Takahiro Isozumi

Mechanism of mutism following the transcallosal approach to the ventricles

SummaryTransient mutism has been known as a common manifestation following callosotomy for medically intractable epilepsy, but its cause has not been clearly elucidated. In this paper, we report three cases of mutism following a transcallosal approach to tumours in the lateral and third ventricles and retrospectively analyze the surgical, neurological and radiological features which may suggest the cause of this type of mutism.Mutism may be a result of division of the corpus callosum. Suppression of the limbic system caused by lesions in the anterior cingulate gyrus, septum pellucidum, and fornix may have been of importance in at least two of these three cases. Impairments of the supplementary motor cortex, thalamus and basal ganglia may also be factors reducing speech production. The mechanism of such transient mutism seems to be a complex of two or more of these factors, and their combinations may be different from one case to the other.

Poikilothermia in a female patient with a germinoma in the basal ganglia

SummaryAn unusual association of poikilothermia and a germinoma originating in the left basal ganglia is described in a 17-year-old female. The tumour was found extending into the hypothalamic structures. Following irradiation therapy, the patient gradually regained her regulation of body temperature.

Increased expression of phosphotyrosine after axotomy in the dorsal motor nucleus of the vagus nerve and the hypoglossal nucleus

To investigate the role of tyrosine kinase underlying glial cell proliferation after axotomy, the localization of phosphotyrosine was studied immunohistochemically in the dorsal motor nucleus of the vagus nerve and the hypoglossal nucleus after nerve transection in adult rats. An anti-phosphotyrosine antibody weakly stained the cytoplasm of the neurons and some glial cells on the control side of both nuclei, while preferentially staining the plasma membrane of perineuronal microglial cells and neurons weakly on the severed side 2 days after axotomy and intensely between 3 and 7 days. Some of the microglial cells reacted positively with both anti-bromodeoxyuridine and antiphosphotyrosine antibodies, suggesting that tyrosine kinase is involved in microglial cell proliferation. Proliferation of numerous microglial cells was observed in the severed nuclei between 2 and 4 days after axotomy, while only a few were detected on days 5 and 7. These findings suggest that tyrosine kinase is involved in not only the proliferation of perineuronal microglial cells but also in some retrograde neuronal reactions such as differentiation and regeneration.

Altered expression of src tyrosine kinase after axotomy

Abstract Although most peripheral neurons show regenerative changes after axotomy, neurons of some nuclei show degenerative changes. To study the mechanisms responsible for such differences in neuronal reactions after axotomy, we investigated the changes of pp60c-src and phosphotyrosine (pTyr) in the dorsal motor nucleus of the vagus nerve and the hypoglossal nucleus after transection of each nerve in adult rats using immunohistochemistry. Polyclonal antibody against pp60v-src stained the cytoplasm of neurons homogeneously in both the severed and non-severed sides of the vagal and hypoglossal nuclei from days 1 to 56 after axotomy. On the other hand, the monoclonal antibody against pp60v-src (mAb327, which recognizes src homology 3 region in pp60src as an epitope) showed different immunoreactivities. No pp60c-src immunoreactivity was observed in neurons in either the vagal and hypoglossal nuclei of the non-severed side between days 1 and 56, whereas in the severed side of the hypoglossal nucleus intense pp60c-src immunoreactivity was observed along the plasma membrane of neurons from days 5 to 28 after axotomy. In contrast, in the severed side of the vagal nucleus pp60c-src immunoreactivity appeared along the plasma membrane of neurons on day 5 and remained until day 7. Conformational changes accompanying the activation of pp60c-src are suggested to cause differences in immunoreactivities of these antibodies. The expression (or activation) of pp60c-src in the neurons was stronger and longer lasting in the hypoglossal nucleus, which regenerates successfully after axotomy, than in the dorsal motor nucleus of the vagus nerve, which undergoes necrobiotic reaction. These results indicate that pp60c-src plays an important role in regeneration after axotomy.