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Search Results: 1 - 10 of 785334 matches for " Martinez A.M.B. "
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Early myelin breakdown following sural nerve crush: a freeze-fracture study
Martinez, A.M.B.;Canavarro, S.;
Brazilian Journal of Medical and Biological Research , 2000, DOI: 10.1590/S0100-879X2000001200012
Abstract: in this study we describe the early changes of the myelin sheath following surgical nerve crush. we used the freeze-fracture technique to better evaluate myelin alterations during an early stage of wallerian degeneration. rat sural nerves were experimentally crushed and animals were sacrificed by transcardiac perfusion 30 h after surgery. segments of the nerves were processed for routine transmission electron microscopy and freeze-fracture techniques. our results show that 30 h after the lesion there was asynchrony in the pattern of wallerian degeneration, with different nerve fibers exhibiting variable degrees of axon disruption. this was observed by both techniques. careful examination of several replicas revealed early changes in myelin membranes represented by vacuolization and splitting of consecutive lamellae, rearrangement of intramembranous particles and disappearance of paranodal transverse bands associated or not with retraction of paranodal myelin terminal loops from the axolemma. these alterations are compatible with a direct injury to the myelin sheath following nerve crush. the results are discussed in terms of a similar mechanism underlying both axon and myelin breakdown.
Early myelin breakdown following sural nerve crush: a freeze-fracture study
Martinez A.M.B.,Canavarro S.
Brazilian Journal of Medical and Biological Research , 2000,
Abstract: In this study we describe the early changes of the myelin sheath following surgical nerve crush. We used the freeze-fracture technique to better evaluate myelin alterations during an early stage of Wallerian degeneration. Rat sural nerves were experimentally crushed and animals were sacrificed by transcardiac perfusion 30 h after surgery. Segments of the nerves were processed for routine transmission electron microscopy and freeze-fracture techniques. Our results show that 30 h after the lesion there was asynchrony in the pattern of Wallerian degeneration, with different nerve fibers exhibiting variable degrees of axon disruption. This was observed by both techniques. Careful examination of several replicas revealed early changes in myelin membranes represented by vacuolization and splitting of consecutive lamellae, rearrangement of intramembranous particles and disappearance of paranodal transverse bands associated or not with retraction of paranodal myelin terminal loops from the axolemma. These alterations are compatible with a direct injury to the myelin sheath following nerve crush. The results are discussed in terms of a similar mechanism underlying both axon and myelin breakdown.
Quantitative evidence for neurofilament heavy subunit aggregation in motor neurons of spinal cords of patients with amyotrophic lateral sclerosis
Mendon?a, D.M.F.;Chimelli, L.;Martinez, A.M.B.;
Brazilian Journal of Medical and Biological Research , 2005, DOI: 10.1590/S0100-879X2005000600015
Abstract: amyotrophic lateral sclerosis (als), a neurodegenerative disease of unknown etiology, affects motor neurons leading to atrophy of skeletal muscles, paralysis and death. there is evidence for the accumulation of neurofilaments (nf) in motor neurons of the spinal cord in als cases. nf are major structural elements of the neuronal cytoskeleton. they play an important role in cell architecture and differentiation and in the determination and maintenance of fiber caliber. they are composed of three different polypeptides: light (nf-l), medium (nf-m) and heavy (nf-h) subunits. in the present study, we performed a morphological and quantitative immunohistochemical analysis to evaluate the accumulation of nf and the presence of each subunit in control and als cases. spinal cords from patients without neurological disease and from als patients were obtained at autopsy. in all als cases there was a marked loss of motor neurons, besides atrophic neurons and preserved neurons with cytoplasmic inclusions, and extensive gliosis. in control cases, the immunoreaction in the cytoplasm of neurons was weak for phosphorylated nf-h, strong for nf-m and weak for nf-l. in als cases, anterior horn neurons showed intense immunoreactivity in focal regions of neuronal perikarya for all subunits, although the difference in the integrated optical density was statistically significant only for nf-h. furthermore, we also observed dilated axons (spheroids), which were immunopositive for nf-h but negative for nf-m and nf-l. in conclusion, we present qualitative and quantitative evidence of nf-h subunit accumulation in neuronal perikarya and spheroids, which suggests a possible role of this subunit in the pathogenesis of als.
Quantitative evidence for neurofilament heavy subunit aggregation in motor neurons of spinal cords of patients with amyotrophic lateral sclerosis
Mendon?a D.M.F.,Chimelli L.,Martinez A.M.B.
Brazilian Journal of Medical and Biological Research , 2005,
Abstract: Amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of unknown etiology, affects motor neurons leading to atrophy of skeletal muscles, paralysis and death. There is evidence for the accumulation of neurofilaments (NF) in motor neurons of the spinal cord in ALS cases. NF are major structural elements of the neuronal cytoskeleton. They play an important role in cell architecture and differentiation and in the determination and maintenance of fiber caliber. They are composed of three different polypeptides: light (NF-L), medium (NF-M) and heavy (NF-H) subunits. In the present study, we performed a morphological and quantitative immunohistochemical analysis to evaluate the accumulation of NF and the presence of each subunit in control and ALS cases. Spinal cords from patients without neurological disease and from ALS patients were obtained at autopsy. In all ALS cases there was a marked loss of motor neurons, besides atrophic neurons and preserved neurons with cytoplasmic inclusions, and extensive gliosis. In control cases, the immunoreaction in the cytoplasm of neurons was weak for phosphorylated NF-H, strong for NF-M and weak for NF-L. In ALS cases, anterior horn neurons showed intense immunoreactivity in focal regions of neuronal perikarya for all subunits, although the difference in the integrated optical density was statistically significant only for NF-H. Furthermore, we also observed dilated axons (spheroids), which were immunopositive for NF-H but negative for NF-M and NF-L. In conclusion, we present qualitative and quantitative evidence of NF-H subunit accumulation in neuronal perikarya and spheroids, which suggests a possible role of this subunit in the pathogenesis of ALS.
Effect of perimuscular injection of Bothrops jararacussu venom on plasma creatine kinase levels in mice: influence of dose and volume
Calil-Elias, S.;Thattassery, E.;Martinez, A.M.B.;Melo, P.A.;
Brazilian Journal of Medical and Biological Research , 2002, DOI: 10.1590/S0100-879X2002001000018
Abstract: the effect of dose and volume of a perimuscular injection of bothrops jararacussu venom on myonecrosis of skeletal muscle was studied in mice. an increase of the venom dose (0.25 to 2.0 μg/g) at a given volume (50 μl) resulted in an increase in plasma creatine kinase (ck) levels 2 h after injection. plasma ck activity increased from the basal level of 129.27 ± 11.83 (n = 20) to 2392.80 ± 709.43 iu/l (n = 4) for the 1.0 μg/g dose. histological analysis of extensor digitorum longus muscle 4 h after injection showed lesion of peripheral muscle fibers, disorganization of the bundles or the complete degeneration of muscle fibers. these lesions were more extensive when higher doses were injected. furthermore, an increase in volume (12.5 to 100 μl) by dilution of a given dose (0.5 μg/g) also increased plasma ck levels from 482.31 ± 122.79 to 919.07 ± 133.33 iu/l (n = 4), respectively. these results indicate that care should be taken to standardize volumes and sites of venom injections.
Effect of perimuscular injection of Bothrops jararacussu venom on plasma creatine kinase levels in mice: influence of dose and volume
Calil-Elias S.,Thattassery E.,Martinez A.M.B.,Melo P.A.
Brazilian Journal of Medical and Biological Research , 2002,
Abstract: The effect of dose and volume of a perimuscular injection of Bothrops jararacussu venom on myonecrosis of skeletal muscle was studied in mice. An increase of the venom dose (0.25 to 2.0 μg/g) at a given volume (50 μl) resulted in an increase in plasma creatine kinase (CK) levels 2 h after injection. Plasma CK activity increased from the basal level of 129.27 ± 11.83 (N = 20) to 2392.80 ± 709.43 IU/l (N = 4) for the 1.0 μg/g dose. Histological analysis of extensor digitorum longus muscle 4 h after injection showed lesion of peripheral muscle fibers, disorganization of the bundles or the complete degeneration of muscle fibers. These lesions were more extensive when higher doses were injected. Furthermore, an increase in volume (12.5 to 100 μl) by dilution of a given dose (0.5 μg/g) also increased plasma CK levels from 482.31 ± 122.79 to 919.07 ± 133.33 IU/l (N = 4), respectively. These results indicate that care should be taken to standardize volumes and sites of venom injections.
Diversity among satellite glial cells in dorsal root ganglia of the rat
Nascimento, R.S.;Santiago, M.F.;Marques, S.A.;Allodi, S.;Martinez, A.M.B.;
Brazilian Journal of Medical and Biological Research , 2008, DOI: 10.1590/S0100-879X2008005000051
Abstract: peripheral glial cells consist of satellite, enteric glial, and schwann cells. in dorsal root ganglia, besides pseudo-unipolar neurons, myelinated and nonmyelinated fibers, macrophages, and fibroblasts, satellite cells also constitute the resident components. information on satellite cells is not abundant; however, they appear to provide mechanical and metabolic support for neurons by forming an envelope surrounding their cell bodies. although there is a heterogeneous population of neurons in the dorsal root ganglia, satellite cells have been described to be a homogeneous group of perineuronal cells. our objective was to characterize the ultrastructure, immunohistochemistry, and histochemistry of the satellite cells of the dorsal root ganglia of 17 adult 3-4-month-old wistar rats of both genders. ultrastructurally, the nuclei of some satellite cells are heterochromatic, whereas others are euchromatic, which may result from different amounts of nuclear activity. we observed positive immunoreactivity for s-100 and vimentin in the cytoplasm of satellite cells. the intensity of s-100 protein varied according to the size of the enveloped neuron. we also noted that vimentin expression assumed a ring-like pattern and was preferentially located in the cytoplasm around the areas stained for s-100. in addition, we observed nitric oxide synthase-positive small-sized neurons and negative large-sized neurons equal to that described in the literature. satellite cells were also positive for nadph-diaphorase, particularly those associated with small-sized neurons. we conclude that all satellite cells are not identical as previously thought because they have different patterns of glial marker expression and these differences may be correlated with the size and function of the neuron they envelope.
Pulsed ultrasound therapy accelerates the recovery of skeletal muscle damage induced by Bothrops jararacussu venom
Saturnino-Oliveira, J.;Tomaz, M.A.;Fonseca, T.F.;Gaban, G.A.;Monteiro-Machado, M.;Strauch, M.A.;Cons, B.L.;Calil-Elias, S.;Martinez, A.M.B.;Melo, P.A.;
Brazilian Journal of Medical and Biological Research , 2012, DOI: 10.1590/S0100-879X2012007500033
Abstract: we studied the effect of pulsed ultrasound therapy (ust) and antibothropic polyvalent antivenom (pav) on the regeneration of mouse extensor digitorum longus muscle following damage by bothrops jararacussu venom. animals (swiss male and female mice weighing 25.0 ± 5.0 g; 5 animals per group) received a perimuscular injection of venom (1 mg/kg) and treatment with ust was started 1 h later (1 min/day, 3 mhz, 0.3 w/cm2, pulsed mode). three and 28 days after injection, muscles were dissected and processed for light microscopy. the venom caused complete degeneration of muscle fibers. ust alone and combined with pav (1.0 ml/kg) partially protected these fibers, whereas muscles receiving no treatment showed disorganized fascicules and fibers with reduced diameter. treatment with ust and pav decreased the effects of the venom on creatine kinase content and motor activity (approximately 75 and 48%, respectively). sonication of the venom solution immediately before application decreased the in vivo and ex vivo myotoxic activities (approximately 60 and 50%, respectively). the present data show that ust counteracts some effects of b. jararacussu venom, causing structural and functional improvement of the regenerated muscle after venom injury.
Experimental chronic entrapment of the sciatic nerve in adult hamsters: an ultrastructural and morphometric study
Prinz, R.A.D.;Nakamura-Pereira, M.;De-Ary-Pires, B.;Fernandes, D.S.;Fabi?o-Gomes, B.D.S.V.;Bunn, P.S.;Martinez, A.M.B.;Pires-Neto, M.A.;Ary-Pires, R.;
Brazilian Journal of Medical and Biological Research , 2003, DOI: 10.1590/S0100-879X2003000900015
Abstract: entrapment neuropathy is a group of clinical disorders involving compression of a peripheral nerve and interference with nerve function mostly through traction injury. we have investigated the chronic compression of peripheral nerves as an experimental procedure for detecting changes in ultrastructural nerve morphology. adult hamsters (mesocricetus auratus, n = 30) were anesthetized with a 25% pentobarbital solution and received a cuff around the right sciatic nerve. left sciatic nerves were not operated (control group). animals survived for varying times (up to 15 weeks), after which they were sacrificed and both sciatic nerves were immediately fixed with a paraformaldehyde solution. experimental nerves were divided into segments based upon their distance from the site of compression (proximal, entrapment and distal). semithin and ultrathin sections were obtained and examined by light and electron microscopy. ultrastructural changes were qualitatively described and data from semithin sections were morphometrically analyzed both in control and in compressed nerves. we observed endoneurial edema along with both perineurial and endoneurial thickening and also the existence of whorled cell-sparse structures (renaut bodies) in the subperineurial space of compressed sciatic nerves. morphometric analyses of myelinated axons at the compression sites displayed a remarkable increase in the number of small axons (up to 60%) in comparison with the control axonal number. the distal segment of compressed nerves presented a distinct decrease in axon number (up to 40%) comparatively to the control group. the present experimental model of nerve entrapment in adult hamsters was shown to promote consistent histopathologic alterations analogous to those found in chronic compressive neuropathies.
Impacts of Shading on Flower Formation and Longevity, Leaf Chlorophyll and Growth of Bougainvillea glabra
M. Saifuddin,A.M.B.S. Hossain,O. Normaniza
Asian Journal of Plant Sciences , 2010,
Abstract: Bougainvillea plants were exposed to artificially reduced light intensity to capture different Photosynthetic Photon Flux Density (PPFD), 0% (direct sunlight), 30, 50 and 75% shading and to observe the effects of shading on flower formation and longevity, leaf chlorophyll and sugar content and quality of plants. Plant attained the greatest leaf size with maximum branching when seedlings were grown in 30 and 50% shading, whereas 0% shading showed the lowest value. Growth parameters related to the plant characteristics such as branch initiation, branch growth and potassium content increased under high shading treatments. Plants exposed to 0% shade showed the highest sugar content and the sugar content decreased by increasing shading. The low light intensity that results in decreased sugar and chlorophyll contents may be attributed to the reduction of flower initiation and in turn to the acceleration of flower abscission. In addition, more than 30% shading led to stop up flower initiation completely. Hence, it is suggested that 0% shading can be applied to maintain frequent flower initiation and flower longevity.
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