RESUMEN

Sense of time is a complex construct, and its neural correlates remain to date in most part unknown. To complicate the frame, physical attributes of the stimulus, such as its intensity or movement, influence temporal perception. Although previous studies have shown that time perception can be compromised after a brain lesion, the evidence on the role of the left and right hemispheres are meager. In two experiments, the study explores the ability of temporal estimation of multi-second actions and non-biological movements in 33 patients suffering from unilateral brain lesion. Furthermore, the modulatory role of induced embodiment processes is investigated. The results reveal a joint contribution of the two hemispheres depending not only on different durations but also on the presence of actions. Indeed, the left hemisphere damaged patients find it difficult to estimate 4500 ms or longer durations, while the right hemisphere damaged patients fail in 3000 ms durations. Furthermore, the former fail when a biological action is shown, while the latter fail in non-biological movement. Embodiment processes have a modulatory effect only after right hemisphere lesions. Among neuropsychological variables, only spatial neglect influences estimation of non-biological movement.

Asunto(s)

RESUMEN

Personal neglect is a disorder in the perception and representation of the body that causes the patients to behave as if the contralesional side of their body does not exist. This clinical condition has not been adequately investigated in the past as it has been considered a symptom of unilateral spatial neglect, which has mainly been studied with reference to extrapersonal space. Only a few studies with small samples have investigated the neuroanatomical correlates of personal neglect, and these have mainly focused on discrete cortical lesions and modular accounts, as well as being based on the hypothesis that this disorder is associated with somatosensory and spatial deficits. In the present study, we tested the novel hypothesis that personal neglect may be associated not only with discrete cortical and subcortical lesions, but also with disconnections of white matter tracts. We performed an advanced lesion analyses in a large sample of 104 right hemisphere damaged patients, 72 of whom were suffering from personal neglect. Results from the analyses of the grey and white matter were controlled for co-occurrent clinical variables such as extrapersonal neglect, anosognosia for hemiplegia and motor deficits, along with other lesion-related variables such as lesion size and the interval from the lesion onset to neuroimaging recordings. Our results reveal that personal neglect is associated with lesions in a medial network which involves the temporal cortex (Heschl's gyrus), the ventro-lateral nuclei of the thalamus and the fornix. This suggests that personal neglect involves a convergence between sensorimotor processes, spatial representation and the processing of self-referred information (episodic memory).

Asunto(s)

RESUMEN

Although in the last three decades philosophers, psychologists and neuroscientists have produced numerous studies on human cognition, the debate concerning its nature is still heated and current views on the subject are somewhat antithetical. On the one hand, there are those who adhere to a view implying 'disembodiment' which suggests that cognition is based entirely on symbolic processes. On the other hand, a family of theories referred to as the Embodied Cognition Theories (ECT) postulate that creating and maintaining cognition is linked with varying degrees of inherence to somatosensory and motor representations. Spinal cord injury induces a massive body-brain disconnection with the loss of sensory and motor bodily functions below the lesion level but without directly affecting the brain. Thus, SCI may represent an optimal model for testing the role of the body in cognition. In this review, we describe post-lesional cognitive modifications in relation to body, space and action representations and various instances of ECT. We discuss the interaction between body-grounded and symbolic processes in adulthood with relevant modifications after body-brain disconnection.

Asunto(s)

RESUMEN

Recent studies on recovery of consciousness of subjects in a vegetative state (VS) admitted to rehabilitation units have focused mainly on the identification of prognostic factors, whereas few studies have focused on outcome. The aim of this study was to compare demographic and clinical data and report functional outcome of patients in a VS due to severe acquired brain injury (ABI) of different aetiologies. The study was a retrospective multicentre cohort study and involved 492 patients in a VS due to traumatic (TBI) or non-traumatic (NTBI) severe ABI admitted to 29 Italian rehabilitation units. Demographic and clinical data recorded included age, gender, aetiology, Glasgow Coma Scale score; onset-to-admission interval; length of stay in the rehabilitation unit; the department from which they were referred; and the presence of percutaneous endoscopic gastrostomy or tracheostomy. Recovery of consciousness and disability were evaluated using a discharge Disability Rating Scale. At discharge, 53.11% patients had emerged from VS, with TBI subjects significantly more likely to recover consciousness than NTBI ones. Subjects with NTBI had a significantly worse prognosis than those with TBI, and within the NTBI group, subjects with a cerebrovascular aetiology had a better outcome than those with an anoxic aetiology. Among the patients who emerged from VS, 71.30% of TBI and 83.06% of NTBI subjects presented extremely severe disability. Only 37.93% of subjects affected by TBI and 17.44% of those affected by NTBI who presented extremely severe disability returned home after their rehabilitation stay. Even though almost a half of the patients emerged from VS, a large number of these subjects showed severe disability, often making it impossible for them to return home. This situation has a major impact on the healthcare system.

Asunto(s)

RESUMEN

Categorizing an individual as a friend or foe plays a pivotal role in navigating the social world. According to the stereotype content model (SCM), social perception relies on two fundamental dimensions, warmth and competence, which allow us to process the intentions of others and their ability to enact those intentions, respectively. Social cognition research indicates that, in categorization tasks, people tend to classify other individuals as more likely to belong to the out-group than the in-group (in-group overexclusion effect, IOE) when lacking diagnostic information, probably with the aim of protecting in-group integrity. Here, we explored the role of warmth and competence in group-membership decisions by testing 62 participants in a social-categorization task consisting of 150 neutral faces. We assessed whether (a) warmth and competence ratings could predict the in-group/out-group categorization, and (b) the reliance on these two dimensions differed in low-IOE versus high-IOE participants. Data showed that high ratings of warmth and competence were necessary to categorize a face as in-group. Moreover, while low-IOE participants relied on warmth, high-IOE participants relied on competence. This finding suggests that the proneness to include/exclude unknown identities in/from one's own in-group is related to individual differences in the reliance on SCM social dimensions. Furthermore, the primacy of the warmth effect seems not to represent a universal phenomenon adopted in the context of social evaluation.

Asunto(s)

RESUMEN

Residual forms of awareness have recently been demonstrated in subjects affected by anosognosia for hemiplegia, but their potential effects in recovery of awareness remain to date unexplored. Emergent awareness refers to a specific facet of motor unawareness in which anosognosic subjects recognise their motor deficits only when they have been requested to perform an action and they realise their errors. Four participants in the chronic phase after a stroke with anosognosia for hemiplegia were recruited. They took part in an "error-full" or "analysis of error-based" rehabilitative training programme. They were asked to attempt to execute specific actions, analyse their own strategies and errors and discuss the reasons for their failures. Pre- and post-training and follow-up assessments showed that motor unawareness improved in all four patients. These results indicate that unsuccessful action attempts with concomitant error analysis may facilitate the recovery of emergent awareness and, sometimes, of more general aspects of awareness.

Asunto(s)

RESUMEN

Steam-exploded fibers from flax (Linum usitatissimum) are heterogeneously acetylated using acetic anhydride and sulfuric acid as catalyst, with the aim to modify the surface properties without changing fiber structure and morphology. The acetylation reaction follows first-order kinetics up to a reaction time that depends on catalyst concentration (15 h when using 0.4 vol % of H(2)SO(4) or 50 h with 0.1 vol %). The fibers undergo no structural and/or morphological changes under either reaction condition. On the contrary, surface damage and structural modifications appear after longer reaction times, when the reaction kinetics change. The extent of biodegradation of acetylated fibers, evaluated from the weight percent remaining after 13 days of exposure to previously isolated cellulolytic bacteria Cellvibrio sp., decreases with increasing acetylation degree. After biodegradation the fibers show a higher acetyl content than before the experiment, indicating that the bacteria preferentially biodegrade unsubstituted cellulose, though also acetylated chains are cleaved. Biodegradable acetylated cellulose fibers with modified surface chemistry and unchanged structure are obtained for applications as polymer composite reinforcements.

Asunto(s)

RESUMEN

A novel type of hydrolase was purified from culture fluid of Paucimonas (formerly Pseudomonas) lemoignei. Biochemical characterization revealed an unusual substrate specificity of the purified enzyme for amorphous poly((R)-3-hydroxyalkanoates) (PHA) such as native granules of natural poly((R)-3-hydroxybutyrate) (PHB) or poly((R)-3-hydroxyvalerate) (PHV), artificial cholate-coated granules of natural PHB or PHV, atactic poly((R,S)-3-hydroxybutyrate), and oligomers of (R)-3-hydroxybutyrate (3HB) with six or more 3HB units. The enzyme has the unique property to recognize the physical state of the polymeric substrate by discrimination between amorphous PHA (good substrate) and denatured, partially crystalline PHA (no substrate). The pentamers of 3HB or 3HV were identified as the main products of enzymatic hydrolysis of native PHB or PHV, respectively. No activity was found with any denatured PHA, oligomers of (R)-3HB with five or less 3HB units, poly(6-hydroxyhexanoate), substrates of lipases such as tributyrin or triolein, substrates for amidases/nitrilases, DNA, RNA, casein, N-alpha-benzoyl-l-arginine-4-nitranilide, or starch. The purified enzyme (M(r) 36,209) was remarkably stable and active at high temperature (60 degrees C), high pH (up to 12.0), low ionic strength (distilled water), and in solvents (e.g. n-propyl alcohol). The depolymerase contained no essential SH groups or essential disulfide bridges and was insensitive to high concentrations of ionic (SDS) and nonionic (Triton and Tween) detergents. Characterization of the cloned structural gene (phaZ7) and the DNA-deduced amino acid sequence revealed no homologies to any PHB depolymerase or any other sequence of data banks except for a short sequence related to the active site serine of serine hydrolases. A classification of the enzyme into a new family (family 9) of carboxyesterases (Arpigny, J. L., and Jaeger, K.-E. (1999) Biochem. J. 343, 177-183) is suggested.

Asunto(s)

RESUMEN

Two-dimensional spatially resolved microfocus X-ray diffraction has been used to investigate spherulites of pure bacterial poly(3-hydroxybutyrate) (PHB) and of a blend of natural and synthetic atactic PHB (a-PHB) crystallized at a relatively high temperature (Tc = 140 degrees C). Both samples investigated contained practically two-dimensional spherulites, characterized by wide extinction bands (band spacing > 80 microns). The X-ray diffraction patterns confirmed that the unit cell alpha-axis is oriented along the spherulite radius in PHB and that the same is true for the a-PHB containing blend. Comparison of the matrix of diffraction patterns with the polarized optical micrograph of the scanned sample area indicated a very clear correlation between pattern changes and banding, yielding a straightforward picture of the structural variations within the spherulite.

Asunto(s)

RESUMEN

Blends of poly(vinyl alcohol) (PVA) with collagen and gelatin, prepared from aqueous solution by solvent casting, were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). After conditioning at 51% relative humidity, collagen and PVA show nearly coincident glass transition temperatures (Tg approximately 35 degrees C), while gelatin has a higher Tg (approximately 70 degrees C). Gelatin/PVA blends show two invariant Tgs, whose temperature and associated specific heat increment clearly indicate the coexistence of two amorphous phases composed of the pure components. Owing to similarity of the Tgs of collagen and PVA after humidity conditioning, DSC offers no indication on miscibility of collagen/PVA blends. In DMTA experiments, where absorbed water freely evaporates from the samples during the thermal scan, PVA shows a glass transition relaxation at about 50 degrees C, while both gelatin and collagen display an intense glass transition in the vicinity of 230 degrees C. The DMTA spectra of collagen/PVA and gelatin/PVA blends show two invariant glass transition relaxations at about 50 and 230 degrees C. Absence of any Tg shift with composition demonstrates that the blend components are immiscible. However, blends of PVA with collagen and gelatin form optically clear films with good mechanical properties over the whole range of compositions. It is found that at T > Tg (PVA) the elastic modulus (E') of the blends strongly increases with increasing content of the biopolymer. In the case of collagen/PVA blends, experimental E' values agree with the predictions of a simple two-phase composite model with phases connected in parallel. It is concluded that, though thermodynamically immiscible with both native and denatured collagen, PVA forms mechanically compatible blends with collagen and gelatin.

Asunto(s)

RESUMEN

High-performance liquid chromatography (HPLC) was used in combination with radioactivity detection and mass spectrometry (MS) to elucidate the metabolic fate of GV104326, a novel tricyclic beta-lactam antibacterial agent. Metabolic profiles were obtained by analysis of rat urine samples collected after intravenous administration of the 14C-labelled drug at the dose of 50 mg kg-1 (12.95 MBq kg-1). Methods for solid-phase extraction from urine samples and for reversed-phase chromatographic separation of drug related material were developed. HPLC-MS was used to confirm that the parent compound corresponded to the principal peak in the chromatograms, and two minor peaks were identified as potential metabolites of GV104326. They were shown to be an open beta-lactam ring derivative (GV173923) and a dimeric compound (GV196359).

Asunto(s)

RESUMEN

Dextran, pullulan and amylose have been investigated by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical and dielectric spectroscopy over a wide range of temperatures and frequencies. No melting or glass transition is seen below the range of thermal degradation (about 300 degrees C) for either amylose or pullulan; only dextran shows a Tg at 223 degrees C (delta cp = 0.40 J/g deg). The viscoelastic spectrum of the 'dry' polysaccharides is characterized by a low temperature relaxation that occurs at -94, -73 and -59 degrees C, at 1 kHz, (activation energy 32, 39 and 52 kJ/mol) in dextran, pullulan and amylose respectively and is assigned to small entity local motions of the polysaccharide backbone. Absorbed water strongly modifies the relaxation spectrum, inducing a new relaxation below room temperature and dissipation regions associated with water loss above room temperature. The former appears at temperatures higher than the relaxation characteristic of the dry polymer and moves to lower temperature with increasing water content. In normal 'room humidity' conditions (about 10% absorbed water) the water-induced relaxation, attributed to the motion of complex polymer-water relaxing units, is the only observable feature in the dynamic mechanical and dielectric spectrum below room temperature.

Asunto(s)

RESUMEN

3-Hydroxybutyrate-3-hydroxyvalerate (3HB-3HV) as well as 3-hydroxybutyrate-4-hydroxybutyrate (3HB-4HB) copolyesters have been investigated by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical spectroscopy, over a wide range of compositions (0-95 mol% 3HV; 0-82 mol% 4HB). Both series of isolated copolyesters are partially crystalline at all compositions. Quenched samples show a glass transition that decreases linearly with increasing co-monomer molar fraction, more markedly when the co-monomer is 4HB. Above Tg, all copolyesters, rich in 3HB units, show a cold crystallization phenomenon followed by melting, while at the other end crystallization on heating is observed only in 3HB-3HV copolymers. The viscoelastic spectrum, strongly affected by thermal history, shows two relaxation regions: the glass transition, whose location depends on copolymer type and composition, and a secondary dispersion region at low temperatures (-130/-80 degrees C). The latter results from a water-related relaxation analogous to that of P(3HB) and, in 3HB-4HB copolymers, from another overlapping absorption peak centered at -130 degrees C, attributed to local motion of the methylene groups in the linear 4HB units.

Asunto(s)

RESUMEN

The mass spectrometric behaviour of five structurally different cephalosporins has been studied in detail by means of different ionization/desorption methods (electron impact, fast atom bombardment, desorption chemical ionization, laser-induced vaporization) and metastable ion studies (linked scans and mass-analysed ion kinetic energy spectrometry). The best results were obtained by fast atom bombardment mass spectrometry, leading to both molecular ions and fragment ions diagnostic for structural identification.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The interaction of ox ligamentum nuchae elastin (native, purified and soluble) with four different solvents was investigated by Differential Scanning Calorimetry. The freezable solvent content was determined, at different total solvent contents, from the melting endotherms, and the amount of unfreezable solvent was obtained by extrapolation. For two bifunctional solvents, water and ethylene glycol, the molar ratio "bound solvent/elastin residue" was the same for all the elastin samples investigated, and very close to 1.5. This result is identical to that obtained by other workers for the "water/CO-NH group" of synthetic amorphous polyamides, and it can suggest that the hydration of elastin is interpretable on the basis of a similar model. The model is based on a direct interaction of water with the peptide group, and suggests that 0.5 moles of water are strongly bound, and 1.0 moles are loosely bound to the CO-NH group. The ratio "bound water/elastin residue" is larger for the soluble beta elastin. Different molar ratios are also obtained for monofunctional solvents such as methanol and trifluoroethanol.

Asunto(s)

Asunto(s)