Influence of separate and mixed experimental designs on reaction times to two simple visual stimuli

Testing contexts have been shown to critically influence experimental results in psychophysical studies. One of these contexts that show important modulation of the behavioral effects of different stimulatory conditions is the separate (blocked) or mixed presentation of these stimulatory conditions. The study presents evidence that the apparent discriminabilities of two target stimuli can change according to which of these two testing contexts is used. A cross inside a ring and a vertical line inside a ring were presented as go stimuli in a go/no-go reaction time task. In one experiment, each of these stimuli was presented to a different group of volunteers and in another experiment they were presented to the same group of volunteers, randomly mixed in the blocks of trials. Similar reaction times were obtained for the two stimuli in the first experiment, and different reaction times (faster for the cross) in the second experiment. The latter result indicates that the two stimuli have different discriminabilities from the no-go stimulus; the cross having greater discriminability. This difference is however masked, presumably by the adoption of specific compensatory attentional sets, in a separate testing context.

Hypothyroidism decreases proinsulin gene expression and the attachment of its mRNA and eEF1A protein to the actin cytoskeleton of INS-1E cells

The actions of thyroid hormone (TH) on pancreatic beta cells have not been thoroughly explored, with current knowledge being limited to the modulation of insulin secretion in response to glucose, and beta cell viability by regulation of pro-mitotic and pro-apoptotic factors. Therefore, the effects of TH on proinsulin gene expression are not known. This led us to measure: a) proinsulin mRNA expression, b) proinsulin transcripts and eEF1A protein binding to the actin cytoskeleton, c) actin cytoskeleton arrangement, and d) proinsulin mRNA poly(A) tail length modulation in INS-1E cells cultured in different media containing: i) normal fetal bovine serum - FBS (control); ii) normal FBS plus 1 µM or 10 nM T3, for 12 h, and iii) FBS depleted of TH for 24 h (Tx). A decrease in proinsulin mRNA content and attachment to the cytoskeleton were observed in hypothyroid (Tx) beta cells. The amount of eEF1A protein anchored to the cytoskeleton was also reduced in hypothyroidism, and it is worth mentioning that eEF1A is essential to attach transcripts to the cytoskeleton, which might modulate their stability and rate of translation. Proinsulin poly(A) tail length and cytoskeleton arrangement remained unchanged in hypothyroidism. T3 treatment of control cells for 12 h did not induce any changes in the parameters studied. The data indicate that TH is important for proinsulin mRNA expression and translation, since its total amount and attachment to the cytoskeleton are decreased in hypothyroid beta cells, providing evidence that effects of TH on carbohydrate metabolism also include the control of proinsulin gene expression.

The effects of nitric oxide on the immune response during giardiasis

Nitric oxide (NO) is a free radical synthesized from L-arginine by different isoforms NO-synthases. NO possesses multiple and complex biological functions. NO is an important mediator of homeostasis, and changes in its generation or actions can contribute or not to pathological states. The knowledge of effects of NO has been not only important to our understanding of immune response, but also to new tools for research and treatment of various diseases. Knowing the importance of NO as inflammatory mediator in diverse infectious diseases, we decided to develop a revision that shows the participation/effect of this mediator in immune response induced against Giardia spp. Several studies already demonstrated the participation of NO with microbicidal and microbiostatic activity in giardiasis. On the other hand, some works report that Giardia spp. inhibit NO production by consuming the intermediate metabolite arginine. In fact, studies in vitro showed that G. lamblia infection of human intestinal epithelial cells had reduced NO production. This occurs due to limited offer of the crucial substrate arginine (essential aminoacid for NO production), consequently reducing NO production. Therefore, the balance between giardial arginine consumption and epithelial NO production could contribute to the variability of the duration and severity of infections by this ubiquitous parasite.

Effects of Laser on the Synovial Fluid in the Inflammatory Process of the Knee Joint of the Rabbit

Objective: The purpose of this study was to evaluate the effects of low-level laser (LLL) energy on the clinical signs of inflammation and the cellular composition of synovial fluid (SF) in the inflamed knee of the rabbit. Background Data: There are few findings related to the effects of LLL on SF in inflammatory processes and there is little knowledge about the optimal parameters for reducing joint inflammation. Materials and Methods: Inflammation in the right knee of 36 rabbits was induced by intracapsular injection (0.2 mL) of Terebinthina commun (Tc). The animals were randomly assigned to three groups: acute experimental group (AEG), chronic experimental group (CEG), and control group (CG), which only received Tc. Each group was divided in two subgroups of six animals each. The AEG and CEG groups began to receive laser treatment 2 and 5 d after the induction of inflammation, respectively. Laser irradiation at a wavelength of 830 nm, power output of 77 mW, and power density of 27.5 W/cm(2) was applied daily for 7 d for either 0.12 sec or 0.32 sec, resulting in doses of 3.4 J/cm(2) and 8 J/cm(2), respectively. Body mass, joint perimeter, joint temperature, and the morphology of the SF were analyzed. Results: There was no statistically significant differences between groups in the body mass, joint perimeter, and SF morphology. Conclusion: Laser irradiation with the selected parameters produced only a few subtle differences in the inflammatory signs and the SF. The lack of effects may have been due to the short irradiation time.

Brain nitric oxide production by a proline-rich decapeptide from Bothrops jararaca venom improves baroreflex sensitivity of spontaneously hypertensive rats

Baroreflex sensitivity is disturbed in many people with cardiovascular diseases such as hypertension. Brain deficiency of nitric oxide (NO), which is synthesized by NO synthase (NOS) in the citrulline-NO cycle (with argininosuccinate synthase (ASS) activity being the rate-limiting step), contributes to impaired baroreflex. We recently showed that a decapeptide isolated from Bothrops jararaca snake venom, denoted Bj-PRO-10c, exerts powerful and sustained antihypertensive activity. Bj-PRO-10c promoted vasodilatation dependent on the positive modulation of ASS activity and NO production in the endothelium, and also acted on the central nervous system, inducing the release of GABA and glutamate, two important neurotransmitters in the regulation of autonomic systems. We evaluated baroreflex function using the regression line obtained by the best-fit points of measured heart rate (HR) and mean arterial pressure (MAP) data from spontaneously hypertensive rats (SHRs) treated with Bj-PRO-10c. We also investigated molecular mechanisms involved in this effect, both in vitro and in vivo. Bj-PRO-10c mediated an increase in baroreflex sensitivity and a decrease in MAP and HR. The effects exerted by the peptide include an increase in the gene expression of endothelial NOS and ASS. Bj-PRO-10c-induced NO production depended on intracellular calcium fluxes and the activation of a G(i/o)-protein-coupled metabotropic receptor. Bj-PRO-10c induced NO production and the gene expression of ASS and endothelial NOS in the brains of SHRs, thereby improving baroreflex sensitivity. Bj-PRO-10c may reveal novel approaches for treating diseases with impaired baroreflex function. Hypertension Research (2010) 33, 1283-1288; doi: 10.1038/hr.2010.208

Chemoprevention of rat hepatocarcinogenesis with histone deacetylase inhibitors: Efficacy of tributyrin, a butyric acid prodrug

Hepatocellular carcinoma (HCC) ranks in prevalence and mortality among top 10 cancers worldwide. Butyric acid (BA), a member of histone deacetylase inhibitors (HDACi) has been proposed as an anticareinogenic agent. However, its short half-life is a therapeutical limitation. This problem could be circumvented with tributyrin (TB), a proposed BA prodrug. To investigate TB effectiveness for chemoprevention, rats were treated with the compound during initial phases of ""resistant hepatocyte"" model of hepatocarcinogenesis, and cellular and molecular parameters were evaluated. TB inhibited (p < 0.05) development of hepatic preneoplastic lesions (PNL) including persistent ones considered HCC progression sites. TB increased (p < 0.05) PNL remodeling, a process whereby they tend to disappear. TB did not inhibit cell proliferation in PNL, but induced (p < 0.05) apoptosis in remodeling ones. Compared to controls, rats treated with TB presented increased (P < 0.05) hepatic levels of BA indicating its effectiveness as a prodrug. Molecular mechanisms of TB-induced hepatocarcinogenesis chemoprevention were investigated. TB increased (p < 0.05) hepatic nuclear histone H3K9 hyperacetylation specifically in PNL and p21 protein expression, which could be associated with inhibitory HDAC effects. Moreover, it reduced (p < 0.05) the frequency of persistent PNL with aberrant cytoplasmic p53 accumulation, an alteration associated with increased malignancy. Original data observed in our study support the effectiveness of TB as a prodrug of BA and as an HDACi in hepatocarcinogenesis chemoprevention. Besides histone acetylation and p21 restored expression, molecular mechanisms involved with TB anticarcinogenic actions could also be related to modulation of p53 pathways. (C) 2008 Wiley-Liss, Inc.

Characterization of the stimulus for reactive oxygen species generation in calcium-overloaded mitochondria

We have used two different probes with distinct detection properties, dichlorodihydrofluorescein diacetate and Amplex Red/horseradish peroxidase, as well as different respiratory substrates and electron transport chain inhibitors, to characterize the reactive oxygen species (ROS) generation by the respiratory chain in calcium-overloaded mitochondria. Regardless of the respiratory substrate, calcium stimulated the mitochondrial generation of ROS, which were released at both the mitochondrial-matrix side and the extramitochondrial space, in a way insensitive to the mitochondrial permeability transition pores inhibitor cyclosporine A. In glutamate/malate-energized mitochondria, inhibition at complex I or complex III (ubiquinone cycle) similarly modulated ROS generation at either mitochondrial-matrix side or extramitochondrial space; this also occurred when the backflow of electrons to complex I in succinate-energized mitochondria was inhibited. On the other hand, in succinate-energized mitochondria the modulation of ROS generation at mitochondrial-matrix side or extra-mitochondrial space depends on the site of complex III which was inhibited. These results allow a straight comparison between the effects of different respiratory substrates and electron transport chain inhibitors on ROS generation at either mitochondrial-matrix side or extra-mitochondrial space in calcium-overloaded mitochondria.

Effect of estrogen on vascular smooth muscle cells is dependent upon cellular phenotype

To investigate the growth-regulating action of estrogen on vascular smooth muscle cells (SMC), effects of beta-17-estradiol (beta-E-2) on phenotypic modulation and proliferation of rabbit aortic SMC were observed in vitro. At 10(-8) M, beta-E-2 significantly slowed the decrease in volume fraction of myofilaments (V(v)myo) of freshly dispersed SMCs in primary culture, indicating an inhibitory effect of beta-E-2 On spontaneous phenotypic modulation of SMC from a contractile to a synthetic phenotype. Freshly dispersed SMCs treated with beta-E-2 also had a relatively longer quiescent phase than control cells before intense proliferation occurred. This was in contrast to SMCs in passage 2-3 (synthetic state), where beta-E-2-treated cells replicated significantly faster than untreated cells. beta-E-2 also markedly enhanced the serum-induced DNA synthesis of synthetic SMCs in a concentration-dependent manner within physiological range (10(-10) to 10-8 M). These findings indicate that the growth-regulating effect of estrogen on vascular SMC is dependent on the cell's phenotypic stare. It delays the cell cycle re-entry of the contractile SMCs by retarding their phenotypic modulation however, once cells have modulated to the synthetic phenotype, it promotes their replication. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.

GABAergic REGULATION OF AUDITORY SENSORY GATING IN LOW- AND HIGH-ANXIETY RATS SUBMITTED TO A FEAR CONDITIONING PROCEDURE

The inferior colliculus (IC) is primarily involved in the processing of acoustic stimuli, being in a position to send auditory information to motor centers that participate in behaviors such as prey catching and predators` avoidance The role of the central nucleus of the IC (CIC) on fear and anxiety has been suggested on the basis that rats are able to engage in tasks to decrease the aversiveness of CIC stimulation, increased Fos immunolabeling during diverse aversive states and increased CIC auditory evoked potentials (AEP) induced by conditioned fear stimuli Additionally it was shown that brainstem AEP, represented by wave V, for which the main generator is the IC, is increased during experimentally induced anxiety Rats segregated according to their low or high emotional reactivity have been used as an important tool in the study of fear and anxiety The IC contains a high density of GABA receptors Since the efficacy of an anxiolytic compound is a function of the animal`s anxiety level, it is possible that GABA-benzodiazepine (Bzp) agents affect LA and HA animals differently In this study we investigated the GABA-Bzp influence on the modulation of AEP in rats with low (LA) or high-anxiety (HA) levels, as assessed by the elevated plus maze test (EPM) GABA-Bzp modulation on the unconditioned AEP response was analyzed by using intra CIC injections (0 2 mu l) of the GABA-Bzp agonists muscimol (121 ng) and diazepam (30 mu g) or the GABA inhibitors bicuculline (10 ng) and semicarbazide (7 mu g) In a second experiment, we evaluate the effects of contextual aversive conditioning on AEP using foot shocks as unconditioned stimuli On the unconditioned fear paradigm GABA inhibition in creased AEP in LA rats and decreases this measure in HA counterparts Muscimol was effective in reducing AEP in both LA and HA rats Contextual fear stimuli increased the magnitude of AEP In spite of no effect obtained with diazepam in LA rats the drug inhibited AEP in HA animals The specificity of the regulatory mechanisms mediated by GABA Bzp for the ascending neurocircuits responsible for the acquisition of aversive information in LA and HA animals shed light on the processing of sensory information underlying the generation of defensive reactions (C) 2010 IBRO Published by Elsevier Ltd All rights reserved

5-HT1A receptors of the lateral septum regulate inhibitory avoidance but not escape behavior in rats

Serotonin in the lateral septum (LS) has been implicated in the modulation of defensive behaviors and in anxiety. However, it is currently unknown whether changes in 5-HT mechanisms in this brain area may selectively affect defensive responses associated with specific subtypes of anxiety disorders recognized in clinical settings. To address this question, we evaluated the effect of the intra-LS injection of the 5-HT1A/7 receptor agonist 8-CH-DPAT (0.6, 3.0, 15.0 nmol) in male Wistar rats exposed to the elevated T-maze animal model of anxiety. This test allows the measurement of two behavioral defensive responses in the same rat: inhibitory avoidance and escape behavior. In clinical terms, these responses have been respectively related to generalized anxiety and panic disorder. The effects of 8-OH-DPAT were compared to those caused by a standard anxiolytic compound, the benzodiazepine receptor agonist midazolam (MDZ, 20 nmol). We also investigated whether the intra-LS injection of the 5-HT1A receptor antagonist WAY-100635 (0.37 nmol) was able to block the effects of 8-OH-DPAT. All animals were also tested in an open field for locomotor activity assessments. Results showed that whereas intra-LS administration of MDZ decreased avoidance latencies, suggesting an anxiolytic action, 8-OH-DPAT caused the opposite effect. Neither drug affected the escape performance. Intra-LS administration of WAY-100635 blocked the anxiogenic effect caused by 8-OH-DPAT. No changes to locomotion were detected in the open field. The data suggests that LS 5-HT1A receptors are involved in the control of inhibitory avoidance behavior and that a failure in this regulatory mechanism may be of importance to the physiopathology of generalized anxiety disorder. (c) 2008 Elsevier Inc. All rights reserved.

Cardiovascular responses to microinjection of noradrenaline into the medial amygdaloid nucleus of conscious rats result from alpha(2)-receptor activation and vasopressin release

The medial amygdaloid nucleus (MeA) is involved in the modulation of physiological and behavioral processes, as well as regulation of the autonomic nervous system. Moreover, MeA electrical stimulation evokes cardiovascular responses. Thus, as noradrenergic receptors are present in this structure, the present study tested the effects of local noradrenaline (NA) microinjection into the MeA on cardiovascular responses in conscious rats. Moreover, we describe the types of adrenoceptor involved and the peripheral mechanisms involved in the cardiovascular responses. Increasing doses of NA (3, 9, 27 or 45 nmol/100 nL) microinjected into the MeA of conscious rats caused dose-related pressor and bradycardic responses. The NA cardiovascular effects were abolished by local pretreatment of the MeA with 10 nmol/100 nL of the specific alpha(2)-receptor antagonist RX821002, but were not affected by local pretreatment with 10 nmol/100 nL of the specific alpha(1)-receptor antagonist WB4101. The magnitude of pressor response evoked by NA microinjected into the MeA was potentiated by intravenous pretreatment with the ganglion blocker pentolinium (5 mg/kg), and blocked by intravenous pretreatment with the selective V(1)-vasopressin antagonist dTyr(CH(2))(5)(Me)AVP (50 mu g/kg). In conclusion, our results show that microinjection of NA into the MeA of conscious rats activates local alpha(2)-adrenoceptors, evoking pressor and bradycardic responses, which are mediated by vasopressin release.

BED NUCLEUS OF THE STRIA TERMINALIS alpha(1)- AND alpha(2)-ADRENOCEPTORS DIFFERENTIALLY MODULATE THE CARDIOVASCULAR RESPONSES TO EXERCISE IN RATS

Dynamic exercise evokes sustained blood pressure and heart rate (HR) increases. Although it is well accepted that there is a CNS mediation of cardiovascular adjustments during dynamic exercise, information on the role of specific CNS structures is still limited. The bed nucleus of the stria terminalis (BST) is involved in exercise-evoked cardiovascular responses in rats. However, the specific neurotransmitter involved in BST-related modulation of cardiovascular responses to dynamic exercise is still unclear. In the present study, we investigated the role of local BST adrenoceptors in the cardiovascular responses evoked when rats are submitted to an acute bout of exercise on a rodent treadmill. We observed that bilateral microinjection of the selective alpha 1-adrenoceptor antagonist WB4101 into the BST enhanced the HR increase evoked by dynamic exercise without affecting the mean arterial pressure (MAP) increase. Bilateral microinjection of the selective alpha 2-adrenoceptor antagonist RX821002 reduced exercise-evoked pressor response without changing the tachycardiac response. BST pretreatment with the nonselective beta-adrenoceptor antagonist propranolol did not affect exercise-related cardiovascular responses. BST treatment with either WB4101 or RX821002 did not affect motor performance in the open-field test, which indicates that effects of BST adrenoceptor antagonism in exercise-evoked cardiovascular responses were not due to changes in motor activity. The present findings are the first evidence showing the involvement of CNS adrenoceptors in cardiovascular responses during dynamic exercise. Our results indicate an inhibitory influence of BST alpha 1-adrenoceptor on the exercise-evoked HR response. Data also point to a facilitatory role played by the activation of BST alpha 2-adrenoceptor on the pressor response to dynamic exercise. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Lipoxin A(4) attenuates zymosan-induced arthritis by modulating endothelin-1 and its effects

BACKGROUND AND PURPOSE Lipoxin A(4) (LXA(4)) is a lipid mediator involved in the resolution of inflammation. Increased levels of LXA(4) in synovial fluid and enhanced expression of the formyl peptide receptor 2/lipoxin A(4) receptor (FPR2/ALX) in the synovial tissues of rheumatoid arthritis patients have been reported. Endothelins (ETs) play a pivotal pro-inflammatory role in acute articular inflammatory responses. Here, we evaluated the anti-inflammatory role of LXA(4), during the acute phase of zymosan-induced arthritis, focusing on the modulation of ET-1 expression and its effects. EXPERIMENTAL APPROACH The anti-inflammatory effects of LXA(4), BML-111 (agonist of FPR2/ALX receptors) and acetylsalicylic acid (ASA) pre- and post-treatments were investigated in a murine model of zymosan-induced arthritis. Articular inflammation was assessed by examining knee joint oedema; neutrophil accumulation in synovial cavities; and levels of prepro-ET-1 mRNA, leukotriene (LT)B(4), tumour necrosis factor (TNF)-alpha and the chemokine KC/CXCL1, after stimulation. The direct effect of LXA(4) on ET-1-induced neutrophil activation and chemotaxis was evaluated by shape change and Boyden chamber assays respectively. KEY RESULTS LXA(4), BML-111 and ASA administered as pre- or post-treatment inhibited oedema and neutrophil influx induced by zymosan stimulation. Zymosan-induced preproET-1 mRNA, KC/CXCL1, LTB(4) and TNF-alpha levels were also decreased after LXA(4) pretreatment. In vitro, ET-1-induced neutrophil chemotaxis was inhibited by LXA4 pretreatment. LXA(4) treatment also inhibited ET-1-induced oedema formation and neutrophil influx into mouse knee joints. CONCLUSION AND IMPLICATION LXA(4) exerted anti-inflammatory effects on articular inflammation through a mechanism that involved the inhibition of ET-1 expression and its effects.

N-Methyl-D-aspartate glutamate receptors in the hypothalamic paraventricular nucleus modulate cardiac component of the baroreflex in unanesthetized rats

In the present study, we investigated the role played by the hypothalamic paraventricular nucleus (PVN) in the modulation of cardiac baroreflex activity in unanesthetized rats. Bilateral microinjections of the nonselective neurotransmission blocker CoCl(2) into the PVN decreased the reflex bradycardic response evoked by blood pressure increases, but had no effect on reflex tachycardia evoked by blood pressure decreases. Bilateral microinjections of the selective NMDA glutamate receptor antagonist LY235959 into the PVN caused effects that were similar to those observed after microinjections of CoCl(2), decreasing reflex bradycardia without affecting tachycardic response. The microinjection of the selective non-NMDA glutamate receptor antagonist NBQX into the PVN did not affect the baroreflex activity. Also, the microinjection of L-glutamate into the PVN increased the reflex bradycardia, an effect opposed to that observed after PVN treatment with CoCl(2) or LY235959, and this effect of L-glutamate was blocked by PVN pretreatment with LY235959. LY235959 injected into the PVN after iv. treatment with the selective beta(1)-adrenoceptor antagonist atenolol still decreased the reflex bradycardia. Taken together, our results suggest a facilitatory influence of the PVN on the bradycardic response of the baroreflex through activation of local NMDA glutamate receptors and a modulation of the cardiac parasympathetic activity. (C) 2010 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

Opioidergic and GABAergic mechanisms in the rostral ventromedial medulla modulate the nociceptive response of vocalization in guinea pigs

Vocalization generated by the application of a noxious stimulus is an integrative response related to the affective-motivational component of pain. The rostral ventromedial medulla (RVM) plays an important role in descending pain modulation, and opiates play a major role in modulation of the antinociception mediated by the RVM. Further, it has been suggested that morphine mediates antinociception indirectly, by inhibition of tonically active GABAergic neurons. The current study evaluated the effects of the opioids and GABA agonists and antagonists in the RVM on an affective-motivational pain model. Additionally, we investigated the opioidergic-GABAergic interaction in the RVM in the vocalization response to noxious stimulation. Microinjection of either morphine (4.4 nmo1/0.2 mu l) or bicuculline (0.4 nmo1/0.2 mu l) into the RVM decreased the vocalization index, whereas application of the GABA(A) receptor agonist, musci-mol (0.5 nmo1/0.2 mu l) increased the vocalization index during noxious stimulation. Furthermore, prior microinjection of either the opioid antagonist naloxone (2.7 nmo1/0.2 mu l) or muscimol (0.25 nmo1/0.2 mu l) into the RVM blocked the reduction in vocalization index induced by morphine. These observations suggest an antinociceptive and pro-nociceptive role of the opioidergic and GABAergic neurotransmitters in the RVM, respectively. Our data show that opioids have an antinociceptive effect in the RVM, while GABAergic neurotransmission is related to the facilitation of nociceptive responses. Additionally, our results indicate that the antinociceptive effect of the opioids in the RVM could be mediated by a disinhibition of tonically active GABAergic interneurons in the downstream projection neurons of the descending pain control system; indicating an interaction between the opioidergic and GABAergic pathways of pain modulation. (C) 2010 Elsevier Inc. All rights reserved.