bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of the temporal fidelity of synaptic transmission by a presynaptic high voltage‐activated transient K+ current
Authors: D'Incamps B. Lamotte , Hess D. , El Manira A. 
Published: June 2004

AbstractThe type of K+ channels controlling the waveform of the presynaptic spike and synaptic transmission were examined in the lamprey spinal cord. Reticulospinal neuron somata displayed a transient K+ current with a high voltage‐activation and inactivation. This current was selectively blocked by catechol at 100 µm. Reticulospinal axons also displayed a high voltage‐activated fast K+ current sensitive to catechol. The function of this presynaptic high voltage‐activated fast K+ current in controlling synaptic transmission was investigated by using paired intracellular recordings from reticulospinal axons and their targets. Blockade of this current by catechol (100 µm) prolonged the presynaptic spike elicited by a single stimulus leading to a potentiation of the postsynaptic EPSP. Calcium imaging of reticulospinal axons showed an increase in presynaptic calcium transients after blockade of the presynaptic K+ current by catechol. During high frequency firing, catechol revealed an activity‐dependent decrease in the spike duration, which resulted in a depression of synaptic transmission. These results suggest that the presynaptic high voltage‐activated transient K+ current acts to optimize the temporal fidelity of synaptic transmission by minimizing activity‐dependent changes in the presynaptic spike waveform and calcium dynamics.
Effects of visual contrast on visual evoked potentials and Doppler signal
Authors: Zaletel Marjan , Strucl Martin , Pogacnik Tomaz , Zvan Bojana 
Published: June 2004

AbstractWe studied visually evoked cerebral blood flow responses (VEFR) and visual evoked potentials (VEP) to different visual contrasts and analysed the relationship between them. The records were made from 35 healthy volunteers aged 38.6 ± 10.1 years. The stimulus was a black‐and‐white checkerboard with visual contrasts (VC) of 1%, 10% and 100%. The VEFR were measured in the posterior cerebral artery using transcranial Doppler, and the VEP were recorded from the occipital leads. We found the relationship between visual contrast and VEFR (r = 0.79, P < 0.01) as well as between visual contrast and VEP (r = 0.71, P < 0.01). We also found moderate association between the VEP and the VEFR (r = 0.69, P < 0.01). The analysis of the regression slopes between two different age subgroups (P < 0.01) did not show a significant difference (P = 0.020). We concluded that a simultaneous recording of VEFR and VEP to visual contrasts could allow an assessment of neurovascular coupling in humans.
Galanin type 2 receptors regulate neuronal survival, susceptibility to seizures and seizure‐induced neurogenesis in the dentate gyrus
Authors: Mazarati Andrey , Lu Xiaoying , Kilk Kalle , Langel Ülo , Wasterlain Claude , Bartfai Tamas 
Published: June 2004

AbstractThe neuropeptide galanin has been implicated in inhibiting seizures and protecting hippocampal neurons from excitotoxic injury. In the hippocampus galanin acts through two receptor subtypes, GalR1, expressed in CA1, and GalR2, abundant in dentate gyrus. We developed an approach to induce and to study selective semichronic knockdown of GalR2 in the rat hippocampus. A 50% reduction of GalR2 binding was achieved by continuous infusion of complementary peptide nucleic acid antisense oligonucleotide into the dentate gyrus. This resulted in an increase in the severity of self‐sustaining status epilepticus induced by electrical stimulation of the perforant path, induced mild neuronal injury in the dentate hilus, augmented seizure‐induced hilar injury and inhibited seizure‐induced neurogenesis in the subgranular zone of the dentate gyrus. Our data suggest that in the dentate gyrus, galanin, acting through GalR2, inhibits seizures, promotes viability of hilar interneurons and stimulates seizure‐induced neurogenesis. These results are important for understanding the role of galanin and galanin receptor subtypes in the hippocampus both under normal conditions and in excitotoxic injury.
Transfer of plastid DNA from tobacco to the soil bacterium Acinetobacter sp. by natural transformation
Authors: De Vries Johann , Herzfeld Thilo , Wackernagel Wilfried 
Published: June 2004

SummaryAcquisition of new genetic information by horizontal gene transfer is a major mechanism of genetic adaptation and evolution in prokaryotes. Naturally transformable cells of Acinetobacter sp. were exposed to plant DNA from leaf and root tissue of transplastomic tobacco. With the aadA gene (resistance against spectinomycin and streptomycin) as anchor se‐quence, the transfer of segments of the tobacco plastid DNA to Acinetobacter by homology‐facilitated illegitimate recombination occurred at a frequency of 1.2 × 10−7 per cell, which was about 0.1% of the frequency of fully homologous transfers. Without anchor sequence, transfer was not detected (≤1.3 × 10−10). The integrated plastid DNA segments extended up to 2539 nucleotides and often encompassed tobacco genes (trnL, ycf5). Expression of trnL (leucyl‐tRNA) in a transformant was shown by reverse transcription polymerase chain reaction. About 44% of integration events occurred at a single hot‐spot and 38% at other multiply used sites. All illegitimate recombination sites were GC‐rich microhomologies of 3–6 bp often neighboured by further microhomologies. The sites were located in plant DNA at the ends of distinct larger high‐GC regions, which suggests a role for GC‐aided association of heterologous sequences in illegitimate DNA end joining. The results show that integration of plant DNA into a bacterial genome by natural transformation is possible and is probably stimulated by hot‐spots of illegitimate recombination.
Isolation and characterisation of a class of carbohydrate oxidases from higher plants, with a role in active defence
Authors: Custers Jerôme H.H.V. , Harrison Stuart J. , Sela‐Buurlage Marianne B. , Van Deventer Els , Lageweg Wessel , Howe Peter W. , Van Der Meijs Pieter J. , Ponstein Anne S. , Simons Bert H. , Melchers Leo S. , Stuiver Maarten H. 
Published: June 2004

SummaryIn a search for novel plant‐derived antimicrobial proteins, we screened extracts from salicylic acid (SA)‐treated lettuce and sunflower leaves. These extracts displayed very potent antimicrobial activity against a set of phytopathogens. Characterisation of these extracts revealed that in both extracts, proteins of approximately 60 kDa were responsible for the antimicrobial activity. Further characterisation of these proteins and cloning of the respective cDNAs revealed close homology to a range of (plant) oxidases. Dissection of the enzymatic activity of both proteins revealed them to be carbohydrate oxidases (Helianthus annuus carbohydrate oxidase (Ha‐CHOX) and Lactuca sativa carbohydrate oxidase (Ls‐CHOX)) with broad substrate specificity and with hydrogen peroxide (H2O2) as one of the reaction products. The sunflower transcript, in addition to being SA inducible, was also inducible by fungal pathogens but not by ethylene and jasmonate. To determine whether Ha‐CHOX plays a role in pathogen defence, it was transformed into tobacco and the effect of resistance to Pectobacterium carotovorum ssp. carotovorum was examined. Transgenic plants overexpressing Ha‐CHOX displayed enhanced resistance to infection by this pathogen, and the resistance level was proportional to enzyme expression.
Disruption of the novel plant protein NEF1 affects lipid accumulation in the plastids of the tapetum and exine formation of pollen, resulting in male sterility in Arabidopsis thaliana
Authors: Ariizumi Tohru , Hatakeyama Katsunori , Hinata Kokichi , Inatsugi Rie , Nishida Ikuo , Sato Shusei , Kato Tomohiko , Tabata Satoshi , Toriyama Kinya 
Published: June 2004

SummaryA novel male‐sterile mutant of Arabidopsis thaliana was isolated by means of T‐DNA tagging. Pollen abortion of the mutant was evident after microspore release, and pollen grains were completely absent at anthesis. Transmission electron microscope analysis revealed that primexine was coarsely developed, and that although sporopollenin was produced, it was not deposited onto the microspore plasma membrane. The sporopollenin that failed to be deposited aggregated and accumulated within the locule and on the locule wall. Finally, as no exine formation was observed, the mutant was named nef1. The plastoglobuli within the plastids of the tapetum were reduced, and lipid accumulation was considerably decreased. The mutant had a significantly altered leaf chloroplast ultrastructure and showed various growth defects. Lipid analysis revealed that the total lipid content in nef1 was lower than that in the wild type, which indicated that Nef1 was involved in lipid metabolism. Cloning of the full‐length Nef1 indicated that the gene encodes a novel plant protein of 1123 amino acids with limited sequence similarities to membrane proteins or transporter‐like proteins, and the NEF1 is predicted to be a plastid integral membrane protein. Motif analysis revealed that NEF1 contains prokaryotic membrane lipoprotein lipid attachment sites that are involved in maintaining cell envelope integrity. It is predicted that the Nef1 encodes a membrane protein that maintains the envelope integrity in the plastids.
Endocytosis against high turgor: intact guard cells of Vicia faba constitutively endocytose fluorescently labelled plasma membrane and GFP‐tagged K+‐channel KAT1
Authors: Meckel Tobias , Hurst Annette C. , Thiel Gerhard , Homann Ulrike 
Published: June 2004

SummaryThe relevance of endocytosis in plants against high turgor pressure has frequently been questioned on the basis of energetic considerations. Here, we examine the dynamics of the plasma membrane (PM) in turgid guard cells of Vicia faba by monitoring with confocal microscopy the fate of fluorescent styryl dyes (FM1‐43, FM2‐10 and FM4‐64). As a second marker, we also observe the retrieval of a fluorescent chimaera of the K+‐inward rectifying channel from Arabidopsis thaliana and the green fluorescent protein (KAT1::GFP). Analysis of cytoplasmic structures, which became labelled by the different styryl dyes, revealed that only FM4‐64, the most hydrophobic dye, was a reliable marker of endocytosis, whereas the two other styryl dyes resulted also in an unspecific labelling of different cytoplasmic structures including mitochondria. Over some minutes of incubation in continuous presence of these dyes, endocytic vesicles in the cortical cytoplasm beneath the PM were fluorescently labelled. The identification is based on the observation that the size distribution of these structures is very similar to that of endocytic vesicles obtained from patch‐clamp capacitance recordings. Also, these structures are frequently co‐labelled with KAT1::GFP. Taken together, the data show that turgid guard cells undergo vigorous constitutive endocytosis and retrieve membrane including the K+‐channel KAT1 from the PM via endocytic vesicles.
The calcium‐dependent protein kinase HvCDPK1 mediates the gibberellic acid response of the barley aleurone through regulation of vacuolar function
Authors: McCubbin Andrew G. , Ritchie Sian M. , Swanson Sarah J. , Gilroy Simon 
Published: June 2004

SummaryIn the aleurone cells of the cereal grain, gibberellic acid (GA) induces the secretion of hydrolases that mobilize endosperm reserves to fuel early seedling growth. GA is known to trigger a range of cellular responses, including increases in cytoplasmic calcium, vacuolar reserve mobilization, gene transcription, and the synthesis and secretion of hydrolases. To further define elements of the Ca2+‐dependent GA response machinery, we have cloned a Ca2+‐dependent protein kinase (HvCDPK1) from these cells. Although expression of an inactivated (D140N) version of this kinase did not affect GA‐induced gene expression or changes in cytosolic Ca2+, it did inhibit secretion, cell vacuolation, and vacuolar acidification, all responses linked to the GA response. Additionally, recombinant wild‐type HvCDPK1 activated the V‐type H+‐ATPase present in isolated aleurone vacuoles. These results suggest HvCDPK1 may mediate Ca2+‐dependent events of the GA response, such as control of vacuolar function, that lie downstream of transcriptional regulation.
Virus‐induced gene silencing in Solanum species
Authors: Brigneti Gianinna , Martín‐Hernández Ana M. , Jin Hailing , Chen Judy , Baulcombe David C. , Baker Barbara , Jones Jonathan D. G. 
Published: June 2004

SummaryVirus‐induced gene silencing (VIGS) has been used routinely in Nicotiana benthamiana to assess functions of candidate genes and as a way to discover new genes required for diverse pathways, especially disease resistance signalling. VIGS has recently been shown to work in Arabidopsis thaliana and in tomato. Here, we report that VIGS using the tobacco rattle virus (TRV) viral vector can be used in several Solanum species, although the choice of vector and experimental conditions vary depending on the species under study. We have successfully silenced the phytoene desaturase (PDS) gene in the diploid wild species Solanum bulbocastanum and S. okadae, in the cultivated tetraploid S. tuberosum and in the distant hexaploid relative S. nigrum (commonly known as deadly nightshade). To test whether the system could be utilised as a rapid way to assess gene function of candidate resistance (R) genes in potato and its wild relatives, we silenced R1 and Rx in S. tuberosum and RB in S. bulbocastanum. Silencing of R1, Rx and RB successfully attenuated R‐gene‐mediated disease resistance and resulted in susceptible phenotypes in detached leaf assays. Thus, the VIGS system is an effective method of rapidly assessing gene function in potato.
Disruption of AtMRP4, a guard cell plasma membrane ABCC‐type ABC transporter, leads to deregulation of stomatal opening and increased drought susceptibility
Authors: Klein Markus , Geisler Markus , Suh Su Jeoung , Kolukisaoglu H. Üner , Azevedo Louis , Plaza Sonia , Curtis Mark D. , Richter Andreas , Weder Barbara , Schulz Burkhard , Martinoia Enrico 
Published: June 2004

SummaryATP‐binding cassette (ABC) transporters are membrane proteins responsible for cellular detoxification processes in plants and animals. Recent evidence shows that this class of transporters may also be involved in many other cellular processes. Because of their homology with human multidrug resistance‐associated proteins (MRP), cystic fibrosis transmembrane conductance regulator (CFTR) and sulfonylurea receptor (SUR), some plant ABC transporters have been implicated in the regulation of ion channel activities. This paper describes an investigation of the AtMRP4 gene and its role in stomatal regulation. Reporter gene studies showed that AtMRP4 is highly expressed in stomata and that the protein is localized to the plasma membrane. Stomatal aperture in three independent atmrp4 mutant alleles was larger than in wild‐type plants, both in the light and in the dark, resulting in increased water loss but no change in the photosynthetic rate. In baker's yeast, AtMRP4 shows ATP‐dependent, vanadate‐sensitive transport of methotrexate (MTX), an antifolate and a substrate of mammalian MRPs. Treatment with MTX reduced stomatal opening in wild‐type plants, but had no effect in atmrp4 mutants. These results indicate the involvement of AtMRP4 in the complex regulation of stomatal aperture.
The plant CDF family member TgMTP1 from the Ni/Zn hyperaccumulator Thlaspi goesingense acts to enhance efflux of Zn at the plasma membrane when expressed in Saccharomyces cerevisiae
Authors: Kim Donggiun , Gustin Jeffery L. , Lahner Brett , Persans Michael W. , Baek Dongwon , Yun Dae‐Jin , Salt David E. 
Published: June 2004

SummaryTo avoid metal toxicity, organisms have evolved mechanisms including efflux of metal ions from cells and sequestration into internal cellular compartments. Members of the ubiquitous cation diffusion facilitator (CDF) family are known to play an important role in these processes. Overexpression of the plant CDF family member metal tolerance protein 1 (MTP1) from the Ni/Zn hyperaccumulator Thlaspi goesingense (TgMTP1), in the Saccharomyces cerevisiaeΔ zinc resistance conferring (zrc)1Δ cobalt transporter (cot)1 double mutant, suppressed the Zn sensitivity of this strain. T. goesingense was found to contain several allelic variants of TgMTP1, all of which confer similar resistance to Zn in Δzrc1Δcot1. Similarly, MTP1 from various hyperaccumulator and non‐accumulator species also confer similar resistance to Zn. Δzrc1Δcot1 lacks the ability to accumulate Zn in the vacuole and has lower accumulation of Zn after either long‐ or short‐term Zn exposure. Expression of TgMTP1 in Δzrc1Δcot1 leads to further lowering of Zn accumulation and an increase in Zn efflux from the cells. Expression of TgMTP1 in a V‐type ATPase‐deficient S. cerevisiae strain also confers increased Zn resistance. In vivo and in vitro immunological staining of hemagglutinin (HA)‐tagged TgMTP1::HA reveals the protein to be localized in both the S. cerevisiae vacuolar and plasma membranes. Taken together, these data are consistent with MTP1 functioning to enhance plasma membrane Zn efflux, acting to confer Zn resistance independent of the vacuole in S. cerevisiae. Transient expression in Arabidopsis thaliana protoplasts also reveals that TgMTP1::green fluorescent protein (GFP) is localized at the plasma membrane, suggesting that TgMTP1 may also enhance Zn efflux in plants.
Floral induction in tissue culture: a system for the analysis of LEAFY‐dependent gene regulation
Authors: Wagner Doris , Wellmer Frank , Dilks Kieran , William Dilusha , Smith Michael R. , Kumar Prakash P. , Riechmann José Luis , Greenland Andrew J. , Meyerowitz Elliot M. 
Published: June 2004

SummaryWe have developed a versatile floral induction system that is based on ectopic overexpression of the transcription factor LEAFY (LFY) in callus. During shoot regeneration, flowers or floral organs are formed directly from root explants without prior formation of rosette leaves. Morphological and reporter gene analyses show that leaf‐like structures are converted to floral organs in response to LFY activity. Thus, increased levels of LFY activity are sufficient to bypass normal vegetative development and to direct formation of flowers in tissue culture. We found that about half of the cultured cells respond to inducible LFY activity with a rapid upregulation of the known direct target gene of LFY, APETALA1 (AP1). This dramatic increase in the number of LFY‐responsive cells compared to whole plants suggested that the tissue culture system could greatly facilitate the analysis of LFY‐dependent gene regulation by genomic approaches. To test this, we monitored the gene expression changes that occur in tissue culture after activation of LFY using a flower‐specific cDNA microarray. Induction of known LFY target genes was readily detected in these experiments. In addition, several other genes were identified that had not been implicated in signaling downstream of LFY before. Thus, the floral induction system is suitable for the detection of low abundance transcripts whose expression is controlled in an LFY‐dependent manner.
Nitric oxide attenuates ischaemia‐reperfusion (I/R) injury in the diabetic liver
Authors: Rogers Hollis , Zibari Gazi B , Roberts Jenifer , Turnage Richard , Lefer David J 
Published: June 2004

Abstract:  Background:  Liver ischaemia‐reperfusion (I/R) occurs during resuscitation from haemorrhagic shock, hepatic transplantation and anatomic resection of the liver. This injury is associated with hepatocellular enzyme release and hepatocyte necrosis. The impact of chronic illnesses such as diabetes mellitus (DM) on hepatic I/R is unknown. This study determines the effect of DM on liver I/R using a murine model of type II DM in which the leptin receptor is defective. Preliminary studies suggest that animal models of DM have impaired endothelial nitric oxide (NO) release. Other studies suggest that NO attenuates hepatic I/R in phenotypically normal animals. We postulated that DM exacerbates hepatic I/R and that exogenous NO administration will attenuate hepatocellular injury.Methods:  Non‐diabetic and diabetic (db/db) mice were anaesthetized and underwent laparotomy with the placement of a microvascular clip on the hepatic artery and portal vein supplying the medial and left lateral lobes of the liver rendering about 70% of the liver ischaemic. Hepatic ischaemia was maintained for 45 min after which time the clip was removed and the liver segments reperfused. The abdomen was closed and the animals maintained for 5 h of reperfusion. Hepatic injury was then assessed by measuring serum alanine and aspartate transaminases (ALT, AST) spectrophotometrically. Sections of liver reperfused for 24 h were stained with haematoxylin and eosin and the percentage of hepatocyte necrosis evaluated using morphometric techniques. Other animals undergoing hepatic I/R received the NO donor (DETA 100 µg/kg, i.v. 5 min prior to reperfusion). Time‐matched, sham‐operated animals served as controls. The data are expressed as mean ± SEM and analysed by ANOVA.Results:  Serum AST and ALT levels were significantly higher in db/db animals vs. non‐diabetics, even in the absence of hepatic I/R (P < 0.01). Serum AST and ALT levels in db/db mice undergoing hepatic I/R were nearly five times greater than that of non‐diabetic animals (P < 0.01). Histologic examination of the livers of the diabetic animals undergoing I/R demonstrated significantly greater hepatocellular necrosis (zone III; 30–40%) when compared with non‐diabetic animals sustaining the same injury (zone III; 3–10%). The NO donor DETA totally prevented the increase in serum ALT and AST release associated with I/R in both the diabetic and non‐diabetic mice when compared with animals not receiving this agent (P < 0.01).Conclusion:  This is the first study suggesting that DM exacerbates hepatic I/R and that NO donors will prevent this hepatocellular injury in the diabetic. Sixteen million Americans have DM. Understanding the effect of this chronic illness on the inflammatory response to injury is essential to improving clinical outcomes in these medically compromised patients.