Subsurface tubular system in the outer sensory cells of the rat cochlea

Summary The system of subsurface tubules in the outer sensory cells of the rat cochlea consists of tubules lying immediately beneath the cell membrane. The tubules extend from the region below the cuticular plate, follow without interruption along the contours of the cell membrane, and terminate as a complicated, branched system under the nucleus. Several mitochondria are found on the cytoplasmic side of the tubules. Microtubules are observed in the space between the subsurface tubules and the mitochondria, in contact with the membranes of the subsurface system and, rarely, in contact with small, stalked vesicles.Current theories on the role of the subsurface system are discussed and a new one, considering possible involvement of the system in transport of the synaptic transmitter, is proposed.     

phorest: a web‐based tool for comparative analyses of expressed sequence tag data

Comparative analysis of expressed sequence tags is becoming an important tool in molecular ecology for comparing gene expression in organisms grown in certain environments. Additionally, expressed sequence tag database information can be used for the construction of DNA microarrays and for the detection of single nucleotide polymorphisms. For such applications, we present phorest , a web‐based tool for managing, analysing and comparing various collections of expressed sequence tags. It is written in PHP (PHP: Hypertext Preprocessor) and runs on UNIX, Microsoft Windows and Macintosh (Mac OS X) platforms.     

Holocene tree‐line fluctuations and climate in central troms,Northern Norway

Based mainly on pollen influx data, an attempt is made at reconstructing Holocene tree‐line fluctuations and palaeotemperatures in central Troms, North Norway. Both past and present‐day (Tauber trap) pollen influx data suggest that influx rates exceeding 250–300 pollen/cm²/year for each of the major arboreal taxa (Betula pubescens and Pinus sylvestris) are only found at sites with corresponding forest types in the immediate surroundings. High influx rates, raised tree‐lines and favourable climatic periods are recorded at 7500–4500 and 3000–2600 B.P. Betula and Pinus woodlands may have reached more than 200 m above their present altitude limits, suggesting a July mean temperature 2°C higher than at present during the Holocene optimum.     

The photoprotective role of humus-DOC for Selenastrum and Daphnia

Cell numbers and fluorescence of the green algae Selenastrum capricornutuum and survival of Daphnia magna exposed to simulated sun-light was assessed along a gradient of DOC (0, 1, 5 10 and 50 mg C l^–1). When exposed to UV-doses and spectral distribution (295–750 nm) closely resembling surface solar radiation during mid summer, Selenastrum showed major losses of cell fluorescence. In the absence of DOC, fluorescence was severely depressed, with successively decreasing effects with increased DOC. Surviving cells also required an extensive recovery period (10–12 d) for regrowth after exposure, while an almost immediate recovery was observed at concentrations above 1 mg DOC l^–1. For Daphnia, survival was reduced to less than 10% after 4 h exposure, and almost zero after 8 h exposure in the absence of humus DOC, while no effects were observed in treatments with 10 and 50 mg C l^–1. Selenastrum and Daphnia that were not directly irradiated, but exposed to UV-irradiated water with the same concentrations of DOC did not reveal negative effects. This indicates negligible indirect effects mediated by long-lived free radicals or other toxic compounds. Irradiation of Daphnia under increased oxygen concentration (200% saturation) did not indicate acute effects, suggesting that effects of ambient radicals and oxidants would be of minor importance relative to intracellular photoproducts.     

Investigation of the effect of clinically relevant interferents on glucose monitoring using near-infrared spectroscopy

Near infrared spectroscopy (NIR) is a promising technique for continuous blood glucose monitoring for diabetic patients. Four interferents, at physiological concentrations, were introduced to study how the glucose predictions varied with a standard multivariate calibration model. Lactate and ethanol were found to interfere strongly with the glucose predictions unless they were included in the calibration models. Lactate was mistaken for glucose and gave erroneously high glucose predictions, with a dose response of 0.46 mM/mM. The presence of ethanol resulted in too low glucose predictions, with a dose response of −0.43 mM/mM. Acetaminophen, a known interferent in the glucose monitoring devices used for diabetes management today, was not found to be an interferent in NIR spectroscopy, nor was caffeine. Thus, interferents that may appear in high concentrations, such as ethanol and lactate, must be included in the calibration or model building of future NIR-based glucose measurement devices for diabetes monitoring.     

Vegetation history of Molinia heaths in Tysvær, Rogaland, western Norway

Investigations were undertaken in an area of western Norway, approximately 30 km from the coast. The area is dominated by Molinia caerulea heaths on gentle slopes of silt-dominated glacial deposits. Pollen analyses were made on 3 soil profiles. Each profile could be divided into 2 local pollen assemblage zones (PAZs) corresponding with a change from dry to damp soils. From a comparison of the fossil pollen assemblages with pollen assemblages from surface samples collected from present-day Molinia heaths, and a radiocarbon date, the Molinia heaths can be shown to have originated about 1900 years BP. The persistence of the Molinia heaths is probably related to the high water-holding capacity of the sediments and the influence of human activity.     

The influence of turbidity on growth and survival of fish larvae: a numerical analysis

Growth and survival through the early larval phase probably limit the production potential of many commercially important fish stocks. Attempts to increase the production of these stocks by restocking of juveniles have generally failed. Here, we analyse how enhanced concentrations of phytoplankton and zooplankton affect the survival of fish larvae during their early life stages. The analysis is developed for larvae feeding on copepod eggs and nauplii, with fish and invertebrates as major predators. A model of feeding and growth of fish larvae is applied to assess the benefit of enhanced phytoplankton and zooplankton abundance. The analysis shows that the shading effect of higher phytoplankton concentration may reduce predation rates on fish larvae substantially. This `top-down' effect may be more important for the cohort survivorship than the `bottom-up' mechanism in situations when larval food is sufficiently abundant. However, while increased algal biomass will improve recruitment at high zooplankton concentration, it may also reduce recruitment at low zooplankton concentrations and shallow mixing depths. Both the larvae and their vertebrate predators are dependent on light to detect their prey, and the longer reactive distance of the predators make them more susceptible than the larvae to reduced light levels and increased turbidity. We discuss the implications of reduced predation and increased zooplankton abundance on recruitment and production of fish larvae, and point at environmental conditions where changing algal biomass is likely to affect recruitment success.