Entamoeba histolytica. 3. Summary. Entamoeba histolytica is an invasive, pathogenic protozoan, causing amoebiasis, and an important cause of diarrhea in developing countries. Our understanding of its epidemiology has dramatically changed since this amoeba was distinguished from another morphologically similar one, Entamoeba dispar, a non. Entamoeba histolytica; pathogenesis; amoebiasis. 1. Introduction The protozoan parasite, Entamoeba histolytica, is the causative agent of amoebiasis in humans. According to the best estimates (Walsh 1986) approximately 48 million individuals suffer from amoebiasis throughout the world. In 1984, at least 40,000 death 1- Entamoeba histolytica trophozoites are found in: a- Duodenum of infected human. b- Jejunum of infected human. c- Caecum of infected human. d- All of the above. 2- Infection with Entamoeba histolytica occurs through eating green salad contaminated with: a- Trophozoites of Entamoeba histolytica. b- Cysts of Entamoeba histolytica Entamoeba coli • Life cycle and location identical to . E. histolytica. • Most common endocommensal in people; has a worldwide distribution and 10-50% of the population can be infected in different parts of the world. • Not pathogenic. • Feeds on bacteria and any other cells available; does not invade tissue. Trophozoites 20-30 . Entamoeba histolytica is a protozoan parasite that causes amebic dysentery and liver abscess. The disease is common in tropical regions of the world where hygiene and sanitation is often approximate. The epidemiology of E. histolytica has been studied around the world
Entamoeba Histolytica: Updates in Clinical Manifestation, Pathogenesis, and Vaccine Development MicaellaKantor , 1 AnarellaAbrantes , 1 AndreaEstevez , 1 AlanSchiller, 1 JoseTorrent, Entamoeba histolytica, a protozoan parasite, is the etiologic agent of amoebiasis in humans. It exists in two forms—the trophozoite which is the active, dividing form, and the cyst which is dormant and can survive for prolonged periods outside the host. In most infected individuals the trophozoites exist as commensals. In a small percentage of infections, the trophozoites become invasive and. Entamoeba histolytica: Morphology, life cycle, Pathogenesis, clinical manifestation, lab diagnosis and Treatment Entamoeba histolytica is a common protozoan parasite found in the large intestine of human. The parasite is responsible for amoebiasis and liver absceses. It is the third leading parasite cause of death in the developing countries Entamoeba histolytica causes dysentery by invading the mucosa and submucosa layers of the large intestine in human beings. E. histolytica are commonly found in tropical and subtropical countries. The life cycle of E. histolytica begins and ends inside one single host, i.e., an individual human being
Entamoeba histolytica. pathogenesis. Entamoeba histolytica is a protozoan parasite of humans that causes 40 000-100 000 deaths annually. Clinical amoebiasis results from the spread of the normally luminal parasite into the colon wall and beyond; the key development in understanding this complex multistage process has been the publication of. Entamoeba histolytica and pathogenesis: A calcium connection. Entamoeba histolytica. and pathogenesis: A calcium connection. Mrigya Babuta, Current address: Beth Israel Deaconess Medical Centre, Department of Medicine, Division of Gastroenterology, Centre for Life Science, Boston, Massachusetts, United States of America The major clinical manifestations of Entamoeba histolytica infection are amoebic colitis and amoebic liver abscesses. Amoebic colitis is characterized by ulceration and inflammation of the colon. The gut inflammation can be so severe that amoebic colitis can be confused with inflammatory bowel disease1, 2.Neutrophils are the prominent host inflammatory cell early in infection Entamoeba histolytica is the responsible parasite of amoebiasis and remains one of the top three parasitic causes of mortality worldwide.With increased travel and emigration to developed countries, infection is becoming more common in nonendemic areas. Although the majority of individuals infected with E. histolytica remain asymptomatic, some present with amoebic colitis and disseminated disease Entamoeba histolytica: an Overview - PDF Free Download. Curr Trop Med Rep DOI 10.1007/s40475-017-0100-z. TROPICAL MEDICINE IN THE MEDITERRANEAN REGION (F BRUSCHI, SECTION EDITOR) Entamoeba histolytica: an Overview Nadia A. El-Dib 1. # Springer International Publishing AG 2017
Entamoeba histolytica: Life Cycle, Diseases, Lab Diagnosis. Entamoeba histolytica is an enteric protozoan parasite with worldwide distribution. It is responsible for amoebic dysentery (bloody diarrhea) and invasive extraintestinal amebiasis (such as liver abscess, peritonitis, pleuropulmonary abscess). Other species of Entamoeba; Entamoeba. E. histolytica was discovered by Losch in 1875 Demonstrated the parasite in the dysenteric feces of a patient in St.Petersburg in Russia. 4. MORPHOLOGY LIFE CYCLE PATHOGENESIS & CLINICAL FEATURES LABORATORY DIAGNOSIS TREATMENT PREVENTION 5. E.histolytica occurs in 3 forms Trophozoite Precyst Cyst 6 Introduction. Entamoeba histolytica (Eh), the causative agent of amebiasis, is an intestinal protozoan parasite that colonizes the intestinal lumen asymptomatically (known as noninvasive disease) in approximately 90% of cases.However, in 10% of individuals, this asymptomatic relationship breaks down and the parasite breaches the innate mucosal barrier and invades the underlying lamina propria. Entamoeba histolytica is the responsible parasite of amoebiasis and remains one of the top three parasitic causes of mortality worldwide. With increased travel and emigration to developed countries, infection is becoming more common in nonendemic areas. Although the majority of individuals infected with E. histolytica remain asymptomatic, some present with amoebic colitis and disseminated disease
Amoebiasis, the infection of humans with Entamoeba histolytica, has a worldwide distribution; humans are the main reservoir and source of infection(1), although some other primates can also be infected. The motile trophozoite of E. histolytica (Fig. 1) lives in the lumen of the large intestine where Entamoeba histolytica- Morphology, Epidemiology, Life cycle, Pathogenesis, Clinical findings. 500 Million populations are infected over the world. 60-70% population in Pakistan is infected; Entamoeba histolytica caused amebic dysentery and liver abscess. Morphology. Trophozoites; A cyst (egg) Cyst= it is immovable and has disease-causing form THERAPEUTIC EFFECT OF TAMARINDUS INDICA EXTRACTS ON THE PATHOGENESIS OF ENTAMOEBA HISTOLYTICA IN-VIVO Mansour Abdulnabi H. Mehdi * 1, Gozif Mohammed N. Omar 2, Mazahar Farooqui 1 and Vidya Pradhan 1 Dr. Rafiq Zakaria College for Women 1, Aurangabad - 431001, Maharashtra, India Few organisms are more aptly named than Entamoeba histolytica, an intestinal protozoan parasite that can lyse and destroy human tissue. Within the past four years, new models of E. histolytica infection have begun to illuminate how amoebic trophozoites cause intestinal disease and liver abscess, and have expanded our understanding of the remarkable killing ability of this parasite Pathogenesis and clinical features Entamoeba histolytica causes intestinal and extraintestinal amoebiasis. Incubation period is highly variable. On an avg , it ranges from 4 days to 4 months. Intestinal amoebiasis The amoebae cause disease only when they invade the intestinal tissues. this happens only in about 10% of cases of infection
Entamoeba histolytica was first described by Schaudinn in 1903 as the Entamoeba species associated with human dysentery [].The species found in healthy individuals was originally named as Entamoeba coli.The concept of the two species of Entamoeba, one involved in the human disease and the other, a nonpathogenic form though capable of infecting human, was felt even in early days [] SUMMARY In spite of a wealth of knowledge on the biochemistry and cellular and molecular biology of Entamoeba histolytica, little has been done to apply these advances to our understanding of the lesions observed in patients with intestinal amebiasis. In this review, the pathological and histological findings in acute amebic colitis are related to the molecular mechanisms of E. histolytica.
NAME: Entamoeba histolytica. SYNONYM OR CROSS REFERENCE: Amebiasis, Amebic dysentery, Ameboma. CHARACTERISTICS: Obligate parasite of human alimentary tract; possess both cyst (10-15 µm in diameter) and trophozoite forms; trophozoite (12-50 µm in diameter) are microaerophilic with a granular, vacuolated endoplasm and clear ectoplasm with. E histolytica is transmitted via ingestion of the cystic form (infective stage) of the protozoa. Viable in the environment for weeks to months, cysts can be found in fecally contaminated soil. Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates causing amoebiasis, E. histolytica is estimated to infect about 35-50 million people worldwide. E. histolytica infection is estimated to kill more than 55,000 people each year. Previously, it was thought that 10% of the world population was infected, but. Entamoeba histolytica makes a man so called amoebiasis (amoebosis). he most common clinical forms of amoebiasis are: Acute dysentery, intestinal amoebiasis: he disease begins when trophozoites of E. histolytica are adhered to the epithelial cells of the colon with a special Gal/GalNAc lectin, a heterodimer comprised of three subunits with a.
E. histolytica. Amoebaeofthis groupwerepreviously described as the large race andonlythese amoebaeareresponsible forinvadingtissue in man.This progress report concerns the pathogenicity oftrue E. histolytica. Differences in Virulence betweenDifferent Isolates Entamoeba histolytica lives primarily as a commensal in the large intestin Entamoeba histolytica and Entamoeba dispar Basic guidelines A. Multiple stool samples (at least 3) should be tested before a negative result is reported. B. To maximize recovery of cysts, stool samples in formalin, or other fixatives, should be concen-trated prior to microscopic examination (e.g.,10 min at 500 × g when using the formalin-ethyl • Entamoeba histolytica • Entamoeba dispar • Entamoeba coli • Entamoeba hartmanni • Endolimax nana • Iodamoeba bütschlii Entamoeba histolytica one of the most potent killers in nature Entamoeba histolytica • worldwide distribution (cosmopolitan) • higher prevalence in tropical or developing countries (20%
Entamoeba histolytica- Morphology - The Biology Notes Entamoeba histolytica: Morphology, life cycle, Pathogenesis, clinical manifestation, lab diagnosis and Treatment Entamoeba histolytica is a common protozoan parasite found in the large intestine of human. The parasite is responsible for amoebiasis and liver absceses Epidemiology of entamoeba histolytica pdf Life cycle Entamoeba histolytica is a protozoan parasite that accounts for an estimated 100,000 annual deaths (71). Infection ranges from asymptomatic colonization of the large bowel to severe invasive intestinal and extra-intestinal disease Entamoeba histolytica is a protozoan parasite that accounts for an estimated 100,000 annual deaths ( 71 ). Infection ranges from asymptomatic colonization of the large bowel to severe invasive intestinal and extra-intestinal disease. The parasite life cycle is relatively simple: humans orally ingest the cyst form from contaminated sources.
Biology and Pathogenesis of Entamoeba. Editors: Nozaki, Tomoyoshi, Bhattacharya, Alok (Eds.) Free Preview. Is the first comprehensive book on biology and pathogenesis of amebiasis in the last 15 years. Includes all aspects of amebiasis study, from genomics, pathogenesis, and immunology to drug development. Contains contributions from almost all. The first chapter describes the continuously expanding Entamoeba universe; a multi-branched (phylogenetic) tree which has grown explosively from the seed planted 20 years ago by the realization that most people excreting cysts of Entamoeba histolytica were in fact infected with Entamoeba dispar. Cheap and rapid DNA sequencing has driven. Part I deals with four topics. The first chapter describes the continuously expanding Entamoeba universe; a multi-branched (phylogenetic) tree which has grown explosively from the seed planted twenty years ago by the realization that most people excreting cysts of Entamoeba histolytica were in fact infected with Entamoeba dispar
OVERVIEW: What every clinician needs to know Parasite name and classification Entamoeba histolytica - protozoan parasite E. histolytica is one of three morphologically identical species of Entamoeba commonly found in humans; the others are E. dispar and E. moshkovskii. Only E. histolytica causes invasive disease in humans; the others are non-pathogenic. Continue Reading What i Author(s): Melendez-Lopez, Samuel G. | Abstract: Amebiasis, defined as invasive intestinal or extra- intestinal infection with the protozoan parasite Entamoeba histolytica, is a major cause of morbidity in developing countries and the second leading cause of death from parasitic disease worldwide. More than 500 million people worldwide are infected with Entamoeba, causing about 50 million. Pathophysiology of amoebiasis. Few organisms are more aptly named than Entamoeba histolytica, an intestinal protozoan parasite that can lyse and destroy human tissue. Within the past four years, new models of E. histolytica infection have begun to illuminate how amoebic trophozoites cause intestinal disease and liver abscess, and have expanded. Entamoeba histolytica is a pathogenic parasite in the intestine of human beings and many other primates. It inhabits the mucous and sub-mucous layers of the large intestine. It feeds mainly on the tissues of the intestinal wall and often produces severe ulcers and abscesses. In chronic cases, it may enter the blood circulation to reach the. The mechanism whereby Entamoeba histolytica (Eh) binding with macrophages at the intercellular junction triggers aggressive pro-inflammatory responses in disease pathogenesis is not well understood
Entamoeba histolytica is an invasive, pathogenic protozoan, causing amoebiasis, and an important cause of diarrhea in developing countries. Our understanding of its epidemiology has dramatically changed since this amoeba was distinguished from another morphologically similar one, Entamoeba dispar, a non pathogenic and commensal parasite.These two species can now be distinguished mainly through. Entamoeba histolytica is the causative agent of human intestinal and liver amebiasis. The extraordinary phagocytic activity of E. histolytica trophozoites has been accepted as one of the virulence mechanisms responsible for their invasive capacity. The recognition of the noninvasive Entamoeba dispar as a different species has raised the question as to whether the lack of pathogenic potential. Entamoeba histolytica is the third-leading cause of parasitic mortality globally.E. histolytica infection generally does not cause symptoms, but the parasite has potent pathogenic potential. The origins, benefits, and triggers of amoebic virulence are complex. Amoebic pathogenesis entails depletion of the host mucosal barrier, adherence to the colonic lumen, cytotoxicity, and invasion of the. Entamoeba histolytica is an anaerobic intestinal amoeba parasite that predominantly affects a man and causes amoebic dysentery and liver abscess.. History. Entamoeba histolytica was first discovered by Lösch in 1875 in Leningrad, Russia for causing disease in humans. Lösch discovered amoeba in ulcers of the colon at autopsy and induced it to a dog by rectal inoculation with human faeces alleviated by Prx downregulation [6], which implicates Prx in the pathogenesis of E. histolytica infection. There are more than 20 di erent transcripts of Prx in E. histolytica. In a previous study, we cloned and expressed a Prx of E. histolytica (XP_648522.1), which represents a typical 2-Cys Prx containing tw
File Type PDF Amebiasis Biology And Pathogenesis Of Entamoeba Amebiasis Biology And Pathogenesis Of Entamoeba As recognized, adventure as without difficulty as experience about lesson, amusement, as without difficulty as deal can be gotten by just checking out a ebook amebiasis biology and pathogenesis of entamoeba next it is not directly done, you could allow even more concerning this life. PATHOPHYSIOLOGY OF AMEBIC COLITIS. The first step in bowel invasion is adherence of E. histolytica trophozoites to colonic epithelial cells.The primary molecule implicated in the adhesive process is a galactose/N-acetylgalactosamine-specific lectin, which consists of noncovalently linked 170-kDa and 35- or 31-kDa subunits ().The heavy subunit contains the carbohydrate binding domain and a. Impact of collagen fibres networks on Entamoeba histolytica invasive process of the human colon mucosa 12:50-13:10 Young Ah Lee, Yonsei University, South Korea Cysteine protease activity of Entamoeba histolytica is closely involved in amoebic adherence and host cell apoptosis. 13:10-13:30 Katherine Ralston, University of Virginia, US Protein kinases (PKs) of parasitic protozoa are being evaluated as drug targets. A large number of protein kinases within the protein kinome of Entamoeba histolytica strongly suggest that protein phosphorylation is a key component of pathogenesis regulation by this parasite. PI3 K and Src are kinases previously described in this parasite, but their role is poorly understood G protein signaling pathways, as key components of physiologic responsiveness and timing, are frequent targets for pharmacologic intervention. Here, we identify an effector for heterotrimeric G protein α subunit (EhGα1) signaling from Entamoeba histolytica, the causative agent of amoebic colitis. EhGα1 interacts with this effector and guanosine triphosphatase-accelerating protein, EhRGS.
Research Article Erythrophagocytosis in Entamoeba histolytica and Entamoeba dispar : A Comparative Study DanielTalamás-Lara, 1 BibianaChávez-Munguía, 1 ArturoGonzález-Robles, 1 PatriciaTalamás-Rohana, 1 LizbethSalazar-Villatoro, 1 ÁngelDurán-Díaz, 2 andAdolfoMartínez-Palomo 1 Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, IPN 2.2. Entamoeba histolytica Human amebiasis is caused by E. histolytica (Amoebozoa, Amorphaea). All pathogenic Entamoeba are classified as E. histolytica, whereas the species Entamoeba dispar comprises non-pathogenic Entamoeba strains [22]. As for G. lamblia, two stages can be distinguished, namely, trophozoites and cysts capable. of supporting pathogenesis amebas. The microfolora amebic presence could of P-0651 ZYMODEME ISOLATED Kdar S. PATTERNS OF ENTAMOEBA FROM CLINICAL Bahar iH. HISTOLYTICA STRAINS he an important noted bacteria on of importance with this agent. The in the as transient of protozoa, same bacteria of amebas than could in be E. cloacae. Entamoeba histolytica is a parasite and lives in the mucous and sub-mucous layers of the large intestine of man. It may occur in the liver and lungs. Rarely it invades brain, spleen etc. causing ulcers. The disease caused by the parasite is known as Amoebic dysentery.. It occurs in two forms—Trophic and Cystic
Human amoebiasis is caused by the parasitic protozoan Entamoeba histolytica that lives in the large intestine of hosts, where can produce asymptomatic colonization until severe invasive infections with blood diarrhea and spreading to other organs. The amoebic abscesses in liver are the most frequent form of amoebiasis outside intestine and still there are doubts about the pathogenic mechanisms. Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus Entamoeba.[1] Predominantly infecting humans and other primates causing. Entamoeba Polecki is an intestinal protozoan which is best known for its infection and never identified or were misdiagnosed as E. histolytica Entamoeba histolytica is an anaerobic parasitic protozoan that infects the digestive tract of predominantly humans and other primates. It is a parasite that infects an estimated 50 million people around the world and is a significant cause of morbidity and mortality in developing countries Genus - Entamoeba. Species — Histolytica. Entamoeba histolytica is a protozoan endoparasite inhabiting the mucosa and sub-mucosa layers of the large intestine of human beings, causing dysentery and liver abscess. The parasite was first discovered by Lambl (1859) S. chaudin (1903) differentiated pathogenic and non- pathogenic form of amoebae Background: Entamoeba histolytica (Eh) causes amebiasis in humans and is in charge of 100,000 deaths yearly, making it the third driving reason for death because of a protozoan parasite. Giardiasis is a main diarrheal disease with international allocation caused by Giardia lamblia. Aim of the Study: To show the current prevalence of Eh and G. lamblia infection among people living in Al.
Entamoeba histolytica, a major agent of human amoebiasis, expresses two distinct forms of α-actinin, a ubiquitous actin-binding protein that is present in most eukaryotic organisms. In contrast to all metazoan α-actinins, in both isoforms the intervening rod domain that connects the N-terminal actin-binding domain with the C-terminal EF-hands is much shorter Entamoeba histolytica is a protozoan parasite inhabiting the colon of man and other vertebrates. It has a worldwide distribution Pathogenesis at the tissue level The symptoms of intestinal amebiasis are colitis, fever, and amebic diarrhea (with resultant dehydration) with flecks of blood-. Abstract. Stocks of Entamoeba histolytica isolated and maintained in a variety of culture media, both axenic and polyxenic, were compared with each other and with strains previously characterized. The present stocks were isolated from subjects living in various cities in India. Using the enzyme patterns of: E C 5319 glucose phosphate isomerase (GPI); E C 11140 L-malate: NADP + oxidoreductase. Background There is a dearth of information on liver abscesses in the United Arab Emirates. Herein, we describe the clinical features of liver abscesses and determine their incidence rates and clinical outcomes. Methods We retrospectively reviewed the clinical charts of adult patients with a primary diagnosis of liver abscess at a major hospital over a 7-year period. Results Amongst 45. In order to define the role of neutrophils in the innate resistance to Entamoeba histolytica liver infection in mice, we examined the pattern of liver lesion induced by direct injection of E. histolytica trophozoites in normal mice and in neutrophil‐depleted mice.A variety of histological lesions were found, the extent of liver damage was considerably higher in the neutrophil‐depleted mice
The protozoan parasite Entamoeba histolytica colonizes the human large bowel. Invasion of the intestinal epithelium causes amoebic colitis and opens the route for amoebic liver abscesses. The parasite relies on its dynamic actomyosin cytoskeleton and on surface adhesion molecules for dissemination in the human tissues FAX Life Science Open Day ∙ 2008 ∙ Weizmann Institute of Science i Department of Epigenetic silencing of multiple genes in Entamoeba histolytica 972 8 934 4511 david.mirelman@weizmann.ac.i There are two exceptions (I. bütschlii, E. polecki) that have been suspected of mild pathogenesis (Roberts and Janovy 2009). Entamoeba histolytica is a tissue-lysing luminal protozoan parasite of the family Entamoebae that is found throughout the world (McLaughlin and Aley 1985). Its life cycle includes two stages, the infectious (cyst) stage. Application of structural biology in the pathogenesis of Entamoeba histolytica: ZHAO Yan-qing, CHENG Xun-jia: Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, Chin Apoptotic killing of host by Entamoeba histolytica: electron microscopic appearance of murine myeloid cells incubated in vitro with E. histolytica for 30 min at 37°C. Compacted chromatin, cytoplasmic condensation and convolution, membrane blebbing, and nuclear envelope swelling are illustrated. Magnification, ×9425
The l-cysteine is crucial for growth, survival, defense against oxidative stress, and pathogenesis of Entamoeba histolytica. The de novo biosynthesis of l-cysteine in E. histolytica, has a two-step pathway, where O-acetylserine sulfhydrylase (OASS) catalyses the last step by converting OAS to l-cysteine Entamoeba histolytica manifests its pathogenicity through several cellular processes triggered by external stimuli that activate signal transduction pathways. The intense secretory activity resulting from stimulation is not correlated with a typical endoplasmic reticulum (ER) or Golgi organization, and little is known in this parasite about endocytic/exocytic pathways Entamoeba histolytica is the causative agent of amoebiasis in humans and is responsible for an estimated 100 000 deaths annually, making it the second leading cause of death due to a protozoan parasite after Plasmodium.Pathogenesis appears to result from the potent cytotoxic activity of the parasite, which kills host cells within minutes Excretory-secretory (ES) proteins of E. histolytica are thought to play important roles in the host invasion, metabolism, and defence. Elucidation of the types and functions of E. histolytica ES proteins can further our understanding of the disease pathogenesis. Thus, the aim of this study is to use proteomics approach to better understand the complex ES proteins of the protozoa
BACKGROUND: Factors that prevent colonic mucosal invasion by pathogenic Entamoeba histolytica are not understood. A key initial step in pathogenesis of injury induced by amoeba is adherence to target cells mediated by a surface glycoprotein lectin on E histolytica. Mucin degrading bacteria normally present in the colon lumen produce glycosidases that degrade soluble or cell surface. Entamoeba histolytica is a parasitic human protozoan that infects 500,000,000 people worldwide annually. In the course of the parasite's life cycle, motile trophozoites breach the colonic mucosa, invade through the epithelial layer and extracellular matrix (ECM) and occasionally disseminate through portal blood vessels to distant organs. Membrane rafts are small heterogeneous, highly dynamic. Entamoeba histolytica has a worldwide distribution, with a higher incidence of amebiasis in developing countries. Risk groups in industrialized countries include homosexual males, travelers and recent immigrants (although disease may develop months to years after exposure), and institutionalized populations.The majority of morbidity and mortality occurs in Asia, Central and South America, and. Entamoeba histolytica is an intestinal protozoan parasite that causes amoebiasis in humans, affecting up to 50 million people worldwide each year and causing 40,000 to 100,000 deaths annually. EhCP112 is a cysteine proteinase of E. histolytica able to disrupt cell monolayers and digest extracellular matrix proteins, it is secreted by trophozoites and it can be active in a wide range of. Surface molecules are of major importance for host-parasite interactions. During Entamoeba histolytica infections, these interactions are predicted to be of prime importance for tissue invasion, induction of colitis and liver abscess formation. To date, however, little is known about the molecules involved in these processes, with only about 20 proteins or protein families found exposed on the.