Interpretation of lake quality from contemporary diatom assemblages

Diatom assemblages from the topmost sediment of 49 lakes were ordinated by means of a program for detrended correspondence analysis and reciprocal averaging (Decorana). Five lake groups were separated, each having more or less characteristic diatom assemblages and water quality. Shifts from one group to another caused by factors such as acidification, artificial drainage, diffuse nutrient loading and sewage are discussed.     

Quantitation of junctional and extrajunctional acetylcholine receptors by electron microscope autoradiography after (125)I-α-bungarotoxin binding at mouse neuromuscular junctions

The distribution and quantitation of 125I-alpha-bungarotoxin (alpha-BTX) binding sites and thus acetylcholine receptor (AChR) were determined in mouse sternomastoid muscle by electron microscope autoradiography. We found that a valid criterion for receptor saturation at the neuromuscular junction was the complete elimination of neurally evoked tetanic muscle contractions, since, when such a criterion was used for the endpoint of toxin incubation, alpha-BTX was bound to approximately 90% of total available endplate sites. When, without implying localization, the presynaptic axonal membrane was used as a convenient reference structure, the concentration of alpha-BTX relative to this membrane was determined to be 46,000 +/- 27% sites/mum2.     

Palaeolimnological study of an environmental monitoring area,or, are there pristine lakes in Finland?

A palaeolimnological study of Lake Iso-Hietajärvi in Patvinsuo National Park, Lieksa, East Finland was conducted. The drainage area of the lake is one of four Integrated Monitoring areas established in Finland. Lead-210 dating reveals a period of increased sedimentation in the lake from 1920 to 1950. Increased atmospheric burden of several heavy metals in the order Pb > Cu> Zn > Ti = Al > Cr = Ni = V is recorded. The first to expand during the 19th century is Pb, whilst V increases after 1950. Sedimentary chlorophyll derivatives expand in the early part of the 20th century. Assemblages of diatoms and Cladocera were also changed somewhat during this time, but water quality seems not to have varied much: e.g. the diatom-inferred pH has remained in the range 6.4–6.8 (with a slight decrease) throughout the period of study.     

Diatom, chrysophyte and protozoan distributions along a latitudinal transect in Fennoscandia

Diatoms, chrysophyte scales and cysts, and the siliceous plates of thecoamoebae were studied from the surface sediments of 20 freshwater habitats in Fennoscandia The study sites are distributed along a latitudinal transect extending from southern Finland to northern Norway, spanning boreal forest through arctic tundra vegetational zones Diatom assemblages were usually dominated by acidophilic, periphytic members of the genera Achnanthe, Fragilaria and Navicula Marked shifts in diatom assemblage composition were recorded along the latitudinal transect, whereas scaled chrysophytes were rare in all study sites Meanwhile, siliceous protozoa were common, but did not exhibit any noticeable trends in assemblage composition with changing latitude A comparison of the Fennoscandian diatom assemblages with those recorded from freshwater sites near Yellowknife (central Northwest Territories, Canada) revealed similar trends in diatom assemblage composition with changing ecoclimatic zones in both regions Moreover, canonical correspondence analysis showed that diatom assemblages in cold, dilute tundra sites were effectively separated from sites with forested catchments from both the Fennoscandian and Canadian transects The general similarity between the two regions suggests that autecological data and the resulting environmental transfer functions based on diatom assemblages may eventually be joined from North American and European regions     

T-cell activation without proliferation in juvenile idiopathic arthritis

A study was done to determine if the differentiation and activation phenotype of T cells in synovial fluid (SF) from patients with juvenile idiopathic arthritis (JIA) is associated with T-cell proliferation in situ. Mononuclear cells were isolated from 44 paired samples of peripheral blood and SF. Differentiation and activation markers were determined on CD4 and CD8 T cells by flow cytometry. Cell-cycle analysis was performed by propidium iodide staining, and surface-marker expression was also assessed after culture of the T cells under conditions similar to those found in the synovial compartment. The majority of the T cells in the SF were CD45RO⁺CD45RB^dull. There was greater expression of the activation markers CD69, HLA-DR, CD25 and CD71 on T cells from SF than on those from peripheral blood. Actively dividing cells accounted for less than 1% of the total T-cell population in SF. The presence or absence of IL-16 in T-cell cultures with SF or in a hypoxic environment did not affect the expression of markers of T-cell activation. T cells from the SF of patients with JIA were highly differentiated and expressed early and late markers of activation with little evidence of in situ proliferation. This observation refines and extends previous reports of the SF T-cell phenotype in JIA and may have important implications for our understanding of chronic inflammation.     

Needle ontogeny of mature Scots pines under enhanced UV-B radiation

The aim of this work was to test our hypothesis that pine needles protect themselves against UV-B radiation via anatomical changes in the epidermal layer. This could lead to needle growth reductions if large quantities of assimilates are allocated for the epidermal protective mechanisms at the expense of photosynthetic area. Effects of enhanced UV-B radiation on the needle ontogeny of mature Scots pines (Pinus sylvestris L.) were studied during the second season of a field experiment. Depending on the season and the time of the year (1996-1997), the enhanced UV-B irradiance varied from 0.92 to 5.09 kJ m^-2 day^-1 UV-B_BE compared to 0.54-2.44 kJ m^-2 day^-1 UV-B_BE of ambient radiation. It was found that UV-B treatment accelerated the early development of needles. In 6-day-old enhanced UV-B-treated needles, mesophyll and hypodermic cells were fully differentiated, whereas in ambient-treated needles, no lobate mesophyll cells were seen and hypodermic cells had not yet developed. In fully grown needles, no accelerated differentiation was seen, except that the epidermal cross-sectional area was smaller. The continuation of the experiment will show if such a significant difference only occurs irregularly and incidentally or if it is of consistent significance for needles.     

Prolonged increase in dietary phosphate intake alters bone mineralization in adult male rats

Excessive intake of dietary phosphate without the company of calcium causes serum parathyroid hormone (s-PTH) concentration to rise. We investigated the effect of a modest but prolonged increase in dietary intake of inorganic phosphate on the bone quantitative factors of mature male rats. Twenty Wistar rats were divided into two groups and fed a high-phosphate diet (1.2% phosphate) or a control diet (0.6% phosphate) for 8 weeks. In the beginning and at the end of the study period, femur and lumbar bone mineral density (BMD), bone mineral content and area were measured using DXA, s-PTH was analyzed from the blood sample, and after sacrifice, right femur was cut loose and processed into paraffin cuts. Bone diameter, inner diameter and cortical width was measured from the hematoxylin- and eosin-dyed femur cuts. Tibias were degraded and calcium and phosphate content was analyzed by inductively coupled plasma-mass spectrometer. Femoral BMD increased significantly more in the control group than in the phosphate group (P=.005). Lumbar BMD values decreased in both groups, and the fall was greater in the control group (P=.007). The phosphate group had significantly higher s-PTH values (P=.0135). Femoral histomorphometric values or tibial mineral contents did not differ between groups. In conclusion, increase in dietary phosphate intake caused s-PTH to rise and hindered mineral deposition into cortical bone, leading to lower BMD. The effect on trabecular bone was opposing as mineral loss was less in the lumbar spine of phosphate group animals. These results are in concurrence with the data stating that skeletal response to PTH is complex and site dependent.     

Cost of trichome production and resistance to a specialist insect herbivore in <Emphasis Type="Italic">Arabidopsis lyrata</Emphasis>

Theory predicts that trade-offs between resistance to herbivory and other traits positively affecting fitness can maintain genetic variation in resistance within plant populations. In the perennial herb Arabidopsis lyrata, trichome production is a resistance trait that exhibits both qualitative and quantitative variation. Using a paternal half-sib design, we conducted two greenhouse experiments to ask whether trichomes confer resistance to oviposition and leaf herbivory by the specialist moth Plutella xylostella, and to examine potential genetic constraints on evolution of increased resistance and trichome density. In addition, we examined whether trichome production is induced by insect herbivory. We found strong positive genetic and phenotypic correlations between leaf trichome density and resistance to leaf herbivory, demonstrating that the production of leaf trichomes increases resistance to leaf damage by P. xylostella. Also resistance to oviposition tended to increase with increasing leaf trichome density, but genetic and phenotypic correlations were not statistically significant. Trichome density and resistance to leaf herbivory were negatively correlated genetically with plant size in the absence of herbivores, but not in the presence of herbivores. There was no evidence of increased trichome production after leaf damage by P. xylostella. The results suggest that trichome production and resistance to leaf herbivory are associated with a cost and that the direction of selection on resistance and trichome density depends on the intensity of herbivory.     

Long-term effects of tripeptide Ile-Pro-Pro on osteoblast differentiation in vitro

Bone mineralization is a result of the function of bone-forming osteoblasts. Osteoblast differentiation from their precursors is a carefully controlled process that is affected by many signaling molecules. Protein-rich food-derived bioactive peptides are reported to express a variety of functions in vivo. We studied the long-term in vitro effect of bioactive tripeptide Ile-Pro-Pro (IPP) on osteoblasts differentiated from human mesenchymal stem cells. Osteoblast bone alkaline phosphatase activity (bALP), bone-forming capacity and gene expression were investigated. Treatment with 50 microM IPP had no effect on bALP activity, but osteoblast mineralization was increased. Gene expression of beta-catenin, Cbfa1/Runx2, PTHrP, CREB-5, osteoglycin, osteocalcin, caspase-8, osteoprotegerin (OPG) and RANKL was analyzed by quantitative real-time PCR on Days 13, 17 and 20 of culture. The results indicate that IPP increased mineral formation due to enhanced cell survival and matrix formation. In addition, IPP reduced the RANKL/OPG ratio. Bioactive peptides, such as IPP, could be one method by which a protein-rich diet promotes bone integrity.