MeerKAT’s large number (64) of 13.5 m diameter antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of ...angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900−1670 MHz) observations of 115 galaxy clusters, observed for ∼6−10 h each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at ∼8″ resolution, and enhanced spectral and polarisation image cubes at ∼8″ and 15″ resolutions. Typical sensitivities for the full-resolution MGCLS image products range from ∼3−5 μJy beam−1. The basic cubes are full-field and span 2° × 2°. The enhanced products consist of the inner 1.2° × 1.2° field of view, corrected for the primary beam. The survey is fully sensitive to structures up to ∼10′ scales, and the wide bandwidth allows spectral and Faraday rotation mapping. Relatively narrow frequency channels (209 kHz) are also used to provide H I mapping in windows of 0 < z < 0.09 and 0.19 < z < 0.48. In this paper, we provide an overview of the survey and the DR1 products, including caveats for usage. We present some initial results from the survey, both for their intrinsic scientific value and to highlight the capabilities for further exploration with these data. These include a primary-beam-corrected compact source catalogue of ∼626 000 sources for the full survey and an optical and infrared cross-matched catalogue for compact sources in the primary-beam-corrected areas of Abell 209 and Abell S295. We examine dust unbiased star-formation rates as a function of cluster-centric radius in Abell 209, extending out to 3.5 R 200. We find no dependence of the star-formation rate on distance from the cluster centre, and we observe a small excess of the radio-to-100 μm flux ratio towards the centre of Abell 209 that may reflect a ram pressure enhancement in the denser environment. We detect diffuse cluster radio emission in 62 of the surveyed systems and present a catalogue of the 99 diffuse cluster emission structures, of which 56 are new. These include mini-halos, halos, relics, and other diffuse structures for which no suitable characterisation currently exists. We highlight some of the radio galaxies that challenge current paradigms, such as trident-shaped structures, jets that remain well collimated far beyond their bending radius, and filamentary features linked to radio galaxies that likely illuminate magnetic flux tubes in the intracluster medium. We also present early results from the H I analysis of four clusters, which show a wide variety of H I mass distributions that reflect both sensitivity and intrinsic cluster effects, and the serendipitous discovery of a group in the foreground of Abell 3365.
Summary
The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of antigenically diverse proteins is expressed on the surface of human erythrocytes infected with the malaria parasite ...P. falciparum, and mediates cytoadherence to the host vascular endothelium. In this report, we show that export of PfEMP1 is slow and inefficient as it takes several hours to traffic newly synthesized proteins to the erythrocyte membrane. Upon removal by trypsin treatment, the surface‐exposed population of PfEMP1 is not replenished during subsequent culture indicating that there is no cycling of PfEMP1 between the erythrocyte surface and an intracellular compartment. The role of Maurer's clefts as an intermediate sorting compartment in trafficking of PfEMP1 was investigated using immunoelectron microscopy and proteolytic digestion of streptolysin O‐permeabilized parasitized erythrocytes. We show that PfEMP1 is inserted into the Maurer's cleft membrane with the C‐terminal domain exposed to the erythrocyte cytoplasm, whereas the N‐terminal domain is buried inside the cleft. Transfer of PfEMP1 to the erythrocyte surface appears to involve electron‐lucent extensions of the Maurer's clefts. Thus, we have delineated some important aspects of the unusual trafficking mechanism for delivery of this critical parasite virulence factor to the erythrocyte surface.
A single troop of free-ranging chacma baboons (Papio ursinus) was found to be infected with tuberculosis caused by Mycobacterium bovis. It is assumed that some members of the troop originally became ...infected when feeding on a tuberculous carcass in the veld or on tuberculous material scavenged at a nearby post mortem facility. Subsequently, apparent aerosol transmission took place while sleeping in an unused room. Oral transmission probably also occurred due to continuous contamination of the floor of this room and the common, narrow access (a train bridge crossing the Sabi River) to it with faeces and urine. A macroscopic prevalence of 50 % was found and the disease was noted to progress rapidly in infected baboons. A variety of organs had typical tuberculous lesions, of which the spleen, lungs and mesenteric lymph nodes were consistently, grossly affected. Using Restriction Fragment Length Polymorphism analysis, all but one of the baboon isolates were found to be identical to the most common African buffalo (Syncerus caffer) isolate (genotype 1) in this Park. The opportunistic sleeping facility was made inaccessible to the troop, which was forced to revert to sleeping in trees. A follow-up survey six months after closure, demonstrated that the disease had disappeared from the troop, and that no spillover infection had occurred into neighbouring troops.
Many pathogens evade the host immune response or adapt to their environment by expressing surface proteins that undergo rapid switching. In the case of Plasmodium falciparum, products of a multigene ...family known as var are expressed on the surface of infected red cells, where they undergo clonal antigenic variation and contribute to malaria pathogenesis by mediating adhesion to a variety of host endothelial receptors and to uninfected red blood cells by forming rosettes. Herein we show that a second gene family, rif, which is associated with var at subtelomeric sites in the genome, encodes clonally variant proteins (rifins) that are expressed on the infected red cell surface. Their high copy number, sequence variability, and red cell surface location indicate an important role for rifins in malaria host-parasite interaction.
Healthy and sick crocodiles of varying sizes were examined from the Olifants River in the central part of the Kruger National Park, the Sabi River in the southern part and the Shingwedzi River in the ...northern region. Blood was collected for the determination of certain parameters and samples of fat, muscle, kidney and liver tissue were collected and analyzed for their heavy metal content. The results of the blood analyses are within the range recorded in the literature, but the metal analyses were inconclusive as similar data are not available for comparison. The results of the metal analyses are presented here for use as baseline and reference data.
Five kudus (Tragelaphus strepsiceros), three bulls and two cows, within the Greater Kruger National Park complex, were diagnosed with generalized tuberculosis caused by Mycobacterium bovis. The ...lesions seen in these animals were similar to those previously reported in kudus and included severe tuberculous lymphadenitis of the nodes of the head and neck (that resulted in noticeable uni- or bilateral swelling beneath the ear), thorax, and the mesentery. All the animals also suffered from severe granulomatous pneumonia. The lesions in the lungs were more severe cranially and had a miliary distribution elsewhere in the lungs. Based on the DNA patterns of the M. bovis isolates, at least some of these kudus were infected with strains commonly present in tuberculous buffaloes, lions, cheetahs, and baboons in the Park whereas other strains from these kudus were quite different and may reflect another source of infection. The presence of tuberculous kudus in the Park is expected to complicate control measures that may be instituted to contain or eradicate the disease in the Park.
Bovine tuberculosis (BTB) was first detected in Kruger National Park (KNP) in a single African buffalo (Syncerus caffer) in 1990. In 1991/1992, 2,071 African buffalo were examined for BTB as part of ...a culling program that removed animals from all known herds in KNP. The prevalence of BTB in 1991/1992 was estimated to be 0%, 4.4% (±0.6%), and 27.1% (±1.4%), in the north, central, and south zones of KNP, respectively. In 1998, a stratified, two-stage cluster sampling method was used to estimate that the prevalence of BTB was 1.5% (±2.5%), 16% (±5.3%), and 38.2% (±6.3%), in the north, central, and south zones, respectively. This represented a significant increase in prevalence (P ≤ 0.05) in the south and central zones, but not in the north zone. Continued monitoring of BTB in KNP is important for understanding disease transmission risks, potential population effects, and the efficacy of disease management strategies. The methodology and sample sizes used in 1998 are appropriate for future BTB monitoring in KNP.
Bovine tuberculosis was diagnosed for the first time in an African buffalo (Syncerus caffer) in the Kruger National Park (KNP). The index case was a 2-year-old, emaciated bull which had been found ...recumbent and obviously ill, near the south-western boundary of the KNP, in July 1990. During a follow-up random sampling of 57 buffalo, from two herds in close proximity to this initial case, nine more suspect cases were found. Mycobacterium bovis was isolated from a lung and thoracic lymph node, respectively, of two of these cases. Histopathologically, all nine of these animals had granulomatous lesions compatible with a diagnosis of mycobacteriosis, but acid-fast organisms could be demonstrated in only one animal.
Binding of infected erythrocytes to brain venules is a central pathogenic event in the lethal malaria disease complication, cerebral malaria. The only parasite adhesion trait linked to cerebral ...sequestration is binding to intercellular adhesion molecule-1 (ICAM-1). In this report, we show that Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) binds ICAM-1. We have cloned and expressed PfEMP1 recombinant proteins from the A4tres parasite. Using heterologous expression in mammalian cells, the minimal ICAM-1 binding domain was a complex domain consisting of the second Duffy binding-like (DBL) domain and the C2 domain. Constructs that contained either domain alone did not bind ICAM-1. Based on phylogenetic criteria, there are five distinct PfEMP1 DBL types designated α,β,γ,δ , and ε . The DBL domain from the A4tres that binds ICAM-1 is DBLβ type. A PfEMP1 cloned from a distinct ICAM-1 binding variant, the A4 parasite, contains a DBLβ domain and a C2 domain in tandem arrangement similar to the A4tres PfEMP1. Anti-PfEMP1 antisera implicate the DBLβ domain from A4var PfEMP1 in ICAM-1 adhesion. The identification of a P. falciparum ICAM-1 binding domain may clarify mechanisms responsible for the pathogenesis of cerebral malaria and lead to interventions or vaccines that reduce malarial disease.
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