The Magnetic Electron Ion Spectrometer: A Review of On-Orbit Sensor Performance, Data, Operations, and Science.

Measurements from NASA's Van Allen Probes have transformed our understanding of the dynamics of Earth's geomagnetically-trapped, charged particle radiation. The Van Allen Probes were equipped with the Magnetic Electron Ion Spectrometers (MagEIS) that measured energetic and relativistic electrons, along with energetic ions, in the radiation belts. Accurate and routine measurement of these particles was of fundamental importance towards achieving the scientific goals of the mission. We provide a comprehensive review of the MagEIS suite's on-orbit performance, operation, and data products, along with a summary of scientific results. The purpose of this review is to serve as a complement to the MagEIS instrument paper, which was largely completed before flight and thus focused on pre-flight design and performance characteristics. As is the case with all space-borne instrumentation, the anticipated sensor performance was found to be different once on orbit. Our intention is to provide sufficient detail on the MagEIS instruments so that future generations of researchers can understand the subtleties of the sensors, profit from these unique measurements, and continue to unlock the mysteries of the near-Earth space radiation environment. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11214-021-00855-2.

RBSP-ECT Combined Spin-Averaged Electron Flux Data Product.

We describe a new data product combining the spin-averaged electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration's Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of spectra for September 2013 to the present. Three-minute-averaged flux spectra are provided spanning energies from 15 eV up to 20 MeV. This new data product provides additional utility to the ECT data and offers a consistent cross calibrated data set for researchers interested in examining the dynamics of the inner magnetosphere across a wide range of energies.

What effect do substorms have on the content of the radiation belts?

Substorms are fundamental and dynamic processes in the magnetosphere, converting captured solar wind magnetic energy into plasma energy. These substorms have been suggested to be a key driver of energetic electron enhancements in the outer radiation belts. Substorms inject a keV "seed" population into the inner magnetosphere which is subsequently energized through wave-particle interactions up to relativistic energies; however, the extent to which substorms enhance the radiation belts, either directly or indirectly, has never before been quantified. In this study, we examine increases and decreases in the total radiation belt electron content (TRBEC) following substorms and geomagnetically quiet intervals. Our results show that the radiation belts are inherently lossy, shown by a negative median change in TRBEC at all intervals following substorms and quiet intervals. However, there are up to 3 times as many increases in TRBEC following substorm intervals. There is a lag of 1-3 days between the substorm or quiet intervals and their greatest effect on radiation belt content, shown in the difference between the occurrence of increases and losses in TRBEC following substorms and quiet intervals, the mean change in TRBEC following substorms or quiet intervals, and the cross correlation between SuperMAG AL (SML) and TRBEC. However, there is a statistically significant effect on the occurrence of increases and decreases in TRBEC up to a lag of 6 days. Increases in radiation belt content show a significant correlation with SML and SYM-H, but decreases in the radiation belt show no apparent link with magnetospheric activity levels.

A CD18 monoclonal antibody reduces multiple organ injury in a model of ruptured abdominal aortic aneurysm.

The role of CD18 antibody (anti-CD18) in remote and local injury in a model of ruptured abdominal aortic aneurysm repair was investigated. Rats were divided into sham, shock, clamp, and shock + clamp groups. Shock + clamp animals received anti-CD18 or a control monoclonal antibody. One hour of hemorrhagic shock was followed by 45 min of supramesenteric aortic clamping. Intestinal and pulmonary permeability to (125)I-labeled albumin was determined. Myeloperoxidase (MPO) activity, F(2)-isoprostane levels, and transaminases were also measured. Only shock + clamp resulted in statistically significant increases in pulmonary and intestinal permeability, which were associated with significant increases in MPO activity and F(2)-isoprostane levels. Treatment with anti-CD18 significantly decreased intestinal and pulmonary permeability in shock + clamp animals. These reductions were associated with significantly reduced intestinal and hepatic MPO activity and pulmonary F(2)-isoprostane levels and reduced alanine and aspartate aminotransferase levels; however, anti-CD18 had no effect on intestinal or hepatic F(2)-isoprostane levels or on pulmonary MPO activity. These results suggest CD18-dependent and -independent mechanisms of local and remote organ injury in this model of ruptured abdominal aortic aneurysm.

Effects of plain and controlled-ileal-release budesonide formulations in experimental ileitis.

BACKGROUND: Budesonide combines a topical anti-inflammatory activity with high first-pass hepatic extraction. This study compared the effects of plain and controlled-ileal-release (CIR) formulations of budesonide on intestinal inflammation. METHODS: Ileitis was induced in hamsters by an intraluminal injection of trinitrobenzene sulphonic acid. Inflammation was assessed histologically and by measuring mastocytosis and myloperoxidase activity. Adrenal-pituitary axis suppression was assessed by radio-immunoassay of plasma cortisol. Animals received budesonide (200 or 800 micrograms/kg/day), CIR budesonide (200 micrograms/kg/day), or placebo. RESULTS: Plain budesonide (200 micrograms/kg/day) did not reduce intestinal inflammation despite significantly lowered plasma cortisol levels. Plain budesonide (800 micrograms/kg/day), on the other hand, significantly reduced intestinal inflammation but further decreased plasma cortisol levels. CIR budesonide (200 micrograms/kg/day) was as effective in reducing inflammation as plain budesonide (800 micrograms/kg/day). CONCLUSIONS: CIR budesonide was significantly more effective in reducing intestinal inflammation than plain budesonide. These results suggest that the site of delivery influences the effectiveness of budesonide and that local (topical) rather than systemic action of this compound is primarily responsible for its anti-inflammatory effect.

Intestinal microcirculation and leukocyte behavior in ischemia-reperfusion injury.

Polymorphonuclear leukocytes are thought to play a pivotal role in the generation of ischemia-reperfusion-induced mucosal injury; however, their behavior in the intestinal microvasculature following this injury has not been directly examined. In this study intravital microscopy was used to investigate the dynamics of blood flow and leukocyte behavior in the villus, serosal, and mesenteric microcirculation during ischemia-reperfusion in anesthetized hamsters. Thirty minutes of ischemia and 90 min of reperfusion resulted in almost complete microvascular stasis in the villi of control animals, whereas only a few serosal and mesenteric microvessels exhibited stasis. Following reperfusion, there was a significant increase in leukocyte accumulation in all three tissues; however, significantly fewer leukocytes adhered in the villus microvasculature than in the rest of either the mucosa, serosa, or mesentery. Treatment with gamma-hydroxybutyrate (GHB), a compound that we have previously demonstrated to be highly effective in preventing ischemia-reperfusion injury, significantly reduced both the microvascular stasis and leukocyte accumulation in all three vascular beds. This study demonstrates that there are significant differences in the response to ischemia-reperfusion in various intestinal layers and that areas most susceptible to damage are not necessarily those exhibiting the greatest leukocyte accumulation.

The cardiovascular effects of gamma-hydroxybutyrate following hemorrhage.

We have previously shown that gamma-hydroxybutyrate (GHB) protects the small intestine against ischemia/reperfusion injury. This study examined the effects of GHB on cardiovascular function and intestinal microcirculation following hemorrhage. Hypotension was induced in control group of hamsters by controlled hemorrhage to a mean arterial pressure (MAP) of 40 mm Hg. Following 60 minutes of hypovolemia the shed blood was returned. This procedure resulted in complete intestinal mucosal microvascular stasis 2 hours following the return of shed blood. A second group of animals was treated with GHB (600 mg/kg body weight) and, despite the loss of 37% of total blood volume, GHB treatment completely prevented the microcirculatory stasis, following the reinfusion of shed blood. In male Wistar rats treated with GHB (200 mg/kg) after the induction of hemorrhage, blood pressure rapidly increased to pre-hemorrhage levels following treatment, even though the shed blood was not returned. Cardiac output (CO) also increased to pre-hemorrhage levels. Sodium chloride solution, in the same molar concentration as GHB (23% NaCl), produced much smaller, but statistically significant, increases in MAP and CO. In animals given an equal volume of normal saline, a gradual increase in MAP was observed, reaching statistical significance at 75 minutes following treatment. Three hours following hemorrhage, serum levels of creatine kinase were 3-fold higher, whereas aspartate aminotransaminase and alanine aminotransferase levels were 2-fold higher in both normal saline and hypertonic saline-treated animals than in GHB-treated animals. These experiments suggest that GHB can prevent ischemic complications following a hypovolemic episode and may improve survival following severe hemorrhage.

The protective effect of gamma-hydroxybutyrate in regional intestinal ischemia in the hamster.

The purpose of this study was to determine whether gamma-hydroxybutyrate provides protection against intestinal ischemia/reperfusion injury and to compare its effect with that of allopurinol and vitamin E. Thirty minutes of total regional ischemia, followed by 3 hours of reperfusion, produced intestinal damage that was completely prevented by gamma-hydroxybutyrate pretreatment. Naloxone partially blocked this protective effect. Allopurinol provided only partial protection against this injury, whereas vitamin E provided none. Treatment with gamma-hydroxybutyrate after ischemia but before reperfusion also provided significant protection. This study clearly demonstrates that gamma-hydroxybutyrate provides significant protection against intestinal ischemic injury and that it may do so via an opiate receptor-mediated mechanism.

Evidence for the involvement of 5-lipoxygenase products in ethanol-induced intestinal plasma protein loss.

In this study we investigated whether the products of 5-lipoxygenase (5-LO) were involved in the jejunal microvascular injury induced by intraluminal ethanol (ETH). A group of rabbits was given orally a selective inhibitor of 5-LO (L-651,392, Merck Frosst Canada) in two 10-mg doses, 24 and 2 h before the experiments (treated group). Another group received no such treatment (untreated group). In each animal of both groups, a jejunal segment was perfused with a control solution (control segment) and an adjacent segment with an ETH-containing (6% wt/vol) solution (ETH-perfused segment). In a series of experiments, we measured 5-LO activity of the jejunal segments of both groups using the generation of leukotriene B4 (LTB4) as an index. In a second series of experiments, we determined the ETH-induced intraluminal protein loss, which was taken as a measure of mucosal microvascular damage. In the untreated group, LTB4 generation (pg/mg tissue) by the ETH-treated segment (2.49 +/- 0.70) was higher (P less than 0.005) than that by the control segment (0.68 +/- 0.14). In the treated group, the LTB4 generation decreased (P less than 0.05) both in the control (0.15 +/- 0.03) and the ETH-perfused segments (0.44 +/- 0.09), but the difference between the two segments still remained significant. ETH caused a 13-fold increase (P less than 0.01) in jejunal protein loss in the untreated group but only a 5-fold increase (P less than 0.05) in the treated group. The ETH-induced increase in protein loss was significantly lower in the treated than in the untreated group (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Computer model of the absorption and distribution of colostral immunoglobulins in the newborn calf.

The transfer of immunoglobulin (Ig) isotypes (IgG1, IgG2, IgM), gamma-glutamyl transpeptidase (gamma-GT) and added D-xylose from colostrum to serum was investigated in newborn Holstein bull calves. Significant differences were observed in the time courses of the serum concentrations of these colostrum constituents following absorption from pooled colostrum. A computer model was devised to simulate the process of absorption of Ig isotypes, gamma-GT and D-xylose from colostrum in the newborn calf. A Fortran program was used to generate plots of the time course of the concentration of colostrum constituents in serum and other body fluids following a single feed of colostrum. These plots show how the changes in serum concentration of absorbed Ig isotypes, gamma-GT and D-xylose are affected by different rates of intestinal absorption, redistribution in body fluids and removal from plasma. A critical examination of data from the computer model and from the calf feeding experiments supports the view that the absorption of IgG1, IgG2 and IgM is not selective in the calf. The data were compared with earlier studies of the efficiency of the colostral transfer of Ig to the calf. In the present study the transfer efficiencies of IgG1, IgG2, IgM, gamma-GT and D-xylose were 46 per cent, 49 per cent, 47 per cent, 18 per cent and 21 per cent, respectively.

A Scottish case of nephropathy due to Hantaan virus infection.

An illness characterised by acute renal failure, fever, conjunctivitis and a macular erythematous centrifugal rash is described in a Scot who had not recently travelled abroad. There was serological evidence that the illness was due to Hantaan or a closely related virus.