bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microelectrode Study of the Genesis of the Monophasic Action Potential by Contact Electrode Technique
Authors: KNOLLMANN BJÖRN C. , TRANQUILLO JOSEPH , SIRENKO SYEVDA G. , HENRIQUEZ CRAIG , FRANZ MICHAEL R. 
Published: August 2003

Monophasic Action Potential Genesis.
Introduction: Despite widespread use of the contact electrode for recording monophasic action potentials (MAPs) in both clinical and experimental research, the mechanism underlying the genesis of the contact MAP remains unproven. The “Franz hypothesis” assumes that the MAP is driven by a current source originating at the boundary between cells depolarized by the MAP electrode pressure and normal cells immediately adjacent to it. To date, no direct experimental data exist to support this hypothesis. Methods and Results: In 10 Langendorff‐perfused mouse hearts, a miniaturized MAP probe was inserted into the right ventricle (RV) and gently pressed against the endocardium of the upward‐facing RV free wall. During stable contact and stable MAP recording, KCl‐filled glass microelectrodes were lowered from above the RV to record transmembrane action potentials (TAPs) at the center of and 0.05 and 0.2 mm outside the perimeter of the MAP electrode contact site. TAPs at the center had normal resting potentials (RP) in epicardial layers (−78 ± 4 mV) but showed gradual decrease toward deeper layers, reaching a minimum RP of −23 ± 0.8 mV directly above the MAP electrode surface. RPs at 0.05 mm outside the MAP perimeter were normal at the epicardial surface and with increasing transmural depth showed significantly less decrease than central recordings (min RP −41 ± 0.8 mV, n = 11, P < 0.00001). TAPs at 0.2 mm from the MAP electrode perimeter had normal RPs across the entire RV wall. Conclusion: These direct data are the first to support the hypothesis that the MAP is generated locally through pressure depolarization of a circumscript volume of cells that (1) has sharp voltage gradients toward normal cells, (2) provides a strong local current source, and (3) when simulated with a circuit model creates the field potential recorded by the contact MAP electrode.
Is There an Optimal Pacing Site to Prevent Atrial Fibrillation?: An Experimental Study in the Chronically Instrumented Goat
Authors: DUYTSCHAEVER MATTIAS , DANSE PETER , EYSBOUTS SABINE , ALLESSIE MAURITS 
Published: August 2003

Preventive Atrial Pacing in AF.
Introduction: Atrial pacing can reduce the number of recurrences of atrial fibrillation (AF). It is unclear the extent to which this effect is determined by the site(s) of pacing. Methods and Results: In six electrically remodeled goats (24‐hour AF), the window of inducibility of AF was determined by applying premature stimuli (S1‐S2) at the right (RA) or left (LA) atrium (baseline values). Determination of the window of inducibility of AF at RA and LA was repeated during preventive pacing at four sites: RA, LA, Bachmann's bundle (BB), and RA + LA (biatrial). Mapping was used to elucidate the mechanisms of prevention of AF. At baseline, the window of inducibility of AF was 49 ± 9 msec at RA and 45 ± 17 msec at LA. Initiation of AF was associated with conduction block of the premature beat at BB. Preventive pacing at BB markedly shortened the window of inducibility of AF at RA (25 ± 11 msec) and LA (17 ± 8 msec, P < 0.01). Pacing at RA only shortened the window of inducibility of AF at LA (23 ± 9 msec, P < 0.01), whereas pacing at LA only shortened the window of inducibility of AF at RA (23 ± 11 msec, P < 0.01). Biatrial pacing failed to shorten the window of inducibility of AF both at RA and LA. Prevention of AF by pacing was due to prolongation of the premature interval at BB. Conclusion: In the caprine model of AF, BB is a critical area of conduction of premature beats and initiation of AF. Pacing at BB can prevent but not completely abolish the initiation of AF by single premature beats (shortening of the window of inducibility). Prevention of AF by pacing is based on prolongation of the premature interval at BB, thus preventing conduction block and reentry. In general, the optimal site for preventive pacing is close to the area of block and remote from the origin of premature beats.
Partial Vagal Denervation Increases Vulnerability to Vagally Induced Atrial Fibrillation
Authors: HIROSE MASAMICHI , LEATMANORATN ZENG , LAURITA KENNETH R. , CARLSON MARK D. 
Published: August 2003

Partial Vagal Denervation on AF.
Introduction: Cervical vagal stimulation shortens the atrial effective refractory period (ERP) primarily in the high right atrium (HRA) and facilitates induction of atrial fibrillation (AF) by single premature HRA extrastimuli. We hypothesized that vagal denervation of the HRA prevents both ERP shortening in the HRA and AF induction during vagal stimulation. Methods and Results: Vagal denervation of the HRA was achieved using radiofrequency catheter ablation (RFA) of the fat pad at the right pulmonary vein‐atrial junction (RPV fat pad). Programmed stimulation was performed at each of four atrial sites to measure ERP and inducibility of AF during vagal stimulation. RPV fat pad RFA increased only the HRA ERP during vagal stimulation (70 ± 8.7 vs 117 ± 14.8, P < 0.05). RPV fat pad RFA increased measures of dispersion of refractoriness, the standard deviation of ERP (24 ± 2.1 vs 33 ± 2.0, P < 0.01), and the standard deviation of AF cycle length (11 ± 0.8 vs 22 ± 1.7, P < 0.001) during vagal stimulation. RPV fat pad RFA increased the incidence of AF (15/28 vs 24/28, P < 0.05) and the vulnerability (22 ± 4.7 vs 39 ± 5.6, P < 0.01) to AF induction during vagal stimulation, particularly from left atrial premature beats. After RPV fat pad RFA, premature beats induced AF by causing conduction block primarily in the HRA and macroreentrant activation around the block. Conclusion: Partial right atrial vagal denervation facilitated rather than prevented initiation of vagally mediated AF.
Demonstration of Electrical and Anatomic Connections Between Marshall Bundles and Left Atrium in Dogs: Implications on the Generation of P Waves on Surface Electrocardiogram
Authors: OMICHI CHIKAYA , CHOU CHUNG‐CHUAN , LEE MOON‐HYOUNG , CHANG CHE‐MING , LAI ANGELA C. , HAYASHI HIDEKI , ZHOU SHENGMEI , MIYAUCHI YASUSHI , OKUYAMA YUJI , HAMABE AKIRA , HWANG CHUN , FISHBEIN MICHAEL C. , LIN SHIEN‐FONG , KARAGUEUZIAN HRAYR S. , CHEN PENG‐SHENG 
Published: August 2003

Marshall Bundle and P Wave.
Introduction: The muscle bundles within the ligament of Marshall (LOM) are electrically active. The importance of these muscle bundles (Marshall bundle [MB]) to atrial activation and the generation of the ECG P wave is unclear. Methods and Results: We used optical mapping techniques to study epicardial activation patterns in isolated perfused left atrium in four dogs. In another seven dogs, P waves were studied before and after in vivo radiofrequency (RF) ablation of the connection between coronary sinus (CS) and the LOM. Computerized mapping was performed before and after RF ablation. Optical mapping studies showed that CS pacing resulted in broad wavefronts propagating from the middle and distal LOM directly to the adjacent left atrium (LA). Serial sections showed direct connection between MB and LA near the orifice of the left superior pulmonary vein in two dogs. In vivo studies showed that MB potentials were recorded in three dogs. After ablation, the duration of P waves remained unchanged. In the other four dogs, MB potentials were not recorded. Computerized mapping showed that LA wavefronts propagated to the MB region via LA‐MB connection and then excited the CS. After ablation, the activation of CS muscle sleeves is delayed, and P wave duration increased from 65.3 ± 14.9 msec to 70.5 ± 17.2 msec (P = 0.025). Conclusion: In about half of the normal dogs, MB provides an electrical conduit between LA free wall and CS. Severing MB alters the atrial activation and lengthens the P wave. MB contributes to generation of the P wave on surface ECG.
Three Nicotianamine Synthase Genes Isolated from Maize Are Differentially Regulated by Iron Nutritional Status
Authors: Mizuno Daichi , Higuchi Kyoko , Sakamoto Tatsuya , Nakanishi Hiromi , Mori Satoshi , Nishizawa Naoko K. 
Published: August 2003

Abstract
Nicotianamine synthase (NAS) is an enzyme that is critical for the biosynthesis of the mugineic acid family of phytosiderophores in graminaceous plants, and for the homeostasis of metal ions in nongraminaceous plants. We isolated one genomic NAS clone, ZmNAS3, and two cDNA NAS clones, ZmNAS1 and ZmNAS2, from maize (Zea mays cv Alice). In agreement with the increased secretion of phytosiderophores with Fe deficiency, ZmNAS1 and ZmNAS2 were positively expressed only in Fe-deficient roots. In contrast, ZmNAS3 was expressed under Fe-sufficient conditions, and was negatively regulated by Fe deficiency. This is the first report describing down-regulation of NAS gene expression in response to Fe deficiency in plants, shedding light on the role of nicotianamine in graminaceous plants, other than as a precursor in phytosiderophore production. ZmNAS1-green fluorescent protein (sGFP) and ZmNAS2-sGFP were localized at spots in the cytoplasm of onion (Allium cepa) epidermal cells, whereas ZmNAS3-sGFP was distributed throughout the cytoplasm of these cells. ZmNAS1 and ZmNAS3 showed NAS activity in vitro, whereas ZmNAS2 showed none. Due to its duplicated structure, ZmNAS2 was much larger (65.8 kD) than ZmNAS1, ZmNAS3, and previously characterized NAS proteins (30–38 kD) from other plant species. We reveal that maize has two types of NAS proteins based on their expression pattern and subcellular localization.
Purification and Characterization of Four β-Expansins (Zea m 1 Isoforms) from Maize Pollen
Authors: Li Lian-Chao , Bedinger Patricia A. , Volk Carol , Jones A. Daniel , Cosgrove Daniel J. 
Published: August 2003

Abstract
Four proteins with wall extension activity on grass cell walls were purified from maize (Zea mays) pollen by conventional column chromatography and high-performance liquid chromatography. Each is a basic glycoprotein (isoelectric point = 9.1–9.5) of approximately 28 kD and was identified by immunoblot analysis as an isoform of Zea m 1, the major group 1 allergen of maize pollen and member of the β-expansin family. Four distinctive cDNAs for Zea m 1 were identified by cDNA library screening and by GenBank analysis. One pair (GenBank accession nos. AY104999 and AY104125) was much closer in sequence to well-characterized allergens such as Lol p 1 and Phl p 1 from ryegrass (Lolium perenne) and Phleum pretense, whereas a second pair was much more divergent. The N-terminal sequence and mass spectrometry fingerprint of the most abundant isoform (Zea m 1d) matched that predicted for AY197353, whereas N-terminal sequences of the other isoforms matched or nearly matched AY104999 and AY104125. Highly purified Zea m 1d induced extension of a variety of grass walls but not dicot walls. Wall extension activity of Zea m 1d was biphasic with respect to protein concentration, had a broad pH optimum between 5 and 6, required more than 50 μg mL-1 for high activity, and led to cell wall breakage after only approximately 10% extension. These characteristics differ from those of α-expansins. Some of the distinctive properties of Zea m 1 may not be typical of β-expansins as a class but may relate to the specialized function of this β-expansin in pollen function.
Thylakoid-Bound Ascorbate Peroxidase Mutant Exhibits Impaired Electron Transport and Photosynthetic Activity
Authors: Danna Cristian H. , Bartoli Carlos G. , Sacco Francisco , Ingala Lorena R. , Santa-María Guillermo E. , Guiamet Juan J. , Ugalde Rodolfo A. 
Published: August 2003

Abstract
In chloroplasts, stromal and thylakoid-bound ascorbate peroxidases (tAPX) play a major role in the removal of H2O2 produced during photosynthesis. Here, we report that hexaploid wheat (Triticum aestivum) expresses three homeologous tAPX genes (TaAPX-6A, TaAPX-6B, and TaAPX-6D) mapping on group-6 chromosomes. The tAPX activity of a mutant line lacking TaAPX-6B was 40% lower than that of the wild type. When grown at high-light intensity photosystem II electron transfer, photosynthetic activity and biomass accumulation were significantly reduced in this mutant, suggesting that tAPX activity is essential for photosynthesis. Despite the reduced tAPX activity, mutant plants did not exhibit oxidative damage probably due to the reduced photochemical activity. This might be the result of a compensating mechanism to prevent oxidative damage having as a consequence a decrease in growth of the tAPX mutant plants.
Resemblance and Dissemblance of Arabidopsis Type II Peroxiredoxins: Similar Sequences for Divergent Gene Expression, Protein Localization, and Activity
Authors: Bréhélin Claire , Meyer Etienne H. , de Souris Jean-Paul , Bonnard Géraldine , Meyer Yves 
Published: August 2003

Abstract
The Arabidopsis type II peroxiredoxin (PRXII) family is composed of six different genes, five of which are expressed. On the basis of the nucleotide and protein sequences, we were able to define three subgroups among the PRXII family. The first subgroup is composed of AtPRXII-B, -C, and -D, which are highly similar and localized in the cytosol. AtPRXII-B is ubiquitously expressed. More striking is the specific expression of AtPRXII-C and AtPRXII-D localized in pollen. The second subgroup comprises the mitochondrial AtPRXII-F, the corresponding gene of which is expressed constitutively. We show that AtPRXII-E, belonging to the last subgroup, is expressed mostly in reproductive tissues and that its product is addressed to the plastid. By in vitro enzymatic experiments, we demonstrate that glutaredoxin is the electron donor of recombinant AtPRXII-B for peroxidase reaction, but the donors of AtPRXII-E and AtPRXII-F have still to be identified.
Overexpression of the Disease Resistance Gene Pto in Tomato Induces Gene Expression Changes Similar to Immune Responses in Human and Fruitfly
Authors: Mysore Kirankumar S. , D'Ascenzo Mark D. , He Xiaohua , Martin Gregory B. 
Published: August 2003

Abstract
The Pto gene encodes a serine/threonine protein kinase that confers resistance in tomato (Lycopersicon esculentum) to Pseudomonas syringae pv tomato strains that express the type III effector protein AvrPto. Constitutive overexpression of Pto in tomato, in the absence of AvrPto, activates defense responses and confers resistance to several diverse bacterial and fungal plant pathogens. We have used a series of gene discovery and expression profiling methods to examine the effect of Pto overexpression in tomato leaves. Analysis of the tomato expressed sequence tag database and suppression subtractive hybridization identified 600 genes that were potentially differentially expressed in Pto-overexpressing tomato plants compared with a sibling line lacking Pto. By using cDNA microarrays, we verified changes in expression of many of these genes at various time points after inoculation with P. syringae pv tomato (avrPto) of the resistant Pto-overexpressing line and the susceptible sibling line. The combination of these three approaches led to the identification of 223 POR (Pto overexpression responsive) genes. Strikingly, 40% of the genes induced in the Pto-overexpressing plants previously have been shown to be differentially expressed during the human (Homo sapiens) and/or fruitfly (Drosophila melanogaster) immune responses.
BWMK1, a Rice Mitogen-Activated Protein Kinase, Locates in the Nucleus and Mediates Pathogenesis-Related Gene Expression by Activation of a Transcription Factor
Authors: Cheong Yong Hwa , Moon Byeong Cheol , Kim Jong Kyong , Kim Cha Young , Kim Min Chul , Kim Ihn Hyoung , Park Chan Young , Kim Jong Cheol , Park Byung Ouk , Koo Seong Cheol , Yoon Hae Won , Chung Woo Sik , Lim Chae Oh , Lee Sang Yeol , Cho Moo Je 
Published: August 2003

Abstract
Mitogen-activated protein kinase (MAPK) cascades are known to transduce plant defense signals, but the downstream components of the MAPK have as yet not been elucidated. Here, we report an MAPK from rice (Oryza sativa), BWMK1, and a transcription factor, OsEREBP1, phosphorylated by the kinase. The MAPK carries a TDY phosphorylation motif instead of the more common TEY motif in its kinase domain and has an unusually extended C-terminal domain that is essential to its kinase activity and translocation to the nucleus. The MAPK phosphorylates OsEREBP1 that binds to the GCC box element (AGCCGCC) of the several basic pathogenesis-related gene promoters, which in turn enhances DNA-binding activity of the factor to the cis element in vitro. Transient co-expression of the BWMK1 and OsEREBP1 in Arabidopsis protoplasts elevates the expression of the β-glucuronidase reporter gene driven by the GCC box element. Furthermore, transgenic tobacco (Nicotiana tabacum) plants overexpressing BWMK1 expressed many pathogenesis-related genes at higher levels than wild-type plants with an enhanced resistance to pathogens. These findings suggest that MAPKs contribute to plant defense signal transduction by phosphorylating one or more transcription factors.
Expression of U1 Small Nuclear Ribonucleoprotein 70K Antisense Transcript Using APETALA3 Promoter Suppresses the Development of Sepals and Petals
Authors: Golovkin Maxim , Reddy Anireddy S.N. 
Published: August 2003

AbstractU1 small nuclear ribonucleoprotein (snRNP)-70K (U1-70K), a U1 snRNP-specific protein, is involved in the early stages of spliceosome formation. In non-plant systems, it is involved in constitutive and alternative splicing. It has been shown that U1snRNP is dispensable for in vitro splicing of some animal pre-mRNAs, and inactivation of U1-70K in yeast (Saccharomyces cerevisiae) is not lethal. As in yeast and humans (Homo sapiens), plant U1-70K is coded by a single gene. In this study, we blocked the expression of Arabidopsis U1-70K in petals and stamens by expressing U1-70K antisense transcript using the AP3 (APETALA3) promoter specific to these floral organs. Flowers of transgenic Arabidopsis plants expressing U1-70K antisense transcript showed partially developed stamens and petals that are arrested at different stages of development. In some transgenic lines, flowers have rudimentary petals and stamens and are male sterile. The severity of the phenotype is correlated with the level of the antisense transcript. Molecular analysis of transgenic plants has confirmed that the observed phenotype is not due to disruption of whorl-specific homeotic genes, AP3 or PISTILLATA, responsible for petal and stamen development. The AP3 transcript was not detected in transgenic flowers with severe phenotype. Flowers of Arabidopsis plants transformed with a reporter gene driven by the same promoter showed no abnormalities. These results show that U1-70K is necessary for the development of sepals and petals and is an essential gene in plants.
Characterization of Tocopherol Cyclases from Higher Plants and Cyanobacteria. Evolutionary Implications for Tocopherol Synthesis and Function
Authors: Sattler Scott E. , Cahoon Edgar B. , Coughlan Sean J. , DellaPenna Dean 
Published: August 2003

Abstract
Tocopherols are lipophilic antioxidants synthesized exclusively by photosynthetic organisms and collectively constitute vitamin E, an essential nutrient for both humans and animals. Tocopherol cyclase (TC) catalyzes the conversion of various phytyl quinol pathway intermediates to their corresponding tocopherols through the formation of the chromanol ring. Herein, the molecular and biochemical characterization of TCs from Arabidopsis (VTE1 [VITAMIN E 1]), Zea mays (SXD1 [Sucrose Export Deficient 1]) and Synechocystis sp. PCC6803 (slr1737) are described. Mutations in the VTE1, SXD1, or slr1737 genes resulted in both tocopherol deficiency and the accumulation of 2,3-dimethyl-6-phytyl-1,4-benzoquinone (DMPBQ), a TC substrate. Recombinant SXD1 and VTE1 proteins are able to convert DMPBQ to γ-tocopherol in vitro. In addition, expression of maize SXD1 in a Synechocystis sp. PCC6803 slr1737 knockout mutant restored tocopherol synthesis, indicating that TC activity is evolutionarily conserved between plants and cyanobacteria. Sequence analysis identified a highly conserved 30-amino acid C-terminal domain in plant TCs that is absent from cyanobacterial orthologs. vte1-2 causes a truncation within this C-terminal domain, and the resulting mutant phenotype suggests that this domain is necessary for TC activity in plants. The defective export of Suc in sxd1 suggests that in addition to presumed antioxidant activities, tocopherols or tocopherol breakdown products also function as signal transduction molecules, or, alternatively, the DMPBQ that accumulates in sxd1 disrupts signaling required for efficient Suc export in maize.
Pea DNA Topoisomerase I Is Phosphorylated and Stimulated by Casein Kinase 2 and Protein Kinase C
Authors: Tuteja Narendra , Reddy Malireddy Kodandarami , Mudgil Yashwanti , Yadav Badam Singh , Chandok Meena Rani , Sopory Sudhir Kumar 
Published: August 2003

AbstractDNA topoisomerase I catalyzes the relaxation of superhelical DNA tension and is vital for DNA metabolism; therefore, it is essential for growth and development of plants. Here, we have studied the phosphorylation-dependent regulation of topoisomerase I from pea (Pisum sativum). The purified enzyme did not show autophosphorylation but was phosphorylated in an Mg2+-dependent manner by endogenous protein kinases present in pea nuclear extracts. This phosphorylation was abolished with calf intestinal alkaline phosphatase and lambda phosphatase. It was also phosphorylated by exogenous casein kinase 2 (CK2), protein kinase C (PKC; from animal sources), and an endogenous pea protein, which was purified using a novel phorbol myristate acetate affinity chromatography method. All of these phosphorylations were inhibited by heparin (inhibitor of CK2) and calphostin (inhibitor of PKC), suggesting that pea topoisomerase I is a bona fide substrate for these kinases. Spermine and spermidine had no effect on the CK2-mediated phosphorylation, suggesting that it is polyamine independent. Phospho-amino acid analysis showed that only serine residues were phosphorylated, which was further confirmed using antiphosphoserine antibody. The topoisomerase I activity increased after phosphorylation with exogenous CK2 and PKC. This study shows that these kinases may contribute to the physiological regulation of DNA topoisomerase I activity and overall DNA metabolism in plants.
Peptide and Amino Acid Transporters Are Differentially Regulated during Seed Development and Germination in Faba Bean
Authors: Miranda Manoela , Borisjuk Ljudmilla , Tewes Annegret , Dietrich Daniela , Rentsch Doris , Weber Hans , Wobus Ulrich 
Published: August 2003

Abstract
Two peptide transporter (PTR) homologs have been isolated from developing seeds of faba bean (Vicia faba). VfPTR1 was shown to be a functional peptide transporter through complementation of a yeast mutant. Expression patterns of VfPTR1 and VfPTR2 as well as of the amino acid permease VfAAP1 (Miranda et al., 2001) were compared throughout seed development and germination. In developing seeds, the highest levels of VfPTR1 transcripts were reached during midcotyledon development, whereas VfAAP1 transcripts were most abundant during early cotyledon development, before the appearance of storage protein gene transcripts, and were detectable until late cotyledon development. During early germination, VfPTR1 mRNA appeared first in cotyledons and later, during seedling growth, also in axes and roots. Expression of VfPTR2 and VfAAP1 was delayed compared with VfPTR1, and was restricted to the nascent organs of the seedlings. Localization of VfPTR1 transcripts showed that this PTR is temporally and spatially regulated during cotyledon development. In germinating seeds, VfPTR1 mRNA was localized in root hairs and root epidermal cells, suggesting a role in nutrient uptake from the soil. In seedling roots, VfPTR1 was repressed by a dipeptide and by an amino acid, whereas nitrate was without influence.