A microtubule subunit protein found in large quantities in mammalian brain. It has also been isolated from SPERM FLAGELLUM; CILIA; and other sources. Structurally, the protein is a dimer with a molecular weight of approximately 120,000 and a sedimentation coefficient of 5.8S. It binds to COLCHICINE; VINCRISTINE; and VINBLASTINE.
Agents that interact with TUBULIN to inhibit or promote polymerization of MICROTUBULES.
Slender, cylindrical filaments found in the cytoskeleton of plant and animal cells. They are composed of the protein TUBULIN and are influenced by TUBULIN MODULATORS.
A major alkaloid from Colchicum autumnale L. and found also in other Colchicum species. Its primary therapeutic use is in the treatment of gout, but it has been used also in the therapy of familial Mediterranean fever (PERIODIC DISEASE).
Proteins found in the microtubules.
High molecular weight proteins found in the MICROTUBULES of the cytoskeletal system. Under certain conditions they are required for TUBULIN assembly into the microtubules and stabilize the assembled microtubules.
An alkaloid isolated from Colchicum autumnale L. and used as an antineoplastic.
A lignan (LIGNANS) found in PODOPHYLLIN resin from the roots of PODOPHYLLUM plants. It is a potent spindle poison, toxic if taken internally, and has been used as a cathartic. It is very irritating to skin and mucous membranes, has keratolytic actions, has been used to treat warts and keratoses, and may have antineoplastic properties, as do some of its congeners and derivatives.
A ubiquitous phosphoprotein that serves as an intracellular substrate for a variety of SIGNAL TRANSDUCTION PATHWAYS. PHOSPHORYLATION of stathmin occurs during CELL CYCLE progression, and stathmin functions as a microtubule-destabilizing protein that promotes MICROTUBULE depolymerization during INTERPHASE and late MITOSIS. Stathmin is expressed at very high levels in a variety of human CANCERS.
Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.
Antitumor alkaloid isolated from Vinca rosea. (Merck, 11th ed.)
A cyclodecane isolated from the bark of the Pacific yew tree, TAXUS BREVIFOLIA. It stabilizes MICROTUBULES in their polymerized form leading to cell death.
Compounds formed by the joining of smaller, usually repeating, units linked by covalent bonds. These compounds often form large macromolecules (e.g., BIOPOLYMERS; PLASTICS).
Somewhat flattened, globular echinoderms, having thin, brittle shells of calcareous plates. They are useful models for studying FERTILIZATION and EMBRYO DEVELOPMENT.
An ansa macrolide isolated from the MAYTENUS genus of East African shrubs.
Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.
The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.
Ligases that catalyze the joining of adjacent AMINO ACIDS by the formation of carbon-nitrogen bonds between their carboxylic acid groups and amine groups.
The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.
Polymers synthesized by living organisms. They play a role in the formation of macromolecular structures and are synthesized via the covalent linkage of biological molecules, especially AMINO ACIDS; NUCLEOTIDES; and CARBOHYDRATES.
Nocodazole is an antineoplastic agent which exerts its effect by depolymerizing microtubules.
Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.
A seven-membered aromatic ring compound. It is structurally related to a number of naturally occurring antifungal compounds (ANTIFUNGAL AGENTS).
Populations of thin, motile processes found covering the surface of ciliates (CILIOPHORA) or the free surface of the cells making up ciliated EPITHELIUM. Each cilium arises from a basic granule in the superficial layer of CYTOPLASM. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)
The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm.
Changes in the amounts of various chemicals (neurotransmitters, receptors, enzymes, and other metabolites) specific to the area of the central nervous system contained within the head. These are monitored over time, during sensory stimulation, or under different disease states.
A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.
A peptide that is a homopolymer of glutamic acid.
The rate dynamics in chemical or physical systems.
A microtubule structure that forms during CELL DIVISION. It consists of two SPINDLE POLES, and sets of MICROTUBULES that may include the astral microtubules, the polar microtubules, and the kinetochore microtubules.
A microtubule-associated mechanical adenosine triphosphatase, that uses the energy of ATP hydrolysis to move organelles along microtubules toward the plus end of the microtubule. The protein is found in squid axoplasm, optic lobes, and in bovine brain. Bovine kinesin is a heterotetramer composed of two heavy (120 kDa) and two light (62 kDa) chains. EC 3.6.1.-.
Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.
A group II chaperonin found in eukaryotic CYTOSOL. It is comprised of eight subunits with each subunit encoded by a separate gene. This chaperonin is named after one of its subunits which is a T-COMPLEX REGION-encoded polypeptide.
A group of indole-indoline dimers which are ALKALOIDS obtained from the VINCA genus of plants. They inhibit polymerization of TUBULIN into MICROTUBULES thus blocking spindle formation and arresting cells in METAPHASE. They are some of the most useful ANTINEOPLASTIC AGENTS.
A bundle of MICROTUBULES and MICROTUBULE-ASSOCIATED PROTEINS forming the core of each CILIUM or FLAGELLUM. In most eukaryotic cilia or flagella, an axoneme shaft has 20 microtubules arranged in nine doublets and two singlets.
A systemic agricultural fungicide used for control of certain fungal diseases of stone fruit.
The posterior filiform portion of the spermatozoon (SPERMATOZOA) that provides sperm motility.
The parts of a macromolecule that directly participate in its specific combination with another molecule.
Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).
A genus of protozoa, formerly also considered a fungus. Characteristics include the presence of violet to brown spores.
Formation of an acetyl derivative. (Stedman, 25th ed)
A guanine nucleotide containing two phosphate groups esterified to the sugar moiety.

Mammalian staufen is a double-stranded-RNA- and tubulin-binding protein which localizes to the rough endoplasmic reticulum. (1/5514)

Staufen (Stau) is a double-stranded RNA (dsRNA)-binding protein involved in mRNA transport and localization in Drosophila. To understand the molecular mechanisms of mRNA transport in mammals, we cloned human (hStau) and mouse (mStau) staufen cDNAs. In humans, four transcripts arise by differential splicing of the Stau gene and code for two proteins with different N-terminal extremities. In vitro, hStau and mStau bind dsRNA via each of two full-length dsRNA-binding domains and tubulin via a region similar to the microtubule-binding domain of MAP-1B, suggesting that Stau cross-links cytoskeletal and RNA components. Immunofluorescent double labeling of transfected mammalian cells revealed that Stau is localized to the rough endoplasmic reticulum (RER), implicating this RNA-binding protein in mRNA targeting to the RER, perhaps via a multistep process involving microtubules. These results are the first demonstration of the association of an RNA-binding protein in addition to ribosomal proteins, with the RER, implicating this class of proteins in the transport of RNA to its site of translation.  (+info)

Mutations of oncoprotein 18/stathmin identify tubulin-directed regulatory activities distinct from tubulin association. (2/5514)

Oncoprotein 18/stathmin (Op18) is a recently identified phosphorylation-responsive regulator of the microtubule (MT) system. It was originally proposed that Op18 specifically regulates dynamic properties of MTs by associating with tubulin, but it has subsequently been proposed that Op18 acts simply by sequestering of tubulin heterodimers. We have dissected the mechanistic action of Op18 by generation of two distinct classes of mutants. One class has interruptions of the heptad repeats of a potential coiled-coil region of Op18, and the other involves substitution at all four phosphorylation sites with negatively charged Glu residues. Both types of mutation result in Op18 proteins with a limited decrease in tubulin complex formation. However, the MT-destabilizing activities of the coiled-coil mutants are more severely reduced in transfected leukemia cells than those of the Glu-substituted Op18 derivative, providing evidence for tubulin-directed regulatory activities distinct from tubulin complex formation. Analysis of Op18-mediated regulation of tubulin GTPase activity and taxol-promoted tubulin polymerization showed that while wild-type and Glu-substituted Op18 derivatives are active, the coiled-coil mutants are essentially inactive. This suggests that Op18-tubulin contact involves structural motifs that deliver a signal of regulatory importance to the MT system.  (+info)

Gibberellic acid stabilises microtubules in maize suspension cells to cold and stimulates acetylation of alpha-tubulin. (3/5514)

Gibberellic acid is known to stabilise microtubules in plant organs against depolymerisation. We have now devised a simplified cell system for studying this. Pretreatment of a maize cell suspension with gibberellic acid for just 3 h stabilised protoplast microtubules against depolymerisation on ice. In other eukaryotes, acetylation of alpha-tubulin is known to correlate with microtubule stabilisation but this is not established in plants. By isolating the polymeric tubulin fraction from maize cytoskeletons and immunoblotting with the antibody 6-11B-1, we have demonstrated that gibberellic acid stimulates the acetylation of alpha-tubulin. This is the first demonstrated link between microtubule stabilisation and tubulin acetylation in higher plants.  (+info)

Arsenic targets tubulins to induce apoptosis in myeloid leukemia cells. (4/5514)

Arsenic exhibits a differential toxicity to cancer cells. At a high concentration (>5 microM), As2O3 causes acute necrosis in various cell lines. At a lower concentration (0.5-5 microm), it induces myeloid cell maturation and an arrest in metaphase, leading to apoptosis. As2O3-treated cells have features found with both tubulin-assembling enhancers (Taxol) and inhibitors (colchicine). Prior treatment of monomeric tubulin with As2O3 markedly inhibits GTP-induced polymerization and microtubule formation in vitro but does not destabilize GTP-induced tubulin polymers. Cross-inhibition experiments indicate that As2O3 is a noncompetitive inhibitor of GTP binding to tubulin. These observations correlate with the three-dimensional structure of beta-tubulin and suggest that the cross-linking of two vicinal cysteine residues (Cys-12 and Cys-213) by trivalent arsenic inactivates the GTP binding site. Furthermore, exogenous GTP can prevent As2O3-induced mitotic arrest.  (+info)

Identification of a domain in guanylyl cyclase-activating protein 1 that interacts with a complex of guanylyl cyclase and tubulin in photoreceptors. (5/5514)

The membrane-bound guanylyl cyclase in rod photoreceptors is activated by guanylyl cyclase-activating protein 1 (GCAP-1) at low free [Ca2+]. GCAP-1 is a Ca2+-binding protein and belongs to the superfamily of EF-hand proteins. We created an oligopeptide library of overlapping peptides that encompass the entire amino acid sequence of GCAP-1. Peptides were used in competitive screening assays to identify interaction regions in GCAP-1 that directly bind the guanylyl cyclase in bovine photoreceptor cells. We found four regions in GCAP-1 that participate in regulating guanylyl cyclase. A 15-amino acid peptide located adjacent to the second EF-hand motif (Phe73-Lys87) was identified as the main interaction domain. Inhibition of GCAP-1-stimulated guanylyl cyclase activity by the peptide Phe73-Lys87 was completely relieved when an excess amount of GCAP-1 was added. An affinity column made from this peptide was able to bind a complex of photoreceptor guanylyl cyclase and tubulin. Using an anti-GCAP-1 antibody, we coimmunoprecipitated GCAP-1 with guanylyl cyclase and tubulin. Complex formation between GCAP-1 and guanylyl cyclase was observed independent of [Ca2+]. Our experiments suggest that there exists a tight association of guanylyl cyclase and tubulin in rod outer segments.  (+info)

Characterization of two related Drosophila gamma-tubulin complexes that differ in their ability to nucleate microtubules. (6/5514)

gamma-tubulin exists in two related complexes in Drosophila embryo extracts (Moritz, M., Y. Zheng, B.M. Alberts, and K. Oegema. 1998. J. Cell Biol. 142:1- 12). Here, we report the purification and characterization of both complexes that we name gamma-tubulin small complex (gammaTuSC; approximately 280,000 D) and Drosophila gammaTuRC ( approximately 2,200,000 D). In addition to gamma-tubulin, the gammaTuSC contains Dgrip84 and Dgrip91, two proteins homologous to the Spc97/98p protein family. The gammaTuSC is a structural subunit of the gammaTuRC, a larger complex containing about six additional polypeptides. Like the gammaTuRC isolated from Xenopus egg extracts (Zheng, Y., M.L. Wong, B. Alberts, and T. Mitchison. 1995. Nature. 378:578-583), the Drosophila gammaTuRC can nucleate microtubules in vitro and has an open ring structure with a diameter of 25 nm. Cryo-electron microscopy reveals a modular structure with approximately 13 radially arranged structural repeats. The gammaTuSC also nucleates microtubules, but much less efficiently than the gammaTuRC, suggesting that assembly into a larger complex enhances nucleating activity. Analysis of the nucleotide content of the gammaTuSC reveals that gamma-tubulin binds preferentially to GDP over GTP, rendering gamma-tubulin an unusual member of the tubulin superfamily.  (+info)

Genetic analysis of viable Hsp90 alleles reveals a critical role in Drosophila spermatogenesis. (7/5514)

The Hsp90 chaperone protein maintains the activities of a remarkable variety of signal transducers, but its most critical functions in the context of the whole organism are unknown. Point mutations of Hsp83 (the Drosophila Hsp90 gene) obtained in two different screens are lethal as homozygotes. We report that eight transheterozygous mutant combinations produce viable adults. All exhibit the same developmental defects: sterile males and sterile or weakly fertile females. We also report that scratch, a previously identified male-sterile mutation, is an allele of Hsp82 with a P-element insertion in the intron that reduces expression. Thus, it is a simple reduction in Hsp90 function, rather than possible altered functions in the point mutants, that leads to male sterility. As shown by light and electron microscopy, all stages of spermatogenesis involving microtubule function are affected, from early mitotic divisions to later stages of sperm maturation, individualization, and motility. Aberrant microtubules are prominent in yeast cells carrying mutations in HSP82 (the yeast Hsp90 gene), confirming that Hsp90 function is connected to microtubule dynamics and that this connection is highly conserved. A small fraction of Hsp90 copurifies with taxol-stabilized microtubule proteins in Drosophila embryo extracts, but Hsp90 does not remain associated with microtubules through repeated temperature-induced assembly and disassembly reactions. If the spermatogenesis phenotypes are due to defects in microtubule dynamics, we suggest these are indirect, reflecting a role for Hsp90 in maintaining critical signal transduction pathways and microtubule effectors, rather than a direct role in the assembly and disassembly of microtubules themselves.  (+info)

Mechanisms of action of and resistance to antitubulin agents: microtubule dynamics, drug transport, and cell death. (8/5514)

PURPOSE: To analyze the available data concerning mechanisms of action of and mechanisms of resistance to the antitubulin agents, vinca alkaloids and taxanes, and more recently described compounds. DESIGN: We conducted a review of the literature on classic and recent antitubulin agents, focusing particularly on the relationships between antitubulin agents and their intracellular target, the soluble tubulin/microtubule complex. RESULTS AND CONCLUSION: Although it is widely accepted that antitubulin agents block cell division by inhibition of the mitotic spindle, the mechanism of action of antitubulin agents on microtubules remains to be determined. The classic approach is that vinca alkaloids depolymerize microtubules, thereby increasing the soluble tubulin pool, whereas taxanes stabilize microtubules and increase the microtubular mass. More recent data suggest that both classes of agents have a similar mechanism of action, involving the inhibition of microtubule dynamics. These data suggest that vinca alkaloids and taxanes may act synergistically as antitumor agents and may be administered as combination chemotherapy in the clinic. However, enhanced myeloid and neurologic toxicity, as well as a strong dependence on the sequence of administration, presently exclude these combinations outside the context of clinical trials. Although the multidrug resistance phenotype mediated by Pgp appears to be an important mechanism of resistance to these agents, alterations of microtubule structure resulting in altered microtubule dynamics and/or altered binding of antitubulin agents may constitute a significant mechanism of drug resistance.  (+info)

Tubulin is a type of protein that forms microtubules, which are hollow cylindrical structures involved in the cell's cytoskeleton. These structures play important roles in various cellular processes, including maintaining cell shape, cell division, and intracellular transport. There are two main types of tubulin proteins: alpha-tubulin and beta-tubulin. They polymerize to form heterodimers, which then assemble into microtubules. The assembly and disassembly of microtubules are dynamic processes that are regulated by various factors, including GTP hydrolysis, motor proteins, and microtubule-associated proteins (MAPs). Tubulin is an essential component of the eukaryotic cell and has been a target for anti-cancer drugs such as taxanes and vinca alkaloids.

Tubulin modulators are a class of drugs that target and alter the function or structure of tubulin, which is a key component of microtubules in cells. These drugs can either stabilize or destabilize microtubules by interacting with tubulin, leading to various effects on cell division and other processes that rely on microtubule dynamics.

There are two main types of tubulin modulators:

1. Microtubule stabilizers: These drugs promote the assembly and stability of microtubules by binding to tubulin, preventing its disassembly. Examples include taxanes (e.g., paclitaxel) and vinca alkaloids (e.g., vinblastine). They are primarily used as anticancer agents because they interfere with the division of cancer cells.
2. Microtubule destabilizers: These drugs inhibit the formation and stability of microtubules by binding to tubulin, promoting its disassembly. Examples include colchicine, vinca alkaloids (e.g., vinorelbine), and combretastatins. They can also be used as anticancer agents because they disrupt the mitotic spindle during cell division, leading to cancer cell death.

Tubulin modulators have various other effects on cells beyond their impact on microtubules, such as interfering with intracellular transport and signaling pathways. These diverse actions contribute to their therapeutic potential in treating diseases like cancer, but they can also lead to side effects that limit their clinical use.

Microtubules are hollow, cylindrical structures composed of tubulin proteins in the cytoskeleton of eukaryotic cells. They play crucial roles in various cellular processes such as maintaining cell shape, intracellular transport, and cell division (mitosis and meiosis). Microtubules are dynamic, undergoing continuous assembly and disassembly, which allows them to rapidly reorganize in response to cellular needs. They also form part of important cellular structures like centrioles, basal bodies, and cilia/flagella.

Colchicine is a medication that is primarily used to treat gout, a type of arthritis characterized by sudden and severe attacks of pain, swelling, redness, and tenderness in the joints. It works by reducing inflammation and preventing the formation of uric acid crystals that cause gout symptoms.

Colchicine is also used to treat familial Mediterranean fever (FMF), a genetic disorder that causes recurrent fevers and inflammation in the abdomen, chest, and joints. It can help prevent FMF attacks and reduce their severity.

The medication comes in the form of tablets or capsules that are taken by mouth. Common side effects of colchicine include diarrhea, nausea, vomiting, and abdominal pain. In rare cases, it can cause more serious side effects such as muscle weakness, nerve damage, and bone marrow suppression.

It is important to follow the dosage instructions carefully when taking colchicine, as taking too much of the medication can be toxic. People with certain health conditions, such as liver or kidney disease, may need to take a lower dose or avoid using colchicine altogether.

Microtubule proteins are a class of structural proteins that make up the microtubules, which are key components of the cytoskeleton in eukaryotic cells. The main microtubule protein is tubulin, which exists in two forms: alpha-tubulin and beta-tubulin. These tubulins polymerize to form heterodimers, which then assemble into protofilaments, which in turn aggregate to form hollow microtubules. Microtubules are dynamic structures that undergo continuous assembly and disassembly, and they play crucial roles in various cellular processes, including intracellular transport, cell division, and maintenance of cell shape. Other microtubule-associated proteins (MAPs) also bind to microtubules and regulate their stability, dynamics, and interactions with other cellular structures.

Medical Definition:
Microtubule-associated proteins (MAPs) are a diverse group of proteins that bind to microtubules, which are key components of the cytoskeleton in eukaryotic cells. MAPs play crucial roles in regulating microtubule dynamics and stability, as well as in mediating interactions between microtubules and other cellular structures. They can be classified into several categories based on their functions, including:

1. Microtubule stabilizers: These MAPs promote the assembly of microtubules and protect them from disassembly by enhancing their stability. Examples include tau proteins and MAP2.
2. Microtubule dynamics regulators: These MAPs modulate the rate of microtubule polymerization and depolymerization, allowing for dynamic reorganization of the cytoskeleton during cell division and other processes. Examples include stathmin and XMAP215.
3. Microtubule motor proteins: These MAPs use energy from ATP hydrolysis to move along microtubules, transporting various cargoes within the cell. Examples include kinesin and dynein.
4. Adapter proteins: These MAPs facilitate interactions between microtubules and other cellular structures, such as membranes, organelles, or signaling molecules. Examples include MAP4 and CLASPs.

Dysregulation of MAPs has been implicated in several diseases, including neurodegenerative disorders like Alzheimer's disease (where tau proteins form abnormal aggregates called neurofibrillary tangles) and cancer (where altered microtubule dynamics can contribute to uncontrolled cell division).

Demecolcine is a medication that belongs to the class of drugs called anticholinergics. It is derived from the plant alkaloid colchicine and has been used in medical research for its ability to arrest cells in metaphase, a specific stage of cell division. This property makes demecolcine useful in various laboratory procedures such as chromosome analysis and the production of cultured cell lines.

In clinical settings, demecolcine is not commonly used due to its narrow therapeutic index and potential for toxicity. However, it has been used off-label in some cases to treat conditions associated with uncontrolled cell division, such as certain types of cancer. Its use in these situations is typically reserved for when other treatments have failed or are not well tolerated.

It's important to note that demecolcine should only be administered under the close supervision of a healthcare professional and its use is generally avoided in pregnant women due to the risk of fetal harm.

Podophyllotoxin is a pharmaceutical agent derived from the podophyllum plant. It is an antimitotic compound that inhibits microtubule assembly, leading to cell cycle arrest and apoptosis. It is primarily used in topical form as a treatment for genital warts, caused by certain types of human papillomavirus (HPV). Podophyllotoxin works by interfering with the growth of the wart cells, eventually causing them to die off.

It's important to note that podophyllotoxin is a potent cytotoxic agent and should only be used under the supervision of a healthcare professional. It should not be taken orally or applied to open wounds, and it should be kept out of reach of children.

Stathmin, also known as oncoprotein 18 or OP18, is a microtubule-associated protein that plays a crucial role in the regulation of microtubule dynamics. It is involved in the destabilization of microtubules by promoting the depolymerization and inhibiting the polymerization of tubulin dimers. Stathmin has been found to be overexpressed in various types of cancer, making it a potential target for cancer therapy. Additionally, stathmin has been implicated in the regulation of cell division, differentiation, and motility, as well as in neuronal development and plasticity.

Guanosine triphosphate (GTP) is a nucleotide that plays a crucial role in various cellular processes, such as protein synthesis, signal transduction, and regulation of enzymatic activities. It serves as an energy currency, similar to adenosine triphosphate (ATP), and undergoes hydrolysis to guanosine diphosphate (GDP) or guanosine monophosphate (GMP) to release energy required for these processes. GTP is also a precursor for the synthesis of other essential molecules, including RNA and certain signaling proteins. Additionally, it acts as a molecular switch in many intracellular signaling pathways by binding and activating specific GTPase proteins.

Vinblastine is an alkaloid derived from the Madagascar periwinkle plant (Catharanthus roseus) and is primarily used in cancer chemotherapy. It is classified as a vinca alkaloid, along with vincristine, vinorelbine, and others.

Medically, vinblastine is an antimicrotubule agent that binds to tubulin, a protein involved in the formation of microtubules during cell division. By binding to tubulin, vinblastine prevents the assembly of microtubules, which are essential for mitosis (cell division). This leads to the inhibition of cell division and ultimately results in the death of rapidly dividing cells, such as cancer cells.

Vinblastine is used to treat various types of cancers, including Hodgkin's lymphoma, non-Hodgkin's lymphoma, testicular cancer, breast cancer, and others. It is often administered intravenously in a healthcare setting and may be given as part of a combination chemotherapy regimen with other anticancer drugs.

As with any medication, vinblastine can have side effects, including bone marrow suppression (leading to an increased risk of infection, anemia, and bleeding), neurotoxicity (resulting in peripheral neuropathy, constipation, and jaw pain), nausea, vomiting, hair loss, and mouth sores. Regular monitoring by a healthcare professional is necessary during vinblastine treatment to manage side effects and ensure the safe and effective use of this medication.

Paclitaxel is a chemotherapeutic agent derived from the bark of the Pacific yew tree (Taxus brevifolia). It is an antimicrotubule agent that promotes the assembly and stabilization of microtubules, thereby interfering with the normal dynamic reorganization of the microtubule network that is essential for cell division.

Paclitaxel is used in the treatment of various types of cancer including ovarian, breast, lung, and pancreatic cancers. It works by inhibiting the disassembly of microtubules, which prevents the separation of chromosomes during mitosis, leading to cell cycle arrest and apoptosis (programmed cell death).

Common side effects of paclitaxel include neutropenia (low white blood cell count), anemia (low red blood cell count), alopecia (hair loss), peripheral neuropathy (nerve damage causing numbness or tingling in the hands and feet), myalgias (muscle pain), arthralgias (joint pain), and hypersensitivity reactions.

In the context of medical definitions, polymers are large molecules composed of repeating subunits called monomers. These long chains of monomers can have various structures and properties, depending on the type of monomer units and how they are linked together. In medicine, polymers are used in a wide range of applications, including drug delivery systems, medical devices, and tissue engineering scaffolds. Some examples of polymers used in medicine include polyethylene, polypropylene, polystyrene, polyvinyl chloride (PVC), and biodegradable polymers such as polylactic acid (PLA) and polycaprolactone (PCL).

I'm happy to help! However, it seems there might be a bit of confusion here. "Sea urchins" is a common name that refers to a type of marine invertebrate animal, typically characterized by their round, spiny shells. They belong to the class Echinoidea within the phylum Echinodermata.

Medically speaking, there isn't a specific definition for "sea urchins." However, if you come into contact with sea urchins while swimming or diving and accidentally step on them, their spines can puncture your skin and potentially cause an infection. In this case, medical attention may be necessary to remove the embedded spines and treat any resulting infection.

If you were referring to a specific medical term related to sea urchins, could you please clarify? I'm here to help!

Maytansine is not typically defined in a medical dictionary as it is not a medical term itself, but rather a chemical compound. Maytansine is a natural product that was initially isolated from the bark of the African shrub Maytenus ovatus. It is a potent antimitotic agent, which means it interferes with cell division and has been studied for its potential use in cancer treatment.

In medical contexts, maytansine is often discussed in relation to specific drugs or therapies that utilize this compound. For example, the drug DM1 (also known as maytansinoid 1) is a derivative of maytansine and has been conjugated with monoclonal antibodies for targeted cancer therapy.

Therefore, when discussing 'Maytansine' in a medical context, it generally refers to the chemical compound or its derivatives that have potential use as anticancer agents.

Electron microscopy (EM) is a type of microscopy that uses a beam of electrons to create an image of the sample being examined, resulting in much higher magnification and resolution than light microscopy. There are several types of electron microscopy, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and reflection electron microscopy (REM).

In TEM, a beam of electrons is transmitted through a thin slice of the sample, and the electrons that pass through the sample are focused to form an image. This technique can provide detailed information about the internal structure of cells, viruses, and other biological specimens, as well as the composition and structure of materials at the atomic level.

In SEM, a beam of electrons is scanned across the surface of the sample, and the electrons that are scattered back from the surface are detected to create an image. This technique can provide information about the topography and composition of surfaces, as well as the structure of materials at the microscopic level.

REM is a variation of SEM in which the beam of electrons is reflected off the surface of the sample, rather than scattered back from it. This technique can provide information about the surface chemistry and composition of materials.

Electron microscopy has a wide range of applications in biology, medicine, and materials science, including the study of cellular structure and function, disease diagnosis, and the development of new materials and technologies.

The brain is the central organ of the nervous system, responsible for receiving and processing sensory information, regulating vital functions, and controlling behavior, movement, and cognition. It is divided into several distinct regions, each with specific functions:

1. Cerebrum: The largest part of the brain, responsible for higher cognitive functions such as thinking, learning, memory, language, and perception. It is divided into two hemispheres, each controlling the opposite side of the body.
2. Cerebellum: Located at the back of the brain, it is responsible for coordinating muscle movements, maintaining balance, and fine-tuning motor skills.
3. Brainstem: Connects the cerebrum and cerebellum to the spinal cord, controlling vital functions such as breathing, heart rate, and blood pressure. It also serves as a relay center for sensory information and motor commands between the brain and the rest of the body.
4. Diencephalon: A region that includes the thalamus (a major sensory relay station) and hypothalamus (regulates hormones, temperature, hunger, thirst, and sleep).
5. Limbic system: A group of structures involved in emotional processing, memory formation, and motivation, including the hippocampus, amygdala, and cingulate gyrus.

The brain is composed of billions of interconnected neurons that communicate through electrical and chemical signals. It is protected by the skull and surrounded by three layers of membranes called meninges, as well as cerebrospinal fluid that provides cushioning and nutrients.

Peptide synthases are a group of enzymes that catalyze the formation of peptide bonds between specific amino acids to produce peptides or proteins. They are responsible for the biosynthesis of many natural products, including antibiotics, bacterial toxins, and immunomodulatory peptides.

Peptide synthases are large, complex enzymes that consist of multiple domains and modules, each of which is responsible for activating and condensing specific amino acids. The activation of amino acids involves the formation of an aminoacyl-adenylate intermediate, followed by transfer of the activated amino acid to a thiol group on the enzyme. The condensation of two activated amino acids results in the formation of a peptide bond and release of adenosine monophosphate (AMP) and pyrophosphate.

Peptide synthases are found in all three domains of life, but are most commonly associated with bacteria and fungi. They play important roles in the biosynthesis of many natural products that have therapeutic potential, making them targets for drug discovery and development.

Protein binding, in the context of medical and biological sciences, refers to the interaction between a protein and another molecule (known as the ligand) that results in a stable complex. This process is often reversible and can be influenced by various factors such as pH, temperature, and concentration of the involved molecules.

In clinical chemistry, protein binding is particularly important when it comes to drugs, as many of them bind to proteins (especially albumin) in the bloodstream. The degree of protein binding can affect a drug's distribution, metabolism, and excretion, which in turn influence its therapeutic effectiveness and potential side effects.

Protein-bound drugs may be less available for interaction with their target tissues, as only the unbound or "free" fraction of the drug is active. Therefore, understanding protein binding can help optimize dosing regimens and minimize adverse reactions.

Biopolymers are large molecules composed of repeating subunits known as monomers, which are derived from living organisms or synthesized by them. They can be natural or synthetic and are often classified based on their origin and structure. Some examples of biopolymers include proteins, nucleic acids (DNA and RNA), polysaccharides (such as cellulose and starch), and some types of polyesters (such as polyhydroxyalkanoates or PHAs). Biopolymers have a wide range of applications in various industries, including medicine, food, packaging, and biotechnology.

Nocodazole is not a medical condition or disease, but rather a pharmacological agent used in medical research and clinical settings. It's a synthetic chemical compound that belongs to the class of drugs known as microtubule inhibitors. Nocodazole works by binding to and disrupting the dynamic assembly and disassembly of microtubules, which are important components of the cell's cytoskeleton and play a critical role in cell division.

Nocodazole is primarily used in research settings as a tool for studying cell biology and mitosis, the process by which cells divide. It can be used to synchronize cells in the cell cycle or to induce mitotic arrest, making it useful for investigating various aspects of cell division and chromosome behavior.

In clinical settings, nocodazole has been used off-label as a component of some cancer treatment regimens, particularly in combination with other chemotherapeutic agents. Its ability to disrupt microtubules can interfere with the proliferation of cancer cells and enhance the effectiveness of certain anti-cancer drugs. However, its use is not widespread due to potential side effects and the availability of alternative treatments.

"Cattle" is a term used in the agricultural and veterinary fields to refer to domesticated animals of the genus *Bos*, primarily *Bos taurus* (European cattle) and *Bos indicus* (Zebu). These animals are often raised for meat, milk, leather, and labor. They are also known as bovines or cows (for females), bulls (intact males), and steers/bullocks (castrated males). However, in a strict medical definition, "cattle" does not apply to humans or other animals.

Tropolone is not a medical term, but a chemical compound. It is an organic compound with the formula C7H6O2 and is a colorless solid that is slightly soluble in water. Tropolone has a seven-membered ring containing six carbon atoms and one oxygen atom, which is aromatic.

Tropolone and its derivatives have been studied for their potential medicinal properties, including anti-inflammatory, antimicrobial, and anticancer activities. However, there are no tropolone-based drugs currently approved for medical use in humans.

Cilia are tiny, hair-like structures that protrude from the surface of many types of cells in the body. They are composed of a core bundle of microtubules surrounded by a protein matrix and are covered with a membrane. Cilia are involved in various cellular functions, including movement of fluid or mucus across the cell surface, detection of external stimuli, and regulation of signaling pathways.

There are two types of cilia: motile and non-motile. Motile cilia are able to move in a coordinated manner to propel fluids or particles across a surface, such as those found in the respiratory tract and reproductive organs. Non-motile cilia, also known as primary cilia, are present on most cells in the body and serve as sensory organelles that detect chemical and mechanical signals from the environment.

Defects in cilia structure or function can lead to a variety of diseases, collectively known as ciliopathies. These conditions can affect multiple organs and systems in the body, including the brain, kidneys, liver, and eyes. Examples of ciliopathies include polycystic kidney disease, Bardet-Biedl syndrome, and Meckel-Gruber syndrome.

The cytoskeleton is a complex network of various protein filaments that provides structural support, shape, and stability to the cell. It plays a crucial role in maintaining cellular integrity, intracellular organization, and enabling cell movement. The cytoskeleton is composed of three major types of protein fibers: microfilaments (actin filaments), intermediate filaments, and microtubules. These filaments work together to provide mechanical support, participate in cell division, intracellular transport, and help maintain the cell's architecture. The dynamic nature of the cytoskeleton allows cells to adapt to changing environmental conditions and respond to various stimuli.

Brain chemistry refers to the chemical processes that occur within the brain, particularly those involving neurotransmitters, neuromodulators, and neuropeptides. These chemicals are responsible for transmitting signals between neurons (nerve cells) in the brain, allowing for various cognitive, emotional, and physical functions.

Neurotransmitters are chemical messengers that transmit signals across the synapse (the tiny gap between two neurons). Examples of neurotransmitters include dopamine, serotonin, norepinephrine, GABA (gamma-aminobutyric acid), and glutamate. Each neurotransmitter has a specific role in brain function, such as regulating mood, motivation, attention, memory, and movement.

Neuromodulators are chemicals that modify the effects of neurotransmitters on neurons. They can enhance or inhibit the transmission of signals between neurons, thereby modulating brain activity. Examples of neuromodulators include acetylcholine, histamine, and substance P.

Neuropeptides are small protein-like molecules that act as neurotransmitters or neuromodulators. They play a role in various physiological functions, such as pain perception, stress response, and reward processing. Examples of neuropeptides include endorphins, enkephalins, and oxytocin.

Abnormalities in brain chemistry can lead to various neurological and psychiatric conditions, such as depression, anxiety disorders, schizophrenia, Parkinson's disease, and Alzheimer's disease. Understanding brain chemistry is crucial for developing effective treatments for these conditions.

Mitosis is a type of cell division in which the genetic material of a single cell, called the mother cell, is equally distributed into two identical daughter cells. It's a fundamental process that occurs in multicellular organisms for growth, maintenance, and repair, as well as in unicellular organisms for reproduction.

The process of mitosis can be broken down into several stages: prophase, prometaphase, metaphase, anaphase, and telophase. During prophase, the chromosomes condense and become visible, and the nuclear envelope breaks down. In prometaphase, the nuclear membrane is completely disassembled, and the mitotic spindle fibers attach to the chromosomes at their centromeres.

During metaphase, the chromosomes align at the metaphase plate, an imaginary line equidistant from the two spindle poles. In anaphase, sister chromatids are pulled apart by the spindle fibers and move toward opposite poles of the cell. Finally, in telophase, new nuclear envelopes form around each set of chromosomes, and the chromosomes decondense and become less visible.

Mitosis is followed by cytokinesis, a process that divides the cytoplasm of the mother cell into two separate daughter cells. The result of mitosis and cytokinesis is two genetically identical cells, each with the same number and kind of chromosomes as the original parent cell.

Polyglutamic acid (PGA) is not a medical term per se, but it is a term used in biochemistry and cosmetics. Medically, it may be mentioned in the context of certain medical conditions or treatments. Here's a definition:

Polyglutamic acid is a polymer of glutamic acid, a type of amino acid. It is a natural substance found in various foods such as natto, a traditional Japanese fermented soybean dish. In the human body, it is produced by certain bacteria during fermentation processes.

PGA has been studied for its potential medical applications due to its unique properties, including its ability to retain moisture and form gels. It has been explored as a wound dressing material, drug delivery vehicle, and anti-aging cosmetic ingredient. However, it is not a widely used or recognized medical treatment at this time.

In the context of medicine and pharmacology, "kinetics" refers to the study of how a drug moves throughout the body, including its absorption, distribution, metabolism, and excretion (often abbreviated as ADME). This field is called "pharmacokinetics."

1. Absorption: This is the process of a drug moving from its site of administration into the bloodstream. Factors such as the route of administration (e.g., oral, intravenous, etc.), formulation, and individual physiological differences can affect absorption.

2. Distribution: Once a drug is in the bloodstream, it gets distributed throughout the body to various tissues and organs. This process is influenced by factors like blood flow, protein binding, and lipid solubility of the drug.

3. Metabolism: Drugs are often chemically modified in the body, typically in the liver, through processes known as metabolism. These changes can lead to the formation of active or inactive metabolites, which may then be further distributed, excreted, or undergo additional metabolic transformations.

4. Excretion: This is the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys (urine) and the liver (bile).

Understanding the kinetics of a drug is crucial for determining its optimal dosing regimen, potential interactions with other medications or foods, and any necessary adjustments for special populations like pediatric or geriatric patients, or those with impaired renal or hepatic function.

The spindle apparatus is a microtubule-based structure that plays a crucial role in the process of cell division, specifically during mitosis and meiosis. It consists of three main components:

1. The spindle poles: These are organized structures composed of microtubules and associated proteins that serve as the anchoring points for the spindle fibers. In animal cells, these poles are typically formed by centrosomes, while in plant cells, they form around nucleation sites called microtubule-organizing centers (MTOCs).
2. The spindle fibers: These are dynamic arrays of microtubules that extend between the two spindle poles. They can be categorized into three types: kinetochore fibers, which connect to the kinetochores on chromosomes; astral fibers, which radiate from the spindle poles and help position the spindle within the cell; and interpolar fibers, which lie between the two spindle poles and contribute to their separation during anaphase.
3. Regulatory proteins: Various motor proteins, such as dynein and kinesin, as well as non-motor proteins like tubulin and septins, are involved in the assembly, maintenance, and dynamics of the spindle apparatus. These proteins help to generate forces that move chromosomes, position the spindle, and ultimately segregate genetic material between two daughter cells during cell division.

The spindle apparatus is essential for ensuring accurate chromosome separation and maintaining genomic stability during cell division. Dysfunction of the spindle apparatus can lead to various abnormalities, including aneuploidy (abnormal number of chromosomes) and chromosomal instability, which have been implicated in several diseases, such as cancer and developmental disorders.

Kinesin is not a medical term per se, but a term from the field of cellular biology. However, understanding how kinesins work is important in the context of medical and cellular research.

Kinesins are a family of motor proteins that play a crucial role in transporting various cargoes within cells, such as vesicles, organelles, and chromosomes. They move along microtubule filaments, using the energy derived from ATP hydrolysis to generate mechanical force and motion. This process is essential for several cellular functions, including intracellular transport, mitosis, and meiosis.

In a medical context, understanding kinesin function can provide insights into various diseases and conditions related to impaired intracellular transport, such as neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, and Huntington's disease) and certain genetic disorders affecting motor neurons. Research on kinesins can potentially lead to the development of novel therapeutic strategies targeting these conditions.

Macromolecular substances, also known as macromolecules, are large, complex molecules made up of repeating subunits called monomers. These substances are formed through polymerization, a process in which many small molecules combine to form a larger one. Macromolecular substances can be naturally occurring, such as proteins, DNA, and carbohydrates, or synthetic, such as plastics and synthetic fibers.

In the context of medicine, macromolecular substances are often used in the development of drugs and medical devices. For example, some drugs are designed to bind to specific macromolecules in the body, such as proteins or DNA, in order to alter their function and produce a therapeutic effect. Additionally, macromolecular substances may be used in the creation of medical implants, such as artificial joints and heart valves, due to their strength and durability.

It is important for healthcare professionals to have an understanding of macromolecular substances and how they function in the body, as this knowledge can inform the development and use of medical treatments.

Chaperonin Containing TCP-1 (CCT) is a protein complex that assists in the folding of other proteins in the cytosol of eukaryotic cells. It is composed of two rings, each containing eight different subunits (designated as CCTα, CCTβ, CCTγ, CCTδ, CCTε, CCTζ, CCTη, and CCTθ or TCP-1, TCP-2, TCP-3, TCP-4, TCP-5, TCP-6, TCP-7, and TCP-8). CCT plays a crucial role in the proper folding of newly synthesized polypeptides and helps maintain protein homeostasis within the cell.

Vinca alkaloids are a group of naturally occurring chemicals derived from the Madagascar periwinkle plant, Catharanthus roseus. They are known for their antineoplastic (cancer-fighting) properties and are used in chemotherapy to treat various types of cancer. Some examples of vinca alkaloids include vinblastine, vincristine, and vinorelbine. These agents work by disrupting the normal function of microtubules, which are important components of the cell's structure and play a critical role in cell division. By binding to tubulin, a protein that makes up microtubules, vinca alkaloids prevent the formation of mitotic spindles, which are necessary for cell division. This leads to cell cycle arrest and apoptosis (programmed cell death) in cancer cells. However, vinca alkaloids can also affect normal cells, leading to side effects such as neurotoxicity, myelosuppression, and gastrointestinal disturbances.

An axoneme is the microtubular structure that forms the core of a cilium or flagellum in eukaryotic cells. It is composed of nine pairs of peripheral microtubules, known as doublets, surrounding two central single microtubules, forming a "9+2" arrangement. The axoneme is anchored to the cell membrane through a basal body and provides the structural framework for the movement of cilia and flagella. It is composed of tubulin proteins and accessory structures such as dynein arms, which are responsible for generating the force required for ciliary or flagellar movement.

Benomyl is a systemic fungicide that is derived from methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate. It works by inhibiting the synthesis of microtubules in fungal cells, which are necessary for cell division and growth. Benomyl is used to control a wide range of fungal diseases in crops such as cereals, fruits, vegetables, and ornamental plants. However, it has been banned or restricted in many countries due to its potential toxicity to non-target organisms, including humans.

In medical contexts, benomyl is not used as a drug or therapy. It can be harmful if ingested, inhaled, or comes into contact with the skin, and may cause symptoms such as nausea, vomiting, diarrhea, abdominal pain, dizziness, headache, and respiratory difficulties. Long-term exposure to benomyl has been linked to neurological and reproductive effects in animals, but its effects on human health are not well understood.

The "sperm tail" is also known as the flagellum, which is a whip-like structure that enables the sperm to move or swim through fluid. The human sperm tail is made up of nine microtubule doublets and a central pair of microtubules, which are surrounded by a mitochondrial sheath that provides energy for its movement. This complex structure allows the sperm to navigate through the female reproductive tract in order to reach and fertilize an egg.

In the context of medical and biological sciences, a "binding site" refers to a specific location on a protein, molecule, or cell where another molecule can attach or bind. This binding interaction can lead to various functional changes in the original protein or molecule. The other molecule that binds to the binding site is often referred to as a ligand, which can be a small molecule, ion, or even another protein.

The binding between a ligand and its target binding site can be specific and selective, meaning that only certain ligands can bind to particular binding sites with high affinity. This specificity plays a crucial role in various biological processes, such as signal transduction, enzyme catalysis, or drug action.

In the case of drug development, understanding the location and properties of binding sites on target proteins is essential for designing drugs that can selectively bind to these sites and modulate protein function. This knowledge can help create more effective and safer therapeutic options for various diseases.

"Swine" is a common term used to refer to even-toed ungulates of the family Suidae, including domestic pigs and wild boars. However, in a medical context, "swine" often appears in the phrase "swine flu," which is a strain of influenza virus that typically infects pigs but can also cause illness in humans. The 2009 H1N1 pandemic was caused by a new strain of swine-origin influenza A virus, which was commonly referred to as "swine flu." It's important to note that this virus is not transmitted through eating cooked pork products; it spreads from person to person, mainly through respiratory droplets produced when an infected person coughs or sneezes.

"Physarum" is not a term that has a specific medical definition. It is a genus of slime molds, which are single-celled organisms that can behave as multicellular entities under certain conditions. They are often studied in biological research for their unique behaviors and abilities, but they do not have direct relevance to human medicine.

Acetylation is a chemical process that involves the addition of an acetyl group (-COCH3) to a molecule. In the context of medical biochemistry, acetylation often refers to the post-translational modification of proteins, where an acetyl group is added to the amino group of a lysine residue in a protein by an enzyme called acetyltransferase. This modification can alter the function or stability of the protein and plays a crucial role in regulating various cellular processes such as gene expression, DNA repair, and cell signaling. Acetylation can also occur on other types of molecules, including lipids and carbohydrates, and has important implications for drug metabolism and toxicity.

Guanosine diphosphate (GDP) is a nucleotide that consists of a guanine base, a sugar molecule called ribose, and two phosphate groups. It is an ester of pyrophosphoric acid with the hydroxy group of the ribose sugar at the 5' position. GDP plays a crucial role as a secondary messenger in intracellular signaling pathways and also serves as an important intermediate in the synthesis of various biomolecules, such as proteins and polysaccharides.

In cells, GDP is formed from the hydrolysis of guanosine triphosphate (GTP) by enzymes called GTPases, which convert GTP to GDP and release energy that can be used to power various cellular processes. The conversion of GDP back to GTP can be facilitated by nucleotide diphosphate kinases, allowing for the recycling of these nucleotides within the cell.

It is important to note that while guanosine diphosphate has a significant role in biochemical processes, it is not typically associated with medical conditions or diseases directly. However, understanding its function and regulation can provide valuable insights into various physiological and pathophysiological mechanisms.

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