Keratin is one of a family of fibrous structural proteins. It is the key structural material making up hair, horns, claws and the outer layer of human skin. Keratin is the protein that protects epithelial cells from damage or stress. Keratin is insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds and mammals; the only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin filaments are abundant in keratinocytes in the cornified layer of the epidermis. In addition, keratin filaments are present in epithelial cells in general. For example, mouse thymic epithelial cells are known to react with antibodies for keratin 5, keratin 8, keratin 14; these antibodies are used as fluorescent markers to distinguish subsets of TECs in genetic studies of the thymus. The α-keratins are found in all vertebrates, they form the hair, stratum corneum, nails and hooves of mammals and the hagfish slime threads.
The harder β-keratins are found only in the sauropsids, all living reptiles and birds. They are found in the nails and claws of reptiles, some reptile shells, in the feathers and claws of birds. Additionally, the baleen plates of filter-feeding whales are made of keratin. Keratins are polymers of type I and type II intermediate filaments, which have only been found in the genomes of chordates. Nematodes and many other non-chordate animals seem to only have type VI intermediate filaments, which have a long rod domain; the human genome encodes 54 functional keratin genes which are located in two clusters on chromosomes 12 and 17. This suggests; the keratins include the following proteins of which KRT23, KRT24, KRT25, KRT26, KRT27, KRT28, KRT31, KRT32, KRT33A, KRT33B, KRT34, KRT35, KRT36, KRT37, KRT38, KRT39, KRT40, KRT71, KRT72, KRT73, KRT74, KRT75, KRT76, KRT77, KRT78, KRT79, KRT8, KRT80, KRT81, KRT82, KRT83, KRT84, KRT85 and KRT86 have been used to describe keratins past 20. The first sequences of keratins were determined by Fuchs.
These sequences revealed that there are two distinct but homologous keratin families which were named as Type I keratin and Type II keratins. By analysis of the primary structures of these keratins and other intermediate filament proteins and Fuchs suggested a model that keratins and intermediate filament proteins contain a central ~310 residue domain with four segments in α-helical conformation that are separated by three short linker segments predicted to be in beta-turn conformation; this model has been confirmed by the determination of the crystal structure of a helical domain of keratins. Fibrous keratin molecules supercoil to form a stable, left-handed superhelical motif to multimerise, forming filaments consisting of multiple copies of the keratin monomer; the major force that keeps the coiled-coil structure is hydrophobic interactions between apolar residues along the keratins helical segments. Limited interior space is the reason why the triple helix of the structural protein collagen, found in skin and bone has a high percentage of glycine.
The connective tissue protein elastin has a high percentage of both glycine and alanine. Silk fibroin, considered a β-keratin, can have these two as 75–80% of the total, with 10–15% serine, with the rest having bulky side groups; the chains are antiparallel, with an alternating C → N orientation. A preponderance of amino acids with small, nonreactive side groups is characteristic for structural proteins, for which H-bonded close packing is more important than chemical specificity. In addition to intra- and intermolecular hydrogen bonds, the distinguishing feature of keratins is the presence of large amounts of the sulfur-containing amino acid cysteine, required for the disulfide bridges that confer additional strength and rigidity by permanent, thermally stable crosslinking—in much the same way that non-protein sulfur bridges stabilize vulcanized rubber. Human hair is 14% cysteine; the pungent smells of burning hair and skin are due to the volatile sulfur compounds formed. Extensive disulfide bonding contributes to the insolubility of keratins, except in a small number of solvents such as dissociating or reducing agents.
The more flexible and elastic keratins of hair have fewer interchain disulfide bridges than the keratins in mammalian fingernails and claws, which are harder and more like their analogs in other vertebrate classes. Hair and other α-keratins consist of α-helically coiled single protein strands, which are further twisted into superhelical ropes that may be further coiled; the β-keratins of reptiles and birds have β-pleated sheets twisted together stabilized and hardened by disulfide bridges. It has been proposed that keratins can be divided into'hard' and'soft' forms, or'cytokeratins' and'other keratins'; that model is now understood to be correct. A new nuclear addition in 2006 to describe keratins takes this into account. Keratin filaments are intermediate filaments. Like all intermediate filaments, keratin proteins form filamentous polymers in a series of assembly steps beginning with dimerization.
Surgical treatment of ingrown toenails
Surgical treatments of ingrown toenails include a number of different options. If conservative treatment of a minor ingrown toenail does not succeed or if the ingrown toenail is severe, surgical management by a podiatrist is recommended; the initial surgical approach is a partial avulsion of the nail plate known as a wedge resection or a complete removal of the toenail. If the ingrown toenail recurs despite this treatment, destruction of the germinal matrix with phenol is recommended. Antibiotics are not needed; the physician will perform an onychectomy in which the nail along the edge, growing into the skin is cut away and the offending piece of nail is pulled out. Any infection is surgically drained; this process is not permanent. The entire procedure may be performed in a physician's office in thirty to forty-five minutes depending on the extent of the problem; the patient is allowed to go home the same day and the recovery time is anywhere from two weeks to two months barring any complications such as infection.
As a follow-up, a physician may prescribe an oral or topical antibiotic or a special soak to be used for about a week after the surgery. Some use "lateral onychoplasty," or "wedge resection," as the method of choice for ingrown toenails. A wide wedge resection, with a total cleaning of nail matrix, has a nearly 100% success rate; some physicians will not perform a complete nail avulsion except under extreme circumstances. In most cases, these physicians will remove both sides of a toenail and coat the nail matrix on both sides with a chemical or acid to prevent re-growth; this ensures that the problem of ingrowth will not recur. There are possible disadvantages if the nail matrix is not coated with the applicable chemical or acid and is allowed to re-grow; the underlying condition can still become symptomatic if the nail grows back within a year: the nail matrix could be growing a nail, too curved, wide or otherwise irregular to allow normal growth. Furthermore, the flesh can become injured by concussion, tight socks, quick twisting motions while walking, or because the nail is growing incorrectly.
This hypersensitivity to continued injury can mean chronic ingrowth. If the nail becomes ingrown again after a wedge resection, more invasive surgery may be needed, although this rather drastic measure may not be necessary: less invasive repeat treatments such as destruction of the nail bed, should be considered; this surgery takes longer than the minor wedge resection. The toe is torniqued and incisions made from the front of the toe to around 1 cm behind the rear of the visible part of the nail; these incisions are quite deep and will require stitching and will scar. The nail will be cut out, much like a wedge resection and the nail bed will be broken to prevent regrowth; the nail will be narrower and may appear visibly deformed but will not become ingrown again. Note: if undertaking this surgery it is advisable to rest for at least four days before resuming regular walking as with painkillers this can be very painful. If one's work requires standing up for extended periods of time, arrangements for time-off may be necessary for up to two weeks.
In case of recurrence after complete removal, if the patient never felt any pain before inflammation occurred, the condition is more to be onychia, confused for an ingrown or ingrowing nail. Complete removal of the whole nail is a simple procedure. Anaesthetic is injected and the nail is removed by pulling it outward from the toe; the patient can function right after the procedure and most of the discomfort goes away in a few days. The entire procedure can be performed in 20 minutes and is less complex than the wedge resection; the nail grows back, in most cases it can cause more problems by becoming ingrown again. It can get in some cases grows back too thick, too wide or deformed; this procedure can result in chronic ingrown nails causing more pain. Accordingly, in some cases as determined by a doctor, the nail matrix is coated with a chemical so none of the nail will grow back; this is known as a permanent or full nail avulsion, or full matrixectomy, phenolisation, or full phenol avulsion. As can be seen in the images below, the nail-less toe does not look like a normal toe.
Fake nails or nail varnish can still be applied to the area to provide a normal appearance. In a few cases phenolisation has to be repeated. Podiatrists warn patients of this possibility of regrowth; the Vandenbos procedure was first described by Vandenbos KQ and Bowers WP in 1959 in the US Armed Forces Medical Journal. They reported. Since 1988 Dr. Henry Chapeskie has performed this procedure on over 2,700 patients who had no recurrences. Unlike other procedures, the Vandenbos procedure doesn't touch the nail. In this procedure, the affected toe is anesthetized with a digital block and a tourniquet is applied. An incision is made proximally from the base of the nail about 5 mm extended toward the side of the toe/toenail in an elliptical sweep to end up under the tip of the nail about 3–4 mm in from the edge, it is important. The excision must be adequate leaving
A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates. Some languages have different names for foot digits. In other languages, e.g. Russian, Spanish, Italian, Tagalog, Turkish and Persian, there are no specific one-word names for fingers and toes. Humans have five digits on each extremity; each digit is formed by several bones called phalanges, surrounded by soft tissue. Human fingers have a nail at the distal phalanx; the phenomenon of polydactyly occurs. Each finger has an orderly somatotopic representation on the cerebral cortex in the somatosensory cortex area 3b, part of area 1 and a distributed, overlapping representation in the supplementary motor area and primary motor area; the somatosensory cortex representation of the hand is a dynamic reflection of the fingers on the external hand: in syndactyly people have a clubhand of webbed, shortened fingers. However, not only are the fingers of their hands fused, but the cortical maps of their individual fingers form a club hand.
The fingers can be surgically divided to make a more useful hand. Surgeons did this at the Institute of Reconstructive Plastic Surgery in New York to a 32-year-old man with the initials O. G.. They touched O. G.'s fingers after surgery while using MRI brain scans. Before the surgery, the fingers mapped onto his brain were fused close together. Two ideas about the homology of arms and digits exist. Digits are unique to tetrapods. Antecedents were present in the fins of early sarcopterygian fish. However, 2008 research which created a three-dimensional reconstruction of a Panderichthys, a coastal fish from the Devonian period 385 million years ago, shows that these animals had many of the homologous bones present in the forelimbs of limbed vertebrates. For example, they had fin radials, bones similar to rudimentary fingers but positioned in the arm-like base of their fins, thus there was in the evolution of tetrapods a shift such that the outermost part of the fins were lost and came to be replaced by early digits.
This change is consistent with additional evidence from the study of actinopterygians and lungfish that the digits of tetrapods arose from pre-existing distal radials present in more primitive fish. Controversy still exists since Tiktaalik, a vertebrate considered to be the missing link between fishes and land-living animals, had stubby leg-like limbs that lacked the finger-like radial bones found in the Panderichthys; the researchers of the paper commented that "It is difficult to say whether this character distribution implies that Tiktaalik is autapomorphic, that Panderichthys and tetrapods are convergent, or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures."p. 638. Birds and theropod dinosaurs have three digits on their hands. Paradoxically the two digits that are missing are different: the bird hand is thought to derive from the second and fourth digits of the ancestral five-digit hand.
In contrast, the theropod dinosaurs seem to have the first and third digits. A Jurassic theropod intermediate fossil Limusaurus has been found in the Junggar Basin in western China that has a complex mix: it has a first digit stub and full second and fourth digits but its wrist bones are like those that are associated with the second and fourth digits while its finger bones are those of the first and third digits; this suggests the evolution of digits in birds resulted from a "shift in digit identity characterized early stages of theropod evolution" Polydactyly in early tetrapods Polydactyly
In biological morphology and anatomy, a sulcus is a furrow or fissure. It may be a groove in the surface of a limb or an organ, notably in the surface of the brain, but in the lungs, certain muscles, as well as in bones, elsewhere. Many sulci are the product of a surface fold or junction, such as in the gums, where they fold around the neck of the tooth. In invertebrate zoology, a sulcus is a fold, groove, or boundary at the edges of sclerites or between segments. Anterior interventricular sulcus calcaneal sulcus coronal sulcus femoral sulcus or intercondylar fossa of femur gingival sulcus gluteal sulcus interlabial sulci intermammary sulcus intertubercular sulcus, the groove between the lesser and greater tubercules of the humerus lacrimal sulcus malleolar sulcus patellar sulcus or intercondylar fossa of femur posterior interventricular sulcus preauricular sulcus radial sulcus sagittal sulcus separatoral sulcus sigmoid sulcus sulcus arteriæ vertebralis sulcus subtarsalis in the eyelid sulcus tubae auditivae tympanic sulcus urethral sulcus Fissure Sinus Sulcus sign
The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss; the epidermis is composed of multiple layers of flattened cells that overlie a base layer composed of columnar cells arranged perpendicularly. The rows of cells develop from stem cells in the basal layer. Cellular mechanisms for regulating water and sodium levels are found in all layers of the epidermis; the word epidermis is derived through Latin from Ancient Greek epidermis, itself from Ancient Greek epi, meaning'over, upon' and from Ancient Greek dermis, meaning'skin'. Something related to or part of the epidermis is termed epidermal; the human epidermis is a familiar example of epithelium a stratified squamous epithelium The epidermis consists of keratinocytes, which comprise 90% of its cells, but contains melanocytes, Langerhans cells, Merkel cells, inflammatory cells.
Epidermal thickenings called. Blood capillaries are found beneath the epidermis, are linked to an arteriole and a venule; the epidermis itself has no blood supply and is nourished exclusively by diffused oxygen from the surrounding air. Epidermal cells are interconnected to serve as a tight barrier against the exterior environment; the junctions between the epidermal cells are of the adherens junction type, formed by transmembrane proteins called cadherins. Inside the cell, the cadherins are linked to actin filaments. In immunofluorescence microscopy, the actin filament network appears as a thick border surrounding the cells, although the actin filaments are located inside the cell and run parallel to the cell membrane; because of the proximity of the neighboring cells and tightness of the junctions, the actin immunofluorescence appears as a border between cells. The epidermis is composed depending on the region of skin being considered; those layers in descending order are: cornified layer Composed of 10 to 30 layers of polyhedral, anucleated corneocytes, with the palms and soles having the most layers.
Corneocytes contain a protein envelope underneath the plasma membrane, are filled with water-retaining keratin proteins, attached together through corneodesmosomes and surrounded in the extracellular space by stacked layers of lipids. Most of the barrier functions of the epidermis localize to this layer.clear/translucent layer This narrow layer is found only on the palms and soles. The epidermis of these two areas is known as "thick skin" because with this extra layer, the skin has 5 epidermal layers instead of 4.granular layer Keratinocytes lose their nuclei and their cytoplasm appears granular. Lipids, contained into those keratinocytes within lamellar bodies, are released into the extracellular space through exocytosis to form a lipid barrier; those polar lipids are converted into non-polar lipids and arranged parallel to the cell surface. For example glycosphingolipids become ceramides and phospholipids become free fatty acids.spinous layer Keratinocytes become connected through desmosomes and start produce lamellar bodies, from within the Golgi, enriched in polar lipids, glycosphingolipids, free sterols and catabolic enzymes.
Langerhans cells, immunologically active cells, are located in the middle of this layer.basal/germinal layer. Composed of proliferating and non-proliferating keratinocytes, attached to the basement membrane by hemidesmosomes. Melanocytes are present, connected to numerous keratinocytes in this and other strata through dendrites. Merkel cells are found in the stratum basale with large numbers in touch-sensitive sites such as the fingertips and lips, they are associated with cutaneous nerves and seem to be involved in light touch sensation. The Malpighian layer is both stratum spinosum; the epidermis is separated from its underlying tissue, by a basement membrane. As a stratified squamous epithelium, the epidermis is maintained by cell division within the stratum basale. Differentiating cells delaminate from the basement membrane and are displaced outward through the epidermal layers, undergoing multiple stages of differentiation until, in the stratum corneum, losing their nucleus and fusing to squamous sheets, which are shed from the surface.
Differentiated keratinocytes secrete keratin proteins, which contribute to the formation of an extracellular matrix, an integral part of the skin barrier function. In normal skin, the rate of keratinocyte production equals the rate of loss, taking about two weeks for a cell to journey from the stratum basale to the top of the stratum granulosum, an additional four weeks to cross the stratum corneum; the entire epidermis is replaced by new cell growth over a period of about 48 days. Keratinocyte differentiation throughout the epidermis is in part mediated by a calcium gradient, increasing from the stratum basale until the outer stratum granulosum, where it reaches its maximum, decreasing in the stratum corneum. Calcium concentration in the stratum corneum is low in part because those dry cells are not able to dissolve the ions; this calcium gradient parallels keratinocyte differentiation and as such is considered a key regulator in the formation of the epidermal layers. El
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the
Orthopedic surgery or orthopedics spelled orthopaedics, is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections and congenital disorders. Nicholas Andry coined the word in French as orthopédie, derived from the Ancient Greek words ὀρθός orthos and παιδίον paidion, published Orthopedie in 1741; the word was assimilated into English as orthopædics. Though, as the name implies, the discipline was developed with attention to children, the correction of spinal and bone deformities in all stages of life became the cornerstone of orthopedic practice; as with many words derived with the "æ" ligature, simplification to either "ae" or just "e" is common in North America. In the US, the majority of college and residency programs, the American Academy of Orthopaedic Surgeons, still use the spelling with the digraph ae, though hospitals use the shortened form.
Elsewhere, usage is not uniform: in Canada, both spellings are acceptable. Many developments in orthopedic surgery have resulted from experiences during wartime. On the battlefields of the Middle Ages the injured were treated with bandages soaked in horses' blood which dried to form a stiff, but unsanitary, splint; the term orthopedics meant the correcting of musculoskeletal deformities in children. Nicolas Andry, a professor of medicine at the University of Paris coined the term in the first textbook written on the subject in 1741, he advocated the use of exercise and splinting to treat deformities in children. His book was directed towards parents, while some topics would be familiar to orthopedists today, it included'excessive sweating of the palms' and freckles. Jean-André Venel established the first orthopedic institute in 1780, the first hospital dedicated to the treatment of children's skeletal deformities, he developed the club-foot shoe for children born with foot deformities and various methods to treat curvature of the spine.
Advances made in surgical technique during the 18th century, such as John Hunter's research on tendon healing and Percival Pott's work on spinal deformity increased the range of new methods available for effective treatment. Antonius Mathijsen, a Dutch military surgeon, invented the plaster of Paris cast in 1851. However, up until the 1890s, orthopedics was still a study limited to the correction of deformity in children. One of the first surgical procedures developed was percutaneous tenotomy; this involved cutting a tendon the Achilles tendon, to help treat deformities alongside bracing and exercises. In the late 1800s and first decades of the 1900s, there was significant controversy about whether orthopedics should include surgical procedures at all. Examples of people who aided the development of modern orthopedic surgery were Hugh Owen Thomas, a surgeon from Wales, his nephew, Robert Jones. Thomas became interested in orthopedics and bone-setting at a young age and, after establishing his own practice, went on to expand the field into general treatment of fracture and other musculoskeletal problems.
He advocated enforced rest as the best remedy for fractures and tuberculosis and created the so-called'Thomas Splint', to stabilize a fractured femur and prevent infection. He is responsible for numerous other medical innovations that all carry his name:'Thomas's collar' to treat tuberculosis of the cervical spine,'Thomas's manoeuvre', an orthopedic investigation for fracture of the hip joint, Thomas test, a method of detecting hip deformity by having the patient lying flat in bed,'Thomas's wrench' for reducing fractures, as well as an osteoclast to break and reset bones. Thomas's work was not appreciated in his own lifetime, it was only during the First World War that his techniques came to be used for injured soldiers on the battlefield. His nephew, Sir Robert Jones, had made great advances in orthopedics in his position as Surgeon-Superintendent for the construction of the Manchester Ship Canal in 1888, he was responsible for the injured among the 20,000 workers, he organized the first comprehensive accident service in the world, dividing the 36 mile site into 3 sections, establishing a hospital and a string of first aid posts in each section.
He had the medical personnel trained in fracture management. He managed 3,000 cases and performed 300 operations in his own hospital; this position enabled him to improve the standard of fracture management. Physicians from around the world came to Jones’ clinic to learn his techniques. Along with Alfred Tubby, Jones founded the British Orthopaedic Society in 1894. During the First World War, Jones served as a Territorial Army surgeon, he observed that treatment of fractures both at the front and in hospitals at home was inadequate, his efforts led to the introduction of military orthopedic hospitals. He was appointed Inspector of Military Orthopaedics, with responsibility over 30,000 beds; the hospital in Ducane Road, Hammersmith became the model for both British and American military orthopedic hospitals. His advocacy of the use of Thomas splint for the initial treatment of femoral fractures reduced mortality of compound fractures of the femur from 87% to less than 8% in the period from 1916 to 1918.
The use of intramedullary rods to treat fractures of the femur and tibi