Additional Cambrian Series 3, Stage 5, trilobite fauna comprising Peronopsis sp., Eosoptychoparia cf. Spinosa Gaotanaspis cf. pingzhaiensis and Gaotanaspis cf. transversa have been recorded just immediately above the known Oryctocephalus indicus biozone (Cambrian Series 3, Stage 5) in the Parahio valley section (Spiti region). The FAD of Peronopsis and LAD of Gaotanaspis are used to establish a Peronopsis–Gaotanaspis concurrent biozone immediately above the Oryctocephalus indicus biozone. The first records of Gaotanaspis cf. pingzhaiensis and G.transversa from the Cambrian of Spiti region and the other faunal elements are correlated with the Peronopsis taijiangensis biozone of the Kaili Formation (South China). The stratigraphic thickness from the base of the O.indicus biozone to the top of the Peronopsis–Gaotanaspis concurrent biozone in the Kunzam La (=Parahio) Formation and its comparison to the Kaili Formation (South China) indicate a possible stratigraphic condensation in the basal part of the Cambrian Series 3, Stage 5 of the Parahio valley (Spiti). Sedimentological and sequence stratigraphic analysis supports this contention. 相似文献
Introduction: Auto-immunity against pancreatic beta-cells leads to an absolute shortage of the hormone insulin, resulting in hyperglycemia and the onset of type 1 diabetes (T1D). Proteomic approaches have been used to elucidate the mechanisms of beta-cell dysfunction and death.
Areas covered: In the present review, we discuss discoveries in the beta-cell proteome that have contributed to better insights in the role of the beta-cell in T1D. Techniques, such as 2D-DIGE and MALDI imaging, together with new approaches for sample preparation, including laser capture microdissection and immunopeptidomics, have resulted in novel mechanistic insights in the pathogenesis of T1D. We describe how proteomic studies in beta-cell lines as well as isolated islets from animal models and humans have discovered intracellular signaling pathways leading to beta-cell destruction, the generation of neo-antigens through post-translational modifications of beta-cell antigens as well as better biomarkers of disease progression.
Expert commentary: Proteomics has contributed to the discovery of beta-cell neo-autoantigen generation through post-translational modifications, hybrid insulin peptide formation and the generation of defective ribosomal gene products. These concepts are revolutionizing our insights in the pathogenesis of T1D, acknowledging a central role for the beta-cell in its own destruction. 相似文献
Ammonia‐oxidizing bacteria (AOB) perform the rate‐limiting step of nitrification, a key ecosystem process that in part determines the fate of nitrogen in ecosystems. However, little is known about the factors that determine soil AOB diversity or composition, especially in tropical systems. Using a set of study systems in Costa Rica, we examined whether plant diversity or land‐use influenced AOB diversity or composition and whether AOB diversity or composition were associated with nitrification rates. We characterized the molecular diversity and composition of AOB via polymerase chain reaction amplification, cloning, and sequencing of 16S rDNA. We found that AOB diversity or composition did not change significantly across plant diversity treatments. In contrast, AOB differed among land‐use types in some measures of diversity and in composition, and differences in AOB composition among land‐use types were correlated with potential rates of nitrification. Our results suggest that anthropogenic changes of ecosystems can alter microbial communities in ways that may affect the processes they mediate. 相似文献
Difficulty in balancing the global carbon budget has lead to increased attention on tropical forests, which have been estimated to account for up to one third of global gross primary production. Whether tropical forests are sources, sinks, or neutral with respect to their carbon balance with the atmosphere remains unclear. To address this issue, estimates of net ecosystem exchange of carbon (NEE) were made for 3 years (1998–2000) using the eddy‐covariance technique in a tropical wet forest in Costa Rica. Measurements were made from a 42 m tower centred in an old‐growth forest. Under unstable conditions, the measurement height was at least twice the estimated zeroplane height from the ground. The canopy at the site is extremely rough; under unstable conditions the median aerodynamic roughness length ranged from 2.4 to 3.6 m. No relationship between NEE and friction velocity (u*) was found using all of the 30‐min averages. However, there was a linear relationship between the nighttime NEE and averaged u* (R2 = 0.98). The diurnal pattern of flux was similar to that found in other tropical forests, with mean daytime NEE ca. ? 18 μ mol CO2 m?2 s?1 and mean nighttime NEE 4.6 μ mol CO2 m?2 s?1. However, because ~ 80% of the nighttime data in this forest were collected during low u* conditions ( < 0.2 m s?1), nighttime NEE was likely underestimated. Using an alternative analysis, mean nighttime NEE increased to 7.05 μ mol CO2 m?2 s?1. There were interannual differences in NEE, but seasonal differences were not apparent. Irradiance accounted for ~ 51% of the variation in the daytime fluxes, with temperature and vapour pressure deficit together accounting for another ~ 20%. Light compensation points ranged from 100 to 207 μ mol PPFD m?2 s?1. No was relationship was found between 30‐min nighttime NEE and tower‐top air temperature. A weak relationship was found between hourly nighttime NEE and canopy air temperature using data averaged hourly over the entire sampling period (Q10 = 1.79, R2 = 0.17). The contribution of below‐sensor storage was fairly constant from day to day. Our data indicate that this forest was a slight carbon source in 1998 (0.05 to ?1.33 t C ha?1 yr?1), a moderate sink in 1999 (?1.53 to ?3.14 t C ha?1 yr?1), and a strong sink in 2000 (?5.97 to ?7.92 t C ha?1 yr?1). This trend is interpreted as relating to the dissipation of warm‐phase El Niño effects over the course of this study. 相似文献
Both the validity and practicability of a direct progesterone radioimmunoassay based on radioiodinated progesterone tracers were studied. The results obtained show the reliability of the assay; when compared with assays based on 3H-progesterone tracers there are fewer steps for assay execution, saving time and reducing the number of reagents used. Various commercially available 125I-progesterone tracers were assayed, and only those with an 11 alpha-hemisuccinate bridge were suitably bound by antisera raised against progesterone-bovine serum albumin conjugates having identical bridge structure. The bridge effect caused no observable alteration in validity parameters. Finally, our results support the utility of this assay as a practical method of early diagnosis of pregnancy and as a reliable experimental technique to monitor cow ovarian function. 相似文献
Changes in the activity of DNA polymerase-α and in subcellular distribution were studied during gastrulation of the sea urchin, Hemicentrotus pulcherrimus. Although the activity of DNA polymerase-α for each embryo was constant up to the blastula stage as reported previously, the enzyme activity increased during gastrulation by about twofold prior to an increase in its DNA content. Thereafter the enzyme activity remained constant at a high level until the early pluteus stage. During gastrulation, an increase in the fraction of DNA polymerase-α was associated with the rough endoplasmic reticulum. During the period between the gastrula and pluteus stages, the cytoplasmic DNA polymerase-α activity decreased gradually with a concomitant increase of activity in the nucleus fraction. The timing of this increase in the nucleus coincided with the increase of DNA content per embryo. These results suggest that DNA polymerase-α accumulates on the rough endoplasmic reticulum during gastrulation and then translocates to the nucleus for DNA synthesis as seen before the blastula stage. DNA polymerase-α obtained from gastrula nuclei did not associate with the endoplasmic reticulum from gastrulae. DNA polymerase-α obtained from the gastrula endoplasmic reticulum membranes became bound to the salt-washed membranes from gastrulae but not to those from unfertilized eggs. Likewise, DNA polymerase-α from the rough endoplasmic reticulum of unfertilized eggs became attached to salt-washed membranes from unfertilized eggs, but not to those from gastrulae. This suggests that DNA polymerase-α is synthesized anew, and a transition of both DNA polymerase-α and endoplasmic reticulum occurs at the gastrula stage. 相似文献