Luiza da Silva Lopes

Characterization of juvenile and young adult mice following induction of hydrocephalus with kaolin

Hydrocephalus is a common neurological problem in humans, usually caused by an impairment of cerebrospinal fluid (CSF) flow or absorption. A reliable induced model of chronic hydrocephalus in mice would be useful to test hypotheses using genetic mutants. Our goal was to characterize behavioral and histological changes in juvenile and young adult mice with kaolin (aluminum silicate)-induced hydrocephalus. Seven-day old and 7-8 week old mice received injection of kaolin into the cisterna magna. Behavior was assessed repeatedly. Seven or 14 days following kaolin, magnetic resonance (MR) imaging was used to assess ventricle size. In hydrocephalic mice, body weight was significantly lower than in age-matched saline-injected sham controls and the gait and posture score were impaired. Juvenile mice developed severe ventriculomegaly and had reduced corpus callosum thickness with gross white matter destruction by 14 days. Reactive astroglial change in white matter and cortex and reduced cellular proliferation in the subependymal zone were also apparent. Young adult mice developed only moderate ventricular enlargement without overt white matter destruction, although there was corpus callosum atrophy and mild astroglial reaction in white matter. Glial fibrillary acidic protein content was significantly higher in juvenile and young adult hydrocephalic mice at 7 and 14 days, but myelin basic protein content was not significantly altered. In conclusion, hydrocephalus induced by percutaneous injection of kaolin in juvenile and young adult mice is feasible. The associated periventricular alterations are essentially the same as those reported in rats of comparable ages.

Cerebral White Matter Oxidation and Nitrosylation in Young Rodents With Kaolin-Induced Hydrocephalus

Abstract Hydrocephalus is associated with reduced blood flow in periventricular white matter. To investigate hypoxic and oxidative damage in the brains of rats with hydrocephalus, kaolin was injected into the cisterna magna of newborn 7- and 21-day-old Sprague-Dawley rats, and ventricle size was assessed by magnetic resonance imaging at 7, 21, and 42 days of age. In-situ evidence of hypoxia in periventricular capillaries and glial cells was shown by pimonidazole hydrochloride binding. Biochemical assay of thiobarbituric acid reaction and immunohistochemical detection of malondialdehyde and 4-hydroxy-2-nonenal indicated the presence of lipid peroxidation in white matter. Biochemical assay of nitrite indicated increased nitric oxide production. Nitrotyrosine immunohistochemistry showed nitrosylated proteins in white matter reactive microglia and astrocytes. Activities ofthe antioxidant enzymes catalase and glutathione peroxidase were notincreased, and altered hypoxia-inducible factor 1&agr; was not detectedby quantitative reverse transcription–polymerase chain reaction. Cerebral vascular endothelial growth factor expression determined byquantitative reverse transcription–polymerase chain reaction and enzyme-linked immunosorbent assay was not changed, but vascular endothelial growth factor immunoreactivity was increased in reactive astrocytes of hydrocephalic white matter. To determine if nitric oxide synthase is involved in the pathogenesis, we induced hydrocephalus in 7-day-old wild-type and neuronal nitric oxide synthase–deficient mice. At 7 days, the wild-type and mutant mice exhibited equally severe ventriculomegaly and no behavioral differences, although increased glial fibrillary acidic protein was less in the mutant mice. We conclude that hypoxia, via peroxidation and nitrosylation, contributes to brain changes in young rodents with hydrocephalus and that compensatory mechanisms are negligible.

Sciatic nerve regeneration in rats by a nerve conduit engineering with a membrane derived from natural latex

PURPOSE To evaluate the capacity of natural latex membrane to accelerate and improve the regeneration quality of the of rat sciatic nerves. METHODS Forty male adult Wistar rats were used, anesthetized and operated to cut the sciatic nerve and receive an autograft or a conduit made with a membrane derived from natural latex (Hevea brasiliensis). Four or eight weeks after surgery, to investigate motor nerve recovery, we analyzed the neurological function by walking pattern (footprints analysis and computerized treadmill), electrophysiological evaluation and histological analysis of regenerated nerve (autologous nerve graft or tissue cables between the nerve stumps), and anterior tibial and gastrocnemius muscles. RESULTS All functional and morphological analysis showed that the rats transplanted with latex conduit had a better neurological recovery than those operated with autologous nerve: quality of footprints, performance on treadmill (p<0.01), electrophysiological response (p<0.05), and quality of histological aspects on neural regeneration. CONCLUSION The data reported showed behavioral and functional recovery in rats implanted with latex conduit for sciatic nerve repair, supporting a complete morphological and physiological regeneration of the nerve.

Changes caused by hidrocephalus, induced by kaolin, in the corpus callosum of adult dogs

PURPOSE: To analyze the ventricular enlargement and myelination of the corpus callosum in adult dogs after four and eight weeks of kaolin-induction of hydrocephalus. METHODS: 36 dogs were randomly divided into 3 groups: 1 - without hydrocephalus, 2 - kaolin-induction of hydrocephalus until the fourth week, and 3 - kaolin-induction of hydrocephalus until the eighth week. Ventricular ratios and volumes were calculated using magnetic resonance images, and myelination of the corpus callosum were histologically evaluated using solocromo-cianin stain. RESULTS: Radiological hydrocephalus was observed in 93.75% and overall mortality was 38.4%. Ventricular volumes and ratios were higher in groups 2 and 3 compared to group 1 and similar when measures in the fourth and eighth weeks were compared in the group 3. Indices of luminescence in the knee and in the splenium of the corpus callosum were higher in group 2 than in group 1 indicating that there was loss of myelin in group 2, and similar in groups 1 and 3, showing a tendency to remyelination after 8 weeks. CONCLUSION: The corpus callosum of dogs with kaolin-induced hydrocephalus responds with demyelination of the knee and splenium by the fourth week with a tendency to remyelination by the eighth week.

Study of corpus callosum in experimental hydrocephalic wistar rats

OBJETIVO: A hidrocefalia causa inumeros danos cerebrais, especialmente nas estruturas ao redor dos ventriculos cerebrais. As criancas com hidrocefalia apresentam deficits nas aquisicoes nao verbais mais do que nas verbais, nem sempre revertidos com o tratamento precoce. Como o corpo caloso tem um papel essencial nas aquisicoes nao verbais, e provavel que as lesoes nesta estrutura estejam envolvidas com as disfuncoes cognitivas dessas criancas. Este trabalho procura estabelecer as alteracoes causadas pela hidrocefalia, induzida pela injecao de caulim intracisternal ao corpo caloso de ratos Wistar em desenvolvimento. METODOS: Sete, 14 e 21 dias apos a injecao, os animais foram sacrificados, sendo o corpo caloso dissecado e processado para estudo das fibras axonais. RESULTADOS E CONCLUSOES: Os ratos com 7 dias de evolucao da hidrocefalia apresentaram um atraso na mielinizacao em relacao aos controles. Em ratos com 14 dias de evolucao da hidrocefalia, o corpo caloso mostrou recuperacao da mielina, mas em ratos com hidrocefalia com 21 dias de evolucao, as fibras apresentavam-se lesadas e reduzidas em numero.

Biochemical evaluation of focal non-reperfusion cerebral ischemia by middle cerebral artery occlusion in rats

Cerebral ischemia is an important event in clinical and surgical neurological practice since it is one of the diseases that most compromise the human species. In the present study 40 adult rats were submitted to periods of focal ischemia of 30, 60 and 90 min without reperfusion and animals submitted to a sham procedure were used as controls. We analyzed the levels of ATP, malondialdehyde and caspase-3. No significant differences in the biochemical measurements were observed between the right and left brain hemispheres of the same animal in each experimental group. Reduced ATP levels were observed after the three periods of ischemia compared to the sham group. No significant increase in malondialdehyde or caspase-3 levels was observed. Despite significant changes in ATP levels, the results indicated cell viability in the ischemic region as shown by the low rates of lipid peroxidation and apoptosis, findings probably related to the lack of reperfusion.

Ultrastructural study of the lateral ventricle choroid plexus in experimental hydrocephalus in Wistar rats

Hydrocephalus is one of the most frequent and complex neurological diseases characterized by the abnormal buildup of cerebrospinal fluid (CSF) in the ventricles of the brain, due to an altered CSF dynamics. To detect possible ultrastructural alterations of the lateral ventricles choroid plexus (responsible for the CSF production), rats seven days after birth were submitted to an intracisternal injection of 20% kaolim (hydrated aluminum silicate) for the hydrocephalus induction. Twenty-eight or 35 days after injection, injected animals and respective controls were processed for observation under a transmission electron microscopy. Alterations found: presence of concentric cell membrane fragments, larger number of primary and secondary lysossomes, vacuoles, and cytoplasmic vesicles, and an enlargement of the intercellular space and between the basolateral interdigitation of the choroid epithelium. The alterations observed are probably associated to an increase of the ventricular pressure, inducing morpho-functional effects on the choroid plexus integrity.

Pre- and Postshunting Magnetization Transfer Ratios Are in Accordance with Neurological and Behavioral Changes in Hydrocephalic Immature Rats

Hydrocephalus is a common neurological condition in children characterized by an imbalance between the production and absorption of cerebrospinal fluid (CSF), causing abnormal fluid accumulation in the brain cavities. Shunt systems have been used to drain excess CSF and to prevent progressive ventricular enlargement. However, despite improvements in these systems, neurological and structural changes cannot always be reversed. Our aim was to evaluate the magnetization transfer ratio as a biomarker for the effectiveness of a CSF shunt system to treat neurological and behavioral disorders observed in experimental hydrocephalus. Seven-day-old Wistar rats were used in this study. The pups were subjected to hydrocephalus induction via 20% kaolin intracisternal injection. After confirmation of ventriculomegaly by magnetic resonance imaging (MRI), a group of animals underwent placement of a ventriculosubcutaneous shunt (VSS). The reduction in ventricular size in hydrocephalic rats operated with functional VSS was observed as a decrease in ventricular ratio values and preservation of the corpus callosum thickness. Magnetization transfer values were significantly increased and matched to the recovery process of axonal myelination observed based on more-intense blue staining by solochrome cyanin. The histopathological analysis revealed a reduction in reactive astrocytes by means of GFAP immunostaining. The hydrocephalic rats operated with functional VSS also showed significant progress in motor and exploratory activities, similar to the control animals, at the end of the experiment. In conclusion, the VSS system employed 7 days after hydrocephalus induction was able to prevent structural damage and restore the axonal myelination process in periventricular structures by stabilizing and reducing the ventricular enlargement, and the results are in accordance with the magnetization transfer ratio in MRI.Hydrocephalus is a common neurological condition in children characterized by an imbalance between the production and absorption of cerebrospinal fluid (CSF), causing abnormal fluid accumulation in the brain cavities. Shunt systems have been used to drain excess CSF and to prevent progressive ventricular enlargement. However, despite improvements in these systems, neurological and structural changes cannot always be reversed. Our aim was to evaluate the magnetization transfer ratio as a biomarker for the effectiveness of a CSF shunt system to treat neurological and behavioral disorders observed in experimental hydrocephalus. Seven-day-old Wistar rats were used in this study. The pups were subjected to hydrocephalus induction via 20% kaolin intracisternal injection. After confirmation of ventriculomegaly by magnetic resonance imaging (MRI), a group of animals underwent placement of a ventriculosubcutaneous shunt (VSS). The reduction in ventricular size in hydrocephalic rats operated with functional VSS was observed as a decrease in ventricular ratio values and preservation of the corpus callosum thickness. Magnetization transfer values were significantly increased and matched to the recovery process of axonal myelination observed based on more-intense blue staining by solochrome cyanin. The histopathological analysis revealed a reduction in reactive astrocytes by means of GFAP immunostaining. The hydrocephalic rats operated with functional VSS also showed significant progress in motor and exploratory activities, similar to the control animals, at the end of the experiment. In conclusion, the VSS system employed 7 days after hydrocephalus induction was able to prevent structural damage and restore the axonal myelination process in periventricular structures by stabilizing and reducing the ventricular enlargement, and the results are in accordance with the magnetization transfer ratio in MRI.

Morphological and Morphometric Analysis of the Hippocampus in Wistar Rats with Experimental Hydrocephalus

Background: The present study aims at better establishing the alterations caused by the usual enlargement of brain ventricles in this structure. Methods: Hydrocephalus was induced in 7-day-old Wistar rats by the injection of kaolin into the cisterna magna. Morphological studies were performed on the hippocampus 7, 14 and 21 days after injection. The total number of neurons in each hippocampus subarea as well as that of pyknotic neurons were counted. Then we calculated the pyknotic index (PI) by hippocampal subarea, taking into account the level of ventricular dilatation and time of induction of hydrocephalus. Results: PI was statistically larger in the CA1 subarea of the experimental group after 1 week of hydrocephalus induction as compared to the corresponding control as well as in animals that had developed mild hydrocephalus in groups G1, G2 and G3. Conclusion: Hydrocephalus caused morphological alterations in the hippocampus, leading to important changes in its shape.

0.1T magnetic resonance image in the study of experimental hydrocephalus in rats. Accuracy of the method in the measurements of the ventricular size

PURPOSE To investigate the accuracy of 1.0T Magnetic Resonance Imaging (MRI) to measure the ventricular size in experimental hydrocephalus in pup rats. METHODS Wistar rats were subjected to hydrocephalus by intracisternal injection of 20% kaolin (n=13). Ten rats remained uninjected to be used as controls. At the endpoint of experiment animals were submitted to MRI of brain and killed. The ventricular size was assessed using three measures: ventricular ratio (VR), the cortical thickness (Cx) and the ventricles area (VA), performed on photographs of anatomical sections and MRI. RESULTS The images obtained through MR present enough quality to show the lateral ventricular cavities but not to demonstrate the difference between the cortex and the white matter, as well as the details of the deep structures of the brain. There were no statistically differences between the measures on anatomical sections and MRI of VR and Cx (p=0.9946 and p=0.5992, respectively). There was difference between VA measured on anatomical sections and MRI (p<0.0001). CONCLUSION The parameters obtained through 1.0T MRI were sufficient in quality to individualize the ventricular cavities and the cerebral cortex, and to calculate the ventricular ratio in hydrocephalus rats when compared to their respective anatomic slice.