Tetsuro Katayama

Effect of lateral cerebroventricular injection of the appetite-stimulating neuropeptide, orexin and neuropeptide Y, on the various behavioral activities of rats

The effect of lateral cerebroventricular injection of the appetite-stimulating neuropeptide, orexin and neuropeptide Y (NPY), on the behavior of rats was investigated. An immediate increase in face washing activity was observed after injection of orexin A or orexin B, but not NPY. Orexin A had a more potent effect on face washing behavior than orexin B. Grooming and burrowing activities also increased significantly after injection of orexin A, whereas, orexin B significantly increased burrowing and searching behavior. Feeding behavior and food consumption increased dramatically within 10 min of injection of NPY. Although the significant increase in feeding behavior was also observed after injection of orexin A, total food intake did not change significantly. These results suggest that orexin may be involved in the regulation of several other behavioral activities in rats, besides feeding.

Development of regulation of melatonin release in pineal cells in chick embryo.

Melatonin release in a pineal cell culture from 13- and 14-day-old chick embryos increased during the dark phase and decreased during the light phase of a 12 h light:12 h dark cycle. When the light-dark cycle was reversed, the pattern of melatonin release in the culture also reversed. 8-Bromo cyclic-AMP stimulated melatonin release in both the light and dark phases. However, no rhythm of melatonin release was detected under constant dark (DD) conditions in a cell culture from 14-day-old chick embryos. In 18-day-old chick embryos, the pineal cell culture expressed a circadian rhythm of melatonin release under DD conditions. These results indicate that mechanisms regulating melatonin synthesis in the avian pineal gland are established during embryonic life.

Daily Wheel Running Activity Modifies the Period of Free-Running Rhythm in Rats Via Intergeniculate Leaflet

The period of free-running rhythms (tau) in rats, as measured using a running wheel, is different from that measured using an Automex. The aim of this work was to examine the effects of lesions of the intergeniculate leaflet (IGL) on the tau of these two activity rhythms. When blind rats were transferred from a cage with a running wheel to a cage without a running wheel, the tau lengthened. The tau of the wheel-running activity was associated with the number of wheel revolutions per day. A complete lesion of the IGL lengthened the tau of the wheel-running activity, and caused a reduction in the number of wheel revolutions per day in all rats. In rats housed in cages without a running wheel, locomotor activity was reduced by IGL lesions, although the tau was unaffected. When IGL-lesioned rats were transferred from a cage with a running wheel to a cage without a running wheel, no further change was observed. These results indicate that the tau is modified by the daily activity of wheel-running, but not by general locomotor activity, and that the IGL may be involved in this modification.

Synergistic action of gastrin and ghrelin on gastric acid secretion in rats

Gastrin and ghrelin are secreted from G cells and X/A-like cells in the stomach, respectively, and respective hormones stimulate gastric acid secretion by acting through histamine and the vagus nerve. In this study, we examined the relationship between gastrin, ghrelin and gastric acid secretion in rats. Intravenous (iv) administration of 3 and 10 nmol of gastrin induced transient increases of ghrelin levels within 10 min in a dose-dependent manner. Double immunostaining for ghrelin and gastrin receptor revealed that a proportion of ghrelin cells possess gastrin receptors. Although (iv) administration of gastrin or ghrelin induced significant gastric acid secretion, simultaneous treatment with both hormones resulted in a synergistic, rather than additive, increase of gastric acid secretion. This synergistic increase was not observed in vagotomized rats. These results suggest that gastrin may directly stimulate ghrelin release from the stomach, and that both hormones may increase gastric acid secretion synergistically.

Effects of daily injections of melatonin on locomotor activity rhythms in rats maintained under constant bright or dim light

It has been demonstrated that daily melatonin injections entrain free-running locomotor activity rhythms in rats kept in constant darkness, and synchronize disrupted circadian patterns of wheel-running activity under constant light. Contrary to these previous observations, our result did not show that daily injections of melatonin synchronize disrupted locomotor activity in rats maintained under constant bright light. On the other hand, daily treatment with melatonin entrained the intact free-running rhythm in rats kept in constant dim light. This entrainment took place only when the time of injection corresponded to the activity onset time, and similar results were obtained in blinded rats. Pinealectomy had no influences on either the free-running rhythm or melatonin-induced entrainment. To examine whether a behavioral feedback mechanism is involved in melatonin-induced entrainment, rats were immobilized for 3 h after each daily melatonin injections. This did not interfere with melatonin-induced entrainment. These results suggest that the mechanism underlying melatonin-induced entrainment of activity rhythms may be different from those in photic and behavioral entrainment.

Prototype of the device driver generation system for UNIX-like operating systems

Writing device drivers takes much time and requires effort because it needs knowledge of the target device and operating system (OS). In order to lighten the burden, the authors have proposed a model to generate device drivers and a device-driver generation system. The system generates the source code of a device driver from three inputs: the device driver specification, an OS-dependent specification and a device-dependent specification. The device drivers generated in the model are evolutionary because their features can be expanded easily. However, they are not always effective because the burden of describing the device-dependent specification, which is one of the inputs, is nearly as same as in the traditional method. In this paper, to aim at a greater reduction of the burden, device drivers are abstracted again, each input is defined afresh, and then a prototype of the system is implemented. As an example of the generation, we chose an interrupt handler of a network device, FreeBSD and Linux as the target OSs, and Etherlink XL as the target device. The OS-dependent specification and the device-dependent specification can be reused in each OS and each device, respectively. As a result, an identical device-dependent specification can be applied to both OSs. The burden in generating new device drivers or in porting device drivers to other OSs can thus be reduced.

Nutritional and environmental factors affecting plasma ghrelin and leptin levels in rats

We examined which factors suppress the rise of ghrelin secretion under hunger in 16-h-starved rats, and compared the responses of plasma ghrelin and leptin levels to various exogenous and endogenous stimuli in intact rats. Although an acute expansion of the stomach by infusion of 6 ml air or 3 ml water in rats starved for 16 h did not change the level of plasma acyl-ghrelin 3 ml corn starch solution, corn oil, or 20% ethanol significantly decreased it. Vagotomy inhibited suppression by nutrients but not by ethanol. Chronic infusion of ethanol into the stomach for 3 weeks in free-feeding rats caused widespread injury of the stomach mucosa, and increased both plasma ghrelin levels and the number of ghrelin cells. In intact rats, low temperature did not change ghrelin levels, but increased leptin levels. On the other hand, restriction stress decreased plasma ghrelin levels, but had the reverse effect on plasma leptin levels. Although insulin decreased and 20% glucose increased plasma glucose levels, they both decreased plasma ghrelin levels. Insulin elevated plasma leptin levels, but glucose had no effect. These results indicate that 1) acyl-ghrelin secretion from the stomach under fasting condition is suppressed by nutrients but not by mechanical expansion of the stomach; 2) high and low environmental temperature, stress, or administration of insulin reciprocally affect plasma levels of ghrelin and leptin; and 3) an increase of stomach ghrelin cell number and plasma ghrelin levels after chronic ethanol treatment may be involved in restoration of gastric mucosae.

Comparison of feeding suppression by the anorexigenic hormones neuromedin U and neuromedin S in rats

We compared the central mechanisms of feeding suppression by the anorexigenic hormones neuromedin U (NMU) and neuromedin S (NMS) in rats. I.c.v. injection of either NMU or NMS dose dependently decreased 3-h food intake during the first quarter of a dark period. Pretreatment involving i.c.v. injection of a specific anti-NMS IgG blocked the suppression of food intake induced by i.c.v.- and i.p.-injected leptin, but anti-NMU IgG elicited no blockade. Quantitative PCR analysis revealed that i.c.v. injection of NMU or NMS caused a dose-dependent increase in CRH and proopiomelanocortin mRNA expression in the paraventricular nucleus (PVN) and arcuate nucleus (Arc) respectively. In tissue cultures of the Arc, secretion of α-melanocyte-stimulating hormone was stimulated by NMU and NMS, with more potent stimulation by NMS. The time-course curves of the increase in neuronal firing rate in Arc slices in response to NMU and NMS showed almost the same pattern, with a peak 10-15 min after treatment, whereas the time-course curves for the PVN slices differed between NMU and NMS. These results suggest that NMS and NMU may share anorexigenic effects, depending on physiological conditions.

Analysis of antibody response by temperature-sensitive measles vaccine strain in the cotton rat model.

Measles virus (MeV) vaccine strain, AIK-C, is temperature sensitive (ts), which is thought to be associated with attenuation of virus pathogenicity. In this study, replication and antibody response were examined in cotton rats using viruses carrying different forms of the P gene, which is responsible for the ts phenotype of strain AIK-C and its parental Edmonston strain. When cotton rats were inoculated intranasally, ts viruses neither replicated in lungs, nor reproducibly generated an antibody response. When inoculated intramusculary (i.m.), however, ts strains raised an antibody titer in all animals. This response was not observed when ultraviolet-inactivated virus was used. ts virus, inoculated i.m., was recovered from cotton rat drainage lymph nodes. These results suggest that ts virus, inoculated i.m., could replicate in the cotton rat, presumably at the superficial lymph node, and induce an antibody response. Therefore, cotton rats can serve as a small-animal model for investigating immune responses to safer ts vaccine, as well as recombinant vaccine using AIK-C as a vector for protection against other infectious agents.

Inhibitor of protein synthesis phase-shifts the circadian oscillator and inhibits the light induced-phase shift of the melatonin rhythm in pigeon pineal cells

Our recent study showed that dissociated pigeon pineal cells expressed a circadian oscillation of melatonin release which entrained to light-dark cycle and persisted under constant darkness in vitro, suggesting that pigeon pineal cells contain the circadian oscillator and photoreceptors. Six-hour pulses of anisomycin, an inhibitor of protein synthesis that acts at hte 80S ribosomal subunit, induced steady state and phase depended phase shifts of the circadian oscillation of melatonin release. The phase advances and delays were produced at CT 7.9 h and between CT 18.6 h and CT 4.5 h, respectively. The magnitudes of phase shifts were dose dependent and correlated with the magnitudes of inhibition of protein synthesis determined at CT 4.5 h. Furthermore, anisomycin blocked the light-induced phase advance. Two dimensional electrophoresis revealed that synthesis of two proteins with Mr of 17,600 and less than 5000 are stimulated by a 3-h light pulse at CT 18.6 h which corresponds to the light-induced phase advance region. These results suggest that 80S ribosomal protein synthesis is involved in normal or light-entrainment functions of the circadian oscillator in pigeon pineal cells.