Scarboro Town Report - 1915

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Sedimentary ancient DNA from Lake Skartjorna, Svalbard: assessing the resilience of arctic flora to Holocene climate change

Reconstructing past vegetation and species diversity from arctic lake sediments can be challenging because of low pollen and plant macrofossil concentrations. Information may be enhanced by metabarcoding of sedimentary ancient DNA (sedaDNA). We developed a Holocene record from Lake Skartjørna, Svalbard, using sedaDNA, plant macrofossils and sediment properties, and compared it with published records. All but two genera of vascular plants identified as macrofossils in this or a previous study were identified with sedaDNA. Six additional vascular taxa were found, plus two algal and 12 bryophyte taxa, by sedaDNA analysis, which also detected more species per sample than macrofossil analysis. A shift from Salix polaris-dominated vegetation, with Koenigia islandica, Ranunculaceae and the relatively thermophilic species Arabis alpina and Betula, to Dryas octopetala-dominated vegetation ~6600–5500 cal. BP suggests a transition from moist conditions 1–2°C warmer than today to colder/drier conditions. This coincides with a decrease in runoff, inferred from core lithology, and an independent record of declining lacustrine productivity. This mid-Holocene change in terrestrial vegetation is broadly coincident with changes in records from marine sediments off the west coast of Svalbard. Over the Holocene sedaDNA records little floristic change, and it clearly shows species persisted near the lake during time intervals when they are not detected as macrofossils. The flora has shown resilience in the presence of a changing climate, and, if future warming is limited to 2°C or less, we might expect only minor floristic changes in this region. However, the Holocene record provides no analogues for greater warming

Alleviative effect of quercetin on germ cells intoxicated by 3-methyl-4-nitrophenol from diesel exhaust particles*

As a component of diesel exhaust particles, 3-methyl-4-nitrophenol (4-nitro-m-cresol, PNMC) is also a metabolite of the insecticide fenitrothion and imposes hazardous effects on human health. In the present study, the alleviative effect of a common antioxidant flavonoid quercetin on mouse germ cells intoxicated by PNMC was investigated. Results showed that a single intraperitoneal injection of PNMC at 100 mg/kg induced severe testicular damage after one week. PNMC-treated mice showed a significant loss of germ cells (approximate 40% loss of round germ cells). PNMC caused an increase of hydroxyl radical and hydrogen peroxide production and lipid peroxidation, as well as a decrease in glutathione level, superoxide dismutase and glutathione peroxidase activities. Furthermore, treatment of PNMC increased expression of the pro-apoptotic protein Bax and decreased expression of the anti-apoptotic protein Bcl-XL in germ cells. In addition, testicular caspase-3 activity was significantly up-regulated and germ cell apoptosis was significantly increased in the PNMC-treated mice. In contrast, combined administration of quercetin at 75 mg/kg significantly attenuated PNMC-induced testicular toxicity. These results indicate that the antioxidant quercetin displays a remarkable protective effect on PNMC-induced oxidative damage in mouse testes and may represent an efficient supplement to attenuate reproductive toxicity by environmental toxicants to ensure healthy sperm production