bluuebunny/crossref_metadata_2025_split huggingface dataset:
The regenerative nidi of the locust midgut as a model to study epithelial cell differentiation from stem cells
Authors: Illa-Bochaca Irineu , Montuenga Luis M. 
Published: May 2006

SUMMARYA better knowledge of the regulatory mechanisms involved in stem cell proliferation and/or differentiation could reveal new methods for the treatment of some diseases. Most previous studies in the field of stem cell biology have been carried out on cultured isolated cells. In the case of adult tissue stem cells, mesenchymal bone marrow derived cells have been most widely studied, while the undifferentiated stem cells present in the epithelial tissues are less known. In order to advance further our understanding of epithelial tissue stem cells, new in vivo models are required. The present study focuses on the dynamics of a new and simple model of intestinal epithelial regeneration found in the midgut of the migratory locust, Locusta migratoria (Linnaeus 1758). The locust midgut consists of three cell types: columnar cells, endocrine cells and undifferentiated regenerative clustered cells. The undifferentiated epithelial midgut cells give rise to two other cell types and are located in a nest of regenerative cells known as regenerative niche. We have performed single and continuous bromodeoxyuridine (BrdU) administration experiments to study regeneration niches and their cellular dynamics. Immunocytochemistry and immunofluorescence techniques were used to detect the incorporation of BrdU into regenerative niches and the presence of FMRFamide-like immunoreactivity, as a marker for endocrine cell differentiation. Some isolated label retaining cells (LRC) were observed at the niche base 10-15 days after the final BrdU administration. We propose that these cells are the stem cells of this epithelial tissue. We also calculated the length of the cell cycle phases for a subpopulation of transit amplifying cells within the regenerative niche: G1, 2.5±0.5 h; S,5.5±0.5 h; G2, 0.75±0.25 h; M, 2.5±0.5 h. These amplifying cells will give rise to the columnar epithelial non-endocrine lineage. The differentiation of an endocrine cell from a niche stem cell occurs less frequently and thus leads to a lower proportion of endocrine cells as compared with epithelial columnar digestive cells (up to three endocrine cells per niche). Endocrine cell commitment seems to occur very early in the differentiation process within the niche, as double-labelled BrdU and FMRF endocrine cells have never been found. The only exception is the endocrine cells located in the ampullar region of the midgut, some of which show double immunostaining after long-term chronic BrdU injection. In summary, we have characterized a new and simple animal model of epithelial stem cell regeneration that may be useful for understanding the complex biological process that drives tissue renewal from undifferentiated and uncommitted progenitor cells.
Involvement of ryanodine-operated channels intert-butylhydroperoxide-evoked Ca2+ mobilisation in pancreatic acinar cells
Authors: Martínez-Burgos María A. , Granados María P. , González Antonio , Rosado Juan A. , Yago María D. , Salido Ginés M. , Martínez-Victoria Emilio , Mañas Mariano , Pariente José A. 
Published: May 2006

SUMMARYReactive oxygen species and related oxidative damage have been implicated in the initiation of acute pancreatitis, a disease characterised in its earliest stages by disruption of intracellular Ca2+ homeostasis. The present study was carried out in order to establish the effect of the organic pro-oxidant, tert-butylhydroperoxide (tBHP), on the mobilisation of intracellular Ca2+ stores in isolated rat pancreatic acinar cells and the mechanisms underlying this effect. Cytosolic free Ca2+ concentrations ([Ca2+]c) were monitored using a digital microspectrofluorimetric system in fura-2 loaded cells. In the presence of normal extracellular Ca2+ concentrations([Ca2+]o), perfusion of pancreatic acinar cells with 1 mmol l-1tBHP caused a slow sustained increase in[Ca2+]c. This increase was also observed in a nominally Ca2+-free medium, indicating a release of Ca2+ from intracellular stores. Pretreatment of cells with tBHP abolished the typical Ca2+ response of both the physiological agonist CCK-8 (1 nmol l-1) and thapsigargin (TPS, 1 μmol l-1), an inhibitor of the SERCA pump, in the absence of extracellular Ca2+. Similar results were observed with carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP, 0.5 μmol l-1),a mitochondrial uncoupler. In addition, depletion of either agonist-sensitive Ca2+ pools by CCK-8 or TPS or mitochondrial Ca2+ pools by FCCP were unable to prevent the tBHP-induced Ca2+release. By contrast, simultaneous administration of TPS and FCCP clearly abolished the tBHP-induced Ca2+ release. These results show that tBHP releases Ca2+ from agonist-sensitive intracellular stores and from mitochondria. On the other hand, simultaneous application of FCCP and of 2-aminoethoxydiphenylborane (2-APB), a blocker of IP3-mediated Ca2+release, was unable to suppress the increase in [Ca2+]c induced by tBHP, while the application of 50 μmol l-1 of ryanodine (which is able to block the ryanodine channels) inhibits tBHP-evoked Ca2+mobilisation. These findings indicate that tBHP releases Ca2+ from non-mitochondrial Ca2+ pools through ryanodine channels.
Evidence that blue petrel,Halobaena caerulea,fledglings can detect and orient to dimethyl sulfide
Authors: Bonadonna F. , Caro S. , Jouventin P. , Nevitt G. A. 
Published: May 2006

SUMMARYProcellariiform seabirds (the petrels, albatrosses and shearwaters) are recognized for their acute sense of smell. These pelagic seabirds forage over thousands of miles of ocean to find patchily distributed prey resources. Over the past decade, much headway has been made in unravelling the variety of olfactory foraging strategies that Antarctic species employ, and it is becoming clearer that olfaction plays a key role in foraging, particularly for burrow nesting species. Now we are beginning to explore how these behaviours develop in chicks. Procellariiform chicks fledge and survive the open seas without aid or instruction from a parent, but how they are able to accomplish this task is unknown. Here we explore whether chicks leave the nest pre-tuned to olfactory cues necessary for foraging. In this study, we tested the hypothesis that blue petrel chicks (Halobaena caerulea) are able to detect and orient to a foraging cue (dimethyl sulphide, DMS) used by adults without ever having experienced this odour at sea. We first established that chicks could detect DMS at a biologically relevant concentration that they will later naturally encounter at sea (&lt;10 pmol l-1). We then performed preference tests in a Y-maze on a group of birds 1-6 days before they fledged. Sixteen out of 20 fledglings preferred DMS (e.g. DMS+propylene glycol) to a `control' odour (propylene glycol alone). Our results suggest that chicks can detect and may already recognize DMS as an orientation cue even before they leave the nest to forage for the first time.
Nutrient regulation in relation to diet breadth: a comparison ofHeliothissister species and a hybrid
Authors: Lee Kwang Pum , Behmer, Spencer T. , Simpson, Stephen J. 
Published: May 2006

SUMMARYWe examined the nutritional correlates of diet breadth in insect herbivores by comparing patterns of diet selection, nutrient balancing, post-ingestive utilization and development in two sister species of caterpillar and a hybrid between them. One species, Heliothis virescens (HV) has a broad host range, feeding on plants in at least 14 families. The other, Heliothis subflexa (HS), is a specialist on plants in the genus Physalis(Solanaceae). Experiments using synthetic foods showed that when the caterpillars were allowed to mix their diet, the generalist self-selected a higher-protein diet whereas the specialist ate almost equal amounts of protein and carbohydrate, which accords with differences between the two species in the nutrient content of their natural diets. When confined to nutritionally imbalanced diets, the generalist showed a propensity to over-eat high protein:carbohydrate (P:C) diets to a greater degree than did the specialist and maintained higher rates of development. The generalist did not, however,over-eat low P:C diets to the same degree as the specialist. The hybrid selected a diet composition that was indistinguishable to that of its generalist father (HV), while its response to imbalanced diets was closely similar to that of the specialist mother (HS). The generalist converted ingested nutrient to growth with lower efficiency than did the specialist and the hybrid. Our findings imply that different behavioural and physiological traits linked to nutrient regulation are under genetic control and are explicable in terms of the different life-histories, feeding ecologies and presumed levels of nutritional heterogeneity in the environments of the two insects.
Hydrodynamic consequences of flexural stiffness and buoyancy for seaweeds: a study using physical models
Authors: Stewart Hannah Louise 
Published: May 2006

SUMMARYAn upright posture in the water column may expose benthic marine organisms to faster flow higher in the water column than near the substratum,potentially increasing rates of mass exchange while also exposing the organisms to higher hydrodynamic forces. Benthic organisms maintain upright postures in the water column by one of two mechanisms, stiffness or buoyancy. Turbinaria ornata is a tropical macroalga that uses either buoyancy or flexural stiffness (EI), depending on its flow habitat. This study used physical models of T. ornata to compare the effect of different magnitudes of these two mechanisms on relative water velocity and hydrodynamic forces in both unidirectional and wavy flow. Models of the alga were constructed to span and exceed natural levels of T. ornata's EI and buoyancy. Models with high EI and high buoyancy maintained upright postures in both unidirectional flow and waves, and experienced higher forces than models with low EI and moderate or low buoyancy that deflected in the direction of water motion. In waves, buoyant models that were deflected by high velocity rebounded back into upright positions when the flow slowed. Non-buoyant, flexible models were also pushed over by flow but lacked the ability to rebound upright, which led to decreased force in unidirectional flow, but high force in waves.
The human gluteus maximus and its role in running
Authors: Lieberman Daniel E. , Raichlen David A. , Pontzer Herman , Bramble Dennis M. , Cutright-Smith Elizabeth 
Published: May 2006

SUMMARYThe human gluteus maximus is a distinctive muscle in terms of size, anatomy and function compared to apes and other non-human primates. Here we employ electromyographic and kinematic analyses of human subjects to test the hypothesis that the human gluteus maximus plays a more important role in running than walking. The results indicate that the gluteus maximus is mostly quiescent with low levels of activity during level and uphill walking, but increases substantially in activity and alters its timing with respect to speed during running. The major functions of the gluteus maximus during running are to control flexion of the trunk on the stance-side and to decelerate the swing leg; contractions of the stance-side gluteus maximus may also help to control flexion of the hip and to extend the thigh. Evidence for when the gluteus maximus became enlarged in human evolution is equivocal, but the muscle's minimal functional role during walking supports the hypothesis that enlargement of the gluteus maximus was likely important in the evolution of hominid running capabilities.
In vivocranial suture function and suture morphology in the extant fishPolypterus: implications for inferring skull function in living and fossil fish
Authors: Markey Molly J. , Main Russell P. , Marshall, Charles R. 
Published: May 2006

SUMMARYThis study describes the mechanical role that cranial sutures play in fish during feeding. The long-term goal of our work is to establish relationships between suture form and function, so that functional inferences can be made from suture morphology in fossil taxa. To this end, strain gauges were surgically implanted across selected sutures in the skull roof of four individuals of Polypterus endlicherii. After surgery, bone and suture strains during feeding were recorded along with high-speed video of the feeding events. Each trial was designated as a suction feeding or biting on prey trial, and neurocranial elevation, hyoid position and gape were quantified to aid in interpreting the strain data. The strains due to suction feeding are different from those observed during biting. Suction feeding results in a fairly stereotyped strain pattern, with the interfrontal and frontoparietal sutures experiencing tension, while the interparietal suture is compressed. Biting causes much more variable strain patterns. However, both suction and biting result in compression in the back of the skull, and tension between the frontals. Peak strains, and the time at which they occur in the feeding cycle, were compared between suction and biting. In general, peak suture strains are higher during suction than during biting, but not all of these differences are significant. Peak suture and bone strains occur at or near maximum gape during both suction and biting, suggesting that these strains are caused by muscle contraction involved in mouth opening and closing. Micro-computed tomography (microCT) scans of the experimental specimens indicate that the interfrontal and frontoparietal sutures, typically loaded in tension, are less interdigitated in cross section than the interparietal suture, which experiences compression. This is consistent with published correlations of suture form and function in mammals, where interdigitated sutures indicate compression and lack of interdigitation is associated with tension.
Sensitive and Quantitative Measurement of Gene Expression Directly from a Small Amount of Whole Blood
Authors: Zheng Zhi , Luo Yuling , McMaster Gary K 
Published: May 2006

Abstract
Background: Accurate and precise quantification of mRNA in whole blood is made difficult by gene expression changes during blood processing, and by variations and biases introduced by sample preparations. We sought to develop a quantitative whole-blood mRNA assay that eliminates blood purification, RNA isolation, reverse transcription, and target amplification while providing high-quality data in an easy assay format.
Methods: We performed single- and multiplex gene expression analysis with multiple hybridization probes to capture mRNA directly from blood lysate and used branched DNA to amplify the signal. The 96-well plate singleplex assay uses chemiluminescence detection, and the multiplex assay combines Luminex-encoded beads with fluorescent detection.
Results: The single- and multiplex assays could quantitatively measure as few as 6000 and 24 000 mRNA target molecules (0.01 and 0.04 amoles), respectively, in up to 25 μL of whole blood. Both formats had CVs &lt;10% and dynamic ranges of 3–4 logs. Assay sensitivities allowed quantitative measurement of gene expression in the minority of cells in whole blood. The signals from whole-blood lysate correlated well with signals from purified RNA of the same sample, and absolute mRNA quantification results from the assay were similar to those obtained by quantitative reverse transcription-PCR. Both single- and multiplex assay formats were compatible with common anticoagulants and PAXgene-treated samples; however, PAXgene preparations induced expression of known antiapoptotic genes in whole blood.
Conclusions: Both the singleplex and the multiplex branched DNA assays can quantitatively measure mRNA expression directly from small volumes of whole blood. The assay offers an alternative to current technologies that depend on RNA isolation and is amenable to high-throughput gene expression analysis of whole blood.
Ultraviolet B Light Stimulates lnterleukin‐20 Expression by Human Epithelial Keratinocytes
Authors: Hunt David W. C. , Boivin Wendy A. , Fairley Lindsay A. , Jovanovic Miroslava M. , King Diane E. , Salmon Ruth A. , Utting Oliver B. 
Published: May 2006

ABSTRACTThe proinflammatory cytokine interleukin‐20 (IL‐20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL‐20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL‐1 and rIL‐8 increased, while hydrocortisone reduced, NHEK supernatant IL‐20 levels. Elevation of NHEK IL‐20 mRNA and maximal supernatant IL‐20 levels occurred with a UVB light dose (40 mJ cm−2) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL‐1α and IL‐8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL‐20 expression. However, the elevation in IL‐20 levels was fully inhibited by the p38 mitogen‐activated protein kinase (MAPK) inhibitor SB‐203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor‐α (TNF‐α) or recombinant interferon‐γ (rIFN‐γ) either had little effect or decreased NHEK supernatant IL‐20 levels. Reduced IL‐20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN‐γ. Neither rIL‐20 supplementation nor anti‐IL‐20 antibody treatments affected cell viability indicating that soluble IL‐20 did not affect the short‐term survival of UVB light‐irradiated NHEK. Stimulation of IL‐20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever‐present environmental factor and potentially has a role in UV light‐associated dermatoses.
Two‐Photon Singlet Oxygen Microscopy: The Challenges of Working with Single Cells
Authors: Skovsen Esben , Snyder John W. , Ogilby Peter R. 
Published: May 2006

ABSTRACTA microscope is described in which singlet molecular oxygen, O2(a 1Δg), is produced in a femtoliter focal volume via a nonlinear two‐photon photosensitized process, and the 1270 nm phosphorescence from this population of O2(a 1Δg) is detected in a photon counting experiment. Although two‐photon excitation of a sensitizer is less efficient than excitation by a one‐photon process, nonlinear excitation has several distinct advantages with respect to the spatial resolution accessible. Pertinent aspects of this two‐photon O2(a 1Δg) microscope were characterized using bulk solutions of photo‐sensitizers. These data were compared to those obtained from a single biological cell upon linear one‐photon excitation of a sensitizer incorporated in the cell. On the basis of the results obtained, we outline the challenges of using nonlinear optical techniques to create O2(a 1Δg) at the single cell level and to then optically detect the O2(a 1Δg) thus produced in a time‐resolved experiment.
New Strategies of Photoprotection
Authors: Verschooten Lien , Claerhout Sofie , Van Laethem An , Agostinis Patricia , Garmyn Marjan 
Published: May 2006

ABSTRACTAdequate photoprotection is essential to control UV‐related disorders, including sunburn, photoaging and photocarcinogenisis. Sun avoidance, protection of skin with clothing, and sunscreens are presently the best way of photoprotection, assuming that they are used properly. However, new strategies, which are based on or make use of the endogenous protective response to UV light, may further improve currently used photoprotective means. The addition of repair enzymes and/or antioxidants has a positive effect on skin's recovery from UV‐induced DNA‐damage. Several botanical agents, mainly vitamins and polyphenols, have shown to influence signal transduction pathways leading to photo‐protective effects. Also stimulation of endogenous UV‐response pathways via irradiation with a low UV dose or via simulation of UV‐induced DNA‐damage results in photo‐protective effects. Future research in this field and combination of different photoprotective strategies will hopefully lead to improved photoprotection.
Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes
Authors: Yang Li , Zhang Zhengxi , Yao Bingjia , Gao Xuhui , Sakai Hitoshi , Takahashi Tomonori 
Published: May 2006

AbstractHydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes during preparation process were investigated. After thermal treatment in air, the composite membranes exhibited high hydrogen permeability and permselectivity. The sealing process did not change the states of Pd, Ag and O, although an X‐ray photoelectron spectroscopic (XPS) signal of sulfide was found. At the same time, the sealing process led to an increase in concentration of carbon and sulfur contaminants in the surface layer, resulting in a decrease of hydrogen permeability. Moreover, carbon was present as graphite and covered membrane surfaces after running the sealing process six times. On the other hand, the thermal treatment in air led to oxidization of Pd and formation of the PdO state, and XPS data showed a significant enrichment of the Pd element at the surface of membranes. Carbon contamination concentration at the top surface of membranes decreased during thermal treatment, and carbon dioxide was found on the surface of activated membranes; at the same time, the surface state of sulfur changed to a new state of sulfate, which eventually resulted in recovery of hydrogen permeability. © 2006 American Institute of Chemical Engineers AIChE J, 2006
The onset of mixed convection in a porous layer heated with a constant heat flux
Authors: Park Joung Hwan , Chung Tae Joon , Choi Chang Kyun , Kim Min Chan 
Published: May 2006

AbstractThe onset of mixed convection in a fluid‐saturated porous layer between two horizontal plates heated from below with a constant heat flux is investigated theoretically. In the present study, the Darcy model is applied and the resulting nonlinear equations are solved by using the finite volume method. In order to analyze the growth behavior of convective instabilities, the local growth rates of mean temperature and its fluctuations are examined. Based on the numerical results, characteristic distances to represent the onset of secondary flow and also the manifestation of mixed convection are clarified to a certain degree in comparison with available experimental data. The critical distance to mark the onset of intrinsic thermal instability is predicted from a new stability criterion. It is interesting that the propagation theory yields almost the same critical conditions as the numerical ones. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Synthesis and characterization of some methylbismuth (III) O,O‐alkylenedithiophosphates: convenient transformation of and to pure Bi2S3
Authors: Jain Amit K. , Bohra Rakesh 
Published: May 2006

AbstractA series of methylbismuth(III)O,O‐alkylenedithiophosphates of the type [where G = CH2CH(CH3) (1), (CH2)4 (2), CH2CH2CH(CH3) (3), CH(CH3)CH(CH3) (4), CH2CHCH2CH3 (5), CH(CH3)CH2C(CH3)2 (6) and C(CH3)2C(CH3)2 (7)] have been isolated by the reaction of methylbismuth(III) dichloride with potassium salt of O,O‐alkylenedithiophosphoric acids in 1:2 molar ratio in anhydrous benzene. These newly synthesized derivatives were characterized by elemental analyses, FT IR and multinuclear NMR (1H, 13C and 31P) spectral studies. Thermogravimetric analysis of 6 has shown a single‐step decomposition of complex to Bi2S3 at 154.3 °C. Transformation of 2 and 6 to pure Bi2S3 was carried out successfully at refluxing xylene temperature (142 °C) as revealed by XRD and SEM analyses. Copyright © 2006 John Wiley & Sons, Ltd.