S. Persson

Distribution of vesicular glutamate transporters 1 and 2 in the rat spinal cord, with a note on the spinocervical tract

To evaluate whether the organization of glutamatergic fibers systems in the lumbar cord is also evident at other spinal levels, we examined the immunocytochemical distribution of vesicle glutamate transporters 1 and 2 (VGLUT1, VGLUT2) at several different levels of the rat spinal cord. We also examined the expression of VGLUTs in an ascending sensory pathway, the spinocervical tract, and colocalization of VGLUT1 and VGLUT2. Mainly small VGLUT2‐immunoreactive varicosities occurred at relatively high densities in most areas, with the highest density in laminae I–II. VGLUT1 immunolabeling, including small and medium‐sized to large varicosities, was more differentiated, with the highest density in the deep dorsal horn and in certain nuclei such as the internal basilar nucleus, the central cervical nucleus, and the column of Clarke. Lamina I and IIo displayed a moderate density of small VGLUT1 varicosities at all spinal levels, although in the spinal enlargements a uniform density of such varicosities was evident throughout laminae I–II in the medial half of the dorsal horn. Corticospinal tract axons displayed VGLUT1, indicating that the corticospinal tract is an important source of small VGLUT1 varicosities. VGLUT1 and VGLUT2 were cocontained in small numbers of varicosities in laminae III–IV and IX. Anterogradely labeled spinocervical tract terminals in the lateral cervical nucleus were VGLUT2 immunoreactive. In conclusion, the principal distribution patterns of VGLUT1 and VGLUT2 are essentially similar throughout the rostrocaudal extension of the spinal cord. The mediolateral differences in VGLUT1 distribution in laminae I–II suggest dual origins of VGLUT1‐immunoreactive varicosities in this region. J. Comp. Neurol. 497:683–701, 2006.

Vegetation development after the exclusion of grazing cattle in a meadow area in the south of Sweden

A study of 24 years of secondary succession was based on data from semi-permanent quadrats from investigations in 1952, 1955, 1968 and 1976, involving two exclosures, the first in a meadow grazed for hundreds of years but now abandoned, the second in a meadow mowed for hundreds of years and grazed for the last 50 years. A first order classification of quadrats produced units, which formed distinct spatial patterns indicating similar gradients, but also differences in response to the ceased grazing, in the two exclosures. A second order classification of units into groups revealed a rather simple structure of spatial and temporal relations. Eleven groups of species with similar behaviour could be recognized within a system of spatial and temporal species distributions. The vegetation in both exclosures developed towards an increased differentiation and heterogeneity or patchiness. The border between two soil types was clearly reflected in the spatial pattern of units. Rates of change were greatest in the beginning and were shown to closely follow logarithmic functions of time. The average number of species per m2 decreased in all plots, in some cases as much as 50%. It was concluded that the diversity had decreased as a consequence of decreased species richness, decreased evenness and decreased pattern diversity. Many individual species distributions showed a pattern of nuclei surrounded with marginal belts. Differences in rate of change and persistence of spatial patterns between the plots, could be attributed to the differences in management history. These differences have disappeared as the succession has proceeded. The two exclosures have instead both conformed to the same floristic gradient, in turn based on a similar pattern of environmental gradients, primarily moisture. In the observed changes the emphasis was on the shifting importance of competing species populations, as some gained in importance at the expense of others. Competition has so far been a more important process in the vegetation development than immigration/extinction rates.

Succession in a South Swedish Deciduous Wood: A Numerical Approach

Successions in a South Swedish deciduous wood, which is a national park and has been almost undisturbed since 1918, are studied using semipermanent plots. These plots were originally established in 1935 and reestablished in 1969–70 and 1975–76. Each plot is represented by a record, which combines fieldlayer data from spring- and summer aspects. The accuracy of the approach of semipermanent plots is evaluated from a slightly displaced sample. Vegetational and successional gradients are revealed in a classification of the entire dataset. Successional trends are analysed through ordinations of site- period data. A converging successional trend is found. The vegetational and successional gradients are found to coineide. A considerable reduction in the variation and diversity of the fieldlayer is evident. An analysis of the development in smaller groups of corresponding quadrats shows consistent, and in some cases rather drastic, changes in cover and/or frequency for many species. Characteristic indicator values are used to connect these changes to environmental factors, and changes in light regime and nitrogen status are indicated. The spatial-temporal pattern is analysed through maps.

Vegetational Succession in a South Swedish Deciduous Wood

In 1918 the small area of woodland, Dalby Soderskog, in southwestern Skane was designated as a national park. It was regarded as ‘the only remaining representative of the type of deciduous forest, that during periods long ago commonly occurred in the southernmost province of our country’ (translation from Lindquist 1938, p. 61).

Leaf litter fall and soil acidity during half a century of secondary succession in a temperate deciduous forest

Vegetation, leaf litter fall and soil pH were sampled repeatedly within semipermanent plots in a South-Swedish deciduous forest, 1935–1983. Leaf litter fall was summarized in a litter quality index. Vegetation types were differentiated along similar gradients in soil pH and leaf litter quality. The greatest shifts in dominance among field layer species were found in those plots where the quality of the leaf litter had improved. These plots also showed a halt in the general tendency towards a decreasing pH in the top soil.

The mid-rapidity calorimeter for the relativistic heavy-ion experiment WA80 at CERN

Abstract A sampling calorimeter designed for use at mid-rapidity in the relativistic heavy-ion experiment WA80 at CERN is described. Calibration and performance results are presented. Over the energy range of 2 to 50 GeV, the response of the mid-rapidity calorimeter was linear, and its energy resolution σ E was found to be given by 0.014 + 0.11 √E and 0.034+0.34 √E for electromagnetic and hadronic showers, respectively. Signal ratios of 1.2 and 1.4 were obtained for the e h ratio of the lead-scintillator electromagnetic section and the iron-scintillator hadronic section, respectively. The calorimeter provided an accurate transverse energy trigger. The response and resolution for high-energy heavy ions were slightly better than anticipated on the basis of the low-energy calibrations.

The Paradox of Weak State Power: A Research and Literature Overview

The primary aim of this article is to present an inventory of the propositions that have been made concerning the ways in which small states can exercise influence over Great Powers. The paradox of relatively resourceless states sometimes being able to exercise substantial influence in international relations received some attention in the late 1960s and early 1970s. The weak state — powerful state relations have, however, also been dealt with in a number of more recent studies, some of which have discussed the paradox of weak state power. In this article we revisit the subject area and take stock of the work by presenting the factors which have been mentioned as conceivable explanations to the phenom enon. The factors are divided into two groups, with four and three subcategories, respectively. The first group consists of the propositions which focus on power bases and statements about the effects of various basic conditions in the international system. The second group contain the propositions which discuss more direct conceivable causes, such as certain strategies and tactics open to the smaller states.

Multiplicities and rapidity densities in 200 A GeV 16O interactions with emulsion nuclei

Abstract We report on an experiment in which emulsion chambers were exposed to a beam of 200 A GeV 16 O at the CERN SPS. Pseudo-rapidity distributions are measured with high precision. Pseudo-rapidity densities of 140 particles per unit rapidity corresponding to an energy density of about 3 GeV/fm3 are observed. Pseudo-rapidity density distributions and fluctuations are found to satisfactorily agree with the Lund Monte Carlo model Fritiof, although new and unknown sources for fluctuations might still be present.

A computer based coordinate measuring station for nuclear emulsion chambers

Abstract We describe a computer based coordinate measuring station designed for measuring high multiplicity events recorded in vertically exposed nuclear emulsion chamber. This setup has a very good angular resolution, especially in the forward region. The hardware is essentially built up with commercially available equipment, but the special software developed makes the system very efficient. We also describe the track fitting technique and the full event reconstruction.

Quantitative analysis of immunogold labeling indicates low levels and non-vesicular localization of L-aspartate in rat primary afferent terminals.

The role of L‐aspartate as an excitatory neurotransmitter in primary afferent synapses in the spinal cord dorsal horn is disputed. To further investigate this issue, we examined the presence of aspartate‐like immunoreactivity in primary afferent nerve terminals and other tissue components of the dorsal horn. We also examined the relationship between aspartate and glutamate immunogold labeling density and the density of synaptic vesicles in primary afferent terminals and presumed inhibitory terminals forming symmetric synapses. Weak aspartate immunosignals, similar to or lower than those displayed by presumed inhibitory terminals, were detected in both C‐fiber primary afferent terminals in lamina II (dense sinusoid axon terminals, identified by morphological criteria) and in A‐fiber primary afferent terminals in laminae III–IV (identified with anterograde transport of choleragenoid‐horseradish peroxidase conjugate). The aspartate immunogold signal in primary afferent terminals was only about one‐fourth of that in deep dorsal horn neuronal cell bodies. Further, whereas significant positive correlations were evident between synaptic vesicle density and glutamate immunogold labeling density in both A‐ and C‐fiber primary afferent terminals, none of the examined terminal populations displayed a significant correlation between synaptic vesicle density and aspartate immunogold labeling density. Thus, our results indicate relatively low levels and a non‐vesicular localization of aspartate in primary afferent terminals. It is therefore suggested that aspartate, rather than being a primary afferent neurotransmitter, serves a role in the intermediary metabolism in primary afferent terminals. J. Comp. Neurol. 430:147–159, 2001.