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1.
Triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-(1,2,4-triazol-1-yl)-2-butanone], 1.5–2.0 μ/ml, inhibited the multiplication of sporidia of Ustilago avenae more strongly than it did the increase of dry weight. The treated sporidia appeared swollen, multicellular, and branched. At concentrations of 1.5–100 μg of triadimefon/ml, the oxidation of glucose was not affected. Increase in dry weight and synthesis of protein, RNA, and DNA were inhibited slightly, whereas cell division was acutely arrested. After an incubation period of 9.5 hr, microscopic studies revealed that daughter cells of the treated sporidia also contained one nucleus. In sporidia treated for 6 hr with triadimefon, both the total lipid content and its composition of fatty acids were not appreciably altered. The treated cells, however, differed from control cells by a higher content of free fatty acids. Triadimefon markedly interfered in sterol biosynthesis in Ustilago avenae. Gas chromatographic (glc) analysis and [14C]acetate incorporation studies indicated that ergosterol biosynthesis was almost completely inhibited by triadimefon; on the other hand, sterol compounds representing precursors of ergosterol (probably 4,4-dimethyl and C-4-methyl sterols) accumulated in treated sporidia. As the results indicate, the inhibition of conversion of immediate sterol precursors to ergosterol may be regarded as the primary target for the action of triadimefon in Ustilago avenae.  相似文献   

2.
3-Phenylindole is an antimicrobial compound active towards many fungi and gram-positive bacteria. At 5 μg/ml it inhibits growth of Aspergillus niger. Higher concentrations (50 μg/ml) also suppress spore germination; they do not kill the fungus. Dry weight of the fungus still increases for 1 or 2 days after fungicide treatment. The toxicant has no effect on O2 uptake even at higher concentrations (100 μg/ml). The compound markedly affects composition of the lipid fraction of A. niger inducing a decrease in phospholipid concentration with a coincident increase in free fatty acids. Sterol pattern and sterol concentration were not affected. Antifungal activity was reversed by phospholipids added to the medium. 3-Phenylindole induced a slight leakage of 32P-labeled compounds from the treated cells under growth conditions but not under nongrowth conditions. A strain of A. niger resistant to 3-phenylindole had the same phospholipid and sterol pattern as the wild type, but the level of both components was higher (40–60%). The 3-phenylindole-resistant strain showed resistance to triarimol and pimaricin. The wild type and the resistant strain both took up 3-phenylindole quite rapidly and accumulated it in the mycelium. 3-Phenylindole possibly interferes with phospholipid function in cell membranes, although the specific site of action has not yet been elucidated.  相似文献   

3.
The effects of HEOD and some of its metabolites on synaptic transmission in the frog motor end-plate were studied by means of intracellular microelectrodes. HEOD itself and the metabolites 9-syn-hydroxy-HEOD and the aldrin-derived dicarboxilic acid had no significant effect on frequency and amplitude of miniature end-plate potentials, nor on end-plate membrane potential. In sharp contrast with this aldrin-transdiol (6,7-trans-dihydroxy-dihydro-aldrin) was very potent in exerting both pre- and postsynaptic actions. This metabolite caused a rapid and marked increase in miniature end-plate potential frequency, together with a decrease in their amplitude. Evidence is presented suggesting that the spontaneous transmitter release is enhanced by two prejunctional mechanisms: partly by a calcium-dependent effect, probably a depolarization of the nerve terminal, and partly by a calcium-independent action. Another typical prejunctional action of aldrin-transdiol is the reduction of the amount of transmitter released in response to high external potassium concentration. Aldrin-transdiol also affected the evoked transmitter release and caused a marked increase in end-plate potential amplitude followed by a decrease, and finally a complete blockade of neuromuscular transmission was observed. This transient increase in transmitter release was shown to be due to a transient increase in quantal content. The subsequent fall in end-plate potential amplitude and the fall in miniature end-plate potential amplitude are probably the result of a reduction of the sensitivity of the postsynaptic membrane to acetylcholine as demonstrated by ionophoretic application of this transmitter. There was no aldrin-transdiol-effect on the end-plate membrane potential. The present results strongly support the hypothesis that HEOD must be converted to aldrin-transdiol before it can exert its neurotoxic action.  相似文献   

4.
Colony growth and germ tube emergence of sporangia and encysted zoospores of Phytophthora infestans were highly sensitive to cymoxanil (ED50 0.5–1.5 μg/ml), whereas differentiation of sporangia and zoospore release were insensitive at concentrations up to 100 μg/ml. Treated sporangia did not show distorted germ tubes. Oxygen consumption for glucose oxidation by germinating sporangia and zoospore motility were not inhibited at concentrations up to 100 μg/ml. Cymoxanil hardly affected the uptake of radiolabeled precursors of DNA, RNA, and protein at concentrations up to 100 μg/ml. Incorporation of [14C]phenylalanine into protein was completely insensitive. RNA synthesis as measured by [3H]uridine incorporation was differentially inhibited in the various developmental stages of the fungus. Inhibition did not occur at differentiation of sporangia, whereas at cyst and sporangial germination and mycelial growth this process was inhibited 20–45% at a concentration of 100 μg cymoxanil/ml. Endogenous RNA polymerase activity of isolated nuclei was not inhibited by cymoxanil. DNA synthesis as measured by [methyl-3H]thymidine incorporation was inhibited 20–80% at the various stages of development at cymoxanil concentrations higher than 10 μg/ml. Metalaxyl, a specific inhibitor of ribosomal RNA synthesis, inhibited [3H]uridine incorporation 40–60% at all developmental stages. The data suggest that although DNA synthesis is affected more than RNA synthesis, inhibition of both biosynthetic processes is a secondary effect. The primary mode of action of cymoxanil thus remains unknown.  相似文献   

5.
When applied at concentrations of one nM or higher to a house fly larval neuromuscular preparation, deltamethrin (DM) and fenvalerate (FV) greatly increased miniature excitatory postsynaptic potential (mepsp) rate and blocked neuromuscular transmission. The DM-induced mepsp discharge was abolished by tetrodotoxin (TTX), removal of Ca2+ from the saline, or by application of hyperpolarizing stimuli to the nerve, indicating that it was due to depolarization of the presynaptic terminals. Also, in the presence of TTX, K+ depolarization increased mepsp rate at the same external K+ concentration before and after DM treatment, confirming that DM released transmitter by depolarizing the nerve terminals rather than by altering the voltage dependence of transmitter release. The potassium channel blocker tetraethylammonium (TEA) increased mepsp rate somewhat, while aconitine (20 μM), which keeps sodium channels open, increased mepsp rate consistently. Pretreatment of nerves with a subthreshold dose of TEA greatly increased the mepsp rate-increasing activity of DM and aconitine, while a subthreshold level of aconitine did not synergize DM. These observations suggest that DM, like aconitine, depolarized nerves by modifying the sodium channels. Knockdown resistant (kdr) larvae were resistant to the depolarizing action of DM and aconitine but not to that of TEA, indicating that the kdr gene produced a modified sodium channel which was less sensitive to the action of pyrethroids and aconitine. During sustained transmitter release by DM, evoked release gradually declined, resulting in a condition called early block in which spontaneous release was high and release could be evoked by electrotonic depolarization of the nerve terminals, but not by a nerve action potential. Early block was probably due to conduction block in the nerve terminals. Early block eventually gave way to late block, characterized by the decline of spontaneous release to subnormal levels and complete failure of evoked release. After late block, the calcium ionophore X-537A could not release transmitter, suggesting that late block was due to depletion of available transmitter. DM did not have a direct effect upon extrasynaptic muscle membrane. However, after late block, muscles were left insensitive to the putative transmitters glutamate and aspartate when these were bath or iontophoretically applied. A low rate of mepsps persisted after late block, indicating that the muscles were still sensitive to the natural transmitters.  相似文献   

6.
In an attempt to indicate the site of action of tridemorph in ergosterol biosynthesis by Ustilago maydis the nature of the sterol intermediates accumulating in treated cells was studied. At low growth-inhibiting concentrations of the toxicant (10 and 15 μg/ml) decline of ergosterol content during 6 hr of incubation was accompanied by an accumulation of various sterol intermediates of which ergosta-8,14-dien-3β-ol appeared to be the major sterol. After isolation of this intermediate its identity was further confirmed by direct comparisonof its ultraviolet, glc, and mass spectrum with those of an authentic synthesized sample of ergosta-8,14-dien-3β-ol (ignosterol). Results indicate that toxicity of tridemorph is caused by a specific inhibitive effect on the enzyme Δ14-reductase which is responsible for 1415 double-bond reduction in sterol biosynthesis.  相似文献   

7.
Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole) inhibits melanin synthesis in Pyricularia oryzae at concentrations less than 0.01 μg/ml. The primary site of inhibition in the biosynthetic pathway occurs between scytalone and vermelone. Accumulation of several metabolites derived from melanin precursors along branch pathways is associated with inhibition of melanin biosynthesis. At low tricyclazole concentrations (0.01–1 μg/ml), predominant accumulation of 2-hydroxyjuglone and 3,4-dihydro-3,4,8-trihydroxy-1-(2H)-naphthalenone (3,4,8-DTN) occurs as a result of the primary block between 1,3,8-trihydroxynaphthalene and vermelone. As the concentration of tricyclazole is increased from 1 to 10 μg/ml, flaviolin accumulation is markedly enhanced, whereas that of 3,4,8-DTN and 3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone is depressed, indicating possible secondary sites of inhibition in the main and branch pathways. Five melanin-deficient mutants of P. oryzae that phenotypically resemble the tricyclazole-treated wild-type strain were nonpathogenic or rarely infected two rice varieties. Three of the mutants studied were genetically defective in the melanin biosynthetic pathway at the site blocked by tricyclazole in the wild type. The wild-type strain converted both scytalone and vermelone to melanin; whereas the three mutants and the tricyclazole-treated wild type converted only vermelone to melanin. The data suggest a relationship between melanin biosynthesis and pathogenicity in P. oryzae.  相似文献   

8.
The effects of two pesticides, dieldrin and captan, upon the growth and macromolecular syntheses of the vegetative cells of Dictyostelium discoideum strain Ax-2 were investigated. Dieldrin at a concentration of 5 μg/ml inhibited growth as well as the synthesis of RNA, DNA, and protein, while as little as 1 μg/ml of captan produced the same effects. After a 1-hr exposure to either pesticide, all macromolecular syntheses ceased. Within a period of 5 to 10 hr the amoebae began to shrink, and eventually some lysis occurred. Lysis was most pronounced in cells incubated with captan. When the amoebae were grown in the presence of 5 μg/ml of either pesticide and then washed and resuspended in fresh medium, the effects on growth were annulled. No growth inhibition was observed when 0.05 M cysteine was added prior to the addition of 5 μg/ml of captan. Further experimentation to study possible degradation effects of these two synthetic pesticides upon RNA and protein molecules showed that breakdown of these macromolecules into TCA-soluble units did not occur. Preliminary studies have also shown that [2-14C]uracil and [14C]amino acids are taken up in their respective pools in the presence of captan or dieldrin.  相似文献   

9.
Fluotrimazole [BUE 0620; 1-(3-trifluoromethyltriphenyl) 1,2,4-triazole] (20 μg/ml of nutrient solution) and clotrimazole [Bay b 5097; bisphenyl(2-chlorophenyl)-1-imidazolyl methane] (5 μg/ml) did not inhibit dry weight increase and only slightly reduced multiplication of sporidia of Ustilago avenae during the first doubling period (about 4 hr). After 8 hr, both fluotrimazole and clotrimazole more strongly inhibited sporidia multiplication than dry weight increase. As a consequence of treatment with both fungicides the usually single-celled sporidia appear swollen, multicellular, and branched. Both chemicals at a concentration range of 5–100 μg/ml did not affect oxidation of glucose. The effect of fluotrimazole and clotrimazole on protein, DNA, and RNA synthesis was similar to that on dry weight. Following a 6-hr incubation period total lipid synthesis was quantitatively unaffected by both chemicals. As the analysis of major fatty acids of total lipids revealed fluotrimazole substantially induced the synthesis of 20:4 carbon fatty acids, while in clotrimazole-treated sporidia the pattern of fatty acids did not differ from that of control sporidia. Fluotrimazole and clotrimazole produced a higher quantity of free fatty acids in sporidia of U. avenae. Gas-liquid chromatographic analysis of sterol fractions in treated and control sporidia (6 hr) indicated that both fluotrimazole and clotrimazole seriously inhibited ergosterol biosynthesis and concomitantly caused an accumulation of immediate ergosterol precursors which represent C-4-methyl and 4,4-dimethyl sterols. Incorporation of [14C]acetate for 2 hr into various lipid fractions of sporidia of U. avenae also revealed that radioactivity in C-4-desmethyl sterols in both fluotrimazole- and clotrimazole-treated sporidia was drastically reduced, while the radioactivity of C-4-methyl and 4,4-dimethyl sterols distinctly increased. The data suggest that fluotrimazole and clotrimazole are specific inhibitors of the oxidative demethylation of the C-14-methyl group during ergosterol biosynthesis in U. avenae.  相似文献   

10.
Alkaline-dissolved crystal δ-endotoxin from Bacillus thuringiensis var. israelensis (serovar H 14) was injected into mice and seven species of insects representing the orders Lepidoptera, Orthoptera, Coleoptera, Hemiptera, and Diptera. High in vivo toxicity, at 1 to 5 ppm (μg toxin/g body wet wt), was observed with mice and some insects, including some that are not sensitive to the toxin when administered orally. Neuromuscular effects were observed when the toxin was injected directly into the body cavity of the test animals. Biochemical studies suggested that different protein fragments within the crystal δ-endotoxin may be responsible for the majority of the mosquito larvacidal activity and the neurotoxic symptoms observed in larvae of Trichoplusia ni.  相似文献   

11.
Application of the formamidine pesticides chlordimeform (CDM) and desmethylchlordimeform (DCDM) induced the release of hyperlipemic hormone from the isolated corpus cardiacum (CC) of the locust, Locusta migratoria. Pretreatment of locusts with reserpine (10 μg/locust) had no effect on formamidine-induced release of the hyperlipemic hormone. The action of CDM and DCDM on isolated CC was blocked by the α-adrenergic-receptor blocker, phenoxybenzamine, but not by the β-adrenergic blocker, propranolol. These formamidines also potentiated the release of the hyperlipemic hormone induced by electrical stimulation of nervus corpus cardiacum II (NCC II). The evidence presented in this paper indicates that, in locusts, CDM and DCDM, or their metabolites, act on postsynaptic aminergic (octopamine) receptors in the glandular lobe of the CC, inducing the release of hyperlipemic hormone.  相似文献   

12.
Antifungal activity of oligochitosan against nine phytopathogens was investigated in vitro. Oligochitosan was more effective than chitosan in inhibiting mycelial growth of Phytophthora capsici and its inhibition on different stages in life cycle of P. capsici was observed. Rupture of released zoospores induced by oligochitosan was reduced by addition of 100 mM glucose. The effects of oligochitosan on mycelial growth and zoospore release, but not zoospore rupture, were reduced largely when pH value was above 7. The ultrastructural study showed that oligochitosan caused distortion and disruption of most vacuoles, thickening of plasmalemma, and appearance of unique tubular materials. Plasmalemmasomes in hyphal tip cells were not found in the presence of oligochitosan. These results suggest polycationic nature of oligochitosan contributes only partly to its antifungal activity and multiple modes of action of oligochitosan exist including the disruption of endomembrane system.  相似文献   

13.
A series of 25 pyrethroids were assessed for their effects on Na+-dependent norepinephrine release and on Ca2+ uptake in vitro using a crude rat brain synaptosomal preparation. The most effective pyrethroids required a concentration of 3–10 μM to promote norepinephrine release. Plotting release data versus lipophilicity (as log P) for each compound resulted in a parabolic curve with log Popt being 5.4 for maximal release. The release promoted by most of the compounds assessed at 30 μM could not be or was only partially reversed by either tetrodotoxin or substituting choline for Na+ conditions which readily reversed the release promoting effects of veratridine. Thus, many pyrethroids, particularly those without the α-cyano group, did not display their expected effects on the Na+ channel in rat brain. When assessed at 5 μM, pyrethroids inhibited, had no effect, or caused increases in the amount of Ca2+ incorporated in the presence of ATP. The effectiveness of the various pyrethroids to inhibit Ca2+ uptake again displayed a parabolic relationship with log Popt being 6.4. It was concluded that the variations in pyrethroid effects on norepinephrine release and Ca2+ uptake are not solely related to their particular chemical structures, but to lipophilicity. The effects of many pyrethroids on Ca2+ metabolism, particularly displacement of bound Ca2+, better explain the transmitter release promoting properties in vitro rather than a direct effect on the Na+ channel. No direct relationship between known toxicity to mammals and Ca2+ inhibition by pyrethroids was established.  相似文献   

14.
Inhibition of chicken brain neurotoxic esterase (NTE) by a series of O-halogenated-phenyl-O-alkyl phenylphosphonates was studied in vitro. The “apparent” activity was found to consist of “true” NTE (sensitive to mipafox) plus a minor mipafox-resistant component. The pI50 of O-(2,6-dichlorophenyl) O-methyl phenylphosphonate for “true” NTE was 6.65, whereas it was about 3 for mipafox-resistant hydrolysis of phenyl valerate. This compound is suitable as an alternative to mipafox in the assay of “true” NTE, whereas the use of leptophos oxon gives a less accurate measure. The ethoxy analogs are about as potent in vitro as the corresponding methoxy compounds. Leptophosoxon and ethoxyleptophosoxon are more potent in vitro inhibitors than desbromoleptophosoxon. Within a like group of chlorinated phenylphosphonates, a reasonable correlation between in vitro neurotoxic esterase inhibition of the oxon and in vivo delayed neurotoxic potential by the corresponding phosphonothionate exists. In vivo inhibition of “apparent” NTE from chicken brain, studied 24 hr after an oral dose, is dose dependent for leptophos, ethoxyleptophos, and desbromoleptophos, the latter one being a very potent in vivo inhibitor. Ethoxyleptophos and leptophos have about equal in vivo esterase inhibitory properties. For desbromoleptophos and leptophos there is good agreement between the minimum dose causing delayed neurotoxicity and the dose leading to substantial inhibition of “apparent” NTE; ethoxyleptophos, on the other hand, inhibits the esterase at a dose much lower than the one which is neurotoxic. Several possible explanations for this discrepancy are considered.  相似文献   

15.
The oral toxicity of 5-benzyl-3-furylmethyl-(1R, cis)-chrysanthemate (cismethrin) to female rats decreased as their environmental temperature was raised. Acute oral LD50 values increased from 157 mg/kg at 4°C to 197 mg/kg at 20°C and to > 1000 mg/kg at 30°C. Cismethrin was much more toxic given intravenously when the LD50 was 4.5 mg/kg. This value did not change at different environmental temperatures. Irrespective of the environmental temperature, or route of adminstration, following the respective LD50's cismethrin caused tremors in rats when brain levels of 0.5–1.0 μg/g were reached and, at death, brain concentrations were 3.9–5.1 μg/g. These results suggested that the accumulation of cismethrin by the brain could be used as a model for the nervous system as a whole. The isomeric 5-benzyl-3-furylmethyl-(1R, trans)-chrysanthemate (bioresmethrin) was about 50 times less toxic to rats than cismethrin. After an intravenous LD50, tremors started when brain concentrations were 4–5 μg/g. At death, brain levels were 25–35 μg/g. Plasma esterases were about equally active in hydrolysing cismethrin and bioresmethrin, whereas liver microsomal esterases hydrolyzed bioresmethrin over 10 times more rapidly than cismethrin. It is suggested that the lower toxicity of bioresmethrin is not only due to its faster metabolism but to an intrinsically lower toxicity at the critical site of action in the nervous system.  相似文献   

16.
The purpose of this study was to examine the differential activities of proso millet (Panicum miliaceum L.) and corn (Zea mays L.) with respect to atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine] and EPTC (S-ethyldipropyl thiocarbamate) metabolism. GSH-S-transferase was isolated from proso millet shoots and roots. When assayed spectrophotometrically using CDNB (1-chloro 2,4-dinitrobenzene) as a substrate, the shoot enzyme had only 10% of the activity of corn shoot enzyme while the root enzyme had 33% the activity of corn root enzyme. However, when proso millet shoot GSH-S-transferase was assayed in vitro using 14C-ring-labeled atrazine, it degraded the atrazine to water-soluble products at the same rate as the corn shoot enzyme. Incubation of excised proso millet and corn roots with [14C]EPTC indicated that uptake of EPTC was similar in both plants. However, proso millet metabolized the EPTC to water-soluble products at only half the rate of corn. Glutathione levels of proso millet roots were 35.9 μg GSH/g fresh wt, compared with 65.4 μg GSH/g fresh wt for corn. However, a 2.5-day pretreatment with R-25788 (N,N-diallyl-2-2-dichloroacetamide) elevated proso millet GSH levels to 62.7 μg GSH/g fresh wt. R-25788 did not elevate the activity of proso millet GSH-S-transferase, in contrast to its effects on corn. We conclude that differences in response to atrazine and EPTC in proso millet and corn are a result of their differential metabolism.  相似文献   

17.
α-Terthienyl, a common chemical constituent in the Asteraceae, was administered to fifth-stadium larvae (Day 1) of the tobacco hornworm, Manduca sexta (L.) (Sphingidae), by incorporation into artificial diet and by topical application. Toxicity toward larvae was elicite by simultaneous exposure to this allelochemical and uv-A irradiation (320–400 nm). Larval treatment with either α-terthienyl or uv-A irradiation alone caused no apparent adverse effects. A single, ingested dose of α-terthienyl (50 μg g larval weight?1), followed by irradiation for 4 hr, resulted in delayed and abnormal pupal formation with no subsequent adult emergence. Topical application of the plant compound (50 μg g?1) and uv-A irradiation led to tissue necrosis that affected both sclerotization and melanization of the pupal case in later development.  相似文献   

18.
Male and female Japanese quail (Coturnix coturnix japonica) were given intraperitoneal injections of [14C]DDT in ethanol at a rate of 13.4 mg/kg body wt. Fifty-six days later the tissues and droppings were analysed for total 14C and metabolites. The rate of loss of 14C in droppings was very similar in males and females. The maximal rate was reached on the third day, and 65–66% of the injected dose was voided by the fifty-sixth day. Ninety-three to ninety-four percent of the 14C in droppings and 83–90% of the 14C in tissues were extracted by solvents. Combined extracts from males and females were used for determination of DDT and its metabolites. Expressing all results as percentages of injected dose, the following were isolated from droppings: DDA (24%), DDT (3%), DDD (5.1%), DDE (11%), and uncharacterised polar metabolites (17%). Twenty-five percent of the dose was retained in the tissues and this was largely accounted for as DDT (10.4%) and DDE (10.5%). Of the total metabolites found 31% was DDE (almost equally divided between tissues and droppings) and 35% was DDA (almost entirely in droppings). Since DDD was not found in significant quantities in tissues, the substantial quantities in droppings were probably produced from DDT by the action of microorganisms.  相似文献   

19.
Mycelial uptake of [14C]fenarimol (10 μg/ml) by 20 fenarimol-resistant mutants of Aspergillus nidulans was compared with uptake by wild-type strain 003. Uptake of the fungicide during the initial 10 min of incubation was significantly lower in all mutant strains than in the wild-type strain indicating that resistance is related with reduced uptake. Upon prolonged incubation a gradual decrease of accumulated radioactivity in the wild-type strain was observed. A few mutants displayed resistance to unrelated chemicals such as p-fluorophenylalanine or d-serine; this phenomenon appeared not to be due to a decreased uptake of the corresponding natural amino acids. Incorporation of [3H]adenine and [14C]leucine by mycelium of mutant M193 was hardly inhibited after 5 hr of incubation with the fungicide, whereas a distinct effect was found with the wild-type strain. At this time also fungitoxicity to the wild-type strain became apparent. Probably, this effect is indirectly caused by inhibition of ergosterol biosynthesis. Mycelium of mutant M193 incorporated [14C]acetate slightly less effectively than the wild-type strain. After 2 hr of incubation with this radiochemical leakage of [14C]acetate metabolites from mycelium of the mutant strain was observed. This indicates that resistance might be correlated with increased excretion of fungal metabolites, which in turn may be related with reduced fitness of fenarimol-resistant mutants.  相似文献   

20.
Organochlorine and organophosphorus insecticides, in the concentration range of 1–10 μM, induce the release of hyperlipemic (adipokinetic) hormone from the isolated corpora cardiaca of the locust Locusta migratoria. Treatment of locusts with these insecticides in vivo also provokes the release of hyperlipemic hormone. The insecticide-induced release of hormone in vivo was found to precede the onset of poisoning symptoms. The insecticides tested in this study modulate the electrical activity of the isolated corpora cardiaca at doses lower than those required to have similar effects on the central nervous system. The results indicate that the insecticide-induced release of hormone may be mediated by the action of insecticides directly on neurosecretory cells.  相似文献   

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