bluuebunny/crossref_metadata_2025 huggingface dataset:
TransientuidAgene expression in electroporated cotyledonary protoplasts ofPinus nigrassp.salzmanniiand in bombarded cotyledons
Authors: López Marian , Humara Jaime M , Rodríguez Roberto , Ordás Ricardo J
Published: April 2011

We have developed a method for the routine isolation of Pinus nigra Arn. ssp. salzmannii (Dunal) Franco protoplasts. The optimized electroporation conditions for uidA gene (gene for beta-glucuronidase) expression in protoplasts from cotyledons excised from 8-day-old seedlings were determined using an exponential pulse wave generator for gene transfer. The protoplasts were electroporated with plasmids containing the chimeric uidA gene under the control of several promoters, and in parallel, cotyledons were bombarded with the same constructs using a biolistic gun. Both techniques confirmed that gene expression was higher when controlled by the sunflower polyubiquitin gene promoter than by the cauliflower mosaic virus CaMV35S promoter, whereas the rice actin and maize alcohol dehydrogenase promoters resulted in lower uidA expression levels, as determined fluorometrically. In this study, the electroporation procedure has been more effective than the particle bombardment procedure to determine the promoter strength on transient gene expression in P. nigra.
Carry-over effects on growth and transpiration in Fagus sylvatica seedlings after drought at various stages of development
Authors: Löf M , Welander N T
Published: April 2011

In the two experiments carried out, newly emerged F. sylvatica seedlings were grown in pots with sand for 2 years in a controlled environmental chamber. Seedling dry mass, leaf area, and number of leaves decreased because of drought in the previous and in the current year. The decrease in area per leaf was due only to the current-year drought. Drought in both the previous and the current year reduced the number of shoots in the current year. Shoot length was mainly affected by previous-year drought. Current-year seedling transpiration decreased because of drought both in the previous and in the current year. The transpiration rate per unit leaf area was not affected by previous-year drought, whereas an after-effect was found within the growing season. The recovery of transpiration following a drought was up to 20 days. Water-use efficiency was influenced by drought during shoot development. The correlation between integrated transpiration and dry mass increase was high. This study shows that both previous as well as current environmental conditions must be taken into consideration when explaining seedling growth.
Calibration of small-area estimates for map errors in multisource forest inventory
Authors: Katila M , Heikkinen J , Tomppo E
Published: April 2011

A multisource inventory method has been applied in the Finnish National Forest Inventory (NFI) since 1990.The method utilizes satellite images and digital map data,in addition to field measurements, and produces estimates of allfield parameters for computation units as well as thematic maps. Information from base mapsis employed in delineating forestry land from other land use classes.The map data are not necessarily up-to-date and often containsignificant errors. This paper introduces a statistical calibration method aimed atreducing the effect of map errors on multisource forest resourceestimates. The correction is based on theconfusion matrix between land use classes of the field sample plots and corresponding map information.The proposed method is illustrated in a realistic setting using data from the ninth NFI.
Comparison of changes evoked by GABA (γ-aminobutyric acid) and anoxia in [K+]o, [Cl-]o, and [Na+]o in stratum pyramidale and stratum radiatum of the guinea pig hippocampus
Authors: Obrocea G V , Morris M E
Published: April 2011

Ion-selective microelectrode recordings were made to assess a possible contribution of extracellular γ-aminobutyric acid (GABA) accumulation to early responses evoked in the brain by anoxia and ischemia. Changes evoked by GABA or N2 in [K+]o, [Cl-]o, [Na+]o, and [TMA+]o were recorded in the cell body and dendritic regions of the stratum pyramidale (SP) and stratum radiatum (SR), respectively, of pyramidal neurons in CA1 of guinea pig hippocampal slices. Bath application of GABA (1-10 mM) for approximately 5 min evoked changes in [K+]o and [Cl-]o with respective EC50 levels of 3.8 and 4.1 mM in SP, and 4.7 and 5.6 mM in SR. In SP 5 mM GABA reversibly increased [K+]o and [Cl-]o and decreased [Na+]o; replacement of 95% O2 -5% CO2 by 95% N2 -5% CO2 for a similar period of time evoked changes which were for each ion in the same direction as those with GABA. In SR both GABA and N2 caused increases in [K+]o and decreases in [Cl-]o and [Na+]o. The reduction of extracellular space, estimated from levels of [TMA+]o during exposures to GABA and N2, was 5-6% and insufficient to cause the observed changes in ion concentration. Ion changes induced by GABA and N2 were reversibly attenuated by the GABAA receptor antagonist bicuculline methiodide (BMI, 100 µM). GABA-evoked changes in [K+]o in SP and SR and [Cl-]o in SP were depressed by >=90%, and of [Cl-]o in SR by 50%; N2-evoked changes in [K+]o in SP and SR were decreased by 70% and those of [Cl-]o by 50%. BMI blocked Δ [Na+]o with both GABA and N2 by 20-30%. It is concluded that during early anoxia: (i) accumulation of GABA and activation of GABAA receptors may contribute to the ion changes and play a significant role, and (ii) responses in the dendritic (SR) regions are greater than and (or) differ from those in the somal (SP) layers. A large component of the [K+]o increase may involve a GABA-evoked Ca2+-activated gk, secondary to [Ca2+]i increase. A major part of [Cl-]o changes may arise from GABA-induced gCl and glial efflux, with strong stimulation of active outward transport and anion exchange at SP, and inward Na+/K+/2Cl- co-transport at SR. Na+ influx is attributable mainly to Na+-dependent transmitter uptake, with only a small amount related to GABAA receptor activation. Although the release and (or) accumulation of GABA during anoxia might be viewed as potentially protectant, the ultimate role may more likely be an important contribution to toxicity and delayed neuronal death.

Key words: brain slices, ion-selective microelectrodes, stratum pyramidale, stratum radiatum, bicuculline methiodide, extracellular space shrinkage.
Renal adenosine A3 receptors in the rat: assessment of functional role
Authors: Mozaffari Mahmood S , Abebe Worku , Warren Brett K
Published: April 2011

The functional roles of adenosine A3 receptors in the rat kidney were assessed for the first time with respect to A1 receptor-mediated responses. Utilizing a chronically instrumented conscious rat preparation, we tested renal excretory responses to acute administration of the A3 receptor antagonists 3-ethyl - 5-benzyl-2-methyl-6-phenyl- 4-phenylethynyl-1,4-(+)-dihydropridine-3,5-dicarboxylate (MRS-1191) and 9-chloro-2-(2-furyl)-5-phenylacetylamino- [1,2,4]-triazolo[1,5-c]quinazoline (MRS-1220) with reference to the effects of the A1 receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The intravenous administration of DPCPX resulted in significant increases in fluid and sodium excretions without affecting glomerular filtration rate (GFR). This suggests that DPCPX-induced diuretic and natriuretic responses are related to decreased tubular reabsorption. However, neither MRS-1191 nor MRS-1220 alone affected fluid or sodium excretions, or GFR, indicating lack of an effect of either compound on renal function. On the other hand, the co-administration of MRS-1220 with DPCPX abolished both the diuretic and natriuretic responses to DPCPX, being suggestive of antagonism between these two compounds. MRS-1191, however, did not affect the DPCPX-induced fluid and sodium excretions. Neither the A1 nor the A3 receptor antagonists altered potassium excretion individually or in combination. The data suggest that while adenosine A1 receptors are involved in the regulation of renal fluid and sodium transport, A3 receptors do not appear to have a major role in regulation of renal excretory function under baseline physiological conditions.

Key words: adenosine A3 receptor, adenosine antagonist, diuresis, natriuresis, rat.
Inhibition of cystic fibrosis transmembrane conductance regulator chloride channel currents by arachidonic acid
Authors: Linsdell Paul
Published: April 2011

Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl-channel is inhibited by a number of different classes of organic anions which are able to enter and block the channel pore from its cytoplasmic end. Here I show, using patch clamp recording from CFTR-transfected baby hamster kidney cell lines, that the cis-unsaturated fatty acid arachidonic acid also inhibits CFTR Cl-currents when applied to the cytoplasmic face of excised membrane patches. This inhibition was of a relatively high affinity compared with other known CFTR inhibitors, with an apparent Kdof 6.5 ± 0.9 µM. However, in contrast with known CFTR pore blockers, inhibition by arachidonic acid was only very weakly voltage dependent, and was insensitive to the extracellular Cl-concentration. Arachidonic acid-mediated inhibition of CFTR Cl-currents was not abrogated by inhibitors of lipoxygenases, cyclooxygenases or cytochrome P450, suggesting that arachidonic acid itself, rather than some metabolite, directly affects CFTR. Similar inhibition of CFTR Cl-currents was seen with other fatty acids, with the rank order of potency linoleic [Formula: see text] arachidonic [Formula: see text] oleic > elaidic [Formula: see text] palmitic [Formula: see text] myristic. These results identify fatty acids as novel high affinity modulators of the CFTR Cl-channel.Key words: CFTR, chloride channel, fatty acid, channel block, cystic fibrosis.
Ontogeny of intestinal nutrient transport
Authors: Thiesen A , Wild G , Keelan M , Clandinin M T , McBurney M , Aerde J Van , Thomson A BR
Published: April 2011

Children born prematurely lack the ability to digest and to absorb nutrients at rates compatible with their nutritional needs. As a result, total parenteral nutrition may need to be given. While this nutritional support may be life-saving, the baby who receives this therapy is exposed to the risks of possible sepsis, catheter dysfunction, and liver disease. The rodent model of postnatal development provides a useful framework to investigate some of the cellular features of human intestinal development. The up-regulation of intestinal gene expression and precocious development of intestinal nutrient absorption can be achieved by providing growth factor(s) or by modifying the composition of the maternal diet during pregnancy and nursing or the weaning diet of the infant. Accelerating the digestive and absorptive functions of the intestine would thereby allow for the maintenance of infant nutrition through oral food intake, and might possibly eliminate the need for, and risks of, total parenteral nutrition. Accordingly, this review was undertaken to focus on the adaptive processes available to the intestine, to identify what might be the signals for and mechanisms of the modified nutrient absorption, and to speculate on approaches that need to be studied as means to possibly accelerate the adaptive processes in ways which would be beneficial to the newborn young.Key words: absorption, adaptation, diet, peptides.
A role for calcitonin gene-related peptide in rabbit knee joint ligament healing
Authors: McDougall Jason J , Yeung Grace , Leonard Catherine A , Bray Robert C
Published: April 2011

Knee joint ligament healing has been shown to be improved when the torn ligament ends remain in contact, however, the rationale for these effects is unknown. The sensory neuropeptide calcitonin gene related peptide (CGRP) has potent trophic and vasodilatatory properties and as such is thought to be advantageous in wound repair. In ascertaining a role for CGRP in rabbit medial collateral ligament healing, the present study examined changes in CGRP-like immunoreactivity (CGRP-LI) and CGRP-mediated vasomotor responses in gap injured (non-contact), Z-plasty apposed (contact), and sham operated control medial collateral ligaments. At 6 weeks post-trauma, CGRP-LI decreased in the healing zone of gap injured and Z-plasty apposed medial collateral ligaments compared with controls, and non-contact ligament nerve fibres exhibited an abnormal morphology. Topical administration of CGRP (10-13to 10-9mol) caused a dose-dependent increase in ligament perfusion in each experimental group of knees. The CGRP-mediated vasodilatation associated with gap injured ligaments was not significantly different from controls (P = 0.06), whereas apposed medial collateral ligaments showed an augmented response to the peptide (P < 0.0005). These findings indicate that the beneficial effects of ligament interposition post-trauma may be related to an enhanced responsiveness to CGRP in conjunction with a more typical re-innervation profile. Conversely, the aberrant characteristics of CGRP-LI nerves occurring in gap injured tissue is suggestive of impaired CGRP release which may explain the poor functional recovery associated with these ligaments.Key words: blood flow, injury, knee joint, neuropeptides, wound repair.
Identification of a respiratory related area in the rat insular cortex
Authors: Aleksandrov Vjacheslav G , Aleksandrova Nina P , Bagaev Vitaly A
Published: April 2011

The aim of this study was to map areas within the rat insular cortex from which respiratory responses originate and compare those sites with gastrointestinal control regions. The insular cortex was systematically microstimulated and histological location of responsive sites determined. Increased inspiratory airflow and decreased respiratory cycle duration were considered to be respiratory excitatory responses. The responses were localized in dysgranular and agranular insular cortex at levels caudal to the joining of the anterior commissure. More rostrally, respiratory inhibitory responses were elicited: these were manifested as a decrease in inspiratory airflow without a significant alteration in respiratory cycle duration. Respiratory inhibitory responses were usually accompanied by changes in gastric motility. These results suggest that the respiratory area in the rat insular cortex consist of two distinct zones which overlap a region modulating the gastrointestinal activity.Key words: rats, insular cortex, respiration, gastrointestinal motility.
Block of inwardly rectifying K+ currents by extracellular Mg2+ and Ba2+ in bovine pulmonary artery endothelial cells
Authors: Leung Yuk Man , Kwan Chiu Yin , Daniel Edwin E
Published: April 2011

Using whole-cell patch clamp technique, we investigated the blocking effects of extracellular Ba2+ and Mg2+ on the inwardly rectifying K+ (KIR) currents of bovine pulmonary artery endothelial cells (BPAEC). The BPAEC KIR channel has recently been identified as Kir2.1 of the Kir2.0 subfamily. Block of KIR currents by Mg2+ (3-30 mM) was instantaneous, and increased with hyperpolarization slightly (Kd at -160 and 0 mV was 9.5 and 23.2 mM, respectively). The apparent fractional electrical distance (δ) of the Mg2+ binding site is calculated to be 0.07 from the outer mouth of the channel pore. Ba2+ (0.3-10 µM) time-dependently blocked the KIR currents with a much higher potency and stronger voltage-dependence (Kd at -160 and 0 mV was 1.0 and 41.6 µM, respectively). The Ba2+ binding site had a δ value of 0.34. Our data suggest that Mg2+ binds to a very superficial site of the KIR channel, while Ba2+ binds to a much deeper site, sensing much more of the membrane electric field. Thus, the BPAEC Kir2.1 appears to be pharmacologically different from the Kir2.1 reported before in bovine aortic endothelial cells (BAEC), which has 2 sites for Mg2+ block (a deep site in addition to a shallow one), and a superficial and low-sensitivity site for Ba2+ block.Key words: inwardly rectifying K+ channel, patch clamp, Ba2+, Mg2+, endothelial cells.
Effects of soybean lipoxygenase on Na+/K+-ATPase activity in vitro
Authors: Kumarathasan Rajkumar , Leenen Frans HH
Published: April 2011

Oxidized metabolites of polyunsaturated fatty acids produced by lipoxygenase are among the endogenous regulators of Na+/K+-ATPase. The direct effect of lipoxygenase on Na+/K+-ATPase activity was assessed in vitro using soybean lipoxygenase. Treatment of 4.2 µg/mL Na+/K+-ATPase (from dog kidneys) with 4.2 µg/mL of soybean lipoxygenase caused 20 ± 2% inhibition of ATPase activity. A 10-fold increase in lipoxygenase concentration (41.6 µg/mL) led to 30 ± 0.3% inhibition. In the presence of 12 µg/mL phenidone (a lipoxygenase inhibitor) and 15.4 µg/mL glutathione (a tripeptide containing a cysteine residue) inhibition of Na+/K+-ATPase activity was blocked and an increase in ATPase activity was observed. The presence of lipoxygenase enhanced the inhibition of Na+/K+-ATPase activity caused by 20 ng/mL ouabain (31 ± 2 vs. 19 ± 2) but had little or no effect with higher concentrations of ouabain. These findings suggest that lipoxygenase may regulate Na+/K+-ATPase by acting directly on the enzyme.Key words: Na+/K+-ATPase, soybean lipoxygenase, hypertension, oxidation, inhibition.
Influence of T-type Ca2+(mibefradil) and Cl-(indanyloxyacetic acid 94) channel antagonists on α1-adrenoceptor mediated contractions in rat aorta
Authors: Duggan Jennifer A , Tabrizchi Reza
Published: April 2011

The effects of the T-type and L-type Ca2+channel antagonists, mibefradil and nifedipine, respectively, and those of a Cl-channel antagonist, indanyloxyacetic acid 94, on mechanical responses elicited by selective activation of α1-adrenoceptors using cirazoline were examined in rat isolated aortic rings. The presence of mibefradil (300 nM), indanyloxyacetic acid, 94 (30 µM) and nifedipine (300 nM) alone inhibited mechanical responses elicited by cirazoline. The concentration-response curves to cirazoline were displaced to the right with significant increases in the EC50and significant depressions of the maximal responses in the presence of the individual agents mibefradil, indanyloxyacetic acid 94, or nifedipine. A combination of mibefradil and indanyloxyacetic acid 94 further inhibited the mechanical activity produced by cirazoline. The further reduction in the maximal response to cirazoline, in the presence of mibefradil and nifedipine, was insignificant when compared with the effects of nifedipine alone. In addition, maximal mechanical responses produced by cirazoline were not significantly affected by a combination of nifedipine and indanyloxyacetic acid 94 when compared with either nifedipine alone or mibefradil and indanyloxyacetic acid 94 combined. Our current findings indicate that mibefradil, indanyloxyacetic acid 94, and nifedipine can inhibit cirazoline-induced contractions to a varying degree. Moreover, based on our present data it would be reasonable to suggest that the contribution of T-type versus L-type Ca2+channels to contractile responses obtained with cirazoline are approximately 21% and 35%, respectively, of the Emax. It would appear that L-type Ca2+channels play a greater role in processes that are involved in excitation-contraction coupling subsequent to stimulation of α1-adrenoceptors. In addition, Cl-channels also appear to be involved in the process of contraction following α1-adrenoceptor activation.Key words: T-type Ca2+channels, L-type Ca2+channels, Cl-channels, isolated aortic rings.
Activation of Rho signaling contributes to lysophosphatidic acid-induced contraction of intact ileal smooth muscle of guinea-pig
Authors: Mori Mayumi , Tsushima Hiromi
Published: April 2011

To elucidate the possible role of Rho A/Rho-kinase on lysophosphatidic acid (LPA)-induced contraction in intact guinea-pig ileal smooth muscle, we examined effects of pretreatment with a specific inhibitor of Rho-kinase (Y-27632) on the LPA-induced contraction and MLC20phosphorylation. In addition, we investigated whether LPA actually elicits an activation of Rho A by studying subcellular distribution of Rho A in unstimulated and stimulated smooth muscles by LPA. LPA induced a less intense, but sustained, contraction compared with ACh, and was accompanied by significant increases in MLC20phosphorylation. The effects of LPA on tension and MLC20phosphorylation were inhibited by Y-27632. The ACh-induced contraction, but not increases in MLC20phosphorylation, was partially inhibited by Y-27632. High K+-induced contraction was unaffected by the inhibitor. LPA stimulated translocation of Rho A from the cytosol to the membrane fraction of the muscle. Translocation of Rho A was also induced by ACh and high K+. These results suggest that LPA-induced contraction of intact ileal smooth muscle is dominated through activation of Rho A and Rho-kinase and subsequent increases in MLC20phosphorylation.Key words: lysophosphatidic acid, Rho, Rho-kinase, ileal smooth muscle.
2,4-dinitrophenol acutely inhibits rabbit atrial Ca2+-sensitive Cl- current (ITO2)
Authors: Ravesloot J H , Rombouts E
Published: April 2011

We investigated the effects of 2,4-dinitrophenol (DNP), the uncoupler of mitochondrial oxidative phosphorylation, on the Ca2+-sensitive Cl- current component of the transient outward current (ITO2). Amphotericin B perforated-patch, whole-cell patch-clamp technique was employed (35°C) using enzymatically isolated single rabbit atrial myocytes. We defined ITO2 as the amplitude of the 2 mM 4-aminopyridine resistant transient outward current sensitive to anthracene-9-carboxylic acid (A9C). Between +5 and +45 mV, 0.2 mM A9C inhibited ITO2 by ~70% (n = 13). Within 30 s after application of 0.2 mM DNP, both normal ITO2 transients (n = 8) and the ITO2 transients that remained after A9C treatment (n = 8) were inhibited completely. In cells expressing ITO2 (70% of total), DNP also suppressed an A9C-insensitive slow outward current by ~40%, but the holding current at -80 mV was unaffected. There was a ~2 min latency between inhibitory effects of DNP and subsequent membrane current increase, presumably caused by activation of the ATP-sensitive K+ channels (n = 16). We conclude that DNP acutely inhibits ITO2 via a mechanism presumably separate from metabolic inhibition.Key words: patch clamp, rabbit heart, simulated ischemia, calcium-sensitive chloride current.
Acid-base analysis during experimental anemia in rats
Authors: Pesquero J , Alfaro V , Palacios L
Published: April 2011

The present study evaluated the acid-base status of anemic rats by using two approaches of acid-base analysis: one based on the base excess (BE) calculation and the other based on Stewart's physicochemical analysis. Two sets of experimental data, derived from two different methods of inducing anemia, were used: repetitive doses of phenylhydrazine (PHZ) and bleeding (BL). A significant uncompensated respiratory alkalosis was found in both groups of anemic rats. BE increased slightly, whereas strong ion difference ([SID]) and weak acid buffers ([ATOT]) remained unchanged in anemic rats. The reasons for the absence of compensation for hypocapnia and the differences in the behaviour of acid-base variables are discussed. BE increase was considered paradoxical; its calculation was affected by the experimental conditions and BE had little physiological relevance during anemia. The absence of metabolic renal compensation in anemic rats could be due to a lower pH in the kidney due to anemic hypoxia. Finally, the changes in buffer strength related to low Hb and low Pc02 might influence plasma [SID] through counteracted shifts of strong ions between erythrocytes and plasma, finally resulting in unchanged [SID] during anemia.Key words: anemia, phenylhydrazine, bleeding, base excess, strong ion difference, non-carbonic buffers.
Role of motor cortex in coordinating multi-joint movements: Is it time for a new paradigm?
Authors: Scott Stephen H
Published: April 2011

Reaching movements to spatial targets require motor patterns at the shoulder to be coordinated carefully with those at the elbow to smoothly move the hand through space. While the motor cortex is involved in this volitional task, considerable debate remains about how this cortical region participates in planning and controlling movement. This article reviews two opposing interpretations of motor cortical function during multi-joint movements. On the one hand, studies performed predominantly on single-joint movement generally support the notion that motor cortical activity is intimately involved in generating motor patterns at a given joint. In contrast, studies on reaching demonstrate correlations between motor cortical activity and features of movement related to the hand, suggesting that the motor cortex may be involved in more global features of the task. Although this latter paradigm involves a multi-joint motor task in which neural activity is correlated with features of movement related to the hand, this neural activity is also correlated to other movement variables. Therefore it is difficult to assess if and how the motor cortex contributes to the coordination of motor patterns at different joints. In particular, present paradigms cannot assess whether motor cortical activity contributes to the control of one joint or multiple joints during whole-arm tasks. The final point discussed in this article is the development of a new experimental device (KINARM) that can both monitor and manipulate the mechanics of the shoulder and elbow independently during multi-joint motor tasks. It is hoped that this new device will provide a new approach for examining how the motor cortex is involved in motor coordination.Key words: reaching movements, biomechanics, motor coordination, proximal arm.
Inhibition of inducible nitric oxide synthesis by the herbal preparation Padma 28 in macrophage cell line
Authors: Moeslinger Thomas , Friedl Roswitha , Volf Ivo , Brunner Monika , Koller Elisabeth , Spieckermann Paul Gerhard
Published: April 2011

Padma 28 is a mixture of herbs used in traditional Tibetan medicine with anti-inflammatory activities. We investigated the effects of Padma 28 on nitric oxide (NO) production by the inducible nitric oxide synthase (iNOS) in lipopolysaccharide stimulated mouse macrophages (RAW 264.7). Padma 28 (0-900 µg/mL) induced a concentration dependent inhibition of inducible nitric oxide synthesis. iNOS protein expression showed a concentration dependent reduction as revealed by immunoblotting when cells were incubated with increasing amounts of Padma 28. Padma 28 decreased iNOS mRNA levels as shown by RT-PCR. Aqueous extracts from costi amari radix (costus root, the dried root of Saussurea lappa) and the outer cover of myrobalani fructus (the dried fruit of Terminalia chebula), constituents of the complex herb preparation Padma 28, were found to inhibit inducible nitric oxide synthesis by decreasing iNOS protein and iNOS mRNA levels. The inhibition of inducible nitric oxide synthesis might contribute to the anti-inflammatory activities of Padma 28.Key words: inducible nitric oxide synthase, mouse macrophages, myrobalans, radix costae.
Enhancement of haloperidol-induced catalepsy by nicotine: an investigation of possible mechanisms
Authors: Boye Sandra M , Clarke Paul BS
Published: April 2011

Nicotine has been reported to potentiate the cataleptic effect of the dopamine receptor antagonist haloperidol in rats. This effect is paradoxical, since nicotine alone tends to increase nigrostriatal dopamine release. In the present experiments, a pro-cataleptic effect of nicotine was confirmed statistically but was small and variable. Three potential mechanisms underlying this effect were investigated. (i) Desensitization of brain nicotinic receptors appears to make little if any contribution to the pro-cataleptic effect of nicotine, insofar as the latter was not mimicked by two centrally active nicotinic antagonists (mecamylamine and chlorisondamine). (ii) Depolarization inactivation resulting from combined treatment with haloperidol and nicotine does not appear to be critical, since the pro-cataleptic effect of nicotine was not enhanced by chronic haloperidol administration, a treatment designed to enhance depolarization inactivation. (iii) The slow emergence and persistence of the acute pro-cataleptic effect of nicotine suggested possible mediation by a nicotine metabolite. However, neither cotinine nor nornicotine, the principal pharmacologically-active metabolites of nicotine, exerted a significant pro-cataleptic effect. In conclusion, the pro-cataleptic effect of nicotine was weak and variable in the present study, and its mechanism remains obscure.Key words: catalepsy, nicotine, haloperidol, Tourette's Syndrome, dopamine, nornicotine.
Effect of angiotensin inhibition on the coronary artery lower pressure limit in anesthetized dogs
Authors: Rouleau Jacques R , Simard Denis , Kingma Jr. Jonh G
Published: April 2011

The renin-angiotensin system plays a critical role in regulating vasoconstriction and vasodilatation that can influence myocardial blood flow and its transmural distribution. We tested the hypothesis that angiotensin inhibition can induce a leftward shift of the coronary autoregulatory pressure-flow relation and preserve distribution of myocardial blood flow at lower coronary perfusion pressures. We established circumflex artery pressure-flow relations under baseline conditions and after intracoronary enalaprilat or losartan potassium. Thereafter, transmural myocardial blood flow was measured at baseline and at the lower coronary pressure limit (LPL). With enalaprilat, the LPL was shifted leftward from 48 ± 6 mmHg at baseline to 43 ± 3 mmHg (P = 0.026); with losartan, the LPL was shifted leftward from 48 ± 10 mmHg at baseline to 41 ± 5 mmHg (P = 0.027). The leftward shift occurred while cardiac hemodynamics and M[Formula: see text]O2were maintained at control levels. These results indicate that angiotensin inhibition extends the range of coronary autoregulation to lower LPL while preserving myocardial blood flow distribution, a physiologic effect that might explain the lower incidence of coronary events in treated patients.Key words: angiotensin, microcirculation, microspheres, myocardium.
Modulation of the SNARE core complex by dopamine
Authors: Fisher Heather , Braun Janice EA
Published: April 2011

Communication between nerve cells in the brain occurs primarily through specialized junctions called synapses. Recently, many details of synaptic transmission have emerged. The identities of specific proteins important for synaptic vesicle release have now been established. We have investigated three synaptic proteins, VAMP (vesicle associated membrane protein; also called synaptobrevin), syntaxin, and SNAP25 (synaptosomal associated protein of 25kDa) as possible targets in the dopamine-mediated modulation of synaptic function in rat striatal slices. These three proteins form a SNARE (soluble N-ethylmalemide-sensitive factor attachment protein receptors) core complex that is known to be essential for synaptic transmission. Although it is envisioned that the SNAREs undergo dynamic and cyclic interactions to elicit synaptic vesicle release, their precise functions in neurotransmission remains unknown. We have examined SNARE complexes in intact rat striatal slices. Cellular proteins were solubilized, separated electrophoretically by SDS-PAGE, and then identified immunologically. Application of dopamine to striatal slices results in SNAREs favoring the SNARE core complex, a complex which forms spontaneously in the absence of crosslinking agents, rather than the monomer form. In addition, rapid crosslinking of dopamine-treated striatal slices demonstrates that the SNARE complex is increased 4 fold in dopamine treated striatal slices compared with control slices. Haloperidol blocked the dopamine-induced change in the core complex. These results suggest that changes in the activities of SNAREs may be involved in the underlying cellular mechanisms(s) of dopamine-regulated synaptic plasticity of the striatum.Key words: dopamine, striatium, VAMP, syntaxin, SNAP25.
Induction de l'apoptose dans les lymphocytes spléniques de souris par un faisceau d'ions carbone
Authors: Holl V , Coelho D , Weltin D , Dufour P , Denis J M , Florentin I , Mathieu J , Gueulette J , Bischoff P
Published: April 2011

To assess the capacity of heavy ions to induce apoptosis in lymphocytes, mice have been irradiated with accelerated carbon ions (95 MeV/nucleon) at doses ranging from 0.1 to 4 Gy. Their spleens were removed 24 h later and gently dissociated to prepare a single cell suspension. Mononuclear cells were then maintained in culture at 37°C, and the occurrence of apoptosis in these cells was analysed 24 h later. Lymphocytes were also irradiated in vitro, in the presence of Ac-DEVD-CHO, a potent caspase-3 and -7 inhibitor. Results from three experiments performed at the Grand Accelerateur National d'Ions Lourds (GANIL, Caen, France) are reported here. They indicate that carbon ions induce a marked, dose-dependent, reduction of the spleen weight and cellularity. However, in sharp contrast with spleen cells prepared from X-ray irradiated mice, only a slight increase of apoptosis is evidenced in cultured lymphocytes from mice irradiated with heavy ions. The significance of such results is discussed. So far, few data exist concerning the biological effects of heavy ions, in particular their capacity to induce apoptosis in lymphocytes; the present study provides useful clues for further investigations.Key words : lymphocytes, apoptosis, heavy ions, splenic model, caspases.
Molecular characterization of the prolactin receptor in two fish species, tilapiaOreochromis niloticusand rainbow trout,Oncorhynchus mykiss: A comparative approach
Authors: Prunet P , Sandra O , Rouzic P Le , Marchand O , Laudet V
Published: April 2011

We present recent information on the molecular characterization of the prolactin receptor (PRL-R) in two teleost species, tilapia (Oreochromis niloticus) and rainbow trout (Oncorhynchus mykiss), in the perspective of improved understanding of the physiological differences in the control of osmoregulatory function between these two fish species. Although our interest will mainly focus on osmoregulatory organs, we will also discuss evidence of the presence of PRL-R in other tissues such as gonads and hematopoietic organs. The first fish PRL-R was characterized in tilapia. This receptor is similar to that of the long form of mammalian PRL-R, but the most conserved region (extracellular domain) has only 53% identity with mammalian PRL-R. A rainbow trout PRL-R cDNA has been also isolated and appeared very similar in structure to tilapia PRL-R. Expression of the PRL-R gene was studied by Northern blotting for various tissues from tilapia and trout, and a unique transcript size of 3.2-3.4 kb was observed in all tissues studied (including male and female gonads, skin, brain, spleen, head, kidney, and circulating lymphocytes). Osmoregulatory organs (gills, kidney, intestine) were the richest tissues. Using in situ hybridization, PRL-R transcripts were localized in gill chloride cells, both in trout and tilapia. Analysis of PRL-R transcript levels in gills, kidney, and intestine indicated the maintenance of a high level of expression during adaptation to a hyperosmotic environment. These results support PRL being a pleiotropic hormone in fish and suggest the presence of a unique PRL-R form in tilapia and in trout. Finally, characterization of hormone receptor binding has been carried out in both species using a radioreceptor assay (in tilapia) or surface plasmon resonance (SPR) technology (in trout). These studies indicated the presence of a stable hormone-receptor complex in tilapia, while PRL binds to its receptor through an unstable homodimeric complex in trout. Thus, the characteristics of PRL binding on its receptor appear to be significantly different in tilapia and trout. Whether such differences may lead to different signal transduction mechanisms and osmoregulatory actions of PRL in these two euryhaline species merits further investigation.Key words: prolactin receptor, genetic expression, hormone-receptor interaction, surface plasmon resonance, fish osmoregulation.
Effect of temperature on post-tetanic potentiation in human dorsiflexor muscles
Authors: Gossen E Roderich , Allingham Kerry , Sale Digby G
Published: April 2011

The effect of temperature on post-tetanic potentiation (PTP) has been examined in the muscles of small mammals but not in human skeletal muscle. We examined PTP in the ankle dorsiflexor muscles of 10 young men by evoking twitches before and after a 7-second tetanus at 100 Hz in a control (room air ~21°C) condition and after immersion of the lower leg in warm (45°C) and cold (10°C) water baths for 30 min. Exposure to cold decreased tetanus and pre-tetanus twitch peak torque, but increased rise time, half-relaxation time, and muscle action potential (M-wave) amplitude; exposure to warm water had little effect. PTP was smallest in cold exposure 5 s post-tetanus, but persisted throughout the 12 min test period, whereas PTP had subsided by 6 min post-tetanus in control and warm exposures. M-wave amplitude initially decreased after exposure to warm water, recovered, then decreased again by 11 min post-tetanus. In contrast, exposure to cold had no initial effect but did increase the M-wave amplitude during the last half of the 12 min test period, similar to that seen in the control. The greatest immediate decrease in rise time and half-relaxation time was observed in the control; however, by 12 min post-tetanus warm exposure showed the greatest increase in rise time and half-relaxation time above pre-tetanus values. The decrease in the unpotentiated twitch torque with cooling in human dorsiflexors is typical for muscles with a predominance of type I (slow) fibres. The effect of cold on PTP is similar to that seen previously in mammalian muscles with a predominance of type II (fast) fibres, although the underlying mechanism of the cooling effect appears to differ.Key words: contraction, muscle, twitch.
Effect of ischemia-reperfusion on the renal brush-border membrane sodium-dependent phosphate cotransporter NaPi-2
Authors: Xiao Yansen , Desrosiers Richard R , Béliveau Richard
Published: April 2011

To understand the mechanisms underlying ischemia-reperfusion-induced renal proximal tubule damage, we analyzed the expression of the Na+-dependent phosphate (Na+/Pi) cotransporter NaPi-2 in brush border membranes (BBM) isolated from rats which had been subjected to 30 min renal ischemia and 60 min reperfusion. Na+/Picotransport activities of the BBM vesicles were also determined. Ischemia caused a significant decrease (about 40%, P < 0.05) in all forms of NaPi-2 in the BBM, despite a significant increase (31 ± 3%, P < 0.05) in the Na+/Picotransport activity. After reperfusion, both NaPi-2 expression and Na+/Picotransport activity returned to control levels. In contrast with Na+/Picotransport, ischemia significantly decreased Na+-dependent glucose cotransport but did not affect Na+-dependent proline cotransport. Reperfusion caused further decreases in both Na+/glucose (by 60%) and Na+/proline (by 33%) cotransport. Levels of NaPi-2 were more reduced in the BBM than in cortex homogenates, suggesting a relocalization of NaPi-2 as a result of ischemia. After reperfusion, NaPi-2 levels returned to control values in both BBM and homogenates. These data indicate that the NaPi-2 protein and BBM Na+/Picotransport activity respond uniquely to reversible renal ischemia and reperfusion, and thus may play an important role in maintaining and restoring the structure and function of the proximal tubule.Key words: kidney, ischemia, reperfusion, phosphate, transport.
Diabetes reduces right atrial β-adrenergic signaling but not agonist stimulation of heart rate in swine
Authors: Stanley William C , Dore Justin J , Hall Jennifer L , Hamilton C Dawn , Pizzurro Robert D , Roth David A
Published: April 2011

This study assessed the effects of streptozotocin diabetes in swine on the heart rate response to β-adrenergic stimulation the adenylyl cyclase signal transduction pathway. Diabetic animals (n = 9) were hyperglycemic compared to the control group (n = 10) (12.6 ± 1.0 vs. 3.53 ± 0.29 mM). There were no significant differences between the diabetic and nondiabetic groups in the heart rate response to isoproterenol, however, there was a significant reduction (14%) in β-adrenergic receptor density in the right atrium in the diabetic (61 ± 3 fmol/mg protein) versus the nondiabetic group (71 ± 3) (P < 0.05). The content of guanosine triphosphate binding regulatory proteins (Gs and Gi) in the right atrium was not affected by diabetes, nor was adenylyl cyclase activity under unstimulated conditions or with receptor-dependent stimulation with isoproterenol. On the other hand, adenylyl cyclase activity was 34% lower when directly stimulated with forskolin, and it was reduced by 23% when stimulated through Gs with Gpp(NH)p. In conclusion, beta-adrenergic stimulation of heart rate with isoproteronol and the receptor-dependent signal transduction pathway remained intact in the right atrium of diabetic swine despite reduced beta-adrenergic receptor density, G-protein content, and direct stimulation of adenylyl cyclase activity.Key words: diabetes, G-proteins, heart rate, receptors, signal transduction.
Arotinolol is a weak partial agonist on β3-adrenergic receptors in brown adipocytes
Authors: Zhao Jin , Golozoubova Valeria , Cannon Barbara , Nedergaard Jan
Published: April 2011

Arotinolol, a clinically used α/β-adrenergic blocker, has been demonstrated to be an anti-obesity agent. The anti-obesity effect of arotinolol was suggested to be the result of direct activation of thermogenesis in brown-fat cells. We tested the ability of arotinolol to stimulate thermogenesis (oxygen consumption) in isolated brown-fat cells and in intact animals. Arotinolol stimulated thermogenesis in brown-fat cells isolated from mouse and hamster. A relatively low sensitivity to the β-adrenergic antagonist propranolol (pKB [Formula: see text] 6) indicated that arotinolol interacted with the β3-adrenergic receptor. On the β3-receptor, arotinolol was a very weak (EC50 [Formula: see text] 20 µM) and only partial ([Formula: see text]50 %) agonist, but arotinolol also demonstrated the properties of being a β3-receptor antagonist with a pKB of 5.7. In intact animals, only the antagonistic action of arotinolol could be observed. Because arotinolol is only a very weak and partial agonist on the β3-receptors, direct stimulation of thermogenesis in brown adipose tissue is unlikely to be sufficient to cause significant weight loss. It may be necessary to invoke additional pathways to explain the anti-obesity effects of chronic treatment with arotinolol.Key words: arotinolol, β3-adrenergic receptor, brown adipose tissue, thermogenesis, mouse, hamster, rat.
Hemodynamic effects of Salvia miltiorrhiza on cirrhotic rats
Authors: Huang Yi-Tsau , Lee Tzung-Yan , Lin Han-Chieh , Chou Teh-Ying , Yang Ying-Ying , Hong Chuang-Ye
Published: April 2011

Salvia miltiorrhiza (Sm) administration has been shown to reduce hepatic fibrosis in rats. We investigated the hemodynamic effects of Sm on bile duct ligated (BDL) rats. Hemodynamic, histological, and vascular contractile studies were conducted in rats 4 weeks after bile duct ligation. An aqueous extract of Sm (0.2 g twice per day) or vehicle was administered for 4 weeks to BDL rats. Sm treatment in BDL rats significantly reduced histological grades of fibrosis and ameliorated the portal hypertensive state (including portal venous pressure, superior mesenteric artery blood flow, cardiac index, and total peripheral resistance) as compared with vehicle treatment. Moreover, Sm treatment enhanced the vascular sensitivity of mesenteric arteries to phenylephrine in BDL rats. Sm treatment had no effect on plasma biochemical profiles of either BDL or normal rats. Our results suggest that 4-week Sm treatment ameliorates the portal hypertensive state in BDL rats.Key words: hemodynamics, fibrosis, portal hypertension, vascular contractile response, Salvia miltiorrhiza.
Properties and modulation of alpha human atrial natriuretic peptide (α-hANP)-formed ion channels
Authors: Kourie Joseph I , Hanna Emily A , Henry Christine L
Published: April 2011

Using the lipid bilayer technique we have optimized recording conditions and confirmed that alpha human atrial natriuretic peptide [α-hANP(128)] forms single ion channels. The single channel currents recorded in 250/50 mM KCl cis/trans chambers show that the ANP-formed channels were heterogeneous, and differed in their conductance, kinetic, and pharmacological properties. The ANP-formed single channels were grouped as: (i) H2O2- and Ba2+-sensitive channel with fast kinetics; the nonlinear current-voltage (I-V) relationship of this channel had a reversal potential (Erev) of 28.2 mV, which is close to the equilibrium potential for K+ (EK = 35 mV) and a maximal slope conductance (gmax) of 68 pS at positive potentials. Sequential ionic substitution (KCl, K gluconate and choline Cl) of the cis solution suggests that the current was carried by cations. The fast channel had three modes (spike mode, burst mode, and open mode) that differed in their kinetics but not in their conductance properties. (ii) A large conductance channel possessing several subconductance levels that showed time-dependent inactivation at positive and negative membrane potentials (Vm). The inactivation ratio of the current at the end of the voltage step (Iss) to the initial current (Ii) activated immediately after the voltage step, (Iss/Ii), was voltage dependent and described by a bell-shaped curve. The maximal current-voltage (I-V) relationship of this channel, which had an Erev of +17.2 mV, was nonlinear and the value of gmax was 273 pS at negative voltages. (iii) A transiently-activated channel: the nonlinear I-V relationship of this channel had an Erev of 29.8 mV and the value of gmax was 160 pS at positive voltages. We propose that the voltage-dependence of the ionic currents and the kinetic parameters of these channel types indicate that if they were formed in vivo and activated by cytosolic factors they could change the membrane potential and the electrolyte homeostasis of the cell.Key words: natriuretic peptides, channel forming peptides, heterogeneous channels, signal transduction.
Regulation of the ANF and BNP promoters by GATA factors: Lessons learned for cardiac transcription
Authors: McBride Kevin , Nemer Mona
Published: April 2011

The identification and molecular cloning of the cardiac transcription factors GATA-4, -5, and -6 has greatly contributed to our understanding of how tissue-specific transcription is achieved during cardiac growth and development. Through analysis of their interacting partners, it has also become apparent that a major mechanism underlying spatial and temporal specificity within the heart as well as in the response to cardiogenic regulators is the combinatorial interaction between cardiac-restricted and inducible transcription factors. The cardiac GATA factors appear to be fundamental contributors to these regulatory networks. Two of the first targets identified for the cardiac GATA factors were the natriuretic peptide genes encoding atrial natriuretic factor (ANF) and B-type natriuretic peptide (BNP), the major heart secretory products that are also accepted clinical markers of the diseased heart. Studies using the ANF and BNP promoters as models of cardiac-specific transcription have unraveled the pivotal role that GATA proteins play in cardiac gene expression. We review the current knowledge on the modulation of the natriuretic peptide promoters by GATA factors, including examples of combinatorial interactions between GATA proteins and diverse transcription factors.Key words: ANF, BNP, GATA factors, cardiac transcription.