bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Prebudding Arrest of ER Export in Animal Cell Mitosis and its Role in Generating Golgi Partitioning Intermediates
Authors: Prescott Alan R. , Farmaki Theodora , Thomson Calum , James John , Paccaud Jean‐Pierre , Tang Bor‐Luen , Hong Wanjin , Quinn Martyn , Ponnambalam Sreenivasan , Lucocq John
Published: March 2003

During mitosis the interconnected Golgi complex of animal cells breaks down to produce both finely dispersed elements and discrete vesiculotubular structures. The endoplasmic reticulum (ER) plays a controversial role in generating these partitioning intermediates and here we highlight the importance of mitotic ER export arrest in this process. We show that experimental inhibition of ER export (by microinjecting dominant negative Sar1 mutant proteins) is sufficient to induce and maintain transformation of Golgi cisternae to vesiculotubular remnants during interphase and telophase, respectively. We also show that buds on the ER, ER exit sites and COPII vesicles are markedly depleted in mitotic cells and COPII components Sec23p, Sec24p, Sec13p and Sec31p redistribute into the cytosol, indicating ER export is inhibited at an early stage. Finally, we find a markedly uneven distribution of Golgi residents over residual exit sites of metaphase cells, consistent with tubulovesicular Golgi remnants arising by fragmentation rather than redistribution via the ER. Together, these results suggest selective recycling of Golgi residents, combined with prebudding cessation of ER export, induces transformation of Golgi cisternae to vesiculotubular remnants in mitotic cells. The vesiculotubular Golgi remnants, containing populations of slow or nonrecycling Golgi components, arise by fragmentation of a depleted Golgi ribbon independently from the ER.
Neurotransmitter Receptor Trafficking and the Regulation of Synaptic Strength
Authors: Kittler Josef T. , Moss Stephen J.
Published: March 2003

Modulation of the strength of synapses is thought to be one of the mechanisms that underlies learning and memory and is also likely to be important in processes of neuropathology and drug tolerance. This review focuses on the emerging role of postsynaptic neurotransmitter receptor trafficking as an essential mechanism underlying the dynamic regulation of synaptic strength.
Achieving Molecular Selectivity in Imaging Using Multiphoton Raman Spectroscopy Techniques
Authors: Holtom Gary R. , Thrall Brian D. , Chin Beek‐Yoke , Wiley H. Steven , Colson Steven D.
Published: March 2003

In the case of most optical imaging methods, contrast is generated either by physical properties of the sample (Differential Image Contrast, Phase Contrast), or by fluorescent labels that are localized to a particular protein or organelle. Standard Raman and infrared methods for obtaining images are based upon the intrinsic vibrational properties of molecules, and thus obviate the need for attached fluorophores. Unfortunately, they have significant limitations for live‐cell imaging. However, an active Raman method, called Coherent Anti‐Stokes Raman Scattering (CARS), is well suited for microscopy, and provides a new means for imaging specific molecules. Vibrational imaging techniques, such as CARS, avoid problems associated with photobleaching and photo‐induced toxicity often associated with the use of fluorescent labels with live cells. Because the laser configuration needed to implement CARS technology is similar to that used in other multiphoton microscopy methods, such as two‐photon fluorescence and harmonic generation, it is possible to combine imaging modalities, thus generating simultaneous CARS and fluorescence images. A particularly powerful aspect of CARS microscopy is its ability to selectively image deuterated compounds, thus allowing the visualization of molecules, such as lipids, that are chemically indistinguishable from the native species.
Junctions as Organizing Centers in Epithelial Cells? A Fly Perspective
Authors: Lecuit Thomas , Wieschaus Eric
Published: March 2003

Junctions isolate the apical from the basal–lateral surfaces and are required for the polarization of epithelial cells. Genetics of junction formation in Drosophila has identified numerous transmembrane and scaffolding proteins that assemble in membrane‐associated complexes. This review focuses on recent findings suggesting that junctions are autonomous organizing centers for the establishment and maintenance of apical‐basal polarity in epithelial cells as well as other polarized processes such as the orientation of the division apparatus.
Localization of HCMV UL33 and US27 in Endocytic Compartments and Viral Membranes
Authors: Fraile‐Ramos Alberto , Pelchen‐Matthews Annegret , Kledal Thomas N. , Browne Helena , Schwartz Thue W. , Marsh Mark
Published: March 2003

The human cytomegalovirus genome encodes four putative seven transmembrane domain chemokine receptor‐like proteins. Although important in viral pathogenesis, little is known about the properties or functions of these proteins. We previously reported that US28 is located in endocytic vesicles and undergoes constitutive endocytosis and recycling. Here we studied the cellular distributions and trafficking of two other human cytomegalovirus chemokine receptor‐like proteins, UL33 and US27, in transfected and human cytomegalovirus‐infected cells. Immunofluorescence staining indicated that UL33 and US27 are located at the cell surface, although the majority of both proteins was seen in intracellular organelles located in the perinuclear region of the cell. The intracellular pools of UL33 and US27 showed overlap with markers for endocytic organelles. Antibody‐feeding experiments indicated that cell surface US27 undergoes endocytosis. By immunogold labeling of cryosections and electron microscopy, UL33 was seen to localize to multivesicular bodies (MVBs or multivesicular endosomes). Electron microscopy analysis of human cytomegalovirus‐infected cells showed that most virus particles wrapped individually into short membrane cisternae, although virus particles were also occasionally seen within and budding into MVBs. Electron microscopy immunolocalization of viral UL33 and US27 on ultrathin cryosections of human cytomegalovirus‐infected cells showed gold particles over the membranes into which virions were wrapping, in small membrane tubules and vesicles and in MVBs. Labeling of the human cytomegalovirus glycoproteins gB and gH indicated that these proteins were also present in the same membrane structures. This first electron microscopy analysis of human cytomegalovirus assembly using immunolabeling suggests that the localization of UL33, US27 and US28 to endosomes may allow these proteins to be incorporated into the viral membrane during the final stages of human cytomegalovirus assembly.
Calcium‐Dependent Transferrin Receptor Recycling in Bovine Chromaffin Cells
Authors: Knight Derek E.
Published: March 2003

The release of regulated secretory granules is known to be calcium dependent. To examine the Ca2+‐dependence of other exocytic fusion events, transferrin recycling in bovine chromaffin cells was examined. Internalised 125I‐transferrin was released constitutively from cells with a half‐time of about 7 min. Secretagogues that triggered catecholamine secretion doubled the rate of 125I‐transferrin release, the time courses of the two triggered secretory responses being similar. The triggered 125I‐transferrin release came from recycling endosomes rather than from sorting endosomes or a triggered secretory vesicle pool. Triggered 125I‐transferrin release, like catecholamine secretion from the same cells, was calcium dependent but the affinities for calcium were very different. The extracellular calcium concentrations that gave rise to half‐maximal evoked secretion were 0.1 mm for 125I‐transferrin and 1.0 mm for catecholamine, and the intracellular concentrations were 0.1 μm and 1 μm, respectively. There was significant 125I‐transferrin recycling in the virtual absence of intracellular Ca2+, but the rate increased when Ca2+ was raised above 1 nm, and peaked at 1 μm when the rate had doubled. Botulinum toxin type D blocked both transferrin recycling and catecholamine secretion. These results indicate that a major component of the vesicular transport required for the constitutive recycling of transferrin in quiescent cells is calcium dependent and thus under physiological control, and also that some of the molecular machinery involved in transferrin recycling/fusion processes is shared with that for triggered neurosecretion.
The Melanocytic Protein Melan‐A/MART‐1 Has a Subcellular Localization Distinct from Typical Melanosomal Proteins
Authors: De Mazière Ann M. , Muehlethaler Katja , Van Donselaar Elly , Salvi Suzanne , Davoust Jean , Cerottini Jean‐Charles , Lévy Frédéric , Slot Jan W. , Rimoldi Donata
Published: March 2003

To delineate the role of the melanocyte lineage‐specific protein Melan‐A/MART‐1 in melanogenic functions, a set of biochemical and microscopical studies was performed. Biochemical analysis revealed that Melan‐A/MART‐1 is post‐translationally acylated and undergoes a rapid turnover in a pigmented melanoma cell line. Immunofluorescence and immunoelectron microscopy analyses indicated that Melan‐A/MART‐1 is mainly located in the Golgi area and only partially colocalizes with melanosomal proteins. Quantitative immunoelectron microscopy showed that the highest proportion of the cellular content of Melan‐A/MART‐1 was found in small vesicles and tubules throughout the cell, whereas the concentration was maximal in the Golgi region, particularly the trans‐Golgi network. Substantial labeling was also present on melanosomes, endosomes, ER, nuclear envelope, and plasma membrane. In early endosomes, Melan‐A was enriched in areas of the limiting membrane covered by a bi‐layered coat, a structural characteristic of melanosomal precursor compartments. Upon melanosome maturation, Melan‐A concentration decreased and its predominant localization shifted from the limiting membrane to internal vesicle membranes. In conjunction with its acylation, the high expression levels of Melan‐A in the trans‐Golgi network, in dispersed vesicles, and on the limiting membrane of premelanosomes indicate that the protein may play a role during the early stage of melanosome biogenesis.
A Kinetic Proof‐reading Mechanism for Protein Sorting
Authors: Weiss Matthias , Nilsson Tommy
Published: March 2003

Resident proteins of the exocytic pathway are maintained at various levels through coatomer protein I (COPI)‐mediated recycling. Sorting of cargo by COPI requires GTP hydrolysis by ADP‐ribosylation factor 1 (ARF‐1). This small GTPase recruits coatomer onto Golgi membranes and upon hydrolysis, is thought to release coatomer back into the cytosol. This step requires the activating protein, ARFGAP1. By coupling sorting to a cargo‐induced sequestering of ARFGAP1, we have formulated a kinetic proof‐reading model that explains how a GTP hydrolysis‐driven coat release can yield an active sorting event. The sorting scheme predicts a dependency on the amount of ARFGAP1 and explains the recent experimental findings that ARF‐1 and COPI detach with different time constants from the Golgi membrane in vivo.
The effect of commercially available saliva substitutes on predemineralized bovine dentin in vitro
Authors: Meyer‐Lueckel H , Schulte‐Mönting J , Kielbassa AM
Published: March 2003

OBJECTIVE: The objective of this study was to evaluate the effects of various saliva substitutes (Artisial®; Glandosane®; Oralube®; Saliva medac®; Oralbalance®) on the lesion depth and the mineral content of predemineralized bovine dentin in vitro.

MATERIALS AND METHODS: Ninety‐six dentin samples were prepared from 24 freshly extracted bovine incisors. The samples were predemineralized (pH 5.5; 10 days), and subsequently exposed to the various artificial salivas. A carbonate‐reduced mineral water (Hirschquelle®) as well as the mouthwash solutions Meridol® and biotène® served as controls. Lesion depth and mineral loss were evaluated from microradiographs of thin sections (110 μm) by a dedicated software package (TMR 1.24).

RESULTS: After storage in Glandosane® and biotène®, the results indicated a significant mineral loss and an increase in lesion depth (P < 0.01; Wilcoxon). In contrast, specimens stored in Oralube® showed a decrease in lesion depth and an increase in mineral content (P < 0.05; Wilcoxon).

CONCLUSIONS: Thus, the use of neither Glandosane® nor biotène® can be recommended in dentate patients with severe xerostomia.
Nitric oxide synthesis and severity of human periodontal disease
Authors: Batista AC , Silva TA , Chun JH , Lara VS
Published: March 2003

The expression of the inducible nitric oxide synthase enzyme (iNOS) is a response to an inflammatory stimulus and produces a large amount of nitric oxide (NO), which may act as a cytotoxic molecule against the invading microorganism and may be related to both harmful and beneficial effects to tissues.

OBJECTIVE AND MATERIAL AND METHODS: Inorder to further characterize the presence of NO in human periodontal disease, we undertook a quantitative study of iNOS positive cells in samples of clinically healthy gingival tissues, plaque‐induced gingivitis and localized chronic periodontitis using immunohistochemistry.

RESULTS: A significant increase in the number of iNOS+ cells mm−2 was found in the samples of the gingivitis and periodontitis compared with those of the control. In all groups most of the polymorphonuclear cells showed intense immunoreactivity for iNOS independent of the disease stage, and the percentage of iNOS+ polymorphonuclear cells increased significantly in periodontal disease when compared with the control.

CONCLUSION: Our results indicate that iNOS increases in the presence of periodontal disease. In addition, our findings suggest that polymorphonuclear cells present anadditional activation pathway in periodontal disease, expressing significant iNOS and probably representing an important source of NO in human periodontal disease that has not been previously reported.
The use of bone scintigraphy in temporomandibular joint disorders
Authors: Epstein JB , Rea A , Chahal O
Published: March 2003

INTRODUCTION: The use of bone scintigraphy (bone scan) in the diagnosis of temporomandibular joint (TMJ) disease has been infrequent, as compared with traditional radiographic techniques. Bone scans have the potential to detect active bone remodeling whereas corresponding radiographs may be normal or document past structural change in the joint. Traditional radiographic findings and relevant clinical signs and symptoms correlated with bone scans may aid in the diagnosis of TMJ disease and possibly affect treatment and prognosis of individual cases. The use of bone scans as an additional tool in diagnosing TMJ disease was assessed in this series of patients.

METHODS: Thirty consecutive subjects with TMJ tenderness were selected for bone scintigraphy using technetium diphosphonate 99 mTc and single photon emission computerized tomography. These subjects received bone scans as well as other selected imaging modalities for diagnostic purposes.

RESULTS AND DISCUSSION: The findings on bone scan were evaluated and a change in preliminary clinical diagnosis or treatment was made in 60% of cases because of the findings on bone scintigraphy. Bone scintigraphy may be valuable to assess progress of TMJ inflammation or remodeling, and may affect diagnosis and treatment of patients with TMJ tenderness.
Opinions about oral cancer prevention and early detection among dentists practising along the Texas–Mexico border
Authors: Alonge OK , Narendran S
Published: March 2003

OBJECTIVES: The purpose of this study was to assess dentists’ opinions about oral cancer (OC) prevention and early detection.

METHODS: Data were collected by a self‐administered mail questionnaire sent to all 398 registered dentists practising along the Texas–Mexico border.

RESULTS: The effective response rate to the survey was 40%. While 90% of respondents agreed that oral cancer examinations (OCE) should be provided annually for patients 40 years of age and older, only 59% of respondents believed their OC knowledge was current. While 99% agreed that dentists were qualified to perform OCE, only 54 and 68% respectively, agreed that dental hygienists and physicians were similarly qualified. Dentists who rated their undergraduate OC training favorably (OR=2.68, 1.23–5.81,P=0.011), had attended their last oral cancer continuing education (OCCE) course within the past 5 years (OR=2.46, 1.25–4.86,P=0.009), and those who performed OCE on all patients 40 years and older (OR=2.64, 1.32–5.26,P=0.005), were more likely to agree their OC knowledge was current.

CONCLUSIONS: Respondents expressed diverse opinions about OC prevention and early detection. Positive opinion on currency of OC knowledge was associated with performance of OCE. Results indicate a need for OCCE targeting the study population as well as increased emphasis on OC curriculum in dental schools.
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

We 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

The 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

There 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

There 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

Proinflammatory 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

Equine 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

A 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

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

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

The 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

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

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

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

Fossil 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
Inference of a detailed P–T path from P–T pseudosections using metapelitic rocks of variable composition from a single outcrop, Shackleton Range, Antarctica
Authors: Zeh A.
Published: March 2003

Generally, P–T pseudosections for reduced compositional systems, such as K2O–FeO–MgO–Al2O3–SiO2–H2O, Na2O–K2O–FeO–MgO–Al2O3–SiO2–H2O and MnO–K2O–FeO–MgO–Al2O3–SiO2–H2O, are well suited for inferring detailed P–T paths, comparing mineral assemblages observed in natural rocks with those calculated. Examples are provided by P–T paths inferred for four metapelitic samples from a 1 m2 wide outcrop of the Herbert Mountains in the Shackleton Range, Antarctica. The method works well if the bulk composition used is reconstituted from average mineral modes and mineral compositions (AMC) or when X‐ray fluorescence (XRF) data are corrected for Al2O3 and FeO. A plagioclase correction is suitable for Al2O3. Correction for FeO is dependent on additional microscopic observations, e.g. the kind and amount of opaque minerals. In some cases, all iron can be treated as FeOtot, whereas in others a magnetite or hematite correction yields much better results. Comparison between calculated and observed mineral modes and mineral compositions shows that the AMC bulk composition is best suited to the interpretation of rock textures using P–T pseudosections, whereas corrected XRF data yield good results only when the investigated sample has few opaque minerals. The results indicate that metapelitic rocks from the Herbert Mountains of the Northern Shackleton Range underwent a prograde P–T evolution from about 600 °C/5.5 kbar to 660 °C/7 kbar, followed by nearly adiabatic cooling to about 600 °C at 4.5 kbar.
Developing and evaluating dialogue games for collaborative e–learning
Authors: Ravenscroft A. , Matheson M.P.
Published: March 2003

Abstract This paper argues that developments in collaborative e‐learning dialogue should be based on pedagogically sound principles of discourse, and therefore, by implication, there is a need to develop methodologies which transpose — typically informal — models of educational dialogue into cognitive tools that are suitable for students. A methodology of ‘investigation by design’ is described which has been used to design computer‐based dialogue games supporting conceptual change and development in science — based on the findings of empirical studies. An evaluation of two dialogue games for collaborative interaction, a facilitating game and an elicit‐inform game, has shown that they produce significant improvements in students conceptual understanding, and they are differentially successful — depending on the nature of the conceptual difficulties experienced by the learners. The implications this study has for the role of collaborative dialogue in learning and designing computer‐based and computer–mediated collaborative interaction are discussed.
The effects of case libraries on problem solving
Authors: Hernandez‐Serrano J. , Jonassen D.H.
Published: March 2003

Abstract The purpose of the study was to investigate the effects of providing access to a case library of related stories while undergraduates solved ill‐structured problems. While solving complex food product development problems, the experimental group accessed experts' stories of similar, previously solved problems; the comparable group accessed fact sheets (expository representation of stories' content); and the control group accessed text selected at random from a textbook dealing with issues unrelated to the stories. On multiple‐choice questions assessing processes related to problem solving (prediction, inferences, explanations, etc.), experimental students out‐performed the comparable and control groups. Performance on short‐answer questions also assessing problem‐related skills was not significantly different, in part because of test fatigue. Analysis of interviews identified a number of factors that students used in deciding how to apply their study strategies, including causal factors, grounding phenomenon, grounding in context, and outcomes.
Olfactory memory in the mosquito Culex quinquefasciatus
Authors: Mccall P. J. , Eaton G.
Published: March 2003

Abstract. The cosmotropical urban mosquito Culex quinquefasciatus Say (Diptera: Culicidae) uses chemical cues to locate suitable water pools for oviposition. Although gravid females are innately attracted to or repelled by certain compounds, this study found that an individual mosquito's preferences for these odours could be altered greatly by prior experience. Mosquitoes reared in water containing skatole, at a level normally repellent to ovipositing females, preferred to oviposit in water containing that compound rather than in water with an otherwise attractive odour compound (P‐cresol). This behaviour occurred regardless of whether mosquitoes were tested individually or in groups of up to 50 per cage. The F1 progeny of conditioned mosquitoes did not exhibit the parental preference, but were as susceptible to conditioning as their parents. Moreover, rearing mosquitoes in infusions of hay or animal (guinea‐pig) faeces produced a similar although less dramatic change, such that the innate propensity for hay infusion could be cancelled by rearing in guinea‐pig faeces infusion. The results demonstrated a change in odour preference by Cx. quinquefasciatus following exposure to the odour during development or pupal eclosion, suggesting that some form of larval conditioning or early adult imprinting occurred. Precisely when that conditioning occurred remains to be determined.
Larviposition by nasopharyngeal bot fly parasites of Columbian black‐tailed deer: a correction
Authors: Anderson J. R.
Published: March 2003

Abstract. Previous reports of Cephenemyia jellisoni Townsend (Diptera: Oestridae) larvipositing onto the lips/lower muzzle of deer, with larvae invading via the mouth, are shown to be erroneous. Additional studies with deer models baited with CO2, 1‐octen‐3‐ol and Deer Trail Scent, and muzzle and nostrils treated with insect adhesive, revealed that only C. apicata Bennett & Sabrosky larviposited onto the lips/lower muzzle; C. jellisoni, by contrast, larviposited into the nostrils. Larval depositions were associated with females of both species observed attacking models. Females of both species also were found stuck on adhesive‐treated, baited models not attended by observers. During several seasons of exposure, such models received 89 C. jellisoni larvipositions into the nostrils and 87 C. apicata larvipositions onto the lips/lower muzzle. In laboratory experiments nearly all larvae of both species remained stuck in adhesive within 1 mm or less of where they were deposited.
Design, function and evolution in the wings of holometabolous insects
Authors: Wootton Robin J.
Published: March 2003

The wings of Holometabola are reviewed in functional terms. Two basic types, anteroposteriorly symmetric (‘symmetric’) and anteroposteriorly asymmetric (‘asymmetric’), are recognized and their modes of operation discussed. Most neuropteroids have asymmetric wings, whereas relative anteroposterior symmetry appears plesiomorphic for mecopteroids. Wing coupling has only occurred in lineages with wings of symmetric type, but anteroposterior asymmetry of the wing couple has later developed several times in association with improved, more versatile, flight performance. Coleoptera wings seem to have developed from predecessors of symmetric type, but their morphology is strongly influenced by the need to fold up at rest. Diptera provide an excellent illustration of the evolution of asymmetric, high‐performance wings from the symmetric, ‘mecopteran’ type. Asymmetric and symmetric wings can both be derived from less specialized types. Both are well represented as fossils from the Permian onwards, and these supply further examples of the evolution of asymmetry from the symmetric pattern.