Acceleration of serotonin transporter transport-associated current by 3,4-methylenedioxymethamphetamine (MDMA) under acidic conditions

3,4-Methylenedioxymethamphetamine (MDMA) selectively releases serotonin (5-HT) from neurons after uptake by the serotonin transporter (SERT) and causes psychostimulant effects accompanied by hyperthermia. Since rapid increases in CNS lactate levels are suggested in response to MDMA, we investigated the effects of the physiologically-relevant increase in H(+) concentration on the two conducting states of SERT expressed in Xenopus oocytes. Perfusion with SERT substrates at pH 7.4 dose-dependently evoked a transport-associated inward current response with the following rank order of potency: 5-HT>MDMA>dopamine>>norepinephrine. In the absence of transport substrates, a step hyperpolarization pulse activated a transient Na(+) leak current, which was inhibited by SERT substrates with the same rank, as well as by a SERT inhibitor, citalopram. At pH 6.4, the K(m) values of 5-HT and dopamine for the transport-associated current were not altered, while that of MDMA was three-fold lower. In contrast, the K(i) values of all these substrates for transient leak current were unchanged at pH 6.4, suggesting that the affinities to SERT binding sites are not influenced. These results suggest that the effect of MDMA on SERT is enhanced by acidic conditions.

Sperm DNA fragmentation: awakening the sleeping genome

We have recently demonstrated that mammalian spermatozoa have the ability to degrade their DNA by a mechanism that is similar to apoptosis in somatic cells. When this mechanism is activated, the DNA is first degraded into loop-sized fragments by TOP2B (topoisomerase IIB). This degradation, termed sperm chromatin fragmentation, can be reversed by EDTA, which causes TOP2B to religate the double-stranded breaks it originally produced. Under certain conditions, a nuclease then degrades the sperm DNA further, digesting the entire sperm genome. When mouse spermatozoa which have been treated to induce TOP2B-mediated DNA breaks are injected into oocytes, the paternal DNA is specifically and completely degraded. This total digestion of paternal DNA occurs at the time of DNA synthesis initiation. In the present study, we explore the significance of an active TOP2B in the nucleus for mouse sperm function.

Nematode infection in Alymphoplasia (aly) mice: worm species-dependent differential effect of defects of the gut-associated lymphatic tissue system

Mice homologous for the alymphoplasia mutation (aly) show the systemic absence of secondary lymphoid tissues, with disorganized splenic architecture, including the absence of the germinal centre and follicular dendritic cells. In this study, we examined the influence of defects of gut-associated lymphoid tissue (GALT), such as Peyer's patches and the mesenteric lymph nodes, on the host response to helminth infection in aly/aly mice. The present study showed that most of the worms were expelled by day 7 after Nippostrongylus brasiliensis infection in both control aly/+ and aly/aly mice. In aly/aly mice, the number of peripheral blood eosinophils, intestinal goblet cells and mucosal mast cells were increased by N. brasiliensis infection in aly/aly mice to the same level as in the controls. Conversely, aly/aly mice developed more severe Heligmosomoides polygyrus infections than control aly/+ mice, as demonstrated by increased faecal egg counts, with reduced immune responses such as the numbers of intestinal goblet cells and mucosal mast cells. These results suggested that the dependency of GALT in activation of Th2 responses against gastrointestinal nematodes was different depending on the species of nematode.

An analysis of flow volume curves during artificial ventilation

Expiratory flow-volume curves during artificial ventilation (FV-av) were analyzed in 48 patients undergoing general anesthesia. They were divided into 4 groups according to preoperative respiratory disorders; obstructive type (group 1), restrictive type (group 2), small airway disease (group 3) and normal control (group 4). Expiratory flow rates and volumes during artificial ventilation were plotted on an X-Y recorder to calculate V50/V25, mean time constant ratio (MTCR), obstructive index (OI) and slope ratio (SR). FV-av values were compared among groups. FV-av values in groups 2 were significantly higher than those in group 4. The values in group 1 and those in group 3 were not significantly different from those in group 4. FV-av values may reflect restrictive respiratory dysfunctions but they are not sensitive enough to detect obstructive lung disease.

Spin dependence in the survival probability of metastable He (2(3)S) atoms during the scattering from ferromagnetic surfaces

The use of a spin-polarized metastable helium (He(*)) atom beam has demonstrated that the survival probability (SP) of He(*) during the scattering from ferromagnetic surfaces depends on the electron spin of He(*). The spin asymmetry in the SP of He(*) scattered from a clean Fe/Cu(100) surface changed its polarity with H2O adsorption. We argue that the reversal is caused by the change in the spin polarization of the surface electronic states at around the Fermi level.