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Biomedical subjects

A A Barreira

Publications and source records attributed to A A Barreira.

At least 19 recordsLinked to original sources
PubMed2004

Hereditary motor and autonomic neuronopathy 1 maps to chromosome 20q13.2-13.3.

The spinal muscular atrophies (SMA) or hereditary motor neuronopathies result from the continuous degeneration and death of spinal cord lower motor neurons, leading to progressive muscular weakness and atrophy. We describe a large Brazilian family exhibiting an extremely rare, late-onset, dominant, proximal, and progressive SMA accompanied by very unusual manifestations, such as an abnormal sweating pattern, and gastrointestinal and sexual dysfunctions, suggesting concomitant involvement of the autonomic nervous system. We propose a new disease category for this disorder, 'hereditary motor and autonomic neuronopathy', and attribute the term, 'survival of motor and autonomic neurons 1' (SMAN1) to the respective locus that was mapped to a 14.5 cM region on chromosome 20q13.2-13.3 by genetic linkage analysis and haplotype studies using microsatellite polymorphic markers. This locus lies between markers D20S120 and D20S173 showing a maximum LOD score of 4.6 at D20S171, defining a region with 33 known genes, including several potential candidates. Identifying the SMAN1 gene should not only improve our understanding of the molecular mechanisms underlying lower motor neuron diseases but also help to clarify the relationship between motor and autonomic neurons.

Chromosome Mapping↗
PubMed2004

The end-to-side peripheral nerve repair. Functional and morphometric study using the peroneal nerve of rats.

Morphologic and functional recovery following an end-to-side repair was studied comparatively with conventional end-to-end repair in a model of peroneal nerve lesion in rats. Twenty-eight rats were used and divided into four groups according to the reparative procedure following nerve division: (1) nerve stumps buried into neighboring muscles (n = 8); (2) conventional end-to-end repair (n = 7); (3) end-to-side repair onto the tibial nerve (n = 8); (4) sham operation (n = 5). The sciatic functional index (SFI) was evaluated at weekly intervals for 8 weeks, the peroneal nerve being resected on the 56th day for histologic and morphometric studies. The SFI progressively improved in Groups 2 (-16.9) and 3 (-22.7), although it did not reach normal values (around -8). The average nerve fiber density increased to normal values in both Groups 2 and 3, although accompanied by a marked decrease of average minimal and maximal nerve fiber diameter, myelin sheath area and G quotient. The differences between Groups 2 and 3 or Groups 2 and 4 were not significant. We conclude that, although resulting in significant morphologic and functional recovery, end-to-side repair is not as efficient as the conventional end-to-end nerve repair. However, end-to-side repair has a potential for application in selected cases in humans.

Animals↗
PubMed2004

Dejerine-Sottas' neuropathy caused by the missense mutation PMP22 Ser72Leu.

OBJECTIVE: To describe a patient with the Dejerine-Sottas' syndrome due to a de novo Ser72Leu amino acid substitution in the PMP22 protein and summarize the phenotype associated with this frequent mutation. CASE REPORT: The proband has a medical history of early onset, severe, and progressive demyelinating neuropathy, accompanied by mild ptosis and limitations of eye movements. Ulnar nerve motor conduction velocities were extremely reduced (2.6 and 2.2 m/s), and the sural nerve biopsy showed onion bulbs and thinly myelinated axons. Duplication of chromosome 17p11.2 was ruled out, and the Ser72Leu substitution was found upon sequencing the PMP22 gene. CONCLUSION: The Ser72Leu substitution is being confirmed as the most frequent point mutation in the PMP22 gene. This 'hot spot' should be considered in the strategy of looking for point mutations in the hereditary demyelinating neuropathies.

Adolescent↗
PubMed2003

Myalgia as the revealing symptom of multicore disease and fibre type disproportion myopathy.

BACKGROUND: Multicore disease and congenital fibre type disproportion myopathy are diseases assigned to the heterogeneous group of congenital myopathies. Although hypotonia and muscle weakness appearing in early life are the commonest manifestations of these diseases, distinct phenotypes and late onset cases have been described. OBJECTIVE: To report the occurrence of myalgia as the revealing symptom of multicore disease and fibre type disproportion myopathy. METHODS: The clinical cases of three patients with fibre type disproportion myopathy and one with multicore disease are described. Skeletal muscle biopsies were processed for routine histological and histochemical studies. RESULTS: The clinical picture was unusual in that the symptoms were of late onset and the predominant complaint was muscle pain exacerbated by exercise. Muscle weakness was found in only a single patient, the mother of a patient with fibre type disproportion myopathy. Physical examination was unremarkable in the other patients. Muscle biopsies from patients 1 and 2 contained type I fibres that were considerably smaller than the type II fibres, supporting the diagnosis of fibre type disproportion myopathy. Skeletal muscle of patient 4 showed multiple areas, predominantly but not exclusively in the type I fibres, from which oxidative enzyme activities were absent, as seen in multicore disease. CONCLUSIONS: Muscle pain was the main clinical manifestation in our patients. Recognition of the broader clinical expression of these myopathies is important for prognostic reasons and for genetic counselling of the family members.

Adolescent↗
PubMed2001

Arterial baroreceptors and experimental diabetes.

Alterations of the autonomic reflex control of the cardiovasclar system have been demonstrated in clinical and animal models of insulin-dependent diabetes mellitus. Established neuroaxonal dystrophy is considered the neuropathological hallmark of chronic experimental diabetes. However, the afferent arm of the arterial baroreflex, that is, the carotid sinus nerve and the aortic depressor nerve, has received much less attention in studies dealing with this physiopathological model. The attenuation of the pressure response to bilateral carotid occlusion in conscious rats indicates a derangement of the baroreflex, probably involving an alteration of the carotid sinus nerve. There is histological evidence obtained from adult spontaneous insulin-dependent diabetic rats (strain BB/S) of a carotid sinus nerve with signs of axonal swelling and intramyelinic edema, suggesting diabetic neuropathy. The study of aortic baroreceptor activity in anesthetized rats with short- and long-term streptozotocin diabetes by means of cross-spectral analysis of baroreceptor activity versus arterial pressure revealed a dysfunction in the afferent arm of the baroreflex even during a short period of diabetes. The morphology of the aortic depressor nerve of streptozotocin-diabetic rats indicated axonal atrophy by visual analysis remarkably at the distal segments of the nerves. This finding was confirmed by morphometric study of the myelinated fibers. In conclusion, although studies of the arterial baroreceptors related to experimental diabetes are scanty in the literature, there is electrophysiological and histological evidence demonstrating that the carotid sinus and the aortic depressor nerves are abnormal in this experimental model.

Animals↗
PubMed2001

Aortic depressor nerve unmyelinated fibers in spontaneously hypertensive rats.

The objective of the present study was to compare the morphology of the unmyelinated fibers in the aortic depressor nerves (ADN) of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). In anesthetized rats, the ADN was identified by its spontaneous activity synchronous with the arterial pulses. Thin sections of the proximal and distal segments of the ADN were analyzed by electron microscopy, and a morphometric study of the unmyelinated fibers and Schwann cells was performed. The proximal segments of WKY and SHR ADN contain an average of 335 +/- 68 and 130 +/- 14 unmyelinated fibers, respectively (P < 0.05), and the distal segments contain an average of 337 +/- 46 and 242 +/- 77 unmyelinated fibers, respectively (P < 0.05). The distribution of the diameters of unmyelinated fibers was unimodal for both strains, with the histogram from the SHR significantly shifted to the left. Because the unmyelinated fibers play a role in the tonic inhibition of the medullary vasomotor centers, especially in the presence of hypertension, the morphological differences observed in the ADN from SHR may account, at least in part, for the blunted baroreflex of SHR.

Animals↗
PubMed2000

Limitations on the clinical utility of the ulnar dorsal cutaneous sensory nerve action potential.

OBJECTIVE: To validate the clinical use of the ulnar dorsal cutaneous (UDCN) sensory nerve action potential (SNAP) in the topographical analysis of ulnar mononeuropathies and in the process of choosing a sensory nerve for biopsy. METHODS: We surveyed the UDCN SNAP electrophysiological characteristics in both hands of 97 normal volunteers aged 10-84 years. The nerve was recorded from the 4th intermetacarpal space with subcutaneous needle electrodes and percutaneous stimulation was carried out at the wrist. RESULTS: In agreement with other studies, the mean conduction velocity was 58. 6+/-6.7 m/s, but the mean and the lower normal value of the amplitude (32 and 14.7 microV) were significantly higher than previous known data. An important finding was that in 21% of our population study, the UDCN SNAP was absent on at least one side, or a significant degree of asymmetry between the left and right sides was present. CONCLUSION: The UDCN SNAP is technically easy to obtain, but the high frequency of asymmetric or absent potentials detected in this study implies that caution should be taken in using this SNAP in clinical practice.

Action Potentials↗
PubMed1999

Morphology of aortic depressor nerve myelinated fibers in normotensive Wistar-Kyoto and spontaneously hypertensive rats.

Reports on the morphology of the baroreceptor terminal of spontaneously hypertensive rats (SHR) did not demonstrate any difference when compared to the axonal terminal of normotensive rats. Although several studies reporting baroreceptor terminal and blood vessel wall morphology have been carried out to better understand the baroreceptor function and resetting to hypertensive levels, there are no reports examining the morphology of the fibers of the aortic depressor nerve (ADN) in hypertensive models. Therefore, the objective of the present study was to investigate the morphological aspects of SHR ADN compared to Wistar-Kyoto (WKY) rats. Before the morphologic study, the nerves were isolated and the pressure-nerve activity curve was determined for each ADN. SHR exhibited an increase in the threshold pressure for baroreceptor activation, a rightward shift in the pressure-nerve activity curve with decreases in slope and maximum activity. Semithin (0.3 to 0.5 microm thick) sections of the proximal (close to the nodose ganglion) and distal (close to the aortic arch) segments of the ADN were analyzed by light microscopy. A morphometric study of the nerve fascicles and myelinated fibers was performed. Comparison between proximal and distal segments of the two strains revealed that the ADN of WKY rats were consistently larger. All morphometric parameters studied in myelinated fibers and their respective axons were smaller in SHR. The area of the myelin sheath was comparatively larger in WKY rats. These data show morphologic differences between the ADN of SHR and WKY rats, which may explain, at least in part, the decreased slope and maximum activity of the pressure-nerve activity curve observed with the baroreceptor resetting in SHR.

Animals↗
PubMed1997

Experimental benznidazole encephalopathy: I. Clinical-neurological alterations.

Benznidazole (N-benzyl-2-nitro-1-imidazoleacetamide) is an antiprotozoan agent of the nitroimidazole group used extensively in South America to treat Chagas' disease. In humans, its most important side effect is peripheral polyneuropathy, the frequency of which is dose related. To evaluate this effect, we administered benznidazole to adult, male, mongrel dogs at doses ranging from 5 to 40 mg/kg/day (0.5 to 4 times the dose used to treat chagasic patients). Subsequent neurological examination revealed apathy, ataxia, spastic tetraplegia with hyperreflexia of stretching reflexes, balance disorders and asymmetrical gait. These alterations appeared earlier and were more intense at the higher doses. Drug withdrawal also left dose- and time-dependent sequelae like ataxia, hypertonia, hyperreflexia and alterations of balance. No peripheral neuropathy was detected. The present findings suggest that a careful reevaluation of the side effects of benznidazole in humans is necessary.

Animals↗
PubMed1997

Experimental benznidazole encephalopathy: II. Electroencephalographic and morphological alterations.

We describe electroencephalographic (EEG) and morphological alterations in the CNS of dogs treated with benznidazole. The relationship between dose, duration of treatment and intensity of lesions observed was examined and used to establish anatomo-clinical associations. Two predominant EEG patterns were noted in treated dogs. Most of the animals (Group I) that received acute treatment with high doses (30 mg/kg/day) for 15 days followed by treatment at a lower dose (10 mg/kg/day) exhibited a type 2, EEG pattern, i.e., low voltage desynchronized with fast activity (LVFA). In contrast, most of the animals (Group II) that received short-term acute treatment with high doses (40 mg/kg/day) for 7 days followed by chronic treatment at lower doses (20 and 5 mg/kg/day) presented a type 1 EEG pattern. high voltage diffuse with slow activity (HVSA). Even after the drug was discontinued, the animals presented mild EEG alterations. These alterations. observed during and after treatment with benznidazole, suggest the presence of encephalopathy with multifocal characteristics. Several morphological alterations were observed in the animals, the most important being: lymphocytic inflammatory infiltrate, neuronal degeneration, satellitosis, demyelination and axonal degeneration, microglial proliferation, necrosis and gliosis. Such alterations involved the meninges, cerebral cortex, hemispheric white matter and subcortical gray matter, brain stem, cerebellum, and, less frequently, the spinal cord. No histopathological alterations were detected in the peripheral nerves. All encephalic levels were involved in all animals treated although the use of the high doses for 15 days (Group I) appeared to result in more lesions in the subcortical gray matter and the lower brainstem when compared to the use of high doses for 7 days (Group II) which led to greater involvement of the cerebral cortex, hemispheric white matter, cerebellum and medulla.

Animals↗
PubMed1997

A descriptive and quantitative light and electron microscopy study of the aortic depressor nerve in normotensive rats.

There is no literature report of a detailed morphologic study of the aortic depressor nerve. The aim of this study was to describe the general morphological aspects and to obtain morphometric parameters for the aortic depressor nerve of normotensive Wistar rats (n=12). Before the morphologic studies, nerves were isolated and pressure-nerve activity curves were obtained. Basal mean arterial pressure was 117+/-5 mm Hg, the systolic pressure threshold was 100+/-7 mm Hg, and mean arterial pressure at 50% of maximal activity was 115+/-5 mm Hg and the baroreceptor gain 1.99+/-0.09%/mm Hg. Semithin and thin sections of proximal and distal nerve segments were then examined by light and electron microscopy, respectively. The main nerve components were (1) unmyelinated and myelinated axons; (2) Schwann cells; (3) capillary wall endothelial cells and pericytes; (4) collagen fibers in the epineurium and endoneurium and between perineurial cell layers; and (5) fibroblasts and mast cells. The depressor nerves were found to contain 204-996 axons per nerve, 80% of which, on average, were unmyelinated, with a 4:1 unmyelinated/myelinated axon ratio. The unmyelinated axon histogram was unimodal, with a mean diameter of 0.5+/-0.02 microm. Myelinated fibers had axons averaging 1.3+/-0.06 microm in diameter and representing 53% of the total fiber diameter. The ratio between axonal and total fiber diameter of myelinated fiber ranged from 0.4 to 0.8 and tended to increase with axon size. Proximal and distal segments were morphologically similar. In conclusion, the morphologic description of the depressor nerve provides important data for further investigations of the structural basis of altered baroreflex responses in conditions such as arterial hypertension, aging, atherosclerosis, and peripheral neuropathies.

Animals↗
PubMed1997

Mitochondrial encephalomyopathy with coenzyme Q10 deficiency.

Coenzyme Q10 (CoQ10) transfers electrons from complexes I and II of the mitochondrial respiratory chain to complex III. There is one published report of human CoQ10 deficiency describing two sisters with encephalopathy, proximal weakness, myoglobinuria, and lactic acidosis. We report a patient who had delayed motor milestones, proximal weakness, premature exertional fatigue, and episodes of exercise-induced pigmenturia. She also developed partial-complex seizures. Serum creatine kinase was approximately four times the upper limit of normal and venous lactate was mildly elevated. Skeletal muscle biopsy revealed many ragged-red fibers, cytochrome c oxidase-deficient fibers, and excess lipid. In isolated muscle mitochondria, impaired oxygen consumption was corrected by the addition of decylubiquinone. During standardized exercise, ventilatory and circulatory responses were compatible with a defect of oxidation-phosphorylation, which was confirmed by near-infrared spectroscopy analysis. Biochemical analysis of muscle extracts revealed decreased activities of complexes I+II and I+III, while CoQ10 concentration was less than 25% of normal. With a brief course of CoQ10 (150 mg daily), the patient reported subjective improvement. The triad of CNS involvement, recurrent myoglobinuria, and ragged-red fibers should alert clinicians to the possibility of CoQ10 deficiency.

Adult↗
PubMed1997

[Peripheral neuropathies in the State of São Paulo from 1939 to 1985].

Studies on peripheral neuropathies by investigators residing in the State of São Paulo, Brazil, and published since the 1930 and 1940 decades until 1985 were revised in the present survey. Investigations in the area were greatly encouraged by the appearance of the journal Arquivos de Neuro-Psiquiatria(São Paulo). Oswaldo Freitas Julião may be considered the author who began these studies in the State and his most important contributions were related to leprosy and to Andrade disease, although he also published papers on other types of peripheral neuropathies. Horacio Martins Canelas also made a very important contribution to the study of different neuropathies, especially those due to vitamin B12 deficiency. A series of papers on neuropathies published by neurologists residing in the State is summarized. We also present a catalogue of the major university centers where groups of neurologists preferentially devote their time to the study of neuromuscular disease in São Paulo and a selected bibliography about neuropathies by investigators from this State.

Brazil↗
PubMed1997

Normal median near nerve potential.

In routine studies of sensory nerve conduction, only fibers > or = 7 microns in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 +/- 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 M omega or more of entry impedance and a noise level of 0.7 microVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean +/- SD): 26.5 +/- 5.42 microV, 56.8 +/- 5.42 m/s, 3.01 +/- 0.31 ms, 0.12 +/- 0.04 microV, 16.4 +/- 2.95 m/s and 10.6 +/- 2.48 ms. More sophisticated equipment has an internal noise of 0.6 microVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices.

Action Potentials↗