Drosophila melanogaster is a species of fly in the family Drosophilidae. The species is known as the common fruit fly or vinegar fly. Starting with Charles W. Woodworth's proposal of the use of this species as a model organism, D. melanogaster continues to be used for biological research in genetics, microbial pathogenesis, life history evolution. As of 2017, eight Nobel prizes had been awarded for research using Drosophila. D. Melanogaster is used in research because it can be reared in the laboratory, has only four pairs of chromosomes and lays many eggs, its geographic range includes all continents, including islands. D. melanogaster is a common pest in homes and other places where food is served. Flies belonging to the family Tephritidae are called "fruit flies"; this can cause confusion in the Mediterranean and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest. Wildtype fruit flies are yellow-brown, with brick-red eyes and transverse black rings across the abdomen.
They exhibit sexual dimorphism. Males are distinguished from females based on colour differences, with a distinct black patch at the abdomen, less noticeable in emerged flies, the sexcombs. Furthermore, males have a cluster of spiky hairs surrounding the reproducing parts used to attach to the female during mating. Extensive images are found at FlyBase. Under optimal growth conditions at 25 °C, the D. melanogaster lifespan is about 50 days from egg to death. The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. The shortest development time, 7 days, is achieved at 28 °C. Development times increase at higher temperatures due to heat stress. Under ideal conditions, the development time at 25 °C is 8.5 days, at 18 °C it takes 19 days and at 12 °C it takes over 50 days. Under crowded conditions, development time increases. Females lay some 400 eggs, about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes.
The eggs, which are about 0.5 mm long, hatch after 12–15 hours. The resulting larvae grow for about 4 days while molting twice, at about 48 h after hatching. During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself; the mother puts feces on the egg sacs to establish the same microbial composition in the larvae's guts that has worked positively for herself. The larvae encapsulate in the puparium and undergo a 4-day-long metamorphosis, after which the adults eclose; the female fruit fly prefers a shorter duration. Males, prefer it to last longer. Males perform a sequence of five behavioral patterns to court females. First, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Soon after, the male positions himself at the rear of the female's abdomen in a low posture to tap and lick the female genitalia; the male curls his abdomen and attempts copulation. Females can reject males by moving away and extruding their ovipositor.
Copulation lasts around 15–20 minutes, during which males transfer a few hundred long sperm cells in seminal fluid to the female. Females store the sperm in two mushroom-shaped spermathecae. A last male precedence is believed to exist; this precedence was found to occur through both incapacitation. The displacement is attributed to sperm handling by the female fly as multiple matings are conducted and is most significant during the first 1–2 days after copulation. Displacement from the seminal receptacle is more significant than displacement from the spermathecae. Incapacitation of first male sperm by second male sperm becomes significant 2–7 days after copulation; the seminal fluid of the second male is believed to be responsible for this incapacitation mechanism which takes effect before fertilization occurs. The delay in effectiveness of the incapacitation mechanism is believed to be a protective mechanism that prevents a male fly from incapacitating his own sperm should he mate with the same female fly repetitively.
Sensory neurons in the uterus of female D. melanogaster respond to a male protein, sex peptide, found in sperm. This protein makes the female reluctant to copulate for about 10 days after insemination; the signal pathway leading to this change in behavior has been determined. The signal is sent to a brain region, a homolog of the hypothalamus and the hypothalamus controls sexual behavior and desire. Gonadotropic hormones in Drosophila maintain homeostasis and govern reproductive output via a cyclic interrelationship, not unlike the mammalian estrous cycle. Sex Peptide perturbs this homeostasis and shifts the endocrine state of the female by inciting juvenile hormone synthesis in the corpus allatum. D. Melanogaster is used for life extension studies, such as to identify genes purported to increase lifespan when mutated. Females become receptive to courting males about 8–12 hours after emergence. Specific neuron groups in females have been found to affect copulation behavior a
Gustav Giemsa was a German chemist and bacteriologist, a native of Medar-Blechhammer. He is remembered for creating a dye solution known as "Giemsa stain"; this dye is used for the histopathological diagnosis of malaria and parasites such as Plasmodium and Chlamydia. Giemsa studied pharmacy and mineralogy at the University of Leipzig, chemistry and bacteriology at the University of Berlin. Between 1895 and 1898 he worked as a pharmacist in German East Africa, he was an early assistant to Bernhard Nocht at the Institut für Tropenmedizin in Hamburg, where in 1900 he became head of the Department of Chemistry. In 1904 Giemsa published an essay on the staining procedure for flagellates, blood cells, bacteria. Giemsa improved the Romanowsky stain by stabilizing this dye solution with glycerol; this allowed for reproducible staining of cells for microscopy purposes. This method is still used in laboratories today. In 1933 Giemsa signed the Loyalty Oath of German Professors to Adolf Hitler and the National Socialist State.
He joined the NSDAP. Ernst Klee: Das Personenlexikon zum Dritten Reich. Wer war was vor und nach 1945. Fischer Taschenbuch Verlag, Zweite aktualisierte Auflage, Frankfurt am Main 2005, S. 182. Fleischer B. Editorial: 100 years ago: Giemsa's solution for staining of plasmodia. Trop Med Int Health. 2004 Jul. Newspaper clippings about Gustav Giemsa in the 20th Century Press Archives of the German National Library of Economics
Eosin is the name of several fluorescent acidic compounds which bind to and form salts with basic, or eosinophilic, compounds like proteins containing amino acid residues such as arginine and lysine, stains them dark red or pink as a result of the actions of bromine on fluorescein. In addition to staining proteins in the cytoplasm, it can be used to stain collagen and muscle fibers for examination under the microscope. Structures that stain with eosin are termed eosinophilic; the name Eosin comes from Eos, the Ancient Greek word for'dawn' and the name of the Ancient Greek goddess of the dawn. There are two closely related compounds referred to as eosin. Most used is Eosin Y; the other eosin compound is eosin B. The two dyes are interchangeable, the use of one or the other is a matter of preference and tradition. Eosin Y is a tetrabromo derivative of fluorescein. Eosin B is a dibromo dinitro derivative of fluorescein. Eosin is most used as a counterstain to hematoxylin in H&E staining. H&E staining is one of the most used techniques in histology.
Tissue stained with haematoxylin and eosin shows cytoplasm stained pink-orange and nuclei stained darkly, either blue or purple. Eosin stains red blood cells intensely red. For staining, eosin Y is used in concentrations of 1 to 5 percent weight by volume, dissolved in water or ethanol. For prevention of mold growth in aqueous solutions, thymol is sometimes added. A small concentration of acetic acid gives a deeper red stain to the tissue, it is listed as an IARC class 3 carcinogen. Eosin is used as a red dye in inks. Romanowsky stain Merbromin Jocelyn H. Bruce-Gregorios, M. D.: Histopathologic Techniques, JMC Press Inc. Quezon City, Philippines, 1974. Eosin Y - Applications information
Histology microanatomy, is the branch of biology which studies the tissues of animals and plants using microscopy. It is studied using a light microscope or electron microscope, the specimen having been sectioned and mounted on a microscope slide. Histological studies may be conducted using tissue culture, where live animal cells are isolated and maintained in an artificial environment for various research projects; the ability to visualize or differentially identify microscopic structures is enhanced through the use of staining. Histology is one of the major preclinical subjects in medical school. Medical students are expected to be familiar with the morphological features and function of all cells and tissues of the human body from an early stage of their studies, so histology stretches over several semesters. Histopathology, the microscopic study of diseased tissue, is an important tool in anatomical pathology, since accurate diagnosis of cancer and other diseases requires histopathological examination of samples.
Trained physicians licensed pathologists, are the personnel who perform histopathological examination and provide diagnostic information based on their observations. The trained personnel who prepare histological specimens for examination are histotechnicians, histotechnologists, histology technicians, histology technologists, medical scientists, medical laboratory technicians, or biomedical scientists, their support workers, their field of study is called histotechnology. In the 17th century, Italian Marcello Malpighi invented one of the first microscopes for studying tiny biological entities. Malpighi analysed several parts of the organs of bats and other animals under the microscope. Malpighi, while studying the structure of the lung, noticed its membranous alveoli and the hair-like connections between veins and arteries, which he named capillaries, his discovery established how the oxygen enters the blood stream and serves the body. In the 19th century, histology was an academic discipline in its own right.
The French anatomist Bichat introduced the concept of tissue in anatomy in 1801, the term "histology" first appeared in a book of Karl Meyer in 1819. Bichat described twenty-one human tissues, which can be subsumed under the four categories accepted by histologists; the usage of illustrations in histology, deemed as useless by Bichat, was promoted by Jean Cruveilhier. During the 19th century, many fixation techniques were developed by Adolph Hannover, Franz Schulze and Max Schultze, Alexander Butlerov and Benedikt Stilling. In the early 1830, Purkynĕ invented a microtome with high precision. Mounting techniques were developed by Rudolf Heidenhain, Salomon Stricker, Andrew Pritchard and Edwin Klebs. Koelliker's laboratory developed haematoxylin staining, in 1870s, Vysockij introduced eosin as a double or counter staining; the 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. They had conflicting interpretations of the neural structure of the brain based on differing interpretations of the same images.
Cajal won the prize for his correct theory, Golgi for the silver staining technique he invented to make it possible. There are four basic types of animal tissues: muscle tissue, nervous tissue, connective tissue, epithelial tissue. All tissue types are subtypes of these four basic tissue types. Epithelium: the lining of glands, bowel and some organs like the liver and kidney Endothelium: the lining of blood and lymphatic vessels Mesothelium: the lining of pleural and pericardial spaces Mesenchyme: the cells filling the spaces between the organs, including fat, bone and tendon cells Blood cells: the red and white blood cells, including those found in lymph nodes and spleen Neurons: any of the conducting cells of the nervous system Germ cells: reproductive cells Placenta: an organ characteristic of true mammals during pregnancy, joining mother and offspring, providing endocrine secretion and selective exchange of soluble, but not particulate, blood-borne substances through an apposition of uterine and trophoblastic vascularised parts Stem cells: cells with the ability to develop into different cell typesThe tissues from plants and microorganisms can be examined histologically.
Their structure is different from animal tissues. For plants, the study of their tissues is more called as plant anatomy, with the following main types: Dermal tissue Vascular tissue Ground tissue Meristematic tissue Chemical fixatives are used to preserve tissue from degradation, to maintain the structure of the cell and of sub-cellular components such as cell organelles; the most common fixative for light microscopy is 10% neutral buffered formalin. For electron microscopy, the most used fixative is glutaraldehyde as a 2.5% solution in phosphate buffered saline. These fixatives preserve tissues or cells by irreversibly cross-linking proteins; the main action of these aldehyde fixatives is to cross-link amino groups in proteins through the formation of methylene bridges, in the case of formaldehyde, or by C5H10 cross-links in the case of glutaraldehyde. This process, while preserving the structural integrity of the cells and tissue can damage the biological functionality of proteins enzymes, and
Yersinia pestis is a gram-negative, rod-shaped coccobacillus bacteria, with no spores. It is a facultative anaerobic organism, it causes the disease plague, which takes three main forms: pneumonic and bubonic plagues. All three forms were responsible for a number of high-mortality epidemics throughout human history, including: the sixth century's Plague of Justinian; these plagues originated in China and were transmitted west via trade routes. Recent research indicates that the pathogen may have been the cause of what is described as the Neolithic Decline, when European populations declined significantly; this would push the date to much earlier and might be indicative of an origin in Europe rather than Eurasia. Y. pestis was discovered in 1894 by Alexandre Yersin, a Swiss/French physician and bacteriologist from the Pasteur Institute, during an epidemic of the plague in Hong Kong. Yersin was a member of the Pasteur school of thought. Kitasato Shibasaburō, a German-trained Japanese bacteriologist who practised Koch's methodology, was engaged at the time in finding the causative agent of the plague.
However, Yersin linked plague with Y. pestis. Named Pasteurella pestis in the past, the organism was renamed Yersinia pestis in 1944; every year, thousands of cases of the plague are still reported to the World Health Organization, although with proper treatment, the prognosis for victims is now much better. A five- to six-fold increase in cases occurred in Asia during the time of the Vietnam War due to the disruption of ecosystems and closer proximity between people and animals; the plague is now found in sub-Saharan Africa and Madagascar, areas which now account for over 95% of reported cases. The plague has a detrimental effect on nonhuman mammals. In the United States, mammals such as the black-tailed prairie dog and the endangered black-footed ferret are under threat. Y. pestis is a nonmotile, stick-shaped, facultative anaerobic bacterium with bipolar staining that produces an antiphagocytic slime layer. Similar to other Yersinia species, it tests negative for urease, lactose fermentation, indole.
The closest relative is the gastrointestinal pathogen Yersinia pseudotuberculosis, more distantly Yersinia enterocolitica. The complete genomic sequence is available for two of the three subspecies of Y. pestis: strain KIM, strain CO92. As of 2006, the genomic sequence of a strain of biovar Antiqua has been completed. Similar to the other pathogenic strains, signs exist of loss of function mutations; the chromosome of strain KIM is 4,600,755 base pairs long. Like Y. pseudotuberculosis and Y. enterocolitica, Y. pestis is host to the plasmid pCD1. It hosts two other plasmids, pPCP1 and pMT1 that are not carried by the other Yersinia species. PFra codes for a phospholipase D, important for the ability of Y. pestis to be transmitted by fleas. PPla codes for a protease, that activates plasmin in human hosts and is a important virulence factor for pneumonic plague. Together, these plasmids, a pathogenicity island called HPI, encode several proteins that cause the pathogenesis, for which Y. pestis is famous.
Among other things, these virulence factors are required for bacterial adhesion and injection of proteins into the host cell, invasion of bacteria in the host cell, acquisition and binding of iron harvested from red blood cells. Y. pestis is thought to be descended from Y. pseudotuberculosis, differing only in the presence of specific virulence plasmids. A comprehensive and comparative proteomics analysis of Y. pestis strain KIM was performed in 2006. The analysis focused on the transition to a growth condition mimicking growth in host cells. Numerous bacterial small noncoding RNAs have been identified to play regulatory functions; some can regulate the virulence genes. Some 63 novel putative sRNAs were identified through deep sequencing of the Y. pestis sRNA-ome. Among them was Yersinia-specific Ysr141. Ysr141 sRNA was shown to regulate the synthesis of the type III secretion system effector protein YopJ; the Yop-Ysc T3SS is a critical component of virulence for Yersinia species. Many novel sRNAs were identified from Y. pestis grown in vitro and in the infected lungs of mice suggesting they play role in bacterial physiology or pathogenesis.
Among them sR035 predicted to pair with SD region and transcription initiation site of a thermo-sensitive regulator ymoA, sR084 predicted to pair with fur, ferric uptake regulator. Intergenic RNA thermometer In the urban and sylvatic cycles of Y. pestis, most of the spreading occurs between rodents and fleas. In the sylvatic cycle, the rodent is wild, but in the urban cycle, the rodent is the brown rat. In addition, Y. pestis can spread from the urban environment and back. Transmission to humans is through the bite of infected fleas. If the disease has progressed to the pneumonic form, humans can spread the bacterium to others by coughing and sneezing. Several species of rodents serve as the main reservoir for Y. pes
Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are used in biology and medicine to highlight structures in biological tissues for viewing with the aid of different microscopes. Stains may be used to define and examine bulk tissues, cell populations, or organelles within individual cells. In biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes. Biological staining is used to mark cells in flow cytometry, to flag proteins or nucleic acids in gel electrophoresis. Simple staining is staining with only one stain/dye. There are various kinds of multiple staining, many of which are examples of counterstaining, differential staining, or both, including double staining and triple staining. Staining is not limited to biological materials, it can be used to study the morphology of other materials for example the lamellar structures of semi-crystalline polymers or the domain structures of block copolymers.
In vivo staining is the process of dyeing living tissues—in vivo means "in life". By causing certain cells or structures to take on contrasting colour, their form or position within a cell or tissue can be seen and studied; the usual purpose is to reveal cytological details. In vitro staining involves colouring cells or structures that have been removed from their biological context. Certain stains are combined to reveal more details and features than a single stain alone. Combined with specific protocols for fixation and sample preparation and physicians can use these standard techniques as consistent, repeatable diagnostic tools. A counterstain is stain that makes cells or structures more visible, when not visible with the principal stain. For example, crystal violet stains only Gram-positive bacteria in Gram staining. A safranin counterstain is applied that stains all cells, allowing identification of Gram-negative bacteria. While ex vivo, many cells continue to live and metabolize until they are "fixed".
Some staining methods are based on this property. Those stains excluded by the living cells but taken up by the dead cells are called vital stains; those that enter and stain living cells are called supravital stains. However, these stains are toxic to the organism, some more so than others. Due to their toxic interaction inside a living cell, when supravital stains enter a living cell, they might produce a characteristic pattern of staining different from the staining of an fixed cell. To achieve desired effects, the stains are used in dilute solutions ranging from 1:5000 to 1:500000. Note that many stains may be used in both living and fixed cells; the preparatory steps involved depend on the type of analysis planned. Fixation–which may itself consist of several steps–aims to preserve the shape of the cells or tissue involved as much as possible. Sometimes heat fixation is used to kill and alter the specimen so it accepts stains. Most chemical fixatives generate chemical bonds between proteins and other substances within the sample, increasing their rigidity.
Common fixatives include formaldehyde, methanol, and/or picric acid. Pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. Permeabilization involves treatment of cells with a mild surfactant; this treatment dissolves cell membranes, allows larger dye molecules into the cell's interior. Mounting involves attaching the samples to a glass microscope slide for observation and analysis. In some cases, cells may be grown directly on a slide. For samples of loose cells the sample can be directly applied to a slide. For larger pieces of tissue, thin sections are made using a microtome. Most of the dyes used in microscopy are available as BSC-certified stains; this means that samples of the manufacturer's batch have been tested by an independent body, the Biological Stain Commission, found to meet or exceed certain standards of purity, dye content and performance in staining techniques. These standards are published in the Commission's journal Histochemistry.
Many dyes are inconsistent in composition from one supplier to another. The use of BSC-certified stains eliminates a source of unexpected results; some vendors sell stains "certified" by themselves rather than by the Biological Stain Commission. Such products may not be suitable for diagnostic and other applications. A simple staining method for bacteria, successful when the "positive staining" methods detailed below fail, is to use a negative stain; this can be achieved by smearing the sample onto the slide and applying nigrosin or India ink. After drying, the microorganisms may be viewed in bright field micros
Red blood cell
Red blood cells known as RBCs, red cells, red blood corpuscles, erythroid cells or erythrocytes, are the most common type of blood cell and the vertebrate's principal means of delivering oxygen to the body tissues—via blood flow through the circulatory system. RBCs take up oxygen in the lungs, or gills of fish, release it into tissues while squeezing through the body's capillaries; the cytoplasm of erythrocytes 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. The cell membrane is composed of proteins and lipids, this structure provides properties essential for physiological cell function such as deformability and stability while traversing the circulatory system and the capillary network. In humans, mature red blood cells are oval biconcave disks, they lack most organelles, in order to accommodate maximum space for hemoglobin. 2.4 million new erythrocytes are produced per second in human adults. The cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages.
Each circulation takes about 60 seconds. A quarter of the cells in the human body are red blood cells. Nearly half of the blood's volume is red blood cells. Packed red blood cells are red blood cells that have been donated and stored in a blood bank for blood transfusion. All vertebrates, including all mammals and humans, have red blood cells. Red blood cells are cells present in blood; the only known vertebrates without red blood cells are the crocodile icefish. While they no longer use hemoglobin, remnants of hemoglobin genes can be found in their genome. Vertebrate red blood cells consist of hemoglobin, a complex metalloprotein containing heme groups whose iron atoms temporarily bind to oxygen molecules in the lungs or gills and release them throughout the body. Oxygen can diffuse through the red blood cell's cell membrane. Hemoglobin in the red blood cells carries some of the waste product carbon dioxide back from the tissues. Myoglobin, a compound related to hemoglobin, acts to store oxygen in muscle cells.
The color of red blood cells is due to the heme group of hemoglobin. The blood plasma alone is straw-colored, but the red blood cells change color depending on the state of the hemoglobin: when combined with oxygen the resulting oxyhemoglobin is scarlet, when oxygen has been released the resulting deoxyhemoglobin is of a dark red burgundy color. However, blood can appear bluish when seen through skin. Pulse oximetry takes advantage of the hemoglobin color change to directly measure the arterial blood oxygen saturation using colorimetric techniques. Hemoglobin has a high affinity for carbon monoxide, forming carboxyhemoglobin, a bright red in color. Flushed, confused patients with a saturation reading of 100% on pulse oximetry are sometimes found to be suffering from carbon monoxide poisoning. Having oxygen-carrying proteins inside specialized cells was an important step in the evolution of vertebrates as it allows for less viscous blood, higher concentrations of oxygen, better diffusion of oxygen from the blood to the tissues.
The size of red blood cells varies among vertebrate species. The red blood cells of mammals are shaped as biconcave disks: flattened and depressed in the center, with a dumbbell-shaped cross section, a torus-shaped rim on the edge of the disk; this shape allows for a high surface-area-to-volume ratio to facilitate diffusion of gases. However, there are some exceptions concerning shape in the artiodactyl order, which displays a wide variety of bizarre red blood cell morphologies: small and ovaloid cells in llamas and camels, tiny spherical cells in mouse deer, cells which assume fusiform, lanceolate and irregularly polygonal and other angular forms in red deer and wapiti. Members of this order have evolved a mode of red blood cell development different from the mammalian norm. Overall, mammalian red blood cells are remarkably flexible and deformable so as to squeeze through tiny capillaries, as well as to maximize their apposing surface by assuming a cigar shape, where they efficiently release their oxygen load.
Red blood cells in mammals are unique amongst vertebrates. Red blood cells of mammals cells have nuclei during early phases of erythropoiesis, but extrude them during development as they mature; the red blood cells without nuclei, called reticulocytes, subsequently lose all other cellular organelles such as their mitochondria, Golgi apparatus and endoplasmic reticulum. The spleen acts as a reservoir of red blood cells. In some other mammals such as dogs and horses, the spl