PREGNANCY IS A COMPLEX AND WELL-REGULATED TEMPORAL EVENT IN WHICH SEVERAL STEPS ARE FINELY ORCHESTRATED INCLUDING IMPLANTATION, DECIDUALIZATION, PLACENTATION, AND PARTUM AND ANY TEMPORARY ALTERATION HAS SERIOUS EFFECTS ON FETAL AND MATERNAL HEALTH. INTERESTINGLY, ALTERATIONS OF CIRCADIAN RHYTHMS (I.E., SHIFTWORK) HAVE BEEN CORRELATED WITH INCREASED RISK OF PRETERM DELIVERY, INTRAUTERINE GROWTH RESTRICTION, AND PREECLAMPSIA. IN THE LAST FEW YEARS EVIDENCE IS ACCUMULATING THAT THE PLACENTA MAY HAVE A FUNCTIONAL CIRCADIAN SYSTEM AND EXPRESS THE CLOCK GENES BMAL1, PER1-2, AND CLOCK. ON THE OTHER HAND, THERE IS EVIDENCE THAT THE HUMAN PLACENTA SYNTHESIZES MELATONIN, HORMONE INVOLVED IN THE REGULATION OF THE CIRCADIAN SYSTEM IN OTHER TISSUES. MOREOVER, IS UNKNOWN THE ROLE OF THIS LOCAL PRODUCTION OF MELATONIN AND WHETHER THIS PRODUCTION HAVE A CIRCADIAN PATTERN. AVAILABLE INFORMATION INDICATES THAT MELATONIN INDUCES IN PLACENTA THE EXPRESSION OF ANTIOXIDANT ENZYMES CATALASE AND SUPEROXIDE DISMUTASE, PREVENTS THE INJURY PRODUCED BY OXIDATIVE STRESS, AND INHIBITS THE EXPRESSION OF VASCULAR ENDOTHELIAL GROWTH FACTOR (VEGF) A GENE THAT IN OTHER TISSUES IS CONTROLLED BY CLOCK GENES. IN THIS REVIEW WE AIM TO ANALYZE AVAILABLE INFORMATION REGARDING CLOCK GENES AND CLOCK GENES CONTROLLED GENES SUCH AS VEGF AND THE POSSIBLE ROLE OF MELATONIN SYNTHESIS IN THE PLACENTA.

THE CIRCADIAN SYSTEM IS A SUPRAPHYSIOLOGICAL SYSTEM THAT MODULATES DIFFERENT BIOLOGICAL FUNCTIONS SUCH AS METABOLISM, SLEEP-WAKE, CELLULAR PROLIFERATION, AND BODY TEMPERATURE. DIFFERENT CHRONODISRUPTORS HAVE BEEN IDENTIFIED, SUCH AS SHIFT WORK, FEEDING TIME, LONG DAYS, AND STRESS. THE ENVIRONMENTAL CHANGES AND OUR MODERN LIFESTYLE CAN ALTER THE CIRCADIAN SYSTEM AND INCREASE THE RISK OF DEVELOPING PATHOLOGIES SUCH AS CANCER, PREECLAMPSIA, DIABETES, AND MOOD DISORDER. THIS SYSTEM IS ORGANIZED BY TRANSCRIPTIONAL/TRANDUCTIONAL FEEDBACK LOOPS OF CLOCK GENES CLOCK, BMAL1, PER1?3, AND CRY1-2. HOW MOLECULAR COMPONENTS OF THE CLOCK ARE ABLE TO INFLUENCE THE DEVELOPMENT OF DISEASES AND THEIR RISK RELATION WITH GENETIC COMPONENTS OF POLYMORPHISM OF CLOCK GENES IS UNKNOWN. THIS RESEARCH DESCRIBES DIFFERENT GENETIC VARIATIONS IN THE POPULATION AND HOW THESE ARE ASSOCIATED WITH RISK OF CANCER, METABOLIC DISEASES SUCH AS DIABETES, OBESITY, AND DYSLIPIDEMIAS, AND ALSO MOOD DISORDERS SUCH AS DEPRESSION, BIPOLAR DISEASE, EXCESSIVE ALCOHOL INTAKE, AND INFERTILITY. FINALLY, THESE FINDINGS WILL NEED TO BE IMPLEMENTED AND EVALUATED AT THE LEVEL OF GENETIC INTERACTION AND HOW THE ENVIRONMENT FACTORS TRIGGER THE EXPRESSION OF THESE PATHOLOGIES WILL BE EXAMINED.

SEVERAL BIOCHEMICAL CYCLES ARE PERFORMED IN NATURAL WETLANDS (NWS) AND CONSTRUCTED WETLANDS (CWS). KNOWLEDGE OF MICROORGANISMS CAN BE USED TO MONITOR THE RESTORATION OF WETLANDS AND THE PERFORMANCE OF WASTEWATER TREATMENT. THE PHYLUM PROTEOBACTERIA IS THE MOST ABUNDANT IN NWS AND CWS, WHICH PLAYS A ROLE IN NITROGEN (N), PHOSPHORUS (P), AND SULFUR (S) CYCLES, AND IN THE DEGRADATION OF ORGANIC MATTER. OTHER PHYLA WERE PRESENT AT LOWER ABUNDANCE. ARCHAEA PARTICIPATE IN METHANOGENESIS, METHANE OXIDATION, AND METHANOGENIC N2 FIXATION. S AND P CYCLES ARE ALSO PERFORMED BY OTHER MICROORGANISMS, SUCH AS CHLOROFLEXI AND NITROSPIRAE. IN GENERAL, THERE IS MORE INFORMATION ABOUT THE N CYCLE, ESPECIALLY NITRIFICATION AND DENITRIFICATION. PROCESSES WHERE ARCHAEA PARTICIPATE (E.G., METHANE OXIDATION AND METHANOGENIC N2 FIXATION) REMAIN UNCLEAR, AND SEVERAL OF THESE MICROORGANISMS HAVE NOT BEEN ISOLATED SO FAR. IN THIS STUDY, WE USED 16S RDNA OR FUNCTIONAL GENES. THE USE OF FUNCTIONAL GENES PROVIDES INFORMATION TO MONITOR SPECIFIC MICROBIAL POPULATIONS, AND 16S RDNA IS MORE SUITABLE FOR TAXONOMIC CLASSIFICATION. IN ADDITION, SEVERAL CANDIDATUS MICROORGANISMS HAVE NOT BEEN ISOLATED TO DATE. HOWEVER, THEIR METABOLIC ROLES IN THE BIOCHEMICAL CYCLE OF WETLANDS HAVE BEEN DESCRIBED.