Mechanisms of axonal plasticity: lessons from the olfactory pathway.

The olfactory pathway has emerged recently as an effective model for studying general principles of axon extension and regeneration. A variety of both trophic as well as repulsive molecules are found in the olfactory pathway and are being characterized for their roles in promoting the high capacity for plasticity and growth in olfactory receptor cell axons. In addition, olfactory ensheathing cells, which line the olfactory nerve, have been shown to promote axon extension not only in the olfactory pathway but also in the injured spinal cord. This review summarizes some of our current knowledge of these mechanisms and how they may function collectively to promote axon plasticity.

Bilateral posterolateral approach to mirror-image C-2 neurofibromas. Report of four cases.

Multiple nerve root tumors are usually present in patients afflicted with neurofibromatosis Type 1. Although rare, upper cervical mirror-image neurofibromas have been reported in the medical literature, and their surgical management has been addressed in several reports; however, little has been mentioned or is known regarding upper cervical or craniocervical stability following resection of these tumors. In this report the authors describe four cases of large mirror-image C-2 neurofibromas resected in two stages via the posterolateral approach. One patient presented with acute neurological deterioration after a biopsy sample had been obtained, whereas the other three presented with gradual onset of lower-extremity weakness over several months. The time interval between the first and second decompressive surgery ranged from 10 days to 12 weeks. There were no surgery-related complications, and all patients recovered motor function in their extremities. During a follow-up period of 16 to 36 months, there was no clinical or radiological evidence of upper cervical spine instability. Although the series is too small to draw any definitive conclusions, in the authors' experience the posterolateral approach provides a direct route for the successful surgical treatment of bilateral craniocervical nerve root tumors without destabilizing the upper cervical segments.

Olfactory ensheathing cells: bridging the gap in spinal cord injury.

Spinal cord injury (SCI) continues to be an insidious and challenging problem for scientists and clinicians. Recent neuroscientific advances have changed the pessimistic notion that axons are not capable of significant extension after transection. The challenges of recovering from SCI have been broadly divided into four areas: 1) cell survival; 2) axon regeneration (growth); 3) correct targeting by growing axons; and 4) establishment of correct and functional synaptic appositions. After acute SCI, there seems to be a therapeutic window of opportunity within which the devastating consequences of the secondary injury can be ameliorated. This is supported by several observations in which apoptotic glial cells have been identified up to 1 week after acute SCI. Moreover, autopsy studies have identified anatomically preserved but unmyelinated axons that could potentially subserve normal physiological properties. These observations suggest that therapeutic strategies after SCI can be directed into two broad modalities: 1) prevention or amelioration of the secondary injury, and 2) restorative or regenerative interventions. Intraspinal transplants have been used after SCI as a means for restoring the severed neuraxis. Fetal cell transplants and, more recently, progenitor cells have been used to restore intraspinal circuitry or to serve as relay for damaged axons. In an attempt to remyelinate anatomically preserved but physiologically disrupted axons, newer therapeutic interventions have incorporated the transplantation of myelinating cells, such as Schwann cells, oligodendrocytes, and olfactory ensheathing cells. Of these cells, the olfactory ensheathing cells have become a more favorable candidate for extensive remyelination and axonal regeneration. Olfactory ensheathing cells are found along the full length of the olfactory nerve, from the basal lamina of the epithelium to the olfactory bulb, crossing the peripheral nervous system-central nervous system junction. In vitro, these cells promote robust axonal growth, in part through cell adhesion molecules and possibly by secretion of neurotrophic growth factors that support axonal elongation and extension. In animal models of SCI, transplantation of ensheathing cells supports axonal remyelination and extensive migration throughout the length of the spinal cord. Although the specific properties of these cells that govern enhanced axon regeneration remain to be elucidated, it seems certain that they will contribute to the establishment of new horizons in SCI research.

The organization of piriform cortex and the lateral olfactory tract following the loss of mitral cells in PCD mice.

Homozygous Purkinje Cell Degeneration (PCD) mice exhibit a selective loss of olfactory bulb mitral cells (MCs) after 4 months of age. This selective degeneration leaves a subpopulation of denervated granule cells which establish new reciprocal dendro-dendritic synapses with unaffected tufted cells (TCs) (14). This suggests a capacity for plasticity in TCs and raises the question of whether a comparable degree of reorganization occurs in their axonal terminals in piriform cortex (PC) following the loss of MCs. Homozygous (experimental) and heterozygous (control) PCD mice were routinely perfused and processed for electron microscopy. A quantitative electron microscopic analysis was performed on radially oriented micrograph montages spanning from the pia into layer II of PC. After MC loss in the experimental animals there was a decrease in density of larger myelinated axons in the lateral olfactory tract (LOT). Myelinated axons in the LOT had a mean cross-sectional diameter of 1.26 +/- 0.04, and 0.81 +/- 0.025 microm in the control and experimental mice, respectively. In superficial layer I of PC, control mice had presynaptic axonal terminals from mitral and tufted cells with characteristic electron lucent (light) profiles establishing asymmetric synapses with pyramidal cell dendrites. In contrast, the experimental mice showed a decrease in electron lucent terminals and a robust increase in electron dense (dark) presynaptic associational terminals. Although the overall synaptic density did not differ between the control and experimental mice (16.40 +/- 0.94 and 18.10 +/- 0.96 synapses/100 microm2, respectively), an overall decrease in the thickness of Layer 1 suggests that the total number of synapses decreases following MC loss. In addition to the apparent increase of associational terminals, the diameter of terminal enlargements increased as well as the number of multiple synaptic contact per terminals in the experimental animal, suggesting further compensatory mechanisms for the loss of MC presynaptic terminals.

Low-grade gliomas of chronic epilepsy: a distinct clinical and pathological entity.

The authors present a summary of their recent experience regarding the management of patients with a variety of low-grade gliomas found during the evaluation for chronic epilepsy. These tumors are notable because the long-term patient outcome in this population is significantly better than the anticipated results of patients with the same tumors who do not have chronic epilepsy. Based on the long history of preoperative seizures (median 14 years), the frequent cortical location, and the absence of tumor recurrence or anaplastic transformation and the lack of mortality in this population, low-grade gliomas of chronic epilepsy appear to define a specific pathological entity that separates them from other histologically similar low-grade gliomas. Low-grade gliomas of chronic epilepsy also are notable for the absence of morphological features that characterize with dysembryoplastic neuroepithelial tumors (DNTs). Our evidence suggests that low-grade gliomas of chronic epilepsy should be recognized as a distinct pathological entity.

Sarcomas de la mama. / Sarcoma of the breast

Se presenta la casuistica de 16 sarcomas de la mama; 5 primitivos, 8 secundarios y en un tercer grupo, 3 casos disimiles pero en relacion directa o indirecta con aquella. Pertenecen a la Division Cirugia del hospital Teodoro Alvarez en el periodo 1953-1980 y representan el 1,1% de los 1516 carcinomas tratados en el mismo lapso Se relatan en cada grupo por separado, detalles del diagnostico, clinica, anatomia patologica, tratamiento y resultados. Finalmente se hace mencion del seguimiento y resultados generales a los 5, 10 y 15 ano

Carcinoma de mama y embarazo. / Breast carcinoma and pregnancy

Se analizan 22 casos de carcinomas de mama y embarazo. Representan el 1,5% de los 1.516 carcinomas tratados. Trece pertencian a los estadios I y II y 9 a los estadios III y IV. Quince eran embarazadas y 7 puerperas. Su edad promedio fue de 35.5 anos. Se destacan las dificultades para concretar el diagnostico clinico-mamografico. En relacion con la toma del material para biopsia, los autores son partidarios de efectuarla bajo anestesia general. Se mencionan como factores agravantes del pronostico la consulta tardia y el tratamiento demorado, ademas de la relacion huesped-tumor. Se describe el tratamiento realizado en el cual a partir de 1975 no incluye el aborto. Actualmente tratan a la enferma segun un escuema terapeutico. Con variantes relacionadas al embarazo, y se detallan conceptos sobre el aborto los ultimos tramos de la gestacion, la supresion de la lactancia y la terapia radiante. Se comentan los resultados obtenidos y el futuro embarazo de la mastectomizada (10 casos registrados)

Sarcomas de la mama. / Sarcoma of the breast

Se presenta la casuistica de 16 sarcomas de la mama; 5 primitivos, 8 secundarios y en un tercer grupo, 3 casos disimiles pero en relacion directa o indirecta con aquella. Pertenecen a la Division Cirugia del hospital Teodoro Alvarez en el periodo 1953-1980 y representan el 1,1% de los 1516 carcinomas tratados en el mismo lapso Se relatan en cada grupo por separado, detalles del diagnostico, clinica, anatomia patologica, tratamiento y resultados. Finalmente se hace mencion del seguimiento y resultados generales a los 5, 10 y 15 ano

Carcinoma de mama y embarazo. / Breast carcinoma and pregnancy

Se analizan 22 casos de carcinomas de mama y embarazo. Representan el 1,5% de los 1.516 carcinomas tratados. Trece pertencian a los estadios I y II y 9 a los estadios III y IV. Quince eran embarazadas y 7 puerperas. Su edad promedio fue de 35.5 anos. Se destacan las dificultades para concretar el diagnostico clinico-mamografico. En relacion con la toma del material para biopsia, los autores son partidarios de efectuarla bajo anestesia general. Se mencionan como factores agravantes del pronostico la consulta tardia y el tratamiento demorado, ademas de la relacion huesped-tumor. Se describe el tratamiento realizado en el cual a partir de 1975 no incluye el aborto. Actualmente tratan a la enferma segun un escuema terapeutico. Con variantes relacionadas al embarazo, y se detallan conceptos sobre el aborto los ultimos tramos de la gestacion, la supresion de la lactancia y la terapia radiante. Se comentan los resultados obtenidos y el futuro embarazo de la mastectomizada (10 casos registrados)

Patologia benigna de la mama. Fibroadenomixoma - polimastia. / Benign pathology of the breast. Fibroadenomyxoma - polymastia

Se destacan algunas caracteristicas particulares del fibroadenomixoma y de su comportamiento. Los autores son partidarios de su origen comun epitelio-mesenquimatico con el fibroadenoma y establecen por sus observaciones que el primero se originaria en los grandes conductos, mientras que el segundo lo haria a partir de los galactoforos de mediano calibre. Observaron el 41,4% de los casos antes de los 29 anos de edad, en contraste con otras estadisticas que ubican su mayor incidencia en la edad media de la vida. Despues de analizar las distintas imagenes mamograficas, se describen 3 formas macroscopicas fundamentales. Con un seguimiento del 71,4% hallaron que 2 recidivaron y 1 de estos evoluciono a la malignidad (5%). Se describe la polimastia atipica y la aberrante, puntualizando su mayor incidencia en las mujeres e insistiendo que a veces para realizar el diagnostico se requiere la biopsia y posterior estudio histopatologico que indican invariablemente, pues esta anomalia puede ser asiento de diversas patologias. Se pasa revista a algunos aspectos del diagnostico diferencial. Se describen 3 casos de neoplasias en polimastias axilares incompletas

Patologia benigna de la mama. Fibroadenomixoma - polimastia. / Benign pathology of the breast. Fibroadenomyxoma - polymastia

Se destacan algunas caracteristicas particulares del fibroadenomixoma y de su comportamiento. Los autores son partidarios de su origen comun epitelio-mesenquimatico con el fibroadenoma y establecen por sus observaciones que el primero se originaria en los grandes conductos, mientras que el segundo lo haria a partir de los galactoforos de mediano calibre. Observaron el 41,4% de los casos antes de los 29 anos de edad, en contraste con otras estadisticas que ubican su mayor incidencia en la edad media de la vida. Despues de analizar las distintas imagenes mamograficas, se describen 3 formas macroscopicas fundamentales. Con un seguimiento del 71,4% hallaron que 2 recidivaron y 1 de estos evoluciono a la malignidad (5%). Se describe la polimastia atipica y la aberrante, puntualizando su mayor incidencia en las mujeres e insistiendo que a veces para realizar el diagnostico se requiere la biopsia y posterior estudio histopatologico que indican invariablemente, pues esta anomalia puede ser asiento de diversas patologias. Se pasa revista a algunos aspectos del diagnostico diferencial. Se describen 3 casos de neoplasias en polimastias axilares incompletas