Early effects comparison of X-rays delivered at high-dose-rate pulses by a plasma focus device and at low dose rate on human tumour cells.

A comparative study has been performed on the effects of high-dose-rate (DR) X-ray beams produced by a plasma focus device (PFMA-3), to exploit its potential medical applications (e.g. radiotherapy), and low-DR X-ray beams produced by a conventional source (XRT). Experiments have been performed at 0.5 and 2 Gy doses on a human glioblastoma cell line (T98G). Cell proliferation rate and potassium outward currents (IK) have been investigated by time lapse imaging and patch clamp recordings. The results showed that PFMA-3 irradiation has a greater capability to reduce the proliferation rate activity with respect to XRT, while it does not affect IK of T98G cells at any of the dose levels tested. XRT irradiation significantly reduces the mean IK amplitude of T98G cells only at 0.5 Gy. This work confirms that the DR, and therefore the source of radiation, is crucial for the planning and optimisation of radiotherapy applications.

Prefrontal cortex lesions augment the location-related firing properties of area TE/perirhinal cortex neurons in a working memory task.

It has previously been proposed that prefrontal cortex may have some role in keeping temporal cortex-based representations "on-line" during a working memory task. To test this hypothesis, the effects of electrolytic prefrontal cortex lesions on the firing of area TE and perirhinal cortex (PRC) neurons were examined while rats performed a delayed non-match to position task in the T-maze. The behavioural performance of control (n = 4) and lesioned (n = 4) animals were similar during this task, and many neurons displayed a statistically significant location-related variation in firing rate during the sample (44/56 neurons) and test (39/56 neurons) phases. Units from prefrontal-lesioned animals (82%) were more likely to display a significant variation in firing across the maze compared to controls (50%; P < 0.01), and to have more discrete location-related properties (50% of neurons) compared to the control (5%) group (P < 0.0005). This finding suggests that prefrontal cortex normally modulates the transmission and/or processing of spatial information in area TE/PRC during a working memory task. Modulation could be mediated through direct connections between the structures or via prefrontal control of subcortical structures. This finding has implications for our understanding of prefrontal-temporal involvement in memory and cognitive disorders.

Telencephalo-habenulo-interpeduncular connections in the goldfish: a DiI study.

The telencephalo-habenulo-interpeduncular system has been anatomically and neurochemically characterized in mammals. However, little is known about these important forebrain-midbrain connections in non-mammalian vertebrates, although available data suggest that they are evolutionarily relatively conservative. Previous ultrastructural studies in the goldfish confirmed the presence of massive telencephalohabenular and habenulointerpeduncular projections and demonstrated a minor direct telencephalointerpeduncular connection. Here we report the anterograde and retrograde transport of lipophilic fluorescent carbocyanine dye from the interpeduncular nucleus and the habenular nuclei in the fixed goldfish brain. The application of dye into the interpeduncular nucleus resulted in massive labeling of the fasciculus retroflexus and of the habenular neurons. A few scattered neurons were also seen in the dorsal nucleus of area ventralis telencephali. Application of dye into the habenulae resulted in anterograde transport through the medial and lateral olfactory tracts to some cell bodies in the anterior and posterior zone of area ventralis telencephali and in perikarya of the bed nucleus and in the entopeduncular nucleus. These results demonstrate the origin of the direct telencephalointerpeduncular projection in the goldfish and confirm some important homologies with forebrain-midbrain projections in land vertebrates.

Choline acetyltransferase and NADPH-diaphorase localization in the goldfish habenulo-interpeduncular system.

The habenular nuclei are the major sources of projections to the interpeduncular nucleus. The habenular neurons of the goldfish are ChAT and NADPH-diaphorase positive. The localization of these two enzymes in the habenulae suggests the involvement of acetylcholine and nitric oxide (the product of NADPH-diaphorase activity in the nervous tissue) in the habenulo-interpeduncular connection. This finding is supported by the presence of ChAT and NADPH-diaphorase activity in the neuropilar area of the interpeduncular nucleus. This activity was depleted 12 days after habenular ablation. The overlap of ChAT and NADPH-diaphorase localization in goldfish habenular neurons is consistent with previous observations on the co-localization of these two enzymes in some brainstem neurons of other vertebrates. It is, however, not identical to the localization of NADPH-diaphorase in the habenulae and in the interpeduncular nucleus of the rat.

Ultrastructural and immunohistochemical study of the telencephalo-habenulo-interpeduncular connections of the goldfish.

Surgical ablations of telencephalon or telencephalon plus habenular nuclei (HBN) have been performed for studying anatomical connections of the telencephalo-habenulo-interpeduncular system of the goldfish. The results of the ultrastructural studies confirmed the presence of massive telencephalo-habenular and habenulo-interpeduncular projections and, in addition, demonstrated a minor direct telencephalo-interpeduncular connection. Immunohistochemical localization of substance P in the interpeduncular nucleus (IPN) after telencephalic ablation failed to demonstrate the involvement of this neurotransmitter in the direct telencephalo-interpeduncular projection, while telencephalon plus HBN ablation reduced substance P immunoreactivity in the IPN. The different distribution of degenerating terminals converging on the IPN from the HBN and from the telencephalon suggested a subnuclear organization of this area, as described in mammals.