis; class IV is diffuse segmental or global nephritis; class V is *membranous nephropathy; and class VI is advanced sclerotic glomerulonephritis. Untreated, outcomes are poor in classes III and IV, but much improved with immunosuppressant treatment.... lupus nephritis

n. an instrument for producing a greatly magnified image of an object, which may be so small as to be invisible to the naked eye. Light or optical microscopes use light as a radiation source for viewing the specimen and combinations of lenses to magnify the image; these are usually an *objective and an *eyepiece. See also electron microscope; operating microscope; ultramicroscope. —microscopical adj. —microscopy n.... microscope

n. (in microscopy) a substance, such as alum or phenol, used to fix a *stain in a tissue.... mordant

n. (in microscopy) the lens or system of lenses in a light microscope that is nearest to the object under examination and furthest from the *eyepiece. In many types of microscope interchangeable objectives with different powers of magnification are provided.... objective

n. one of a series of hydrocarbons derived from petroleum. Paraffin wax (hard paraffin), a whitish mixture of solid hydrocarbons melting at 45–60°C, is used in medicine mainly as a base for ointments and in microscopy for *embedding specimens. Liquid paraffin is a mineral oil formerly used as a laxative; combined with soft paraffin (white or yellow), it is used as an emollient, as a lubricating ointment for treating dry eyes, and to impregnate gauze dressings to prevent the fibres from sticking.... paraffin

a reaction in which antibodies against the bacterium Streptococcus pneumoniae combine with the bacterial capsule, which becomes swollen and visible to light microscopy.... quellung reaction

a dye used in microscopy for staining basophilic substances in tissue specimens.... toluidine blue

The study of all aspects of micro-organisms (microbes) – that is, organisms which individually are generally too small to be visible other than by microscopy. The term is applicable to viruses (see VIRUS), BACTERIA, and microscopic forms of fungi, algae, and PROTOZOA.

Among the smallest and simplest microorganisms are the viruses. First described as ?lterable agents, and ranging in size from 20–30 nm to 300 nm, they may be directly visualised only by electron microscopy. They consist of a core of deoxyribonucleic or ribonucleic acid (DNA or RNA) within a protective protein coat, or capsid, whose subunits confer a geometric symmetry. Thus viruses are usually cubical (icosahedral) or helical; the larger viruses (pox-, herpes-, myxo-viruses) may also have an outer envelope. Their minimal structure dictates that viruses are all obligate parasites, relying on living cells to provide essential components for their replication. Apart from animal and plant cells, viruses may infect and replicate in bacteria (bacteriophages) or fungi (mycophages), which are damaged in the process.

Bacteria are larger (0·01–5,000 µm) and more complex. They have a subcellular organisation which generally includes DNA and RNA, a cell membrane, organelles such as ribosomes, and a complex and chemically variable cell envelope – but, unlike EUKARYOTES, no nucleus. Rickettsiae, chlamydia, and mycoplasmas, once thought of as viruses because of their small size and absence of a cell wall (mycoplasma) or major wall component (chlamydia), are now acknowledged as bacteria; rickettsiae and chlamydia are intracellular parasites of medical importance. Bacteria may also possess additional surface structures, such as capsules and organs of locomotion (?agella) and attachment (?mbriae and stalks). Individual bacterial cells may be spheres (cocci); straight (bacilli), curved (vibrio), or ?exuous (spirilla) rods; or oval cells (coccobacilli). On examination by light microscopy, bacteria may be visible in characteristic con?gurations (as pairs of cocci [diplococci], or chains [streptococci], or clusters); actinomycete bacteria grow as ?laments with externally produced spores. Bacteria grow essentially by increasing in cell size and dividing by ?ssion, a process which in ideal laboratory conditions some bacteria may achieve about once every 20 minutes. Under natural conditions, growth is usually much slower.

Eukaryotic micro-organisms comprise fungi, algae, and protozoa. These organisms are larger, and they have in common a well-developed internal compartmentation into subcellular organelles; they also have a nucleus. Algae additionally have chloroplasts, which contain photosynthetic pigments; fungi lack chloroplasts; and protozoa lack both a cell wall and chloroplasts but may have a contractile vacuole to regulate water uptake and, in some, structures for capturing and ingesting food. Fungi grow either as discrete cells (yeasts), multiplying by budding, ?ssion, or conjugation, or as thin ?laments (hyphae) which bear spores, although some may show both morphological forms during their life-cycle. Algae and protozoa generally grow as individual cells or colonies of individuals and multiply by ?ssion.

Micro-organisms of medical importance include representatives of the ?ve major microbial groups that obtain their essential nutrients at the expense of their hosts. Many bacteria and most fungi, however, are saprophytes (see SAPROPHYTE), being major contributors to the natural cycling of carbon in the environment and to biodeterioration; others are of ecological and economic importance because of the diseases they cause in agricultural or horticultural crops or because of their bene?cial relationships with higher organisms. Additionally, they may be of industrial or biotechnological importance. Fungal diseases of humans tend to be most important in tropical environments and in immuno-compromised subjects.

Pathogenic (that is, disease-causing) microorganisms have special characteristics, or virulence factors, that enable them to colonise their hosts and overcome or evade physical, biochemical, and immunological host defences. For example, the presence of capsules, as in the bacteria that cause anthrax (Bacillus anthracis), one form of pneumonia (Streptococcus pneumoniae), scarlet fever (S. pyogenes), bacterial meningitis (Neisseria meningitidis, Haemophilus in?uenzae) is directly related to the ability to cause disease because of their antiphagocytic properties. Fimbriae are related to virulence, enabling tissue attachment – for example, in gonorrhoea (N. gonorrhoeae) and cholera (Vibrio cholerae). Many bacteria excrete extracellular virulence factors; these include enzymes and other agents that impair the host’s physiological and immunological functions. Some bacteria produce powerful toxins (excreted exotoxins or endogenous endotoxins), which may cause local tissue destruction and allow colonisation by the pathogen or whose speci?c action may explain the disease mechanism. In Staphylococcus aureus, exfoliative toxin produces the staphylococcal scalded-skin syndrome, TSS toxin-1 toxic-shock syndrome, and enterotoxin food poisoning. The pertussis exotoxin of Bordetella pertussis, the cause of whooping cough, blocks immunological defences and mediates attachment to tracheal cells, and the exotoxin produced by Corynebacterium diphtheriae causes local damage resulting in a pronounced exudate in the trachea.

Viruses cause disease by cellular destruction arising from their intracellular parasitic existence. Attachment to particular cells is often mediated by speci?c viral surface proteins; mechanisms for evading immunological defences include latency, change in viral antigenic structure, or incapacitation of the immune system – for example, destruction of CD 4 lymphocytes by the human immunode?ciency virus.... microbiology

n. (in microscopy) the process of removing the cloudiness from microscopical specimens after *dehydration by means of a clearing agent. This increases the transparency of the specimens. Xylene, cedar oil, methyl benzoate plus benzol, and methyl salicylate plus benzol are commonly used as clearing agents.... clearing

n. (in microscopy) an arrangement of lenses beneath the stage of a microscope. It can be adjusted to provide correct focusing of light on the microscope slide.... condenser

n. (in microscopy) the fixing of a specimen within a mass of firm material in order to facilitate the cutting of thin sections for microscopical study. The embedding medium, e.g. paraffin wax for light microscopy or Araldite for electron microscopy, helps to keep the specimen intact.... embedding

a technique for preparing specimens for electron microscopy. The unfixed tissue is frozen and then split with a knife and a layer of ice is sublimed from the exposed surface. The resultant image is thus not distorted by chemical fixatives.... freeze etching

the commonest cause of *nephrotic syndrome in children and an important cause of this syndrome in adults. The condition is so named because of the apparent lack of abnormalities seen on light microscopy of biopsy samples. Changes can, however, be seen on electron microscopy, with effacement of the *podocyte foot processes along the glomerular basement membrane. It is postulated that minimal change disease is a T-cell disease and that *cytokine damage to the podocytes leads to loss of the selective filtering characteristics of the glomerulus. The condition usually responds to corticosteroids and has a good prognosis, but there is clinical overlap with primary *focal segmental glomerulosclerosis, which may have similar histological appearances in its early stages, tends not to respond to steroids, and is associated with a poor renal prognosis.... minimal change nephropathy

1. n. (in surgery) the act of cutting (the cut or division made is also called a section). For example, an abdominal section is performed for surgical exploration of the abdomen (see laparotomy). A transverse section is a cut made at right angles to a structure’s long axis. See also Caesarean section. 2. n. (in imaging) a three-dimensional reconstruction of body scans obtained by computerized tomography or magnetic resonance imaging. These are reconstituted as transverse, sagittal, and coronal plane sections. 3. n. (in microscopy) a thin slice of the specimen to be examined under a microscope. 4. vb. (in psychiatry) to issue an order for the compulsory admission of a patient to a psychiatric hospital for assessment and/or treatment of a mental disorder under the appropriate provision or section of the *Mental Health Act 1983 as amended by the Mental Health Act 2007. There are formal procedures, such as review and right to appeal, to ensure this legislation is not abused. A patient who otherwise has *capacity may still consent to or refuse treatment for conditions unrelated to the mental disorder for which he or she is detained.... section

n. an instrument for cutting extremely thin sections of tissue (not more than 0.1 ?m thick) for electron microscopy. See also microtome.... ultramicrotome

Abies balsamea

FAMILY: Pinaceae

SYNONYMS: A. balsamifera, Pinus balsamea, balsam fir, balsam tree, American silver fir, balm of Gilead fir, Canada turpentine (oil).

GENERAL DESCRIPTION: A tall, graceful evergreen tree up to 20 metres high, with a tapering trunk and numerous branches giving the tree an overall shape of a perfect cone. It forms blisters of oleoresin (the so-called ‘balsam’) on the trunk and branches, produced from special vesicles beneath the bark. The tree does not produce a ‘true’ balsam, since it does not contain benzoic or cinnamic acid in its esters; it is really an oleoresin, being a mixture of resin and essential oil.

DISTRIBUTION: Native to North America, particularly Quebec, Nova Scotia and Maine.

OTHER SPECIES: The hemlock spruce (Tsuga canadensis) also yields an exudation sold under the name of ‘Canada balsam’. There are also many other species of fir which produce oils from their needles – see entry on silver fir and Botanical Classification section. NB: Not to be confused with the genuine balsam of Gilead (Commiphora opabalsamum), of ancient repute.

HERBAL/FOLK TRADITION: The oleoresin is used extensively by the American Indians for ritual purposes and as an external treatment for burns, sores, cuts and to relieve heart and chest pains. It is also used internally for coughs.

ACTIONS: Antiseptic (genito-urinary, pulmonary), antitussive, astringent, cicatrisant, diuretic, expectorant, purgative, regulatory, sedative (nerve), tonic, vulnerary.

EXTRACTION: 1. The oleoresin is collected by punturing vesicles in the bark. 2. An essential oil is produced by steam distillation from the oleoresin, known as Canada balsam or Canada turpentine. (An essential oil is also produced by steam distillation from the leaf or needles, known as fir needle oil.)

CHARACTERISTICS: 1. The oleoresin is a thick pale yellow or green honeylike mass which dries to crystal clear varnish, with a fresh sweet balsamic, almost fruity odour. 2. A colourless mobile liquid with a sweet, soft-balsamic, pinelike scent. It blends well with pine, cedarwood, cypress, sandalwood, juniper, benzoin and other balsams.

PRINCIPAL CONSTITUENTS: Consists almost entirely of monoterpenes, pinene, phellandrene, esters and alcohols.

SAFETY DATA: Generally non-toxic, non-irritant, non-sensitizing. ‘In large doses it is purgative and may cause nausea.’4

AROMATHERAPY/HOME: USE

Skin Care: Burns, cuts, haemorrhoids, wounds.

Respiratory System: Asthma, bronchitis, catarrh, chronic coughs, sore throat.

Genito-Urinary System: Cystitis, genito-urinary infections.

Nervous System: Depression, nervous tension, stress-related conditions – described as ‘appeasing, sedative, elevating, grounding, opening’.5

OTHER USES: The oil from the oleoresin is used in certain ointments and creams as an antiseptic and treatment for haemorrhoids. Used in dentistry as an ingredient in root canal sealers. Also used as a fixative or fragrance component in soaps, detergents, cosmetics and perfurmes. There is some low-level use in food products, alcoholic and soft drinks. The oleoresin is used as a medium in microscopy and as a cement in glassware.... balsam, canadian