Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers. 相似文献
Summary A Sardinian pedigree described in 1964 for having been found to segregate at the X-linked loci for the Xga antigen, G6PD deficiency, Protan and Deutan color blindness, with an instance of recombination between the last two loci, was re-examined with respect to four common X-linked DNA polymorphisms detected by molecular probes homologous to critical subregions of the human X chromosome. Two branches of this pedigree-including the one with the Protan-Deutan recombinant-were found to segregate also for the common BamHI polymorphism identified with the cDNA probe pHPT-2 of the HPRT gene (Xq26). The analysis of the chromosome haplotypes in the male offspring of the phase known penta-heterozygous mother suggests that the probable order of the relevant loci is HPRT, Deutan, G6PD, Protan, Xq telomere. Though we are fully aware of the risks of generalizing the significance of observations made on a single exceptional pedigree, we believe that this report outlines the potential of families of the type described as reasearch tools to resolve the linear order of tightly X-linked loci and to investigate the biology of genetic recombination in humans. 相似文献
Analysis of the organization of nucleotide sequences in mouse genome is carried out on total DNA at different fragment size, reannealed to intermediate value of Cot, by Ag+-Cs2SO4 density gradient centrifugation. — According to nuclease S-1 resistance and kinetic renaturation curves mouse genome appears to be made up of non-repetitive DNA (76% of total DNA), middle repetitive DNA (average repetition frequency 2×104 copies, 15% of total DNA), highly repetitive DNA (8% of total DNA) and fold-back DNA (renatured density 1.701 g/ml, 1% of total DNA).— Non-repetitive sequences are intercalated with short middle repetitive sequences. One third of non-repetitive sequences is longer than 4500 nucleotides, another third is long between 1800 and 4500 nucleotides, and the remainder is shorter than 1800 nucleotides. —Middle repetitive sequences are transcribed in vivo. The majority of the transcribed repeated sequences appears to be not linked to the bulk of non-repeated sequences at a DNA size of 1800 nucleotides. — The organization of mouse genome analyzed by Ag+-Cs2SO4 density gradient of reannealed DNA appears to be substantially different than that previously observed in human genome using the same technique. 相似文献
Oxygen delivery and metabolism represent key factors for organ function in health and disease. We describe the optical key characteristics of a technique to comprehensively measure oxygen tension (PO2) in myocardium, using oxygen‐dependent quenching of phosphorescence and delayed fluorescence of porphyrins, by means of Monte Carlo simulations and ex vivo experiments. Oxyphor G2 (microvascular PO2) was excited at 442 nm and 632 nm and protoporphyrin IX (mitochondrial PO2) at 510 nm. This resulted in catchment depths of 161 (86) µm, 350 (307) µm and 262 (255) µm respectively, as estimated by Monte Carlo simulations and ex vivo experiments (brackets). The feasibility to detect changes in oxygenation within separate anatomical compartments is demonstrated in rat heart in vivo.
Stenotaenia is one of the largest and most widespread genera of geophilid centipedes in the Western Palearctic, with a very uniform morphology and about fifteen species provisionally recognized. For a better understanding of Stenotaenia species-level taxonomy, we have explored the possibility of using molecular data. As a preliminary assay, we sampled twelve populations, mainly from the Italian region, and analyzed partial sequences of the two genes COI and 28S. We employed a DNA-barcoding approach, complemented by a phylogenetic analysis coupled with divergence time estimation. Assuming a barcoding gap of 10–16% K2P pairwise distances, we found evidence for the presence of at least six Stenotaenia species in the Italian region, which started diverging about 50 million years ago, only partially matching with previously recognized species. We found that small-sized oligopodous species belong to a single clade that originated about 33 million years ago, and obtained some preliminary evidence of the related genus Tuoba being nested within Stenotaenia. 相似文献
Renal tubulo-interstitial fibrosis is a non-specific process, representing the final common pathway for all kidney diseases, irrespective of their initial cause, histological injury, or etiology, leading to gradual expansion of the fibrotic mass which destroys the normal structure of the tissue and results in organ dysfunction and, ultimately, in end-stage organ failure. Proteomic studies of the fibrotic pathophysiological mechanisms have been performed in cell cultures, animal models and human tissues, addressing some of the key issues. This article will review proteomic contribution to the raising current knowledge on renal fibrosis biology and also mention seminal open questions to which proteomic techniques and proteomists could fruitfully contribute. 相似文献
Transplant patients are at high risk of post-transplant lymphoproliferative disorder (PTLD). A strong correlation between Epstein-Barr virus (EBV) and PTLD is observed in pediatric patients with primary infection after transplant. Because many patients have responded to reversal of immunosuppressive therapy, an early identification of EBV is essential for the reduction of immunosuppression and/or introduction of antiviral therapy to prevent PTLD. Polymerase chain reaction (PCR) is a specific and sensitive method to identify EBV DNA in blood. The aim of our study was to establish a protocol for monitoring EBV infection in transplanted patients for early identification those at high risk of PTLD. Viral presence in peripheral blood leukocytes (PBL) and serum samples was revealed by Nested PCR; positive specimens were quantified with Real Time PCR (RT-PCR). DNA in PBL was observed in 12 cases and 6 showed EBV in sera. Quantitative analysis showed a wide range of EBV DNA copies in leukocytes that were higher than in sera. Two patients displayed high viral load values in both PBL and sera associated with clinical evidence of PTLD. Our data suggest that the study of the EBV load represents an essential approach in the diagnosis of PTLD and the analysis of serum samples could provide useful information in the post-transplant monitoring of high-risk patients. 相似文献
In order to develop a non-chemical method such as grafting effective against well-known artichoke soil borne diseases, an anatomical study of union formation in artichoke grafted onto selected wild and cultivated cardoon rootstocks, both resistant to Verticillium wilt, was performed. The cardoon accessions Belgio (cultivated cardoon) and Sardo (wild cardoon) were selected as rootstocks for grafting combinations with the artichoke cv. Romolo. Grafting experiments were carried out in the autumn and spring. The anatomical investigation of grafting union formation was conducted by scanning electron microscopy (SEM) on the grafting portions at the 3rd, 6th, 10th, 12th day after grafting. For the autumn experiment only, SEM analysis was also performed at 30 d after grafting. 相似文献