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).     

Frequent mowing is better than grazing for the conservation value of lowland tussock grasssland at Pontville,Tasmania

Abstract The effects of an unusual high frequency mowing regime, which involved the removal of slash, were compared to moderate grazing through the method of paired quadrats across a fenceline, which was orthogonal to a weak environmental gradient. The mown plots proved superior in their conservation characteristics to the moderately grazed plots. The mowing regime produced greater cover of rare or threatened species, greater native cover and lesser exotic grass cover. It thus presents an opportunity for maintaining or improving the condition of previously grazed remnants in reserves without resorting to the use of stock or fire for biomass reduction.     

Big Moose Basin: simulation of response to acidic deposition

The ILWAS model has been enhanced for application to multiple-lake hydrologic basins. This version of the model has been applied to the Big Moose basin, which includes Big Moose Lake and its tributary streams, lakes, and watersheds. The basin, as defined, includes an area of 96 km², with over 20 lakes and ponds, and 70 km of streams. Hydrologic and chemical calibrations have been made using data from seven sampling stations. When total atmospheric sulfur loading to the basin is halved, the model predicts, after four years of simulation, a decreasing sulfate concentration and to a lesser extent a rising alkalinity at Big Moose Lake outlet. At the end of four years, the results show an increase in pH of 0.1 to 0.5 pH units depending upon season.     

Neurofilament-like and glial fibrillary acidic protein-like immunoreactivities in rat and guinea-pig sympathetic ganglia in situ and after perturbation

Summary The presence of neurofilament (NF)-like and glial fibrillary acidic protein (GFAP)-like immunoreactivities was studied in sympathetic ganglia of adult rats and guinea pigs during normal conditions and after perturbation. In the superior cervical ganglion (SCG) of normal rats, many ganglion cells and nerve fibers show NF immunoreactivity. Some of these nerve fibers disappear after preganglionic decentralization of SCG; this indicates the presence of a mixture of preand postganglionic NF-positive nerves in the ganglion. Cuts in both preand postganglionic nerves result in a marked increase in GFAP immunoreactivity in SCG, whereas NF immunoreactivity increases in nerve cell bodies after preganglionic cuts. Only a few ganglion cells show NF immunoreactivity in the normal SCG of guinea pig. All intraganglionic NF-positive nerves are of preganglionic origin; decentralization abolishes NF immunoreactivity in these nerve fibers. The inferior mesenteric ganglion, the hypogastric nerves and colonic nerves in guinea pigs contain large numbers of strongly NF-immunoreactive nerve fibers.When the SCG of adult rat is grafted to the anterior eye chamber of adult rat recipients, both ganglionic cell bodies and nerve fibers, forming on the host iris from the grafted ganglion, are NF-positive. As only the perikarya of these neurons normally exhibit NF immunoreactivity, and the terminal iris arborizations are NF-negative, it appears that the grafting procedure causes NF immunoreactivity to become more widespread in growing SCG neurons.     

Limitations on Sphagnum growth and net primary production in the foothills of the Philip Smith Mountains,Alaska

Summary In the foothills of the Philip Smith Mountains, Brooks Range, Alaska, tussock tundra occurs on rolling hills and in valleys that were shaped by Pleistocene glaciations. During the 1986 and 1987 summer seasons, Sphagnum growth and production were determined in water tracks on tundra slopes that acted to channel water flow to the valley bottom stream and in intertrack tundra areas that were relatively homogeneous with respect to downslope drainage. Measurements were made under ambient environmental conditions and on mosses receiving supplemental irrigation in each area. Growth rate for Sphagnum spp. (cm shoot length increase/day) was low and relatively constant in intertrack tundra and highest but quite variable in water tracks. A strong negative correlation was found between Sphagnum spp. growth rate and solar irradiance in the shady environment below Salix canopies in the water tracks. Estimates of net annual dry weight (DW) production for Sphagnum spp. ranged from 0.10 g DW dm^-2 yr^-1 in intertrack tundra vegetation to 1.64 g DW dm^-2 yr^-1 in well-shaded water tracks. Experimental water additions had little effect on growth and production in intertrack tundra and well-developed water tracks, but significantly increased growth in a weakly-developed water track community. Low production over large areas of tundra slopes may occur due to presence of slow growing species resistant to dessication in intertrack tundra as opposed to rapidly growing less compact species within the limited extent of water tracks. We hypothesize that species capable of rapid growth occur also in weakly-developed water tracks, and that these are water-limited more often than plants occurring in well-developed water track situations. Where experienced, high light intensity may additionally limit growth due to photoinhibition.     

Immunohistochemical localization of glial fibrillary acidic protein (GFAP) and vimentin in the subcommissural organ of the Mongolian gerbil (Meriones unguiculatus)

Summary The chemical composition of intermediate filaments (IF's) in the ependyma of the subcommissural organ (SCO) of the Mongolian gerbil (Meriones unguiculatus) was investigated immunohistochemically in paraffin-embedded tissue. Antibodies against glial fibrillary acidic protein (GFAP), vimentin, neurofilament proteins and cytokeratins were used. Only GFAP and vimentin were detected in the non-specialized diencephalic ependyma and in the ependymocytes of the SCO. Staining could be observed in apical and basal processes of the SCO-cells. The latter processes extended into the posterior commissure up to the subpial surface, thus establishing a well-developed leptomeningeal route of ependymal projections. In contrast to the homogeneous vimentin-labeling, the SCO was particularly immunoreactive for GFAP in its lateral aspects and in the supraand precommissural parts. The coexpression of GFAP and vimentin in a subclass of SCO-ependymocytes was demonstrated on differentially immunostained semithin sections. The present study confirms the glial nature of the SCO-ependyma, which has been a matter of debate recently. It appears from this investigation that the high degree of secretory activity in the SCO does not necessarily lead to the disappearance of glial IF proteins. Moreover, the SCO-cells belong to the expanding group of mature astroglia, which is characterized by coexpression of GFAP and vimentin. The morphological similarity between SCO-ependymocytes and tanycytes is underscored by their common immunoreactivity against these two IF proteins. In view of the absence of GFAP from the rat SCO, interspecific differences must be considered in the evaluation of the IF protein composition.     

Limnology of naturally acidic,oligotrophic dune lakes in subtropical Australia,including chlorophyll — phosphorus relationships

This study provides the most comprehensive physico-chemical and phytoplankton data yet available for Australian dune lakes, which are among the world's most naturally acidic and oligotrophic freshwaters. Seasonal and spatial variations were examined in Blue Lagoon and Lake Freshwater, two ‘water-table window’ lakes in south-east Queensland. Like other dune lakes, they are acidic (minimum pH 4.20 and 4.55, respectively), polymictic water bodies with low concentrations of marine-derived major ions and almost undetectable levels of trace metals. While linmologically similar in winter, during spring-summer Lake Freshwater has significantly higher levels of chlorophyll-a, total phosphorus (TP) and turbidity than Blue Lagoon and other dune lakes, indicating seasonal mesotrophy. The key nutrient is TP, which has recently increased to a maximum of 17 μ· l⁻¹, due either to inputs from recreational sources, or to the death and decomposition of littoral vegetation resulting from falling water levels over the last decade. Inorganic nitrogen, though present only in small amounts, does not appear to limit the eutrophication process because of a shift in phytoplankton dominance from the usual desmids and dinoflagellates to N₂-fixing blue-green algae. A chlorophyll - TP linear regression derived for dune lakes indicates that at TP < 20 μg · l⁻¹ chlorophyll ‘yield’ is higher than in other lake types represented by regressions from the literature. This may be due to a more efficient utilization of the limited available phosphorus by dune lake algae which have adapted to the naturally oligotrophic environment. The implications of these findings for lake management are discussed.     

Structures of acidic O-linked polylactosaminoglycans on human skim milk mucins

O-Linked glycans were isolated from human skim milk mucins or mucin-derived high-molecular weight glycopeptides and fractionated by anion exchange chromatography into neutral and acidic alditols. Major oligosaccharides contained in the acidic fraction were purified by high performance liquid chromatography and structurally characterized by a combination of fast atom bombardment mass spectrometry, methylation analysis and 500 MHz 1H-nuclear magnetic resonance spectroscopy. The structural aspects exhibited by these major species in the acidic fraction resemble those established previously for the neutral oligosaccharides from human skim milk mucins: 1) the size of the alditols varies from tri- to decasaccharides, 2) the core structure is of the ubiquitous type 2, 3) the backbone sequences are of the poly-N-acetyllactosamine type with a particular preponderance of linearly extended GlcNAc beta(1-3)Gal (major) or GlcNAc beta(1-6)Gal units (minor).     

Coexpression of cytokeratin and vimentin in Rathke's cysts of the human pituitary gland

Summary Immunohistochemistry with monoclonal and polyclonal antibodies revealed the presence of cytokeratins in epithelial cells of Rathke's cysts in the pars intermedia of the human pituitary gland. With monoclonal antibodies specific for individual cytokeratins, the expression of CK 18, CK 8, CK 7, and CK 19 could be shown in these cells. Within the hypophysis, CK 19 and CK 7 were restricted to Rathke's cysts and a few epithelial cell clusters in the pars tuberalis, whereas other cytokeratins were also present in endocrine cells of the pars distalis. Furthermore, vimentin and, focally, glial fibrillary acidic protein (GFAP) were detected in the cystic epithelia. By double labelling, coexpression of cytokeratin and vimentin, GFAP and cytokeratin, and GFAP and vimentin could be demonstrated. Compiled data of all known cases of coexpression of cytokeratin and vimentin in normal cells reveal physiological correlations and suggest a functional significance of this rare type of coexpression of intermediate filament proteins.