The Origin of Transparent and Non-Transparent White Pumice: A Case Study of the 52ka Maninjau Caldera Forming Eruption, Indonesia

The 52ka eruption of Maninjau caldera produced two distinctive type of white pumices: transparent (TWP) and non-transparent (NTWP). Both pumice types are crystal-poor (avg. 3.3 %), having similar mineralogy (pl > qz > bt > px > opq), similar glass compositions (avg. 78.5 wt. % SiO2), and similar plagioclase core compositions (avg. An20-30). We found that the abundance of TWP decrease towards the upper stratigraphic positions, together with the increase in NTWP, grey pumice, banded pumice, and lithic contents. Vesicles in TWP are typically dominated by large vesicles, while NTWP is characterized by abundant-small vesicles. Large vesicle corresponds to the preexisting bubble which formed in magma chamber (pheno-bubble, > 0.1 mm). On the other hand, small vesicle in groundmass (matrix-bubble, < 0.1 mm) is attributed to second nucleation in the conduit during the eruption. We performed quantitative comparison using pheno- and matrix-bubble number densities (PBND and MBND) for these two white pumice types. The correlation between PBND and MBND result in two regimes: (1) decompression-controlled regime, showing nearly constant-PBND correlation for TWP, and (2) phenobubble-controlled regime, showing steeply-decreasing PBND correlation for NTWP. In the first regime, MBNDs value varies dramatically, suggesting the variation of decompression rate by two to three orders of magnitudes. While in the second regime, the slight increase of MBNDs is considered as the effect of the decrease in PBND within the nearly constant decompression rate.

Collembola of the Campanet cave (Mallorca, Balearic Islands), with descriptions of new species of Pseudosinella (Entomobryidae) and Oncopodura (Oncopoduridae)

This paper documents the collembolan fauna of the Campanet cave, in the province of Mallorca (Balearic Islands). Sampling was carried out using pitfall traps baited with beer and checked every 15 days. The cave fauna included the following species: Coecobrya tenebricosa, Disparrhopalites patrizi, Entomobrya pazaristei, Neelus murinus and Dicyrtomina ornata. In addition, two new species were found and are described here: Pseudosinella grauae sp. nov. and Oncopodura siquierae sp. nov. The former is characterised by an unpigmented body, eyes absent, dorsal chaetotaxy R0R1R2001/31/0101+2, with accessory chaeta ‘s’ on Abd IV; all claws with three teeth; posterior chaetae on labial triangle as M1, M2, r, E, L1, L2, all ciliated except for r, a smooth microchaetae and smooth remaining anterior labial chaetae. O. siquierae sp. nov is typified by an unpigmented body; eyes absent; PAO as a single small vesicle; Ant IV with four distal leaf‑shaped sensilla and a basal pointed cylindrical chaeta; dens with one proximal inner spine, one distal inner tooth and a large disto-external hook‑like spine; and mucro with four teeth, the basal one distinctly pointed.

Establishment of the Dorsal–Ventral Axis inXenopus Embryos Coincides with the Dorsal Enrichment of Dishevelled That Is Dependent on Cortical Rotation

Examination of the subcellular localization of Dishevelled (Dsh) in fertilized Xenopus eggs revealed that Dsh is associated with vesicle-like organelles that are enriched on the prospective dorsal side of the embryo after cortical rotation. Dorsal enrichment of Dsh is blocked by UV irradiation of the vegetal pole, a treatment that inhibits development of dorsal cell fates, linking accumulation of Dsh and specification of dorsal cell fates. Investigation of the dynamics of Dsh localization using Dsh tagged with green fluorescent protein (Dsh-GFP) demonstrated that Dsh-GFP associates with small vesicle-like organelles that are directionally transported along the parallel array of microtubules towards the prospective dorsal side of the embryo during cortical rotation. Perturbing the assembly of the microtubule array with D2O, a treatment that promotes the random assembly of the array and the dorsalization of embryos, randomizes translocation of Dsh-GFP. Conversely, UV irradiation of the vegetal pole abolishes movement of Dsh-GFP. Finally, we demonstrate that overexpression of Dsh can stabilize β-catenin in Xenopus. These data suggest that the directional translocation of Dsh along microtubules during cortical rotation and its subsequent enrichment on the prospective dorsal side of the embryo play a role in locally activating a maternal Wnt pathway responsible for establishing dorsal cell fates in Xenopus.

Methane synthesis by membrane vesicles and a cytoplasmic cofactor isolated from Methanobacterium thermoautotrophicum

Methanobacterium thermoautotrophicum when grown on ordinary culture medium has a tough cell wall which is lysozyme-resistant and difficult to disrupt by physical means. The cell wall, however, can be weakened by the addition of D-sorbitol to the growth medium and the organisms form protoplasts after lysozyme addition. This technique allowed the isolation of two types of intracellular small vesicles: (a) isolated by disruption of the total cell population (lysozyme-sensitive and lysozyme-resistant cells) by ultrafrequency sound and (b) isolated by osmotic lysis of protoplasts. For the first time, a small vesicle fraction isolated as in (a) was capable of synthesizing methane from CO2 and H2 without cytoplasm. There was, however, an absolute requirement for a small, heat-stable, oxygen-sensitive cofactor which was isolated from the cytoplasm. Methane synthesis with this vesicle fraction was inhibited by the detergent deoxycholate, and by the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone. Mg2+-ATPase appeared to be located on the outer or cytoplasmic surface of the small vesicle fraction isolated as in (b). The results were consistent with a previously made suggestion [Sauer, Erfle & Mahadevan (1981) J. Biol. Chem. 256, 9843-9848] that the interior of the small intracellular vesicles becomes acid during methane synthesis.

Morphometric analysis of volumes and surface areas in membrane compartments during endocytosis in Acanthamoeba.

Stereologic analysis was made of cell surface membrane (PM) and two interrelated cytoplasmic membrane systems, the vacuole membranes (VM) and small vesicle membranes (SVM). Volumes and surface areas of the three membrane compartments were measured during steady-state pinocytosis, when membrane recycling is rapid, and during phagocytosis, when a shift to a lower rate of membrane uptake by endocytosis occurs (B. Bowers, 1977, Exp. Cell Res. 110:409). Total membrane area in the three compartments was 3.2 micrometers 2/micrometers 3 of protoplasmic volume and was constant throughout the experiments. In pinocytosing cells, 32% of the membrane was in the PM, 25% in the vM, and 43% in the SVM. The vacuole compartment occupies approximately 20% of the total cell volume, and the small vesicle, approximately 3%. As the endocytic uptake of membrane from the surface decreased, there was an increase in PM area and a marked decrease in SVM area. The VM area remained constant even though "empty" vacuoles were almost completely replaced by newly formed phagosomes within 45 min. This demonstrates directly a rapid flux of membrane though this compartment. A model, taking into consideration these and other data on Acanthamoeba, is proposed to account for the observed membrane shifts. The data suggest that the vacuolar (digestive) system of Acanthamoeba is central to cellular control of endocytosis and membrane recycling.