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Background: Pain is an unpleasant feeling which humans experience. It is a warning sign of the damaged tissue. Due to the awful sense of pain, scientists always attempt to relieve it. Retinoic acid (RT), an active metabolite of natural vitamin A has important roles in modulation of the inflammatory responses. The aim of the present study was to analyze the pain threshold of rats which had microinjections of RT, applying acute and chronic models. Methods and Materials: In this study, the tail flick and formalin tests were used to determine pain threshold. In each test, the acute and chronic pain thresholds of 252 Wistar male rats (275 ± 25 gr) were assayed. The druge were injected in the acute model one-dose30 minutes before behavioral testing and in chronic model two-dose for one or two-weeks. The rats of both models divided randomly into six groups (n=7). In four treatment groups retinoic acid (RT) intra cerebro ventricular (i.C.V) were injected as dosagc of 0.5, 3 and 6 (µg/kg) micrograms per kilogram. In control group, was microinjected by ACSF. In vehicle group injected RT solvent (DMSO+ Distil water). Results: The resuits Showed acute injection of RT did not change pain thresholds in the tail-flick methd, but the chronic administration of RT (0.5, 1, 3, 6 µg/kg) reduced tail-flick latencies of the rats (p<0.05) in compare to DMSO group. The threshold of pain in the first phase of formalin test was reduced after injection of 3µg/kg of RT for two weeks. Conclusion: It was concluded that chronic i.c.v. injections of RT can induce significant hyperalgesia in rat.

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Background: Retinoic acid (RA) is a vitamin A derivative and one of the most important inducing signals in vertebrates that is involved in differentiation, morphogenesis, apoptosis, and reproduction. This study was done to evaluate the role of RA in in vitro neural patterning of mouse embryonic stem cells (mESCs).

Materials and Methods: In this experimental study, upon formation, embryoid bodies (EBs) from mESCs, Royan B1, were induced by 1 µM RA for four days and then plated for eight days. Untreated EBs were considered as the control group. Finally, in both groups, neural induction and patterning of EB-derived neural cells were evaluated by using immunostaining, flowcytometry, and RT-PCR methods.

Results: RA induced neurogenesis in ES cells, from which 35% showed to express MAP2. RT-PCR analysis also indicated that RA-treated neural cells derived from ES cells could at the same time express Mash1, Pax6/7, and Dbx1/2 as dorso-ventral (DV) pattering markers and Hoxb4, Hoxc5, and Hoxc8 as the rostro-caudal (RC) axis markers.

Conclusion: RA induces in vitro neural induction along with neural patterning of ES-derived neural cells in DV and RC axes. Keywords: Mouse embryonic stem cells, neural patterning, retinoic acid

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Background: All-trans retinoic acid(RA), an active metabolite of vitamin A, is widely used to induce cell differentiation. It has significant effects on growth and proliferation of epithelial cells. It also causes cell cycle arrest in G0/G1 phase and induces the apoptosis. cisplatin, a chemotherapy compound that cross-linking to DNA, and leads to apoptosis, it is commonly used for treatment of ovarian, head and neck, esophageal, gastric cancers and melanoma. Recent studies showed that RA enhances cytotoxic effects of cisplatin on melanoma and ovarian cancer. Our literature review showed that there is no previous study on the effect of RA in combination with cisplatin on esophageal cancer, hence current study conducted to investigate such combination treatment on esophageal derived cell, KYSE-30.

Materials and Methods: KYSE30 cell line was cultured in presence of different concentration of RA alone and in combination with cisplatin. Then, cell death was investigated by colonogenic assay and acridine orange/ ethedium bromide staining.

Results: The results showed that RA concentrations &ge15µM cause differentiation of KYSE30 to squamous cell morphology, while lower concentrations decreases the colony formation (p&le0.05). These effects were also observed in combination with cisplatin and RA. The best effects on cell death were observed in 10 µM of RA of combination with 5 and 10 µg/ml of cisplatin.

Conclusion: The results suggest that low concentration of RA in combination with cisplatin are more effective than cisplatin alone in terms of apoptosis and necrosis of esophageal cancer, KYSE-30.

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