Exercise training (ET) is well established to induce vascular adaptations on the metabolically active muscles. These adaptations include increased function of vascular potassium channels and enhanced endothelium-dependent relaxations. However, the available data on the effect of ET on vasculatures that normally constrict during exercise, such as mesenteric arteries (MA), are scarce and not conclusive. Therefore, this study hypothesized that 10 weeks of moderate-intensity ET would result in adaptations towards more vasoconstriction or/and less vasodilatation of MA. Young Fischer 344 rats were randomly assigned to a sedentary group (SED; n=24) or exercise training group (EXE; n=28). The EXE rats underwent a progressive treadmill ET program for 10 weeks. Isometric tensions of small (SED; 252.9±29.5 µm, EXE; 248.6±34.4 µm) and large (SED; 397.7±85.3 µm, EXE; 414.0±86.95 µm) MA were recorded in response to cumulative phenylephrine concentrations (PE; 0-30 µM) in the presence and absence of the BKCa channel blocker, Iberiotoxin (100 nM). In another set of experiments, tensions in response to cumulative concentration-response curves of acetylcholine (ACh) or sodium nitroprusside (SNP) were obtained, and pEC50s were compared. Immunoblotting was performed to measure protein expression levels of the BKCa channel subunits and eNOS. ET did not alter the basal tension of small and large MA but significantly increased their responses to PE, and reduced the effect of BKCa channels in opposing the contractile responses to PE without changes in the protein expression level of BKCa subunits. ET also elicited a sizedependent functional adaptations that involved reduced endothelium-independent and endothelium-dependent relaxations. In large MA the sensitivity to SNP was decreased more than in small MA suggesting impaired nitric oxide (NO)-dependent mechanisms within the vascular smooth muscle cells of ET group. Whereas the shift in pEC50 of ACh-induced relaxation of small MA would suggest more effect on the production of NO within the endothelium, which is not changed in large MA of ET group. However, the eNOS protein expression level was not significantly changed between the ET and SED groups. In conclusion, our results indicate an increase in contraction and reduced relaxation of MA after 10 weeks of ET, an adaptation that may help shunt blood flow to metabolically active tissues during acute exercise.
Secondary labour markets usually involve job positions with forced flexibility and non-standard working conditions (part-time contracts, fixed-term contracts, work without a contract). They are characterized by no advancement prospects or opportunities for further education, exhausting physical work with inadequate wages and job insecurity, and a frequently long and tiring commute. The working conditions in this sector of the labour market often contribute to marginalization and then to the social exclusion of those who happen to be caught long term in this sector of the labour market instead of preventing and saving them from the risk of marginalization and social exclusion. One of the ways in which secondarization occurs is the universal introduction of part-time contracts in a particular sector of the labour market which then becomes an involuntary trap of underemployment, underpaid wage, insecurity and discrimination. The profession of cashier in foreigner retail chains is an example of such a development. This qualitative study shows the step by step degradation of the employment conditions in this sector and how the lives of women and men working in the sector have deteriorated. At the same time, the condition and status of the profession overall are declining. This phenomenon is referred to as the "secondarization" process, Marcel Tomášek, Radka Dudová., and Obsahuje bibliografii