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The cellular toxicity of carbon-based nanomaterials was studied as a function of their aspect ratio and surface chemistry. These structures were multiwalled carbon nanotubes, carbon nanofibers, and carbon nanoparticles. Their toxicity was tested in vitro on lung tumor cells. Our work clearly indicated that these materials are toxic while the hazardous effect is size-dependent. Moreover, cytotoxicity is enhanced when the surface of the particles is functionalized after an acid treatment.

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Immunohistochemistry is a powerful diagnostic adjunct in the differential diagnosis between malignant mesothelioma (especially of the epithelial type) and adenocarcinoma metastatic to the serous membranes. Most of the immunological probes commonly used, however, recognize antigens expressed by the epithelial malignancies and absent from mesothelial cells and mesotheliomas. Probes suitable for the positive identification of mesotheliomas are comparatively scarce and much less commonly used because of their reduced sensitivity and specificity, their unsuitability for staining routinely fixed and embedded tissues, or their lack of commercial availability. We now document that two different polyclonal antisera to calretinin consistently immunostain mesothelial cells and malignant mesotheliomas both in routinely fixed and embedded tissue sections and in cytological preparations of serous effusions. The diagnostic sensitivity of this novel immunocytochemical approach reached 100%, allowing immunostaining of all 44 mesotheliomas investigated, which included five biphasic and three sarcomatoid types. The specificity of calretinin immunoreactivity was checked against 294 adenocarcinomas of different origin (19 serosal metastases and 275 primary tumors potentially able to metastatize to serosal membranes) relevant for the discussion of the differential diagnosis with malignant mesothelioma: only 28 cases showed focal immunoreactivity for calretinin. We conclude that calretinin is a most useful marker for the positive identification of malignant mesotheliomas.

gamma-Aminobutyric acid (GABA) is one of the major inhibitory neurotransmitters in the central nervous system. In the cerebral cortex, GABA-containing cells represent a subpopulation of interneurons. With semithin frozen sections, it is possible to demonstrate that most GABA neurons in the rat somatosensory cortex contain the calcium-binding protein parvalbumin and that parvalbumin is found virtually only in GABA neurons. Parvalbumin seems to influence the electrical properties and enzymatic machinery to modulate neuronal excitability and activity. The specific role of parvalbumin in GABA-containing cortical cells may be related to controlling the effectiveness of their inhibitory action.

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GABAergic (GABA ‫؍‬ ␥-aminobutyric acid) neurons from different brain regions contain high levels of parvalbumin, both in their soma and in their neurites. Parvalbumin is a slow Ca 2؉ buffer that may affect the amplitude and time course of intracellular Ca 2؉ transients in terminals after an action potential, and hence may regulate short-term synaptic plasticity. To test this possibility, we have applied paired-pulse stimulations (with 30-to 300-ms intervals) at GABAergic synapses between interneurons and Purkinje cells, both in wild-type (PV؉͞؉) mice and in parvalbumin knockout (PV؊͞؊) mice. We observed pairedpulse depression in PV؉͞؉ mice, but paired-pulse facilitation in PV؊͞؊ mice. In paired recordings of connected interneuronPurkinje cells, dialysis of the presynaptic interneuron with the slow Ca 2؉ buffer EGTA (1 mM) rescues paired-pulse depression in PV؊͞؊ mice. These data show that parvalbumin potently modulates short-term synaptic plasticity.GABA ͉ cerebellum ͉ basket cells ͉ stellate cells ͉ Purkinje cells T he immediate consequences of past neuronal activity on synaptic strength are often examined by measuring the ratio (called paired-pulse ratio, or PPR) between the mean synaptic current in response to a test stimulation over that obtained with a conditioning stimulus. If the PPR is larger than 1, the synapse is considered as facilitating, whereas values smaller than 1 are characteristic of depressing synapses. However, facilitation and depression presumably coexist in all experimental conditions, and the PPR that is measured may be viewed as a balance between these two competing processes (1, 2).Current hypotheses link facilitation to the fact that some of the Ca 2ϩ ions entering the presynaptic terminal during the first stimulus are still present when the second stimulus is delivered (3, 4). Several modes of action have been envisaged for the residual calcium. It could act by binding to high affinity sites of the normal exocytosis machinery (5), by binding to special sites responsible for facilitation (2, 6), or by modulating the degree of saturation of high affinity Ca 2ϩ buffers (7, 8), but direct evidence in favor of any of these possibilities is still lacking.Depression is a complex phenomenon including both pre-and postsynaptic components. It may involve depletion of a readily releasable pool of vesicles, saturation or desensitization of postsynaptic receptors, or still other processes (7, 9).Calcium-binding proteins such as parvalbumin (PV), calretinin, and calbindin D 28k are important modulators of intracellular calcium dynamics in neurons (10) and could therefore influence both facilitation and depression. Effects of these calcium buffers are determined by their affinities for Ca 2ϩ ions and by the kinetics (on and off rates) of binding and releasing of Ca 2ϩ . PV is in this regard interesting because it has a slow dissociation rate (about 1 s Ϫ1 ) and a slow apparent association rate (about 10 7 M Ϫ1 ⅐s Ϫ1 ), due to the fact that Mg 2ϩ ions compete with Ca 2ϩ ions for binding. As a result...