A large oxygen-dominated core from the seismic cartography of a pulsating white dwarf.

White-dwarf stars are the end product of stellar evolution for most stars in the Universe. Their interiors bear the imprint of fundamental mechanisms that occur during stellar evolution. Moreover, they are important chronometers for dating galactic stellar populations, and their mergers with other white dwarfs now appear to be responsible for producing the type Ia supernovae that are used as standard cosmological candles. However, the internal structure of white-dwarf stars-in particular their oxygen content and the stratification of their cores-is still poorly known, because of remaining uncertainties in the physics involved in stellar modelling codes. Here we report a measurement of the radial chemical stratification (of oxygen, carbon and helium) in the hydrogen-deficient white-dwarf star KIC08626021 (J192904.6+444708), independently of stellar-evolution calculations. We use archival data coupled with asteroseismic sounding techniques to determine the internal constitution of this star. We find that the oxygen content and extent of its core exceed the predictions of existing models of stellar evolution. The central homogeneous core has a mass of 0.45 solar masses, and is composed of about 86 per cent oxygen by mass. These values are respectively 40 per cent and 15 per cent greater than those expected from typical white-dwarf models. These findings challenge present theories of stellar evolution and their constitutive physics, and open up an avenue for calibrating white-dwarf cosmochronology.

A compact system of small planets around a former red-giant star.

Planets that orbit their parent star at less than about one astronomical unit (1 AU is the Earth-Sun distance) are expected to be engulfed when the star becomes a red giant. Previous observations have revealed the existence of post-red-giant host stars with giant planets orbiting as close as 0.116 AU or with brown dwarf companions in tight orbits, showing that these bodies can survive engulfment. What has remained unclear is whether planets can be dragged deeper into the red-giant envelope without being disrupted and whether the evolution of the parent star itself could be affected. Here we report the presence of two nearly Earth-sized bodies orbiting the post-red-giant, hot B subdwarf star KIC 05807616 at distances of 0.0060 and 0.0076 AU, with orbital periods of 5.7625 and 8.2293 hours, respectively. These bodies probably survived deep immersion in the former red-giant envelope. They may be the dense cores of evaporated giant planets that were transported closer to the star during the engulfment and triggered the mass loss necessary for the formation of the hot B subdwarf, which might also explain how some stars of this type did not form in binary systems.

Angiofibroma of the nasal cavity in 13 dogs.

This case series describes a rare entity, nasal angiofibroma, in 13 dogs that were presented to the University of Wisconsin, School of Veterinary Medicine from 1988 to 2000. All dogs in this case series presented with clinical signs and radiographic changes that were strongly suggestive of a locally invasive neoplasm. However, histopathology completed on transnostral core biopsy samples revealed benign appearing vascular proliferation with secondary lymphosuppurative inflammation was established despite cytologic criteria of malignancy present in five dogs. On the basis of the outcomes in this case series, nasal angiofibroma should be considered a differential for dogs presenting with clinical signs consistent with a malignant nasal tumour.

Cartilage collagen matrix reorientation and displacement in response to surface loading.

An investigation of collagen fiber reorientation, as well as fluid and matrix movement of equine articular cartilage and subchondral bone under compressive mechanical loads, was undertaken using small angle X-ray scattering measurements and optical microscopy. Small angle X-ray scattering measurements were made on healthy and diseased samples of equine articular cartilage and subchondral bone mounted in a mechanical testing apparatus on station ID18F of ESRF, Grenoble, together with fiber orientation analysis using polarized light and displacement measurements of the cartilage matrix and fluid using tracers. At surface pressures of up to approximately 1.5 MPa, there was reversible compression of the tangential surface fibers and immediately subjacent zone. As load increased, deformation in these zones reached a maximum and then reorientation propagated to the radial deep zone. Between surface pressures of 4.8 MPa and 6.0 MPa, fiber orientation above the tide mark rotated 10 deg from the radial direction, with an overall loss of alignment. With further increase in load, the fibers "crimped" as shown by the appearance of subsidiary peaks approximately +/-10 deg either side of the principal fiber orientation direction. Failure at higher loads was characterized by a radial split in the deep cartilage, which propagated along the tide mark while the surface zone remained intact. In lesions, the fiber organization was disrupted and the initial response to load was consistent with early rupture of fibers, but the matrix relaxed to an organization very similar to that of the unloaded tissue. Tracer measurements revealed anisotropic solid and fluid displacement, which depended strongly on depth within the tissue.

Spectrin maintains the lateral order in phosphatidylserine monolayers.

We investigate the effect of the skeletal protein spectrin on the lateral order in dipalmitoyl phosphatidylserine monolayers spread on aqueous surfaces using grazing incidence X-ray diffraction. Without spectrin, the condensed lipid monolayer exhibits two-dimensional hexagonal packing, characterized by monotonic decrease in the d-spacing and increase in the degree of order with increasing surface pressure between 17 and 36 mN/m. Addition of spectrin to the aqueous subphase at high pressures preserves the monolayers structural parameters unchanged from 36 to 25 mN/m. These results demonstrate for the first time that spectrin could participate in sustaining the two-dimensional order in lipid domains through a direct interaction with phosphatidylserine species.

Two-dimensional order in mammalian pre-ocular tear film.

We report a grazing incidence x-ray diffraction (GIXD) investigation of the surface lipid layer of the pre-ocular tear film. For the first time we demonstrate the existence of 2D order over a wide range of surface pressures in this system, with typical spicing of 3.75A and 4.16A independent of the monolayer surface pressure. Analogous lipid ordering is also found in an artificial lipid mixture of the major lipid components of the tear film, suggesting that the 2D ordering is set by generic lipid-lipid interactions. Fluorescence microscopy of the natural and artificial tear film mixture reveals the co-existence of a dilute and a much more condensed phase in the amphiphilic lipid matrix over the pressure range of 15-45mN/m investigated by GIXD, plus an additional structure due to the much more hydrophobic part of the mixture. This evidence supports the previous hypothesis that tear film has a layered structure.

Regional variations of collagen orientation in normal and diseased articular cartilage and subchondral bone determined using small angle X-ray scattering (SAXS).

OBJECTIVE: To determine regional differences in the orientation of collagen in the articular cartilage of the equine metacarpophalangeal joint as well as describing cartilage orientation in lesions using small angle X-ray scattering (SAXS). DESIGN: SAXS diffraction patterns were taken at the European Synchrotron Radiation Facility (ESRF), with increasing depth into cartilage and bone cross sections. Results for healthy samples were taken at different regions along the joint which receive different loads and differences in collagen orientation were determined. Results were also taken from diseased samples and the collagen orientation changes from that of healthy samples observed. RESULTS: Regions subject to low loads show a lower degree of orientation and regions exposed to the highest loads possess oriented collagen fibres especially in the radial layer. In early lesions the orientations of the collagen fibres are disrupted. Subchondral bone fibres are twisted in regions where the joint receives shear forces. Changes in fibre orientation are also observed in the calcified cartilage even in regions where the cartilage is intact. In more advanced lesions where there is loss of cartilage the fibres in the calcified layer are realigned tangential to the surface. CONCLUSIONS: Regional variations in collagen arrangement show that the highly ordered layers of the articular cartilage are the most important elements in supporting high variable loads. In lesions changes occur in the deep tissue whilst the overlying cartilage appeared normal. We therefore suggest that the interface region is a key element in the early stages of the disease.

An asymptotic-giant-branch star in the progenitor system of a type Ia supernova.

Stars that explode as supernovae come in two main classes. A type Ia supernova is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectrum; this class of supernova is thought to produce the majority of iron-peak elements in the Universe. They are also used as precise 'standard candles' to measure the distances to galaxies. While there is general agreement that a type Ia supernova is produced by an exploding white dwarf star, no progenitor system has ever been directly observed. Significant effort has gone into searching for circumstellar material to help discriminate between the possible kinds of progenitor systems, but no such material has hitherto been found associated with a type Ia supernova. Here we report the presence of strong hydrogen emission associated with the type Ia supernova SN2002ic, indicating the presence of large amounts of circumstellar material. We infer from this that the progenitor system contained a massive asymptotic-giant-branch star that lost several solar masses of hydrogen-rich gas before the supernova explosion.

Regulation of expression of murine transferrin receptor 2.

Complementary and genomic DNA for the murine transferrin receptor 2 (TfR2) were cloned and mapped to chromosome 5. Northern blot analysis showed that high levels of expression of murine TfR2 occurred in the liver, whereas expression of TfR1 in the liver was relatively low. During liver development, TfR2 was up-regulated and TfR1 was down-regulated. During erythrocytic differentiation of murine erythroleukemia (MEL) cells induced by dimethylsulfoxide, expression of TfR1 increased, whereas TfR2 decreased. In MEL cells, expression of TfR1 was induced by desferrioxamine, an iron chelator, and it was reduced by ferric nitrate. In contrast, levels of TfR2 were not affected by the cellular iron status. Reporter assay showed that GATA-1, an erythroid-specific transcription factor essential for erythrocytic differentiation at relatively early stages, enhanced TfR2 promoter activity. Interestingly, FOG-1, a cofactor of GATA-1 required for erythrocyte maturation, repressed the enhancement of the activity by GATA-1. Also, CCAAT-enhancer binding protein, which is abundant in liver, enhanced the promoter activity. Thus, tissue distribution of TfR2 was consistent with the reporter assays. Expression profiles of TfR2 were different from those of TfR1, suggesting unique functions for TfR2, which may be involved in iron metabolism, hepatocyte function, and erythrocytic differentiation.

Correlations between measles, mumps, and rubella serum antibody levels in Olmsted County school children.

We examined correlations between serum antibody levels to determine whether individuals with low levels of antibody to one component of the measles, mumps, and rubella (MMR) vaccine were also likely to have low antibody levels to the other MMR vaccine components. Our results indicate that children who had a low antibody level to one component of the MMR vaccine had a modest probability of having a low antibody level to either of the other MMR vaccine components. Overall, we found small, but statistically significant, correlations between antibody levels that were largely unaffected by race, sex, age at immunization, and time since immunization. While the correlations we observed were modest, approximately 25% of our population was seronegative for at least one component of the MMR vaccine. Therefore, our results support the current policy of continuing to administer the trivalent MMR vaccine even when only a single low antibody titer is observed.

I: Negative effect of cold ischemia on initial renal function.

Correlation between post-transplant function and exposure to cold ischemia (CI) during preservation has been reported. We attempted to identify the effect of CI on renal function using exsanguinous metabolic support (EMS) technology, to eliminate effects of reperfusion complications. Small bovine kidneys were used to evaluate 4 vs. 24 hours of CI, after warm ischemic (WI) exposure of <15, 30 or 60 minutes. After CI, kidneys were warm perfused (30 degrees C to 32 degrees C) ex vivo using EMS technology. Restored renal metabolism and function were quantified by oxygen consumption, urine production, glomerular filtration rate (GFR), and hemodynamic characteristics. The results demonstrate a CI-associated lag phase in the restoration of metabolism, in which the longer cold-preserved kidneys exhibit a lower initial rate of oxygen consumption. However, after 3 hours of EMS perfusion there was no significant difference in the O2 consumed, urine flow, GFR, perfusion flow, or pressure between the kidneys stored for 4 or 24 hours. An initial reduction in metabolism after longer CI may influence the severity of actual reperfusion injury during transplantation. Therefore, these results provide preliminary evidence suggesting that an acellular warm temperature reperfusion ex vivo may enhance restoration of cellular metabolism and minimize damage from the cold seen upon actual reperfusion.

II: Ex vivo viability testing of kidneys after postmortem warm ischemia.

Future approaches to expand the organ donor pool with marginal and nonheartbeating donors, will be dependent upon prospective organ evaluation. Restoration of metabolism by preservation at warmer temperatures could potentially provide the window for such evaluation. Using a small bovine model, kidneys were subjected to either < 15, < 30 or < 60 minutes of warm ischemia (WI) followed by cold ischemia (CI) in ViaSpan. After WI and CI, kidneys were transitioned to a warm temperature perfusion (30 degrees C to 32 degrees C) using exsanguinous metabolic support (EMS) technology. Restored renal metabolism and function was assessed by oxygen consumption, glucose consumption, urine production, glomerular filtration rate, and hemodynamic characteristics. The results of this study suggest that it is feasible to distinguish viable from nonviable organs ex vivo by assessing renal metabolism and function during warm preservation using EMS technology.

Malignant transformation of solitary spinal osteochondroma in two mature dogs.

Canine osteochondroma is an uncommon bony tumor that arises in skeletally immature animals. Consequently, clinical signs typically occur in young dogs as a result of impingement of normal structures by the tumor. Radiographically, osteochondromas are benign in appearance. They are well circumscribed and cause no bony lysis nor periosteal proliferation. Osteochondromas may occur in two forms; solitary or multiple. Although histology and biologic behavior are identical, when in the multiple form the condition has been termed multiple cartilaginous exostoses. Malignant transformation of multiple cartilaginous exostoses has been reported in three mature dogs. We report two dogs with malignant transformation of solitary spinal osteochondromas. Both underwent transformation to osteosarcoma. Despite the benign radiographic appearance of osteochondromas and multiple cartilaginous exostoses, clinical signs should alert the clinician to the possibility of malignant transformation.

Regulation of the sol locus genes for butanol and acetone formation in Clostridium acetobutylicum ATCC 824 by a putative transcriptional repressor.

A gene (orf1, now designated solR) previously identified upstream of the aldehyde/alcohol dehydrogenase gene aad (R. V. Nair, G. N. Bennett, and E. T. Papoutsakis, J. Bacteriol. 176:871-885, 1994) was found to encode a repressor of the sol locus (aad, ctfA, ctfB and adc) genes for butanol and acetone formation in Clostridium acetobutylicum ATCC 824. Primer extension analysis identified a transcriptional start site 35 bp upstream of the solR start codon. Amino acid comparisons of SolR identified a potential helix-turn-helix DNA-binding motif in the C-terminal half towards the center of the protein, suggesting a regulatory role. Overexpression of SolR in strain ATCC 824(pCO1) resulted in a solvent-negative phenotype owing to its deleterious effect on the transcription of the sol locus genes. Inactivation of solR in C. acetobutylicum via homologous recombination yielded mutants B and H (ATCC 824 solR::pO1X) which exhibited deregulated solvent production characterized by increased flux towards butanol and acetone formation, earlier induction of aad, lower overall acid production, markedly improved yields of solvents on glucose, a prolonged solvent production phase, and increased biomass accumulation compared to those of the wild-type strain.

Results of a combined dexamethasone suppression/thyrotropin-releasing hormone stimulation test in healthy horses and horses suspected to have a pars intermedia pituitary adenoma.

OBJECTIVE: To evaluate results of a combined dexamethasone suppression/thyrotropin-releasing hormone (TRH) stimulation test in horses suspected clinically to have a pars intermedia pituitary adenoma (PIPA). DESIGN: Case-control study. ANIMALS: 7 healthy adult horses and 5 horses suspected to have a PIPA. PROCEDURE: A baseline blood sample was collected, and dexamethasone (40 micrograms/kg [18 micrograms/lb] of body weight, IV) was administered; a second blood sample was collected 3 hours later, and TRH (1.1 mg, IV) was administered; serial blood samples were collected 15, 30, 45, 60, and 90 minutes and 21 hours after TRH administration (24 hours after dexamethasone injection). Cortisol concentration was determined for all blood samples. RESULTS: Baseline cortisol concentration was significantly lower in horses suspected to have a PIPA than in healthy horses. Cortisol concentration was suppressed by dexamethasone in both groups; however, after TRH administration, cortisol concentration returned to baseline values in horses suspected to have a PIPA, but not in healthy horses. Concentration was still less than the baseline value 24 hours after dexamethasone administration in healthy horses. CLINICAL IMPLICATIONS: The combined dexamethasone suppression/TRH stimulation test may be a useful diagnostic test in horses suspected to have a PIPA. For clinical application, collection of a blood sample 30 minutes after TRH administration is recommended.

Genetic manipulation of acid formation pathways by gene inactivation in Clostridium acetobutylicum ATCC 824.

Integrational plasmid technology has been used to disrupt metabolic pathways leading to acetate and butyrate formation in Clostridium acetobutylicum ATCC 824. Non-replicative plasmid constructs, containing either clostridial phosphotransacetylase (pta) or butyrate kinase (buk) gene fragments, were integrated into homologous regions on the chromosome. Integration was assumed to occur by a Campbell-like mechanism, inactivating either pta or buk. Inactivation of the pta gene reduced phosphotransacetylase and acetate kinase activity and significantly decreased acetate production. Inactivation of the buk gene reduced butyrate kinase activity, significantly decreased butyrate production and increased butanol production.