Matched Kinetics Process Over Fe2O3-Co/NiO Heterostructure Enables Highly Efficient Nitrate Electroreduction to Ammonia

Tandem nitrate electroreduction reaction (NO3 -RR) is a promising method for green ammonia (NH3) synthesis. However, the mismatched kinetics processes between NO3 --to-NO2 - and NO2 --to-NH3 results in poor selectivity for NH3 and excess NO2 - evolution in electrolyte solution. Herein, a Ni2+ substitution strategy for developing oxide heterostructure in Co/Fe layered double oxides (LDOs) was designed and employed as tandem electrocataltysts for NO3 -RR. (Co0.83Ni0.16)2Fe exhibited a high NH3 yield rate of 50.4 mg ⋅ cm-2 ⋅ h-1 with a Faradaic efficiency of 97.8 % at -0.42 V vs. reversible hydrogen electrode (RHE) in a pulsed electrolysis test. By combining with in situ/operando characterization technologies and theoretical calculations, we observed the strong selectivity of NH3 evolution over (Co0.83Ni0.16)2Fe, with Ni playing a dual role in NO3 -RR by i) modifying the electronic behavior of Co, and ii) serving as complementary site for active hydrogen (*H) supply. Therefore, the adsorption capacity of *NO2 and its subsequent hydrogenation on the Co sites became more thermodynamically feasible. This study shows that Ni substitution promotes the kinetics of the NO3 -RR and provides insights into the design of tandem electrocatalysts for NH3 evolution.

Radar-based sleep stage classification in children undergoing polysomnography: a pilot-study

STUDY OBJECTIVES

Unobtrusive monitoring of sleep and sleep disorders in children presents challenges. We investigated the possibility of using Ultra-Wide band (UWB) radar to measure sleep in children.

METHODS

Thirty-two children scheduled to undergo a clinical polysomnography participated; their ages ranged from 2 months to 14 years. During the polysomnography, the children's body movements and breathing rate were measured by an UWB-radar. A total of 38 features were calculated from the motion signals and breathing rate obtained from the raw radar signals. Adaptive boosting was used as machine learning classifier to estimate sleep stages, with polysomnography as gold standard method for comparison.

RESULTS

Data of all participants combined, this study achieved a Cohen's Kappa coefficient of 0.67 and an overall accuracy of 89.8% for wake and sleep classification, a Kappa of 0.47 and an accuracy of 72.9% for wake, rapid-eye-movement (REM) sleep, and non-REM sleep classification, and a Kappa of 0.43 and an accuracy of 58.0% for wake, REM sleep, light sleep and deep sleep classification.

CONCLUSION

Although the current performance is not sufficient for clinical use yet, UWB radar is a promising method for non-contact sleep analysis in children.

Brain-derived neurotrophic factor-activated astrocytes produce mechanical allodynia in neuropathic pain

Neuropathic pain management is challenging for physicians and a vexing problem for basic researchers. Recent studies reveal that activated spinal astrocytes may play a vital role in nerve injury-induced neuropathic pain, although the mechanisms are not fully understood. We have found increased glial fibrillary acidic protein (GFAP) expression, a hallmark of reactive gliosis, and elevated brain-derived neurotrophic factor (BDNF) expression in the dorsal horn in a rat model of allodynia induced by spinal nerve ligation (SNL). The high GFAP expression and mechanical allodynia that SNL induces were prevented by the intrathecal injection of the BDNF-sequestering fusion protein TrkB/Fc. Additionally, mechanical allodynia and GFAP overexpression was induced by the spinal administration of exogenous BDNF to naive rats, and exogenous BDNF given together with fluorocitrate, an astrocytic metabolism inhibitor, inhibited allodynia and GFAP upregulation. Exogenous BDNF also activated the astrocytes directly when tested in vitro. Furthermore, intrathecal administration of BDNF-stimulated astrocytes also induced mechanical allodynia in naive rats. All of these results indicate that astrocytes activated by BDNF might contribute to mechanical allodynia development in neuropathic pain in rats.

The characteristics of placental transfer and tissue concentrations of nickel in late gestational rats and fetuses

The dynamics of nickel (Ni) uptake, transfer, retention and clearance in fetuses and late gestational rats were investigated by assessing its distributions in placenta, maternal and fetal organs and tissues during the 24 h period after a single dose of (63)Ni intraperitoneal injection on gestational day 20. Peak (63)Ni radioactivity was detected at 0.5 h in maternal blood, at 3 h in placenta, fetal membranes, fetal blood, fetal heart, maternal kidney, lung, stomach, liver and brain, at 9 h in fetal kidney, stomach, liver and brain, and lastly at 24 h in fetal lung and amniotic fluid. The maximal (63)Ni radioactivity among all samples was detected consistently in the fetal membranes and placenta. The (63)Ni radioactivity in fetal blood was higher than that in maternal blood from 3 to 24 h. The fetal liver, heart, stomach and brain exhibited higher (63)Ni radioactivity than the corresponding maternal organs from 6 to 24 h. However, maternal kidney consistently exhibited significantly higher (63)Ni radioactivity than the fetal kidney. The (63)Ni in fetal lung and amniotic fluid increased throughout the period of experimental observation. These observations corroborated previous finding that nickel is actively transferred across the blood-placenta-barrier into fetus, but hardly from fetus to mother. Moreover, these results suggest that the placenta has a high affinity for nickel and its barrier does not protect the fetus from nickel exposure. The fact that nickel concentrations are higher in most fetal organs and tissues than in corresponding maternal organs and tissues in late gestation indicates that, unlike the dam, fetuses lack effective means for getting rid of excessive nickel due to its confined environment and relatively weak kidney functions. The situation is exacerbated by mother-to-fetus unidirectional transfer. Consequently, the fetuses are particularly vulnerable to the damaging effects of nickel.

A GABA-neuropeptide Y (NPY) interplay in LH release

Neuropeptide Y (NPY) stimulates and gamma-amino butyric acid (GABA) inhibits LH release in the rat. Since a sub-population of NPY-producing neurons in the arcuate nucleus (ARC) of the hypothalamus co-express GABA, the possibility of an interplay between NPY and GABA in the release of LH was investigated in two ways. First by employing light and electron microscopic double staining for NPY and GABA, using pre and post-immunolabeling on rat brain sections, we detected GABA in NPY immunoreactive axon terminals in the MPOA, one of the primary sites of action of these neurotransmitters/neuromodulators in the regulation of LH release. These morphological findings raised the possibility that inhibitory GABA co-released with NPY may act to restrain the excitatory effects of NPY on LH release. Muscimol (MUS, 0.44 or 1.76 nmol/rat), a GABA(A) receptor agonist, administered intracerebroventricularly (icv), alone failed to affect LH release, but NPY (0.47 nmol/rat icv) alone stimulated LH release in ovarian steroid-primed ovariectomized rats. On the other hand, administration of MUS blocked the NPY-induced stimulation of LH release in a dose-dependent manner. Similarly, administration of MUS abolished the excitatory effects on LH release of 1229U91, a selective NPY Y4 receptor agonist. These results support the possibility that in the event of co-release of these neurotransmitters/neuromodulators, GABA may act to restrain stimulation of LH release by NPY during the basal episodic and cyclic release of LH in vivo.

Neuropeptide Y counteracts the anorectic and weight reducing effects of ciliary neurotropic factor

Ciliary neurotrophic factor (CNTF), a cytokine of the interleukin-6 superfamily, has been shown to induce hypophagia and weight loss. Neuropeptide Y (NPY) and orexin are potent orexigenic signals in the hypothalamus. Anorexia, normally seen in response to infection, injury and inflammation, may result from diminished hypothalamic orexigenic signalling caused by persistently elevated cytokines, including CNTF. To test this hypothesis, we first examined the effects of chronic intracerebroventricular (i.c.v.) infusion of CNTF for 6-7 days on food intake and body weight as well as hypothalamic NPY and orexin gene expression in male rats. Subsequently, the effectiveness of NPY replacement to counteract the effects of CNTF by coinfusion of NPY and CNTF was evaluated. Chronic i.c.v. infusion of CNTF (2.5 microg/day) reduced body weight (14.3% vs control) at the end of 7 days. Food intake remained suppressed for 5 days postinfusion and subsequently gradually returned to the control range by day 7. Serum leptin concentrations in these rats were in the same range seen in control rats. Chronic i.c.v. infusion of higher doses of CNTF (5.0 microg/day) produced sustained anorexia and body weight loss (29% vs controls) through the entire duration of the experiment. This severe anorexia was accompanied by markedly suppressed serum leptin concentrations. Furthermore, CNTF infusion alone significantly reduced hypothalamic NPY gene expression (P < 0. 05) without affecting orexin gene expression. As expected, in fusion of NPY alone (18 microg/day) augmented food intake (191.6% over the initial control, P < 0.05) and produced a 25.1% weight gain in conjunction with a 10-fold increase in serum leptin concentrations at the end of the 7-day period. Interestingly, coinfusion of this regimen of NPY with the highly effective anorectic and body reducing effects of CNTF (5.0 microg/day) not only prevented the CNTF-induced anorexia and weight loss, but also normalized serum leptin concentrations and hypothalamic NPY gene expression. These results demonstrate that chronic central infusion to produce a persistent elevation of the cytokine at pathophysiological levels (a situation that may normally manifest during infection, injury and inflammation) produced severe anorexia and weight loss in conjunction with reduction in both serum leptin concentrations and hypothalamic NPY gene expression. Reinstatement of hypothalamic NPY signalling by coinfusion of NPY counteracted these CNTF-induced responses.

Regulation of leptin secretion: effects of aging on daily patterns of serum leptin and food consumption

We have investigated the effects of age on the daily rise in serum leptin levels during the dark-phase of the light-dark cycle. The results show that in young 7-week-old rats, serum leptin levels increase significantly at 2300 h from the levels at 1500 h in association with increased food consumption. However, in middle-aged rats 25 weeks old, the dark-phase increase in serum leptin is absent despite retention of the daily dark-phase increase in food consumption. When compared to our earlier published results, these finding show that the loss of dark-phase rise in serum leptin occurred despite the daily increase in adipocyte leptin gene expression. These results are in accord with the view that the daily pattern in serum leptin is unlikely to be a contributor to the daily patterning of food consumption.

Central infusion of interleukin-1 receptor antagonist fails to alter feeding and weight gain

Interleukin-1 (IL-1) administered either i.p. or i.c.v. provokes sickness behaviors, including suppression of feeding. As well, the possibility exists that IL-1 contributes to the cascade of factors that regulate feeding under basal conditions. The current study assessed the contribution of IL-1 in the control of food intake and body weight under physiological conditions in male rats. Pretreatment with an IL- I receptor antagonist (IL-1ra, 16 mg/kg, i.p.) completely blocked the suppression of food intake produced by injection of IL-1beta (4 microg/kg, i.p.). However, neither daily injections of IL-1ra (16 mg/kg, i.p.) for 4 consecutive days nor infusion of IL-1ra (500 microg/day, i.c.v.) for 7 days altered daily food intake and the rate of body weight gain. These findings suggest while IL-1 may play a role in anorexia associated with sickness, this cytokine likely does not play a physiological role in the regulation of daily food intake and long-term energy balance.

Melanocortin signaling is decreased during neurotoxin-induced transient hyperphagia and increased body-weight gain

Hypothalamic neuropeptides play critical roles in the regulation of feeding behavior and body weight (BW). Disruption of signaling in the ventromedial nucleus by microinjection of the neurotoxin, colchicine (COL), produces transient hyperphagia with corresponding BW gain lasting for 4 days. Because the melanocortin system exerts an inhibitory control on food intake, we hypothesized that hyperphagia in COL-treated rats is due to decreased melanocortin-induced restraint on feeding. Melanocortin restraint is exerted through alpha-melanocortin-stimulating hormone derived from proopiomelanocortin (POMC) and is antagonized by agouti-related peptide produced in neurons located in the arcuate nucleus (ARC). COL (4 microg/0.5 microl saline) or saline was microinjected bilaterally into the ventromedial nucleus of adult male rats. In conjunction with BW gain, blood leptin levels were elevated, whereas POMC mRNA in the ARC was significantly decreased in COL-injected rats. Levels of alpha-melanocortin-stimulating hormone were also decreased in the micropunched paraventricular nucleus, dorsomedial nucleus, and perifornical hypothalamus, sites implicated in the control of food intake. That diminution in melanocortin signaling underlies hyperphagia was supported by the observation that intracerebroventricular injection of the MC3/MC4 melanocortin receptor agonist, MTII, prevented the hyperphagia and BW gain. Surprisingly, however, mRNA levels of the orexigenic peptide agouti-related peptide in the ARC were decreased perhaps due to the action of elevated leptin. These results show that transient hyperphagia and BW gain induced by disruption of signaling in the ventromedial nucleus results from two neurochemical rearrangements: development of leptin resistance in POMC neurons and diminution in melanocortin signaling as reflected by decreased POMC gene expression in the ARC and decreased availability of alpha-melanocortin-stimulating hormone for release in feeding relevant sites.

Evidence that stimulation of two modalities of pituitary luteinizing hormone release in ovarian steroid-primed ovariectomized rats may involve neuropeptide Y Y1 and Y4 receptors

A large body of evidence indicates that neuropeptide Y (NPY) is involved in stimulation of basal and cyclic release of hypothalamic LHRH and pituitary LH. To identify the NPY receptor subtypes that mediate the excitatory effects of NPY in these two modalities of LH release, we studied the effects of 1229U91, a selective Y1 receptor antagonist and Y4 receptor agonist, in two experimental paradigms that reproduce the two modalities of LH secretion in steroid-primed ovariectomized (OVX) rats. Rats were ovariectomized and implanted with a permanent cannula into the lateral cerebroventricle. In the first experiment, rats received estradiol benzoate (EB, 30 microg/rat) on day 5, followed 2 days later with progesterone (2 mg/rat) at 1000 h to induce an afternoon LH surge. 1229U91 (30 microg/3 microl) or vehicle (control) was injected intracerebroventricularly into these rats either once at 1300 h or twice (15 microg/injection) at 1100 and 1200 h. Blood samples were collected before progesterone injection at 1000 h and at hourly intervals from 1300 -1800 h via an intrajugular cannula implanted on the previous day. In control rats, serum LH levels rose significantly at 1400 h, and these high levels were maintained until 1700 h. After two injections of 1229U91, LH levels displayed a tendency to rise at 1300-1400 h, as in controls, but thereafter, decreased rapidly below the control range. In the second experiment, the acute effect of 1229U91 on LH release was evaluated in OVX rats pretreated with EB alone. Saline alone or saline containing 1, 3, 10, or 30 microg 1229U91 was injected intracerebroventricularly at 1000 h, and the effects on LH release were analyzed at 10, 20, 30, and 60 min. 1229U91 elicited a dose-dependent stimulation of LH release, with maximal response (950% of basal levels) occurring at 10 min after the 30-microg dose; elevated levels were maintained for 1 h. Because 1229U91 is a potent Y4 agonist with some affinity for Y5 receptors, these results raised the possibility that activation of Y4/Y5 receptors by 1229U91 may augment LH release. Therefore, we examined the effects of icv administration of rat pancreatic polypeptide, a Y4-selective agonist, and [D-Trp32]-NPY, a Y5 agonist on LH release in EB-primed rats. Rat pancreatic polypeptide (0.5-2 microg/rat) stimulated LH release in a dose-related manner, and peak levels (280% of basal levels) were seen at 10-20 min; the response evoked by a higher dose (10 microg) was smaller than that induced by 0.5 or 2 microg. [D-Trp32]-NPY was relatively less effective, because only the highest (10-microg) dose elicited a modest stimulation (244% of basal levels). These results demonstrate that 1229U91, a Y1 antagonist and Y4 agonist, evokes two types of responses; it suppresses the protracted ovarian steroid-induced LH surge, and acutely, it also stimulates LH. These results imply that normally two different types of NPY receptors may mediate the stimulation of LH release. Because 1229U91 is a Y1 receptor antagonist, inhibition of the steroid-induced LH surge by 1229U91 suggests that Y1 receptors may mediate the cyclic release of LH. On the other hand, acute stimulation of LH by 1229U91 implies that the Y4 agonist-like activity of 1229U91 may mediate the basal release of LH and that either NPY or a yet-to-be-identified endogenous Y4 receptor agonist may activate Y4 receptors in the hypothalamus to stimulate LH release.

Relationship between remodeling and function of left ventricle and angiotensin II AT1 receptor expression after myocardial infarction in rats

OBJECTIVE

To determine the relationship between remodeling and dysfunction of left ventricle (LV) and the expression of the angiotensin II AT1 receptor mRNA after myocardial infarction (MI) in rats.

METHODS

Nine MI rats (Group A) and 8 sham-operated rats (Group B) were studied by both Doppler echocardiography and Dot blot using Digoxingenin-labelled cDNA probes.

RESULTS

Compared with Group B, Group A showed the increase in LV internal diastolic diameter (0.87 +/- 0.06 mm vs 0.66 +/- 0.03 mm, respectively, P < 0.01) and volume (0.73 +/- 0.09 ml vs 0.51 +/- 0.05 ml, P < 0.01). In addition, thinning of anterior wall, thickening of posterior wall, increasing of peak early filling velocity (peak E), decreasing of late filling velocity (peak A) and increasing of the E/A were demonstrated in MI rats 7 weeks after MI. The levels of the cardiac angiotensin II AT1 receptor mRNA in Group A were higher than those of Group B (2.2-fold).

CONCLUSIONS

Seven weeks after MI in rats, character of LV remodeling and dysfunction were developed and the expression of cardiac angiotensin II AT1 receptor mRNA was increased.

Interactions between neuropeptide Y and gamma-aminobutyric acid in stimulation of feeding: a morphological and pharmacological analysis

Neuropeptide Y (NPY) produced in neurons in the arcuate nucleus and brain stem and released in the paraventricular nucleus (PVN) and surrounding areas is involved in stimulation of feeding in rats. We recently reported that gamma-aminobutyric acid (GABA) is coexpressed in a subpopulation of NPY neurons in the arcuate nucleus. To determine whether GABA is colocalized in NPY terminals in the PVN, the site of NPY action, light and electron microscopic double staining for NPY and GABA using pre- and postembedding immunolabeling was performed on rat brain sections. GABA was detected in NPY-immunopositive axons and axon terminals within both the parvocellular and magnocellular divisions of the PVN. These morphological findings suggested a NPY-GABA interaction in the hypothalamic control of feeding. Therefore, the effects of muscimol (MUS), a GABA(A) receptor agonist, on NPY-induced food intake were examined in sated rats. When injected intracerebroventricularly, both NPY and MUS elicited dose-dependent feeding responses that were blocked by the administration of 1229U91 (a putative Y1 receptor antagonist) or bicuculline (a GABA(A) receptor antagonist), respectively. Coadministration of NPY and MUS intracerebroventricularly amplified the feeding response over that evoked by NPY or MUS alone. Similarly, microinjection of either NPY or MUS into the PVN stimulated food intake in a dose-related fashion, and coinjection elicited a significantly higher response than that evoked by either individual treatment. These results suggest that GABA and NPY may coact through distinct receptors and second messenger systems in the PVN to augment food intake.

Interacting appetite-regulating pathways in the hypothalamic regulation of body weight

Various aspects of the complex spatio-temporal patterning of hypothalamic signaling that leads to the development of synchronized nocturnal feeding in the rat are critically examined. Undoubtedly, as depicted in Fig. 7, a distinct ARN in the hypothalamus is involved in the control of nocturnal appetite. At least four basic elements operate within this ARN. These are: 1) A discrete appetite-driving or orexigenic network of NPY, NE, GABA, GAL, EOP, and orexin transduces and releases appetite-stimulating signals. 2) Similarly, anorexigenic signal-producing pathways (e.g., CRH, GLP-1, alpha MSH, and CART) orchestrate neural events for dissipation of appetite and to terminate feeding, possibly by interrupting NPY efflux and action at a postsynaptic level within the hypothalamus. It is possible that some of these may represent the physiologically relevant "off" switches under the influence of GABA alone, or AgrP alone, or in combination with NPY released from the NPY-, GABA-, and AgrP-coproducing neurons. 3) Recent evidence shows that neural elements in the VMN-DMN complex tonically restrain the orexigenic signals during the intermeal interval; the restraint is greatly aided by leptin's action via diminution of orexigenic (NPY) and augmentation of anorexigenic (GLP-1, alpha MSH, and CART) signals. Since interruption of neurotransmission in the VMN resulted in hyperphagia and development of leptin resistance, it seems likely that the VMN is an effector site for the restraint exercised by leptin. The daily rhythms in leptin synthesis and release are temporally dissociable because the onset of daily rise in leptin gene expression in adipocytes precedes that in leptin secretion. Nevertheless, these rhythms are in phase with daily ingestive behavior because the peak in circulating leptin levels occurs during the middle of the feeding period. These observations, coupled with the fact that circulating levels of leptin are directly related to adiposity, pose a new challenge for elucidating the precise role of leptin in daily patterning of feeding in the rat. 4) A neural timing mechanism also operates upstream from the ARN in the daily management of energy homeostasis. Although the precise anatomical boundaries are not clearly defined, this device is likely to be composed of a group of neurons that integrate incoming internal and external information for the timely onset of the drive to eat. Evidently, this network operates independently in primates, but it is entrained to the circadian time keeper in the SCN of rodents. Apart from its role in the onset of drive to eat, the circadian patterns of gene expression of NPY, GAL, and POMC denote independent control of the timing device on the synthesis and availability for release of orexigenic signals. The VMN-DMN-PVN complex is apparently an integrated constituent of the timing mechanism in this context, because lesions in each of these sites result in loss of regulated feeding. The accumulated evidence points to the PVN and surrounding neural sites within this framework as the primary sites of release and action of various orexigenic and anorexigenic signals. A novel finding is the identification of the interconnected wiring of the DMN-mPVN axis that may mediate leptin restraint on NPY-induced feeding. The chemical phenotypes of leptin and NPY target neurons in this axis remain to be identified. These multiple orexigenic and anorexigenic pathways in the hypothalamic ARN appear to represent redundancy, a characteristic of regulated biological systems to provide a "fail-safe" neural mechanism to meet an organism's constant energy needs for growth and maintenance. Within this formulation, the coexisting orexigenic signals (NPY, NE, GAL, GABA, and AgrP) represent either another level of redundancy or it is possible that these signals operate within the ARN as reinforcing agents to varying degrees under different circumstances. (ABSTRACT TRUNCATED)

Interacting appetite-regulating pathways in the hypothalamic regulation of body weight

Various aspects of the complex spatio-temporal patterning of hypothalamic signaling that leads to the development of synchronized nocturnal feeding in the rat are critically examined. Undoubtedly, as depicted in Fig. 7, a distinct ARN in the hypothalamus is involved in the control of nocturnal appetite. At least four basic elements operate within this ARN. These are: 1) A discrete appetite-driving or orexigenic network of NPY, NE, GABA, GAL, EOP, and orexin transduces and releases appetite-stimulating signals. 2) Similarly, anorexigenic signal-producing pathways (e.g., CRH, GLP-1, alpha MSH, and CART) orchestrate neural events for dissipation of appetite and to terminate feeding, possibly by interrupting NPY efflux and action at a postsynaptic level within the hypothalamus. It is possible that some of these may represent the physiologically relevant "off" switches under the influence of GABA alone, or AgrP alone, or in combination with NPY released from the NPY-, GABA-, and AgrP-coproducing neurons. 3) Recent evidence shows that neural elements in the VMN-DMN complex tonically restrain the orexigenic signals during the intermeal interval; the restraint is greatly aided by leptin's action via diminution of orexigenic (NPY) and augmentation of anorexigenic (GLP-1, alpha MSH, and CART) signals. Since interruption of neurotransmission in the VMN resulted in hyperphagia and development of leptin resistance, it seems likely that the VMN is an effector site for the restraint exercised by leptin. The daily rhythms in leptin synthesis and release are temporally dissociable because the onset of daily rise in leptin gene expression in adipocytes precedes that in leptin secretion. Nevertheless, these rhythms are in phase with daily ingestive behavior because the peak in circulating leptin levels occurs during the middle of the feeding period. These observations, coupled with the fact that circulating levels of leptin are directly related to adiposity, pose a new challenge for elucidating the precise role of leptin in daily patterning of feeding in the rat. 4) A neural timing mechanism also operates upstream from the ARN in the daily management of energy homeostasis. Although the precise anatomical boundaries are not clearly defined, this device is likely to be composed of a group of neurons that integrate incoming internal and external information for the timely onset of the drive to eat. Evidently, this network operates independently in primates, but it is entrained to the circadian time keeper in the SCN of rodents. Apart from its role in the onset of drive to eat, the circadian patterns of gene expression of NPY, GAL, and POMC denote independent control of the timing device on the synthesis and availability for release of orexigenic signals. The VMN-DMN-PVN complex is apparently an integrated constituent of the timing mechanism in this context, because lesions in each of these sites result in loss of regulated feeding. The accumulated evidence points to the PVN and surrounding neural sites within this framework as the primary sites of release and action of various orexigenic and anorexigenic signals. A novel finding is the identification of the interconnected wiring of the DMN-mPVN axis that may mediate leptin restraint on NPY-induced feeding. The chemical phenotypes of leptin and NPY target neurons in this axis remain to be identified. These multiple orexigenic and anorexigenic pathways in the hypothalamic ARN appear to represent redundancy, a characteristic of regulated biological systems to provide a "fail-safe" neural mechanism to meet an organism's constant energy needs for growth and maintenance. Within this formulation, the coexisting orexigenic signals (NPY, NE, GAL, GABA, and AgrP) represent either another level of redundancy or it is possible that these signals operate within the ARN as reinforcing agents to varying degrees under different circumstances. (ABSTRACT TRUNCATED)

Disruption of neural signaling within the hypothalamic ventromedial nucleus upregulates galanin gene expression in association with hyperphagia: an in situ hybridization analysis

Hypothalamic neuropeptides play critical roles in the regulation of appetite and body weight. We recently reported that disruption of neural signaling in the ventromedial nucleus (VMN) by microinjection of the neurotoxin, colchicine (COL), produced transient hyperphagia with attendant body weight gain lasting for 4 days. The neural mechanism(s) underlying this temporary shift in energy homeostasis is still unknown. Galanin (GAL) is produced in several hypothalamic nuclei and since microinjection of GAL into these sites stimulates feeding, we tested the hypothesis that galaninergic signaling is upregulated in COL-treated rats. COL (4 microgram in 0.5 microliter saline) or saline alone was microinjected into the VMN of adult male rats and GAL mRNA was evaluated in the basal hypothalamus by ribonuclease protection assay on day 1, day 2 and day 4 after injection. Whereas in saline-treated rats body weight and GAL mRNA remained unaffected, they were significantly increased in COL-injected rats through the period of observation. To identify the specific neuronal subpopulations involved, GAL mRNA levels were analyzed in feeding-related hypothalamic nuclei using semiquantitative in situ hybridization histochemistry on day 4 after microinjection of COL or saline into the VMN. In COL-treated rats, GAL mRNA levels increased dramatically over controls in the supraoptic nucleus, paraventricular nucleus (PVN), dorsomedial nucleus (DMN), arcuate nucleus (ARC) and lateral hypothalamic area (LHA); no significant change was observed in the central nucleus of amygdala. These results indicated that disruption of neurotransmission in the VMN upregulated GAL gene expression in those hypothalamic sites (PVN, DMN, LHA and ARC) that are implicated in regulation of feeding, and since GAL stimulates feeding, this neurochemical rearrangement may contribute to the over-eating in these animals. These results also suggest that, normally, neurons in the VMN may suppress GAL neurotransmission in feeding-regulating hypothalamic neural circuits.

Orexins, a novel family of hypothalamic neuropeptides, modulate pituitary luteinizing hormone secretion in an ovarian steroid-dependent manner

Orexin A and orexin B are a newly described family of orexigenic hypothalamic neuropeptides. The distribution of orexin immunoreactive fibers overlaps with the luteinizing hormone-releasing hormone (LHRH) neuronal system in the septo-preoptic area and the arcuate nucleus-median eminence region. To test the hypothesis that orexins may be involved in the regulation of pituitary LH secretion by influencing LHRH release, the effects of orexin A and orexin B on LH secretion were evaluated in ovariectomized (ovx) and ovarian steroid-treated ovx rats. Intracerebroventricular injection of orexin A or orexin B rapidly stimulated LH secretion in a dose- (0.3 and 3.0 nmol) and time-related fashion in estradiol benzoate- (EB) and progesterone (P)-pretreated ovx rats. Peak plasma LH concentration at 10 min were significantly higher in orexin A- than in orexin B-injected rats. On the other hand, both orexins (3 nmol) inhibited LH release in unprimed ovx rats. This ovarian steroid-dependent bimodal LH response is reminiscent of that of other orexigenic neuropeptides, such as neuropeptide Y. These findings show that orexins belong to a group of hypothalamic messengers that neurochemically bridge the regulatory networks that controls reproduction and energy balance.

Diurnal rhythm in cyclic GMP/nitric oxide efflux in the medial preoptic area of male rats

Since nitric oxide (NO) is implicated in the neuroendocrine control of luteinizing hormone-releasing hormone (LHRH) secretion and sexual behavior which show diurnal variations, we monitored cGMP levels (an index of NO activity) in the extracellular compartment of the medial preoptic area (MPOA) using microdialysis. It was observed that MPOA cGMP levels rose significantly in the afternoon in both castrated and intact male rats, thereby suggesting the existence of a diurnal rhythm in MPOA cGMP/NO efflux which may participate in eliciting the well-known diurnal variations in LHRH neuronal activity and male sexual behavior.

Ovarian steroid-independent diurnal rhythm in cyclic GMP/nitric oxide efflux in the medial preoptic area: possible role in preovulatory and ovarian steroid-induced LH surge

The aim of this study was to evaluate the relationship between cyclic LH hypersecretion and nitric oxide (NO) release in the medial preoptic area (MPOA), the hypothalamic site implicated in induction of LH hypersecretion. The MPOA extracellular cyclic GMP (cGMP) efflux (an index of NO release), was monitored by microdialysis. Quite unexpectedly, we observed a daily afternoon rise in the MPOA cGMP efflux in cycling female rats on proestrus and diestrus II, in ovariectomized (ovx) rats and in ovx rats treated with ovarian steroids to induce the LH surge. The daily rise in cGMP efflux occurred earlier in diestrous and in estradiol benzoate (EB)-treated ovx rats than in ovx rats. Progesterone (P) injection to estrogen-primed ovx rats further advanced the onset of the rise close to the earliest time of rise as seen on proestrus. The afternoon increase in the cGMP efflux in proestrous rats was abolished by pentobarbital treatment that blocked the LH surge. Intracerebroventricular (i.c.v.) injection of 1 H-[1,2,4]oxadiazo[4,3-a]quinoxalin-one (ODQ), a selective inhibitor of soluble guanylyl cyclase, suppressed the P-induced LH surge in EB-primed ovx rats, but not basal LH secretion in unprimed ovx rats. Analysis of brain NOS (bNOS) levels in the POA by Western blotting showed that the morning bNOS levels were higher in the POA of EB-treated rats than in unprimed ovx rats. Further, with the exception of ovx rats treated with sequential EB and P treatment, the POA bNOS levels rose significantly in the afternoon in unprimed ovx and EB-treated ovx rats. Collectively, these findings reveal a diurnal rhythm in the MPOA cGMP/NO efflux that is ovarian steroid-independent. Ovarian steroids apparently shift the timing of the afternoon rise in cGMP/NO efflux to synchronize with the activation of steroid-dependent neuronal systems responsible for the LH surge.

Neural substrates for leptin and neuropeptide Y (NPY) interaction: hypothalamic sites associated with inhibition of NPY-induced food intake

Intracerebroventricular (i.c.v.) injection of leptin, the adipocyte hormone, inhibits neuropeptide Y (NPY)-induced feeding in the rat. To identify the neural substrate for leptin and NPY interaction in the hypothalamus, we evaluated the expression of c-fos-like immunoreactivity (FLI), an early marker of neuronal activation, in response to icv administration of leptin, NPY and leptin plus NPY. As expected, leptin significantly decreased NPY-induced feeding in leptin plus NPY-treated rats. A comparative evaluation of the number of FLI-positive neurons in hypothalamic sites showed that both leptin and NPY activated FLI in the parvocellular subdivision of the paraventricular nucleus (pPVN), dorsomedial nucleus (DMN) and ventromedial nucleus (VMN). NPY also augmented the FLI response in the magnocellular PVN (mPVN) and supraoptic nucleus (SON), two sites where leptin alone was ineffective. Combined leptin and NPY treatment significantly decreased the number of FLI-positive neurons in the magnocellular PVN but increased their number in the dorsomedial nucleus as compared to the number of FLI-expressing neurons in these sites after NPY and leptin alone. Because there is morphologic evidence of a link between magnocellular PVN and dorsomedial nucleus, these results suggest the functional involvement of leptin plus NPY responsive elements in these sites in reduction of NPY-induced feeding by leptin.

Comparative effects of losartan and captopril on ventricular remodeling and function after myocardial infarction in the rat

OBJECTIVE

To determine the effects of losartan and captopril treatment on ventricular remodeling and function after myocardial infarction in rats.

METHODS

Thirty-two rats with MI induced by coronary ligation after seven days were divided into four groups randomly and treated with captopril(2 g.liter-1, group A), losartan(10 mg.kg-1.d-1, group B), losartan(30 mg.kg-1.d-1, group C) and placebo (no drug, group D) for six weeks, respectively. Sham-operated rats(group E) served as controls. Echocardiography was performed at 1 and 7 weeks after MI, respectively.

RESULTS

Compared with the results before treatment, both LV end-diastolic internal diameter and volume decreased significantly and the thickened posterior wall was reversed in group A, B and C; the peak early filling velocity decreased whereas the peak velocity was increased in these three groups. There are no significant difference among the three treated groups. However, LV end-diastolic internal diameter and the E/A were still increased, whereas the thickness of anterior wall and the peak velocity of LV outflow were decreased in group A, B, and C after treatment comparing with group E.

CONCLUSION

Both angiotensin converting enzyme inhibitor and angiotensin II receptor antagonist can prevent the ventricular remodeling and improve the ventricular function.

The interactive language of the hypothalamus for the gonadotropin releasing hormone (GNRH) system

The enormous diversity in neurochemical signals employed within the network of afferents to GnRH neurons is well-documented. An examination of novel and accumulating knowledge on the operation of these messengers indicates the presence of an interactive language governing GnRH secretion. The basic operational structures identified to date to affirm this interactive form of communication summarized in this review are the following: (i) the demonstration of interconnections within various components of the afferent network; (ii) coexistence and possible co-release of excitatory and inhibitory neurotransmitters/neuromodulators; (iii) co-action of various messengers at synaptic targets, and (4) modulation by gonadal steroids of the synthesis and release of signals and their receptors, and induction of synaptic plasticity for the timely relay of signals for GnRH secretion. Unraveling the molecular sequelae that promote this interactive communication to elicit periodic GnRH secretion is now a new challenge.

Evidence showing that beta-endorphin regulates cyclic guanosine 3',5'-monophosphate (cGMP) efflux: anatomical and functional support for an interaction between opiates and nitric oxide

Nitric oxide (NO) is now recognized as a diffusible messenger molecule that normally augments intercellular communication in the central nervous system, but is neurotoxic if released in excessive amounts. NO is synthesized from L-arginine by the Ca2+/calmodulin-dependent neuronal isoform NO synthase (NOS) localized in sub-populations of neurons throughout the brain, including the hypothalamus. In the hypothalamus, NO stimulates the release of GnRH, the primary neurohormone governing reproduction in mammals. Although the excitatory amino acid, glutamate, acting through the N-methyl-D-aspartate (NMDA) receptor is believed to be responsible for stimulation of NO release, the neuronal system(s) that inhibits NO efflux is unknown. As the endogenous opioids, primarily beta-endorphin (betaEND), exert a tonic restraint on GnRH secretion, we sought evidence for a possible functional link between betaEND and NOS pathways in the hypothalamus. We observed that restraining the opioid influence with the opiate receptor antagonist, naloxone, in intact, but not in castrated, rats rapidly augmented extracellular cGMP/NO efflux in the medial preoptic area, where GnRH, NOS, and betaEND immunoreactive pathways are coextensive. Pituitary LH secretion increased in conjunction with this augmented cGMP/NO response and pretreatment with the mu opiate receptor agonist, morphine, suppressed these naloxone-induced responses. Further, visualization of hypothalamic sections immunostained for both betaEND and NOS revealed betaEND-immunoreactive axon terminals in close proximity to NOS-positive cell bodies and dendrites in a number of hypothalamic subdivisions, including the medial preoptic area. These close appositions represented conventional synapses between betaEND nerve terminals and NOS-positive perikarya and dendrites under the electron microscope. Clearly, the experimental data, corroborated by morphological evidence, point to a direct inhibitory control of betaEND on NOS-immunoreactive neurons in monitoring cGMP/NO release. These findings together with the previous observations that the glutamate neurotransmitter acting through NMDA receptors located on NOS-immunopositive cells stimulates cGMP/NO efflux and plasma LH selectively in intact rats document the existence of a dual control comprised of the excitatory NMDA and the inhibitory mu opiate receptors in modulating cGMP/NO release, a response also directed by gonadal steroids. This new knowledge of an inhibitory opioid influence on cGMP/NO release is probably extremely important both in the generation of periodicities in GnRH secretion that underlie hypothalamic control of reproduction and in protecting against neurotoxic overstimulation of NO release by excitatory amino acids.

An interactive physiological role of neuropeptide Y and galanin in pulsatile pituitary luteinizing hormone secretion

Both neuropeptide Y (NPY) and galanin (GAL) systems have been implicated in the excitatory regulation of pulsatile LH secretion in the ovariectomized rat. The present studies were designed to examine the possible interaction of these two neuropeptides in controlling episodic LH release by testing the effects of central infusion of antibodies (Ab) to NPY and GAL, alone or in combination; additional studies tested the effects of central administration of an antisense oligodeoxynucleotide (ODN) to NPY and GAL messenger RNA. Rats were ovariectomized, implanted with a cannula in the third ventricle, and used in experiments 2 weeks later. Central infusion, via Alzet osmotic minipumps, of IgG purified from an NPY Ab produced a dose-related suppression of pulsatile LH secretion. Although an Ab dilution of 1:10 was ineffective, a maximal inhibitory effect was obtained using an NPY Ab dilution of 1:1, which decreased the mean levels, pulse frequency, and pulse amplitude of LH. These parameters of episodic LH secretion were also significantly reduced by central injection of antisense NPY ODN compared to those in vehicle- or missense ODN-treated controls. Similar dose-related inhibitory effects on the parameters of LH secretion were seen after central infusion of GAL Ab. Furthermore, infusion of a combination of NPY Ab and GAL Ab, each at the ineffective dilution of 1:10, resulted in a profound inhibition of LH secretion equivalent to the pattern seen with the maximally effective 1:1 Ab dilution. These results strengthen the idea of a physiological role for both NPY and GAL systems in the mechanism underlying the LHRH pulse generator activity and further suggest that these two excitatory neuropeptides act in concert to generate pulsatile LHRH release.

Evidence that gonadal steroids modulate nitric oxide efflux in the medial preoptic area: effects of N-methyl-D-aspartate and correlation with luteinizing hormone secretion

Several lines of evidence suggest that nitric oxide (NO) is involved in the neuroendocrine control of reproductive function. This study was undertaken to determine 1) NO activity in the medial preoptic area (MPOA) where LHRH- and NO synthase-containing neurons are coextensive; 2) whether N-methyl-D-aspartate (NMDA) receptor activation, which stimulates LHRH release, augments NO activity in the MPOA; and 3) whether NO activation in the MPOA underlies the steroid dependency of NMDA-induced pituitary LH release. As extracellular levels of cGMP in discrete brain sites are a reliable index of basal and stimulated activity of NO, extracellular cGMP levels in the MPOA of freely moving, awake rats were measured by microdialysis in the current study. In the first experiment, the MPOA of intact and castrated male rats were microdialyzed with artificial cerebrospinal fluid at a rate of 5 microliters/min. The basal level of cGMP efflux was determined from the initial seven samples collected at 20-min intervals. The NO response to a single i.v. injection of NMDA (10 mg/kg) or saline was assessed in the next five samples. In the second experiment, the basal and NMDA-evoked NO effluxes in the MPOA of ovariectomized (ovx) and estrogen-treated ovx rats were examined. Results showed that in both sexes, the absence of gonadal steroids resulted in significantly lower basal cGMP levels. Additionally, the cGMP response to NMDA was steroid dependent. Whereas in castrated rats it failed to affect cGMP efflux, NMDA in intact male rats promptly raised cGMP levels at 20 min, and these elevated levels were maintained through the duration of the experiment. This NMDA-induced cGMP response, observed selectively in intact rats, was also associated with stimulation of plasma LH levels. In female rats, NMDA similarly enhanced MPOA cGMP efflux and pituitary LH secretion in estradiol benzoate-treated, but not in oil-treated, ovx rats. The NMDA receptor antagonist D,L-amino-5-phosphoropentanoic acid and the NO synthase inhibitor, N omega-nitro-L-arginine, completely blocked the NMDA-induced cGMP and LH responses, thereby demonstrating the specificity of the NMDA receptor --> NO line of communication probably operating in the MPOA in the control of pituitary LH release. Therefore, these results show that gonadal steroids augment basal as well as NMDA-induced MPOA cGMP efflux in male and female rats. It is likely that facilitation of NO/cGMP activity in the MPOA may underlie the steroid dependency of NMDA-evoked LH hypersecretion in the rat.

[The clinical features and long-term follow-up of atrial fibrillation or atrial flutter complicating Wolff-Parkinson-White syndrome]

Twenty six patients (20 male, 6 female, aged 50 +/- 14) with recurrent episodes of atrial fibrillation or atrial flutter (Af/AF) associated with WPW syndrome were retrospectively studied and followed. During Af/AF, 17 patients showed ventricular preexcitation. Of them, 15 patients had hypotention, 8 syncope, 4 precipitating acute heart failure and 4 spontanous degenerated into ventricular fibrillation. Hypotention was found only in 2 of the 9 patients without pre-excited ventricular beats. The mean shortest prexcited R-R intervals of the former were shorter (247 +/- 47 ms) and the average ventricular rates (198 +/- 43 beat/min) were faster than those of the latter (393 +/- 80 ms & 144 +/- 22 beat/min) respectively (P < 0.01). When pre-excited Af/AF occurred, both cardioversion and antiarrhythmic agents of class I and II had marked effect in terminating the Af/AF or slowing pre-exicted ventricular responses. Digitalis and verapamil caused deterioration in the clinical condition of 6 patients (4 with hypotention, one syncope, and one ventricular fibrillation). Management of patients for WPW complicating Af/AF without pre-excited QRS was the same as for the ordinary Af/AF. Over a period of 53 +/- 44 months of follow-up, 5 died (3 of sudden death, one of heart failure, and one of noncardiac cause) in the group with preexcited Af/AF, but all of the patients without preexcited QRS during Af/AF were alive. Conclusion, clinical severity, response to the treatment, and long-term prognosis of patients of WPW with preexcited Af/AF are different from those without.

Cholecystokinin gene expression in rat amygdaloid neurons: normal distribution and effect of morphine tolerance

Previous studies have shown that repeated opioid administration induces a tolerance to opioid, presumably due in part to an opioid-mediated compensatory increase in brain cholecystokinin (CCK) synthesis and/or release. In this study, in situ hybridization histochemistry was used to examine the effect of morphine tolerance on CCK gene expression in the amygdala of rat brains, by using a 35S-labeled synthetic oligonucleotide probe. CCK mRNA-positive neurons in normal rats were seen throughout the amygdaloid complex, with the most heavily labeled neurons in lateral, basal, and cortical nuclei, followed by the medial nucleus. Only a few labeled neurons were found in central and intercalated nuclei. The development of morphine tolerance in the rat was associated with increased hybridization signals for CCK mRNA in each subnucleus of the amygdala. Increases were seen in the numbers of positively labeled neurons and/or the numbers of hybridization grains per positively labeled neuron. Furthermore, differential patterns of increase in CCK mRNA in morphine tolerant rats occurred in different subnuclei of the amygdala, with the highest magnitude of increase in the cortical nucleus, followed in order by the medial, central, basal, intercalated and lateral nuclei. The present study demonstrated that repeated administration of morphine increased CCK gene expression in the amygdaloid complex, and suggested that the development of the tolerance to morphine analgesia is due, in part, to an increase in CCK activity in the amygdaloid complex. These findings substantiate the hypothesis that long-term administration of opioid may induce a compensatory increase in CCK synthesis and/or release, which then results in a progressive antagonism of opioid analgesia.

[Effects of air pollution on health of residents in vicinity of an electrometallurgical factory in Chengdu]

Air pollution in an electrometallurgical plant in Chengdu was monitored in 1988. Results showed that atmospheric TSP and Ni concentrations in the vicinity of the plant were higher than those in control area; and TSP content higher than its health standard level. A population of 262 children was physically examined in the same pollution and control areas in May, 1988. Physical examinations were as follows:otorhinolaryngological examination, skin patch test of Ni and Co, immune function test (including PHA skin test, salivary LZM content), Ni levels in human hair and urine etc. We found that body burdens of Ni in population of pollution area increased because of the pollution of Ni compounds in the atmosphere. Hair Ni content in pollution area was significantly higher than that in control area, and the positive rate of Ni skin patch test was also markedly higher than that in control area. Case history indicated that there was a significant difference in Ni content as detected by otorhinolaryngological examinations between the pollution and control areas. Some measures were suggested to improve the air quality based on the study.

[Quantitative analysis of signal-averaged electrocardiograms]

Quantitative analysis of the high frequency components of the terminal portion of the high-resolution surface QRS was performed in 119 normal subjects (N), 62 patients with ventricular tachycardia (VT) including 20 patients with sustained VT or VF (VTs/VF) and in 565 ischemic and nonischemic cardiac patients (NO-VT). High-resolution surface ECG (SAECG) was obtained during sinus rhythm with noise level below 0.4 microV by ART-1200EPX. The vector magnitude of the filtered and signal-averaged standard bipolar orthogonal leads X, Y, Z (V = square root of X2 + Y2 + Z2) were used for analysis. Total duration of the QRS (QRST), the duration of the low amplitude (40 microV) signals in the terminal portion of the QRS (D40) and the amplitude of the signals in the last 40 ms (V40) were measured at filter settings of both 25Hz and 40Hz by the computer. Specific values for each of the indices were identified at both 25Hz and 40Hz filterings, which could separate N as well as NO-VT from VTs/VF. They were greater than or equal to 120 ms for QRST, greater than or equal to 34 ms for D40 and less than or equal to 25 microV for V40 at 25Hz, greater than or equal to 120 ms for QRST, greater than or equal to 39 ms for D40 and less than or equal to 20 microV for V40 at 40 Hz filtering.(ABSTRACT TRUNCATED AT 250 WORDS)