Refeeding activates neurons in the dorsomedial hypothalamus to inhibit food intake and promote positive valence.

OBJECTIVE: The regulation of food intake is a major research area in the study of obesity, which plays a key role in the development of metabolic syndrome. Gene targeting studies have clarified the roles of hypothalamic neurons in feeding behavior, but the deletion of a gene has a long-term effect on neurophysiology. Our understanding of short-term changes such as appetite under physiological conditions is therefore still limited. METHODS: Targeted recombination in active populations (TRAP) is a newly developed method for labeling active neurons by using tamoxifen-inducible Cre recombination controlled by the promoter of activity-regulated cytoskeleton-associated protein (Arc/Arg3.1), a member of immediate early genes. Transgenic mice for TRAP were fasted overnight, re-fed with normal diet, and injected with 4-hydroxytamoxifen 1 h after the refeeding to label the active neurons. The role of labeled neurons was examined by expressing excitatory or inhibitory designer receptors exclusively activated by designer drugs (DREADDs). The labeled neurons were extracted and RNA sequencing was performed to identify genes that are specifically expressed in these neurons. RESULTS: Fasting-refeeding activated and labeled neurons in the compact part of the dorsomedial hypothalamus (DMH) that project to the paraventricular hypothalamic nucleus. Chemogenetic activation of the labeled DMH neurons decreased food intake and developed place preference, an indicator of positive valence. Chemogenetic activation or inhibition of these neurons had no influence on the whole-body glucose metabolism. The labeled DMH neurons expressed prodynorphin (pdyn), gastrin-releasing peptide (GRP), cholecystokinin (CCK), and thyrotropin-releasing hormone receptor (Trhr) genes. CONCLUSIONS: We identified a novel cell type of DMH neurons that can inhibit food intake and promote feeding-induced positive valence. Our study provides insight into the role of DMH and its molecular mechanism in the regulation of appetite and emotion.

Anomalous pseudocapacitive behavior of a nanostructured, mixed-valent manganese oxide film for electrical energy storage.

While pseudocapacitors represent a promising option for electrical energy storage, the performance of the existing ones must be dramatically enhanced to meet today's ever-increasing demands for many emerging applications. Here we report a nanostructured, mixed-valent manganese oxide film that exhibits anomalously high specific capacitance (∼2530 F/g of manganese oxide, measured at 0.61 A/g in a two-electrode configuration with loading of active materials ∼0.16 mg/cm(2)) while maintaining excellent power density and cycling life. The dramatic performance enhancement is attributed to its unique mixed-valence state with porous nanoarchitecture, which may facilitate rapid mass transport and enhance surface double-layer capacitance, while promoting facile redox reactions associated with charge storage by both Mn and O sites, as suggested by in situ X-ray absorption spectroscopy (XAS) and density functional theory calculations. The new charge storage mechanisms (in addition to redox reactions of cations) may offer critical insights to rational design of a new-generation energy storage devices.

Abscisic acid activates a Ca2+-calmodulin-stimulated protein kinase involved in antioxidant defense in maize leaves.

The role of a calcium-dependent and calmodulin (CaM)-stimulated protein kinase in abscisic acid (ABA)-induced antioxidant defense was determined in leaves of maize (Zea mays). In-gel kinase assays showed that treatments with ABA or H(2)O(2) induced the activation of a 49-kDa protein kinase and a 52-kDa protein kinase significantly. Furthermore, we showed that the 52-kDa protein kinase has the characteristics of CaM-stimulating activity and is sensitive to calcium-CaM-dependent protein kinase II (CaMK II) inhibitor KN-93 or CaM antagonist W-7. Treatments with ABA or H(2)O(2) not only induced the activation of the 52-kDa protein kinase, but also enhanced the total activities of the antioxidant enzymes, including catalase, ascorbate peroxidase, glutathione reductase, and superoxide dismutase. Such enhancements were blocked by pretreatment with a CaMK inhibitor and a reactive oxygen species (ROS) inhibitor or scavenger. Pretreatment with the CaMK inhibitor also substantially arrested the ABA-induced H(2)O(2) production. Kinase activity enhancements induced by ABA were attenuated by pretreatment with an ROS inhibitor or scavenger. These results suggest that the 52-kDa CaMK is involved in ABA-induced antioxidant defense and that cross-talk between CaMK and H(2)O(2) plays a pivotal role in ABA signaling. We infer that CaMK acts both upstream and downstream of H(2)O(2), but mainly acts between ABA and H(2)O(2) in ABA-induced antioxidant-defensive signaling.

Ab initio chemical kinetics for singlet CH(2) reaction with N(2) and the related decomposition of diazomethane.

The kinetics and mechanism for the reaction of singlet state CH(2) with N(2) have been investigated by ab initio calculations with rate constant prediction. The potential energy surface of the reactions has been calculated by single-point calculations at the CCSD(T)/6-311+G(3df,2p) level based on geometries optimized at the B3LYP/6-311+G(3df,2p) level. By comparing the differences in the predicted heats of reaction with the available experimental values, we estimate the uncertainties in the calculated heats of reactions are +/-1.4 kcal/mol. Rate constants for various product channels in the temperature range of 300-3000 K are predicted by the variational transition state and RRKM theories. The predicted total rate constants for (1)CH(2) + N(2) at 760 Torr Ar pressure can be represented by the expressions s-k(total) = 9.67 x 10(+7) x T (-6.88) exp (-1345/T) cm(3) molecule(-1) s(-1) at T = 300-2400 K and 3.15 x 10(-229) x T (+56.18) exp (128 000/T) cm(3) molecule(-1) s(-1) at T = 2400-3000 K. The branching ratios of the primary channels for (1)CH(2) + N(2) are predicted: k(1) for forming singlet s-CH(2)N(2)-a (diazomethane) accounts for 0.97-0.01, k(2) + k(4) for producing HCNN-a + H accounts for 0.00-0.69, k(3) for forming singlet s-CH(2)N(2)-b (3H-diazirine) accounts for 0.03-0.00, k(5) for producing HCN + NH accounts for 0.00-0.18, and k(6) for producing CNNH + H accounts for 0.00-0.11 in the temperature range of 300-3000 K. The rate constant predicted for the unimoclecular decomposition of diazomethane producing (1)CH(2) + N(2) agrees closely with experimental results. Because of the low stability of the two isomeric CH(2)N(2) adducts and the high barriers for production of CN-containing products, the contribution of the CH(2) + N(2) reaction to NO formation becomes very small.

Induction of protection against paraquat-induced oxidative damage by abscisic acid in maize leaves is mediated through mitogen-activated protein kinase.

Mitogen-activated protein kinase (MAPK) cascade has been shown to be important components in stress signal transduction pathway. In the present study, protection of maize seedlings (Zea mays L.) against paraquat-generated oxidative toxicity by abscisic acid (ABA), its association with MAPK and ZmMPK5, a candidate for MAPK were investigated. Treatment of maize leaves with exogenous ABA led to significant decreases in the content of malondialdehyde, the percentage of ion leakage and the level of protein oxidation (in terms of carbonyl groups) under paraquat (PQ) stress. However, such decreases were blocked by the pretreatment with two MAPK kinase inhibitors PD98059 and U0126. The damage caused by PQ was further aggravated by inhibitors. Two inhibitors also suppressed the total activities of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2). Besides, treatment with PQ stimulated the activation of a 46 kDa MAPK, which was identified as ZmMPK5 by in-gel kinase assay with immunoprecipitation. These results reveal that ABA-induced protection against PQ-generated oxidative damage is mediated through MAPK cascade in maize leaves, in which ZmMPK5, a candidate for MAPK, is demonstrated to be involved.

Involvement of protein phosphorylation in water stress-induced antioxidant defense in maize leaves.

Using pharmacological and biochemical approaches, the role of protein phosphorylation and the interrelationship between water stress-enhanced kinase activity, antioxidant enzyme activity, hydrogen peroxide (H2O2) accumulation and endogenous abscisic acid in maize (Zea mays L.) leaves were investigated. Water-stress upregulated the activities of total protein phosphorylation and Ca2+-dependent protein kinase, and the upregulation was blocked in abscisic acid-deficient vp5 mutant. Furthermore, pretreatments with a nicotinamide adenine dinucleotide phosphate oxidase inhibitor and a scavenger of H2O2 significantly reduced the increased activities of total protein kinase and Ca2+-dependent protein kinase in maize leaves exposed to water stress. Pretreatments with different protein kinase inhibitors also reduced the water stress-induced H2O2 production and the water stress-enhanced activities of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase. The data suggest that protein phosphorylation and H2O2 generation are required for water stress-induced antioxidant defense in maize leaves and that crosstalk between protein phosphorylation and H2O2 generation may occur.

Nitric oxide reduces hydrogen peroxide accumulation involved in water stress-induced subcellular anti-oxidant defense in maize plants.

Nitric oxide (NO) is a bioactive molecule involved in many biological events, and has been reported as pro-oxidant as well as anti-oxidant in plants. In the present study, the sources of NO production under water stress, the role of NO in water stress-induced hydrogen peroxide (H2O2) accumulation and subcellular activities of anti-oxidant enzymes in leaves of maize (Zea mays L.) plants were investigated. Water stress induced defense increases in the generation of NO in maize mesphyll cells and the activity of nitric oxide synthase (NOS) in the cytosolic and microsomal fractions of maize leaves. Water stress-induced defense increases in the production of NO were blocked by pretreatments with inhibitors of NOS and nitrate reductase (NR), suggesting that NO is produced from NOS and NR in leaves of maize plants exposed to water stress. Water stress also induced increases in the activities of the chloroplastic and cytosolic anti-oxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR), and the increases in the activities of anti-oxidant enzymes were reduced by pretreatments with inhibitors of NOS and NR. Exogenous NO increases the activities of water stress-induced subcellular anti-oxidant enzymes, which decreases accumulation of H2O2. Our results suggest that NOS and NR are involved in water stress-induced NO production and NOS is the major source of NO. The potential ability of NO to scavenge H2O2 is, at least in part, due to the induction of a subcellular anti-oxidant defense.

Ab initio chemical kinetics for the OH+HNCN reaction.

The kinetics and mechanism of the reaction of the cyanomidyl radical (HNCN) with the hydroxyl radical (OH) have been investigated by ab initio calculations with rate constants prediction. The single and triplet potential energy surfaces of this reaction have been calculated by single-point calculations at the CCSD(T)/6-311+G(3df,2p) level based on geometries optimized at the B3LYP/6-311+G(3df,2p) and CCSD/6-311++G(d,p) levels. The rate constants for various product channels in the temperature range of 300-3000 K are predicted by variational transition-state and Rice-Ramsperger-Kassel-Marcus (RRKM) theories. The predicted total rate constants can be represented by the expressions ktotal=2.66 x 10(+2)xT-4.50 exp(-239/T) in which T=300-1000 K and 1.38x10(-20)xT2.78 exp(1578/T) cm3 molecule(-1) s(-1) where T=1000-3000 K. The branching ratios of primary channels are predicted: k1 for forming singlet HON(H)CN accounts for 0.32-0.28, and k4 for forming singlet HONCNH accounts for 0.68-0.17 in the temperature range of 300-800 K. k2+k7 for producing H2O+NCN accounts for 0.55-0.99 in the high-temperature range of 800-3000 K. The branching ratios of k3 for producing HCN+HNO, k6 for producing H2N+NCO, k8 for forming 3HN(OH)CN, k9 for producing CNOH+3NH, and k5+k10 for producing NH2+NCO are negligible. The rate constants for key individual product channels are provided in a table for different temperature and pressure conditions.

Nitric oxide induced by hydrogen peroxide mediates abscisic acid-induced activation of the mitogen-activated protein kinase cascade involved in antioxidant defense in maize leaves.

* The role of nitric oxide (NO) and the relationship between NO, hydrogen peroxide (H(2)O(2)) and mitogen-activated protein kinase (MAPK) in abscisic acid (ABA)-induced antioxidant defense in leaves of maize (Zea mays) plants were investigated. * Both ABA and H(2)O(2) induced increases in the generation of NO in mesophyll cells of maize leaves, and H(2)O(2) was required for the ABA-induced generation of NO. Pretreatment with NO scavenger and nitric oxide synthase (NOS) inhibitor substantially reduced the ABA-induced production of NO, and partly blocked the activation of a 46 kDa MAPK and the expression and the activities of several antioxidant enzymes induced by ABA. Treatment with the NO donor sodium nitroprusside (SNP) also induced the activation of the MAPK, and enhanced the antioxidant defense systems. * Conversely, SNP treatment did not induce the production of H(2)O(2), and pretreatments with NO scavenger and NOS inhibitor did not affect ABA-induced H(2)O(2) production. * Our results suggest that ABA-induced H(2)O(2) production mediates NO generation, which, in turn, activates MAPK and results in the upregulation in the expression and the activities of antioxidant enzymes in ABA signaling.

Experimental and theoretical studies of rate coefficients for the reaction O(3P)+C2H5OH at high temperatures.

Rate coefficients of the reaction O(3P)+C2H5OH in the temperature range 782-1410 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO2 at 193 nm with an ArF excimer laser; their concentrations were monitored via atomic resonance absorption. Our data in the range 886-1410 K are new. Combined with previous measurements at low temperature, rate coefficients determined for the temperature range 297-1410 K are represented by the following equation: k(T)=(2.89+/-0.09)x10(-16)T1.62 exp[-(1210+/-90)/T] cm3 molecule(-1) s(-1); listed errors represent one standard deviation in fitting. Theoretical calculations at the CCSD(T)/6-311+G(3df, 2p)//B3LYP/6-311+G(3df) level predict potential energies of various reaction paths. Rate coefficients are predicted with the canonical variational transition state (CVT) theory with the small curvature tunneling correction (SCT) method. Reaction paths associated with trans and gauche conformations are both identified. Predicted total rate coefficients, 1.60 x 10(-22)T3.50 exp(16/T) cm3 molecule(-1) s(-1) for the range 300-3000 K, agree satisfactorily with experimental observations. The branching ratios of three accessible reaction channels forming CH3CHOH+OH (1a), CH2CH2OH+OH (1b), and CH3CH2O+OH (1c) are predicted to vary distinctively with temperature. Below 500 K, reaction 1a is the predominant path; the branching ratios of reactions 1b,c become approximately 40% and approximately 11%, respectively, at 2000 K.

Computational study on the kinetics and mechanisms for the unimolecular decomposition of formic and oxalic acids.

The kinetics and mechanisms for the unimolecular decomposition reactions of formic acid and oxalic acid have been studied computationally by the high-level G2M(CC1) method and microcanonical RRKM theory. There are two reaction pathways in the decomposition of formic acid: The dehydration process starting from the Z conformer is found to be the dominant, whereas the decarboxylation reaction starting from the E conformer is less competitive. The predicted rate constants for the dehydration and decarboxylation reactions are in good agreement with the experimental data. The calculated CO/CO2 ratio, 13.6-13.9 between 1300 and 2000 K, is in close agreement with the ratio of 10 measured experimentally by Hsu et al. (In The 19th International Symposium on Combustion; The Combustion Institute: Pittsburgh, PA, 1983; p 89). For oxalic acid, its isomer with two intramolecular hydrogen bonds is the most stable structure, similar to earlier reports. Two primary decomposition channels of oxalic acid producing CO2+HOCOH with barriers of 33-36 kcal/mol and CO2+CO+H2O with a barrier of 39 kcal/mol were found. At high temperatures, the latter process becomes more competitive. The rate constant predicted for the formation of CO2 and HOCOH (the precursor of HCOOH) agrees well with available experimental data. The mechanism for the isomerization of HOCOH to HCOOH is also discussed.

Photodissociation dynamics of nitrobenzene and o-nitrotoluene.

Photodissociation of nitrobenzene at 193, 248, and 266 nm and o-nitrotoluene at 193 and 248 nm was investigated separately using multimass ion imaging techniques. Fragments corresponding to NO and NO(2) elimination from both nitrobenzene and o-nitrotoluene were observed. The translational energy distributions for the NO elimination channel show bimodal distributions, indicating two dissociation mechanisms involved in the dissociation process. The branching ratios between NO and NO(2) elimination channels were determined to be NONO(2)=0.32+/-0.12 (193 nm), 0.26+/-0.12 (248 nm), and 0.4+/-0.12(266 nm) for nitrobenzene and 0.42+/-0.12(193 nm) and 0.3+/-0.12 (248 nm) for o-nitrotoluene. Additional dissociation channels, O atom elimination from nitrobenzene, and OH elimination from o-nitrotoluene, were observed. New dissociation mechanisms were proposed, and the results are compared with potential energy surfaces obtained from ab initio calculations. Observed absorption bands of photodissociation are assigned by the assistance of the ab initio calculations for the relative energies of the triplet excited states and the vertical excitation energies of the singlet and triplet excited states of nitrobenzene and o-nitrotoluene. Finally, the dissociation rates and lifetimes of photodissociation of nitrobenzene and o-nitrotoluene were predicted and compared to experimental results.

Role of nitric oxide in abscisic acid-induced subcellular antioxidant defense of maize leaves.

The sources of nitric oxide (NO) production in response to abscisic acid (ABA) and the role of NO in ABA-induced hydrogen peroxide (H(2)O(2)) accumulation and subcellular antioxidant defense in leaves of maize (Zea mays L.) plants were investigated. ABA induced increases in generation of NO and activity of nitric oxide synthase (NOS) in maize leaves. Such increases were blocked by pretreatment with each of the two NOS inhibitors. Pretreatments with a NO scavenger or NR inhibitors inhibited ABA-induced increase in production of NO, but did not affect the ABA-induced increases in activity of NOS, indicating that ABA-induced NO production originated from sources of NOS and NR. ABA- and H(2)O(2)-induced increases in expression of the antioxidant genes superoxide dismutase 4 (SOD4), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of the chloroplastic and cytosolic antioxidant enzymes were arrested by pretreatments with the NO scavenger, inhibitors of NOS and NR, indicating that NO is involved in the ABA- and H(2)O(2)-induced subcellular antioxidant defense reactions. On the other hand, NO donor sodium nitroprusside (SNP) reduced accumulation of H(2)O(2) induced by ABA, and c-PTIO reversed the effect of SNP in decreasing the accumulation of H(2)O(2). SNP induced increases in activities of subcellular antioxidant enzymes, and the increases were substantially prevented from occurring by the pretreatment with c-PTIO. These results suggest that ABA induces production of H(2)O(2) and NO, which can up-regulate activities of the subcellular antioxidant enzymes, to prevent overproduction of H(2)O(2) in maize plants. There is a negative feedback loop between NO and H(2)O(2) in ABA signal transduction in maize plants.

Experimental and theoretical studies of rate coefficients for the reaction O(3P)+CH3OH at high temperatures.

Rate coefficients of the reaction O((3)P) + CH(3)OH in the temperature range of 835-1777 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO(2) with a KrF excimer laser at 248 nm or an ArF excimer laser at 193 nm; their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O(2) and He. The rate coefficients determined for the temperature range can be represented by the Arrhenius equation, k(T) = (2.29 +/- 0.18) x 10(-10) exp[-(4210 +/- 100)T] cm(3) molecule(-1) s(-1); unless otherwise noted, all the listed errors represent one standard deviation in fitting. Combination of these and previous data at lower temperature shows a non-Arrhenius behavior described as the three-parameter equation, k(T) = (2.74 +/- 0.07) x 10(-18)T(2.25 +/- 0.13) exp[-(1500 +/- 90)T] cm(3)molecule(-1) s(-1). Theoretical calculations at the Becke-3-Lee-Yang-Parr (B3LYP)6-311 + G(3df,2p) level locate three transition states. Based on the energies computed with coupled clusters singles, doubles (triples) [CCSD(T)]/6-311 + G(3df,2p)B3LYP6-311 + G(3df,2p), the rate coefficients predicted with canonical variational transition state theory with small curvature tunneling corrections agree satisfactorily with the experimental observations. The branching ratios of two accessible reaction channels forming OH + CH(2)OH (1a) and OH + CH(3)O (1b) are predicted to vary strongly with temperature. At 300 K, reaction (1a) dominates, whereas reaction (1b) becomes more important than reaction (1a) above 1700 K.

Computational study on the kinetics and mechanism for the unimolecular decomposition of C6H5NO2 and the related C6H5 + NO2 and C6H5O + NO reactions.

The kinetics and mechanisms for the unimolecular dissociation of nitrobenzene and related association reactions C(6)H(5) + NO(2) and C(6)H(5)O + NO have been studied computationally at the G2M(RCC, MP2) level of theory in conjunction with rate constant prediction with multichannel RRKM calculations. Formation of C(6)H(5) + NO(2) was found to be dominant above 850 K with its branching ratio > 0.78, whereas the formation of C(6)H(5)O + NO via the C(6)H(5)ONO intermediate was found to be competitive at lower temperatures, with its branching ratio increasing from 0.22 at 850 K to 0.97 at 500 K. The third energetically accessible channel producing C(6)H(4) + HONO was found to be uncompetitive throughout the temperature range investigated, 500-2000 K. The predicted rate constants for C(6)H(5)NO(2) --> C(6)H(5) + NO(2) and C(6)H(5)O + NO --> C(6)H(5)ONO under varying experimental conditions were found to be in good agreement with all existing experimental data. For C(6)H(5) + NO(2), the combination processes producing C(6)H(5)ONO and C(6)H(5)NO(2) are dominant at low temperature and high pressure, while the disproportionation process giving C(6)H(5)O + NO via C(6)H(5)ONO becomes competitive at low pressure and dominant at temperatures above 1000 K.