Regnier de Graaf
Regnier de Graaf, original Dutch spelling Reinier de Graaf, or Latinized Reijnerus de Graeff was a Dutch physician and anatomist who made key discoveries in reproductive biology. His first name is spelled Reinier or Reynier. De Graaf was born in Schoonhoven and a relative to the De Graeff regent family, he studied medicine in Leiden. There his co-students were Jan Swammerdam, Niels Stensen and Frederik Ruysch, one of their professors was Franciscus Sylvius.. He submitted his doctoral thesis on the pancreas, went to France where he obtained his medical degree from the University of Angers. While in Paris, he turned to the study of the male genitalia, which led to a publication in 1668. Back in the Netherlands in 1667, De Graaf established himself in Delft. Since he was a Catholic in a Protestant country, he was unable to follow a university career. After the early death of a son, De Graaf was buried in the Oude Kerk in Delft; the reason for his death is unknown. He was, affected by his controversy with Swammerdam and the death of his son.
It has been speculated. His friend Antonie van Leeuwenhoek in his writings attributed his death to "choleric substances", in those days thought to be the cause of depression. A few months before his death De Graaf recommended, as a correspondent of the Royal Society in London, that attention be paid to Antonie van Leeuwenhoek and his work on the improvement of the microscope. De Graaf's position in the history of reproduction is unique, summarising the work of anatomists before his time, but unable to benefit from the advances about to be made by microscopy, although he reported its use by Antonie van Leeuwenhoek in 1673, his personal contributions include the description of testicular tubules, the efferent ducts, corpora lutea and to describe the function of the Fallopian tubes and hydrosalpinx. De Graaf may have been the first to understand the reproductive function of the Fallopian tube, described the hydrosalpinx, linking its development to female infertility. De Graaf invented a practical syringe, described in his third treatise.
His eponymous legacy are the Graafian follicles. He himself pointed out that he was not the first to described their development. From the observation of pregnancy in rabbits, he concluded that the follicle contained the oocyte, although he never observed it; the mature stage of the ovarian follicle is called the Graafian follicle in his honour, although others, including Fallopius, had noticed the follicles previously. The term Graafian follicle followed the introduction of the term ova Graafiana by Albrecht von Haller who like De Graaf still assumed that the follicle was the oocyte itself, although De Graaf realised the ovum was much smaller; the discovery of the human egg was made by Karl Ernst von Baer in 1827. De Graaf's contemporary Jan Swammerdam confronted him after his publication of DeMulierum Organis Generatione Inservientibu and accused him of taking credit of discoveries he and Johannes van Horne had made earlier regarding the importance of the ovary and its eggs. De Graaf was affected by the accusation.
De Graaf described female ejaculation and referred to an erogenous zone in the vagina that he himself linked with the male prostate. Further, De Graaf described the anatomy of the testicles and collected secretions of the gall bladder and the pancreas. Despite his contributions, De Graaf made a number of errors in addition to believing that the ovum was the follicle, he never consulted the ancient texts but repeated the accounts of others compounding their inaccuracies. Because he observed rabbits rather than humans, he assumed, he believed. He was not yet aware of the presence of spematozaoa as such. Based upon his rabbit experiments and the description of an ectopic pregnancy in a lady that had died in her 12th pregnancy in Paris, he assumed that the complete entity was present in the ovary, brought to life by the influence of the male ejaculatory fluid, transported to the uterus. De Graaf, R De succi pancreatici natura et usu exercitatio anatomico-medica De Graaf, R De Virorum Organis Generationi Inservientibus, de Clysteribus et de Usu Siphonis in Anatomia De Graaf, R De mulierum organis generationi inservientibus tractatus novus: demonstrans tam homines & animalia caetera omnia, quae vivipara dicuntur, haud minus quàm ovipara ab ovo originem ducere De Graaf, R Alle de Wercken.
Leyden, Netherlands. Houtzager HL. Reinier de Graaf 1641–1673. Rotterdam: Erasmus publishing, 1991. ISBN 90-5235-021-3. Houtzager HL. "Reinier De Graaf and his contribution to reproductive biology". European Journal of Obstetrics and Reproductive Biology. 90: 125–7. Doi:10.1016/S0301-211500258-X. PMID 10825629. Modlin IM. "Regnier de Graaf: Paris and the pancreas". Journal of Clinical Gastroenterology. 30: 109–13. Doi:10.1097/00004836-200003000-00001. PMID 10730914. Longo LD. American Journal of Obstetrics and Gynecology. 174: 794–5. Doi:10.1016/S0002-937870467-2. PMID 8623824. Wiesemann C. "Regnier de Graaf (1641–167
Homology (biology)
In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats, the arms of primates, the front flippers of whales and the forelegs of dogs and horses are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor; the term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, it was explicitly analysed by Pierre Belon in 1555. In developmental biology, organs that developed in the embryo in the same manner and from similar origins, such as from matching primordia in successive segments of the same animal, are serially homologous.
Examples include the legs of a centipede, the maxillary palp and labial palp of an insect, the spinous processes of successive vertebrae in a vertebral column. Male and female reproductive organs are homologous if they develop from the same embryonic tissue, as do the ovaries and testicles of mammals including humans. Sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event or a duplication event. Homology among proteins or DNA is inferred from their sequence similarity. Significant similarity is strong evidence that two sequences are related by divergent evolution from a common ancestor. Alignments of multiple sequences are used to discover the homologous regions. Homology remains controversial in animal behaviour, but there is suggestive evidence that, for example, dominance hierarchies are homologous across the primates. Homology was noticed by Aristotle, was explicitly analysed by Pierre Belon in his 1555 Book of Birds, where he systematically compared the skeletons of birds and humans.
The pattern of similarity was interpreted as part of the static great chain of being through the mediaeval and early modern periods: it was not seen as implying evolutionary change. In the German Naturphilosophie tradition, homology was of special interest as demonstrating unity in nature. In 1790, Goethe stated his foliar theory in his essay "Metamorphosis of Plants", showing that flower part are derived from leaves; the serial homology of limbs was described late in the 18th century. The French zoologist Etienne Geoffroy Saint-Hilaire showed in 1818 in his theorie d'analogue that structures were shared between fishes, reptiles and mammals; when Geoffroy went further and sought homologies between Georges Cuvier's embranchements, such as vertebrates and molluscs, his claims triggered the 1830 Cuvier-Geoffroy debate. Geoffroy stated the principle of connections, namely that what is important is the relative position of different structures and their connections to each other; the Estonian embryologist Karl Ernst von Baer stated what are now called von Baer's laws in 1828, noting that related animals begin their development as similar embryos and diverge: thus, animals in the same family are more related and diverge than animals which are only in the same order and have fewer homologies.
Von Baer's theory recognises that each taxon has distinctive shared features, that embryonic development parallels the taxonomic hierarchy: not the same as recapitulation theory. The term "homology" was first used in biology by the anatomist Richard Owen in 1843 when studying the similarities of vertebrate fins and limbs, defining it as the "same organ in different animals under every variety of form and function", contrasting it with the matching term "analogy" which he used to describe different structures with the same function. Owen codified 3 main criteria for determining if features were homologous: position and composition. In 1859, Charles Darwin explained homologous structures as meaning that the organisms concerned shared a body plan from a common ancestor, that taxa were branches of a single tree of life; the word homology, coined in about 1656, is derived from the Greek ὁμόλογος homologos from ὁμός homos "same" and λόγος logos "relation". Biological structures or sequences in different taxa are homologous if they are derived from a common ancestor.
Homology thus implies divergent evolution. For example, many insects possess two pairs of flying wings. In beetles, the first pair of wings has evolved into a pair of hard wing covers, while in Dipteran flies the second pair of wings has evolved into small halteres used for balance; the forelimbs of ancestral vertebrates have evolved into the front flippers of whales, the wings of birds, the running forelegs of dogs and horses, the short forelegs of frogs and lizards, the grasping hands of primates including humans. The same major forearm bones are found in fossils of lobe-finned fish such as Eusthenopteron; the opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their most recent common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in separated groups, converged functionally to support powered flight, so they are analogous; the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures.
A structure can be only analogous at another. Pterosaur and bat wings are analogous as wings
Mesonephric duct
The mesonephric duct is a paired organ found in mammals including humans during embryogenesis. Wolffian structures are male urogenital structures that include the epididymis, vas deferens, seminal vesicles that differentiate from this structure; the mesonephric duct connects the primitive kidney, the mesonephros, to the cloaca and serves as the anlage for certain male reproductive organs. The mesonephric duct connects the primitive kidney, the mesonephros, to the cloaca and serves as the anlage for certain male reproductive organs. In both the male and the female the mesonephric duct develops into the trigone of urinary bladder, a part of the bladder wall. However, further development differentiates between the sexes in the development of the urinary and reproductive organs. In a male, it develops into a system of connected organs between the efferent ducts of the testis and the prostate, namely the epididymis, the vas deferens, the seminal vesicle; the prostate forms from the urogenital sinus and the efferent ducts form from the mesonephric tubules.
For this it is critical. Testosterone binds to and activates androgen receptor, affecting intracellular signals and modifying the expression of numerous genes. In the mature male, the function of this system is to store and mature sperm, provide accessory semen fluid. In the female, with the absence of anti-Müllerian hormone secretion by the Sertoli cells and subsequent Müllerian apoptosis, the Wolffian duct regresses, inclusions may persist; the epoophoron and Skene's glands may be present. Lateral to the wall of the vagina a Gartner's duct or cyst could develop as a remnant, it is named after Caspar Friedrich Wolff who described the mesonephros and its ducts in his dissertation in 1759. Fetal genital development List of homologues of the human reproductive system Masculinization Müllerian duct Sexual differentiation MedicalMnemonics.com: 1266 How the Body Works / Sex Development / Sexual Differentiation / Duct Differentiation - The Hospital for Sick Children
Electron microscope
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects. A scanning transmission electron microscope has achieved better than 50 pm resolution in annular dark-field imaging mode and magnifications of up to about 10,000,000x whereas most light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000x. Electron microscopes have electron optical lens systems that are analogous to the glass lenses of an optical light microscope. Electron microscopes are used to investigate the ultrastructure of a wide range of biological and inorganic specimens including microorganisms, large molecules, biopsy samples and crystals. Industrially, electron microscopes are used for quality control and failure analysis.
Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the images. In 1926 Hans Busch developed the electromagnetic lens. According to Dennis Gabor, the physicist Leó Szilárd tried in 1928 to convince him to build an electron microscope, for which he had filed a patent; the first prototype electron microscope, capable of four-hundred-power magnification, was developed in 1931 by the physicist Ernst Ruska and the electrical engineer Max Knoll. The apparatus was the first practical demonstration of the principles of electron microscopy. In May of the same year, Reinhold Rudenberg, the scientific director of Siemens-Schuckertwerke, obtained a patent for an electron microscope. In 1932, Ernst Lubcke of Siemens & Halske built and obtained images from a prototype electron microscope, applying the concepts described in Rudenberg's patent. In the following year, 1933, Ruska built the first electron microscope that exceeded the resolution attainable with an optical microscope.
Four years in 1937, Siemens financed the work of Ernst Ruska and Bodo von Borries, employed Helmut Ruska, Ernst's brother, to develop applications for the microscope with biological specimens. In 1937, Manfred von Ardenne pioneered the scanning electron microscope. Siemens produced the first commercial electron microscope in 1938; the first North American electron microscope was constructed in 1938, at the University of Toronto, by Eli Franklin Burton and students Cecil Hall, James Hillier, Albert Prebus. Siemens produced a transmission electron microscope in 1939. Although current transmission electron microscopes are capable of two million-power magnification, as scientific instruments, they remain based upon Ruska’s prototype; the original form of the electron microscope, the transmission electron microscope, uses a high voltage electron beam to illuminate the specimen and create an image. The electron beam is produced by an electron gun fitted with a tungsten filament cathode as the electron source.
The electron beam is accelerated by an anode at +100 keV with respect to the cathode, focused by electrostatic and electromagnetic lenses, transmitted through the specimen, in part transparent to electrons and in part scatters them out of the beam. When it emerges from the specimen, the electron beam carries information about the structure of the specimen, magnified by the objective lens system of the microscope; the spatial variation in this information may be viewed by projecting the magnified electron image onto a fluorescent viewing screen coated with a phosphor or scintillator material such as zinc sulfide. Alternatively, the image can be photographically recorded by exposing a photographic film or plate directly to the electron beam, or a high-resolution phosphor may be coupled by means of a lens optical system or a fibre optic light-guide to the sensor of a digital camera; the image detected by the digital camera may be displayed on a computer. The resolution of TEMs is limited by spherical aberration, but a new generation of hardware correctors can reduce spherical aberration to increase the resolution in high-resolution transmission electron microscopy to below 0.5 angstrom, enabling magnifications above 50 million times.
The ability of HRTEM to determine the positions of atoms within materials is useful for nano-technologies research and development. Transmission electron microscopes are used in electron diffraction mode; the advantages of electron diffraction over X-ray crystallography are that the specimen need not be a single crystal or a polycrystalline powder, that the Fourier transform reconstruction of the object's magnified structure occurs physically and thus avoids the need for solving the phase problem faced by the X-ray crystallographers after obtaining their X-ray diffraction patterns. One major disadvantage of the transmission electron microscope is the need for thin sections of the specimens about 100 nanometers. Creating these thin sections for biological and materials specimens is technically challenging. Semiconductor thin sections can be made using a focused ion beam. Biological tissue specimens are chemically fixed and embedded in a polymer resin to stabilize them sufficiently to allow ultrathin sectioning.
Sections of biological specimens, organic polymers, similar materials may require staining with heavy atom labels in order to achieve the required image contrast. One application of TEM is serial-section electron microscopy, for example in analyzing the connectivity in volumetric samples of brain tissue by imaging many thin sections in sequence; the SEM produces imag
Acid phosphatase
Acid phosphatase is a phosphatase, a type of enzyme, used to free attached phosphoryl groups from other molecules during digestion. It can be further classified as a phosphomonoesterase. Acid phosphatase is stored in lysosomes and functions when these fuse with endosomes, which are acidified while they function; this enzyme is present in many plant species. Different forms of acid phosphatase are found in different organs, their serum levels are used to evaluate the success of the surgical treatment of prostate cancer. In the past, they were used to diagnose this type of cancer. It's used as a cytogenetic marker to distinguish the two different lineages of Acute Lymphoblastic Leukemia: B-ALL is Acid-Phosphatase negative, T-ALL is acid-phosphatase positive. Acid phosphatase catalyzes the following reaction at an optimal acidic pH: Orthophosphoric monoester + H2O → alcohol + H3PO4Phosphatase enzymes are used by soil microorganisms to access organically bound phosphate nutrients. An assay on the rates of activity of these enzymes may be used to ascertain biological demand for phosphates in the soil.
Some plant roots cluster roots, exude carboxylates that perform acid phosphatase activity, helping to mobilise phosphorus in nutrient-deficient soils. Certain bacteria like Nocardia, can utilize it as a carbon source. Tartrate-resistant acid phosphatase may be used as a biochemical marker of osteoclast function during the process of bone resorption; the following genes encode the polypeptide components for various acid phosphatase isoenzymes. ACP1 ACP2 ACPP, Prostatic acid phosphatase ACP5, Tartrate-resistant acid phosphatase ACP6 ACPT, Testicular acid phosphatase Tissue acid phosphatase, or Lysosomal acid phosphatase Alkaline phosphatase Acid+phosphatase at the US National Library of Medicine Medical Subject Headings EC 3.1.3.2
Secretion
Secretion is the movement of material from one point to another, e.g. secreted chemical substance from a cell or gland. In contrast, excretion, is the removal of certain substances or waste products from a cell or organism; the classical mechanism of cell secretion is via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structure at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell. Secretion in bacterial species means the transport or translocation of effector molecules for example: proteins, enzymes or toxins from across the interior of a bacterial cell to its exterior. Secretion is a important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival. Eukaryotic cells, including human cells, have a evolved process of secretion. Proteins targeted for the outside are synthesized by ribosomes docked to the rough endoplasmic reticulum.
As they are synthesized, these proteins translocate into the ER lumen, where they are glycosylated and where molecular chaperones aid protein folding. Misfolded proteins are identified here and retrotranslocated by ER-associated degradation to the cytosol, where they are degraded by a proteasome; the vesicles containing the properly folded proteins enter the Golgi apparatus. In the Golgi apparatus, the glycosylation of the proteins is modified and further posttranslational modifications, including cleavage and functionalization, may occur; the proteins are moved into secretory vesicles which travel along the cytoskeleton to the edge of the cell. More modification can occur in the secretory vesicles. There is vesicle fusion with the cell membrane at a structure called the porosome, in a process called exocytosis, dumping its contents out of the cell's environment. Strict biochemical control is maintained over this sequence by usage of a pH gradient: the pH of the cytosol is 7.4, the ER's pH is 7.0, the cis-golgi has a pH of 6.5.
Secretory vesicles have pHs ranging between 5.0 and 6.0. There are many proteins like FGF2, interleukin-1 etc. which do not have a signal sequence. They do not use the classical ER-golgi pathway; these are secreted through various nonclassical pathways. At least four nonclassical protein secretion pathways have been described, they include 1) direct translocation of proteins across the plasma membrane through membrane transporters, 2) blebbing, 3) lysosomal secretion, 4) release via exosomes derived from multivesicular bodies. In addition, proteins can be released from cells by mechanical or physiological wounding and through nonlethal, transient oncotic pores in the plasma membrane induced by washing cells with serum-free media or buffers. Many human cell types have the ability to be secretory cells, they have a well-developed endoplasmic reticulum and Golgi apparatus to fulfill their function. Tissues in humans that produce secretions include the gastrointestinal tract which secretes digestive enzymes and gastric acid, the lung which secretes surfactants, sebaceous glands which secrete sebum to lubricate the skin and hair.
Meibomian glands in the eyelid secrete sebum to protect the eye. Secretion is not unique to eukaryotes alone - it is present in bacteria and archaea as well. ATP binding cassette type transporters are common to all the three domains of life; the Sec system constituting the Sec Y-E-G complex is another conserved secretion system, homologous to the translocon in the eukaryotic endoplasmic reticulum and the Sec 61 translocon complex of yeast. Some secreted proteins are translocated across the cytoplasmic membrane by the Sec translocon, which requires the presence of an N-terminal signal peptide on the secreted protein. Others are translocated across the cytoplasmic membrane by the twin-arginine translocation pathway. Gram-negative bacteria have two membranes. There are at least six specialized secretion systems in gram-negative bacteria. Many secreted proteins are important in bacterial pathogenesis. Type I secretion is a chaperone dependent secretion system employing the Tol gene clusters; the process begins as a leader sequence HlyA binds HlyB on the membrane.
This signal sequence is specific for the ABC transporter. The HlyAB complex stimulates HlyD which begins to uncoil and reaches the outer membrane where TolC recognizes a terminal molecule or signal on HlyD. HlyD recruits TolC to the inner membrane and HlyA is excreted outside of the outer membrane via a long-tunnel protein channel. Type I secretion system transports various molecules, from ions, drugs, to proteins of various sizes; the molecules secreted vary in size from the small Escherichia coli peptide colicin V, to the Pseudomonas fluorescens cell adhesion protein LapA of 520 kDa. The best characterized are the lipases. Type I secretion is involved in export of non-proteinaceous substrates like cyclic β-glucans and polysaccharides. Proteins secreted through the type II system, or main terminal branch of the general secretory pathway, depend on the Sec or Tat system for initial transport into the periplasm. Once there, they pass through the outer membrane via a multimeric complex of pore forming secretin proteins.
In addition to the secretin protein, 10–15 other inner and outer memb
Surgeon
In modern medicine, a surgeon is a physician who performs surgical operations. There are surgeons in podiatry, dentistry maxillofacial surgeon and the veterinary fields; the first person to document a surgery was Sushruta. He specialized in cosmetic plastic surgery and had documented an operation of open rhinoplasty, his magnum opus Suśruta-saṃhitā is one of the most important surviving ancient treatises on medicine and is considered a foundational text of Ayurveda and surgery. The treatise addresses all aspects of general medicine, but the translator G. D. Singhal dubbed Suśruta "the father of surgical intervention" on account of the extraordinarily accurate and detailed accounts of surgery to be found in the work. After the eventual decline of the Sushruta School of Medicine in India, surgery had been ignored until the Islamic Golden Age surgeon Al-Zahrawi, reestablished surgery as an effective medical practice, he is considered the greatest medieval surgeon to have appeared from the Islamic World, has been described as the father of surgery.
His greatest contribution to medicine is the Kitab al-Tasrif, a thirty-volume encyclopedia of medical practices. He was the first physician to describe an ectopic pregnancy, the first physician to identify the hereditary nature of hæmophilia, his pioneering contributions to the field of surgical procedures and instruments had an enormous impact on surgery but it was not until the eighteenth century that surgery as a distinct medical discipline emerged in England. In Europe, surgery was associated with barber-surgeons who used their hair-cutting tools to undertake surgical procedures at the battlefield and for their employers. With advances in medicine and physiology, the professions of barbers and surgeons diverged. Surgeon continued, however, to be used as the title for military medical officers until the end of the 19th century, the title of Surgeon General continues to exist for both senior military medical officers and senior government public health officers. In 1950, the Royal College of Surgeons of England in London began to offer surgeons a formal status via RCS membership.
The title Mister became a badge of honour, today, in many Commonwealth countries, a qualified doctor who, after at least four years' training, obtains a surgical qualification is given the honour of being allowed to revert to calling themselves Mr, Mrs or Ms in the course of their professional practice, but this time the meaning is different. It is sometimes assumed that the change of title implies consultant status, but the length of postgraduate medical training outside North America is such that a qualified surgeon may be years away from obtaining such a post: many doctors obtained these qualifications in the senior house officer grade, remained in that grade when they began sub-specialty training; the distinction of Mr is used by surgeons in the Republic of Ireland, some states of Australia, New Zealand, South Africa and some other Commonwealth countries. In many English-speaking countries the military title of surgeon is applied to any medical practitioner, due to the historical evolution of the term.
The US Army Medical Corps retains various surgeon MOS' in the ranks of officer pay grades for military personnel dedicated to performing surgery on wounded soldiers. Some physicians who are general practitioners or specialists in family medicine or emergency medicine may perform limited ranges of minor, common, or emergency surgery. Anesthesia accompanies surgery, anesthesiologists and nurse anesthetists may oversee this aspect of surgery. Surgeon's assistant, surgical nurses, surgical technologists are trained professionals who support surgeons. In the United States, the Department of Labor description of a surgeon is "a physician who treats diseases and deformities by invasive, minimally-invasive, or non-invasive surgical methods, such as using instruments, appliances, or by manual manipulation". Sushruta al-Zahrawi, regarded as one of the greatest medieval surgeons and a father of surgery. ) Charles Kelman William Stewart Halsted Alfred Blalock C. Walton Lillehei Christiaan Barnard Victor Chang Australian pioneer of heart transplantation John Hunter Sir Victor Horsley Lars Leksell Joseph Lister Harvey Cushing Paul Tessier Gholam A. Peyman Ioannis Pallikaris Nikolay Pirogov Valery Shumakov Svyatoslav Fyodorov Gazi Yasargil Rene Favaloro (first surgeon to perform bypass
