bluuebunny/crossref_metadata_2025 huggingface dataset:
Surfactant-mediated growth of InGaAs multiple-quantum-well lasers emitting at 2.1μm by metalorganic vapor phase epitaxy
Authors: Sato Tomonari , Mitsuhara Manabu , Watanabe Takao , Kondo Yasuhiro
Published: November 2005

We report on the effect of antimony surfactant on the growth of strained InGaAs multiple-quantum-well (MQW) structure by metalorganic vapor phase epitaxy and the application of the structure to buried-heterostructure (BH) lasers. For a 1.85%-strained MQW, supplying a small amount of antimony during well growth is effective in suppressing the three-dimensional growth and increasing the photoluminescence peak intensity at a wavelength of 2.09μm. The secondary ion mass spectroscopy measurement reveals that hardly any antimony is incorporated into the wells. The fabricated BH laser has an emission wavelength of 2.103μm under continuous-wave operation at 25 °C.
Gain dispersion in visible light photon counters as a function of counting rate
Authors: Bross A. , Büscher V. , Estrada J. , Ginther G. , Molina J.
Published: November 2005

We present measurements of light signals using visible light photon counters (VLPC), that indicate an increase in gain dispersion as the counting rate increases. We show that this dispersion can be understood on the basis of a recent observation of localized field reduction in VLPCs at high input rates.
Cavity-enhanced saturable and two-photon absorption in semiconductors
Authors: Herda Robert , Hakulinen Tommi , Suomalainen Soile , Okhotnikov Oleg G.
Published: November 2005

Two-photon and saturable absorption are studied by placing GaAs and InGaAs materials in a microcavity. We show that field enhancement occurring due to the cavity influences the threshold and dynamic range of rollover in the nonlinear response. This approach can be used in semiconductor laser mirrors with improved capabilities for self-starting passive mode locking with suppressed tendency to Q-switching instability.
Evolution of a stable polarization state in lead zirconate titanate ceramics by repeated partial switching
Authors: Granzow T. , Balke N. , Lupascu D. C. , Rödel J.
Published: November 2005

The development of the ferroelectric polarization of lead–zirconate–titanate (PZT) bulk ceramics under varying electric fields is examined. Repeated partial switching and backswitching results in a decrease of the switchable polarization, but has no effect on the effective strain. This is attributed to a stabilization of the domain structure, which leads to a decrease of the electric losses. The results are discussed with respect to the effective strain of PZT ceramics for piezoelectric actuators.
The Perception of Distances and Spatial Relationships in Natural Outdoor Environments
Authors: Norman J Farley , Crabtree Charles E , Clayton Anna Marie , Norman Hideko F
Published: November 2005

The ability of observers to perceive distances and spatial relationships in outdoor environments was investigated in two experiments. In experiment 1, the observers adjusted triangular configurations to appear equilateral, while in experiment 2, they adjusted the depth of triangles to match their base width. The results of both experiments revealed that there are large individual differences in how observers perceive distances in outdoor settings. The observers' judgments were greatly affected by the particular task they were asked to perform. The observers who had shown no evidence of perceptual distortions in experiment 1 (with binocular vision) demonstrated large perceptual distortions in experiment 2 when the task was changed to match distances in depth to frontal distances perpendicular to the observers' line of sight. Considered as a whole, the results indicate that there is no single relationship between physical and perceived space that is consistent with observers' judgments of distances in ordinary outdoor contexts.
Perceiving Illumination Inconsistencies in Scenes
Authors: Ostrovsky Yuri , Cavanagh Patrick , Sinha Pawan
Published: November 2005

The human visual system is adept at detecting and encoding statistical regularities in its spatiotemporal environment. Here, we report an unexpected failure of this ability in the context of perceiving inconsistencies in illumination distributions across a scene. Prior work with arrays of objects all having uniform reflectance has shown that one inconsistently illuminated target can ‘pop out’ among a field of consistently illuminated objects (eg Enns and Rensink, 1990 Science247 721–723; Sun and Perona, 1997 Perception26 519–529). In these studies, the luminance pattern of the odd target could be interpreted as arising from either an inconsistent illumination or inconsistent pigmentation of the target. Either cue might explain the rapid detection. In contrast, we find that once the geometrical regularity of the previous displays is removed, the visual system is remarkably insensitive to illumination inconsistencies, both in experimental stimuli and in altered images of real scenes. Whether the target is interpreted as oddly illuminated or oddly pigmented, it is very difficult to find if the only cue is deviation from the regularity of illumination or reflectance. Our results allow us to draw inferences about how the visual system encodes illumination distributions across scenes. Specifically, they suggest that the visual system does not verify the global consistency of locally derived estimates of illumination direction.
Spatial and Temporal Properties of Stereoscopic Surface Interpolation
Authors: Wilcox Laurie M , Duke Philip A
Published: November 2005

It is well established that under a wide range of conditions when a sparse collection of texture elements varies smoothly in depth, the spaces between the elements are assigned depth values. This disparity interpolation process has been studied in an effort to define some of its fundamental spatial and temporal constraints. To assess disparity interpolation we employed two tasks: a novel task that relies on the bisection of illusory boundaries created when subjective stereoscopic surfaces intersect, and one that relies on a 3-D shape discrimination. The results of both experiments show that there is no improvement in performance when texture density is increased from near 0.20 to 0.85 or when exposure duration is increased from 50–100 to 1000 ms. This lack of dependence on the addition of features that define the interpolated surface, along with the abrupt decline in performance below a critical value, is consistent with the view that surface interpolation is an important function of human stereoscopic vision.
Effect of egg location and respiratory gas concentrations on developmental success in nests of the leatherback turtle, Dermochelys coriacea
Authors: Ralph Cameron R. , Reina Richard D. , Wallace Bryan P. , Sotherland Paul R. , Spotila James R. , Paladino Frank V.
Published: November 2005

Hatching success of leatherback turtles, Dermochelys coriacea, is typically ~50%, but the reasons for embryonic death are unknown. We investigated the distribution of egg failure within 16 developing nests to determine whether spatial position or respiratory environment was associated with embryonic death. We measured oxygen and carbon dioxide partial pressures during incubation to investigate whether any spatial variation in developmental success was associated with regions of hypoxia or hypercapnia. Eggs in the centre of nests had a significantly lower mean hatching success (42.1 ± 7.6%) than eggs in the intermediate (66.1 ± 5.3%) and peripheral (69.8 ± 3.5%) regions. Of those eggs that died, there were no significant differences in the timing of early- and late-stage embryonic death in central (77.6 ± 7.2% early death, 17.3 ± 8.2% late death) and peripheral (80.8 ± 10.1% early death, 14.7 ± 5.8% late death) regions. Oxygen tension in all regions of nests was significantly lower and carbon dioxide tension was significantly higher than in control nests by Day 35 of incubation. Although spatial variation in respiratory gases was detected, it did not appear to explain spatially variable developmental success because late-stage embryonic death did not increase in the central region where oxygen tension was lowest and carbon dioxide tension was highest.
Morphology and distribution of sweat glands in the Cape fur seal, Arctocephalus pusillus pusillus (Carnivora:Otariidae)
Authors: Rotherham L. S. , van der Merwe M. , Bester M. N. , Oosthuizen W. H.
Published: November 2005

The present study examined whether sweat glands are present in the skin of the Cape fur seal, Arctocephalus pusillus pusillus. Sweat glands have an important role in thermoregulation; the presence or absence of sweat glands in the fur-covered and naked skin areas of the Cape fur seal was investigated using standard histological procedures and light and scanning electron microscopy. Sweat glands were present in both fur-covered and naked skin areas. The skin layers in the naked skin areas were thicker than those in the fur-covered areas, presumably to protect them against abrasions in the absence of hair. The density of apocrine sweat glands did not differ among the body regions; however, both apocrine and eccrine sweat glands were larger in naked skin areas than in fur-covered areas. This increased size of the glands suggests a more active role for the glands in the naked skin areas, and a higher heat-loss capability through evaporative cooling in these body regions.
Cross-fostering, growth and reproductive studies in the brush-tailed rock-wallaby, Petrogale penicillata (Marsupialia:Macropodidae): efforts to accelerate breeding in a threatened marsupial species
Authors: Taggart David A. , Schultz David , White Craig , Whitehead Peter , Underwood Geoff , Phillips Kevin
Published: November 2005

Pouch-young removal and cross-fostering trials were undertaken in the brush-tailed rock-wallaby, Petrogale penicillata, to assess whether this procedure could be used to accelerate breeding and recruitment in this threatened marsupial species. Basic reproductive data, lacking at the time of the study, were also collected. Eighteen pouch young, weighing 1–106 g, were fostered to either tammar wallaby, Macropus eugenii, or yellow-footed rock-wallaby, Petrogale xanthopus, surrogate mothers. Sixteen P. penicillata pouch young were transferred to surrogate mothers whose own young were greater or equal in size to the P. penicillata young being transferred. Fourteen of these young survived (88%). Two of the P. penicillata pouch young were transferred to surrogate mothers whose own young was smaller in size than the P. penicillata young being transferred. Neither survived. Growth curves for pouch young on mothers and surrogate mothers were estimated. P. penicillata young reared by surrogate mothers grew at a similar rate, and were weaned at a similar age, to the pouch young of the foster species. Like other rock-wallaby species, P. penicillata underwent embryonic diapause and had a gestation period of ~30 days. Permanent pouch exit occurred at ~200 days and young became sexually mature at ~23 months for males and no later than 21 months for females. This study clearly demonstrates that pouch young of P. penicillata, as small as 1 g (~8 days old), can be removed and cross-fostered successfully. These procedures can be used to accelerate breeding and recruitment by up to six times in this threatened species provided an adequate source of surrogate mothers is available.
Female dragons, Ctenophorus pictus, do not prefer scent from unrelated males
Authors: Jansson Nina , Uller Tobias , Olsson Mats
Published: November 2005

Female choice for genetic complementarity or unrelated males occurs in several vertebrate taxa, but only a few species per higher-order taxon have so far been studied. This is particularly the case in reptiles, where female choice traditionally has been considered to be less important than in most other vertebrates. Many species of reptiles use scent marking in relation to territory use and, consequently, females may use this information to avoid settling on genetically incompatible (e.g. related) males’ territories. We tested the response of female Australian dragon lizards, Ctenophorus pictus, to pheromones from closely related and unrelated males. Contrary to predictions, females did not prefer to associate with scent from unrelated males. The reason for the lack of differential response to related and unrelated males could be explained by weak selection against inbreeding, high dependence on visual cues, female control over copulation, or post-copulatory female choice. Alternative hypotheses are discussed in relation to the biology of the species and lizard biology in general.
The life history of Pseudocheirus occidentalis (Pseudocheiridae) in the jarrah forest of south-western Australia
Authors: Wayne A. F. , Rooney J. F. , Ward C. G. , Vellios C. V. , Lindenmayer D. B.
Published: November 2005

Life-history attributes are described for the threatened ngwayir or western ringtail possum (Pseudocheirus occidentalis) in inland jarrah (Eucalyptus marginata) forest east of Manjimup, south-western Australia. Data on 81 individuals were collected over 18 months. There was no sexual dimorphism and body size was similar to that found in other P. occidentalis populations, but larger than the closely related P. peregrinus in eastern Australia. Breeding at Chariup was more strongly seasonal than that of coastal populations, with 77% of births in May–June and the remainder in October–November. All neonates were singletons except for one instance of non-viable twins. No females bred twice in the same year. The growth rate of the head length of pouch young (<5 months of age) was 0.245–0.362 mm day–1 and curvilinear toward an asymptote thereafter. Temporal variations in body condition, coat condition and ectoparasites were significant. Mortality was highly seasonal (84% of deaths were April–September) and predominantly caused by predation, mainly by fox (Vulpes vulpes) and cat (Felis catus). More effective and strategic control of introduced predators prior to and during autumn/winter, could therefore improve the viability of jarrah forest populations. Nutrition appears to influence many of the life-history traits of P. occidentalis. Nutrition also may partly explain the differences in size, life history and conservation status between P. occidentalis and P. peregrinus.
How can blind tiger snakes (Notechis scutatus) forage successfully?
Authors: Aubret Fabien , Bonnet Xavier , Pearson David , Shine Richard
Published: November 2005

On a small island off south-western Australia, tiger snakes (Notechis scutatus, Elapidae) continue to survive, feed, grow and reproduce successfully after being blinded by seagulls defending their chicks. We propose two alternative hypotheses to explain this surprising result: either vision is of trivial importance in tiger snake foraging, or the blinded snakes survive on a diet of abundant immobile prey that cannot escape their approach. Laboratory studies in which we blindfolded snakes falsified the first hypothesis: snakes that were unable to see had great difficulty in capturing mobile prey. Field data support the second hypothesis: blind snakes feed almost entirely on seagull chicks, whereas normal-sighted animals also took fast-moving prey (lizards and mice). Thus, the ability of tiger snakes on Carnac Island to survive without vision is attributable to the availability of abundant helpless prey (seagull chicks) in this insular ecosystem.
Newborns' preference for face-relevant stimuli: Effects of contrast polarity
Authors: Farroni Teresa , Johnson Mark H. , Menon Enrica , Zulian Luisa , Faraguna Dino , Csibra Gergely
Published: November 2005

There is currently no agreement as to how specific or general are the mechanisms underlying newborns' face preferences. We address this issue by manipulating the contrast polarity of schematic and naturalistic face-related images and assessing the preferences of newborns. We find that for both schematic and naturalistic face images, the contrast polarity is important. Newborns did not show a preference for an upright face-related image unless it was composed of darker areas around the eyes and mouth. This result is consistent with either sensitivity to the shadowed areas of a face with overhead (natural) illumination and/or to the detection of eye contact.
Regulation of endothelial nitric oxide synthase by small RNA
Authors: Zhang Ming-Xiang , Ou Hesheng , Shen Ying H. , Wang Jing , Wang Jian , Coselli Joseph , Wang Xing Li
Published: November 2005

Repeats (27-nt) in intron 4 have been shown to play a
cis
-acting role in endothelial nitric oxide synthase (eNOS) promoter activity. We hypothesize that the 27-nt repeats could be the source of small nuclear RNA specifically regulating eNOS expression. In this study, we used synthesized 27-nt RNA duplex and found that the eNOS gene transcriptional efficiency was reduced 63% (0.047 ± 0.009 vs. 0.126 ± 0.015,
P
< 0.01) by nuclear run-on assay. In endothelial cells transfected with the 27-nt small RNA duplex, we found that the eNOS mRNA and protein levels were decreased by >64% (
P
< 0.01). Conversely, a randomly selected 27-nt from luciferase gene had no effect on the eNOS expression. Furthermore, this eNOS silencing effect appeared to be reversible under the stimulation of vascular endothelial growth factor (10 ng/ml), which is known to up-regulate eNOS expression. Using
in situ
hybridization and Northern blotting, we observed the presence of endogenous eNOS intron 4-derived 27-nt small RNA, which was confined to the nucleus. In summary, we demonstrated that intron-based microRNAs in eNOS can induce significant gene specific transcriptional suppression, which could be an effective negative feedback regulator for gene expression.
Study of single-nucleotide polymorphisms by means of electrical conductance measurements
Authors: Hihath Joshua , Xu Bingqian , Zhang Peiming , Tao Nongjian
Published: November 2005

Understanding the complexities of DNA has been a hallmark of science for over a half century, and one of the important topics in DNA research is recognizing the occurrence of mutations in the base-stack. In this article, we present a study of SNPs by direct-contact electrical measurements to a single DNA duplex. We have used short, 11- and 12-bp dsDNA to investigate the change in conductance that occurs if a single base pair, a single base, or two separate bases in the stack are modified. All measurements are carried out in aqueous solution with the DNA chemically bound to the electrodes. These measurements demonstrate that the presence of a single base pair mismatch can be identified by the conductance of the molecule and can cause a change in the conductance of dsDNA by as much as an order of magnitude, depending on the specific details of the double helix and the single nucleotide polymorphism.
The effect of
TERC
haploinsufficiency on the inheritance of telomere length
Authors: Goldman Fred , Bouarich Rachida , Kulkarni Shashikant , Freeman Sara , Du Hong-Yan , Harrington Lea , Mason Philip J. , Londoño-Vallejo Arturo , Bessler Monica
Published: November 2005

Telomeres protect chromosome ends from end-to-end fusion and degradation. Loss of telomere function causes cell-cycle arrest or cell death. Autosomal dominant dyskeratosis congenita (AD DC), a rare inherited bone marrow failure syndrome, is caused by mutations in
TERC
, the RNA component of telomerase. Here, we studied the telomere dynamics over three generations in a 32-member extended family with AD DC due to a
TERC
gene deletion. Our analysis shows that peripheral blood cells from family members haploinsufficient for
TERC
have very short telomeres. Telomeres are equally short in all individuals carrying the
TERC
gene deletion irrespective of their age. Chromosome-specific telomere analysis distinguishing the parental origin of telomeres showed that in gene deletion carriers, paternal and maternal telomeres are similarly short and similar in length to those of the affected parent. In children of affected parents who have normal
TERC
genes, parental telomeres are again similar in length, but two generations appear to be necessary to fully restore normal telomere length. These results are consistent with a model in which telomerase preferentially acts on the shortest telomeres. When
TERC
is limiting, this preference leads to the accelerated shortening of longer telomeres. The limited amount of active telomerase in
TERC
RNA haploinsufficiency may not be able to maintain the minimal length of the increasing number of short telomeres. Thus, the number of cells with excessively short telomeres and the degree of residual telomerase activity may determine the onset of disease in patients with AD DC.
Mechanism of mRNA transport in the nucleus
Authors: Vargas Diana Y. , Raj Arjun , Marras Salvatore A. E. , Kramer Fred Russell , Tyagi Sanjay
Published: November 2005

The mechanism of transport of mRNA-protein (mRNP) complexes from transcription sites to nuclear pores has been the subject of many studies. Using molecular beacons to track single mRNA molecules in living cells, we have characterized the diffusion of mRNP complexes in the nucleus. The mRNP complexes move freely by Brownian diffusion at a rate that assures their dispersion throughout the nucleus before they exit into the cytoplasm, even when the transcription site is located near the nuclear periphery. The diffusion of mRNP complexes is restricted to the extranucleolar, interchromatin spaces. When mRNP complexes wander into dense chromatin, they tend to become stalled. Although the movement of mRNP complexes occurs without the expenditure of metabolic energy, ATP is required for the complexes to resume their motion after they become stalled. This finding provides an explanation for a number of observations in which mRNA transport appeared to be an enzymatically facilitated process.
A structural model for unfolded proteins from residual dipolar couplings and small-angle x-ray scattering
Authors: Bernadó Pau , Blanchard Laurence , Timmins Peter , Marion Dominique , Ruigrok Rob W. H. , Blackledge Martin
Published: November 2005

Natively unfolded proteins play key roles in normal and pathological biochemical processes. Despite their importance for function, this category of proteins remains beyond the reach of classical structural biology because of their inherent conformational heterogeneity. We present a description of the intrinsic conformational sampling of unfolded proteins based on residue-specific φ/Ψ propensities from loop regions of a folded protein database and simple volume exclusion. This approach is used to propose a structural model of the 57-aa, natively disordered region of the nucleocapsid-binding domain of Sendai virus phosphoprotein. Structural ensembles obeying these simple rules of conformational sampling are used to simulate averaged residual dipolar couplings (RDCs) and small-angle x-ray scattering data. This protein is particularly informative because RDC data from the equally sized folded and unfolded domains both report on the unstructured region, allowing a quantitative analysis of the degree of order present in this part of the protein. Close agreement between experimental and simulated RDC and small-angle x-ray scattering data validates this simple model of conformational sampling, providing a precise description of local structure and dynamics and average dimensions of the ensemble of sampled structures. RDC data from two urea-unfolded systems are also closely reproduced. The demonstration that conformational behavior of unfolded proteins can be accurately predicted from the primary sequence by using a simple set of rules has important consequences for our understanding of the structure and dynamics of the unstructured state.
Nitric oxide-donating aspirin induces apoptosis in human colon cancer cells through induction of oxidative stress
Authors: Gao Jianjun , Liu Xiaoping , Rigas Basil
Published: November 2005

Nitric oxide-donating aspirin (NO-ASA) is a promising chemoprevention agent against colon cancer and other cancers. It consists of traditional ASA to which a NO-releasing moiety is bound through a spacer. NO-ASA inhibits colon cancer cell growth several hundred times more potently than does ASA. In
Min
mice, NO-ASA inhibited intestinal carcinogenesis without affecting cell proliferation. Thus, we examined whether NO-ASA's most important cell kinetic effect is the induction of apoptosis. After confirming induction of apoptosis in
Min
mice, we studied the underlying mechanism in human colon adenocarcinoma cells. NO-ASA's spacer formed a conjugate with glutathione, depleting glutathione stores. This induced oxidative stress (increased intracellular levels of peroxides and

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) leads to apoptosis by activating the intrinsic apoptosis pathway. NO-ASA disrupted adherens junctions by inducing cleavage of β- and γ-catenin, resulting in cell detachment. NO-ASA inhibited Wnt signaling by a dual mechanism: at low concentrations it blocked the formation of β-catenin/Tcf complexes (dominant mechanism), and at higher concentrations it also cleaved β-catenin. These findings provide a mechanism of action by a potent chemopreventive agent, underscore the significance of these pathways in regulating cell death in the context of cancer chemoprevention, and present a paradigm for developing agents with enhanced cancer cell growth inhibitory properties.
Molecular mechanisms of Sonic hedgehog mutant effects in holoprosencephaly
Authors: Maity Tapan , Fuse Naoyuki , Beachy Philip A.
Published: November 2005

Holoprosencephaly (HPE), a human developmental brain defect, usually is also associated with varying degrees of midline facial dysmorphism. Heterozygous mutations in the
Sonic hedgehog
(
SHH
) gene are the most common genetic lesions associated with HPE, and loss of
Shh
function in the mouse produces cyclopia and alobar forebrain development. The N-terminal domain (ShhNp) of Sonic hedgehog protein, generated by cholesterol-dependent autoprocessing and modification at the C terminus and by palmitate addition at the N terminus, is the active ligand in the Shh signal transduction pathway. Here, we analyze seven reported missense mutations (G31R, D88V, Q100H, N115K, W117G, W117R, and E188Q) that alter the N-terminal signaling domain of Shh protein, and show that two of these mutations (Q100H and E188Q), which are questionably linked to HPE, produce no detectable effects on function. The remaining five alterations affect normal processing, Ptc binding, and signaling to varying degrees. These effects include introduction of a recognition site for furin-like proteases by the G31R alteration, resulting in cleavage of 11 amino acid residues from the N terminus of ShhNp and consequent reduced signaling potency. Two other alterations, W117G and W117R, cause temperature-dependent misfolding and retention in the sterol-poor endoplasmic reticulum, thus disrupting cholesterol-dependent autoprocessing.
Phylogenetic engineering at an interface between large and small subunits imparts land-plant kinetic properties to algal Rubisco
Authors: Spreitzer Robert J. , Peddi Srinivasa R. , Satagopan Sriram
Published: November 2005

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of photosynthetic CO
2
fixation and, thus, limits agricultural productivity. However, Rubisco enzymes from different species have different catalytic constants. If the structural basis for such differences were known, a rationale could be developed for genetically engineering an improved enzyme. Residues at the bottom of the large-subunit α/β-barrel active site of Rubisco from the green alga
Chlamydomonas reinhardtii
(methyl-Cys-256, Lys-258, and Ile-265) were previously changed through directed mutagenesis and chloroplast transformation to residues characteristic of land-plant Rubisco (Phe-256, Arg-258, and Val-265). The resultant enzyme has decreases in carboxylation efficiency and CO
2
/O
2
specificity, despite the fact that land-plant Rubisco has greater specificity than the
Chlamydomonas
enzyme. Because the residues are close to a variable loop between β-strands A and B of the small subunit that can also affect catalysis, additional substitutions were created at this interface. When large-subunit Val-221 and Val-235 were changed to land-plant Cys-221 and Ile-235, they complemented the original substitutions and returned CO
2
/O
2
specificity to the normal level. Further substitution with the shorter βA-βB loop of the spinach small subunit caused a 12-17% increase in specificity. The enhanced CO
2
/O
2
specificity of the mutant enzyme is lower than that of the spinach enzyme, but the carboxylation and oxygenation kinetic constants are nearly indistinguishable from those of spinach and substantially different from those of
Chlamydomonas
Rubisco. Thus, this interface between large and small subunits, far from the active site, contributes significantly to the differences in catalytic properties between algal and land-plant Rubisco enzymes.
Parvoviral virions deploy a capsid-tethered lipolytic enzyme to breach the endosomal membrane during cell entry
Authors: Farr Glen A. , Zhang Li-guo , Tattersall Peter
Published: November 2005

Enveloped viruses deliver their virions into the host cell by fusion with the cellular plasma or endosomal membrane, thus creating topological continuity between the cytosol and the inside of the viral envelope. Nonenveloped viruses are, by their very nature, denied this strategy and must employ alternative methods to breach their host cell's delimiting membrane. We show here that the compact icosahedral parvoviral virion gains entry by deploying a lipolytic enzyme, phospholipase A
2
(PLA
2
), that is expressed at the N terminus of VP1, the minor coat protein. This region of VP1 is normally sequestered within the viral shell but is extruded during the entry process as a capsid-tethered domain. A single amino acid substitution in the active site of the VP1 PLA
2
inactivates enzymatic activity and abrogates infectivity. We have used transencapsidation of a vector expressing green fluorescent protein to show that infection by this PLA
2
-defective mutant can be complemented by coinfection with wild-type or mutant full virions, provided they can express a functional PLA
2
. Even though wild-type empty capsids contain an active form of the enzyme, it is not externalized under physiological conditions, and such capsids are not able to complement the PLA
2
mutant. Significantly, highly efficient rescue can be achieved by polyethyleneimine-induced endosome rupture or by coinfection with adenovirus as long as uptake of the two viruses is simultaneous and the adenovirus is capable of deploying pVI, a capsid protein with endosomolytic activity. Together, these results demonstrate a previously unrecognized enzymatic mechanism for nonenveloped virus penetration.
Pyramidal neurons of upper cortical layers generated by NEX-positive progenitor cells in the subventricular zone
Authors: Wu Sheng-Xi , Goebbels Sandra , Nakamura Kouichi , Nakamura Kazuhiro , Kometani Kouhei , Minato Nagahiro , Kaneko Takeshi , Nave Klaus-Armin , Tamamaki Nobuaki
Published: November 2005

The generation of pyramidal neurons in the mammalian neocortex has been attributed to proliferating progenitor cells within the ventricular zone (VZ). Recently, the subventricular zone (SVZ) has been recognized as a possible source of migratory neurons in brain slice preparations, but the relevance of these observations for the developing neocortex
in vivo
remains to be defined. Here, we demonstrate that a subset of progenitor cells within the SVZ of the mouse neocortex can be molecularly defined by Cre recombinase expression under control of the NEX/Math2 locus, a neuronal basic helix-loop-helix gene that by itself is dispensable for cortical development. NEX-positive progenitors are generated by VZ cells, move into the SVZ, and undergo multiple asymmetrical and symmetrical cell divisions that produce a fraction of the neurons in the upper cortical layers. Our data suggest that NEX-positive progenitors within the SVZ are committed to a glutamatergic neuronal fate and have evolved to expand the number of cortical output neurons that is characteristic for the mammalian forebrain.
Preceramic irrigation canals in the Peruvian Andes
Authors: Dillehay Tom D. , Eling Herbert H. , Rossen Jack
Published: November 2005

One of the most important developments in the existence of human society was the successful shift from a subsistence economy based on foraging to one primarily based on food production derived from cultivated plants and domesticated animals. The shift to plant food production occurred in only a few independent centers around the world and involved a commitment to increased sedentism and social interaction and to permanent agricultural fields and canals. One center was Peru, where early civilization and food production were beginning to develop by at least 4,500 years ago. New archeological evidence points to 5,400- and possible 6,700-year-old small-scale gravity canals in a circumscribed valley of the western Andean foothills in northern Peru that are associated with farming on low terrace benches at the foot of alluvial fans in areas where the canals are drawn from hydraulically manageable small lateral streams. This evidence reveals early environmental manipulation and incipient food production in an artificially created wet agroecosystem rather than simply the intensive harvesting or gardening of plants in moist natural areas. This finding is different from previously conceived notions, which expected early canals in lower-elevated, broad coastal valleys. The evidence also points to communal organization of labor to construct and maintain the canals and to the scheduling of daily activities beyond individual households. The development of early organized irrigation farming was combined with a hunting and gathering economy to support an increase in the local population size.
T cell Ig and mucin 1 (TIM-1) is expressed on
in vivo
-activated T cells and provides a costimulatory signal for T cell activation
Authors: de Souza Anjali J. , Oriss Timothy B. , O'Malley Katherine J. , Ray Anuradha , Kane Lawrence P.
Published: November 2005

Polymorphisms in TIM-1, a member of the T cell Ig and mucin (TIM) domain family, are associated with relative susceptibility to the development of T helper 2-dominated immune responses such as in allergic asthma. Recent data have also suggested that ligation of TIM-1 can augment T cell activation. We have found that the TIM-1 protein is expressed on CD4
+
T cells
in vivo
after intranasal immunization. Ectopic expression of TIM-1 during T cell differentiation results in a significant increase in the number of cells producing IL-4 but not IFN-γ. Furthermore, TIM-1 expression provides a costimulatory signal that increases transcription from the IL-4 promoter and from isolated nuclear factor of activated T cells/activating protein-1 (NFAT/AP-1) elements. Finally, we provide evidence that TIM-1 can be phosphorylated on tyrosine and that TIM-1 costimulation requires its cytoplasmic tail and the conserved tyrosine within that domain. These results constitute evidence that TIM-1 directly couples to phosphotyrosine-dependent intracellular signaling pathways.
Fezl regulates the differentiation and axon targeting of layer 5 subcortical projection neurons in cerebral cortex
Authors: Chen Bin , Schaevitz Laura R. , McConnell Susan K.
Published: November 2005

During the development of the cerebral cortex, progenitor cells produce neurons that migrate to laminar positions appropriate for their birth dates, adopt specific neuronal identities, and form appropriate local and long-distance axonal connections. Here, we report that forebrain embryonic zinc-finger-like protein (
Fezl
), a putative zinc-finger transcriptional repressor, is required for the differentiation of projection neurons in cortical layer 5. In
Fezl
-deficient mice, these neurons display molecular, morphological, and axonal targeting defects. The corticospinal tract was absent in
Fezl
-/-
mice, corticotectal and pontine projections were severely reduced, and
Fezl
-expressing neurons formed aberrant axonal projections. The expression of many molecular markers for deep-layer neurons was reduced or absent in the
Fezl
-/-
cerebral cortex. Most strikingly,
Ctip2
, a transcription factor required for the formation of the corticospinal tract, was not expressed in the
Fezl
-deficient cortex. These results suggest that
Fezl
regulates the differentiation of layer 5 subcortical projection neurons.
A schizophrenia-related sensorimotor deficit links α3-containing GABA
A
receptors to a dopamine hyperfunction
Authors: Yee B. K. , Keist R. , von Boehmer L. , Studer R. , Benke D. , Hagenbuch N. , Dong Y. , Malenka R. C. , Fritschy J.-M. , Bluethmann H. , Feldon J. , Möhler H. , Rudolph U.
Published: November 2005

Overactivity of the dopaminergic system in the brain is considered to be a contributing factor to the development and symptomatology of schizophrenia. Therefore, the GABAergic control of dopamine functions was assessed by disrupting the gene encoding the α3 subunit of the GABA
A
receptor. α3 knockout (α3KO) mice exhibited neither an obvious developmental defect nor apparent morphological brain abnormalities, and there was no evidence for compensatory up-regulation of other major GABA
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-receptor subunits. Anxiety-related behavior in the elevated-plus-maze test was undisturbed, and the anxiolytic-like effect of diazepam, which is mediated by α2-containing GABA
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receptors, was preserved. As a result of the loss of α3 GABA
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receptors, the GABA-induced whole-cell current recorded from midbrain dopamine neurons was significantly reduced. Spontaneous locomotor activity was slightly elevated in α3KO mice. Most notably, prepulse inhibition of the acoustic startle reflex was markedly attenuated in the α3KO mice, pointing to a deficit in sensorimotor information processing. This deficit was completely normalized by treatment with the antipsychotic D2-receptor antagonist haloperidol. The amphetamine-induced hyperlocomotion was not altered in α3KO mice compared with WT mice. These results suggest that the absence of α3-subunit-containing GABA
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receptors induces a hyperdopaminergic phenotype, including a severe deficit in sensorimotor gating, a common feature among psychiatric conditions, including schizophrenia. Hence, agonists acting at α3-containing GABA
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receptors may constitute an avenue for an effective treatment of sensorimotor-gating deficits in various psychiatric conditions.
INFORMATION, WILDLIFE VALUATION, CONSERVATION: EXPERIMENTS AND POLICY
Authors: TISDELL CLEM , WILSON CLEVO
Published: November 2005

The authors use experimental surveys to investigate the association between individuals' knowledge of particular wildlife species and their stated willingness to allocate funds to conserve each. The nature of variations in these allocations between species (e.g., their dispersion) as participants' knowledge increases is examined. Factors influencing these changes are suggested. Willingness‐to‐pay allocations are found not to measure the economic value of species, but are shown to be policy relevant. The results indicate that poorly known species, e.g., in remote areas, may obtain relatively less conservation support than they deserve. (JEL Q51, Q57, Q58)
FACTORS AFFECTING SPECIES' RISK OF EXTINCTION: AN EMPIRICAL ANALYSIS OF ESA AND NATURESERVE LISTINGS
Authors: LABAND DAVID N. , NIESWIADOMY MICHAEL
Published: November 2005

The authors examine the impact of environmental and political variables on two measures of species imperilment across 49 U.S. states: the fraction of all species in a state identified by NatureServe as being “at‐risk” of extinction, and the fraction of species in a state listed under the U.S. Fish & Wildlife Service's (FWS) Endangered Species Act (ESA). A highly significant determinant of both measures is the fraction of species endemic to the state. Population growth increases the at‐risk measure, but not the ESA listings. There is a significant concern for plant imperilment by NatureServe, but not by the FWS.
PRIVATIZATION OF PUBLIC HOUSING: DID IT CAUSE THE 1998 RECESSION IN HONG KONG?
Authors: HO LOK SANG , WONG GARY WAI‐CHUNG
Published: November 2005

The authors find evidence that a public housing privatization program produced adverse effects on housing transactions and the economy in Hong Kong. A scheme announced in December 1997, offering tenants an opportunity to buy their units at deeply discounted prices, reduced public housing tenants' bids for private homes and adversely affected home transactions. This effect is more pronounced than the effects of the Asian Financial Crisis. An effect on housing prices is also indirectly shown though a demonstration that a structural break in the housing price relationship occurred at the time the privatization program was introduced. Declines in housing prices further eroded employment and set off a vicious circle.(JELE32, R21, R31)
STABILIZATION POLICY: A RECONSIDERATION
Authors: YELLEN JANET L. , AKERLOF GEORGE A.
Published: November 2005

Should stabilization policy be a macroeconomic priority? Most central banks consider it a goal, but Robert Lucas has contended that policies to stabilize output, even if effective, yield negligible welfare gains. This article critiques Lucas's argument. Existing literature suggests nontrivial benefits from stabilization due to nonlinearity of the social welfare function and of the short‐run Phillips curve. Our analysis and examination of the evidence from periods of prolonged high unemployment also suggest further significant gains to stabilization since the “accelerationist” hypothesis does not seem to hold in times of very low inflation. (JEL E61, E63)
LABOR‐MARKET CONSEQUENCES OF POOR ATTITUDE AND LOW SELF‐ESTEEM IN YOUTH
Authors: WADDELL GLEN R.
Published: November 2005

Using longitudinal data on a cohort of high‐school graduates, I show that youth who reveal poor attitude and self‐esteem subsequently attain fewer years of postsecondary education relative to their high school cohort, are less likely to be employed 14 years following high school and, where working for pay, realize lower earnings. Furthermore, I find evidence that poor attitude and self‐esteem in high school are significant predictors of structural outcomes, such as the degree of supervision under which individuals subsequently work, job characteristics, and on‐the‐job activities. These relationships suggest that real economic consequence exist in fostering positive attitude and self‐esteem in youth. (JEL J13, J20, J30)
Solomon Huebner and the Development of Life Insurance Sales Professionalism, 1905–1927
Authors: Creek Drew Vande
Published: November 2005

In 1927 the National Association of Life Underwriters collaborated with Professor Solomon Huebner of the University of Pennsylvania to found the American College of Life Underwriters, an institution devoted to establishing and maintaining professional standards for the nation’s life insurance salesmen. Their work sheds light on the new politics of expertise and associations that emerged in the 1920s. While many historians have portrayed the period’s experts as purveyors of new, technical knowledge and apolitical agents of an inevitable modernity, Huebner in fact brought little real knowledge of insurance to his work. Instead, he introduced the industry’s prevailing ideology of public service into his classroom, and it informed his professionalization project as well. The professor worked as a campaigner for professionalism, attempting to persuade life insurance salesmen, industry executives, and the American public to accept the notion that salesmen could become professionals. Ultimately, Huebner’s career shows how a Progressive expert worked directly with a trade association representing a disorganized industry. But instead of merely seeking to build new capacity for economic planning and stabilization, Huebner and the association boldly positioned their industry as a voluntary and private means of providing Americans with basic social welfare benefits and paved the way for the growth of the modern financial services industry.
Competing Research Traditions in American Industry: Uncertain Alliances between Engineering and Science at Westinghouse Electric, 1886–1935
Authors: Kline Ronald R. , Lassman Thomas C.
Published: November 2005

Westinghouse Electric opened a new research laboratory near the company’s main factory in East Pittsburgh, Pennsylvania, in 1916. Located in the suburban borough of Forest Hills, the laboratory was set up to provide scientific knowledge for the older materials testing and product development laboratories at the factory. Unlike its industrial counterparts, however, the Forest Hills laboratory was dominated by a strong engineering research tradition that disrupted efforts undertaken in the 1920s and again in the 1930s to build and sustain a diversified fundamental research program. Whereas Eastman Kodak, DuPont, AT&T, and General Electric had successfully integrated fundamental research into their corporate laboratories, the Forest Hills laboratory remained the site of recurring tensions between two cultures of innovation—one based on fundamental science, the other on engineering research. Although such tensions often resulted in competing research strategies, managerial conflicts, and mismatched corporate priorities, the long-standing culture of engineering research contributed far more to Westinghouse’s strategic growth than even the most advanced fundamental research. More generally, the interactions between the cultures of engineering and science that characterize the early history of industrial research at Westinghouse highlight the evolving and sometimes conflicting patterns of technological innovation and organizational change in American industry before World War II.
The Neglected Legacy of Lancashire Cotton: Industrial Clusters and the U.K. Outdoor Trade, 1960–1990
Authors: Parsons Mike , Rose Mary B.
Published: November 2005

This article considers the neglected legacies of the Lancashire cotton industry and their impact on the U.K. outdoor trade. Studies of the decline of the Lancashire cotton industry after the Second World War have concentrated on the collapse of coarse cotton spinning and weaving, largely ignoring the impact of the knowledge and skills related to the finishing trades. The examination of the evolution of rainwear, coatings, and high-performance fabrics in the nineteenth century provides a backdrop to a study of the innovation process that emerged in the U.K. outdoor trade after 1960.