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Hepadnaviridae
''Hepadnaviridae'' is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family include: liver infections, such as hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis. It is the sole accepted family in the order ''Blubervirales''. Taxonomy The following genera are recognized: * ''Avihepadnavirus'' * ''Orthohepadnavirus'' * '' Herpetohepadnavirus'' * '' Metahepadnavirus'' * '' Parahepadnavirus'' History and discovery Although liver diseases transmissible among human populations were identified early in the history of medicine, the first known hepatitis with a viral etiological agent was Hepatitis A, in the picornaviridae family. Hepatitis B Virus (HBV) was identified as an infection distinct from Hepatitis A through its contamination of measles, mumps, and yellow fever vaccines in the 1930s and 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepadnaviridae
''Hepadnaviridae'' is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family include: liver infections, such as hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis. It is the sole accepted family in the order ''Blubervirales''. Taxonomy The following genera are recognized: * ''Avihepadnavirus'' * ''Orthohepadnavirus'' * '' Herpetohepadnavirus'' * '' Metahepadnavirus'' * '' Parahepadnavirus'' History and discovery Although liver diseases transmissible among human populations were identified early in the history of medicine, the first known hepatitis with a viral etiological agent was Hepatitis A, in the picornaviridae family. Hepatitis B Virus (HBV) was identified as an infection distinct from Hepatitis A through its contamination of measles, mumps, and yellow fever vaccines in the 1930s and 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus
''Hepatitis B virus'' (HBV) is a partially double-stranded DNA virus, a species of the genus ''Orthohepadnavirus'' and a member of the ''Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Disease Despite there being a vaccine to prevent Hepatitis B, HBV remains a global health problem. Hepatitis B can be acute and later become chronic, leading to other diseases and health conditions. In addition to causing hepatitis, infection with HBV can lead to cirrhosis and hepatocellular carcinoma. It has also been suggested that it may increase the risk of pancreatic cancer. Roles in disease Viral infection by ''Hepatitis B virus'' (HBV) causes many hepatocyte changes due to the direct action of a protein encoded by the virus, HBx, and to indirect changes due to a large increase in intracellular reactive oxygen species (ROS) after infection. HBx appears to dysregulate a number of cellular pathways. HBx causes dysregulation in part by binding to genomic DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus
''Hepatitis B virus'' (HBV) is a partially double-stranded DNA virus, a species of the genus ''Orthohepadnavirus'' and a member of the ''Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Disease Despite there being a vaccine to prevent Hepatitis B, HBV remains a global health problem. Hepatitis B can be acute and later become chronic, leading to other diseases and health conditions. In addition to causing hepatitis, infection with HBV can lead to cirrhosis and hepatocellular carcinoma. It has also been suggested that it may increase the risk of pancreatic cancer. Roles in disease Viral infection by ''Hepatitis B virus'' (HBV) causes many hepatocyte changes due to the direct action of a protein encoded by the virus, HBx, and to indirect changes due to a large increase in intracellular reactive oxygen species (ROS) after infection. HBx appears to dysregulate a number of cellular pathways. HBx causes dysregulation in part by binding to genomic DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avihepadnavirus
''Avihepadnavirus'' is a genus of viruses, in the family ''Hepadnaviridae''. Birds serve as natural hosts. There are three species in this genus. Diseases associated with this genus include: hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis. Taxonomy The genus contains the following species: * '' Duck hepatitis B virus'' * ''Heron hepatitis B virus'' * '' Parrot hepatitis B virus'' Structure Viruses in the genus ''Avihepadnavirus'' are enveloped, with spherical geometries, and T=4 symmetry. The diameter is around 42 nm. Genomes are circular, around 3.2kb in length. The genome codes for 7 proteins. Life cycle Viral replication is nucleo-cytoplasmic. Replication follows the dsDNA(RT) replication model. DNA-templated transcription, specifically dsDNA-RT transcription, with some alternative splicing mechanism is the method of transcription. Translation takes place by ribosomal shunting Ribosome shunting is a mechanism of translation initiation in which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthohepadnavirus
''Orthohepadnavirus'' is a genus of viruses, in the family ''Hepadnaviridae''. Humans and other mammals serve as natural hosts. There are 12 species in this genus. Diseases associated with this genus include: hepatitis, hepatocellular carcinoma (chronic infections), and cirrhosis. Taxonomy The genus contains the following species: * '' Capuchin monkey hepatitis B virus'' * ''Chinese shrew hepatitis B virus'' * ''Domestic cat hepatitis B virus'' * ''Ground squirrel hepatitis virus'' * ''Hepatitis B virus'' * '' Long-fingered bat hepatitis B virus'' * ''Pomona bat hepatitis B virus'' * '' Roundleaf bat hepatitis B virus'' * ''Taï Forest hepadnavirus'' * '' Tent-making bat hepatitis B virus'' * ''Woodchuck hepatitis virus'' * ''Woolly monkey hepatitis B virus The ''woolly monkey hepatitis B virus'' (WMHBV) is a viral species of the ''Orthohepadnavirus'' genus of the ''Hepadnaviridae'' family. Its natural host is the woolly monkey (''Lagothrix)'', an inhabitant of South America c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898,Dimmock p. 4 more than 9,000 virus species have been described in detail of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles, or ''virions'', consisting of (i) the genetic material, i.e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Of Hepadnaviruses
The transmission of hepadnaviruses between their natural hosts, humans, non-human primates, and birds, including intra-species host transmission and cross-species transmission, is a topic of study in virology. Hepadnaviruses are a family of viruses that can cause liver infections in humans and animals. They are Group VII viruses that possess double-stranded DNA genomes and replicate using reverse transcriptase. This unique replication strategy, combined with their extremely small genomes and a very narrow host and tissue tropism, has distinguished them enough to be classified in the family Hepadnaviridae. There are two recognized genera: * ''Orthohepadnavirus'', type species: ''hepatitis B virus'' (HBV) * ''Avihepadnavirus'', type species: '' duck hepatitis B virus'' (DHBV) Structure With the example of human HBV: the particular feature of the HBV structure is the presence of three different forms in the plasma of infected patients: * Dane particle (diameter ≈ 42 nm): th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baltimore Classification
Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a distinct group. Seven Baltimore groups are described that take into consideration whether the viral genome is made of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), whether the genome is single- or double-stranded, and whether the sense of a single-stranded RNA genome is positive or negative. Baltimore classification also closely corresponds to the manner of replicating the genome, so Baltimore classification is useful for grouping viruses together for both transcription and replication. Certain subjects pertaining to viruses are associated with multiple, specific Baltimore groups, such as specific forms of translation of mRNA and the host range of different types of viruses. Structural characteristics such as the shape of the vir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retroviridae
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus ''retro'' (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. Although retroviruses have different subfamilies, they have three basic groups: the oncoretroviruses (oncogenic retroviruses), the lentiviruses (slow retroviruses) and the spumaviruses (foamy viruses). The oncoretroviruses are able to cause cancer in some species, the lentivirus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus DNA Polymerase
Hepatitis B virus DNA polymerase is a hepatitis B viral protein. It is a DNA polymerase that can use either DNA or RNA templates and a ribonuclease H that cuts RNA in the duplex. Both functions are supplied by the reverse transcriptase (RT) domain. Structure The hepadnaviral P protein is organized into three domains: an N-terminal domain () covering the terminal and the spacer, an RT domain related to every other reverse transcriptase domain, and a C-terminal domain () regulating the RNase H activity. Furthermore, hepadnavirus polymerases contain a terminal protein (TP) domain that contains a tyrosine residue that serves as a primer for the synthesis of the (-) DNA strand. Function The Hepatitis B virus (HBV) polymerase is a multifunctional enzyme, with both RNA-dependent and DNA-dependent polymerase functions, as well as an RNase H function. It acts on the HBV pre-genomic RNA (pgRNA) to reverse transcribe it to form a new rcDNA molecule within a new capsid. (The pgRNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant taxon, extant members of the order (biology), order Crocodilia, which includes the alligators and caimans (family Alligatoridae), the gharial and false gharial (family Gavialidae) among other extinct taxa. Although they appear similar, crocodiles, alligators and the gharial belong to separate biological family (biology), families. The gharial, with its narrow snout, is easier to distinguish, while Morphology (biology), morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head, with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait is that the upp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turtle
Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked turtles), which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other amniotes (reptiles, birds, and mammals) they breathe air and do not lay eggs underwater, although many species live in or around water. Turtle shells are made mostly of bone; the upper part is the domed carapace, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in scales made of keratin, the material of hair, horns, and claws. The carapace bones develop from ribs that grow sideways and develop into broad flat plates th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
