bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiac Rhabdomyoma in a Neonate: Application of Serial Echocardiography
Authors: Durairaj Manuel , Mangotra Kavita , Makhale Chandrashekhar N. , Shinde Rituparna , Mehta Ajit C. , Sathe Archana S.
Published: May 2006

Primary cardiac neoplasms are rare. Rhabdomyoma is the most common benign congenital tumor found in infancy and has a tendency for spontaneous regression. We report a case of a cardiac rhabdomyoma in a symptomatic neonate in whom serial echocardiography was used for diagnosis and documentation of initial regression as early as 1 month.
Ultraviolet A‐1 as a treatment for ulcerative lichen planus of the feet
Authors: Mansura Adva , Alkalay Ronen , Slodownik Daniel , Ingber Arieh , Ruzicka Thomas , Enk Claes D.
Published: May 2006

Ulcerative lichen planus of the feet is a rare variant of lichen planus characterized by the constellation of a chronic bullous and ulcerative eruption limited to the feet, atrophy of involved skin and nails, and cicatricial alopecia. Only split‐thickness skin grafting has hereto been documented to be effective. We here report a case with ulcerative lichen planus of the feet successfully treated with medium‐dose ultraviolet A‐1
Going Native: Savage Actors and the Play of Textuality in Melville’s Benito Cereno
Authors: Ghorashi Mahni
Published: May 2006

This essay won the 2005 Literature Compass Graduate Essay Prize, American Section.

This essay on Herman Melville’s Benito Cereno (1856) examines the author’s views on savagery not merely as ethnic composition but as a progression through the performative to become a product of language itself. Thus, locating the savage becomes less a task of highlighting cultural otherness than examining how one writes and speaks about the primitive. In Benito Cereno, Melville liberates the discourse of civilized versus savage from what today would be considered a strictly post‐Colonial model – one which seems to fit Melville’s own encounters with the cultural outsider as documented in his early works Typee (1846), Omoo (1847), and Mardi (1849) – and places it in a linguistic sphere. Melville therefore introduces us to a savagery writ so large that only a system of signs becomes large enough to contain it. The critical figure in Benito Cereno is Babo, the mastermind behind a play of such monstrous proportions that even the reader becomes a savage actor in his infernal drama.
Structure–activity relationships of fowlicidin‐1, a cathelicidin antimicrobial peptide in chicken
Authors: Xiao Yanjing , Dai Huaien , Bommineni Yugendar R. , Soulages Jose L. , Gong Yu‐Xi , Prakash Om , Zhang Guolong
Published: May 2006

Cationic antimicrobial peptides are naturally occurring antibiotics that are actively being explored as a new class of anti‐infective agents. We recently identified three cathelicidin antimicrobial peptides from chicken, which have potent and broad‐spectrum antibacterial activities in vitro (Xiao Y, Cai Y, Bommineni YR, Fernando SC, Prakash O, Gilliland SE & Zhang G (2006) J Biol Chem281, 2858–2867). Here we report that fowlicidin‐1 mainly adopts an α‐helical conformation with a slight kink induced by glycine close to the center, in addition to a short flexible unstructured region near the N terminus. To gain further insight into the structural requirements for function, a series of truncation and substitution mutants of fowlicidin‐1 were synthesized and tested separately for their antibacterial, cytolytic and lipopolysaccharide (LPS)‐binding activities. The short C‐terminal helical segment after the kink, consisting of a stretch of eight amino acids (residues 16–23), was shown to be critically involved in all three functions, suggesting that this region may be required for the peptide to interact with LPS and lipid membranes and to permeabilize both prokaryotic and eukaryotic cells. We also identified a second segment, comprising three amino acids (residues 5–7) in the N‐terminal flexible region, that participates in LPS binding and cytotoxicity but is less important in bacterial killing. The fowlicidin‐1 analog, with deletion of the second N‐terminal segment (residues 5–7), was found to retain substantial antibacterial potency with a significant reduction in cytotoxicity. Such a peptide analog may have considerable potential for development as an anti‐infective agent.
Unusual metal specificity and structure of the group I ribozyme from Chlamydomonas reinhardtii 23S rRNA
Authors: Kuo Tai‐Chih , Odom Obed W. , Herrin David L.
Published: May 2006

Group I intron ribozymes require cations for folding and catalysis, and the current literature indicates that a number of cations can promote folding, but only Mg2+ and Mn2+ support both processes. However, some group I introns are active only with Mg2+, e.g. three of the five group I introns in Chlamydomonas reinhardtii. We have investigated one of these ribozymes, an intron from the 23S LSU rRNA gene of Chlamydomonas reinhardtii (Cr.LSU), by determining if the inhibition by Mn2+ involves catalysis, folding, or both. Kinetic analysis of guanosine‐dependent cleavage by a Cr.LSU ribozyme, 23S.5ΔGb, that lacks the 3′ exon and intron‐terminal G shows that Mn2+ does not affect guanosine binding or catalysis, but instead promotes misfolding of the ribozyme. Surprisingly, ribozyme misfolding induced by Mn2+ is highly cooperative, with a Hill coefficient larger than that of native folding induced by Mg2+. At lower Mn2+ concentrations, metal inhibition is largely alleviated by the guanosine cosubstrate (GMP). The concentration dependence of guanosine cosubstrate‐induced folding suggests that it functions by interacting with the G binding site, perhaps by displacing an inhibitory Mn2+. Because of these and other properties of Cr.LSU, the tertiary structure of the intron from 23S.5ΔGb was examined using Fe2+‐EDTA cleavage. The ground‐state structure shows evidence of an unusually open ribozyme core: the catalytic P3–P7 domain and the nucleotides that connect it to the P4–P5–P6 domain are exposed to solvent. The implications of this structure for the in vitro and in vivo properties of this intron ribozyme are discussed.
Understanding the genetics of autoimmune disease: two loci that regulate late onset Addison's disease in Portuguese Water Dogs
Authors: Chase K. , Sargan D. , Miller K. , Ostrander E. A. , Lark K. G.
Published: May 2006

Addison's disease, an immune‐mediated disorder caused by destruction of the adrenal glands, is a rare disorder of Western European populations. Studies indicate that the disorder is polygenic in nature, involving specific alleles of the CTLA‐4, DRB1*04 and DQ, Cyp27B1, VDR and MIC‐A and ‐B loci. A similar immune form of Addison's disease occurs in several breeds of domestic dog, with frequencies ranging from 1.5 to 9.0%. The high frequency of the disease in domestic dog breeds likely reflects the small number of founders associated with many breeds, subsequent inbreeding, and the frequent use of popular sires.

The Portuguese Water Dog (PWD) is a significantly affected breed. An analysis of 11 384 PWDs surveyed between 1985 and 1996 suggests a breed‐specific disease incidence of 1.5%. As with humans, the disease is typically of late onset.

This study involves a genetic comparison of Addison's disease in the PWD to the analogous disease in humans. The study is facilitated by the existence of complete pedigrees and a relatively high degree of inbreeding among PWDs. The breed originated from 31 founders, with 10 animals responsible for 90% of the current gene pool. We describe, specifically, the identification of two disease‐associated loci, on Canis familiaris (CFA) chromosomes CFA12 and 37, which are syntenic with the human DRB1 histocompatibility locus alleles HLA‐DRB1*04 and DRB1*0301, and to a locus for immunosuppression syntenic with CTLA‐4. Strong similarities exist therefore in the complex genetic background of Addison's disease in humans and in the PWD. With the completion of the canine and human genome sequence, the purebred dog is set to become an important comparative model for Addison's as well as other human immune disorders.
HLA class II gene polymorphism in Parsees and Zoroastrians of Iran
Authors: Farjadian S. , Moqadam F. A. , Ghaderi A.
Published: May 2006

Extensive polymorphism of the HLA genes in different ethnic groups has been used as an invaluable tool for anthropological studies. In this study, HLA‐DRB1, DQA1 and DQB1 allele frequencies and haplotypes were determined in 72 Parsees and 65 Zoroastrians living in Iran. The predominant DRB1 allele was *1103 = 4 in Parsees and *0701 in Zoroastrians. DQA1*0501 was the most common alleles in both spopulations. The most frequent DQB1 allele was *0301 in Parsees and *0201 in Zoroastrians. DRB1*1103 = 4‐DQA1*0501‐DQB1*0301 and DRB1*0701‐DQA1*0201‐DQB1*0201 were the most prevalent haplotypes in Parsees and Zoroastrians, respectively. Significant deviation from Hardy–Weinberg equilibrium was observed in DQA1 and DQB1 loci of Zoroastrians. The former locus also departed from neutrality due to balancing selection. All pairs of the studied loci in this study showed significant linkage disequilibrium. Analysis of molecular variance indicated that the main variation was confined to individuals within the studied populations. Neighbour‐joining tree based on Nei's genetic distances according to DRB1 and DQB1 allele frequencies showed that Parsees and Zoroastrians of Iran were located in the same cluster of the phylogenetic tree. Furthermore, Zoroastrians of Iran and Pakistan are very close to each other. This study will serve as a reference for further anthropological studies when the HLA profile of all ethnic groups of Iran is investigated.
THIS ARTICLE HAS BEEN RETRACTED  Cytokine typing: SNP allele frequencies in the Iranian population
Authors: Bagheri M. , Abdi‐Rad I. , Omrani D. , Khalkhali H. R.
Published: May 2006

Single nucleotide polymorphisms within the promoter or other regulatory sequences of cytokine genes were evaluated and compared between an Iranian population and populations of different ethnic/geographical background. In 40 healthy Iranian subjects, cytokine typing was performed by polymerase chain reaction–sequence‐specific primers assay. Allele frequencies were calculated and compared with those of other populations.
CTLA‐4 gene polymorphisms and natural soluble CTLA‐4 protein in psoriasis vulgaris
Authors: Łuszczek W. , Kubicka W. , Jasek M. , Baran E. , Cisło M. , Nockowski P. , Łuczywo‐Rudy M. , Wiśniewski A. , Nowak I. , Kuśnierczyk P.
Published: May 2006

CTLA‐4 molecule is an important inhibitor of T‐lymphocyte activation. Several single nucleotide polymorphisms (SNPs) in the CTLA‐4 gene were found, and their associations with many human diseases were described. So far, however, such studies have not been performed in psoriasis vulgaris in Caucasoids. Therefore, we examined the distribution of three CTLA‐4 SNPs: −1147C/T, −318C/T and +49 A/G in 116 patients with psoriasis vulgaris and 123 healthy blood donors using the polymerase chain reaction–restriction fragment length polymorphism method. For all three SNPs, the frequencies of alleles, genotypes and three‐point haplotypes were very similar in patients and controls, suggesting no contribution of these genetic variants to psoriasis.
STILBENE GLYCOSIDES FROM THE ROOTS OF POLYGONUM MULTIFLORUM THUNB AND THEIR IN VITRO ANTIOXIDANT ACTIVITIES
Authors: LI‐SHUANG L.V. , GU XIAOHONG , HO CHI‐TANG , TANG JIAN
Published: May 2006

Stilbene glycosides (SGs) were isolated from the ethanol extract of the roots of Polygonum multiflorum (PM) Thunb. Three samples were obtained: the crude extract, the fraction separated by macroporous resin and the pure crystal 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside. The structure of the crystals was determined by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectrometry. The antioxidant activities of three samples containing SG were evaluated using different antioxidant tests, including free radical scavenging, superoxide anion scavenging, hydroxyl radical scavenging and the inhibition of lipid peroxide formation in organs (liver, heart and brain) of a rat in vitro. These various antioxidant activities were compared with those of resveratrol, which is structurally similar to SG of PM. The results indicated that all three samples showed antioxidant activities, with the pure SG being the most efficient one. The IC50 values for 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside were 8.06, 2.75 and 0.57 µg/mL for 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) scavenging, hydroxyl radical scavenging and superoxide anion scavenging, respectively. The IC50 values for 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside in inhibiting lipid peroxide formation in liver, heart and brain were 13.68, 16.34 and 17.62 µg/mL, respectively. It was shown that SG from PM has a better antioxidant potency than that of resveratrol.
EFFECTS OF CORN MEAL, VITAL WHEAT GLUTEN, HIGH AMYLOSE STARCH AND EXTRUSION PARAMETERS ON TECHNOLOGICAL PROPERTIES OF WHEAT‐BASED EXTRUDED BREADING
Authors: ACIOLI‐MOURA RICARDO , CHANG YOON KIL
Published: May 2006

A wheat‐based extruded breading was produced using a Brabender single‐screw laboratory scale extruder (model GNF 1014/2) and applied to chicken nuggets. Response surface methodology was applied to study and optimize the effects of formulation and extrusion parameters on pick up, texture, solid loss, oil absorption and adhesiveness of fried coated nuggets. An optimized extruded breading was produced at 160C, 27% moisture content, 15% vital wheat gluten, 8% high amylose starch and 30% corn meal. The product showed pick up of 29.87%, adhesiveness of 100%, texture of 166.1 g, oil absorption of 2.97% and solid losses of 0.0885 absolute. The product presented similar values of pick up and adhesiveness, better texture, lower oil absorption and higher solid loss during deep‐frying, compared with commercial breadings. Acceptance test showed that the product had better overall appearance and fairly similar texture, compared with the commercial ones.
Foundational Issues in Presupposition
Authors: Simons Mandy
Published: May 2006

This essay provides a brief introduction to the topic of presupposition, and then discuses three major approaches to this phenomenon, focusing on the answers which each approach gives to two foundational questions: What is presupposition? And how, or why, does it arise?
Role of the Na+/H+ exchanger NHE1 in cell migration
Authors: Stock C. , Schwab A.
Published: May 2006

Cell migration plays a basic role in many physiological and pathophysiological processes such as embryogenesis, immune defence, wound healing or metastasis. The activity of the ubiquitously expressed NHE1 isoform of the plasma membrane Na+/H+ exchanger is one of the requirements for directed locomotion of migrating cells and also contributes to cell adhesion. The mechanisms by which NHE1 is involved in cell migration are multiple. NHE1 contributes to cell migration by affecting the cell volume, by regulating the intracellular pH and thereby the assembly and activity of cytoskeletal elements, by anchoring the cytoskeleton to the plasma membrane, by signalling, by regulating gene expression and by controlling cell adhesion. The present article gives a review of the different ways in which NHE1 is involved in and contributes to cell migration. These different mechanisms complement one another forming an intricate, integrative process.
Evidence for the role of cell stiffness in modulation of volume‐regulated anion channels
Authors: Byfield F. J. , Hoffman B. D. , Romanenko V. G. , Fang Y. , Crocker J. C. , Levitan I.
Published: May 2006

Aim:  To investigate the link between cell stiffness and volume‐regulated anion current (VRAC) in aortic endothelium.

Method:  Bovine aortic endothelial cells (BAECs) were exposed to methyl‐β‐cyclodextrin (MβCD) to deplete cellular cholesterol and the changes in cellular stiffness were measured by micropipette aspiration. VRAC density was measured electrophysiologically in the same cell populations. Furthermore, to probe the effects of cholesterol depletion on the mechanics of ‘deep’ cytoskeleton, we employ a novel technique to analyse correlated motion of intracellular particles.

Results:  We show that cholesterol depletion results in cellular stiffening and an upregulation of VRAC density. Replenishing cellular sterol pool with epicholesterol, a chiral analogue of cholesterol, abrogates both of these effects. This indicates that cholesterol sensitivity of both cell mechanics and VRAC are due to changes in the physical properties of the membrane rather than due to specific sterol–protein interactions. We also show that cholesterol depletion increases the stiffness of the ‘deep cytoskeleton’ and that disruption of actin filaments abolishes both cell stiffening and upregulation of VRAC due to cholesterol depletion. Furthermore, comparing BAECs to human aortic endothelial cells (HAECs), we show that BAECs that are inherently stiffer also develop larger VRACs.

Conclusions:  Taken together, our observations suggest an increase in the cytoskeleton stiffness has a facilitatory effect on VRAC development. We suggest that stiffening of the cytoskeleton increases tension in the membrane–cytoskeleton layer and that in turn facilitates VRAC.
Cell membrane surface expression and tyrosine kinase regulate the osmolyte channel (skAE1) in skate erythrocytes
Authors: Perlman D. F. , Musch M. W. , Goldstein L.
Published: May 2006

A regulatory volume decrease response occurs when skate (Raja erinacea) erythrocytes are exposed to hyposmotic medium; they swell and then reduce their volume by releasing organic osmolytes (primarily taurine) and associated water. The response involves the red blood cell anion‐exchanger skate anion‐exchanger 1 (skAE1), which has been previously shown to be affected by tyrosine phosphorylation, to form tetramers and to change binding affinities to the cytoskeletal proteins, ankyrin and band 4.1. Our recent studies are focused on determining the sequence and mechanism of these events to better understand the activation of skAE1 upon hyposmotic stimulation. Under isosmotic conditions a large portion of skAE1 is found not only on the plasma membranes but also associated intracellularly in detergent‐resistant membranes or lipid rafts. We hypothesize that an important step in the hyposmotic‐induced increase in taurine transport involves the movement of skAE1 from an intracellular association with lipid rafts into the cell membrane. Inhibition of tyrosine phosphorylation of skAE1 with piceatannol reduces the hyposmotic‐induced increase in taurine transport and also inhibits both the decreased binding of skAE1 to band 4.1 and the increased affinity to ankyrin. However, the phosphorylation inhibitor does not block the movement of the transporter into the plasma membrane or the formation of tetramers. This suggests that tyrosine phosphorylation is important in the hyposmotic‐induced taurine transport but other steps that do not require phosphorylation play an important role.
T‐tubule disorganization and reduced synchrony of Ca2+ release in murine cardiomyocytes following myocardial infarction
Authors: Louch William E. , Mørk Halvor K. , Sexton Joseph , Strømme Tævje A. , Laake Petter , Sjaastad Ivar , Sejersted Ole M.
Published: May 2006

In cardiac myocytes, initiation of excitation–contraction coupling is highly localized near the T‐tubule network. Myocytes with a dense T‐tubule network exhibit rapid and homogeneous sarcoplasmic reticulum (SR) Ca2+ release throughout the cell. We examined whether progressive changes in T‐tubule organization and Ca2+ release synchrony occur in a murine model of congestive heart failure (CHF). Myocardial infarction (MI) was induced by ligation of the left coronary artery, and CHF was diagnosed by echocardiography (left atrial diameter >2.0 mm). CHF mice were killed at 1 or 3 weeks following MI (1‐week CHF, 3‐week CHF) and cardiomyocytes were isolated from viable regions of the septum, excluding the MI border zone. Septal myocytes from SHAM‐operated mice served as controls. T‐tubules were visualized by confocal microscopy in cells stained with di‐8‐ANEPPS. SHAM cells exhibited a regular striated T‐tubule pattern. However, 1‐week CHF cells showed slightly disorganized T‐tubule structure, and more profound disorganization occurred in 3‐week CHF with irregular gaps between adjacent T‐tubules. Line‐scan images of Ca2+ transients (fluo‐4 AM, 1 Hz) showed that regions of delayed Ca2+ release occurred at these gaps. Three‐week CHF cells exhibited an increased number of delayed release regions, and increased overall dyssynchrony of Ca2+ release. A common pattern of Ca2+ release in 3‐week CHF was maintained between consecutive transients, and was not altered by forskolin application. Thus, progressive T‐tubule disorganization during CHF promotes dyssynchrony of SR Ca2+ release which may contribute to the slowing of SR Ca2+ release in this condition.
Different responses of rat cerebellar Purkinje cells and Golgi cells evoked by widespread convergent sensory inputs
Authors: Holtzman Tahl , Rajapaksa Thimali , Mostofi Abteen , Edgley Steve A.
Published: May 2006

While the synaptic properties of Golgi cell‐mediated inhibition of granule cells are well studied, less is known of the afferent inputs to Golgi cells so their role in information processing remains unclear. We investigated the responses of cerebellar cortical Golgi cells and Purkinje cells in Crus I and II of the posterior lobe cerebellar hemisphere to activation of peripheral afferents in vivo, using anaesthetized rats. Recordings were made from 70 Golgi cells and 76 Purkinje cells. Purkinje cells were identified by the presence of climbing fibre responses. Golgi cells were identified by both spontaneous firing pattern and response properties, and identification was confirmed using juxtacellular labelling of single neurones (n= 16). Purkinje cells in Crus II showed continuous firing at relatively high rates (25–60 Hz) and stimulation of peripheral afferents rarely evoked substantial responses. The most common response was a modest, long‐latency, long‐lasting increase in simple spike output. By comparison, the most common response evoked in Golgi cells by the same stimuli was a long‐latency, long‐lasting depression of firing, found in ∼70% of the Golgi cells tested. The onsets of Golgi cell depressions had shorter latencies than the Purkinje cell excitations. Brief, short‐latency excitations and reductions in firing were also evoked in some Golgi cells, and rarely in Purkinje cells, but in most cases long‐lasting depressions were the only significant change in spike firing. Golgi cell responses could be evoked using air puff or tactile stimuli and under four different anaesthetic regimens. Long‐lasting responses in both neurone types could be evoked from wide receptive fields, in many cases including distal afferents from all four limbs, as well as from trigeminal afferents. These Golgi cell responses are not consistent with the conventional feedback inhibition or ‘gain control’ models of Golgi cell function. They suggest instead that cerebellar cortical activity can be powerfully modulated by the general level of peripheral afferent activation from much of the body. On this basis, Golgi cells may act as a context‐specific gate on transmission through the mossy fibre–granule cell pathway.
Effect of repetitive hypoxic apnoeas on baroreflex function in humans
Authors: Monahan Kevin D. , Leuenberger Urs A. , Ray Chester A.
Published: May 2006

Baroreflex function is impaired in patients with obstructive sleep apnoea. We tested the hypothesis that short‐term exposure to repetitive hypoxic apnoeas (RHA) produces prolonged impairment in baroreflex function. Baroreflex function was determined using the modified Oxford technique in 14 subjects (26 ± 1 years). Baroreflex sensitivity (BRS) was quantified from the R‐R interval–systolic blood pressure (BP; cardiovagal BRS), heart rate–systolic BP (HR BRS) and muscle sympathetic nerve activity (MSNA)–diastolic BP (sympathetic BRS) relations. RHA involved subjects performing repetitive end‐expiratory apnoeas (20 s) every minute for 30 min during intermittent hypoxia to accentuate oxygen desaturation. After RHA, BP and MSNA at rest were elevated. BRS was measured ∼7 (Post 1), ∼30 (Post 2) and ∼50 min (Post 3) after RHA to provide insight into the temporal pattern of responses. Cardiovagal BRS (16.8 ± 1.3, 16.5 ± 1.6, 17.6 ± 2.0 and 17.4 ± 1.5 ms mmHg−1 for Pre, Post 1, Post 2 and Post 3, respectively), HR BRS (−1.1 ± 0.1, −1.1 ± 0.1, −1.3 ± 0.1 and −1.4 ± 0.1 beats min−1 mmHg−1) and sympathetic BRS (−4.5 ± 0.6, −4.4 ± 0.7, −3.7 ± 0.5 and −4.7 ± 1.0 arbitrary units (au) beat−1 mmHg−1) were unchanged by RHA. In contrast, the operating points of the baroreflexes were shifted rightward (to higher levels of BP) and upward (to higher levels of heart rate and MSNA) after RHA (P < 0.05). Time control studies performed in five additional subjects showed no change in any of the measured variables over time. Collectively, these data indicate that short‐term exposure to RHA shifts (‘resets’) the baroreflex stimulus–response curve to higher levels of BP without influencing BRS for extended periods of time.
The role of AMP‐activated protein kinase in mitochondrial biogenesis
Authors: Reznick Richard M. , Shulman Gerald I.
Published: May 2006

While it has been known for more than 75 years that physical activity is associated with increased mitochondrial content in muscle, the molecular mechanism for this adaptive process has only recently been elucidated. This brief review examines existing studies that have identified AMPK‐activated protein kinase (AMPK) and several other key regulators of mitochondrial biogenesis, including peroxisome proliferator‐activated receptor‐γ coactivator‐1α and ‐1β, calcium/calmodulin‐dependent protein kinase IV, and nitric oxide. In addition, the potential role of mitochondrial dysfunction in the pathogenesis of insulin resistance associated with ageing and type 2 diabetes mellitus is also discussed.
‘Simplification’ of responses of complex cells in cat striate cortex: suppressive surrounds and ‘feedback’ inactivation
Authors: Bardy Cedric , Huang Jin Yu , Wang Chun , FitzGibbon Thomas , Dreher Bogdan
Published: May 2006

In mammalian striate cortex (V1), two distinct functional classes of neurones, the so‐called simple and complex cells, are routinely distinguished. They can be quantitatively differentiated from each other on the basis of the ratio between the phase‐variant (F1) component and the mean firing rate (F0) of spike responses to luminance‐modulated sinusoidal gratings (simple, F1/F0 > 1; complex, F1/F0 < 1). We investigated how recurrent cortico‐cortical connections affect the spatial phase‐variance of responses of V1 cells in the cat. F1/F0 ratios of the responses to optimally oriented drifting sine‐wave gratings covering the classical receptive field (CRF) of single V1 cells were compared to those of: (1) responses to gratings covering the CRFs combined with gratings of different orientations presented to the ‘silent’ surrounds; and (2) responses to CRF stimulation during reversible inactivation of postero‐temporal visual (PTV) cortex. For complex cells, the relative strength of the silent surround suppression on CRF‐driven responses was positively correlated with the extent of increases in F1/F0 ratios. Inactivation of PTV cortex increased F1/F0 ratios of CRF‐driven responses of complex cells only. Overall, activation of suppressive surrounds or inactivation of PTV ‘converted’ substantial proportions (50 and 30%, respectively) of complex cells into simple‐like cells (F1/F0 > 1). Thus, the simple–complex distinction depends, at least partly, on information coming from the silent surrounds and/or feedback from ‘higher‐order’ cortices. These results support the idea that simple and complex cells belong to the same basic cortical circuit and the spatial phase‐variance of their responses depends on the relative strength of different synaptic inputs.
Delayed synchronization of activity in cortex and subthalamic nucleus following cortical stimulation in the rat
Authors: Magill Peter J. , Sharott Andrew , Bolam J. Paul , Brown Peter
Published: May 2006

Oscillations may play a role in the functional organization of cortico‐basal ganglia‐thalamocortical circuits, and it is important to understand their underlying mechanisms. The cortex often drives basal ganglia (BG) activity, and particularly, oscillatory activity in the subthalamic nucleus (STN). However, the STN may also indirectly influence cortex. The aim of this study was to characterize the delayed (>200 ms) responses of STN neurons to synchronized cortical inputs, focusing on their relationship with oscillatory cortical activity. We recorded the short‐latency and delayed responses of STN units and frontal electrocorticogram (ECoG) to cortical stimulation in anaesthetized rats. Similar to previous studies, stimulation of ipsilateral frontal cortex, but not temporal cortex, evoked a short‐latency triphasic response, followed by a sustained reduction or pause in firing, in rostral STN units. Caudal STN units did not show the short‐latency triphasic response but often displayed a prolonged firing reduction. Oscillations in STN unit activity and ECoG were common after this sustained firing reduction, particularly between 200 and 600 ms after frontal cortical stimulation. These delayed oscillations were significantly coherent in a broad frequency band of 5–30 Hz. Coherence with ECoG at 5–15 Hz was observed throughout STN, though coherence at 15–30 Hz was largely restricted to rostral STN. Furthermore, oscillatory responses at 5–30 Hz in rostral STN predominantly led those in cortex (mean latency of 29 ms) after frontal cortical stimulation. These findings suggest that STN neurons responding to corticosubthalamic inputs may provide a delayed input to cortex, via BG output nuclei, and thence, thalamocortical pathways.
BDNF increases release probability and the size of a rapidly recycling vesicle pool within rat hippocampal excitatory synapses
Authors: Tyler William J. , Zhang Xiao‐lei , Hartman Kenichi , Winterer Jochen , Muller Wolfgang , Stanton Patric K. , Pozzo‐Miller Lucas
Published: May 2006

Exerting its actions pre‐, post‐ and peri‐synaptically, brain‐derived neurotrophic factor (BDNF) is one of the most potent modulators of hippocampal synaptic function. Here, we examined the effects of BDNF on a rapidly recycling pool (RRP) of vesicles within excitatory synapses. First, we estimated vesicular release in hippocampal cultures by performing FM4‐64 imaging in terminals impinging on enhanced green fluorescent protein (eGFP)‐labelled dendritic spines – a hallmark of excitatory synapses. Consistent with a modulation of the RRP, BDNF increased the evoked destaining rate of FM4‐64 only during the initial phase of field stimulation. Multiphoton microscopy in acute hippocampal slices confirmed these observations by selectively imaging the RRP, which was loaded with FM1‐43 by hyperosmotic shock. Slices exposed to BDNF showed an increase in the evoked and spontaneous rates of FM1‐43 destaining from terminals in CA1 stratum radiatum, mostly representing excitatory terminals of Schaffer collaterals. Variance‐mean analysis of evoked EPSCs in CA1 pyramidal neurons further confirmed that release probability is increased in BDNF‐treated slices, without changes in the number of independent release sites or average postsynaptic quantal amplitude. Because BDNF was absent during dye loading, imaging, destaining and whole‐cell recordings, these results demonstrate that BDNF induces a long‐lasting enhancement in the probability of transmitter release at hippocampal excitatory synapses by modulating the RRP. Since the endogenous BDNF scavenger TrkB‐IgG prevented the enhancement of FM1‐43 destaining rate caused by induction of long‐term potentiation in acute hippocampal slices, the modulation of a rapidly recycling vesicle pool may underlie the role of BDNF in hippocampal long‐term synaptic plasticity.
Single‐channel analysis of a point mutation of a conserved serine residue in the S2 ligand‐binding domain of the NR2A NMDA receptor subunit
Authors: Wyllie David J. A. , Johnston Alexander R. , Lipscombe Diane , Chen Philip E.
Published: May 2006

We have examined the function of a conserved serine residue (Ser670) in the S2 ligand‐binding region of the NR2A N‐methyl‐d‐aspartate (NMDA) receptor subunit, using recombinant NR1/NR2A receptors expressed in Xenopus laevis oocytes. Mutation of Ser670 to glycine (S670G) in NR2A reduced the potency of glutamate by 124‐fold. Single‐channel conductance and the duration of apparent open periods of NR2A(S670G) receptor mutants were, however, indistinguishable from wild‐type NMDA receptors. NR1/NR2A(S670G) shut‐time distributions were best described by a mixture of six exponential components, and the four shortest shut intervals of each distribution were considered to occur within a channel activation (burst). Bursts of single‐channel openings were fitted with a mixture of four exponential components. The longest two components carried the majority of the charge transfer and had mean durations of 9.6 ± 0.5 and 29.6 ± 1.5 ms. The overall channel open probability during a burst was high (mean, 0.83 ± 0.06). Consistent with a shortening of NMDA receptor‐channel burst lengths was the observation of an increased deactivation rate of macroscopic currents evoked by brief applications of glutamate to outside‐out membrane patches. Correlations between shut times and adjacent open times were observed in all data records. Noticeably, shorter than average openings tended to occur next to long closed periods, whereas longer than average openings tended to occur next to short closings. Our single‐channel data, together with modelling using a kinetic scheme to describe channel activations, support our hypothesis that the S670G point mutation reduces the dwell time of glutamate in its binding site.
Autoreactive B Cell Responses to RNA-Related Antigens Due to
TLR7
Gene Duplication
Authors: Pisitkun Prapaporn , Deane Jonathan A. , Difilippantonio Michael J. , Tarasenko Tatyana , Satterthwaite Anne B. , Bolland Silvia
Published: May 2006

Antibodies against nuclear self-antigens are characteristic of systemic autoimmunity, although mechanisms promoting their generation and selection are unclear. Here, we report that B cells containing the Y-linked autoimmune accelerator (
Yaa
) locus are intrinsically biased toward nucleolar antigens because of increased expression of TLR7, a single-stranded RNA-binding innate immune receptor. The
TLR7
gene is duplicated in
Yaa
mice because of a 4-Megabase expansion of the pseudoautosomal region. These results reveal high divergence in mouse Y chromosomes and represent a good example of gene copy number qualitatively altering a polygenic disease manifestation.
The Structure of an Infectious P22 Virion Shows the Signal for Headful DNA Packaging
Authors: Lander Gabriel C. , Tang Liang , Casjens Sherwood R. , Gilcrease Eddie B. , Prevelige Peter , Poliakov Anton , Potter Clinton S. , Carragher Bridget , Johnson John E.
Published: May 2006

Bacteriophages, herpesviruses, and other large double-stranded DNA (dsDNA) viruses contain molecular machines that pump DNA into preassembled procapsids, generating internal capsid pressures exceeding, by 10-fold, that of bottled champagne. A 17 angstrom resolution asymmetric reconstruction of the infectious P22 virion reveals that tightly spooled DNA about the portal dodecamer forces a conformation that is significantly different from that observed in isolated portals assembled from ectopically expressed protein. We propose that the tight dsDNA spooling activates the switch that signals the headful chromosome packing density to the particle exterior.
Involvement of Gonadal Steroids and Gamma Interferon in Sex Differences in Response to Blood-Stage Malaria Infection
Authors: Cernetich Amy , Garver Lindsey S. , Jedlicka Anne E. , Klein Pamela W. , Kumar Nirbhay , Scott Alan L. , Klein Sabra L.
Published: May 2006

To examine the hormonal and immunological mechanisms that mediate sex differences in susceptibility to malaria infection, intact and gonadectomized (gdx) C57BL/6 mice were inoculated with
Plasmodium chabaudi
AS-infected erythrocytes, and the responses to infection were monitored. In addition to reduced mortality, intact females recovered from infection-induced weigh loss and anemia faster than intact males. Expression microarrays and real-time reverse transcription-PCR revealed that gonadally intact females exhibited higher expression of interleukin-10 (IL-10), IL-15Rα, IL-12Rβ, Gadd45γ, gamma interferon (IFN-γ), CCL3, CXCL10, CCR5, and several IFN-inducible genes in white blood cells and produced more IFN-γ than did intact males and gdx females, with these differences being most pronounced during peak parasitemia. Intact females also had higher anti-
P. chabaudi
immunoglobulin G (IgG) and IgG1 responses than either intact males or gdx females. To further examine the effector mechanisms mediating sex differences in response to
P. chabaudi
infection, responses to infection were compared among male and female wild-type (WT), T-cell-deficient (TCRβδ
−/−
), B-cell-deficient (μMT), combined T- and B-cell-deficient (RAG1), and IFN-γ knockout (IFN-γ
−/−
) mice. Males were 3.5 times more likely to die from malaria infection than females, with these differences being most pronounced among TCRβδ
−/−
, μMT, and RAG1 mice. Male mice also exhibited more severe weight loss, anemia, and hypothermia, and higher peak parasitemia than females during infection, with WT, RAG1, TCRβδ
−/−
, and μMT mice exhibiting the most pronounced sexual dimorphism. The absence of IFN-γ reduced the sex difference in mortality and was more detrimental to females than males. These data suggest that differential transcription and translation of IFN-γ, that is influenced by estrogens, may mediate sex differences in response to malaria.
Infection of Human Fallopian Tube Epithelial Cells withNeisseria gonorrhoeaeProtects Cells from Tumor Necrosis Factor Alpha-Induced Apoptosis
Authors: Morales Priscilla , Reyes Paz , Vargas Macarena , Rios Miguel , Imarai Mónica , Cardenas Hugo , Croxatto Horacio , Orihuela Pedro , Vargas Renato , Fuhrer Juan , Heckels John E. , Christodoulides Myron , Velasquez Luis
Published: May 2006

Following infection withNeisseria gonorrhoeae, bacteria may ascend into the Fallopian tubes (FT) and induce salpingitis, a major cause of infertility. In the FT, interactions between mucosal epithelial cells and gonococci are pivotal events in the pathogen's infection cycle and the inflammatory response. In the current study, primary FT epithelial cells were infected in vitro with different multiplicities of infection (MOI) of Pil+Opa+gonococci. Bacteria showed a dose-dependent association with cells and induced the secretion of tumor necrosis factor alpha (TNF-α). A significant finding was that gonococcal infection (MOI = 1) induced apoptosis in approximately 30% of cells, whereas increasing numbers of bacteria (MOI = 10 to 100) did not induce apoptosis. Apoptosis was observed in only 11% of cells with associated bacteria, whereas >84% of cells with no adherent bacteria were apoptotic. TNF-α was a key contributor to apoptosis, since (i) culture supernatants from cells infected with gonococci (MOI = 1) induced apoptosis in naïve cultures, suggesting that a soluble factor was responsible; (ii) gonococcal infection-induced apoptosis was inhibited with anti-TNF-α antibodies; and (iii) the addition of exogenous TNF-α induced apoptosis, which was inhibited by the presence of increasing numbers of bacteria (MOI = 10 to 100). These data suggest that TNF-α-mediated apoptosis of FT epithelial cells is likely a primary host defense mechanism to prevent pathogen colonization. However, epithelial cell-associated gonococci have evolved a mechanism to protect the cells from undergoing TNF-α-mediated apoptosis, and this modulation of the host innate response may contribute to establishment of infection. Understanding the antiapoptotic mechanisms used byNeisseria gonorrhoeaewill inform the pathogenesis of salpingitis and could suggest new intervention strategies for prevention and treatment of the disease.
The
Babesia bovis
Merozoite Surface Antigen 1 Hypervariable Region Induces Surface-Reactive Antibodies That Block Merozoite Invasion
Authors: LeRoith Tanya , Berens Shawn J. , Brayton Kelly A. , Hines Stephen A. , Brown Wendy C. , Norimine Junzo , McElwain Terry F.
Published: May 2006

A hypervariable region (HVR) previously identified in the carboxy-terminal one-third of the
Babesia bovis
variable merozoite surface antigen family was more extensively analyzed in merozoite surface antigen 1 (MSA-1) from 16 strains and isolates. The MSA-1 HVR is proline rich and contains three semiconserved motifs nearly identical to those described for the related family member MSA-2. Two MSA-1-specific monoclonal antibodies previously shown to be reactive with the merozoite surface bound to a recombinant construct encoding the HVR, indicating that the HVR is surface exposed and accessible to antibody binding. Importantly, these surface-reactive, HVR-specific monoclonal antibodies were capable of inhibiting merozoite infectivity of the host erythrocyte in vivo. The results indicate that the MSA-1 HVR is involved in erythrocyte invasion and suggest that selection of MSA-1 variants may be driven by invasion-blocking antibodies.
Role for Erbin in Bacterial Activation of Nod2
Authors: Kufer T. A. , Kremmer E. , Banks D. J. , Philpott D. J.
Published: May 2006

Intracellular peptidoglycan (PG) recognition in human cells is mediated by the NACHT-LRR proteins Nod1 and Nod2. Elicitation of these proteins by PG motifs released from invasive bacteria triggers signaling events, resulting in the activation of the NF-κB pathway. In order to decipher the molecular components involved in Nod2 signal transduction, we set out to identify new interaction partners of Nod2 by using a yeast two-hybrid screen. Besides the known interaction partner RIP2, the screen identified the leucine-rich repeat (LRR)- and PDZ domain-containing family member Erbin as a binding partner of Nod2. Erbin showed a specific interaction with Nod2 in coimmunoprecipitation experiments with human HEK 293T cells. Immunofluorescence microscopy with a newly generated anti-Nod2 monoclonal antibody showed that Erbin and Nod2 partially colocalize in human cells. Subsequent analysis of the Erbin/Nod2 interaction revealed that the LRR of Erbin and the caspase activating and recruiting domains of Nod2 were necessary for this interaction. No significant interaction was observed with a Walker B box mutant of Nod2 or a Crohn's disease-associated frameshift mutant of Nod2, indicating that complex formation is dependent on the activity of the molecule. In addition, a change in the dynamics of the Erbin/Nod2 complex was observed during
Shigella flexneri
infection. Furthermore, ectopic expression of increasing amounts of Erbin or short hairpin RNA-mediated knockdown of Erbin showed a negative influence of Erbin on Nod2/muramyl-dipeptide-mediated NF-κB activation. These results implicate Erbin as a potential negative regulator of Nod2 and show that bacterial infection has an impact on Nod2/Erbin complex formation within cells.
Genomic Diversity between Strains of the Same Serotype and Multilocus Sequence Type among Pneumococcal Clinical Isolates
Authors: Silva Nuno A. , McCluskey Jackie , Jefferies Johanna M. C. , Hinds Jason , Smith Andrew , Clarke Stuart C. , Mitchell Tim J. , Paterson Gavin K.
Published: May 2006

The important human pathogen
Streptococcus pneumoniae
is known to be a genetically diverse species. We have used comparative genome hybridization (CGH) microarray analysis to investigate this diversity in a collection of clinical isolates including several capsule serotype 14 pneumococci, a dominant serotype among disease isolates. We have identified three new regions of diversity among pneumococcal isolates and, importantly, clearly demonstrate genetic differences between strains of the same multilocus sequence type (ST) and capsule serotype. CGH may therefore, under certain circumstances, prove to be a valuable tool to supplement current typing methods. Finally, we show that these clonal strains with the same serotype and ST behave differently in an animal model. Strains of the same ST and serotype therefore have important genetic and phenotypic differences.
Resistance of
Streptococcus gordonii
to Polymorphonuclear Leukocyte Killing Is a Potential Virulence Determinant of Infective Endocarditis
Authors: Young Lee Si , Cisar John O. , Bryant Joseph L. , Eckhaus Michael A. , Sandberg Ann L.
Published: May 2006

Significant differences in virulence among seven representative
Streptococcus gordonii
strains were observed by using the rat model of infective endocarditis. Five strains, including
S. gordonii
DL1, caused severe disease, while the other two strains, including
S. gordonii
SK12, caused minimal or no disease. The differences in virulence were evident from the visible presence of streptococci in the vegetations present on the aortic valves of catheterized rats that were challenged with individual strains and also from the much greater recovery of rifampin-resistant
S. gordonii
DLl than of streptomycin-resistant
S. gordonii
SK12 from the hearts of animals coinfected with both organisms. Each
S. gordonii
strain aggregated with human platelets and bound to polymorphonuclear leukocytes (PMNs), as shown by the stimulation of PMN superoxide anion production. These interactions were reduced or abolished by pretreatment of the platelets or PMNs with sialidase, indicating that there was bacterial recognition of host sialic acid-containing receptors. Adhesin-mediated binding of each
S. gordonii
strain to PMNs also triggered phagocytosis. However, the subsequent PMN-dependent killing differed significantly for the seven strains. The five virulent strains included three strains that were not killed and two strains whose numbers were reduced by approximately 50%. In contrast, the level of killing of each avirulent strain under the same conditions was significantly greater and approached 90% of the bacteria added. Parallel studies performed with rat PMNs revealed comparable differences in the resistance or susceptibility of representative virulent and avirulent strains. Thus, the ability of
S. gordonii
to survive in PMNs following adhesin-mediated phagocytosis may be an important virulence determinant of infective endocarditis.
Interaction ofYersinia pestiswith Macrophages: Limitations in YopJ-Dependent Apoptosis
Authors: Zauberman Ayelet , Cohen Sara , Mamroud Emanuelle , Flashner Yehuda , Tidhar Avital , Ber Raphael , Elhanany Eytan , Shafferman Avigdor , Velan Baruch
Published: May 2006

The enteropathogenicYersiniastrains are known to downregulate signaling pathways in macrophages by effectors of the type III secretion system, in which YopJ/YopP plays a crucial role. The adverse effects ofYersinia pestis, the causative agent of plague, were examined by infecting J774A.1 cells, RAW264.7 cells, and primary murine macrophages with the EV76 strain and with the fully virulent Kimberley53 strain.Y. pestisexerts YopJ-dependent suppression of tumor necrosis factor alpha secretion and phosphorylation of mitogen-activated protein kinases and thus resembles enteropathogenicYersinia. However,Y. pestisis less able to activate caspases, to suppress NF-κB activation, and to induce apoptosis in macrophages than the high-virulenceY. enterocoliticaWA O:8 strain. These differences appear to be related to lower efficiency of YopJ effector translocation byY. pestis. The efficiencies of effector translocation and of apoptosis induction can be enhanced either by using a high bacterial load in a synchronized infection or by overexpressing exogenous YopJ inY. pestis. Replacing YopJ with the homologousY. enterocoliticaeffector YopP can further enhance these effects. Overexpression of YopP in ayopJ-deletedY. pestisbackground leads to rapid and effective translocation into target cells, providingY. pestiswith the high cytotoxic potential ofY. enterocoliticaWA O:8. We suggest that the relative inferiority ofY. pestisin triggering cell death in macrophages may be advantageous for its in vivo propagation in the early stages of infection.