bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative analysis of the conformational profile of substance P using simulated annealing and molecular dynamics
Authors: Corcho Francesc J. , Canto Josep , Perez Juan J. 
Published: September 2004

AbstractThe present study describes an extensive conformational search of substance P using two different computational methods. On the one hand, the peptide was studied using the iterative simulated annealing, and on the other, molecular dynamics simulations at 300 and 400 K. With the former method, the peptide was studied in vacuo with a dielectric constant of 80, whereas using the latter study the peptide was studied in a box of TIP3P water molecules. Analysis of the results obtained using both methodologies was carried out using an in‐house methodology using a cluster analysis method based on information theory. Comparison of the two sampling methodologies and the different environment used in the calculations is also analyzed. Finally, the conformational motifs that are characteristic of substance P in a hydrophilic environment are presented and compared with the experimental results available in the literature. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1937–1952, 2004
Towards automation of palynology 3: pollen pattern recognition using Gabor transforms and digital moments
Authors: Zhang Y. , Fountain D. W. , Hodgson R. M. , Flenley J. R. , Gunetileke S. 
Published: September 2004

AbstractThe classification of pollen grains using texture information in combination with shape features is presented in this paper. The surface texture of pollen is characterised by using Gabor transforms, the geometric shape is described by using moment invariants, and the pollen grains are classified by an artificial neural network. In an experiment with five types of pollen grains, more than 97% of samples are correctly classified. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetic and equilibrium study of the reaction of nitroprusside and hydroxide ions: Influence of ionic strength using Pitzer model
Authors: Rubín Eugenia , Rodríguez Pilar , Brandariz Isabel , de Vicente Manuel E. Sastre 
Published: September 2004

AbstractA kinetic and equilibrium study of the addition reaction of hydroxide ions to nitroprusside has been carried out in this paper. Rate and equilibrium constants at different salt concentrations (up to 4 mol kg−1) were obtained, and the influence of ionic strength was studied by means of Pitzer equations. This model is of special interest because it is able to explain the experimental behavior at high ionic strength, when Debye–Huckel limiting law is no longer valid. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 650–660, 2004
Effects of alcohols on micellization and on the reaction methyl 4‐nitrobenzenesulfonate + Br− in cetyltrimethylammonium bromide aqueous micellar solutions
Authors: Muñoz María , del Mar Graciani María , Rodríguez Amalia , Moyá María Luisa 
Published: September 2004

AbstractThe effects of n‐hexanol, n‐pentanol, and n‐butanol on the critical micelle concentration (cmc), on the micellar ionization degree (α), and on the rate of the reaction methyl 4‐nitrobenzenesulfonate + Br− have been investigated in cetyltrimethylammonium bromide (CTAB) aqueous solutions. An increase in the alcohol concentration present in the solution produces a decrease in the cmc and an increase in the micellar ionization degree. Kinetic data show that the observed rate constant decreases as alcohol concentration increases. This result was rationalized by considering variations in the equilibrium binding constant of the methyl 4‐nitrobenzenesulfonate molecules to the micelles, variations in the interfacial bromide ion concentration, and variations in the characteristics of the water–alcohol bulk phase provoked by the presence of alcohols. When these operative factors are considered, kinetic data in this and other works show that the second‐order rate constants in the micellar pseudophases of water–alcohol micellar solutions are quite similar to those estimated in the absence of alcohols. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 634–641, 2004
A Study of Copolymerization of 1‐Hexene with 2,5‐Norbornadiene Using Metallocene Catalysts
Authors: Yanjarappa Mallinamadugu J. , Sivaram Swaminathan 
Published: September 2004

AbstractSummary: Copolymerization of 1‐hexene with a symmetrical diene, namely 2,5‐norbornadiene was studied using four different metallocene catalysts. Copolymerization was found to occur exclusively through one of the two equally reactive endocyclic double bonds with all the four catalysts. Copolymerization results in low molecular weight oligomers with the number average molecular weight ($\overline M _{\rm n}$) varying from 1 000–3 000. End group analysis of the co‐oligomers revealed that the β‐hydrogen transfer after 2,1 insertion also occurs in the presence of highly regiospecific catalysts. The regio errors were also found to depend on various reaction parameters such as polymerization time, Al/Zr mol ratio, metallocene concentration and polymerization temperature.Plots of variation in end groups and NBD incorporation with time.magnified imagePlots of variation in end groups and NBD incorporation with time.
Expression pattern of the maternal factor zygote arrest 1 (Zar1) in bovine tissues, oocytes, and embryos
Authors: Brevini Tiziana A.L. , Cillo F. , Colleoni S. , Lazzari G. , Galli C. , Gandolfi F. 
Published: September 2004

AbstractZygote arrest 1 (Zar1) is an ovary‐specific maternal factor that plays an essential role during the oocyte‐to‐embryo transition in mouse. In this species, Zar1 expression is strictly limited to the oocyte, the zygote and, at a lower level, the 2‐cell embryo. Aim of the present study was to analyze the presence and the expression pattern of the Zar1 ortholog in bovine tissues and embryos. Reverse transcription (RT)‐polymerase chain reaction (PCR) analysis was performed in a panel of bovine tissues, in oocytes and pre‐implantation in vitro produced embryos. The results demonstrated that a Zar1 ortholog is present in cattle. In the adult, the gene is expressed in ovary, testis, muscle, and myocardium. The gene is also expressed in the oocyte, the zygote, and in all the stages of embryonic development until blastocyst formation. A semi‐quantitative RT‐PCR analysis revealed that Zar1 levels are constant through in vitro development with the exception of the 4‐cell stage, when a significant increase is observed. The exposure of fertilized oocytes to the RNA polymerase II inhibitor alpha‐amanitin was able to suppress this Zar1 increase indicating that transcription of this gene occurs at the 4‐cell stage. Zar1 is conserved in cattle but has an expression pattern different from the mouse. In particular, Zar1 expression in the adult is not limited to the ovary and in the embryo is expressed well beyond the oocyte to embryo transition. Moreover, the identification of Zar1 transcription at the 4‐cell stage represents the first characterization of one of the genes expressed in cattle embryos before the major onset of embryonic transcription. Mol. Reprod. Dev. 69: 375–380, 2004. © 2004 Wiley‐Liss, Inc.
Polyol pathway along the bovine epididymis
Authors: Frenette Gilles , Lessard Carl , Sullivan Robert 
Published: September 2004

AbstractDuring the epididymal transit, male gametes acquire new surface proteins necessary for their fertilizing ability. We have previously shown that membranous vesicles, called epididymosomes, interact with sperm surface within the epididymal fluid allowing transfer of some proteins to different subcellular compartments of spermatozoa. We previously showed that one of the major proteins associated with epididymosomes was an aldose reductase (gene: AKR1B5) and confirmed that aldose reductase is located in the epithelial cells bordering the intraluminal compartment of the epididymis. The present study shows that cytosolic aldose reductase activity was maximal in the proximal and middle segments of the epididymis and decreased in the distal epididymis. Western and Northern blot analysis confirmed the distribution pattern of aldose reductase and of the encoding mRNA. The optimal pH of epididymal aldose reductase was 6.0–6.5 when glucose was used as a substrate; this corresponds to the pH of the intraluminal epididymal fluid. In order to evaluate the possible involvement of sorbitol in sperm physiology, Western blot of tissue homogenates were probed with an anti‐sorbitol dehydrogenase antibody. The amount of enzyme immunodetected was higher in the proximal and distal segments of the epididymis when compared to the amount detectable in the middle segment of the epididymis. Sorbitol dehydrogenase activity as well as the level of the encoding mRNA showed the same pattern of distribution. Furthermore, immunohistological studies using the anti‐sorbitol dehydrogenase revealed that this enzyme was synthesized by the epididymal epithelial cells bordering the intraluminal compartment. Knowing the importance of sorbitol and fructose in sperm metabolism, we hypothesized that the polyol pathway is involved in the modulation of sperm motility within the epididymis. Mol. Reprod. Dev. 69: 448–456, 2004. © 2004 Wiley‐Liss, Inc.
KIF2Aβ: A kinesin family member enriched in mouse male germ cells, interacts with translin associated factor‐X (TRAX)
Authors: Bray Jeffrey D. , Chennathukuzhi Vargheese M. , Hecht Norman B. 
Published: September 2004

AbstractTranslin associated factor X (TRAX) is a binding partner of TB‐RBP/Translin. A cDNA encoding the 260 C‐terminal amino acids of KIF2Aβ was isolated from mouse testis cDNAs in a yeast two‐hybrid library screen for specific TRAX‐interacting proteins. KIF2Aβ was expressed predominantly in the mouse testis and enriched in germ cells. The interaction of full‐length KIF2Aβ or its C‐terminus with TRAX was verified using in vitro synthesized fusion proteins. Deletion mapping of the TRAX‐binding region of KIF2Aβ indicated that amino acids 514–659 were necessary and sufficient for the interaction in vivo. Confocal microscopy studies using GFP‐fusion proteins demonstrated that KIF2Aβ colocalizes with TRAX in a perinuclear location. KIF2Aβ does not interact with TB‐RBP, suggesting that either TRAX can function as an adaptor molecule for motor proteins and TB‐RBP, or that this interaction reveals an undescribed role for TRAX in germ cells. The interaction with KIF2Aβ suggests a role for TRAX in microtubule‐based functions during spermatogenesis. Mol. Reprod. Dev. 69: 387–396, 2004. © 2004 Wiley‐Liss, Inc.
Several signaling pathways are involved in the control of cattle oocyte maturation
Authors: Vigneron Céline , Perreau Christine , Dupont Joélle , Uzbekova Svetlana , Prigent Claude , Mermillod Pascal 
Published: September 2004

AbstractThe main limit of in vitro production of domestic mammal embryos comes from the low capacity of in vitro matured oocytes to develop after fertilization. As soon as they are separated from follicular environment, oocytes spontaneously resume meiosis without completion of their terminal differentiation. Roscovitine (ROS), an inhibitor of M‐phase promoting factor (MPF) kinase activity reversibly blocks the meiotic resumption in vitro. However, in cattle maturing oocytes several cellular events such as protein synthesis and phosphorylation, chromatin condensation and nuclear envelope folding escape ROS inhibition suggesting the alternative pathways in oocyte maturation. We compared the level of synthesis and phosphorylation of several protein kinases during bovine cumulus oocyte complex (COC) maturation in vitro in the presence or not of epidermal growth factor (EGF) and ROS. We showed that during the EGF‐stimulated maturation, ROS neither affected the decrease of EGF receptor (EGFR) nor did inhibit totally its phosphorylation in cumulus cells and also did not totally eliminate tyrosine phosphorylation in oocytes. However, ROS did inhibit the Phosphoinositide 3‐kinase (PI3) activity when oocytes mature without EGF. Accumulation of Akt/PKB (protein kinase B), JNK1/2 (jun N‐terminal kinases) and Aurora‐A in oocytes during maturation was not affected by ROS. However, the phosphorylation of Akt but not JNKs was diminished in ROS‐treated oocytes. Thus, PI3 kinase/Akt, JNK1/2 and Aurora‐A are likely to be involved in the regulation of bovine oocyte maturation and some of these pathways seem to be independent to MPF activity and meiotic resumption. This complex regulation may explain the partial meiotic arrest of ROS‐treated oocytes and the accelerated maturation observed after such treatment. Mol. Reprod. Dev. 69: 466–474, 2004. © 2004 Wiley‐Liss, Inc.
Immunolocalization of cubilin, megalin, apolipoprotein J, and apolipoprotein A‐I in the uterus and oviduct
Authors: Argraves W. Scott , Morales Carlos R. 
Published: September 2004

AbstractSpermatozoa maturation and capacitation occurring in the male and female reproductive tracts, respectively, involves the remodeling of the spermatozoa plasma membrane. Apolipoprotein J (apoJ) and apolipoprotein A‐I (apoA‐I) have been implicated in the process of lipid exchange from the spermatozoa plasma membrane to epithelial cells lining the male reproductive tract. Evidence suggests that this process is mediated by the cooperative action of the endocytic lipoprotein receptors megalin and cubilin, which are expressed at the apical surface of absorptive epithelia in various tissues, including the efferent ducts and epididymis. Here, we investigated the possibility that these receptors and their lipid‐binding ligands, apoJ and apoA‐I, might function similarly in the female reproductive tract. We show that megalin and cubilin are expressed in the uterine epithelium at all stages of the estrous cycle, maximally during estrous and metestrous stages. In the oviduct, there is pronounced expression of both megalin and cubilin in the nonciliated cells of the proximal oviduct and epithelial cells of the distal oviduct, particularly during estrous and metestrous stages. In both uterine and oviduct epithelial cells, megalin and cubilin were located on the apical regions of the cells, consistent with a distribution at the cell surface and in endosomes. ApoJ and apoA‐I were both detected in apical regions of uterine and oviduct epithelial cells. Secretory cells of the uterine glands were found to express apoJ and apoA‐I suggesting that the glands are a site of synthesis for both proteins. In summary, our findings indicate that megalin and cubilin function within the female reproductive tract, possibly mediating uterine and oviduct epithelial cell endocytosis of apoJ/apoA‐I‐lipid complexes and thus playing a role in lipid efflux from the sperm plasma membrane, a major initiator of capacitation. Mol. Reprod. Dev. 69: 419–427, 2004. © 2004 Wiley‐Liss, Inc.
Implication of cAMP during porcine sperm capacitation and protein tyrosine phosphorylation
Authors: Tardif Steve , Lefièvre Linda , Gagnon Claude , Bailey Janice L. 
Published: September 2004

AbstractSecond messengers are involved in sperm fertilizing potential, as both motility and the acrosome reaction are influenced by cAMP. Moreover, the activity of cyclic nucleotides is implicated in the appearance of tyrosine phosphorylated sperm proteins, which is associated with capacitation in the mammalian spermatozoa. Nevertheless, the involvement of the cAMP/protein kinase A (PK‐A) pathway during pig sperm capacitation may be different from that observed in other mammals. The objective of the present study was to clarify the cAMP/PK‐A pathway during the capacitation of porcine spermatozoa and to evaluate this impact on the p32 sperm tyrosine phosphoprotein appearance. The presence of p32 was assessed after incubating fresh pig sperm with IBMX/db‐cAMP, H‐89, a PK‐A inhibitor or bistyrphostin, a tyrosine kinase inhibitor, in capacitating (CM) or non‐capacitating conditions (NCM) by immunoblotting SDS‐extracted and separated sperm proteins using an anti‐phosphotyrosine antibody. When pig spermatozoa were incubated in CM supplemented with H‐89 (50 μM) or bistyrphostin (1.2 μM), capacitation decreased significantly (P < 0.001). The p32 sperm tyrosine phosphoprotein, previously shown to be associated with capacitation of porcine sperm though not necessarily an end point of this phenomenon, was not modulated by IBMX/db‐cAMP (100 μM/1 mM), H‐89 (50 μM) nor bistyrphostin (1.2 μM). Our results indicate, therefore, that pig sperm are regulated somewhat differently than as described for other mammals, because although the cAMP/PK‐A and tyrosine kinase pathways are involved in capacitation, they do not influence the appearance of p32. Mol. Reprod. Dev. 69: 428–435, 2004. © 2004 Wiley‐Liss, Inc.
Oocyte‐selective expression of MT transposon‐like element, clone MTi7 and its role in oocyte maturation and embryo development
Authors: Park Chang‐Eun , Shin Mi‐Ra , Jeon Eun‐Hyun , Lee Sook‐Hwan , Cha Kwang‐Yul , Kim Kyungjin , Kim Nam‐Hyung , Lee Kyung‐Ah 
Published: September 2004

AbstractPreviously, we found MT transposon‐like element, clone MTi7 (MTi7) is highly expressed in the mouse ovary. Here, we show that the MTi7 is expressed in the oocyte from the primordial to the preovulatory follicles. For RNA interference (RNAi), double stranded RNAs (dsRNAs) were prepared for MTi7 and c‐mos, a control gene with known functions. Each dsRNA was microinjected into germinal vesicle (GV) stage oocytes or zygotes with pronuclei (PN), after which developmental changes, mRNA expression, and nuclear and microtubular organization were analyzed. We found a 43.4–53% GV arrest in the microinjected oocytes with a concomitant decrease in targeted mRNA expression. In MTi7 dsRNA‐injected early and late PN zygotes, a 92.9% 1‐cell arrest and 76.9% 2‐cell arrest were observed, respectively. This is the first report of an oocyte‐selective expression of MTi7 mRNA, and our results strongly suggest that MTi7 involved in the nuclear membrane breakdown during oocyte maturation and embryo development. Mol. Reprod. Dev. 69: 365–374, 2004. © 2004 Wiley‐Liss, Inc.
Association of female aging with decreased parthenogenetic activation, raised MPF, and MAPKs activities and reduced levels of glutathione S‐transferases activity and thiols in mouse oocytes
Authors: Tarín Juan J. , Gómez‐Piquer Vanessa , Pertusa José F. , Hermenegildo Carlos , Cano Antonio 
Published: September 2004

AbstractThis study aims to determine in the mouse whether oocytes from reproductively old females exhibit a different susceptibility to be parthenogenetically activated when compared to oocytes from young females. At the age of 10–12 (young‐female group) or 60–62 (old‐female group) weeks, hybrid female mice were superovulated using pregnant mare's serum gonadotropin (PMSG) followed by human chorionic gonadotropin (hCG) 48 hr later. After removing the cumulus cells, oocytes were exposed to any of two different activating protocols: (a) 6‐min exposure to 8% ethanol; and (b) treatment with 200 μM thimerosal for 15 min followed by 8 mM dithiothreitol (DTT) for 30 min. Oocytes from old female mice displayed (1) lower total percentage of parthenogenetic activation and extrusion of the second polar body after treatment with either thimerosal + DTT or ethanol; (2) higher M‐phase‐promoting factor (MPF) and mitogen‐activated protein kinases (MAPKs) activities; and (3) lower intracytoplasmic levels of glutathione S‐transferases (GSTs) activity and thiols than oocytes from young females. These data show that female aging is associated with higher resistance of oocytes to be parthenogenetically activated, higher MPF and MAPKs activities and lower intracytoplasmic levels of GSTs activity and thiols. Mol. Reprod. Dev. 69: 402–410, 2004. © 2004 Wiley‐Liss, Inc.
On the uncapacitated K‐commodity network design problem with zero flow‐costs
Authors: Ng Ada Suk‐fung , Sastry Trilochan , Leung Janny M.Y. , Cai X.Q. 
Published: September 2004

AbstractExtending Sastry's result on the uncapacitated two‐commodity network design problem, we completely characterize the optimal solution of the uncapacitated K‐commodity network design problem with zero flow costs for the case when K = 3. By solving a set of shortest‐path problems on related graphs, we show that the optimal solutions can be found in O(n3) time when K = 3, where n is the number of nodes in the network. The algorithm depends on identifying a list of “basic patterns”; the number of basic patterns grows exponentially with K. We also show that the uncapacitated K‐commodity network design problem can be solved in O(n3) time for general K if K is fixed; otherwise, the time for solving the problem is exponential. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Inverse Toeplitz preconditioners for Hermitian Toeplitz systems
Authors: Lin Fu‐Rong , Ching Wai‐Ki 
Published: September 2004

AbstractIn this paper we consider solving Hermitian Toeplitz systems Tnx=b by using the preconditioned conjugate gradient (PCG) method. Here the Toeplitz matrices Tn are assumed to be generated by a non‐negative continuous 2π‐periodic function ƒ, i.e. Tn=𝒯n[ƒ]. It was proved in (Linear Algebra Appl. 1993; 190:181) that if ƒ is positive then the spectrum of 𝒯n[1/ƒ]𝒯n[ƒ] is clustered around 1. We prove that the trigonometric polynomial q (s⩾2, cf. (2) and (3)) converges to 1/ƒ uniformly as n→∞ under the condition that 1/ƒ is in Wiener class. It follows that the computational cost of the PCG method can be reduced by replacing 1/ƒ with q, where N<n. We also extend our method to construct efficient preconditioners for Tn when ƒ has finite zeros of even orders. We prove that with our preconditioners, the preconditioned matrix has spectrum clustered around 1. It follows that the PCG methods converge very fast when applied to solve the preconditioned systems. Numerical results are given to demonstrate the efficiency of our preconditioners. Copyright © 2004 John Wiley & Sons, Ltd.
A preconditioning proposal for ill‐conditioned Hermitian two‐level Toeplitz systems
Authors: Noutsos D. , Capizzano S. Serra , Vassalos P. 
Published: September 2004

AbstractLarge 2‐level Toeplitz systems arise in many applications and thus an efficient strategy for their solution is often needed. The already known methods require the explicit knowledge of the generating function ƒ of the considered system Tnm(ƒ)x=b, an assumption that usually is not fulfilled in real applications. In this paper, we extend to the 2‐level case a technique proposed in the literature in such a way that, from the knowledge of the coefficients of Tnm(ƒ), we determine optimal preconditioning strategies for the solution of our systems. More precisely, we propose and analyse an algorithm for the economical computation of minimal features of ƒ that allow us to select optimal preconditioners. Finally, we perform various numerical experiments which fully confirm the effectiveness of the proposed idea. Copyright © 2004 John Wiley & Sons, Ltd.
The perturbation bounds for eigenvalues of normal matrices
Authors: Li Wen , Sun Weiwei 
Published: September 2004

AbstractIn this paper we present some new absolute and relative perturbation bounds of eigenvalues of normal matrices. The bounds depend upon the closeness of perturbed matrices to normal matrices and improve those previous results (Duke Math. J. 1953; 20:37–39, Linear Algebra Appl. 1996; 246:215–223). Copyright © 2004 John Wiley & Sons, Ltd.
Structured condition numbers of large Toeplitz matrices are rarely better than usual condition numbers
Authors: Böttcher A. , Grudsky S. M. 
Published: September 2004

AbstractWhen working with structured matrices, structured condition numbers are more meaningful than usual condition numbers. The usual condition numbers of Toeplitz matrices may grow exponentially with the dimension of the matrix. The purpose of this note is to show that in this case the structured condition numbers do with high probability also increase exponentially, which supports the claim that one is not likely to win much on the average Toeplitz input by passing from the usual condition numbers of Toeplitz matrices to their structured counterparts. Copyright © 2004 John Wiley & Sons, Ltd.