Morphine diesters. II. Blood metabolism and analgesic activity in the rat

The kinetics of hydrolysis of dipropanoylmorphine (DPM) and dibutanoylmorphine (DBM) in human blood fractions and for diacetylmorphine (DAM) and DBM in rat blood fractions were investigated. In each case the hydrolysis of morphine diesters terminated with the production of the corresponding 6-monoester derivative. Generally, decreases in Km and Vmax were observed for the plasma, red blood cell (RBC) cytosol, and RBC membrane esterases responsible for morphine diester hydrolysis as the alkyl chain length of the ester moiety increased. This resulted in an overall decrease in the rate of hydrolysis of morphine diesters by human or rat blood with longer chain homologs of DAM. The analgesic potency and duration of morphine, DAM, and DBM were assessed at various i.v. dosages in the rat by means of the tail-flick latency test. A comparison of equianalgesic doses of morphine, DAM, and DBM indicated that DAM and DBM were 11.5 and 6 times as potent and 0.8 and 1.2 times as long acting, respectively, as morphine.     

Evaluation of 3,6-dibutanoylmorphine as an analgesic in vivo: comparison with morphine and 3,6-diacetylmorphine

Dibutanoylmorphine (DBM), a synthetic diester of morphine, was compared with morphine (M) and diacetylmorphine (DAM) for analgesic efficacy, potency and duration of action following I.V. administration in rats. Analgesia was assessed in groups of eight animals using both tail-flick and hot-plate testing methods following random administration of five different doses of each drug. DBM was found to be substantially more potent than M, but less potent than DAM in both tail-Flick and hot-plate tests of nociception. Similarly, assessment of duration of action at the ED50 for each drug revealed that DBM has a duration of analgesia which is intermediate between the durations of M and DAM. Thus, in rats in vivo, DBM is an effective analgesic and has a reasonable duration of action release to other opioids.     

Influence of dissolved humic materials on carbon assimilation and alkaline phosphatase activity in natural algal-bacterial assemblages

SUMMARY. Mixed natural assemblages of algae and bacteria exhibited lower rates of ¹⁴C assimilation and high rates of dissimilation of recent photosynthate when amended with low concentrations (7.2 mg 1^-1) of unfractioned dissolved humic materials (DHM). The extent of the inhibition or stimulation was greatest in the smaller (1–5 μm) assemblage particles. In different algal-bacterial assemblages, additions of DHM markedly enhanced community alkaline phosphatase activity (APA), particularly under low light regimes, DHM of low apparent molecular weight was much more stimulatory to both ¹⁴C assimilation and APA than DHM of high apparent molecular weight, supporting the belief that DHM molecular weight is an important determinant of DHM interactive capacity. Higher concentrations of D HM (either unfractionated, or molecular weight fractionated) produced greater APA responses. Addition of phosphate enhanced the disparity in rates of ¹⁴C assimilation of samples incubated under low and high light regimes, increased the rates of ¹⁴C assimilation, and depressed APA. There were indications of interactions between DHM and phosphorus in several experiments. Two hypotheses were invoked to explain increases in APA in response to DHM: (1) increased competition between algae and bacteria for phosphate following bacterial release from substrate limitation, or (2) DHM may have acted as a sequestering agent for organophosphorus compounds, and in so doing, gradually depleted available phosphate. In either case, it is clear that DHM alters phosphorus cycling. This DHM characteristic may be ecologically as important as its ability to complex trace metals.     

Characterization of Two Classes of Opioid Binding Sites in Drosophila melanogaster Head Membranes

Opioid receptors have been characterized in Drosophila neural tissue. [3H]Etorphine (universal opioid ligand) bound stereospecifically, saturably, and with high affinity (KD = 8.8 +/- 1.7 nM; Bmax = 2.3 +/- 0.2 pmol/mg of protein) to Drosophila head membranes. Binding analyses with more specific ligands showed the presence of two distinct opioid sites in this tissue. One site was labeled by [3H]dihydromorphine ([3H]DHM), a mu-selective ligand: KD = 150 +/- 34 nM; Bmax = 3.0 +/- 0.6 pmol/mg of protein. Trypsin or heat treatment (100 degrees C for 15 min) of the Drosophila extract reduced specific [3H]DHM binding by greater than 80%. The rank order of potency of drugs at this site was levorphanol greater than DHM greater than normorphine greater than naloxone much greater than dextrorphan; the mu-specific peptide [D-Ala2,Gly-ol5]-enkephalin and delta-, kappa-, and sigma-ligands were inactive at this site. The other site was labeled by (-)-[3H]ethylketocyclazocine ((-)-[3H]EKC), a kappa-opioid, which bound stereospecifically, saturably, and with relatively high affinity to an apparent single class of receptors (KD = 212 +/- 25 nM; Bmax = 1.9 +/- 0.2 pmol/mg of protein). (-)-[3H]EKC binding could be displaced by kappa-opioids but not by mu-, delta-, or sigma-opioids or by the kappa-peptide dynorphin. Specific binding constituted approximately 70% of total binding at 1 nM and approximately 50% at 800 nM for all three radioligands ([3H]etorphine, [3H]EKC, and [3H]DHM). Specific binding of the delta-ligands [3H][D-Ala2,D-Leu5]-enkephalin and [3H][D-Pen2,D-Pen5]-enkephalin was undetectable in this preparation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contractile properties of intercostal muscles and their functional significance

To have some insight into the functional coupling between the parasternal intercostals (PS) and the diaphragm (DPM), we have examined the isometric contractile properties of bundles from canine PS and DPM muscles. Bundles of external (EXT) and internal (INT) interosseous intercostals were studied for comparison. In addition we have related sonometrically measured length of the intercostals in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We found that 1) intercostal twitch speed is significantly faster than DPM, thus displacing their relative force-frequency curve to the right of that of the DPM; 2) the ascending limb of the active length-tension curve of all intercostals lies below the DPM curve; i.e., at 85% Lo, PS force is 46% of maximal force (Po), whereas DPM force is still 87% Po; 3) for any given length change beyond Lo, all intercostals generate greater passive tension than the DPM; 4) Po is greater for the intercostals than the DPM; and 5) at supine FRC, both EXT and INT in dogs are nearly operating at Lo, whereas the PS are operating at a length greater than Lo. We conclude that 1) PS produce less force than DPM during breathing efforts involving low- (10-20 Hz) stimulation frequencies, but they generate more force than DPM when high- (greater than 50 Hz) stimulation frequencies are required; and 2) the pressure-generating ability of the PS is better preserved than that of the DPM with increases in lung volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

The calcium channel agonist, Bay K-8644, antagonizes effects of diacetyl monoxime on cardiac tissues

Effects of a novel slow channel activator, Bay K-8644 (Bay K), were studied on slow action potential (APs) in young and old embryonic chick hearts, and on its antagonism of the effects of diacetyl monoxime (DAM). The slow APs of young hearts are mediated by slow Na+ channels, whereas those of old hearts are mediated by slow Ca2+ channels. In slow APs of old (13-18 days old) embryonic chick hearts superfused with a high (22 mM) K+ solution, Bay K (10-6 M) gradually increased the amplitude, maximum rate of rise (Vmax), and duration of the slow APs. The actions of Bay K persisted for a long time (greater than 30 min) after washout of the drug. DAM (10 mM) depressed the Vmax, duration and amplitude of the slow APs. Some of the changes in slow AP parameters produced by DAM, e.g., Vmax decrease, were antagonized by the addition of Bay K (10(-6) M). In 3-day-old embryonic chick hearts. Bay K potentiated the slow APs and DAM depressed them; Bay K antagonized these effects of DAM. Thus, the actions of Bay K and DAM are likely to be produced, respectively, via the activation and depression of slow Ca2+ channels in old embryonic chick hearts. In addition, the drugs seem to influence slow Na+ channels found in young embryonic chick hearts.     

Species differences in the reactivation of organophosphate-inhibited plasma esterases by diacetylmonoxime.

A study was conducted to assess whether the protection afforded to organophosphatepoisoned animals by diacetylmonoxime (DAM) was correlated with the reactivation of non-essential aliesterases (AliE). In vitro, the DAM-catalyzed reactivation of plasma AliE and cholinesterases (psi ChE) of rat, rabbit and guinea pig inhibited by 10-5 M diisopropylphosphorofluoridate (DFP) and O,O-dimethyl-2,2-dichlorovinyl phosphate (DDVP) was investigated. Marked reactivation of the rat plasma enzymes was achieved with 10mM DAM. Higher concentrations (30 mM) were necessary for the slow reactivation of rabbit and guinea pig plasma AliE. Reactivation of the psiChE of these species was comparatively slow. Reactivation of DDVP-inhibited esterases proceeded in all species at a more rapid rate than those inhibited by DFP. The dependence of psiChE reactivation upon concomitant more rapid reactivation of AliE by DAM was demonstrated using Sephadex fractionated AliE and psiChE but only a marked effect was observed with the rat, suggesting that the plasma AliE of this species is functionally different. The in vitro observations were confirmed by in vivo studies in rats and rabbits. DAM (50 or 150 mg/kg), administered to atropinized rats 15 min before a lethal dose of DFP, protected the animals. Few severe toxic signs were observed and reactivation of both plasma AliE and psiChE occurred. In contrast, DAM protected the rabbit against a lethal dose of DFP but only reactivation of the erythrocyte acetylcholinesterase was observed.     

Flavor release of diacetyl and 2-heptanone from cream style dressings in three mouth model systems

The release of volatile compounds from a cream style dressing, which consisted of a thickening agent dispersed in the water phase of an oil in water (o/w) type of emulsion, was studied by the purge-and-trap (PT), dynamic head space mastication (DHM) and dynamic headspace (DH) model systems for diacetyl and 2-heptanone as two volatile compounds. Big differences were detected in the quantity of volatiles released by the three models for both diacetyl and 2-heptanone: PT released the most, followed by DHM and DH. Nitrogen gas bubbling in PT and plunger up-and-down motion in DHM mimic mouth movements and promoted volatile release more than DH. The quantity of volatiles released depended on the nitrogen gas flow rate and isolation period with both the PT and the DHM model. Static headspace measurements indicated that no interaction occurred between the volatiles and the dispersion thickening agent, nor between the volatiles and protein of saliva.     

Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Stem cells play a key role in tissue regeneration due to their self-renewal and multidirectional differentiation, which are continuously regulated by signals from the extracellular matrix (ECM) microenvironment. Therefore, the unique biological and physical characteristics of the ECM are important determinants of stem cell behavior. Although the acellular ECM of specific tissues and organs (such as the skin, heart, cartilage, and lung) can mimic the natural microenvironment required for stem cell differentiation, the lack of donor sources restricts their development. With the rapid development of adipose tissue engineering, decellularized adipose matrix (DAM) has attracted much attention due to its wide range of sources and good regeneration capacity. Protocols for DAM preparation involve various physical, chemical, and biological methods. Different combinations of these methods may have different impacts on the structure and composition of DAM, which in turn interfere with the growth and differentiation of stem cells. This is a narrative review about DAM. We summarize the methods for decellularizing and sterilizing adipose tissue, and the impact of these methods on the biological and physical properties of DAM. In addition, we also analyze the application of different forms of DAM with or without stem cells in tissue regeneration (such as adipose tissue), repair (such as wounds, cartilage, bone, and nerves), in vitro bionic systems, clinical trials, and other disease research.     

Degradation of chlorinated and brominated hydrocarbons by Methylomicrobium album BG8

The degradation kinetics of ten halogenated hydrocarbons by Methylomicrobium album BG8 expressing particulate methane monooxygenase (pMMO) and the inhibitory effects of these compounds on microbial growth and whole-cell pMMO activity were measured. When M. album BG8 was grown with methane, growth was completely inhibited by dichloromethane (DCM), bromoform (BF), chloroform (CF), vinyl chloride (VC), 1,1-dichloroethylene (1,1-DCE), and cis-dichloroethylene (cis-DCE). Trichloroethylene (TCE) partially inhibited growth on methane, while dibromomethane (DBM), trans-dichloroethylene (trans-DCE), and 1,1,1-trichloroethane (1,1,1-TCA) had no effect. If the cells were grown with methanol, DCM, BF, CF, and 1,1-DCE completely inhibited growth, while VC, trans-DCE, TCE, and 1,1,1-TCA partially inhibited growth. Both DBM and cis-DCE had no effect on growth with methanol. Whole-cell pMMO activity was also affected by these compounds, with all but 1,1,1-TCA, DCM, and DBM reducing activity by more than 25%. DCM, DBM, VC, trans-DCE, cis-DCE, 1,1-DCE, and TCE were degraded and followed Michaelis-Menten kinetics. CF, BF, and 1,1,1-TCA were not measurably degraded. These results suggested that the products of DCM, TCE, VC, and 1,1-DCE inactivated multiple enzymatic processes, while trans-DCE oxidation products were also toxic but to a lesser extent. cis-DCE toxicity, however, appeared to be localized to pMMO. Finally, DBM and 1,1,1-TCA were not inhibitory, and CF and BF were themselves toxic to M. album BG8. Based on these results, the compounds could be separated into four general categories, namely (1) biodegradable with minimal inactivation, (2) biodegradable with substantial inactivation, (3) not biodegradable with minimal inactivation, and (4) not biodegradable but substantial inactivation of cell activity. Received: 17 June 1999 / Accepted: 3 September 1999     

Selective inhibitors of bacterial DNA adenine methyltransferases

The authors describe the discovery and characterization of several structural classes of small-molecule inhibitors of bacterial DNA adenine methyltransferases. These enzymes are essential for bacterial virulence (DNA adenine methyltransferase [DAM]) and cell viability (cell cycle-regulated methyltransferase [CcrM]). Using a novel high-throughput fluorescence-based assay and recombinant DAM and CcrM, the authors screened a diverse chemical library. They identified 5 major structural classes of inhibitors composed of more than 350 compounds: cyclopentaquinolines, phenyl vinyl furans, pyrimidine-diones, thiazolidine-4-ones, and phenyl-pyrroles. DNA binding assays were used to identify compounds that interact directly with DNA. Potent compounds selective for the bacterial target were identified, whereas other compounds showed greater selectivity for the mammalian DNA cytosine methyltransferase, Dnmt1. Enzyme inhibition analysis identified mechanistically distinct compounds that interfered with DNA or cofactor binding. Selected compounds demonstrated cell-based efficacy. These small-molecule DNA methyltransferase inhibitors provide useful reagents to probe the role of DNA methylation and may form the basis of developing novel antibiotics.     

Diel horizontal migration of zooplankton: costs and benefits of inhabiting the littoral

1. In some shallow lakes, Daphnia and other important pelagic consumers of phytoplankton undergo diel horizontal migration (DHM) into macrophytes or other structures in the littoral zone. Some authors have suggested that DHM reduces predation by fishes on Daphnia and other cladocerans, resulting in a lower phytoplankton biomass in shallow lakes than would occur without DHM. The costs and benefits of DHM, and its potential implications in biomanipulation, are relatively unknown, however. 2. In this review, we compare studies on diel vertical migration (DVM) to assess factors potentially influencing DHM (e.g. predators, food, light, temperature, dissolved oxygen, pH). We first provide examples of DHM and examine avoidance by Daphnia of both planktivorous (PL) fishes and predacious invertebrates. 3. We argue that DHM should be favoured when the abundance of macrophytes is high (which reduces planktivory) and the abundance of piscivores in the littoral is sufficient to reduce planktivores. Food in the littoral zone may favour DHM by daphnids, but the quality of these resources relative to pelagic phytoplankton is largely unknown. 4. We suggest that abiotic conditions, such as light, temperature, dissolved oxygen and pH, are less likely to influence DHM than DVM because weaker gradients of these conditions occur horizontally in shallow lakes relative to vertical gradients in deep lakes. 5. Because our understanding of DHM is rudimentary, we highlight potentially important research areas: studying a variety of systems, comparing temporal and spatial scales of DHM in relation to DVM, quantifying positive and negative influences of macrophytes, focusing on the role of invertebrate predation, testing the performance of cladocerans on littoral versus pelagic foods (quantity and quality), investigating the potential influence of temperature, and constructing comprehensive models that can predict the likelihood of DHM. Our ability to biomanipulate shallow lakes to create or maintain the desired clear water state will increase as we learn more about the factors initiating and influencing DHM.     

Alteration in DNA cross-linking and sequence selectivity of a series of aziridinylbenzoquinones after enzymatic reduction by DT-diaphorase.

DT-diaphorase (DTD) mediated reduction of a series of 2,5-bis-substituted-3,6-diaziridinyl-1,4-benzoquinones was found to increase the level of DNA interstrand cross-linking (ISC) formed at neutral pH with an enhancement observed as the pH was decreased to 5.8. The analogues used were symmetrically alkyl-substituted carbamoyl ester analogues of AZQ (D1-D7), 3,6-diaziridinyl-1,4-benzoquinone (DZQ), the 2,5-dimethyl derivative (MeDZQ), and a 2,5-bis[(2-hydroxyethyl)amino] analogue (BZQ). At pH 5.8, the level of DNA ISC induced by enzymatic reduction was as follows: DZQ greater than MeDZQ much greater than D1 (methyl) greater than D3 (n-propyl) greater than D2 (AZQ; ethyl) greater than D5 (n-butyl) greater than D7 (sec-butyl) greater than D4 (isopropyl) D6 greater than (isobutyl). A similar trend was observed at pH 7.2. The level of DNA ISC induced by BZQ, which is not a substrate for DTD, was not increased by enzymatic reduction. Dicumarol, a known inhibitor of DTD, was capable of inhibiting the DNA ISC induced by these quinones upon enzymatic reduction. MeDZQ and DZQ reacted with guanines, as measured by Maxam and Gilbert sequencing, with a sequence selectivity similar to that of the nitrogen mustard class of antitumor agents. Enzymatic reduction of DZQ and MeDZQ by DTD was found to alter their sequence-selective alkylation. Reduced DZQ showed enhanced guanine alkylation in 5'-GC-3' sequences and new sites of adenine alkylation in 5'-(A/T)AA-3' sequences. Reduced MeDZQ only showed new sites of adenine alkylation at 5'-(A/T)AA-3' sequences but no enhancement of guanine alkylation. The new sites of adenine alkylation were found to be inhibited in the presence of magnesium and rapidly converted into apurinic sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Application of synthetic herbivore‐induced plant volatiles causes increased parasitism of herbivores in the field

We previously reported that Cotesia vestalis (Hymenoptera, Braconidae), a parasitoid of diamondback moth (DBM) (Plutella xylostella; Lepidoptera, Plutellidae) larvae, was attracted to volatiles from crucifer plants infested by moth larvae kept in a desktop acrylic box, and that a blend of four DBM‐induced plant volatiles was responsible for this attraction. In this study, using a specially designed dispenser to release the four compounds, we demonstrated that the wasp was attracted to intact komatsuna plants (Brassica rapa var. perviridis). The experiments were performed in a climate‐controlled room, which was approximately 1000 times larger than the acrylic box used previously. Similarly, using the dispenser in the field, C. vestalis females were attracted to intact komatsuna plants with the dispenser from a distance of three metres. We also examined the effect of the volatile blend on the incidence of parasitism of DBM larvae in the field. Three small containers containing DBM‐infested komatsuna plants with dispensers, and three control containers containing only infested plants (control) were arranged in two lines running perpendicular to a komatsuna field in which both DBM larvae and C. vestalis populations were maintained, at distances of 12, 30 and 70 m. The results showed that the incidence of DBM parasitism was significantly higher in containers containing dispensers than in the control containers, suggesting that the blend could potentially be applied to DBM control in agroecosystems.     

The divergent 5' ends of DPM2 mRNAs originate from the alternative splicing of two adjacent introns: characterization of the hamster DPM2 gene

Mammalian dolichol-phosphate-mannose (DPM) synthase has three subunits, DPM1, DPM2, and DPM3. In this report, an analysis of the gene and cDNAs of hamster DPM2 is presented. The CHO DPM2 gene has two special features. First, the initiation codon ATG is separated from the remainder of the coding region by intron sequences. Second, within these intron sequences the DPM2 gene contains an adjacent 3' splice site (acceptor) and a 5' splice site (donor), suggestive of a deleted exon between the first and second codons. In fact, these sites overlap by four nucleotides (nt) of AGGT. Splicing intermediates using both of these alternative splice sites were observed. This latter feature appears unique and is particularly unusual considering the relatively small size of the gene (2.7 kb) and of introns a (123 bp) and b (152 bp).     

Dihydromyricetin Enhances the Chemo-Sensitivity of Nedaplatin via Regulation of the p53/Bcl-2 Pathway in Hepatocellular Carcinoma Cells

Chemotherapy is an effective weapon in the battle against cancer. Nedaplatin (NDP) is an improved platinum-containing drug with lower cytotoxicity than other similar drugs. However, the repeated use of NDP results in substantial hepatocyte damage as well as drug resistance in hepatocellular carcinoma (HCC) cases. Therefore, the development of effective chemotherapy strategies that enhance tumor sensitivity to chemotherapeutics and reduce the secondary damage to liver cells is urgently needed. Dihydromyricetin (DHM), a natural flavonoid compound, has been shown to have antitumor activity with no obvious toxicity to normal cells in vitro and in vivo. In this study, DHM and NDP were combined to treat liver cancer cells; we found that DHM functions as a protector of normal cells compared with the use of NDP alone. In addition, the synergy of DHM with NDP enhanced the effect of NDP on the induction of HCC cell apoptosis. We found that the combination caused clear changes in the level of reactive oxygen species (ROS). Furthermore, we demonstrated that the combination of DHM and NDP activated the p53/Bcl-2 signaling pathway, which resulted in mitochondrial dysfunction and induced cell death and growth inhibition in HCC cells.     

Mutagenicity of nitro-azabenzo[a]pyrene and its related compounds.

The mutagenicity of nitrated benzo[a]pyrene (BP) and the related compounds, 1- and 3-nitrobenzo[a]pyrene (NBP), 1- and 3-nitro-6-cyanobenzo[a]pyrene (N-6-CBP), 1- and 3-nitro-6-azabenzo[a]-pyrene (N-6-ABP), 1- and 3-nitro-6-azabenzo[a]-pyrene-N-oxide (N-6-ABPO) and 1,6- and 3,6-dinitrobenzo[a]-pyrene (DNBP), was investigated. The mutagenic activities of 3-N-6-CBP and 3-N-6-ABP were 117 and 76 times, respectively, that of 3-NBP. In addition, 3,6-DNBP was more mutagenic than 1,6-DNBP. It is suggested that the mutagenic activation differs with the position of NO2 substitution in the chemical structure. A nitro derivative with NO2 substitution at the 3 position of the aromatic ring of BP was more mutagenic than that with the substitution at the 1 or 6 position. The reducibility of DNBPs was then determined by detecting 1- or 3-amino-6-nitrobenzo[a]pyrene (A-6-NBP), a metabolite of DNBP; 3,6- and 1,6-DNBP were reduced to 3- and 1-A-6-NBP at frequencies of 958 +/- 26 and 79 +/- 8, respectively, pmole per mg of protein, when the compound was incubated anaerobically with rat liver S9 mix at 37 degrees C for 15 min. NO2 substituted at the 3 position of the aromatic ring of BP was readily reduced by a microsome enzyme to form an amino derivative. The result suggests that these compounds have a structure-activity relationship between mutagenicity and NO2 substitution of BP.     

利用寄主干扰效应防控小菜蛾田间种群的有效性

【目的】多寄主对植食性昆虫寄主选择行为具干扰效应。为探究在田间相似寄主混作是否能引起小菜蛾Plutella xylostella (L.)在寄主上的选择困难,减少在寄主上的产卵量,从而实现保护寄主植物的目标。【方法】本研究利用小菜蛾喜好性高的两种寄主（菜心Brassica campestris L.和芥菜B. juncea Coss）为试验对象,通过寄主植物单作、混作及不同配比与间隔种植等田间试验设计,研究了多寄主对小菜蛾寄主选择行为的干扰效应。【结果】在2年的田间试验中,两寄主混作处理上的虫量均低于单一寄主种植;2012年田间种群生命表数据显示,两种寄主田间混作处理上的小菜蛾种群趋势指数（I =4.797）低于单一寄主种植,菜心与芥菜单一种植处理上的I值分别为6.549与6.858;当菜心与芥菜这两种小菜蛾喜好性相近寄主同时存在时,对小菜蛾的干扰程度与两寄主的搭配比例有关,随着菜心所占比重的增大,田间虫量呈现先减后增的抛物线变化趋势;但两寄主间距在2 m内时,不同种植间隔对小菜蛾虫量变化无差异(F_3,8=0.204,P>0.05)。【结论】结果表明,在田间多寄主种植中,除了可利用陷阱作物来防控小菜蛾外,在相邻两畦地间以适当比例同时种植两种小菜蛾喜好性相近的寄主,利用两种寄主植物对植食性昆虫的寄主选择行为产生的干扰效应,也能有效影响田间小菜蛾的种群动态。     

Degradation of 2,3-diethyl-5-methylpyrazine by a newly discovered bacterium, Mycobacterium sp. strain DM-11

A bacterium was isolated from the waste gas treatment plant at a fishmeal processing company on the basis of its capacity to use 2,3-diethyl-5-methylpyrazine (DM) as a sole carbon and energy source. The strain, designated strain DM-11, grew optimally at 25 degrees C and had a doubling time of 29.2 h. The strain did not grow on complex media like tryptic soy broth, Luria-Bertani broth, or nutrient broth or on simple carbon sources like glucose, acetate, oxoglutarate, succinate, or citrate. Only on L?wenstein-Jensen medium was growth observed. The 16S rRNA gene sequence of strain DM-11 showed the highest similarity (96.2%) to Mycobacterium poriferae strain ATCC 35087T. Therefore, strain DM-11 merits recognition as a novel species within the genus Mycobacterium. DM also served as a sole nitrogen source for the growth of strain DM-11. The degradation of DM by strain DM-11 requires molecular oxygen. The first intermediate was identified as 5,6-diethyl-2-hydroxy-3-methylpyrazine (DHM). Its disappearance was accompanied by the release of ammonium into the culture medium. No other metabolite was detected. We conclude that ring fission occurred directly after the formation of DHM and ammonium was eliminated after ring cleavage. Molecular oxygen was essential for the degradation of DHM. The expression of enzymes involved in the degradation of DM and DHM was regulated. Only cells induced by DM or DHM converted these compounds. Strain DM-11 also grew on 2-ethyl-5(6)-methylpyrazine (EMP) and 2,3,5-trimethylpyrazine (TMP) as a sole carbon, nitrogen, and energy source. In addition, the strain converted many pyrazines found in the waste gases of food industries cometabolically.