RESUMO
High resolution XRF scanning documented inter-annual paleolimnological changes of a Subantarctic periglacial lake, during a process of centennial glacier retreat in King George Island, Antarctica. Two major paleoenvironmental stages were inferred from the combined analysis of elemental, molecular and isotopic biomarkers, with a boundary or transition set at about 3200â¯yr BP. The first stage was characterized by a relatively low allochthonous organic content, reduced productivity and nitrogen levels. Such paleoenvironmental conditions are interpreted as a terrestrial system under periglacial influence, where material influx was related to erosion process from the melt water discharge, because of the proximity to the Collins Glacier ice cap. After the major Holocene glacier advance dated at about 3500â¯yr BP, the ice cap retreat led to the formation of Lake Uruguay, which involved in filling processes leading to moraine deposits, proglacial meltwater channels, and lakes next to the land glacier. During the second stage, with the onset of the Current Warm Period, prior to 1900â¯CE the stabilization of the Zr/Rb ratio within the laminated sediments documented the origin of the lacustrine sedimentation system, with subsequent increases in the sedimentation rate and biomass content (total nitrogen and organic carbon). Time series analyses revealed that the lake displayed variability cycles related to El Niño Southern Oscillation (ENSO), as reflected by high resolution sedimentological proxies for grain size, weathering, allochthonous inputs from the watershed, increase of biomass and productivity, and changes in redox conditions, all of which displayed similar oscillation cycles from 2 to 6â¯yr. During this periglacial recession and associated eutrophication process, we detected a striking loss in both bacterial specific richness and diversity as inferred from preliminary selected ancient DNA analyses. Thus, the Antarctic warming scenario leading to glacier depletion appears to exert deterioration consequences on the Subantarctic microbial web.
Assuntos
Camada de Gelo , Lagos , Regiões Antárticas , Eutrofização , UruguaiRESUMO
Oxygen-enriched atmospheres applied as periodic pulses increased conidia production from entomopathogenic fungi in agar surface cultures. However, this advantage has not been obtained in solid-state cultures (SSC), probably as a result of different biomass production between both culture systems. In this work, the biomass formation from two Isaria strains was limited in SSC using 5, 2·5 and 1 initial grams of substrate (gds). In the system with 5 gds, conidia production decreased in 26% oxygen-enriched pulses compared to the normal atmosphere. Conversely, 26% oxygen pulses increased conidiation up to one order magnitude in systems with 2·5 and 1 gds, respective to the normal atmosphere. These results were explained by oxygen depletion and high CO2 accumulation in the 5 gds system. Whereas in systems with 2·5 or 1 gds, oxygen levels remained high enough to stimulate conidiation. These results were attributed to the headspace volume:gds ratio, which is suggested to be ≥48 ml per gds. This ratio is proposed as a scaling-up criterion for bioreactor design when oxygen-enriched pulses are used in SSC for improvement of conidia production. SIGNIFICANCE AND IMPACT OF THE STUDY: Oxygen-enriched atmospheres applied as periodic pulses increase conidiation in entomopathogenic fungi (EF). However, this remained restricted to agar surface cultures, since conidiation decreased when carried out in solid-state culture (SSC) which is used as large-scale production system. We identified that in SSC the ratio between the headspace volume containing 26% oxygen-enriched pulses and the grams of substrate determines the conidiation response to oxygen-enriched pulses. For the first time, oxygen-enriched pulses increased conidiation in SSC respective to the normal atmosphere in four EF. This ratio is proposed as a bioreactor criterion design for large-scale conidia production of EF using oxygen-enriched pulses.
Assuntos
Hypocreales/crescimento & desenvolvimento , Oxigênio/farmacologia , Esporos Fúngicos/crescimento & desenvolvimento , Biomassa , Reatores Biológicos/microbiologia , Meios de CulturaRESUMO
OBJECTIVE: To determine in peripheral blood samples of newborns (NB) cardiac output (Q), cardiac index (CI), systemic vascular resistance index (SVRI), and effective oxygen transport (EO2T), through arteriovenous oxygen content difference ([C(a-v) O2]). DESIGN: Comparative survey. SETTING: Healthy NBs and NBs in intermediate care in third level medical attention units. MATERIAL AND METHODS: Forty-seven NB (17 pre-term) were prospectively studied in August and September/1995. A blood sample of 0.4 mL was taken from the umbilical or femoral vein and from the umbilical, radial or femoral artery. The inferencial statistics were done with a t test and Pearson's correlation coefficient. Significance was considered if p < 0.05. RESULTS: Cardiac output ranged from 0.3 to 1.4, mean = 0.6 L/min +/- 0.24 (+/- SD); CI ranged from 1.8 to 6.4 L/min/m2 body surface area (mean = 3.3 +/- 1.2); SVRI ranged from 533 to 2,391 dyne/sec/cm-5/m2 BSA (mean = 1,317 +/- 494); EO2T ranged from 307 to 1,017 mL/min/m2 BSA (mean = 549 +/- 186); the [C(a-v) O2] ranged from 3.1 to 10.7% in volume (mean = 6.8 +/- 2.1). No significant differences were found in Q between pre-term and full-term NB nor was there any correlation between Q and gestational age. CONCLUSIONS: The [C (a-v)O2] is a good alternative to obtain indexes in peripheral blood of NB without cardiopathy, whenever other less invasive and more sophisticated methods are unavailable. In order to calculate the indexes in critically-ill patients, it is necessary to measure O2 consumption prior to applying this method.