Quantitative analysis of hindlimbs locomotion kinematics in spinalized rats treated with Tamoxifen plus treadmill exercise.

Locomotion recovery after a spinal cord injury (SCI) includes axon regeneration, myelin preservation and increased plasticity in propriospinal and descending spinal circuitries. The combined effects of tamoxifen and exercise after a SCI were analyzed in this study to determine whether the combination of both treatments induces the best outcome in locomotion recovery. In this study, the penetrating injury was provoked by a sharp projectile that penetrates through right dorsal and ventral portions of the T13-L1 spinal segments, affecting propriospinal and descending/ascending tracts. Intraperitoneal application of Tamoxifen and a treadmill exercise protocol, as rehabilitation therapies, separately or combined, were used. To evaluate the functional recovery, angular patterns of the hip, knee and ankle joints as well as the leg pendulum-like movement (PLM) were measured during the unrestricted gait of treated and untreated (UT) animals, previously and after the traumatic injury (15 and 30days post-injury (dpi)). A pattern (curve) comparison analysis was made by using a locally designed Matlab script that determines the Frechet dissimilarity. The SCI magnitude was assessed by qualitative and quantitative histological analysis of the injury site 30days after SCI. Our results showed that all treated groups had an improvement in hindlimbs kinematics compared to the UT group, which showed a poor gait locomotion recovery throughout the rehabilitation period. The group with the combined treatment (tamoxifen+exercise (TE)) presented the best outcome. In conclusion, tamoxifen and treadmill exercise treatments are complementary therapies for the functional recovery of gait locomotion in hemi-spinalized rats.

Stochastic resonance in the synaptic transmission between hair cells and vestibular primary afferents in development.

The stochastic resonance (SR) is a phenomenon of nonlinear systems in which the addition of an intermediate level of noise improves the response of such system. Although SR has been studied in isolated hair cells and in the bullfrog sacculus, the occurrence of this phenomenon in the vestibular system in development is unknown. The purpose of the present study was to explore for the existence of SR via natural mechanical-stimulation in the hair cell-vestibular primary afferent transmission. In vitro experiments were performed on the posterior semicircular canal of the chicken inner ear during development. Our experiments showed that the signal-to-noise ratio of the afferent multiunit activity from E15 to P5 stages of development exhibited the SR phenomenon, which was characterized by an inverted U-like response as a function of the input noise level. The inverted U-like graphs of SR acquired their higher amplitude after the post-hatching stage of development. Blockage of the synaptic transmission with selective antagonists of the NMDA and AMPA/Kainate receptors abolished the SR of the afferent multiunit activity. Furthermore, computer simulations on a model of the hair cell - primary afferent synapse qualitatively reproduced this SR behavior and provided a possible explanation of how and where the SR could occur. These results demonstrate that a particular level of mechanical noise on the semicircular canals can improve the performance of the vestibular system in their peripheral sensory processing even during embryonic stages of development.

The hippocampus participates in the control of locomotion speed.

The hippocampus role in sensory-motor integration remains unclear. In these experiments we study its function in the locomotor control. To establish the connection between the hippocampus and the locomotor system, electrical stimulation in the CA1 region was applied and EMG recordings were obtained. We also evaluated the hindlimbs and forelimbs kinematic patterns in rats with a penetrating injury (PI) in the hippocampus as well as in a cortex-injured group (CI), which served as control. After the PI, tamoxifen a selective estrogen receptor modulator (SERM) that has been described as a neuroprotector and antiinflammatory drug, or vehicle was administered. Electrical stimulation in the hippocampus produces muscle contractions in the contralateral triceps, when 6 Hz or 8 Hz pulse trains were applied. The penetrating injury in the hippocampus reduced the EMG amplitude after the electrical stimulation. At 7 DPI (days post-injury) we observed an increase in the strides speed in all four limbs of the non-treated group, decreasing the correlation percentage of the studied joints. After 15 DPI the strides speed in the non-treated returned to normal. These changes did not occur in the tamoxifen group nor in cortex-injured group. After 30 days, the nontreated group presented a reduction in the number of pyramidal cell layer neurons at the injury site, in comparison to the tam-treated group. The loss of neurons, may cause the interruption of the trisynaptic circuit and changes in the locomotion speed. Tamoxifen preserves the pyramidal neurons after the injury, probably resulting in the strides speed recovery.

Transition of pattern generation: the phenomenon of post-scratching locomotion.

A fundamental problem in neurophysiology is the understanding of neuronal mechanisms by which the central nervous system produces a sequence of voluntary or involuntary motor acts from a diverse repertory of movements. These kinds of transitions between motor acts are extremely complex; however, they could be analyzed in a more simple form in decerebrate animals in the context of spinal central pattern generation. Here, we present for the first time a physiological phenomenon of post-scratching locomotion in which decerebrate cats exhibit a compulsory locomotor activity after an episode of scratching. We found flexor, extensor and intermediate single interneurons rhythmically firing in the same phase during both scratching and the subsequent post-scratching locomotion. Because no changes in phase of these neurons from scratching to post-scratching locomotion were found, we suggest that in the lumbar spinal cord there are neurons associated with both motor tasks. Moreover, because of its high reproducibility we suggest that the study of post-scratching fictive locomotion, together with the unitary recording of neurons, could become a useful tool to study neuronal mechanisms underlying transitions from one rhythmic motor task to another, and to study in more detail the central pattern generator circuitry in the spinal cord.

Aromatase and estrogen receptor alpha mRNA expression as prognostic biomarkers in patients with astrocytomas.

Estrogens are oncogenic hormones at a high level in breast, prostate, endometrial and lung cancer. Estrogens are synthesized by aromatase which has been used as a biomarker both in breast and lung cancer. Estrogen biological activities are executed by their classic receptors (ERα and ERß). ERα has been described as a cancer promoter and ERß, as a possible tumor suppressor. Both receptors are present at low levels in primary multiforme glioblastoma (GBM). The GBM frequency is 50 % higher in men than in women. The GBM patient survival period ranges from 7 to 18 months. The purpose of this pilot study was to evaluate aromatase and estrogen receptor expression, as well as 17ß-estradiol concentration in astrocytoma patients biopsies to obtain a prognosis biomarker for these patients. We analyzed 36 biopsies of astrocytoma patients with a different grade (I-IV) of malignity. Aromatase and estrogen receptor mRNA expression were analyzed by semiquantitative RT-PCR, and the E2 levels, by ELISA. E2 concentration was higher in GBM, compared to grade II or III astrocytomas. The number of cells immunoreactive to aromatase and estrogen receptors decreased as the grade of tumor malignity increased. Aromatase mRNA expression was present in all biopsies, regardless of malignity grade or patient age or gender. The highest expression of aromatase mRNA in GBM patients was associated to the worst survival prognostic (6.28 months). In contrast lowest expression of ERα mRNA in astrocytoma patients had a worst prognosis. In conclusion, aromatase and ERα expression could be used as prognosis biomarkers for astrocytoma patients.

Tamoxifen favoured the rat sensorial cortex regeneration after a penetrating brain injury.

A penetrating brain injury produces a glial scar formed by astrocytes, oligodendrocytes, microglia and NG2 cells. Glial scar is a barrier preventing the extent of damage but it has deleterious effects in the regeneration of the axons. Estradiol and tamoxifen reduce gliosis and have neuroprotective effects in the hippocampus and the spinal cord. We evaluated the proliferation of glia and the electrocorticogram in the sensorial cortex in a brain injury model. At seven days post-injury, estradiol, tamoxifen and estradiol plus tamoxifen reduced the number of resident and proliferative NG2 and reactive astrocyte vimentin+ cells. Estradiol and tamoxifen effects on NG2 cells could be produced by the classical oestrogen receptors found in these cells. The glial scar was also reduced by tamoxifen. At thirty days post-injury, the amount of resident and proliferative astrocytes increased significantly, except in the estradiol plus tamoxifen group, whilst the oligodendrocytes proliferation in the glial scar was reduced in treated animals. Tamoxifen promotes the survival of FOX-3+ neurons in the injured area and a recovery in the amplitude of electrocorticogram waves. At thirty days, estradiol did not favour the survival of neurons but produced a greater number of reactive astrocytes. In contrast, the number of oligodendrocytes was reduced. Tamoxifen could favour brain repair promoting neuron survival and adjusting glial cell number. It seems to recover adequate neural communication.