bluuebunny/crossref_metadata_2025 huggingface dataset:
Diversity of cell lengths in intercalary meristem regions of grasses: location of the proliferative cell population
Authors: Evans Lance S , Perez Rocio K
Published: February 2004

Intercalary meristems are responsible for the production of the majority of cells in stems. The overall objective of the present study was to determine (i) the boundaries of the proliferative parenchyma cells in the intercalary meristems and (ii) the proliferative capacity of cells in the intercalary meristems in stems of a species of Bambusa Schreb. (bamboo), Phragmites australis (Cav.) Trin. ex Steud., Triticum aestivum L., and Zea mays L. Data show that lengths of parenchyma cells within proliferative portions of intercalary meristems were not the same for all intercalary meristems of a species. Lengths of elongated parenchyma cells in internodes were relatively similar among internodes of a species, but lengths of elongated parenchyma cells in internodes were not similar among the four grass species tested. For example, cell lengths of elongated parenchyma cells in internodes of P. australis ranged from 14.8 to 23.0 µm, very different from lengths of elongated cells in Bambusa sp. (69.175.4 µm). The number of proliferative cells in most files of intercalary meristems of Bambusa was less than 15. For many of the intercalary meristems of P. australis, the intercalary meristem consisted of 1025 cells in each file. Fourth intercalary meristems of T. aestivum and Z. mays consisted of 20 and 25 cells in files, respectively. Data showed that none of the cell populations of the intercalary meristems of four species exhibited an exponential cell length distribution. In general, less than half of the 10 groups of cells had percentages of cells that resembled an exponential cell-age distribution. These data lead to the conclusion that not all parenchyma cells of intercalary meristems are rapidly proliferating. Also, potentially prolifera tive cells (short cells) of the intercalary meristems may not be localized into a specific zone but are more scattered throughout the nodal region.Key words: intercalary meristems, proliferative cell populations, Gramineae, cell lengths.
Action of plant growth regulators and salinity on seed germination of Ceratoides lanata
Authors: Khan M Ajmal , Gul Bilquees , Weber Darrell J
Published: February 2004

Ceratoides lanata (Pursh) J.T. Howell is a shrub with numerous annual branchlets from the family Chenopodiaceae and is widely distributed in brackish water playas of northern Utah. Seeds had no dormancy, and about 90% of the seeds germinated in nonsaline control. Seed germination decreased with the increase in salinity, and more than 10% of the seeds germinated at 900 mmol/L NaCl. Almost all seeds germinated in less than 24 h, and no additional seed germinated after this time. Gibberellic acid had no effect in alleviating salinity effects; however, kinetin and fusicoccin substantially alleviated the effect of salinity on germination, while ethephon almost completely reverted the effect of salinity.Key words: Ceratoides lanata, gibberellic acid, ethephon, fusicoccin, halophytes, kinetin.
Are resources allocated differently to symbiosis and reproduction in Geranium sylvaticum under different light conditions?
Authors: Korhonen Jarkko , Kytöviita Minna-Maarit , Siikamäki Pirkko
Published: February 2004

Light levels under the forest canopy are low and generally limit plant photosynthetic gains. We hypothesized that in low-light habitats, plant photosynthate acquisition is too low to allow the same magnitude of resource allocation to symbiosis and reproduction as in high-light habitats. We tested this hypothesis in a field study where Geranium sylvaticum L. plants were collected on three occasions during the growing season from shade and light habitats. In addition, we investigated the relationship between mycorrhizal colonization level and soil nutrient levels in shade and high-light habitats over a growing season. We found that light availability affects resource allocation in G. sylvaticum. Plants were intensively colonized with both arbuscular mycorrhizal and dark septate fungi, and the colonization intensities of these two different groups of fungi correlated positively with each other. In comparison with high-light meadows, mycorrhizal colonization levels were as high or higher in low-light forest habitats, but plants produced fewer flowers. This indicates that allocation to symbiosis was of higher priority than allocation to reproduction in low light. Seed size was not affected by light levels and did not correlate with fungal colonization levels. We found no relationship between fungal colonization levels and soil characteristics.Key words: arbuscular mycorrhiza, dark septate fungi, Geranium sylvaticum, reproduction, shade.
Sucrose synthase isozyme SUS1 in the maize root cap is preferentially localized in the endopolyploid outer cells
Authors: Kladnik Ale , Vilhar Barbara , Chourey Prem S , Dermastia Marina
Published: February 2004

The structure of the maize (Zea mays L.) root cap was studied to quantitatively evaluate the relationship among the size of the cells, their endopolyploidy level, and the abundance of the sucrose synthase isozyme SUS1. Median longitudinal root cap sections were analysed using immunolocalization, quantitative DNA staining, and image cytometry. Both the immunolocalization signal for the SUS1 protein and the endopolyploidy level increased from calyptrogen towards the root cap periphery and were thus the highest in the outer cells. These cells had a nuclear DNA content of mostly 8C or higher and the largest volumes of all root cap cells. The high amount of SUS1 protein in the outer, endopolyploid cells suggests an association between endoreduplication and the abundance of this enzyme. The outer cells are involved in mucilage production; hence, there is a possibility that sucrose synthase provides monosaccharide precursors for mucilage synthesis.Key words: nuclear DNA amount, endoreduplication, immunolocalization, image cytometry, Zea mays L.
Soil as a potential source of nitrogen for mat-forming lichens
Authors: Ellis Christopher J , Crittenden Peter D , Scrimgeour Charles M
Published: February 2004

A field experiment is described, the aim of which was to assess the extent of nitrogen (N) movement from heathland soil upwards into terricolous mat-forming lichens. A molten agar solution of either 15N-labelled glycine or 15N-labelled ammonium (as NH4Cl) was injected onto the soil surface beneath undisturbed cushions of Cladonia por tentosa (Dufour) Coem. Lichen thalli were recovered after 9 months and analysed for 15N content. There was no evidence of 15N uptake by the lichen, though 15N was taken up by vascular plants rooted beneath the lichen cushions. The results suggest that C. portentosa does not compete effectively for soil N. This refutes the conclusions of previous studies, which inferred the efficient uptake of soil organic N by mat-forming lichens based on values of δ15N.Key words: ammonium, lichens, 15N, organic nitrogen, soil nutrients.
Transition states of the high-affinity rabbit Na+/glucose cotransporter SGLT1 as determined from measurement and analysis of voltage-dependent charge movements
Authors: Krofchick Daniel , Huntley Steven A. , Silverman Mel
Published: February 2004

The charge-membrane voltage ( Q-V) distribution of wild-type rabbit Na+/glucose transporter (rSGLT1) expressed in Xenopus oocytes was investigated in the absence of glucose, using the two-electrode voltage-clamp technique. Although this distribution is generally believed to be well represented by a two-state Boltzmann equation, we recently provided evidence for the existence of at least four states (Krofchick D and Silverman M. Biophys J 84: 3690–3702, 2003), confirming an earlier finding for human SGLT1 (Chen XZ, Coady MJ, and Lapointe JY. Biophys J 71: 2544–2552, 1996). We now extend our study of rSGLT1 pre-steady-state currents, employing high-resolution measurement and analysis of the Q-V distribution. A ramp, instead of a step, voltage change was used to prevent saturation of the apparatus in the first ∼1 ms. Transient currents were integrated out to 150 ms, instead of the standard 50–100 ms. Measurements were taken every 10 mV instead of the standard 20 mV. The Q-V distribution was fit with a two-, three-, and four-state Boltzmann equation and was described best by the three-state equation. The three-state fit produced two valences of 0.45 and 1.1 at two V0.5 values of −48 and −7.7, respectively. Our findings are critically compared with other published studies and the differences are discussed. An implication of the three-state fit is that the turnover rate of rSGLT1 is 34 s−1, i.e., 54% greater than previously reported (22 s−1). Our new findings support the concept that the sugar-free model of SGLT1 is more complex than generally accepted, most likely involving a minimum of four transition states.
OKP cells express the Na-dicarboxylate cotransporter NaDC-1
Authors: Aruga Seiji , Pajor Ana M. , Nakamura Kiyoshi , Liu Liping , Moe Orson W. , Preisig Patricia A. , Alpern Robert J.
Published: February 2004

Urinary citrate concentration, a major factor in the formation of kidney stones, is primarily determined by its rate of reabsorption in the proximal tubule. Citrate reabsorption is mediated by the Na-dicarboxylate cotransporter-1 (NaDC-1). The opossum kidney (OKP) cell line possesses many characteristics of the renal proximal tubule. The OKP NaDC-1 (oNaDC-1) cDNA was cloned and encodes a 2.4-kb mRNA. When injected into Xenopus oocytes, the cotransporter is expressed and demonstrates Na-coupled citrate transport with a stoichiometry of ≥3 Na:1 citrate, specificity for di- and tricarboxylates, pH-dependent citrate transport, and pH-independent succinate transport, all characteristics of the other NaDC-1 orthologs. Chronic metabolic acidosis increases proximal tubule citrate reabsorption, leading to profound hypocitraturia and an increased risk for stone formation. Under the conditions studied, endogenous OKP NaDC-1 mRNA abundance is not regulated by changes in media pH. In OKP cells transfected with a green fluorescent protein-oNaDC-1 construct, however, media acidification increases Na-dependent citrate uptake, demonstrating posttranscriptional acid regulation of NaDC-1 activity.
Involvement of anion channel(s) in the modulation of the transient outward K+ channel in rat ventricular myocytes
Authors: Lai Xiao-Gang , Yang Jun , Zhou Shi-Sheng , Zhu Jun , Li Gui-Rong , Wong Tak-Ming
Published: February 2004

The cardiac Ca2+-independent transient outward K+ current ( Ito), a major repolarizing ionic current, is markedly affected by Cl− substitution and anion channel blockers. We reexplored the mechanism of the action of anions on Ito by using whole cell patch-clamp in single isolated rat cardiac ventricular myocytes. The transient outward current was sensitive to blockade by 4-aminopyridine (4-AP) and was abolished by Cs+ substitution for intracellular K+. Replacement of most of the extracellular Cl− with less permeant anions, aspartate (Asp−) and glutamate (Glu−), markedly suppressed the current. Removal of external Na+ or stabilization of F-actin with phalloidin did not significantly affect the inhibitory action of less permeant anions on Ito. In contrast, the permeant Cl− substitute Br− did not markedly affect the current, whereas F− substitution for Cl− induced a slight inhibition. The Ito elicited during Br− substitution for Cl− was also sensitive to blockade by 4-AP. The ability of Cl− substitutes to induce rightward shifts of the steady-state inactivation curve of Ito was in the following sequence: NO3− > Cl− ≈ Br− > gluconate− > Glu− > Asp−. Depolymerization of actin filaments with cytochalasin D (CytD) induced an effect on the steady-state inactivation of Ito similar to that of less permeant anions. Fluorescent phalloidin staining experiments revealed that CytD-pretreatment significantly decreased the intensity of FITC-phalloidin staining of F-actin, whereas Asp− substitution for Cl− was without significant effect on the intensity. These results suggest that the Ito channel is modulated by anion channel(s), in which the actin cytoskeleton may be implicated.
PKC-ε regulation of extracellular signal-regulated kinase: a potential role in phenylephrine-induced cardiocyte growth
Authors: Rao Vijay U. , Shiraishi Hirokazu , McDermott Paul J.
Published: February 2004

Hypertrophic growth of cardiac muscle is dependent on activation of the PKC-ε isoform. To define the effectors of PKC-ε involved in growth regulation, recombinant adenoviruses were used to overexpress either wild-type PKC-ε (PKC-ε/WT) or dominant negative PKC-ε (PKC-ε/DN) in neonatal rat cardiocytes. PKC-ε/DN inhibited acute activation of PKC-ε produced in response to phorbol ester and reduced ERK1/2 activity as measured by the phosphorylation of p42 and p44 isoforms. The inhibitory effects were specific to PKC-ε because PKC-ε/DN did not prevent translocation of either PKC-α or PKC-δ. Overexpression of PKC-ε/DN blunted the acute increase in ERK1/2 phorphorylation induced by the α1-adrenergic agonist phenylephrine (PE ). Inhibition of PKC-δ with rottlerin potentiated the effects of PE on ERK1/2 phosphorylation. PKC-ε/DN adenovirus also blocked cardiocyte growth as measured after 48 h of PE treatment, although the multiplicity of infection was lower than that required to block acute ERK1/2 activation. PE activated p38 mitogen-activated protein kinase as measured by its phosphorylation, but the response was not blocked by PKC inhibitors or by overexpression of PKC-ε/DN. Taken together, these studies show that the hypertrophic agonist PE regulates ERK1/2 activity in cardiocytes by a pathway dependent on PKC-ε and that PE-induced growth is mediated by PKC-ε.
Attenuation of acute hypoxic pulmonary vasoconstriction and hypoxic pulmonary hypertension in mice by inhibition of Rho-kinase
Authors: Fagan Karen A. , Oka Masahiko , Bauer Natalie R. , Gebb Sarah A. , Ivy D. Dunbar , Morris Kenneth G. , McMurtry Ivan F.
Published: February 2004

RhoA GTPase mediates a variety of cellular responses, including activation of the contractile apparatus, growth, and gene expression. Acute hypoxia activates RhoA and, in turn, its downstream effector, Rho-kinase, and previous studies in rats have suggested a role for Rho/Rho-kinase signaling in both acute and chronically hypoxic pulmonary vasoconstriction. We therefore hypothesized that activation of Rho/Rho-kinase in the pulmonary circulation of mice contributes to acute hypoxic pulmonary vasoconstriction and chronic hypoxia-induced pulmonary hypertension and vascular remodeling. In isolated, salt solution-perfused mouse lungs, acute administration of the Rho-kinase inhibitor Y-27632 (1 × 10−5 M) attenuated hypoxic vasoconstriction as well as that due to angiotensin II and KCl. Chronic treatment with Y-27632 (30 mg·kg−1·day−1) via subcutaneous osmotic pump decreased right ventricular systolic pressure, right ventricular hypertrophy, and neomuscularization of the distal pulmonary vasculature in mice exposed to hypobaric hypoxia for 14 days. Analysis of a small number of proximal pulmonary arteries suggested that Y-27632 treatment reduced the level of phospho-CPI-17, a Rho-kinase target, in hypoxic lungs. We also found that endothelial nitric oxide synthase protein in hypoxic lungs was augmented by Y-27632, suggesting that enhanced nitric oxide production might have played a role in the Y-27632-induced attenuation of chronically hypoxic pulmonary hypertension. In conclusion, Rho/Rho-kinase activation is important in the effects of both acute and chronic hypoxia on the pulmonary circulation of mice, possibly by contributing to both vasoconstriction and vascular remodeling.
Influence of maturation on constrictive response to stimulation of C-fiber afferents in isolated guinea pig airways
Authors: Wu Z.-X. , Yang Q. H. , Ruan T. , Lee L.-Y.
Published: February 2004

We investigated whether the airway constrictive response to stimulation of bronchopulmonary C-fiber afferents is altered during the maturation process. Isometric tension was measured in airway rings isolated from three tracheobronchial locations (intrathoracic trachea and main and hilar bronchi) and compared in mature [M, 407 ± 10 (SE) g body wt, n = 36] and immature (IM, 161 ± 5 g body wt, n = 35) guinea pigs. Our results showed no difference in the ACh (10−5 M)- or KCl (40 mM)-induced contraction between M and IM groups, regardless of the airway location. In sharp contrast, the concentration-response curves of 10−8–10−6 M capsaicin were distinctly lower in IM hilar bronchi; for example, response to the same concentration of capsaicin (10−6 M) was 89.2 ± 15.3% of the response to 10−5 M ACh in IM and 284.7 ± 43.2% in M animals. Similar, but smaller, differences in the bronchoconstrictive response to capsaicin between IM and M groups were also observed in the trachea and main bronchus. Electrical field stimulation induced airway constriction in all three locations in M and IM groups. However, after administration of 10−6 M atropine and 10−6 M propranolol, electrical field stimulation-induced contraction was significantly smaller in the hilar bronchus of IM than M animals, and this difference was not prevented by pretreatment with 5 × 10−5 M indomethacin. Although radioimmunoassay showed no difference in the tissue content of substance P between M and IM airways, the constrictive responses to exogenous substance P and neurokinin A were markedly greater in M airways at all three locations. In conclusion, the constriction of isolated airways evoked by C-fiber stimulation was significantly weaker in the IM guinea pigs, probably because of a less potent effect of tachykinins on the airway smooth muscle.
Arginase inhibition increases nitric oxide production in bovine pulmonary arterial endothelial cells
Authors: Chicoine Louis G. , Paffett Michael L. , Young Tamara L. , Nelin Leif D.
Published: February 2004

Nitric oxide (NO) is produced by NO synthase (NOS) from l-arginine (l-Arg). Alternatively, l-Arg can be metabolized by arginase to produce l-ornithine and urea. Arginase (AR) exists in two isoforms, ARI and ARII. We hypothesized that inhibiting AR with l-valine (l-Val) would increase NO production in bovine pulmonary arterial endothelial cells (bPAEC). bPAEC were grown to confluence in either regular medium (EGM; control) or EGM with lipopolysaccharide and tumor necrosis factor-α (L/T) added. Treatment of bPAEC with L/T resulted in greater ARI protein expression and ARII mRNA expression than in control bPAEC. Addition of l-Val to the medium led to a concentration-dependent decrease in urea production and a concentration-dependent increase in NO production in both control and L/T-treated bPAEC. In a second set of experiments, control and L/T bPAEC were grown in EGM, EGM with 30 mM l-Val, EGM with 10 mM l-Arg, or EGM with both 10 mM l-Arg and 30 mM l-Val. In both control and L/T bPAEC, treatment with l-Val decreased urea production and increased NO production. Treatment with l-Arg increased both urea and NO production. The addition of the combination l-Arg and l-Val decreased urea production compared with the addition of l-Arg alone and increased NO production compared with l-Val alone. These data suggest that competition for intracellular l-Arg by AR may be involved in the regulation of NOS activity in control bPAEC and in response to L/T treatment.
Malnutrition impairs alveolar fluid clearance in rat lungs
Authors: Sakuma Tsutomu , Zhao Yabin , Sugita Makoto , Sagawa Motoyasu , Toga Hirohisa , Ishibashi Takaharu , Nishio Matomo , Matthay Michael A.
Published: February 2004

Inadequate nutrition complicates the clinical course of critically ill patients, and many of these patients develop pulmonary edema. However, little is known about the effect of malnutrition on the mechanisms that resolve alveolar edema. Therefore, we studied the mechanisms responsible for the decrease in alveolar fluid clearance in rats exposed to malnutrition. Rats were allowed access to water, but not to food, for 120 h. Then, the left and right lungs were isolated for the measurement of lung water volume and alveolar fluid clearance, respectively. The rate of alveolar fluid clearance was measured by the progressive increase in the concentration of Evans blue dye that was instilled into the distal air spaces with an isosmolar 5% albumin solution over 1 h. Malnutrition decreased alveolar fluid clearance by 38% compared with controls. Amiloride (10−3M) abolished alveolar fluid clearance in malnourished rats. Either refeeding for 120 h following nutritional deprivation for 120 h or an oral supply of sodium glutamate during nutritional deprivation for 120 h restored alveolar fluid clearance to 91 and 86% of normal, respectively. Dibutyryl-cGMP, a cyclic nucleotide-gated cation channel agonist, increased alveolar fluid clearance in malnourished rats supplied with sodium glutamate. Terbutaline, a β2-adrenergic agonist, increased alveolar fluid clearance in rats under all conditions (control, malnutrition, refeeding, and glutamate-treated). These results indicate that malnutrition impairs primarily amiloride-insensitive and dibutyryl-cGMP-sensitive alveolar fluid clearance, but this effect is partially reversible by refeeding, treatment with sodium glutamate, or β-adrenergic agonist therapy.
Genomic structure and promoter characterization of the humanSprouty4gene, a novel regulator of lung morphogenesis
Authors: Ding Wei , Bellusci Saverio , Shi Wei , Warburton David
Published: February 2004

The expression of Sprouty4 ( Spry4), an intracellular FGF receptor antagonist, shows a temporally and spatially restricted pattern in embryonic lung and is induced by ERK signaling. To clarify the molecular mechanisms regulating Spry4 transcription, the genomic structure of the human Sprouty4 ( hSpry4) gene was first determined by using the GenomeWalker kit. The hSpry4 gene spans > 14 kb and is organized in three exons and two introns. Multiple transcription start sites were subsequently mapped by 5′-rapid amplification of cDNA ends. Analysis of up to 4 kb of sequence in the 5′-flanking region of the gene showed the presence of multiple potential transcription factor binding sites but no TATA or CAAT boxes. Transient transfection using luciferase reporter gene constructs with progressive deletions of the hSpry4 5′-flanking region revealed that the core promoter activity is located within the proximal 0.4-kb region, whereas the minimal ERK-inducible promoter activity is between −69 and −31. Homology analysis further showed that the core promoter region of the hSpry4 gene exhibits significant similarity to the 5′-flanking region of the mouse gene.
Mutations in the extracellular loop of α-rENaC alter sensitivity to amiloride and reactive species
Authors: Chen Lan , Fuller Catherine M. , Kleyman Thomas R. , Matalon Sadis
Published: February 2004

We studied the effects of two mutations of the extracellular loop of the α-subunit of the (ENaC) on amiloride-sensitive current in Xenopus laevis oocytes and the inhibition of this current by 3-morpholinosydnonimine (SIN-1). Injection of oocytes with wild-type (wt) α-,β-,γ-rENaC cRNA (8.3 ng/subunit) resulted 48–72 h later in inward Na+currents (−5.5 ± 0.8 μA; means ± SE at −100 mV; n = 21), which were completely inhibited by amiloride. Oocytes injected with either αY279A- or αY283A- and β-,γ-rENaC cRNAs had significantly lower Na+currents. Furthermore, αY279A-,β-,γ-rENaC-injected oocytes had a higher Kifor amiloride (0.54 ± 0.97 vs. 0.10 ± 0.04 μM; P < 0.01). Exposure of oocytes to SIN-1 (1 mM) for 5 min decreased both total Na+and amiloride-sensitive currents across wt and αY279A- but not αY283A-,β-,γ-rENaC. Furthermore, exposure to SIN-1 increased the Kifor amiloride across wt but not αY279A-,β-,γ-rENaC-injected oocytes. These data indicate that both tyrosines are important for proper ENaC function and their oxidative modifications contribute to altered ENaC function.
Involvement of guanylyl cyclase and cGMP in the regulation of Mrp2-mediated transport in the proximal tubule
Authors: Notenboom Sylvia , Miller David S. , Smits P. , Russel Frans G. M. , Masereeuw Rosalinde
Published: February 2004

In killifish renal proximal tubules, endothelin-1 (ET-1), acting through a basolateral ETBreceptor, nitric oxide synthase (NOS), and PKC, decreases cell-to-lumen organic anion transport mediated by the multidrug resistance protein isoform 2 (Mrp2). In the present study, we examined the roles of guanylyl cyclase and cGMP in ET signaling to Mrp2. Using confocal microscopy and quantitative image analysis to measure Mrp2-mediated transport of the fluorescent drug fluorescein methotrexate (FL-MTX), we found that oxadiazole quinoxalin (ODQ), an inhibitor of NO-sensitive guanylyl cyclase, blocked ET-1 signaling. ODQ was also effective when signaling was initiated by nephrotoxicants (gentamicin, amikacin, diatrizoate, HgCl2, and CdCl2), which appear to stimulate ET release from the tubules themselves. ODQ blocked the effects of the NO donor sodium nitroprusside but not of the phorbol ester that activates PKC. Exposing tubules to 8-bromo-cGMP (8-BrcGMP), a cell-permeable cGMP analog, decreased luminal FL-MTX accumulation. This effect was abolished by bisindoylmaleimide (BIM), a PKC inhibitor, but not by NG-methyl-l-arginine, a NOS inhibitor. Together, these data indicate that ET regulation of Mrp2 involves activation of guanylyl cyclase and generation of cGMP. Signaling by cGMP follows NO release and precedes PKC activation.
Altered calcium sensitivity contributes to enhanced contractility of collateral-dependent coronary arteries
Authors: Heaps Cristine L. , Parker Janet L. , Sturek Michael , Bowles Douglas K.
Published: February 2004

Coronary arteries distal to chronic occlusion exhibit enhanced vasoconstriction and impaired relaxation compared with nonoccluded arteries. In this study, we tested the hypotheses that an increase in peak Ca2+ channel current density and/or increased Ca2+ sensitivity contributes to altered contractility in collateral-dependent coronary arteries. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery (LCX) of female miniature swine. Segments of epicardial arteries (∼1 mm luminal diameter) were isolated from the LCX and nonoccluded left anterior descending (LAD) arteries 24 wk after Ameroid placement. Contractile responses to depolarization (10–100 mM KCl) were significantly enhanced in LCX compared with size-matched LAD arterial rings [concentration of KCl causing 50% of the maximal contractile response (EC50); LAD = 41.7 ± 2.3, LCX = 34.3 ± 2.7 mM]. However, peak Ca2+ channel current was not altered in isolated smooth muscle cells from LCX compared with LAD (−5.29 ± 0.42 vs. −5.68 ± 0.55 pA/pF, respectively). Furthermore, whereas half-maximal activation of Ca2+ channel current occurred at nearly the same membrane potential in LAD and LCX, half-maximal inactivation was shifted to a more positive membrane potential in LCX cells. Simultaneous measures of contractile tension and intracellular free Ca2+ (fura 2) levels in arterial rings revealed that significantly more tension was produced per unit change in fura 2 ratio in LCX compared with LAD in response to KCl but not during receptor-agonist stimulation with endothelin-1. Taken together, our data indicate that coronary arteries distal to chronic occlusion display increased Ca2+ sensitivity in response to high KCl-induced depolarization, independent of changes in whole cell peak Ca2+ channel current. Unaltered Ca2+ sensitivity in endothelin-stimulated arteries suggests more than one mechanism regulating Ca2+ sensitization in coronary smooth muscle.
Amplitude and Direction of Saccadic Eye Movements Depend on the Synchronicity of Collicular Population Activity
Authors: Brecht Michael , Singer Wolf , Engel Andreas K.
Published: February 2004

Synchronization of neuronal discharges has been observed in numerous brain structures, but opinions diverge regarding its significance in neuronal processing. Here we investigate whether the motion vectors of saccadic eye movements evoked by electrical multisite stimulation of the cat superior colliculus (SC) are influenced by varying the degree of synchrony between the stimulus trains. With synchronous activation of SC sites, the vectors of the resulting saccades correspond approximately to the averages of the vectors of saccades evoked from each site alone. In contrast, when the pulses of trains applied to the different sites are temporally offset by as little as 5–10 ms, the vectors of the resulting saccades come close to the sum of the individual vectors. Thus saccade vectors depend not only on the site and amplitude of collicular activation but also on the precise temporal relations among the respective spike trains. These data indicate that networks within or downstream from the SC discriminate with high temporal resolution between synchronous and asynchronous population responses. This supports the hypothesis that information is encoded not only in the rate of neuronal responses but also in the precise temporal relations between discharges.
Substrates for Coincidence Detection and Calcium Signaling for Induction of Synaptic Potentiation in the Neonatal Visual Cortex
Authors: Schrader Laura A. , Perrett Stephen P. , Ye Lan , Friedlander Michael J.
Published: February 2004

Regulation of the efficacy of synaptic transmission by activity-dependent processes has been implicated in learning and memory as well as in developmental processes. We previously described transient potentiation of excitatory synapses onto layer 2/3 pyramidal neurons in the visual cortex that is induced by coincident presynaptic stimulation and postsynaptic depolarization. In the adult visual cortex, activation of N-methyl-d-aspartate (NMDA) glutamate receptors is necessary to induce this plasticity. These receptors act as coincidence detectors, sensing presynaptic glutamate release and postsynaptic depolarization, and cause an influx of Ca2+that is necessary for the potentiation. In the neurons of the neonatal visual cortex, on the other hand, coincident presynaptic stimulation and postsynaptic depolarization induce stable long-term potentiation (LTP). In addition, reduced but significant LTP can be induced in many neurons in the presence of the NMDA receptor (NMDAR) antagonist, 2-amino-5-phosphonovaleric acid despite the Ca2+requirement. Therefore there must be an alternative postsynaptic Ca2+source and coincidence detection mechanism linked to the LTP induction mechanism in the neonatal cortex operating in addition to NMDARs. In this study, we find that in layer 2/3 pyramidal neurons, release of Ca2+from inositol trisphosphate (InsP3) receptor-mediated intracellular stores and influx through voltage-gated Ca2+channels (VGCCs) provide alternative postsynaptic Ca2+sources. We hypothesize that InsP3Rs are coincidence detectors, sensing presynaptic glutamate release through linkage with group I metabotropic glutamate receptors (mGluRs), and depolarization, through VGCCs. We also find that the downstream protein kinases, PKA and PKC, have a role in potentiation in layer 2/3 pyramidal neurons of the neonatal visual cortex.
Long-Term Potentiation of Intrinsic Excitability in LV Visual Cortical Neurons
Authors: Cudmore Robert H. , Turrigiano Gina G.
Published: February 2004

Neuronal excitability has a large impact on network behavior, and plasticity in intrinsic excitability could serve as an important information storage mechanism. Here we ask whether postsynaptic excitability of layer V pyramidal neurons from primary visual cortex can be rapidly regulated by activity. Whole cell current-clamp recordings were obtained from visual cortical slices, and intrinsic excitability was measured by recording the firing response to small depolarizing test pulses. Inducing neurons to fire at high-frequency (30–40 Hz) in bursts for 5 min in the presence of synaptic blockers increased the firing rate evoked by the test pulse. This long-term potentiation of intrinsic excitability (LTP-IE) lasted for as long as we held the recording (>60 min). LTP-IE was accompanied by a leftward shift in the entire frequency versus current ( F-I) curve and a decrease in threshold current and voltage. Passive neuronal properties were unaffected by the induction protocol, indicating that LTP-IE occurred through modification in voltage-gated conductances. Reducing extracellular calcium during the induction protocol, or buffering intracellular calcium with bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid, prevented LTP-IE. Finally, blocking protein kinase A (PKA) activation prevented, whereas pharmacological activation of PKA both mimicked and occluded, LTP-IE. This suggests that LTP-IE occurs through postsynaptic calcium influx and subsequent activation of PKA. Activity-dependent plasticity in intrinsic excitability could greatly expand the computational power of individual neurons.
Muscular and Postural Synergies of the Human Hand
Authors: Weiss Erica J. , Flanders Martha
Published: February 2004

Because humans have limited ability to independently control the many joints of the hand, a wide variety of hand shapes can be characterized as a weighted combination of just two or three main patterns of covariation in joint rotations, or “postural synergies.” The present study sought to align muscle synergies with these main postural synergies and to describe the form of membership of motor units in these postural/muscle synergies. Seventeen joint angles and the electromyographic (EMG) activities of several hand muscles (both intrinsic and extrinsic muscles) were recorded while human subjects held the hand statically in 52 specific shapes (i.e., shaping the hand around 26 commonly grasped objects or forming the 26 letter shapes of a manual alphabet). Principal-components analysis revealed several patterns of muscle synergy, some of which represented either coactivation of all hand muscles, or reciprocal patterns of activity (above and below average levels) in the intrinsic index finger and thumb muscles or (to a lesser extent) in the extrinsic four-tendoned extensor and flexor muscles. Single- and multiunit activity was generally a multimodal function of whole hand shape. This implies that motor-unit activation does not align with a single synergy; instead, motor units participate in multiple muscle synergies. Thus it appears that the organization of the global pattern of hand muscle activation is highly distributed. This organization mirrors the highly fractured somatotopy of cortical hand representations and may provide an ideal substrate for motor learning and recovery from injury.
Is Oxidative Stress the Pathogenic Mechanism Underlying Insulin Resistance, Diabetes, and Cardiovascular Disease? The Common Soil Hypothesis Revisited
Authors: Ceriello Antonio , Motz Enrico
Published: February 2004

Type 2 diabetes is a worldwide increasing disease resulting from the interaction between a subject’s genetic makeup and lifestyle. In genetically predisposed subjects, the combination of excess caloric intake and reduced physical activity induces a state of insulin resistance. When beta cells are no longer able to compensate for insulin resistance by adequately increasing insulin production, impaired glucose tolerance appears, characterized by excessive postprandial hyperglycemia. Impaired glucose tolerance may evolve into overt diabetes. These 3 conditions, ie, insulin resistance, impaired glucose tolerance, and overt diabetes, are associated with an increased risk of cardiovascular disease. Because all these conditions are also accompanied by the presence of an oxidative stress, this article proposes oxidative stress as the pathogenic mechanism linking insulin resistance with dysfunction of both beta cells and endothelium, eventually leading to overt diabetes and cardiovascular disease. This hypothesis, moreover, may also contribute to explaining why treating cardiovascular risk with drugs, such as calcium channel blockers, ACE inhibitors, AT-1 receptor antagonists, and statins, all compounds showing intracellular preventive antioxidant activity, results in the onset of new cases of diabetes possibly being reduced.
CD154/CD40-Mediated Expression of CD154 in Endothelial Cells: Consequences for Endothelial Cell–Monocyte Interaction
Authors: Wagner Andreas H. , Güldenzoph Björn , Lienenlüke Bianca , Hecker Markus
Published: February 2004

Objective—CD40 ligand (CD154) expressed on activated T helper cells is a key costimulatory molecule for antigen-presenting cells expressing the corresponding receptor CD40. Moreover, CD40 stimulation in nonimmune cells, such as endothelial cells, may play an important role in atherogenesis. One gene product that is induced in endothelial cells on exposure to CD154 is CD154 itself.

Methods and Results—In human primary cultured endothelial cells, constitutive CD154 expression was virtually absent and insensitive to proinflammatory cytokines such as tumor necrosis factor α and/or interferon-γ. However, CD154 expression was markedly induced, both on the mRNA and protein level, after CD40 stimulation. Moreover, CD40-positive human monocytes (THP-1 cell line) transmigrating through CD154-expressing endothelial cells responded with an increased expression of interleukin-1β (IL-1β) mRNA, indicative of their activation. This increase in IL-1β expression was confirmed on the protein level and could be abrogated by prior treatment of the endothelial cells with a neutralizing anti-CD154 antibody.

Conclusions—By way of CD154-induced CD154 expression, human endothelial cells thus seem capable of influencing the progression of proinflammatory reactions, including atherogenesis through activation of extravasating monocytes.
Pressure Overload–Induced Myocardial Hypertrophy in Mice Does Not Require gp91
phox
Authors: Maytin Melanie , Siwik Deborah A. , Ito Masahiro , Xiao Lei , Sawyer Douglas B. , Liao Ronglih , Colucci Wilson S.
Published: February 2004

Background—

Reactive oxygen species (ROS) may mediate pressure overload–induced myocardial hypertrophy. NADPH oxidase may be involved in this process, because its expression and activity are upregulated by pressure overload and because myocardial hypertrophy caused by a subpressor infusion of angiotensin is attenuated in mice deficient in the gp91
phox
catalytic subunit of NADPH oxidase.

Methods and Results—

To test the role of NADPH oxidase–dependent ROS in mediating pressure overload–induced myocardial hypertrophy, we subjected transgenic mice lacking gp91
phox
to chronic pressure overload caused by constriction of the ascending aorta. Contrary to our hypothesis, neither myocardial hypertrophy nor NADPH-dependent superoxide generation was decreased in gp91
phox
-deficient mice after aortic constriction. Aortic constriction caused an exaggerated increase in p22
phox
and p47
phox
mRNA in gp91
phox
-deficient mice.

Conclusions—

These results indicate that gp91
phox
is not necessary for pressure overload–induced hypertrophy in the mouse and suggest the involvement of another source of ROS, possibly an NADPH oxidase that does not require the gp91
phox
subunit.
Developmental Endothelial Locus-1 (Del-1), a Novel Angiogenic Protein
Authors: Ho Hoai-Ky V. , Jang James J. , Kaji Shuichiro , Spektor Gary , Fong Annie , Yang Phillip , Hu Bob S. , Schatzman Randy , Quertermous Thomas , Cooke John P.
Published: February 2004

Background—

Developmentally regulated endothelial locus-1 (Del-1) is an extracellular matrix protein that is expressed by endothelial cells during embryological vascular development. We speculated that Del-1 may be reexpressed in ischemia and may be involved in endogenous angiogenesis.

Methods and Results—

Del-1 protein was detected by immunohistochemistry in murine ischemic hindlimb after femoral artery excision. To determine whether exogenous Del-1 would augment angiogenesis in vivo, Del-1 or vehicle was administered for 3 weeks by intramuscular injection of murine ischemic hindlimbs. Angiogenesis was quantified by gadolinium-MRI perfusion and capillary densitometry. We used a disc angiogenesis system (DAS) to characterize the angiogenic response to vehicle (PBS), Del-1, Del-1 mutant (altered RGD domain), Del-1 minor (truncated discoidin-I–like domain), or basic fibroblast growth factor. After 14 days, the discs were extracted and sectioned to quantify vascular growth by morphometry. Endogenous Del-1 protein expression was increased in ischemic hindlimbs. Administration of Del-1 increased hindlimb vascular flow index and capillary density. In the DAS, Del-1 doubled fibrovascular growth, as did basic fibroblast growth factor. However, angiogenesis was not enhanced by the Del-1 mutant or Del-1 minor proteins.

Conclusions—

Del-1 is expressed in ischemic tissue. Del-1 stimulates angiogenesis, an effect that is dependent on the RGD motif and a second signaling sequence in the discoidin-I–like domain. Exogenous intramuscular administration of Del-1 significantly enhances angiogenesis in the murine ischemic hindlimb. Del-1 may prove to be a novel therapeutic agent for patients with ischemia.
Effect of CO
2
Insufflation on the Number and Behavior of Air Microemboli in Open-Heart Surgery
Authors: Svenarud P. , Persson M. , van der Linden J.
Published: February 2004

Background—

The risks that the presence of air microemboli implies in open-heart surgery have recently been emphasized by reports that their number is correlated with the degree of postoperative neuropsychological disorder. Therefore, we studied the effect of CO
2
insufflation into the cardiothoracic wound on the incidence and behavior of microemboli in the heart and ascending aorta.

Methods and Results—

Twenty patients undergoing single-valve surgery were randomly divided into 2 groups. Ten patients were insufflated with CO
2
via a gas diffuser, and 10 were not. Microemboli were ascertained by intraoperative transesophageal echocardiography (TEE) and recorded on videotape from the moment that the aortic cross-clamp was released until 20 minutes after end of cardiopulmonary bypass (CPB). The surgeon performed standard de-airing maneuvers without being aware of TEE findings. Postoperatively, a blinded assessor determined the maximal number of gas emboli during each consecutive minute in the left atrium, left ventricle, and ascending aorta. The 2 groups did not differ in the usual clinical parameters. The median number of microemboli registered during the whole study period was 161 in the CO
2
group versus 723 in the control group (
P
<0.001). Corresponding numbers for the left atrium were 69 versus 340 (
P
<0.001), left ventricle 68 versus 254 (
P
<0.001), and ascending aorta 56 versus 185 (
P
<0.001). In the CO
2
group, the median number of detectable microemboli after CPB fell to zero 7 minutes after CPB versus 19 minutes in the control group (
P
<0.001).

Conclusions—

Insufflation of CO
2
into the thoracic wound markedly decreases the incidence of microemboli.
Manifestations of Metabolic Syndrome After Hypertensive Pregnancy
Authors: Pouta Anneli , Hartikainen Anna-Liisa , Sovio Ulla , Gissler Mika , Laitinen Jaana , McCarthy Mark I. , Ruokonen Aimo , Elliott Paul , Järvelin Marjo-Riitta
Published: February 2004

Small follow-up studies of hospital-based series indicate women with preeclampsia have an increased risk of insulin resistance postpartum. However, long-term data are lacking among women with gestational hypertension without proteinuria. Using a general population-based sample of 5889 women from Northern Finland followed longitudinally since birth in 1966, we examined these associations and the influence of the subject’s own birth weight and gestational age on this relationship. At age 31, blood pressure was measured and blood samples collected from 2678 women, of which 1463 women had had at least 1 singleton pregnancy. Of these, 45 had been hospitalized because of gestational hypertension and 49 because of preeclampsia. Women who had had either gestational hypertension or preeclampsia during their first pregnancy (average age 25 years) had increased blood pressure at 31 years compared with women with previous normotensive pregnancy, even after adjustment for body mass index (
P
<0.001 in gestational hypertension,
P
=0.023 in preeclampsia group). When compared with the whole female population, women with previous gestational hypertension at same age still had higher blood pressure, while this difference was weaker for women with previous preeclampsia. Women with gestational hypertension and preeclampsia also had higher waist circumference, waist/hip ratio, and body mass index, as well as increased serum insulin levels and lower glucose/insulin ratio than women with previous normotensive pregnancy. The associations remained after adjustment for participant’s own birth weight or gestational age. Women born before gestational week 37 had a 2-fold risk for gestational hypertension in their first pregnancy (RR: 2.53; 95% CI: 1.0, 6.2).
Protection From Ischemic Heart Injury by a Vigilant Heme Oxygenase-1 Plasmid System
Authors: Tang Yao Liang , Tang Yi , Zhang Y. Clare , Qian Keping , Shen Leping , Phillips M. Ian
Published: February 2004

Although human heme oxygenase-1 (hHO-1) could provide a useful approach for cellular protection in the ischemic heart, constitutive overexpression of hHO-1 may lead to unwanted side effects. To avoid this, we designed a hypoxia-regulated hHO-1 gene therapy system that can be switched on and off. This vigilant plasmid system is composed of myosin light chain-2v promoter and a gene switch that is based on an oxygen-dependent degradation domain from the hypoxia inducible factor-1-α. The vector can sense ischemia and switch on the hHO-1 gene system, specifically in the heart. In an in vivo experiment, the vigilant hHO-1 plasmid or saline was injected intramyocardially into myocardial infarction mice or sham operation mice. After gene transfer, expression of hHO-1 was only detected in the ischemic heart treated with vigilant hHO-1 plasmids. Masson trichrome staining showed significantly fewer fibrotic areas in vigilant hHO-1 plasmids-treated mice compared with saline control (43.0%±4.8% versus 62.5%±3.3%,
P
<0.01). The reduction of interstitial fibrosis is accompanied by an increase in myocardial hHO-1 expression in peri-infarct border areas, concomitant with higher Bcl-2 levels and lower Bax, Bak, and caspase 3 levels in the ischemic myocardium compared with saline control. By use of a cardiac catheter, heart from vigilant hHO-1 plasmids-treated mice showed improved recovery of contractile and diastolic performance after myocardial infarction compared with saline control. This study documents the beneficial regulation and therapeutic potential of vigilant plasmid-mediated hHO-1 gene transfer. This novel gene transfer strategy can provide cardiac-specific protection from future repeated bouts of ischemic injury.
Transmission of Arterial Baroreflex Signals Depends on Neuronal Nitric Oxide Synthase
Authors: Talman William T. , Dragon Deidre Nitschke
Published: February 2004

Because inhibition of neuronal nitric oxide synthase in the nucleus tractus solitarii blocks cardiovascular responses to activation of local glutamate receptors, and because glutamate is a neurotransmitter of baroreceptor afferent nerves, we sought to test the hypothesis that neuronal nitric oxide synthase inhibition would block baroreflex transmission and cause hypertension. We determined reflex heart rate responses to intravenous phenylephrine and sodium nitroprusside in 5 anesthetized rats before and after bilateral microinjection (100 nL) of the neuronal nitric oxide synthase inhibitor AR-R 17477 (7.5 nmol) into the nucleus tractus solitarii. The inhibitor significantly increased mean arterial pressure without affecting heart rate, and it significantly reduced the gain of the baroreflex. After administration of the inhibitor, reflex responses of heart rate to changes in mean arterial pressure were always less than those responses to the same, or less, change in mean arterial pressure in the same animal without administration of the inhibitor. Microinjection of saline (100 nL) bilaterally into the nucleus tractus solitarii did not lead to hypertension or change baroreflex responses. These data support the hypothesis and suggest that neuronal nitric oxide synthase is critical to transmission of baroreflex signals through the nucleus tractus solitarii.