bluuebunny/crossref_metadata_2025_split huggingface dataset:
Consequences of positive ions upon imaging in low vacuum scanning electron microscopy
Authors: Craven J. P. , Baker F. S. , Thiel B. L. , Donald A. M. 
Published: March 2003

SummaryThe effects caused by an excess quantity of ionized gas molecules within the low vacuum, variable pressure and environmental scanning electron microscope (ESEM) are described with reference to mechanisms by which they can influence imaging conditions. These effects can include specimen charging, recombination and development of space charge. They are demonstrated for three different classes of sample: (1) an electrically grounded conductor, (2) an electrically floating conductor, and (3) an electrical insulator. A new device is presented that will aid excess charge removal within the ESEM and help correct for some of these effects, thereby dramatically improving imaging over a wide range of operating conditions and samples. The mechanism of image enhancement is demonstrated with reference to the three classes of sample described above.
A novel sample holder allowing atomic force microscopy on transmission electron microscopy specimen grids: repetitive, direct correlation between AFM and TEM images
Authors: Lin A. C. , Goh M. C. 
Published: March 2003

SummaryA novel sample holder that allows atomic force microscopy (AFM) to be performed on transmission electron microscope (TEM) grids is described. Consequently, AFM and TEM images were repeatedly obtained on exactly the same sample area. For both techniques, a thin carbon film was used as the imaging substrate. Although these techniques have been previously used in conjunction, AFM and TEM images on exactly the same area have not been repeatedly obtained for any system. Correlation of AFM and TEM images is useful for work where the three‐dimensional topographical information provided by the AFM could be used to better interpret the two‐dimensional images provided by the TEM and vice versa. To demonstrate the applicability of such correlation, new results pertaining to a fibrillar collagen system are summarized.
Intraplantar injection of glutamate evokes peripheral adenosine release in the rat hind paw: involvement of peripheral ionotropic glutamate receptors and capsaicin‐sensitive sensory afferents
Authors: Liu Xue Jun , White Thomas D. , Sawynok Jana 
Published: March 2003

AbstractGlutamate receptors have been identified on the peripheral terminals of both primary sensory afferents and sympathetic post‐ganglionic neurons, and activation of these receptors produces peripheral sensitization and enhances nociception. Adenosine is an endogenous agent that has a regulatory effect on pain. In brain and spinal cord, adenosine release can be promoted by excitatory amino acids. In the present study, we used in vivo microdialysis to determine whether glutamate also can release adenosine in peripheral tissues. Rats were anesthetized with pentobarbital and microdialysis probes were implanted into the subcutaneous tissue of the plantar aspect of the rat hind paw. Subcutaneous injection of glutamate (50 μL, 0.3–100 μmol) evoked a short‐lasting adenosine release immediately following drug injection. Co‐administration of either the N‐methyl‐d‐aspartate (NMDA) receptor antagonist, dizocipine maleate (MK‐801, 1 nmol) or the non‐NMDA receptor antagonist, 6‐cyano‐7‐nitroquinoxaline (CNQX, 10 nmol) with glutamate blocked such release, suggesting an involvement of peripheral ionotropic glutamate receptors in this response. Systemic pre‐treatment with capsaicin, a neurotoxin selective for unmyelinated sensory afferents, significantly reduced glutamate‐evoked peripheral adenosine release, but release was not affected by systemic pre‐treatment with 6‐hydroxydopamine, a neurotoxin selective for sympathetic nerve efferents. Neither MK‐801 nor CNQX blocked 5% formalin‐evoked adenosine release, suggesting adenosine release by formalin is not secondary to ionotropic glutamate receptor activation. We conclude that administration of glutamate evokes peripheral adenosine release, and that peripheral ionotropic glutamate receptors on unmyelinated sensory afferents are involved in such release. The released adenosine may provide a negative feedback control on nociception.
Nicotine activates the extracellular signal‐regulated kinase 1/2 via the α7 nicotinic acetylcholine receptor and protein kinase A, in SH‐SY5Y cells and hippocampal neurones
Authors: Dajas‐Bailador F. A. , Soliakov L. , Wonnacott S. 
Published: March 2003

AbstractNeuronal nicotinic acetylcholine receptors (nAChR) can modulate many cellular mechanisms, such as cell survival and memory processing, which are also influenced by the serine/threonine protein kinases ERK1/2. In SH‐SY5Y cells and hippocampal neurones, nicotine (100 µm) increased the activity of ERK1/2. This effect was Ca2+ dependent, and prevented by the α7 nAChR antagonist α‐bungarotoxin (α‐Bgt) and an inhibitor (PD98059) of the upstream kinase MEK. To determine the intervening steps linking Ca2+ entry to MEK‐ERK1/2 activation, inhibitors of Ca2+‐dependent kinases were deployed. In SH‐SY5Y cells, selective blockers for PKC (Ro 31–8220), CaM kinase II (KN‐62) or PI3 kinase (LY 294002) failed to inhibit the nicotine‐evoked increase in ERK1/2 activity. In contrast, two structurally different inhibitors of PKA (KT 5720 and H‐89) completely prevented the nicotine‐dependent increase in ERK1/2 activity. Inhibition of the nicotine‐evoked increase in ERK1/2 activity by H‐89 was also observed in hippocampal cultures. Down stream of PKA, the activity of B‐Raf was significantly decreased by nicotine in SH‐SY5Y cells, as determined by direct measurement of MEK1 phosphorylation or in vitro kinase assays, whereas the modulation of MEK1 phosphorylation by Raf‐1 tended to increase. Thus, this study provides evidence for a novel signalling route coupling the stimulation of α7 nAChR to the activation of ERK1/2, in a Ca2+ and PKA dependent manner.
Formation of carnosine‐Cu(II) complexes prevents and reverts the inhibitory action of copper in P2X4 and P2X7 receptors
Authors: Coddou Claudio , Villalobos Claudio , González Jorge , Acuña‐Castillo Claudio , Loeb Bárbara , Huidobro‐Toro J. Pablo 
Published: March 2003

AbstractTo further analyze the action of copper on brain synaptic mechanisms, the brain dipeptide carnosine (β‐alanyl‐l‐histidine) was tested in Xenopus laevis oocytes expressing the rat P2X4 or P2X7 receptors. Ten micromolar copper halved the currents evoked by ATP in both receptors; co‐application of carnosine plus copper prevented the metal induced‐inhibition with a median effective concentration of 12.1 ± 3.9 and 12.0 ± 5.5 µm for P2X4 and P2X7, respectively. Zinc potentiated only the P2X4 ATP‐evoked currents; carnosine had no effect over this metal. The relative potency and selectivity of classical metal chelators to prevent the copper inhibition was compared between carnosine and penicillamine (PA), bathophenanthroline (BPh) or l‐histidine (His). Their rank order of potency in P2X4 and P2X7 receptors was carnosine = PA = His > BPh > Glycine (Gly) and carnosine = BPh = His > PA >	Gly, respectively. The potency to prevent the zinc‐induced potentiation in the P2X4 receptor was BPh > PA > His; carnosine, Gly and β‐alanine were inactive. Whereas 1–100 µm carnosine or His alone did not modify the ATP‐evoked currents, 10–100 µm PA augmented and 100 µm BPh decreased the ATP‐evoked currents. Carnosine was able to revert the copper‐induced inhibition restoring the maximal ATP gated current in a concentration‐dependent manner. Electronic spectroscopy confirm the formation of carnosine‐Cu(II) complexes, mechanism that can account for the prevention and reversal of the copper inhibition, revealing its potential in copper intoxication treatment.
Prostacyclin‐induced rundown of N‐methyl‐d‐aspartate receptor currents in HEK293 cells is protein kinase A‐dependent and NR2 subunit‐selective
Authors: Woodward John J. 
Published: March 2003

AbstractPrevious studies in neurons have demonstrated a rapid decrease in NMDA receptor currents following tyrosine kinase inhibition or exposure to platelet‐derived growth factor (PDGF). Inhibitors of protein kinase A␣(PKA) block the PDGF‐induced rundown suggesting a multistep pathway that leads to decreased amplitudes of NMDA‐activated currents. In this study, HEK293 cells expressing different NMDA receptor subunits were used to study the effects of prostacyclin receptor‐mediated PKA activation on the magnitude of glutamate‐activated currents. The prostacyclin agonist iloprost induced a rapid and time‐dependent depression of otherwise stable glutamate‐activated currents in cells expressing NR1–2a/2A or NR1–2a/2D receptors but not NR1–2a/2B or NR1–2a/2C receptors. This rundown was prevented by treatment of cells with the PKA inhibitor H89. The iloprost effect persisted in cells coexpressing NR1–2a/2A receptors and either wild‐type or mutant Src kinase (SrcS17A). Co‐expression of PSD‐95 with NR1–2a/2A receptors reduced but did not eliminate the extent of rundown. Iloprost also produced current rundown in cells expressing NR1–2a and a C‐terminal truncated NR2A subunit (NR2A1050stop) but not in those transfected with an NR2A tyrosine mutant (Y842F). The iloprost‐induced rundown of wild‐type NR1–2a/2A receptors was prevented by prior exposure of cells to hypertonic sucrose. These results suggest that PKA influences the functional activity of NMDA receptors in an NR2 subunit‐selective fashion.
Involvement of GABA and cholinergic receptors in the nucleus accumbens on feedback control of somatodendritic dopamine release in the ventral tegmental area
Authors: Rahman Shafiqur , McBride William J. 
Published: March 2003

AbstractThe objectives of the present study were to examine the involvement of GABA and cholinergic receptors within the nucleus accumbens (ACB) on feedback regulation of somatodendritic dopamine (DA) release in the ventral tegmental area (VTA). Adult male Wistar rats were implanted with ipsilateral dual guide cannulae for in vivo microdialysis studies. Activation of the feedback system was accomplished by perfusion of the ACB with the DA uptake inhibitor GBR 12909 (GBR; 100 µm). To assess the involvement of GABA and cholinergic receptors in regulating this feedback system, antagonists (100 µm) for GABAA (bicuculline, BIC), GABAB (phaclofen, PHAC), muscarinic (scopolamine, SCOP), and nicotinic (mecamylamine, MEC) receptors were perfused through the probe in the ACB while measuring extracellular DA levels in the ACB and VTA. Local perfusion of the ACB with GBR significantly increased (500% of baseline) the extracellular levels of DA in the ACB and produced a concomitant decrease (50% of baseline) in the extracellular DA levels in the VTA. Perfusion of the ACB with BIC or PHAC alone produced a 200–400% increase in the extracellular levels of DA in the ACB but neither antagonist altered the levels of DA in the VTA. Co‐perfusion of either GABA receptor antagonist with GBR further increased the extracellular levels of DA in the ACB to 700–800% of baseline. However, coperfusion with BIC completely prevented the reduction in the extracellular levels of DA in the VTA produced by GBR alone, whereas PHAC partially prevented the reduction. Local perfusion of the ACB with either MEC or SCOP alone had little effect on the extracellular levels of DA in the ACB or VTA. Co‐perfusion of either cholinergic receptor antagonist with GBR markedly reduced the extracellular levels of DA in the ACB and prevented the effects of GBR on reducing DA levels in the VTA. Overall, the results of this study suggest that terminal DA release in the ACB is under tonic GABA inhibition mediated by GABAA (and possibly GABAB) receptors, and tonic cholinergic excitation mediated by both muscarinic and nicotinic receptors. Activation of GABAA (and possibly GABAB) receptors within the ACB may be involved in the feedback inhibition of VTA DA neurons. Cholinergic interneurons may influence the negative feedback system by regulating terminal DA release within the ACB.
Evidence for a γ‐hydroxybutyrate (GHB) uptake by rat brain synaptic vesicles
Authors: Muller Claude , Viry Sandrine , Miehe Monique , Andriamampandry Christian , Aunis Dominique , Maitre Michel 
Published: March 2003

Abstractγ‐Hydroxybutyrate (GHB) is an endogenous metabolite of mammalian brain which is derived from GABA. Much evidence favours its role as an endogenous neuromodulator, synthesized, stored and released at particular synapses expressing specific receptors. One key step for GHB involvement in neurotransmission is its uptake by a specific population of synaptic vesicles. We demonstrate that this specific uptake exists in a crude synaptic vesicle pool obtained from rat brain. The kinetic parameters and the pharmacology of this transport are in favour of an active vesicular uptake system for GHB via the vesicular inhibitory amino acid transporter. This result supports the idea that GABA and GHB accumulate together and are coliberated in some GABAergic synapses of the rat brain, where GHB acts as a modulatory factor for the activity of these synapses following stimulation of specific receptors.
Development of anatomical structure of roots of Phragmites australis
Authors: Soukup Aleš , Votrubová Olga , Čížková Hana 
Published: March 2003

Summary

Focusing on characters related to its survival in flooded soils, the anatomy and differentiation of roots of Phragmites australis is reported here.
Roots were examined by anatomical methods and permeability tests using periodate‐, Fe2+‐ and berberine‐based apoplastic tracers.
Root development was characterized by the differentiation of a multiseriate exodermis with suberin lamellae and Casparian bands that formed close to the root tip. Impregnation of the exodermis with lignin and/or suberin appeared closer to the apex than in the endodermis, which is not commonly observed in other plant species. The early developed exodermis proved to be an effective barrier restricting the passive apoplastic penetration of solutes from the rooting medium into the root tissues. Relationships between exodermis, endodermis, aerenchyma and lateral root primordia development were also recorded.
It is concluded that early differentiation of the exodermis was advantageous in flooded substrates. Only a limited proportion of tissue without this apoplastic barrier might be crucial to reduce radial oxygen loss to the sediment and restrain the action of unfavourable factors, such as phytotoxins, in a flooded sediment.
Invasion of vascular cells in vitro by Porphyromonas endodontalis
Authors: Dorn B. R. , Harris L. J. , Wujick C. T. , Vertucci F. J. , Progulske‐Fox A. 
Published: March 2003

AbstractAim The objective of this study was to determine whether laboratory strains and clinical isolates of microorganisms associated with root canal infections can invade primary cultures of cardiovascular cells.Methodology Quantitative levels of bacterial invasion of human coronary artery endothelial cells (HCAEC) and coronary artery smooth muscle cells (CASMC) were measured using a standard antibiotic protection assay. Transmission electron microscopy was used to confirm and visualize internalization within the vascular cells.Results Of the laboratory and clinical strains tested, only P. endodontalis ATCC 35406 was invasive in an antibiotic protection assay using HCAEC and CASMC. Invasion of P. endodontalis ATCC 35406 was confirmed by transmission electron microscopy.Discussion Certain microorganisms associated with endodontic infections are invasive. If bacterial invasion of the vasculature contributes to the pathogenesis of cardiovascular disease, then microorganisms in the pulp chamber represent potential pathogens.
Phylogeny of the Neuropterida (Insecta: Holometabola)
Authors: Aspöck Ulrike 
Published: March 2003

The Neuropterida, with about 6500 known species — living fossils in a way — at the base of the Holometabola (as a sister group of the Coleoptera), comprise Raphidioptera (about 210 species, two families), Megaloptera (about 300 species, two families) and Neuroptera (6000 species, 17 families). Megaloptera + Neuroptera is argued vs. the traditional Raphidioptera + Megaloptera. Raphidioptera are undisputedly monophyletic. Monophyly of Megaloptera is the operational hypothesis, although occasionally questioned. Sucking tubes of the larvae are the most spectacular autapomorphy of Neuroptera. The construction of larval head capsules indicates three evolutionary lines: Nevrorthiformia, and Myrmeleontiformia + Hemerobiiformia. Traditional Myrmeleontiformia is Psychopsidae + (Nemopteridae + (Nymphidae + (Myrmeleontidae + Ascalaphidae))), the present approach is (Psychopsidae + Nemopteridae) + all other Myrmeleontiformia. Hemerobiiformia are based on the ‘maxillary head’ concept. The ithonid clade Ithonidae/Rapismatidae + Polystoechothidae and the dilarid clade Dilaridae + (Mantispidae + (Rhachiberothidae + Berothidae)) are based on robust criteria. Other relationships remain unclear: Hemerobiidae + Chrysopidae (on similarity) and the ‘early offshoot’ concept of coniopterygidae (on autapomorphies) should not be perpetuated. Chysopidae + Osmylidae and (Hemerobiidae + (Coniopterygidae + Sisyridae)) + dilarid clade are discussed. Aquatic larvae, regarded as independent apomorphies of megaloptera and neuropteran Nevrorthidae and Sisyridae for a long time, are re‐interpreted as a synapomorphy of Megaloptera + Neuroptera and thus plesiomorphic within these groups. Terrestrial larvae (with cryptonephry to solve osmotic problems) are consequently apomorphic. Aquatic Sisyridae with cryptonephry of a single malpighian tubule, is conflicting, but larvae may have become secondarily aquatic, after a terrestrial intermezzo.
Anti‐elastase and anti‐hyaluronidase of phenolic substance from Areca catechu as a new anti‐ageing agent
Authors: Lee K.‐K. , Cho J.‐J. , Park E.‐J. , Choi J.‐D. 
Published: March 2003

Synopsis We have previously screened 150 medicinal plants for the inhibition of elastase and found significant inhibitory effects of the extracts of Areca catechu L. on the ageing and inflammation of skin tissues. To isolate and identify the compounds having biological activity, they were further purified by each fraction of solvents, silica gel column chromatography, preparative TLC and reversed‐phase HPLC. The peak in HPLC, which coincided with the inhibitory activity against elastase, was identified as a phenolic substance by using various colorimetric methods, UV and IR. IC50 values of this phenolic substance were 26.9 μg mL−1 for porcine pancreatic elastase (PPE) and 60.8 μg mL−1 for human neutrophil elastase (HNE). This phenolic substance showed more potent activity than that of reference compounds, oleanolic acid (76.5 μg mL−1 for PPE, 219.2 μg mL−1 for HNE) and ursolic acid (31.0 μg mL−1 for PPE, 118.6 μg mL−1 for HNE). According to the Lineweaver–Burk plots, the inhibition against both PPE and HNE by this phenolic substance was competitive inhibition with the substrate. The phenolic substance from A. catechu effectively inhibited hyaluronidase activity (IC50 : 210 μg mL−1 ).These results suggest that the phenolic substance purified from A. catechu has an anti‐ageing effect by protecting connective tissue proteins.
Adapalene biochemistry and the evolution of a new topical retinoid for treatment of acne
Authors: Czernielewski J , Michel S , Bouclier M , Baker M , Hensby C 
Published: March 2003

AbstractThe emergence of oral and topical retinoids was a major advance in the clinical management of acne vulgaris. However, the benefits of these agents were somewhat limited by the degree of side effects caused by these drugs. Over the last 15 years, researchers have sought compounds that can provide the manifold therapeutic benefits obtained with tretinoin and isotretinoin while minimizing the potential for irritation and other unwanted effects. Adapalene, a naphthoic‐acid derivative, is one result of this search, and it serves as an example of rational drug development: the formulation of a novel substance with specific pharmacological properties and clinical objectives in mind. These goals included enhancing stability, enhancing anti‐inflammatory effects, maintaining effectiveness and minimizing cutaneous irritation. This paper reviews the history of the development of adapalene, its unique physical and biochemical properties, and the pharmacological studies that demonstrate a wide range of retinoid‐receptor, genetic and anti‐inflammatory effects, all of which contribute to the therapeutic efficacy and improved tolerability of adapalene observed in the clinical use of this agent for the treatment of acne.
Endocrinological evaluation and hormonal therapy for women with difficult acne
Authors: Thiboutot DM 
Published: March 2003

AbstractAcne vulgaris is the most common skin condition observed in the medical community. Convention is to treat this condition with a combination of comedolytics, anti‐inflammatory and antibacterial topical agents, or if indicated, oral antibiotics or retinoids. In addition to these therapies, hormonal therapy is potentially an option in women whose acne is not responding to conventional treatment or if signs of endocrine abnormalities are present. This paper focuses on the use of hormonal therapy in women with severe or recalcitrant acne. After a brief description of the pathogenesis of acne vulgaris, and the conventional treatment modalities, indications for hormonal therapy are discussed. This is followed by an outline of a suggested endocrine evaluation, and interpretation of the evaluation test results. Various options for hormonal therapy are then described, including a further discussion of oral contraceptives (OCs) in the treatment of acne.
Assessment of proliferative activity of canine dermal mast cells by bromodeoxyuridine and proliferating cell nuclear antigen labelling
Authors: Ordeix Laura , Fondevila Dolors , De Mora Fernando , Fondati Alessandra , Ferrer Lluís 
Published: March 2003

AbstractCutaneous mast cells from skin biopsies of three healthy dogs and three dogs with atopic dermatitis were assessed for their proliferative potential using bromodeoxyuridine and proliferating cell nuclear antigen labelling. Mast cells isolated from the skin of two healthy dogs were also studied using bromodeoxyuridine labelling. Mast cells in skin biopsy specimens and mast cells isolated from the skin of healthy dogs did not incorporate bromodeoxyuridine. Two mast cells expressing proliferating cell nuclear antigen were seen around two superficial vessels in the dermis of one atopic dog. Epidermal cells, glandular epithelial cells, fibroblasts and endothelial cells incorporated bromodeoxyuridine and showed positive staining for proliferating cell nuclear antigen. These results suggest that canine mature mast cells do not proliferate in the dermis.
Evaluation of an enzyme‐linked immunosorbant assay (ELISA) for the serological diagnosis of sarcoptic mange in dogs
Authors: Lower Kimberly S. , Medleau Linda M. , Hnilica Keith , Bigler Beat 
Published: March 2003

AbstractCanine scabies is a challenging disease to diagnose because sarcoptic mites are hard to find on skin scrapings. The purpose of this study was to evaluate a serologic enzyme‐linked immunosorbant assay (ELISA) as an aid in the diagnosis of canine scabies. In addition, serum samples were obtained post treatment to determine the duration and persistence of circulating scabies antibodies after resolution of natural infection. Nineteen dogs diagnosed with sarcoptic mange and 38 control dogs were tested. Sixteen scabies‐infested dogs showed positive pretreatment ELISA results (84.2% sensitivity). Thirty‐four control dogs showed negative ELISA results (89.5% specificity). In the 11 scabies dogs from which multiple post treatment serum samples were obtained, detectable antibodies were not present 1 month after treatment in four cases, but were present for 1–4.5 months post treatment in seven dogs. Our results suggest that this scabies ELISA test is useful in the diagnosis of canine scabies.