Unicellular Health Dictionary

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Unicellular: From 1 Different Sources

adj. describing organisms or tissues that consist of a single cell. Unicellular organisms include the protozoans, most bacteria, and some fungi.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Evolution

An uninterrupted process of change from one condition, form or state to another. In biological evolution, all varieties of living things are seen as having developed by inheritable, incremental changes from unicellular structures to complex organisms such as humankind. Although the likelihood of some form of evolution had been postulated by scientists in the late 18th and early 19th centuries, the prime contribution to the development of biological evolutionary doctrine came from the British scientist, Charles Darwin, who argued in his book The Origin of Species by Means of Natural Selection (1859) that natural selection resulted in the survival of the ?ttest organisms. The precise biological mechanism of evolution was not unravelled until the 20th century, with the discovery of CHROMOSOMES and GENES and the development of the science of genetics. Charles Darwin’s theory was based on his studies of the varied and unique animal life in the Galapagos Islands in the 19th century. He believed that the diversity of life on the planet could be ascribed to the combined effects of random variation in living things, inherited by succeeding generations.... evolution

Fungal And Yeast Infections

These infections, also called mycoses (see MYCOSIS), are common and particularly affect the skin or mucosal membranes in, for example, the mouth, anus or vagina. Fungi consist of threadlike hyphae which form tangled masses or mycelia – common mould. In what is called dermatophyte (multicellular fungi) fungal infection of the hair, nails and SKIN, these hyphae invade the KERATIN. This is usually described as ‘RINGWORM’, although no worm is present and the infection does not necessarily occur in rings. PITYRIASIS versicolor and candidosis (monoliasis – see CANDIDA), called thrush when it occurs in the vulva, vagina and mouth, are caused by unicellular fungi which reproduce by budding and are called yeasts. Other fungi, such as ACTINOMYCOSIS, may cause deep systemic infection but this is uncommon, occurring mainly in patients with immunosuppressive disorders or those receiving prolonged treatment with ANTIBIOTICS.

Diagnosis and treatment Any person with isolated, itching, dry and scaling lesions of the skin with no obvious cause – for example, no history of eczema (see DERMATITIS) – should be suspected of having a fungal infection. Such lesions are usually asymmetrical. Skin scrapings or nail clippings should be sent for laboratory analysis. If the lesions have been treated with topical steroids they may appear untypical. Ultraviolet light ?ltered through glass (Wood’s light) will show up microsporum infections, which produce a green-blue ?uorescence.

Fungal infections used to be treated quite e?ectively with benzoic-acid compound ointment; it has now been superseded by new IMIDAZOLES preparations, such as CLOTRIMAZOLE, MICONAZOLE and terbina?ne creams. The POLYENES, NYSTATIN and AMPHOTERICIN B, are e?ective against yeast infections. If the skin is macerated it can be treated with magenta (Castellani’s) paint or dusting powder to dry it out.

Refractory fungal infection can be treated systematically provided that the diagnosis of the infection has been con?rmed. Terbina?ne, imidazoles and GRISEOFULVIN can all be taken by mouth and are e?ective for yeast infections. (Griseofulvin should not be taken in pregnancy or by people with liver failure or porphyria.) (See also FUNGUS; MICROBIOLOGY.)... fungal and yeast infections

Mehlis’s Glands

A unicellular gland in cestodes, which encircles the ootype. Its function is not known.... mehlis’s glands

Protozoa

The lowest division of the animal kingdom, including unicellular or acellular organisms with a eukaryotic structure.... protozoa

Yeast

This consists of the cells and spores of unicellular fungi belonging to the family of Saccharomycetaceae. The main species of yeast used in medicine is Saccharomyces cerevisiae, which is used in the fermentation industries, such as brewing. It is a rich source of the vitamin B complex (see APPENDIX 5: VITAMINS), but its use has largely been given up since the various components of the vitamin B complex became available as separate entities.... yeast

Bacteria

pl. n. (sing. bacterium) a group of microorganisms all of which lack a distinct nuclear membrane (and hence are considered more primitive than animal and plant cells) and most of which have a cell wall of unique composition (many antibiotics act by destroying the bacterial cell wall). Most bacteria are unicellular; the cells may be spherical (*coccus), rod-shaped (*bacillus), spiral (*Spirillum), comma-shaped (*Vibrio), or corkscrew-shaped (*spirochaete). Generally, they range in size between 0.5 and 5 ?m. Motile species bear one or more fine hairs (flagella) arising from their surface. Many possess an outer slimy *capsule, and some have the ability to produce an encysted or resting form (*endospore). Bacteria reproduce asexually by simple division of cells; incomplete separation of daughter cells leads to the formation of *colonies consisting of different numbers and arrangements of cells. Some colonies are filamentous in shape, resembling those of fungi. Transfer of DNA from one bacterium to another takes place in the process of *conjugation.

Bacteria are very widely distributed. Some live in soil, water, or air; others are parasites of humans, animals, and plants. Many parasitic bacteria do not harm their hosts; some cause diseases by producing poisons (see endotoxin; exotoxin).... bacteria

Cryptococcus

n. a genus of unicellular yeastlike fungi that cause disease in humans. They are found in soil (particularly when enriched with pigeon droppings), and they are common in pigeon roosts and nests. The species C. neoformans causes *cryptococcosis.... cryptococcus

Flagellum

n. (pl. flagella) a fine long whiplike thread attached to certain types of cell (e.g. spermatozoa and some unicellular organisms). Flagella are responsible for the movement of the organisms to which they are attached.... flagellum

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