The Cytotoxicity of Some Organic Solvents on Isolated Hepatocytes in Monolayer Culture

The cytotoxic effects of volatile and water-insoluble organic solvents (ethylbenzene, tetrachloroethylene, n-hexane) were tested on isolated hepatocytes in monolayer culture by using the 3-(4,5 dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) reduction assay. All of the tested compounds inhibited metabolic activity of hepatocytes and this effect depended on the concentration of solvents in the incubatory medium. The presence of fetal calf serum in the medium did not change the cytotoxicity of xenobiotics. IC₅₀ values calculated on the basis of the MTT assay indicated that ethylbenzene was more cytotoxic than tetrachloroethylene and n-hexane. Using hepatocyte monolayer culture and the MTT assay to assess cytotoxicity of organic solvents causes many technical problems. It seems that it cannot be used as a rapid, cheap, and credible method.     

Test Method for Retractable Type Fall Arresters Designed for Horizontal Use

Retractable type fall arresters are designed to protect against falls from a height of people who need freedom of vertical movement. The practice of fall protection shows that the devices are also used to protect people who work on flat roofs. This application creates quite different operating conditions for the devices. In some situations those conditions can be dangerous for users. The article presents a theoretical analysis of phenomena occurring during a fall arrest with retractable type fall arresters arranged horizontally. The analysis was verified with laboratory tests. The article presents a proposal for the construction of a test stand and a test method for estimating retractable type fall arresters intended for horizontal use.     

Locking of Retractable Type Fall Arresters—Test Method and Stand

Retractable type fall arresters are very effective personal equipment protecting against falls from a height. These devices are used under different atmospheric conditions and in the presence of various types of industrial pollution. For this reason appropriate locking after conditioning simulating extreme conditions of a worksite is one of the essential characteristics of retractable type fall arresters. This article presents the requirements for locking of the devices. A previously used locking test method and its disadvantages are discussed. The article suggests an improved test method and test equipment. Measurement of the test mass acceleration is the most important improvement introduced into the test method. The article shows laboratory tests used to verify the method, which turned out to be a valuable source of information concerning the performance of retractable type fall arresters.     

The complexity of nectar: secretion and resorption dynamically regulate nectar features

In this paper, we review the phenomenon of nectar resorption, focusing on its physiological and ecological meaning. Nectar resorption is a phenomenon that has long been known but was rarely reported until the1990s. It has more recently been demonstrated in several species by various direct and indirect methodologies. It has generally been demonstrated in senescent flowers as a phenomenon separate in time from, and independent of, nectar secretion. The significance of this type of resorption is generally recognized as a resource-recovery strategy, recycling at least some materials invested in nectar production. Nevertheless, nectar resorption can occur concomitantly with nectar secretion. Nectar production is therefore best considered as a unified process comprising nectar secretion and resorption. The modulation of these two opposite phases allows nectar concentration to be maintained in a range suitable for pollinators (nectar homeostasis). The mechanism of nectar resorption at the cell level has received little attention, and its molecular basis can only be hypothesized on the basis of recent studies concerning sugar sensing.     

Mechanical,Thermal and Microstructural Characteristic of 3D Printed Polylactide Composites with Natural Fibers: Wood,Bamboo and Cork

Journal of Polymers and the Environment - In the study, polylactide-based (PLA) composites modified with natural particles (wood, bamboo, and cork) and with different levels of infilling (100%,...     

Comparative Assessment of Public Opinion on the Landscape Quality of Two Biosphere Reserves in Europe

The European Landscape Convention (2000) obligates European Union countries to identify and implement landscape quality objectives (LQOs) understood as the specification of public expectations and preferences concerning the landscape of a given area, expressed by competent public authorities. The convention emphasizes the important role of local community representatives in this field. In Poland, the implementation of the LQO concept was first undertaken in two regions with radically different landscape characteristics: (1) the West Polesie Biosphere Reserve and (2) the selected protected areas of the Roztocze–Solska Forest, nominated to the rank of a biosphere reserve. The first stage of the presented study was the recognition of public opinion on the quality of key features of landscape, based on a questionnaire (n = 470). The primary objective of the study was to provide an answer to the following questions: (1) Whether similar social expectations regarding landscape quality exist in spite of radically different landscape characteristics of the regions investigated (landscape quality is understood as spatial arrangement, scenic beauty, and lack of environmental pollution); (2) which landscape features are considered to be most preservation worthy by the representatives of both local communities; and (3) What processes or development impacts pose the greatest threat to the landscape quality of both regions according to the public opinion? The conducted comparative assessment revealed that it is possible to define a set of features fundamental to the quality of both areas and that representatives of local communities pointed out the same threats to the natural and cultural values of both regions investigated.     

Is body size of the water frog Rana esculenta complex responding to climate change?

Recent studies on climate responses in ectothermic (cold-blooded) vertebrates have been few in number and focussed on phenology rather than morphology. According to Bergmann’s rule, endothermic (warm-blooded) vertebrates from cooler climates tend to be larger than congeners from warmer regions. Although amphibians are ectothermic vertebrates, weather and climatic conditions may also impact on their morphology, and thereby affect their survival rates and population dynamics. In this paper, we show, in a unique long-term study during the period 1963–2003 in an agricultural landscape in western Poland, that the body length of two water frog parental species (males of both Rana ridibunda and R. lessonae) increased significantly. However, their hybridogenetic hybrid R. esculenta did not show similar changes. A significant relationship with a large-scale climatic factor, the winter North Atlantic Oscillation index, was found positive for R. ridibunda males and R. lessonae females, and negative for R. esculenta females. Our findings, the first for amphibians, are consistent with other studies reporting that recent climate change has affected the morphology of animals. However, we also show that changes in amphibian phenotype linked to climate may vary independently between (even very similar) species.     

Polybrominated diphenyl ethers (PBDEs) in mussels from selected French coastal sites: 1981-2003

The present study focused on the retrospective analysis of PBDEs in archived blue mussel (Mytilus edulis or Mytilus galloprovincialis) samples collected over the past 22 years (1981-2003) from coastal areas of France. We have found that PBDE levels in mussels from the English Channel increased markedly from 1981 to 1991-1995, doubling approximately every 5-6 years followed by a levelling off and a possible beginning of a decrease. The rate of the decline of hexa- and hepta-BDE congeners was more rapid than the decline of tetra- and penta-BDEs in these mussel samples. The difference in the course of time of lower and higher brominated PBDE concentrations suggests that the congener profile in the mussel samples changes over time. The increase in PBDE concentrations in the mussel samples contrasts with a concomitant constant decrease of chlorobiphenyls (CBs) in the same set of samples. However, pulse inputs of both groups of organohalogen compounds were determined for the mussel samples collected at the mouth of the Seine estuary and were probably related to riverine inundations and a flushing out of the deposited sediments from the internal estuary into the bay of the River Seine, as well as considerable dredging activities taking place during same years. In France, the highest PBDE concentrations were determined in the mussels from the English Channel, more precisely in the bay of the Seine, and the regional differences in PBDE levels were mainly connected to the difference in anthropogenic urban and industrial environmental pressures. Published data comparing PBDE levels in mussels have shown significant differences in concentrations between North/South America and Europe. This observation further confirms that the PBDE levels in the North American environment are higher than in Europe. However, the data used for this comparison of mussel contamination by PBDEs is still relatively sparse.