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.

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.

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.

Plasmodium vivax DBP binding to Aotus nancymaae erythrocytes is Duffy antigen dependent

Plasmodium vivax is the second leading cause of malaria worldwide. Invasion of human erythrocytes by P. vivax merozoites is dependent upon the interaction between the parasite Duffy binding protein (PvDBP) and the erythrocyte Duffy antigen receptor. Therefore, disruption of this vital interaction is an attractive target for therapeutic intervention. Although Aotus nancymaae is a commonly used primate model for human P. vivax infections, it has not been confirmed that the interaction between Ao. nancymaae erythrocytes and P. vivax is Duffy antigen dependent. Our results indicate that normal Ao. nancymaae erythrocytes readily bind to PvDBPII and that this binding is completely abolished with chymotrypsin treatment of the erythrocytes. Furthermore, the results of our inhibition assays show a dose-dependent decrease in binding with increasing amounts of anti-PvDBPII polyclonal rabbit sera or anti-Fy6 monoclonal antibody. These data indicate that the interaction between Ao. nancymaae erythrocytes and P. vivax DBPII is Duffy antigen dependent, validating this model system for in vivo studies of anti-PvDBP inhibition.

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.

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.

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.

Neuropathology of the vegetative state after head injury

A detailed neuropathological study of patients identified clinically after head injury as either severely disabled (SD, n = 30) or vegetative (VS, n = 35) has been carried out to determine the nature and frequency of the various pathologies that form the basis of these clinical states. Patients who were SD were older (SD median 49.5 yrs vs. VS median 38 yrs, p = .04), more likely to have a lucid interval (SD 31% vs. VS 9%, p = .03), and to have had an acute intracranial haematoma (SD 70% vs. VS 26%, p < .001). SD patients less often had severe, Grades (2 or 3) of traumatic diffuse axonal injury (SD 30% vs. VS 71%, p = .001) and less often had thalamic damage (SD 37% vs. VS 80%, p < .001). Similar features of both focal and diffuse damage were present in some SD and VS cases with both groups having considerable damage to white matter and to the thalamus. It is concluded that the principal structural basis of both SD and VS is diffuse traumatic axonal injury (DAI) with widespread damage to white matter and changes in the thalami. However, both ischaemic brain damage and the vascular complications of raised intracranial pressure contributed to the clinical signs and symptoms.

The structural basis of moderate disability after traumatic brain damage

The objective was to discover the nature of brain damage in survivors of head injury who are left with moderate disability. Macroscopic and microscopic examination was carried out on the brains of 20 persons who had died long after a head injury that had been treated in a neurosurgical unit. All had become independent but had various disabilities (moderate disability on the Glasgow outcome scale) Most deaths had been sudden, which had led to their referral from forensic pathologists. Post-traumatic epilepsy was a feature in 75%. An intracranial haematoma had been evacuated in 75%, and in 11 of the 15 with epilepsy. Diffuse axonal injury was found in six patients, five of the mildest type (grade 1) and one of grade 2. No patient had diffuse thalamic damage but one had a small focal ischaemic lesion in the thalamus. No patient had severe ischaemic brain damage, but three had moderate lesions which were bilateral in only one. No patient had severe cortical contusions. In conclusion, the dominant lesion was focal damage from an evacuated intracranial haematoma. Severe diffuse damage was not found, with diffuse axonal injury only mild and thalamic damage in only one patient.

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.

Exploring the transcriptome of the malaria sporozoite stage

Most studies of gene expression in Plasmodium have been concerned with asexual and/or sexual erythrocytic stages. Identification and cloning of genes expressed in the preerythrocytic stages lag far behind. We have constructed a high quality cDNA library of the Plasmodium sporozoite stage by using the rodent malaria parasite P. yoelii, an important model for malaria vaccine development. The technical obstacles associated with limited amounts of RNA material were overcome by PCR-amplifying the transcriptome before cloning. Contamination with mosquito RNA was negligible. Generation of 1,972 expressed sequence tags (EST) resulted in a total of 1,547 unique sequences, allowing insight into sporozoite gene expression. The circumsporozoite protein (CS) and the sporozoite surface protein 2 (SSP2) are well represented in the data set. A BLASTX search with all tags of the nonredundant protein database gave only 161 unique significant matches (P(N) < or = 10(-4)), whereas 1,386 of the unique sequences represented novel sporozoite-expressed genes. We identified ESTs for three proteins that may be involved in host cell invasion and documented their expression in sporozoites. These data should facilitate our understanding of the preerythrocytic Plasmodium life cycle stages and the development of preerythrocytic vaccines.

Omeprazole determination using HPLC with coulometric detection

A sensitive high performance liquid chromatography (HPLC) method for the determination of omeprazole and three related benzimidazoles is reported. Coulometric detection was carried out at +800 mV using a porous carbon electrode. The linear range is 0.01-10 microg/ml. The method has a high degree of precision; the relative standard deviation of omeprazole at a concentration of 1.06 microg/ml was 0.7% (n=4). The cyclic voltammogram of omeprazole is consistent with the hydrodynamic voltammogram exhibiting a single major irreversible oxidative wave with a peak potential at +1105 mV. The response factors for the four compounds are similar indicating that the oxidative process does not involve the sulfur moiety exclusively. The data are most consistent with oxidation primarily of the benzimidazole groups. The method was applied successfully to the determination of omeprazole in a paste formulation.

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.

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.

The neuropathology of the vegetative state after an acute brain insult

The vegetative state is often described clinically as loss of function of the cortex while the function of the brainstem is preserved. In an attempt to define the structural basis of the vegetative state we have undertaken a detailed neuropathological study of the brains of 49 patients who remained vegetative until death, 1 month to 8 years after an acute brain insult. Of these, 35 had sustained a blunt head injury and 14 some type of acute non-traumatic brain damage. In the traumatic cases the commonest structural abnormalities identified were grades 2 and 3 diffuse axonal injury (25 cases, 71%). The thalamus was abnormal in 28 cases (80%), and in 96% of the cases who survived for more than 3 months. Other abnormalities included ischaemic damage in the neocortex (13 cases, 37%) and intracranial haematoma (nine cases, 26%). In the non-traumatic cases there was diffuse ischaemic damage in the neocortex in nine cases (64%) and focal damage in four (29%); the thalamus was abnormal in every case. There were cases in both groups where the cerebral cortex, the cerebellum and the brainstem were of structurally normal appearance. In every case, however, there was profound damage to the subcortical white matter or to the major relay nuclei of the thalamus, or both. These lesions render any structurally intact cortex unable to function because connections between different cortical areas via the thalamic nuclei are no longer functional, and there is also extensive damage to afferent and efferent cerebral connections.

Naturally acquired and vaccine-elicited antibodies block erythrocyte cytoadherence of the Plasmodium vivax Duffy binding protein

Malaria merozoites require the presence of specific surface receptors on the red blood cell for invasion. Plasmodium vivax, requires the Duffy blood group antigen as an obligate receptor for invasion. The parasite Duffy binding protein (DBP) is the ligand involved in this process, making the DBP a potential vaccine candidate. A preliminary objective was to study whether people exposed to vivax malaria acquire antibodies that have the ability to block erythrocyte cytoadherence to the PvDBP. In comparison, we studied the immunogenicity of various recombinant DBP vaccines and investigated their potential to induct antifunctional antibodies. In order to do so, recombinant proteins to different regions of the putative ectodomain of the DBP and a DNA vaccine were used to immunize laboratory animals. An in vitro cytoadherence assay was used to investigate the presence of antifunctional antibodies in plasmas from people naturally exposed to vivax malaria, as well as in antisera obtained by animal vaccination. Our results showed that human plasma from populations naturally exposed to vivax malaria, as well as antisera obtained by vaccination using recombinant proteins, a DNA vaccine, and a synthetic peptide to DBP, inhibited in vitro binding of human erythrocytes to the DBP ligand domain (DBP(II)) in correlation to their previously measured antibody titer. Our results provide further evidence for the vaccine potential of this essential parasite adhesion molecule.

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.

The relationship among John Henryism, hostility, perceived stress, social support, and blood pressure in African-American college students

African Americans' rates of hypertension-related morbidity and mortality are several times that of white Americans. A number of behavioral and psychological variables may influence these differences. John Henryism, characterized by active coping to overcome obstacles, is one such variable. Prior research indicates that among highly educated individuals, high levels of John Henryism may be associated with decreased hypertension risk. The purpose of this study was to identify a cohort of well-educated African Americans to establish a baseline examination of the relationships between John Henryism, hostility, perceived stress, social support and resting systolic and diastolic blood pressures (SBP and DBP, respectively). Participants completed measures of study variables and resting blood pressures were taken. Results indicated that high family and friendship support were related to reports of lowered levels of stress (P<.001). Family support was associated with decreased risk for elevated DBP (P<.05). A positive association between hostility and DBP was found (P<.01). Perceived stress was negatively associated with SBP (P<.05), but did not have an independent effect on DBP. Similarly, no interactive effects of John Henryism and perceived stress were found on blood pressure. Examination of this cohort over time will reveal the impact of John Henryism and other variables on blood pressure elevations and hypertension.

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.

Cholesterol concentrations and cardiovascular reactivity to stress in African American college volunteers

Cholesterol levels and cardiovascular responses to emotionally arousing stimuli were examined in 60 healthy African American males and females. Cardiac output, stroke volume, contractile force, heart rate, and blood pressure were measured as the participants viewed two racially noxious scenes on videotape. Total serum cholesterol, high-density lipoproteins (HDL), low-density lipoproteins (LDL), and triglycerides were measured within 2 weeks of viewing the scenes. Multiple regression analysis showed that LDL and HDL were significant predictors of blood pressure responses. A correlation analysis revealed that total serum cholesterol and LDL were positively correlated with stroke volume, contractile force, and blood pressure reactivity. A possible relationship among stress, beta-adrenergic activity, and nonmetabolized free fatty acids is discussed. These findings suggest that cardiovascular reactivity to stress may be a new risk factor for heart and vascular diseases.

Serologic responses to recombinant Plasmodium vivax Duffy binding protein in a Colombian village

The Plasmodium vivax Duffy binding protein (DBP) is essential during merozoite invasion into human erythrocytes. Because of its biological importance, the DBP is also seen to have potential use as a malaria blood-stage vaccine. We have used a soluble recombinant DBP (rDBP) containing the functional ligand domain to assess the natural immunogenicity of DBP in a low-endemic vivax malaria region. Human sera from adult residents from a Colombian village with unstable vivax malaria transmission reacted specifically with the rDBP as determined by ELISA. There was a significant positive correlation between increased antibody response (average, median, and percent positives) and age of patients, although the level of responses did vary considerably in their reactivity to the rDBP from negative to very high level within each age group. These data confirm previous findings on the serologic reactivity of the DBP in exposed populations and that immunologic boosting to the DBP occurs in malaria-endemic regions even with low-level transmission.

Miranda mediates asymmetric protein and RNA localization in the developing nervous system

Neuroblasts undergo asymmetric stem cell divisions to generate a series of ganglion mother cells (GMCs). During these divisions, the cell fate determinant Prospero is asymmetrically partitioned to the GMC by Miranda protein, which tethers it to the basal cortex of the dividing neuroblast. Interestingly, prospero mRNA is similarly segregated by the dsRNA binding protein, Staufen. Here we show that Staufen interacts in vivo with a segment of the prospero 3' UTR. Staufen protein and prospero RNA colocalize to the apical side of the neuroblast at interphase, but move to the basal side during prophase. Both the apical and basal localization of Staufen are abolished by the removal of a conserved domain from the carboxyl terminus of the protein, which interacts in a yeast two-hybrid screen with Miranda protein. Furthermore, Miranda colocalizes with Staufen protein and prospero mRNA during neuroblast divisions, and neither Staufen nor prospero RNA are localized in miranda mutants. Thus Miranda, which localizes Prospero protein, also localizes prospero RNA through its interaction with Staufen protein.

A family of chimeric erythrocyte binding proteins of malaria parasites

Proteins sequestered within organelles of the apical complex of malaria merozoites are involved in erythrocyte invasion, but few of these proteins and their interaction with the host erythrocyte have been characterized. In this report we describe MAEBL, a family of erythrocyte binding proteins identified in the rodent malaria parasites Plasmodium yoelii yoelii and Plasmodium berghei. MAEBL has a chimeric character, uniting domains from two distinct apical organelle protein families within one protein. MAEBL has a molecular structure homologous to the Duffy binding-like family of erythrocyte binding proteins located in the micronemes of merozoites. However, the amino cysteine-rich domain of MAEBL has no similarity to the consensus Duffy binding-like amino cysteine-rich ligand domain, but instead is similar to the 44-kDa ectodomain fragment of the apical membrane antigen 1 (AMA-1) rhoptry protein family. MAEBL has a tandem duplication of this AMA-1-like domain, and both of these cysteine-rich domains bound erythrocytes when expressed in vitro. Differential transcription and splicing of the maebl locus occurred in the YM clone of P. yoelii yoelii. The apical distribution of MAEBL suggested localization within the rhoptry organelles of the apical complex. We propose that MAEBL is a member of a highly conserved family of erythrocyte binding proteins of Plasmodium involved in host cell invasion.

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.

Expression and serologic activity of a soluble recombinant Plasmodium vivax Duffy binding protein

Plasmodium vivax Duffy binding protein (DBP) is a conserved functionally important protein. P. vivax DBP is an asexual blood-stage malaria vaccine candidate because adhesion of P. vivax DBP to its erythrocyte receptor is essential for the parasite to continue development in human blood. We developed a soluble recombinant protein of P. vivax DBP (rDBP) and examined serologic activity to it in residents of a region of high endemicity. This soluble rDBP product contained the cysteine-rich ligand domain and most of the contiguous proline-rich hydrophilic region. rDBP was expressed as a glutathione S-transferase (GST) fusion protein and was isolated from GST by thrombin treatment of the purified fusion protein bound on glutathione agarose beads. P. vivax rDBP was immunogenic in rabbits and induced antibodies that reacted with P. vivax and Plasmodium knowlesi merozoites. Human sera from adult residents of a region of Papua New Guinea where malaria is highly endemic or P. vivax-infected North American residents reacted with rDBP in an immunoblot and an enzyme-linked immunosorbent assay. The reactivity to reduced, denatured P. vivax rDBP and the cross-reactivity with P. knowlesi indicated the presence of immunogenic conserved linear B-cell epitopes. A more extensive serologic survey of Papua New Guinea residents showed that antibody response to P. vivax DBP is common and increases with age, suggesting a possible boosting of the antibody response in some by repeated exposure to P. vivax. A positive humoral response to P. vivax DBP correlated with a significantly higher response to P. vivax MSP-1(19). The natural immunogenicity of this DBP should strengthen its usefulness as a vaccine.

Plasmodium vivax: favored gene frequencies of the merozoite surface protein-1 and the multiplicity of infection in a malaria endemic region

In this study, we present an analysis of the Plasmodium vivax MSP-1 polymorphic region 5 and identify a new recombinant gene element. In clinical isolates from Papua New Guinea (PNG), the P. vivax MSP-1 gene type was characterized by restriction fragment length polymorphisms and by Southern blot oligonucleotide hybridizations using probes to type-specific sequences. There were three pairs of dimorphic gene elements in the MSP-1 polymorphic region 5; four of the eight potential different combinations of sequence elements for this region have been identified. The center gene segment was the most polymorphic, especially for the glutamine (Q) repeat element with virtually every gene containing a different length of Q repeats, a finding consistent with database sequence information. The frequencies of all of the polymorphic MSP-1 gene elements were approximately equal except for the first segment, which was biased 10:1 for the Type II (Sal-1 type) versus Type I (Belem type) gene segment. In fact, only one combination (I/Q/S) of the genetic elements containing the type I gene segment for polymorphic region 5 was identified, a finding consistent with sequences reported to gene data banks. Considering only the multiplicity of MSP-1 gene types, 38% of the patients were identified as having multiple infections; when correlated with the circumsporozoite protein and the Duffy antigen binding protein gene types, the multiple infection rate increased to 65% of 23 isolates characterized. Increased age was the only clinical parameter that positively correlated with multiclonal infections and there was no other apparent bias or linkage of gene types among the three loci. These data identify multiple clonal populations of P. vivax in the PNG population and potentially a high rate of concurrent infections in clinical cases. The extreme polymorphism of the MSP-1 polymorphic region 5 suggests that frequent recombination occurs within this gene. The bias in frequency for one recombinant gene motif indicates that intrinsic host or parasite factors may engender increased frequency of one genetic element over another. Failure to identify this type of discrete clonal marker as well as reliance on a single marker can mask the true multiclonal nature of an infection and lead to underestimation of the multiplicity of infection.

Low energy ions in the heavy ions in space (HIIS) experiment on LDEF

We present data from the Lexan top stacks in the Heavy Ions In Space (HIIS) experiment which was flown for six years (April 1984-Jan 1990) onboard the LDEF spacecraft in 28.5 degrees orbit at about 476 km altitude. HIIS was built of passive (i.e. no timing resolution) plastic track detectors which collected particles continuously over the entire mission. In this paper we present data on low energy heavy ions (10 < or = Z, 20MeV/nuc < E < 200 MeV/nuc). These ions are far below the geomagnetic cutoff for fully ionized ions in the LDEF orbit even after taking into account the severe cutoff suppression caused by occasional large geomagnetic storms during the LDEF mission. Our preliminary results indicate an unusual elemental composition of trapped particles in the inner magnetosphere during the LDEF mission, including both trapped anomalous cosmic ray species (Ne, Ar) and other elements (such as Mg and Fe) which are not found in the anomalous component of cosmic rays. The origin of the non-anomalous species is not understood, but they may be associated with the solar energetic particle events and geomagnetic disturbances of 1989.

LET spectra of trapped anomalous cosmic rays in low-Earth orbit

Observations aboard Cosmos satellites discovered trapped anomalous cosmic rays (ACRs), tracked the variation in their intensity in 1986-1988, and measured their fluence, spectrum, and composition at solar minimum in the previous solar cycle. The MAST instrument aboard the SAMPEX satellite has observed trapped anomalous cosmic rays in the present solar cycle, confirmed the general features of the Cosmos data, and provided the first detailed observations of trapped ACRs. In this paper we apply theoretical modeling of trapped ACRs, which is shown to provide a reasonably good description of both the Cosmos and SAMPEX data, to calculate the integral linear-energy-transfer (LET) spectra due to trapped ACRs in typical low-Earth orbits. We compare these calculations with the LET spectra produced by galactic cosmic rays (GCRs) and non-trapped ACRs in order to assess the relative radiation hazard posed by trapped ACRs.

Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989

The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.

Charged-particle telescope experiment on Clementine

The charged-particle telescope (CPT) onboard the Clementine spacecraft measured the fluxes of energetic protons emitted in solar energetic particle events. Protons in the energy range from 10 to 80 MeV were of greatest interest for radiation effects such as total dose and single event upsets. Energetic electrons were also of interest for spacecraft charging and their contribution to total dose. The lower-energy CPT electron channels (25-500 keV) were mainly of geophysical interest. While orbiting the moon, the CPT observed the wake created by the moon when it blocked the flow of energetic particles in the magnetotail region. The CPT provided opportunities to observe energetic electron bursts during magnetic storms and magnetospheric substorms. CPT data are particularly useful in multispacecraft studies of interplanetary disturbances and their interaction with the magnetosphere. The proton channels on the CPT provided data on solar energetic protons and storm-time protons associated with the passage of an interplanetary shock at 0903 UT on Feb. 21, 1994. Results are compared with those from GOES-7, SAMPEX, and GEOTAIL.

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.

Axonal injury: a universal consequence of fatal closed head injury?

beta-Amyloid precursor protein immunostaining has recently been shown to be a reliable method for detecting the damage to axons associated with fatal head injury. In an attempt to compare the efficacy of this technique with conventional histological detection of axonal damage, we have reanalysed sections from a large well-characterised series of head-injured and control patients. The results indicate that the frequency of axonal injury has been vastly underestimated using conventional silver techniques, and that axonal injury may in fact be an almost universal consequence of fatal head injury.

Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein

The blood-stage development of malaria parasites is initiated by the invasion of merozoites into susceptible erythrocytes. Specific receptor-ligand interactions must occur for the merozoites to first attach to and then invade erythrocytes. Because the invasion process is essential for the parasite's survival and the merozoite adhesion molecules are exposed on the merozoite surface during invasion, these adhesion molecules are candidates for antibody-dependent malaria vaccines. The Duffy binding protein of Plasmodium vivax belongs to a family of erythrocyte-binding proteins that contain functionally conserved cysteine-rich regions. The amino cysteine-rich regions of these homologous erythrocyte-binding proteins were recently identified for P. vivax, Plasmodium knowlesi, and Plasmodium falciparum as the principal erythrocyte-binding domains (C. Chitnis and L. H. Miller, J. Exp. Med. 180:497-506, 1994, and B. K. L. Sim, C. E. Chitnis, K. Wasniowska, T. J. Hadley, and L. H. Miller, Science 264:1941-1944, 1994). We report that amino acids in this critical ligand domain of the P. vivax Duffy binding protein are hypervariable, but this variability is limited. Hypervariability of the erythrocyte-binding domain suggests that this domain is the target of an effective immune response, but conservation of amino acid substitutions indicates that functional constraints limit this variation. In addition, the amino cysteine-rich region and part of the hydrophilic region immediately following it were the site of repeated homologous recombinations as represented by tandem repeat sequence polymorphisms. Similar polymorphisms have been identified in the same region of the homologous genes of P. falciparum and P. knowlesi, suggesting that there is a common mechanism of recombination or gene conversion that occurs in these Plasmodium genes.

Hippocampal pathology in fatal human head injury without high intracranial pressure

Traumatically induced hippocampal damage is a frequent sequela of fatal human head injury and is traditionally considered to be the result of decreased cerebral perfusion secondary to raised intracranial pressure (ICP). However, in previous studies employing an experimental model of acceleration head injury, hippocampal lesions have been observed in the absence of high ICP. To further elucidate the role of raised ICP in the production of posttraumatic hippocampal neuronal damage, 14 cases of fatal human nonmissile head injury, in which the measured ICP was less than 20 mm Hg, were subjected to light microscopic evaluation for the frequency and anatomic distribution of hippocampal damage. The mean maximal ICP of the 14 patients was 17.6 mm Hg. Detailed light microscopic evaluation revealed hippocampal lesions in 12 of the 14 cases studied (86%). These lesions were typically bilateral foci of selective neuronal loss in the CA1 subfield of the hippocampus. The nature and distribution of hippocampal lesions were similar to those previously reported both in fatal human head injury associated with elevated ICP and in experimental acceleration head injury without raised ICP. These results provide further evidence that the occurrence of hippocampal neuronal loss following head injury is not exclusively dependent on elevated ICP. Other mechanisms, such as pathologic excitation of neurons, may be involved.

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.

Hippocampal damage in fatal paediatric head injury

The hippocampus is known to be frequently involved in head injury. In adults, such hippocampal lesions frequently include regions of selective neuronal necrosis. The present report examines the frequency and distribution of hippocampal damage in 37 cases of fatal head injury in children. Damage to the hippocampus was noted in 27 of 37 cases (73%). Lesions were often focal areas of selective neuronal necrosis located in the CA-1 subfield. Other subfields of the hippocampus were involved to lesser degrees. The frequency and distribution of hippocampal damage in fatal childhood head injury is similar to that reported for fatal head injuries of all ages. Pathological evidence of high intracranial pressure and/or hypoxic brain damage in other anatomical locations was present in the majority of cases. Clinical seizures prior to death occurred in 22% of the cases studied. However, these factors could not account for all cases of hippocampal damage in the present report. Thus, the hippocampus is frequently damaged in fatal head injury in children. The mechanisms involved in the production of such damage may involve hypoxia, raised intracranial pressure and altered cerebral perfusion. However, other, yet to be elucidated, mechanisms may be involved.

Traumatic damage to the nodal axolemma: an early, secondary injury

Electronmicroscopical investigations were made in a model of optic nerve damage in guinea-pigs on the development of acute axonal damage on an ultrastructural basis. It was expected to obtain thereby further information on mechanisms underlying axonal damage in traumatic brain injury. For that purpose an injury apparatus was employed to deliver defined elongation and/or tensile strains to the optic nerve. Transmission electronmicrographs were examined of longitudinal and transverse nerve sections throughout its entire length. The most severe abnormalities were identified in the prechiasmatic portion of the nerve. Among others, elongations of the nodes of Ranvier were encountered, swollen axons with accumulation of organelles, and even disrupted axons having a morphology similar to retraction balls. In all instances, abnormal axons were found together with axons having a normal structural appearance. Nodes of Ranvier demonstrated outward dilatations of the nodal axolemma and of the adjacent axoplasm, which are named as nodal blebs. Nodal blebs occurred already 15 min after injury, and were fully developed at 6 or 24 hrs. The blebs had disappeared again after 5-7 days. The axoplasm in the blebs demonstrated considerable disorganization of cytoskeletal elements with an array of amorphous material appearing as granular degeneration. Taken together, the present experimental model is a useful approach to analyse axonal damage at the ultrastructural level as it may occur in white matter of the central nervous system.