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

Background: Listeria is a gram positive bacterium, facultive intracellular pathogene. Prf A gene has an important role in virulence. The purpose of this study was to determine of the presence of Listeria monocytogenes in various meat products and presence of prf A gene in bacteria isolated from food samples and compare them with clinical samples and standard samples.

Materials and Methods: During 6 months of 60 samples of beef, chicken, ham, cocktail, sausage, from a butchery’s Khoramabad and shops in Khoramabad and Tehran were collected. L. monocytogenes was isolated according to cold enrichment method and prf A gene were analyzed by PCR (polymerase chain reaction) method. Statistical analysis was performed with the software SPSS (statistical package for social science).

Results: From 60 samples of meat and meat products, 8 (13.3%) were positive for Listeria spp. Among in these samples, 4 cases of L. monocytogenes (6.6%), 3 cases (5%), L. innocua and 1 case (1.6%) L. welshimri, were isolated which L. innocua was isolated from meat and poultry samples and L. monocytogens from meat, chicken, ham and L. welshimeri from meat were isolated. Prf A gene was detected in isolated L. monocytogenes and donated bacteria from dairy products, clinical and standard samples, 2 cases of donated samples of vegetable contained prf A genes.

Conclusion: The prf A gene (activator of transcription and regulators the expression of other virulence genes), in the studied samples were observed. This gene plays a role in pathogenesis. Because these bacteria are transmitted through food and is a serious threat to public health. Thus identification of bacteria especially its genes could be possible to find some ways to prevent the bacteria and avoid disease from it.