Classification and ordination of plant communities along an altitudinal gradient on the Presidential Range,New Hampshire,USA

An analysis of vegetation along an altitudinal gradient on the Presidential Range, New Hampshire, USA, using the Braun–Blanquet approach followed by multivariate data analysis is presented. Twelve main plant communities have been distinguished. Floristic information is presented in twelve tables and one appendix. The relationships of the communities to complex environmental gradients are analyzed using Correspondence Analysis. Floristic composition and community structure are controlled primarily by the altitudinal gradient (temperature, precipitation), and by mesotopographic conditions (snow accumulation, exposure and cryoturbation, slope position, and soil moisture).     

Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin

doi:10.1111/j.1741‐2358.2009.00333.x
Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth.     

Immunocytochemistry of contractile and cytoskeletal proteins in smooth muscle: Lowicryl,LR White,and polyvinylalcohol compared

Summary Three embedding media have been compared with respect to post-embedding immunolabeling of contractile and cytoskeletal antigens in aldehyde-fixed smooth muscle tissue: the methacrylate derivates lowicryl K4M (cured at –35 or 60°C) and LR White (cured at 0 or 60°C) and the water soluble resin, polyvinylalcohol (dried at 60°C). Measurements of intensity of labeling of ultrathin sections in the fluorescence microscope showed that five antigens (actin, myosin light chain, tropomyosin, filamin and vinculin) reacted more or less equally with their respective antibodies in all the embedding media, including those cured at 60°C. One antibody (anti-light meromyosin) reacted well only with polyvinylalcohol-embedded tissue. In contrast to the relative invariance of antibody reactivity between media clear differences in the preservation of ultrastructural integrity were observed. Embedding in polyvinylalcohol (dried at 60°C) and in Lowicryl (cured at –35°C) resulted in superior preservation as compared to Lowicryl or LR White cured at 60°C. Examples of uitrastructural immunocytochemistry with the antibodies against filamin and myosin light chain, using the immunogold staining procedure are presented: the sites of localization by these antibodies were the same with all the media tried. The relative merits of the different methods are discussed.Abbreviations EGTA Ethyleneglycol-bis(-amino ethyl ether)N,N,N,N-tetra acetic acid - PIPES 1,4-Piperazinediethanesulfonic acid - LR London Resin     

The growth and asymmetry of neighbouring plants of white clover (Trifolium repens L.)

Summary Transplants of white clover (Trifolium repens L.) were grown isolated from each other and in pairs placed at different distances apart. The paired plants developed asymmetrically and at the interface between paired clones both the density of nodes and of stolons appeared to reach ceiling values that were of the same order as those achieved in isolated clones. It is argued that the growth of plants of T. repens is controlled by the local conditions experienced by the plant parts and not by integrated growth of the whole. Transplants of three different genotypes of T. repens, which differed in growth form, were grown as neighbouring pairs and the calculated asymmetry of the plants was used to compare their mutual aggressivenes. The more compact (phalangeal) genotypes induced greater asymmetry in their neighbours than the more diffuse forms.     

Domains of neuronal heparan sulphate proteoglycans involved in neurite growth on laminin

Summary A single neuronal cell assay of neurite growth was utilized to determine types and domains of neuronal proteoglycans involved in neurite growth on laminin. Perturbations of biosynthesis and processing, enzymatic digestion with specific lyases, and competition with glycosaminoglycan side chains produced complementary data consistent with a molecular model implicating glycosaminoglycan (GAG) residues of heparan sulphate proteoglycans (HSPGs) in neurite growth. The observations suggest that HSPGs promote neurite growth on laminin by bridging between binding domains for HSPGs on laminin and on the neuronal cell surface, and that the bridge is tethered at both ends by noncovalent interactions between the binding domains and GAG side chains. Sulphation of the GAGs of HSPGs appears to be critical to the tethering and/or neurite growth-promoting activity of neuronal HSPGs.     

Primary production and respiration of the phytoplankton in the Blue and White Niles at Khartoum

Phytoplankton production and respiration in the Blue Nile and White Nile at Khartoum were measured during the period November 1969–January 1971 using the light and dark bottle technique. Maximum rates of production coincided with periods of maximum phytoplankton densities. In the Blue Nile gross production varied between 0.00 gCm^–3d^–1 during the flood season and 2.19 gCm^–3d^–1 (0.49 mgO₂l^–1h^–1) during November 1969. In the White Nile the range was from 0.41 gCm^–3d^–1 (0.09 MgO₂l^–1h^–1) in May to 3.74 gCm^–3d^–1 (0.83 MgO₂l^–1h^–1) in November. The maximum rates of respiration in the Blue Nile and White Nile were 0.10 and 0.63 MgO₂l^–1h^–1 respectively. The ratios net:gross production were generally higher in the White Nile than in the Blue Nile.     

Seasonal abundance,breeding and sex-structure of populations of Tilapia nilotica (L.) and Labeo niloticus (F.) in the Jebel Aulia Dam area of the White Nile

Seasonal abundance, maturation and sex-structure were studied in populations of T. nilotica and L. niloticus in the Jebel Aulia reservoir and in the White Nile below the dam. L. niloticus showed a single annual breeding cycle from mid-July to December and was most abundant in October in the lake, and in early November in the river. T. nilotica showed two distinct annual seasons of abundance: summer (April to June) and autumn (November to October). Spawning activity was highest in summer (April to June) and autumn (late July to September). The sex-ratio varied inversely with age (size); males were predominant in populations of older fish, perhaps because of their greater endurance to adverse conditions as evidenced by their better survival in hypoxic water.