bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Basis of Immune Evasion at the Site of CD4 Attachment on HIV-1 gp120
Authors: Chen Lei , Do Kwon Young , Zhou Tongqing , Wu Xueling , O’Dell Sijy , Cavacini Lisa , Hessell Ann J. , Pancera Marie , Tang Min , Xu Ling , Yang Zhi-Yong , Zhang Mei-Yun , Arthos James , Burton Dennis R. , Dimitrov Dimiter S. , Nabel Gary J. , Posner Marshall R. , Sodroski Joseph , Wyatt Richard , Mascola John R. , Kwong Peter D.
Published: November 2009

Anti-HIV Antibody Constraints

Despite significant efforts, an effective vaccine against the HIV-1 virus remains elusive. A site on the HIV-1 gp120 envelope glycoprotein that binds to the CD4 receptor on host cells is vulnerable to antibody, but only rarely are antibodies against this site broadly neutralizing.

L. Chen
et al.

(p.
1123
) have determined crystal structures for two weakly neutralizing antibodies in complex with gp120. The epitopes recognized by these antibodies were similar to those bound by CD4 or a broadly neutralizing antibody. However, small differences in recognition induced conformational shifts in gp120 that were incompatible with formation of a functional viral spike. Thus, the antibody-vulnerable site on HIV-1 is protected by conformational constraints.
Shape-Controlled Colloidal Interactions in Nematic Liquid Crystals
Authors: Lapointe Clayton P. , Mason Thomas G. , Smalyukh Ivan I.
Published: November 2009

Hairy Polygon Solution

The packing of rods on the surface of a sphere leads to packing defects at the opposite poles. It is, however, possible to flat-pack rods onto a torus. This topological problem is well known as the hairy ball theorem, and arises when you place spherical particles inside a nematic liquid crystal.

Lapointe
et al.

(p.
1083
) considered the packing of liquid crystal molecules onto lithographically fabricated polygons and found that the number of dipoles that formed depended upon whether the polygon had an odd or even number of sides. The defect structures were attracted to each other, such that the liquid crystal could pull together the particles in a form of controlled self-assembly.
Overexpression of Alpha2A-Adrenergic Receptors Contributes to Type 2 Diabetes
Authors: Rosengren Anders H. , Jokubka Ramunas , Tojjar Damon , Granhall Charlotte , Hansson Ola , Li Dai-Qing , Nagaraj Vini , Reinbothe Thomas M. , Tuncel Jonatan , Eliasson Lena , Groop Leif , Rorsman Patrik , Salehi Albert , Lyssenko Valeriya , Luthman Holger , Renström Erik
Published: November 2009

Ratting Out a Diabetes Gene

Inbred animals with inherited susceptibility to disease can be especially informative regarding pathogenetic mechanisms because they carry naturally occurring genetic variants of the same type that cause disease in humans. This principle is illustrated byRosengrenet al.(p.217; published online 19 November), whose analysis of an inbred strain of rats prone to develop type 2 diabetes led to the discovery of a gene whose aberrant overexpression suppresses pancreatic insulin secretion in both rats and humans. The culprit gene, ADRA2A, encodes the alpha2A adrenergic receptor and is potentially a valuable lead for diabetes therapy because it can be targeted pharmacologically.
A First-Generation Haplotype Map of Maize
Authors: Gore Michael A. , Chia Jer-Ming , Elshire Robert J. , Sun Qi , Ersoz Elhan S. , Hurwitz Bonnie L. , Peiffer Jason A. , McMullen Michael D. , Grills George S. , Ross-Ibarra Jeffrey , Ware Doreen H. , Buckler Edward S.
Published: November 2009

A-Maize-ing

Maize is one of our oldest and most important crops, having been domesticated approximately 9000 years ago in central Mexico.

Schnable
et al.

(p.
1112
; see the cover) present the results of sequencing the B73 inbred maize line. The findings elucidate how maize became diploid after an ancestral doubling of its chromosomes and reveals transposable element movement and activity and recombination.

Vielle-Calzada
et al.

(p.
1078
) have sequenced the
Palomero Toluqueño
(
Palomero
) landrace, a highland popcorn from Mexico, which, when compared to the B73 line, reveals multiple loci impacted by domestication.

Swanson-Wagner
et al.

(p.
1118
) exploit possession of the genome to analyze expression differences occurring between lines. The identification of single nucleotide polymorphisms and copy number variations among lines was used by

Gore
et al.

(p.
1115
) to generate a Haplotype map of maize. While chromosomal diversity in maize is high, it is likely that recombination is the major force affecting the levels of heterozygosity in maize. The availability of the maize genome will help to guide future agricultural and biofuel applications (see the Perspective by

Feuillet and Eversole

).
Strengthening Individual Memories by Reactivating Them During Sleep
Authors: Rudoy John D. , Voss Joel L. , Westerberg Carmen E. , Paller Ken A.
Published: November 2009

During sleep, memories can be influenced in a specific and systematic manner.
Monitoring Earth's Critical Zone
Authors: Richter Daniel deB. , Mobley Megan L.
Published: November 2009

Earth's rapidly changing near-surface environment needs systematic observation to better manage future crop production, climates, and water quality.
Phosphorylation of H2A by Bub1 Prevents Chromosomal Instability Through Localizing Shugoshin
Authors: Kawashima Shigehiro A. , Yamagishi Yuya , Honda Takashi , Ishiguro Kei-ichiro , Watanabe Yoshinori
Published: November 2009

Recruiting the Components for Cell Division

A complete chromosome set must be apportioned to each daughter cell during cell division. A number of molecular mechanisms check that chromosome pairs or homologs are correctly aligned and attached to microtubules just before they separate to the two daughters; their spatial orientation ensures an even inheritance of the genome. One critical component of this system is the protein kinase Bub1.

Kawashima
et al.

(p.
172
, see the Perspective by

Javerzat

; published online 19 November) now show that the main substrate for Bub1 kinase activity in fission yeast is the chromatin protein histone H2A. Phosphorylation of H2A recruits the shugoshin proteins to chromatin, and especially to centromeres, where they also act to ensure correct chromosome segregation. This link between Bub1, histone H2A phosphorylation, and shugoshin is conserved in budding yeast and mammalian cells.
Universality in Three- and Four-Body Bound States of Ultracold Atoms
Authors: Pollack Scott E. , Dries Daniel , Hulet Randall G.
Published: November 2009

More Is Different, Few Is Exotic

As powerful as theoretical physics can be, when it comes to describing the dynamics of several interacting particles, it stumbles at three. This few-body physics is interesting in many contexts, particularly interactions within the nucleus and between atoms and molecules. Although predicted 40 years ago for the special case of resonant interaction, which occurs at the edge of where two-particle bound states start to form, Efimov trimers were only recently observed in ultracold Bose gases. More work followed, revealing evidence of multiple trimer, and even tetramer, states. Now,

Pollack
et al.

(p.
1683
, published online 19 November; see the Perspective by
Modugno
) observe as many as 11 features near a lithium resonance that can be directly related to different few-body processes. The positions of the features with respect to each other are in excellent agreement with the theoretical prediction, although some deviations, attributed to short-range interactions, present a challenge for a future, more detailed theory.
Recurrence of Kills of Atlantic Herring (Clupea harengus harengus) Caused by Dinoflagellate Toxins Transferred Through Herbivorous Zooplankton
Authors: White Alan W.
Published: November 2009

Kills of adult herring occurred in two locations in the southwestern Bay of Fundy in July 1979 during a bloom of the toxic dinoflagellate Gonyaulax excavata. Fish showed the same symptoms as in a herring kill linked to G. excavata toxins in 1976. Herring stomachs contained G. excavata toxins (66–245 μg/100 g guts), the cladoceran Evadne nordmanni, and yellow-brown material probably of algal origin. At the time of the kills the zooplankton community was overwhelmingly dominated by E. nordmanni. Furthermore, bioassays showed the presence of G. excavata toxins in the zooplankters (18 μg/g wet plankton). Combined with evidence from the 1976 kill in which pteropods were vectors of the toxins, and with results from recent field and laboratory studies, these new observations and results substantiate that (1) G. excavata toxins can, and do, cause herring kills in nature with planktonic herbivores, E. nordmanni in this case, acting as vectors, and (2) the toxin transfer mechanism is a general phenomenon among herbivorous zooplankton. Similar food chain events may affect finfish in other areas of the world which experience blooms of toxic dinoflagellates.Key words: dinoflagellate toxins, Gonyaulax excavata, herring kills, Clupea harengus harengus, cladoceran, Evadne nordmanni, red tides, zooplankton, fish kills
Depression of Primary Productivity by Humic Matter in Lake and Reservoir Waters of the Boreal Forest Zone
Authors: Jackson Togwell A. , Hecky Robert E.
Published: November 2009

Analysis of water from backwater and main-stem regions of three reservoirs and a natural lake belonging to major river systems in northern Manitoba (Canada) showed that primary productivity was inversely related to total "dissolved" (<0.45 μm) organic carbon and non-dialyzable dissolved iron, organic carbon, nitrogen, and H-bonded polymeric hydroxyl groups. The chemical data apparently represent allochthonous humic–FeOOH complexes with strong, covalent metal-ligand bonds. The results suggest that humic matter depressed primary productivity by making iron unavailable to phytoplankton, but not by attenuating light, lowering the pH, or sequestering phosphate (although the dissolved phosphorus appeared to be mostly in the form of humic-iron-phosphate complexes). Relatively stagnant backwater bays, where humic mater accumulates, were less productive than the more rapidly flushed, less humic main-stem waters. In addition, the reservoirs, which had been formed 6 mo, 3 yr, and 14 yr prior to the time of sampling, revealed short-term anomalies caused by impoundment. Evidently three distinct stages of geochemical and trophic development are represented, the sequence of stages being tentatively generalized as follows for reservoirs of this region: (1) soon after impoundment, rapid leaching of nutrients from submerged land causes a brief rise in productivity and aberrantly high levels of dissolved low molecular weight phosphorus and nitrogen in the backwaters; (2) subsequently, a "pulse" of soil humic matter released more gradually into the backwaters depresses productivity by fixation of minor elements such as iron, even if the dissolved phosphorus levels are high; (3) finally, a steady state is restored when this anomalous accumulation of humic matter is removed from the water column by sedimentation or flushing, allowing productivity to return to higher levels. But even under unperturbed natural conditions humic matter restricts the productivity of surface waters in this geographic region to a greater or lesser extent.Key words: humic matter, organic matter, primary productivity, iron, lakes, reservoirs, nutrient availability, Canadian Shield, water quality, phytoplankton ecology
Accumulation of Benzo[a]pyrene in a Larval Bivalve via Trophic Transfer
Authors: Dobroski Jr. C. J. , Epifanio C. E.
Published: November 2009

The diatom Thalassiosira pseudonana was cultured in 10 μg/L 14C-benzo[a]pyrene (B[a]P) and subsequently fed to larvae of the hard clam Mercenaria mercenaria. The rate of direct uptake of B[a]P from seawater by the diatoms was much greater than the rate of trophic transfer of B[a]P from the diatoms to the clam larvae. This was attributed to greater efficiency of direct uptake and to the larger quantity of B[a]P available in the water. A comparison of direct uptake by bivalves (as reported in the literature) with trophic transfer measured in the present investigation indicated that the processes may be equally important in accumulation of B[a]P in natural populations of bivalves.Key words: benzo[a]pyrene, trophic transfer, bivalve larvae
Possible Sexing Technique for Humpback Whales (Megaptera novaeangliae)
Authors: Jurasz V. P. , McSweeney D. , Jurasz C. M.
Published: November 2009

By comparing photographs of humpback whales (Megaptera novaeangliae) photographed at the peak of their arch during a dive, we found some to be smooth and others to be scalloped middorsally caudal to the dorsal fin. Out of 410 photographs taken in southeast Alaska and Hawaii, 66% were found to be smooth and 34% scalloped. All females with calves were smooth. One pregnant female was smooth and only one female who was pregnant was slightly scalloped. One known male was scalloped and one "singer" on the Hawaiian breeding grounds was scalloped. We suggest that the smoothness or scalloping of this region is a morphological feature and can be used with reasonable accuracy to determine sex in humpback whales.Key words: humpback whales, morphology, sex
Daily Patterns of Feeding Behavior, Daily Rations, and Diets of Juvenile Pink Salmon (Oncorhynchus gorbuscha) in Two Marine Bays of British Columbia
Authors: Godin Jean-Guy J.
Published: November 2009

Stomach analyses showed that pink salmon fry fed mainly during daylight hours in the littoral zone of Departure Bay and Hammond Bay, British Columbia, in May. Although the diurnal feeding patterns of the fish differed slightly between the two bays, maximum mean prey biomass in the fishes' stomachs occurred near or at dusk in both bays. Daily rations consumed by Departure Bay and Hammond Bay fish were estimated to be 13.1 and 6.6% of their dry body weight, respectively. The fry consumed similar prey items in both bays, but in differing proportions. Harpacticoid copepods, copepod nauplii, and barnacle larvae comprised numerically 93.1 and 86.2% of the diets of Departure Bay and Hammond Bay fish, respectively. About 38% of the diet of Departure Bay fish and 51% of the diet of Hammond Bay fish comprised epibenthic prey, mainly harpacticoid copepods. The data provide additional support for the importance of the detritus-microbe-consumer type food chain supporting the production of pink salmon during their early period of marine residency.Key words: pink salmon, feeding behavior, daily rhythm, diet, ration, British Columbia
Effect of Boron on Primary Production of Nanoplankton
Authors: Rao D. V. Subba
Published: November 2009

Addition of boron (30 mg L−1) to 20-μm fractions (nanoplankton) of phytoplankton collected from Bedford Basin had a significant effect on primary production. During November through May when a high level of nitrates, phosphates, and silicates and low temperature were prevailing, consistent stimulation (up to a maximum of 168%) of primary production (mg C m3 h−1) and carbon assimilation rates (mg C mg Chl a−1 h−1) were observed in the presence of boron, while during June–October when the nutrients were low and temperature was high, photosynthesis was inhibited (to a maximum of 62%). Similar treatment with boron inhibited photosynthesis in 5-d-old unialgal cultures but enhanced photosynthesis in 14-d-old cultures of certain species, showing that the effects of boron could be species specific. It appears that boron, under conditions of boron excess, could alleviate nutrient deficiency in some phytoplankters and might cause temporal variations of phytoplankton composition in coastal waters.Key words: boron pollution, primary production, nanoplankton, algal cultures
Environmental and Genetic Contributions to Morphological Differentiation in Ciscoes (Coregoninae) of the Great Lakes
Authors: Todd Thomas N. , Smith Gerald R. , Cable Louella E.
Published: November 2009

Laboratory-produced progeny of Coregonus alpenae, C. zenithicus, C. hoyi, and C. kiyi and their wild parents were used to examine the contributions of genotype and environment to morphology. Morphological differences between parents and offspring were generally greater than those between species, indicating strong environmental effects. The phenotypic effects on most characters can probably be attributed to different developmental temperatures and perhaps to stresses in the hatchery not encountered in the Great Lakes. Genetic differences were inferred from morphological differences between offspring of different species raised under identical conditions. Genetic differences were demonstrated between C. hoyi and C. kiyi but not between C. alpenae and C. zenithicus which suggested that our samples of C. alpenae and C. zenithicus represented only a single species. The presence of unique stocks of coregonines in the Great Lakes, as well as of several species, suggests that management strategies should focus on both levels of diversity.Key words: Salmonidae, Coregoninae, Coregonus, morphology, Great Lakes, development, stocks
Pathways and Mechanisms for Removal of Dissolved Organic Carbon from Leaf Leachate in Streams
Authors: Dahm Clifford N.
Published: November 2009

Removal of dissolved organic carbon (DOC) from water resulting from adsorption and microbial uptake was examined to determine the importance of biotic and abiotic pathways. Physical–chemical adsorption to components of the stream sediment or water and biotic assimilation associated with the microbial population was determined in recirculating chambers utilizing leachate from alder (Alnus rubra). Adsorptive mechanisms were further separated into interactions involving (1) specific clay minerals, (2) amorphous solid phases of hydrous aluminum and iron oxides, and (3) fine particulate organic matter. Physical–chemical adsorptive mechanisms for alder leachate removal exhibited rapid kinetic equilibration between the DOC and solid phases, but only a specific fraction of the DOC, likely containing certain chemical functional groups, was adsorbed. The amorphous aluminum and iron oxides possessed a much higher potential capacity than the clay minerals or fine particulate organics for DOC adsorption. Microbial uptake of DOC from the alder leachate was kinetically slower than adsorptive uptake. However, microbial activity was overall much more effective in the removal and degradation of the total DOC pool leached from alder leaves. Over a 48-h period, 97% of added 14C labeled leachate was removed from solution by adsorption (~ 20%) and microbial utilization (~ 77%). The rate of microbial uptake was 45 μg C/g sediment C∙h−1 or 14 mg C∙m−2∙h−1.
Temperature-Dependent Growth and Production by a Marine Copepod
Authors: McLaren I. A. , Corkett C. J.
Published: November 2009

Highly synchronous cohorts of the copepod Eurytemora herdmani at a station near Halifax, Nova Scotia, were followed in samples taken during late July and early August, 1980. Individuals from the same population were reared in the laboratory from copepodite I (CI) to adult in conditions of food satiation. Development times and adult body sizes in nature were about the same as predicted for comparable temperatures in the laboratory. Weight increments between CI and adult male in samples from nature were exponential. Females became heavier, because of eggs, after CIII, but developed more slowly, so that their specific growth rates were about the same as for males. Production estimated from weights and stage increments in successive samples (cohort method) was adequately predicted from biomasses in samples and temperature-dependent development times from the laboratory. Production of egg matter by adult females was also adequately predicted by temperature-dependent growth rates of younger stages. These "rules" of development, growth, and production need wider empirical testing and theoretical justification.Key words: Copepoda, temperature, life cycles, development, growth, production
Influence of Temperature and Light on Rates of Inorganic Nitrogen Transport by Algae in an Arctic Lake
Authors: Whalen S. C. , Alexander V.
Published: November 2009

Nitrogen-15 tracer techniques were used to assess the individual effects of temperature and light on maximum rates of dissolved inorganic nitrogen (DIN) transport by phytoplankton in an arctic lake. Transport rates of NO3−and NH4+as a function of temperature in the range 3–30 °C were adequately described by second- or third-order polynomial functions. The optimum temperature for DIN transport was greater than the ambient water temperature by as much as 13°; thus, transport at the ambient water temperature averaged only 55–60% of optimum. Mean temperature coefficients [Formula: see text] for NO3−and NH4+transport in the temperature range >0–15 °C were 2.3 ± 0.5 and 2.4 ± 0.3. The ratio of dark to light-saturated DIN transport (ρD/ρL) was used as a measure of light dependence in maximum rates of DIN transport. Values of ρD/ρL[Formula: see text] for NO3−and NH4+were 0.15 ± 0.09 and 0.41 ± 0.11, indicating a stronger light dependence for NO3−than NH4+transport. In cases where dark NO3−transport was negligible, light was treated as a substrate and the Michaelis–Menten relationship fitted to the data. The half-saturation constant for light intensity in maximum NO3−transport ranged from 7 to 29 μE∙m−2∙s−1, which was 6–31% of the photosynthetically active radiation at the lake surface.
Lethal and Sublethal Toxicity of Drilling Fluids to Larvae of the American Lobster,Homarus americanus
Authors: Derby Jennifer G. Smith , Capuzzo Judith M.
Published: November 2009

The lethal and sublethal effects of five used, whole drilling fluids on the larval stages of the American lobster (Homarus americanus) were assessed in laboratory experiments using a continuous-flow bioassay. Although the five tested drilling fluids varied markedly in their toxicity, some were highly toxic, with LC50 values as low as 74 mg/L. Sublethal exposures to drilling fluids at concentrations as low as 10–50 mg/L resulted in reduced respiration rates, reduced O:N ratios, and increased protein:lipid ratios, demonstrating a change in energetics of the larval lobsters. Growth and development of the larvae were seriously impaired by exposure to three of the five drilling fluids at concentrations of 50 and 100 mg/L. The feeding rates were also significantly reduced after a 24-h exposure to 50 mg/L drilling fluid. Exposure of larvae to barite (a major component of drilling fluids) and to a field-collected, fine-grained sediment did not result in deleterious effects. We suggest that the chemical components and not the physical properties of the drilling fluids are primarily responsible for detrimental effects. From results of the chemical analyses of the tested drilling fluids, we consider that the adverse effects of these drilling fluids cannot be attributed to any one group of chemicals. For example, diesel oil, a known toxicant, was present in the more toxic drilling fluids; however, there was no direct correlation between the toxicity of a drilling fluid and diesel oil concentration. Phenolic compounds, various metals, and other components probably also contributed to the toxicity of these drilling fluids.
Influence of Chlorine on the Susceptibility of Striped Bass (Morone saxatilis) to Vibrio anguillarum
Authors: Hetrick F. M. , Hall Jr. L W. , Wolski S. , Graves W. C. , Roberson B. S. , Burton D. T.
Published: November 2009

Exposure of striped bass (Morone saxatilis) for 96 h to sublethal concentrations of total residual chlorine (TRC) (0.05–0.23 mg/L) did not increase their susceptibility to infection with the bacterial pathogen Vibrio anguillarum. Variables examined were TRC concentrations, length of exposure to chlorine, and the order of exposure to chlorine and the pathogen. Mortalities in the groups exposed to both chlorine and pathogen were not significantly different from those seen in groups receiving the bacteria only. The LD50 of V. anguillarum for striped bass was influenced by the water temperature as well as the size and immune status of the fish.
META-STABLE BRANE CONFIGURATIONS WITH FIVE NS5-BRANES
Authors: AHN CHANGHYUN
Published: November 2009

From an [Formula: see text] supersymmetric electric gauge theory with the gauge group SU (Nc) × SU (N′c) with fundamentals for each gauge group, the bifundamentals and a symmetric flavor and a conjugate symmetric flavor for SU (Nc), we apply Seiberg dual to each gauge group independently and obtain two [Formula: see text] supersymmetric dual magnetic gauge theories with dual matters including the gauge singlets. By analyzing the F-term equations of the dual magnetic superpotentials, we describe the intersecting brane configurations of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of these gauge theories. The case where the above symmetric flavor is replaced by an antisymmetric flavor is also discussed.
PHASE STRUCTURE OF MULTIFERMION INTERACTION MODELS IN WEAKLY CURVED SPACE–TIME
Authors: HAYASHI MASAKO , INAGAKI TOMOHIRO , TAKATA HIROYUKI
Published: November 2009

The phase structure of a model with a scalar type eight-fermion interaction is investigated in weakly curved space–time. The ground state of the model is obtained by observing the minimum of the effective potential. Applying the Riemann normal coordinate expansion, we calculate an effective potential of the model in a weakly curved space–time. The result is extended to models with multifermion interactions. We numerically show the behavior of the effective potential and obtain the phase structure of the model.
High-resolution entrainment mapping of gastric pacing: a new analytical tool
Authors: O'Grady Gregory , Du Peng , Lammers Wim J. E. P. , Egbuji John U. , Mithraratne Pulasthi , Chen Jiande D. Z. , Cheng Leo K. , Windsor John A. , Pullan Andrew J.
Published: November 2009

Gastric pacing has been investigated as a potential treatment for gastroparesis. New pacing protocols are required to improve symptom and motility outcomes; however, research progress has been constrained by a limited understanding of the effects of electrical stimulation on slow-wave activity. This study introduces high-resolution (HR) “entrainment mapping” for the analysis of gastric pacing and presents four demonstrations. Gastric pacing was initiated in a porcine model (typical amplitude 4 mA, pulse width 400 ms, period 17 s). Entrainment mapping was performed using flexible multielectrode arrays (≤192 electrodes; 92 cm2) and was analyzed using novel software methods. In the first demonstration, entrainment onset was quantified over successive waves in spatiotemporal detail. In the second demonstration, slow-wave velocity was accurately determined with HR field analysis, and paced propagation was found to be anisotropic (longitudinal 2.6 ± 1.7 vs. circumferential 4.5 ± 0.6 mm/s; P < 0.001). In the third demonstration, a dysrhythmic episode that occurred during pacing was mapped in HR, revealing an ectopic slow-wave focus and uncoupled propagations. In the fourth demonstration, differences were observed between paced and native slow-wave amplitudes (0.24 ± 0.08 vs. 0.38 ± 0.14 mV; P < 0.001), velocities (6.2 ± 2.8 vs. 11.5 ± 4.7 mm/s; P < 0.001), and activated areas (20.6 ± 1.9 vs. 32.8 ± 2.6 cm2; P < 0.001). Entrainment mapping enables an accurate quantification of the effects of gastric pacing on slow-wave activity, offering an improved method to assess whether pacing protocols are likely to achieve physiologically and clinically useful outcomes.
Differential protein abundance and function of UT-B urea transporters in human colon
Authors: Collins D. , Winter D. C. , Hogan A. M. , Schirmer L. , Baird A. W. , Stewart G. S.
Published: November 2009

Facilitative UT-B urea transporters enable the passage of urea across cell membranes. Gastrointestinal urea transporters are thought to play a significant role in the urea nitrogen salvaging process that occurs between mammalian hosts and their gut bacteria. This study investigated the expression of UT-B urea transporters in different segments of human colon. Immunoblot analysis showed that human colon expressed a 35-kDa glycosylated UT-B protein in the colonic mucosa. The 35-kDa UT-B transporter was predominantly located in plasma membrane-enriched samples ( P < 0.001; n = 6), and its expression was greater in the ascending colon compared with the descending colon ( P < 0.01; n = 3). At the cellular level, UT-B transporters were located throughout colonocytes situated in the upper portion of the colonic crypts. Bidirectional trans-epithelial urea transport was significantly greater in the ascending colon than the descending colon ( P < 0.05; n = 6). In addition, the facilitative urea transporter inhibitor 1,3,dimethylurea significantly reduced urea transport in the ascending colon ( P < 0.05; n = 6) but had no effect in the descending colon (NS; n = 6). These results illustrate differential protein abundance of functional UT-B protein in different sections of the human colon, strongly correlating to regions that contain the largest populations of intestinal bacteria. This study suggests an important role for UT-B urea transporters in maintaining the symbiotic relationship between humans and their gut bacteria.
H2S ameliorates oxidative and proteolytic stresses and protects the heart against adverse remodeling in chronic heart failure
Authors: Mishra Paras K. , Tyagi Neetu , Sen Utpal , Givvimani Srikanth , Tyagi Suresh C.
Published: November 2009

Reactive oxygen and nitrogen species (ROS and RNS, respectively) generate nitrotyrosine and activate latent resident myocardial matrix metalloproteinases (MMPs). Although in chronic heart failure (CHF) there is robust increase in ROS, RNS, and MMP activation, recent data suggest that hydrogen sulfide (H2S, a strong antioxidant gas) is cardioprotective. However, the role of H2S in mitigating oxidative and proteolytic stresses in cardiac remodeling/apoptosis in CHF was unclear. To test the hypothesis that H2S ameliorated cardiac apoptosis and fibrosis by decreasing oxidative and proteolytic stresses, arteriovenous fistula (AVF) was created in wild-type (C57BL/6J) mice. The hearts were analyzed at 0, 2, and 6 wk after AVF. To reverse the remodeling, AVF mice were treated with NaHS (an H2S donor, 30 μmol/l in drinking water) at 8 and 10 wk. The levels of MMPs were measured by gelatin-gel zymography. The levels of nitrotyrosine, tissue inhibitors of metalloproteinase (TIMPs), β1-integrin, and a disintegrin and metalloproteinase-12 (ADAM-12) were analyzed by Western blots. The levels of pericapillary and interstitial fibrosis were identified by Masson trichrome stains. The levels of apoptosis were measured by identifying the TdT-mediated dUTP nick end labeling (TUNEL)-positive cells and caspase-3 levels. The results suggested robust nitrotyrosine and MMP activation at 2 and 6 wk of AVF. The treatment with H2S donor mitigated nitrotyrosine generation and MMP activation (i.e., oxidative and proteolytic stresses). The levels of TIMP-1 and TIMP-3 were increased and TIMP-4 decreased in AVF hearts. The treatment with H2S donor reversed this change in TIMPs levels. The levels of ADAM-12, apoptosis, and fibrosis were robust and integrin were decreased in AVF hearts. The treatment with H2S donor attenuated the fibrosis, apoptosis, and decrease in integrin.
State-dependent vs. central motor effects of ethanol on breathing
Authors: Vecchio Laura M. , Grace Kevin p. , Liu Hattie , Harding Stephen , Lê Anh D. , Horner Richard L.
Published: November 2009

Ethanol, one of the most widely used drugs in Western society, worsens obstructive sleep apnea in humans. No studies, however, have distinguished between two primary mechanisms that could mediate suppression of genioglossus (GG) activity with ethanol. We test the hypothesis that ethanol suppresses GG activity by effects at the hypoglossal motor pool and/or by state-dependent regulation of motor activity via independent influences on sleep/arousal processes. Intraperitoneal injections of ethanol (1.25 g/kg, n = 6 rats) resulted in maximum blood levels of 125.5 ± 15.8 mg/dl, i.e., physiologically relevant levels for producing behavioral impairment in rats and humans. Ethanol decreased wakefulness, reduced sleep latency, and increased non-rapid eye movement sleep ( P < 0.001, n = 10 rats) and significantly reduced postural muscle tone and electroencephalogram frequencies, consistent with sedation. Ethanol also caused a state-dependent (wakefulness only) decrease in respiratory-related GG activity ( P = 0.018) but did not affect diaphragm amplitude or rate, with the magnitude of GG decrease related to baseline activity ( P < 0.0002). Ethanol did not alter GG activity when applied to the hypoglossal motor pool (0.025–1 M, n = 16 isoflurane-anesthetized rats). In conclusion, ethanol promoted sleep and altered electroencephalogram and postural motor activities, indicative of sedation. The lack of effect on GG with ethanol at the hypoglossal motor pool indicates that the GG and postural motor suppression following systemic administration was mediated via effects on state-dependent/arousal-related processes. These data show that ethanol can suppress GG by primary influences on state-dependent aspects of central nervous system function independent of effects on the respiratory network per se, a distinction that has not previously been identified experimentally.
Global Behavior of Four Competitive Rational Systems ofDifference Equations in the Plane
Authors: Garić-Demirović M. , Kulenović M. R. S. , Nurkanović M.
Published: November 2009

We investigate the global dynamics of solutions of four distinct competitive rational
systems of difference equations in the plane. We show that the basins of attractions of
different locally asymptotically stable equilibrium points are separated by the global stable
manifolds of either saddle points or nonhyperbolic equilibrium points. Our results give
complete answer to Open Problem 2 posed recently by Camouzis et al. (2009).
Absence of Myeloid COX-2 Attenuates Acute Inflammation but Does Not Influence Development of Atherosclerosis in Apolipoprotein E Null Mice
Authors: Narasimha Ajay J. , Watanabe Junji , Ishikawa Tomo-o , Priceman Saul J. , Wu Lily , Herschman Harvey R. , Reddy Srinivasa T.
Published: November 2009

Objective—

The role of myeloid cell cyclooxygenase-2 (COX-2) in the progression of atherosclerosis has not been clearly defined.

Methods and Results—

We investigated the role of COX-2 expressed in the myeloid lineage in the development of atherosclerosis using a myeloid-specific COX-2
−/−
(COX-2
−M/−M
) mouse on a hyperlipidemic apolipoprotein (apo) E
−/−
background (COX-2
−M/−M
/apoE
−/−
). Myeloid COX-2 depletion resulted in significant attenuation of acute inflammation corresponding with decreased PGE
2
levels in an air pouch model. COX-2 depletion in myeloid cells did not influence development of atherosclerosis in COX-2
−M/−M
/apoE
−/−
when compared to apoE
−/−
littermates fed either chow or western diets. The unanticipated lack of contribution of myeloid COX-2 to the development atherosclerosis is not attributable to altered maintenance, differentiation, or mobilization of myeloid and lymphoid populations. Moreover, myeloid COX-2 depletion resulted in unaltered serum prostanoid levels and cellular composition of atherosclerotic lesions of COX-2
−M/−M
/apoE
−/−
mice.

Conclusions—

Our results suggest that COX-2 expression in myeloid cells, including macrophages, does not influence the development of atherosclerosis in mice.
Arrestin Orchestrates Crosstalk Between G Protein-Coupled Receptors to Modulate the Spatiotemporal Activation of ERK MAPK
Authors: Cervantes David , Crosby Catherine , Xiang Yang
Published: November 2009

Rationale:G protein-coupled receptors (GPCRs) respond to diversified extracellular stimuli to modulate cellular function. Despite extensive studies investigating the regulation of single GPCR signaling cascades, the effects of concomitant GPCR activation on downstream signaling and cellular function remain unclear.

Objective:We aimed to characterize the cellular mechanism by which GPCR crosstalk regulates mitogen-activated protein kinase (MAPK) activation.

Methods and Results:Adrenergic receptors on cardiac fibroblasts were manipulated to examine the role of arrestin in the spatiotemporal regulation of extracellular signal-regulated kinase (ERK)1/2 MAPK signaling. We show a general mechanism in which arrestin activation by one GPCR is capable of regulating signaling originating from another GPCR. Activation of Gq coupled-receptor signaling leads to prolonged ERK1/2 MAPK phosphorylation, nuclear accumulation, and cellular proliferation. Interestingly, coactivation of these receptors with the β-adrenergic receptors induced transient ERK signaling localized within the cytosol, which attenuated cell proliferation. Further studies revealed that recruitment of arrestin3 to the β2-adrenergic receptor orchestrates the sequestration of Gq-coupled receptor-induced ERK to the cytosol through direct binding of ERK to arrestin.

Conclusions:This is the first evidence showing that arrestin3 acts as a coordinator to integrate signals from multiple GPCRs. Our studies not only provide a novel mechanism explaining the integration of mitogenic signaling elicited by different GPCRs, but also underscore the critical role of signaling crosstalk among GPCRs in vivo.
Relationship Between White-Matter Hyperintensities and Hematoma Volume and Growth in Patients With Intracerebral Hemorrhage
Authors: Lou Min , Al-Hazzani Adel , Goddeau Richard P. , Novak Vera , Selim Magdy
Published: November 2009

Background and Purpose—

The presence of white-matter hyperintensities (WMHs) has been linked to intracerebral hemorrhage (ICH). We sought to determine whether the severity of WMHs influences hematoma growth and ICH volume.

Methods—

We retrospectively reviewed prospectively collected clinical, laboratory, and radiologic data from 79 consecutive ICH patients who had brain magnetic resonance imaging performed within 72 hours of ICH symptom onset. We assessed the severity of WMHs on magnetic resonance imaging on the modified Scheltens scale and performed logistic-regression analysis to examine the association between WMHs and ICH volume. We also examined the association between WMH score and hematoma growth in a subset of 34 patients who had a baseline computed tomography scan within 12 hours of ICH onset and a follow-up scan within 72 hours.

Results—

The ICH volume at 37.6±22.3 hours from ICH onset was 2-fold higher in patients with a high WMH score (≥14) than in those with a lower score. A high WMH score was independently associated with a larger ICH volume (odds ratio=1.152; 95% CI, 1.035 to 1.282;
P
=0.01). There was a trend for an association between WMH score and ICH volume growth (odds ratio=1.286; 95% CI, 0.978 to 1.692;
P
=0.062).

Conclusion—

Severe WMHs are associated with larger ICH volumes and, to a lesser extent, with hematoma growth. Our findings suggest that WMHs may provide important prognostic information on patients with ICH and may have implications for treatment stratification. These findings require prospective validation, and the links between WMHs and ICH growth require further investigations.
Ebbinghaus Revisited: Influences of the BDNF Val66Met Polymorphism on Backward Serial Recall Are Modulated by Human Aging
Authors: Li Shu-Chen , Chicherio Christian , Nyberg Lars , von Oertzen Timo , Nagel Irene E. , Papenberg Goran , Sander Thomas , Heekeren Hauke R. , Lindenberger Ulman , Bäckman Lars
Published: November 2009

The brain-derived neurotrophic factor (BDNF) plays an important role in activity-dependent synaptic plasticity, which underlies learning and memory. In a sample of 948 younger and older adults, we investigated whether a common Val66Met missense polymorphism (rs6265) in the BDNF gene affects the serial position curve—a fundamental phenomenon of associative memory identified by Hermann Ebbinghaus more than a century ago. We found a BDNF polymorphism effect for backward recall in older adults only, with Met-allele carriers (i.e., individuals with reduced BDNF signaling) recalling fewer items than Val homozygotes. This effect was specific to the primacy and middle portions of the serial position curve, where intralist interference and associative demands are especially high. The poorer performance of older Met-allele carriers reflected transposition errors, whereas no genetic effect was found for omissions. These findings indicate that effects of the BDNF polymorphism on episodic memory are most likely to be observed when the associative and executive demands are high. Furthermore, the findings are in line with the hypothesis that the magnitude of genetic effects on cognition is greater when brain resources are reduced, as is the case in old age.
Neural Mechanisms of Context Effects on Face Recognition: Automatic Binding and Context Shift Decrements
Authors: Hayes Scott M. , Baena Elsa , Truong Trong-Kha , Cabeza Roberto
Published: November 2009

Although people do not normally try to remember associations between faces and physical contexts, these associations are established automatically, as indicated by the difficulty of recognizing familiar faces in different contexts (“butcher-on-the-bus” phenomenon). The present fMRI study investigated the automatic binding of faces and scenes. In the face–face (F–F) condition, faces were presented alone during both encoding and retrieval, whereas in the face/scene–face (FS–F) condition, they were presented overlaid on scenes during encoding but alone during retrieval (context change). Although participants were instructed to focus only on the faces during both encoding and retrieval, recognition performance was worse in the FS–F than in the F–F condition (“context shift decrement” [CSD]), confirming automatic face–scene binding during encoding. This binding was mediated by the hippocampus as indicated by greater subsequent memory effects (remembered > forgotten) in this region for the FS–F than the F–F condition. Scene memory was mediated by right parahippocampal cortex, which was reactivated during successful retrieval when the faces were associated with a scene during encoding (FS–F condition). Analyses using the CSD as a regressor yielded a clear hemispheric asymmetry in medial temporal lobe activity during encoding: Left hippocampal and parahippocampal activity was associated with a smaller CSD, indicating more flexible memory representations immune to context changes, whereas right hippocampal/rhinal activity was associated with a larger CSD, indicating less flexible representations sensitive to context change. Taken together, the results clarify the neural mechanisms of context effects on face recognition.
Memory Capacities for Synaptic and Structural Plasticity
Authors: Knoblauch Andreas , Palm Günther , Sommer Friedrich T.
Published: November 2009

Neural associative networks with plastic synapses have been proposed as computational models of brain functions and also for applications such as pattern recognition and information retrieval. To guide biological models and optimize technical applications, several definitions of memory capacity have been used to measure the efficiency of associative memory. Here we explain why the currently used performance measures bias the comparison between models and cannot serve as a theoretical benchmark. We introduce fair measures for information-theoretic capacity in associative memory that also provide a theoretical benchmark.

In neural networks, two types of manipulating synapses can be discerned: synaptic plasticity, the change in strength of existing synapses, and structural plasticity, the creation and pruning of synapses. One of the new types of memory capacity we introduce permits quantifying how structural plasticity can increase the network efficiency by compressing the network structure, for example, by pruning unused synapses. Specifically, we analyze operating regimes in the Willshaw model in which structural plasticity can compress the network structure and push performance to the theoretical benchmark. The amount C of information stored in each synapse can scale with the logarithm of the network size rather than being constant, as in classical Willshaw and Hopfield nets (⩽ ln 2 ≈ 0.7). Further, the review contains novel technical material: a capacity analysis of the Willshaw model that rigorously controls for the level of retrieval quality, an analysis for memories with a nonconstant number of active units (where C ⩽ 1/eln 2 ≈ 0.53), and the analysis of the computational complexity of associative memories with and without network compression.
Coronary Intimal Thickening in Newborn Babies and ≤1-Year-Old Infants
Authors: Milei José , Grana Daniel R. , Navari Carlos , Azzato Francisco , Guerri-Guttenberg Roberto A. , Ambrosio Giuseppe
Published: November 2009

We performed a morphological characterization of intimal thickenings in coronary arteries in the very early stages of life to obtain insights into initial coronary atherogenesis. We examined specimens from 67 infants who had died of noncardiac causes within their first year of life. Serially cut sections were stained with hematoxylin-eosin, Azan, Alcian blue, acetic orceine, and immunotypified for CD68, CD34, and α-smooth muscle (SM) actin. Substantial changes were detected in about 1 of 3 participants. Alterations ranged from focal areas with mild myointimal thickening to diffuse moderate thickening. In those lesions, smooth muscle cells (SMCs) showed loss of polarity, infiltrating the subendothelium, mostly with rupture of the internal elastic lamina and without neoangiogenesis. Morphometrically, in musculoelastic intimal thickenings, neointimal thickness averaged 58.3 ± 17.8 µm, affecting 46% of the internal elastic membrane perimeter; lumen stenosis averaged 13.7% ± 5.0%. These lesions can be present very early in life and SMCs seem to play an essential role.
L1-Spanish Speakers’ Acquisition of the English /i/—/ / Contrast II: Perception of Vowel Inherent Spectral Change1
Authors: Morrison Geoffrey Stewart
Published: November 2009

L1-Spanish learners of English have been reported to distinguish English /i/ and / / on the basis of duration cues, whereas L1-English listeners primarily use spectral cues. Morrison (2008a) hypothesized that duration-based perception is a secondary developmental stage that emerges from an initial stage of multidimensional-category-goodness assimilation of tokens of English /i/ and / / to Spanish /i/, with English vowel tokens perceived to be good examples of Spanish /i/ labeled as English / / and poor examples labeled as English /i/.
How Authoritarian Rule Works
Authors: O'Brien Kevin J.
Published: November 2009

Common features of the articles by Xueguang Zhou and Jiang Shigong include attention to governance rather than reform or regime change, to informal as well as formal rules, and to practice over texts. The articles differ mainly in their level of abstraction and the reach of their findings. But even here, Zhou’s “organizational practices” are essentially micro-level variants of the broader, constitutional principles that Jiang explores. Both authors make a persuasive case that there are abiding rules that pattern behavior between Chinese political elites, though what these rules are, and what distinguishes constitutional principles from other institutions (and temporary political compromises), await further study.