An excess of cosmic ray electrons at energies of 300-800 GeV.

Galactic cosmic rays consist of protons, electrons and ions, most of which are believed to be accelerated to relativistic speeds in supernova remnants. All components of the cosmic rays show an intensity that decreases as a power law with increasing energy (for example as E(-2.7)). Electrons in particular lose energy rapidly through synchrotron and inverse Compton processes, resulting in a relatively short lifetime (about 10(5) years) and a rapidly falling intensity, which raises the possibility of seeing the contribution from individual nearby sources (less than one kiloparsec away). Here we report an excess of galactic cosmic-ray electrons at energies of approximately 300-800 GeV, which indicates a nearby source of energetic electrons. Such a source could be an unseen astrophysical object (such as a pulsar or micro-quasar) that accelerates electrons to those energies, or the electrons could arise from the annihilation of dark matter particles (such as a Kaluza-Klein particle with a mass of about 620 GeV).

A Review of the EUSO-Balloon Pathfinder for the JEM-EUSO Program.

EUSO-Balloon is a pathfinder for JEM-EUSO, the mission concept of a spaceborne observatory which is designed to observe Ultra-High Energy Cosmic Ray (UHECR)-induced Extensive Air Showers (EAS) by detecting their UltraViolet (UV) light tracks "from above." On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. After reaching a floating altitude of 38 km, EUSO-Balloon imaged the UV light in the wavelength range ∼290-500 nm for more than 5 hours using the key technologies of JEM-EUSO. The flight allowed a good understanding of the performance of the detector to be developed, giving insights into possible improvements to be applied to future missions. A detailed measurement of the photoelectron counts in different atmospheric and ground conditions was achieved. By means of the simulation of the instrument response and by assuming atmospheric models, the absolute intensity of diffuse light was estimated. The instrument detected hundreds of laser tracks with similar characteristics to EASs shot by a helicopter flying underneath. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. The reconstruction of the direction of the laser tracks was performed. In this work, a review of the main results obtained by EUSO-Balloon is presented as well as implications for future space-based observations of UHECRs.

Naturally acquired inhibitory antibodies to Plasmodium vivax Duffy binding protein are short-lived and allele-specific following a single malaria infection.

The Duffy binding protein of Plasmodium vivax (DBP) is a critical adhesion ligand that participates in merozoite invasion of human Duffy-positive erythrocytes. A small outbreak of P. vivax malaria, in a village located in a non-malarious area of Brazil, offered us an opportunity to investigate the DBP immune responses among individuals who had their first and brief exposure to malaria. Thirty-three individuals participated in the five cross-sectional surveys, 15 with confirmed P. vivax infection while residing in the outbreak area (cases) and 18 who had not experienced malaria (non-cases). In the present study, we found that only 20% (three of 15) of the individuals who experienced their first P. vivax infection developed an antibody response to DBP; a secondary boosting can be achieved with a recurrent P. vivax infection. DNA sequences from primary/recurrent P. vivax samples identified a single dbp allele among the samples from the outbreak area. To investigate inhibitory antibodies to the ligand domain of the DBP (cysteine-rich region II, DBP(II)), we performed in vitro assays with mammalian cells expressing DBP(II) sequences which were homologous or not to those from the outbreak isolate. In non-immune individuals, the results of a 12-month follow-up period provided evidence that naturally acquired inhibitory antibodies to DBP(II) are short-lived and biased towards a specific allele.

Limited immunological recognition of critical malaria vaccine candidate antigens.

Current vaccine development strategies for malaria depend on widespread immunological responsiveness to candidate antigens such as the zygote surface antigens and the sporozoite coat protein, the circumsporozoite (CS) protein. Since immunological responsiveness is controlled mainly by genes mapping within the major histocompatibility complex (MHC), the humoral immune response to the zygote surface antigens and the cytotoxic T lymphocyte (CTL) response to the CS protein were examined in MHC-disparate congenic mouse strains. Only two of six strains responded to the 230-kilodalton zygote surface antigen and another two strains responded to the 48/45-kilodalton surface antigen. From two mouse strains, expressing between them five different class I MHC molecules, there was recognition of only a single CTL epitope from the CS protein, which was from a polymorphic segment of the molecule. The restricted CTL response to this protein parallels the restricted antibody response to this protein observed in humans and mice. These findings suggest that subunit malaria vaccines now being developed may be ineffective.

Inhibitory properties of the antibody response to Plasmodium vivax Duffy binding protein in an area with unstable malaria transmission.

The function of the Plasmodium vivax Duffy binding protein (DBP) during the erythrocyte invasion process is critical for successful parasite growth and pathogenesis in human infections. Although DBP is the subject of intensive malaria vaccine research, investigations on the functional proprieties of anti-DBP antibodies in the human population have been limited [Infect Immun68 (2000) 3164]. In the present study, we examined the ability of sera from different populations of the Brazilian Amazon--an area of markedly unstable malaria transmission--to inhibit the erythrocyte-binding function of the DBP ligand domain (region II, DBP(II)). We found that long-term exposure to malaria in the Amazon area elicits DBP-specific antibodies that inhibit the binding of different DBP(II) variants to erythrocytes. Despite the great variability of inhibitory antibody responses observed among study participants, we observed a positive correlation between erythrocyte binding-inhibitory activity and enzyme-linked immunosorbent assay anti-DBP antibodies. Of importance, there was a non-significant tendency towards increased levels of anti-DBP antibodies among individuals with asymptomatic P. vivax infections.

Solar particle event storm shelter requirements for missions beyond low Earth orbit.

Protecting spacecraft crews from energetic space radiations that pose both chronic and acute health risks is a critical issue for future missions beyond low Earth orbit (LEO). Chronic health risks are possible from both galactic cosmic ray and solar energetic particle event (SPE) exposures. However, SPE exposures also can pose significant short term risks including, if dose levels are high enough, acute radiation syndrome effects that can be mission- or life-threatening. In order to address the reduction of short term risks to spaceflight crews from SPEs, we have developed recommendations to NASA for a design-standard SPE to be used as the basis for evaluating the adequacy of proposed radiation shelters for cislunar missions beyond LEO. Four SPE protection requirements for habitats are proposed: (1) a blood-forming-organ limit of 250 mGy-equivalent for the design SPE; (2) a design reference SPE environment equivalent to the sum of the proton spectra during the October 1989 event series; (3) any necessary assembly of the protection system must be completed within 30 min of event onset; and (4) space protection systems must be designed to ensure that astronaut radiation exposures follow the ALARA (As Low As Reasonably Achievable) principle.

Effects of nuclear cross sections at different energies on the radiation hazard from galactic cosmic rays.

The radiation hazard for astronauts from galactic cosmic rays (GCR) is a major obstacle to long-duration human space exploration. Space radiation transport codes have been developed to calculate the radiation environment on missions to the Moon, Mars, and beyond. We have studied how uncertainties in fragmentation cross sections at different energies affect the accuracy of predictions from such radiation transport calculations. We find that, in deep space, cross sections at energies between 0.3 and 0.85 GeV/nucleon have the largest effect in solar maximum GCR environments. At the International Space Station, cross sections at higher energies have the largest effect due to the geomagnetic cutoff.

The nature, distribution and causes of traumatic brain injury.

The identification and interpretation of brain damage resulting from a non-missile head injury is often not easy with the result that the most obvious structural damage identified postmortem may not be the most important in trying to establish clinicopathological correlations. For example patients with a fracture of the skull, quite severe cerebral contusions or a large intracranial haematoma that is successfully treated can make an uneventful and complete recovery if no other types of brain damage are present. However, not infrequently more subtle forms of pathology are present and ones that can only be identified microscopically. A systematic and pragmatic approach through the autopsy is therefore required and one that recognises the need for tissue to be retained in ways that are appropriate for cellular and molecular studies.

Duffy-null promoter heterozygosity reduces DARC expression and abrogates adhesion of the P. vivax ligand required for blood-stage infection.

The Duffy blood group antigen is an essential receptor for Plasmodium vivax entry into erythrocytes in a process mediated by the parasite ligand, the Duffy binding protein (DBP). Recently, individuals living in a malaria endemic region of Papua New Guinea were identified as heterozygous for a new allele conferring Duffy negativity, which results in 50% less Duffy antigen on their erythrocytes. We demonstrate that DBP adherence to erythrocytes is significantly reduced for erythrocytes from heterozygous individuals who carry one Duffy antigen negativity allele. These data provide evidence that emergence of this new allelic form of Duffy negativity is correlated with resistance against vivax malaria.

Neuropathology in vegetative and severely disabled patients after head injury.

OBJECTIVE: To discover if the neuropathology differs in head-injured patients who were in a vegetative state (VS) or were severely disabled at time of death. METHODS: Review of 35 VS cases and 30 severely disabled cases treated in this institute in the acute stage, surviving at least a month; all brains were fixed for 3 weeks before full neuropathologic examination. RESULTS: The severely disabled cases were older, had a higher incidence of skull fracture and of evacuated intracranial hematoma, and they had more cortical contusions. Diffuse axonal injury (DAI) was less common in the severely disabled cases, particularly its most severe grade. Structural damage in the thalamus was much less common in severely disabled cases. Half of the severely disabled patients had neither grade 2 or 3 DAI nor thalamic damage and 10 of these 15 cases did not have ischemic brain damage either. These combinations did not occur in a single VS case. However, some severely disabled cases had similar lesions to VS cases, and this included some patients who were in a minimally conscious state as well as some who were out of bed and mobile. CONCLUSIONS: Half the severely disabled cases had only focal brain damage, a feature not found in any VS cases. In the severely disabled patients with lesions similar to those of VS cases it is likely that a greater quantitative amount of damage occurred in the VS cases.

Aortic size and aortic calcification. A necropsy Study.

Measurements of aortic length and circumference in 336 post-mortem specimens confirm earlier, neglected observations on the progressive increase in aortic size which occurs with advancing years. The increase is not related to atherosclerosis , or to hypertension and seems to be part of a true ageing process. The value of measurement of aortic size in body age determination merits exploration by forensic pathologists. Aortic calcification is found in raised and complicated atherosclerotic plaques and its prevalence and severity closely follows the accepted pattern of plaque severity, occurring earlier and more severely in men, in the abdominal aorta and in patients with overt vascular disease in other territories such as patients with cardiac infarcts. No association was found between the amount of calcification and the presence of hypertension, diabetes or neoplasia.

Plasmodium yoelii YM MAEBL protein is coexpressed and colocalizes with rhoptry proteins.

We have previously cloned genes from multiple rodent malaria species exhibiting characteristics of the genes encoding Duffy binding like-erythrocyte binding proteins (DBL-EBP). Homology is seen in the intron/exon structure of the genes and in the carboxyl terminal region (including the deduced carboxyl cysteine-rich domain) of the proteins they encode. However, the amino termini of these proteins are not homologous to the DBL-EBP but contain tandem cysteine-rich regions that are similar to the cysteine-rich region of AMA-1 (apical membrane antigen-1), a rhoptry protein. This new family of proteins has been termed MAEBL and these are paralogues of both AMA-1 and the DBL-EBP. Serum against the carboxyl cysteine-rich region of the Plasmodium yoelii YM MAEBL reacted to parasites with a punctate fluorescence pattern characteristic of apical organelle proteins and also localized MAEBL to the surface of merozoites within schizonts. This antiserum immunoprecipitated a protein doublet (120/128 kDa) that was unexpectedly insoluble when compared to members of the DBL-EBP. Characterization of MAEBL was extended through colocalization studies comparing the P. yoelii YM MAEBL to other parasite proteins. This protein appeared to be located in the rhoptry organelles as it colocalized with both AMA-1 and the P. yoelii 235 kDa rhoptry proteins within parasites. In addition, MAEBL is expressed relatively early in schizont development and appears on the merozoite surface after segmentation. Both the pattern and time of expression of the P. yoelii YM MAEBL are consistent with a rhoptry rather than a microneme protein.

The erythrocyte binding motif of plasmodium vivax duffy binding protein is highly polymorphic and functionally conserved in isolates from Papua New Guinea.

The Duffy binding protein (DBP) of Plasmodium vivax is a critical adhesion ligand that participates in merozoite invasion of human Duffy positive reticulocytes. Binding domains have been shown to lie within a conserved N-terminal cyteine-rich region, region II, that contains 330-aa and the critical binding residues have been recently mapped to 170-aa stretch within this region. Previous studies on few isolates indicated a significant degree of polymorphism in region II (DBPII). To examine further the degree of variability of DBPII, and whether these variants produce functional changes, DBPII was amplified by nested PCR from 24 isolates from Papua New Guinea, and the amplicons were cloned and sequenced. One synonymous and 18 non-synonymous mutations were identified. Altogether, 93% of the cumulative polymorphisms lie within the 170-aa region. Targeted surface expression of region II of two different alleles on the surface of Cos7 cells did not affect their binding to Duffy positive erythrocytes. These results indicate that polymorphisms in the critical binding motifs do not alter its function. If DBPII variation arose to avert mechanisms of protective immunity targeting the DBP, vaccine development employing the parasite binding ligand may require strategies to minimize the effect of this polymorphism.

Spatial and temporal dynamics of the secretory pathway during differentiation of the Plasmodium yoelii schizont.

A specialized complex of apical organelles facilitates Plasmodium merozoite invasion into the erythrocyte. Even though the apical organelles are crucial to the invasion process, relatively little is known about how they function or their biosynthesis during asexual replication. MAEBL is an erythrocyte binding protein located in the rhoptries and on the surface of mature merozoites and is expressed at the beginning of schizogony before the first nuclear division. Therefore, we have characterized MAEBL as a marker for the biosynthetic pathway of the rhoptry apical organelle during the final phase of intraerythrocytic development and as a marker for the nascent rhoptry vesicle in the immature schizont. An extensive proliferation of the endoplasmic reticulum occurred at the onset of schizogony and was seen as a complex but transient tubule array near the parasite surface. Both the rhoptry protein MAEBL and surface protein MSP-1 appeared to be present in this tubular reticular network together with endoplasmic reticulum markers. MAEBL then transits through Golgi bodies positioned near the parasite plasma membrane, directly adjacent to the network. Rhoptry organelle precursors are seen at the three to four nuclei stage of schizont development, remaining near the plasma membrane throughout schizogony. These studies constitute the first direct evidence that proteins of the rhoptry organelles transit through compartments of the 'classical' secretory pathway.

Dimorphism and intergenic recombination within the microneme protein (MP-1) gene family of Plasmodium knowlesi.

The microneme protein-1 (MP-1) of Plasmodium knowlesi and Plasmodium vivax facilitates merozoite invasion of the erythrocyte by binding to Duffy blood group antigens. Since this protein is important in the invasion process and is a potential vaccine candidate, it is important to understand the nature of diversity within the MP-1 gene. Nine MP-1 gene sequences were compared from 2 isolates of P. knowlesi and a laboratory strain of P. vivax. The MP-1 genes of P. knowlesi were dimorphic based upon the central hydrophilic regions (III and IV) that were well conserved as alpha and beta types. Other regions were conserved among all P. knowlesi genes except for the amino cysteine-rich region (region II), a region predicted to be the initial contact site of the erythrocyte binding domain. Two distinct sequence motifs and part of a third were identified in region II that had a common identity of 68%. In some MP-1 genes recombination had occurred to create hybrids of the two sequence types. All cysteines and aromatic amino acids of region II were conserved in all genes or within a sequence type. There were 2 apparent recombination points within region II where switching occurred between sequence types. Another possible recombination site, identified as a common sequence motif, was identified in the middle of the hydrophilic region, at the beginning of regions III or IV. Nonsynonymous mutations within region II were biased towards radical amino acid changes, especially towards the carboxyl third, where there were 3 distinct types of sequence. Most synonymous and nonsynonymous nucleotide mutations within regions I, V, and VI were infrequent, individual events and not associated with any particular sequence type. Cysteine-rich regions of the P. vivax MP-1 gene compared to the P. knowlesi genes were characterized by an increased number of synonymous and nonsynonymous changes. This data identifies 2 mechanisms for generation of diversity in the MP-1 gene family, intergenic recombination and nucleotide mutations. Both may be mechanisms the parasite uses to evade the host immune response or to alter erythrocyte receptor specificity.

Erythrocyte binding protein homologues of rodent malaria parasites.

Erythrocyte invasion by malaria parasites requires specific molecular interactions between the merozoite and erythrocyte surface receptors. A well-conserved, functionally important family of erythrocyte binding proteins is the EBP family. The EBP family includes the Plasmodium vivax, P. knowlesi Duffy binding protein (DBP) family and the P. falciparum erythrocyte binding antigen-175 (EBA-175). The EBP are transmembrane proteins, characterized by two conserved cysteine-rich domains, expressed in the micronemes of invasive merozoites. Oligonucleotide primers matching the region encoding the carboxyl cysteine-rich domain of the EBA-175 were used in a polymerase chain reaction to identify homologous genes in P. berghei and P. yoelii yoelii, leading to the isolation of a P. berghei partial genomic clone. This clone contained a 323 bp region that had high deduced amino acid sequence similarity to the amino acid sequences of the carboxyl cysteine-rich domains of the DBP family and EBA-175. The P. berghei carboxyl cysteine-rich domain was followed by a putative transmembrane domain and a cytoplasmic domain, demonstrating an exon-intron structure at the 3' end homologous to P. vivax dbp and P. falciparum eba-175. The carboxyl cysteine-rich domain is also highly conserved among P. berghei, P. y. yoelii, P. chabaudi and P. vinckei and is encoded by a single copy gene. Antisera prepared against the carboxyl cysteine-rich domain of the rodent malaria EBP homologues reacted with a 120 and 128 kDa protein doublet on Western blots of P. berghei parasite antigen and showed an apical localization pattern within merozoites by indirect immunofluorescence assays.

Cloning of the Plasmodium vivax Duffy receptor.

Plasmodium vivax and Plasmodium knowlesi merozoites invade only Duffy blood group-positive human erythrocytes. Soluble P. vivax and P. knowlesi merozoite proteins of 135 kDa bind specifically to Duffy blood group determinants. The gene encoding a member of the Duffy receptor gene family of P. knowlesi has been cloned. We report here the molecular cloning of the presumptive Duffy receptor gene of P. vivax, using the P. knowlesi gene as a probe. There is a single gene in P. vivax which codes for a protein of 1115 amino acids. The deduced amino acid sequence predicts a putative signal sequence at the amino-terminus and a transmembrane region followed by 45 amino acids at the carboxy-terminus. The three introns found at the 3' end of the P. knowlesi gene were conserved in P. vivax, including high homology for the sequences of the introns. Comparison of the portion of the proteins amino to the transmembrane region between P. vivax and the partial sequence of P. knowlesi indicated at least three domains. Two homologous regions were separated by a non-homologous region. The cysteines in the homologous regions were conserved in number and position, indicating that the folding is similar and suggesting that these regions may be the Duffy blood group binding domains. In both P. vivax and P. knowlesi, the non-homologous region is hydrophilic and proline-rich, although the position of the prolines is not conserved. As prolines tend to stiffen a protein, this region may act as a 'hinge region' similar to those in the immunoglobulin gene family.

Erythrocyte-binding activity of Plasmodium yoelii apical membrane antigen-1 expressed on the surface of transfected COS-7 cells.

Malaria merozoite surface and apical organellar molecules facilitate invasion into the host erythrocyte. The underlying molecular mechanisms of invasion are poorly understood, and there are few data to delineate roles for individual merozoite proteins. Apical membrane antigen-1 (AMA-1) is a conserved apicomplexan protein present in the apical organelle complex and at times on the surface of Plasmodium and Toxoplasma zoites. AMA-1 domains 1/2 are conserved between Plasmodium and Toxoplasma and have similarity to the defined ligand domains of MAEBL, an erythrocyte-binding protein identified from Plasmodium yoelii. We expressed selected portions of the AMA-1 extracellular domain on the surface of COS-7 cells to assay for erythrocyte-binding activity. The P. yoelii AMA-1 domains 1/2 mediated adhesion to mouse and rat erythrocytes, but not to human erythrocytes. Adhesion to rodent erythrocytes was sensitive to trypsin and chymotrypsin, but not to neuraminidase. Other parts of the AMA-1 ectodomain, including the full-length extracellular domain, mediated significantly less erythrocyte adhesion activity than the contiguous domains 1/2. The results support the role of AMA-1 as an adhesion molecule during merozoite invasion of erythrocytes and identify highly conserved domains 1/2 as the principal ligand of the Plasmodium AMA-1 and possibly the Toxoplasma AMA-1. Identification of the AMA-1 ligand domains involved in interaction between the parasite and host cell should help target the development of new therapies to block growth of the blood-stage malaria parasites.

The effect of agents which modify platelet behaviour and of magnesium ions on thrombus formation in vivo.

The ability of potential anti-thrombotic agents to modify platelet-thrombus formation in injured cerebral arteries in the rabbit was tested. Low doses of heparin were without effect, while higher doses produced variable suppression of white body formation but at the expense of bleeding. Aspirin did not inhibit white body formation but another non-steroid anti-inflammatory agent, flurbiprofen was able to do so, as was the anti-gout agent, sulphinpyrazone. Magnesium salts both topically and parenterally, suppressed thrombus formation and increased the concentration of ADP which was required to initiate thrombus production at minor injury sites.

Low molecular weight immunosuppressors secreted by adult Nematospiroides dubius.

Adult Nematospiroides dubius excretory-secretory products (ES) were collected from worms cultured in vitro, separated by sodium dodecyl sulphate--polyacrylamide gel electrophoresis (SDS-PAGE) into four fractions (FI-IV), electroeluted and assessed for their ability to inhibit the proliferation of mouse lymphocytes stimulated by mitogens in vitro. The proliferation of mitogen- and ES-stimulated mouse spleen lymphocytes from normal and infected mice was inhibited by low mol. wt ES F-IV (less than 26,000).