Abstract: 1-(2-Fluoro-4-thio-?-D-arabinofuranosyl)-5-methyluracil exhibits an anti-EB virus activity, and is therefore effective as a prophylactic or therapeutic agent for a disease associated with an EB virus. Each of a plasmid capable of expressing EB virus-TK and a plasmid capable of expressing human-TK is introduced into a TK-defect cell, thereby producing two types of cells respectively having the plasmids introduced therein. By using the two types of cells, it is possible to screen a medicinal agent which has cytotoxicity against the cell having the plasmid capable of expressing EB virus-TK introduced therein but has no toxicity against the cell having the plasmid capable of expressing human-TK introduced therein. In this manner, it becomes possible to screen a medicinal agent which specifically exhibits an anti-EB virus activity.

Abstract: To provide a novel anti-psychosocial stress agent which is highly safety and can be continuously taken, more particularly, a novel anti-psychosocial stress agent which prevents or alleviates psychosocial stress. The invention provides an anti-psychosocial stress agent containing, as an active ingredient, uridylic acid, uridine, or uracil. Since uridylic acid, uridine, or uracil, which is an active ingredient of the anti-psychosocial stress agent of the present invention, is inexpensively available and is a biological component, the agent exhibits high safety and can be continuously taken. Therefore, the anti-psychosocial stress agent of the present invention is effective for mitigating, alleviating, or relieving psychosocial stress, which is an issue in modern society. When the anti-psychosocial stress agent is taken before development of symptoms associated with psychosocial stress, the symptoms can be prevented.

Abstract: 1-(2-Fluoro-4-thio-?-D-arabinofuranosyl)-5-methyluracil exhibits an anti-EB virus activity, and is therefore effective as a prophylactic or therapeutic agent for a disease associated with an EB virus. Each of a plasmid capable of expressing EB virus-TK and a plasmid capable of expressing human-TK is introduced into a TK-defect cell, thereby producing two types of cells respectively having the plasmids introduced therein. By using the two types of cells, it is possible to screen a medicinal agent which has cytotoxicity against the cell having the plasmid capable of expressing EB virus-TK introduced therein but has no toxicity against the cell having the plasmid capable of expressing human-TK introduced therein. In this manner, it becomes possible to screen a medicinal agent which specifically exhibits an anti-EB virus activity.

Abstract: To provide a novel anti-psychosocial stress agent which is highly safety and can be continuously taken, more particularly, a novel anti-psychosocial stress agent which prevents or alleviates psychosocial stress. The invention provides an anti-psychosocial stress agent containing, as an active ingredient, uridylic acid, uridine, or uracil. Since uridylic acid, uridine, or uracil, which is an active ingredient of the anti-psychosocial stress agent of the present invention, is inexpensively available and is a biological component, the agent exhibits high safety and can be continuously taken. Therefore, the anti-psychosocial stress agent of the present invention is effective for mitigating, alleviating, or relieving psychosocial stress, which is an issue in modern society. When the anti-psychosocial stress agent is taken before development of symptoms associated with psychosocial stress, the symptoms can be prevented.

Abstract: The present invention provides a novel purine 4'-thioarabinonucleoside represented by the following formula ?1!: ##STR1## wherein B represents a purine base other than adenine. Also disclosed are a method for preparing the purine 4'-thioarabinonucleoside and pharmaceutical compositions containing the purine 4'-thioarabinonucleoside.