Toxoplasma gondii infection damages the perineuronal nets in a murine model

BACKGROUND Behavioral and neurochemical alterations associated with toxoplasmosis may be influenced by the persistence of tissue cysts and activation of an immune response in the brain of Toxoplasma gondii-infected hosts. The cerebral extracellular matrix is organised as perineuronal nets (PNNs) that are both released and ensheath by some neurons and glial cells. There is evidences to suggest that PNNs impairment is a pathophysiological mechanism associated with neuropsychiatric conditions. However, there is a lack of information regarding the impact of parasitic infections on the PNNs integrity and how this could affect the host's behavior. OBJECTIVES In this context, we aimed to analyse the impact of T. gondii infection on cyst burden, PNNs integrity, and possible effects in the locomotor activity of chronically infected mice. METHODS We infected mice with T. gondii ME-49 strain. After thirty days, we assessed locomotor performance of animals using the open field test, followed by evaluation of cysts burden and PNNs integrity in four brain regions (primary and secondary motor cortices, prefrontal and somesthetic cortex) to assess the PNNs integrity using Wisteria floribunda agglutinin (WFA) labeling by immunohistochemical analyses. FINDINGS AND MAIN CONCLUSIONS Our findings revealed a random distribution of cysts in the brain, the disruption of PNNs surrounding neurons in four areas of the cerebral cortex and hyperlocomotor behavior in T. gondii-infected mice. These results can contribute to elucidate the link toxoplasmosis with the establishment of neuroinflammatory response in neuropsychiatric disorders and to raise a discussion about the mechanisms related to changes in brain connectivity, with possible behavioral repercussions during chronic T. gondii infection.

Afferent projections from motoneurons innervating extraocular muscles to the cerebellum demonstrated by the retrograde double-labeling technique.

The objective of this study was to investigate the characteristics and distributions of neuronal origin of cerebellar afferents from motor cranial nerve nuclei innervating extraocular muscles by the method of retrograde transport of two fluorescence tracers in rats. Under deep anesthesia and aseptic conditions, 5 microl of 3% solution of Fluoro-Gold (FG) in phosphate buffer solution (PBS) was injected into the bellies of the six extraocular muscles to study the labeling of motoneurons innervating corresponding extraocular muscles. The cerebellum was exposed by craniotomy, and 0.3 microl of 10% solution of Dextran Tetramethyl Rhodamine Biotin (Micro Ruby: or MR) in PBS was injected into many regions of the anterior vermis (lobule I, II) and the posterior vermis (lobule VI, VII, IX, X), the flocculus, the paraflocculus and the deep cerebellar nuclei. Multiple injections were made to cover the entire cerebellum in order to obtain a near maximum labeling of cerebellar afferent neurons. In other cases, only small single or a few injections were made in specific areas of the cerebellum to study specific distributions and topographic organization. In one group of rats, injections were made both in the extraocular muscles with FG and in the cerebellum with MR to study the double labeling of neurons, which project their axons to both the extraocular muscle and the cerebellum. Another group of rats were injected in both sites with only PBS and served as the control for auto-fluorescence background. After 3 days postoperative survival time, all animals were deeply reanesthetized and perfused with heparinized normal saline solution, followed by 4% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4, and 30% sucrose solution in PBS. The brainstem and the cerebellum were removed immediately, and stored in sucrose solution in PBS at 4 degrees C. Serial transverse sections of the brainstem and sagittal sections of the cerebellum were obtained by a freezing microtome at 40 microm thickness, collected on uncoated glass slides, and immediately dried. All sections were examined under an epifluorescence or confocal microscope equipped with filter systems for FG and MR. The presence of both single and double retrograde labeled neurons in the Oculomotor (CN 3), Trochlear (CN 4) and Abducens (CN 6) nuclei was recorded, photographed, stored as computer images files and printed out as hard copies. The labeling neurons in the vicinity of the CN 3, 4, 6 from all sections were plotted onto diagrams and counted Neurons labeled only with MR retrogradely transported from injection sites in the cerebellum were found bilaterally and scattered throughout in the Oculomotor, Trochlear and Abducens nuclei. These neurons labeled only with MR were small and medium-sized interneurons and represented only a small proportion of the entire population. Neurons labeled only with FG retrogradely transported from injection sites in the extraocular muscles were the most numerous, and distributed almost throughout the entire population of small, medium-sized and large motoneurons, which innervate the extraocular muscles. A smaller proportion of small and medium-sized FG labeled neurons within these nuclei were also double labeled with MR, indicating that they project their axon collaterals to both extraocular muscles and the cerebellum. In conclusion, the present findings provide clear anatomical evidence that a small population of motoneurons in the Oculomotor, Trochlear and Abducens nuclei of the rat project their axon collaterals directly to the cerebellum and the extraocular muscle, in addition to the cerebellar afferents from other interneurons within these nuclei. The findings also indicate that cerebellar neuronal circuits play more direct roles in monitoring and controlling eye movements than previously known.

Precise localization of motor branching and motor points: a cadeveric study.

In order to facilitate precise localization of motor nerves and motor points, and to increase effectiveness and minimize complications of neurolytic blocks. Locations of motor branching points and motor points of 31 cadavers were measured as relative to medial femoral condyle and mid posterior calf line. Needle insertion points 1.5 centimeters and 0.5 centimeters proximal to the level of medial femoral condyle yielded the best chance (66.25%-76.19%) of finding motor branches to medial gastrocnemius muscles and lateral gastrocnemius respectively. The points with greatest chance of success (67.69%-86.41%) for soleus, tibialis posterior and flexor hallucis longus motor branches blocks were found to be at 2.5, 6, and 11 centimeters distal to the level of medial femoral condyle respectively. However; even if these points are used as guidelline when performing motor branch block prodedure, the risk of sensory nerve fiber injury are still as high as 20.98% upto 50.0%. To avoid such complication, the authors have proposed a set of landmarks that would make it possible to access all of the motor branches of any single calf muscle with only three or less needle insertions, and still maintaining about 1% risk of sensory fiber injury.

Factor de crecimiento neuronal y sus posibles implicaciones terapéuticas en la actualidad / Nerve growth factor and its possible therapeutical implications today

Desde 1934 se realizaron estudios analizando los efectos que sobre las células sensitivas y neuronas motoras espinales que inervaban las extremidades de animales, producía la extirpación de primordios nerviosos. Las observaciones obtenidas de estos estudios (después de algunos años) permitieron el descubrimiento de un factor promotor del crecimiento neuronal, al cual se designó como factor de crecimiento neuronal (NGF). El NFG es la sustancia mejor caracterizada dentro de una familia de moléculas que se requieren para la supervivencia y el desarrollo de neuronas durante etapas embrionarias del crecimiento y durante la vida adulta. Se ha observado que, bajo ciertas circunstancias, la infusión exógena de BGF puede promover la supervivencia neuronal y la regeneración axonal, por lo cual, en la actualidad, se ha intentado la utilización de este factor para mejorar algunas condiciones patológicas en las cuales el principal componente es el daño neuronal, pudiendo producirse este último por diferentes mecanismos. Dado lo anterior, se ha postulado que la administración de BGF recombinante humano pudiera ser, en el futuro, de utilidad para el tratamiento de enfermedades del sistema nervioso central y periférico, ya que en algunos de los estudios realizados se ha demostrado que este factor puede tener efectos benéficos

Efectos de la estimulación versus privación sensorio-motriz sobre el desarrollo neuronal en la corteza motora / Effects of sensor-motor stimulation versus deprivation on neuronal development in the motor cortex

El objetivo del presente estudio experimental fue evaluar el efecto de la estimulación vs. privación sensorio-motriz temprana sobre el desarrollo neuronal y conductual. Se utilizaron ratas albinas de la cepa Sprague-Dawley, las cuales fueron expuestas a 3 ambientes diferenciales (estimulado, control y deprivado), entre los días postnatales 5 y 21 (período crítico). Una vez realizada la evaluación conductual, los sujetos fueron sacrificados en día postnatal 22 y sus cerebros impregnados con le método de Golgi-Cox-Sholl, estudiándose bajo cámara lúcida dos variables estructurales en la corteza motora: desarrollo dendrítico basal/neurona y grado de citodiferenciación de grupos neuronianos. Los resultados obtenidos muestran que tanto la estimulación como la deprivación, realizada durante el período de lactancia, modifican el desarrollo neuronal en la corteza motora, tradicionalmente considerada menos plástica que las áreas sensoriales; resultados que son consistentes con la capacidad exploratoria analizada en el test de campo abierto