Biomedical subjects

D Nico

Publications and source records attributed to D Nico.

12 recordsLinked to original sources

PubMed2006

Assessment of the monoterpene, glycidic and triterpene-moieties' contributions to the adjuvant function of the CP05 saponin of Calliandra pulcherrima Benth during vaccination against experimental visceral leishmaniasis.

The CP05 saponin from Calliandra pulcherrima Benth, shows remarkable similarities to the QS21 saponin of Quillaja saponaria Molina. Both shared a monoterpene hydrophobic moiety, a glycidic chain attached to the triterpene C28, and three sugars attached to C3. Different from QS21, the CP05 does not show the aldehyde group in triterpene C4 involved in TH1 response. Balb/c mice were immunized either intact saponin (CP05), the monoterpene-deprived (BS), the C28 carbohydrate-deprived (HS) or the sapogenin fraction, in formulation with the FML antigen of Leishmania donovani and challenged with 2 x 10(8) amastigotes of L. chagasi. While the CP05 induced 90% survival and 92.1% parasite reduction, a 100% survival and 94.1% protection were detected after the BS-vaccine treatment, indicating that the monoterpene acylated moiety, absent in the BS vaccine, is not necessary for the induction of a protective global TH1 response. Only the DTH response of BS vaccines was mildly lower than that of CP05 vaccinees. Maximal anti-FML antibody, CD4(+) and CD8(+) Leishmania specific lymphocytes, IFN-gamma splenocyte secretion, reduction in parasite load and survival was also detected for the BS vaccine. The HSFML vaccine showed diminished responses in all tested variables, except for IFN-gamma secretion, indicating that the integrity of the carbohydrate moiety attached to C28 is mandatory for the these functions. No protection was induced by the sapogenin-FML indicating that the CP05 triterpene which lacks the C4 aldehyde group, is not a immunostimulating compound. No contribution to protection was detected in the CP05 saponin treated control group supporting the specificity of the FML antigenic preparation.

Adjuvants, Immunologic↗

PubMed2006

Acylated and deacylated saponins of Quillaja saponaria mixture as adjuvants for the FML-vaccine against visceral leishmaniasis.

The adjuvant of the FML-vaccine against murine and canine visceral leishmaniasis, the Riedel de Haen saponin mixture, was fractionated by ion exchange chromatography on DEAE-cellulose to afford one TLC homogeneous Quillaja saponaria Molina QS21 saponin fraction (18.0%), a mixture of two deacylsaponins (19.4%), sucrose (39.9%), sucrose and glucose (19.7%), rutin (0.8%) and quercetin (2.2%), that were identified by comparison of 1H and 13C NMR spectroscopy. The QS21 shows the typical aldehyde group in C-23 (65% equatorial) and a normonoterpene moiety acylated in C-28. The deacylsaponins show the aldehyde group but do not have the normonoterpene moiety. Balb/c mice were vaccinated with 150 microg of FML antigen of Leishmania donovani and 100 microg of each obtained fraction and further challenged by infection with 10(8) amastigotes of Leishmania chagasi. The safety analysis and the effect on humoral and cellular immune responses and in clinical signs showed that the QS21 saponin and the deacylsaponins are the most active adjuvant compounds of the Riedel the Haen saponin mixture. Both induced the highest and non-significantly different increases in DTH, CD4+ T lymphocytes in spleen, IFN-gamma in vitro, body weight gain and the most pronounced reduction of parasite burden in liver (95% for QS21 and 86% for deacylsaponins; p>0.05). While the QS21 showed mild toxicity, significant adjuvant effect on the anti-FML humoral response before and after infection, and decrease in liver relative weight, the deacylsaponins showed no toxicity, less haemolysis and antibody and DTH responses increased mainly after infection, still inducing a stronger Leishmania-specific in vitro splenocyte proliferation. Our results confirm in the Riedel de Haen saponin extract the presence of deacylsaponins normonoterpene-deprivated which are non-toxic and capable of inducing a specific and strong immunoprotective response in vaccination against murine visceral leishmaniasis.

Acylation↗

PubMed2005

Cortical plasticity following surgical extension of lower limbs.

Human cortical plasticity has been studied after peripheral sensory alterations due to amputations or grafts, while sudden 'quasi-physiological' changes in the dimension of body parts have not been investigated yet. We examined the cortical reorganization in achondroplastic dwarfs submitted to progressive elongation (PE) of lower limbs through the Ilizarov technique. This paradigm is ideal for studying cortical plasticity because it avoids the perturbation connected with deafferentation and re-afferentation. Somatosensory evoked-potentials (SEP) and fMRI studies were performed before and after PE during foot and knee stimulation, above and below the surgical fracture. A body schema test was also performed. Following PE, cortical modifications were observed in the primary somatosensory cortex for foot stimulation and in higher order somatosensory cortices for foot and knee. The former modifications tended to decrease 6 months after the elongation ending, whereas the latter tended to persist. Results are interpreted in terms of cortical adaptation mediated by temporary disorganization.

Achondroplasia↗

PubMed1999

Effectiveness of sensory stimulation on tactile extinction.

Eleven brain-damaged patients with extinction were asked to report double tactile stimuli before, during, and after optokinetic stimulation and transcutaneous electrical stimulation of the posterior neck region. The goal of the study was to test whether tactile extinction is sensitive to these experimental manipulations in order to better understand the nature of the disorder. Both of these sensory stimulations are known to be effective in modulating only higher-order (cognitive) disorders of spatial coding, such as visual hemineglect, deficit of position sense, hemianesthesia, etc. When applied to the side contralateral to the cerebral lesion, both optokinetic and transcutaneous electrical stimulation significantly affected patients' performances, increasing the amount of detections of contralesional double stimuli. A tendency towards worse performance was observed when sensory stimulation was applied to the ipsilesional side. The reported effectiveness in reducing tactile extinction suggests that the deficit can not be fully ascribed to a peripheral sensory disorder and that it reflects damage to a higher-order cognitive function involved in contralesional space representation or in the deployment of attention to that side of space. The nature of the close relationship between extinction and hemineglect is also discussed from the point of view of extinction as a deficit of space coding.

Aged↗

PubMed1999

The endpoints' task: an analysis of length reproduction in unilateral neglect.

When patients with left hemineglect are shown the centre of a memorised line and are asked to mark both the endpoints, they place the left one significantly farther. This contralesional bias appears to be incoherent with respect to most current interpretations of neglect [7]. In the present study, ten patients with left hemineglect and two control groups were presented the centre of a line and one of its endpoints and had to mark the missing one at the correct distance. With this modification, subjects had not to rely on stored information about the line, but simply to reproduce a distance either to the left or to the right separately. The task was performed in three different spatial locations with respect to subjects' body midline. Similarly to the original endpoints' task, neglect patients showed a leftward bias, placing the left endpoint significantly farther than the right one. However, this was not associated with a paradoxical contralesional over-extension with respect to the distance to reproduce. Indeed, when marking the left endpoint, patients were accurate (when performing in the right hemispace) or even underestimated the distance to reproduce (when performing centrally and in the left hemispace). Instead, the leftward bias was due to severe underestimation errors when marking the right endpoint, which were independent of the stimulus location. These results demonstrate that the leftward bias in the endpoints' task is relative rather than absolute and does not reflect a paradoxical overestimation in length reproduction towards the left side.

Adult↗

PubMed1997

Believing what you feel: using proprioceptive feedback to reduce unilateral neglect.

Unilateral spatial neglect declines when participants reach to grip the center of long metal rods compared with when they point to the perceived center, suggesting that visuomotor control systems are less affected by neglect than other representational systems (I. H. Robertson, D. Nico, & B. Hood, 1995). In this study, 16 participants with unilateral left neglect actually picked up rods, and we predicted short-term improvements in neglect because of induced conflict between a phenomenally symmetrical visual world on the one hand and a proprioceptively conveyed rightward-biased world on the other. With participants serving as their own controls, significant short-term improvements in neglect were found on 2 out of 4 neglect tasks after participants experienced proprioceptive feedback discrepant from the judgments they made on the basis of visual information alone.

Aged↗

PubMed1997

Motor deficits and optokinetic stimulation in patients with left hemineglect.

Optokinetic stimulation with left direction of the movement of luminous dots temporarily improved motor weakness of the left hand in two right-brain-damaged patients with left spatial hemineglect. Stimulation to the right had no effect. In two left-brain-damaged patients, optokinetic stimulation did not affect the right motor weakness, regardless of direction of the movement of the optokinetic stimuli. We suggest that in patients with left hemineglect, contralesional motor deficits have a neglect-related component, which, as other aspects of the neglect syndrome, may be improved by optokinetic stimulation. The mechanisms may include a temporary restoration of the spatial coordinates of bodily representations, pathologically distorted towards the side of the lesion.

Aged↗

PubMed1996

Detecting directional hypokinesia: the epidiascope technique.

A new technique to detect directional hypokinesia is proposed.. Subjects with unilateral neglect were administered cancellation tests with an epidiascope used to dissociate visual input from motor output. Two different cancellation tasks were performed in order to compare this technique with the method devised by Tegner and Levander [Brain 114, 1943-1951, 1991]. No difference in detecting hypokinetic deficits was observed; however, our method was easier to perform and more suitable for clinical testing.

Aged↗

PubMed1996

Left neglect dyslexia and the processing of neglected information.

A patient (ES) with a right fronto-temporo-parieto-occipital lesion, and left neglect dyslexia, is reported. ES performed reading and association tasks on written words, composed of two embedded words, one to the left and one to the right of the division point. The meaning of the whole stimulus differed from that of the embedded words, and could not be inferred from either of them. ES produced appropriate associations even to those stimuli on which she made neglect paralexic errors. This dissociation reflects a distinction between processes which use co-ordinate spatial systems and subserve perceptual awareness, impaired in hemineglect, and processes which do not. The latter analyse left-sided information to a large extent, without reaching awareness.

Aged↗

PubMed1996

Beyond unilateral neglect.

When required to set the endpoints of an imaginary horizontal line of a given length on the basis of its midpoint printed on a sheet of paper, left neglect patients most frequently misplaced endpoints leftwards. Though giving rise to the very same disproportion usually found with these patients on canonical line bisection tasks, this behaviour cannot be accommodated by current explanations of unilateral neglect. When the task was executed during leftward optokinetic stimulation (OKS), a manoeuvre known temporarily to improve neglect symptoms, the disproportion increased instead of vanishing. We therefore suggest that unilateral neglect is a manifestation of a disorder primarily implying a horizontal anisometry of space representation and that manipulations such as OKS may remove neglect without normalizing the representational medium itself.

Adult↗

PubMed1995

The intention to act improves unilateral left neglect: two demonstrations.

Unilateral neglect involves a spatial bias to one side of space, usually to the right. Perceptual and motor systems interact in the manifestation of this disorder, and there is also evidence that motor manipulative responses may have access to unique streams of information not available for non-motoric judgements. It is therefore predicted that the manifestation of neglect may be alterable by changing the purpose of otherwise very similar responses to spatially extended objects. In Experiment 1, neglect-based deviation to the right of centre was significantly less when subjects reached towards metal rods as if to pick them up in the centre, compared to when they pointed to their centres. In Experiment 2, subjects pointed to the centre of a rectangular box with a swivelled lid. They were then asked to place a coin at the centre of this lid, in a position sufficiently central to prevent the lid tilting and the coin falling into the box; in fact, the lid was fixed and subjects never received feedback. Responses were significantly more central with the balancing response than with the pointing one. These results suggest that prehensive movements towards objects allow 'leakage' of information about their spatial extent, via an unaffected stream of information available for motor-manipulative responses.

Aged↗

PubMed1995

Spatial hemineglect in back space.

The subjective location of the mid-sagittal plane was assessed by a free-field auditory localization task in the front and in the back half-spaces in 11 right brain-damaged patients with spatial hemineglect, 10 right brain-damaged patients without spatial hemineglect, and 11 normal control subjects. In patients with hemineglect the subjective mid-sagittal plane was found to be displaced rightwards in both half-spaces. Both patients without hemineglect and controls, in contrast, made a minor error, and showed a greater displacement towards the left side in the back half-space. In four right brain-damaged patients the rightward displacement was confined either to the front, or to the back half-space. This pattern of impairment may be explained by a rightward, ipsilesional, pathological translation of an egocentric co-ordinate system, rather than by a rotation around the vertical axis of the body.

Aged↗