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Hepadnavirus
''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 ... [...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] |
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 ... [...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 ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Reading Frames
In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames will be "open" (the "reading", however, refers to the RNA produced by transcription of the DNA and its subsequent interaction with the ribosome in translation). Such an ORF may contain a start codon (usually AUG in terms of RNA) and by definition cannot extend beyond a stop codon (usually UAA, UAG or UGA in RNA). That start codon (not necessarily the first) indicates where translation may start. The transcription termination site is located after the ORF, beyond the translation stop codon. If transcription were to cease before the stop codon, an incomplete protein would be made during translation. In eukaryotic genes with multiple exons, introns are removed and exons are then joined together after transcription to yield the fin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NTCP
Sodium/bile acid cotransporter also known as the Na+-taurocholate cotransporting polypeptide (NTCP) or liver bile acid transporter (LBAT) is a protein that in humans is encoded by the ''SLC10A1'' (solute carrier family 10 member 1) gene. Structure Sodium/bile acid cotransporters are integral membrane glycoproteins. Human NTCP contains 349 amino acids and has a mass of 56 kDa. Function Bile acid:sodium symporters participate in the enterohepatic circulation of bile acids. Two homologous transporters are involved in the reabsorption of bile acids. One of these absorbs bile acids from the intestinal lumen, the bile duct, and the kidney with an apical localization ( ileal sodium/bile acid cotransporter). The other is this protein and is expressed in the basolateral membranes of hepatocytes (NTCP). As a cotransporter, NTCP binds two sodium ions and one (conjugated) bile salt molecule, thereby providing a hepatic influx of bile salts. Other transported molecules include ste ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads ( cranial kinesis). To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. Lizards have evolved elongate bodies without limbs or with greatly reduced limbs about twenty-five times independently via convergent evolution, leading to many lineages of legless lizards. These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, although this rule is not universal (see Amphisbae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crocodile
Crocodiles (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 members of the 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 families. The gharial, with its narrow snout, is easier to distinguish, while 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 upper and lower jaws of the crocodiles are the same width, and the teeth in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Host Switch
In parasitology and epidemiology, a host switch (or host shift) is an evolutionary change of the host specificity of a parasite or pathogen. For example, the human immunodeficiency virus used to infect and circulate in non-human primates in West-central Africa, but switched to humans in the early 20th century. All symbiotic species, such as parasites, pathogens and mutualists, exhibit a certain degree of host specificity. This means that pathogens are highly adapted to infect a specific host - in terms of but not limited to receptor binding, countermeasures for host restriction factors and transmission methods. They occur in the body (or on the body surface) of a single host species or – more often – on a limited set of host species. In the latter case, the suitable host species tend to be taxonomically related, sharing similar morphology and physiology. Speciation is the creation of a new and distinct species through evolution and so unique differences exist between all l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (genetics)
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The main components of the cytoplasm are cytosol (a gel-like substance), the organelles (the cell's internal sub-structures), and various cytoplasmic inclusions. The cytoplasm is about 80% water and is usually colorless. The submicroscopic ground cell substance or cytoplasmic matrix which remains after exclusion of the cell organelles and particles is groundplasm. It is the hyaloplasm of light microscopy, a highly complex, polyphasic system in which all resolvable cytoplasmic elements are suspended, including the larger organelles such as the ribosomes, mitochondria, the plant plastids, lipid droplets, and vacuoles. Most cellular activities take place within the cytoplasm, such as many metabolic pathways including glycolysis, and proc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
