Midbrain circuits that set locomotor speed and gait selection.

Locomotion is a fundamental motor function common to the animal kingdom. It is implemented episodically and adapted to behavioural needs, including exploration, which requires slow locomotion, and escape behaviour, which necessitates faster speeds. The control of these functions originates in brainstem structures, although the neuronal substrate(s) that support them have not yet been elucidated. Here we show in mice that speed and gait selection are controlled by glutamatergic excitatory neurons (GlutNs) segregated in two distinct midbrain nuclei: the cuneiform nucleus (CnF) and the pedunculopontine nucleus (PPN). GlutNs in both of these regions contribute to the control of slower, alternating-gait locomotion, whereas only GlutNs in the CnF are able to elicit high-speed, synchronous-gait locomotion. Additionally, both the activation dynamics and the input and output connectivity matrices of GlutNs in the PPN and the CnF support explorative and escape locomotion, respectively. Our results identify two regions in the midbrain that act in conjunction to select context-dependent locomotor behaviours.

The histamine H3 receptor antagonist thioperamide rescues circadian rhythm and memory function in experimental parkinsonism.

Parkinson's disease (PD) is a common neurodegenerative disorder, characterized by motor impairment and a wide range of non-motor symptoms, including sleep disorders and cognitive and affective deficits. In this study, we used a mouse model of PD based on 6-hydroxydopamine (6-OHDA) to examine the effect of thioperamide, a histamine H3 receptor antagonist, on circadian activity, recognition memory and anxiety. A partial, bilateral 6-OHDA lesion of the striatum reduces motor activity during the active phase of the 24 h cycle. In addition, the lesion disrupts the endogenous circadian rhythm observed when mice are maintained in constant darkness. Administration of thioperamide to 6-OHDA-lesion mice rescues the normal rest/activity cycle. Moreover, thioperamide counteracts the deficit of novel object recognition produced by 6-OHDA. Our experiments show that this memory impairment is accompanied by disrupted gamma oscillations in the hippocampus, which are also rescued by thioperamide. In contrast, we do not observe any modification of the anxiogenic effect of 6-OHDA in response to administration of thioperamide. Our results indicate that thioperamide may act as a multifunctional drug, able to counteract disruptions of circadian rhythm and cognitive deficits associated with PD.

Expression of trypsin-like serine peptidases in pre-imaginal stages of Aedes aegypti (Diptera: Culicidae).

This study reports the biochemical characterization and comparative analyses of highly active serine proteases in the larval and pupal developmental stages of Aedes aegypti (Linnaeus) using substrate-SDS-PAGE. Zymographic analysis of larval stadia detected proteolytic activity in 6-8 bands with apparent molecular masses ranging from 20 to 250 kDa, with activity observed from pH 5.5 to 10.0. The pupal stage showed a complex proteolytic activity in at least 11 bands with apparent Mr ranging from 25 to 250 kDa, and pH optimum at 10.0. The proteolytic activities of both larval and pupal stages were strongly inhibited by phenyl-methyl sulfonyl-fluoride and N-α-Tosyl-L-lysine chloromethyl ketone hydrochloride, indicating that the main proteases expressed by these developmental stages are trypsin-like serine proteases. The enzymes were active at temperatures ranging from 4 to 85°C, with optimal activity between 37 and 60°C, and low activity at 85°C. Comparative analysis between the proteolytic enzymes expressed by larvae and pupae showed that substantial changes in the expression of active trypsin-like serine proteases occur during the developmental cycle of A. aegypti.

Serine protease activities in Oxysarcodexia thornax (Walker) (Diptera: Sarcophagidae) first instar larva

We report for the first time the expression of multiple protease activities in the first instar larva (L1) of the flesh fly Oxysarcodexia thornax (Walker). Zymographic analysis of homogenates from freshly obtained L1 revealed a complex proteolytic profile ranging from 21.5 to 136 kDa. Although some activities were detected at pH 3.5 and 5.5, the optimum pH for most of the proteolytic activities was between pH 7.5 and 9.5. Seven of 10 proteases were completely inactivated by phenyl-methyl sulfonyl-fluoride, suggesting that main proteases expressed by L1 belong to serine proteases class. Complete inactivation of all enzymatic activities was obtained using N-p-Tosyl-L-phenylalanine chloromethyl ketone (100 µM), a specific inhibitor of chymotrypsin-like serine proteases.

Insights into the role of gp63-like proteins in lower trypanosomatids.

Any actual understanding of trypanosomatids in general requires a comprehensive analysis of the less-specialized species as thorough as our knowledge of the more specialized Leishmania and Trypanosoma. In this context, we have shown by antibody cross-reactivity that purified extracellular metallopeptidases from Phytomonas françai, Crithidia deanei (cured strain) and Crithidia guilhermei share common epitopes with the leishmanial gp63. Flow cytometry and fluorescence microscopy analyses indicated the presence of gp63-like molecules on the cell surface of these lower trypanosomatids. Binding assays with explanted guts of Aedes aegypti incubated with purified gp63 and the pretreatment of trypanosomatids with anti-gp63 antibodies indicated that the gp63-like molecules are involved in the adhesive process of these trypanosomatids to the A. aegypti gut wall. In addition, our results indicate for the first time that the gp63-like molecule binds to a polypeptide of 50 kDa on the A. aegypti gut epithelium extract.