bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Spontaneous Firing in Dorsomedial Suprachiasmatic Nucleus Neurons
Authors: Jackson Alexander C. , Yao Gui Lan , Bean Bruce P.
Published: September 2004

We studied acutely dissociated neurons from the dorsomedial (shell) region of the rat suprachiasmatic nucleus (SCN) with the aim of determining the ionic conductances that underlie spontaneous firing. Most isolated neurons were spontaneously active, firing rhythmically at an average frequency of 8 ± 4 Hz. After application of TTX, oscillatory activity generally continued, but more slowly and at more depolarized voltages; these oscillations were usually blocked by 2 μmnimodipine. To quantify the ionic currents underlying normal spontaneous activity, we voltage clamped cells using a segment of the spontaneous activity of each cell as voltage command and then used ionic substitution and selective blockers to isolate individual currents. TTX-sensitive sodium current flowed throughout the interspike interval, averaging -3 pA at -60 mV and -11 pA at -55 mV. Calcium current during the interspike interval was, on average, fourfold smaller. Except immediately before spikes, calcium current was outweighed by calcium-activated potassium current, and in current clamp, nimodipine usually depolarized cells and slowed firing only slightly (average, ∼8%). Thus, calcium current plays only a minor role in pacemaking of dissociated SCN neurons, although it can drive oscillatory activity with TTX present. During normal pacemaking, the early phase of spontaneous depolarization (-85 to -60 mV) is attributable mainly to background conductance; cells have relatively depolarized resting potentials (with firing stopped by TTX and nimodipine) of -55 to -50 mV, although input resistance is high (9.5 ± 4.1 GΩ). During the later phase of pacemaking (positive to -60 mV), TTX-sensitive sodium current is dominant.
Tlx, an Orphan Nuclear Receptor, Regulates Cell Numbers and Astrocyte Development in the Developing Retina
Authors: Miyawaki Takaya , Uemura Akiyoshi , Dezawa Mari , Yu Ruth T. , Ide Chizuka , Nishikawa Shinichi , Honda Yoshihito , Tanabe Yasuto , Tanabe Teruyo
Published: September 2004

Tlx belongs to a class of orphan nuclear receptors that underlies many aspects of neural development in the CNS. However, the fundamental roles played by Tlx in the control of eye developmental programs remain elusive. By usingTlxknock-out (KO) mice, we show here that Tlx is expressed by retinal progenitor cells in the neuroblastic layer during the period of retinal layer formation, and it is critical for controlling the generation of appropriate numbers of retinal progenies through the activities of cell cycle-related molecules, cyclin D1 and p27Kip1. Tlx expression is restricted to Müller cells in the mature retina and appears to control their proper development. Furthermore, we show that Tlx is expressed by immature astrocytes that migrate from the optic nerve onto the inner surface of the retina and is required for their generation and maturation, as assessed by honeycomb network formation and expression of R-cadherin, a critical component for vasculogenesis. The impaired astrocyte network formation on the inner retinal surface is accompanied by the loss of vasculogenesis inTlxKO retinas. Our studies thus indicate that Tlx underlies a fundamental developmental program of retinal organization and controls the generation of the proper numbers of retinal progenies and development of glial cells during the protracted period of retinogenesis.
Failed Clearance of Aneuploid Embryonic Neural Progenitor Cells Leads to Excess Aneuploidy in theAtm-Deficient But Not theTrp53-Deficient Adult Cerebral Cortex
Authors: McConnell Michael J. , Kaushal Dhruv , Yang Amy H. , Kingsbury Marcy A. , Rehen Stevens K. , Treuner Kai , Helton Robert , Annas Emily G. , Chun Jerold , Barlow Carrolee
Published: September 2004

Aneuploid neurons populate the normal adult brain, but the cause and the consequence of chromosome abnormalities in the CNS are poorly defined. In the adult cerebral cortex of three genetic mutants, one of which is a mouse model of the human neurodegenerative disease ataxia-telangiectasia (A-T), we observed divergent levels of sex chromosome (XY) aneuploidy. Although both A-T mutated (Atm)- and transformation related protein 53 (Trp53)-dependent mechanisms are thought to clear newly postmitotic neurons with chromosome abnormalities, we found a 38% increase in the prevalence of XY aneuploidy in the adultAtm-/-cerebral cortex and a dramatic 78% decrease inTrp53-/-mutant mice. A similar 43% decrease in adult XY aneuploidy was observed in DNA repair-deficientXrcc5-/-mutants. Additional investigation found an elevated incidence of aneuploid embryonic neural progenitor cells (NPCs) in all three mutants, but elevated apoptosis, a likely fate of embryonic NPCs with severe chromosome abnormalities, was observed only inXrcc5-/-mutants. These data lend increasing support to the hypothesis that hereditary mutations such as ATM-deficiency, which render abnormal cells resistant to developmental clearance, can lead to late-manifesting human neurological disorders.
Dual-Phenotype GABA/Glutamate Neurons in Adult Preoptic Area: Sexual Dimorphism and Function
Authors: Ottem Erich N. , Godwin Jonathan G. , Krishnan Sudha , Petersen Sandra L.
Published: September 2004

It is generally assumed that the inhibitory neurotransmitter GABA and the stimulatory neurotransmitter glutamate are released from different neurons in adults. However, this tenet has made it difficult to explain how the same afferent signals can cause opposite changes in GABA and glutamate release. Such reciprocal release is a central mechanism in the neural control of many physiological processes including activation of gonadotropin-releasing hormone (GnRH) neurons, the neural signal for ovulation. Activation of GnRH neurons requires simultaneous suppression of GABA and stimulation of glutamate release, each of which occurs in response to a daily photoperiodic signal, but only in the presence of estradiol (E2). In rodents, E2and photoperiodic signals converge in the anteroventral periventricular nucleus (AVPV), but it is unclear how these signals differentially regulate GABA and glutamate secretion. We now report that nearly all neurons in the AVPV of female rats express both vesicular glutamate transporter 2 (VGLUT2), a marker of hypothalamic glutamatergic neurons, as well as glutamic acid decarboxylase and vesicular GABA transporter (VGAT), markers of GABAergic neurons. These dual-phenotype neurons are the main targets of E2in the region and are more than twice as numerous in females as in males. Moreover, dual-phenotype synaptic terminals contact GnRH neurons, and at the time of the surge, VGAT-containing vesicles decrease and VGLUT2-containing vesicles increase in these terminals. Thus, we propose a new model for ovulation that includes dual-phenotype GABA/glutamate neurons as central transducers of hormonal and neural signals to GnRH neurons.
ATP Induces a Rapid and Pronounced Increase in 2-Arachidonoylglycerol Production by Astrocytes, a Response Limited by Monoacylglycerol Lipase
Authors: Walter Lisa , Dinh Thien , Stella Nephi
Published: September 2004

The cytoplasm of neural cells contain millimolar amounts of ATP, which flood the extracellular space after injury, activating purinergic receptors expressed by glial cells and increasing gliotransmitter production. These gliotransmitters, which are thought to orchestrate neuroinflammation, remain widely uncharacterized. Recently, we showed that microglial cells produce 2-arachidonoylglycerol (2-AG), an endocannabinoid known to prevent the propagation of harmful neuroinflammation, and that ATP increases this production by threefold at 2.5 min (Witting et al., 2004). Here we show that ATP increases 2-AG production from mouse astrocytes in culture, a response that is more rapid (i.e., significant within 10 sec) and pronounced (i.e., 60-fold increase at 2.5 min) than any stimulus-induced increase in endocannabinoid production reported thus far. Increased 2-AG production from astrocytes requires millimolar amounts of ATP, activation of purinergic P2X7receptors, sustained rise in intracellular calcium, and diacylglycerol lipase activity. Furthermore, we show that astrocytes express monoacylglycerol lipase (MGL), the main hydrolyzing enzyme of 2-AG, the pharmacological inhibition of which potentiates the ATP-induced 2-AG production (up to 113-fold of basal 2-AG production at 2.5 min). Our results show that ATP greatly increases, and MGL limits, 2-AG production from astrocytes. We propose that 2-AG may function as a gliotransmitter, with MGL inhibitors potentiating this production and possibly restraining the propagation of harmful neuroinflammation.
Glucocorticoid Effects on Memory Retrieval Require Concurrent Noradrenergic Activity in the Hippocampus and Basolateral Amygdala
Authors: Roozendaal Benno , Hahn Emily L. , Nathan Sheila V. , de Quervain Dominique J.-F. , McGaugh James L.
Published: September 2004

Previous findings indicate that administration of aβ-adrenoceptor antagonist systemically blocks glucocorticoid impairment of memory retrieval. Here, we report that β-adrenoceptor activation in the hippocampus and the basolateral complex of the amygdala (BLA) is implicated in the impairing effects of glucocorticoids on memory retrieval. The specific glucocorticoid receptor (GR) agonist 11β,17β-dihydroxy-6,21-dimethyl-17α-pregna-4,6-trien-20yn-3-one (RU 28362) (15 ng) infused into the hippocampus of male Sprague Dawley rats 60 min before water maze retention testing, 24 hr after training, impaired probe trial retention performance, as assessed by quadrant search time and initial latency to cross the platform location. Because we found previously that RU 28362 infused into the hippocampus does not affect water maze acquisition or immediate recall, the findings suggest that the GR agonist-induced retention impairment was attributable to a selective influence on long-term memory retrieval. Likewise, systemic injections of the β1-adrenoceptor partial agonist xamoterol (3.0 or 10.0 mg/kg, s.c.) 60 min before the probe trial dose-dependently impaired retention performance. The β-adrenoceptor antagonist propranolol (2.0 mg/kg) administered subcutaneously before retention testing did not affect retention performance alone, but blocked the memory retrieval impairment induced by concurrent intrahippocampal infusions of RU 28362. Pretest infusions of the β1-adrenoceptor antagonist atenolol into either the hippocampus (1.25 μg in 0.5 μl) or the BLA (0.5 μg in 0.2 μl) also prevented the GR agonist-induced memory retrieval impairment. These findings suggest that glucocorticoids impair retrieval of long-term spatial memory by facilitating noradrenergic mechanisms in the hippocampus, and additionally, that norepinephrine-mediated BLA activity is critical in enabling hippocampal glucocorticoid effects on memory retrieval.
Neuronal Toxicity inCaenorhabditis elegansfrom an Editing Site Mutant in Glutamate Receptor Channels
Authors: Aronoff Rachel , Mellem Jerry E. , Maricq Andres Villu , Sprengel Rolf , Seeburg Peter H.
Published: September 2004

Ionotropic glutamate receptors (iGluRs) inCaenorhabditis elegansare predicted to have high permeability for Ca2+because of glutamine (Q) residues in the pore loop. This contrasts to the low Ca2+permeability of similar iGluRs in principal neurons of mammals, because of an edited arginine (R) at the critical pore position in at least one channel subunit. Here, we introduced the R residue into the pore loop of a glutamate receptor subunit, GLR-2, inC. elegans. GLR-2(R) participated in channel formation, as revealed by decreased rectification of kainate-evoked currents in electrophysiological recordings when GLR-2(R) and the wild-type GLR-2(Q) were coexpressed in worms. Notably, the transgenic worms exhibited, at low penetrance, strong phenotypic impairments including uncoordination, neuronal degeneration, developmental arrest, and lethality. Penetrance of adverse phenotypes could be enhanced by transgenic expression of an optimal GLR-2(Q)/(R) ratio, implicating channel activity as the cause. In direct support, a mutation ineat-4, which prevents glutamatergic transmission, suppressed adverse phenotypes. Suppression was also achieved by mutation in calreticulin, which is necessary for maintainance of intracellular Ca2+stores in the endoplasmic reticulum. Thus, synaptically activated GLR-2(R)-containing iGluR channels appear to trigger inappropriate, neurotoxic Ca2+release from intracellular stores.
Activation of the IκB Kinase Complex and Nuclear Factor-κB Contributes to Mutant Huntingtin Neurotoxicity
Authors: Khoshnan Ali , Ko Jan , Watkin Erin E. , Paige Lisa A. , Reinhart Peter H. , Patterson Paul H.
Published: September 2004

Transcriptional dysregulation by mutant huntingtin (Htt) protein has been implicated in the pathogenesis of Huntington's disease (HD). We find that cultured cells expressing mutant Htt and striatal cells from HD transgenic mice have elevated nuclear factor-κB (NF-κB) activity. Furthermore, NF-κB is concentrated in the nucleus of neurons in the brains of HD transgenic mice. In inducible PC12 cells and in HD transgenic mice, mutant Htt activates the IκB kinase complex (IKK), a key regulator of NF-κB. Activation of IKK is likely mediated by direct interaction with mutant Htt, because the expanded polyglutamine stretch and adjacent proline-rich motifs in mutant Htt interact with IKKγ, a regulatory subunit of IKK. Activation of IKK may also influence the toxicity of mutant Htt, because expression of IKKγ promotes aggregation and nuclear localization of mutant Htt exon-1. Moreover, in acute striatal slice cultures, inhibition of IKK activity with an N-terminally truncated form of IKKγ blocks mutant Htt-induced toxicity in medium-sized spiny neurons (MSNs). In addition, blocking degradation of NF-κB inhibitors with a dominant-negative ubiquitin ligase β-transducin repeat-containing protein also reduces the toxicity of mutant Htt in MSNs. Therefore, aberrant NF-κB activation may contribute to the neurodegeneration induced by mutant Htt.
Rejection of False Matches for Binocular Correspondence in Macaque Visual Cortical Area V4
Authors: Tanabe Seiji , Umeda Kazumasa , Fujita Ichiro
Published: September 2004

A plane lying in depth is vividly perceived by viewing a random-dot stereogram (RDS) with a slight binocular disparity. Perception of a plane-in-depth is lost by reversing the contrast of dots seen by one of the eyes to generate an anticorrelated RDS. From a computational perspective, the visual system cannot find a globally consistent solution for matching the left and right eye images of an anticorrelated RDS. The neural representation of a global match should therefore be insensitive to binocular disparity in an anticorrelated RDS. Most neurons in the striate cortex (V1) respond to binocular disparity in anticorrelated RDSs, suggesting that further cortical processing in extrastriate areas is necessary to fully account for the matching computation. We examined neural responses to dynamic RDSs, both normal (correlated) and anticorrelated, in area V4 of the monkey visual cortex. More than half of the V4 cells were sensitive to the horizontal disparity embedded in a correlated RDS. Most of them greatly attenuated their selectivity for disparity when the RDS was anticorrelated. This attenuation was apparent from the response onset, and the degree of attenuation did not correlate with neuronal response latencies. Unlike the disparity tuning of V1 neurons to anticorrelated RDSs, that of V4 neurons was not an inversion of tuning to normal RDSs. Our results suggest that responses to false matches between contrast-reversed dots in the left and right eye images elicited in V1 are substantially reduced by the stage of V4.
Did the instigator intend to provoke? A key moderator in the relation between trait aggression and aggressive behavior
Authors: Tremblay Paul F. , Belchevski Mirjana
Published: September 2004

The purpose of this study was to investigate the cross‐situational consistency of trait aggression in provoking situations where an instigator (1) clearly intended to provoke, (2) clearly intended not to provoke, or (3) where presence of intention was ambiguous. It was hypothesized that cross‐situational consistency would be substantial, and that trait aggression would have the greatest impact on aggressive behavior in ambiguous situations. Participants were 80 female and 38 male undergraduate students. They completed the Aggression Questionnaire [Buss and Perry, J Pers Soc Psychol, 1992, pp. 452], read a set of 24 vignettes depicting conflict situations and rated their perceived likelihood of becoming angry and aggressive in those situations. An overall cross‐situational consistency correlation coefficient of r=.47 was found. It was also found that trait aggression had a significantly greater effect on the likelihood of aggressive responses in the ambiguous and intentional situations than it did in the unintentional situations. These results are discussed in relation to trait activation and hostile attribution bias. Aggr. Behav. 30:409–424, 2004. © 2004 Wiley‐Liss, Inc.
The impact of direct and indirect bullying on the mental and physical health of Italian youngsters
Authors: Baldry Anna C.
Published: September 2004

The aim of the present study was to determine the extent to which direct and indirect bullying and victimization at school affects the mental and physical health of 661 Italian boys and girls, aged 11 to 15 years old. The impact of bullying and victimization is assessed by taking into account the relative buffering effect of a positive relationship with one or both parents. Internalizing symptoms such as withdrawn behaviors, somatic complaints, and anxiety and depression, measured with the self‐administered Youth Form of the Achenbach's Child Behavioral Checklist, are indicators of maladjustment. Multiple regression analyses revealed that being a girl is a strong significant risk factor for all internalizing symptoms. Being a victim of indirect bullying is the strongest predictor of withdrawn behaviors, somatic complaints, and anxiety/depression, independent of direct victimization, which significantly predicts somatic complaints, anxiety, and depression, but not withdrawn behaviors. Bullying others directly by hitting, threatening, or calling names is not a significant predictor the poor mental and somatic health of youngsters, whereas indirect bullying (spreading rumors or not talking to someone on purpose) does significantly predict anxiety and depression, as well as withdrawn behaviors. The negative impact of victimization and bullying is buffered by youngsters' positive relationship with one or both parents. Recommendations are provided with regard to possible intervention strategies underlying the importance of distinguishing between different forms of bullying and victimization and providing social support in each different case. Aggr. Behav. 30:343–355, 2004. © 2004 Wiley‐Liss, Inc.
Consistency of aggressive temperament in domestic pigs: The effects of social experience and social disruption
Authors: D'Eath Richard B.
Published: September 2004

Resident‐intruder (R‐I) tests can be used to measure the aggressive temperament of domestic pigs (Sus scrofa), and have previously been shown to predict the severity and persistence of aggression when unfamiliar pigs are mixed. To study the consistency of individual differences in aggressiveness over time, 112 pigs (eight from each of fourteen litters) were given two R‐I tests at each of three ages (46, 80, and 113 days). Pigs were R‐I tested singly in an arena within the home pen, where a smaller unfamiliar intruder pig was introduced to a resident pig. Latency to the first attack by the resident was recorded, and the test was stopped as soon as an attack occurred, otherwise the test lasted five minutes. Pigs from eight of the litters used here had been allowed to mix with another litter prior to weaning (days 10–30; socialised), while pigs in six litters remained in littermate groups (control). To determine whether consistency would survive the effects of social disruption, pigs were mixed into new groups on two occasions between the first and second test, then remained in these groups until the third test. Evidence of consistency was found, despite the social disruption. Socialised pigs were more aggressive than controls, females were more aggressive than males, and certain litters were more aggressive than others. After adjusting for these, consistent differences between individuals were still evident. Consistency was higher between the second and third tests compared to the first and second, possibly because of stable group membership or the effects of age or experience. In support of the idea that social experience improves consistency, socialised pigs were more consistent than controls throughout. Evidence of consistent individual differences in aggressive temperament suggests that breeding or changes to early life experiences could have a long‐lasting influence on aggressive behaviour in pigs. Aggr. Behav. 30:435–448, 2004. © 2004 Wiley‐Liss, Inc.
Web Communities for Learning Community Work
Authors: Gahagan James
Published: September 2004

The author reviews several Web-based resources that can help untangle the complex work of launching and sustaining learning communities.
Maps and Inventories
Authors: Maki Peggy L.
Published: September 2004

Opportunities for students to learn what we wish them to are tucked in nooks and crannies of their college experience as much as they are in the obvious places. The author presents two strategies for revealing all the corners where learning occurs and those where it should but might be missing.
Cognitive load and the imagination effect
Authors: Leahy Wayne , Sweller John
Published: September 2004

When presented with a procedure or concept to learn, imagining the procedure or concept may be an effective instructional technique compared to conventional studying, thus generating an imagination effect. However, it was hypothesized that the importance of learning through imagining as an instructional technique depends on modes of presentation. Experiment 1 tested adults studying or imagining contour maps as participants and was designed to verify the generality of the imagination effect. Imagination instructions were superior to study instructions on subsequent test questions. Experiment 2 further investigated the effect by comparing much younger students (Grade 4), studying or imagining temperature/time graphs presented in either a split‐attention (spatially separated diagram and text) or an integrated (spatially combined diagram and text) format. Results on a subsequent test indicated that the Grade 4 students found imagining beneficial to their learning, compared with studying the material but the effect was only obtained using an integrated rather than a split‐attention format. Experiment 3 was conducted to obtain verbal protocols from Grade 4 imagination and study groups using the same instructional materials to throw light on the cognitive mechanisms behind the imagination effect. Copyright © 2004 John Wiley & Sons, Ltd.
A tuning algorithm for multivariable restricted structure control systems using subspace identification
Authors: Sánchez A. , Katebi M. R. , Johnson M. A.
Published: September 2004

This paper presents a new method to design a restricted structure controller driving a multivariable plant using subspace identification methods. The algorithm employs data collected from closed‐loop operation to identify an open‐loop model of the plant using subspace identification. The method also requires knowledge of the first N impulse responses from the controller. The multivariable controller parameters are calculated by minimising a finite horizon LQG criterion subject to nonlinear constraints. Three simulation case studies are presented. Copyright © 2004 John Wiley & Sons, Ltd.
Genetics of atrioventricular conduction disease in humans
Authors: Benson D. Woodrow
Published: September 2004

Atrioventricular (AV) conduction disease (block) describes impairment of the electrical continuity between the atria and ventricles. Classification of AV block has utilized biophysical characteristics, usually the extent (first, second, or third degree) and site of block (above or below His bundle recording site). The genetic significance of this classification is unknown. In young patients, AV block may result from injury or be the major cardiac manifestation of neuromuscular disease. However, in some cases, AV block has unknown or idiopathic cause. In such cases, familial clustering has been noted and published pedigrees show autosomal dominant inheritance; associated heart disease is common (e.g., congenital heart malformation, cardiomyopathy). The latter finding is not surprising given the common origin of working myocytes and specialized conduction system elements. Using genetic models incorporating reduced penetrance (disease absence in some individuals with disease gene), variable expressivity (individuals with disease gene have different phenotypes), and genetic heterogeneity (similar phenotypes, different genetic cause), molecular genetic causes of AV block are being identified. Mutations identified in genes with diverse functions (transcription, excitability, and energy homeostasis) for the first time provide the means to assess risk and offer insight into the molecular basis of this important clinical condition previously defined only by biophysical characteristics. © 2004 Wiley‐Liss, Inc.
Evaluation of mechanisms of azinphos‐methyl resistance in the codling moth Cydia pomonella (L.)
Authors: Reuveny Haim , Cohen Ephraim
Published: September 2004

Resistance of the codling moth Cydia pomonella (L.) to azinphos‐methyl is not based on enhanced detoxifying enzymes like oxidation mediated by mixed function oxidases or by glutathione S‐transferases. Synergism by S,S,S‐tributylphosphoro‐trithioate was evident, but the overall activity of general esterases using p‐nitrophenyl acetate as the substrate was similar in resistant and susceptible insects. In comparison to acetylcholinesterase (AChE) from susceptible adult codling moth, the enzyme of insects resistant to azinphos‐methyl has low affinities (higher Km values) to the substrates acetylthiocholine (ATCh) and propionylthiocholine. This difference indicates a possible amino acid alteration at the catalytic or anionic binding sites of the resistant enzyme. Inhibition studies revealed no apparent differences in sensitivity of AChE enzymes from resistant and susceptible moths to organophosphorus compounds (OPs), carbamate insecticides and quaternary ammonium ligands. MEPQ (7‐Methylethoxyphosphinyloxy)‐1‐methylquinolinium) is the most powerful OP inhibitor acting at a nM range, while chlopyrifos oxon, azinphos‐methyl oxon and paraoxon are less inhibitory by 22.9, 82.3 and 475 fold, respectively.

The codling moth AChE is a typical enzyme that displays substrate inhibition by ATCh, negligible hydrolysis of butyrylthiocholine, very high sensitivity to the bisquaternary ammonium compound BW284c51 and it is not inhibited by the powerful butyrylcholinesterase inhibitor iso‐OMPA. Of the three carbamates examined, only carbaryl was inhibitory at the mM range while pirimicarb and aldicarb were inactive. Of the quaternary ammonium ligands (except for the powerful BW284c51), edrophonium and decamethonium displayed appreciable inhibition rates, while d‐tubocuraine was practically inactive. Arch. Insect Biochem. Physiol. 57:92–100, 2004. © 2004 Wiley‐Liss, Inc.
A validated method for analysis of chromium picolinate in nutraceuticals by reversed phase high performance liquid chromatography
Authors: Koll Michael , Hoenen Hubertus , Aboul‐Enein Hassan Y.
Published: September 2004

A validated high performance liquid chromatographic method was developed for the determination of chromium picolinate in pharmaceutical dosage forms. The analysis was performed at room temperature using a reversed‐phase Supelcosil LC‐18 (250 × 4.6 mm, 5 µm) column. The mobile phase consisted of acetonitrile:water (40:60 v/v) at a ﬂow rate of 0.8 mL/min. The UV‐detector was set at 264 nm. The developed method showed a good linear relationship in the concentration range from 0.125 to 12.5 µg/mL with a correlation coefﬁcient from 0.999. The limit of detection and limit of quantiﬁcation were 0.091 and 0.181 µg/mL, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Influence of testosterone on polyunsaturated fatty acid biosynthesis in Sertoli cells in culture
Authors: Hurtado de Catalfo G. E. , de Gómez Dumm I. N. T.
Published: September 2004

Sertoli cells play a central role in spermatogenesis, its development and regulation. They are target cells for androgen action in the seminiferous tubules. The Sertoli cell is considered to be the most important cell type in the testis with regard to essential fatty acid metabolism. We studied the response to testosterone of cultured Sertoli cells from immature rats by determining the fatty acid composition of total cellular lipids as well as by the biosynthesis of polyunsaturated fatty acids. Fatty acid methyl esters were analysed by gas liquid chromatography and radiochromatography. Two doses of testosterone were tested (150 and 300 ng ml−1). Significant differences were found in fatty acids derived from total cellular lipids after 8 days in culture in the presence of testosterone (300 ng ml−1, for 48 h). Compared to controls, the hormone produced a significant increase of 16:1 and 18:1 n‐9, and of 18:2 n‐6, and a decrease of 20:4 and 22:5 n‐6 in total cellular lipids. The decrease in the n‐6 fatty acid ratios 20:4/20:3, 20:4/18:2 and 24:5/24:4, and the increase in 18:1n‐9/18:0 and 16:1n‐9/16:0 ratios were taken as an indirect signal of testosterone effects on Δ5, Δ6 and Δ9 desaturase activities. The drop in Δ5 and Δ6 desaturase activities was corroborated by analysing the transformation of [1‐14C]20:3 n‐6 into its higher homologues. We concluded that testosterone modifies the fatty acid pattern of cultured Sertoli cells, and this hormone is involved in polyunsaturated fatty acid biosynthesis, modulating Δ5 and Δ6 desaturases activity. Copyright © 2004 John Wiley & Sons, Ltd.
Studies on the endogenous phospholipids of mammalian kidney and their in vitro hydrolysis by endogenous phospholipases: a thin layer chromatographic and densitometric study
Authors: Helmy Fatma M. , Hassanein Mohamed , Juracka Amal
Published: September 2004

The phosphoglycerides profile of six species of mammalian kidney (guinea pig, pig, cat, dog, mouse and rat) and their in vitro response to the endogenous phospholipases were determined by TLC technology in conjunction with densitometric measurements. Changes in their phospholipids profile subsequent to in vitro incubation of whole tissue homogenate of these kidneys for 60 min, at pH 7.4, 38°C, and prior to phospholipids extraction have shown that the deacylation of the endogenous cardiolipin (CL) is the most prevalent lipolytic event of all mammalian kidneys studied. Concurrent with the deacylation of CL, there was also formation of monolysocardiolipin (MLCL) and a reduction in CL level. To a much lesser extent, lyso alkenyl phosphatidyl ethanolamine (LPE) was also produced concomitant with a decrease of the endogenous alkenyl phosphatidyl ethanolamine (PE) level. The deacylation of PE plasmalogen to its lyso form confirms the action of endogenous PLA2 releasing sn‐2 fatty acids. Copyright © 2004 John Wiley & Sons, Ltd.
Ultrastructural determination of gingival Langerhans cells in alloxan‐induced diabetic rats
Authors: Özsoy Nesrin , Gül Nursel , Bostanci Hamit , Ayvali Cevat
Published: September 2004

The ultrastructure of Langerhans cells has not been fully investigated in diabetes‐associated gingival tissues. The present study was carried out to investigate the ultrastructure of gingival Langerhans cells in alloxan‐induced diabetic rats. Gingival biopsies were obtained from 22 diabetic and 18 control rats. Langerhans cells were observed by transmission electron microscopy (TEM) in the basal layers of healthy oral epithelium. On rare occasions, Langerhans cells were found in the suprabasal layers of the oral epithelium. Langerhans cells in the oral epithelium of diabetic rats were seen in the basal and suprabasal layers. Usually, Langerhans cells had clear cytoplasm and convoluted or indented nuclei and few or no specific granules. The clear cytoplasm contained mitochondria, lysosomes and a small number of rough‐surfaced endoplasmic reticulum regions, but it lacked tonofilament. Occasionally, centrioles were also observed in the cytoplasm. The membrane of Langerhans cells had no junctional complexes such as desmosomes. In diabetic rats, Langerhans cell precursors were developed into specific granule‐bearing cells. Both Langerhans cells and their granules were more frequent in the gingiva of diabetic rats than in the control group. These data suggest that Langerhans cells play an important role in explaining the pathogenesis and development of diabetic gingivitis. Copyright © 2004 John Wiley & Sons, Ltd.
The long‐term effect of mesh bioprosthesis in inguinal hernia repair on testicular nitric oxide metabolism and apoptosis in rat testis
Authors: Taneli Fatma , Aydede Hasan , Vatansever Seda , Ulman Cevval , Ari Zeki , Uyanık Bekir Sami
Published: September 2004

Polypropylene mesh is the most widely used material in inguinal hernia repair. Although polypropylene mesh is known as an inert material, it is experimentally proven that mesh generates a chronic inflammatory tissue reaction. The aim of the present study was to investigate the long‐term effects of polypropylene mesh material used in inguinal hernia operations on testicular function, testicular nitric oxide (NO) metabolism and germ cell‐specific apoptosis in rats. The study comprised 40 male rats that were randomly allocated into two groups. In group 1, the left spermatic cord was elevated and a 0.5 × 1 cm polypropylene mesh was placed behind the left inguinal spermatic cord and group 2 consisted of the sham‐operated controls. Blood samples were taken at 6 months preoperatively and postoperatively after to assess luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels for hormonal evaluation. Testicular NO was evaluated by the Griess method, apoptosis by a TUNEL method and inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) expressions by immunohistochemical staining. Mild ( + ) eNOS expression was observed in all specimens. Mild ( + ) iNOS expression was only detected in ipsilateral testis of the mesh‐implanted study group. Apoptotic cells were not detected in any samples. We are of the opinion that long‐term polypropylene mesh implantation has no effect on testicular hormonal function and only a limited effect on nitric oxide levels and this effect is not sufficient to cause apoptosis in testis that could lead to infertility. It seems that mesh implantation is a reliable method in inguinal hernia repair; however, further work is required by more sensitive methods to fully elucidate the potential testicular damage. Copyright © 2004 John Wiley & Sons, Ltd.
Comparative studies of the endogenous phospholipids and their in vitro hydrolysis by endogenous phospholipases of various tissues from 7‐day‐old chicks: a thin layer chromatographic and densitometric analysis
Authors: Helmy Fatma M.
Published: September 2004

The phospholipid profiles of heart, kidney, and pectoral muscle of 7‐day‐old chicks and their in vitro response to the endogenous lipolytic enzymes (mainly in the phospholipase group) at pH 7.4 and 38°C for 60 min were analysed by TLC technology and densitometry. The noticeable preferential deacylation of cardiolipin (CL) as detected by the formation of monolysocardiolipin (MLCL) and concurrent reduction of CL level were the most prevalent lipolytic events of chick cardiac muscle, but the least prevalent in chick pectoral muscle. Deacylation of ethanolamine plasmalogen (PE) as revealed by the formation of the corresponding lyso alkenyl derivative was also prominent in cardiac muscle, but much less so in kidney and none at all was detected in pectoral muscle. The level of sphingomyelin (SM) was much higher in kidney than heart and pectoral muscle. Following in vitro incubation, the reduction in the level of SM and the high level of ceramide (Cer) production were most conspicuous in kidney, less in cardiac muscle and least in pectoral muscle. The hydrolysis of PE and SM confirm the action of endogenous PLA2 and endogenous sphingomyelinase on PE and SM respectively. These data clearly illustrate the differential response of the endogenous substrates (phospholipids) to the endogenous phospholipases of the tissues studied and are probably related to their physiological activities in vivo. Copyright © 2004 John Wiley & Sons, Ltd.
Cytochrome P4501A1 polymorphisms in the Amerindian and Mestizo populations of Mexico
Authors: Fragoso José Manuel , Juárez‐Cedillo Teresa , Hernández‐Pacheco Guadalupe , Ramírez Erick , Zuñiga Joaquín , Izaguirre Raul , de la Peña Aurora , Granados Julio , Vargas‐Alarcón Gilberto
Published: September 2004

Several polymorphisms in the CYP1A1 locus have been identified and their genotypes appear to exhibit population frequencies that depend on ethnicity. We studied two CYP1A1 polymorphic sites (position 4889 and 6235) in a group of 212 unrelated healthy individuals belonging to three different Mexican populations (106 Mexican Mestizos, 52 Teenek and 54 Mayos). Comparison among Mexican populations showed increased frequency of the *Ile allele (A on position 4889) in Mexican Mestizos when compared to Amerindians (p < 0.05). The analysis of position 6235 showed increased frequencies of *m2 (C in this position) allele in Teenek when compared to Mestizos and Mayos (p < 0.05) and of *m2/*m2 genotype when compared to Mestizos (p < 0.05). Amerindian populations (from Mexico and South America) presented the lowest frequencies of *Ile (position 4889) and *m1 (position 6235) alleles, however these frequencies vary according to the ethnic group studied. Mexican Amerindian groups together with other South Amerindian populations showed the highest frequencies for *Val at position 4889 and the *m2 allele at position 6235. The present study corroborates the high frequencies of*Val and *m2 alleles in the Amerindian populations and detects some differences between Mexican populations that correlate with linguistic differences. Our data could be helpful in understanding the distribution of these polymorphisms and in clarifying their roles as genetic and evolution markers in Amerindian populations. Copyright © 2004 John Wiley & Sons, Ltd.
CD147 and matrix metalloproteinase‐2 protein expression as significant prognostic factors in esophageal squamous cell carcinoma
Authors: Ishibashi Yoshio , Matsumoto Tomoe , Niwa Mikio , Suzuki Yutaka , Omura Nobuo , Hanyu Nobuyoshi , Nakada Koji , Yanaga Katsuhiko , Yamada Kyosuke , Ohkawa Kiyoshi , Kawakami Makio , Urashima Mitsuyoshi
Published: September 2004

BACKGROUND

The authors investigated whether the presence of matrix metalloproteinase‐2 (MMP‐2) and its inducer, CD147, in cancerous esophageal lesions and surrounding tissue might help to predict patient prognosis.

METHODS

Tissue samples from 101 patients with esophageal squamous cell carcinoma were stained with anti‐CD147 and anti–MMP‐2 antibodies for immunohistochemical analysis.

RESULTS

CD147 was expressed in cancerous and dysplastic lesions, but not in normal tissue. In contrast, MMP‐2 was detected mainly in normal interstitial tissue adjacent to cancerous lesions, but it was detected also in cancerous lesions in some patients. Pathologic findings demonstrated that the intensity of MMP‐2 staining in normal tissue was associated positively with the depth of tumor infiltration and the stage of disease, whereas MMP‐2 staining in cancerous tissue was associated positively with vascular and lymphatic vessel invasion as well as with immature differentiation of cancer cells. Using a proportional hazard model, including information on CD147 staining patterns within cancerous lesions along with clinical cancer staging, improved the accuracy of predicting patient prognosis.

CONCLUSIONS

These results suggested that measurement of CD147 and MMP‐2 expression with simple immunohistochemical staining may enhance further the understanding of the pathophysiology of invading tumor cells and, when used in combination with cancer staging, may increase the ability of investigators to predict prognosis in patients with esophageal squamous cell carcinoma. Cancer 2004. © 2004 American Cancer Society.
Femtosecond Pump‐Probe Measurements of Solvation by Hydrogen‐Bonding Interactions
Authors: Pines Ehud , Pines Dina , Ma Ying‐Zhong , Fleming Graham R.
Published: September 2004

An additional ultrafast blue shift in the transient absorption spectra of hydrogen‐bonding complexes of a strong photoacid, 8‐hydroxypyrene 1,3,6‐trisdimethylsulfonamide (HPTA), over the solvation response of the uncomplexed HPTA and also over that of the methoxy derivative of the photoacid (MPTA) in the presence of the hydrogen‐bonding base was observed on optical excitation of the photoacid. The additional 55±10 fs solvation response was found to be about 35 % and 19 % of the total C(t) of HPTA in dichloromethane (DCM) when it was hydrogen‐bonded to dimethylsulfoxide (DMSO) and dioxane, respectively, and about 29 % of the total C(t) of HPTA in dichloroethane (DCE) when it was hydrogen‐bonded to DMSO. We have assigned this additional dynamic spectral shift to a transient change in the hydrogen bond (OH⋅⋅⋅O) that links HPTA to the complexing base, after the electronic excitation of the photoacid.
The Effect of Ge Incorporation on the Brønsted Acidity of ZSM‐5
Authors: van de Water Leon G. A. , Zwijnenburg Martijn A. , Sloof Willem G. , van der Waal Jan C. , Jansen Jacobus C. , Maschmeyer Thomas
Published: September 2004

The effect of the isomorphous substitution of some of the Si atoms in ZSM‐5 by Ge atoms on the Brønsted acid strength has been investigated by i) DFT calculations on cluster models of the formula ((HO)3SiO)3‐Al‐O(H)‐T‐(OSi(OH)3)3, with T=Si or Ge, and ((HO)3SiO)3‐Al‐O(H)‐Si‐(OGe(OH)3)(OSi(OH)3)2, ii) a 31P NMR study of zeolite samples contacted with trimethyl phosphine oxide probe molecules and iii) a X‐ray photoelectron spectroscopy (XPS) study of ZSM‐5 and Ge‐ZSM‐5 samples. The calculations reveal that the effect of Ge incorporation on the framework acidity strongly depends on the degree of substitution and on the exact T‐atom positions that are occupied by Ge. High Ge concentrations allow for enhanced stabilisation of the deprotonated Ge‐ZSM‐5 through structural relaxation, resulting in a slightly higher acidity as compared to ZSM‐5. This structural relaxation is not achievable in Ge‐ZSM‐5 with a low Ge content, which therefore has a slightly lower acidity than ZSM‐5. The NMR study indicates no difference between the Brønsted acidity of ZSM‐5(47) and Ge(0.09)ZSM‐5(36). Instead, evidence for the presence of a substantial amount of GeOH groups in the Ge‐containing samples was obtained from the NMR results, which is consistent with earlier FTIR studies. The XPS results do not point to an effect of Ge on the framework acidity of ZSM‐5(47), instead, the results can be best interpreted by assuming the presence of additional GeOH and SiOH groups near the surface of the Ge(0.08)ZSM‐5(47) sample.
Ultrafast Electron Dynamics in Metals
Authors: Pitarke Jose M. , Zhukov Vladlen P. , Keyling Robert , Chulkov Evgueni V. , Echenique Pedro M.
Published: September 2004

During the last decade, significant progress has been achieved in the rapidly growing field of the dynamics of hot carriers in metals. Here we present an overview of the recent achievements in the theoretical understanding of electron dynamics in metals, and focus on the theoretical description of the inelastic lifetime of excited hot electrons. We outline theoretical formulations of the hot‐electron lifetime that originates in the inelastic scattering of the excited quasiparticle with occupied states below the Fermi level of the solid. First‐principles many‐body calculations are reviewed. Related work and future directions are also addressed.
A Computational Investigation of HCN2+ Isomeric Structures: Implications for the Chemistry of Titan's Atmosphere
Authors: Antoniotti Paola , Borocci Stefano , Bronzolino Nicoletta , Grandinetti Felice
Published: September 2004

The structure and stability of various HCN2+ isomeric structures have been investigated at the complete active space SCF (CASSCF) and multireference–configuration interaction [MR‐CI‐SD(Q)] levels of theory with the 6‐31G(d) and 6‐311G(d,p) basis sets. The investigated species include the singlet (S) and triplet (T) open‐chain HNCN+ ions 1S, 1S′, and 1T, the open‐chain HCNN+ ions 2S, 2S′, and 2T, the HCN2+ cyclic structures 3S and 3T, and the HNCN+ cyclic structures 4S and 4T. All these species have been identified as true energy minima on the CASSCF(8,7)/6‐31G(d) potential energy surface, and their optimised geometries, refined at the CASSCF(8,8)/6‐31G(d) level of theory, have been used to perform single point calculations at the [MR‐CI‐SD(Q)]/6‐311G(d,p) computational level. The most stable structure was the HNCN+ ion 1T, whose absolute enthalpy of formation at 298.15 K has been estimated as 333.9±2 kcal mol−1 using the Gaussian‐3 (G3) procedure. The two species closest in energy to 1T are the triplet HCNN+ ion 2T and the singlet diazirinyl cation 3S, whose G3 enthalpies of formation at 298.15 K are 343.5±2 and 340.6±2 kcal mol−1, respectively. Finally, we have discussed the implications of our calculations for the detailed structure of the HCN2+ ions formed in the reaction between N3+ and HCN, experimentally observed by flowing afterglow‐selected ion flow/drift tube mass spectrometry and possibly occurring in Titan's atmosphere.
The Diels–Alder Reaction of Ethene and 1,3‐Butadiene: An Extended Multireference ab initio Investigation
Authors: Lischka Hans , Ventura Elizete , Dallos Michal
Published: September 2004

The concerted and stepwise mechanisms of the Diels–Alder reaction between 1,3‐butadiene and ethene have been investigated using highly correlated multireference methods (MRAQCC) and extended basis sets. Full MRAQCC geometry optimizations have been performed in all cases. The best estimate for the energy barrier of the Diels–Alder reaction is 22 kcal mol−1. Anti‐ and gauche‐out minima for the biradical structures and corresponding fragmentation saddle points have been determined. The biradical anti fragmentation saddle point is located 6.5 kcal mol−1 above the concerted saddle point. The gauche‐in structure does not correspond to a local minimum, but leads on geometry optimization directly to cyclohexene.
Surface Chemistry and Structure of Purified, Ozonized, Multiwalled Carbon Nanotubes Probed by NEXAFS and Vibrational Spectroscopies
Authors: Banerjee Sarbajit , Hemraj‐Benny Tirandai , Balasubramanian Mahalingam , Fischer Daniel A. , Misewich James A. , Wong Stanislaus S.
Published: September 2004

Understanding of oxidative processes such as solution‐phase ozonolysis in multiwalled carbon nanotubes (MWNTs) is of fundamental importance in devising applications of these tubes as components in composite materials, as well as for development of cutting and filling protocols. We present here an evaluation of various spectroscopic tools to study the structure and composition of functionalized nanotubes. We demonstrate near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy as a particularly useful and effective technique for studying the surface chemistry of carbon nanotubes.