A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell.

An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolved MHz X-ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤103 s-1), where up to 352 diffraction images can be collected from a single pulse train. The set-up employs piezo-driven dDACs capable of compressing samples in ≥340 µs, compatible with the maximum length of the pulse train (550 µs). Results from rapid compression experiments on a wide range of sample systems with different X-ray scattering powers are presented. A maximum compression rate of 87 TPa s-1 was observed during the fast compression of Au, while a strain rate of ∼1100 s-1 was achieved during the rapid compression of N2 at 23 TPa s-1.

Exertional Heat Injury: Effects of Adding Cold (4°C) Intravenous Saline to Prehospital Protocol.

This article reviews current prehospital treatment for heat casualties and introduces a retrospective study on the addition of cold (4 °C) intravenous (IV) saline to prehospital treatment and its effect on morbidity. The study is a retrospective cohort reviewing electronic medical records of 290 heat casualties admitted to Martin Army Community Hospital, Ft. Benning, GA, comparing two treatment groups; U.S. Army Training and Doctrine Command (ice-sheeting and ambient temperature IV saline) versus Benning (ice-sheeting and cold IV saline). U.S. Army Training and Doctrine Command group significantly differed from Benning group on a number of measures, the median length of stay in the hospital was 3 and 2 d, respectively (P < 0.0001); pCr were 1.8 to 1.4 mg·dL, respectively (difference of 0.4 mg·dL pCr, P < 0.0001). However, creatine phosphokinase, aspartate aminotransferase, and alanine aminotransferase were not significantly different across groups. Findings demonstrate that adding cold IV saline to ice-sheeting as a protocol reduces the length of hospitalization of heat casualties and lowers their peak creatinine values.

The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages.

Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in conjunction with expansion or contraction of thermal habitat acts to compress or stretch marine species assemblages, which may respectively amplify or dilute species interactions to an extent that is rarely considered. Overall, regional differences in climate change effects on the movement and extent of species assemblages hold important implications for management, mitigation, and adaptation on the U.S. Northeast Shelf.

Insulin and fibroblast growth factor 2 activate a neurogenic program in Müller glia of the chicken retina.

We have reported previously that neurotoxic damage to the chicken retina causes Müller glia to dedifferentiate, proliferate, express transcription factors common to retinal progenitors, and generate new neurons and glia, whereas the majority of newly produced cells remain undifferentiated (Fischer and Reh, 2001). Because damaged retinal cells have been shown to produce increased levels of insulin-related factors and FGFs, in the current study we tested whether intraocular injections of growth factors stimulate Müller glia to proliferate and produce new neurons. We injected growth factors and bromodeoxyuridine into the vitreous chamber of the eyes of chickens and assayed for changes in glial phenotype and proliferation within the retina. Although insulin or FGF2 alone had no effect, the combination of insulin and FGF2 caused Müller glia to coexpress transcription factors common to retinal progenitors (Pax6 and Chx10) and initiated a wave of proliferation in Müller cells that began at the retinal margin and spread into peripheral regions of the retina. Most of the newly formed cells remain undifferentiated, expressing Pax6 and Chx10, whereas some differentiate into Müller glia, and a few differentiate into neurons that express the neuronal markers Hu or calretinin. There was no evidence of retinal damage in eyes treated with insulin and FGF2. We conclude that the combination of insulin and FGF2 stimulated Müller glia to dedifferentiate, proliferate, and generate new neurons. These findings imply that exogenous growth factors might be used to stimulate endogenous glial cells to regenerate neurons in the CNS.

Retinoid X receptor (gamma) is necessary to establish the S-opsin gradient in cone photoreceptors of the developing mouse retina.

PURPOSE: The retinoid X receptors (RXRs) are members of the family of ligand-dependent nuclear hormone receptors. One of these genes, RXRgamma, is expressed in highly restricted regions of the developing central nervous system (CNS), including the retina. Although previous studies have localized RXRgamma to developing cone photoreceptors in several species, its function in these cells is unknown. A prior study showed that thyroid hormone receptor beta2 (TRbeta2) is necessary to establish proper cone patterning in mice by activating medium-wavelength (M) cone opsin and suppressing short-wavelength (S) cone opsin. Thyroid hormone receptors often regulate gene transcription as heterodimeric complexes with RXRs. METHODS: To determine whether RXRgamma cooperates with TRbeta2 to regulate cone opsin patterning, the developmental expression of RXRgamma was examined, and cone opsin expression in RXRgamma-null mice was analyzed. RESULTS: RXRgamma was expressed in postmitotic cones and was transiently downregulated at the time of S-opsin onset in both mouse and human cones. RXRgamma-null mice expressed S-opsin in all cones, similar to the TRbeta2-null mice. Unlike TRbeta2-null mice, which did not express M-opsin, RXRgamma-null mice had a normal pattern of M-opsin expression. CONCLUSIONS: RXRgamma is essential (along with TRbeta2) for suppressing S-opsin in all immature cones and in dorsal cones in the mature retina, but it is not necessary for M-opsin regulation. These results demonstrate a critical role for RXRs in regulating cell differentiation in the CNS and highlight a remarkable conservation of opsin regulation from Drosophila to mammals.

Experimental studies of adaptation in Clarkia xantiana. I. Sources of trait variation across a subspecies border.

Both genetic differentiation and phenotypic plasticity might be expected to affect the location of geographic range limits. Co-gradient variation (CoGV), plasticity that is congruent with genetic differentiation, may enhance performance at range margins, whereas its opposite, counter-gradient variation (CnGV) may hinder performance. Here we report findings of reciprocal transplant experiments intended to tease apart the roles of differentiation and plasticity in producing phenotypic variation across a geographic border between two plant subspecies. Clarkia xantiana ssp. xantiana and C. xantiana ssp. parviflora are California-endemic annuals that replace each other along a west-east gradient of declining precipitation. We analyzed variation in floral traits, phenological traits, and vegetative morphological and developmental traits by sowing seeds of 18 populations (six of ssp. xantiana and 12 of ssp. parviflora) at three sites (one in each subspecies' exclusive range and one in the subspecies' contact zone), in two growing seasons (an exceptionally wet El Niño winter and a much drier La Niña winter). Significant genetic differences between subspecies appeared in 11 of 12 traits, and differences were of the same sign as in nature. These findings are consistent with the hypothesis that selection is responsible for subspecies differences. Geographic variation within subspecies over part of the spatial gradient mirrored between-subspecies differences present at a larger scale. All traits showed significant plasticity in response to spatial and temporal environmental variation. Plasticity patterns ranged from spatial and temporal CoGV (e.g., in node of first flower), to spatial CnGV (e.g., in flowering time), to patterns that were neither CoGV nor CnGV (the majority of traits). Instances of CoGV may reflect adaptive plasticity and may serve to increase performance under year-to-year environmental variation and at sites near the subspecies border. However, the presence of spatial CnGV in some critical traits suggests that subspecies ranges may also be constrained by patterns of plasticity.

Different aspects of gliosis in retinal Muller glia can be induced by CNTF, insulin, and FGF2 in the absence of damage.

PURPOSE: In response to acute damage, Muller glia in the retina have been shown to dramatically alter their expression of filamentous proteins. Since damaged retinal cells are known to produce growth factors such as insulin-like growth factor (IGF), ciliary neurotrophic factor (CNTF) and fibroblast growth factor (FGF), the altered expression of filaments in Muller glia in response to retinal damage may be induced by some of these factors. The purpose of this study was to assay whether growth factors influence the expression of filamentous proteins in Muller glia in the intact retinas of postnatal chickens. METHODS: We assayed for changes in expression levels of IGF-I, IGF-II, CNTF, FGF1, and FGF2 in N-methyl-D-aspartate(NMDA) damaged retinas by using quantitative PCR. In undamaged retinas, we assayed whether intraocular injections of insulin, CNTF, or FGF2 influenced glial expression of glial fibrillary acidic protein (GFAP), neurofilament, RA4, vimentin and beta3 tubulin by using immunocytochemistry on frozen sections. RESULTS: We demonstrated that levels of mRNA for IGF-II, FGF1, FGF2, and CNTF were increased in the postnatal chicken retina in response to neurotoxic damage. This was coincident with increased glial expression of GFAP and filamentous neuronal proteins. The combination of insulin and FGF2 caused postmitotic Muller glia to transiently increase their expression of vimentin and putative neuron specific filamentous proteins such as neurofilament, beta3 tubulin and RA4. By comparison, insulin or FGF2 alone had minor effects on glial expression of cytoskeletal proteins. Although neurofilament expression was not induced by CNTF, this growth factor stimulated Muller glia to express GFAP. CONCLUSIONS: We conclude that the phenotype of postmitotic Muller glia is plastic and can be regulated by retinal damage, and these damage induced changes in phenotype can be induced by exogenous growth factors in the absence of damage.

Sonic hedgehog regulates proliferation of the retinal ciliary marginal zone in posthatch chicks.

The ciliary marginal zone (CMZ) has long been known to be a source of postembryonic neuronal production in the retinas of fish and amphibians, and more recently, birds. However, there is little known about the factors that are required for the maintenance of this neural stem cell zone. The cells of the CMZ respond to mitogens such as endothelial growth factor, insulin-like growth factor-1, and insulin, factors that are also mitogenic for embryonic retinal progenitors, suggesting that the continued expression of embryonic mitogenic factors might be required to maintain the postembryonic proliferative potential of the CMZ. To test this hypothesis, we examined the expression and functional role of a critical embryonic retinal progenitor mitogen, Sonic hedgehog (Shh) in the regulation of proliferation of the cells of the CMZ. We have found that Shh is concentrated at the retinal margin of postembryonic chicks. Moreover, we report that intraocular injection of Shh stimulates proliferation of the CMZ cells, whereas cyclopamine, an inhibitor of the Shh pathway, inhibits CMZ proliferation. We conclude that Shh signaling is an important factor in the maintenance of postembryonic retinal neurogenesis.