| cloning vector | <molecular biology> A DNA molecule originating from a virus (plasmid vector), or the cell of a higher organism into which another DNA fragment of appropriate size can be integrated without loss of the vectors capacity for self- replication. Vectors introduce foreign DNA into host cells, where it can be reproduced in large quantities. They are also used to insert DNA from one cell type to another. Examples are plasmids, cosmids, and yeast artificial chromosomes, vectors are often recombinant molecules containing DNA sequences from several sources. Cloning vectors are usually designed to have convenient restriction sites that can be cut to generate sticky end to which the DNA that is to be cloned can be ligated easily. (12 Mar 1998) |
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| secretion vector | <molecular biology> A DNA vector in which the protein product is both expressed and secreted (excreted) from the cell. (09 Oct 1997) |
| shuttle vector | <molecular biology> Cloning vector that replicate in cells of more than one organism, for example E. Coli and yeast. This combination allows DNA from yeast to be grown in E. Coli and tested directly for complementation in yeast. Shuttle vectors are constructed so that they have the origins of replication of the various hosts. (18 Nov 1997) |
| spatial vector | A cardiac vector represented in more than one plane simultaneously; two-or three-dimensional orientation of a vector. (05 Mar 2000) |
| instantaneous vector | The resultant vector of the heart's action currents at any given moment, usually represented as an arrow of appropriate direction and magnitude. (05 Mar 2000) |
| expression vector | <molecular biology> A cloning vector that contains the necessary regulatory sequences to allow transcription and translation of a cloned gene or genes and thus transcribe and clone DNA. (13 Nov 1997) |
| accidental host | One that harbors an organism which usually does not infect it. (05 Mar 2000) |
| amplifier host | A host in which infectious agents multiply rapidly to high levels, providing an important source of infection for vectors in vector-borne diseases. (05 Mar 2000) |
| parasite-host ecosystem | Complex of all parasite species and individuals associated with a specific host. Synonym: parasite-host ecosystem. Origin: parasite + G. Koinos, common, together (05 Mar 2000) |
| paratenic host | An intermediate host in which no development of the parasite occurs, although its presence may be required as an essential link in the completion of the parasite's life cycle; e.g., the successive fish host's that carry the plerocercoid of Diphyllobothrium latum, the broad fish tapeworm, to larger food fish eventually eaten by man or other final host's. Synonym: transport host. (05 Mar 2000) |
| reservoir host | The host of an infection in which the infectious agent multiplies and/or develops, and upon which the agent is dependent for survival in nature; the host essential for the maintenance of the infection during times when active transmission is not occurring. (05 Mar 2000) |
| graft-versus-host disease | <haematology> A common and serious, complication of bone marrow transplantation where there is a reaction of donated bone marrow against a patient's own tissue. When donor lymphocytes or a graft containing lymphocytes that are immunologically competent are given to a patient that has low immunological competence, an incompatibility reaction can result. This is due to antibodies from the donor against antigens in the host. This is due to mismatch of MHC Class I antigens and can produce lymphocyte clones that will react by a variety of processes against the host and cause damage. The clinical condition can be fatal and is due to the donor's immune cells recognising the host cells as foreign. The clinical entity characterised by anorexia, diarrhoea, loss of hair, leukopenia, thrombocytopenia, growth retardation, and eventual death brought about by the graft-versus-host reaction. It can occur in either chronic or acute forms and is treatable by immunosuppressive drugs. Seen most commonly following bone marrow transplantation, acute disease is seen after 5-40 days and chronic disease weeks to months after transplantation, affecting, principally, the gastrointestinal tract, liver, and skin. Radiological appearances of the gastrointestinal tract include; thickened wall, mucosal folds thickened or effaced, increased secretions most likely to be rapid transit of GI tract, mass most likely to be focal oedema, fibrosis, hallmark: diffuse, uniform thickening of small bowel. Synonym: GVH disease. Acronym: GVHD (20 Sep 2002) |
| graft-versus-host reaction | <haematology> A common and serious, complication of bone marrow transplantation where there is a reaction of donated bone marrow against a patient's own tissue. When donor lymphocytes or a graft containing lymphocytes that are immunologically competent are given to a patient that has low immunological competence, an incompatibility reaction can result. This is due to antibodies from the donor against antigens in the host. This is due to mismatch of MHC Class I antigens and can produce lymphocyte clones that will react by a variety of processes against the host and cause damage. The clinical condition can be fatal and is due to the donor's immune cells recognising the host cells as foreign. The clinical entity characterised by anorexia, diarrhoea, loss of hair, leukopenia, thrombocytopenia, growth retardation, and eventual death brought about by the graft-versus-host reaction. It can occur in either chronic or acute forms and is treatable by immunosuppressive drugs. Seen most commonly following bone marrow transplantation, acute disease is seen after 5-40 days and chronic disease weeks to months after transplantation, affecting, principally, the gastrointestinal tract, liver, and skin. Radiological appearances of the gastrointestinal tract include; thickened wall, mucosal folds thickened or effaced, increased secretions most likely to be rapid transit of GI tract, mass most likely to be focal oedema, fibrosis, hallmark: diffuse, uniform thickening of small bowel. Synonym: GVH disease. Acronym: GVHD (20 Sep 2002) |
| graft-versus-host response | <haematology> A common and serious, complication of bone marrow transplantation where there is a reaction of donated bone marrow against a patient's own tissue. When donor lymphocytes or a graft containing lymphocytes that are immunologically competent are given to a patient that has low immunological competence, an incompatibility reaction can result. This is due to antibodies from the donor against antigens in the host. This is due to mismatch of MHC Class I antigens and can produce lymphocyte clones that will react by a variety of processes against the host and cause damage. The clinical condition can be fatal and is due to the donor's immune cells recognising the host cells as foreign. The clinical entity characterised by anorexia, diarrhoea, loss of hair, leukopenia, thrombocytopenia, growth retardation, and eventual death brought about by the graft-versus-host reaction. It can occur in either chronic or acute forms and is treatable by immunosuppressive drugs. Seen most commonly following bone marrow transplantation, acute disease is seen after 5-40 days and chronic disease weeks to months after transplantation, affecting, principally, the gastrointestinal tract, liver, and skin. Radiological appearances of the gastrointestinal tract include; thickened wall, mucosal folds thickened or effaced, increased secretions most likely to be rapid transit of GI tract, mass most likely to be focal oedema, fibrosis, hallmark: diffuse, uniform thickening of small bowel. Synonym: GVH disease. Acronym: GVHD (20 Sep 2002) |
| cutaneous graft versus host reaction | An acute erythematous maculopapular reaction with bulla formation in the most severe cases; chronic changes may resemble lichen planus or scleroderma. (05 Mar 2000) |