bluuebunny/crossref_metadata_2025_split huggingface dataset:
Culture of pachytene spermatocytes for analysis of meiosis
Authors: Handel M. A. , Caldwell K. A. , Wiltshire T. 
Published: May 2005

AbstractAn impediment to the investigation of mammalian spermatogenic meiosis has been the lack of an appropriate system for experimental manipulation of meiotic prophase cells. We report here the use of a simple system for the short‐term culture of pachytene spermatocytes. We have assayed parameters of cell function pertinent to meiotic prophase, namely chromosome pairing and synapsis. During the culture period of 24–48 hr, cells maintained typical pachytene morphology, chromatin condensation patterns, and chromosome pairing, as assessed by light and electron microscopy. Uridine incorporation, monitored by autoradiography, reflected the chromosomal distribution found in vivo in that the autosomal chromosomes were transcriptionally active, while the sex chromosomes were not. Thus features of chromosome pairing and sex chromatin inactivation are maintained in these cultures. We have conducted experiments to demonstrate that cultured pachytene spermatocytes can be useful for the analysis of agents, some of which may be suspected mutagens, that might affect chromosome structure and function during meiosis. Treatment of cells with actinomycin D revealed a differential effect on chromatin condensation in the autosomes versus the sex chromosomes. Carnptothecin, a topoisomerase inhibitor, induced desynapsis of paired chromosomes. Okadaic acid, a phosphatase inhibitor, induced premature metaphase‐I condensation of pachytene chromosomes. This last experiment suggests that these cultured cells may be useful for analysis of meiotic cell cycle controls. Taken together, these results demonstrate a culture system that can be useful for analysis of meiotic events as well as in screening for potential mutagenic agents that might affect meiotic chromosome structure and function. © 1995 Wiley‐Liss, Inc.
Regulation of β‐tubulin function and expression in Drosophila spermatogenesis
Authors: Hoyle Henry D. , Hutchens Jeffrey A. , Turner F. Rudolf , Raff Elizabeth C. 
Published: May 2005

AbstractIn this study we examined two aspects of β‐tubulin function in Drosophila spermatogenesis: 1) β‐tubulin structural requirements for assembly of different categories of microtubules and 2) regulatory requirements for production of the correct tubulin protein level. In normal Drosophila spermatogenesis, the testis‐specific β2‐tubulin isoform supports multiple microtubule functions. Our previous work showed that another Drosophila isoform, β3, cannot support spermatogenesis, whereas a carboxyl‐truncated form of β2, β2ΔC, can at least to some extent provide all of β2′s normal functions, save one: β2ΔC cannot support organization of axonemal microtubules into the supramolecular architecture of the axoneme. Here, to test whether β2 carboxyl sequences can rescue the functional failure of the β3 isoform in spermatogenesis, we constructed a gene encoding a chimeric protein, β3β2C, in which β3 sequences in the carboxyl region are replaced with those of β2. Unlike either β3 or β2ΔC, β3β2C can provide partial function for both assembly of axonemal microtubules and their organization into the supramolecular architecture of the axoneme. In particular, the β2 carboxyl sequences mediate morphogenesis of the axoneme doublet tubule complex, including accessory microtubule assembly and attachment of spokes and linkers. However, our data also reveal aspects of β2‐specific function that require structural features other than the primary sequence of the isotype‐defining variable regions, the C terminus and the internal variable region. Tests of fecundity in males that co‐express Δ2 and the chimeric Δ3Δ2C protein showed that in Drosophila there are differential requirements for sperm motility in the male and in the female reproductive tract. Since some aspects of microtubule function in spermatogenesis are sensitive to the tubulin pool size, we examined the mechanisms for control of tubulin protein levels in the male germ cells. We found that both Δ2‐tubulin mRNA accumulation and protein synthesis are dependent on gene dose, and that the level of expression is regulated by 3′ noncoding sequences in the Δ2 gene. Our data show that the regulatory mechanisms that control tubulin pool levels in the Drosophila male germ line differ from those observed in cultured animal somatic cells. Finally, expression of transgenic constructs is consistent with early cessation of × chromosome expression in Drosophila spermatogenesis. © 1995 Wiley‐Liss, Inc.
Differential expression of fork head genes during early Xenopus and zebrafish development
Authors: Dirksen Marie‐Luise , Jamrich Milan 
Published: May 2005

AbstractIntense efforts have been devoted to the identification of genes that are causatively involved in pattern‐forming events of invertebrates and vertebrates. Several gene families involved in this process have been identified. Here we focus on the Xenopus fork head domain gene family. One of its members, XFKHl/Pintallavis/XFD1, has been shown previously to be involved in axial formation, and the expression patterns of the other family members discussed below suggest that they too play a major role in the initial steps of patterning and axial organization. In this report, we describe four Xenopus fork head genes XFKH3, 4, 5, and 6) and analyze the distribution of their transcripts during early development. XFKH3 is expressed in developing somites but not notochord, XFKH4 in forebrain, anterior retina, and neural crest cells, and XFKH5 in a subset of epidermal cells and the neural floor plate. Finally, transcripts of XFKH6 are seen in neural crest‐derived cranial ganglia. In addition, we show that at least some of the zebrafish fork head genes might serve a comparable function. Zebrafish zf‐FKHl has a similar expression pattern as Xenopus XFKHl/Pintallavis/XFDl. It is transcribed in the notochord and neural floor plate. The polster or “pillow” also shows very high levels of zf‐FKHl mRNA. © 1995 Wiley‐Liss, Inc.
Imprinting of IGF2, insulin‐dependent diabetes, immune function, and apoptosis: A hypothesis
Authors: Polychronakos Constantin , Giannoukakis Nick , Deal Cheri L. 
Published: May 2005

AbstractParental genomic imprinting is the phenomenon in which the behavior of a gene is modified, depending on the sex of the transmitting parent [Peterson and Sapienza (1993): Annu Rev Genet 27:7–31]. Recent observations have revealed that the inheritance patterns, age‐of‐onset, severity, and etiology of certain human diseases can be explained by aberrations in the establishment or the maintenance of the imprint. Examples include the Prader‐Willi, Angelman, and Beckwith‐Wiedemann syndromes [Nicholls (1994): Am J Hum Genet 54:733–740], malignancy [Sapienza (1990): Biochim Biophys Acta 1072:51–61; Feinberg (1993): Nat Genet 4:110–113], and insulin‐ependent diabetes mellitus (IDDM) [Julier et al. (1994) Nature 354:155–159; Bennett et al. (1995) Nat Genet 9:284–292]. We review the evidence that implicates an imprinted gene in the INS‐IGF2 region of chromosome llp15 in the etiology of IDDM (referred to as the IDDM2 locus) and show that in human fetal pancreas, INS is not imprinted, thus providing an argument against INS as the candidate gene. We also examine imprinting effects on the expression of IGF2 in components of the human immune system believed to be important in IDDM and show imprinted expression in fetal thymus as early as 15 weeks gestation. We demonstrate further that in the circulating mononuclear cells of two individuals, lectin‐stimulated IGF2 transcription was biallelic, indicating relaxation of imprinting, whereas in one individual, transcription was monoallelic. Finally, we review the current available data supporting a role for insulin‐like growth factor‐ll (IGF‐II) in the immune system and, more specifically, discuss the evidence supporting a role for the IGFs in the prevention of apoptosis. These data have led us to formulate a novel hypothesis that could mechanistically explain the involvement of the IDDM2 locus in the pathogenesis of IDDM. © 1995 Wiley‐Liss, Inc.
Developmental alteration of the chromatin state at promoter/replication origin region of the aldolase b locus precedes transcriptional activation in the liver
Authors: Ito Kikukatsu , Tsutsumi Reiko , Ishikawa Kiichi , Tsutsumi Ken‐Ichi 
Published: May 2005

AbstractLiver‐specific expression of the rat aldolase B (AldB) gene is conferred by proximal promoter region (‐200 bp to + 1 bp), which is centered on an origin region of DNA replication. Transcriptional activation of the gene in the liver occurs during the late one‐third of fetal stage. To know the mechanism involved in such activation, we studied developmental changes in chromatin structure and in the extent of CpG methylation in the promoter/origin region of the gene. At an early fetal stage, when the AldB gene in the liver is not yet activated, the gene chromatin had two DNase l‐hypersensitive sites in the promoter region. One corresponded to that typical of AldB‐expressing cells in the adult. The other, located ∼200 bp upstream of the above site, disappeared as the activation of transcription started. A CpG dinucleotide in the promoter/origin region was heavily methylated at an early stage of gestation, but progressively demethylated as the liver develops. This CpG site is located at the center of an important binding site for a transcription factor. These changes occurred early in the fetal stage, prior to the gene activation, and were thus thought to be associated with differentiation of the liver cell or with cessation of cell proliferation.
Cloning and developmental expression of the ecdysone receptor gene from the spruce budworm, choristoneura fumiferana
Authors: Kothapalli Ravi , Palli Subba R. , Ladd Tim R. , Sohi Sardar S. , Cress Dean , Dhadialla Tarlochan S. , Tzertzinis George , Retnakaran Arthur 
Published: May 2005

AbstractDegenerate oligonucleotides were designed on the basis of conserved amino acid sequences in the DNA and ligand‐binding regions of the members of the steroid hormone receptor superfamily. Using these oligonucleotides in RNA‐PCR, a cDNA fragment was isolated from the spruce budworm, Choristoneura fumiferana. Comparison of the deduced amino acid sequence of this cDNA fragment with the members of the steroid hormone receptor superfamily suggested that this PCR fragment is a region of the ecdysone receptor from C. fumiferana. Using this cDNA fragment as a probe, 10 clones were isolated from a cDNA library that was constructed using the RNA from 4‐ and 5‐day old embryos of C. fumiferana. Two cDNA clones (1.3 and 3 kb) that overlap and show amino acid identity with Drosophila melanogaster ecdysone receptor B‐1 isoform (DmEcR) were characterized and sequenced. The longest open reading frame had 539 codons and covered the complete EcR coding region. The deduced amino acid sequence of this open reading frame had all five of the regions typical for a steroid hormone nuclear receptor. The C domain or DNA binding region showed the highest identity with EcR proteins from D. melanogaster, Chironomus tentans, Aedes aegypti, Manduca sexta and Bombyx mori. The A/B region, D domain or hinge region, E domain, or ligand binding region also showed significant amino acid similarity with the EcR proteins from the five insects mentioned above. The C. fumiferana ecdysteroid receptor (CfEcR) cDNA probe detected a 6.0‐kb mRNA that was present throughout the development of C. fumiferana. The CfEcR mRNA increases in abundance at the time of the ecdysteroid peak during the molting phase in the embryonic, larval and pupal stages but remains low during the intermolt period. In the 6th instar larvae, the 6‐kb CfEcR mRNA was detected in the epidermis, fat body, and midgut and maximum expression was observed during the prepupal peak of ecdysteroids in the hemolymph. CfEcR mRNA was induced in ecdysone treated CF‐203 cells as well as in the epidermis and midgut of larvae that were fed the nonsteroidal ecdysteroid agonist, RH‐5992. The induction occurred within an hour and reached maximum levels around 3 hr, after which it decreased to the basal level by 6 hr. In vitro transcription and translation of the CfEcR cDNA yielded a 67‐Kda protein that bound to the ecdysone response element (EcRE) as a heterodimer, along with the ultraspiracle protein.
Complete Structural Elucidation of a Novel Lipooligosaccharide from the Outer Membrane of the Marine Bacterium Shewanella pacifica
Authors: Silipo Alba , Leone Serena , Molinaro Antonio , Sturiale Luisa , Garozzo Domenico , Nazarenko Evgeny L. , Gorshkova Raisa P. , Ivanova Elena P. , Lanzetta Rosa , Parrilli Michelangelo 
Published: May 2005

AbstractShewanella pacifica is a Gram‐negative microrganism that is able to grow in sea water. A novel lipooligosaccharide (LOS) has been isolated from the outer membrane of this bacterium and its primary structure fully characterised. For the first time, the presence of a 2,3‐dihydroxypropanoic acid residue (glyceric acid) has been identified in the core region. The complete structure of the LOS was determined by compositional and methylation analyses, by MALDI mass spectrometry, and by 1H, 13C and 31P NMR spectroscopy on the oligosaccharides formed by selective degradation of the LOS. Strong alkaline treatment, aimed at recovering and identifying the complete carbohydrate backbone, was carried out by hydrazinolysis followed by de‐N‐acylation with hot KOH, whereas mild hydrazinolysis (de‐O‐acylation) allowed us to gain information about the nature of the phosphate and other non‐carbohydrate substituents on the core oligosaccharide. Mild acid hydrolysis was employed to obtain a lipid A moiety with which further degradation and mass spectrometry experiments were carried out in order to determine its primary structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Adsorptive stripping tensammetry of commercially available oxyethlated alcohols. Part 1. Surfactants having C10–C13hydrophobes
Authors: Szymanski Andrzej , Lukaszewski Zenon 
Published: May 2005

AbstractThe behavior of oxyethylated oxoalcohols (e.g., Oxetals D104, T105, and C114, and oxyethylatedn‐dodecanol BRIJ‐35) was investigated. The dependence of peak height on concentration of surfactant, preconcentration time, and preconcentration potential was examined. To improve the analytical signal of Oxetals C114 and T105, the influence of methanol on their tensammetric curves was investigated. Roughly, all the surfactants exhibit two peaks: a wide one, corresponding the monomer form, which shifts toward the negative direction with an increase in concentration, and a narrow one, corresponding to the associate form, whose position is stable. Oxetals C114 and T105 exhibit additional peaks, which complicate the determination. The addition of 20% of methanol removes such difficulties and only one peak remains.
Electroluminescence
Authors: Velasco Jaime González 
Published: May 2005

AbstractA definition of electrogenerated luminescence (ECL) is given. Chemiluminescent reactions of different kinds are cited, as well as various types of pathway to the formation of the emitting excited state. After a consideration of the energetic and kinetic requirements for ECL‐producing reactions, the experimental conditions are examined. The important concept of ECL efficiency is introduced, as well as the feasibility of elucidating the mechanisms of ECL reactions. Some interesting new ECL systems are mentioned, together with examples of analytical applications of such schemes.
Immobilized enzyme carbon paste electrodes as amperometric sensors
Authors: Lorenzo E. , González E. , Pariente F. , Hernández L. 
Published: May 2005

AbstractThe construction and performance of new carbon paste enzyme electrodes as amperometric sensors is described. Xanthine oxidase and alkaline phosphatase have been adsorbed on a carbon paste electrode (CPE), and physically entrapped with a semipermeable membrane. The product of enzymatic reaction, uric acid or p‐nitrophenol, was electrochemically oxidized versus an Ag/AgCl electrode at +0.4 or +0.8 V, respectively, yielding a steady‐state current directly related to the substrate concentration. Response characteristics as well as kinetic parameters have been evaluated.
pH‐ISFET with NMOS technology
Authors: Alegret S. , Bartrolí J. , Jiménez C. , del Valle M. , Domínguez C. , Cabruja E. , Merlos A. 
Published: May 2005

AbstractThe construction of a pH‐ISFET (ion‐selective field effect transistor) fabricated with standard negative‐channel MOS technology, compatible with complementary MOS technology, and using silicon nitride as a pH‐sensitive material, is described. Its main analytical characteristics are discussed. The resulting calibration plot is linear over the pH range from 2 to 11; with a slope of 54 mV per pH unit.
Voltammetric determination of cadmium on a carbon paste electrode modified with a chelating resin
Authors: Agraz Raquel , Sevilla M. Term , Pinilla Jose M. , Hernandez Lucas 
Published: May 2005

AbstractA method is described for determination of cadmium using a carbon pas electrode modified with Amberlite IRC 718 chelating resin and voltammetric measurement of the collected ion. Optimal conditions for the preconcentration of cadmium were 10 minutes stirring at open circuit in 0.001 M ammonium buffer, pH 9. For electrochemical measurements, the optimal parameters include the use of a 0.1 M HCl solution, a delay time of 36 seconds at −1.1 V (vs. Ag/AgCl) and a 400 mV/s scan rate. The well‐defined anodic peak at −0.7 V obtained is adequate for the quantitation of cadmium at very low concentration levels, with a detection limit of 0.005 mg/L. The method was used with good results for the determination of cadmium in polluted river waters.
Electrochemical behavior of the psychotropic drug pivazepam in determinations in pharmaceutical formulations and in urine
Authors: Rivera Paloma , Bermejo Esperanza , Zapardiel Antonio , López José Antonio Pérez , Hernández Lucas 
Published: May 2005

AbstractThe electrochemical reduction of pivazepam was investigated by differential pulse polarography. Reduction of the drug was carried out in one irreversible, diffusion‐controlled step using Britton–Robinson buffers. The peak potential at pH 5.0 and 10% methanol–water solutions was −0.95 V (vs. Ag/AgCl/3M KCl). Pivazepam can be determined (down to the nanomolar level) by using adsorptive preconcentration prior to the differential pulse voltammetric scan. The applicability to assays of commercial preparations and human urine is described. The detection limit was 15 ng per milliliter of urine with 60 seconds adsorption, and the mean standard deviation was lower than 4.6% for 200 ng/mL sample (n = 5, 60 seconds), with a mean recovery of 82%.
Voltammetric determination of cocaine in confiscated samples
Authors: Abedul María Teresa Fernández , Rodríguez José Ramón Barreira , García Agustín Costa , Blanco Paulino Tuñón 
Published: May 2005

AbstractThe electrochemical behavior of the abuse drug cocaine has been studied. Cocaine undergoes an irreversible oxidation process on carbon paste electrodes. It was calculated that 2 electrons were involved, and the value obtained for the charge transfer coefficient was 0.362 ± 0.006. Comparative voltammetric experiments yielded an estimated diffusion coefficient value for cocaine of 0.27 × 10−5 cm2 s−1. A linear calibration plot from 1.0 × 10−6 to 1.0 × 10−4M was obtained by using a scan rate of 50 mV s−1. A simple and reproducible procedure is proposed for the determination of cocaine in illegal dosage forms confiscated by police authorities; the results agree with those of a HPLC‐UV method.
Determination of Dinoseb by adsorptive stripping voltammetry
Authors: Pedrero María , de Villena F. Javier Manuel , Pingarrón José M. , Polo Luis M. 
Published: May 2005

AbstractA sensitive method is described for the determination of Dinoseb (2‐sec‐butyl‐4, 6‐dinitrophenol) at nanomolar levels by adsorptive stripping voltammetry (AdSV) at the hanging mercury drop electrode. Cyclic voltammetry studies showed two well‐defined reduction peaks, at −0.21 and −0.36 V, and demonstrated the adsorption of Dinoseb and its intermediate reduction product on the electrode. A systematic study of the experimental parameters that affect the stripping response was carried out using differential pulse voltammetry. Using a 120 second adsorption time, the limits of determination and detection were 1.5 × 10−9 and 4.6 × 10−10 M, respectively, and the relative standard deviation (n = 10) was 3.9% at a concentration level of 6.0 × 10−9 M.
Fluoride and chloride determination in cheese with ion‐selective electrodes
Authors: González M. A. , Aller A. J. , Pardo R. , Barrado E. , Deban L. 
Published: May 2005

AbstractWe studied the possibility, of using ion‐selective electrodes (ISEs) for the determination of chloride and fluoride anions in cheese samples. For chloride, we propose the use of potentiometric titration with silver and direct potentiometry, whereas for fluoride, best results were obtained with a standard additions method. The proposed procedures have been applied to Spanish cheese samples. Chloride was found in all samples in concentrations ranging between 3200 and 25,000 g/kg. Fluoride was present only in some types of cheese, in concentrations lesser than 0.7 mg/kg.
Electrochemistry of cyclodextrins and cyclodextrin inclusion complexes
Authors: Bersier Pierre M. , Bersier Jacques , Klingert Bernd 
Published: May 2005

AbstractThe state of the art of the electrochemistry of α‐, β‐, and γ‐cyclodextrins (CDs) and cyclodextrin inclusion complexes and their polarographic and voltammetric assay are reviewed. The polarographic and voltammetric determination of physicochemical parameters of CD inclusion complexes are discussed. Practical applications of adsorption and inclusion effects for electroanalytical purposes are presented future prospects are discussed, and 95 references are given.
Flow injection stripping analysis
Authors: Luque Castro M. D. De , Izquierdo A. 
Published: May 2005

AbstractA review of the two main electrochemical stripping techniques (voltammetric and potentiometric), associated with flow injection analysis (FIA), is presented. The versatility and flexibility provided by the FIA, manifold for performing unique stripping procedures such as medium exchange, flow reversal, and subtractive operation are evaluated. The instrumentation, features and applications of these associations are critically discussed, and unexplored possibilities are commented on. These developments are summarized in 58 references.
The determination of trace levels of iron in seawater, using adsorptive cathodic stripping voltammetry
Authors: Van Berg C. M. G. Den , Nimmo M. , Abollino O. , Mentasti E. 
Published: May 2005

AbstractA sensitive procedure to determine trace levels of iron in, seawater is proposed which utilizes adsorptive deposition of the complex of Fe(III) with 1‐nitroso‐2‐naphthol (1‐N‐2‐N) on the mercury drop electrode. Optimized conditions include a solution concentration of 20 μM 1‐N‐2‐N and a pH of 6.9; an adsorption potential of −0.25 V is applied, and the potential scan is in the linear sweep mode. The limit of detection is 0.2 nM Fe using a deposition time of 10 minutes. Peak instability due to adsorption of Fe(III) on either the voltammetric cell or rejected mercury drops is eliminated by addition of hydroxylammonium, which reduces the dissolved Fe(III) to Fe(II). The reaction mechanism of the analytical procedure therefore includes oxidation of Fe(II) to Fe(III) at the electro surface with the subsequent complexation by 1‐N‐2‐N and adsorption on the mercury drop; the reduction current of the adsorbed and complexed, Fe(III) is then measured.