Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu.

Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu's surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-meter-long elliptical crater. This exposed material is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500 to 700 kilograms per cubic meter, which is about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 grams of material, which will be delivered to Earth in 2023.

Initial Orbit Determination and Event Reconstruction From Estimation of Particle Trajectories About (101955) Bennu.

The OSIRIS-REx mission has observed multiple instances of particles being ejected from the surface of near-Earth asteroid (101955) Bennu. The ability to quickly identify the particle trajectories and origins is necessary following a particle ejection event. Using proven initial orbit determination techniques, we can rapidly estimate particle trajectories and ejection locations. We present current results pertaining to the identification of particle tracks, an evaluation of the estimated orbits and the excess velocity necessary to induce the particle ejection from the surface, and the uncertainty quantification of the ejection location. We estimate energies per particle ranging from 0.03 to 11.03 mJ for the largest analyzed events and velocities ranging from 5 to 90 cm/s, though we exclude the highest-velocity particles in this technique. We estimate ejection times for eight events and constrain six of the analyzed ejection events to have occurred between about 16:30 and 19:00 local solar time, with the largest events occurring between 16:30 and 18:05.

Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu.

The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu's equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O'Keefe-Radzievskii-Paddack cycle or arising during Bennu's accretion following the disruption of its parent body.

Shape of (101955) Bennu indicative of a rubble pile with internal stiffness.

The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu's shape. Here, we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu's top-like shape, considerable macroporosity, and prominent surface boulders suggest that it is a rubble pile. High-standing, north-south ridges that extend from pole to pole, many long grooves, and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin leading to its current shape. Today, Bennu might follow a different evolutionary pathway, with interior stiffness permitting surface cracking and mass wasting.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Influence of the bacterial flora on collagen-induced arthritis in susceptible and resistant strains of rats.

Collagen-induced arthritis is an experimental model for rheumatoid arthritis which can be elicited in susceptible strains of rats by intradermal injection of native type II collagen. In order to investigate whether bacterial flora may alter the pathogenic response to type II collagen, we have immunized germ-free (GF) male rats from either highly resistant Fisher (F344) or highly susceptible Dark Agouti (DA) strains. The disease was markedly enhanced in GF DA as compared to conventional (CV) DA rats. The humoral response was also stronger in GF rats of both strains. Neither GF nor CV F344 developed arthritis, although GF F344 exhibited later inflammation of the tail. These data support a suppressive influence of bacterial flora on collagen-induced arthritis.

[Actiopathogenic study of per and postoperative haemorrhage in adenotonsillectomy in the child (author's transl)]. / Etude étiopathogénique des hémorragies per et postopératoires dans les adéno-tonsillectomies de l'enfant.

This study involved 4 201 records between July 1st 1969 and February 28th 1979. Various parameters represented by specific patient data (age, sex, ENT infections), laboratory examinations, operative findings and weather conditions were studied. Adenoidectomy was found to be more haemorrhagic than adenotonsillectomy, in particular in the presence of a large clump of adenoids and in autumn or winter. Use of a halothane-nitrous oxide-oxygen mixture decreased the number of haemorrhages which by contrast were increased by an operative position in a dorsal horizontal position. Finally, any deviation from standard meterological conditions would appear to be a pejorative factor. The authors conclude by stating that no serious complications were seen and that it is important to undertake a precise and complete preoperative laboratory assessment. Finally, mutual confidence between surgeon and anaesthetist is an additional factor in decreasing risk.

Inhibition of a vesicular stomatitis virus mutant by rifampin.

Rifampin reversibly inhibits the intracellular replication of a VSV mutant, whereas a revertant variant selected from this viral population, as well as the wild strain, are not affected by this drug. Rifampin inhibits transcriptase activity of the sensitive mutant only and, consequently, total viral RNA synthesis decreases significantly in the cells.

Effect of the gastrointestinal microflora on induction and maintenance of oral tolerance to ovalbumin in C3H/HeJ mice.

The effect of the digestive microflora on oral tolerance to ovalbumin was studied by using axenic (germfree) and conventional C3H/HeJ mice. In contrast to reported results of studies with sheep erythrocytes, oral administration of ovalbumin induced tolerance in axenic mice, but the maintenance of tolerance was found to be of shorter duration than was with conventional mice. These data indicate that the contribution of the microflora to oral tolerance depends on the antigen used.

Oral tolerance to ovalbumin in mice: induction and long-term persistence unaffected by Staphylococcus aureus enterotoxin B and Clostridium perfringens type A enterotoxin.

Oral administration of dietary antigen (Ag) results in the systemic Ag-specific immunologic unresponsiveness termed oral tolerance. Its induction is of importance in the young where numerous symptoms are associated with IgE-mediated food-hypersensitivity reactions. Two related enterotoxins, cholera toxin and Escherichia coli heat-labile enterotoxin, have been shown to abrogate oral tolerance (i.e. IgG and IgE antibody (Ab) unresponsiveness) to an unrelated and simultaneously fed Ag. However, a critical role has been suggested for the gut flora in recovery of a hyporesponsive state. The purpose of the present study was to investigate whether the Staphylococcus aureus enterotoxin B (SEB) and Clostridium perfringens type A enterotoxin (CPE), involved in many diarrheas, could affect the induction and long-term persistence of oral tolerance to ovalbumin (OVA). Using conventional and germ-free mice fed once or twice with enterotoxin plus OVA, we investigated the possible role of the indigenous gut flora. In addition, we tested the influence of CPE synthesized in vivo in the digestive tract of gnotobiotic mice on the induction of OVA-specific oral tolerance. Mice were immunized intraperitoneally with OVA twice, and IgG and IgE Ab levels were measured by ELISA. Neither SEB nor CPE, orally given or synthesized in vivo (CPE), prevented the induction of oral tolerance to OVA. Moreover, the IgG Ab unresponsiveness persisted over 2 mo in the conventional mice fed with toxin plus OVA as also observed in the OVA controls. The results indicate that, independent of the gut flora's influence, SEB and CPE did not affect the induction nad long-term persistence of oral tolerance to co-ingested Ag.

Rifampin-susceptible mutant of vesicular stomatitis virus: protein and RNA synthesis.

A rifampin-susceptible strain (VSV Rif+) was selected from the wild vesicular stomatitis virus (VSV) population unsusceptible to rifampin. The VSV Rif+ was blocked in its intracellular replication in the presence of rifampin. In cells, rifampin affected primarily VSV Rif+ transcription, but to a different extent than in a cell-free system. In addition, a decrease in the amount of VSV Rif+ protein M was detected, linked to a stimulation of protein NS. In the absence of rifampin, protein M, although synthesized, was not immediately incorporated into the cell membrane. An interpretation of these observations is proposed.

Gut flora allows recovery of oral tolerance to ovalbumin in mice after transient breakdown mediated by cholera toxin or Escherichia coli heat-labile enterotoxin.

Oral tolerance, the antigen-specific immunologic unresponsiveness after antigen (Ag) feeding, is of physiologic importance in preventing antibody (Ab) responses to dietary proteins. This is important in the young, especially at weaning when numerous dietary Ag are encountered for the first time. Two related enterotoxins responsible for much diarrhea in the infant, cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT), have been shown to abrogate oral tolerance to an unrelated Ag fed simultaneously. The main objective of this study was to determine whether the gut flora can play a role in the CT- or LT-mediated abrogation of oral tolerance to the dietary protein ovalbumin (OVA), on a short-term and long-term basis. Conventional and germ-free mice were fed once or twice with toxin plus OVA. After two intraperitoneal immunizations with OVA, anti-OVA IgG and IgE Ab levels were measured. Because IgG and IgE Ab responses were detected, both CT and LT abrogated oral tolerance to OVA in conventional and germ-free mice. As time progressed (observations over 3 mo), whereas the specific IgG Ab response in the germ-free mice remained similar to that of the bicarbonate-fed controls, a hyporesponsive state was observed in conventional mice. The results showed that, although the gut flora did not prevent the CT- and LT-mediated abrogation of oral tolerance, it did shorten the effect and allow oral tolerance to be recovered.

The absence of gut flora, the doses of antigen ingested and aging affect the long-term peripheral tolerance induced by ovalbumin feeding in mice.

Several factors have been shown to affect the induction of peripheral tolerance induced by the oral route, also called oral tolerance. In the present study, we explored factors that shorten the duration of the IgG and IgE antibody unresponsiveness induced after ingestion of ovalbumin (OVA). Accordingly, we explored the effects of aging, the absence of gut flora, and ingestion of either one dose of 20 mg OVA or 5 doses of 1 mg OVA in young adult conventional (CV) mice and germ-free (GF) mice, and older CV mice. In young CV mice fed 20 mg OVA, IgG and IgE antibody unresponsiveness were still observed 2 to 3 months after feeding. In CV mice, neither aging nor 5 low doses of OVA prevented the induction of IgG and IgE antibody unresponsiveness but they reduced its duration. In young GF mice given 20 mg OVA, IgG antibody unresponsiveness only lasted between 7 and 21 days after feeding, but IgE antibody unresponsiveness lasted much longer. We believe these findings should be taken into account in the treatment of autoimmune and allergic diseases, for cases requiring conditions of antigen ingestion suitable for lasting suppression of peripheral antibody responses. The animal models used here might be of interest for better understanding of the mechanisms involved in the long-term persistence of oral tolerance.

[Kinetics of establishment of digestive microflora in the human newborn infant as a function of the kind of milk]. / Cinétique d'établissement de la microflore digestive chez le nouveau-né humain en fonction de la nature du lait.

The digestive tract of human infants, sterile at birth, is colonized by some bacterial genera within less than 48 h. Among the factors involved in the implantation of a given bacterial genus, the type of milk fed plays a major role. We studied the development of fecal flora in 1 to 8-day old babies, either breast-fed or bottle-fed with humanized milk. In breast-fed infants the microflora reached an equilibrium towards the age of 5 days and then hardly varied until the change of feeding. Escherichia coli and Streptococcus were established first and Bifidobacterium later. At the age of 5 days, the strictly anaerobic flora was exclusively composed of Bifidobacterium in 85% of cases. The development of other strictly anaerobic bacteria was repressed, particularly that of Bacteroides. In infants receiving humanized milk, Escherichia coli (or sometimes other enterobacteria) also appeared very early in the digestive tract. However, the strictly anaerobic flora was either absent (40% of cases) or composed of one or more genera (e.g. Bacteroides, Bifidobacterium, Plectridium). These findings in human infants show that it is mainly the establishment of the strictly anaerobic flora which is affected by the type of milk fed.

[Relationship between the development of the intestinal IgA immune system and the establishment of microbial flora in the digestive tract of young holoxenic mice]. / Relation entre le développement du système immunitaire intestinal à IgA et l'établissement de la flore microbienne dans le tube digestif du souriceau holoxénique.

The intestinal villi of axenic mice contain ten-fold less IgA plasmocytes than that of conventional ones. The major stimulus for proliferation of plasma cells synthetizing IgA in the gut of axenic mice is the total microbial flora from adult conventional mice. In young mice, the intestinal IgA immune system (intestinal IgA IS) is fully developed at the age of six weeks. The purpose of this work was to determine the role of intestinal flora on the development of the intestinal IgA IS. To that end, the complete digestive microflora from 1-25 day-old mice was transferred into adult axenic mice. The adult recipient mice harboured the same proportion of the same bacteria as the 1-4 day-old donor mice, Lactobacillus excepted. Thus, development of Lactobacillus is inhibited in recipient mice, whereas we did not observe any inhibition in young donor mice. For the 7-25 day-old donor mice, we still observed some resemblance between the flora of the donors and that of the recipients. However, the number of bacteria belonging to the genera Bacteroides and Eubacterium was larger in recipient than in donor mice. The microflora obtained from 1-23 day-old donor mice did not fully stimulate the development of the intestinal IgA IS of the recipient mice. In contrast, the microflora obtained from a 25 day-old mouse induced a full stimulation of the intestinal IgA IS in the recipient mice. Attempt to isolate the bacteria responsible for this complete stimulation were unsuccessful. We only know that these bacteria are present in a large proportion (10 8/g of faeces), that they are heat-sensible (70 degrees C, 10 min) and bacitracin-sensible. These results showed the important role of the sequential implantation of intestinal microflora in the development of intestinal IgA IS.

Hydrolysis of urea in the gastrointestinal tract of "monoxenic" rats: effect of immunization with strains of ureolytic bacteria.

Axenic rats, in whose feces urea is ordinarily excreted, were inoculated with ureolytic strains of Lactobacillus or Actinobacillus originally derived from the microflora of "holoxenic" rats. In these "monoxenic" animals, harboring one or another of the bacterial strains, fecal urea was hydrolyzed, with a more rapid onset of ureolysis in the case of Actinobacillus as compared with Lactobacillus. In vitro, a parallel difference between the two strains with regard to the onset of ureolysis was observed, hydrolysis beginning at the onset of growth in the case of Actinobacillus and only at the end of the exponential growth phase in the case of Lactobacillus. Extracellular urease activity was demonstrated in cultures of Lactobacillus, whereas none was found extracellularly with Actinobacillus. The pH optimum for the Lactobacillus urease in vitro was found to be 3.0, whereas the corresponding value for Actinobacillus was 6.0. In the two types of monoxenic rats, urea was consistently present in the small intestine and virtually absent from cecum and colon. Hydrolysis of urea in stomach was almost complete in rats bearing Lactobacillus but much less so in animals monoxenic with Actinobacillus, despite essentially equal numbers of organisms in that location. When rats carrying a monoflora of ureolytic Lactobacillus were immunized with either whole cells or soluble extract of the same organism, urea appeared in cecum and feces, indicating suppression of ureolytic activity. Immunization with an extract of nonureolytic Lactobacillus failed to produce such a result. Similar immunization techniques applied to animals monoassociated with ureolytic Actinobacillus did not alter ureolysis, and no appreciable quantity of urea appeared in feces. These studies demonstrate that it is indeed possible to inhibit the ureolytic activity of some bacteria in vivo by immunological means, but that the urease system of other organisms may not be as amenable to such manipulation.

[Induction of dolykaryocytes by vesicular stomatitis virus in XC rat cells]. / Induction de polycaryocytes par le virus de la stomatite vésiculaire dans les cellules de rat XC

V.S.V. induced polycaryocytes in rat embryonic fibroblasts, transformed by the Prague strain of Sarcoma Rous (XC cells). This fusion is strictly dependent on the expression of the viral genome and is probably due to the incorporation of viral antigens in the cell membrane. The integrity of cellular RNA synthesis is however not required. The fusion is probably due to a membrane structure characteristic of these transformed cells.