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Biomedical subjects

P Pantano

Publications and source records attributed to P Pantano.

At least 55 records · Page 3Linked to original sources
PubMed1995

Monitoring an oxidative stress mechanism at a single human fibroblast.

Easily oxidizable substances inside human diploid fibroblast cell strains were monitored amperometrically with a platinized carbon-fiber microelectrode. The experiment involved positioning a microelectrode over a single biological cell, forcing the electrode tip into the cell via micromanipulator control, and measuring the transient current corresponding to the complete electrolysis of electroactive species released by the cell. A second series of experiments involved puncturing a hole into the cell with a micropipet and measuring the transient current corresponding to the complete electrolysis of electroactive species emitted by the cell with an electrode positioned above the cell. The selectivity of both amperometric measurements was demonstrated through the use of known hydrogen peroxide scavengers (added catalase or intracellular peroxidase + added o-dianisidine) to the media bathing the cells. The abolition of the amperometric signal under these conditions suggested that hydrogen peroxide was the primary substance detected. The magnitude and the time course of the transient current measured implied that the hydrogen peroxide detected was not only that initially present in the cell before its membrane was pierced but represented mostly an oxidative stress response of the cell to its injury.

Cells, Cultured↗
PubMed1995

Combined imaging and chemical sensing using a single optical imaging fiber.

Despite many innovations and developments in the field of fiber-optic chemical sensors, optical fibers have not been employed to both view a sample and concurrently detect an analyte of interest. While chemical sensors employing a single optical fiber or a noncoherent fiberoptic bundle have been applied to a wide variety of analytical determinations, they cannot be used for imaging. Similarly, coherent imaging fibers have been employed only for their originally intended purpose, image transmission. We herein report a new technique for viewing a sample and measuring surface chemical concentrations that employs a coherent imaging fiber. The method is based on the deposition of a thin, analyte-sensitive polymer layer on the distal surface of a 350-microns-diameter imaging fiber. We present results from a pH sensor array and an acetylcholine biosensor array, each of which contains approximately 6000 optical sensors. The acetylcholine biosensor has a detection limit of 35 microM and a fast (< 1 s) response time. In association with an epifluorescence microscope and a charge-coupled device, these modified imaging fibers can display visual information of a remote sample with 4-microns spatial resolution, allowing for alternating acquisition of both chemical analysis and visual histology.

Acetylcholinesterase↗
PubMed1995

Prolonged muscular flaccidity after stroke. Morphological and functional brain alterations.

Patients with a motor deficit due to ischaemic stroke usually develop muscular spasticity, but in some cases they may remain with a prolonged muscular flaccidity which impairs their recovery. Little is known about the causes of these two different functional outcomes. We correlated CT/MRI and 99mTc HM-PAO SPECT with clinical findings in 42 patients at a mean time interval of 3 months after stroke. The patients were divided into two cohorts with either flaccid (prolonged muscular flaccidity) or spastic (muscular spasticity) hemiparesis. Although patients with prolonged muscular flaccidity had a greater motor deficit, the mean structural volume of the ischaemic lesion was similar to that of the muscular spasticity cohort. There was a significantly higher prevalence of structural involvement of the lentiform nucleus in prolonged muscular flaccidity cases. Relative perfusion in the lentiform nucleus, thalamus and contralateral cerebellar hemisphere was significantly lower in prolonged muscular flaccidity than in muscular spasticity patients. A subgroup with only subcortical structural lesions also showed significantly lower relative perfusion in the ipsilateral frontal association areas. A primary involvement of the lentiform nucleus by the structural lesion seems to be crucial for the persistence of flaccidity after stroke. However, cerebral blood flow (CBF) changes in other structurally intact regions indicate their additional role. It is likely that both subcortical-cortical loops involved in motor control, i.e. cortex-basal ganglia-thalamus-cortex and cortex-pons-cerebellum-thalamus-cortex, are more widely and more severely affected in patients with prolonged muscular flaccidity.

Adult↗
PubMed1994

Paramedian diencephalic syndrome.

The clinical characteristics of paramedian diencephalic syndrome (PDS) are described on the basis of two recently observed cases: one with paramedian thalamic infarct, the other with paramedian thalamopeduncular infarct. Analysis of the clinical symptoms and the results of CBF study show that PDS is a complex neurological syndrome characterized by symptoms due to both anatomical lesions and functional disconnections.

Aged↗
PubMed1994

Motor recovery after early brain damage. A case of brain plasticity.

BACKGROUND: Motor recovery is remarkable when the brain is damaged early in life. We describe a case of early damage to the right hemisphere with remarkable reorganization and plastic functional changes, studied by computed neuroimaging. CASE DESCRIPTION: A 31-year-old man had a left-sided hemiplegia at the age of 12, followed by good motor recovery despite a large right cortical-subcortical lesion. Single-photon emission computed tomography with motor activation study showed cerebral blood flow increase in the left premotor and sensorimotor cortices irrespective of the hand he was moving, without flow changes in the right hemisphere. CONCLUSIONS: A remarkable reorganization and plastic brain functional changes occurred in a patient after early diffuse damage of the right hemisphere. The study points to a potential role of ipsilateral cortical efferent pathways in subserving hand movements after early cerebral damage.

Adult↗
PubMed1994

Mesial temporal cortex hypoperfusion is associated with depression in subcortical stroke.

BACKGROUND AND PURPOSE: This study was conducted to evaluate local cerebral blood flow changes in patients with depression after a subcortical stroke. METHODS: Clinical and neuropsychological assessments were performed in 15 patients with a single subcortical lesion. Depression was assessed by DSM-III-R. In addition, the Hamilton Rating Scale for depression, the Zung Self-Rating Depression Scale, and the Beck scale were administered to each patient. Single-photon emission-computed tomography study was performed with 99mTc hexamethylpropyleneamine oxime. RESULTS: In all patients cortical regions ipsilateral to subcortical lesions were significantly less perfused than the contralateral cortex. Cerebral blood flow values were significantly lower in depressed patients (n = 8) than in nondepressed patients (n = 7) only in the mesial temporal cortex of the affected hemisphere. Cerebral blood flow values in the mesial temporal cortex of the affected hemisphere significantly correlated with the severity of depression. CONCLUSIONS: Temporal lobe hypoperfusion may reflect a dysfunction of the limbic system, suggesting that this location may be critical for the occurrence of depressive symptoms in patients with subcortical stroke.

Aged↗
PubMed1993

Characterization of the chemical architecture of carbon-fiber microelectrodes. 2. Correlation of carboxylate distribution with electron-transfer properties.

Correlation of the chemical architecture of the surface of 10-microns-diameter carbon-fiber microelectrodes (illustrated by the fluorescence intensity of FITC-labeled carboxylates) and the rate of electron transfer of the surface (illustrated by the intensity of the electrogenerated chemiluminescence of luminol) allows the development of quantitative relationships between the chemical structure of an electrode surface and its electron-transfer properties. A fluorescence microscope equipped with a Peltier-cooled charge-coupled device was used to image these electrode surfaces with submicron spatial resolution. The total fluorescence emission observed at electrochemically treated electrodes was higher than that of controls while the voltammetric behavior and integrated ECL intensity of luminol were very similar. Imaging spectroscopy with submicron spatial resolution was able to demonstrate the microscopic heterogeneity of these surfaces and to assess the effect of the production of carboxylates on the rate of electron transfer of luminol.

Carbon↗
PubMed1993

Unilateral neglect restricted to visual imagery.

Disorders in perceiving and exploring the visual space contralateral to a brain lesion have been frequently described. Many patients with hemi-neglect for extrapersonal space also show neglect in a representational domain when the task requires imagining a well-known piazza from a given vantage point or comparing two visual images. Cognitive and psychophysiological studies show a functional parallelism between the perceptual and imaginative domain, indicating that spatial perception and imagery share the same neural substrata. Here we describe a patient with a persistent disorder in visual imagery for familiar piazzas in the absence of any neglect for stimuli located in a far or near space or on his own body. Contrary to previous cases involving imagery disorders, computerized tomography scans showed a lesion confined to the right frontal lobe, suggesting the role of the frontal lobe in some specific types of mental imagery.

Cerebrovascular Disorders↗
PubMed1993

Dehydrogenase-modified carbon-fiber microelectrodes for the measurement of neurotransmitter dynamics. 1. NADH voltammetry.

The voltammetry of NADH has been characterized at carbon-fiber microelectrodes at scan rates up to 100 V/s. Electrochemical pretreatment of the electrode dramatically changed the properties of the modified electrode. Anodic pretreatment of the surface resulted in an adsorptive wave for NADH oxidation, while less adsorption was evident under more moderate conditions. The pH of the buffer used for the anodization played a critical role in determining the voltammetric peak shape. Oxidation of NADH at slow scan rates (< 10 V/s) fouled the electrode. In contrast, consistent and reproducible voltammetry of NADH was observed at faster scan rates (100 V/s). This voltammetric measurement was used to monitor NADH generated during the oxidative deamination of glutamate catalyzed by glutamate dehydrogenase. A 150-microns-l.d. microdialysis fiber was used to entrap the enzyme near the microelectrode tip, forming the dehydrogenase-modified carbon-fiber microelectrode.

Biosensing Techniques↗
PubMed1993

Dehydrogenase-modified carbon-fiber microelectrodes for the measurement of neurotransmitter dynamics. 2. Covalent modification utilizing avidin-biotin technology.

Dehydrogenase enzymes are immobilized onto carbon-fiber microelectrode surfaces via avidin-biotin technology and a covalently linked hydrophilic tether. The avidin-biotin coupling strategy allows the selectivity of the electrochemical measurement to be easily changed without reoptimizing the immobilization conditions. Optimized derivatization conditions are demonstrated for dimer, tetramer, and hexamer dehydrogenases. Nonelectroactive substrates (ethanol, glucose-6-phosphate, and glutamate) are quantitated through the detection of enzyme-generated NADH by fast scan cyclic staircase voltammetry (100 V/s). The glutamate dehydrogenase-modified microelectrode possesses a 300-ms response time with a detection limit of 0.5 mM glutamate and a 1-60 mM linear concentration range.

Avidin↗
PubMed1993

Motor activation by single-photon emission computed tomography. A comparison of xenon-133 and technetium-99m HM-PAO "split-dose" methods.

Single-photon emission computed tomography (SPECT) was used to investigate the feasibility of the technetium 99m-hexamethylpropyleneamineoxime ( 99mTc HM-PAO) split-dose method to evidence changes in regional cerebral blood flow during a motor activation task, in comparison with a quantitative method using the inhalatory xenon-133. Four subjects were studied twice with both methods, at rest and during finger opposition movements. On the activated cerebral hemisphere, a significant increase in regional cerebral blood flow was observed over the motor cortical areas. The average increases were +28.1 +/- 5.6% for the xenon-133 method and +12.3 +/- 5.2% for the 99mTc HM-PAO method. By using the linearization algorithm for the 99mTc HM-PAO method, a mean increase of +22.5 +/- 8.9% was calculated. This study demonstrated that the split-dose method allows the motor activation SPECT studies with 99mTc HM-PAO to be done in a single session.

Analysis of Variance↗
PubMed1992

Motor stimulation response by technetium-99m hexamethylpropylene amine oxime split-dose method and single photon emission tomography.

We applied the technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) split-dose method in order to evaluate the feasibility of assessing cerebral blood flow (CBF) changes with single photon emission tomography (SPET) during a motor activation task. Eleven normal subjects were studied using the Tomomatic 564 (Medimatic, DK). Five subjects were studied twice at rest and 6 subjects at rest and during a motor task performance (finger opposition movements). A total of 28 mCi of 99mTc-HMPAO was injected in 2 doses with a 1:3 ratio. The first scan was obtained after injection of 7 mCi at rest in all subjects. The second scan was obtained a few minutes later, after injection of the remaining dose (21 mCi), under similar resting conditions or during a motor task performance. The mean brain uptake was proportional to the amount of tracer injected and to the acquisition time for both the first scan (5263 +/- 1266 counts x mCi x min) and the second (5034.4 +/- 966 counts x mCi x min). The grey/white matter ratio was 1.67 +/- 0.019 and 1.67 +/- 0.097 for the two scans, respectively. A three-way analysis of variance (ANOVA) for repeated measure showed no significant effects of side, slice and region of interest (ROI) on the CBF in the 5 subjects studied twice at rest, and the mean regional CBF change was -0.2% +/- 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1992

Reversed laterality of cerebral functions in a non-right-hander: neuropsychological and spect findings in a case of 'atypical' dominance.

A 54-year-old non-right-handed man with positive familial sinistrality showed a pure right hemisphere syndrome following a left hemisphere stroke. Severe right side hemineglect, transcortical motor dysprosodia, spatial dysgraphia and visuo-constructive impairments were observed. At no time were the expected left hemisphere abnormalities such as aphasia, alexia, right-left disorientation or finger agnosia noted. A left fronto-temporal subcortical lesion was documented on CT scan. A Tc-99m HM-PAO SPECT study revealed no cerebral blood flow changes in the right hemisphere while in the left hemisphere a fronto-temporo-parietal cerebral blood flow reduction was evident. This case of a complete reversed laterality of cognitive functions argues for a distinction to be made between 'anomalous' cerebral dominance and 'atypical' cerebral dominance.

Brain↗
PubMed1992

Good recovery in visual scanning in a patient with persistent anosognosia.

A patient with hemineglect disturbance (N.G.) due to a right hemispheric lesion was admitted to rehabilitative training which featured the use of procedures devised in a previous study (Pizzamiglio et al., 1990) both in a standard way and with the addition of optokinetic stimulation. This latter paradigm produces an automatic reaction which favors the spatial orienting of the patient toward his (left) neglected side. N.G. showed good recovery in visual scanning and, by the end of training, reached a level of recovery similar to other neglect patients. However, his recovery was particularly slow and no change was observed in his attitude toward the visual disturbance. The conclusion is reached that recovery in visual scanning also can be obtained in patients with persistent anosognosic disturbances. Stimulations such as the optokinetic condition which influence patients' behavior at an automatic level may play an important role in this recovery. CBF studies obtained before and after training showed a CBF improvement mainly in the right temporoparietal regions, behind the lesion, and in the left frontal cortex. The implications of these findings on various theoretical interpretations of the hemineglect disturbance are briefly discussed.

Adaptation, Psychological↗
PubMed1992

Pattern of CBF in the rehabilitation of visuospatial neglect.

The CBF was assessed in seven patients before and after rehabilitation for visuospatial neglect. Two months of treatment produced an increased perfusion both in the right posterior and left anterior areas of the brain. However, only the left anterior CBF increase was correlated with the neglect disorders. The left anterior improvement in CBF was inversely correlated with right-left cerebellum asymmetry in pre- and post-treatment. The present data suggest the role of the frontal eye-fields in the mechanism of recovery of visual exploration in patients with severe neglect.

Adult↗
PubMed1991

Characterization of the chemical architecture of carbon-fiber microelectrodes. 1. Carboxylates.

A new method to characterize the chemical architecture of a carbon-fiber microelectrode surface is described. Derivatization of carboxyl groups on the carbon surface with a poly(oxyalkalene)diamine (Jeffamine ED-600), followed by biotinylation of the free amine, allowed the attachment of a fluorescein isothiocyanate (FITC) conjugate of ExtrAvidin. The fluorescence observed after excitation at 488 nm was imaged with a fluorescence microscope equipped with a CCD camera, yielding a spatial map of the distribution of modified carboxyl groups on the surface of the carbon fiber with 0.5-micron resolution. Colloidal gold particles (15 nm diameter) coated with ExtrAvidin were used in place of the FITC-ExtrAvidin, and the carbon-fiber surface was imaged with scanning electron microscopy on a submicron scale. This selective information regarding surface-bound functional groups (i.e. carboxylates) has proven invaluable toward the rational design of novel sensors based on surface-modified ultramicroelectrodes.

Biotin↗
PubMed1991

Quantitative assessment of cerebral blood flow in partial epilepsy using Xe-133 inhalation and SPECT.

The Xe-133 inhalation method was used to study rCBF in 12 patients with partial epilepsy during the interictal phase. SPECT images evidenced a focal CBF defect in 10 out of 12 patients, while quantitative analysis showed CBF abnormalities in all the patients. The focal CBF defect corresponded to the site of EEG abnormalities in nine patients. Additional low-flow areas beyond the EEG focus were found. Five patients presented a significant CBF decrease in the cerebellar hemisphere contralateral to the EEG focus. In five patients with unilateral EEG abnormalities, a CBF reduction was found in the contralateral cerebral hemisphere, mirror to the EEG focus. Finally, a widespread CBF decrease involving one or both cerebral hemispheres was observed in seven patients. Global and rCBF values were not correlated with age, duration of disease, frequency of seizures, secondary generalization, or specific therapy. SPECT may be useful in evaluating EEG epileptic foci, and quantitative SPECT allows the detection of functional effects of the epileptic focus on anatomically connected remote areas, probably due to the decrease of afferent inputs (diaschisis phenomenon).

Administration, Inhalation↗