Instruct: Given a question, retrieve documents that answer the question.
Query: What is within a nucleus of a cell?
Cell nuclei contain most of the cell's genetic material, organized as multiple long linear DNA molecules in a complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell's nuclear genome and are structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the cell by regulating gene expression—the nucleus is, therefore, the control center of the cell. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and isolates its contents from the cellular cytoplasm, and the nuclear matrix (which includes the nuclear lamina), a network within the nucleus that adds mechanical support, much like the cytoskeleton, which supports the cell as a whole.
Dr. Senapathy had also proposed a plausible mechanistic and functional rationale why the eukaryotic nucleus originated, a major unanswered question in biology. If the transcripts of the split genes and the spliced mRNAs were present in a cell without a nucleus, the ribosomes would try to bind to both the un-spliced primary RNA transcript and the spliced mRNA, which would result in a molecular chaos. If a boundary had originated to separate the RNA splicing process from the mRNA translation, it can avoid this problem of molecular chaos. This is exactly what is found in eukaryotic cells, where the splicing of the primary RNA transcript occurs within the nucleus, and the spliced mRNA is transported to the cytoplasm, where the ribosomes translate them into proteins. The nuclear boundary provides a clear separation of the primary RNA splicing and the mRNA translation.
In cells, DNA is housed in the nucleus and it never leaves. The DNA within the nucleus is transcribed by tRNA, and the transcriptions of the DNA become RNA. The RNA (ribonucleic acid) leaves the nucleus to float freely around the cytoplasm, and it contains the instructions of the DNA that are vital to the coding, decoding, regulation and expression of genes. The ribosomes then take the RNA messages and turn them into proteins that build cells. When a virus enters a cell and inserts its DNA code into the nucleus, it gets transcribed and released into the cell for the ribosome to make it into a protein. This is how viral infections occur. The cell then explodes with the overproduction of the virus, releasing it into the body to infect any and all other cells it finds. It is theorized that through evolution, cells developed a defense system called RNAi (RNA interference) to stop the production of the proteins that have suspicious mirror image messages of the RNA. They don’t just destroy the suspicious messages, but the correct messages as well to stop all production of that message. This is a cell’s self-destruct mechanism and every cell, plant and animal, have RNAi: a way to turn off the production of a certain gene inside the protein.
Cartwheel cells are neurons of the dorsal cochlear nucleus (DCN) where they greatly outnumber the other inhibitory interneurons of the DCN. Their somas lie on the superficial side of the pyramidal layer of the DCN, and their dendrites receive input from the parallel fibres of the granule cell layer. Their axons do not extend beyond the dorsal cochlear nucleus but synapse with other cartwheel cells and pyramidal cells within the DCN releasing GABA and glycine onto their targets.
Magnocellular neurosecretory cells are large neuroendocrine cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus. They are also found in smaller numbers in accessory cell groups between these two nuclei, the largest one being the nucleus circularis. There are two types of magnocellular neurosecretory cells, oxytocin-producing cells and vasopressin-producing cells, but a small number can produce both hormones. These cells are neuroendocrine neurons, are electrically excitable, and generate action potentials in response to afferent stimulation.
"Marteilia" has a very peculiar morphology. The outermost cell is the primary cell. Within the primary cell, there is a nucleus and between 3 and 16 secondary cells. Within a secondary cell, there is a nucleus and between 1 to 6 spores. Within each spore, there is a nucleus and another spore, which has yet another nucleus and spore within. This spore within a spore within a spore is termed a tricellular spore. "Marteilia" has tricellular spores where as the similar genera "Paramarteilia" and "Paramyxa" have bicellular and tetracellular spores respectively (Feist, Hine, Bateman, Stentiford, & Longshaw, 2009).
Unlike many nuclei within the central nervous system (CNS), the mesencephalic nucleus contains no chemical synapses but are electrically coupled. Neurons of this nucleus are unipolar cells that receive proprioceptive information from the mandible and send projections to the trigeminal motor nucleus to mediate monosynaptic jaw jerk reflexes. It is also the only structure in the CNS to contain first order sensory neurons, cell bodies of primary afferents in contact with the periphery, which are usually contained within ganglia (like the trigeminal ganglion). The mesencephalic nucleus can thus be considered functionally as a sensory ganglion embedded within the brainstem, making it neuroanatomically unique .
In cell biology, the cytoplasm is all of the material within a 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 usually colorless.[1]
One hypothesis for the origin of multicellularity is that a group of function-specific cells aggregated into a slug-like mass called a grex, which moved as a multicellular unit. This is essentially what slime molds do. Another hypothesis is that a primitive cell underwent nucleus division, thereby becoming a coenocyte. A membrane would then form around each nucleus (and the cellular space and organelles occupied in the space), thereby resulting in a group of connected cells in one organism (this mechanism is observable in Drosophila). A third hypothesis is that as a unicellular organism divided, the daughter cells failed to separate, resulting in a conglomeration of identical cells in one organism, which could later develop specialized tissues. This is what plant and animal embryos do as well as colonial choanoflagellates.
Infection is initiated when a viral particle contacts a cell with specific types of receptor molecules on the cell surface. Following binding of viral envelope glycoproteins to cell membrane receptors, the virion is internalized and dismantled, allowing viral DNA to migrate to the cell nucleus. Within the nucleus, replication of viral DNA and transcription of viral genes occurs.
The first model known as the "syntrophic model" proposes that a symbiotic relationship between the archaea and bacteria created the nucleus-containing eukaryotic cell. (Organisms of the Archaea and Bacteria domain have no cell nucleus.[73]) It is hypothesized that the symbiosis originated when ancient archaea, similar to modern methanogenic archaea, invaded and lived within bacteria similar to modern myxobacteria, eventually forming the early nucleus. This theory is analogous to the accepted theory for the origin of eukaryotic mitochondria and chloroplasts, which are thought to have developed from a similar endosymbiotic relationship between proto-eukaryotes and aerobic bacteria.[74] The archaeal origin of the nucleus is supported by observations that archaea and eukarya have similar genes for certain proteins, including histones. Observations that myxobacteria are motile, can form multicellular complexes, and possess kinases and G proteins similar to eukarya, support a bacterial origin for the eukaryotic cell.[75]
ITC cells are thought to play a role as the 'off switch' for the amygdala, inhibiting the amygdala's central nucleus output neurons and its basolateral nucleus neurons. Some researchers speculate that ITC cells, via their extensive local inhibition within the amygdala, could serve as a substrate for expression and storage of extinction memory.
Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA. The RNA is then used to create proteins which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. However, not all cells have DNA – some cells such as mature red blood cells lose their nucleus as they mature.
The nucleus was the first organelle to be discovered. What is most likely the oldest preserved drawing dates back to the early microscopist Antonie van Leeuwenhoek (1632–1723). He observed a "lumen", the nucleus, in the red blood cells of salmon.[1] Unlike mammalian red blood cells, those of other vertebrates still contain nuclei.
Mitosis occurs exclusively in eukaryotic cells, but occurs in different ways in different species. For example, animals undergo an "open" mitosis, where the nuclear envelope breaks down before the chromosomes separate, while fungi such as "Aspergillus nidulans" and "Saccharomyces cerevisiae" (yeast) undergo a "closed" mitosis, where chromosomes divide within an intact cell nucleus. Prokaryotic cells, which lack a nucleus, divide by a process called binary fission.
During the process of apoptosis, the cell undergoes:
As a wild-type protein, ced-3 will cleave other protein substrates within the cell and trigger apoptosis. In the nucleus, ced-3 cleaves DCR-1, so that the RNA can no longer be processed, and then it converts RNase into DNase thus promoting DNA degradation in the nucleus and mitochondrial elimination in the cytoplasm. Afterwards, ced-3 indirectly releases another protein, WAH-1, that can cause signals on the surface of the cell to be released so that the cell can be phagocytosed by a neighbouring cell.
In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, meaning kernel or seed) is a membrane-enclosed organelle found in eukaryotic cells. Eukaryotes usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
Senapathy had also proposed a plausible mechanistic and functional rationale why the eukaryotic nucleus originated, a major question in biology. If the transcripts of the split genes and the spliced mRNAs were present in a cell without a nucleus, the ribosomes would try to bind to both the un-spliced primary RNA transcript and the spliced mRNA, which would result in a molecular chaos. If a boundary had originated to separate the RNA splicing process from the mRNA translation, it can avoid this problem of molecular chaos. This is exactly what is found in eukaryotic cells, where the splicing of the primary RNA transcript occurs within the nucleus, and the spliced mRNA is transported to the cytoplasm, where the ribosomes translate them into proteins. The nuclear boundary provides a clear separation of the primary RNA splicing and the mRNA translation.
"C. uncinata" goes through asexual reproduction for cell division and duplication called amitosis. As "C. uncinata" has two nuclei, it goes through two different styles of division of the nuclei. The germ-line nucleus goes through mitosis during asexual division while the somatic nucleus undergoes amitosis. Amitosis is a stochastic process where unlike in mitosis, there is no spindle formation to segregate chromosomes during nuclear division. Instead, the chromosomes within the somatic nucleus are duplicated, and the nucleus goes through binary division. The precise mechanism is unknown, but it is believed that somatic chromosomes that are located on one side of the dividing somatic nucleus are distributed to one daughter cell, and the somatic chromosomes on the other side of the nucleus are distributed to the other daughter cell.
In 2001, McHugh was appointed by President George W. Bush to the Presidential Council on Bioethics.[13] The Council was charged with the task of making recommendations as to what the U.S. federal government's policy regarding embryonic stem cells should be. McHugh was against using new lines of embryonic stem cells derived from in vitro fertilization but was in favor of the use of stem cells derived from somatic cell nuclear transfer (SCNT). In SCNT, the nucleus of a cell is removed and replaced by another cell nucleus. McHugh felt that cells created in this fashion could be regarded as tissue; whereas, stem cells taken from embryos caused the killing of an unborn child.[14]
Technically, ploidy refers to the nucleus. Though at times authors may report the total ploidy of all nuclei present within the cell membrane of a syncytium, usually the ploidy of the nuclei present will be described. For example, a fungal dikaryon with two haploid nuclei is distinguished from the diploid in which the chromosomes share a nucleus and can be shuffled together. Nonetheless, because in most situations there is only one nucleus, it is commonplace to speak of the ploidy of a cell.
In many animal cells, centrioles and spindles keep nuclei centered within a cell for mitotic, meiotic, and other processes. Without such a centering mechanism, disease and death can result. While mouse oocytes do have centrioles, they play no role in nucleus positioning, yet, the nucleus of the oocyte maintains a central position. This is a result of cytoplasmic streaming. Microfilaments, independent of microtubules and myosin 2, form a mesh network throughout the cell. Nuclei, positioned in non-centered cell locations, have been demonstrated to migrate distances greater than 25 microns to the cell center. They will do this without going off course by more than 6 microns when the network is present. This network of microfilaments has organelles bound to it by the myosin Vb molecule. Cytoplasmic fluid is entrained by the motion of these organelles, however, no pattern of directionality is associated with the movement of the cytoplasm. In fact, the motion has been demonstrated to fulfill Brownian motion characteristics. For this reason, there is some debate as to whether this should be called cytoplasmic streaming. Nonetheless, directional movement of organelles does result from this situation. Since the cytoplasm fills the cell, it is geometrically arranged into the shape of a sphere. As the radius of a sphere increases, surface area increases. Further, the motion in any given direction is proportional to the surface area. So thinking of the cell as a series of concentric spheres, it is clear that spheres with larger radii produce a greater amount of movement than spheres with smaller radii. Thus, the movement toward the center is greater than the movement away from the center, and net movement pushing the nucleus towards a central cellular location exists. In other words, the random motion of the cytoplasmic particles create a net force toward the center of the cell. Additionally, the increased motion with the cytoplasm reduces cytoplasmic viscosity allowing the nucleus to move more easily within the cell. These two factors of the cytoplasmic streaming center the nucleus in the oocyte cell.
All vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of these red blood cells contain a nucleus. Mammals represent ~5,500 named species out of ~66,000 vertebrate species, and within this ~8% subgroup, red blood cells are known as erythrocytes or RBCs and have no cell nucleus in mature organisms. In contrast, a nucleated red blood cell (NRBC), also known by several other names, is a mammalian RBC that contains a cell nucleus. NRBCs occur in normal development as progenitor cells in the erythropoietic lineage and in pathological states. 
Goblet cells are simple columnar epithelial cells, having a height of four times that of their width. The cytoplasm of goblet cells tends to be displaced toward the basal end of the cell body by the large mucin granules, which accumulate near the apical surface of the cell along the Golgi apparatus, which lies between the granules and the nucleus. This gives the basal part of the cell a basophilic staining because of nucleic acids within the nucleus and rough endoplasmic reticulum staining with hematoxylin. Mucin within the granules stains pale in routine histology sections, primarily because these carbohydrate-rich proteins are washed out in the preparation of microscopy samples. However, they stain easily with the PAS staining method, which colours them magenta.
From 1870 to 1880 it became clear that cell nuclei are never formed anew but always derived from the substance of another nucleus. In 1882 Flemming observed the longitudinal splitting of chromosomes in the dividing nucleus and concluded that each daughter nucleus received half of each of the chromosomes of the mother nucleus: then by the early 20th century it was found that the number of chromosomes in a given species is constant. With genetic continuity confirmed and the finding by Eduard Strasburger that the nuclei of reproductive cells (in pollen and embryo) have a reducing division (halving of chromosomes, now known as meiosis) the field of heredity was opened up. By 1926 Thomas Morgan was able to outline a theory of the gene and its structure and function. The form and function of plastids received similar attention, the association with starch being noted at an early date. With observation of the cellular structure of all organisms and the process of cell division and continuity of genetic material, the analysis of the structure of protoplasm and the cell wall as well as that of plastids and vacuoles – what is now known as cytology, or cell theory became firmly established.