SDSpolyacrylamide gel electrophoresis

Electrophoresis in polyacrylamide gels of proteins denatured with the anionic detergent sodium dodecyl sulfate (SDS). The treatment with SDS usually gives proteins equal charge per unit molecular weight and thus the proteins are separated according to their molecular weight.

sea-bass virus-1 (SBV) An unassigned virus in the family Picornaviridae.

seal distemper virus A strain of Phocine distemper virus in the family

Paramyxoviridae.

Barrett T et al (1999) In Encyclopedia of Virology, Second edition, edited by A Granoff and RG Webster. London: Academic Press, p.1559

seal influenza virus Occasional isolations of influenza viruses have been made from seals and whales and the viruses are found to be close relatives of avian influenza viruses. In 1980, an epizootic of H7N7 influenza occurred in seals on the coast near Boston, USA with more than 100 deaths. Transmission of this virus to a laboratory worker was recorded. From other disease outbreaks in seals H4N5 influenza viruses have been recovered, and H1N1 viruses have been isolated from Pacific ocean whales. In so far as these viruses have been characterized, they appear to be closely related to avian influenza virus species.

Webster RG et al (1992) Microbiol Rev 56, 152

seal morbillivirus See Phocine distemper virus.

sealpox virus A tentative species in the genus Parapoxvirus. Morphologically similar to Orf virus. Isolated from a captive Californian sea lion, Zalophus californi-anus. Causes a severe disease in wild and captive sea lions.

Wilson TM and Poglayen-Neuwall I (1971) Can J Comp Med 35, 174

Sebokele virus An unclassified virus. Isolated in suckling mice from the pooled brain, liver, spleen and heart tissue of an adult female rodent of Hylomyscus sp, trapped in a banana plantation at Botambi, Central African Republic. Infectivity not sensitive to chloroform. Not reported to cause disease in humans.

secondary attack rate A measure of the infectivity of an agent.

Longini IM et al (1982) Am J Epid 115, 736

sedimentation coefficient The sedimentation rate of a protein or other macromolecule per unit of applied gravitational force is termed the 'sedimentation coefficient' or constant, s, and is defined by the equation:

ra 2rdt where r = radius (the distance in cm between the particle and the center of rotation); ra = the angular velocity in radians/s of the centrifuge head;

— = the rate of movement of the dt particle in cm/s.

The units of s are reciprocal seconds; for convenience, the basic unit is taken as 10-13 s, and termed one Svedberg unit (S). With this unit, the sedimentation coefficients of most proteins fall between 1 and 50S.

Svedberg T and Pedersen KO (1940) The Ultracentrifuge. London: Oxford University Press sedimentation rate The velocity at which a particle (assumed to be approximately a sphere) settles under a given set of conditions. It is proportional to the square of the particle diameter and to the difference between the particle density and the density of the suspending medium. It decreases as the viscosity of the suspending medium increases and increases with the gravitational force.

where d = diameter of the particle; pP = particle density; pL = suspending medium density; | = viscosity of suspending medium; g = gravitational force.

It is measured in cm/s.

Sedlec virus A possible arbovirus of the family Bunyaviridae. Isolated from the reed warbler, Acrocephalus scirpaceus (Herm), in the former Czechoslovakia.

Hubalek Z et al (1989) Acta Sci Nat, Brno 23, 1

Seletar virus (SELV) A serotype of Wad Medani virus in the genus Orbivirus, belonging to the Wad Medani complex of the Kemerovo virus serogroup. Isolated from the tick, Boophilus microplus, in Singapore and peninsular Malaysia. Antibodies found in cattle, carabao (water buffalo) and pigs. Not reported to cause disease in humans.

Sembalam virus An unclassified virus. Isolated from herons in Tamil Nadu, India. Not reported to cause disease in humans.

semi-conservative replication A model for DNA replication as it normally occurs in nature. The double strand becomes separated and each base in the single strand becomes attached to complementary nucleotides to form two new double strands, in which one strand of each daughter molecule will be derived from the original DNA.

Semliki Forest virus (SFV) (Semliki means 'I do not know' - the reply given by natives when asked the name of the forest.) A species in the genus Alphavirus.

sequencing

The natural host and vector are not known but antibodies are found in humans and wild primates in Uganda, Mozambique, Cameroon, Central African Republic, Kenya, Nigeria, northern Borneo and Malaysia. Multiplies in the mosquito, Aedes aegypti. Not associated with any disease, and generally considered to be non-pathogenic for humans although a fatal case of encephalitis in a laboratory worker has been associated with the virus. Causes encephalitis in adult mice on experimental injection by various routes and on i.c. injection in guinea pigs, rabbits and rhesus monkeys. Most inoculated animals have shown kidney damage. Viremia occurs in inoculated birds of several species and in hamsters. Virus can be propagated in eggs killing the embryo and in cell cultures of many species with CPE.

Willens WR et al (1979) Science 203, 1127

Sena Madureira virus (SMV) An unas-signed species in the family Rhabdoviridae, belonging to the Timbo serogroup. Isolated from Ameiva ameiva ameiva in Brazil in 1976. Not reported to cause disease in humans.

Sendai virus (SeV) A species in the genus Paramyxovirus. Can be isolated in embry-onated eggs, the allantoic cavity being the most sensitive, or in primary cultures of mouse, human, chick and other species. Less exacting in requirements for replication and causing a more definite CPE than parainfluenza virus type 1 human. Produces plaques in human, bovine and simian cells. Inactivated virus is used experimentally to cause cell fusion. On mouse to mouse passage there is an increase in virulence resulting in pneumonia. An inactivated chick embryo vaccine is available to protect laboratory mice. Not generally accepted as causing human infection. Injected i.c. in mice it causes a fatal infection but serial passage by this route is not possible. Causes inapparent infection in ferrets, monkeys and pigs and occurs as a latent infection of laboratory mice, rats and guinea pigs. Used extensively as a model paramyx-ovirus for molecular studies, and to induce cell fusion.

Synonyms: hemagglutinating virus of Japan; murine parainfluenza virus type 1.

Ishida N and Homma M (1978) Adv Virus Res 23, 349

sentinel animal An animal exposed captive in the wild to contact infection from the environment, usually from insects. Used to test for the presence of viruses in a particular geographical area.

sentinel case An isolated case of some infectious disease or the first case in an outbreak.

sentinel virus (SNNV) A TTV-like virus isolated from sera of non A-G hepatitis patients by representational difference analysis.

Mushahwar IK (2000) J Med Virol 62, 399

Sen virus (SENV) ATTV-like virus isolated from an HIV patient (initials SEN).

Mushahwar IK (2000) J Med Virol 62, 399

Seoul virus (SEOV) A species in the genus Hantavirus. First isolated from rats in 1980 in Korea. Infects Rattus rattus and Rattus norvegicus and has been isolated in Japan, Korea, China, Egypt and the USA. Human infection can occur where there is close contact with rats, and there is evidence of nephropathy following these infections. The virus is probably distributed worldwide in Rattus species, but does not cause disease in the natural host.

Sepik virus (SEPV) A species in the genus Flavivirus, in the Yellow fever virus group. Isolated from mosquitoes in New Guinea. Causes a febrile illness in humans.

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