Occurrence viruses

Short replication cycles that may be completed within a few hours, a large amount of viral progeny from one infected host-cell, as well as the general inaccuracy of viral nucleic acid polymerases result in an evolution occurring in fast motion, allowing rapid adaptation of viruses to selective pressures (see chapter by Boucher and Nijhius, this volume). Generalizing, it can be stated that any effective antiviral therapy will lead to the occurrence of resistance mutations. A well studied example... 

Najera I, Richman DD, Olivares I, Rojas JM, Peinado MA, Perucho M, Najera R, Lopez GaHndez C (1994) Natural occurrence of drug resistance mutations in the reverse transcriptase of human immunodeficiency virus type 1 isolates. AIDS Res Hum Retroviruses 10 1479-1488 Nijhuis M, Boucher CAB, Schipper R Leitner T, Schuurman R, Albert J (1998) Stochastic processes strongly influence HIV-1 evolution during suboptimal protease inhibitor therapy. Proc Natl Acad Sci USA 95 14441-14446... 

Certain types of infechous agent (e.g. influenza virus) are able to combat herd immunity sueh as this through undergoing major antigenic changes. These render the majority of the population susceptible, and their occurrence is often aeeompanied by spread of the disease aeross the entire globe (pandemies). 

Suffredini, E., Corrain, C., Arcangeli, G., Fasolato, L., Manfrin, A., Rossetti, E., Biazzi, E., Mioni, R., Pavoni, E., Losio, M. N., Sanavio, G., and Croci, L. (2008). Occurrence of enteric viruses in shellfish and relation to climatic-environmental factors. Lett. Appl. Microbiol. 47, 467-474. 

The occurrence of smallpox infection among people who handled laundry from infected patients is well documented, and it is believed that virus in such material remains viable for extended periods. In this situation, the virus could be detected in the environment, but investigators would already know it was there because of the presence of the associated illness. 

Human foamy virus Causes foamy vacuolation in infected cells little is known of its occurrence or pathogenic potential... 

Shingles herpes zoster, infection due to the re-activation of the latent varicella zoster virus Status epilepticus occurrence of continuous seizures Striae scars in the skin... 

Many chemicals (including pharmaceuticals but also environmental and occupational chemicals) are known to stimulate the immune system in a way that autoimmune diseases occur [61]. However, because of its multifactorial nature, the occurrence of autoimmune-like (including drug allergic) diseases is rare if considered on a compound-by-compound base. But, in some cases (e.g., in case of HIV or Herpes virus-infected individuals), adverse reactions occur at a higher rate [65, 66]. 

Polyspecific Response Associated with CNS Autoimmune Diseases. The oligoclonal, intrathecally synthesized IgG contains numerous specific antibodies and autoantibodies. Antibodies are frequently found with specificities against measles, the rubella virus and the varicella-zoster virus, but seldom against the herpes simplex virus. The occurrence of one, two, or three of these antibodies is referred to as the MRZ reaction. The corresponding antigens are not present in these cases. The MRZ reaction is typical of multiple sclerosis as well as cerebral lupus erythematosus and is a chronically evolving immune process (F5, KIO, S16). 

Systemic infections are those that have microorganisms (bacteria, viruses, yeasts, parasites) spread, usually via the bloodstream, beyond the portal of entry or original site of localized infection to multiple compartments of the body. When infections, either localized or systemic, are accompanied by signs and symptoms of a systemic inflammatory response (fever, rapid pulse, increase in white blood cells) the syndrome is called sepsis. Severe sepsis is defined by the additional occurrence of organ failure (either kidney, liver, brain, lungs), and is a potentially fatal condition (mortality around 50%). If there is hypotension not responding on fluid resuscitation it is called septic shock and the mortally is even higher (60-70%). 

Like many other nonreceptor tyrosine kinases, Abl tyrosine kinase may be converted by mutations into a dominant oncoprotein and thus contribute to tumor formation. Abl tyrosine kinase was first discovered as the oncogene of murine Abelson leukemia virus. Chronic myelogenic leukemia in humans is cause by a chromosome translocation in which a fusion protein is created of Abl tyrosine kinase and a Bcr protein (c Chapter 14). The result is a greatly increased tyrosine kinase activity, to which a causal role in occurrence of this leukemia is attributed. 

Despite the co-occurrence of sleep disturbances with virtually all infectious diseases, relatively few studies have looked at the exact nature of sleep changes associated with infection. Reports of sleep during rhinovirus 23 infection (the cold virus) have included a decrease in sleep duration and sleep efficiency, with an associated reduction in neurobehavioral performance (vigilance) and a trend for reduced subjective vigor (Profile of Mood States, POMS) (190). 

The term nucleoside was originally proposed by Levene and Jacobs in 1909 for the carbohydrate derivatives of purines (and, later, of pyrimidines) isolated from the alkaline hydrolyzates of yeast nucleic acid. The phosphate esters of nucleosides are the nucleotides, which, in polymerized forms, constitute the nucleic acids of all cells.2 The sugar moieties of nucleosides derived from the nucleic acids have been shown, thus far, to be either D-ribose or 2-deoxy-D-eri/fAro-pentose ( 2-deoxy-D-ribose ). The ribo-nucleosides are constituents of ribonucleic acids, which occur mainly in the cell cytoplasm whereas 2-deoxyribo -nucleosides are components of deoxypentonucleic acids, which are localized in the cell nucleus.3 The nucleic acids are not limited (in occurrence) to cellular components. They have also been found to be important constituents of plant and animal viruses. 

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