Effect of a single oral dose of DDT on intestinal uptake of nutrients and brush border enzymes in protein-calorie-malnourished monkeys

The effect of a single oral dose of DDT (150 mg/kg body wt) has been investigated on the intestinal uptake of certain nutrients and on brush border enzymes in protein-calorie-malnourished monkeys. In contrast to the stimulatory action of DDT on intestinal functions in normal-fed monkeys (A. Mahmood, N. Agarwal, S. Sanyal, P.K. Dudeja, and D. Subrahmanyam, Pest. Biochem. Physiol.12, 141 (1979)) pesticide feeding to malnourished animals inhibited the uptake of alanine and phenylalanine and depressed sucrase, lactase, and leucine amino-peptidase activities. Glucose and leucine uptake was also reduced, albeit insignificantly and alkaline phosphatase activity was unaffected under these conditions. Protein-energy malnutrition per se considerably elevated the uptake of nutrients and disaccharidase activities. Analysis of the chemical composition of microvillus membrane in underfed and pesticide-exposed malnourished animals revealed alterations in protein, sialic acid, and phospholipid fractions of the brush borders. Membrane cholesterol and triglyceride contents remained unaltered in protein-energy-deficient and DDT-fed monkeys.     

Binding of [14C]DDT and [14C]dicyclohexylcarbodi-imide to a lipoprotein of the membrane sector of mitochondrial ATpase

Intact mitochondria, isolated from red coxal muscle of the American cockroach (Periplaneta americana L.), were incubated in the presence of 1,1,1-trichloro-2,2-bis(4-chloro[¹⁴C]phenyl)ethane ([¹⁴C]DDT) to isolate a suspected binding site for DDT in the membrane sector of the mitochondrial ATPase. The requirements for the binding of DDT were compared with those for the binding of dicyclohexyl[¹⁴C]carbodi-imide([¹⁴C]DCCD), a potent inhibitory probe of mitochondrial ATPase activity. [¹⁴C]DDT appeared to bind to a proteolipid of the membrane sector, which also binds [¹⁴C]DCCD. Exchange experiments, with [¹⁴C]DCCD, [¹⁴C]DDT and unlabelled DDT at different concentrations, indicated that DDT and DCCD may be acting on a similar protein. This protein may act as the energy transducing protonophore required for the synthesis and hydrolysis of ATP in coupled mitochondria. Inhibition of mitochondrial ATPase activity may be a consequence of DDT and DCCD binding to this proteolipid protonophore, resulting in the disruption of energy transduction in muscle and nerve.     

Effects of DDT on electrical properties of lecithin-decane bilayer membranes

Lecithin-decane bilayer membranes were treated with DDT and valinomycin, either by adding the compounds to the electrolyte around the membrane or by adding them directly to the lecithin-decane. Membrane capacitance was calculated using the dc transient technique. Specific capacitance was determined from capacitance versus area regressions and was not significantly altered by DDT. Specific K⁺ conductance was decreased by DDT, but only when DDT and the K⁺ carrier, valinomycin, were administered to the electrolyte where they may have interacted hydrophobically. It is concluded that the valinomycin-induced conductance of artificial membranes is inappropriate as a model for investigating the effects of DDT on the electrical properties of excitable membranes.     

Binding of three Cry1A toxins in resistant and susceptible strains of cotton bollworm (Helicoverpa armigera)

Evolution of resistance by pests is the greatest threat to the continuous success of theBacillus thuringiensis (Bt) toxins used in conventional sprays or in transgenic plants. The most common mechanism of insect resistance to Bt is reduced binding of toxins to target sites in the brush border membrane of the larval mid-gut. In this paper, binding experiments were performed with three ¹²⁵I-Cry1A toxins and the brush border membrane vesicles from Cry1Ac resistant or susceptible strains of Helicoverpa armigera. The homologous competition test showed that there was no significant difference in Cry1Ac-binding affinity, but the concentration of Cry1Ac-binding sites dramatically decreased in the resistant strain (R_t decreased from 5.87 ± 1.40 to 2.23 ± 0.80). The heterologous competition test showed that there were three Cry1Ac-binding sites in the susceptible strain. Among them, site 1 bound with all three Cry1A toxins, site 2 bound with both Cry1Ab and Cry1Ac, and site 3 only bound with Cry1Ac. In the Cry1Ac resistant strain, the binding capability of site 1 with Cry1Ab decreased and site 2 did not bind with Cry1Ac. It is suggested that the absence of one binding site is responsible for H. armigera resistance to Cry1Ac. This result also showed that the resistance fitted the “mode 1” pattern of Bt resistance described previously.     

DDT effects on certain ATP related systems in the peripheral nervous system of the lobster Homarus americanus

Effects of DDT (1,1,1-trichloro-2,2-bis-(p-chlorophenyl) ethane) on various ATP utilizing enzymes in the lobster peripheral nerve were studied. On the basis of inhibition by ouabain and DDT, four classes of ATPase enzymes were recognized. They are: (1) ATPase activity that is sensitive to both ouabain and DDT inhibition, or Type A, (2) ATPase activity that is sensitive to DDT inhibition only, or Type B, (3) ATPase activity that is sensitive to ouabain only, and (4) ATPase activity that is not sensitive to either ouabain or DDT. The Type A ATPase is considered to be a part of the total (Na⁺K⁺) ATPase enzyme associated with the electrogenic pump. The Type B ATPase consisted of an uncharacterized Na⁺, K⁺, and Mg²⁺ stimulated ATPase and includes also a small portion of Mg²⁺ stimulated ATPase. Ca²⁺ stimulated ATPase activity was also detected but was not significantly affected by DDT. Proteins with actomyosin-like properties were also recognized to be present, though this superprecipitation process was only slightly affected by DDT.Other systems studied include the transfer of (γ-³²P) ATP to endogenous proteins and added histone in the presence and absence of c-AMP. DDT generally stimulated the process of ³²P incorporation, while it inhibited a portion of the specific c-AMP dependent protein kinase activity.It was concluded from these studies that DDT has a potential to inhibit or otherwise interfere with a variety of enzymatic reactions that utilize ATP as a substrate. Of these systems, the Type B ATPase bore overall resemblance to the possible target for DDT.     

Resistance mechanisms to DDT and transpermethrin in Aedes aegypti

Penetration, metabolism and excretion of [¹⁴C]DDT and [³H]transpermethrin were studied in three strains of Aedes aegypti L. after topical application of 10 nl of a solution of the insecticide in 2-ethoxyethanol. The standard susceptible strain was compared with a DDT-selected strain (BKS) and a permethrin-selected strain (BKPM). No significant penetration resistance was observed in either resistant strain, but both showed high DDT-dehydrochlorinase activity which contributed to the DDT resistance. A non-metabolic factor was also involved. Rates of transpermethrin metabolism were very similar in all three strains and substantially higher internal concentrations of transpermethrin were required to produce toxic effects in both BKS and BKPM mosquitoes. By analogy with other insect species, it is concluded that transpermethrin resistance in these strains is of the kdr type, while the DDT resistance is a mixture of kdr and DDT-dehydrochlorinase.     

Mechanisms of DDT resistance in larvae of the mosquito Aedes aegypti L

Larvae of eight strains of Aedes aegypti were exposed to DDT and compared for resistance, DDT uptake, in-vivo breakdown of DDT and residual unmetabolised DDT. Resistance varied widely between strains, three being fully susceptible, two almost immune and three of intermediate resistance. Breakdown of DDT by dehydrochlorination to 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (pp'-DDE) occurred in all strains and was greater in the five resistant types, but there was no significant correlation between the extent of breakdown in the resistant strains and the level of resistance. Moreover the overall difference between susceptible and resistant strains disappeared when they were compared at a low, almost sublethal, concentration of DDT. Larvae of resistant strains carried a greater absolute quantity of unmetabolised DDT in the body and were able to tolerate levels of DDT that were lethal to susceptible larvae. However the two most resistant strains (T8 and B51) contained significantly less DDT plus pp'-DDE than strains of intermediate resistance (T30 and BSJ) from which they had been derived. Addition of the synergist chlorfenethol to DDT increased its knockdown effect on all resistant strains, suggesting that dehydrochlorination was a factor in resistance. Three strains, two DDT-resistant and one DDT-susceptible, were tested with 1,1-bis(4-ethoxyphenyl)-2,2-dimethylpropane (I), an insecticide that cannot be dehydrochlorinated. All the strains were relatively tolerant to it although the DDT-susceptible strains were less tolerant. Addition of the synergist sesamex decreased the level of tolerance to I in all strains which suggested that microsomal oxidation made some contribution to it. It is concluded that three factors contribute to larval DDT resistance in A. aegypti; (a) increased metabolism to pp'-DDE; (b) increased tolerance to unmetabolised internal DDT; and (c) reduced content of DDT+pp'-DDE (only in the most resistant strains and due either to reduced absorption or increased excretion). These factors are discussed in relation to known larval resistance genes R^DDT1 and y.     

DDT and pyrethroids: Receptor binding and mode of action in the house fly

The mode of action of DDT and pyrethroids was investigated in the house fly, Musca domestica L, using drug:receptor binding techniques. Both in vivo and in vitro binding studies demonstrated the existence of membrane receptors which bind specifically to [¹⁴C]DDT and [¹⁴C]cis-permethrin. The receptors show properties to be expected of a critical target site of these insecticides. These include negative temperature correlation with binding, relatively nonsensitivity to DDE, and sensitivity to Ca²⁺. The receptor sites are readily saturated at 45–90 nM [¹⁴C]DDT and have an apparent disassociation constant (K_d) of 12.2 nM. The maximum number of binding sites was estimated to be 17 pmol DDT/mg membrane protein (0.34 pmol/house fly head). Competition studies showed DDT, cis-permethrin, and cypermethrin bind to the same receptor but not at precisely the same site. The addition of Ca²⁺ to the incubation buffer significantly inhibited the binding of both [¹⁴C]DDT and [¹⁴C]cis-permethrin, suggesting the receptor binding is Ca²⁺ sensitive and may have a role in ion conductance.     

DDT and sodium transport in the eel electroplaque

DDT inhibits the ATPase activity of the intact eel electroplaque. At a concentration of 10^?5M, DDT inhibited 46% of the total ATPase activity, and 10^?4M DDT inhibited 62% of the total ATPase activity and 62% of the ouabain-sensitive ATPase activity. The latter concentration of DDT reduced the rate of Na efflux from intact electroplaques and slowed the rate of recovery of the membrane potential following a large depolarization produced by carbamylcholine application. Repetitive direct stimulation of the innervated membrane at 10 Hz during the application of 10^?4M DDT produced a significant irreversible depolarization. Ouabain, 10^?4M, produced similar effects. The possible role of the inhibition of active NaK transport in producing the symptoms of DDT poisoning is discussed.     

DDT and inflammatory responses: 2. Bacterial endotoxin-induced pulmonary oedema in mice and rats

Escherichia coli endotoxin instilled intranasally into mice and rats caused a severe pulmonary oedema associated with progressive increases in lung weights of up to 30% within 2 days. When mice were injected with DDT (20 mg/kg) 20 and 2 hr prior to the administration of endotoxin the animals were found to be tolerant to the endotoxin. The inflammatory oedema induced by endotoxin is caused by release of lung histamine, and as DDT injections also lowered histamine content in the lungs, the protective effect of DDT against the oedema induced by endotoxin appears to be due to its prior depletion of the lung histamine stores. An opposite effect, increased and accelerated inflammation, was observed by chronic exposure of rats to dietary DDT (150 ppm) fed for 36 days. The long-term feeding of DDT is known to cause adaptations in many physiological systems. One of these may be increased histamine synthesis and subsequently increased severity of histamine mediated reactions.     

钙对低温胁迫下玉米幼苗氧化损伤的保护作用

采用室内盆栽试验,利用不同浓度的CaCl₂（0、5、10、15、20 mmol·L^-1）处理低温胁迫下的玉米幼苗,研究了钙对玉米幼苗抗冷性的作用。结果表明：与对照相比,低温处理明显抑制了玉米幼苗的生长,减缓了可溶性蛋白和可溶性糖含量的积累,抗氧化酶活性下降,脯氨酸含量减少,丙二醛（MDA）含量增加,质膜透性增大。适宜浓度的钙（5～10 mmol·L^-1）能减缓低温胁迫下玉米幼苗质膜相对透性和丙二醛（MDA）含量的增加,促进脯氨酸(Pro)、可溶性糖和可溶性蛋白的积累,提高超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性,其中10 mmol·L^-1 Ca²⁺处理的效果最为明显。     

A comparison of DDT and its biodegradable analogues tested on ATPase enzymes in cockroach

Analogues of DDT (ethoxymethyl and methoxymethio derivatives) compared with DDT for their inhibitory action on the ATPase system from tissues of the cockroach, Periplaneta americana show similar, but less inhibitory effects. The mitochondrial (oligomycin-sensitive) Mg²⁺ ATPase activity from coxal muscle preparations was more sensitive to DDT than the two analogues; whereas, the muscle and nerve cord homogenates showed about equal sensitivity to the biodegradable analogues. The mitochondrial Mg²⁺ ATPase from nerve cord preparation was more sensitive to the three compounds than the Na⁺K⁺ ATPase activity. The significance of these results in relation to recent reports on the effect of DDT on Na⁺K⁺ ATPase is discussed.     

Mechanism of DDT resistance in larvae of the mosquito Aedes aegypti L.; The effect of DDT selection

Selection with pp'-DDT was applied to fourth-stage larvae of Aedes aegypti along four lines, starting with larvae of the F₂ generation from crosses between a susceptible strain and each of four resistant strains (two of Trinidad origin and two of Bangkok origin). Larval resistance increased substantially along each line but there was little or no change in the percentage breakdown of DDT to 1,1-dichloro-2,2-bis(4-chloro-phenyl)ethylene (pp'-DDE) in vivo and in no line were these two variables significantly correlated. Percentage breakdown was generally higher at 10 mg than at 50 mg litre^?1. DDT uptake (defined as content of DDT+pp'-DDE) was generally higher after exposure to 50 mg than to 10 mg litre^?1. It increased significantly with selection in the TE×NS line; it remained unchanged in the T8 × NS line; and in the other two lines (BSJ × NS and B51 × NS), it increased initially but dropped as selection progressed, the reduction being highly significant in the second of these lines. The amount of internal residual (unmetabolised) DDT tolerated by larvae of the TE × NS line also increased significantly with resistance. The levels in the other lines followed the pattern of uptake, remaining steady in T8 × NS despite the increase in survival, rising at first and then declining in the two Bangkok lines. Thus selection produced a higher tolerance to internal unmetabolised DDT in the two Trinidad lines but led ultimately to a lower content of DDT+pp'-DDE in the two Bangkok lines. The reasons for this behaviour are discussed.     

Differential inhibition responses caused by DDT on oligomycin-sensitive Mg2+-ATPase activity: Nature of the requirements for DDT sensitivity

Earlier communications from this laboratory have shown that DDT inhibited oligomycin-sensitive Mg²⁺-ATPase (EC 3.6.1.3) but that its active component, F₁, was not affected. In the present investigation evidence has been obtained to determine the nature of the requirements for DDT sensitivity. The results showed that DDT sensitivity was conferred to F₁ from pig heart mitochondrial preparations when it was bound to F₀ from the same preparation. The F₁ from house fly (Musca domestica L) thorax was able to bind to F₀ from pig heart. This combination showed similar sensitivity to that of the original F₁-F₀ combination from pig heart mitochondria. However, when F₁ from pig heart mitochondria was incorporated into F₀ depleted in oligomycin sensitivity-conferring protein (OSCP) from the same source, the resulting ATPase activity was insensitive to DDT. Addition of crude (50–200 μg) or purified (5–20 μg) OSCP in the above preparation restored DDT sensitivity. Presence of dioleyl or dipalmitoyl phosphatidyl choline or Triton X-100 in the reaction medium antagonized the DDT inhibitions. Depletion of phospholipids from submitochondrial membrane preparations (SMP) decreased ATPase activity. Addition of dioleyl or soybean phosphatidyl choline to this lipid-depleted preparation restored DDT sensitivity. Evidence presented suggests that DDT acted on F₁ in association with one or more membrane components and that OSCP and phospholipid were essential for DDT sensitivity.     

Resistance management strategies in malaria vector mosquito control. A large-scale field trial in Southern Mexico

A resistance management programme comparing rotations, mosaics and single use of insecticides for residual house-spraying against the insect vectors of malaria is being carried out in Southern Mexico. The area was chosen because of its prior history of insecticide use, relatively sedentary vector, and physical features of the area which limit inward migration of insects to the study area. A high level of resistance to DDT and low levels of organophosphorus (OP), carbamate and pyrethroid resistance were detected by WHO discriminating-dose assays in field populations of Anopheles albimanus in the pre-spray period in the region where this resistance management project is being undertaken. After the first year of spraying, resistance, as measured by a discriminating-dose assay, was still at a high level for DDT and had risen for all the other insecticides. Biochemical assays showed that DDT resistance was primarily caused by elevated levels of glutathione S-transferase (GST) activity leading to increased rates of metabolism of DDT to DDE. The numbers of individuals with elevated GST and DDT resistance were well correlated, suggesting that this is the only major DDT resistance mechanism in this population. The carbamate resistance in this population was conferred by an altered acetylcholinesterase (AChE) mechanism. The level of resistance in bioassays correlated well with the frequency of individuals homozygous for the altered AChE allele. This suggests that the level of resistance conferred by this mechanism in its heterozygous state is below the level of detection of the bioassay. The low levels of OP and pyrethroid resistance could be conferred by either the elevated esterase or monooxygenase enzymes. The esterases, however, are elevated only with p-nitrophenyl acetate (PNPA), and are unlikely to be causing broad-spectrum OP resistance. The altered AChE mechanism may also be contributing to the OP but not the pyrethroid resistance. There were significant differences in some resistance gene frequencies for insects obtained by different indoor and outdoor trapping methods. To determine whether the different sampling methods were effectively sampling the same interbreeding population, RAPD analysis of insects obtained by different collection methods in different villages was undertaken. There was no observed variability in the RAPD patterns for the different mosquito samples with a number of primers. ©1997 SCI     

Influence of calmodulin and ATP on DDT inhibition of Na/Ca exchange in the axolemma-rich nerve preparation from the American lobster

The effects of DDT on the Na/Ca exchange system were studied by using an axolemma-rich nerve membrane preparation from walking legs of Homerus americanus, the American lobster. The Na/Ca exchange system was measured by using two criteria: Na⁺ stimulated ⁴⁵Ca²⁺ uptake by the membrane vesicles and Na⁺Ca²⁺ protein kinase-phosphatase (formally called Ca-ATPase) as measured by the production of ³²P-labeled inorganic phosphate from [γ-³²P]ATP in the presence of Na⁺ and Ca²⁺. Activities of both systems were stimulated by the addition of exogenous calmodulin. DDT's inhibitory actions on both systems were reduced when an excess of calmodulin was added. Also addition of large amounts of ATP (or γ-thio-ATP) to the former system had an effect to reduce levels of DDT inhibition. DDT appears to act on the protein kinase proper as well as calmodulin itself in this system in a reversible manner.     

Studies on octylphenoxy surfactants. Part 2: Effects on foliar uptake and translocation

The effects of octylphenol (OP) and four of its ethoxylated derivatives on uptake into, and distribution within, maize leaf of 2-deoxy-glucose (2D-glucose), atrazine and o, p′-DDT are reported. The surfactants and OP (2 g litre^?1 in aqueous acetone) increased the uptake, at both 1.5 and 24 h, of the three model compounds (applied at 1 g litre^?1) having water solubilities in the g, mg and μg litre^?1 ranges. The uptake of 2D-glucose was positively correlated with the hygroscopicity of the surfactants. The uptake of DDT and atrazine increased with the uptake of the surfactants, being inversely related to their hydrophile:lipophile balance (HLB). Uptake of 2D-glucose and atrazine was enhanced at high humidity, the relative enhancement for atrazine increasing with increasing ethylene oxide (EO) content of the surfactants. A significant proportion of the atrazine and DDT entering the leaf was recovered from the epicuticular wax, the amount of atrazine recovered from the wax increasing with the EO content of the surfactants. The proportion of the surfactants taken up which was recovered from the epicuticular wax was minimal at an EO content of 12.5–16 mole equivalents. The appearance of the deposits on the leaf surface differed markedly among the surfactants, with similar trends for all three chemicals and without visible evidence for infiltration of the stomatal pores. The total quantities of glucose and atrazine translocated were increased by all surfactants but that of DDT was not, despite increases in uptake of up to 7.5-fold. Relative translocation (export from treated region of leaf as a percentage of chemical penetrating beyond the epicuticular wax) was reduced in all cases in the presence of surfactant. Up to 30% of the applied [¹⁴C]chemicals was not recovered from the treated leaf after 24 h. The reduced recovery of 2D-glucose, but not that of atrazine and DDT, was largely attributable to movement out of the treated leaf, with approximately 70% of the chemical taken up being translocated basipetally. Loss of atrazine and DDT was a result of volatilisation. There was no evidence that either [14C]2 D-glucose or [¹⁴C]atrazine was metabolised to [¹⁴C]carbon dioxide.     

玉米幼苗对风速变化的逆境生理响应

为了解玉米幼苗对不同强度风吹危害的逆境生理响应特征,2013年在内蒙古东部科尔沁沙地研究了0（CK）、9、15 m·s^-1和18 m·s^-1净风吹袭20 min下玉米幼苗丙二醛含量（MDA）、膜透性、保护酶活性和渗透调节物质含量的变化。结果表明：随着风吹强度增加,玉米的株高、茎粗生长量和地上生物量下降,其中18 m·s^-1处理的株高和茎粗生长量及地上生物量分别较CK下降4.48%、11.28%和13.23%;风吹胁迫下玉米幼苗丙二醛含量与CK没有显著差异,但各处理膜透性均显著高于CK,其中15 m·s^-1和18 m·s^-1处理膜透性分别较CK增加84.36%和116.62%;随着风吹强度增强,SOD、POD和CAT活性均趋于增加,其中18 m·s^-1处理分别较CK增加37.45%、94.65%和82.14%;随着风吹强度增强,可溶性糖含量明显增加,脯氨酸含量趋于下降,和CK相比,18 m·s^-1处理的可溶性糖含量增加31.48%,脯氨酸含量下降40.26%。结果表明,20 min风吹处理已对玉米生长产生抑制作用,虽未导致玉米幼苗明显的膜脂过氧化,却使其细胞膜受损,SOD、POD和CAT在防止其膜脂过氧化过氧化过程中共同发挥了保护细胞膜的作用,可溶性糖起到了渗透调节作用。     

Excretion of DDT residues into milk of the Indian buffalo,Bubalus bubalis (L.) after oral and dermal exposure

Three groups of buffaloes were fed with 20, 100 and 400 mg of p,p′-DDT in their daily rations. The DDT residues in the milk fat of the treated animals showed an initial rapid rise but soon attained a dose-dependent equilibrium. The transfer coefficient of DDT residues in milk at ‘plateau’ levels showed an average value of about 12%. Half-life values for the rate of decline of DDT residues during the post-dosing period were computed according to a two-open-compartment model. Dermal application of p,p′-DDT to buffaloes also resulted in excretion of a significant amount of its residues in milk. TDE was the predominant compound present in milk when buffaloes had ingested p,p′-DDT, whilst p,p′-DDT itself was present in greater quantity than its metabolites when animals were treated dermally.     

The in vivo sensitivity of ATPases to DDT,DDE, and physical immobilization in American cockroaches

American cockroaches injected with sublethal doses of DDT (0.75 μg/roach) at 5-day intervals showed a 40% reduction in oligomycin-sensitive Mg²⁺ATPase from muscle homogenates, and a 23% reduction of Na⁺-K⁺ATPase from nerve cords. Thus, the maximum effect measured occurred with the same enzyme and tissue as determined from in vitro studies. The metabolite, DDE, used at 15 μg per roach, gave no significant change in activity of the ATPase system following injection. In contrast, high single doses of DDT (7.5 μg/roach) and 100 μg DDE and dicofol per roach caused over 30% increase in oligomycin-sensitive Mg²⁺ATPase of muscle and a 10–15% increase in Na⁺-K⁺ATPase of nerve cords measured 24 and 48 hr later. While a similar response was observed for Mg²⁺ATPase activities in cockroaches that were immobilized, the increase in enzyme activities were much greater than that caused by the pesticides.