bluuebunny/crossref_metadata_2025 huggingface dataset:
METRIC CONSIDERATIONS CONCERNING THE MIXED LITTLEWOOD CONJECTURE
Authors: BUGEAUD YANN , HAYNES ALAN , VELANI SANJU
Published: March 2011

The main goal of this paper is to develop a metrical theory of Diophantine approximation within the framework of the de Mathan–Teulié Conjecture — also known as the "Mixed Littlewood Conjecture". Let p be a prime. A consequence of our main result is that, for almost every real number α, [Formula: see text]
ON A THEOREM OF GARZA REGARDING ALGEBRAIC NUMBERS WITH REAL CONJUGATES
Authors: HÖHN GERALD
Published: March 2011

We give a new proof of a theorem on the height of algebraic numbers with real conjugates.
PLONGEMENTS LOCAUX ET EXTENSIONS DE CORPS DE NOMBRES
Authors: MAIRE CHRISTIAN
Published: March 2011

Dans ce travail, nous nous intéressons au plongement [Formula: see text] des T-unités d'un corps de nombres K dans une partie de ses complétés p-adiques construite sur l'ensemble S. Nous montrons que l'injectivité de [Formula: see text] permet d'obtenir des informations sur la structure du groupe de Galois de certaines extensions de K où la ramification est liée à S et la décomposition à T. Nous étudions également le comportement asymptotique du noyau de [Formula: see text] le long d'une extension p-adique analytique sans p-torsion.

In this article, we are interested in the embedding [Formula: see text] of the T-units of a number field K in some part of its p-adic completions at S. We show that the injectivity of [Formula: see text] allows us to obtain some information on the structure of the Galois group of some extensions of K where the ramification is attached at S and the decomposition at T. Moreover, we study the asymptotic behavior of the kernel [Formula: see text] along a p-adic analytic extension.
ON INTERPOLATION FUNCTIONS FOR GENERALIZED Li COEFFICIENTS IN THE SELBERG CLASS
Authors: ODŽAK ALMASA , SMAJLOVIĆ LEJLA
Published: March 2011

We prove that there exists an entire complex function of order one and finite exponential type that interpolates the Li coefficients λF(n) attached to a function F in the class [Formula: see text] that contains both the Selberg class of functions and (unconditionally) the class of all automorphic L-functions attached to irreducible, cuspidal, unitary representations of GL n(ℚ). We also prove that the interpolation function is (essentially) unique, under generalized Riemann hypothesis. Furthermore, we obtain entire functions of order one and finite exponential type that interpolate both archimedean and non-archimedean contribution to λF(n) and show that those functions can be interpreted as zeta functions built, respectively, over trivial zeros and all zeros of a function [Formula: see text].
ASYMPTOTIC BEHAVIOR OF THE SMALLEST EIGENVALUE OF MATRICES ASSOCIATED WITH COMPLETELY EVEN FUNCTIONS (mod r)
Authors: HONG SHAOFANG , LOEWY RAPHAEL
Published: March 2011

In this paper, we present systematically analysis on the smallest eigenvalue of matrices associated with completely even functions ( mod r). We obtain several theorems on the asymptotic behavior of the smallest eigenvalue of matrices associated with completely even functions ( mod r). In particular, we get information on the asymptotic behavior of the smallest eigenvalue of the famous Smith matrices. Finally some examples are given to demonstrate the main results.
ON SOME NEW CONGRUENCES FOR BINOMIAL COEFFICIENTS
Authors: SUN ZHI-WEI , TAURASO ROBERTO
Published: March 2011

In this paper we establish some new congruences involving central binomial coefficients as well as Catalan numbers. Let p be a prime and let a be any positive integer. We determine [Formula: see text] for d = 0, …, pa and [Formula: see text] for δ = 0, 1. We also show that [Formula: see text] for every n = 0, 1, 2, …, where Cm is the Catalan number [Formula: see text], and [Formula: see text] is the Legendre symbol.
ON MURATA DENSITIES
Authors: BALLOT CHRISTIAN , CAR MIREILLE
Published: March 2011

In this paper, we set up an abstract theory of Murata densities, well tailored to general arithmetical semigroups. In [On certain densities of sets of primes, Proc. Japan Acad. Ser. A Math. Sci.56(7) (1980) 351–353; On some fundamental relations among certain asymptotic densities, Math. Rep. Toyama Univ.4(2) (1981) 47–61], Murata classified certain prime density functions in the case of the arithmetical semigroup of natural numbers. Here, it is shown that the same density functions will obey a very similar classification in any arithmetical semigroup whose sequence of norms satisfies certain general growth conditions. In particular, this classification holds for the set of monic polynomials in one indeterminate over a finite field, or for the set of ideals of the ring of S-integers of a global function field (S finite).
THE EXCEPTIONAL SET IN THE POLYNOMIAL GOLDBACH PROBLEM
Authors: POLLACK PAUL
Published: March 2011

For each natural number N, let R(N) denote the number of representations of N as a sum of two primes. Hardy and Littlewood proposed a plausible asymptotic formula for R(2N) and showed, under the assumption of the Riemann Hypothesis for Dirichlet L-functions, that the formula holds "on average" in a certain sense. From this they deduced (under ERH) that all but Oϵ(x1/2+ϵ) of the even natural numbers in [1, x] can be written as a sum of two primes. We generalize their results to the setting of polynomials over a finite field. Owing to Weil's Riemann Hypothesis, our results are unconditional.
S-INTEGRAL POINTS ON HYPERELLIPTIC CURVES
Authors: GALLEGOS-RUIZ HOMERO R.
Published: March 2011

Let C : Y2 = an Xn + ⋯ + a0 be a hyperelliptic curve with the ai rational integers, n ≥ 5, and the polynomial on the right irreducible. Let J be its Jacobian. Let S be a finite set of rational primes. We give a completely explicit upper bound for the size of the S-integral points on the model C, provided we know at least one rational point on C and a Mordell–Weil basis for J(ℚ). We use a refinement of the Mordell–Weil sieve which, combined with the upper bound, is capable of determining all the S-integral points. The method is illustrated by determining the S-integral points on the genus 2 hyperelliptic model Y2 - Y = X5 - X for the set S of the first 22 primes.
A REFINED MODULAR APPROACH TO THE DIOPHANTINE EQUATION x2 + y2n = z3
Authors: DAHMEN SANDER R.
Published: March 2011

Let n be a positive integer and consider the Diophantine equation of generalized Fermat type x2 + y2n = z3 in nonzero coprime integer unknowns x,y,z. Using methods of modular forms and Galois representations for approaching Diophantine equations, we show that for n ∈ {5,31} there are no solutions to this equation. Combining this with previously known results, this allows a complete description of all solutions to the Diophantine equation above for n ≤ 107. Finally, we show that there are also no solutions for n ≡ -1 (mod 6).
TERAI'S CONJECTURE ON EXPONENTIAL DIOPHANTINE EQUATIONS
Authors: MIYAZAKI TAKAFUMI
Published: March 2011

Let a, b, c be relatively prime positive integers such that ap + bq = cr with fixed integers p, q, r ≥ 2. Terai conjectured that the equation ax + by = cz has no positive integral solutions other than (x, y, z) = (p, q, r) except for specific cases. Most known results on this conjecture concern the case where p = q = 2 and either r = 2 or odd r ≥3. In this paper, we consider the case where p = q = 2 and r > 2 is even, and partially verify Terai's conjecture.
COMMON DIVISORS OF VALUES OF POLYNOMIALS AND COMMON FACTORS OF INDICES IN A NUMBER FIELD
Authors: AYAD MOHAMED , KIHEL OMAR
Published: March 2011

Let K be a number field of degree n over ℚ, Â be the set of integers of K that are primitive over ℚ and let I(K) be its index. The prime factors of I(K) are called common factors of indices or inessential discriminant divisors. We show that these primes divide another index i(K) previously defined by Gunji and McQuillan as i(K) = lcm θ∈Âi(θ), where i(θ) = gcd x∈ℤFθ(x) and Fθ(x) is the characteristic polynomial of θ over ℚ. It is shown that there exists θ ∈ Â such that i(K) = i(θ) and an algorithm is given for the computation of such an integer. For any prime p|i(K), an integer ρK(p) defined as the number of [Formula: see text] such that p|i(θ) is investigated. It is shown that this integer determines in some cases the splitting type of p in K. Some open questions related to I(K), i(K) and ρK(p) are stated.
ROOTS OF POLYNOMIALS WITH DOMINANT TERM
Authors: DUBICKAS ARTŪRAS
Published: March 2011

We characterize all algebraic numbers which are roots of integer polynomials with a coefficient whose modulus is greater than or equal to the sum of moduli of all the remaining coefficients. It turns out that these numbers are zero, roots of unity and those algebraic numbers β whose conjugates over ℚ (including β itself) do not lie on the circle |z| = 1. We also describe all algebraic integers with norm B which are roots of an integer polynomial with constant coefficient B and the sum of moduli of all other coefficients at most |B|. In contrast to the above, the set of such algebraic integers is "quite small". These results are motivated by a recent paper of Frougny and Steiner on the so-called minimal weight β-expansions and are also related to some work on canonical number systems and tilings.
SOME FOURTH-ORDER LINEAR DIVISIBILITY SEQUENCES
Authors: WILLIAMS H. C. , GUY R. K.
Published: March 2011

We extend the Lucas–Lehmer theory for second-order divisibility sequences to a large class of fourth-order sequences, with appropriate laws of apparition and of repetition. Examples are provided by the numbers of perfect matchings, or of spanning trees, in families of graphs, and by the numbers of points on elliptic curves over finite fields. Whether there are fourth-order divisibility sequences not covered by our theory is an open question.
DENSITY OF TWO SQUARES OF PRIMES AND POWERS OF 2
Authors: LIU ZHIXIN , LÜ GUANGSHI
Published: March 2011

As the generalization of the problem of Romanoff, we establish that a positive proportion of integers can be written as the sum of two squares of primes and two powers of 2. We also prove that every large even integer can be written as the sum of two primes and 12 powers of 2.
A BÖCHERER-TYPE CONJECTURE FOR PARAMODULAR FORMS
Authors: RYAN NATHAN C. , TORNARÍA GONZALO
Published: March 2011

In the 1980s Böcherer formulated a conjecture relating the central value of the quadratic twists of the spinor L-function attached to a Siegel modular form F to the coefficients of F. He proved the conjecture when F is a Saito–Kurokawa lift. Later Kohnen and Kuß gave numerical evidence for the conjecture in the case when F is a rational eigenform that is not a Saito–Kurokawa lift. In this paper we develop a conjecture relating the central value of the quadratic twists of the spinor L-function attached to a paramodular form and the coefficients of the form. We prove the conjecture in the case when the form is a Gritsenko lift and provide numerical evidence when it is not a lift.
AN ADDITIVE PROBLEM INVOLVING PIATETSKI-SHAPIRO PRIMES
Authors: WANG XINNA , CAI YINGCHUN
Published: March 2011

Let Pr denote an almost-prime with at most r prime factors, counted according to multiplicity. In this paper it is proved that there exist infinitely many primes of the form p = [nc] such that p + 2 = Pr, where r is the least positive integer satisfying certain inequalities. In particular for [Formula: see text] we have r = 5. This result constitutes an improvement upon that of T. P. Peneva.
EQUIDISTRIBUTION OF ALGEBRAIC NUMBERS OF NORM ONE IN QUADRATIC NUMBER FIELDS
Authors: PETERSEN KATHLEEN L. , SINCLAIR CHRISTOPHER D.
Published: March 2011

Given a fixed quadratic extension K of ℚ, we consider the distribution of elements in K of norm one (denoted [Formula: see text]). When K is an imaginary quadratic extension, [Formula: see text] is naturally embedded in the unit circle in ℂ and we show that it is equidistributed with respect to inclusion as ordered by the absolute Weil height. By Hilbert's Theorem 90, an element in [Formula: see text] can be written as [Formula: see text] for some [Formula: see text], which yields another ordering of [Formula: see text] given by the minimal norm of the associated algebraic integers. When K is imaginary we also show that [Formula: see text] is equidistributed in the unit circle under this norm ordering. When K is a real quadratic extension, we show that [Formula: see text] is equidistributed with respect to norm, under the map β ↦ log |β|( mod log |ϵ2|) where ϵ is a fundamental unit of [Formula: see text].
A ZERO-FREE REGION FOR HYPERGEOMETRIC ZETA FUNCTIONS
Authors: HASSEN ABDUL , NGUYEN HIEU D.
Published: March 2011

This paper investigates the location of "trivial" zeros of some hypergeometric zeta functions. Analogous to Riemann's zeta function, we demonstrate that they possess a zero-free region on a left-half complex plane, except for infinitely many zeros regularly spaced on the negative real axis.
NON-ABELIAN CONGRUENCES BETWEEN SPECIAL VALUES OF L-FUNCTIONS OF ELLIPTIC CURVES: THE CM CASE
Authors: BOUGANIS THANASIS
Published: March 2011

In this work we prove congruences between special values of L-functions of elliptic curves with CM that seem to play a central role in the analytic side of the non-commutative Iwasawa theory. These congruences are the analog for elliptic curves with CM of those proved by Kato, Ritter and Weiss for the Tate motive. The proof is based on the fact that the critical values of elliptic curves with CM, or what amounts to the same, the critical values of Grössencharacters, can be expressed as values of Hilbert–Eisenstein series at CM points. We believe that our strategy can be generalized to provide congruences for a large class of L-values.
JUMPING CHAMPIONS AND GAPS BETWEEN CONSECUTIVE PRIMES
Authors: GOLDSTON D. A. , LEDOAN A. H.
Published: March 2011

The most common difference that occurs among the consecutive primes less than or equal to x is called a jumping champion. Occasionally there are ties. Therefore there can be more than one jumping champion for a given x. In 1999 Odlyzko, Rubinstein and Wolf provided heuristic and empirical evidence in support of the conjecture that the numbers greater than 1 that are jumping champions are 4 and the primorials 2, 6, 30, 210, 2310,…. As a step toward proving this conjecture they introduced a second weaker conjecture that any fixed prime p divides all sufficiently large jumping champions. In this paper we extend a method of Erdős and Straus from 1980 to prove that the second conjecture follows directly from the prime pair conjecture of Hardy and Littlewood.
A QUANTITATIVE ASPECT OF NON-UNIQUE FACTORIZATIONS: THE NARKIEWICZ CONSTANTS
Authors: GAO WEIDONG , GEROLDINGER ALFRED , WANG QINGHONG
Published: March 2011

Let K be an algebraic number field with non-trivial class group G and let [Formula: see text] be its ring of integers. For k ∈ ℕ and some real x ≥ 1, let Fk (x) denote the number of non-zero principal ideals [Formula: see text] with norm bounded by x such that a has at most k distinct factorizations into irreducible elements. It is well known that Fk (x) behaves, for x → ∞, asymptotically like x( log x)-1+1/|G|( log log x) N k(G). We study N k (G) with new methods from Combinatorial Number Theory.
SOME CONGRUENCES DEDUCIBLE FROM RAMANUJAN'S CUBIC CONTINUED FRACTION
Authors: BARUAH NAYANDEEP DEKA , OJAH KANAN KUMARI
Published: March 2011

We present some interesting Ramanujan-type congruences for some partition functions arising from Ramanujan's cubic continued fraction. One of our results states that if p3(n) is defined by [Formula: see text], then p3(9n + 8) ≡ 0 (mod 34).
TWO IDENTITIES INVOLVING THE CUBIC PARTITION FUNCTION
Authors: XIONG XINHUA
Published: March 2011

We give a very elementary proof of an identity involving the cubic partition function and we also give an elementary proof of a new identity for the cubic partition function which is analogs to Zuckerman's identity for the ordinary partition function.
ALGEBRAIC INDEPENDENCE OF VALUES OF MODULAR FORMS
Authors: GUN SANOLI , RAM MURTY M. , RATH PURUSOTTAM
Published: March 2011

We investigate values of modular forms with algebraic Fourier coefficients at algebraic arguments. As a consequence, we conclude about the nature of zeros of such modular forms. In particular, the singular values of modular forms (that is, values at CM points) are related to the recent work of Nesterenko. As an application, we deduce the transcendence of critical values of certain Hecke L-series. We also discuss how these investigations generalize to the case of quasi-modular forms with algebraic Fourier coefficients.
A p-ADIC FAMILY OF DIHEDRAL (φ, Γ)-MODULES
Authors: BERGER LAURENT
Published: March 2011

The goal of this paper is to construct explicitly a p-adic family of representations (which are dihedral representations), to construct their attached (φ, Γ)-modules by writing down explicit matrices for φ and for the action of Γ, and finally to determine which of these are trianguline.
WEBER'S CLASS NUMBER PROBLEM IN THE CYCLOTOMIC ℤ2-EXTENSION OF ℚ, III
Authors: FUKUDA TAKASHI , KOMATSU KEIICHI
Published: March 2011

Let hn denote the class number of [Formula: see text] which is a cyclic extension of degree 2n over the rational number field ℚ. There are no known examples of hn > 1. We prove that a prime number ℓ does not divide hn for all n ≥ 1 if ℓ is less than 109 or ℓ satisfies a congruence relation ℓ ≢ ± 1 (mod 32).
NONVANISHING OF THE FAMILY OF Γ1(q)-AUTOMORPHIC L-FUNCTIONS AT THE CENTRAL POINT
Authors: DJANKOVIĆ GORAN
Published: March 2011

We investigate proportion of nonvanishing central values L(f, 1/2) of L-functions associated to the basis of holomorphic modular forms of fixed weight k with respect to Γ1(q), in the limit when q → ∞ along the primes. Motivation is a contrast between Γ0(q) and Γ1(q) families in the sense of underlying harmonic analysis.
CONTINUED FRACTIONS AND JACOBI SYMBOLS
Authors: GIRSTMAIR KURT
Published: March 2011

We consider the regular continued fraction expansion of a rational number m/N, m ≥ 0, N ≥ 1, (m, N) = 1. Let s/t, (s, t) = 1, be the kth convergent of this expansion and p/q, (p, q) = 1, be the complete quotient belonging to s/t. We give some relations for Jacobi symbols, a typical example of which is [Formula: see text] for k, t, q, N odd, with a simple right-hand side depending on t, q, N (mod 4). As an application, we prove the periodicity of the Jacobi symbol [Formula: see text] for the convergents s/t of infinite purely periodic continued fractions.
COUNTING MULTISECTIONS IN CONIC BUNDLES OVER A CURVE DEFINED OVER 𝔽q
Authors: TÜRKELLI SEYFI
Published: March 2011

For a given conic bundle X over a curve C defined over 𝔽q, we count irreducible branch covers of C in X of degree d and height e ≫ 1. As a special case, we get the number of algebraic numbers of degree d and height e over the function field 𝔽q(C).
CONOYAUX DE CAPITULATION ET MODULES D'IWASAWA
Authors: PITOUN FRÉDÉRIC
Published: March 2011

Soit F un corps de nombres totalement réel et p un premier impair, on note K0 = F(ζp). Pour n ∈ ℕ, Kn désigne le n-ième étage de la ℤp-extension cyclotomique K∞/K0, An est la p-partie du groupe des classes de Kn, [Formula: see text] et N∞ est l'extension de K∞ obtenue en extrayant des racines p-primaires d'unités. Le but de cet article est de montrer que le dual de Pontryagin de la partie plus des conoyaux de capitulation [Formula: see text], sur laquelle l'action de Γ a été tordue une fois par le caractère cyclotomique et la partie moins de la ℤp-torsion du groupe de Galois Gal (N∞ ∩ L∞/K∞) sont isomorphes.

Let F be a totally real number field and p an odd prime, we note K0 = F(ζp). For an integer n, Kn is the nth floor of the ℤp-cyclotomic extension K∞/K0, An is the p-part of the class group of Kn, [Formula: see text] and N∞ is the extension of K∞ generated by p-primary roots of units. In this article, we prove that the plus part of the capitulation's cokernel [Formula: see text], on which Γ-action was twisted on time by the cyclotomic character, and the minus part of the ℤp-torsion of the Galois group Gal (N∞ ∩ L∞/K∞) is isomorphic.
Comparative physiology: a “crystal ball” for predicting consequences of global change
Authors: Somero George N.
Published: March 2011

Comparative physiology offers powerful approaches for developing causal, mechanistic explanations of shifts in biogeographic patterning occurring in concert with global change. These analyses can identify the cellular loci and intensities of stress-induced perturbation and generate predictions about ecosystem alterations in a changing world. Congeneric species adapted to different abiotic conditions offer excellent study systems for these purposes. Several findings have emerged from such comparative studies: 1) In aquatic and terrestrial habitats, the most heat-tolerant ectotherms may be most threatened by further increases in temperature, due to proximity of these species' thermal optima and tolerance limits to current maximal ambient temperatures and limited capacities for acclimatization to higher temperatures. 2) Cardiac function is a “weak link” in acute thermal tolerance. 3) Stress-induced changes in gene expression comprise a graded response involving genes linked to damage repair, lysis of irreversibly damaged molecules, and downregulation of cell proliferation. Transcriptomic and proteomic analyses provide “biomarkers” for diagnosing degrees of stress. 4) Different abiotic stresses may have synergistic or opposing effects on gene expression, a complexity needing consideration when developing integrated pictures of effects of global change. 5) Adaptation of proteins can result from one to a few amino acid substitutions, which can occur at many sites in a protein, a discovery with implications for rates of adaptive evolution. 6) Greater thermal tolerance of invasive species may favor their replacement of natives. 7) Losses of protein-coding genes and temperature-responsive gene regulatory abilities in stenothermal ectotherms of the Southern Ocean may lead to broad extinctions.
GLT-1 overexpression attenuates bladder nociception and local/cross-organ sensitization of bladder nociception
Authors: Yang M. , Roman K. , Chen D.-F. , Wang Z.-G. , Lin Y. , Stephens R. L.
Published: March 2011

Glutamatergic pathways mediate transmission of pain. Strategies to reduce glutamatergic neurotransmission may have beneficial effects to mitigate nociception. Recent work revealed that overexpression of the astrocytic glutamate transporter (GLT-1) by transgenic or pharmacologic approaches produced a diminished visceral nociceptive response to colonic distension. The purpose of this study was to determine the effect of GLT-1 overexpression on the visceromotor response to bladder distension. Increased glutamate uptake activity produced by 1-wk ceftriaxone (CTX) treatment attenuated 60–64% the visceromotor response to graded bladder distension compared with vehicle-treated mice. One-hour pretreatment with selective GLT-1 antagonist dihydrokainate reversed the blunted visceromotor response to bladder distension produced by 1-wk CTX, suggesting that GLT-1 overexpression mediated the analgesic effect of CTX. Moreover, sensitization of the visceromotor response to bladder distension produced by local bladder irritation (acrolein) was also attenuated by 1-wk CTX treatment. A model of cross-organ sensitization of bladder visceromotor response to distension was next studied to determine whether increased expression of GLT-1 can mitigate colon to bladder sensitization. Intracolonic trinitrobenzene sulfonic acid (TNBS) administered 1 h before eliciting the visceromotor response to graded bladder distension produced a 75–138% increase in visceromotor response compared with animals receiving intracolonic vehicle. In marked contrast, animals treated with 1-wk CTX + intracolonic TNBS showed no enhanced visceromotor response compared with the 1-wk vehicle + intracolonic vehicle group. The study suggests that GLT-1 overexpression attenuates the visceromotor response to bladder distension and both local irritant-induced and cross-organ-sensitized visceromotor response to bladder distension.
Proximal tubular injury and rapid formation of atubular glomeruli in mice with unilateral ureteral obstruction: a new look at an old model
Authors: Forbes Michael S. , Thornhill Barbara A. , Chevalier Robert L.
Published: March 2011

Unilateral ureteral obstruction (UUO), employed extensively as a model of progressive renal interstitial fibrosis, results in rapid parenchymal deterioration. Atubular glomeruli are formed in many renal disorders, but their identification has been limited by labor-intensive available techniques. The formation of atubular glomeruli was therefore investigated in adult male mice subjected to complete UUO under general anesthesia. In this species, the urinary pole of Bowman's capsule is normally lined by tall parietal epithelial cells similar to those of the proximal tubule, and both avidly bind Lotus tetragonolobus lectin. Following UUO, these cells became flattened, lost their affinity for Lotus lectin, and no longer generated superoxide (revealed by nitroblue tetrazolium infusion). Based on Lotus lectin staining, stereological measurements, and serial section analysis, over 80% of glomeruli underwent marked transformation after 14 days of UUO. The glomerulotubular junction became stenotic and atrophic due to cell death by apoptosis and autophagy, with concomitant remodeling of Bowman's capsule to form atubular glomeruli. In this degenerative process, transformed epithelial cells sealing the urinary pole expressed α-smooth muscle actin, vimentin, and nestin. Although atubular glomeruli remained perfused, renin immunostaining was markedly increased along afferent arterioles, and associated maculae densae disappeared. Numerous progressive kidney disorders, including diabetic nephropathy, are characterized by the formation of atubular glomeruli. The rapidity with which glomerulotubular junctions degenerate, coupled with Lotus lectin as a marker of glomerular integrity, points to new investigative uses for the model of murine UUO focusing on mechanisms of epithelial cell injury and remodeling in addition to fibrogenesis.
Thiazolidinediones inhibit MDCK cyst growth through disrupting oriented cell division and apicobasal polarity
Authors: Mao Zhiguo , Streets Andrew J. , Ong Albert C. M.
Published: March 2011

Thiazolidinediones have been reported to retard cystic disease in rodent models by uncertain mechanisms. We hypothesized that their major effect in retarding cystogenesis was through inhibiting cell proliferation or stimulating apoptosis. In the Madin-Darby canine kidney cell (MDCK) model, rosiglitazone inhibited cyst growth in a time- and dose-dependent manner and this was accompanied by a reduction in basal proliferation and an increase in apoptosis. Unexpectedly, we also observed a striking abnormality in lumen formation resulting in a characteristic multiple lumen or loss of lumen phenotype in treated cells at doses which did not inhibit cell proliferation. These changes were preceded by mislocalization of gp135 and Cdc42, misorientation of the mitotic spindle, and retardation in centrosome reorientation with later changes in primary cilia length and mislocalization of E-cadherin. Cdc42 activation was unaffected by rosiglitazone in monolayer culture but was profoundly inhibited in three-dimensional culture. MDCK cells stably expressing mutant Cdc42 showed a similar mislocalization of gp135 expression and multilumen phenotype in the absence of rosiglitazone. We conclude that rosiglitazone influences MDCK cyst growth by multiple mechanisms involving dosage-dependent effects on proliferation, spindle orientation, centrosome migration, and lumen formation. Correct spatial Cdc42 activation is critical for lumen formation, but the effect of rosiglitazone is likely to involve both Cdc42 and non-Cdc42 pathways.
N-methyl-d-aspartate receptor subunit NR3a expression and function in principal cells of the collecting duct
Authors: Sproul Adrian , Steele Stacy L. , Thai Tiffany L. , Yu ShanPing , Klein Janet D. , Sands Jeff M. , Bell P. Darwin
Published: March 2011

N-methyl-d-aspartate receptors (NMDARs) are Ca2+-permeable, ligand-gated, nonselective cation channels that function as neuronal synaptic receptors but which are also expressed in multiple peripheral tissues. Here, we show for the first time that NMDAR subunits NR3a and NR3b are highly expressed in the neonatal kidney and that there is continued expression of NR3a in the renal medulla and papilla of the adult mouse. NR3a was also expressed in mIMCD-3 cells, where it was found that hypoxia and hypertonicity upregulated NR3a expression. Using short-hairpin (sh) RNA-based knockdown, a stable inner medullary collecting duct (IMCD) cell line was established that had ∼80% decrease in NR3a. Knockdown cells exhibited an increased basal intracellular calcium concentration, reduced cell proliferation, and increased cell death. In addition, NR3a knockdown cells exhibited reduced water transport in response to the addition of vasopressin, suggesting an alteration in aquaporin-2 (AQP2) expression/function. Consistent with this notion, we demonstrate decreased surface expression of glycosylated AQP2 in IMCD cells transfected with NR3a shRNA. To determine whether this also occurred in vivo, we compared AQP2 levels in wild-type vs. in NR3a−/−mice. Total AQP2 protein levels in the outer and inner medulla were significantly reduced in knockout mice compared with control mice. Finally, NR3a−/−mice showed a significant delay in their ability to increase urine osmolality during water restriction. Thus NR3a may play a renoprotective role in collecting duct cells. Therefore, under conditions that are associated with high vasopressin levels, NR3a, by maintaining low intracellular calcium levels, protects the function of the principal cells to reabsorb water and thereby increase medullary osmolality.
Genetic loci that affect aristolochic acid-induced nephrotoxicity in the mouse
Authors: Rosenquist Thomas A.
Published: March 2011

Aristolochic acids (AA) are plant-derived nephrotoxins and carcinogens found in traditional medicines and herbal remedies. AA causes aristolochic acid nephropathy (AAN) and is a suspected environmental agent in Balkan endemic nephropathy (BEN) and its associated upper urothelial cancer. Approximately 5–10% of individuals exposed to AA develop renal insufficiency and/or cancer; thus a genetic predisposition to AA sensitivity has been proposed. The mouse is an established animal model of AAN, and inbred murine strains vary in AA sensitivity, confirming the genetic predisposition. We mapped quantitative trait loci (QTL) correlated with proximal tubule dysfunction after exposure to AA in an F2 population of mice, derived from breeding an AA-resistant strain ( C57BL/6J) and an AA-sensitive strain ( DBA/2J). A single main QTL was identified on chromosome 4 ( Aanq1); three other interacting QTLs, ( Aanq2–4) also were detected. The Aanq1 region was also detected in untreated mice, raising the possibility that preexisting differences in proximal tubule function may affect the severity of AA-elicited toxicity. This study lays the groundwork for identifying the genetic pathways contributing to AA sensitivity in the mouse and will further our understanding of human susceptibility to AA found widely in traditional medicines.
Functional selectivity in sensory-deprived cortices
Authors: Dormal Giulia , Collignon Olivier
Published: March 2011

In a recent study, Lomber, Meredith, and Kral (2010) investigated crossmodal reorganization in congenitally deaf cats. They demonstrated that specific regions of the auditory cortex are responsible for distinct supranormal visual performances following early auditory deprivation. These exciting results are considered in light of recently increasing research suggesting that crossmodal plasticity associated with early sensory deprivation follows organizational principles that maintain the functional specialization of the colonized brain regions.
GABAB receptor-mediated tonic inhibition of noradrenergic A7 neurons in the rat
Authors: Wu Yeechan , Wang Han-Ying , Lin Chia-Ching , Lu Hung-Chi , Cheng Sin-Jhong , Chen Chih-Cheng , Yang Hsiu-Wen , Min Ming-Yuan
Published: March 2011

Noradrenergic (NAergic) A7 neurons that project axonal terminals to the dorsal horn of the spinal cord to modulate nociceptive signaling are suggested to receive tonic inhibition from local GABAergic interneurons, which are under the regulation of descending analgesic pathways. In support of this argument, we presently report GABAB receptor (GABABR)-mediated tonic inhibition of NAergic A7 neurons. Bath application of baclofen induced an outward current ( IBac) in NAergic A7 neurons that was blocked by CGP 54626, a GABABR blocker. The IBac was reversed at about −99 mV, displayed inward rectification, and was blocked by Ba2+ or Tertipian-Q, showing it was mediated by G protein-activated inward-rectifying K+ (GIRK) channels. Single-cell RT-PCR results suggested that GIRK1/3 heterotetramers might dominate functional GIRK channels in NAergic A7 neurons. Under conditions in which GABAA and glycine receptors were blocked, bath application of GABA inhibited the spontaneous firing of NAergic A7 neurons in a dose-dependent manner. Interestingly, CGP 54626 application not only blocked the effect of GABA but also increased the firing rate to 126.9% of the control level, showing that GABABRs were constitutively active at an ambient GABA concentration of 2.8 μM and inhibited NAergic A7 neurons. GABABRs were also found at presynaptic excitatory and inhibitory axonal terminals in the A7 area. Pharmacological activation of these GABABRs inhibited the release of neurotransmitters. No physiological role was found for GABABRs on excitatory terminals, whereas those on the inhibitory terminals were found to exert autoregulatory control of GABA release.
Kv1.3 channels regulate synaptic transmission in the nucleus of solitary tract
Authors: Ramirez-Navarro Angelina , Glazebrook Patricia A. , Kane-Sutton Michelle , Padro Caroline , Kline David D. , Kunze Diana L.
Published: March 2011

The voltage-gated K+channel Kv1.3 has been reported to regulate transmitter release in select central and peripheral neurons. In this study, we evaluated its role at the synapse between visceral sensory afferents and secondary neurons in the nucleus of the solitary tract (NTS). We identified mRNA and protein for Kv1.3 in rat nodose ganglia using RT-PCR and Western blot analysis. In immunohistochemical experiments, anti-Kv1.3 immunoreactivity was very strong in internal organelles in the soma of nodose neurons with a weaker distribution near the plasma membrane. Anti-Kv1.3 was also identified in the axonal branches that project centrally, including their presynaptic terminals in the medial and commissural NTS. In current-clamp experiments, margatoxin (MgTx), a high-affinity blocker of Kv1.3, produced an increase in action potential duration in C-type but not A- or Ah-type neurons. To evaluate the role of Kv1.3 at the presynaptic terminal, we examined the effect of MgTx on tract evoked monosynaptic excitatory postsynaptic currents (EPSCs) in brain slices of the NTS. MgTx increased the amplitude of evoked EPSCs in a subset of neurons, with the major increase occurring during the first stimuli in a 20-Hz train. These data, together with the results from somal recordings, support the hypothesis that Kv1.3 regulates the duration of the action potential in the presynaptic terminal of C fibers, limiting transmitter release to the postsynaptic cell.
Transcranial direct current stimulation effects on I-wave activity in humans
Authors: Lang Nicolas , Nitsche Michael A. , Dileone Michele , Mazzone Paolo , De Andrés-Arés Javier , Diaz-Jara Luis , Paulus Walter , Di Lazzaro Vincenzo , Oliviero Antonio
Published: March 2011

Transcranial direct current stimulation (tDCS) of the human cerebral cortex modulates cortical excitability noninvasively in a polarity-specific manner: anodal tDCS leads to lasting facilitation and cathodal tDCS to inhibition of motor cortex excitability. To further elucidate the underlying physiological mechanisms, we recorded corticospinal volleys evoked by single-pulse transcranial magnetic stimulation of the primary motor cortex before and after a 5-min period of anodal or cathodal tDCS in eight conscious patients who had electrodes implanted in the cervical epidural space for the control of pain. The effects of anodal tDCS were evaluated in six subjects and the effects of cathodal tDCS in five subjects. Three subjects were studied with both polarities. Anodal tDCS increased the excitability of cortical circuits generating I waves in the corticospinal system, including the earliest wave (I1 wave), whereas cathodal tDCS suppressed later I waves. The motor evoked potential (MEP) amplitude changes immediately following tDCS periods were in agreement with the effects produced on intracortical circuitry. The results deliver additional evidence that tDCS changes the excitability of cortical neurons.
Involvement of TRP channels in the CO2 chemosensitivity of locus coeruleus neurons
Authors: Cui Ningren , Zhang Xiaoli , Tadepalli Jyothirmayee S. , Yu Lei , Gai Hongyu , Petit James , Pamulapati Ravi T. , Jin Xin , Jiang Chun
Published: March 2011

Catecholaminergic neurons in the locus coeruleus (LC) play a role in the ventilatory response to hypercapnia. Here, we show evidence for the involvement of transient receptor potential (TRP) channels. We found that the input resistance was reduced during an exposure to 8% CO2 in ∼35% LC neurons in mouse brain slices, accompanied by depolarization and higher firing activity. The neuronal responses suggest the opening of Na+ or nonselective cationic channels instead of the closure of K+ channels. As a major group of cationic channels, the TRP channels are expressed in the brain, some of which are activated by acidic pH. We therefore screened all representative TRP channels using the quantitative real-time PCR analysis. High levels of mRNA expression of TRPC5, TRPM2, and TRPM7 were found in the LC tissue. Of them, the TRPC5 transcript was the most abundant. The TRPC5 channel was activated by extracellular acidification when expressed in human embryonic kidney (HEK) cells. The TRPC5 currents started to be activated at pH 7.4 with pKa 6.9. The TRPC5 currents were also activated by isohydric hypercapnic and intracellular acidosis in a Ca2+-dependent manner. Consistently, the LC neurons were stimulated by both extra- and intracellular acidosis. The stimulatory effect of hypercapnia on LC neurons was eliminated by selective TRPC inhibitor SKF-96365 with and without the blockade of synaptic transmission. Single-cell PCR analysis indicated that TRPC5 mRNAs existed in the LC neurons. Thus these results strongly suggest that the TRP channels are likely to play a role in the CO2 chemosensitivity of LC neurons, especially TRPC5.
Risk sensitivity in a motor task with speed-accuracy trade-off
Authors: Nagengast Arne J. , Braun Daniel A. , Wolpert Daniel M.
Published: March 2011

When a racing driver steers a car around a sharp bend, there is a trade-off between speed and accuracy, in that high speed can lead to a skid whereas a low speed increases lap time, both of which can adversely affect the driver's payoff function. While speed-accuracy trade-offs have been studied extensively, their susceptibility to risk sensitivity is much less understood, since most theories of motor control are risk neutral with respect to payoff, i.e., they only consider mean payoffs and ignore payoff variability. Here we investigate how individual risk attitudes impact a motor task that involves such a speed-accuracy trade-off. We designed an experiment where a target had to be hit and the reward (given in points) increased as a function of both subjects' endpoint accuracy and endpoint velocity. As faster movements lead to poorer endpoint accuracy, the variance of the reward increased for higher velocities. We tested subjects on two reward conditions that had the same mean reward but differed in the variance of the reward. A risk-neutral account predicts that subjects should only maximize the mean reward and hence perform identically in the two conditions. In contrast, we found that some (risk-averse) subjects chose to move with lower velocities and other (risk-seeking) subjects with higher velocities in the condition with higher reward variance (risk). This behavior is suboptimal with regard to maximizing the mean number of points but is in accordance with a risk-sensitive account of movement selection. Our study suggests that individual risk sensitivity is an important factor in motor tasks with speed-accuracy trade-offs.
Relationship between size and latency of action potentials in human muscle sympathetic nerve activity
Authors: Salmanpour Aryan , Brown Lyndon J. , Steinback Craig D. , Usselman Charlotte W. , Goswami Ruma , Shoemaker J. Kevin
Published: March 2011

We employed a novel action potential detection and classification technique to study the relationship between the recruitment of sympathetic action potentials (i.e., neurons) and the size of integrated sympathetic bursts in human muscle sympathetic nerve activity (MSNA). Multifiber postganglionic sympathetic nerve activity from the common fibular nerve was collected using microneurography in 10 healthy subjects at rest and during activation of sympathetic outflow using lower body negative pressure (LBNP). Burst occurrence increased with LBNP. Integrated burst strength (size) varied from 0.22 ± 0.07 V at rest to 0.28 ± 0.09 V during LBNP. Sympathetic burst size (i.e., peak height) was directly related to the number of action potentials within a sympathetic burst both at baseline ( r = 0.75 ± 0.13; P < 0.001) and LBNP ( r = 0.75 ± 0.12; P < 0.001). Also, the amplitude of detected action potentials within sympathetic bursts was directly related to the increased burst size at both baseline ( r = 0.59 ± 0.16; P < 0.001) and LBNP ( r = 0.61 ± 0.12; P < 0.001). In addition, the number of detected action potentials and the number of distinct action potential clusters within a given sympathetic burst were correlated at baseline ( r = 0.7 ± 0.1; P < 0.001) and during LBNP ( r = 0.74 ± 0.03; P < 0.001). Furthermore, action potential latency (i.e., an inverse index of neural conduction velocity) was decreased as a function of action potential size at baseline and LBNP. LBNP did not change the number of action potentials and unique clusters per sympathetic burst. It was concluded that there exists a hierarchical pattern of recruitment of additional faster conducting neurons of larger amplitude as the sympathetic bursts become stronger (i.e., larger amplitude bursts). This fundamental pattern was evident at rest and was not altered by the level of baroreceptor unloading applied in this study.
Vocal babbling in songbirds requires the basal ganglia-recipient motor thalamus but not the basal ganglia
Authors: Goldberg Jesse H. , Fee Michale S.
Published: March 2011

Young songbirds produce vocal “babbling,” and the variability of their songs is thought to underlie a process of trial-and-error vocal learning. It is known that this exploratory variability requires the “cortical” component of a basal ganglia (BG) thalamocortical loop, but less understood is the role of the BG and thalamic components in this behavior. We found that large bilateral lesions to the songbird BG homolog Area X had little or no effect on song variability during vocal babbling. In contrast, lesions to the BG-recipient thalamic nucleus DLM (medial portion of the dorsolateral thalamus) largely abolished normal vocal babbling in young birds and caused a dramatic increase in song stereotypy. These findings support the idea that the motor thalamus plays a key role in the expression of exploratory juvenile behaviors during learning.
Own-species bias in the representations of monkey and human face categories in the primate temporal lobe
Authors: Sigala R. , Logothetis N. K. , Rainer G.
Published: March 2011

Face categorization is fundamental for social interactions of primates and is crucial for determining conspecific groups and mate choice. Current evidence suggests that faces are processed by a set of well-defined brain areas. What is the fine structure of this representation, and how is it affected by visual experience? Here, we investigated the neural representations of human and monkey face categories using realistic three-dimensional morphed faces that spanned the continuum between the two species. We found an “own-species” bias in the categorical representation of human and monkey faces in the monkey inferior temporal cortex at the level of single neurons as well as in the population response analyzed using a pattern classifier. For monkey and human subjects, we also found consistent psychophysical evidence indicative of an own-species bias in face perception. For both behavioural and neural data, the species boundary was shifted away from the center of the morph continuum, for each species toward their own face category. This shift may reflect visual expertise for members of one's own species and be a signature of greater brain resources assigned to the processing of privileged categories. Such boundary shifts may thus serve as sensitive and robust indicators of encoding strength for categories of interest.
Brain activity at rest: a multiscale hierarchical functional organization
Authors: Doucet Gaëlle , Naveau Mikaël , Petit Laurent , Delcroix Nicolas , Zago Laure , Crivello Fabrice , Jobard Gaël , Tzourio-Mazoyer Nathalie , Mazoyer Bernard , Mellet Emmanuel , Joliot Marc
Published: March 2011

Spontaneous brain activity was mapped with functional MRI (fMRI) in a sample of 180 subjects while in a conscious resting-state condition. With the use of independent component analysis (ICA) of each individual fMRI signal and classification of the ICA-defined components across subjects, a set of 23 resting-state networks (RNs) was identified. Functional connectivity between each pair of RNs was assessed using temporal correlation analyses in the 0.01- to 0.1-Hz frequency band, and the corresponding set of correlation coefficients was used to obtain a hierarchical clustering of the 23 RNs. At the highest hierarchical level, we found two anticorrelated systems in charge of intrinsic and extrinsic processing, respectively. At a lower level, the intrinsic system appears to be partitioned in three modules that subserve generation of spontaneous thoughts (M1a; default mode), inner maintenance and manipulation of information (M1b), and cognitive control and switching activity (M1c), respectively. The extrinsic system was found to be made of two distinct modules: one including primary somatosensory and auditory areas and the dorsal attentional network (M2a) and the other encompassing the visual areas (M2b). Functional connectivity analyses revealed that M1b played a central role in the functioning of the intrinsic system, whereas M1c seems to mediate exchange of information between the intrinsic and extrinsic systems.