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Haemozoin
Haemozoin is a disposal product formed from the digestion of blood by some blood-feeding parasites. These hematophagous organisms such as malaria parasites (''Plasmodium spp.''), ''Rhodnius'' and '' Schistosoma'' digest haemoglobin and release high quantities of free heme, which is the protein component of haemoglobin. Heme is a prosthetic group consisting of an iron atom contained in the center of a heterocyclic porphyrin ring. Free heme is toxic to cells, so the parasites convert it into an insoluble crystalline form called hemozoin. In malaria parasites, hemozoin is often called ''malaria pigment''. Since the formation of hemozoin is essential to the survival of these parasites, it is an attractive target for developing drugs and is much-studied in ''Plasmodium'' as a way to find drugs to treat malaria (malaria's Achilles' heel). Several currently used antimalarial drugs, such as chloroquine and mefloquine, are thought to kill malaria parasites by inhibiting haemozoin biocry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Louis Alphonse Laveran
Charles Louis Alphonse Laveran (18 June 1845 – 18 May 1922) was a French physician who won the Nobel Prize in Physiology or Medicine in 1907 for his discoveries of parasitic protozoans as causative agents of infectious diseases such as malaria and trypanosomiasis. Following his father, Louis Théodore Laveran, he took up military medicine as his profession. He obtained his medical degree from University of Strasbourg in 1867. At the outbreak of the Franco-Prussian War in 1870, he joined the French Army. At the age of 29 he became Chair of Military Diseases and Epidemics at the École de Val-de-Grâce. At the end of his tenure in 1878 he worked in Algeria, where he made his major achievements. He discovered that the protozoan parasite ''Plasmodium'' was responsible for malaria, and that ''Trypanosoma'' caused trypanosomiasis or African sleeping sickness. In 1894 he returned to France to serve in various military health services. In 1896 he joined Pasteur Institute as Chief of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringent P
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polariza ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achilles' Heel
An Achilles' heel (or Achilles heel) is a weakness in spite of overall strength, which can lead to downfall. While the mythological origin refers to a physical vulnerability, idiomatic references to other attributes or qualities that can lead to downfall are common. Origin In Greek mythology, when Achilles was an infant, it was foretold that he would perish at a young age. To prevent his death, his mother Thetis took Achilles to the River Styx, which was supposed to offer powers of invulnerability. She dipped his body into the water but, because she held him by his heel, it was not touched by the water of the river. Achilles grew up to be a man of war who survived many great battles. Although the death of Achilles was predicted by Hector in Homer’s ''Iliad'', it does not actually occur in the ''Iliad,'' but it is described in later Greek and Roman poetry and drama concerning events after the ''Iliad'', later in the Trojan War. In the myths surrounding the war, Achilles was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Oxygen Species
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () produces superoxide (), which is the precursor to most other reactive oxygen species: :O2 + e^- -> \ ^\bullet O2- Dismutation of superoxide produces hydrogen peroxide (): :2 H+ + \ ^\bullet O2^- + \ ^\bullet O2^- -> H2O2 + O2 Hydrogen peroxide in turn may be partially reduced, thus forming hydroxide ions and hydroxyl radicals (), or fully reduced to water: :H2O2 + e^- -> HO^- + \ ^\bullet OH :2 H+ + 2 e- + H2O2 -> 2 H2O In a biological context, ROS are byproducts of the normal metabolism of oxygen. ROS have roles in cell signaling and homeostasis. ROS are intrinsic to cellular functioning, and are present at low and stationary levels in normal cells. In plants, ROS are involved in metabolic processes related to photoprotection and toleran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pro-oxidant
Pro-oxidants are chemicals that induce oxidative stress, either by generating reactive oxygen species or by inhibiting antioxidant systems. The oxidative stress produced by these chemicals can damage cells and tissues, for example an overdose of the analgesic paracetamol (acetaminophen) can fatally damage the liver, partly through its production of reactive oxygen species. Some substances can serve as either antioxidants or pro-oxidants, depending on conditions. Some of the conditions that are important include the concentration of the chemical and if oxygen or transition metals are present. While thermodynamically very favored, reduction of molecular oxygen or peroxide to superoxide or hydroxyl radical respectively is spin forbidden. This greatly reduces the rates of these reactions, thus allowing aerobic life to exist. As a result, the reduction of oxygen typically involves either the initial formation of singlet oxygen, or spin-orbit coupling through a reduction of a transitio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoporphyrin
Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not soluble in water. The name is often abbreviated as PPIX. Protoporphyrin IX contains a porphine core, a tetrapyrrole macrocycle with a marked aromatic character. Protoporphyrin IX is essentially planar, except for the N-H bonds that are bent out of the plane of the rings, in opposite (trans) directions. Nomenclature The general term protoporphyrin refers to porphine derivatives that have the outer hydrogen atoms in the four pyrrole rings replaced by other functional groups. The prefix proto often means 'first' in science nomenclature (such as carbon protoxide), hence Hans Fischer is thought to have coined the name protoporphyrin as the first class of porphyrins. Fischer described iron-deprived heme becoming the "proto-" porphyrin, particula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Westenra Sambon
Louis Westenra Sambon (original first name Luigi, 7 November 1867 – 30 August 1931) was an Italian-English physician who played important roles in understanding the causes ( etiology) of diseases. He described many pathogenic protozoans, insects, and helminths including the name '' Schistosoma mansoni'' for a blood fluke. He was an authority on the classification of parasitic tongue worms called Pentastomida (Linguatulida), and one of the genus ''Sambonia'' is named after him. Sambon was born in Milan, Italy, and obtained an M.D. from the University of Naples Federico II. He moved to England to work at the Liverpool School of Tropical Medicine. He originated theories on the nature of diseases such as sleeping sickness, malaria, pellagra, and cancer. Biography Sambon was born in Milan to an Italian father and an English mother. His father was an Italian soldier Commendatore (Commander) Jules Sambon, and her mother, Laura Elizabeth Day, was a distant relative of Charles Dickens. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization. The melanin pigments are produced in a specialized group of cells known as melanocytes. Functionally, eumelanin serves as protection against Ultraviolet, UV radiation. There are five basic types of melanin: eumelanin, pheomelanin, neuromelanin, allomelanin and pyomelanin. The most common type is eumelanin, of which there are two types— brown eumelanin and black eumelanin. Pheomelanin, which is produced when melanocytes are malfunctioning due to derivation of the gene to its recessive format is a cysteine-derivative that contains polybenzothiazine portions that are largely responsible for the of red yellow tint given to some skin or hair colors. Neuromelanin is found in the brain. Research ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ronald Ross
Sir Ronald Ross (13 May 1857 – 16 September 1932) was a British medical doctor who received the Nobel Prize for Physiology or Medicine in 1902 for his work on the transmission of malaria, becoming the first British Nobel laureate, and the first born outside Europe. His discovery of the malarial parasite in the gastrointestinal tract of a mosquito in 1897 proved that malaria was transmitted by mosquitoes, and laid the foundation for the method of combating the disease. Ross was a polymath, writing a number of poems, published several novels, and composed songs. He was also an amateur artist and mathematician. He worked in the Indian Medical Service for 25 years. It was during his service that he made the groundbreaking medical discovery. After resigning from his service in India, he joined the faculty of Liverpool School of Tropical Medicine, and continued as Professor and Chairman of Tropical Medicine of the institute for 10 years. In 1926, he became Director-in-Chief of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Blood Cell
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "hollow vessel", with ''-cyte'' translated as "cell" in modern usage), are the most common type of blood cell and the vertebrate's principal means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system. RBCs take up oxygen in the lungs, or in fish the gills, and release it into tissues while squeezing through the body's capillaries. The cytoplasm of a red blood cell is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells and the blood. Each human red blood cell contains approximately 270 million hemoglobin molecules. The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johann Heinrich Meckel
Johann Friedrich Meckel (17 October 1781 – 31 October 1833), often referred to as Johann Friedrich Meckel, the Younger, was a German anatomist born in Halle. He worked as a professor of anatomy, pathology and zoology at the University of Halle, Germany. Life and research In 1802, he received his medical doctorate from the University of Halle, defending his doctoral thesis ''De cordis conditionibus abnormibus'' on 8 April 1802. At Halle he had as instructors, Kurt Sprengel (1766-1833) and Johann Christian Reil (1759-1813). After graduation, Meckel continued his education in Würzburg, Vienna and Paris. In Paris, he assisted zoologist Georges Cuvier (1769–1832) with systematic analysis of anatomical and zootomical specimens. In 1810 he finished translating Cuvier's five-volume ''Leçons d’anatomie Comparée'' from French into German. In 1808, he became a full professor of normal and pathological anatomy, surgery and obstetrics at the University of Halle, replacing Justus Chr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biocrystallization
Biocrystallization is the formation of crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...s from organic macromolecules by living organisms. This may be a stress response, a normal part of metabolism such as processes that dispose of waste compounds, or a pathology. Template mediated crystallization is qualitatively different from ''in vitro'' crystallization. Enzyme inhibitor, Inhibitors of biocrystallization are of interest in drug design efforts against lithiasis and against pathogens that feed on blood, since many of these organisms use this process to safely dispose of heme. DNA Under severe stress conditions the bacteria ''Escherichia coli'' protects its DNA from damage by sequestering it within a crystalline structure. This process is mediated by the stress response ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
