Effect of Cocaine on the Histaminergic Neuron System in the Rat Brain

Abstract: To examine the effect of cocaine on the brain histamine neuron system, histamine levels and histamine N -methyl-transferase activity in the rat brain were measured after the administration of cocaine. Moreover, we examined the effect of l -histidine on cocaine-induced wheel-running behavior. The administration of cocaine (20 mg/kg) increased histamine levels and histamine N -methyltransferase activity in the striatum, nucleus accumbens, and amygdala 1 h later. The pretreatment with l -histidine (350 and 700 mg/kg) inhibited the cocaine (20 mg/kg)-induced increase of wheel-running activity in a dose-dependent manner. These findings suggest that cocaine activates the brain histamine neuron system, which may play the role of inhibiting the cocaine-induced wheel-running behavior.     

Different recognition of transgenic HLA-DQw6 molecules by mouse CD4+ and CD8+ T cells

Address correspondence and offprint requests to: T. Sasazuki.     

Dextransucrase as an Enzyme Associating with Alkaline Earth Metal Ions

Dextransucrase (EC. 2.4.1.5) of Leuconostoc mesenteroides was purified from the culture filtrate by precipitation with solid ammonium sulfate in the presence of egg white albumin followed by successively treating with columns of DEAE-cellulose and Bio Gel P-150.

The purified enzyme lost the activity upon dialysis against EDTA, and was reactivated by the addition of alkaline arth metal ions. The best reactivation was brought about by calcium ion. The enzyme inactivated by EDTA was unstable and readily denatured irreversibly. Several other properties of the purified enzyme were also investigated and discussed.     

Detecting spatial interactions in the ragweed (<Emphasis Type="Italic">Ambrosia artemissifolia</Emphasis> L.) and the ragweed beetle (<Emphasis Type="Italic">Ophraella communa</Emphasis> LeSage) populations

We observed a weed (Ambrosia artemissifolia)–beetle herbivore (Ophraella communa) system for three years in a spatially continuous field (≈200 ha). We analyzed our field data in the light of two contrasting theories: the resource-concentration hypothesis and reaction–diffusion theory. For the resource-concentration hypothesis, we calculated the correlation coefficients between weed and beetle abundances for every season in each year. Although we found weak support for resource concentration in some seasons, we could not find any clear relationships in other seasons. We discuss a dispersal-based mechanism to explain the differences observed among seasons in lieu of the resource-concentration hypothesis. For the reaction–diffusion theory, we estimated the nonparametric spatial covariance functions for the spatial autocorrelation of weeds and beetles. Although we could not find any strong spatial structure for the individual species, we found evidence of spatial interactions between weeds and beetles using time lagged cross-correlation functions. Weed abundance enhanced local beetle abundance. Through time, there was evidence of beetle spillover to adjacent locations at roughly the one beetle-generation time scale. Sites with large number of beetles did not seem to reduce subsequent weed abundance.     

Synovial Mononuclear Cells Consist with T Cells Which Produce High Levels of Tumor Necrosis Factor α

To determine whether synovial mononuclear cells include a population of tumor necrosis factor α-produeing T cells, we measured tumor necrosis α levels in culture supernatants of synovial mononuclear cells by ELISA and analyzed tumor necrosis α mRNA-positive cell frequencies. There were no significant differences in the spontaneous levels of TNF α between synovial mononuclear cells and peripheral mononuclear cells. The frequency of tumor necrosis factor α mRNA-positive cells in synovial mononuclear cells was higher than that of peripheral mononuclear cells. When stimulated with a superantigen, mononuclear cells from the synovial fluid of rheumatoid arthritis patients showed higher levels of tumor necrosis factor α production (1,035 ± 817 pg/ml) than did mononuclear cells from their peripheral blood (236 ± 180 pg/ml). In addition, we observed that a few T cell clones were resistant to superantigenic restimulation in vitro. We conclude that when these types of T cells persist in the synovium, they play a role in the development of rheumatoid arthritis via a mechanism involving tumor necrosis factor α production.