Antinociceptive effects of spinally administered nociceptin/orphanin FQ and its N-terminal fragments on capsaicin-induced nociception

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand for the N/OFQ peptide (NOP) receptors, has been shown to be metabolized into some fragments. We examined to determine whether intrathecal (i.t.) N/OFQ (1-13), (1-11) and (1-7) have antinociceptive activity in the pain-related behavior after intraplantar injection of capsaicin. The i.t. administration of N/OFQ (0.3-1.2 nmol) produced an appreciable and dose-dependent inhibition of capsaicin-induced paw-licking/biting response. The N-terminal fragments of N/OFQ, (1-13) and (1-11), were antinociceptive with a potency lower than N/OFQ. Calculated ID₅₀ values (nmol, i.t.) were 0.83 for N/OFQ, 2.5 for N/OFQ (1-13) and 4.75 for N/OFQ (1-11), respectively. The time-course effect revealed that the antinociceptive effects of these N-terminal fragments lasted longer than those of N/OFQ. Removal of amino acids down to N/OFQ (1-7) led to be less potent than N/OFQ and its fragments, (1-13) and (1-11). Antinociception induced by N/OFQ or N/OFQ (1-13) was reversed significantly by i.t. co-injection of [Nphe¹]N/OFQ (1-13)NH₂, a peptidergic antagonist for NOP receptors, whereas i.t. injection of the antagonist did not interfere with the action of N/OFQ (1-11) and (1-7). Pretreatment with the opioid receptor antagonist naloxone hydrochloride did not affect the antinociception induced by N/OFQ and its N-terminal fragments. These results suggest that N-terminal fragments of N/OFQ are active metabolites and may modulate the antinociceptive effect of N/OFQ in the spinal cord. The results also indicate that N/OFQ (1-13) still possess antinociceptive activity through NOP receptors.     

Structural Modifications of the N-terminal Tetrapeptide Segment of [D-Ala]Deltorphin I: Effects on Opioid Receptor Affinities and Activities In Vitro and on Antinociceptive Potency

Schmidt, R., D. Menard, C. Mrestani-Klaus, N. N. Chung, C. Lemieux and P. W. Schiller. Structural modifications of the N-terminal tetrapeptide segment of [d-Ala²]deltorphin I: effects on opioid receptor affinities and activities in vitro and on antinociceptive potency. Peptides 18(10) 1615–1621, 1997.—A series of deltorphin I analogs containing d- or l-N-methylalanine (MeAla), d- or l-proline (Pro), α-aminoisobutyric acid (Aib), sarcosine (Sar) or D-tert-leucine (Tle) in place of d-Ala², or phenylalanine in place of Tyr¹, was synthesized. The opioid activity profiles of these peptides were determined in μ and δ opioid receptor-representative binding assays and bioassays in vitro as well as in the rat tail flick test in vivo. In comparison with the deltorphin I parent, both the l- and the d-MeAla²-analog were slightly more potent δ agonists in the mouse vas deferens (MDV) assay, and the d-MeAla²-analog showed two-fold higher antinociceptive potency in the analgesic test. In view of the fact that deltorphin analogs with an unsubstituted l-amino acid residue in the 2-position generally lack opioid activity, the observed high δ opioid potency of [l-MeAla²]deltorphin I is postulated to be due to the demonstrated presence of a conformer with a cis Tyr¹-MeAla² peptide bond, since the cis conformer allows for a spatial arrangement of the pharmacophoric moieties in the N-terminal tripeptide segment similar to that in active deltorphin analogs containing a d-amino acid residue in the 2-position. Substitution of Aib in the 2-position led to a compound, H-Tyr-Aib-Phe-Asp-Val-Val-Gly-NH₂, which displayed lower δ receptor affinity than the parent peptide but higher δ selectivity and, surprisingly, three times higher antinociceptive potency. The d- and l- Pro²-, Sar²- and d-Tle²-analogs showed much reduced δ receptor affinities and were inactive in the tail flick test. Replacement of Tyr¹ in deltorphin I with Phe produced a 32-fold decrease in δ receptor affinity but only a 7-fold drop in antinociceptive potency.     

The effect of substance P1-7 amide on nociceptive threshold in diabetic mice

We previously demonstrated that intrathecal treatment with substance P metabolite substance P_1-7 induced anti-hyperalgesia in diabetic mice. In the present study, we have used a synthetic analog of this peptide, the substance P_1-7 amide, showing higher binding affinitiy than the native heptapeptide, for studies of the tail-flick response in diabetic and non-diabetic mice. Intrathecal injection of substance P_1-7 amide produced prolongation of the tail-flick latency in both diabetic and non-diabetic mice, an effect that was more pronounced in diabetic mice than non-diabetic mice. Moreover, the observed antinociceptive potency of the substance P_1-7 amide was higher in both diabetic and non-diabetic mice in comparison with the native substance P_1-7. The antinociceptive effect of substance P_1-7 amide was reversed by naloxone but not by the selective opioid receptor antagonist β-funaltrexamine, naltrindole or nor-binaltorphimine, selective for the μ-, δ- or κ-opioid receptor, respectively. In addition, the antinociceptive effect induced by substance P_1-7 amide was partly reversed by the σ₁ receptor agonist (+)-pentazocine, suggesting a possible involvement of the σ₁ receptor for the action of this peptide. These results suggest that the actions of substance P_1-7 amide mimic the effects of the native substance P fragment but with higher potency and that the mechanisms for its action may involve the σ₁ receptor system.     

Novel Inhibitors of Enkephalin-Degrading Enzymes II: N5-Substituted-4-Thioxohydantoic Acids as Aminopeptidase Inhibitors

Abstract

Some 2-substituted-(2′-aminophenyl)-4-thioxohydantoic acids (o-amino PTC-amino acids) have antinociceptive activity when administered (icv) alone (IC₅₀ = 0.04-0.87 μM/animal) and show a striking prolongation of the antinociceptive action of (D-Ala-² D-Leu⁵)-enkephalin (DADL) in combination. The effects are thought to be mediated via opioid receptors since they are naloxone-reversible. Although inhibitors of the enkephalin degrading puromycin-insensitive, bestatin-sensitive aminopeptidase (possibly aminopeptidase M) their action is weak (IC₅₀ = 32μM leucine, 536μM, glycine) and they might be considered to have a direct antinociceptive effect on opioid receptors. The titled compounds constitute novel ‘lead’ compounds for the development of potent aminopeptidase M inhibitors.     

Lipo-Endomorphin-1 Derivatives with Systemic Activity against Neuropathic Pain without Producing Constipation

To enhance the drug-like properties of the endogenous opioid peptide endomorphin-1 (1 = Tyr-Pro-Trp-Phe-NH₂), the N-terminus of the peptide was modified with 2-aminodecanoic acid, resulting in compound 3. Tyr in compound 1 was replaced with 2,6-dimethyltyrosine yielding compound 2. Derivative 2 was also substituted with 2-aminodecanoic acid producing compound, 4. Lipoamino acid-modified derivatives showed improved metabolic stability and membrane permeability while maintaining high μ-opioid (MOP) receptor binding affinity and acting as a potent agonist. In vivo studies showed dose-dependent antinociceptive activity following intravenous (i.v.) administration of compounds 3 and 4 in a chronic constriction injury (CCI)-rat model of neuropathic pain with ED₅₀ values of 1.22 (±0.93) and 0.99 (±0.89) µmol/kg, respectively. Pre-treatment of animals with naloxone hydrochloride significantly attenuated the anti-neuropathic effects of compound 3, confirming the key role of opioid receptors in mediating antinociception. In contrast to morphine, no significant constipation was produced following i.v. administration of compound 3 at 16 µmol/kg. Furthermore, following chronic administration of equi-potent doses of compound 3 and morphine to rats, there was less antinociceptive tolerance for compound 3 compared with morphine.     

Induction of pain facilitation by sustained opioid exposure: relationship to opioid antinociceptive tolerance

Opioid analgesics are frequently used for the long-term management of chronic pain states, including cancer pain. The prolonged use of opioids is associated with a requirement for increasing doses to manage pain at a consistent level, reflecting the phenomenon of analgesic tolerance. It is now becoming clearer that patients receiving long-term opioid therapy can develop unexpected abnormal pain. Such paradoxical opioid-induced pain, as well as tolerance to the antinociceptive actions of opioids, has been reliably measured in animals during the period of continuous opioid delivery. Several recent studies have demonstrated that such pain may be secondary to neuroplastic changes that result, in part, from an activation of descending pain facilitation mechanisms arising from the rostral ventromedial medulla (RVM). One mechanism which may mediate such pain facilitation is through the increased activity of CCK in the RVM. Secondary consequences from descending facilitation may be produced. For example, opioid-induced upregulation of spinal dynorphin levels seem to depend on intact descending pathways from the RVM reflecting spinal neuroplasticity secondary to changes at supraspinal levels. Increased expression of spinal dynorphin reflects a trophic action of sustained opioid exposure which promotes an increased pain state. Spinal dynorphin may promote pain, in part, by enhancing the evoked release of excitatory transmitters from primary afferents. In this regard, opioids also produce trophic actions by increasing CGRP expression in the dorsal root ganglia. Increased pain elicited by opioids is a critical factor in the behavioral manifestation of opioid tolerance as manipulations which block abnormal pain also block antinociceptive tolerance. Manipulations that have blocked enhanced pain and antinociceptive tolerance include reversible and permanent ablation of descending facilitation from the RVM. Thus, opioids elicit systems-level adaptations resulting in pain due to descending facilitation, upregulation of spinal dynorphin and enhanced release of excitatory transmitters from primary afferents. Adaptive changes produced by sustained opioid exposure including trophic effects to enhance pain transmitters suggest the need for careful evaluation of the consequences of long-term opioid administration to patients.     

Spatiotemporal variation in N2O flux within a slope in a Japanese cedar (Cryptomeria japonica) forest

Topographic factors affect nitrogen cycling in forest soils, including nitrous oxide (N₂O) emissions, which contribute to the greenhouse effect. We measured the N₂O flux at 14 chambers placed along a 65-m transect on a slope for 1 year at 2- to 3-week intervals. We applied a hierarchical Bayesian model with a conditional autoregressive (CAR) model to assess the spatiotemporal N₂O flux along a slope and quantify the effects of environmental factors on N₂O emissions. N₂O fluxes at chambers located at lower positions along the slope were relatively greater than those at higher positions. During the non-soil-freezing period, N₂O fluxes fluctuated seasonally depending on soil temperature. The soil temperature dependency of N₂O fluxes at each chamber increased with descending slope position (the median of the Q₁₀ equivalent simulated from posterior distribution ranged from 1.18 to 3.64). According to the Bayesian hierarchical model, this trend could be partially explained by the C/N ratio at each chamber position. During the soil-freezing period, relatively high N₂O fluxes were observed at lower positions along the slope.     

Discovery of two novel branched peptidomimetics containing endomorphin-2 and RF9 pharmacophores: Synthesis and neuropharmacological evaluation

It is well known that opioid analgesics produce side effects including tolerance and constipation. Since neuropeptide FF (NPFF) receptor antagonists reversed opioid-induced hyperalgesia and analgesic tolerance, the present work was performed to synthetize two branched peptidomimetics, EKR and RKE, containing the opioid peptide endomorphin-2 (EM-2) and the NPFF receptor antagonist RF9. Our data obtained from the in vitro cyclic adenosine monophosphate experiment demonstrated that EKR functioned as a mixed mu-, delta-opioid receptors agonist and NPFF₁ receptor antagonist/NPFF₂ receptor partial agonist, whereas RKE acted as a multi-functional peptidomimetic with the mu-opioid agonism and the NPFF₁ antagonism/NPFF₂ partial agonism. Furthermore, EKR and RKE completely blocked the NPFF₂ receptor-mediated neurite outgrowth of Neuro 2A cells. In vivo antinociception studies found that supraspinal administration of EKR and RKE dose-dependently produced potent antinociception via the mu-opioid receptor in the tail-flick test. In carrageenan inflammatory pain model, spinal administration of EKR and RKE induced dose-related analgesia, which was significantly reduced by the opioid antagonist naloxone and the NPFF antagonist RF9. Notably, compared with morphine, intracerebroventricular repeated administration of EKR and RKE maintained prolonged antinociceptive effectiveness. In addition, at the antinociceptive doses, these two branched peptidomimetics did not significantly inhibit gastrointestinal transit. Taken together, the present work suggest that EKR and RKE behave as multi-functional ligands with the opioid agonism and the NPFF₁ antagonism/NPFF₂ partial agonism, and produce prolonged antinociception with limited side effects. Moreover, our results imply that EKR and RKE might be interesting pharmacological tools for further investigating the biological function of the NPFF and opioid systems.     

好氧氨氧化过程中的关键酶及N2O排放研究进展

氧化亚氮(nitrous oxide, N₂O)排放量的持续增加对全球生态平衡造成了严重的威胁。微生物N₂O排放占主要来源。其中,好氧氨氧化过程是氨在有氧的条件下氧化为亚硝酸盐,其直接或间接地影响着全球产生N₂O与释放量。氨氧化古菌(ammonia-oxidizing archaea, AOA)、氨氧化细菌(ammonia-oxidizing bacteria, AOB)、全程氨氧化菌(complete ammonia oxidization, Comammox)和异养氨氧化菌(heterotrophic ammonium oxidizing bacteria, HAOB)是氨氧化过程中主要的参与者,明确这四类微生物N₂O产生的机制对缓解全球N₂O排放是必要的。本文综述了AOA、AOB、Comammox和HAOB在好氧氨氧化过程中驱动的N₂O产生途径,并结合酶学分析了一些关键酶在N₂O产生途径中的作用。本文旨在为调控生物N₂O排放提供理论基础。     

The legacy effect of biochar application on soil nitrous oxide emissions

Existing studies suggest that biochar application can reduce soil nitrous oxide (N₂O) emissions, mainly based on short-term results. However, it remains unclear what the effects (i.e., legacy effects) and underlying mechanisms are on N₂O emissions after many years of a single application of biochar. Here, we collected intact soil columns from plots without and with biochar application in a subtropical tea plantation 7 years ago for an incubation experiment. We used the N₂O isotopocule analysis combined with ammonia oxidizer-specific inhibitors and molecular biology approaches to investigate how the legacy effect of biochar affected soil N₂O emissions. Results showed that the soil in the presence of biochar had lower N₂O emissions than the control albeit statistically insignificant. The legacy effect of biochar in decreasing N₂O emissions may be attributed to the reduced effectiveness of the soil substrate, nitrification and denitrification activities, and the promotion of the further reduction of N₂O. The legacy effect of biochar reduced the relative contribution of nitrifier denitrification/bacterial denitrification, nitrification-related N₂O production, and the relative abundance of several microorganisms involved in the nitrogen cycle. Our global meta-analysis also showed that the reduction of N₂O by biochar increased with increasing application rate but diminished and possibly even reversed with increasing experimental time. In conclusion, our findings suggest that the abatement capacity of biochar on soil N₂O emissions may weaken over time after biochar application, but this remains under further investigation.     

Influences of Land Use/Cover Types on Nitrous Oxide Emissions during Freeze-Thaw Periods from Waterlogged Soils in Inner Mongolia

Nitrous oxide emissions during freeze/thaw periods contribute significantly to annual soil N₂O emissions budgets in middle- and high-latitude areas; however, the freeze/thaw-related N₂O emissions from waterlogged soils have hardly been studied in the Hulunber Grassland, Inner Mongolia. For this study, the effects of changes in land use/cover types on N₂O emissions during freeze–thaw cycles were investigated to more accurately quantify the annual N₂O emissions from grasslands. Soil cores from six sites were incubated at varying temperature (ranging from −15 to 10°C) to simulate freeze–thaw cycles. N₂O production rates were low in all soil cores during freezing periods, but increased markedly after soil thawed. Mean rates of N₂O production differed by vegetation type, and followed the sequence: Leymus chinensis (LC) and Artemisia tanacetifolia (AT) steppes > LC steppes ≥ Stipa baicalensis (SB) steppes. Land use types (mowing and grazing) had differing effects on freeze/thaw-related N₂O production. Grazing significantly reduced N₂O production by 36.8%, while mowing enhanced production. The production of N₂O was related to the rate at which grassland was mowed, in the order: triennially (M3) > once annually (M1) ≥ unmown (UM). Compared with the UM control plot, the M3 and M1 mowing regimes enhanced N₂O production by 57.9% and 13.0% respectively. The results of in situ year-round measurements showed that large amounts of N₂O were emitted during the freeze–thaw period, and that annual mean fluxes of N₂O were 9.21 μg N₂O-N m^-2 h^-1 (ungrazed steppe) and 6.54 μg N₂O-N m^-2 h^-1 (grazed steppe). Our results further the understanding of freeze/thaw events as enhancing N₂O production, and confirm that different land use/cover types should be differentiated rather than presumed to be equivalent, regarding nitrous oxide emission. Even so, further research involving multi-year and intensive measurements of N₂O emission is still needed.     

Treatment with Antisense Oligodeoxynucleotide to a Conserved Sequence of Opioid Receptors Inhibits Antinociceptive Effects of Delta Subtype Selective Ligands

Abstract

Previous work has suggested the existence of subtypes of the delta opioid receptor (DOR) which have been termed δ₁ and δ₂. [D-Ala², Glu⁴]deltorphin has been suggested to selectively elicit antinociception via the δ₂ receptor while [D-Pen², D-Pen⁵]enkephalin (DPDPE) is thought to act via the δ₁ receptor. Treatment with an antisense oligodeoxynucleotide (oligo) directed towards the N-terminal portion of the cloned DOR has been demonstrated to selectively inhibit the antinociceptive actions of [D-Ala², Glu⁴]deltorphin, but not of DPDPE, suggesting that the cloned DOR corresponds to that pharmacologically defined as δ₂. Here, an antisense oligo (or a mismatch sequence) was designed to target a conserved region of the cloned μ δ and opioid receptor. These oligos were employed in order to determine whether the antinociceptive effects of [DAla², Glu⁴]deltorphin, as well as DPDPE, could be inhibited. The data indicate that the antinociceptive actions of both ligands were inhibited by treatment with this antisense, but not with the mismatch oligo. Taken together, the results of the treatments with oligos directed towards the N-terminal portion of the cloned DOR and with that directed to the conserved region of the opioid receptors suggest that (a) DPDPE effects are mediated by a subtype of the DOR which shares a domain common to the cloned opioid receptors, and (b) the N-terminal region differs between these putative DOR subtypes.     

Divergent terrestrial responses of soil N2O emissions to different levels of elevated CO2 and temperature

Understanding the responses of soil nitrous oxide (N₂O) emissions from terrestrial ecosystems to future CO₂ enrichment and warming is critical for the development of mitigation and adaptation policies. The effects of continuous increase in elevated CO₂ (EC) and elevated temperature (ET) on N₂O emissions are not fully known. We synthesized 209 measurements from 70 published studies and carried out a meta-analysis to examine individual and interactive effects of EC and ET on N₂O emissions from grasslands, croplands and forests. On average, a significant increase of 23% in N₂O emissions was observed under EC across all case studies. EC did not affect N₂O emissions from grasslands or forests, but significantly increased N₂O emissions in croplands by 38%. The extent of ET effects on N₂O emissions was nonsignificant and there was no significant difference in N₂O emission responses among these three terrestrial systems. ET only promoted N₂O emissions in forest by about 32% when ET was less than 2°C. The interactive effect of EC and ET on N₂O emissions was significantly synergistic, showing a greater increase than the sum of the effects caused by EC and ET alone. Our findings indicated that the combination of EC and ET substantially promoted soil N₂O and highlighted the urgent need to explore its mechanisms to better understand N₂O responses under future climate change.     

Morphine and Clonidine Combination Therapy Improves Therapeutic Window in Mice: Synergy in Antinociceptive but Not in Sedative or Cardiovascular Effects

Opioids are used to manage all types of pain including acute, cancer, chronic neuropathic and inflammatory pain. Unfortunately, opioid-related adverse effects such as respiratory depression, tolerance, physical dependence and addiction have led to an underutilization of these compounds for adequate pain relief. One strategy to improve the therapeutic utility of opioids is to co-administer them with other analgesic agents such as agonists acting at α₂-adrenergic receptors (α₂ARs). Analgesics acting at α₂ARs and opioid receptors (ORs) frequently synergize when co-administered in vivo. Multimodal analgesic techniques offer advantages over single drug treatments as synergistic combination therapies produce analgesia at lower doses, thus reducing undesired side effects. This inference presumes, however, that the synergistic interaction is limited to the analgesic effects. In order to test this hypothesis, we examined the effects of α₂AR/OR combination therapy in acute antinociception and in the often-undesired side effects of sedation and cardiovascular depression in awake unrestrained mice. Morphine, clonidine or their combination was administered by spinal or systemic injection in awake mice. Antinociception was determined using the warm water tail flick assay (52.5°C). Sedation/motor impairment was evaluated using the accelerating rotarod assay and cardiovascular function was monitored by pulse oximetry. Data were converted to percent maximum possible effect and isobolographic analysis was performed to determine if an interaction was subadditive, additive or synergistic. Synergistic interactions between morphine and clonidine were observed in the antinociceptive but not in the sedative/motor or cardiovascular effects. As a result, the therapeutic window was improved ∼200-fold and antinociception was achieved at non-sedating doses with little to no cardiovascular depression. In addition, combination therapy resulted in greater maximum analgesic efficacy over either drug alone. These data support the utility of combination adrenergic/opioid therapy in pain management for antinociceptive efficacy with reduced side-effect liability.     

Soil nitrous oxide emissions following crop residue addition: a meta‐analysis

Annual production of crop residues has reached nearly 4 billion metric tons globally. Retention of this large amount of residues on agricultural land can be beneficial to soil C sequestration. Such potential impacts, however, may be offset if residue retention substantially increases soil emissions of N₂O, a potent greenhouse gas and ozone depletion substance. Residue effects on soil N₂O emissions have gained considerable attention since early 1990s; yet, it is still a great challenge to predict the magnitude and direction of soil N₂O emissions following residue amendment. Here, we used a meta‐analysis to assess residue impacts on soil N₂O emissions in relation to soil and residue attributes, i.e., soil pH, soil texture, soil water content, residue C and N input, and residue C : N ratio. Residue effects were negatively associated with C : N ratios, but generally residue amendment could not reduce soil N₂O emissions, even for C : N ratios well above ca. 30, the threshold for net N immobilization. Residue effects were also comparable to, if not greater than, those of synthetic N fertilizers. In addition, residue effects on soil N₂O emissions were positively related to the amounts of residue C input as well as residue effects on soil CO₂ respiration. Furthermore, most significant and stimulatory effects occurred at 60–90% soil water‐filled pore space and soil pH 7.1–7.8. Stimulatory effects were also present for all soil textures except sand or clay content ≤10%. However, inhibitory effects were found for soils with >90% water‐filled pore space. Altogether, our meta‐analysis suggests that crop residues played roles beyond N supply for N₂O production. Perhaps, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N₂O production. Our meta‐analysis highlights the necessity to connect the quantity and quality of crop residues with soil properties for predicting soil N₂O emissions.     

Evaluating four mathematical models for nitrous oxide production by autotrophic ammonia‐oxidizing bacteria

There is increasing evidence showing that ammonia‐oxidizing bacteria (AOB) are major contributors to N₂O emissions from wastewater treatment plants (WWTPs). Although the fundamental metabolic pathways for N₂O production by AOB are now coming to light, the mechanisms responsible for N₂O production by AOB in WWTP are not fully understood. Mathematical modeling provides a means for testing hypotheses related to mechanisms and triggers for N₂O emissions in WWTP, and can then also become a tool to support the development of mitigation strategies. This study examined the ability of four mathematical model structures to describe two distinct mechanisms of N₂O production by AOB. The production mechanisms evaluated are (1) N₂O as the final product of nitrifier denitrification with NO as the terminal electron acceptor and (2) N₂O as a byproduct of incomplete oxidation of hydroxylamine (NH₂OH) to NO. The four models were compared based on their ability to predict N₂O dynamics observed in three mixed culture studies. Short‐term batch experimental data were employed to examine model assumptions related to the effects of (1) NH concentration variations, (2) dissolved oxygen (DO) variations, (3) NO accumulations and (4) NH₂OH as an externally provided substrate. The modeling results demonstrate that all these models can generally describe the NH, NO, and NO data. However, none of these models were able to reproduce all measured N₂O data. The results suggest that both the denitrification and NH₂OH pathways may be involved in N₂O production and could be kinetically linked by a competition for intracellular reducing equivalents. A unified model capturing both mechanisms and their potential interactions needs to be developed with consideration of physiological complexity. Biotechnol. Bioeng. 2013; 110: 153–163. © 2012 Wiley Periodicals, Inc.     

Synthesis,characterization and nociceptive screening of new VV-hemorphin-5 analogues

In the present study, some new analogues of VV-hemorphin-5, modified at position 1 and 7 by the non-proteinogenic and/or natural amino acids followed the structures Xxx-Val-Val-Tyr-Pro-Trp-Thr-Gln-NH₂ and Val-Val-Tyr-Pro-Trp-Thr-Yyy-NH₂, where Xxx is Ile or Aib and Yyy is Lys/Orn/Dap/Dab were synthesized to investigate their potential antinociceptive activities. We report also the redox potentials and the acid/base properties as pKa values of these peptide analogues which were compared toward electrochemical behaviour of tryptophan containing peptides. All analogues showed a short lasting initial antinociceptive effect, however H2 hemorphin analogue is characterized with prolong and strong antinociceptive effect, while the other peptide analogues exerted more variable effects on the visceral nociception depending on the dose or time after the intracerebral injection.     

Effect of Soil pH Increase by Biochar on NO,N2O and N2 Production during Denitrification in Acid Soils

Biochar (BC) application to soil suppresses emission of nitrous- (N₂O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N₂O and N₂) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N₂O and NO and increased N₂ production during denitrification, irrespective of the effect on denitrification rate. The extent of N₂O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N₂O and NO net production. Just like untreated BCs, NaOH reduced net production of N₂O and NO while increasing that of N₂. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.     

Mapping study of Achatina giant neurons sensitive to molluscan peptides

1. Mapping studies of the Achatina identifiable neuron types sensitive to the following 6 molluscan peptides were examined under current-clamp.2. These were Ser-Mytilus inhibitory peptide (Ser-MIP), catch-relaxing peptide (CARP), oxytocin, small cardioactive peptide_b (SCP_b), α-bag cell peptide (α-BCP) and egg-laying hormone (ELH).3. These peptides at 10⁻³ M (3 × 10⁻⁴ M for ELH), with 0.5% Fast Green, were applied locally to the neuron to be tested by pneumatic pressure ejection (2 kg/cm² and 400 msec in duration).4. Ser-MIP showed the inhibitory (hyperpolarizing) effects on the majority of neuron types tested.5. CARP also produced inhibition of the 3 neuron types out of 16 types tested.6. Oxytocin had an excitatory effect on two neuron types.7. SCP_b showed excitatory effects on 4 neuron types: the membrane conductance of 1 neuron type, d-RPeAN, measured under voltage-clamp was reduced by the peptide.8. α-BCP showed no effect.9. ELH produced slight inhibition of the 2 neuron types.     

Impact of six lignocellulosic biochars on C and N dynamics of two contrasting soils

Both soil and biochar properties are known to influence greenhouse gas emissions from biochar‐amended soils, but poor understanding of underlying mechanisms challenges prediction and modeling. Here, we examine the effect of six lignocellulosic biochars produced from the pyrolysis of corn stover and wood feedstocks on CO₂ and N₂O emissions from soils collected from two bioenergy cropping systems. Effects of biochar on total accumulated CO₂‐C emissions were minimal (<0.45 mg C g^?1 soil; <10% of biochar C), consistent with mineralization and hydrolysis of small labile organic and inorganic C fractions in the studied biochars. Comparisons of soil CO₂ emissions with emissions from microbially inoculated quartz–biochar mixtures (‘quartz controls’) provide evidence of soil and biochar‐specific negative priming. Five of six biochar amendments suppressed N₂O emissions from at least one soil, and the magnitude of N₂O emissions suppression varied with respect to both biochar and soil types. Biochar amendments consistently decreased final soil NO₃^? concentrations, while contrasting effects on pH, NH₄⁺, and DOC highlighted the potential for formation of anaerobic microsites in biochar‐amended soils and consequential shifts in the soil redox environment. Thus, results implicated both reduced substrate availability and redox shifts as potential factors contributing to N₂O emission suppression. More research is needed to confirm these mechanisms, but overall our results suggest that soil biochar amendments commonly reduce N₂O emissions and have little effect on CO₂ emissions beyond the mineralization and/or hydrolysis of labile biochar C fractions. Considering the large C credit for the biochar C, we conclude that biochar amendments can reduce greenhouse gas emissions and enhance the climate change mitigation potential of bioenergy cropping systems.