To examine the effect of melatonin on in vitro fertilization and embryonic development, mouse embryos after insemination in vitro were cultured in a physiological medium with or without melatonin. Melatonin increased the fertilization rate significantly at a concentration between 10(-6) and 10(-4) M (27.6 vs. 43.9 or 40.4%, P < 0.01). Furthermore, a significant increase in the rate of embryos reaching the four-cell stage (16.0 vs. 26.7%, P < 0.01), the eight-cell stage (12.1 vs. 25.8 or 23.5%, P < 0.01), and blastulation (8.9 vs. 23.5 or 17.5%, P < 0.01) was observed when the embryos were cultured in a medium containing 10(-8) or 10(-6) M melatonin. These results demonstrate that melatonin supports fertilization and early embryo development after in vitro fertilization.

Although intervertebral disc herniation and associated sciatica is a common disease, its molecular pathogenesis is not well understood. Immune responses are thought to be involved. This study provides direct evidence that even nondegenerated nucleus pulposus (NP) cells elicit immune responses. An in vitro colony forming inhibition assay demonstrated the suppressive effects of autologous spleen cells on NP cells and an in vitro cytotoxicity assay showed the positive cytotoxic effects of natural killer (NK) cells and macrophages on NP cells. Non-degenerated rat NP tissues transplanted into wild type rats and immunedeficient mice demonstrated a significantly higher NP cell survival rate in immune-deficient mice. Immunohistochemical staining showed the presence of macrophages and NK cells in the transplanted NP tissues. These results suggest that even non-degenerated autologous NP cells are recognized by macrophages and NK cells, which may have an immunological function in the early phase of disc herniation. These findings contribute to understanding resorption and the inflammatory reaction to disc herniation.

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Cerebellar hemorrhage is an unpredictable complication of spinal surgery. We encountered a case of cerebellar hemorrhage presenting with delayed emergence from anesthesia and hemiplegia after resection of an intradural extramedullar tumor from the cervical spine. Postoperative brain computed tomography revealed hematoma in the cerebellar vermis and right cerebellar hemisphere. The patient made a gradual recovery with conservative treatment. Although the mechanism of cerebellar hemorrhage remains speculative, loss of cerebrospinal fluid may play an important role. Cerebellar hemorrhage must therefore be considered in patients with unexplained neurological deterioration or disturbance on emergence from anesthesia after spinal surgery.

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