Cell and Tissue Journal

Abstract In daily life, stress in one of the important and potent modulators of behaviour. Inhibitory or faciliatory effects of acute and chronic stress exposure on memory performance (acquisition, consolidation and retrieval) have shown in previous researches. Under such circumstances, the levels of (nor) epinephrine (NE) rapidly increases in the memory related area including hippocampus and amygdala. Along with NE, the hypothalamic-pituitary-adrenocortical axis activates. Glocorticoids (GCs) hormones are the main end-products of the HPA axis activation. In different animal models have been shown that NE and glocorticoids mediate the modulatory effect of stress on memory. Microglia that originally form in the yolk sac are immune cells in the central nervous system and act as the brain's first line of cellular defense against various pathogens. These cells release inflammatory mediators and neurotrophic factors and also phagocytes cellular debris. In addition, are also shown to play a role in the development of brain. During embryonic development, microglia remove apoptotic cells and regulate synaptic pruning. These cells play an essential role in regulating of synapse regeneration, neurogenesis, synaptic function, angiogenesis and myelination. They are dynamic cells in the adult brain and have the ability to rapidly change their morphology to properly respond to the functional needs of the brain. Microglia is activated in M1 and M2 phenotype. M1 microglia activation is induced by gamma interferon and LPS and promotes inflammation via release of inflammatory mediators such as tumor necrosis factor alpha (αTNF) and interleukins. M2 activation mainly is related to secretion of glucocorticoids, extracellular matrix proteins and anti-inflammatory cytokines. It has been reported that microglia as a key regulator of neuronal function have NE and GCs receptors, suggesting a critical role of these brain cells in modulating stress effects. Several lines of studies indicates that microglia regulate learning and memory via the formation and stability of synapses. Microglia actively contribute in synaptic pruning via classical complement cascade mechanism. Apoptotic, immature or poorly growing synapses are labeled with complement components, C1q and C3. Microglia recognize these complement components through the complement receptor CR3 and eliminate C1q and C3-labeled synapses. Microglia also detect and remove inactive synapses by the triggering receptor expressed on myeloid cells 2 (TREM2) consequently regulate brain connectivity and activity. Moreover, microglia regulatory negative feedback mechanism prevents neuron hyperactivity. Microglia play an important role in the stability of long-term potentiation. In addition, microglial fractalkine signaling is potentially involved in LTD. The number and morphology of hippocampal microglia is altered in response to chronic stress exposure thus consequently becomes reactive phenotype. This effect is mediated via stress hormones. Evidence show that stress also affect expression of microglial genes (cytokines, TNF-α and interleukins) that have regulatory role in learning and memory. Microglial–neuronal crosstalk which is crucial for memory processing is another site for stress-induced memory changes. Moreover, stress exposure alters glutamate transmission through negative effect on kynurenine pathway. These effects support the involvement of microglia in destructive effect of stress on memory. In this review article, focusing on newly published articles, we examine the role of microglia in synaptic plasticity, learning and memory, and especially the role of activated microglia in the effects of stress on learning and memory. By examining these processes, our aim is to provide an overview of the role of microglia in synaptic plasticity and learning and memory, and the possibility of using microglia targeting as a therapeutic method to improve cognitive deficits associated with stressful conditions

Abstract Aim: In this study the effects of stress on induction of structural chromosomal abnormalities on L929 cell line using micronucleus assay on cytokinesis-blocked binucleated cells were investigated in vitro. Material and methods: L929 cells were cultured in DMEM containing 10% FBS. The cells were divided into four groups including; control, 2Gy gamma-irradiated cells, and cells treated with doses of 25, 50 and 100 µg/ml hydrocortisone, and cells co-treated with these three doses of hydrocortisone and irradiation. The treated cells were harvested, stained and chromosome abnormalities were scored using micronucleus assay. Results: Results showed that hydrocortisone did not induce micronuclei as compared to the control group. However, the frequency of micronuclei in cells co-treated with doses of hydrocortisone and irradiation was significantly higher than cells treated only with gamma irradiation (p < 0.05). Conclusion: According to the data of this study, stress hormones are not able to induce any chromosomal abnormalities; however, they are able to increase the cell susceptibility to clastogenic effects of irradiation. Key words: Stress, Hydrocortisone, L929, Gamma ray, Micronucleus      

Abstract Aim: The purpose of this study was to evaluate the effects of sub-lethal osmotic stress (325, 350, 375 and 400 mOsm) during cryopreservation in commercially diluter medium (Bioexcell) on Holstein mail cow sperm qualitative characters after freezing-thawing. Material and Methods: Semen was collected from four Holstein mail cows using artificial vagina two times for a week. All of obtained semen mixed together and then were divided into five equal parts. Each part was freeze-melted according to the experimental treatments consisting of different osmotic stresses. 300 mOsm treatment medium was applied as control group. Sperms motility and progressive motility were assessed by computer assessment semen analysis. Also sperms viability, membrane integrity, mitochondria activity and membrane lipid peroxidation of frozen-thawed semen were assessed using Eosin-Nigrosin, hypo osmotic swelling test, Hankok, Rhodamin 123 and TBA procedures, respectively. Results: Results showed that 375 mOsm osmotic stress treatment had the most significant improvement of motility%, progressive motility and viability in comparison with other treatments. Also mitochondria activity in 350 and 375 mOsm osmotic pressures treatments was significantly higher than other experimental treatments (p < 0.05). Different osmotic stresses treatments did not show significant effect on sperm morphology and membrane lipid proxidation. Conclusion: It is seemed that mild and sub-lethal osmotic stresses induction in cow sperm freezing diluters can significantly improved some of sperm qualitative characters such as their motility and viability.

Abstract Aim: The purpose of this study was to consider the effect of mild oxidative stress period on the frozen-thawed bull semen performance.
Material and Methods: In this study, 120 minutes was considered for equilibration of sperm before freezing. One µm of Nitric Oxide (NO) at the 0, 45, 90 and 120 cooling period was added to the diluant before cryopreservation. Sperm motion parameters, plasma membrane integrity, acrosome integrity, viability, apoptosis and mitochondria activity were assessed.
Results: Induction of oxidative stress with nitric oxide in the T0 and T45 groups led to significant improvement of total (88.4 ± 2.8, 84.7 ± 2.7) and progressive motility (50.4 ± 2.5, 49.5 ± 2.5) when compared to other groups. Percentage of plasma membrane integrity and viability were not different in T0 (74.4 ± 2.9 and 85.6 ± 2.9) and T45 (75.6 ± 2.9 and 84.6 ± 2.3) groups, where as it was significantly higher when compared with T90 (63.6 ± 2.9 and 69.6 ± 2.3) and T120 (61.5 ± 2.9 and 54 ± 2.3). Moreover, the highest significant percentage of spermatozoa with active mitochondria was observed in the T0 (82.5 ± 3.1) when compared with T45 (65.7 ± 3.1), T90 (42 ± 3.1) and T120 (43 ± 3.1). Acrosome integrity and linearity of sperm were not affected by the oxidative stress treatment time.
Conclusion: It seems that applying oxidative stress using 1 µM NO would improve post-thawed bull sperm quality at the T0 and T45 time of cooling.

Abstract Aim: In this study, the effect of salt stress on PSII of Dunaliella bardawil as a photosynthesis species model was invesigated to determines more effects of this stress and appropriate solutions to salt stress.
Material and methods: In this study, OJIP-test method was used for analyzing of chlorophyll a fluorescence under stress. Different concentrations of NaCl, 1 to 2 M and 1 to 3 M, were applied at light and dark conditions.
Results: The results showed in both light and dark regimes, the rate of Fv/Fo, Φ_Po, ψ_o , Φ_Eo, Φ_Ro and PI_ABS were reduced by salt stress of 1 to 3 M NaCl at primary hours after salt stress while Φ _Do was increased. After first hours, the efficiency of PSII did not increased in dark regime unlike the samples in light condition.
Conclusion: According to the results, salt stress led to reduction of water-splitting complex activity and the function of other electron acceptor in PSII. The rate of electron transport to pheophytin, Q_A, Q_B and the other electron acceptors is also reduced. Hence it could be finalized that water-splitting complex is the first site damaged by salt stress. On the other hand, studying on salt stress under light and dark regimes showed that light accompanied by the other mechanisms such as photosynthesis and chlorophyll production increase the efficiency of algae system and recover to the condition before stress.