Peripheral serotoninergic response to physical exercise in athletic horses

The purpose of this study was to evaluate the influence of exercise on plasma tryptophan (TRP) and free serotonin (f5-HT), whole blood-5-HT (WB-5-HT) and f5-HT/WB-5-HT ratio in Italian Saddle horses. Six clinically healthy Italian Saddle horses were subjected to a 450 meters obstacles course. Blood samples were collected from each horse by jugular venipuncture using vacutainer tubes with K3-EDTA at rest, immediately after exercise, and after 30 min. TRP, f5-HT and WB-5-HT were analyzed by HPLC. Immediately after exercise, statistically significant increases of f5-HT (p<0.001) and WB-5-HT (p<0.001) were observed. After 30 min, f5-HT and WB-5-HT decreased compared to immediately after exercise, but were still significantly higher than rest values (p<0.01 and p<0.05, respectively). A significant linear regression between f5-HT and WB-5-HT was observed during experimental conditions. f5-HT and WB-5-HT modifications after exercise suggest an important role of peripheral serotoninergic markers in response to physical activity. The possible source of extra serotonin detected after show jumping should be clarified by further investigation

Serotonin Augments Gut Pacemaker Activity via 5-HT3 Receptors

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca2+ and electric activities in ICC were performed by employing fluorescent Ca2+ imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca2+ antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca2+ oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT3 receptor antagonist suppressed spontaneous Ca2+ activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT3 receptor agonist, restored it. GR113808, a selective antagonist for 5-HT4, and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT3 receptors, had little effect on ICC Ca2+ activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT3 receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT3 receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome

Retirement home? France’s migrant worker hostels and the dilemma of late-in-life return.

Unlike many of their North African and West African compatriots who reunified with family and settled in France in the 1970s and 80s, the decision of migrant worker hostel residents not to return definitively to places of origin at retirement is puzzling. Firstly, it calls into question the assumptions of the ‘myth of return’ literature, which explains non-return on the basis of family localisation. In the case of ‘geographically-single’ hostel residents, however, the grounds for non-return cannot be family localisation, since the men’s families remain in places of origin. Secondly, older hostel residents also remain unmoved by the financial incentives of a return homewards, where their French state pensions would have far greater purchasing power. Instead of definitive return, the overwhelming preference of hostel residents is for back-and-forth migration, between the hostel in France and communities of origin. The aim of this dissertation is to resolve this puzzle, by asking: What explains the hostel residents’ preference for back-and-forth mobility over definitive return at retirement? In order to make sense of these mobility decisions, several theories of migration are presented and evaluated against qualitative data from a multi-sited research design incorporating ethnography, life story and semi-structured interviews, and archive material. This fieldwork was carried out across France, Morocco and Senegal. Although no one theory adequately accounts for all the phenomena observed, the added value of each theory becomes most apparent when levels of analysis are kept distinct: at the household level as regards remittances; at the kinship/village level as regards re-integration in the home context; at the meso-level of ethnic communities in terms of migrants’ transnational ties; and at the macro-level of social systems concerning inclusion in healthcare and administrative organisations. Widening the focus beyond the puzzle/dilemma of late-in-life mobility, the thesis concludes by questioning what ‘home’ can mean for the retired hostel residents. An innovative way of theorising home – building on conventional conceptions of home based on territory and community – is outlined, arguing that to be ‘at home’ can also mean to be ‘included’ in different ‘social systems’. With this argument the thesis aims to contribute to broader debates on what it means for immigrants to belong and achieve inclusion in society