Circadian Rhythm and Endocrinological Control on the Swimming and Sand Burrowing Behaviors of Japanese Sand Lances Ammodytes spp. (Uranoscopiformes, Ammodytidae).

In diurnal and nocturnal organisms, daily activity is regulated by the perception of environmental stimuli and circadian rhythms, which enable organisms to maintain their essential behaviors. The Japanese sand lances genus Ammodytes are coastal marine fish that exhibit unique nocturnal sand burrowing behavior. To elucidate the extrinsic and intrinsic regulation of this behavior and its endocrinological basis, we conducted a series of rearing experiments under various light conditions and hormone administrations. Under a light-dark photoperiod, the fish showed three types of behavior: sand buried, head-exposed from sand, and swimming/feeding. During the transition from dark to light periods, the fish first showed head exposure, followed by swimming and foraging, and buried themselves in the sand immediately after shifting to the dark period. Under constant light conditions, fish exhibited swimming behavior during the period corresponding to the acclimated light period. In addition, swimming did not occur under constant dark conditions but head exposure was observed at the time of the dark-light transition during acclimation. These observations indicate that the essential behavior of sand lances is regulated by both light and circadian rhythms. Subsequently, a melatonin-containing diet promoted the onset of burrowing in 10 to 120 min in a dose-dependent manner at 0.3-128 µg/g-diet, suggesting the direct behavioral regulation by this hormone. These findings suggest that the behavior of sand lances is strictly regulated by an intrinsic mechanism and that melatonin is a regulatory endocrine factor that induces burrowing behavior.

rt-PA with Antithrombotic Therapies in a Case with Capsular Warning Syndrome.

We herein report a case of capsular warning syndrome (CWS) that was successfully treated with recombinant tissue plasminogen activator (rt-PA). A 70-year-old woman had repeated stereotyped transient ischemic attacks (TIAs) of right hemiparesis and dysarthria. After hospitalization, argatroban, aspirin, and cilostazol were started but were ineffective. Thirteen hours after the first episode of TIAs, severe symptoms occurred. Magnetic resonance imaging showed acute infarctions in the internal capsule to corona radiata, so we used rt-PA. Since then, the TIAs have not occurred, and the symptoms have considerably improved. This case suggests that rt-PA might be effective and safe for use in treating CWS.

Peripheral circulation monitored by surface temperature and autonomic nervous function in hypobaric hypoxic environment: effects of submaximal exercise.

Hypothermia and frostbite are frequently seen in accidents in remote wilderness environment, especially in hypobaric hypoxic conditions. The aim of this study was to clarify how hypobaric hypoxic conditions affects peripheral circulation. Peripheral skin temperature and autonomic nervous functions were assessed in two 1000-m ascent exercises. Subjects (n = 15) ascended from 1000 m above sea level in Study 1, and ascended from 2400 m in Study 2. Conditions other than environmental oxygen pressure were mostly identical in both studies. The autonomic nervous activities were decreased solely in Study 2. The relative sympathetic activity was significantly increased in the lower barometric pressure in Study 2 (p < 0.01). Peripheral skin temperature was significantly decreased after the exercise in Study 2 (p < 0.01). In conclusion, hypobaric hypoxia itself induced peripheral low temperature during exercise at high altitudes. Relative sympathetic hyperactivity may be responsible for the compromised peripheral circulation.