bluuebunny/crossref_metadata_2025_split huggingface dataset:
Somatosensory Stimuli Evoke Norepinephrine Release in the Anterior Ventromedial Hypothalamus of Sexually Receptive Female Rats
Authors: Etgen A. M. , Morales J. C. 
Published: March 2003

AbstractWe used in vivo brain microdialysis to determine the role of specific copulatory stimuli in mating‐induced release of norepinephrine in the lateral ventromedial hypothalamus (VMH) of hormone‐treated, sexually receptive female rats. Ovariectomized rats implanted with a unilateral guide cannula aimed at the ventrolateral VMH received systemic injections of estradiol benzoate daily for 2 days before and progesterone 4 h before the initiation of a 1‐h behavioural test. Dialysis probes were lowered immediately after progesterone administration, and 20‐min dialysis samples were collected until 1 h after the termination of behavioural testing. Norepinephrine content of dialysates was quantified by high performance liquid chromatography with electrochemical detection. During mating tests with male rats, dialysate levels of norepinephrine increased significantly over baseline in sexually receptive females with probe placements in the anterior but not posterior VMH. Norepinephrine levels were unchanged if rats were nonreceptive, even if males mounted vigorously and probes were located in the anterior VMH. Hormone‐treated females that were placed on male‐soiled bedding for 1 h showed no changes in dialysate levels of norepinephrine. Similarly, females in which vaginocervical stimulation was prevented by a vaginal mask failed to show increased levels of norepinephrine in dialysates collected from the anterior VMH, even if they displayed high levels of lordosis behaviour. Thus, the release of norepinephrine is not a result of executing the lordosis posture. The findings suggest that mating‐induced increases in norepinephrine release in hormone‐treated, sexually receptive rats are confined to the anterior VMH and that somatosensory rather than chemosensory stimuli evoke norepinephrine release. Moreover, experiments with vaginal masks indicate that vaginocervical stimulation is necessary for mating‐evoked norepinephrine release in the anterior VMH.
Carbon isotope discrimination and wood anatomy variations in mixed stands of Quercus robur and Quercus petraea
Authors: Ponton S. , Dupouey J.‐L. , Bréda N. , Feuillat F. , Bodénès C. , Dreyer E. 
Published: March 2003

AbstractThe two most common oak species in western Europe, Quercus robur and Quercus petraea, display different ecological behaviours, particularly with respect to their responses to drought. The ecophysiological basis of this niche difference is not understood well. Here we test the hypothesis that these two species present distinct water use efficiencies (WUEs), using the carbon isotope discrimination approach. Leaves and 13 dated ring sequences were sampled in 10 pairs of adult trees growing side by side. Carbon isotope composition was measured on cellulose extracts. In addition, relationships between carbon isotope discrimination and wood anatomy were assessed at the tree level. Quercus robur displayed a 1·0‰ larger isotopic discrimination than Q. petraea, and therefore a lower intrinsic WUE (−13%). This interspecific difference of isotopic discrimination was quite stable with time and independent of tree radial growth and climate fluctuations. A strong positive correlation was observed between average tree values of earlywood vessel surface area and 13C isotopic discrimination. This correlation was even higher with 13C of the 1976 dry year (r = 0·86). These observations led to the hypothesis that hydraulic properties of xylem could exert a constraint on leaf gas exchange, resulting in a larger WUE for individuals with smaller vessel cross‐section area.
Plant aquaporins: multifunctional water and solute channels with expanding roles
Authors: Tyerman S. D. , Niemietz C. M. , Bramley H. 
Published: March 2003

AbstractThere is strong evidence that aquaporins are central components in plant water relations. Plant species possess more aquaporin genes than species from other kingdoms. According to sequence similarities, four major groups have been identified, which can be further divided into subgroups that may correspond to localization and transport selectivity. They may be involved in compatible solute distribution, gas‐transfer (CO2, NH3) as well as in micronutrient uptake (boric acid). Recent advances in determining the structure of some aquaporins gives further details on the mechanism of selectivity. Gating behaviour of aquaporins is poorly understood but evidence is mounting that phosphorylation, pH, pCa and osmotic gradients can affect water channel activity. Aquaporins are enriched in zones of fast cell division and expansion, or in areas where water flow or solute flux density would be expected to be high. This includes biotrophic interfaces between plants and parasites, between plants and symbiotic bacteria or fungi, and between germinating pollen and stigma. On a cellular level aquaporin clusters have been identified in some membranes. There is also a possibility that aquaporins in the endoplasmic reticulum may function in symplasmic transport if water can flow from cell to cell via the desmotubules in plasmodesmata. Functional characterization of aquaporins in the native membrane has raised doubt about the conclusiveness of expression patterns alone and need to be conducted in parallel. The challenge will be to elucidate gating on a molecular level and cellular level and to tie those findings into plant water relations on a macroscopic scale where various flow pathways need to be considered.
ABA‐based chemical signalling: the co‐ordination of responses to stress in plants
Authors: Wilkinson S. , Davies W. J. 
Published: March 2003

AbstractThere is now strong evidence that the plant hormone abscisic acid (ABA) plays an important role in the regulation of stomatal behaviour and gas exchange of droughted plants. This regulation involves both long‐distance transport and modulation of ABA concentration at the guard cells, as well as differential responses of the guard cells to a given dose of the hormone. We will describe how a plant can use the ABA signalling mechanism and other chemical signals to adjust the amount of water that it loses through its stomata in response to changes in both the rhizospheric and the aerial environment. The following components of the signalling process can play an important part in regulation: (a) ABA sequestration in the root; (b) ABA synthesis versus catabolism in the root; (c) the efficiency of ABA transfer across the root and into the xylem; (d) the exchange of ABA between the xylem lumen and the xylem parenchyma in the shoot; (e) the amount of ABA in the leaf symplastic reservoir and the efficiency of ABA sequestration and release from this compartment as regulated by factors such as root and leaf‐sourced changes in pH; (f) cleavage of ABA from ABA conjugates in the leaf apoplast; (g) transfer of ABA from the leaf into the phloem; (h) the sensitivity of the guard cells to the [ABA] that finally reaches them; and lastly (i) the possible interaction between nitrate stress and the ABA signal.
Chloroquine decreases cell‐surface expression of tumour necrosis factor receptors in human histiocytic U‐937 cells
Authors: Jeong Jae‐Yeon , Choi Jae Won , Jeon Kye‐Im , Jue Dae‐Myung 
Published: March 2003

SummaryProinflammatory cytokine tumour necrosis factor (TNF) mediates its diverse effects through cell surface receptors. A variety of inflammatory signals are known to modulate TNF activities by changing expression and shedding of cell‐surface TNF receptors. We have examined the effects of anti‐rheumatic drug chloroquine on the expression of cell surface and soluble TNF receptors in human histiocytic U‐937 cells. Chloroquine partially reduced production of soluble p55 and p75 TNF receptors in cells stimulated with phorbol 12‐myristate 13‐acetate (PMA). In these cells, induction of both TNF receptor mRNA was not changed and the levels of cell‐associated TNF receptors were rather increased by chloroquine. Flow cytometric analysis revealed that chloroquine does not inhibit the PMA‐triggered shedding of TNF receptors from cell surface, while it was suppressed by a metalloproteinase inhibitor BB‐3103. Treatment of U‐937 cells with chloroquine significantly reduced the level of cell surface TNF receptors and a similar effect was observed with human peripheral blood monocytes. Other weak‐base amines, including hydroxychloroquine, ammonium chloride and methylamine, also induced reduction of cell surface TNF receptors, whereas lysosomal proteinase inhibitor, leupeptin, and BB‐3013 were without effect. Our results suggest that chloroquine down‐regulates cell surface TNF receptors by retarding their transport to the cell surface, while cleavage of cell surface receptors is not inhibited by chloroquine.
Identification of broadly recognized, T helper 1 lymphocyte epitopes in an equine lentivirus
Authors: Fraser Darrilyn G. , Oaks J. Lindsay , Brown Wendy C. , McGuire Travis C. 
Published: March 2003

SummaryEquine infectious anaemia virus (EIAV) is a horse lentivirus causing lifelong, persistent infection. During acute infection, CD8+ cytotoxic T lymphocytes (CTL) are probably involved in terminating plasma viraemia. However, only a few EIAV CTL epitopes, restricted to fewer horse major histocompatibility complex (MHC) class I alleles, are known. As interferon‐γ (IFN‐γ)‐secreting CD4+, T helper 1 (Th1) lymphocytes promote CTL activity and help maintain memory CTL, identifying broadly recognized EIAV Th1 epitopes would contribute significantly to vaccine strategies seeking to promote strong CTL responses among horses with varying class I haplotypes. To this end, peripheral blood mononuclear cells (PBMC) from 10 MHC disparate, EIAV‐infected horses were tested in T‐lymphocyte proliferation assays for recognition of peptides from the Gag p26 capsid region and a portion of Pol. Both regions are highly conserved among EIAV isolates, and this Pol region is 51–63% homologueous to other lentiviral Pol proteins. Seven of 10 horses recognized peptide Gag 221–245, and peptides Gag 242–261 and Pol 323–344 were recognized by five and four horses, respectively. Furthermore, the Gag peptides were recognized by two additional horses after resolving their initial plasma viraemia, indicating that these two peptides can be immunodominant early in infection. Gag peptide‐responsive PBMC produced only IFN‐γ, indicating a Th1 response, while Pol 323–344‐responsive PBMC produced IFN‐γ both with and without interleukin‐4. PBMC from uninfected horses failed to either proliferate or secrete cytokines in response to peptide stimulation. Finally, CD4+ T lymphocytes were required for proliferation responses, as shown by assays using CD4‐ versus CD8‐depleted PBMC.
A feline CD2 homologue interacts with human red blood cells
Authors: Shimojima Masayuki , Nishimura Yorihiro , Miyazawa Takayuki , Kato Kentaro , Nakamura Kazuya , Izumiya Yoshihiro , Akashi Hiroomi , Tohya Yukinobu 
Published: March 2003

SummaryA cDNA encoding a feline homologue of CD2 (fCD2) was identified. Several amino acids (aa) important for ligand interaction, molecular folding or signal transduction, found in other mammalian CD2, were found to be highly conserved in the predicted fCD2 aa sequence. fCD2‐expressing cells were able to form rosettes with human red blood cells (probably via human CD58), and the rosette formation was inhibited by an anti‐fCD2 monoclonal antibody. These results are indicative of the similarity of feline and human CD2 structures. fCD2 was found to be expressed in feline peripheral blood T lymphocytes, monocytes and cultured lymphoid cells.
Community persistence among stream invertebrates tracks the North Atlantic Oscillation
Authors: Bradley David C. , Ormerod S. J. 
Published: March 2003

Summary

The North Atlantic Oscillation (NAO) affects marine ecosystems, lakes and some terrestrial ecosystems around the Atlantic rim, but evidence for effects on rivers is scarce. For 14 years, we sampled riverine macroinvertebrates in eight independent streams from the Llyn Brianne experimental catchments in central Wales. We assessed whether year‐to‐year persistence in rank abundance and species composition tracked the NAO.
Persistence was quasi‐cyclical and varied synchronously across all streams, irrespective of chemistry and catchment land use. Invertebrate communities in all stream types or habitats switched significantly from being highly persistent during negative phases of the NAO (winter index < 1 = cold, dry winters) to unstable during positive phases (> 1 = mild, wet winters). These effects occurred in both rare and common taxa.
Acid episodes could not explain low persistence in positive NAO years because variations in acid‐base status were not linked to the NAO. Moreover, fluctuations in persistence were apparent even in well‐buffered streams.
Discharge in adjacent gauged catchments increased in positive NAO years by 15–18% but neither flow variability nor flow maxima were higher. Nor were variations in invertebrate persistence at Llyn Brianne directly correlated with discharge pattern. Discharge variations alone were therefore insufficient to explain links between persistence and the NAO, but we cannot exclude subtle effects due either to flow or temperature.
These data illustrate how the persistence of invertebrate communities varies through time in fluctuating environments. Positive phases of the NAO are accompanied by ecological instability in the Llyn Brianne streams, although the exact mechanisms are currently unclear. The effects of the NAO might confound or obscure other long‐term change in rivers such as recovery from acidification or the effects of global warming.
The effect of reproduction on nitrogen use‐efficiency of three species of the carnivorous genus Pinguicula
Authors: Eckstein R. Lutz , Karlsson P. Staffan 
Published: March 2003

Summary

Life history theory predicts that reproduction incurs costs in terms of future growth and survival. In infertile environments reproductive events may accelerate nutrient turnover such that losses of limiting nutrients cannot be replenished by uptake from the soil.
We compared the effect of reproduction on nitrogen (N) turnover and N use‐efficiency, i.e. the annual dry matter produced per unit N lost, of three carnivorous species of the genus Pinguicula on an infertile subarctic heath. We hypothesized that reproduction should increase N turnover, unless a larger N pool or improved N resorption can compensate for the losses associated with reproduction.
These carnivorous herbs showed a nitrogen use strategy similar to that of non‐carnivorous plants (herbs and grasses) with a relatively low mean residence time (MRT) of N and a large dry matter productivity per unit N in the plant (annual N productivity). N pool size and the efficiency of N resorption from senescent leaves were similar in reproductive and non‐reproductive individuals. Reproductive individuals had significantly larger annual N losses and thus a lower average MRT (0.8 vs. 1.8 years), with values < 1 indicating that the annual N losses are greater than the annual average N pool. Unless plants can enhance their nutrient acquisition, flowering may therefore impact on future growth and survival.
This study presents evidence for a direct link between reproduction, reflected in a higher relative allocation to inflorescences, turnover and N use‐efficiency; the latter being reduced because of increased N turnover. The ranking of species in terms of reproductive allocation was the reverse of their ranking in terms of their N use‐efficiency.
The α7 nicotinic receptors in human fetal brain and spinal cord
Authors: Falk Lena , Nordberg Agneta , Seiger Åke , Kjældgaard Anders , Hellström‐Lindahl Ewa 
Published: March 2003

AbstractThe α7 nicotinic acetylcholine receptor subtype is believed to be involved in the regulation of neuronal growth, differentiation and synapse formation during the development of the human brain. In this study the expression of the α7 nicotinic acetylcholine receptor was investigated in human fetal brain and spinal cord of 5–11 weeks gestational age. Both the specific binding of [125I]α‐bungarotoxin to prenatal brain membranes and the expression of α7 mRNA were significantly higher in the pons, medulla oblongata, mesencephalon and spinal cord of 9–11 weeks gestational age compared with cerebellum, cortex and subcortical forebrain. A significant positive correlation between gestational age and the expression of α7␣mRNA was observed in all brain regions except cortex. A positive correlation was also observed between the gestational age and the [125I]α‐bungarotoxin binding in the pons, medulla oblongata, mesencephalon, and cerebellum. Consequently, a significant relationship between the α7 mRNA levels and the binding sites for [125I]α‐bungarotoxin was found in the fetal brain. The increasing levels of the α7 nicotinic acetylcholine receptor during the first trimester support the important role of nAChRs for the development of the central nervous system.
Resource allocation to vegetative growth and reproduction at shoot level in Eurya japonica (Theaceae): a hierarchical investment?
Authors: Suzuki Arata 
Published: March 2003

Summary

A previous study suggested that Eurya japonica, a dioecious woody plant, made a hierarchical investment; that is, this species only invested in reproduction resources surplus to its requirements for functions associated with survival, such as growth. If so, it was predicted that between‐year fluctuation in flowering intensity (number of flowers) should be much greater than that in shoot length.
Examinations of between‐year fluctuations of shoot growth and flowering intensity were made on E. japonica trees, during 1997 and 1998, in an experimental forest in Japan.
Between‐year fluctuation was found to be significantly greater in flowering intensity than in shoot length. Furthermore, between‐year fluctuation in flowering intensity of the female was stronger than that of the male. Relationships between shoot growth and flowering intensity were examined for each order branch and the results compared with those from a previous study. For the same‐order branches, the length of the current‐year shoots was found to be independent of flowering intensity for both sexes in both studies.
The results reported here support the hierarchical investment hypothesis.
Climatic control of peat erosion in a North Wales blanket mire
Authors: Ellis Christopher J. , Tallis John H. 
Published: March 2003

Summary

This study investigates the palaeoecology of a hummock‐and‐hollow complex from a partially eroded upland blanket mire at the Migneint, north Wales, UK.
Three peat cores were collected and analysed for pollen and botanical macrofossils, two for peat humification and a third was radiocarbon‐dated. In the interpretation of the palaeoecological record particular attention was paid to the ecology of the moss Racomitrium lanuginosum.
We delimit two periods in the development of the hummock‐hollow complex: an earlier period of climatically controlled blanket‐mire development; and a later period of mire erosion (initiated between c. 2000 and 1350 Cal. year BP) when ‘natural’ climatically controlled mire development was modified by excessive drying of the mire surface.
The data support recent studies in suggesting that the development of British blanket mires is sensitive to climate change. However, climatically controlled blanket‐mire development appears to have been pre‐empted at the Migneint by the development of the erosion‐complex, the initiation of which coincides with the zenith of an extensive deforestation during the Late Bronze Age, Iron Age and Romano‐British periods.
Mycorrhizal synthesis between fungal strains of the Hymenoscyphus ericae aggregate and potential ectomycorrhizal and ericoid hosts
Authors: Vrålstad Trude , Schumacher Trond , Taylor Andy F. S. 
Published: March 2003

Summary

Fungal strains of the ‘Hymenoscyphus ericae aggregate’ (Helotiales, Ascomycota) were tested for their ability to form ecto‐(ECM) and ericoid (ERM) mycorrhizas.
Twelve fungal test isolates were inoculated in vitro onto sterile ectomycorrhizal and ericoid host plants.
Five isolates of ectomycorrhizal origin formed ECM, three isolates of ericoid origin formed ERM, but none of the tested isolates was able to form both ECM and ERM. Confirmed ectomycorrhizal strains formed the characteristic black‐and‐hyaline mantles of the Piceirhiza bicolorata morphotype. This morphology represented an intermediate stage, where mantle‐colour changed from light brown to black. The progressive darkening appeared to result from a gradual acropetal melanization of the outer mantle layer.
The synthesis results confirm that the ability to form both ecto‐ and ericoid mycorrhizal symbioses has evolved within the H. ericae aggregate. In addition, a phylogeny based on ITS1–5.8S–ITS2 rDNA sequences showed that the aggregate includes the ect(endo)mycorrhizal dark septate fungus Phialophora finlandia, grouping with four of the ECM‐forming strains. The H. ericae aggregate therefore contains a number of closely related taxa with wide ecological attributes.
Selection pressures on stomatal evolution
Authors: Raven John A. 
Published: March 2003

SummaryFossil evidence shows that stomata have occurred in sporophytes and (briefly) gametophytes of embryophytes during the last 400 m yr. Cladistic analyses with hornworts basal are consistent with a unique origin of stomata, although cladograms with hornworts as the deepest branching embryophytes require loss of stomata early in the evolution of liverworts. Functional considerations suggest that stomata evolved from pores in the epidermis of plant organs which were at least three cell layers thick and had intercellular gas spaces and a cuticle; an endohydric conducting system would not have been necessary for low‐growing rhizophytes, especially in early Palaeozoic CO2‐rich atmospheres. The ‘prestomatal state’ (pores) would have permitted higher photosynthetic rates per unit ground area. Functional stomata, and endohydry, permit the evolution of homoiohydry and the loss of vegetative desiccation tolerance and plants > 1 m tall. Stomatal functioning would then have involved maintenance of hydration, and restricting the occurrence of xylem embolism, under relatively desiccating conditions at the expense of limiting carbon acquisition. The time scale of environmental fluctuations over which stomatal responses can maximize carbon gain per unit water loss varies among taxa and life forms.

Contents

Summary
371

I.
Introduction
371

II.
Monophyly of stomata?
372

III.
Roles of stomata in extant plants
373

IV.
Ecophysiology of ancestrally astomatous terrestrial plants
375

V.
Evolution of stomata
379

VI.
Ecophysiological implications of losses of stomata
382

VII.
Conclusions
384

Acknowledgements
384

References
384