bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulus Dependent Redistribution of Membrane Raft Cholesterol in Human Platelets
Authors: Boesze‐Battaglia Kathleen , Schimmel Richard J. , Gretzula Cheryl
Published: January 2005

Cell membranes provide a requisite dynamic interface to facilitate communication between the extracellular environment and the intracellular milieu. These membranes contain proteins that span and/or are loosely associated with the lipid bilayer. The organization of lipids and proteins components into membrane micro‐domains provides a temporal and spatial signaling platform for communication. Recently, cholesterol and sphingomyelin enriched membrane micro‐domains known as lipid rafts have been implicated in cell signaling events. In these studies we have advanced our hypothesis that stimulus dependent rearrangement of cholesterol into and out of membrane rafts provides a unique lipid–mediated regulatory mechanism. Using fluorescent derivatives of cholesterol, we have shown that membrane raft associated cholesterol was altered in response to collagen‐induced platelet aggregatory stimulation. Collagen stimulation resulted in a rapid redistribution of cholesterol from the outer to the inner membrane monolayer. The reorganization of the outer membrane monolayer resulted in a concomitant increase in outer monolayer fluidity. These studies are the first to show that membrane cholesterol was released from the exchangeable membrane raft pool in response to physiological stimuli.
Interaction of Polyunsaturated Fatty Acids with Cholesterol: A Role in Lipid Raft Phase Separation
Authors: Wassall Stephen R. , Shaikh Saame Raza , Brzustowicz Michael R. , Cherezov Vadim , Siddiqui Rafat A. , Caffrey Martin , Stillwell William
Published: January 2005

Unequal affinity between lipids has been hypothesized to be a mechanism for the formation of microdomains/rafts in membranes. Our studies focus upon the interaction of cholesterol with polyunsaturated fatty acid (PUFA)‐containing phospholipids. They support the proposal that steric incompatibility of the rigid steroid moiety for highly disordered PUFA chains, in particular docosahexaenoic acid (DHA), provides a sensitive trigger for lateral segregation of lipids into PUFA‐rich/sterol‐poor and PUFA‐poor/sterol‐rich regions. Solid state 2H NMR and x‐ray diffraction (XRD) demonstrate that the solubility of cholesterol is reduced in 1‐palmitoyl‐2‐docosahexaenoyl‐phosphatidylethanolamine (16‐0:22:6PE) bilayers. In mixed membranes of phosphatidylethanolamine (PE) with the lipid raft forming molecules egg sphingomyelin (SM) and cholesterol, diminished affinity of the sterol for 16:0‐22:6PE relative to 1‐palmitoyl‐2‐oleoylphosphatidylethanolamine (16:0‐18:1PE) is identified by 2H NMR order parameters and detergent extraction. Phase separation of the PUFA‐containing phospholipid from SM/cholesterol rafts is the implication, which may be associated with the myriad of health benefits of dietary DHA.
Probing the Interdigitated Phase of a DPPC Lipid Bilayer by Micropipette Aspiration
Authors: Ly Hung V. , Longo Marjorie L.
Published: January 2005

We used micropipette aspiration of giant unilamellar vesicles to directly measure the areal expansion of gel (Lβ′) phase 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC) lipid bilayers induced by exposure to ethanol/water mixtures. Areal expansion began in 7 vol% ethanol and increased monotonically as the concentration of ethanol was increased to 15 vol% at which point areal expansion reached a plateau of 50%. This ethanol concentration range is in good agreement with that of the interdigitated phase (LβI) of DPPC, therefore, we believe that this is the first direct measurement of the areal expansion accompanying interdigitation of gel‐phase lipids. Our observations are consistent with the presence of coexisting LβI and Lβ′ phases in ethanol concentrations between 7% and 15 vol% and 100% LβI phase in 15 vol% ethanol and higher. We observed a bimodal distribution of areal expansion (0% and 20%) induced by 7 vol% ethanol indicating that at the threshold concentration, interdigitation is induced in only a portion of DPPC vesicles. Areal expansion could not be easily reversed, consistent with kinetic trapping of the LβI phase. DPPC vesicles exposed to butanol at the known threshold and plateau concentrations for the LβI phase displayed areal expansion behavior consistent with our ethanol observations. However, the area expanded significantly faster for DPPC bilayers exposed to butanol vs. ethanol, which we attribute to enhanced partitioning of the longer‐chained butanol into the lipid headgroups. Ethanol‐induced areal expansion of DPPC bilayers was inhibited by inclusion of 10 mol% and 25 mol% cholesterol in the bilayer. However, areal expansion could be induced by application of tensions (∼8 mN/m) similar to the phenomena of interdigitation induced by high pressure. The presence of 20 vol% ethanol significantly decreased surface cohesion of DPPC bilayers containing 25 mol% cholesterol as evidenced by a decreased area compressibility modulus and lysis tension.
Calcium‐Alginate Nanoparticles Formed by Reverse Microemulsion as Gene Carriers
Authors: You Jin‐Oh , Peng Ching‐An
Published: January 2005

Natural biopolymers are widely used in the field of drug and gene delivery. In this study, alginate nanoparticles were prepared using water‐in‐oil microemulsion as a template followed by calcium crosslinking of guluronic acid units of alginate polymer. After collected by ultracentrifugation, alginate nanoparticles were analyzed by electron microscopy to obtain the size and morphology which were varied with the ratio of water, oil, and surfactant used. To examine the potency of Ca‐alginate nanoparticles as carriers for gene delivery, GFP‐encoding plasmids were encapsulated in these nanoparticles to investigate the degree of endocytosis by NIH 3T3 cells and ensuing transfection rate. Our results showed that Ca‐alginate nanoparticles with an average size around 80 nm in diameter are very efficient gene carriers, in comparison with plasmid DNA condensed by polyethyleneimine (PEI).
Wnt signalling and the mechanistic basis of tumour development
Authors: Ilyas Mohammad
Published: January 2005

Abnormalities in the Wnt signalling pathway are found in a wide range of cancers. The diverse origin of these malignancies implies that the contribution that disrupted Wnt signalling makes to tumourigenesis is not limited to specific tissue types and thus can be regarded as a step which is ‘generic’ to the process of carcinogenesis. In recent years, rapid progress has been made in the understanding of the Wnt signalling pathway, giving an insight into how inappropriate activation of this pathway may facilitate the neoplastic conversion of a normal cell. Furthermore, elucidation of the mechanisms that regulate Wnt signalling has led to the possibility of manipulating these mechanisms in order to down‐regulate Wnt signalling in established tumours. In this review, the Wnt signalling pathway is described. The role of aberrant Wnt signalling in tumour development is discussed together with its clinical implications for anti‐tumour therapy. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
New approaches for modelling cancer mechanisms in the mouse
Authors: Maddison Kathryn , Clarke Alan R
Published: January 2005

Mouse models of human cancer are vital to our understanding of the neoplastic process, and to advances in both basic and clinical research. Indeed, models of many of the major human tumours are now available and are subject to constant revision to more faithfully recapitulate human disease. Despite these advances, it is important to recognize that limitations do exist to the current range of models. The principal approach to modelling has relied upon the use of constitutive gene knockouts, which can often result in embryonic lethality, can potentially be affected by developmental compensation, and which do not mimic the sporadic development of a tumour expanding from a single cell in an otherwise normal environment. Furthermore, simple knockouts are usually designed to lead to loss of protein function, whereas a subset of cancer‐causing mutations clearly results in gain of function. These drawbacks are well recognized and this review describes some of the approaches used to address these issues. Key amongst these is the development of conditional alleles that precisely mimic the mutations found in vivo, and which can be spatially and tissue‐specifically controlled using ‘smart’ systems such as the tetracycline system and Cre‐Lox technology. Examples of genes being manipulated in this way include Ki‐Ras, Myc, and p53. These new developments in modelling mean that any mutant allele can potentially be turned on or off, or over‐ or under‐expressed, in any tissue at any stage of the life‐cycle of the mouse. This will no doubt lead to ever more accurate and powerful mouse models to dissect the genetic pathways that lead to cancer. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Molecular mechanisms of drug resistance
Authors: Longley DB , Johnston PG
Published: January 2005

Resistance to chemotherapy limits the effectiveness of anti‐cancer drug treatment. Tumours may be intrinsically drug‐resistant or develop resistance to chemotherapy during treatment. Acquired resistance is a particular problem, as tumours not only become resistant to the drugs originally used to treat them, but may also become cross‐resistant to other drugs with different mechanisms of action. Resistance to chemotherapy is believed to cause treatment failure in over 90% of patients with metastatic cancer, and resistant micrometastic tumour cells may also reduce the effectiveness of chemotherapy in the adjuvant setting. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanisms of drug resistance that operate to reduce drug sensitivity in cancer cells. Drug resistance can occur at many levels, including increased drug efflux, drug inactivation, alterations in drug target, processing of drug‐induced damage, and evasion of apoptosis. Advances in DNA microarray and proteomic technology, and the ongoing development of new targeted therapies have opened up new opportunities to combat drug resistance. We are now able to characterize the signalling pathways involved in regulating tumour cell response to chemotherapy more completely than ever before. This will facilitate the future development of rational combined chemotherapy regimens, in which the newer targeted therapies are used in combination with cytotoxic drugs to enhance chemotherapy activity. The ability to predict response to chemotherapy and to modulate this response with targeted therapies will permit selection of the best treatment for individual patients. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Insulin‐like growth factor ligands, receptors, and binding proteins in cancer
Authors: Foulstone E , Prince S , Zaccheo O , Burns JL , Harper J , Jacobs C , Church D , Hassan AB
Published: January 2005

This review aims to summarize experimental evidence supporting the role of the insulin‐like growth factor (IGF) signalling system in the progression, maintenance, and treatment of cancer. These data implicate the IGF system as an important modifier of cancer cell proliferation, survival, growth, and treatment sensitivity. The role of the IGF system in cancer should be examined in the context of the extra‐cellular and intra‐cellular signalling networks, in particular: phosphatidylinositol 3‐kinase (PI3K), protein kinase B (Akt/PKB), mammalian target of rapamycin (mTOR), and forkhead transcription factors (FOXO). This review highlights evidence derived from molecular structure and functional genetics with respect to how the extra‐cellular components of the IGF system function normally, and their subsequent modifications in cancer. The therapeutic relevance of the research evidence described is also addressed, as the challenge is to apply this knowledge to human health. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Effect of electron–phonon energy exchange on thermal wave propagation in semiconductors considering carrier diffusion and recombination
Authors: Villegas‐Lelovsky L. , Gonzalez de la Cruz G. , Volovichev I. N.
Published: January 2005

The electron, hole, and phonon temperatures are calculated in semiconductors by taking into account the finite carrier diffusion and nonradiative recombination time in the sample. We assume that the energy of the modulated excitation radiation is greater than the energy gap and absorbed at the surface of the semiconductor, therefore, a source of heat and carrier generation at the surface of the sample are time dependent and must be considered in the photothermal theory. Under this situation, the coupled one‐dimensional heat transport (for each quasiparticle system) and carrier diffusion equations in the strong hole–phonon energy interaction approximation and charge quasineutrality condition are solved. Since the nonequilibrium carrier concentration depends sensitively on the electron and phonon fluctuation temperature, the heat power density generated in the sample due to the recombination of the electron–hole pair will be greatly influenced by the inhomogeneous quasiparticle temperature distributions. This latter effect comes through the recombination rate of carriers and it will be considered in the photothermal signal. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intraband relaxation time in InGaNAs quantum‐well lasers and comparison with experiment
Authors: Park Seoung‐Hwan
Published: January 2005

The intraband relaxation time is investigated theoretically for InGaNAs/InGaNAs/GaAs QW lasers. The result is compared with that obtained from comparison between the experimental gain spectra and theoretical gain. The InGaNAs/InGaNAs QW shows smaller intraband relaxation time than InGaAs/InGaAsP QW. This is due to the fact that the InGaNAs/InGaNAs structure has larger electron effective masses than the InGaAs/InGaAsP QW. The calculated gain spectra is in good agreement with the experiment. The intraband relaxation time τin obtained from fitting the experimental data is 60 fs. This value reasonably agrees well with the calculated value of 62 fs at the subband edge, considering that the electrons and the holes are mostly near the subband edge. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A teaching framework for cross‐cultural genetic counseling
Authors: Weil Jon , Mittman Ilana
Published: January 2005

The increasing diversity of American society has brought growing recognition of the need to bridge cultures in the delivery of genetic counseling services. New immigrants and members of diverse ethnic groups face multiple barriers to genetic counseling services. The need to train genetic counselors to deal with cultural diversity is especially crucial in the new genetic era, given the rapid expansion of available technology, with the resulting social and ethical ramifications. A framework for teaching cross‐cultural issues in genetic counseling training programs is presented that can be implemented in step‐wise fashion, consistent with available resources. Cross‐cultural issues can be incorporated into existing teaching and training modalities by expanding the orientation from monocultural to multicultural. Relevant clinical experience, exploration of students' preconceptions and biases, reading materials, and lectures by invited speakers can all enhance students' knowledge and sensitivity. It is critically important that training programs furnish students with the basic tools necessary for the ongoing process of learning about cultural diversity.
A survey of reimbursement for cystic fibrosis carrier testing
Authors: Bernhardt Barbara A.
Published: January 2005

To assess the current status of reimbursement for cystic fibrosis (CF) carrier testing, we surveyed individuals tested in the Mid‐Atlantic region. Results show that CF testing was covered by insurance in part or in full for greater than 50% of respondents. The test was nearly always covered when performed during pregnancy because of a positive family history, but it was also covered for more than 50% of pregnant respondents with a negative family history. There were no significant differences in coverage by type of insurance. Many respondents needed to supply additional information about the testing to their insurance company before a coverage decision could be made. Before population‐based CF screening programs are initiated, more data are needed on insurance reimbursement for testing, especially when performed pre‐conceptually.
Scientific aspects of early eugenics
Authors: Lubinsky Mark S.
Published: January 2005

The eugenics movement supported applications of scientific breeding principles to humans, ultimately to encourage a better society, but actually with often disastrous social consequences. Although mostly viewed as quackery today, legitimate scientific considerations of fact and theory had an important role in determining the course of eugenics. A school of eugenics arose formally from attempts to apply Darwinian principles to humans in the context of biometry, a school that used statistical approaches to biology. Biometry emphasized blending inheritance and continuous traits, in marked contrast to the particulate inheritance of unit traits in Mendelism. Genetics was therefore a scientific challenge to eugenics, which was rooted in biometry. A Mendelian eugenics arose in the United States primarily under the influence of Charles Davenport. This paper reviews some of the technical issues involved in the development of this new paradigm, as well as Davenport's role as a scientist in this process.
5‐Enolpyruvylshikimate‐3‐phosphate synthase from Staphylococcus aureus is insensitive to glyphosate
Authors: Priestman Melanie A. , Funke Todd , Singh Inder M. , Crupper Scott S. , Schönbrunn Ernst
Published: January 2005

The enzyme 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS) catalyzes the penultimate step of the shikimate pathway, and is the target of the broad‐spectrum herbicide glyphosate. Kinetic analysis of the cloned EPSPS from Staphylococcus aureus revealed that this enzyme exerts a high tolerance to glyphosate, while maintaining a high affinity for its substrate phosphoenolpyruvate. Enzymatic activity is markedly influenced by monovalent cations such as potassium or ammonium, which is due to an increase in catalytic turnover. However, insensitivity to glyphosate appears to be independent from the presence of cations. Therefore, we propose that the Staphylococcus aureus EPSPS should be classified as a class II EPSPS. This research illustrates a critical mechanism of glyphosate resistance naturally occurring in certain pathogenic bacteria.
Synergistic action of MLL, a TRX protein with template activating factor‐I, a histone chaperone
Authors: Shimoyama Tae , Kato Kohsuke , Miyaji-Yamaguchi Mary , Nagata Kyosuke
Published: January 2005

MLL is involved in the process of gene activity maintenance. It is shown that the amino‐terminal region of MLL (MLLN) interacts with TAF‐Iβ/SET. In this study, using yeast two‐hybrid assays, we have found that the acidic region of TAF‐Iβ is essential for its binding to MLLN. Pull‐down assays using GST‐MLLN demonstrated that TAF‐Iβ and histones interact with GST‐MLLN. MLLN and TAF‐Iβ synergistically upregulated the transcription level of Hoxa9 and co‐immunoprecipitated in chromatin containing the Hoxa9 promoter region. These results suggest that TAF‐Iβ plays an important role in MLL‐mediated transcription and possibly chromatin maintenance.
Phosphodiesterase inhibitors stimulate osteoclast formation via TRANCE/RANKL expression in osteoblasts: possible involvement of ERK and p38 MAPK pathways
Authors: Takami Masamichi , Cho Eun Sook , Lee Soo Young , Kamijo Ryutaro , Yim Mijung
Published: January 2005

Phosphodiesterases (PDEs) are enzymes that degrade intracellular cAMP. In the present study, 3‐isobutyl‐1‐methylxanthine (IBMX) and pentoxifylline, PDE inhibitors, induced osteoclast formation in cocultures of mouse bone marrow cells and calvarial osteoblasts. These inhibitors induced the expression of the osteoclast differentiation factor, TNF‐related activation induced cytokine (TRANCE, identical to RANKL, ODF, and OPGL), in calvarial osteoblasts. IBMX induced phosphorylation of extracellular signal‐regulated kinase (ERK) and p38 mitogen‐activated protein kinase (MAPK) in osteoblasts. Induction of TRANCE expression by IBMX was partially suppressed by the inhibitors of protein kinase A (PKA), ERK, and p38 MAPK, suggesting that activation of ERK and p38 MAPK, as well as PKA, is involved in TRANCE expression by IBMX. Osteoblasts expressed PDE4, a PDE subtype, and rolipram, a selective inhibitor of PDE4, induced TRANCE expression. These results suggest that PDE4 is a key regulator of TRANCE expression in osteoblasts, which in turn controls osteoclast formation.
The conserved histidine 106 of large thioredoxin reductases is likely to have a structural role but not a base catalyst function
Authors: Jacob Judit , Schirmer R. Heiner , Gromer Stephan
Published: January 2005

The catalytic activity of selenocysteine‐containing thioredoxin reductases can be mimicked by cysteine‐variants if the local environment at the C‐terminal redox center supports thiol activation. This concept of a linear catalytic site was challenged by structural data suggesting that the invariant residue His106 functions as a base catalyst for the dithiol‐disulphide exchange reaction between enzyme and substrate. As reported here, we changed His106 to asparagine, glutamine, and phenylalanine in various C‐terminal mutants of Drosophila melanogaster thioredoxin reductase. The catalytic activity dropped considerably, yet pH‐profiles did not reveal differences, rendering a function for His106 as a base catalyst unlikely. Interestingly, the phenylalanine‐mutants, designed as negative controls were the most active mutants which suggests rather a structural role of His106.
Clinical Homeopathic use of RNA: evidence from two provings
Authors: Zagon A , Riley D
Published: January 2005

Two homeopathic drug provings (HDPs) of RNA have been published. The methods are reviewed. Our method is double-blind and placebo-controlled, conforms to GCP and includes run-in and follow-up phases. Symptoms are selected from diaries according to predefined criteria. The results of the provings are compared with each other and with the homeopathic clinical use of RNA. At this stage it is difficult to draw conclusions concerning the clinical use of RNA. Further HDPs are required, they should follow GCP and standard, transparent protocols.
Coherence–incoherence transition in nonlinear wave interactions
Authors: FRICHEMBRUDER M. , PAKTER R. , RIZZATO F. B.
Published: January 2005

In this paper we analyze the transition from coherent to incoherent wave dynamics in a broad-band triplet interaction, where, in contrast to previous models, wave vector selection rules are imposed on the nonlinear terms of the governing equations. As a general rule, nonlinear terms induce coherence via a phase-locking process. However, wave vector spread also results from nonlinearity and can affect coherence when resonant modes are excited.
Fleshy pulp enhances the location of Syagrus romanzoffiana (Arecaceae) fruits by seed-dispersing rodents in an Atlantic forest in south-eastern Brazil
Authors: Guimarães Paulo R. , Lopes Priscila F. M. , Lyra Mariana L. , Muriel Ana Paula
Published: January 2005

Rodents are the most diverse group of terrestrial mammals in neotropical forests (Emmons & Feer 1997). The interaction of rodents with plants is often pivotal for seed survival (Peres & Baider 1997, Vander Wall 1990). Many rodent species are seed predators (Brewer 2001, Galetti et al. 1992, Hoch & Adler 1997). However, some neotropical rodents, especially dasyproctids (such as Dasyprocta and Myoprocta) and echimyids (Proechimys), are important secondary seed dispersers for large-seeded plants (Forget 1993, 1994; Hoch & Adler 1997, Wenny 1999).
Edge effects on post-dispersal seed removal in a fragmented rain forest in French Guiana
Authors: Chauvet Stéphanie , Forget Pierre-Michel
Published: January 2005

Forest fragmentation results in the creation of edge habitats, which can be responsible for large modifications in community dynamics (Murcia 1995, Saunders et al. 1991). Plant recruitment along edges is favoured for early successional species but is limited for core forest species (Fox et al. 1997, Williams-Linera 1990). Because the former generally produce large quantities of small seeds while the latter produce fewer large seeds (Hammond & Brown 1995), seed resource availability along the edge is biased in favour of smaller seeds. Such seeds are more likely to attract small rodents than large scatterhoarding species (Adler 1998, Forget et al. 1998). Moreover, the density and activity of forest animals in edge habitats can also be altered as a consequence of their specific responses to habitat changes, varying from edge avoidance to edge preference (Bowers & Dooley 1993, Goosem 2000). These changes in seed resource availability and rodent communities can have cascading effects on plant–rodent interactions in edge habitats and post-dispersal seed predation processes (Holl & Lulow 1997).
Influence of faeces on seed removal from gibbon droppings in a dipterocarp forest in Central Borneo
Authors: McConkey Kim R.
Published: January 2005

Many frugivorous animals disperse seeds in their faeces (Corlett 1998, van der Pijl 1982), which may enhance the ability of secondary seed dispersers and post-dispersal seed predators to locate seeds (Andresen 2001, Chapman 1989, Feer 1999, Janzen 1982). By destroying and moving seeds these animals can radically alter the primary seed shadows generated by frugivorous animals and, consequently, have the potential to influence plant recruitment (Alcántara et al. 2000, Crawley 1992). Nevertheless, the influence of faeces on seed removal in South-East Asian forests has not previously been investigated and our knowledge currently comes from studies in Neotropical forests (Andresen 2001, Chapman 1989, Feer 1999, Janzen 1982).
Post-dispersal removal of seeds of pioneer species from five Panamanian forests
Authors: Fornara D. A. , Dalling J. W.
Published: January 2005

Variation among forests in environmental and biotic conditions may strongly influence seed fate with important consequences for the abundance and distribution of plant species. Here we examine the post-dispersal seed removal rates of six pioneer species (Cecropia peltata, Miconia argentea, Luehea seemannii, Trema micrantha, Apeiba aspera and Jacaranda copaia) from the soil surface at five sites in Panama varying in elevation (0–1100 m) and seasonality (0–4 mo dry season). We compared removal rates of washed seeds placed in vertebrate exclosures, invertebrate exclosures, and unprotected controls in January and June. Overall, removal rates of unprotected seeds were similar among sites. Almost all seed removal could be attributed to litter ants in two subfamilies (Myrmicinae and Ponerinae). Little or no removal was recorded from invertebrate exclosures while vertebrate exclosures had no effect on removal either in lowland and montane forests. Seed removal rates were high for four animal-dispersed species (mean 45% removed over 2 d), whereas two wind-dispersed species were largely untouched (mean 2% removed). These results indicate that seed dispersal characteristics, rather than site characteristics, may be the strongest determinant of the post-dispersal seed fate of pioneers.
The importance of phyllosphere microbial populations in nitrogen cycling in the Chaco semi-arid woodland
Authors: Abril Adriana B. , Torres Patricia A. , Bucher Enrique H.
Published: January 2005

In tropical rain forest, the interface between leaf surfaces and the atmosphere is a fundamental pathway for nutrient cycling (particulary nitrogen), possibly even more important than the soil–plant interface (Parker 1994, Silver et al. 1996). Most important nutrient exchanges in the phyllosphere–atmosphere interface are mediated by microbial populations. For example, some authors have considered that nitrogen fixation in the phyllosphere is the main mechanism for nitrogen gain in humid tropical ecosystems, because of the substantial nutrient demand resulting from a high plant productivity and the constraint imposed by the generally low nitrogen availability in soil (Ruinen 1974, Salati et al. 1982, Silver et al. 1996).
A long-term evaluation of fruiting phenology: importance of climate change
Authors: Chapman Colin A. , Chapman Lauren J. , Struhsaker Thomas T. , Zanne Amy E. , Clark Connie J. , Poulsen John R.
Published: January 2005

Within the last decade the study of phenology has taken on new importance because of its contribution to climate-change research. However, phenology data sets spanning many years are rare in the tropics, making it difficult to evaluate possible responses of tropical communities to climate change. Here we use two data sets (1970–1983 and 1990–2002) to describe the fruiting patterns of the tropical tree community in Kibale National Park, Uganda. To address variation in spatial patterns, we describe fruiting over 2–3 y among four sites each separated by 12–15 km. Presently, the Kibale region is receiving c. 300 mm more rain than it did at the start of the century, droughts are less frequent, the onset of the rainy season is earlier, and the average maximum monthly temperature is 3.5 °C hotter than it was 25 y ago. The 1990–2002 phenology data illustrated high temporal variability in the proportion of the populations fruiting. Interannual variation in community-wide fruit availability was also high; however, the proportion of trees that fruited has increased over the past 12+y. At the species level a variety of patterns were exhibited; however, a number of the most common species currently rarely fruit, and when they do, typically <4% of the individuals take part in fruiting events. Combining the data set from 1990 to 2002 with that from 1970 to 1983 for specific species again reveals an increase in the proportion of trees fruiting between 1990 and 2002; however, the proportion of the populations fruiting decreased during the earlier period. When one examines particular species over this whole period a variety of patterns are evident. For example, Pouteria altissima exhibited a relatively regular pattern of fruiting during the 1970s; however, it rarely fruited in the 1990s. Contrasting phenological patterns at four sites revealed that at the community level the fruiting patterns of only one of the six pair-wise site combinations were correlated. Relationships between rainfall and fruiting were variable among sites. Contrasting changes in fruiting patterns over the 30 y with differences among the four sites varying in rainfall, suggests that the changes observed in fruiting may be due to climate change. Responses to this climate change are likely complex and will vary among species. However, for some species, current conditions appear unsuitable for fruiting.
Niche opportunity and ant invasion: the case of Wasmannia auropunctata in a New Caledonian rain forest
Authors: Le Breton Julien , Jourdan Hervé , Chazeau Jean , Orivel Jérôme , Dejean Alain
Published: January 2005

Due to the unbalanced distribution of their fauna and flora, which leads to the creation of a niche opportunities, it is generally accepted that island communities offer weak biotic resistance to biological invasion. In order to empirically test this statement, we compared resource use by ants in the understorey of an undisturbed New Caledonian rain forest recently invaded by the little fire ant, Wasmannia auropunctata. We tested the exploitation of: (1) food sources by placing baits on all trees with trunks greater than 5 cm in diameter; and (2) nesting sites on two tree species likely to shelter ant colonies. In non-invaded areas, the native ants occupied only 44.6% of the baits after 2 h of exposure, while in invaded areas all the baits were occupied by numerous W. auropunctata workers. Similarly, in non-invaded areas only 48.9% of Meryta coriacea (Araliaceae) trees and 64.5% of Basselinia pancheri (Arecaceae) sheltered ants, while in invaded areas W. auropunctata nested in 92.6–98.3% of these trees. Also, workers attended native Margarodidae (Hemiptera) for which they promoted the development of populations significantly larger than those attended by native ants. Thus native ants appear unable to efficiently exploit and defend several of the available food sources and nesting sites, providing a niche opportunity for an invader like W. auropunctata.
Host specialization and species richness of fruit flies (Diptera: Tephritidae) in a New Guinea rain forest
Authors: Novotny Vojtech , Clarke Anthony R. , Drew Richard A. I. , Balagawi Solomon , Clifford Barbara
Published: January 2005

Frugivorous dacine fruit flies were studied in a lowland tropical rain forest in Papua New Guinea to determine their host specificity, abundance, and the number of species attacking various plant species. Plant species hosted 0–3 fruit fly species at median (1–3 quartile) densities of 1 (0–17) fruit flies per 100 fruits. Fruit flies were mostly specialized to a single plant family (83% species) and within each family to a single genus (88% species), while most of the species (66%) were able to feed on >1 congeneric plant species. Only 30 from the 53 studied plant species were colonized by fruit flies. The plant–fruit fly food web, including these 30 plant species and the total of 29 fruit fly species feeding on them, was divided into 14 compartments, each including 1–8 plant species hosting mutually disjunct assemblages of fruit flies. This structure minimizes indirect interactions among plant species via shared herbivores. The local species pool was estimated at 152±32 (±SE) fruit fly species. Forty per cent of all taxonomically described species known from Papua New Guinea were reared or trapped in our study area. Such a high proportion indicates low beta-diversity of fruit flies. Steiner traps were highly efficient in sampling the lure-responsive fruit fly species as they re-collected 84% of all species trapped in the same area 5 y before. Fruit fly monitoring by these traps is a cheap, simple and efficient method for the study of spatial and temporal changes in rain-forest communities.
IMPACT OF PRENATAL DIAGNOSIS ON THE PAEDIATRIC MANAGEMENT OF HEART DEFECTS
Authors: ALLAN LINDSEY
Published: January 2005

Ultrasound has been used in cardiac diagnosis since the 1960s. The original modality used was M-mode, which recorded the movement of heart structures relative to a single line of sound passed through the heart and was displayed as a paper tracing. During the 1970s, a two-dimensional image became possible, but it was a static image, which had limited value for cardiac evaluation. However, by the end of the 1970s, advances in ultrasound equipment allowed the heart to be displayed in real-time. This technology was applied initially in the adult and subsequently in the child. Echocardiography proved particularly suitable for children, partly because it is non-invasive and repeatable, but also because most heart disease in children is due to malformation of anatomical structure, which ultrasound can ideally display. At the same time, obstetric ultrasound was progressing rapidly and descriptions of the appearances of malformations in most fetal systems began to be published by the end of the 1970s. It was not until real-time equipment became generally available in obstetrics that the fetal heart could be satisfactorily evaluated. This led to descriptions by several authors of normal fetal cardiac anatomy as seen echocardiographically in 1980. The appearances of the echocardiogram in different forms of congenital heart disease (CHD) in children were published in the late 1970's, setting the stage for diagnosis in fetal life. As a result, by the mid-1980's, most major forms of CHD had been detected prenatally.
Necessary conditions for geosynchronous magnetopause crossings
Authors: Suvorova A. , Dmitriev A. , Chao J.‐K. , Thomsen M. , Yang Y.‐H.
Published: January 2005

The International Solar Terrestrial Physics database of the magnetic measurements on GOES and plasma measurements on Los Alamos National Laboratory (LANL) geosynchronous satellites is used for selection of 169 case events containing 638 geosynchronous magnetopause crossings (GMCs) in 1995 to 2001. The GMCs and magnetosheath intervals associated with them are identified using advanced methods that take into account (1) strong deviation of the magnetic field measured by GOES from the magnetospheric field, (2) high correlation between the GOES magnetic field and interplanetary magnetic field (IMF), and (3) substantial increase of the midenergy ion and electron fluxes measured by LANL. Accurate determination of the upstream solar wind conditions for the GMCs is performed using correlation of geomagnetic activity (Dst(SYM‐H) index) with the upstream solar wind pressure. The location of the GMCs and associated upstream solar wind conditions are ordered in an aberrated GSM coordinate system (aGSM) with X‐axis directed along the solar wind flow. In the selected data set of GMCs the solar wind total pressurePswvaries up to 100 nPa and the southward IMFBzreaches 60 nT. We study the conditions necessary for geosynchronous magnetopause crossings using scatterplots of the GMCs in the coordinate space ofPswversusBz. In such a representation the upstream solar wind conditions show a sharp envelope boundary beyond which no GMCs are observed. The boundary has two straight horizontal branches whereBzdoes not influence the magnetopause location. The first branch is located in the range ofPsw= 21 nPa for large positiveBzand is associated with a regime of pressure balance. The second branch asymptotically approaches the range ofPsw= 4.8 nPa under strong negativeBz, and it is associated with a regime in which theBzinfluence saturates. The intermediate region of the boundary ranges from moderate negative to moderate positive IMFBzand can be well approximated by a hyperbolic tangent function. We interpret the envelope boundary as a range of necessary upstream solar wind conditions required for the magnetopause to reach geosynchronous orbit at its closest approach to the Earth (its “perigee” location).
Structural evolution of the Thetford Mines Ophiolite Complex, Canada: Implications for the southern Québec ophiolitic belt
Authors: Schroetter Jean‐Michel , Bédard Jean H. , Tremblay Alain
Published: January 2005

The Thetford Mines Ophiolite Complex (TMOC) preserves a complete ophiolitic sequence, and occupies the hanging wall of a major SE dipping normal fault, the Saint‐Joseph fault. Preobduction, synobduction, and postobduction structures can be recognized in the TMOC. NS trending, preobduction, paleonormal faults are parallel to ultramafic minor intrusions, and to sheeted dykes, recording extension related to seafloor‐spreading in a pericontinental suprasubduction zone basin. WNW trending synobduction, synmetamorphic fabrics are found toward the base of the TMOC and in the underlying continental margin rocks, but are absent in the upper part of the TMOC and overlying sedimentary rocks. These Ordovician (Taconian) structures record the development of a dynamothermal aureole immediately below the mantle/margin contact, and emplacement of the young ophiolite onto the continental margin. Postobduction structures include Late Silurian/Early Devonian, SE verging backthrusts and back folds that inverted the TMOC; and Middle Devonian (Acadian) NW verging folds and reverse faults. The tectonic history established for the TMOC is consistent with that of the adjacent Laurentian margin, and can be applied to the southern Québec ophiolitic belt as a whole. The structural synthesis of the ophiolitic belt, complemented with new observations and our compilation of stratigraphical, geochemical, geochronological, and petrological data, suggests that the southern Québec ophiolites may represent the remnants of the obduction of a single large slab of suprasubduction oceanic lithosphere extending for over a 100 km of strike length.
On the use of anion exchange chromatography for the characterization of water soluble organic carbon
Authors: Chang Hui , Herckes Pierre , Collett Jeffrey L.
Published: January 2005

An increasingly popular anion exchange chromatography method [Decesari et al., 2000] was used to separate organic matter in fog samples and water soluble organic carbon (WSOC) extracted from aerosol samples according to acidity. Analysis of both fog and aerosol WSOC samples showed results similar to previous studies, with peaks typically identified as corresponding to neutral/basic compounds, mono‐ and dicarboxylic acids and polyacids. In one example this approach was shown to classify a total of 82% of the WSOC into these three chromatographic fractions. Challenges to the classification scheme were made by injection of single compound solutions. Compounds were chosen to be representative of compounds observed in atmospheric samples. In many cases test compounds eluted in fractions other than expected based on classifying compound structure according to the three classes outlined above. The impact of classification errors is impossible to quantify without understanding the complete organic speciation of a sample, but is serious enough that researchers relying on this method to provide a suitable model for organic aerosol composition should interpret results with caution. The most severe problems are likely for fog samples, due to a prevalence of low molecular weight carboxylic acid and carbonyl compounds which exhibit greater tendency to be misclassified.
Remote reemergence areas of winter sea surface temperature anomalies in the North Pacific
Authors: Sugimoto Shusaku , Hanawa Kimio
Published: January 2005

Taking account of water movement, we detect pairs of ‘formation’ and ‘reemergence’ areas of winter sea surface temperature (SST) anomalies in the North Pacific, by analyzing various kinds of data sets. Two pairs of formation and reemergence areas are detected. One pair is located in the northern subtropical gyre, and water properties in both the formation and reemergence areas well correspond to those of North Pacific central mode water (NPCMW). Another pair is found in the western to central part of the subtropical gyre. The formation area corresponds well to that of North Pacific subtropical water (NPSTMW), but the reemergence area is remote from the formation area. Examinations on upper ocean current field, trace of temperature anomalies in the subsurface, and change of water properties from the formation area to the reemergence area, clearly indicate that waters with winter SST anomalies move from the formation area to the reemergence area in a year.
First ground‐based measurements of OI 6300 Å daytime aurora over Boston in response to the 30 October 2003 geomagnetic storm
Authors: Pallamraju D. , Chakrabarti S.
Published: January 2005

High spectral resolution measurements of OI 6300 Å emissions during daytime on 30 October 2003 from Boston revealed prolonged auroral activity from 1415–1900 LT. The solar zenith angles varied from 70°–115° during that interval. Intense enhancement in brightness of 38 Kilo Rayleighs were observed at 1509 LT, which were six times larger than the normal daytime emission rates for that day. During this event the solar zenith angle was 74° and the solar background continuum was 4 × 106 Rayleighs Å−1. Such large enhancement in brightness were due to the daytime aurora generated in response to an X‐class Coronal Mass Ejection on the Sun. The measured daytime airglow emissions show good agreement, both, in the magnitudes and in the temporal variability with the emissions modeled by using as inputs the Ne, Te and Ti profiles that were measured by the Millstone Hill Incoherent Scatter Radar (ISR) located approximately 60 km away from the spectrograph.
A “loss cone” precursor of an approaching shock observed by a cosmic ray muon hodoscope on October 28, 2003
Authors: Munakata K. , Kuwabara T. , Yasue S. , Kato C. , Akahane S. , Koyama M. , Ohashi Y. , Okada A. , Aoki T. , Mitsui K. , Kojima H. , Bieber J. W.
Published: January 2005

We analyze a loss cone anisotropy observed by a ground‐based muon hodoscope at Mt. Norikura in Japan for 7 hours preceding the arrival of an interplanetary shock at Earth on October 28, 2003. Best fitting a model to the observed anisotropy suggests that the loss cone in this event has a rather broad pitch‐angle distribution with a half‐width about 50° from the IMF. According to numerical simulations of high‐energy particle transport across the shock, this implies that the shock is a “quasi‐parallel” shock in which the angle between the magnetic field and the shock normal is only 6°. It is also suggested that the lead‐time of this precursor is almost independent of the rigidity and about 4 hour at both 30 GV for muon detectors and 10 GV for neutron monitors.
Relativistic solar neutrons and protons on 28 October 2003
Authors: Bieber John W. , Clem John , Evenson Paul , Pyle Roger , Ruffolo David , Sáiz Alejandro
Published: January 2005

The solar cosmic ray event associated with the X17.2 class flare of 28 October 2003 was unusual in several respects: (1) Several high‐latitude neutron monitors observed a large, highly anisotropic spike at event onset. (2) The earliest onset was detected by stations viewing towards the anti‐Sunward hemisphere. (3) The event displayed an extremely slow, protracted decay. (4) The near‐equatorial monitor in Tsumeb, Africa recorded a small increase consistent with a solar neutron event ≈7 minutes prior to the onset at high latitudes. We analyze these signals and infer that relativistic solar neutrons were emitted over a duration of ≈9 minutes, starting ≈7 minutes before the main injection of relativistic protons.
How does extratropical warming affect ENSO?
Authors: Yang Haijun , Zhang Qiong , Zhong Yafang , Vavrus Steve , Liu Zhengyu
Published: January 2005

Idealized experiments in a coupled climate model show that the remote impact of the extratropics on the tropics can modulate the behavior of El Niño‐Southern Oscillation (ENSO) phenomenon. An extratropical warming can weaken the Hadley cells and slow down the shallow meridional overturning circulations in the upper Pacific, causing reductions in the equatorward cold water supply and the equatorial upwelling and thus a weakened stratification of the equatorial thermocline. Therefore, weaker and longer ENSO cycle would occur in the stabilized equatorial coupled system resulted from the extratropical warming.
Sunspot cycle 24: Smallest cycle in 100 years?
Authors: Svalgaard Leif , Cliver Edward W. , Kamide Yohsuke
Published: January 2005

Predicting the peak amplitude of the sunspot cycle is a key goal of solar‐terrestrial physics. The precursor method currently favored for such predictions is based on the dynamo model in which large‐scale polar fields on the decline of the 11‐year solar cycle are converted to toroidal (sunspot) fields during the subsequent cycle. The strength of the polar fields during the decay of one cycle is assumed to be an indicator of peak sunspot activity for the following cycle. Polar fields reach their peak amplitude several years after sunspot maximum; the time of peak strength is signaled by the onset of a strong annual modulation of polar fields due to the 7° tilt of the solar equator to the ecliptic plane. Using direct polar field measurements, now available for four solar cycles, we predict that the approaching solar cycle 24 (∼2011 maximum) will have a peak smoothed monthly sunspot number of 75 ± 8, making it potentially the smallest cycle in the last 100 years.