Magma mixing by convective entrainment

On the conditions of magma mixing and its bearing on andesite production in the crust

Mixing between magmas is thought to affect a variety of processes, from the growth of continental crust to the triggering of volcanic eruptions, but its thermophysical viability remains unclear. Here, by using high-pressure mixing experiments and thermal calculations, we show that hybridization during single-intrusive events requires injection of high proportions of the replenishing magma during short periods, producing magmas with 55-58 wt% SiO2 when the mafic end-member is basaltic. High strain rates and gas-rich conditions may produce more felsic hybrids. The incremental growth of crustal reservoirs limits the production of hybrids to the waning stage of pluton assembly and to small portions of it. Large-scale mixing appears to be more efficient at lower crustal conditions, but requires higher proportions of mafic melt, producing more mafic hybrids than in shallow reservoirs. Altogether, our results show that hybrid arc magmas correspond to periods of enhanced magma production at depth.

Study on the abundance of CFCs varying with the latitude at the bottom of the troposphere in the southern hemisphere

As the main ozone depleting compounds, the abundance of CFCs in the troposphere and stratosphere has been focused on all the while. However, there are few reports concerning on the CFCs' latitudinal dependence. Relying on the longterm monitoring that has been performed in Shanghai from 1997 and Cooperating with the Chinese Third Antarctic Inland Ice-sheet Traversal Party, we did intensive sampling in the southern hemisphere from the beginning of November to the end of December in 1998 and then got the corresponding concentrations of CFC-12, CFC-11, and CFC-113 according to the latitude. The data were studied inductively in accordance with the geographical location and meteorological condition of every sampling point. In summary, the average concentrations of CFCs (refer to CFC-11, CFC-12, and CFC-113) in equatorial area are the highest in the southern hemisphere; however, the concentrations in prevailing west-wind belt and polar east-wind belt are much lower and at the same levels, which should be a perfect implication of the mean background in the southern hemisphere. Being related to the special polar circumfluence, the concentrations of CFCs on the glacier reveal a special rise. Compared with the mean background of the southern hemisphere that is represented by the data of the prevailing west-wind belt and Polar east-wind belt, the concentrations in Shanghai bear the same level.

Are mast cells MASTers in HIV-1 infection?

HIV-1 gp120 interacts with IgE V(H)3(+) on the surface of human basophils and mast cells (Fc epsilon RI(+) cells), acting as a viral immunoglobulin superantigen. gp120 from different clades induces mediator release from Fc epsilon RI(+) cells. gp120 also induces IL-4 and IL-13 synthesis in human basophils. The chemokine receptors CCR3 and CXCR4, which are coreceptors of HIV-1 infection, are expressed by human Fc epsilon RI(+) cells. HIV-1 Tat protein is a potent chemoattractant for basophils and lung mast cells, interacting with CCR3. Incubation of basophils with Tat protein upregulates the surface expression of the CCR3 receptor. There is evidence that human Fc epsilon RI(+) cells could be infected in vitro by M-tropic HIV-1 strains.

Hypothalamic digoxin, hemispheric dominance and the acquired immunodeficiency syndrome

OBJECTIVES

Hypothalamic digoxin, an isoprenoidal metabolite, is an endogenous regulator of membrane Na(+)-K(+) ATPase activity, immune activation and synaptic neurotransmission. The objective of this study was to assess the role of hypothalamic digoxin and hemispheric dominance in the pathogenesis of the acquired immunodeficiency syndrome (AIDS) and in the genesis of sexual orientation.

METHODS

The isoprenoid-pathway-related cascade - (i) isoprenoidal metabolites - digoxin, dolichol and ubiquinone, (ii) tryptophan/tyrosine catabolic patterns, (iii) glycoconjugate metabolism, (iv) free radical metabolism and (v) membrane composition were assessed in AIDS (CDC stage - group IV - subgroup C), individuals with differing hemispheric dominance as well as in individuals with differing sexual orientation. Statistical analysis was done by Student's t test with modified degrees of freedom.

RESULTS

The HMG CoA reductase activity was increased with increased digoxin and dolichol levels and reduced ubiquinone levels in AIDS. The membrane Na(+)-K(+) ATPase activity and serum magnesium levels were reduced. The tryptophan catabolites (serotonin, quinolinic acid, nicotine and strychnine) were increased and the tyrosine catabolites (morphine, dopamine and noradrenaline) were reduced. The serum glycoconjugate metabolites were increased and lysosomal stability was reduced in AIDS. There was reduced incorporation of glycoconjugates into membranes and an increased membrane cholesterol:phospholipid ratio. Lipid peroxidation products and NO were increased while free radical scavenging enzymes and reduced glutathione were reduced. The biochemical patterns obtained in AIDS correlated with those obtained in right-hemispheric dominance and homosexuals/bisexual states.

CONCLUSIONS

Hypothalamic digoxin and right-hemispheric dominance is important in the predisposition to AIDS as well as homosexual/bisexual states.

Mucosal HIV infection

The gastrointestinal tract is not only a major site of clinical manifestations of the acquired immune deficiency syndrome but also an important compartment for HIV infection at all stages of the disease. In intestinal biopsies HIV has been detected so far mainly in mononuclear cells of the lamina propria but also in epithelial cells. Primary and permanent epithelial cell lines can be productively infected by HIV in vitro and epithelial cell monolayers can rapidly transport HIV by transcytosis. Both phenomena are most effective for cell-associated virus and do not require CD4 expression but seem to involve the interaction of gp120 with galactosyl ceramide. In vivo, productive HIV infection of epithelial cells appears to be rare if it occurs at all. Mucosal HIV infection is highly active at all stages of HIV infection and the gastrointestinal tract is probably a major source of HIV in the body. Highest mucosal HIV production is found rather early in HIV disease and is associated with histological abnormalities and gastrointestinal symptoms. The excessive production of HIV in the intestine appears to be due to transcriptional or translational upregulation and local variations in HIV production correlate with local cytokine levels.

Chemokines, renal disease, and HIV infection

Renal disease is characterized by the influx of leukocytes into the injured tissue. Before leukocytes can exert their effects on renal damage or repair, they have to reach the site of injury. To recruit specific populations of leukocytes during inflammation is the role of a family of cytokines called chemokines. The characterization of this family has emerged within the past years, yet chemokines have already been the subject of thousands of scientific reports and promise to have many clinical applications. There is good evidence that chemokines contribute to leukocyte infiltration in glomeruli and interstitium and that they play a pivotal role in various renal diseases. The fact that there exist so many chemokines suggests the biological need for redundancy to effect recruitment of immune cells. Although they were originally defined as host defense proteins, chemokines clearly have other functions that extend well beyond the regulation of leukocyte migration. The recent suggestion that chemokines may contribute to a slow progression of the human immunodeficiency virus (HIV) infection and the very recent identification of chemokine receptors as docking molecules for HIV infection add another aspect to chemokine research. The speed at which researchers are exploring the HIV-chemokine connection is evident in the large number of publications on this topic as well as the rapid translation of publications into possible therapeutic applications. Delineating a precise role for chemokines in mediating pathologic changes is an area of fruitful investigation.

Serum HIV-1 RNA levels compared to soluble markers of immune activation to predict disease progression in HIV-1-infected individuals

We assessed the value of HIV-1 RNA level compared to soluble immune activation markers, namely neopterin, beta2-microglobulin and soluble TNF receptor 75 (sTNFR-75), to predict the change in the number of CD4+ T cells over a 1-year period, the development of AIDS, and survival (median follow-up 54 months). The study population comprised a cohort of 47 individuals for the analysis of the change in CD4+ T cells and survival (20 died), and a subgroup of 31 individuals with a baseline CD4+ T cells above 200 x 10(6)/l for the development of AIDS (11 developed AIDS). HIV-1 RNA was measured from stored sera by quantitative PCR. The CD4+ T cell count obtained at study entry strongly correlated with baseline serum HIV-1 RNA levels (r=-0.47), and to a lesser extent with neopterin (r=-0.41) and beta2-microglobulin (r=-0.29). The percentage change in CD4+ T cells over a 1-year period correlated with HIV-1 RNA levels (r=-0.32, p=0.03), however, stronger correlations were found for neopterin, beta2-microglobulin and sTNFR-75 (r=-0.51, r=-0.41, r=-0.42; p< 0.01). No progression to AIDS or death was observed in individuals with baseline HIV-1 RNA levels below 20,000 copies/ml (10 of 31 and 15 of 47 individuals, respectively). A Cox's proportional hazard model to predict AIDS revealed that HIV-1 RNA, the change in CD4+ cells over a 1-year period and sTNFR-75 levels independently predict AIDS; the change in CD4+ cells, the absolute CD4+ T cell count and neopterin were jointly significant to predict death. All results were adjusted for nucleoside monotherapy. In conclusion, to improve the predictive power, quantitation of HIV-1 RNA as a 'natural history marker' may be supplemented by measurement of sTNFR-75 for 'early'-stage disease progression and neopterin for 'late'-stage disease progression.

HIV-1 tat molecular diversity and induction of TNF-alpha: implications for HIV-induced neurological disease

Activation and infection by HIV-1 of glial cells and infiltrating macrophages are cardinal features of AIDS-related neurological disease. Tumor necrosis factor-alpha (TNF-alpha) is released by these cell types, and increased TNF-alpha mRNA and protein levels are associated with the development and severity of HIV-induced neurological disease. HIV-1 proteins have been implicated in HIV neuropathogenesis including Tat which has been shown to be a potent inducer of TNF-alpha. We review our data showing the induction of TNF-alpha by Tat in primary human fetal astrocytes, human peripheral blood mononuclear cells, macrophages, and astrocytic and macrophage cell lines. TNF-alpha induction was NF-kappaB dependent and was eliminated by inhibiting protein kinase A, phospholipase C and protein tyrosine kinase activity. In addition, we examined the molecular diversity of the tat genome in the brains of HIV-infected patients from different HIV-1 clades. Comparison of matched brain- and spleen-derived tat sequences indicated that homology among brain-derived clones was greater than that between the brain- and spleen-derived clones. The brain-derived tat sequences were markedly heterogeneous in regions which influence viral replication and intracellular transport. Future studies using Tat, encoded by different sequences, will be necessary to determine the functional significance of tat molecular diversity. Nonetheless, these studies suggest that Tat is an important inducer of TNF-alpha production and thus may play a key role in the pathogenesis of HIV-related neurological disease.