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comparison of hemolymph proteins from resistant and susceptible oysters, crassostrea virginica, exposed to the parasite haplosporidium nelsoni (msx). 19863084662
infection and mortality patterns in strains of oysters crassostrea virginica selected for resistance to the parasite haplosporidium nelsoni (msx).strains of oysters crassostrea virginica resistant to mortality caused by the parasite haplosporidium nelsoni (msx) were developed and tested through 6 generations. in addition, strains in each generation were followed for up to 6 yr of continuous exposure to the parasite in nature. selected strains responded to challenge by the parasite with gradually improved survival in successive generations. they were slower to develop patent infections than were unselected groups and were able to delay mor ...19873108479
lectin binding characteristics of haemocytes and parasites in the oyster, crassostrea virginica, infected with haplosporidium nelsoni (msx).lectin-binding surface receptors on haemocytes from host oysters were compared with those on plasmodial stages of the ascetosporan parasite haplosporidium nelsoni (msx). haemocytes were agglutinated, in descending order of strength, by wga, hpa, lpa, cona, and cfa. gma, pha, and rma lectins failed to agglutinate at 100 micrograms/ml, the highest concentration tested. these results indicate that haemocytes contain surface receptors resembling n-acetyl-d-glucosamine and alpha-methylmannopyranoside ...19901964721
evidence for regular sporulation by haplosporidium nelsoni (msx) (ascetospora; haplosporidiidae) in spat of the american oyster, crassostrea virginica.the spore stage of haplosporidium nelsoni, the ascetosporan parasite causing multinucleated sphere unknown (msx) disease in oysters, crassostrea virginica, has been reported so rarely (less than 0.01% of infected oysters) that a second host has been postulated. however, recent intensive sampling of young (less than 1 year) oysters in delaware bay, u.s. suggests that spore formation occurs regularly in this group and that spores are produced in at least 75-85% of all infections reaching the advan ...19911787418
haplosporidiosis of the pacific oyster, crassostrea gigas.haplosporidan parasites were observed in 10/100 spat and 1/171 adult pacific oysters, crassostrea gigas, reared in matsushima bay, japan. eight of the infected spat contained mild to severe plasmodial infections. the multinucleated plasmodia were 6-12 microm x 7-15 microm and were associated with an infiltration of hemocytes that occurred throughout the vesicular connective tissues of all infected oysters. two oysters, one adult and one spat, contained advanced sporogonic infections. these were ...19911787325
cellular responses of oysters infected with haplosporidium nelsoni: changes in circulating and tissue-infiltrating hemocytes.the protozoan parasite haplosporidium nelsoni (msx) elicits an inflammatory-type response in oysters, crassostrea virginica. we assayed circulating hemocytes of oysters exposed to h. nelsoni to quantify the effects of parasitism, selection for resistance, and season on total and differential counts. all factors had a significant (p < 0.02) effect on total counts, but explained relatively little of the overall variance [season (12%) > selection (4%) > infection (2%)]. circulating hemocyte densiti ...19938426068
small subunit ribosomal rna gene sequence of the parasitic protozoan haplosporidium nelsoni provides a molecular probe for the oyster msx disease. 19938114818
further evidence of regular sporulation by haplosporidium nelsoni in small oysters, crassostrea virginica.during a field study to determine the susceptibility of the pacific oyster crassostrea gigas to chesapeake bay oyster pathogens, sporulation of haplosporidium nelsoni was observed in eastern oysters crassostrea virginica being used as controls. the c. virginica were obtained from 2 sources on 19 may 1993, a wild population in the upper rappahannock river, virginia (59.6 mm mean shell height) and a hatchery-reared population from chesapeake mari-culture that was held in the wye river, maryland (4 ...19947799147
small subunit ribosomal rna gene sequence of minchinia teredinis (haplosporidia: haplosporidiidae) and a specific dna probe and pcr primers for its detection.minchinia teredinis is a pathogen of wood-boring molluscs (shipworms), teredo spp., along the middle atlantic coast of the u.s. genomic dna was extracted from m. teredinis spores and small subunit (ssu) rdna was amplified by pcr, cloned, and sequenced. the sequence of m. teredinis ssu rdna was aligned with that of haplosporidium nelsoni and various protists in genbank. a 22-base oligonucleotide probe unique to m. teredinis, designated min702, was commercially synthesized and tested for sensitivi ...19957745284
molecular phylogenetic evidence that the phylum haplosporidia has an alveolate ancestry.the phylogenetic position of the phylum haplosporidia among other protists was investigated with the complete 16s-like rrna gene sequences from two species in the phylum: haplosporidium nelsoni, a parasite of oysters, and minchinia teredinis, a parasite of shipworms. because the lack of obvious morphological homologies with other protists hampered decisions regarding taxonomic composition for sequence alignment and phylogenetic analysis, the complete sequences for these two haplosporidians were ...19957659013
a sensitive and specific dna probe for the oyster pathogen haplosporidium nelsoni.haplosporidium nelsoni is a pathogen of the eastern oyster, crassostrea virginica, along the middle atlantic coast of the u.s. genomic dna was extracted from h. nelsoni plasmodia and small subunit (ssu) rdna was amplified by pcr, cloned and sequenced. the sequence of h. nelsoni ssu rdna was aligned with that of another haplosporidian, minchinia teredinis, and with ssu rdna data of c. virginica and various protists in genbank. a 21-base oligonucleotide unique to h. nelsoni, designated msx1347, wa ...19957620459
characterization of the small subunit ribosomal rna gene of the oyster parasite haplosporidium costale.the small subunit ribosomal rna (ssu rrna) gene of the oyster parasite haplosporidium costale was characterized from spore dna by polymerase chain reaction (pcr) and molecular cloning. sequence analysis showed that identical clones were obtained from separate batches of spore samples. the gene is 1791 nucleotides in size. it has 84.5% sequence similarity to that of a related oyster parasite, haplosporidium nelsoni, 71.8% similarity to that of its oyster host, crassostrea virginica, and 75.4% sim ...19957670599
southern hemisphere mollusc diseases and an overview of associated risk assessment problems.in australia and new zealand, bonamia sp. causes epizootics in flat oysters (tiostrea chilensis, ostrea angasi); marteilia sydneyi and mikrocytos roughleyi cause mortality in farmed rock oysters (saccostrea commercialis); and perkinsus olseni is pathogenic in abalone (haliotis spp.). marteilia lengehi, marteilioides branchialis, other marteilioides spp. and two species of haplosporidium are regarded as potential pathogens. a review of the pathogens causing diseases listed in the office internati ...19968890381
phylogeny of the haplosporidia (eukaryota: alveolata) based on small subunit ribosomal rna gene sequence.the phylogenetic position of the phylum haplosporidia was investigated with the complete small subunit rrna gene sequences from 5 species in the phylum: haplosporidium nelsoni and haplosporidium costale, parasites of the eastern oyster crassostrea virginica; haplosporidium louisiana, a parasite of the mudcrab panopeus herbstii; minchinia teredinis, a parasite of shipworms (teredo spp.) and urosporidium crescens, a hyperparasite found in metacercariae of the trematode megalophallus sp. in the blu ...19968691370
haplosporidium nelsoni (msx) epizootic in the piscataqua river estuary (maine/new hampshire, usa.).a major epizootic of haplosporidium nelsoni occurred during 1995 in the piscataqua river estuary, near the northern distributional limit of the parasite. prevalence of h. nelsoni in samples of oysters, crassostrea virginica, collected between 5 september and 18 december 1995 from sites in maine and new hampshire ranged from 15 to 81%, with up to 50% systemic infections. associated proportions of dead oysters ranged from 25 to 83%. the epizootic was most likely triggered by unusually warm and dry ...19979057712
altered response of oyster hemocytes to haplosporidium nelsoni (msx) plasmodia treated with enzymes or metabolic inhibitors.to avoid phagocytosis, parasites may mask themselves with host-like molecules that prevent recognition as nonself or they may produce substances that interfere with host cellular defenses. the protozoan parasite haplosporidium nelsoni, which causes msx disease in the eastern oyster crassostrea virginica, is not ingested by host hemocytes. to assess potential avoidance mechanisms, oyster hemocytes were incubated with plasmodial stages of the parasite that had been pretreated with one of a variety ...19989709017
detection of cryptosporidium oocysts and giardia cysts in the tissues of eastern oysters (crassostrea virginica) carrying principal oyster infectious diseases.the potential cross-reactivity of the combined cryptosporidium/giardia direct immunofluorescence antibodies (ifa) of merifluor and hydrofluor-combo tests was examined against tissues containing known developmental stages of 12 pathogens causing the principal infectious diseases in oysters. spores of haplosporidium nelsoni and haplosporidium costale produced positive acid-fast stain (afs) reactions similar in intensity to cryptosporidium parvum oocysts. hexamia nelsoni trophozoites produced posit ...19989794651
a pcr-elisa method for direct detection of the oyster pathogen haplosporidium nelsoni.: a rapid method, utilizing both polymerase chain reaction (pcr) and enzyme-linked immunosorbent assay (elisa), was developed for detection of oyster msx disease. the technique included using haplosporidium nelsoni pathogen-specific pcr primers (based on ribosomal rna genes), a chelex resin (for rapid dna extraction from oyster mantle tissues), and cloned h. nelsoni rrna plasmid dna (for use as a capture probe). digoxigenin was incorporated into the pathogen-specific pcr products, which were cap ...199910373623
haplosporidiosis in the pacific oyster crassostrea gigas from the french atlantic coast.two cases of haplosporidian infection occurred during 1993 in pacific oysters crassostrea gigas from the french atlantic coast. the localization and ultrastructure of the plasmodia are described. in situ hybridization of infected tissue sections was conducted with dna probes for oyster-infecting haplosporidians. the haplosporidium nelsoni-specific dna probe msx1347 hybridized with the c. gigas parasite, and the h. costale-specific probe sso1318 did not hybridize. total genomic dna was extracted ...200011104072
detection of bonamia ostreae based on small subunit ribosomal probe.bonamia ostreae is a protozoan parasite of the flat oyster, ostrea edulis, which has caused significant loss of oysters in europe over the last decade. b. ostreae was purified from infected flat oysters and dna was extracted. the nearly complete small subunit rdna gene of b. ostreae was amplified using universal oligonucleotides and the pcr product was cloned and sequenced. blast research with this sequence revealed similarities to haplosporidium nelsoni, haplosporidium costale, and minchinia te ...200010963400
use of competitive pcr to detect and quantify haplosporidium nelsoni infection (msx disease) in the eastern oyster (crassostrea virginica).this study was undertaken to develop a quantitative polymerase chain reaction assay that would improve the utility of pcr for detecting haplosporidium nelsoni (msx), a serious parasite of the eastern oyster crassostrea virginica. a competitive pcr sequence was generated from the h. nelsoni small subunit ribosomal dna fragment, originally described by stokes and colleagues, that was amplified by the same pcr primers and had similar amplification performance. assays performed using competitor dilu ...200011246412
lipid class composition of the protozoan perkinsus marinus, an oyster parasite, and its metabolism of a fluorescent phosphatidylcholine analog.perkinsus marinus is one of two important protozoan parasites of the eastern oyster, crassostrea virginica. the other is haplosporidium nelsoni. lipids extracted from 7-d-old in vitro cultured p. marinus meronts, incubated with fluorescent-labeled phosphatidylcholine (fl pc) and nonincubated p. marinus meronts, were analyzed by a high-performance liquid chromatography (hplc) system equipped with a diol phase column, in combination with thin-layer chromatography coupled with a flame-ionization de ...200011202001
transmission of the haplosporidian parasite msx haplosporidium nelsoni to the eastern oyster crassostrea virginica in an upweller system.the haplosporidian oyster parasite msx (multinucleated sphere x) haplosporidium nelsoni was transmitted to eastern oysters crassostrea virginica. hatchery-raised, msx-free juvenile oysters were placed in upweller tanks. water to the tanks was filtered through a screen with 1 mm2 openings and originated from the water column overlaying naturally infected oysters beds (msx prevalence 17 to 57%). msx was diagnosed by histopathological analysis. msx-disease (57% prevalence) with increased mortality ...200011023255
development of a multiplex pcr for the detection of haplosporidium nelsoni, haplosporidium costale and perkinsus marinus in the eastern oyster (crassostrea virginica, gmelin, 1971).haplosporidium costale (sso), haplosporidium nelsoni (msx) and perkinsus marinus (dermo) have caused oyster mortality on the north american east coast since the 1950s. currently, the monitoring of oyster populations for these pathogens depends on histopathology for h. nelsoni, h. costale and the ray/mackin assay for p. marinus. in this study we describe the development and optimization of a multiplex polymerase chain reaction (mpcr) for the detection of h. nelsoni, h. costale and p. marinus. in ...200111851382
apoptosis in the pathogenesis of infectious diseases of the eastern oyster crassostrea virginica.apoptosis, or programmed cell death, has been reported as being pivotal in infectious diseases of different organisms. the effects of apoptosis on the progression and transmission of the protistan parasites perkinsus marinus and haplosporidium nelsoni in the eastern oyster crassostrea virginica were studied. oysters were diagnosed for their respective infections by standard methods, and apoptosis was detected using in situ hybridization to detect dna fragments by end labeling on paraffin section ...200314598992
systematic evaluation of factors controlling perkinsus marinus transmission dynamics in lower chesapeake bay.the transmission of perkinsus marinus in eastern oysters crassostrea virginica in relation to water temperature, host oyster mortality, and water-column abundance of anti-p. marinus antibody-labeled cells was systematically examined for 20 mo at a site in the lower york river, virginia, usa. uninfected sentinel oysters were naturally exposed to the parasite at 2 wk intervals throughout the course of the study to determine the periodicity and rates of parasite transmission. the timing and magnitu ...200314524504
detection of the oyster parasite bonamia ostreae by fluorescent in situ hybridization.bonamia ostreae is an economically significant protistan parasite of the flat oyster ostrea edulis in europe and north america. management of this parasite depends partly upon its reliable identification in wild and aquacultured oyster populations, but b. ostreae is small and difficult to detect by traditional microscopic methods. we designed a fluorescent in situ hybridization (fish) assay to sensitively detect b. ostreae in standard histopathological sections of b. ostreae-infected oysters usi ...200313677511
flow cytometry as a tool to quantify oyster defence mechanisms.the fast growing oyster aquaculture industry is greatly hindered by perkinsus marinus and haplosporidium nelsoni which can kill up to 80% of the production. the relationship between parasites and oyster defence mechanisms is unclear. two defence mechanisms of the eastern oyster (crassostrea virginica) were quantified at the single cell level utilising flow cytometry. phagocytosis was measured using fluorescent beads. respiratory burst activity was quantified as the h2o2-specific increase in dich ...200415123295
application of a multiplex pcr for the detection of protozoan pathogens of the eastern oyster crassostrea virginica in field samples.populations of eastern oysters crassostrea virginica along the east coast of north america have repeatedly experienced epizootic mass mortality due to infections by protozoan parasites, and molecular diagnostic methodologies are fast becoming more widely available for the diagnosis of protozoan diseases of oysters. in this study we applied a modified version of an existing multiplex polymerase chain reaction (pcr) for detection of the eastern oyster parasites haplosporidium nelsoni, h. costale a ...200415212297
spore ornamentation of haplosporidium nelsoni and haplosporidium costale (haplosporidia), and incongruence of molecular phylogeny and spore ornamentation in the haplosporidia.spore ornamentation of haplosporidium nelsoni and haplosporidium costale was determined by scanning electron microscopy. for h. nelsoni, the spore surface was covered with individual ribbons that were tightly bound together and occurred as a single sheet. in some spores, this layer was overlaid with a network of branching fibers, about 0.05 microm in diameter, which often was dislodged from the spore at the aboral pole. for h. costale, ornamentation consisted of a sparse network of branching fib ...200617304810
prevalence of perkinsus marinus (dermo), haplosporidium nelsoni (msx), and qpx in bivalves of delaware's inland bays and quantitative, high-throughput diagnosis of dermo by qpcr.restoration of oyster reef habitat in the inland bays of delaware was accompanied by an effort to detect and determine relative abundance of the bivalve pathogens perkinsus marinus, haplosporidium nelsoni, and qpx. both the oyster crassostrea virginica and the clam mercenaria mercenaria were sampled from the bays. in addition, oysters were deployed at eight sites around the bays as sentinels for the three parasites. perkinsus marinus prevalence was measured with a real-time, quantitative polymer ...200718070329
detection of minchinia sp., in rock oysters saccostrea cuccullata (born, 1778) using dna probes.haplosporidian parasites infect various invertebrate hosts including some commercially important shellfish. haplosporidium nelsoni (along with perkinsus marinus) has severely affected eastern oyster production on the eastern seaboard of the united states and flat oyster production in europe has been severely impacted by bonamia ostreae. these parasites are also often present at a very low prevalence and there are a variety of morphologically similar species that can be difficult to differentiate ...200817709114
spore ornamentation of minchinia occulta n. sp. (haplosporidia) in rock oysters saccostrea cuccullata (born, 1778).a minchinia sp. (haplosporidia: haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by hine and thorne (2002) using light microscopy and transmission electron microscopy (tem). the parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern western australia. however, attempts to identify the parasite f ...200818752707
inter-relationships of haplosporidians deduced from ultrastructural studies.we reviewed papers reporting haplosporidian ultrastructure to compare inter-relationships based on ultrastructure with those based on molecular data, to identify features that may be important in haplosporidian taxonomy, and to consider parasite taxonomy in relation to host taxonomy. there were links between the following: (1) the plasmodia of an abalone parasite, haplosporidium nelsoni and urosporidium crescens in the release of haplosporosomes; (2) h. costale and h. armoricanum in haplosporoso ...200919402456
using bivalves as particle collectors with pcr detection to investigate the environmental distribution of haplosporidium nelsoni.recently, pcr technology has been applied to search for marine microorganisms in environmental samples. such sampling, however, has drawbacks, including the need to collect and filter large volumes of water, and the presence of substances in environmental samples that may destroy dna or interfere with dna isolation and amplification. we explored the possibility of using suspension-feeding bivalves in conjunction with pcr to investigate the environmental distribution of microparasites using the o ...200919326797
a 1-year investigation of the parasite haplosporidium nelsoni (msx) in the pacific oyster crassostrea gigas from dayaowan bay, china.the infection prevalence of the protozoan parasite haplosporidium nelsoni (msx) in pacific oysters (crassostrea gigas), collected from dayaowan bay on the north coast of the yellow sea, china, was investigated in 2007. the traditional histological method of diagnosing h. nelsoni infection in oysters was compared to that of polymerase chain reaction (pcr). histology and the first pcr analysis detected infection in 21 (a total of 240 oysters) (8.75%) oysters, and the second pcr revealed infection ...201020369255
haplosporidium nelsoni and h. costale in the pacific oyster crassostrea gigas from china's coasts.we examined 220 pacific oysters crassostrea gigas obtained from 11 locations along china's coasts for the presence of the 2 protistan parasites haplosporidium nelsoni (msx; multinucleated sphere x) and h. costale (sso; seaside organism). haplosporidium-like plasmodia were histologically observed in 9 oysters (4.09%) from 7 locations. five oysters had mixed infections, and 4 oysters were infected only with h. nelsoni as determined by in situ hybridization (ish) and polymerase chain reaction (pcr) ...201020481089
widespread survey finds no evidence of haplosporidium nelsoni (msx) in gulf of mexico oysters.the advent of molecular detection assays has provided a set of very sensitive tools for the detection of pathogens in marine organisms, but it has also raised problems of how to interpret positive signals that are not accompanied by visual confirmation. pcr-positive results have recently been reported for haplosporidium nelsoni (msx), a pathogen of the oyster crassostrea virginica in 31 of 40 oysters from 6 sites in the gulf of mexico and the caribbean sea. histological confirmation of the pcr r ...201121516978
Haplosporidium nelsoni (MSX) in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China.The protozoan parasite Haplosporidium nelsoni (MSX) was identified in Japanese scallops Patinopecten yessoensis (Jay, 1857) from Dalian along the northern coast of the Yellow Sea, China by histopathologic examination, polymerase chain reaction (PCR) amplification, and in situ hybridization (ISH) assay. H. nelsoni plasmodia-like structures were identified in the digestive glands of scallops by histologic examination, but no parasite spores were observed. PCR using the Hap-F2, R2 primer pair produ ...201121984367
quantitative pcr assay to determine prevalence and intensity of msx (haplosporidium nelsoni) in north carolina and rhode island oysters crassostrea virginica.the continuing challenges to the management of both wild and cultured eastern oyster crassostrea virginica populations resulting from protozoan parasites has stimulated interest in the development of molecular assays for their detection and quantification. for haplosporidium nelsoni, the causative agent of multinucleated sphere unknown (msx) disease, diagnostic evaluations depend extensively on traditional but laborious histological approaches and more recently on rapid and sensitive (but not qu ...201223269385
a comparison of two methods for colorimetric in situ hybridization using paraffin-embedded tissue sections and digoxigenin-labeled hybridization probes.two methods for colorimetric in situ dna probe hybridization (cish) assays on paraffin-embedded tissue sections were compared. the heated method used heat (90-100°c) to denature dna in the sample prior to probe hybridization, while the unheated method used a standard hybridization temperature of 42°c. both procedures were tested on tissue samples that harbored the mollusk protozoan pathogens perkinsus marinus, p. chesapeaki, or haplosporidium nelsoni, the protozoan and bacterial fish pathogens m ...201323697605
the occurrence of haplosporidian parasites, haplosporidium nelsoni and haplosporidium sp., in oysters in ireland.the phylum haplosporidia is a group of obligate protozoan parasites that infect a number of freshwater and marine invertebrates. haplosporidian parasites have caused significant mortalities in commercially important shellfish species worldwide. in this study, haplosporidia were detected in pacific oysters crassostrea gigas originating in ireland and were subsequently identified independently in laboratories both in ireland and in spain as haplosporidium nelsoni. in ireland, h. nelsoni plasmodia ...201323238163
molecular and ultrastructural characterization of haplosporidium diporeiae n. sp., a parasite of diporeia sp. (amphipoda, gammaridea) in the laurentian great lakes (usa).the phylum haplosporidia contains coelozoic and histozoic, spore-forming, obligate protozoan endoparasites that infect a number of freshwater and marine invertebrates including bivalves, crustaceans, and polychaetes. in amphipods, haplosporidians cause systemic infection resulting in a range of pathologies. while amphipods belonging to the genus diporeia (gammarideae) have been shown to host haplosporidians, the taxonomic relationship of the diporeia haplosporidian(s) is largely unknown due to t ...201425060227
performance characteristics of polymerase chain reaction and histological methods for the detection of haplosporidium nelsoni in the eastern oyster (crassostrea virginica).fitness for purpose and validation are increasingly becoming a benchmark in the development of test methods for the diagnosis of infectious diseases in aquatic animals. the design of the evaluation and the analysis of data are critical to demonstrate test method performance characteristics and fitness for purpose, as stated in the world organization for animal health pathway for test validation. three test methods for the detection of the oyster parasite haplosporidium nelsoni were selected for ...201526179094
genetic improvement for disease resistance in oysters: a review.oyster species suffer from numerous disease outbreaks, often causing high mortality. because the environment cannot be controlled, genetic improvement for disease resistance to pathogens is an attractive option to reduce their impact on oyster production. we review the literature on selective breeding programs for disease resistance in oyster species, and the impact of triploidy on such resistance. significant response to selection to improve disease resistance was observed in all studies after ...201526037230
survey for protozoan parasites in eastern oysters (crassostrea virginica) from the gulf of maine using pcr-based assays.protozoan pathogens represent a serious threat to oyster aquaculture, since they can lead to significant production loses. moreover, oysters can concentrate human pathogens through filter feeding, thus putting at risk raw oyster consumers' health. using pcr-based assays in oysters (crassostrea virginica) from maine, we expand the northeast range in the usa for the protozoans perkinsus marinus, perkinsus chesapeaki, and haplosporidium nelsoni, and report for the first time the detection of the hu ...201525889457
new perspective on the haplosporidian parasites of molluscs.the protist phylum haplosporidia comprises over 40 described species with representatives infecting a range of mollusc hosts, including several ecologically and economically significant pathogens. continuing exploration of haplosporidian diversity has added ten new species in recent years and brought the phylogenetics of the group into somewhat clearer focus, with monophyletic bonamia and minchinia lineages continuing to be supported. however, the addition of new sequences to phylogenetic analys ...201526264670
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