Nitrogen budgets of the Polish agriculture 1960–2000: implications for riverine nitrogen loads to the Baltic Sea from transitional countries

The Oder and the Vistula rivers are responsible for about 25% of the total riverine nitrogen input to the Baltic Sea and of this 60% have been estimated to originate from diffuse sources. In this study we have tested the hypothesis that changes in agricultural practices in Poland have changed the riverine nitrogen export from the rivers Oder and Vistula to the Baltic Sea. We calculated agricultural long-term nitrogen budgets (1960–2000) for the catchments of the Oder and the Vistula rivers. Poland went through severe economical changes in the early 1990s, which led to a drastic decrease in fertilizer consumption. The role of the calculated nitrogen surplus as an eutrophication capacitor and the potential to reduce this important capacitor to improve the environmental state of the Baltic Sea is discussed. N surplus for the entire country showed a maximum in 1980 (58 kg ha⁻¹ sown area⁻¹) and it dropped to 39 kg ha⁻¹ sown area⁻¹ in 2000. The surplus was, however, up to two times lower than that in other transitional countries, and much lower than in Western Europe with intensive agriculture. An observed decrease in nitrogen concentrations in both Polish rivers is not ascribed to drop in fertilizer use, but it results from nutrient removal in municipal wastewater treatment plants with tertiary treatment facilities. Comparison of trends in nitrogen concentrations in different transition countries indicates that factors other than reduced fertilizer application influenced the inertia of the water quality response. Hence, the potential to reduce diffuse nitrogen emissions from agriculture by reducing fertilization is constricted in areas with low-nitrogen surplus. In transitional countries like Poland the largest potential for nutrient reductions seem to be in improving the connectivity to waste water treatment plants with tertiary treatment.     

Barremian–Bedoulian flint humanly transported from the west bank of the Rhône to the Massif-Central Highlands–A diachronic perspective

Petro-archaeology is a powerful tool useful in understanding the origin and management of rocks discovered in prehistoric sites and the complexity of human territories. This research technique has been applied extensively to the Massif Central and its margins, allowing the revaluation of lithic imports from the Rhodanian corridor. Flint derived from Oligocene conglomerates at Rochemaure–Cruas (Ardèche) was a perennial and often preferred source for prehistoric groups inhabiting the Vivarais lowlands and was exported through the Monts d’Ardèche to the Velay highlands (Haute-Loire) during the upper Pleistocene and the Holocene. This modifies the previously drawn litho-spaces occupied by Neanderthals and Modern Humans and questions their land-use strategies in these contrasting natural landscapes.     

Black-white disparities during an epidemic: Life expectancy and lifespan disparity in the US, 1980–2000

Covid-19 has demonstrated again that epidemics can affect minorities more than the population in general. We consider one of the last major epidemics in the United States: HIV/AIDS from ca. 1980–2000. We calculate life expectancy and lifespan disparity (a measure of variance in age at death) for thirty US states, finding noticeable differences both between states and between the black and white communities. Lifespan disparity allows us to examine distributional effects, and, using decomposition methods, we find that for six states lifespan disparity for blacks increased between 1980 and 1990, while life expectancy increased less than for whites. We find that we can attribute most of this to the impact of HIV/AIDS.     

Sex-biased parasitism is not universal: evidence from rodent–flea associations from three biomes

The distribution of parasites among individual hosts is characterised by high variability that is believed to be a result of variations in host traits. To find general patterns of host traits affecting parasite abundance, we studied flea infestation of nine rodent species from three different biomes (temperate zone of central Europe, desert of Middle East and tropics of East Africa). We tested for independent and interactive effects of host sex and body mass on the number of fleas harboured by an individual host while accounting for spatial clustering of host and parasite sampling and temporal variation. We found no consistent patterns of the effect of host sex and body mass on flea abundance either among species within a biome or among biomes. We found evidence for sex-biased flea infestation in just five host species (Apodemus agrarius, Myodes glareolus, Microtus arvalis, Gerbillus andersoni, Mastomys natalensis). In six rodent species, we found an effect of body mass on flea abundance (all species mentioned above and Meriones crassus). This effect was positive in five species and negative in one species (Microtus arvalis). In M. glareolus, G. andersoni, M. natalensis, and M. arvalis, the relationship between body mass and flea abundance was mediated by host sex. This was manifested in steeper change in flea abundance with increasing body mass in male than female individuals (M. glareolus, G. andersoni, M. natalensis), whereas the opposite pattern was found in M. arvalis. Our findings suggest that sex and body mass are common determinants of parasite infestation in mammalian hosts, but neither of them follows universal rules. This implies that the effect of host individual characteristics on mechanisms responsible for flea acquisition may be manifested differently in different host species.     

Impacts of large dams on riparian vegetation: applying global experience to the case of China’s Three Gorges Dam

Dams are widely recognised as having significant negative consequences for the surrounding natural ecosystems and environment. China’s Three Gorges Dam, being one of the largest in the world, stands to inflict more damage than most for numerous reasons. This paper reviews the current knowledge on the impacts of dams and impoundments with regard to reservoir riparian vegetation in order to apply this knowledge to the Three Gorges Project. It also summarises research performed to date on the effects of the Three Gorges Dam on the local riparian zone and vegetation. The known and potential outcomes for local plant communities are examined in terms of their responses to the increased water levels, altered hydrological characteristics and other adverse effects associated with the construction of the dam. Vegetation responses will be diverse and change over time, but will ultimately result in a markedly different landscape and riparian zone within the Three Gorges Reservoir. These changes will take place through a loss of previous vegetation, potential invasion by exotics and result from the significant alteration in hydrological regimes and also erosion and sedimentation processes influencing and creating novel plant communities. Management of the environmental consequences of the Three Gorges Project should take into account factors associated with these processes, in order to facilitate vegetation recovery in the reservoir and to conserve biodiversity of the surrounding ecosystems.     

Human Dietary Exposure to Fumonisin B1 from Iranian Maize Harvested During 1998–2000

Fumonisin B₁ (FB₁) is the most abundant of the fumonisin mycotoxins, mainly produced in maize by F. verticillioides and F. proliferatum. A previous study on the FB1 contamination of maize harvested in Mazandaran and Isfahan Provinces of Iran in 1998 and 1999 demonstrated contamination in both provinces. This present study was undertaken to further investigate the variation in levels of contamination and to estimate possible levels of human exposure to fumonisins in Iran. The mean level of FB₁ in 49 visually healthy maize samples collected from Mazandaran Province during 2000 was 6.14 mg/kg, which is higher than that found during 1998 and 1999 (2.27 and 3.18 mg/kg, respectively). Although these levels are higher than the Iranian legislative limits for fumonisins in maize intended for humans, the relatively low estimated consumption of maize in Iran (3.3 g/person/day) implies that average exposures (0.011 and 0.215 μg/kg body weight/day in Isfahan and Mazandaran, respectively) are within the provisional maximum tolerable daily intake of 2 μg/kg body weight/day set by the Joint FAO/WHO Expert Committee on Food Additives. Nevertheless, certain sections of the population who may consume higher amounts of maize or who may replace all or some of their consumption of other cereals with maize, could well exceed this limit.     

Zizimauritic acids A–C,three novel nortriterpenes from Ziziphus mauritiana

Zizimauritic acids A–C (1–3), three novel nortriterpenes with a unique A-nor-E-seco spiro-lactone ceanothane-type triterpene skeleton, together with 3 known triterpenes ceanothenic acid (4), betulinic acid (5), and ceanothic acid (6), were isolated from the roots of Ziziphus mauritiana. Compounds 1–4 showed cytotoxicities with the IC₅₀ values ranging from 5.05 to 11.94 μg/ml, and compounds 1 and 3 showed an inhibitory effect on the growth of Staphylococcus aureus with the IC₅₀ values 2.17 and 12.79 μg/ml. A plausible biosynthetic pathway of compounds 1-3 was proposed.     

Is cytochrome P-450 transported from the endoplasmic reticulum to the Golgi apparatus in rat hepatocytes?

The Golgi apparatus mediates intracellular transport of not only secretory and lysosomal proteins but also membrane proteins. As a typical marker membrane protein for endoplasmic reticulum (ER) of rat hepatocytes, we have selected phenobarbital (PB)-inducible cytochrome P- 450 (P-450[PB]) and investigated whether P-450(PB) is transported to the Golgi apparatus or not by combining biochemical and quantitative ferritin immunoelectron microscopic techniques. We found that P-450(PB) was not detectable on the membrane of Golgi cisternae either when P-450 was maximally induced by phenobarbital treatment or when P-450 content in the microsomes rapidly decreased after cessation of the treatment. The P-450 detected biochemically in the Golgi subcellular fraction can be explained by the contamination of the microsomal vesicles derived from fragmented ER membranes to the Golgi fraction. We conclude that when the transfer vesicles are formed by budding on the transitional elements of ER, P-450 is completely excluded from such regions and is not transported to the Golgi apparatus, and only the membrane proteins destined for the Golgi apparatus, plasma membranes, or lysosomes are selectively collected and transported.     

Nitrogen enrichment modifies plant community structure via changes to plant–soil feedback

We tested the hypothesis that N enrichment modifies plant-soil feedback relationships, resulting in changes to plant community composition. This was done in a two-phase glasshouse experiment. In the first phase, we grew eight annual plant species in monoculture at two levels of N addition. Plants were harvested at senescence and the effect of each species on a range of soil properties was measured. In the second phase, the eight plant species were grown in multi-species mixtures in the eight soils conditioned by the species in the first phase, at both levels of N addition. At senescence, species performance was measured as aboveground biomass. We found that in the first phase, plant species identity strongly influenced several soil properties, including microbial and protist biomass, soil moisture content and the availability of several soil nutrients. Species effects on the soil were mostly independent of N addition and several were strongly correlated with plant biomass. In the second phase, both the performance of individual species and overall community structure were influenced by the interacting effects of the species identity of the previous soil occupant and the rate of N addition. This indicates that N enrichment modified plant-soil feedback. The performance of two species correlated with differences in soil N availability that were generated by the species formerly occupying the soil. However, negative feedback (poorer performance on the soil of conspecifics relative to that of heterospecifics) was only observed for one species. In conclusion, we provide evidence that N enrichment modifies plant-soil feedback relationships and that these modifications may affect plant community composition. Field testing and further investigations into which mechanisms dominate feedback are required before we fully understand how and when feedback processes determine plant community responses to N enrichment.     

三峡工程运行后对洞庭湖湿地的影响

长江三峡工程建成运行后,其下游第一个大型通江湖泊——洞庭湖的水文、水质以及湿地环境等均发生了很大变化。三峡工程已经开始影响到洞庭湖的泥沙淤积、水位波动、水质以及植被演替等。以三峡水库调度运行方案、河湖交互作用和洞庭湖湿地植被分布格局为基础,从长江三峡工程对洞庭湖水文、水质以及湿地植被演替等方面综述了三峡工程对洞庭湖湿地的综合影响。三峡工程减缓了长江输入洞庭湖泥沙的淤积速率,对短期内增加洞庭湖区调蓄空间、延长洞庭湖寿命有利。总体上减少了洞庭湖上游的来水量,改变了洞庭湖原来的水位/量变化规律。给洞庭湖水环境质量造成了直接或间接的影响,对其水质改变尚存一定争议,但至少在局部地区加剧了污染。水位变化和泥沙淤积趋缓协同改变了洞庭湖湿地原有植被演替方式,改以慢速方式演替,即群落演替的主要模式为:水生植物—虉草或苔草—芦苇—木本植物。展望了今后的研究趋势与方向,为三峡工程与洞庭湖关系的进一步研究提供参考。     

Caveolin-rich lipid rafts of the plasma membrane of mature cerebellar granule neurons are microcompartments for calcium/reactive oxygen and nitrogen species cross-talk signaling

In previous works, we have shown that L-type voltage-operated calcium channels, N-methyl-d-aspartate receptors (NMDAr), neuronal nitric oxide synthase (nNOS) and cytochrome b₅ reductase (Cb₅R) co-localize within the same lipid rafts-associated nanodomains in mature cerebellar granule neurons (CGN). In this work, we show that the calcium transport systems of the plasma membrane extruding calcium from the cytosol, plasma membrane calcium pumps (PMCA) and sodium–calcium exchangers (NCX), are also associated with these nanodomains. All these proteins were found to co-immunoprecipitate with caveolin-1 after treatment with 25 mM methyl-β-cyclodextrin, a lipid rafts solubilizing agent. However, the treatment of CGN with methyl-β-cyclodextrin largely attenuated the rise of cytosolic calcium induced by l-glutamate through NMDAr. Fluorescence energy transfer imaging revealed that all of them are present in sub-microdomains of a size smaller than 200 nm, with a peripheral distribution of the calcium extrusion systems PMCA and NCX. Fluorescence microscopy images analysis revealed high calcium dynamic sub-microcompartments near the plasma membrane in fura-2-loaded CGN at short times after addition of l-glutamate. In addition, the close proximity between sources of nitric oxide (nNOS) and superoxide anion (Cb₅R) suggests that these nanodomains are involved in the fast and efficient cross-talk between calcium and redox signaling in neurons.     

Excess iron-induced changes in the photosynthetic characteristics of sweet potato

Iron (Fe) is an essential nutrient for plant growth and development. In plant tissues, approximately 80% of Fe is found in photosynthetic cells. This study was carried out to determine the effect of different iron concentrations on the photosynthetic characteristics of sweet potato plants. The fluorescence transient of chlorophyll a (OJIP), chlorophyll index and gas exchange were measured in plants grown for seven days in Hoagland solution containing an iron concentration of 0.45, 0.90, 4.50 or 9.00 mM Fe (as Fe-EDTA). The initial and maximum fluorescence increased in the plants receiving 9.00 mM Fe. In the analysis of the fluorescence kinetic difference, L- and K-bands appeared in all of the treatments, but the amplitude was higher in plants receiving 4.50 or 9.00 mM Fe. In plants grown in 9.00 mM Fe, the parameters of the JIP-Test indicated a better efficiency in the capture, absorption and use of light energy, and although the chlorophyll index was higher, the net photosynthesis was lower. The overall data showed that sweet potato plants subjected to high iron concentrations may not exhibit the toxicity symptoms, but the light reactions of photosynthesis can be affect, which may result in a declining net assimilation rate.