bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dopamine D2‐like receptors on human peripheral blood lymphocytes: a radioligand binding assay and immunocytochemical study
Authors: Amenta F. , Bronzetti E. , Felici L. , Ricci A. , Tayebati S. K. 
Published: March 2003

1 Peripheral blood lymphocytes express dopamine D1‐like and D2‐like receptors which were investigated using radioligand binding assay and molecular biology techniques. Analysis of dopamine D2‐like receptors expressed by human peripheral blood lymphocytes with radioligand binding assay may offer a rapid technique for assessing receptor changes in disorders characterized by involvement of the dopaminergic system. However, the suitability of radioligand binding assay techniques to measure dopamine D2‐like receptors is questioned.2 In view of the discrepancy between data of dopamine D2‐like receptor determination with molecular biology and radioligand binding assay techniques, we have assayed dopamine D2‐like receptors expressed by human peripheral blood lymphocytes using as radioligands the dopamine receptor agonist 7‐[3H]‐hydroxy‐N,N‐di‐n‐propyl‐2‐aminotetraline ([3H]‐7‐OH‐DPAT) and two antagonists ([3H]‐spiperone and [3H]‐nemonapride).3 Analysis of saturation curves revealed a concentration‐dependent binding of all compounds to human peripheral blood lymphocytes. Dissociation constant (Kd) values averaged between 0.15 and 0.40 n
m for different radioligands. The maximum density of binding sites (Bmax) was low, ranging from 4.15 ± 0.05 fmol/106 cells with [3H]‐spiperone and 8.66 ± 0.04 fmol/106 cells with [3H]‐7‐OH‐DPAT.4 Displacement curves of [3H]‐7‐OH‐DPAT, [3H]‐spiperone and [3H]‐nemonapride binding to human peripheral blood lymphocytes revealed, using radioligand concentrations giving the highest specific:non‐specific binding ratio, a pharmacological profile consistent with the labelling of dopamine D2‐like receptors. The use of higher radioligand concentrations resulted in a poorly displaceable and characterizable binding.5 Detection of dopamine D2, D3 and D4 receptor immunoreactivity in cytospin centrifuged peripheral blood lymphocytes revealed dopamine D3 and D4 but not D2 receptor immunostaining.6 The above findings indicate in agreement with molecular biology studies, that dopamine D2‐like receptors expressed by human peripheral blood lymphocytes belong to the D3 and D4 receptor subtypes. These receptors are detectable using either dopamine D2‐like receptor agonists and antagonists as radioligands if controlled experimental conditions are followed. The standardisation of immunocytochemical techniques for detecting human peripheral blood lymphocyte dopamine receptors may contribute to clarify their role in lymphocyte function or as a peripheral marker of the status of the dopaminergic system.
P2X7 receptors in rat parotid acinar cells: formation of large pores
Authors: Gibbons Simon J. , Washburn Katrina B. , Talamo Barbara R. 
Published: March 2003

1 Permeabilization of cells mediated by P2X7 receptors occurs to varied degrees in native and heterologous expression systems. Previous studies on P2X7 receptors in parotid acinar cells suggested that ATP does not permeabilize these cells. 2 Modification of the assay conditions showed that ATP permeabilizes freshly dissociated rat parotid acinar cells to the fluorescent dye YOPRO‐1. 3 The pharmacological and physiological properties of this effect indicate that permeabilization is mediated by the P2X7 receptor. Adenosine 5′‐triphosphate (ATP) and 3′‐O‐(4‐benzoyl)benzoyl adenosine 5′‐triphosphate (BzBzATP) were effective agonists with EC50 values of 49.3 and 0.6 μM, respectively. 4 Permeabilization was best observed in low divalent cation concentrations and at physiological temperatures. Previous studies failed to detect permeabilization because of the sensitivity of this effect to temperature and divalent cations. 5 An important consideration in understanding the effect of divalent cations is that the fluorescence of YOPRO‐1/nucleic acid complexes is directly quenched by addition of divalent cations. This must be considered if quantitative study of the interaction of divalent cations with P2X7 receptors is carried out using fluorescent DNA‐binding dyes. 6 In summary, our data show that P2X7 receptors in parotid acinar cells can form large pores in the plasma membrane. This property likely contributes to signalling and may be cytotoxic and have particular significance in damaged or inflamed salivary glands.
Effects of restraint stress on responsiveness of atria and vas deferens in Sprague–Dawley rats
Authors: Singh A. , Einstein R. , Lavidis N. 
Published: March 2003

Summary 1 The effects of stress in rats were evaluated by measuring changes in body weight and in responsiveness to noradrenaline (NA) in the isolated vas deferens and atria after the animals had been exposed to restraint or restraint and isolation. 2 Animals which were subjected to restraint alone (1 h day−1 for 3, 7 or 28 days) had a significantly reduced rate of body weight gain. This effect was not potentiated by the additional stress of isolation. 3 Restraint alone did not produce significant changes in the responsiveness of the vas deferens to NA. However, adding isolation to restraint, as an additional stress, produced a further leftward shift of the NA dose–response curve for the vas deferens, so that there was a significant increase in sensitivity compared with control. 4 There was a significant rightward shift in the NA dose–response curves or reduction in sensitivity in the atria from animals which had been restrained for 7 or 28 days. Isolation did not produce a further rightward shift in the NA dose–response curve. 5 The results from this study indicate that the stress associated with repeated restraint reduces the rate of weight gain and reduces the responsiveness of the atria to NA. The responsiveness of the vas deferens to NA was increased by stress, but the combined effect of isolation and restraint was required to produce a significant effect. The differences in the effects of stress on these tissues could be associated with differences in presynaptic receptor populations.
Phylogeny and biogeography in the evolution of migration: shorebirds of the Charadrius complex
Authors: Joseph Leo , Lessa Enrique P. , Christidis Leslie 
Published: March 2003

Summary Aim We explore whether molecular phylogeny and biogeography can complement evolutionary ecology in developing a method to address a long‐standing issue in the evolution of migration: have migrations between breeding and non‐breeding grounds, which may be on different continents, evolved through origins in the breeding grounds with successive shifts of the non‐breeding distribution or vice versa? Methods To accommodate the biology of migration, we treated breeding and non‐breeding distributions as characters to be mapped onto a phylogeny derived from mitochondrial DNA sequence data and so examined the ancestral home issue as a study in the direction of character evolution. Results Our main findings from applying this approach to a subset of the Charadrius complex of shorebirds (Aves: Charadriinae) are that a case can be made for shifts of breeding distributions having occurred in the ancestries of C. alexandrinus and C. veredus as those species evolved their present migration patterns. Our results also argue for a southern hemisphere origin (specifically South America) for the Charadrius complex as a whole. A South American origin implies other shifts in breeding distributions having occurred in the evolution of the species C. semipalmatus and C. vociferus. On applying the methods we developed for dealing with phylogenetic uncertainty, these results are reinforced and the merit of testing them further is suggested. Conclusions By way of a new approach to the evolution of migration, our study adds to a consensus emerging from the evolutionary ecology of migrant birds, arguing that shifts of breeding distributions are commonly, though not necessarily exclusively, involved in the evolution of migration.
An alternative hypothesis for the origin of Amazonian bird diversity
Authors: Nores Manuel 
Published: March 2003

Summary AimTo determine the origin of the high diversity of birds and other animals and plants in Amazonia. Previous hypotheses are: palaeogeography hypothesis, river hypothesis, river‐refuge hypothesis, refuge hypothesis, disturbance‐vicariance hypothesis, gradient hypothesis, pest‐pressure hypothesis, intermediate disturbance hypothesis, riverine disturbance hypothesis, models of fine‐scale habitat heterogeneity, lake hypothesis, and museum hypothesis. MethodsAt present there is agreement between areas of high species diversity and sites located over 100 m. As these sites would have been islands during a sea‐level rise of this value, it was important to determine the probable distribution of these islands in Amazonia during a marine transgression. For that purpose, I traced the 100 m contour line from topographic maps. ResultsTwo broad marine transgressions would have been produced from the Atlantic Ocean via the Amazon and Orinoco rivers. Two very large islands would have been formed to the north of the Amazon River, and other islands and archipelagos would have been formed along the coastal lowlands of Guiana, and at the periphery of the Amazon basin. The area located between the SolimoÃ½es and Negro rivers and in the lower Branco would have been completely covered by the sea. Main conclusionsA substantial part of the high diversity of forest and nonforest birds in lowland Amazonia can be hypothetysed to have originated during sea‐level rises of about 100 m in the Quaternary and late Tertiary. These transgressions would have fragmented the Amazonian lowland into a large number of true islands and archipelagos, thus favouring active allopatric speciation. Values appreciably higher than 100 m above the present sea‐level during previous periods of the Tertiary would have produced segregation of the biota earlier than the Tertiary–Quaternary boundary. Sea‐level rises and vegetational changes (by aridity or cooling) would thus have driven the speciation pump, and local disturbances and other processes, would maintain the diversity.
Early Holocene plant and animal remains from North‐east Greenland
Authors: Bennike Ole , Björck Svante , Böcher Jens , Hansen Louise , Heinemeier Jan , Wohlfarth Barbara 
Published: March 2003

Summary Aim The aim of this paper is to describe and interpret early Holocene floras and faunas. Location The floras and faunas come from various localities in North‐east Greenland. Methods Sediment samples were wet sieved, and macrofossils picked out and dated by the AMS radiocarbon‐dating method. Results
Sediments, dated to the first centuries after the last glacial stage came to an abrupt end, contain a macroflora of bryophytes and a few herbs, and we suggest that these plant remains represent a pioneer vegetation entirely without woody plants. The named species of herbs are either confined to the northern parts of Greenland at present, or they become increasingly more important towards the north. Crowberry is the oldest woody plant recovered; it was present at 10.4 cal. ka BP, and it appears to have been common during the early Holocene in East Greenland. Main conclusions We suggest that the majority of the extant flora of vascular plants of East Greenland arrived by long distance dispersal during the Holocene. Some species may also have arrived during the late‐glacial, and a few hardy species that are adapted to low summer temperatures may have survived the last glacial stage in nonglaciated areas. Some hardy animals may also have survived, but the majority of the fauna are considered Holocene immigrants. We suggest that migrating birds and storms, perhaps in combination, are under‐appreciated dispersal vectors.
From bobolinks to bears: interjecting geographical history into ecological studies, environmental interpretation, and conservation planning
Authors: Foster David R. 
Published: March 2003

AbstractIn these days of supercomputer‐based global climate models, large ecosystem experiments including Biosphere II, and aircraft‐borne sensors of ozone holes it is often overlooked that many fundamental insights into ecological processes and major environmental issues come not through reductionist or high‐tech studies of modern conditions but from thoughtful consideration of nature’s history. In fact, it is foolhardy to make any ecological interpretation of modern landscapes or environments or to formulate policy in conservation or natural resource management without an historical context that extends back decades, at least, but preferably centuries or millennia. Oftentimes, the ecological and conservation communities, in their search for more detail on the present and simulation of the future, appear to have forgotten the value of a deep historical perspective in research and application. However, the willingness of the geographical sciences to embrace broad temporal and spatial perspectives and to consider cultural as well as natural processes is worth emulating as we address environmental subjects in the new millennium.
Pollen signatures of the arid to humid grasslands of North America
Authors: Hoyt C. A. 
Published: March 2003

AbstractAimMany studies have shown that the pollen record can be used to distinguish grasslands from other vegetation types at the biome level, but few have attempted to use pollen to distinguish between specific prairie types. This study was undertaken to determine whether the tallgrass, mixed‐grass, shortgrass, and desert grasslands of North America have unique pollen signatures that can be used to distinguish between grasslands at the community‐scale, rather than at the scale of the biome.LocationData was collected from the southern North American grasslands of Oklahoma, Texas, and New Mexico.MethodsHigh resolution, annual pollen‐influx data gathered in Tauber pollen traps were analyzed using cluster analysis to summarize the pollen signature from each trap locality and to catagorize the samples into discrete grassland groups.ResultsBased on the results of the cluster analysis, each grassland produces a distinctive pollen signature that can be used to distinguish between grassland types. In addition, pollen influx is shown to be closely correlated with annual precipitation.Main conclusionsThe ability to distinguish between grassland types and to relate annual influx to annual precipitation has important implications for understanding the evolution of grasslands during the Holocene, for palaeoclimatic studies, and for monitoring ecosystem changes in the present‐day grasslands.
Ichthyofaunistic biogeography of the Japan (East) Sea
Authors: Kafanov Alexander I. , Volvenko Igor V. , Fedorov Vladimir V. , Pitruk Dmitry L. 
Published: March 2003

AbstractAimThe aim of the present study is the distribution analysis of species richness of ichthyofauna at the east and west coasts of the Japan Sea for the purpose of identification of natural biogeographic boundaries, subsequent faunistic zoning and comparison between faunistic and bioclimatic (bio‐oceanographic) zoning patterns.LocationJapan Sea (Korean–East Sea).MethodsAll statistical procedures are based on well‐tried and widely accepted numerical methodology and the statistica program package. For identifying the statistically meaningful (non‐random) maxima and minima in species richness, arithmetical differences in the number of species at ith and i + 1st latitudes are calculated, also trend residuals obtained by smoothing the moving average by three points and residuals in polynomial trends are analysed. Subsequent clustering of species lists for separate biogeographical units marked by local maxima and minima in species richness permits to identify the extent of mutual correspondence between the units and to make an outline for faunistic zoning. Similarity degree of faunistic lists was estimated in terms of Czekanowski–Sörensen coefficient.ResultsQuantitative analysis of latitudinal distribution of species richness (1130 species) of the Japan Sea ichthyofauna is indicative of the position of the following 10 local maxima and minima: at 35, 40, 43, 47, 49 and 51° N on the west coast and at 36, 39, 43 and 46° N on the east coast. In most cases local minima of the polynomial trend residuals are coincident with southern boundaries of faunistic units while local maxima with northern boundaries. Separated analysis of qualitative composition of ichthyofauna of the west and east coasts of the Japan Sea discloses 11 areas of the greatest faunistic similarity.Main conclusionsThe latitudinal variations in the species richness near both sea coasts represent an alternation between relatively flattened smooth portions (each 1 unit long) and sufficiently steep jumps between them. Regular interchange between local minima and maxima of species richness is accountable to spatial non‐uniformity of hydrological structure resulting from alternation of variously directed and differently heated (warm and cold) circulations of waters and frontal zones. It is notable that faunistic zoning does not initially require any exact knowledge of biotic taxonomic composition and may be produced only from the variation pattern of the species richness under study. The suggested faunistic zoning scheme distinguishes the following provinces: South Korea, East Korea, South Primorie, North Primorie, Northern Japan Sea, Middle Honshu, Uetsu, Tsugaru, Soya and West Sakhalin. The comparison between faunistic units and distribution of temperature parameters and currents permits identification of subarctic, cold–temperate, mild–temperate and warm–temperate bioclimatic zones existing in the Japan Sea.
Detecting migration routes and barriers by examining the distribution of species in an apomictic species complex
Authors: Tyler Torbjörn 
Published: March 2003

AbstractAimThe distribution of taxa (‘microspecies’) in the apomictic species complexes Hieracium L. sect. Hieracium and H. sect. Vulgata (Griseb.) Willk. and Lange have been analysed to test whether the geographical distribution of species within each complex will reflect historical processes and phenomena, e.g. historical barriers to migration and range expansion. It is argued that apomictic species can be used for phylogeographic analysis in the same way as organelle haplotypes or multilocus genotypes.LocationThe investigated area is the Nordic countries excluding Iceland, together with the Baltic islands of Saarema (Estonia) and Rügen (Germany).MethodsThe presence or absence of 160 species of H. sect. Hieracium and 165 species of H. sect. Vulgata was recorded in 39 geographical areas. Based on this dataset, Jaccard similarity indices were calculated and subjected to upgma cluster analysis and non‐metric multidimensional scaling (MDS).ResultsFor both species complexes, the larger water surfaces were found to represent discontinuities in species composition, interpreted as migration barriers. Some inland migration barriers were also indicated, e.g. in northern‐central Sweden. The Scandes seems to have constituted a migration barrier for H. sect. Vulgata. Some areas in south‐western Sweden represent discontinuities in the distribution of species within H. sect. Hieracium.Main conclusionsThe revealed geographical patterns in species composition, as well as the differences in the patterns for the two species complexes, are readily explainable as reflecting historical migration routes and barriers. Further analysis using apomictic taxa as ‘markers’ may give important phylogeographic insights. The pros and cons of using microspecies, as opposed to molecular markers, in historical biogeography is discussed.
Maps of Pleistocene sea levels in Southeast Asia: shorelines, river systems and time durations
Authors: Voris Harold K. 
Published: March 2003

AbstractAimGlaciation and deglaciation and the accompanying lowering and rising of sea levels during the late Pleistocene are known to have greatly affected land mass configurations in Southeast Asia. The objective of this report is to provide a series of maps that estimate the areas of exposed land in the Indo‐Australian region during periods of the Pleistocene when sea levels were below present day levels.LocationThe maps presented here cover tropical Southeast Asia and Austral‐Asia. The east–west coverage extends 8000 km from Australia to Sri Lanka. The north–south coverage extends 5000 km from Taiwan to Australia.MethodsPresent‐day bathymetric depth contours were used to estimate past shore lines and the locations of the major drowned river systems of the Sunda and Sahul shelves. The timing of sea level changes associated with glaciation over the past 250,000 years was taken from multiple sources that, in some cases, account for tectonic uplift and subsidence during the period in question.ResultsThis report provides a series of maps that estimate the areas of exposed land in the Indo‐Australian region during periods of 17,000, 150,000 and 250,000 years before present. The ancient shorelines are based on present day depth contours of 10, 20, 30, 40, 50, 75, 100 and 120 m. On the maps depicting shorelines at 75, 100 and 120 m below present levels the major Pleistocene river systems of the Sunda and Sahul shelves are depicted. Estimates of the number of major sea level fluctuation events and the duration of time that sea levels were at or below the illustrated level are provided.Main conclusionsPrevious reconstructions of sea‐level change during the Pleistocene have emphasized the maximum lows. The perspective provided here emphasizes that sea levels were at their maximum lows for relatively short periods of time but were at or below intermediate levels (e.g. at or below 40 m below present‐day levels) for more than half of each of the time periods considered.
Plant diversity and endemism in sub‐Saharan tropical Africa
Authors: Linder H. P. 
Published: March 2003

AimThis paper has as its central aim the location of centres of species richness and endemism in the sub‐Saharan African flora. Previous postulation of these centres has been based on an intuitive interpretation of distributional data; this paper provides a test of these centres. A second aim is to establish whether the two indices, richness and endemism, locate the same centres. Thirdly the relationship between species richness and endemism, and latitude and rainfall are explored.LocationThe study area includes much of sub‐Saharan Africa, but excludes the species‐poor southern margin of the Sahara and the Namib–Kalahari regions.MethodsAnalyses were based on 1818 species, scored on a 2.5 × 2.5 degree grid. Species richness was inferred from a simple grid‐diversity count; endemism was determined by three measures: the number of species restricted to two grids, the sum of the inverse of the ranges of the component species of each grid, and the proportion of the species in each grid that have restricted ranges.ResultsThe African flora shows a remarkably profound patterning, both in species richness and endemism. The two measures locate largely the same centres, although the rank order among them differs. These centres are: the Cape Floristic Region, East Coast, Congo‐Zambezi watershed, Kivu, Upper and Lower Guinea. Richness is strongly related to maximum rainfall, but there are no obvious correlations between modern climate and endemism. Species richness and endemism north of the equator is much more concentrated into centres than south of the equator.Main conclusionsThere are strongly developed refugia in sub‐Saharan Africa. North of the equator, these refugia are sharply delimited and rather small, separated by large areas of very low endemism. South of the equator endemism tends to be more generally distributed. Variation in species richness in sub‐Saharan Africa can be explained largely by modern rainfall, while endemism may be related to palaeoclimatic fluctuations. Both species richness and endemism show a strong skewing towards the south, indicating that the fluctuations in the Sahara might have influenced the modern distribution of plants in Africa.