Distribution of phenolic compounds and antioxidant activity between young and old leaves of Carthamus tinctorius L. and their induction by salt stress

In the present work, we investigated the effect of salt stress on the distribution of safflower (Carthamus tinctorius L.) antioxidant system in relation to leaf age. The study was carried out under growth chamber conditions using seedlings of three cultivars which were subjected to 0 and 50 mM NaCl for 3 weeks. Leaf growth, water content, lipid peroxidation, and phenolic compound (total polyphenols, total flavonoids, and proanthocyanidins) concentration were measured at two leaf stages (young and old leaves). Leaf growth was affected by salinity only in Kairouan cultivar that also showed a significant decrease in old leaf water content. By contrast, Gabes and Tazarka cultivars maintained their old leaf water content constant and showed a reduction in that of young leaves. This could be attributed to a higher aptitude of the latter two cultivars to use absorbed sodium and chloride for osmotic adjustment in old leaves, keeping potassium for specific functions. Salt-induced lipid peroxidation was observed only in old leaves, whereas the accumulation of the major phenolic compounds under saline conditions was higher in young leaves, except in Gabes cultivar where no significant difference was found between the two leaf stages. A significant variability was also found between the three cultivars. The better behavior of salt-challenged leaves of Gabes and Tazarka cultivars compared to that of Kairouan cultivar may be related to their higher water content and the accumulation of polyphenols, in particular flavonoids that were shown to be efficiently involved in the restriction of salt-induced oxidative damages.     

Fibroblasts from long‐lived species of mammals and birds show delayed,but prolonged,phosphorylation of ERK

Fibroblasts from long‐lived mutant mice show diminished phosphorylation of the stress‐activated protein kinases ERK1/2 after exposure to peroxide, cadmium, or paraquat. We have now evaluated the kinetics of ERK phosphorylation in fibroblasts from long‐lived and short‐lived species of mammals and birds in response to stress by cadmium or hydrogen peroxide. Fibroblasts from the shorter‐lived species of rodents and birds showed rapid induction of ERK phosphorylation, with a decline to basal level within 60 min. In contrast, cells from longer‐lived species showed slower and more prolonged activation of ERK phosphorylation. These results suggest that fibroblasts from long‐lived species may be less susceptible to the early phases of damage from cadmium or peroxide and suggest that altered kinetics of ERK activity may contribute to their stress resistance properties.     

Circadian variation in hepatic toxicity of the immunosuppressive agent “Mycophenolate Mofetil” in rats

Immunosuppressive drugs may have varying toxicity or efficacy depending on the administration time. This study investigates whether the liver toxicity of the mycophenolate mofetil (MMF) varies according to the circadian dosing-time in rats. 300 mg/kg of MMF was injected by intraperitonal route to different groups of animals at four different circadian stages (1, 7, 13, and 19 h after light onset, HALO). Biochemical variable (transaminase, alkaline phosphatase) and histopathological examinations on liver section were performed. The results obtained showed that MMF treatment induced hepato-toxicity depending on the circadian time. A severe toxicity in the liver was observed when the drug was injected at 7 HALO. The data obtained indicate that the maximum of hepato-toxicity is observed when MMF was injected in the middle of the light-rest span of rats which is physiologically analogous to the end of the activity of the diurnal phase in human patients.     

The necroptotic cell death pathway operates in megakaryocytes,but not in platelet synthesis

Necroptosis is a pro-inflammatory cell death program executed by the terminal effector, mixed lineage kinase domain-like (MLKL). Previous studies suggested a role for the necroptotic machinery in platelets, where loss of MLKL or its upstream regulator, RIPK3 kinase, impacted thrombosis and haemostasis. However, it remains unknown whether necroptosis operates within megakaryocytes, the progenitors of platelets, and whether necroptotic cell death might contribute to or diminish platelet production. Here, we demonstrate that megakaryocytes possess a functional necroptosis signalling cascade. Necroptosis activation leads to phosphorylation of MLKL, loss of viability and cell swelling. Analyses at steady state and post antibody-mediated thrombocytopenia revealed that platelet production was normal in the absence of MLKL, however, platelet activation and haemostasis were impaired with prolonged tail re-bleeding times. We conclude that MLKL plays a role in regulating platelet function and haemostasis and that necroptosis signalling in megakaryocytes is dispensable for platelet production.Subject terms: Necroptosis, Experimental models of disease     

Different antioxidant responses to salt stress in two different provenances of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> L.

Seedlings of two Tunisian Carthamus tinctorius L. provenances (Kairouan and Tazarka) differing in salt sensitivity were hydroponically grown at 0 and 50 mM NaCl over 21 days. Leaves of Kairouan (salt-sensitive) showed a 48% restriction in their growth at 50 mM NaCl although they accumulated less sodium than those of Tazarka (less salt-sensitive) that maintained an unchanged growth. Salt treatment induced oxidative stress in C. tinctorius and the effect was more pronounced in the leaves of the more salt sensitive provenance, Kairouan. Both provenances exhibited a stimulation of antioxidant enzyme activities with higher catalase (CAT) and superoxide dismutase (SOD) activities in Tazarka and higher peroxidase (POD) activity in Kairouan. But, it seems that antioxidant activities were more correlated with polyphenol content. Actually, leaves of Tazarka experienced higher polyphenol and antioxidant activity than Kairouan at 50 mM NaCl. Hence, moderate salinity (3 g NaCl L⁻¹) enhanced bioactive molecule yield in the less salt sensitive provenance, Tazarka. In addition, C. tinctorius was found rich in ascorbic acid, but the moderate salt stress enhanced its production only in the sensitive provenance.     

Relative growth and reproductive cycle in two populations of <Emphasis Type="Italic">Bolinus brandaris</Emphasis> (Gastropoda: Muricidae) from northern Tunisia (Bizerta Lagoon and small Gulf of Tunis)

A study on the relative growth and reproductive cycle of the purple dye murex (Bolinus brandaris) was performed from March 2007 to February 2008 in two populations with contrasting imposex levels (Carthage Byrsa — CB in the small Gulf of Tunis and Menzel Abderrahmane — MA in the Bizerta Lagoon). Both populations presented balanced sex ratios. Comparison of allometric relationships established between linear and ponderal variables (sexes confounded) revealed higher growth in CB than in MA. Mature individuals were found throughout the year, except for September in MA. Spawning periods occurred from March–April to May and from June to August in both sites. Spawning was associated to an increase in seawater temperature. Besides increasing the current knowledge on the biology of B. brandaris from the southern Mediterranean, the information gathered in the present study constitutes a useful baseline for the sustainable management of local wild stocks, namely by prohibiting collection of snails during the spawning season.     

Transmission of visceral leishmaniasis in a previously non‐endemic region of Tunisia: Detection of Leishmania DNA in Phlebotomus perniciosus

Visceral leishmaniasis (VL) has been endemic in northern Tunisia and has occurred sporadically in the center of Tunisia. Recently, there have been several cases from areas known to be free of VL. We report in this work all human and canine cases of VL recorded between 2003 and 2011 and an entomological study of phlebotomine fauna in a previously non‐endemic region. Sixty‐three cases of VL were diagnosed and identified as L. infantum using several different methods. Eight species of 179 sand flies were caught and identified by both morphological and molecular methods. Two genera were present, Phlebotomus and Sergentomya, with an abundance of the subgenus Phlebotomus (Larrousius) spp., a classic vector of VL in Tunisia. Moreover, Leishmania DNA was detected in seven unfed Phlebotomus pernicousus and L. infantum was identified in three of them. This result confirms the establishment of a transmission cycle of VL in the studied region by the coexistence of infected vectors with infected hosts.