Biomedical subjects

G Dibó

Publications and source records attributed to G Dibó.

14 recordsLinked to original sources

PubMed2003

Dopaminergic contributions to the visual categorization of natural scenes: evidence from Parkinson's disease.

Recent evidence raised the possibility that dopaminergic mechanisms in the neostriatum play an important role in categorization. In this study, we examined the electrophysiological correlates of natural scene categorization in Parkinson's disease (PD), which is characterized by the depletion of dopamine in the neostriatum. Event-related potentials (ERPs) were recorded in PD patients and age-matched control subjects using a natural scene categorization task. Subjects had to decide whether a briefly presented image contained animals or non-animals. In the control group, the mean amplitudes of N1 (150-250 ms) and N2 components (400-600 ms) were more negative for non-animal scenes as compared with stimuli containing animals, whereas P2 (250-350 ms) was more positive for animals. In contrast, in the PD group the mean amplitudes of N1 and N2 components were similar for both animal and non-animal stimuli, and the P2 amplitudes were reduced. In the case of N1 peak latency, there was no between-group difference, whereas the N2 and P2 components were significantly delayed in the PD group. These results suggest that both perceptual (N1) and semantic (N2) processes related to the categorization of natural scenes are specifically impaired in PD. In the temporal domain, the slowed semantic processing is preceded by a relatively normally paced perceptual analysis. These findings are in agreement with the hypothesis emphasizing the importance of striatal dopaminergic mechanisms in classification functions.

Aged↗

PubMed2000

[Initial experiences with 123-Iodine-IBZM neuroreceptor scintigraphy in extrapyramidal disorders].

The receptor scintigraphy of the dopaminergic system of the brain is of interest in the evaluation of movement disorders. The 123I-IBZM is a radiopharmaceutical with affinity predominantly to postsynaptic D2 receptors. The aim of this study was to evaluate the role of IBZM SPECT investigations in the differentiation of disorders with Parkinson's syndrome. Eight patients with idiopathic Parkinson's syndrome and 8 patients Parkinson's syndrome with other etiology were investigated with 123I-IBZM SPECT (6 females, 10 males, mean age +/- SD: 59 +/- 9). The patients according to the clinical signs and symptoms, results of CT/MRI and rCBF SPECT investigation were categorized. The reconstructed SPECT slices were evaluated visually and quantitatively. The visual interpretation of the images were performed by two observer and scored the radiopharmaceutical uptake (from 1-3) of the cortex and the striatum separately. For quantification striatum/frontal cortex activity ratio were calculated with ROI technique. The differences between the patient groups were statistically analyzed by two tailed t-test. The IBZM uptake were different in the two group of patients. The striatal IBZM accumulation was higher in the idiopathic Parkinson's syndrome patients compared to the other parkinsonians. The striatum/frontal lobe activity ratio was 1.69 +/- 0.9 (mean +/- SD) in the right, 1.67 +/- 0.04 (mean +/- SD) in the left hemisphere of the patients with idiopathic Parkinson's syndrome. The corresponding data in the nonidiopathic parkinsonian group were 1.53 +/- 0.06 (mean +/- SD), 1.52 +/- 0.04 (mean +/- SD) respectively (p < 0.01). The quantitative data correlated with the results of the visual evaluation. According to the data presented IBZM-SPECT is an effective tool in the differentiation of disorders with Parkinson syndrome.

Adult↗

PubMed2000

P300 component of visual event-related potentials distinguishes patients with idiopathic parkinson's disease from patients with essential tremor.

A considerable rate of misdiagnosis has recently been reported in movement disorders. One of the most difficult clinical problems is the differentiation of Parkinson's disease and essential tremor. In this study, we have examined whether event-related potentials (ERPs) could aid in the solution of this differential diagnostic problem. Visual ERPs were obtained by using an "oddball" paradigm in 20 patients with idiopathic Parkinson's disease (IPD), 20 patients with essential tremor (ET), and 20 age-matched control subjects. We found that the P300 amplitudes were selectively reduced in the IPD group at the midline (Fz, Cz, Pz) electrode sites, whereas the ET group exhibited selectively elevated P300 amplitudes at the left parietal and frontal (F3, P3) recording sites. The patients with IPD, but not ET, showed a significant prolongation of the P300 latency at each electrode site. Similarly, only the IPD patients were significantly slower in responding to the target stimulus. The primary visual evoked potential (P100) did not distinguish among the IPD, ET, and control subjects. These results suggest that visual ERPs might provide a useful diagnostic method for differentiating IPD from ET.

Aged↗

PubMed1998

Polyneuropathy with endoneurial immune complex deposition as the first manifestation of systemic lupus erythematosus.

A 72-year-old male presented with progressive sensorimotor polyneuropathy. Later weight loss, proteinuria and deteriorating renal function were noted. The electrophysiological examinations revealed extensive, symmetrical demyelinating and axonal polyneuropathy. Frozen sections obtained from sural nerve biopsy sample showed the presence of immune complexes and complements in the walls of the epi- and endoneurial blood vessels, and perineurium suggestive of systemic lupus erythematous (SLE). IgG and Clq deposits were also present along the basement membranes of Schwann cells. The electron microscopy confirmed the presence of immune complex deposition. Diagnosis of SLE was proven by positive serology (anti-nuclear antibodies, anti-Sm, anti-RNP, anti-double-stranded DNA) and renal biopsy showing membranous lupus nephritis with extensive immune complex deposition in the tubular basement membranes. Despite combined immunosuppressive treatment for 10 months, the patient died of complications of generalized immune complex vasculitis. The manifestation of SLE in elderly patients, especially in males, is very rare. Moreover, the polyneuropathy is an unusual initial symptom of SLE. Immune complex deposition in Schwann cell basement membrane probably plays an important role in the pathomechanism of sensorimotor polyneuropathy in SLE.

Aged↗

PubMed1996

Analysis of macromolecular branched chain polypeptides by capillary electrophoresis and micellar electrokinetic chromatography.

Amphoteric poly(Lys-[Glu1.0-DL-Ala4.1]), (EAK) and anionic poly(Lys-Ac-Glu0.98-DL-Ala3.98]), (AcEAK) branched chain polypeptides were analyzed by capillary electrophoresis (CE) and micellar elektrokinetic chromatography (MEKC) in the following buffers. A1: 0.25 N triethyl ammonium phosphate (TEAP) buffer (pH 2.25); A2: 100 mM sodium dodecyl sulfate (SDS) in buffer A1; B1: Na-borate buffer (pH 7.7); B2: 100 mM SDS in buffer B1; C1: Na-borate buffer (pH 11.0); C2: 100 mM SDS in buffer C1. Both EAK and AcEAK could be separated by a CE mechanism at pH 2.25 and by an MEKC mechanism at pH 11.0. Optimum results were achieved with CE in buffer A1 and with MEKC in buffer C2.

Buffers↗

PubMed1992

Side chain distribution and enantiomer composition of biodegradable branched polypeptides with polylysine backbone.

A detailed investigation is reported about the primary structure of biodegradable branched polypeptides suitable for carrier function. The side chain distribution of poly[Lys(DL-Alam)], m approximately 3.5, the common inside area of a branched polypeptide model system, was determined by automated Edman degradation. These data indicate that 65% of the branches consist of 2-4 Ala residues and 25% of the side chains are longer than 4 amino-acid residues. The enantiomer composition of poly[Lys(Xi-DL-Alam)], (X = Glu, D-Glu, Leu, D-Leu) and of poly[Lys(DL-Ala2.9-Leu0.79)] polypeptides was investigated by HPLC analysis of their hydrolysates following derivatization with N-(5-fluoro-2,4-dinitrophenyl)-L-alanine amide (Marfey's reagent). The results proved that the synthesis methods applied for the preparation of branched polypeptides produce compounds whose enantiomer compositions are in good agreement with calculated expectations. These findings could be useful for the reliable interpretation of various biological phenomena observed in connection with the presence of L- or D-amino-acid residues in the side chains.

Amino Acid Sequence↗

PubMed1991

Primary structure of nuclease P1 from Penicillium citrinum.

The primary structure of nuclease P1, which cleaves both RNA and single-stranded DNA, from Penicillium citrinum was elucidated. The complete amino acid sequence consisting of 270 residues was determined by analysis of peptides obtained by digestion with Achromobacter protease I of the reduced and S-aminoethylated protein and by digestion with Staphylococcus aureus V8 protease of the reduced and S-carboxymethylated protein. Four half-cystine residues were assigned to Cys72-Cys217 and Cys80-Cys85. N-Glycosylated asparagine residues were identified at positions 92, 138, 184 and 197. Fast-atom-bombardment and laser-ionization MS were successfully used to confirm the determined amino acid sequences of peptides and to estimate the molecular mass of this glycoprotein having heterogenous sugar moieties, respectively. Comparison of the amino acid sequence of nuclease P1 with other nucleases revealed that the protein has a high degree of sequence identity (50%) with nuclease S1 from Aspergillus oryzae. The His-Phe-Xaa-Asp-Ala sequence (positions 60-64) is similar to the sequence (His-Phe-Asp-Ala) involving the active-site His119 of bovine pancreatic RNase A, and the Pro-Leu-His sequence (positions 124-126) is identical with the sequence involving the active-site His134 of porcine pancreatic DNase I.

Amino Acid Sequence↗

PubMed1991

Amino acid sequence of nuclease S1 from Aspergillus oryzae.

The amino acid sequence of nuclease S1, a nuclease which cleaves both single-stranded DNA and RNA, from Aspergillus oryzae was determined. Reduced and S-carboxymethylated or S-aminoethylated nuclease S1 was digested with Achromobacter protease I, Staphylococcus aureus V8 protease, or endoproteinase Asp-N. Peptides thus obtained were purified by reverse-phase high-performance liquid chromatography and sequenced, and the complete primary structure was established. Nuclease S1 consists of a single peptide chain of 267 amino acid residues bearing N-glycosylated Asns 92 and 228. Five half-cystine residues are present at positions 25, 72, 80, 85, and 216, and the latter four residues are implicated in the formation of disulfide bonds by analogy with those in nuclease P1. Two short stretches of sequences involving His 60 and His 125 are shown to be identical with those involving active site His 119 in bovine ribonuclease A and active-site His 134 in porcine deoxyribonuclease I, respectively.

Amino Acid Sequence↗

PubMed1991

General method for rapid synthesis of multicomponent peptide mixtures.

A method is suggested for the synthesis of multicomponent peptide mixtures. The method is a solid phase synthesis modified in order to give a closely equimolar mixture of peptides with predetermined sequences. The main point of modification is that before every coupling cycle the resin is divided into equal parts and each portion is coupled with a different amino acid. Then the portion are mixed and before the next coupling cycle the resin is again distributed into equal portions. The method is illustrated by the synthesis of a mixture of 27 tetrapeptides and that of 180 pentapeptides.

Amino Acid Sequence↗

PubMed1987

Position of the peptide linkage in glutamyl-taurine from calf brain synaptic vesicles.

To elucidate the position of the peptide bond in glutamyl-taurine this dipeptide was extracted from calf brain synaptic vesicles and subjected to paper electrophoresis. It was analyzed further in an automatic amino acid analyzer prior and subsequent to acid hydrolysis. Both alpha- and gamma-forms were found to be present in approximately equal amounts.

Animals↗

PubMed1983

An improved method for isolation of the C-terminal fragment of proteins.

An efficient and easily realizable method for the isolation of the C-terminal fragment is described. Proteins are esterified by methanolic HCl and subsequently digested with pepsin. The peptide mixture is submitted to paper electrophoresis in pH 2.1 buffer. The identification of the C-terminal peptide is performed by preparing a guide peptide map, using pH 5.5 buffer in the second dimension. The C-terminal fragment appears as an on-diagonal spot. It can be isolated by a pH 5.5 run of the corresponding band from the first (pH 2.1) electrophoretogram. Since the C-terminal peptide is the fastest moving component, there is no need for its further purification. The expected yield is about 40%.

Amino Acid Sequence↗

PubMedDate not supplied

Depressed baroreflex sensitivity in patients with Alzheimer's and Parkinson's disease.

Parkinson's disease (PD) and Alzheimer's dementia (AD) are often associated with an autonomic neuropathy. The extent of autonomic involvement, however is poorly defined and unpredictable. In order to assess the autonomic cardiovascular regulation baroreflex sensitivity (BRS) was determined non-invasively in 23 patients (age: 65 +/- 9.3 years) with PD and 24 patients with AD (age: 72.3 +/- 7.2 years). The results were compared with those on 22 healthy age- and sex-matched volunteers. Patients with PD and AD exhibited marked abnormalities in cardiovascular autonomic reflex regulation showed by markedly depressed BRS. The possible predictive value of centrally based depression of baroreflex sensitivity necessitates further studies.

Aged↗

PubMedDate not supplied

Chronic recurrent transverse myelitis or multiple sclerosis.

The simultaneous occurrence of multiple sclerosis and transverse myelitis is known in the literature. Apart from the spinal symptoms, other neurological signs of brain involvement are usually found and magnetic resonance imaging (MRI) reveals disseminated foci in the brain. The positive evoked responses, the immunological abnormalities of the cerebrospinal fluid (CSF), and the oligoclonality together prove the presence of multiple sclerosis. In these cases the symptoms of transverse myelitis can separately precede other signs of multiple sclerosis, or appear as a relapse. Recurrent transverse myelitis as an independent entity, with negative MRI and CSF immunology, is an exciting topic in terms of the etiological factors and therapeutic considerations. The view in the literature is that the occurrence of transverse myelitis as an independent entity is rather rare. The present article reports the case of a female patient with recurrent spinal cord signs, and negative MRI and CSF immunology. During a ten-year follow-up observation period, symptoms of multiple sclerosis did not develop. Further studies of such cases are needed in order to clarify the etiological factors, the pathomechanism and the therapeutic considerations relating to this relatively new and probably independent clinical entity.

Adult↗

PubMedDate not supplied

Neurotoxins and neurodegenerative disorders.

There is a hypothesis that excitotoxic pathomechanisms underlie neuronal tissue degeneration in neurological disorders. It is proposed that target neurons are overexcited, the result being energy disturbance and pathobiochemical changes that culminate in nerve cell death. Domoic acid (structural analogue of kainic acid) and beta-N-oxalylamino-L-alanine (BOAA) are powerful excitotoxins. Diminished energy supplies may result either in excessive release of glutamate or an inability of the neuron to restore ionic balance after stimulation. Impairment of intracellular energy metabolism induced by cyanide, amino-oxyacetic acid (AOAA), 3-acetylpiridine, thiamine deficiency, azide, 3-nitropropionic acid, methyl-phenyltetrahydro-pyridinum ion (MPP+), carbon monoxide, methanol intoxication and manganese (Mn) is discussed. Furthermore, the endogenous substance kynurenine is metabolised to kynurenic acid (excitotoxin antagonist) and quinolinic acid (excitotoxin agonist) Probenecid (inhibitor of kynurenic acid excretion from the extracellular fluid) has an antiexcitatory effect.

Animals↗