bluuebunny/crossref_metadata_2025 huggingface dataset:
Myasthenia Gravis Experimentally Induced with Muscle‐specific Kinase
Authors: Shigemoto Kazuhiro , Kubo Sachiho , Jie Chen , Hato Naohito , Abe Yasuhito , Ueda Norifumi , Kobayashi Naoto , Kameda Kenji , Mominoki Katsumi , Miyazawa Atsuo , Ishigami Akihito , Matsuda Seiji , Maruyama Naoki
Published: June 2008

Here we present the first evidence that muscle‐specific kinase (MuSK) antigen can cause myasthenia in animals. MuSK is expressed at the postsynaptic membranes of neuromuscular junctions (NMJ) and forms complexes with acetylcholine receptors (AChR) and rapsyn. MuSK is activated by agrin, which is released from motoneurons, and induces AChR clustering and subsequent formation of NMJ in embryos. Notably, autoantibodies against MuSK were found in a proportion of patients with generalized myasthenia gravis (MG) but without the characteristic AChR autoantibodies. However, MuSK autoantibodies had no known pathogenic potential, and animals immunized with purified MuSK proteins did not develop MG in former studies. In contrast, we have now injected rabbits with MuSK ectodomain protein in vivo and evoked a MG‐like muscle weakness with a reduction of AChR clustering at the NMJ. Our results showed that MuSK is required for maintenance of synapses and that interference with that function by MuSK antibodies causes myasthenic weakness. In vitro, AChR clustering in myotubes is induced by agrin and agrin‐independent inducers, which do not activate MuSK. Neither the receptor nor the activation mechanisms of AChR clustering induced by agrin‐independent inducers has been identified with certainty, but MuSK autoantibodies in myasthenic animals inhibited both agrin and agrin‐independent AChR clustering. MuSK plays multiple roles in pre‐patterning of the postsynaptic membrane before innervation and formation of NMJ in embryos. Some of these mechanisms may also participate in the maintenance of mature NMJ. This model system would provide new knowledge about the molecular pathogenesis of MG and MuSK functions in mature NMJ.
Structural Factors Influencing the Efficacy of Neuromuscular Transmission
Authors: Slater Clarke R.
Published: June 2008

Neuromuscular junctions (NMJs) in different species share many features of structure and function. At the same time, important differences distinguish, for example, human NMJs from those in other species. An understanding of the biological context of the human NMJ helps in the interpretation of the effects of disease on the biophysical properties of neuromuscular transmission. Many NMJs consist of a number of spot‐like synaptic regions 1–5 μm across. Usually only a few multimolecular “quanta” of transmitter are released from each presynaptic “bouton” by a single nerve impulse. The total number of quanta released from an NMJ is roughly proportional to its total area. For example, human NMJs are about 10‐fold smaller than those in frogs and release about 20 quanta/impulse versus 100–200 in frog NMJ. Although human NMJs release relatively few quanta, the effect of the transmitter is amplified by the high density of voltage‐gated sodium channels (NaV1.4) in the highly folded postsynaptic membrane. A genetic influence on NMJ size has recently been discovered in some patients with limb‐girdle myasthenia (LGM). Mutations of the gene encoding Dok‐7, an essential component of the agrin–muscle‐specific kinase pathway that controls postsynaptic differentiation at the mammalian NMJ, results in impaired transmission because the NMJs are abnormally small and have reduced folding but have a normal local density of normal acetylcholine receptors. This condition emphasizes the importance of structural features in achieving reliability of neuromuscular transmission.
Thymectomy for NonthymomatousMyasthenia Gravis
Authors: Sonett Joshua R. , Jaretzki III Alfred
Published: June 2008

There continues to be debate concerning which thymectomy technique is the procedure of choice in the treatment of nonthymomatous myasthenia gravis (MG). The debate persists primarily because of the lack of controlled prospective studies but also because of the varying presentations and clinical courses of MG patients. Analysis has been complicated by the absence, until very recently, of accepted objective definitions of severity of the illness and response to therapy as well as variable patient selection, timing of surgery, type of surgery, and methods of analysis of results. Without resolution of these issues by properly designed prospective studies, there can be no unequivocally valid comparison of the various thymectomy techniques. In this review, attempts have been made to clarify some of the controversial issues concerning the selection of a thymectomy technique in the treatment of nonthymomatous MG and to make limited recommendations based on the best available evidence.
Neuronal Acetylcholine Receptor Autoimmunity
Authors: Vernino Steven
Published: June 2008

Nicotinic acetylcholine receptors (AChRs) are ligand‐gated cation channels that are present throughout the nervous system. The muscle AChR mediates transmission at the neuromuscular junction; antibodies against the muscle AChR are the cause of myasthenia gravis. There are numerous subtypes of AChRs present throughout the nervous system. These neuronal AChRs are closely related to the muscle AChR structurally, but are pharmacologically and immunologically distinct. The ganglionic (α3‐type) neuronal AChR mediates fast synaptic transmission in sympathetic, parasympathetic, and enteric autonomic ganglia. Ganglionic AChR antibodies are found in up to 50% of patients with autoimmune autonomic ganglionopathy (AAG). Patients with AAG present with severe autonomic failure. Major clinical features include orthostatic hypotension, gastrointestinal dysmotility, anhidrosis, bladder dysfunction, and sicca symptoms. Impaired pupillary light reflex is often seen. Like myasthenia, AAG is an antibody‐mediated neurological disorder. Patients may improve with plasma exchange treatment or other immunomodulatory treatment. Experimental AAG, which recapitulates many of the features of the human disease, can be induced in rabbits by immunization against the ganglionic AChR or by passive transfer of antibodies to mice. Ganglionic AChR IgG inhibits nicotinic membrane current in cultured neuroblastoma cells. Central nervous system neuronal AChRs may also be targets of autoimmunity. For example, antibodies against α7‐type AChRs have been identified in a few patients with encephalitis. It is still unclear if antibodies against receptors in the central nervous system can directly cause disease.
Thoracoscopic Thymectomy with the da Vinci Robotic System for Myasthenia Gravis
Authors: Rückert Jens C. , Ismail Mahmoud , Swierzy Marc , Sobel Holger , Rogalla Patrik , Meisel Andreas , Wernecke Klaus D. , Rückert Ralph I. , Müller Joachim M.
Published: June 2008

Complete thymectomy (Thx) is a crucial part of treatment for myasthenia gravis (MG) and thymoma. The discussion about the necessity of radical, complete Thx and reduced invasiveness has led to no less than 14 different surgical approaches for Thx. The latest development is robotic‐assisted surgery. Though its impact on minimally invasive surgery is not yet clear, it seems to be most promising for surgery in remote, narrow anatomical regions like the mediastinum. One hundred six consecutive robotic‐assisted thymectomies (rThx) with the da Vinci robotic surgical system were performed between January 2003 and April 2007 in a prospective single‐center study. Postoperative morbidity was recorded according to the Myasthenia Gravis Foundation of America (MGFA) classification. With zero mortality, the overall postoperative morbidity rate was 2%. The cumulative complete stable remission rate of MG was > 40% for all patients, and there was no statistical difference as compared to non‐thymomatous MG patients. The cumulative rate of minimal manifestations (MM0–MM3) according to the MGFA classification showed a postoperative improvement in quality of life for most of the patients. The da Vinci robotic system allowed for technical refinements of the well‐defined operation technique of thoracoscopic Thx (tThx). From the technical point of view, rThx has advantages for mediastinal dissection. rThx had a shorter learning curve. There might be better outcome results for rThx in MG patients, as compared with nonrobotic tThx. Therefore, rThx is a promising technique for minimally invasive Thx.
Regulatory and Pathogenic Mechanisms in Human Autoimmune Myasthenia Gravis
Authors: Le Panse Rozen , Cizeron‐Clairac Géraldine , Cuvelier Mélinée , Truffault Frédérique , Bismuth Jacky , Nancy Patrice , De Rosbo Nicole Kerlero , Berrih‐Aknin Sonia
Published: June 2008

The thymus is frequently hyperplastic in young female myasthenia gravis (MG) patients presenting with anti‐acetylcholine receptor (AChR) antibodies. This thymic pathology is characterized by the presence of ectopic germinal centers (GCs) containing B cells involved at least partially in the production of pathogenic anti‐AChR antibodies. Our recent studies have furthered our understanding of the mechanisms leading to GC formation in the hyperplastic thymus. First, we showed that CXCL13 and CCL21, chemokines involved in GC formation, are overexpressed in MG thymus. Second, we demonstrated an increase in pro‐inflammatory activity in the thymus from MG patients and its partial normalization by glucocorticoids, as evidenced by gene expression profile. Third, we found that pro‐inflammatory cytokines are able to upregulate the expression of AChR subunits in thymic epithelial and myoid cells. Fourth, we showed that the function of T regulatory (Treg) cells, whose role is to downregulate the immune response, is severely impaired in the thymus of MG patients; such a defect could explain the chronic immune activation observed consistently in MG thymic hyperplasia. Altogether, these new data suggest that CXCL13 and CCL21, which are produced in excess in MG thymus, attract peripheral B cells and activated T cells, which are maintained chronically activated in the inflammatory thymic environment because of the defect in suppressive activity of Treg cells. Presence of AChR in the thymus and upregulation of its expression by the pro‐inflammatory environment contribute to the triggering and maintenance of the anti‐AChR autoimmune response.
Antisense Treatment for Myasthenia Gravis
Authors: Sussman Jon D. , Argov Zohar , McKee David , Hazum Eli , Brawer Solli , Soreq Hermona
Published: June 2008

Acetylcholinesterase pre‐mRNA is susceptible to alternative splicing. Myasthenia gravis has been shown to be associated with the expression of the readthrough transcript (AChE‐R), which, unlike the normal “synaptic” transcript (AChE‐S) is not tethered to the post‐synaptic membrane, but is a soluble monomer in the synaptic cleft. In rats with experimental autoimmune myasthenia gravis (EAMG), inhibition of production of AChE‐R using antisense is associated with a significant reduction in synaptic expression of AChE‐R mRNA and protein, with improved muscle strength and stamina and increased survival. Synaptic AChE does not appear to be significantly affected by the induction of EAMG or treatment with antisense to AChE‐R. Monarsen (EN101) is a synthetic 20‐base antisense oligodeoxynucleotide directed against the human AChE gene. It is modified to achieve stability for oral administration. Sixteen patients with seropositive myasthenia gravis who were responsive to pyridostigmine were withdrawn from it and treated with Monarsen. Fourteen patients experienced a clinically significant response. In some, the improvement was dramatic. Although the dose of pyridostigmine was not optimized before the study, the majority of responders achieved better Quantitative Myasthenia Gravis scores than on pyridostigmine. The response of an individual muscle group to Monarsen was related to the degree of deterioration following the withdrawal of pyridostigmine. Cholinergic side effects were conspicuous by their absence. Monarsen is now being investigated in a phase II study.
Strategies for Treating Autoimmunity
Authors: Meriggioli Matthew N. , Sheng Jian Rong , Li Liangcheng , Prabhakar Bellur S.
Published: June 2008

Current treatments for myasthenia gravis (MG) rely upon the administration of immunosuppressive agents which result in global, nonspecific attenuation of the immune response. An alternative approach would be to attempt to design therapies that specifically dampen autoreactivity without affecting general immunity. Recently, dendritic cells (DCs) have been shown to possess potent capabilities to tolerize T cells in an antigen‐specific manner. We have observed that the selective activation of particular subsets of DCs utilizing granulocyte–macrophage colony‐stimulating factor (GM‐CSF) had profound effects on the induction of experimental autoimmune myasthenia gravis (EAMG). Specifically, treatment with GM‐CSF effectively suppressed the induction of EAMG and down‐modulated anti‐AChR T cell and pathogenic antibody responses. These effects were associated with the activation of tolerogenic DCs, the enhanced production of suppressive cytokines, such as IL‐10, and the mobilization of CD4+CD25+and FoxP3+regulatory T cells (Tregs). We have further shown that GM‐CSF effectively ameliorates clinical disease severity in mice with active, ongoing EAMG. Based on these observations, we hypothesize that the selective activation of particular DC subsetsin vivousing pharmacologic agents, like GM‐CSF, can suppress ongoing anti‐AChR immune responses by mobilizing antigen‐specific Tregs capable of suppressing autoimmune MG.
Etanercept Treatment in Myasthenia Gravis
Authors: Rowin Julie
Published: June 2008

Etanercept is a tumor necrosis factor (TNF) blocking agent that has been shown to suppress ongoing experimental autoimmune myasthenia gravis (EAMG). This subcutaneously administered TNF blocking agent has also been shown to be safe and effective in several rheumatological diseases including rheumatoid arthritis, psoriasis, and ankylosing spondylitis. A prospective clinical pilot trial of etanercept in corticosteroid‐dependent autoimmune myasthenia gravis (MG) patients supports further study into etanercept as a treatment for MG.
Immunosuppression of EAMG by IVIG Is Mediated by a Disease‐specific Anti‐immunoglobulin Fraction
Authors: Fuchs Sara , Feferman Tali , Meidler Roberto , Margalit Raanan , Sicsic Camille , Brenner Talma , Laub Orgad , Souroujon Miriam C.
Published: June 2008

Intravenous immunoglobulin (IVIG) administration has been beneficially used for the treatment of a variety of autoimmune diseases including myasthenia gravis (MG). We have demonstrated that IVIG administration in experimental autoimmune MG (EAMG) results in suppression of disease that is accompanied by decreased Th1 cell and B cell proliferation. Chromatography of pooled human immunoglobulins (IVIG) on immobilized IgG, isolated from rats with EAMG or from MG patients, results in a depletion of the suppressive activity of the IVIG. Moreover, reconstitution of the activity‐depleted IVIG with the eluted minute IVIG fractions that had been adsorbed onto the EAMG‐ or MG‐specific columns recovers the depleted immunosuppressive activity. This study supports the notion that the therapeutic effect of IVIG is mediated by an antigen‐specific anti‐immunoglobulin (anti‐idiotypic) activity that is essential for its suppressive activity.
Treatment and Clinical Research in Myasthenia Gravis
Authors: Barohn Richard J.
Published: June 2008

Although once an often fatal illness, myasthenia gravis can now be well managed with relatively safe and effective therapies. Prior to 1960 mortality for myasthenia gravis was approximately 30%. In the current era, mortality should be less than 5%. Major therapeutic advances by decade were: physostigmine and thymectomy (1930s); mechanical ventilation (1950s); corticosteroids and plasmapheresis (1960s); azathioprine (1960s–1970s); cyclosporine (1980s); intravenous gamma globulins (1980s–1990s); and most recently mycophenolate mofetil (1990s–2000s). Modern management involves a graded approach, beginning with cholinesterase inhibitors for mild symptoms and advancing to immunomodulating medications for more severe weakness. We now have several immunomodulating agents from which to choose: selection is based largely on time to clinical effect and adverse effects. The various available treatment modalities all have their limitations. In addition, some controversies remain regarding the effectiveness of some of the commonly used myasthenia gravis treatments. Recently completed and ongoing clinical trials suggest that there is still equipoise regarding the benefit of mycophenolate mofetil and thymectomy. Hopefully, the future will be promising, with clinical trials involving novel immunotherapeutic strategies.
Extraocular Muscle Susceptibility to Myasthenia Gravis
Authors: Soltys Jindrich , Gong Bendi , Kaminski Henry J. , Zhou Yuefang , Kusner Linda L.
Published: June 2008

Extraocular muscle (EOM) is susceptible to neuromuscular junction disorders, in particular, myasthenia gravis (MG). While EOM physiological characteristics and the ocular motor system requirements contribute to the propensity of ocular motor deficits observed among patients with MG, the authors propose that EOM have immunological features that place the muscles at risk for immune attack. Genomic profiling studies have demonstrated that genes associated with the immune response are differentially expressed in EOM, with particular differences in both classical and alternative complement‐mediated immune response pathways. Intrinsic complement regulators are expressed at lower levels at rodent EOM neuromuscular junctions, which would put them at risk for the complement‐mediated injury that occurs in MG. In fact, systemic C inhibition in experimental autoimmune MG (EAMG) induced by administration of acetylcholine receptor (AChR) antibodies or immunization with AChR will eliminate complement deposition at junctions of other skeletal muscle, but not EOM. Also, EOM junctions have greater injury in active and passive EAMG by several measures, suggesting that the lack of complement inhibition puts the EOM at risk. Among ocular myasthenia patients, serum AChR antibody levels are low, which would support the concept that EOM junctions are more susceptible to antibody injury than are other junctions. These observations suggest that complement inhibitory therapies may prove to be particularly effective in treatment of ocular myasthenia.
IVIG Treatment for Myasthenia Gravis
Authors: Zinman Lorne , Bril Vera
Published: June 2008

Acquired myasthenia gravis (MG) is an autoimmune disorder treated with cholinesterase inhibitors and a number of immunotherapies. Intravenous immunoglobulin (IVIG) is an expensive and commonly used immunotherapy for patients with an exacerbation of MG, but its effectiveness has only recently been demonstrated in a randomized clinical trial. This paper describes the study design, results, and limitations of a double‐blind, randomized, placebo‐controlled trial designed to definitively determine if IVIG benefits patients with MG who present with worsening weakness. Fifty‐one patients with worsening weakness due to MG were randomized to receive either 2 g/kg of IVIG over 2 days or an equivalent volume of placebo (5% dextrose in water). The Quantitative MG Score (QMG Score) for Disease Severity, a validated clinical composite scale and the primary outcome measure in the study, was calculated by a masked observer 14 and 28 days after treatment. Patients treated with IVIG demonstrated a significant improvement in QMG Score for Disease Severity at day 14 and the response persisted at day 28. The largest clinical improvement occurred in patients with more severe disease. IVIG was well tolerated with no significant side effects observed. Given the observed efficacy and safety of IVIG demonstrated in this trial, future studies are necessary to determine if there is a role for interval IVIG treatments in chronic MG.
Further Observations in Congenital Myasthenic Syndromes
Authors: Engel Andrew G. , Shen Xin‐Ming , Selcen Duygu , Sine Steven M.
Published: June 2008

During the past five years many patients suffering from congenital myasthenic syndromes (CMS) have been identified worldwide and novel causative genes and mutations have been discovered. The disease genes now include those encoding each subunit of the acetylcholine receptor (AChR), the ColQ part of acetylcholinesterase (AChE), choline acetyltransferase, Nav1.4, MuSK, and Dok‐7. Moreover, emerging genotype–phenotype correlations are providing clues for targeted mutation analysis. This review focuses on the recent observations in selected CMS.
Somatostatin Receptors 1, 2, and 5 Cooperate in the Somatostatin Inhibition of C6 Glioma Cell Proliferation in Vitro via a Phosphotyrosine Phosphatase-η-Dependent Inhibition of Extracellularly Regulated Kinase-1/2
Authors: Barbieri Federica , Pattarozzi Alessandra , Gatti Monica , Porcile Carola , Bajetto Adriana , Ferrari Angelo , Culler Michael D. , Florio Tullio
Published: June 2008

Somatostatin inhibits cell proliferation through the activation of five receptors (SSTR1–5) expressed in normal and cancer cells. We analyzed the role of individual SSTRs in the antiproliferative activity of somatostatin in C6 rat glioma cells. Somatostatin dose-dependently inhibited C6 proliferation, an effect mimicked, with different efficacy or potency, by BIM-23745, BIM-23120, BIM-23206 (agonists for SSTR1, -2, and -5) and octreotide. The activation of SSTR3 was ineffective, although all SSTRs are functionally active, as demonstrated by the inhibition of cAMP production. All SSTRs induced cytostatic effects through the activation of the phosphotyrosine phosphatase PTPη and the inhibition of ERK1/2. For possible synergism between SSTR subtypes, we tested the effects of the combined treatment with two agonists (SSTR1+2 or SSTR2+5) or bifunctional compounds. The simultaneous activation of SSTR1 and SSTR2 slightly increased the efficacy of the individual compounds with an IC50 in between the single receptor activation. SSTR2+5 activation displayed a pattern of response superimposable to that of the SSTR5 agonist alone (low potency and higher efficacy, as compared with BIM-23120). The simultaneous activation of SSTR1, -2, and -5 resulted in a response similar to somatostatin. In conclusion, the cytostatic effects of somatostatin in C6 cells are mediated by the SSTR1, -2, and -5 through the same intracellular pathway: activation of PTPη and inhibition of ERK1/2 activity. Somatostatin is more effective than the individual agonists. The combined activation of SSTR1 and -2 shows a partial synergism as far as antiproliferative activity, whereas SSTR2 and -5 activation results in a response resembling the SSTR5 effects.
Novel Regulated Expression of the SLIT/ROBO Pathway in the Ovary: Possible Role during Luteolysis in Women
Authors: Dickinson Rachel E. , Myers Michelle , Duncan W. Colin
Published: June 2008

The human corpus luteum (CL) undergoes luteolysis, associated with marked tissue and vascular remodeling, unless conception occurs and the gland is rescued by human chorionic gonadotropin (hCG). In Drosophila the Slit gene product, a secreted glycoprotein, acts as a ligand for the roundabout (robo) transmembrane receptor. Together they influence the guidance and migration of neuronal and nonneuronal cells. In vertebrates three Slit (Slit1, Slit2, Slit3) and four Robo (Robo1, Robo2, Robo3/Rig-1, Robo4/Magic Robo) genes have been identified. ROBO1, SLIT2, and SLIT3 are also inactivated in human cancers and may regulate apoptosis and metastasis. Because processes such as apoptosis and tissue remodeling occur during the regression of the CL, the aim of this study was to investigate the expression, regulation, and effects of the SLIT and ROBO genes in human luteal cells. Immunohistochemistry and RT-PCR revealed that SLIT2, SLIT3, ROBO1, and ROBO2 are expressed in luteal steroidogenic cells and fibroblast-like cells of the human CL. Furthermore, using real-time quantitative PCR, expression of SLIT2, SLIT3, and ROBO2 was maximal in the late-luteal phase and significantly reduced after luteal rescue in vivo with exogenous hCG (P < 0.05). Additionally, hCG significantly inhibited SLIT2, SLIT3, and ROBO2 expression in cultured luteinized granulosa cells (P < 0.05). Blocking SLIT-ROBO activity increased migration and significantly decreased levels of apoptosis in primary cultures of luteal cells (P < 0.05). Overall, these results suggest the SLIT/ROBO pathway could play an important role in luteolysis in women.
Relationship between Androgen Action in the “Male Programming Window,” Fetal Sertoli Cell Number, and Adult Testis Size in the Rat
Authors: Scott Hayley M. , Hutchison Gary R. , Jobling Matthew S. , McKinnell Chris , Drake Amanda J. , Sharpe Richard M.
Published: June 2008

Fetal androgen action is an important determinant of Sertoli cell (SC) number at birth. Androgens “program” reproductive tract development in rats between embryonic d (e) 15.5 and e17.5 (“male programming window”), and this is reflected for life by anogenital distance (AGD). We investigated if androgen regulation of SC number/proliferation was also programmed by androgens in this window. Pregnant rats were treated in various fetal time windows with vehicle (control) or 500 mg/kg·d di(n-butyl) phthalate (DBP), which suppresses fetal intratesticular testosterone (ITT). ITT and SC number/proliferation index were determined at e17.5 or e21.5; AGD was also determined at e21.5. In controls, SC number increased 11-fold and ITT by 10-fold from e17.5–e21.5. In animals exposed daily to DBP from e13.5, SC number was reduced by approximately 50% at e21.5, but increased 6-fold, as did ITT, from e17.5–e21.5; DBP had no effect on ITT at e15.5, reduced ITT by 50% at e17.5, and by more than 75% at e19.5–21.5. DBP exposure just in the male programming window did not alter SC number at e17.5 or 21.5 but reduced AGD. DBP treatment beyond e19.5 caused major reductions in SC number/proliferation index and ITT at e21.5. Only DBP treatments that included the male programming window led to reduced AGD at e21.5, but SC number was clearly not programmed in this window. Nevertheless, testis weight correlated highly (P < 0.001) with AGD at e21.5, and postnatal d 25 and 90 in animals exposed in utero to vehicle or DBP (e13.5–e21.5). Thus, AGD may predict adult testis size but probably not through a direct relationship with SC number.
Thyroid Hormone Transport and Metabolism by Organic Anion Transporter 1C1 and Consequences of Genetic Variation
Authors: van der Deure Wendy M. , Hansen Pia Skov , Peeters Robin P. , Kyvik Kirsten Ohm , Friesema Edith C. H. , Hegedüs Laszlo , Visser Theo J.
Published: June 2008

Organic anion transporting polypeptide (OATP) 1C1 has been characterized as a specific thyroid hormone transporter. Based on its expression in capillaries in different brain regions, OATP1C1 is thought to play a key role in transporting thyroid hormone across the blood-brain barrier. For this reason, we studied the specificity of iodothyronine transport by OATP1C1 in detail by analysis of thyroid hormone uptake in OATP1C1-transfected COS1 cells. Furthermore, we examined whether OATP1C1 is rate limiting in subsequent thyroid hormone metabolism in cells cotransfected with deiodinases. We also studied the effect of genetic variation in the OATP1C1 gene: polymorphisms were determined in 155 blood donors and 1192 Danish twins and related to serum thyroid hormone levels. In vitro effects of the polymorphisms were analyzed in cells transfected with the variants. Cells transfected with OATP1C1 showed increased transport of T4 and T4 sulfate (T4S), little transport of rT3, and no transport of T3 or T3 sulphate, compared with mock transfected cells. Metabolism of T4, T4S, and rT3 by cotransfected deiodinases was greatly augmented in the presence of OATP1C1. The OATP1C1-intron3C>T, Pro143Thr, and C3035T polymorphisms were not consistently associated with thyroid hormone levels, nor did they affect transport function in vitro. In conclusion, OATP1C1 mediates transport of T4, T4S, and rT3 and increases the access of these substrates to the intracellular active sites of the deiodinases. No effect of genetic variation on the function of OATP1C1 was observed.
Protein Phosphatase 1, Protein Phosphatase 2A, and Calcineurin Play a Role in Estrogen-Mediated Neuroprotection
Authors: Don Yi Kun , Simpkins James W.
Published: June 2008

It is becoming increasingly clear that protein phosphatases are important modulators of cellular function and that disruption of these proteins are involved in neurodegenerative disease processes. Serine/threonine protein phosphatases (PP) such as protein phosphatase PP1, PP2A, and calcineurin are involved in hyperphosphorylation of τ- as well as β-amyloid-induced cell death. We have previously shown serine/threonine protein phosphatases to be involved in estrogen-mediated neuroprotection. The purpose of this study was to delineate the role of PP1, PP2A, and calcineurin in the mechanism of estrogen mediated neuroprotection against oxidative stress and excitotoxicity. Treatment with protein phosphatases inhibitor II, endothall, or cyclosporin A, which are specific inhibitors of PP1, PP2A, and calcineurin, respectively, did not have an effect on cell viability. However, in combination, these inhibitors adversely affected cell survival, which suggests the importance of serine/threonine protein phosphatases in maintenance of cellular function. Inhibitors of PP1, PP2A, and calcineurin attenuated the protective effects of estrogen against glutamate-induced -neurotoxicity but did not completely abrogate the estrogen-mediated protection. The attenuation of estrogen-induced neuroprotection was achieved through decrease in the activity of theses serine/threonine phosphatases without the concomitant decrease in protein expression. In an animal model, transient middle cerebral artery occlusion caused a 50% decrease in levels of PP1, PP2A, and PP2B ipsilateral to the lesion in a manner that was prevented by estradiol pretreatment. Therefore, we conclude that in the face of cytotoxic challenges in vitro and in vivo, estrogens maintain the function of PP1, PP2A, and calcineurin.
Estimating mean sojourn time and screening sensitivity using questionnaire data on time since previous screening
Authors: Weedon-Fekjær Harald , Lindqvist Bo H , Vatten Lars J , Aalen Odd O , Tretli Steinar
Published: June 2008

Objectives

Mean sojourn time (MST) and screening test sensitivity (STS), is usually estimated by Markov models using incidence data from the first screening round and the interval between screening examinations. However, several screening programmes do not have full registration of cancers submerging after screening, and increased use of opportunistic screening over time can raise questions regarding the quality of interval cancer registration.

Methods/settings

Based on the earlier used Markov model, formulas for expected number of cases given time since former screening activity was developed. Using questionnaire data for 336,533 women in the Norwegian Breast Cancer Screening Programme (NBCSP), mean square regression estimates of MST and STS were calculated.

Results

In contrast to the previously used method, the new approach gave satisfactory model fit. MST was estimated to 5.6 years for women aged 50–59 years, and 6.9 years for women aged 60–69 years, and STS was estimated to 55% and 60%, respectively. Attempts to add separate parameters for breast cancer incidence without screening, or previous STS, resulted in wide confidence intervals if estimated separately, and non-identifiably if combined.

Conclusion

Previously published results of long MST and low screen test sensitivity were confirmed with the new approach. Questionnaire data on time since previous screening can be used to estimate MST and STS, but the approach is sensitive to relaxing the assumptions regarding the expected breast cancer incidence without screening and constant STS over time.
The false-positive and false-negative predictive value of HIV antibody test in the Chinese population
Authors: Liu Pei , Shi Zhixu , Wang Cannan , Yang Haitao , Li Lei , Dai Yudong , Liu Yuanbao , Sun Jinfang , Pu Yuepu
Published: June 2008

Objectives

To analyse the relationship between the false-positive/false-negative predictive value (FPPV/FNPV) of the HIV-antibody (HIV-Ab) test and prevalence in different Chinese population groups.

Methods

HIV prevalence among different population groups was obtained by a screening survey of blood donors and the national HIV/AIDS surveillance programme in China. Given the sensitivity and specificity of a test kit and the prevalence of HIV infection, the estimated values of FPPV/FNPV were calculated using Bayes' formula. The actual value of FPPV of blood donors was obtained by screening 1,195,286 blood donors.

Results

This study indicates that the FPPV of HIV-Ab enzyme-linked immunosorbent assay (ELISA) assays varies widely in different Chinese populations: about 99.5% in the blood donor population, but only 3.2% in the injecting-drug users in high-risk areas. In 1,195,286 sera specimens from the blood donors, 2439 specimens were HIV-Ab positive by third ELISA, and 11 HIV cases were confirmed by Western blot. The HIV prevalence of the blood donor population in this survey was 0.0009% (11/1,195,286), but the HIV-Ab positive rate of third ELISA is 0.2% (2439/1,195,286) and 222 times higher than the prevalence.

Conclusions

Evaluation of HIV prevalence through the HIV-Ab positive rate by third ELISA will significantly overestimate the true prevalence in a low-prevalence population. Individual HIV-infection status should be taken into consideration when analysing the results of HIV-Ab tests in a population with low infection.
Research Note—Structural Demand Estimation with Varying Product Availability
Authors: Bruno Hernán A. , Vilcassim Naufel J.
Published: June 2008

This paper develops a model that extends the traditional aggregate discrete-choice-based demand model (e.g. Berry et al. 1995) to account for varying levels of product availability. In cases where not all products are available at every consumer shopping trip, the observed market share is a convolution of two factors: consumer preferences and the availability of the product in stores. Failing to account for the varying degree of availability would produce incorrect estimates of the demand parameters. The proposed model uses information on aggregate availability to simulate the potential assortments that consumers may face in a given shopping trip. The model parameters are estimated by simulating potential product assortment vectors by drawing multivariate Bernoulli vectors consistent with the observed aggregate level of availability. The model is applied to the UK chocolate confectionery market, focusing on the convenience store channel. We compare the parameter estimates to those obtained from not accounting for varying availability and analyze some of the substantive implications.
Lock-in-Shearografie: Prinzip und Anwendung (Lock-in Shearography: Principle and Application)
Authors: Menner Philipp , Gerhard Henry , Busse Gerhard
Published: June 2008

Die Shearografie ist ein etabliertes optisches Verfahren zur Erfassung verborgener Defekte in Bauteilen. Es eignet sich für die kontaktfreie flächige zerstörungsfreie Prüfung, wobei nur mechanisch relevante Defekte erfasst werden. Die Verwendung einer periodischen Bauteilbelastung und einer speziellen Auswertung (Lock-in-Technik) bietet im Vergleich zur konventionellen Shearografie erhebliche Vorteile, wie z.B. Defektselektivität, verbessertes Signal-Rausch-Verhältnis und Tiefenauflösung. Die Leistungsfähigkeit dieser Lock-in-Shearografie wird im Folgenden anhand von Modellproben und Realbauteilen vorgestellt.
Streustrahlungskorrektur bei Gammatomographie auf der Grundlage einer Faltungsoperation (Scattered Radiation Correction in Gamma Tomography, based on Convolution Operation)
Authors: Hoppe Dietrich
Published: June 2008

Entwickelt wird eine einfache und leicht handhabbare Methode, die sich vorzugsweise bei der Gammatomographie mit hoch- und monoenergetischer Strahlung zur Korrektur von Streustrahlungsartefakten eignet. Der Grundgedanke besteht darin, dass zwischen der im Untersuchungsobjekt bestehenden Schwächungsverteilung der Primärstrahlung und der Verteilung der vom einzelnen Objektpunkt ausgehenden Streustrahlung eine Faltungsoperation vorgenommen wird.
Relationship between Aluminum in Soils and Soil Water in Mineral Horizons of a Range of Acid Forest Soils
Authors: Gruba P. , Mulder J.
Published: June 2008

Previous studies suggest that the solubility of Al in acid forest soils may be expressed as the log Al3+ activity = −n pH + log KH‐Al + log Alp/Cp concentration ratio, with Alp and Cp representing pyrophosphate‐extractable Al and C, respectively, and KH‐Al is the binding constant of Al to protonated complexation sites on soil organic matter (SOM). We show that a slightly modified model, in which Alp is replaced by Alorg (= Alp − KCl‐extractable Al), successfully describes the concentration of Al in A and B horizons of a wide range of acid forest soils (Typic Dystochrepts) developed in different parent materials from a large number of spruce [Picea abies (L.) Karst.] and mixed forest stands in southern Poland. Analysis of the data suggests a reaction stoichiometry of n = 1.27 and log KH‐Al = 1.98 with R2 = 0.76. Furthermore, statistical analysis of a large set of published data, in addition to our own data from the Polish soils, indicates that log[Alorg/Cp] is significantly correlated with soil pH measured in 1 mol L−1 KCl (pHKCl), suggesting that the Al binding to SOM is less at small pHKCl due to increased competition with H+: log[Alorg/Cp] = 0.82 pHKCl − 4.16 (R2 = 0.77, n = 276). Combining the two equations gives a simple Al solubility model for mineral horizons in acid forest soils: log Al = −1.27pH + 0.82pHKCl − 2.18 (R2 = 0.82, n = 127). In this equation, pHKCl relates to chemical soil properties, whereas the pH of soil water also depends on solution characteristics like ionic strength. The equation may be applied to acid forest soils having a soil solution pH in the range of 3.0 to 4.2. Such conditions are rather common in surface horizons (A, E, and upper B) of acid forest soils of the temperate and boreal zones.
Clarification and Calibration of Reflection Coefficient for Electrical Conductivity Measurement by Time Domain Reflectometry
Authors: Lin C.-P. , Chung C.-C. , Huisman J. A. , Tang S.-H.
Published: June 2008

Measurement of electrical conductivity by time domain reflectometry (TDR) requires knowledge of the source step voltage, which is often implicitly accounted for in the measured reflection coefficient. Errors may arise, however, from imperfect amplitude calibration when transforming the voltage signal into the reflection coefficient signal. This instrument error was identified as a considerable source of error in addition to cable resistance for TDR electrical conductivity measurements. The effect of the instrument error due to imperfect amplitude calibration was theoretically examined by the direct current circuit model and experimentally verified. The instrument error resulted in an overestimation of electrical conductivity while the cable resistance led to an underestimation. We clarified that the series resistors model for correction of cable resistance is accurate if the measured reflection coefficient is corrected for the instrument error. A calibration (correction) method for the measured reflection coefficient was proposed to account for both the instrument error and the effect of cable resistance, leading to a simple, accurate, and theoretically sound procedure for TDR electrical conductivity measurements.
Response of Potentially Mineralizable Soil Nitrogen and Indices of Nitrogen Availability to Tillage System
Authors: Sharifi Mehdi , Zebarth Bernie J. , Burton David L. , Grant Cynthia A. , Bittman Shabtai , Drury Craig F. , McConkey Brian G. , Ziadi Noura
Published: June 2008

Tillage practices may affect the active fraction of soil organic N. As part of a national project to examine soil management and environmental controls on the active fraction of organic N, this study examined the effects of no‐till (NT) and conventional tillage (CT) systems on the quantity of potentially mineralizable soil N (N0) and mineralizable N pools, and the potential to detect changes in these pools using N availability indices. Preplant soil samples from the top 15 cm were collected from four long‐term tillage experiments at Swift Current, SK; Woodslee, ON; L'Acadie, QC; and Agassiz, BC. Potentially mineralizable N was determined by aerobic incubation at 25°C and periodic leaching for 24 wk. The N0 was greater under NT than under CT, but only at Swift Current. The labile and intermediate mineralizable N pools were significantly higher under NT than under CT at three of the four sites. The stable mineralizable N pool and the mineralization rate coefficient (k) were greater under NT than under CT at only one of the four sites. Adoption of NT influenced the quality of the active organic N fraction at three sites, as indicated by an increased proportion of mineralizable N in the more labile N pools. Among tested indices of N availability, KCl‐extractable NH4–N, NaOH‐extractable N, Illinois Soil N Test, phosphate‐borate buffer extractable N, and particulate organic C were most sensitive to tillage‐induced changes in the active organic N fraction. Tillage‐induced changes in the size and quality of the active organic N fraction may influence soil N supply and should be considered in optimizing fertilizer N management.
Substituting Stem's Water Content by Electrical Conductivity for Monitoring Water Status Changes
Authors: Nadler Arie , Tyree Melvin T.
Published: June 2008

Rapid and sensitive detection of stress in trees due to irrigation practices, draught, salinity, pollution, lack of nutrients, or diseases may be useful for research and practical purposes. Tree stress could be monitored by following changes in wood water content via time domain reflectometry (TDR). We have searched for a user‐friendly and less expensive tool because, although TDR is perhaps the most suitable method, it is too expensive and complicated for everyday use. The objective of this study was to understand the relations between the electrical conductivity (σstem) and water content (θstem) in tree stem segments of seven species with TDR probes installed. By leaching stem segments with salt solutions or air we were able to change the salinity and water content independently. We have shown that (i) σstemis more sensitive to changes in θstemthan to changes in salinity of the sap, and (ii) 30‐mm‐long rods on the TDR probe can sensitively and accurately measure θstemWe propose that σstemchanges might be used as a proxy for changes in stem water content or stem water potential. Hence, electrical resistivity measurements may substitute for water content measurements with the following advantages: improved accuracy, higher flexibility in probe construction, application to stem diameters <30 mm, and significantly lower costs.
The Moore–Sikora Buffer for Lime Requirement Determinations
Authors: Sikora F. J. , Moore K. P.
Published: June 2008

Paranitrophenol in the Adams–Evans (AE) buffer used for determining lime requirement (LR) is considered a hazardous chemical due to its toxicity. The Moore–Sikora (MS) buffer, which mimics AE soil‐buffer pH, was developed without hazardous chemicals and is currently used for routine soil testing at Clemson University. The MS buffer was designed by considering probable chemicals with pKa values in the desired pH range, potential reaction of the components with soil, and longevity of the buffer during storage. Boric acid, 3‐(N‐morpholino)propanesulfonic acid (MOPS), and 2‐(N‐morpholino)ethanesulfonic acid hydrate (MES) were considered for the new buffer. Once chemicals were identified, a technique of finding appropriate concentrations was utilized by using an equation that could predict the acid titration of a buffer and refining pKa and concentration values until a match was found with measured pH titrations of the AE buffer. The MS buffer contains 212, 131, and 34.8 mmol L−1 of B(OH)3, MOPS, and MES, respectively. The buffer also contains 200 mmol L−1 KOH and 1 mol L−1 KCl. The MS buffer was compared with the AE buffer for determining soil‐buffer pH values on 222 South Carolina soils and 41 North American Proficiency Testing Program soils. The MS soil‐buffer pH was strongly related to AE soil‐buffer pH (r2 > 0.98). Soil‐buffer pH was slightly less with MS buffer than AE buffer, with a mean difference of 0.03 pH units. The lower soil‐buffer pH with MS buffer caused a slightly higher LR than the AE buffer, with a mean difference of 0.34 Mg ha−1 on South Carolina soils. Forty‐four percent of the samples indicating a need for lime did not have a difference in LR between the two buffers. The slightly higher LR with the MS buffer on some of the samples is not expected to raise soil pH too high above target pH values.
Detecting Water Stress in Trees Using Stem Electrical Conductivity Measurements
Authors: Nadler Arie , Raveh Eran , Yermiyahu Uri , Lado Marcos , Nasser Ahmed , Barak Mordechai , Green Steve
Published: June 2008

Using time domain reflectometry (TDR), we studied stem water content (θstem), stem electrical conductivity (σstem), and their ratio for 220 d in stressed, installation‐cured, living trees of four species. Lysimeter‐grown mango (Mangifera indica L.), banana (Musa acuminata Colla), date (Phoenix dactylifera L.), and olive (Olea europaea L.) were subjected to several types of mild (intensity and duration) water stresses simulating horticultural orchard irrigation practices. This study of living trees was triggered by our previous study accomplished in uncured, thawed, native, cut stem segments. We have confirmed in living trees our earlier findings that θstem reacts sensitively and within minutes to water stress. This response is the main driver of σstem changes, by far exceeding the salinity effect on σstem Known irrigation rates, half‐hourly tree weights from load cells, and frequent sampling of drainage solution for volume and salinity independently confirmed our findings. Relative to θstem, resistivity measurements have lower scatter because θstem–dielectric constant (ε) relationships are exponential and θstem–resistivity relationships are linear. With resistivity, there is no need to match impedances among meter, cable, and probe, implying a larger flexibility in probe geometry, longer cables, and higher accuracy with shorter rods. There is a clear economic advantage in resistivity over ε measurements. The linkage between stem resistivity and water status (designated as the linkage factor) for lysimeter plants, orchard trees, and cut stem segments demonstrates the potential in scheduling irrigation according to plant water needs with an inexpensive, direct, and simple resistivity measurement.