Crosstalk between Bak/Bax and mTOR signaling regulates radiation-induced autophagy

Bax and Bak, act as a gateway for caspase-mediated cell death. mTOR, an Akt downstream effector, plays a critical role in cell proliferation, growth and survival. The inhibition of mTOR induces autophagy, whereas apoptosis is a minor cell death mechanism in irradiated solid tumors. We explored possible alternative pathways for cell death induced by radiation in Bax/Bak-/- double knockout (DKO) MEF cells and wild-type cells, and we compared the cell survival: the Bax/Bak-/- cells were more radiosensitive than the wild-type cells. The irradiated cells displayed an increase in the pro-autophagic proteins ATG5-ATG12 and Beclin-1. These results are surprising in the fact that the inhibition of apoptosis resulted in increasing radiosensitivity; indicating that perhaps autophagy is the cornerstone in the cell radiation sensitivity regulation. Furthermore, irradiation upregulates autophagic programmed cell death in cells that are unable to undergo Bax/Bak-mediated apoptosis. We hypothesize the presence of a phosphatase-possibly PTEN, an Akt/mTOR negative regulator that can be inhibited by Bax/Bak. This fits with our hypothesis of Bax/Bak as a downregulator of autophagy. We are currently conducting experiments to explore the relationship between apoptosis and autophagy. Future directions in research include strategies targeting Bax/Bak in cancer xenografts and exploring novel radiosensitizers targeting autophagy pathways.     

Physicochemical and Functional Properties of Typical Tunisian Drink: Date Palm Sap (Phoenix dactylifera L.)

The present work aimed to study the physicochemical characteristics and the functional properties of the male date palm sap (Phoenix dactylifera L.). The surface properties at the air–water interface were studied on the basis of the drop volume method. Foaming properties (foam capacity and stability) were evaluated using bubbling method by optical and conductimetric measurements (foamscan). Composition analysis revealed a high sugar content (92.29% w/w dry matter basis) with dominance of sucrose. Sap contains also 5.14% w/w of proteins and 2.57% w/w of ash. Proteins are probably the source of the surface activity and the observed foam power. At higher contents of dry matter, lyophilized sap solutions showed Newtonian comportment and improved surface activity and foam properties. Results present some interesting functional properties that suggest to deepen research particularly in sap proteins.     

Date seed oil limit oxidative injuries induced by hydrogen peroxide in human skin organ culture

The skin is chronically exposed to pro-oxidant agents, leading to the generation of reactive oxygen species (ROS). To protect the skin against an over-load of oxidant species, we studied the chemoprotective effect of one new natural product: "date seed oil: DSO". This oil may serve as a potential source of natural antioxidants such as phenols and tocopherols. Here, the antioxidative potential of DSO was compared that of to extra virgin olive oil. Adult human skin was maintained in organ culture in the presence of the DSO and extra virgin olive oil before the addition of hydrogen peroxide (H2O2), in order to prevent the tissue from its oxidizing effects. Skin specimens were collected for histology and for melanin studies. In the investigated model system, DSO protects skin against oxidative injuries. It has a significant chemoprotective effect, by inhibition of damage caused by H_{2}O_{2} compared with specimens without such addition endowing with a radical scavenging ability. The various components from DSO were much more potent antioxidant and more free radical scavengers of the H2O2 than those of olive oil. Our study shows that topical DSO treatment of the skin stimulates events in the epidermis leading to repair skin damage possibly due to antioxidant synergisms.     

Physiological and antioxidant responses of <Emphasis Type="Italic">Mentha pulegium</Emphasis> (Pennyroyal) to salt stress

Mentha pulegium L. is a medicinal and aromatic plant belonging to the Labiatae family present in the humid to the arid bioclimatic regions of Tunisia. We studied the effect of different salt concentrations on plant growth, mineral composition and antioxidant responses. Physiological and biochemical parameters were assessed in the plant organs after 2 weeks of salt treatment with 25, 50, 75 and 100 mM NaCl. Results showed that, growth was reduced even by 25 mM, and salt effect was more pronounced in shoots (leaves and stems) than in roots. This growth decrease was accompanied by a restriction in tissue hydration and K⁺ uptake, as well as an increase in Na⁺ levels in all organs. Considering the response of antioxidant enzymes to salt, leaves and roots reacted differently to saline conditions. Leaf and root guaiacol peroxidase activity showed an increase by different concentration of NaCl, but superoxide dismutase activity in the same organs showed a slight modification in NaCl-treated leaves and roots. Moreover, polyphenol contents and antioxidant activity were analysed in M. pulegium leaves and roots under salt constraint. The analysis showed an increase of total polyphenol content (2.41–8.17 mg gallic acid equivalent g⁻¹ dry weight) in leaves. However, methanol extract of leaves at 100 mM NaCl displayed the highest DPPH· scavenging ability with the lowest IC₅₀ value (0.27 μg ml⁻¹) in comparison with control which exhibited IC₅₀ equal to 0.79 μg ml⁻¹.     

Effect of age,pubertal stage and season on testosterone concentration in male dromedary camel

The present study was conducted in the Laboratory of Animal Physiology and Biotechnology, Department of Animal Production, Faculty of Agriculture, Mansoura University, Egypt. The present investigation aimed at studying effects of ages, pubertal stages and seasons of the year on testosterone concentrations in blood plasma and tissue homogenate of the testes. The testes used in the current study were collected from a total of 104 one-humped male camels (Camelus dromedarius). Samples were taken from pre (1–3.5 years) and post (3.5–13 years) pubertal camels. Testes were studied for a two consecutive seasons. The freshly prepared homogenate of the testicular tissue and blood plasma were used for determining the concentrations of testosterone in plasma and testicular extract. The concentrations of testosterone in blood plasma and testicular tissue were significantly increased during the breeding season compared with that of non-breeding season; the concentration of testosterone was higher in testicular tissue than in blood plasma.Testosterone concentrations in plasma and testicular tissue were increased in breeding than in non-breeding season. In addition, the testosterone concentrations were closely related with seasonal changes, stage of puberty and advancing age.     

Changes in benzodiazepine receptors in the limbic system following kindling of the olfactory bulb in rats

Repeated electrical stimulations of the olfactory bulb led to the progressive development of a generalized epilepsy (kindling effect). One week after the last stimulation eliciting a stage 5 seizure, diazepam-(3H) binding was studied in olfactory bulb-kindled rats. Numbers of benzodiazepine receptors were increased in kindled olfactory bulb and amygdala. No significant change was observed in hippocampus. This modification could be considered as a response of the inhibitory mechanisms to repeated seizures which is insufficient to counteract the installation of the kindling effect.     

Effects of constitutive heterochromatin and genotype on frequency and distribution of chiasmata in the seven individual rye bivalents

Summary Number and distribution of chiasmata were studied in the single pair of homologous rye chromosomes in 29 chromosomal F₁ hybrids between the seven disomic wheat rye addition lines of Chinese Spring/ Imperial and five selected inbred genotypes of cultivated rye by using the differential Giemsa staining technique. The results indicate that the number and position of chiasmata is independent from the amount and position of C-heterochromatin. Genotype had an effect on chiasma number, whereas chiasma distribution within bivalents appeared to be determined by morphological features of chromosomes. Late replicating DNA in constitutive heterochromatin may delay the separation of half bivalents if chiasmata are formed between them and the centromere.Supported by Deutsche Forschungsgemeinschaft, Bonn     

The organochlorine insecticide 1,2,3,4,5,6-hexachlorocyclohexane (lindane) but not 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) augments the nocturnal increase in pineal N-acetyltransferase activity and pineal and serum melatonin levels

The effect of organochlorine insecticides lindane (1,2,3,4,5,6-hexachlorocyclohexane) and DDT (1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane) were studied in terms of their effects on the rat pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity and pineal and serum melatonin levels during the day (2000h) and at night (2300 and 0100h). Additionally, pineal levels of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) were estimated. Nocturnal NAT activity was increased after lindane administration; likewise, lindane augmented pineal and serum melatonin levels at 2300h. Conversely, DDT was without a statistically significant effect on either NAT activity or on pineal or serum melatonin levels. Neither lindane nor DDT significantly influenced pineal HIOMT values either during the day or at night. Likewise, neither insecticide consistently influenced pineal levels of either 5-HTP, 5-HT or 5-HIAA. The results indicate that the organochlorine insecticide, lindane, modifies pineal melatonin synthesis in vivo.