Methylcobalamin induces a long-lasting enhancement of the field potential in rat suprachiasmatic nucleus slices

Optic nerve stimulation has been reported to evoke a field potential (FP) in rat suprachiasmatic nucleus (SCN) slices. Methylcobalamin,δ-(5,6-dymethylbenzimidazoyl)-Co-methyl-cobamide (Me-B₁₂) enhanced this FP and the enhancement lasted more than 1 h after washing out. Maximal enhancement (143.6±9.8%) was achieved at a concentration of 10 μM. By contrast, cyanocobalamin containing CN- instead of CH₃-showed no enhancement of the amplitude in the FP. Me-B₁₂ induced enhancement of FP was strongly blocked by an N-methyl- -aspartate (NMDA) receptor antagonist, -2-amino-5-phosphonovaleric acid (APV). These results indicate that CH₃- in the Me-B₁₂ is required to modulate the FP amplitude and the NMDA receptor is involved in the long-lasting FP enhancement induced by Me-B₁₂. The present results suggest that Me-B₁₂ modifies the photic entrainment of the circadian clock in the suprachiasmatic nucleus via an activation of NMDA receptors.     

心肌梗死患者窦性心律震荡的检测及其临床意义

目的：探讨心肌梗死（心梗）患者窦性心律震荡检测的临床意义。方法：测定24小时动态心电监测的170例心梗患者和116例正常人室性早搏（室早）后的震荡初始（TO）和震荡斜率（TS）值及平均值，并进行对比分析。结果：心梗患者室早后的TO值明显高于对照组、鸭值明显低于对照组（P〈0．05和P〈0．01），TO和／或TS异常组死亡率明显高于TO和鸭均正常组（P〈0．001）。结论：心梗后患者窦性心律震荡现象减弱或消失时，其猝死的发生率增高，及时检测心梗患者室早后的TO和TS值，对发生猝死的高危患者的检出、危险度分层以及对其进行干预治疗都有重要的临床意义。     

Noninvasive,automatic 24-h ambulatory blood pressure monitoring in normotensive subjects

Summary The reliability of noninvasive, automatic blood pressure monitoring is not yet clearly established. A 24-h ambulatory blood pressure profile was obtained in 9 healthy, normotensive subjects with an automatic, noninvasive device. The blood pressure profile showed the typical circadian pattern with lower systolic and diastolic values during sleep, although pulse pressure was fairly constant (about 40 mm Hg). The systolic blood pressure rose steeply in the early morning hours — before waking up. The results were compared with simultaneous hourly readings using the auscultatory method. There were no statistically significant differences between the automatic and auscultatory readings, 13 of the 18 mean values at. different time points being within 2 mm Hg of each other. All the auscultatory means fell within the 95% confidence limits of those measured hourly by the automatic method. Although the automatic method seemed to be reliable compared with the auscultatory method, its sensitivity to motion artifacts is a disadvantage in a truly ambulatory setting.     

Longitudinal study of daily variation of rats' behavior in the elevated plus-maze

We conducted a longitudinal study about daily variation of Wistar male rats' behavior in the elevated plus-maze (EPM) evaluated in the 1st, 2nd, 3rd, 6th, 12th, and 18th months of life. Animals were submitted to the plus-maze in 12 sessions at 2-h intervals (n=72, 6 per time point). Spontaneous rest-activity rhythm of four animals was assessed by observation of 24-h videotape records. Time series were analyzed by Cosinor method. Behavioral rates on the six occasions and in light and dark phases were compared by means of two-way ANOVA with repeated measures. Exploratory behavior in EPM was smaller in the light phase and in older animals. Higher values of open and closed arms exploration were observed in the first and third months of the dark phase, and in the first month of the light phase. Adjustment to the 24-h period was significant at all stages for rest-activity data, number of entries in closed arms, and time on center, and for three to five stages for open-arm exploration. In general, 24 h variability was more pronounced in younger animals compared with older ones. The present study showed that: (1). a significant amount of total variability of the behavioral indexes analyzed could be attributed to 24 h variation, (2). light/dark phases differences in EPM exploration were present at all developmental stages, (3). older Wistar rats explored less the EPM and were less active in their home cage compared with younger ones, and (4). behavioral indexes (EPM) decrease was phase related and partially related to a reorganization of rest-activity rhythm.     

Effect of limited access to sucrose on overeating and patterns of feeding

Four groups of adult rats, housed on a 12-12, light-dark cycle, were allowed access to a nutritionally complete diet and water. Three of these groups were also offered a 32% solution of sucrose. The sucrose was available for either the 24-hour period, the 12 hours of light or the 12 hours of dark. Access to sucrose led to overeating and excessive weight gain. These effects were more pronounced when the sucrose was available for the 24-hour period or during the dark. Limited access to sucrose produced a reversal of the rat's usual circadian pattern of feeding when the sucrose was available during the light and increased the rat's nocturnal hyperphagia when it was available during the dark. Sucrose intake and the proportion of calories taken from sucrose were higher in the 24-hour access group and the dark access group than the light access group. Access to sucrose did not induce a pattern of dietary selection that compromised growth or health. It appears that access to a palatable carbohydrate solution can lead to overeating and major changes in the circadian organization of feeding behavior. These data emphasize the potent role that external factors can play in the control of ingestive behavior.     

In normal development pulmonary veins are connected to the sinus venosus segment in the left atrium

Background: Classic theories descibe that the common pulmonary vein develops as an outgrowth from either the sinus venosus or atrial segment. Recent studies show that the pulmonary veins are connected to the sinu-atrial region before its differentiation into a sinus venosus and atrial segment. Methods: The development of the sinu-atrial region with regard to the developing common pulmonary vein and the growth of the atrial septum was investigated in avian embryos, using both scanning electron microscopy and immunohistochemistry. Embryos ranging between stage HH12 and HH28 were incubated with QH-1 that recognizes quail endothelial cells and precursors, HNK-1, that appears in this study to detect the myocardium of the sinus venosus, or with HHF-35, being specific for muscle actins. Also vascular casts of the heart were produced by injecting prepolymerized Mercox into the vascular system. Results: In preseptation stages the common pulmonary vein drains into the left part of the sinus venosus, that is clearly demarcated by the sinuatrial fold and HNK-1 expression. During atrial septation the left part of the sinus venosus, in contrast to the right part, loses its HNK-1 antigen from stage HH23 onwards, while at the same time the sinu-atrial fold in the left atrial dorsal wall flattens and disappears. From stage HH25 onwards HNK-1 expression is restricted to the right part of the sinus venosus, which contributes to the right atrium. The myocardial atrial septum never expresses the HNK-1 antigen, suggesting that the septum is of atrial origin. Discussion: It appeared that the sinus venosus does not only contribute to the sinus venarum of the right atrium, but also to the left atrium. © 1995 Wiley-Liss, Inc.     

Potent depressant effects of adenosine analogs on hippocampal slow-wave activity in the unanesthetized rat

Summary Adenosine and its analogs have previously been shown to exert a depressant effect on several measures of hippocampal excitability in the hippocampal slice and intact anesthetized preparation. In the present report, we examined the effects of intraventricular injections of adenosine analogs on hippocampal slow-wave activity in the freely moving rat. Each of three adenosine analogs— 5-N-ethylcarboxamidoadenosine (NECA) and N⁶-(phenylisopropyl) adenosine (L- and D-PIA) — were found to strongly suppress hippocampal electroencephalographic (EEG) activity. For instance, low doses of NECA (0.5 g) produced an 80–90% decrease in the amplitude of the hippocampal EEG. NECA was approximately 20-fold more potent than L-PIA, and L-PIA was twice the potency of D-PIA. In separate experiments in the anesthetized rat, NECA and L-PIA were found to block completely the activation of the hippocampal theta rhythm elicited with brainstem stimulation. The effects of adenosine analogs on both the hippocampal EEG and theta rhythm were very effectively reversed with methylxanthine, 8-para-sulphophenyl-theophylline (8-PSPT). The present findings demonstrate that adenosine analogs exert a powerful depressant effect on the hippocampal EEG in the natural unanesthetized state, and suggest that changes in the levels of endogenous adenosine may play a significant role in modulating the normal activity and function of the hippocampus.This work was supported in part by National Science Foundation grant BNS-8403544 to RPV     

Central control of upper airway resistance regulating respiratory airflow in mammals

This article reviews recent studies on the importance of glycine receptors for both the spontaneous and the reflex respiratory modulation of the laryngeal abductors and adductors. Our findings show that strychnine blockade of glycine receptors within the brainstem changes the eupneic three-phase respiratory pattern into two phases. This has major implications for glottal control: (i) the inspiratory glottic abduction and early expiratory adduction were both compromised--a finding mimicked by 5% hypoxia; (ii) closure of the glottis during defensive upper airway reflexes became intermittent and the reflex apnoea reversed to sustained inspiratory discharge. Based on these data, we predict that periods of prolonged hypoxia, such as those that occur during sleep apnoeas, will constrain inspiratory glottic abduction thereby impeding inhalation.     

Strain differences of the light-dark preference in inbred rats

he present study examined strain differences in the light-dark preference among four strains of rats. The test was done in the home-cage situation under 12L:12D cycles. Data from four strains were compared: BN/Kyo, BDIX/Nem, Wistar/Nu, and F344/NSlc. These strains differed in the light-dark preference measured by the ratio of the time spent in the field area of the home cage during the light period. BN/Kyo and BDIX/Nem spent the most time (approx. 23%) in the field during the light period, while F344/NSlc spent the least time (approx. 5%). Wistar/Nu fell between the two (approx. 12%).This study was conducted as partial fulfillment for the master's degree, submitted to Nagoya University by the first author. It was presented at the 47th Annual Conference of the Japanese Society of Animal Psychology.     

Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications

At older ages, the circadian rhythm of body temperature shows a decreased amplitude, an advanced phase, and decreased stability. The present review evaluates to what extent these changes may result from age-related deficiencies at several levels of the thermoregulatory system, including thermoreception, thermogenesis and conservation, heat loss, and central regulation. Whereas some changes are related to the aging process per se, others appear to be secondary to other factors, for which the risk increases with aging, notably a decreased level of fitness and physical activity. Moreover, functional implications of the body temperature rhythm are discussed. For example, the relation between circadian rhythm and thermoregulation has hardly been investigated, while evidence showed that sleep quality is dependent on both aspects. It is proposed that the circadian rhythm in temperature in homeotherms should not be regarded as a leftover of ectothermy in early evolution, but appears to be of functional significance for physiology from the level of molecules to cognition. A new view on the functional significance of the circadian rhythm in peripheral vasodilation and the consequent out-of-phase rhythms in skin and core temperature is presented. It is unlikely that the strong, daily occurring, peripheral vasodilation primarily represents heat loss in response to a lowering of set point, since behavioral measures are simultaneously taken in order to prevent heat loss. Several indications rather point towards a supportive role in immunological host defense mechanisms. Given the functional significance of the temperature rhythm, research should focus on the feasibility and effectiveness of methods that can in principle be applied in order to enhance the weakened circadian temperature rhythm in the elderly.