SynopsisThe confinement of male rats in complete dankness from birth until 47 days of age resulted in severe retardation of reproductive function. The supply of light-on condition for the last one week caused a remarkable overshoot of testosterone secretion beyond the level of intact animals, associating with a significant weight increase in accessory reproductive organs. Eye-enucleation nullified these effects. This androgen overshoot was considered to be occurred as a result of the removal of inhibitory effect of dark condition rather than a result of positive stimulatory effect of light-on condition.The possibility to simulate the inhibitory effect of dark condition was examined. The intra-ocular injection of a serotonin precursor (5-hydroxytryptophan) at the initiation of 7 days of light-on treatment, lowered both androgen titer and weight of accessory reproductive organs to the light-off level. This might suggest a possible role of serotonin as an inhibitory dark substance involved in neuroendocrine mechanisms.It has been widely admitted that light exerts a major influence on the reproductive function of mammals. Emphasis hitherto has been placed on photoperiodic or seasonal responses, and little attention has been paid to the effects of light on polyestrous species such as the rat. Sufficient information accumulated, however, to indicate that lighting conditions can profoundly influence pituitarygonadal function in this species. Light has been considered to play a role of a cue of rythm on which rat estrous cycle depends (Takahashi and Suzuki, 1969), and its stimulatory effect in setting the pace of sexual development is also recognized (Critchlow, 1963) apart from the synchronizer role.We have demonstrated already a remarkable suppressive effect of light-off condition on the initiation of gonadal function by the response of prepubertal male rats reared in continuous complete darkness condition from birth (Suzuki et al., 1968). Experiments were carried out to investigate the effect of light-on condition upon these animals. And a mechanism of mediation of light-on or-off information was discussed. Materials and MethodsThe albino rats established as a closed colony. in our laboratory originally Wistar strain were used. They were maintained on commercial rat chow supplemented with alfalfa meal pellet (RC-5, Oriental Co.) and dried sardine twice a week and given water ad libitum.From 40 to 47 days old male rats under various experimental conditions were utilized. To obtain these young male rats, pregnant females reared in the normal lighting condition (NL, 14L:10D), were exposed at their 14th day of pregnancy to the three kinds of lighting conditions; NL, the continuous lighting (CL) or the continuous complete darkness (CCD) conditions, thus, the given lighting conditions had been provided before the birth of pups. The last

Introduction of biologic agents to treat patients with rheumatic diseases and cancer has improved clinical outcomes. However, this advance increases the risk of hepatitis B virus (HBV) reactivation in hepatitis B surface antigen carrier and even in resolved HBV infection, which can lead to liver failure and even death. In particular, the risk of HBV reactivation is heightened by the use of B-cell depleting agents such as rituximab, high dose corticosteroid, and anti-tumor necrosis factor-α. Therefore, identification of individuals at risk, and understanding the mechanism of HBV reactivation are essential to preventing HBV reactivation before initiating immunosuppressive therapy. Here, we review the mechanism, incidence, and prevention of HBV reactivation in the setting of immunosuppression. (J Rheum Dis 2017;24:261-270)

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