Mandible bone resorption as determined from panoramic radiographs in edentulous male individuals aged 25–80 years

Routine panoramic radiographs of 173 healthy edentulous males, aged 25–80 years, were measured for estimated bone loss using the Wical and Swoope (1974) technique. Results using this simple technique were comparable to other studies using more sophisticated methods but did not require exposure to additional radiation. Mean ratios of height of mandible (indicative of mandibular bone loss) decreased both with age of subject and with time after extraction. Efforts should be made to determine the usefulness of such archival radiographic films for a variety of studies.     

人工种植星星草的光合蒸腾日变化

对松嫩碱化草地上人工种植生物一至三年星星草光合蒸腾特性的日变化进行了测定。二年生和三年生星草光合蒸腾的日变化规律比较一致,而一年生星星草不同于二者。一年生星星草光合速率和蒸腾速率的日变化幅度大于二年生和三年生星星划,其水分利用效率在一日中也均氏于二年生和三年生星星草。     

Fluorescence study on transmembrane Ca2+ gradient-mediated conformation changes of sarcoplasmic reticulum Ca2+-ATPase

The conformational states of Ca²⁺-ATPase in sarcoplasmic reticulum (SR) vesicles with or without a thousand-fold transmembrane Ca²⁺ gradient have been studied by fluorescence spectroscopy and fluorescence quenching. In consequence of the establishment of the transmembrane Ca²⁺ gradient, the steady-state fluorescence results revealed a reproducible 8% decrease in the intrinsic fluorescence while time-resolved fluorescence measurements showed that 13 tryptophan residues in SR · Ca²⁺-ATPase could be divided into three groups. The fluorescence lifetime of one of these groups increased from 5.5 ns to 5.95 ns in the presence of a Ca²⁺ gradient. Using KI and hypocrellin B (a photosensitive pigment obtained from a parasitic fungus, growing in Yunnan, China), the fluorescence quenching further indicated that the dynamic change of this tryptophan group, located at the protein-lipid interface, is a characteristic of transmembrane Ca²⁺ gradient-mediated conformational changes in SR · Ca²⁺-ATPase.Abbreviations SR sarcoplasmic reticulum - HB hypocrellin B - Trp tryptophan - DMSO dimethysulfoxide - Hepes N-2-hydroxyethyl piperazine-N-ethanesulfonic acad - SR(50005) SR vesicles with 1000-fold transmembrane Ca²⁺ gradient - SR(5050) SR vesicles without Ca²⁺ gradient - K_sv(app) apparent Stern-Volmer constant - K_svi Stern-Volmer constant of component i for dynamic quenching     

Overwintering waterfowl on Swiss lakes: how are abundance and species richness influenced by trophic status and lake morphology?

During the period 1980–1990 long-term physical, chemical and ecological studies were carried out, to study the changes induced by the building of a storm-surge barrier in the mouth of the Oosterschelde estuary and two large auxiliary compartment dams in the rear ends of the estuary. The storm-surge barrier was constructed in the mouth of Oosterschelde estuary (SW Netherlands) during the period 1979–1986. The barrier allows the tides to enter the estuary freely, and, on the other hand, the barrier guarantees safety for the human population and their properties when a stormflood threatens the area.Oosterschelde estuary is isolated from the river input, the rear ends of the ecosystem were separated from the estuary by sea-walls and the strongly decreased tidal exchange with the North Sea induced sheltered circumstances. The Oosterschelde changed from a turbid estuary into a tidal bay, and yet primary production responses appear to be robust and resilient, and the biological communities showed only quantitative shifts from the dominance of specific species assemblages to other assemblages. In many cases predicted changes in the structure of the biological communities could not be verified owing to the large natural variability mainly caused by physical factors (e.g. temperature).     

Predation risk of typical ovoid and ‘winged’ morphs of Euplotes (Protozoa,Ciliophora)

Freshwater species of the genus Euplotes (Protozoa, Ciliophora) change their morphology in the presence of some of their predators. The ciliates develop extended lateral wings as well as dorsal and ventral projections which make engulfment by predators more difficult. In a series of laboratory experiments ingestion rates of four protozoan predators, the ciliates Lembadion bullinum, Dileptus anser, Stylonychia mytilus and Urostyla grandis, and one metazoan predator, the turbellarian Stenostomum sphagnetorum, on three species of Euplotes (E. octocarinatus, E. patella and E. aediculatus) were determined. It was calculated that the probability of rejection by a predator changed from 1:1 for ovoid morphs of Euplotes to about 2:1–20:1 for winged morphs of Euplotes, dependent on the prey and predator species that were combined. The nutritional condition of the prey also had some influence. In mixed-species cultures of prey and predators, transformed cells of E. octocarinatus survived for several months.     

Germinal potentialities during sexual state changes in a protandric hermaphrodite, Amphipnon frenatus (Teleostei, Pomacentridae)

In Amphiprion frenatus , a protandric hermaphrodite, male sex inversion is characterized by a decrease of spermatogenic activity in the ovotestis followed by a degeneration of male gevm cells and an increase of oogenic activity. Among female germ cells, undifferentiated primordial germ cells (PGCs) were identified; their participation in building up the ovary is suggested. In addition, the unusual association of juveniles with a single adull member or juvenile groupings lacking the presence of a monogamous pair, induced in juveniles the anticipated sex differentiations (in either male or female orientation) in which not only spermatogonia and oogonia but also PGCs are involved.     

Seasonal Changes in the Cambium of Trees. I. Sucrose Content in Thuja occidentalis

Cambium samples of Thuja occidentalis L. were collected at five different times, covering spring reactivation and early and late resting period, and used for sucrose determinations. Fragments of the different cell types - xylem ray, cambial initials, sieve-elements including phloem parenchyma cells, phloem ray - were dissected from freeze-dried radial sections and analyzed individually. Results show large differences in sucrose concentrations in the different cell types of the cambial layer. In addition, each cell type also shows seasonal fluctuations in sucrose content, whose amplitudes and patterns of variation appear specific for the particular cell type.     

鲁西、南平原农作区小型兽类群落组成及季节变化

作者于１９９２年３月至１９９３年３月在鲁西和鲁南平原农作区对小型兽类群落进行了调查,其群落组成以啮齿动物为主,可划为６类群落：河滩高他的黑线仓鼠群落,河滩高地人房附近的黑线仓鼠＋小家鼠群落,缓平坡地的黑线仓鼠＋黑线姬鼠群落,浅平洼地的黑线姬鼠＋黑线仓鼠＋大仓鼠群落,洼地农作区的黑线仓鼠＋黑线姬鼠＋大仓鼠群落和洼地蔬菜种植区的黑线姬鼠＋黑线仓鼠群落。群落的季节变化明显,１１月至次年２月以黑线仓鼠为优势种,其它月份则黑线姬鼠或大仓鼠较多;人房附近农作区小家鼠也有季节性迁移现象。     

A multidisciplinary approach to understanding the recent and historical occurrence of the freshwater plant, Littorella uniflora

1. The vulnerability of softwater, oligotrophic lakes to eutrophication has caused the disappearance of many, if not most, of the unique isoetid plant communities. We tested whether the presence or disappearance of the isoetid Littorella uniflora (L.) could be predicted from environmental parameters, soil types and land use in the catchment area, and atmospheric nitrogen deposition. 2. We found that the topographic catchment area of a lake was an irrelevant unit to study effects of soil type and land use. Instead, using a GIS‐generated buffer zone around the lakes it proved feasible to classify 472 lakes into historical (if L. uniflora had disappeared) or recent (if L. uniflora was still present) Littorella lakes, based on soil type and land use. Our analysis showed that aeolian sand deposits and heath in the buffer zone favoured the presence of L. uniflora, whereas moraine clay and agriculture were strongly linked to the disappearance of L. uniflora. 3. However, in order to understand fully the presence or disappearance of L. uniflora, environmental data were needed in addition to soil types, land use and nitrogen deposition, and the use of discriminant analysis allowed us to classify 96% of the investigated lakes correctly into recent or historical sites. Alkalinity, total phosphorus, total nitrogen, aeolian sand deposits and heath were the most important parameters explaining the presence or disappearance of L. uniflora. Our analysis also indicated that eutrophication, rather than acidification, has likely caused the disappearance of L. uniflora from 218 of the 472 lakes investigated. 4. Our findings have widespread implications for the conservation or restoration of isoetid habitats and we recommend applying a wide buffer zone around lakes, with restrictions on farming and traditional forestry activities. In addition, our buffering concept may prove a useful tool for aquatic ecologists to investigate relationships between catchment features and organisms (plants, insects and amphibians) with aquatic as well as terrestrial life forms.     

Assessment of unanticipated unintended effects of genetically modified plants on non‐target organisms: a controversy worthy of pursuit?

A typical risk hypothesis addressed during the environmental risk assessment (ERA) of genetically modified (GM) plants for cultivation is that the novel traits intentionally introduced into GM plants do not adversely affect non‐target organisms (NTOs). However, genetic modification may potentially also lead to unintended changes in the GM plant which could raise safety concerns. Therefore, the European Food Safety Authority (EFSA) advocates the characterization of ecological interactions between the GM plant and representative NTOs as part of the ERA of GM plants for cultivation in the European Union. Yet, this requirement is not unanimously accepted by stakeholders. Here, we present EFSA's approach to assess potential adverse effects on NTOs and summarize some of the stakeholders' views, mostly opposing EFSA's position on scientific grounds.