bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic Mechanism of Long-Lasting Discharges of Action Potentials Triggered by Membrane Hyperpolarization in the Medial Lateral Habenula
Authors: Chang Su-youne , Kim Uhnoh
Published: March 2004

The activation of inhibitory synapses typically suppresses the generation of action potentials by hyperpolarizing the membrane of postsynaptic cells. In contrast to such conventional action of inhibitory synapses, we report here the ionic mechanism through which hyperpolarizing synapses trigger long-lasting discharges of action potentials that persist up to several tens of seconds. By using extracellular and intracellular recordings in slice preparations, we demonstrate that the activation of synaptic input from the limbic forebrain generates transient hyperpolarizing postsynaptic potentials in neurons of the medial part of the lateral habenular nucleus of the epithalamus. The synaptic hyperpolarization then sets off the coordinated activation of a distinct set of membrane ion channels and intracellular Ca2+mobilization by internal stores. The activation of these cellular events in distinct temporal order drives a persistent depolarization of habenular cells and promotes long-lasting discharges of tonic action potentials. The cells in the medial division of the lateral habenula project to dopamine and serotonin cells in the midbrain. We suggest that these habenular cells, by generating persistent action potentials in response to a transient increase in the activity of the limbic forebrain, may contribute to the regulation of the serotonergic and dopaminergic activity in the brain.
Avoidance Response in Goldfish: Emotional and Temporal Involvement of Medial and Lateral Telencephalic Pallium
Authors: Portavella Manuel , Torres Blas , Salas Cosme
Published: March 2004

The hippocampus and the amygdala are involved in avoidance learning in mammals. The medial and lateral pallia of actinopterygian fish have been proposed as homologous to the mammalian pallial amygdala and hippocampus, respectively, on the basis of neuroanatomical findings. This work was aimed at studying the effects of ablation of the medial telencephalic pallia (MP) and lateral telencephalic pallia (LP) in goldfish on the retention of a conditioned avoidance response previously acquired in two experimental conditions. In the first experiment, fish were trained in nontrace avoidance conditioning. In the second experiment, fish were trained in trace avoidance conditioning in which temporal cues were crucial for the learning process. An MP lesion affected the retention of the avoidance response in both procedures; in contrast, an LP lesion impaired the retention only in the trace-conditioning procedure. These data support the presence of two different systems of memory in fish, based on discrete telencephalic areas: the MP, involved in an emotional memory system; and the LP, involved in a spatial, relational, or temporal memory system. Moreover, these differential effects were similar to those produced by amygdalar and hippocampal lesions in mammals. We conclude that these specialized systems of memory could have appeared early during phylogenesis and could have been conserved throughout vertebrate evolution.
Loss of Glutamatergic Pyramidal Neurons in Frontal and Temporal Cortex Resulting from Attenuation of FGFR1 Signaling Is Associated with Spontaneous Hyperactivity in Mice
Authors: Shin Dana M. , Korada Sailaja , Raballo Rossana , Shashikant Cooduvalli S. , Simeone Antonio , Taylor Jane R. , Vaccarino Flora
Published: March 2004

Fibroblast growth factor receptor (FGFR) gene products (Fgfr1, Fgfr2, Fgfr3) are widely expressed by embryonic neural progenitor cells throughout the CNS, yet their functional role in cerebral cortical development is still unclear. To understand whether the FGF pathways play a role in cortical development, we attenuated FGFR signaling by expressing a tyrosine kinase domain-deficient Fgfr1 (tFgfr1) gene construct during embryonic brain development. Mice carrying the tFgfr1 transgene under the control of theOtx1gene promoter have decreased thickness of the cerebral cortex in frontal and temporal areas because of decreased number of pyramidal neurons and disorganization of pyramidal cell dendritic architecture. These alterations may be, in part, attributable to decreased genesis of T-Brain-1-positive early glutamatergic neurons and, in part, to a failure to maintain radial glia fibers in medial prefrontal and temporal areas of the cortical plate. No changes were detected in cortical GABAergic interneurons, including Cajal-Retzius cells or in the basal ganglia. Behaviorally, tFgfr1 transgenic mice displayed spontaneous and persistent locomotor hyperactivity that apparently was not attributable to alterations in subcortical monoaminergic systems, because transgenic animals responded to both amphetamine and guanfacine, an α2A adrenergic receptor agonist. We conclude that FGF tyrosine kinase signaling may be required for the genesis and growth of pyramidal neurons in frontal and temporal cortical areas, and that alterations in cortical development attributable to disrupted FGF signaling are critical for the inhibitory regulation of motor behavior.
Engineering Novel Spinal Circuits to Promote Recovery after Spinal Injury
Authors: Campos Lucas , Meng Zhuo , Hu Guoli , Chiu David T. W. , Ambron Richard T. , Martin John H.
Published: March 2004

We have developed an innovative way to establish a functional bridge around a spinal lesion. We disconnected the T13 nerve from its muscle targets, leaving the proximal end intact. The cut end was inserted either into an intact spinal cord, to assess regeneration of T13 axons into the cord and synapse formation with spinal neurons, or caudal to a hemisection at L2/3, to assess restoration of function below the injury. Four to 28 weeks later, anterograde tracers indicated that axons from the inserted T13 nerve regenerated into the ventral horn, the intermediate zone, and dorsal horn base, both in intact and hemisected animals. Antibodies to cholinergic markers showed that many regenerating axons were from T13 motoneurons. Electrical stimulation of the T13 nerve proximal to the insertion site 4 weeks or more after insertion into the intact cord evoked local field potentials in the intermediate zone and ventral horn, which is where T13 axons terminated. Stimulation of T13 in 71% of the animals (8 hemisected, 7 intact) evoked contraction of the back or leg muscles, depending on the level of insertion. Animals in which T13 was inserted caudal to hemisection had significantly less spasticity and muscle wasting and greater mobility at the hip, knee, ankle, and digits in the ipsilateral hindlimb than did animals with a hemisection only. Thus, T13 motor axons form novel synapses with lumbosacral motor circuits. Because the T13 motor neurons retain their connections to the brain, these novel circuits might restore voluntary control to muscles paralyzed below a spinal lesion.
Reflective verbalization improves solutions—the effects of question‐based reflection in design problem solving
Authors: Wetzstein Annekatrin , Hacker Winfried
Published: March 2004

In this experimental study (N=60), the impact of question‐based reflective verbalization on the quality of a design solution was investigated. Participants first designed an everyday object (garden grill) using various design strategies and then either answered questions of a naive partner, where they had to verbally describe, explain, justify and evaluate their solution (experimental group), or were given a filler task (control group). After the intervention, participants continued their design. The improvement in the design quality was significantly larger for the experimental group than for the control group. Significantly more participants of the experimental group developed new principles and added new explanations of functions to their design, whereas in the control group only corrections were made. We suggest that the dialogue specific style of reflective verbalization in the experimental group is linked to a specific way of thinking which is important for solving complex problems. Copyright © 2004 John Wiley & Sons, Ltd.
The role of self‐rated ability in the accuracy of confidence judgements in eyewitness memory and general knowledge
Authors: Perfect Timothy J.
Published: March 2004

It is argued that confidence stems in part from self‐rated ability in a domain of knowledge and that in eyewitness memory such perceptions are erroneous. Two experiments tested these hypotheses. In both experiments participants rated their relative ability in the domains of eyewitness memory and general knowledge and subsequently took tests of each, giving confidence ratings for each item attempted. In both studies, self‐rated ability predicted performance for general knowledge, but not eyewitness memory. Across participants confidence ratings were significant predictors of accuracy for general knowledge, but not for eyewitness memory. In Experiment 1 self‐rated ability was predictive of confidence ratings for both domains, although this effect was weaker in Experiment 2. The argument that the accuracy of confidence judgements in eyewitness memory is undermined by a lack of insight into relative expertise is therefore supported. Copyright © 2004 John Wiley & Sons, Ltd.
Misunderstanding standardized language in research interviews
Authors: Schober Michael F. , Conrad Frederick G. , Fricker Scott S.
Published: March 2004

Leaving the interpretation of words up to participants in standardized survey interviews, aptitude tests, and experiment instructions can lead to unintended interpretation; more collaborative interviewing methods can promote uniform understanding. In two laboratory studies (a factorial experiment and a more naturalistic investigation), respondents interpreted ordinary survey concepts like ‘household furniture’ and ‘living in a house’ quite differently than intended in strictly standardized interviews, when the interpretation was left entirely up to them. Comprehension was more accurate when interviewers responded to requests for clarification with non‐standardized paraphrased definitions, and most accurate when interviewers also provided clarification whenever they suspected respondents needed it. Copyright © 2004 John Wiley & Sons, Ltd.
The effects of rapport‐building style on children's reports of a staged event
Authors: Roberts Kim P. , Lamb Michael E. , Sternberg Kathleen J.
Published: March 2004

Three‐ to nine‐year‐old children (n=144) interacted with a photographer and were interviewed about the event either a week or a month later. The informativeness and accuracy of information provided following either open‐ended or direct rapport building were compared. Children in the open‐ended rapport‐building condition provided more accurate reports than children in the direct rapport‐building condition after both short and long delays. Open‐ended rapport‐building led the three‐ to four‐year‐olds to report more errors in response to the first recall question about the event, but they went on to provide more accurate reports in the rest of the interview than counterparts in the direct rapport‐building condition. These results suggest that forensic interviewers should attempt to establish rapport with children using an open‐ended style. Published in 2004 by John Wiley & Sons, Ltd.
Prior beliefs and methodological concepts in scientific reasoning
Authors: Greenhoot Andrea Follmer , Semb George , Colombo John , Schreiber Thomas
Published: March 2004

This investigation focuses on the relations between prior beliefs, methodological concepts, and college students' (N=211) scientific reasoning in different problem contexts. Participants were presented with exercises that described the method and results of experiments, and were asked to draw conclusions about the causal status of variables that violated their prior beliefs. Participants drew conclusions in both abstract (i.e. recommend a conclusion for the fictional experimenter), and personal settings (i.e. draw their own conclusions about the phenomenon). Participants' recommendations for the hypothetical experimenter were predicted by their understanding of two methodological concepts: the function of empirical evidence and experimental control. Students' personal conclusions were predicted by their prior beliefs and their appreciation of the objectivity of inquiry. Thus, even when students understand in the abstract how data should relate to scientific conclusions, prior beliefs often take precedence in their own conclusions, especially when they do not understand the issue of objectivity. Copyright © 2004 John Wiley & Sons, Ltd.
Smoking attenuates regular aerobic exercise benefits to episodic free recall immediately following strenuous physical activity
Authors: Bunce David , Hays Kate , Pring Linda
Published: March 2004

The present study was designed to evaluate the extent to which free recall performance is influenced by competing demands on physiological resources dependent on blood‐oxygen levels. Fifty‐six healthy young adults (mean age=20 years) were allocated to groups (n1–4=14) according to their level of exercise (more than 6 h aerobic exercise per wk, or sedentary1

Here sedentary refers to individuals with no regular exercise routines

.) and smoking (more than 10 cigarettes per day, or none) behaviour. Participants performed two free recall tasks, one under normal physically inactive conditions and the other immediately following strenuous physical exertion (a step‐up test for 2 min). We predicted that recall would suffer following strenuous physical activity among smoking aerobic exercisers. We reasoned this would be due to the oxygen‐carrying capacity of the blood being compromised in this group by higher levels of smoking‐related carbon monoxide in the blood stream. The results supported this prediction. We interpret our findings according to a resource model of cognitive function, mediated by physiological mechanisms. Copyright © 2004 John Wiley & Sons, Ltd.
Face recognition: cognitive and computational processes. S. S. Rakover & B. Cahlon (eds). John Benjamins Publishing Co., Amsterdam, The Netherlands, 2001. ISBN 90 272 5151 7. Price EUR 55.00 (paperback)
Authors: Brace Nicola
Published: March 2004

An Erratum has been published for this article in Applied Cognitive Psychology 18(6) 2004, 787.

No abstract
Composite adaptive and input observer‐based approaches to the cylinder flow estimation in spark ignition automotive engines
Authors: Stotsky A. , Kolmanovsky I. , Eriksson S.
Published: March 2004

The performance of air charge estimation algorithms in spark ignition automotive engines can be enhanced using advanced estimation techniques available in the controls literature. This paper illustrates two approaches of this kind that can improve the cylinder flow estimation for gasoline engines without external exhaust gas recirculation (EGR). The first approach is based on an input observer, while the second approach relies on an adaptive estimator. Assuming that the cylinder flow is nominally estimated via aspeed‐densitycalculation, and that the uncertainty is additive to the volumetric efficiency, the straightforward application of an input observer provides an easy to implement algorithm that corrects the nominal air flow estimate. The experimental results that we report in the paper point to a sufficiently good transient behaviour of the estimator. The signal quality may deteriorate, however, for extremely fast transients. This motivates the development of an adaptive estimator that relies mostly on the feedforward speed‐density calculation during transients, while during engine operation close to steady‐state conditions, it relies mostly on the adaptation. In our derivation of the adaptive estimator, the uncertainty is modelled as an unknown parameter multiplying the intake manifold temperature. We use the tracking error between the measured and modelled intake manifold pressure together with an appropriately definedprediction error estimateto develop an adaptation algorithm with improved identifiability and convergence rate. A robustness enhancement, via a σ‐modification with the σ‐factor depending on the prediction error estimate, ensures that in transients the parameter estimate converges to a pre‐determineda priorivalue. In close to steady‐state conditions, the σ‐modification is rendered inactive and the evolution of the parameter estimate is determined by both tracking error and prediction error estimate. Further enhancements are made by incorporating a functional dependence of thea priorivalue on the engine operating conditions such as the intake manifold pressure. The coefficients of this function can belearnedduring engine operation from the values to which the parameter estimate converges in close to steady‐state conditions. This feedforward learning functionality improves transient estimation accuracy and reduces the convergence time of the parameter estimate. Copyright © 2004 John Wiley & Sons, Ltd.
Application of a multivariable adaptive control strategy to automotive air conditioning systems
Authors: Shah Rajat , P. Rasmussen Bryan , Alleyne Andrew G.
Published: March 2004

This paper presents the application of a multivariable adaptive control strategy to a typical automotive air conditioning system. An experimentally validated physical model for the air conditioning (a/c) cycle is first presented and is subsequently used to choose a relevant model structure for indirect adaptive control. Recursive identification of this model structure is carried out using a multi‐input multi‐output (MIMO) parameter estimation algorithm to obtain an equivalent discrete‐time state space model of the a/c system. Linear quadratic regulator (LQR) design is implemented on the estimated model with the objectives of reference tracking and disturbance rejection. Simulation studies are presented to evaluate the advantages of using the electronic expansion valve and the air flow rate over the evaporator to control the efficiency and the capacity of a general automotive a/c unit using this adaptive control approach. The results demonstrate the efficacy of the MIMO controller and motivate further research in this area. Copyright © 2004 John Wiley & Sons, Ltd.
Nanoröhrchen durch Templatbenetzung: ein Baukastensystem
Authors: Steinhart Martin , Wehrspohn Ralf B. , Gösele Ulrich , Wendorff Joachim H.
Published: March 2004

Die Benetzung poröser Template mit Polymerschmelzen und ‐lösungen oder polymerhaltigen Mischungen ist eine ebenso einfache wie vielseitige Methode zur Herstellung von röhrchenförmigen Strukturen mit Durchmessern von wenigen zehn Nanometern bis in den Mikrometerbereich. Ihre Wände können dabei aus einer Vielzahl von Materialien bestehen, die bisher zum Teil nicht oder nur mit erheblichen Einschränkungen nanostrukturierbar waren. Beispiele sind Hochleistungspolymere wie Polytetrafluorethylen, Edelmetalle wie Palladium oder ferroelektrische Oxide. Die Methode ermöglicht eine vielfältige Modifizierung der Röhrchen, beispielsweise durch kontrollierte Erzeugung von Poren oder Einbettung von Nanopartikeln in die Röhrchenwände. Die Templatbenetzung bietet einen vielversprechenden Zugang zu funktionalisierten Nanoröhrchen‐Templat‐Hybridsystemen und freistehenden Nanoröhrchen.
Nanotubes by Template Wetting: A Modular Assembly System
Authors: Steinhart Martin , Wehrspohn Ralf B. , Gösele Ulrich , Wendorff Joachim H.
Published: March 2004

The wetting of porous templates with polymer melts and solutions or polymer‐containing mixtures is a simple and versatile method for the preparation of tubular structures with diameters ranging from a few tens of nanometers to micrometers. The tube walls can be made of a multitude of materials, some of which have thus far been altogether impossible to use or very limited in their ability to be incorporated into nanostuctures. Template wetting also makes it possible to modify the nanotubes in a variety of ways, for example through the controlled generation of pores or the embedding of nanoparticles into the walls. This method offers a promising approach to functionalized nanotube–template hybrid systems and free‐standing nanotubes.
Induction of myeloperoxidase and nitrotyrosine formation in a human eosinophilic leukemia cell line, EoL‐1
Authors: Kodama Norio , Kambayashi Yasuhiro , Kubo Masayuki , Nobukuni Yoshitaka , Kimura Shingo , Nakamura Hiroyuki , Ogino Keiki
Published: March 2004

The human eosinophilic leukemia cell line, EoL‐1, differentiated with butyrate as an eosinophilic cellular model was evaluated for peroxidase‐dependent tyrosine nitration. Butyrate suppressed cell growth and induced eosinophilic granules in EoL‐1 cells after 9 days of culture. Peroxidase activity was detected biochemically and histochemically from 3‐day cultures and it increased in a time dependent manner. This peroxidase activity was inhibited by cyanide. Nitrotyrosine formation catalysed by peroxidase using hydrogen peroxide and nitrite was detected at a high level similar to that of mature eosinophils. However, no expression of eosinophil peroxidase (EPO) was detected by RT‐PCR or immunocytochemistry. In contrast, the induction of myeloperoxidase (MPO) by butyrate was clearly detected by RT‐PCR, Northern blot, and immunocytochemical staining. These results suggest that butyrate induces MPO rather than EPO in EoL‐1 cells and that the formation of nitrotyrosine in butyrate‐induced cells is dependent on MPO. Copyright © 2003 John Wiley & Sons, Ltd.
The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver γ‐glutamyltranspeptidase
Authors: Hemmings Susan J. , Barker Lorraine
Published: March 2004

The effect of exposure to, followed by consumption of, 10% flax chow from the 18th day of gestation to the 86th day after birth was examined in male and female Fischer 344 rats. Growth curves of the flax chow‐fed rats were identical to those of regular chow‐fed rats, as were such developmental milestones as pinna development, growth of hair and eye opening. Acoustical startle and the righting reflexes, developmental behavioural indices, were also the same. Blood glucose levels were comparable in flax chow‐fed and regular chow‐fed rats at all stages of development, indicating that flax is without effect on glucose balance. There were no signs of toxicity in the flax chow‐fed rats since their plasma levels of alanine aminotransferase and γ‐glutamyltranspeptidase (γGT) were the same as those of regular chow‐fed rats. The activity of γGT displayed an increase in the livers of flax chow‐fed rats after puberty, more so in the male—four‐fold—than in the female—1.38‐fold. This is suggestive of an estrogenic effect which implicates an effect of an estrogenic flax lignan. An hepatobeneficial effect of the flax‐induced increase in liver γGT is discussed. In summary, dietary 10% flax chow is without long‐term effect on growth, development and behaviour, is non‐toxic and may be hepatoprotective. Copyright © 2003 John Wiley & Sons, Ltd.
The investigation of the ultrastructural neutrophil changes in alloxan‐induced diabetes in rats: response to a chemotactic challenge
Authors: Özsoy Nesrin , Bostancı Hamit , Ayvalı Cevat
Published: March 2004

Experimental diabetes is one of the most popular conditions in which to study the relation between neutrophil leukocyte activity and periodontal destruction. The aetiology of neutrophil dysfunction in the gingival tissue associated with diabetes has yet to be clarified. Diabetes in rats decreases neutrophil chemotactic activity in proportion to the severity of this systemic disorder. The present study was carried out to evaluate the relationship between the severity of diabetes and the neutrophil response to two chemotactic agents, and to correlate the observed neutrophil defects with the degree of diabetes. In this study two chemotactic agents, casein (0.2 μl, 2 mg ml−1) or N‐formylmethionylleucylphenylalanine (FMLP; 0.2 μl, 10−4 M), were placed into the gingival crevices of alloxan‐induced diabetic rats. Gingival biopsies were taken 15 min later and then at 5‐min intervals up to 45 min and investigated by electron microscopy. Adherence and migration were observed in the rats with moderate diabetes 30 min after the application of casein. There was chemotaxis after 35 min of administration of the peptide FMLP. By 40 min neutrophils with pyknotic nuclei were observed. At 45 min neutrophils with a decreased number of granules were present. As the severity of the diabetes increased, the neutrophils degenerated and were structurally distorted. In the rats which had alloxan‐induced diabetes there was abnormal periodontal damage. This damage is thought to be related to dysfunctional neutrophils. These findings many contribute to an answer to the following question: why is there an apparent variability in the susceptibilty of periodontal breakdown in diabetics? Copyright © 2003 John Wiley & Sons, Ltd.
Tyrosine aminotransferase and gamma‐glutamyl transferase activity in human fetal hepatocyte primary cultures under proliferative conditions
Authors: Rehman Khaja K. , Ayesha Qamar , Khan Aleem A. , Ahmed Niyaz , Habibullah Chittor M.
Published: March 2004

The ontogeny of gamma‐glutamyl transferase (GGTase; E.C.2.3.2.2) and tyrosine aminotransferase (TAT; E.C.2.6.1.5) activities in 14 to 36 weeks gestational and neonatal hepatocytes during development of human fetal liver was studied. Subsequently, 20–24 weeks gestational hepatocytes were cultured in media supplemented with epidermal growth factor (EGF) and insulin with or without glucagon and dexamethasone to investigate the proliferation and differentiation of fetal hepatocyte in vitro using GGTase and TAT as biochemical markers. During the development of the liver, the activity of GGTase increased continuously from the first trimester through the third trimester and decreased (p < 0.001) in neonates. A low basal level of TAT activity was seen only during the third trimester, which then increased significantly (p < 0.001) in neonates. Fetal hepatocytes, in the presence of EGF and insulin, undergo proliferation from the fourth to 10th day with an increase in cell number (p < 0.001) and concomitant increase (p < 0.001) in GGTase activity. As the cells attain confluence, enzyme activity decreased significantly (p < 0.001) from the 10th to 16th day. Maximal TAT activity (p < 0.001) was observed at 48 h of culture, which decreased, but not significantly, during cell proliferation and the enzyme activity was regained as the cultures attained confluence. Furthermore, TAT activity was induced synergistically (p<0.001) in the presence of glucagon and dexamethasone, while GGTase was inhibited (p<0.001). These results indicate that GGTase increases with proliferation, whereas TAT, once it has been expressed, is not suppressed during cell proliferation. In conclusion, human fetal hepatocytes undergo enzymic differentiation by 48 h of culture, and proliferate with an increase in GGTase in the presence of growth factors with maintenance of differentiated status up to the studied 16 days of culture. Copyright © 2003 John Wiley & Sons, Ltd.
Protective effect of glycine supplementation on the levels of lipid peroxidation and antioxidant enzymes in the erythrocyte of rats with alcohol‐induced liver injury
Authors: Senthilkumar R. , Sengottuvelan M. , Nalini N.
Published: March 2004

We studied the effect of glycine supplementation on lipid peroxidation and antioxidants in the erythrocyte membrane, plasma and hepatocytes of rats with alcohol‐induced hepatotoxicity. Administering ethanol (20%) for 60 days to male Wistar rats resulted in significantly elevated levels of erythrocyte membrane, plasma and hepatocyte thiobarbituric acid reactive substances (TBARS) as compared with those of the experimental control rats. Decreased activities of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione reductase (GR) were also observed on alcohol supplementation as compared with those of the experimental control rats. Glycine was administered at a dose of 0.6 g kg−1 body weight to rats with alcohol‐induced liver injury, which significantly decreased the levels of TBARS and significantly elevated the activities of SOD, CAT, GSH, GPx and GR in the erythrocyte membrane, plasma and hepatocytes as compared to that of untreated alcohol supplemented rats. Thus, our data indicate that supplementation with glycine offers protection against free radical‐mediated oxidative stress in the erythrocyte membrane, plasma and hepatocytes of animals with alcohol‐induced liver injury. Copyright © 2003 John Wiley & Sons, Ltd.
The protective effect of ursodeoxycholic acid in alloxan‐induced diabetes
Authors: Lukivskaya Oxana , Lis Ruslan , Egorov Alexander , Naruta Elena , Tauschel Horst‐Dietmar , Buko Vyacheslav U.
Published: March 2004

The purpose of this work was to study the effect of ursodeoxycholic acid (UDCA) on the morphological and functional alterations in pancreatic islet β‐cells in rats with diabetes induced by alloxan (150 mg kg−1, i.p.). UDCA (40 mg kg−1, i.g.) was administered daily from the fifth to the 35th day after the alloxan treatment. The treatment of diabetic rats with UDCA improved the pancreatic morphology disturbed by the alloxan treatment: UDCA increased the number of pancreatic islets and β‐cells, the β‐/α‐cell ratio and decreased the number of α‐cells. As the morphometric data suggest, the treatment of diabetic animals with UDCA significantly increased the area of β‐cell cytoplasmatic granules stained by paraldehyde–fuchsin. The concentration of blood glucose in diabetic rats was gradually decreased after the UDCA treatment, and at the end of the experiment reached the control value. The treatment with UDCA raised the serum insulin level in diabetic rats about 2.5‐fold, but this concentration was significantly lower as compared to the control group. The content of lipid peroxidation end‐products, hydroxyalkenals and malondialdehyde, was significantly elevated in the alloxan‐treated rats, whereas the treatment with UDCA normalized these parameters. The present data indicate that UDCA acts as an effective antidiabetic agent in alloxan‐induced diabetes and its beneficial effects in diabetic rats can be related to the antioxidant properties of UDCA. Copyright © 2003 John Wiley & Sons, Ltd.
Crystal Refinement and Magnetic Structure of KNi4(PO4)3: A Novel Example of Three Interacting Magnetic Sub‐Lattices
Authors: López María‐Luisa , Durio Cristina , Daidouh Abdelaali , Pico Carlos , Veiga María‐Luisa
Published: March 2004

KNi4(PO4)3 has been synthesised following a method previously reported by some of us and studied on the basis of magnetization and neutron powder diffraction (NPD) data. Magnetization measurements suggest the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions: magnetization versus magnetic field curves present a remanent magnetization of around 2.15 μB at T=2 K. The magnetic structure of the KNi4(PO4)3 has been determined at low temperature from the NPD data. These measurements show that there are three magnetic sub‐lattices of Ni2+ ions, which interact through common oxygen or phosphate groups, giving rise to FM and AFM couplings. The resulting interactions are FM in nature. Such a complex behaviour could provide an interesting model to analyse magnetic interactions in more condensed systems, such in mixed metal oxides.
More Arrows in the Quiver: New Pathways and Old Problems with Heavy Alkaline Earth Metal Diphenylmethanides
Authors: Alexander Jacob S. , Ruhlandt‐Senge Karin
Published: March 2004

Progress in the field of σ‐bonded alkaline earth organometallics has been handicapped by numerous complications, such as high reactivity, low solubility, and the limited availability of suitable starting materials. Here we present two synthetic methods, hydrocarbon elimination and desilylation, as alternative routes into this chemistry. A novel barium diphenylmethanide was prepared using these routes delineating that both methods provide a powerful, versatile synthetic access route to an extended library of organometallic alkaline earth derivatives.
A Surface‐Modified Dendrimer Set for Potential Application as Drug Delivery Vehicles: Synthesis, In Vitro Toxicity, and Intracellular Localization
Authors: Fuchs Sabine , Kapp Timo , Otto Henning , Schöneberg Torsten , Franke Peter , Gust Ronald , Schlüter A. Dieter
Published: March 2004

The synthesis, cytotoxicity, and behavior in cell culture of a new set of first‐ (G1) and second‐generation (G2) dendrimers is reported. The surface functionality of these dendrimers has been varied to see whether structure/toxicity relations can be observed. The outermost functional groups are amines that are decorated either with protons, tert‐butoxycarbonyl (Boc) or benzyloxycarbonyl (Cbz) protecting groups, Boc‐protected or unprotected natural amino acid residues, ethylenediamine ligands, and/or dansyl fluorescence labels. The cytotoxicity was determined in vitro in concentration‐dependent assays using the human MCF‐7 breast cancer cell line. Cellular uptake and intracellular distribution was monitored by confocal fluorescence microscopy after internalization of the dansyl‐labeled dendrimers by HeLa cells.
Solid‐Phase Synthesis of DOTA–Peptides
Authors: De León‐Rodriguez Luis M. , Kovacs Zoltan , Dieckmann Gregg R. , Sherry A. Dean
Published: March 2004

A general synthetic route to two DOTA‐linked N‐Fmoc amino acids (DOTA‐F and DOTA‐K) is described that allows insertion of DOTA at any endo‐position within a peptide sequence. Three model pentapeptides were prepared to test the general utility of these derivatives in solid‐phase peptide synthesis. Both DOTA derivatives reacted smoothly by means of standard HBTU activation chemistry to the point of insertion of the DOTA amino acid, but extension of the peptide chain beyond the DOTA‐amino acid insertion required the use of pre‐activated C‐pentafluorophenyl ester N‐α‐Fmoc amino acids. Three Gal‐80 binding peptides (12‐mers) were then prepared by using this methodology with DOTA positioned either at the N terminus or at one of two different internal positions;the binding of the resulting GdDOTA‐12‐mers to Gal‐80 were compared. The methodology described here allows versatile, controlled introduction of DOTA into any location within a peptide sequence. This provides a potential method for the screening of libraries of DOTA‐linked peptides for optimal targeting properties.
Steric and Electronic Effects in Cyclic Alkoxyamines—Synthesis and Applications as Regulators for Controlled/Living Radical Polymerization
Authors: Wetter Christian , Gierlich Johannes , Knoop Christoph Alexander , Müller Christoph , Schulte Tobias , Studer Armido
Published: March 2004

The synthesis of new six‐ and seven‐membered cyclic alkoxyamines bearing ethyl groups at the α‐N position of the alkoxyamines is described. The key step in the synthesis of the sterically hindered six‐membered cyclic alkoxyamines is a Wadsworth–Horner–Emmons olefination with bisphosphonate 1. The seven‐membered cyclic alkoxyamines were prepared from the corresponding six‐membered keto alkoxyamines by ring‐enlargement with trimethylsilyl(TMS)‐diazomethane. The use of the new alkoxyamines as regulators/initiators for radical polymerization is discussed. Efficient controlled and living polymerization of styrene and n‐butyl acrylate was obtained with the six‐membered tetraethyl alkoxyamine 13. Controlled polymerizations can be conducted even at 90 °C. In addition, alkoxyamine 13 can be used for the preparation of AB diblock and ABA triblock copolymers with narrow polydispersities. The influence of the replacement of methyl groups in the α‐position of the N atom in cyclic alkoxyamines by larger ethyl groups on the styrene polymerization (reaction time, PDI, kinetics of the CO bond homolysis) is discussed. In addition, thermal decomposition of the new alkoxyamines was studied. Furthermore, the synthesis of N,N‐bissilylated alkoxyamines is described. The silylated alkoxyamines are not suitable as regulators/initiators for the controlled/living radical polymerization. The CO bonds in silylated alkoxyamines are stronger than the CO bonds in analogous N,N‐dialkylated alkoxyamines. The experimental results are verified by calculations with Gaussian 98 (A. 9).
Functionalization of Octavinylsilsesquioxane by Ruthenium‐Catalyzed Silylative Coupling versus Cross‐Metathesis
Authors: Itami Y. , Marciniec B. , Kubicki M.
Published: March 2004

Functionalization of octavinylsilsesquioxane (Vi8T8, 1) by two reactions catalyzed by ruthenium complexes is reported: a silylative coupling reaction catalyzed by [RuHCl(CO)(PCy3)2] (I) and cross‐metathesis catalyzed by first‐ (II) and second‐generation (III) Grubbs’ catalysts. The two reactions of 1 with styrene take place highly regio‐ and stereoselectively (the X‐ray structure of the product 2 has also been obtained); the cross‐metathesis of 1‐hexene and allyltrimethylsilane occurs quite effectively, whereas the silylative coupling with these compounds gives a mixture of isomers. Functionalization of 1 with heteroatom‐substituted vinyl derivatives (Si, O, N) by silylative coupling reaction has been found to be highly efficient, but cross‐metathesis appears to be the more effective method for the synthesis of S‐substituted vinyl‐silsesquioxane.
1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity
Authors: Mayr Monika , Wurst Klaus , Ongania Karl‐Hans , Buchmeiser Michael R.
Published: March 2004

The synthesis of novel 1,3‐diaryl‐ and 1,3‐dialkylpyrimidin‐2‐ylidene‐based N‐heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (7), bromo(cod)(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (8) (cod=η4‐1,5‐cyclooctadiene, mesityl=2,4,6‐trimethylphenyl), chloro(cod)(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (9), and chloro(cod)[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (10) were prepared by reaction of [{Rh(cod)Cl}2] with lithium tert‐butoxide followed by addition of 1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidinium bromide (3), 1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidinium tetrafluoroborate (4), 1,3‐di‐2‐propyl‐3,4,5,6‐tetrahydropyrimidinium bromide (6), and 1,3‐di‐2‐propyl‐3,4,5,6‐tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P21/n, and 8 in the monoclinic space group P21. Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (11), and dicarbonylchloro[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (12). The wavenumbers ν(CO I)/ν(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm−1, respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis‐NHC complexes [Ag(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)2]AgBr2 (13) and [Ag{1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene}2]AgBr2 (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)22+(Ag2Br2Cl44−)1/2 (15) and Pd[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)2]Cl2 (16). Complex 15 crystallizes in the monoclinic space group P21/c, and 16 in the monoclinic space group C2/c. The catalytic activity of 15 and 16 in Heck‐type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2 000 000. Stabilities of 15 and 16 under Heck‐couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.
Synthesis and Supramolecular Association of Immobilized NCN‐Pincer Platinum(II) Complexes on Hyperbranched Polyglycerol Supports
Authors: Stiriba Salah‐Eddine , Slagt Martijn Q. , Kautz Holger , Klein Gebbink Robertus J. M. , Thomann Ralf , Frey Holger , van Koten Gerard
Published: March 2004

Pertosylation of hyperbranched polyglycerol (Mn=2000; Mw/Mn=1.3) followed by partial displacement of the tosyl groups with carboxylic acid functionalized NCN‐pincer platinum(II) complexes [PtI‐2,6‐(NMe2CH2)2C6H2‐4‐COOH], resulted in covalent attachment of the NCN‐pincer complexes to the polyglycerol. These functionalized hyperbranched macromolecules have been characterized by 1H, 13C, and 195Pt NMR, UV‐visible, and IR spectroscopy. The presence of Pt and I atoms renders them directly visible by transmission electron microscopy (TEM) without staining procedures, which offers images of associated hyperbranched macromolecules. TEM micrographs show disk‐shaped structures with a small size‐distribution (15–20 nm), and characteristic core‐shell ring structures. The thickness of the corona observed in TEM could be correlated with the substitution degree with pincer platinum moieties.
Hexasubstituted Donor–Acceptor Benzenes as Nonlinear Optically Active Molecules with Multiple Charge‐Transfer Transitions
Authors: Traber Boris , Wolff J. Jens , Rominger Frank , Oeser Thomas , Gleiter Rolf , Goebel Mark , Wortmann Rüdiger
Published: March 2004

The synthesis of three novel nonlinear optical (NLO) chromophores with threefold symmetry, namely 1,3,5‐tris(4‐N,N‐diethylaminophenyl)‐2,4,6‐tris(4‐nitrophenyl)benzene (3), 1,3,5‐tris(4‐N,N‐dihexylaminophenylbutadiynyl)‐2,4,6‐tris(4‐nitrophenyl)benzene (13) and 1,3,5‐tris(4‐N,N‐dihexylaminophenylethynyl)‐2,4,6‐tris(4‐nitrophenylethynyl)benzene (4 b), is reported. We used the [Co2(CO)8]‐catalysed trimerisation of 4‐N,N‐diethylamino‐4′‐nitrotolane (5) to prepare 3. The trimerisation experiment carried out with 1‐(4‐N,N‐diethylaminophenyl)‐6‐(4‐N,N‐nitrophenyl)hexatriyne (6) and [Rh(PPh3)3Cl] afforded 13. A stepwise approach was used to prepare 4 b. 1,3,5‐Trichloro‐2,4,6‐triiodobenzene (8 b) was coupled with 4‐nitrophenyl‐acetylene (14) under Pd0 catalysis to yield 1,3,5‐trichloro‐2,4,6‐tris(4‐nitrophenylethynyl)benzene (15). The coupling reaction of 15 with 4‐N,N‐dihexylaminophenylethynyltributylstannane (21) led to 4 b. X‐ray investigations on 3, 4 b and 13 confirmed the structural assignments and revealed that the peripheral aryl rings in 4 b are less twisted around the connecting bonds than in 3 and 13. A large second‐order polarisability (β) of 4 b relative to 3 and 13 was determined by hyper‐Rayleigh scattering (HRS). Compound 4 b represents an NLO chromophore with second‐order polarisabily among the highest obtained so far for two‐dimensional nondipolar NLO chromophores.
Chromo‐ and Fluororeactands: Indicators for Detection of Neutral Analytes by Using Reversible Covalent‐Bond Chemistry
Authors: Mohr Gerhard J.
Published: March 2004

Chromo‐ and fluororeactands are indicator dyes that allow the optical detection of electrically neutral analytes. Unlike complexing agents such as calixarenes, cyclodextrines or cyclophanes, reactands form a reversible covalent bond with the analyte molecule. This chemical reaction causes strong changes in absorbance or fluorescence. In this article reactands for analytes such as amines, alcohols, aldehydes, saccharides, carbon dioxide and sulfur dioxide are presented. Methods to enhance the sensitivity of the reactands as well as the operational and shelf lives of the corresponding optical sensors are discussed.
Cover Picture: Photocontrolled Release and Uptake of a Porphyrin Guest by Dithienylethene‐Tethered β‐Cyclodextrin Host Dimers (Chem. Eur. J. 5/2004)
Authors: Mulder Alart , Juković Amela , van Leeuwen Fijs W. B. , Kooijman Huub , Spek Anthony L. , Huskens Jurriaan , Reinhoudt David. N.
Published: March 2004

The cover picture shows the reversible photocontrolled release and uptake of a tetrasulfonatophenyl porphyrin (TSPP) from a photoswitchable dithienylethene‐tethered β‐cyclodextrin dimer. The background displays the interplay of the two elements involved: light and water. The open flexible form of the dimer binds TSPP strongly in aqueous solution (orange structure). Irradiation of the complex with UV‐light (blue arrow) closes the dithienylethene tether of the β‐cyclodextrin dimer and hence places the two β‐cyclodextrin cavities further apart from each other (blue structure, top). The stability of this closed dimer–TSPP complex is significantly lower and TSPP is released from the dimer to the aqueous solution (blue structure, right). By irradiation with visible light (orange arrow) the dithienylethene tether can be completely converted back to the more flexible open form, allowing the dimer to once again strongly bind TSPP and leading to the uptake of TSPP from aqueous solution. This chemistry is described in more detail by J. Huskens, D. N. Reinhoudt, et al. on p. 1114ff.
The ongoing evaluation of breast cancer screening
Authors: Smith Robert A.
Published: March 2004

Two articles in this issue of Cancer are representative of an evolving trend in breast cancer screening research. Each raises unique issues regarding how clinicians should view the role of screening in the control of breast cancer and the importance of continuing to address questions concerning its early detection.

See also pages 1331–6 and 1337–44.
On the psychology of procedural justice: reactions to procedures of ingroup vs. outgroup authorities
Authors: Ståhl Tomas , Van Prooijen Jan‐Willem , Vermunt Riël
Published: March 2004

Theorizing on procedural justice has assumed that people's reactions to outgroup authorities are to a large extent based on instrumental concerns. Therefore, attention is primarily directed to outcomes rather than procedures in encounters with outgroup authorities. In the current article we propose that in order for people dealing with outgroup authorities to be strongly affected by procedural fairness, the available outcome information should be ambiguous. Furthermore, we argue that people confronted with an outgroup authority react particularly negatively to unfair procedures that give them negative outcome expectancies. These patterns are not expected in encounters with ingroup authorities. Two experiments support our line of reasoning. The discussion focuses on the implications of these findings for the integration of theoretical perspectives on procedural justice. Copyright © 2004 John Wiley & Sons, Ltd.
Sources of respect: the effects of being liked by ingroups and outgroups
Authors: Ellemers Naomi , Doosje Bertjan , Spears Russell
Published: March 2004

We investigated the effects of ingroup and outgroup sources of respect, defined as positive social evaluations of self, on group members' emotional reactions and collective self‐esteem. We used both natural group memberships (Studies 1 and 2) and laboratory groups (Study 3). We expected that the positive effects of respect derived from an ingroup would not hold when derived from an outgroup source. In Study 1 (N = 294) respect was manipulated as deriving either from ingroup or outgroup. Although respect produced a positive emotional reaction irrespective of source, collective self‐esteem was only enhanced by an ingroup source. In Study 2 (N = 248), we investigated the concurrent effects of ingroup respect and outgroup respect. As in Study 1, ingroup and outgroup respect both produced positive emotional reactions, but collective self‐esteem was only affected by ingroup respect. Additionally, outgroup respect intensified the shame people experienced due to lack of ingroup respect. In Study 3 (N = 66), participants were immersed in experimental groups and ingroup and outgroup respect were manipulated orthogonally. Interactive effects of the two sources of respect indicated that high outgroup respect could not compensate for low ingroup respect, and if anything had an adverse effect. Copyright © 2004 John Wiley & Sons, Ltd.