bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in experimental valproate encephalopathy and after valproate withdrawal
Authors: Sobaniec‐Lotowska Maria E.
Published: September 2003

Summary.  The aim of the study was to analyse the astrocyte ultrastructure within the hippocampal gyre cortex and neocortex of the temporal lobe in valproate encephalopathy induced by chronic administration of an anti‐epileptic drug – sodium valproate (VPA) to rats for 1, 3, 6, 9 and 12 months, once daily intragastrically, in a dose of 200 mg/kg b.w. and after its withdrawal for 1 and 3 months. Prolonged application of VPA caused damage to protoplasmic astrocytes of the cortex regions examined, mainly in the pyramidal layer, which intensified in the later stages of the experiment, especially after 9 and 12 months. Ultrastructural alterations in astroglia during this experiment did not differ significantly between the hippocampal cortex and neocortex. The most pronounced astroglial abnormalities, concerning about 2/3 of protoplasmic astrocytes after 9 and 12 months, were characterized by considerable swelling of cells, with the presence of empty vacuolar structures in the cytoplasm, a substantial decrease in the number of gliofilaments or even their complete loss, which indicated fibrillopoietic failure of the cell, and the appearance of astrocytes showing phagocytic activity. The astrocytic changes coexisted with distinct damage to neurones and structural elements of the blood–brain barrier. One month after termination of chronic exposure to the drug, the abnormalities did not subside, whereas after 3 months features of distinct normalization could be observed in a considerable number, more than a half, of astrocytes. In valproate encephalopathy, apart from any direct effect of VPA and/or its metabolites on astrocytes, the main cause of the protoplasmic astroglial damage in the cortex of the CNS structures examined could be associated with changes in microcirculation in the cortex (vasogenic factor), leading to its ischaemia.
Induction of glomerular alkaline phosphatase after challenge with lipopolysaccharide
Authors: Kapojos Jola J. , Poelstra Klaas , Borghuis Theo , Van Den Berg Anke , Baelde Hans J. , Klok Pieter A. , Bakker Winston W.
Published: September 2003

Summary.  Alkaline phosphatase (AP) can be considered as a host defence molecule since this enzyme is able to detoxify bacterial endotoxin at physiological pH. The question emerged whether this anti‐endotoxin principle is inducible in the glomerulus and if so, which glomerular cells might be involved in the expression of ectoAP after stimulation with pro‐inflammatory agents. Therefore kidneys of rats treated with either lipopolysaccharide (LPS), E. coli bacteria or non‐toxic monophosphoryl lipid A (MPLA) were examined for AP activity 6 or 24 h after challenge. In addition cultures of endothelial cells or mesangial cells were evaluated for AP activity after stimulation with either LPS, TNFα or IL‐6, and mRNA for AP was studied in TNFα‐stimulated and control mesangial cells. The results show significant up‐regulation of glomerular AP in LPS‐ or E. coli‐injected rats compared to rats injected with MPLA. Endothelial and mesangial cells in vitro showed significant up‐regulation of AP activity following stimulation with LPS, TNFα or IL‐6, whereas increased mRNA for AP was observed in mesangial cells after TNFα stimulation compared to non‐stimulated control cells. Since it appeared that hydrolysis occurred when endotoxin was used as a substrate in the histochemical staining, we concluded that inducible glomerular ectoAP may reflect a local endotoxin detoxifying principle of the kidney.
Monoclonal Antibodies Inducing Conformational Changes on the Antigen Molecule
Authors: Roguin L. P. , Retegui L. A.
Published: September 2003

Monoclonal antibodies (MoAbs) are extensively used as biological tools because of their invariable specificity. However, the interpretation of results can be misled by the behaviour of MoAb displaying allosteric effects, i.e. long‐range conformational changes on the antigen (Ag). It has been shown that some MoAbs are able to modify the spatial structure of the corresponding protein Ag, affecting in this way its biological activity as well as its binding to a second MoAb. Thus, a researcher using a MoAb as a tool to investigate some features of an antigenic molecule must be aware of the possible positive or negative allosteric properties of the antibody.
Modulation of Host Immune Responses by Overexpression of Immunodominant Antigens of Mycobacterium tuberculosis in Bacille Calmette–Guérin
Authors: Rao V. , Dhar N. , Tyagi A. K.
Published: September 2003

Based on their immunodominant nature and ability to induce appropriate immune responses in the host, several antigens of Mycobacterium tuberculosis have shown promise of protection. However, most of the candidate vaccines developed by employing various strategies have afforded protection that is at best comparable with bacillus Calmette–Guérin (BCG) in animal models. Due to the inherent ability of BCG to prime cellular responses in the host, it has become an attractive vehicle for development of a vaccine against intracellular infections. In this study, we have cloned the genes of three immunodominant antigens of M. tuberculosis viz. the ESAT6 (Rv3875), the 19 kDa lipoprotein (Rv3763) and the 38 kDa antigen (Pst homolog) (Rv0934) in pSD5 under the transcriptional control of Trrn, a strong mycobacterial promoter, and expressed them in BCG. The19 kDa antigen and the 38 kDa antigen were expressed at levels that were approximately five and eightfolds higher in the cytosols of recombinant BCG strains rBCG19T and rBCG38T, respectively, as compared with their corresponding levels in M. bovis BCG. Both these antigens were also secreted into the extracellular medium at enhanced levels (19 kDa antigen fourfold and 38 kDa antigen twofold) by rBCG strains in comparison with the wild type BCG. ESAT6 antigen, which is absent in M. bovis BCG, was also expressed at a very high level in the cytosol of the rBCG strain (rBCGE6T). Evaluation of immune responses induced by these three rBCG strains in mice shows a markedly different pattern. The rBCG strain overexpressing the 38 kDa antigen exhibited a predominant T helper 1 (Th1) response with high levels of interferon‐γ (IFN‐γ) production, whereas overexpression of the 19 kDa antigen resulted in completely polarized Th2 responses against the BCG sonicate. The rBCG‐expressing ESAT6 antigen induced a mixed Th1/Th2 response. Our observations suggest that the 38 kDa antigen may hold excellent promise in the rBCG approach for the development of a vaccine against tuberculosis.
Release of Non‐Glycosylated Polymeric Immunoglobulin Receptor Protein
Authors: Matsumoto N. , Asano M. , Ogura Y. , Takenouchi‐Ohkubo N. , Chihaya H. , Chung‐Hsing W. , Ishikawa K. , Zhu L. , Moro I.
Published: September 2003

Using a recombinant vaccinia virus containing the T7 RNA polymerase, we have established a system for the transient expression of human polymeric immunoglobulin receptor (pIgR) in baby hamster kidney cells, a baby hamster‐derived fibroblastic cell line. This transfection system resulted in the successful expression of pIgR in these cells, and Western blot analysis showed that human pIgR was expressed as two different molecular weight forms of 92 and 107 kDa. Treatment with endoglycosidase H showed that the difference between these two forms was due to the glycosylation status of the protein. In order to examine the functional role of glycosylation, we treated the transfected cells with tunicamycin, which prevents a core glycosylation step in the endoplasmic reticulum. Non‐glycosylated pIgR was released into the culture medium of the transfected cells, albeit with extremely low efficiency. Taking these results together, we conclude that the glycosylation of pIgR may play a positive role in the efficient transport or release of free pIgR.
Periextubation caffeine in preterm neonates: A randomized dose response trial
Authors: Steer PA , Flenady VJ , Shearman A , Lee TC , Tudehope DI , Charles BG
Published: September 2003

Objective:  To compare the effectiveness of three dosing regimens of caffeine for preterm infants in the periextubation period.

Methods:  A randomized double‐blind clinical trial of three dosing regimens of caffeine citrate (3, 15 and 30 mg/kg) for periextubation management of ventilated preterm infants was undertaken. Infants born <32 weeks gestation who were ventilated for>48 h were eligible for the study. Caffeine citrate was given as a once daily dose for a period of 6 days commencing 24 h prior to a planned extubation, or within 6 h of an unplanned extubation. The primary outcome measure was extubation failure, defined as neonates who were unable to be extubated within 48 h of caffeine loading or who required reventilation or doxapram dose within 7 days of caffeine loading. Continuous recordings of oxygen saturation and heart rate were undertaken in a subgroup of enrolled infants.

Results:  A total of 127 babies were enrolled into the study (42, 40, 45, in the 3, 15, and 30 mg/kg groups, respectively). No statistically significant difference was demonstrated in the incidence of extubation failure between dosing groups (19, 10, and 11 infants in the 3, 15, and 30 mg/kg groups, respectively), however, infants in the two higher dose groups had statistically significantly less documented apnoea than the lowest dose group. Of the 37 neonates with continuous pulse oximetry recordings, those on higher doses of caffeine recorded a statistically significantly higher mean heart rate, oxygen saturations and less time with oxygen saturations <85%.

Conclusions:  This trial indicated there were short‐term benefits of decreased apnoea in the immediate periextubation period for ventilated infants born <32 weeks gestation receiving higher doses of caffeine. Further studies with larger numbers of infants assessing longer‐term outcomes are necessary to determine the optimal dosing regimen of caffeine in preterm infants.
Prevalence of fetal alcohol syndrome in the Top End of the Northern Territory
Authors: Harris KR , Bucens IK
Published: September 2003

Objective:  To establish the prevalence of fetal alcohol syndrome (FAS) in the Top End of the Northern Territory (NT), Australia, in both the indigenous and non‐indigenous populations. Fetal alcohol syndrome is a preventable disease that is a major cause of intellectual handicap worldwide. The prevalence of FAS in the NT, and in Australia as a whole, is unknown.

Methodology:  Cases were identified through retrospective review of medical records and outpatient letters of children seen by Royal Darwin Hospital paediatric staff. Cases were also identified by tracing potentially affected siblings, or incidentally during clinical work. All children were born between 1990 and 2000, and lived in the Top End of the NT.

Results:  Seventeen children were identified with definite FAS. Twenty‐six children with partial FAS or alcohol‐related neurodevelopmental disorder (ARND) were also identified. The prevalence of FAS in the Top End of the NT was calculated to be 0.68 per 1000 live births. The prevalence might be as high as 1.7 per 1000 live births, if cases identified as partial FAS or ARND because of insufficient records, were assumed to have full FAS. In indigenous children, the corresponding prevalence was calculated to be between 1.87 and 4.7 per 1000 live births. The difference between indigenous and non‐indigenous rates of FAS was significant (P < 0.0001).

Conclusions:  The prevalence of FAS in indigenous children of the Top End of the NT is comparable to the high rates in indigenous populations worldwide.
Perinatal cytomegalovirus infection associated with lung cysts
Authors: Bradshaw JH , Moore PPC
Published: September 2003

Abstract:  Lung disease, caused by perinatally acquired cytomegalovirus (CMV), is usually described as pneumonitis or interstitial pneumonia. A 30‐week‐old gestation infant developed CMV infection and multicystic lung disease that resolved spontaneously. The differential diagnosis of lung cysts in the newborn should include CMV infection.
Factors affecting the reproductive biology of Melittobia digitata and failure to meet the sex ratio predictions of Hamilton's local mate competition theory
Authors: Cooperband M.F. , Matthews R.W. , Vinson S.B.
Published: September 2003

Melittobia digitata Dahms (Eulophidae, Tetrastichini), a species of parasitic wasp satisfying all of Hamilton's local mate competition requisites, does not exhibit the predicted change in sex ratio with increased foundress number. A multifactorial design was used to test how age, oviposition experience, feeding experience, mating, and foundress number affect host‐acceptance, number of offspring, and sex ratio of this species developing on honey bee pupae, Apis mellifera (L.) (Apidae, Apini). All factors significantly affected the time it took for oviposition to commence. Females oviposited soonest when they were 2 days old, mated, had previous feeding and oviposition experience, and were placed on hosts with multiple foundresses. Although the age difference between 2‐ and 5‐day‐old females is small, it significantly affected reproductive behavior. Age, mating, and foundress number were found to have an effect on sex ratio, however, the foundress effect was found to be a mathematical artifact of the limited host size. After correcting for this variable, females were found to have a constant sex ratio of approximately 0.05. Several 2‐way interactions between factors were revealed: age and experience, age and foundress number, age and mating, foundress number and experience, and foundress number and mating. One 3‐way interaction was found between age, mating, and foundress number. This study demonstrates that the sex ratio of M. digitata is not altered with increased foundresses, as predicted by Hamilton, and that slight changes in preconditioning may modify reproductive behavior.
Glutathione S‐transferase detoxification as a potential pyrethroid resistance mechanism in the maize weevil, Sitophilus zeamais
Authors: Fragoso Daniel B. , Guedes Raul Narciso C. , Rezende Sebastião T.
Published: September 2003

Insecticide resistance patterns among 16 Brazilian populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were recognized by surveying resistance to three organophosphates (chlorpyrifos‐methyl, malathion, and pirimiphos‐methyl) and three pyrethroids (cypermethrin, deltamethrin, and permethrin). Two population clusters were obtained: one with three populations (Bragança Paulista, Cristalina, and Nova Andradina) showing low frequency of cypermethrin resistance (13–36%) and negligible frequency of deltamethrin resistance (2–9%); and another with six populations (Campos dos Goytacazes, Ivinhema, Patos de Minas, Penápolis, Uberlândia, and Venda Nova) showing low to negligible levels of pyrethroid resistance (0–23%). The remaining seven populations, including a susceptible, and a DDT‐ and pyrethroid‐resistant reference populations (Sete Lagoas and Jacarezinho, respectively), were significantly different from each other and from the two recognized clusters. In contrast with pyrethroid resistance, organophosphate resistance was negligible except for chlorpyrifos‐methyl in two populations (Fátima do Sul and Penápolis). There was no correlation between geographic distance and the Mahalanobis distance estimated from the resistance pattern ordination of the populations by canonical variate analysis, suggesting local selection and/or broad dispersal of resistant populations by grain trade. The results of biochemical in vitro studies measuring the activity of detoxification enzymes (esterases and glutathion S‐transferases) in conjunction with canonical correlation analysis suggest a major involvement of enhanced conjugation by glutathione S‐transferases (> 2‐fold increase) in pyrethroid resistance and, in the case of cypermethrin resistance, enhanced phosphotriesterase activity.
Impact of a parasitoid on the bacterial symbiosis of its aphid host
Authors: Cloutier Conrad , Douglas Angela E.
Published: September 2003

Embryo production in aphids is absolutely dependent on the function of symbiotic bacteria, mainly Buchnera, and the growth and development of koinobiont parasitoids in aphids requires the diversion of nutrients from aphid embryo production to the parasitoid. The implication that the bacterial symbiosis may be promoted in parasitized aphids to support the growing parasitoid was explored by analysis of the number and biomass of mycetocytes, and the aphid cells bearing Buchnera, in the pea aphid Acyrthosiphon pisum Harris (Hemiptera: Aphididae) parasitized by the wasp Aphidius ervi Haliday (Hymenoptera: Braconidae). Aphids hosting a young larval parasitoid bore more mycetocytes of greater total biomass, and embryos of lower biomass than unparasitized aphids. Furthermore, one of the three aphid clones tested, which limited teratocyte growth (giant cells of parasitoid origin having a trophic role), bore smaller mycetocytes and larger embryos, than one or both of the two aphid clones with greater susceptibility to the parasitoid. These data suggest that susceptibility of the aphid‐Buchnera symbiosis to parasitoid‐mediated manipulation may, directly or indirectly, contribute to aphid susceptibility to parasitoid exploitation.
Screening for resistance in apple cultivars to lightbrown apple moth, Epiphyas postvittana, and greenheaded leafroller, Planotortrix octo, and its relationship to field damage
Authors: Wearing C.H. , Colhoun K. , Attfield B. , Marshall R.R. , McLaren G.F.
Published: September 2003

The mature leaves of 38 apple (Malus domestica Borkh.) (Rosaceae) cultivars were screened for resistance to laboratory colonies of Epiphyas postvittana (Walker) and Planotortrix octo Dugdale (Lepidoptera: Tortricidae) by measuring larval survival and development rate, and pupal weight, in no‐choice laboratory bioassays in early summer. There were few cultivar effects on larval mortality but Nevis 1, A40R04T119, and ‘Sir Prize’ reduced survival of E. postvittana. Effects on development time and weight were correlated, and were integrated into a single measure of resistance Rc. Rc varied greatly between cultivars for both leafroller species, and identified 15 and 11 cultivars with partial resistance to E. postvittana and P. octo, respectively. A further experiment with three of the cultivars in midsummer, using the laboratory colonies in comparison with new colonies (from field collected larvae), produced similar results for E. postvittana, but there was no survival of new colony P. octo larvae on two cultivars. These results for P. octo are consistent with other recent research showing extreme cultivar resistance and critical colony and seasonal influences. A series of 4‐year field trials with the 38 cultivars showed poor correlation between laboratory and field resistance for the dominant leafroller species in the field, E. postvittana. The combined data, however, identified ‘Red Dougherty’, ‘Sir Prize’, and A40R04T119 as potentially useful in breeding for resistance to this species. The implications of these findings for integrated pest management (IPM) programmes and for the breeding of leafroller‐resistant apple cultivars are discussed.
Second and third trophic level effects of differences in plant species reflect dietary specialisation of herbivores and their endoparasitoids
Authors: Sznajder Beata , Harvey Jeffrey A.
Published: September 2003

In natural populations, plants demonstrate an array of indirect and direct defence strategies that help to protect them from their herbivores and pathogens. Indirect defences include the release of odours that attract the natural enemies of herbivores, whereas direct defences may include the production of secondary compounds, allelochemicals that impair herbivore development or repel herbivore attack. Although both strategies have been well studied independently, comparatively little attention has been paid to examining the conflict that may arise between indirect and direct defences, such as when the performance of ‘recruited’ parasitoids or predators is negatively affected by plant allelochemicals. Here, we examine the growth and development of polyphagous and oligophagous folivores and their respective endoparasitoids on three crucifer species. One of the species, Brassica oleracea, was recently cultivated, whereas populations of B. nigra and Barbarea vulgaris occur naturally. Additionally, these species possess contrasting life‐history patterns and are also known to exhibit differences in secondary chemistry. The development of the generalist herbivore–parasitoid system was much more variable over the three crucifers than that exhibited by the specialists. Moreover, generalist herbivore and/or parasitoid fitness‐related traits (survival, development time, pupal, or adult size) were much more negatively affected on the wild crucifers than in the specialist association. Our results suggest that the relative importance of direct and indirect defences in plants may rest on the degree of dietary specialisation exhibited by herbivores and their natural enemies, and on the level of toxicity in the plant species under investigation.
Silicon nutrition promotes root growth and tissue mechanical strength insymbiotic cowpea
Authors: Dakora Felix D. , Nelwamondo Aziwe
Published: September 2003

Application of metasilicic acid (0, 0.04, 0.08, 0.20, 0.40 or 0.80 g L–1) to hydroponically-grown, Bradyrhizobium-infected cowpea [Vigna unguiculata (L.) Walp.] plants showed an increased assimilation of silicon into roots and shoots, which triggered a significant (P<0.05) promotion of root growth, but not shoot growth. Root : shoot ratio therefore, increased markedly (P<0.05) with higher metasilicate application. Mechanical strength of stems and peduncles also increased significantly (P<0.05) with silicon nutrition compared with control plants receiving no metasilicate. But the mechanical strength of roots was not affected. Radioimmunoassay of lateral roots, free of nodules, from plants fed metasilicate revealed markedly (P<0.05) increased concentrations of endogenous ABA, a hormonal signal that stimulates root growth. In contrast, a decreasing concentration of the cytokinin zeatin ribose was obtained with increasing metasilicate supply. These data show that silicon nutrition in symbiotic cowpea promotes an increase in mechanical strength of stems, which bear the entire weight of shoots, and peduncles, which, in turn, support weighty reproductive structures including developing pods and seeds. The increased concentration of ABA in roots as a result of improved silicon nutrition suggests that this element might be an elicitor of ABA biosynthesis and / or its accumulation, which then affected lateral root growth in this study.
Smart dust: Self-assembling, self-orienting photonic crystals of porous Si
Authors: Link Jamie R. , Sailor Michael J.
Published: September 2003

Micrometer-sized one-dimensional photonic crystals of porous Si that spontaneously assemble, orient, and sense their local environment are prepared. The photonic crystals are generated by electrochemically etching two discrete porous multilayered dielectric mirrors into Si, one on top of the other. The first mirror is chemically modified by hydrosilylation with dodecene before the etching of the second mirror, which is prepared with an optical reflectivity spectrum that is distinct from the first. The entire film is removed from the substrate, and the second mirror is then selectively modified by mild thermal oxidation. The films are subsequently fractured into small particles by sonication. The chemically asymmetric particles spontaneously align at an organic liquid–water interface, with the hydrophobic side oriented toward the organic phase and the hydrophilic side toward the water. Sensing is accomplished when liquid at the interface infuses into the porous mirrors, inducing predictable shifts in the optical spectra of both mirrors.
Semipermeable species boundaries betweenAnopheles gambiaeandAnopheles arabiensis: Evidence from multilocus DNA sequence variation
Authors: Besansky N. J. , Krzywinski J. , Lehmann T. , Simard F. , Kern M. , Mukabayire O. , Fontenille D. , Touré Y. , Sagnon N'F.
Published: September 2003

Attempts to reconstruct the phylogenetic history of theAnopheles gambiaecryptic species complex have yielded strongly conflicting results. In particular,An. gambiae, the primary African malaria vector, is variously placed as a sister taxon to eitherAnopheles arabiensisorAnopheles merus. The recent divergence times for members of this complex complicate phylogenetic analysis, making it difficult to unambiguously implicate interspecific gene flow, versus retained ancestral polymorphism, as the source of conflict. Using sequences at four unlinked loci, which were determined from multiple specimens within each of five species in the complex, we found contrasting patterns of sequence divergence between the X chromosome and the autosomes. The isolation model of speciation assumes a lack of gene flow between species since their separation. This model could not be rejected forAn. gambiaeandAn. arabiensis, although the data fit the model poorly. On the other hand, evidence from gene trees supports genetic introgression of chromosome 2 inversions betweenAn. gambiaeandAn. arabiensis, and also points to more broad scale genetic exchange of autosomal sequences between this species pair. That such exchange has been relatively recent is suggested not only by the lack of fixed differences at three autosomal loci but also by the sharing of full haplotypes at two of the three loci, which is in contrast to several fixed differences and considerably deeper divergence on the X. The proposed acquisition byAn. gambiaeof sequences from the more arid-adaptedAn. arabiensismay have contributed to the spread and ecological dominance of this malaria vector.
Nitric oxide regulates K
+
and Cl
-
channels in guard cells through a subset of abscisic acid-evoked signaling pathways
Authors: Garcia-Mata Carlos , Gay Robert , Sokolovski Sergei , Hills Adrian , Lamattina Lorenzo , Blatt Michael R.
Published: September 2003

Abscisic acid (ABA) triggers a complex sequence of signaling events that lead to concerted modulation of ion channels at the plasma membrane of guard cells and solute efflux to drive stomatal closure in plant leaves. Recent work has indicated that nitric oxide (NO) and its synthesis are a prerequisite for ABA signal transduction in
Arabidopsis
and
Vicia
guard cells. Its mechanism(s) of action is not well defined in guard cells and, generally, in higher plants. Here we show directly that NO selectively regulates Ca
2+
-sensitive ion channels of
Vicia
guard cells by promoting Ca
2+
release from intracellular stores to raise cytosolic-free [Ca
2+
]. NO-sensitive Ca
2+
release was blocked by antagonists of guanylate cyclase and cyclic ADP ribose-dependent endomembrane Ca
2+
channels, implying an action mediated via a cGMP-dependent cascade. NO did not recapitulate ABA-evoked control of plasma membrane Ca
2+
channels and Ca
2+
-insensitive K
+
channels, and NO scavengers failed to block the activation of these K
+
channels evoked by ABA. These results place NO action firmly within one branch of the Ca
2+
-signaling pathways engaged by ABA and define the boundaries of parallel signaling events in the control of guard cell movements.
Carboxyl-terminal-truncated apolipoprotein E4 causes Alzheimer's disease-like neurodegeneration and behavioral deficits in transgenic mice
Authors: Harris Faith M. , Brecht Walter J. , Xu Qin , Tesseur Ina , Kekonius Lisa , Wyss-Coray Tony , Fish Jo Dee , Masliah Eliezer , Hopkins Paul C. , Scearce-Levie Kimberly , Weisgraber Karl H. , Mucke Lennart , Mahley Robert W. , Huang Yadong
Published: September 2003

Apolipoprotein (apo) E4 increases the risk and accelerates the onset of Alzheimer's disease (AD). However, the underlying mechanisms remain to be determined. We previously found that apoE undergoes proteolytic cleavage in AD brains and in cultured neuronal cells, resulting in the accumulation of carboxyl-terminal-truncated fragments of apoE that are neurotoxic. Here we show that this fragmentation is caused by proteolysis of apoE by a chymotrypsin-like serine protease that cleaves apoE4 more efficiently than apoE3. Transgenic mice expressing the carboxyl-terminal-cleaved product, apoE4(Δ272–299), at high levels in the brain died at 2–4 months of age. The cortex and hippocampus of these mice displayed AD-like neurodegenerative alterations, including abnormally phosphorylated tau (p-tau) and Gallyas silver-positive neurons that contained cytosolic straight filaments with diameters of 15–20 nm, resembling preneurofibrillary tangles. Transgenic mice expressing lower levels of the truncated apoE4 survived longer but showed impaired learning and memory at 6–7 months of age. Thus, carboxyl-terminal-truncated fragments of apoE4, which occur in AD brains, are sufficient to elicit AD-like neurodegeneration and behavioral deficits
in vivo
. Inhibiting their formation might inhibit apoE4-associated neuronal deficits.
Endothelial cell diversity revealed by global expression profiling
Authors: Chi Jen-Tsan , Chang Howard Y. , Haraldsen Guttorm , Jahnsen Frode L. , Troyanskaya Olga G. , Chang Dustin S. , Wang Zhen , Rockson Stanley G. , van de Rijn Matt , Botstein David , Brown Patrick O.
Published: September 2003

The vascular system is locally specialized to accommodate widely varying blood flow and pressure and the distinct needs of individual tissues. The endothelial cells (ECs) that line the lumens of blood and lymphatic vessels play an integral role in the regional specialization of vascular structure and physiology. However, our understanding of EC diversity is limited. To explore EC specialization on a global scale, we used DNA microarrays to determine the expression profile of 53 cultured ECs. We found that ECs from different blood vessels and microvascular ECs from different tissues have distinct and characteristic gene expression profiles. Pervasive differences in gene expression patterns distinguish the ECs of large vessels from microvascular ECs. We identified groups of genes characteristic of arterial and venous endothelium. Hey2, the human homologue of the zebrafish gene
gridlock
, was selectively expressed in arterial ECs and induced the expression of several arterial-specific genes. Several genes critical in the establishment of left/right asymmetry were expressed preferentially in venous ECs, suggesting coordination between vascular differentiation and body plan development. Tissue-specific expression patterns in different tissue microvascular ECs suggest they are distinct differentiated cell types that play roles in the local physiology of their respective organs and tissues.
From micro to nano contacts in biological attachment devices
Authors: Arzt Eduard , Gorb Stanislav , Spolenak Ralph
Published: September 2003

Animals with widely varying body weight, such as flies, spiders, and geckos, can adhere to and move along vertical walls and even ceilings. This ability is caused by very efficient attachment mechanisms in which patterned surface structures interact with the profile of the substrate. An extensive microscopic study has shown a strong inverse scaling effect in these attachment devices. Whereas μm dimensions of the terminal elements of the setae are sufficient for flies and beetles, geckos must resort to sub-μm devices to ensure adhesion. This general trend is quantitatively explained by applying the principles of contact mechanics, according to which splitting up the contact into finer subcontacts increases adhesion. This principle is widely spread in design of natural adhesive systems and may also be transferred into practical applications.
The role of certain Post classes in Boolean network models of genetic networks
Authors: Shmulevich Ilya , Lähdesmäki Harri , Dougherty Edward R. , Astola Jaakko , Zhang Wei
Published: September 2003

A topic of great interest and debate concerns the source of order and remarkable robustness observed in genetic regulatory networks. The study of the generic properties of Boolean networks has proven to be useful for gaining insight into such phenomena. The main focus, as regards ordered behavior in networks, has been on canalizing functions, internal homogeneity or bias, and network connectivity. Here we examine the role that certain classes of Boolean functions that are closed under composition play in the emergence of order in Boolean networks. The closure property implies that any gene at any number of steps in the future is guaranteed to be governed by a function from the same class. By means of Derrida curves on random Boolean networks and percolation simulations on square lattices, we demonstrate that networks constructed from functions belonging to these classes have a tendency toward ordered behavior. Thus they are not overly sensitive to initial conditions, and damage does not readily spread throughout the network. In addition, the considered classes are significantly larger than the class of canalizing functions as the connectivity increases. The functions in these classes exhibit the same kind of preference toward biased functions as do canalizing functions, meaning that functions from this class are likely to be biased. Finally, functions from this class have a natural way of ensuring robustness against noise and perturbations, thus representing plausible evolutionarily selected candidates for regulatory rules in genetic networks.
Distinct geographic patterns of genetic diversity are maintained in wild barley (
Hordeum vulgare
ssp.
spontaneum
) despite migration
Authors: Morrell Peter L. , Lundy Karen E. , Clegg Michael T.
Published: September 2003

Mutations arise in a single individual and at a single point in time and space. The geographic distribution of mutations reflects both historical population size and frequency of migration. We employ coalescence-based methods to coestimate effective population size, frequency of migration, and level of recombination compatible with observed genealogical relationships in sequence data from nine nuclear genes in wild barley (
Hordeum vulgare
ssp.
spontaneum
), a highly self-fertilizing grass species. In self-fertilizing plants, gamete dispersal is severely limited; dissemination occurs primarily through seed dispersal. Also, heterozygosity is greatly reduced, which renders recombination less effective at randomizing genetic variation and causes larger portions of the genome to trace a similar history. Despite these predicted effects of this mating system, the majority of loci show evidence of recombination. Levels of nucleotide variation and the patterns of geographic distribution of mutations in wild barley are highly heterogeneous across loci. Two of the nine sampled loci maintain highly diverged, geographic region-specific suites of mutations. Two additional loci include region-specific haplotypes with a much shallower coalescence. Despite inbreeding, sessile growth habit, and the observation of geographic structure at almost half of sampled loci, parametric estimates of migration suggest that seed dispersal is sufficient for migration across the ≈3,500-km range of the species. Recurrent migration is also evident based on the geographic distribution of mutational variation at some loci. At one locus a single haplotype has spread rapidly enough to occur, unmodified by mutation, across the range of the species.
Combinatorial auction design
Authors: Porter David , Rassenti Stephen , Roopnarine Anil , Smith Vernon
Published: September 2003

Combinatorial auctions allow for more expressive bidding in which participants can submit package bids with logical constraints that limit allowable outcomes. This type of auction can be useful when participants' values are complementary or when participants have production and financial constraints. However, combinatorial auctions are currently rare in practice. The main problems confronted in implementing these auctions are that they have computational uncertainty (i.e., there is no guarantee that the winning bids for such an auction can be found in a “reasonable” amount of time when the number of bidders and items becomes larger) and that the auction is cognitively complex and can lead participants to pursue perverse bidding strategies. This article describes a type of combinatorial auction that, during laboratory testing, eliminated these problems and produced extremely efficient outcomes.
Funnel sculpting for
in silico
assembly of secondary structure elements of proteins
Authors: Fain Boris , Levitt Michael
Published: September 2003

We present a method for designing a funnel-shaped free-energy surface that reproducibly assembles secondary structure elements of proteins into their native conformations from a random extended configuration. Assuming
a priori
knowledge of secondary structure, our method can design a funnel-shaped surface for folding of α, β, and αβ structures individually. We design energy surfaces that fold up to five unrelated sequences with the same energy parameters. We develop a measure of the foldability of an energy landscape
in silico
and present an alternative way to view energy landscapes.
Population dynamics of rapid fixation in cytotoxic T lymphocyte escape mutants of influenza A
Authors: Gog Julia R. , Rimmelzwaan Guus F. , Osterhaus Albert D. M. E. , Grenfell Bryan T.
Published: September 2003

The dynamics of cellular immunity against pathogens, and its interaction with the human MHC system, is a key area for empirical research, both within individual hosts and in population genetic surveys. However, in contrast with humoral immunity, the dynamics of cellular immunity have not been modeled at the population level. Here, we address this lacuna with a model of recently observed dramatic invasions of cytotoxic T lymphocyte escape mutants in human influenza A. In particular, we offer an explanation for the rapid fixation of a HLA-B27 restricted cytotoxic T lymphocyte escape mutant on the nucleoprotein that emerged in the 1993–1994 season. We find that the dynamics within a single season of influenza do not provide a realistic description, but a model of the full annual dynamics can offer a possible explanation. Our model is deterministic for the winter epidemic, and stochastic for the summer period. An escape mutant that leads to a slightly longer infection in a small proportion of hosts has a substantial advantage through summer persistence. Furthermore, if a small number of founding cases are responsible for initiating each epidemic, then this effect of rapid mutant fixation is amplified.
The plant homolog to the human sodium/dicarboxylic cotransporter is the vacuolar malate carrier
Authors: Emmerlich Vera , Linka Nicole , Reinhold Thomas , Hurth Marco A. , Traub Michaela , Martinoia Enrico , Neuhaus H. Ekkehard
Published: September 2003

Malate plays a central role in plant metabolism. It is an intermediate in the Krebs and glyoxylate cycles, it is the store for CO
2
in C4 and crassulacean acid metabolism plants, it protects plants from aluminum toxicity, it is essential for maintaining the osmotic pressure and charge balance, and it is therefore involved in regulation of stomatal aperture. To fulfil many of these roles, malate has to be accumulated within the large central vacuole. Many unsuccessful efforts have been made in the past to identify the vacuolar malate transporter; here, we describe the identification of the vacuolar malate transporter [
A. thaliana
tonoplast dicarboxylate transporter (
At
tDT)]. This transporter exhibits highest sequence similarity to the human sodium/dicarboxylate cotransporter. Independent T-DNA [portion of the Ti (tumor-inducing) plasmid that is transferred to plant cells]
Arabidopsis
mutants exhibit substantially reduced levels of leaf malate, but respire exogenously applied [
14
C]malate faster than the WT. An
At
tDT-GFP fusion protein was localized to vacuole. Vacuoles isolated from
Arabidopsis
WT leaves exhibited carbonylcyanide
m
-chlorophenylhydrazone and citrate inhibitable malate transport, which was not stimulated by sodium. Vacuoles isolated from mutant plants import [
14
C]-malate at strongly reduced rates, confirming that this protein is the vacuolar malate transporter.
A small molecule HIV-1 inhibitor that targets the HIV-1 envelope and inhibits CD4 receptor binding
Authors: Lin Pin-Fang , Blair Wade , Wang Tao , Spicer Timothy , Guo Qi , Zhou Nannan , Gong Yi-Fei , Wang H.-G. Heidi , Rose Ronald , Yamanaka Gregory , Robinson Brett , Li Chang-Ben , Fridell Robert , Deminie Carol , Demers Gwendeline , Yang Zheng , Zadjura Lisa , Meanwell Nicholas , Colonno Richard
Published: September 2003

BMS-378806 is a recently discovered small molecule HIV-1 inhibitor that blocks viral entrance to cells. The compound exhibits potent inhibitory activity against a panel of R5-(virus using the CCR5 coreceptor), X4-(virus using the CXCR4 coreceptor), and R5/X4 HIV-1 laboratory and clinical isolates of the B subtype (median EC
50
of 0.04 μM) in culture assays. BMS-378806 is selective for HIV-1 and inactive against HIV-2, SIV and a panel of other viruses, and exhibits no significant cytotoxicity in the 14 cell types tested (concentration for 50% reduction of cell growth, >225 μM). Mechanism of action studies demonstrated that BMS-378806 binds to gp120 and inhibits the interactions of the HIV-1 envelope protein to cellular CD4 receptors. Further confirmation that BMS-378806 targets the envelope in infected cells was obtained through the isolation of resistant variants and the mapping of resistance substitutions to the HIV-1 envelope. In particular, two substitutions, M426L and M475I, are situated in the CD4 binding pocket of gp120. Recombinant HIV-1 carrying these two substitutions demonstrated significantly reduced susceptibility to compound inhibition. BMS-378806 displays many favorable pharmacological traits, such as low protein binding, minimal human serum effect on anti-HIV-1 potency, good oral bioavailability in animal species, and a clean safety profile in initial animal toxicology studies. Together, the data show that BMS-378806 is a representative of a new class of HIV inhibitors that has the potential to become a valued addition to our current armamentarium of antiretroviral drugs.
Trace amounts of copper in water induce β-amyloid plaques and learning deficits in a rabbit model of Alzheimer's disease
Authors: Sparks D. Larry , Schreurs Bernard G.
Published: September 2003

Despite the crucial role played by cholesterol and copper in nutrition and normal brain function, recent evidence indicates that they may both be important factors in the etiology of Alzheimer's disease (AD). Here we provide critical evidence for the role of cholesterol and copper in AD by showing that the addition of trace amounts of copper (0.12 ppm) to water given to cholesterol-fed rabbits can induce β-amyloid (Aβ) accumulation, including senile plaque-like structures in the hippocampus and temporal lobe, and can significantly retard the ability of rabbits to learn a difficult trace conditioning task. The Aβ deposits do not affect the ability of rabbits to detect or respond to the training stimuli nor to learn a simpler delay conditioning task. Trace amounts of copper in drinking water may influence clearance of Aβ from the brain at the level of the interface between the blood and cerebrovasculature and combined with high cholesterol may be a key component to the accumulation of Aβ in the brain, having a significant impact on learning and memory. Cholesterol-fed rabbits have at least 12 pathological markers seen in AD, suggesting that the cholesterolfed rabbit is a good animal model for studying AD.
The EBV nuclear antigen 1 (EBNA1) enhances B cell immortalization several thousandfold
Authors: Humme Sibille , Reisbach Gilbert , Feederle Regina , Delecluse Henri-Jacques , Bousset Kristine , Hammerschmidt Wolfgang , Schepers Aloys
Published: September 2003

The Epstein–Barr virus (EBV) nuclear antigen 1 (EBNA1) is one of the earliest viral proteins expressed after infection and is the only latent protein consistently expressed in viral-associated tumors. EBNA1's crucial role in viral DNA replication, episomal maintenance, and partitioning is well examined whereas its importance for the immortalization process and the tumorgenicity of EBV is unclear. To address these open questions, we generated, based on the maxi-EBV system, an EBNA1-deficient EBV mutant and used this strain to infect primary human B cells. Surprisingly, lymphoblastoid cell lines (LCL) emerged from these experiments, although with very low frequency. These cell lines were indistinguishable from normal LCLs with respect to proliferation and growth conditions. A detailed analysis indicated that the entire viral DNA was integrated into the cellular genome. At least 5 of the 11 latent EBV proteins were expressed, indicating the integrity of the EBV genome. EBNA1-positive and ΔEBNA1-EBV-LCLs were injected into severe combined immunodeficient (SCID) mice to examine their tumorgenicity in comparison. Both groups supported tumor growth, indicating that EBNA1 is not mandatory for EBV's oncogenic potential. The results shown provide genetic evidence that EBNA1 is not essential to establish LCLs but promotes the efficiency of this process significantly.
Odor maps of aldehydes and esters revealed by functional MRI in the glomerular layer of the mouse olfactory bulb
Authors: Xu Fuqiang , Liu Nian , Kida Ikuhiro , Rothman Douglas L. , Hyder Fahmeed , Shepherd Gordon M.
Published: September 2003

Odorant identity is believed to be encoded in the olfactory bulb (OB) by glomerular activity patterns. It has not yet been possible to visualize and compare entire patterns for different odorants in the same animal because of technical limitations. For this purpose we used high-resolution functional MRI at 7 T, combined with glomerular-layer flat maps, to reveal responses to aliphatic homologues in the mouse OB. These odorants elicited reproducible patterns in the OB, with the medial and lateral regions containing the most intense signals. Unexpectedly, in view of the symmetrical projections of olfactory receptor neurons to medial and lateral glomeruli, the activity patterns in these regions were asymmetrical. The highly activated medial and lateral areas were shared by homologous members, generating a conserved “family signature” for a homologous series. The moderately active areas, including the dorsal region that has been extensively studied by optical imaging, were more sensitive to the length of the carbon chain, producing more subtle features of individual members and different changing trends among homologues. The global mapping with functional MRI not only extended previous studies but also revealed additional rules for representation of homologues in the OB. Insights into possible relations between the functional patterns, molecular projections, and odor perception may now be obtained based on the global from the olfactory epithelium to the OB glomerular activity patterns.
Intra-G
1
arrest in response to UV irradiation in fission yeast
Authors: Nilssen Esben A. , Synnes Marianne , Kleckner Nancy , Grallert Beáta , Boye Erik
Published: September 2003

G
1
is a crucial phase of cell growth because the decision to begin another mitotic cycle is made during this period. Occurrence of DNA damage in G
1
poses a particular challenge, because replication of damaged DNA can be deleterious and because no sister chromatid is present to provide a template for recombinational repair. We therefore have studied the response of
Schizosaccharomyces pombe
cells to UV irradiation in early G
1
phase. We find that irradiation results in delayed progression through G
1
, as manifested most critically in the delayed formation of the pre-replication complex. This delay does not have the molecular hallmarks of known checkpoint responses: it is independent of the checkpoint proteins Rad3, Cds1, and Chk1 and does not elicit inhibitory phosphorylation of Cdc2. Irradiated cells eventually progress into S phase and arrest in early S by a
rad3
- and
cds1
-dependent mechanism, most likely the intra-S checkpoint. Caffeine alleviates both the intra-G
1
- and intra-S-phase delays. We suggest that intra-G
1
delay may be widely conserved and discuss significance and possible mechanisms.