CO2: Adsorption on palagonite and the Martian regolith

Possible scenarios for the evolution of the Martian climate are discussed. In the interest of determining an upper limit on the absorptive capacity of the Martian regolith, researchers examined the results of Fanale and Cannon (1971, 1974) for CO2 adsorption on nontronite and basalt. There appeared to be a strong proportionality between the capacity of the absorbent and its specific surface area. A model of the Martian climate is given that allows the researchers to make some estimates of exchangeable CO2 abundances

Atmospheric H2O and the search for Martian brines

Abundant martian brines would have important implication for current theories of volatile migration on Mars, since, although the presence of metastable brines is quite plausible, any brine in the reasonably near-surface should be completely depleted on a timescale short in relation to the age of Mars. It is important to determine whether brines exist in the martian subsurface, for the current paradigm for understanding martian volatile regime requires substantial alteration if they are found to exist. It is determined, however, that the prospect for detection of a subsurface brine via atmospheric water vapor measurements is marginal. Four reasons are given for this conclusion

Dorsalization of the neural tube by the non-neural ectoderm

The patterning of cell types along the dorsoventral axis of the spinal cord requires a complex set of inductive signals. While the chordamesoderm is a well-known source of ventralizing signals, relatively little is known about the cues that induce dorsal cell types, including neural crest. Here, we demonstrate that juxtaposition of the non-neural and neural ectoderm is sufficient to induce the expression of dorsal markers, Wnt-1, Wnt-3a and Slug, as well as the formation of neural crest cells. In addition, the competence of neural plate to express Wnt-1 and Wnt-3a appears to be stage dependent, occurring only when neural tissue is taken from stage 8–10 embryos but not from stage 4 embryos, regardless of the age of the non-neural ectoderm. In contrast to the induction of Wnt gene expression, neural crest cell formation and Slug expression can be induced when either stage 4 or stage 8–10 neural plates are placed in contact with the non-neural ectoderm. These data suggest that the non-neural ectoderm provides a signal (or signals) that specifies dorsal cell types within the neural tube, and that the response is dependent on the competence of the neural tissue

Southern hemispheric halon trends and global halon emissions, 1978–2011

The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania, between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s, but those of H-1301 continue to increase up to mid-2011. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The observations suggest that the contribution of the halons to total tropospheric bromine at Cape Grim has begun to decline from a peak in 2008 of about 8.1 ppt. An extrapolation of halon mixing ratios to 2060, based on reported banks and predicted release factors, shows this decline becoming more rapid in the coming decades, with a contribution to total tropospheric bromine of about 3 ppt in 2060. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid-1990s, but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA (University of East Anglia) top-down model-derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). The implications of an alternative set of steady-state atmospheric lifetimes are discussed. Using a lifetime of 14 yr or less for H-1211 to calculate top-down emissions estimates would lead to small, or even negative, estimated banks given reported production data. Finally emissions of H-1202, a product of over-bromination during the production process of H-1211, have continued despite reported production of H-1211 ceasing in 2010. This raises questions as to the source of these H-1202 emissions

Distinct Intracellular Trafficking Patterns of Host IgG by Herpes Virus Fc-Receptors

Members of both alpha and beta herpes viruses affects 50–98% of people around the world. They cause severe symptoms in congenitally infected newborns, a lifelong latent infection that is lethal in immunocompromised individuals, and are associated with several types of cancer. Human cytomegalovirus (HCMV) and herpes simplex virus type 1 (HSV-1) viruses express proteins (HCMV gp68 and gp34; HSV-1 gE-gI) that function as Fc receptors (FcRs) by binding to the Fc regions of human IgG. In addition to binding free IgG, these viral FcRs can bind to IgG complexed with an antigen to form an antibody bipolar bridged (ABB) complex. Although HCMV gp68 and HSV-1 gE-gI have an overlapping binding site on Fc, the finding that the gp68/Fc interaction is stable at pH values between 5.6 and 8.1 but that gE-gI binds only at neutral or basic pH suggests distinct pH-based downstream events after IgG is internalized via receptor-mediated endocytosis into intracellular compartments. Here we developed a cell-based in vitro model system to define the fates of ABB complexes formed by the two types of viral FcRs. We found that alpha (HSV-1) and beta (HCMV) herpes virus FcRs displayed distinct intracellular trafficking patterns to target internalized ligands: HSV-1 gE-gI dissociates from its IgG-antigen ligand in acidic endosomal compartments and recycles back to the cell surface, whereas HCMV FcRs (gp68) are transported together with IgG-antigen complexes to lysosomes for degradation. In both cases, anti-viral IgGs and their viral targets are selectively degraded, a potential immune evasion strategy allowing herpes viruses to escape from IgG-mediated immune responses

Severity of disease and risk of malignant change in hereditary multiple exostoses. A genotype-phenotype study

We performed a prospective genotype-phenotype study using molecular screening and clinical assessment to compare the severity of disease and the risk of sarcoma in 172 individuals (78 families) with hereditary multiple exostoses. We calculated the severity of disease including stature, number of exostoses, number of surgical procedures that were necessary, deformity and functional parameters and used molecular techniques to identify the genetic mutations in affected individuals. Each arm of the genotype-phenotype study was blind to the outcome of the other. Mutations EXT1 and EXT2 were almost equally common, and were identified in 83% of individuals. Non-parametric statistical tests were used. There was a wide variation in the severity of disease. Children under ten years of age had fewer exostoses, consistent with the known age-related penetrance of this condition. The severity of the disease did not differ significantly with gender and was very variable within any given family. The sites of mutation affected the severity of disease with patients with EXT1 mutations having a significantly worse condition than those with EXT2 mutations in three of five parameters of severity (stature, deformity and functional parameters). A single sarcoma developed in an EXT2 mutation carrier, compared with seven in EXT1 mutation carriers. There was no evidence that sarcomas arose more commonly in families in whom the disease was more severe. The sarcoma risk in EXT1 carriers is similar to the risk of breast cancer in an older population subjected to breast-screening, suggesting that a role for regular screening in patients with hereditary multiple exostoses is justifiable. ©2004 British Editorial Society of Bone and Joint Surgery