Bifurcation analysis of a periodically forced relaxation oscillator: differential model versus phase-resetting map.

We compare the dynamics of the periodically forced FitzHugh-Nagumo oscillator in its relaxation regime to that of a one-dimensional discrete map of the circle derived from the phase-resetting response of this oscillator (the "phase-resetting map"). The forcing is a periodic train of Gaussian-shaped pulses, with the width of the pulses much shorter than the intrinsic period of the oscillator. Using numerical continuation techniques, we compute bifurcation diagrams for the periodic solutions of the full differential equations, with the stimulation period being the bifurcation parameter.

[Growth and metabolite production of the marine cyanobacterium Synechococcus sp. (Chroococcales) in function to irradiance].

Changes in salinity, temperature and irradiance during wet and dry seasons have induced metabolic versatility in cyanobacteria from saline environments. Cyanobacteria from these environments have biotechnological potential for the production of metabolites with pharmaceutical and industrial interest. We studied the growth, dry mass and metabolite production of the cyanobacterium Synechococcus sp.

A neurofunctional evaluation strategy for presurgical selection of temporal lobe epilepsy patients.

Introduction Temporal lobe epilepsy (TLE) is the prototype of a surgically correctable syndrome. Successful surgical outcomes depend on a thorough presurgical evaluation aimed primarily at identifying the epileptogenic zone. Objective Describe the noninvasive presurgical selection and evaluation strategy for TLE patients introduced at the International Neurological Restoration Center (CIREN) in Havana, Cuba, and evaluated between 2001 and 2006 for its accuracy in identifying candidates for non-lesional resection surgery.

Ethanol changes the electroencephalographic correlation of the ventral tegmental area and nucleus accumbens, components of the mesoaccumbens system in rats.

Alcohol consumption produces various behavioral effects and its administration is associated with increases of dopamine (DA) levels in the nucleus accumbens (Acc). However, it is not yet clear if these behavioral and neurochemical effects are associated with a different functionality of the Acc and ventral tegmental area (VTA), the neural structures that constitute the dopaminergic mesoaccumbens system. The present study was designed to analyze whether the electroencephalographic (EEG) correlation between the Acc and VTA shows characteristic changes after the forced administration of ethanol in male rats.

[Heptavalent-pneumococcal conjugate vaccine (Prevenar). Differences in effectiveness between populations].

This article reviews the publications on the effectiveness of heptavalent-pneumococcal conjugate vaccine (PCV7) in the prevention of invasive pneumococcal disease (IPD) in children under five years of age. It also analyses the characteristics of the vaccine and its impact on the epidemiology of IPD in different places. Before the introduction of PCV7, the percentage of cases of IPD due to vaccine serogroups oscillated between 89% in the United States and 43% in Asia.

Phase resetting, phase locking, and bistability in the periodically driven saline oscillator: experiment and model.

The saline oscillator consists of an inner vessel containing salt water partially immersed in an outer vessel of fresh water, with a small orifice in the center of the bottom of the inner vessel. There is a cyclic alternation between salt water flowing downwards out of the inner vessel into the outer vessel through the orifice and fresh water flowing upwards into the inner vessel from the outer vessel through that same orifice. We develop a very stable (i.

Differential alpha coherence hemispheric patterns in men and women during pleasant and unpleasant musical emotions.

Potential sex differences in EEG coherent activity during pleasant and unpleasant musical emotions were investigated. Musical excerpts by Mahler, Bach, and Prodromidès were played to seven men and seven women and their subjective emotions were evaluated in relation to alpha band intracortical coherence. Different brain links in specific frequencies were associated to pleasant and unpleasant emotions.

Electrophysiological correlates of the mesoaccumbens system during male rat sexual behaviour.

It is well known that during the male rat sexual interaction different levels of arousal or sexual motivation are involved and that these motivational changes are associated with variations in the level of dopamine (DA); however, it is not yet known if these changes are associated with a different functionality of the nucleus Accumbens (Acc) and Ventral Tegmental Area (VTA), neural structures that constitute the DA mesoaccumbens system. Thus, in this study was simultaneously recorded the electroencephalogram (EEG) from the VTA and the Acc in order to determine if the EEG correlation (r) between these structures shows characteristic patterns in relation to four different conditions of sexual arousal during the male rat sexual interaction: 1) basal-quiet state (BS); 2) exposure to an inaccessible oestrous female (IF); 3) post-intromission (PI); and, 4) post-ejaculation (PE). Both Acc and VTA showed an increased relative power (RP) in the 8-12 Hz band during the PI condition as compared to the other periods.

Hyponatremia in cirrhosis: pathogenesis, clinical significance, and management.

Hyponatremia is a frequent complication of advanced cirrhosis related to an impairment in the renal capacity to eliminate solute-free water that causes a retention of water that is disproportionate to the retention of sodium, thus causing a reduction in serum sodium concentration and hypo-osmolality. The main pathogenic factor responsible for hyponatremia is a nonosmotic hypersecretion of arginine vasopressin (or antidiuretic hormone) from the neurohypophysis related to circulatory dysfunction. Hyponatremia in cirrhosis is associated with increased morbidity and mortality.

Brain activity and temporal coupling related to eye movements during REM sleep: EEG and MEG results.

EEG and MEG REM sleep gamma activity was studied immediately before rapid eye movement onset (PRE-EM), during REM sleep with eye movements away from eye movement onset -phasic-REM (Ph-REM)--and during REM sleep without eye movements, or tonic REM (T-REM). For this purpose, activity was segmented into three different time windows: of 62.5, 250 and 500 ms.

Motivational influences on the degree and direction of sexual attraction.

Motivation can be defined as a class of central nervous processes determining the likelihood of display of a behavior and the intensity of the behavior if displayed. All behavior is, according to this definition, caused and controlled by motivation. Although the concept of motivation eventually could be replaced by an entirely mechanistic explanation of the causes of behavior, in terms of neural events, such explanations would be overly complex for everyday use.

Temporal variation of biomass and productivity of Thalassia testudinum (Hydrocharitaceae) in Venezuela, Southern Caribbean.

Annual biomass and productivity of Thalassia testudinum were determined during a year at a seagrass bed located in the Parque Nacional Morrocoy, Venezuela. Leaf, rhizome and root biomass were determined monthly, together with short-shoot density, from February 1992 to January 1993, from nine replicated core samples. Productivity was measured using the methodology by Zieman (1974) with minor modifications, and leaf turnover rate was calculated.

Terlipressin and albumin vs albumin in patients with cirrhosis and hepatorenal syndrome: a randomized study.

Background & Aims: Hepatorenal syndrome is common in patients with advanced cirrhosis and constitutes a major problem in liver transplantation. There is no effective medical treatment for hepatorenal syndrome.

Methods: Forty-six patients with cirrhosis and hepatorenal syndrome, hospitalized in a tertiary care center, were randomly assigned to receive either terlipressin (1-2 mg/4 hour, intravenously), a vasopressin analogue, and albumin (1 g/kg followed by 20-40 g/day) (n = 23) or albumin alone (n = 23) for a maximum of 15 days.

Ciprofloxacin in primary prophylaxis of spontaneous bacterial peritonitis: a randomized, placebo-controlled study.

Background/aims: Low protein concentration in ascitic fluid has been identified as a risk factor for spontaneous bacterial peritonitis (SBP). Until now, primary prophylaxis has not been recommended in these patients. The aim was to investigate the efficacy of long-term administration of ciprofloxacin to prevent SBP.

Chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses by dogs to select corn fibers.

The objective was to examine the chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses of fiber-rich corn coproducts resulting from corn wet milling. Native corn fibers, native corn fibers with fines, hydrolyzed corn fibers, and hydrolyzed extracted corn fibers were analyzed chemically and their capacity to produce short-chain fatty acids determined. Ash content was low (<1.

Evaluation of uranium incorporation from contaminated areas using teeth as bioindicators--a case study.

The Southwest region of the Bahia state in Brazil hosts the largest uranium reserve of the country (100 kton in uranium, only), plus the cities of Caetité, Lagoa Real and Igaporã. In this work, aim was at the investigation of uranium burdens on residents of these cities by using teeth as bioindicators, as a contribution for possible radiation protection measures. Thus, a total of 41 human teeth were collected, plus 50 from an allegedly uranium free area (the control region).

"Contrasting patterns of selection at Pinus pinaster Ait. Drought stress candidate genes as revealed by genetic differentiation analyses".

The importance of natural selection for shaping adaptive trait differentiation among natural populations of allogamous tree species has long been recognized. Determining the molecular basis of local adaptation remains largely unresolved, and the respective roles of selection and demography in shaping population structure are actively debated. Using a multilocus scan that aims to detect outliers from simulated neutral expectations, we analyzed patterns of nucleotide diversity and genetic differentiation at 11 polymorphic candidate genes for drought stress tolerance in phenotypically contrasted Pinus pinaster Ait.

[Sepsis caused by pigmented and no pigmented Chromobacterium violaceum].

Chromobacterium violaceum sepsis is rare but associated with a high mortality rate. We report a fatal case of C. violaceum sepsis in a 6 years old Venezuelan indian boy.

[Hepatorenal syndrome].

Hepatorenal syndrome (HRS) is a severe complication in patients with cirrhosis and ascites. Renal insufficiency is functional and is caused by renal vasoconstriction. HRS occurs in 10% of patients with advanced cirrhosis.

Food availability and reproduction affects lipid and fatty acid composition of the brown mussel, Perna perna, raised in suspension culture.

We examined the influence of the reproductive cycle and environmental factors on variations of the condition index (CI), tissue dry mass, shell size, total lipid content, and relative percent of fatty acids in the mussel, Perna perna. Spat or juveniles were reared to commercial size (70 mm) in suspension culture in the Golfo de Cariaco, Venezuela between May and October 2004. The dry mass of soft tissues and shell, a visual assessment of gonadal status and the organism lipid profile were established every fortnight.

Roles of glycosylation on the antifungal activity and apoplast accumulation of StAPs (Solanum tuberosum aspartic proteases).

Specific roles of glycosylation appear to be protein-dependent. Plant aspartic proteases (APs) contain two or more consensus N-glycosylation sites; however, the importance of them is not well understood. StAPs (Solanum tuberosum aspartic proteases) are bifunctional proteins with both proteolytic and antimicrobial activities.

Rhythms of high-grade block in an ionic model of a strand of regionally ischemic ventricular muscle.

Electrical alternans, a beat-to-beat alternation in the electrocardiogram or electrogram, is frequently seen during the first few minutes of acute myocardial ischemia, and is often immediately followed by malignant cardiac arrhythmias such as ventricular tachycardia and ventricular fibrillation. As ischemia progresses, higher-order periodic rhythms (e.g.

Potato aspartic proteases (StAPs) exert cytotoxic activity on bovine and human spermatozoa.

Objective: To evaluate the in vitro spermicidal activity of Solanum tuberosum aspartic proteinases (StAPs) on bovine and human sperm.

Design: Controlled laboratory study.

Setting: Three research laboratories at a university of biologic science.

Metabolic and electric brain patterns during pleasant and unpleasant emotions induced by music masterpieces.

Brain correlates comparing pleasant and unpleasant states induced by three dissimilar masterpiece excerpts were obtained. Related emotional reactions to the music were studied using Principal Component Analysis of validated reports, fMRI, and EEG coherent activity. A piano selection by Bach and a symphonic passage from Mahler widely differing in musical features were used as pleasing pieces.