Implication of different domains of the Leishmania major metacaspase in cell death and autophagy.

Metacaspases (MCAs) are cysteine peptidases expressed in plants, fungi and protozoa, with a caspase-like histidine-cysteine catalytic dyad, but differing from caspases, for example, in their substrate specificity. The role of MCAs is subject to debate: roles in cell cycle control, in cell death or even in cell survival have been suggested. In this study, using a Leishmania major MCA-deficient strain, we showed that L. major MCA (LmjMCA) not only had a role similar to caspases in cell death but also in autophagy and this through different domains. Upon cell death induction by miltefosine or H2O2, LmjMCA is processed, releasing the catalytic domain, which activated substrates via its catalytic dyad His/Cys and a proline-rich C-terminal domain. The C-terminal domain interacted with proteins, notably proteins involved in stress regulation, such as the MAP kinase LmaMPK7 or programmed cell death like the calpain-like cysteine peptidase. We also showed a new role of LmjMCA in autophagy, acting on or upstream of ATG8, involving Lmjmca gene overexpression and interaction of the C-terminal domain of LmjMCA with itself and other proteins. These results allowed us to propose two models, showing the role of LmjMCA in the cell death and also in the autophagy pathway, implicating different protein domains.

Involvement of NO-synthase and nicotinic receptors in learning in the honey bee.

Restrained worker honey bees (Apis mellifera) are one of the main models for the comparative study of learning and memory processes. Bees easily learn to associate a sucrose reward to antennal tactile scanning of a small metal plate (associative learning). Their proboscis extension response can also be habituated through repeated sucrose stimulations (non-associative learning). We studied the role of nitric oxide synthase and nicotinic acetylcholine receptors in these two forms of learning. The nicotinic antagonist MLA or the nitric oxide synthase inhibitor l-NAME impaired the formation of tactile associative long-term memory that specifically occurs during multiple-trial training; however these drugs had no effect on single-trial training. None of the drugs affected retrieval processes. These pharmacological results are consistent with data previously obtained with olfactory conditioning and indicate that MLA-sensitive nicotinic receptors and NO-synthase are specifically involved in long-term memory. MLA and l-NAME both reduced the number of trials required for habituation to occur. This result suggests that a reduction of cholinergic nicotinic neurotransmission promotes PER habituation in the honey bee.

Antennal tactile learning in the honeybee: effect of nicotinic antagonists on memory dynamics.

Restrained worker honeybees (Apis mellifera L.) are able to learn to associate antennal-scanning of a metal plate with a sucrose reinforcement delivered to the mouthparts. Learning occurs reliably in a single association of the two sensory stimuli. The involvement of nicotinic pathways in memory formation and retrieval processes was tested by injecting, into the whole brain through the median ocellus, either mecamylamine (0.6 microg per bee) or alpha-bungarotoxin (2.4 ng per bee). Saline served as a control. Mecamylamine injected 10 min before the retrieval test impairs the retention level tested 3 h and 24 h after single- or multi-trial learning. Retrieval tests performed at various times after the injection show that the blocking effect of mecamylamine lasts about 1 h. The drug has no effect on the reconsolidation or extinction processes. Mecamylamine injected 10 min before conditioning impairs single-trial learning but has no effect on five-trial learning and on the consolidation process. By contrast, alpha-bungarotoxin only impairs the formation of long-term memory (24 h) induced by the five-trial learning and has no effect on medium-term memory (3 h), on single-trial learning or on the retrieval process. Hence, owing to previous data, at least two kinds of nicotinic receptors seem to be involved in honeybee memory, an alpha-bungarotoxin-sensitive and an alpha-bungarotoxin-insensitive receptor. Our results extend to antennal mechanosensory conditioning the role of the cholinergic system that we had previously described for olfactory conditioning in the honeybee. Moreover, we describe here in this insect a pharmacological dissociation between alpha-bungarotoxin sensitive long-term memory and alpha-bungarotoxin insensitive medium-term memory, the last one being affected by mecamylamine.

Effect of morphine on caloric intake and macronutrient selection in male and female Lou/c/jall rats during ageing.

Previous studies have showed a shift of preferences from carbohydrate to fat in the Lou/c/jall rat with advancing age when they are submitted to a self-selection procedure. Protein intake also decreased according to the age, earlier for males (after 16 months) than for females (29 months). The present study aimed at investigating the mechanism underlying these modifications. We analysed the effect of the reference mu agonist, morphine (5 mg/kg subcutaneous), on the caloric intake, body weight and macronutrient intake of 30 male and 30 female rats divided in four age groups: young adults (10), mature (17), old (24) and senescent rats (29 months). During the experiment, animals had the choice between separate sources of the three pure macronutrients. Morphine injection reduced total daily caloric intake and induced a decrease in body weight. The weight loss was age- and sex-related (males and old rats were more affected by the drugs). The injection of morphine evoked a triphasic influence on the chronology of the intake. A brief (1 h) hypophagia was followed by an hyperphagia (3 h) and a persistent hypophagia (8 h). No modification in the diet composition was observed. These results did not support a clear involvement of the opioid system concerning the modifications in macronutrient rates in diet previously observed across ageing.

Prevalence of psychological impairment in city and country samples.

A study was conducted of the psychological health of 125 married French women aged between 35 and 39 years, divided into five professional groups of 25 subjects. Two of these groups were taken from a rural area, three from Paris. The criteria of health have been psychiatric symptomatology, psychological impairment, and the frequency of the periods of impairment. A significant difference was found between the farmers and all the other groups. Differential data are also given regarding the medical assistance received by the groups.