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Sublethal Dose (sublethal + dose)

Distribution by Scientific Domains

Life Sciences	66%
Medical Sciences	20%
Chemistry	13%

Selected Abstracts

Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003
Mary-Kate Gilbertson
Abstract An injection study and a field study were used to investigate the hypothesis that environmental xenobiotics have the potential to alter the immune function of northern leopard frogs (Rana pipiens). Three assays, IgM-specific antibody response to keyhole limpet hemocyanin linked to dinitrophenyl (KLH-DNP), zymozan induced chemiluminescence (CL) of whole blood and the delayed-type hypersensitivity (DTH), were used to assay humoral, innate and cell-mediated immune endpoints. Sublethal doses of DDT (923 ng/g wet wt), malathion (990 ng/g wet wt), and dieldrin (50 ng/g wet wt) were used in the injection study. In all pesticide-injected groups, antibody response was dramatically suppressed, DTH reactions were enhanced, and respiratory burst was lower. When the order of administration of pesticides and antigens was reversed, no differences in immune function between the control and dosed groups were apparent, indicating that frogs exposed to pathogens prior to pesticide exposure can still respond. A field study found significant differences in immune function between frog populations in pesticide-exposed and pesticide-free locations. The antibody response and CL were suppressed and the DTH enhanced in frogs from Essex County (ON, Canada). Overall, the results suggest that exposure to these pesticides can cause both stimulatory and suppressive immune changes in adult frogs and is doing so in wild populations. [source]

Effects of sublethal dose of chlorfluazuron on testicular development and spermatogenesis in the common cutworm, Spodoptera litura

PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2000
Farzana Perveen
Summary This paper describes the physiological mechanism of action of chlorfluazuron on testicular development and spermatogenesis when sublethal doses (LD10: 1.00 ng/larva or LD30: 3.75 ng/larva) are applied topically to the cuticle of newly moulted fifth instars of the common cutworm Spodoptera litura (F.) (Lepidoptera, Noctuidae). These doses disrupt the growth and development of testes by decreasing the volume and weight of testes and thickness of testes sheath as compared with that of the controls. Sublethal doses of chlorfluazuron also significantly reduce the protein content of the testis, but do not affect the carbohydrate and lipid contents in newly emerged treated males when measured in ,g/mg of testis as compared with that of the controls. Additionally, such doses disrupt spermatogenesis by reducing the number and size of eupyrene and apyrene sperm bundles in the testis. Very few or no eupyrene sperm bundles are observed in vas deferens of pre- and newly moulted adults compared with controls. This result shows that the transfer of sperm bundles from testes to vas deferens is delayed in treated males. The effects of chlorfluazuron on testicular development and spermatogenesis is thought to be one of the factors responsible for the reduction in fecundity, fertility and hatchability caused by sublethal doses of chlorfluazuron. [source]

Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)

JOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2008
X.-Y. Wang
Abstract Effects of sublethal concentrations (LC25) of six insecticides (imidacloprid, rotenone, fenvalerate, abamectin, pirimicarb and azadirachtin) on fecundity and wing dimorphism of the green peach aphid, Myzus persicae (Sulzer), were studied both under laboratory and greenhouse conditions. In the laboratory, aphid reproduction reduced by 44.29% and 54.01% when rotenone and abamectin treatments were applied at sublethal dose, respectively, and sublethal fenvalerate application resulted in markedly lower average reproduction per female per day compared with control. Reproductive duration of aphid treated with abamectin significantly decreased by 44.19%. But in the greenhouse, there were no evident differences in the aphid fecundity and reproductive duration between treatments and control. Life-table parameters also demonstrated that the six insecticides at sublethal doses did not stimulate the aphid reproductive potential. In the laboratory, after being exposed to sublethal doses of imidacloprid and fenvalerate, the proportions of alate progeny in aphid progeny were significantly higher than that of the control. In the greenhouse, percentages of alate offspring from the mother aphids treated with imidacloprid, fenvalerate and abamectin increased pronouncedly compared with control. Mortality rates of offspring in the nymphal stages from adults treated with insecticides revealed no significant changes between laboratory and greenhouse. The developmental time in days of the offspring varied in all treatments. Mechanisms of insecticide-induced resurgence are discussed. [source]

Sublethal effects of chlorfluazuron on reproductivity and viability of Spodoptera litura (F. ) (Lep., Noctuidae)

JOURNAL OF APPLIED ENTOMOLOGY, Issue 5-6 2000
F. Perveen
To clarify the sublethal effects of chlorfluazuron on reproductivity and viability of common cutworm, Spodoptera litura, some experiments were conducted under laboratory conditions. The LD50 was found to be 12.0 ng/larva when evaluated up to pupation and 9.9 ng/larva up to adult emergence. At lethal dosages the development of different instars, moulting to pupae and emergence into adults were found to be more affected. Reduction in the body weight was also observed in the larvae and pupae when treated with a sublethal dose (LD30 : 3.75 ng/larva) and in the adults when treated with sublethal doses (LD10 : 1.00 ng/larva; LD30 : 3.75 ng/larva) as newly moulted fifth instar larvae of S. litura, although the number of matings per female and life span of adult females and males remained unaffected by the same treatments. When sublethal doses were applied only to females or only to males, or both sexes, the average fecundity reduction was up to 35,44%. When only females were treated with sublethal doses, fertility was reduced by 49,58%; when only males were treated fertility was reduced by 65,81% and when both sexes were treated, fertility was reduced by 68,83%. Hatchability was reduced by 22,26% when only females were treated, by 44,66% when only males were treated and by 45,72% when both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. The results from these observations suggest that the fecundity was reduced to a similar degree when only females or only males or both sexes were treated with LD10 or LD30 doses as newly moulted fifth instars. However the fertility and hatchability were affected more when only males were treated with LD10 and much more when treated with LD30. Currently, work is in progress to find out the main reasons for the sublethal effects of chlorfluazuron on reproductivity and viability. [source]

A comparison of the potency of newly developed oximes (K027, K048) and commonly used oximes (obidoxime, HI-6) to counteract tabun-induced neurotoxicity in rats

JOURNAL OF APPLIED TOXICOLOGY, Issue 4 2006
í Kassa
Abstract The neuroprotective effects of newly developed oximes (K027, K048) and currently available oximes (obidoxime, HI-6) in combination with atropine in rats poisoned with tabun at a sublethal dose (170 µg kg,1 i.m.; 80% of LD50 value) were studied. The tabun-induced neurotoxicity was monitored using a functional observational battery and an automatic measurement of motor activity. The neurotoxicity of tabun was monitored at 24 h and 7 days following tabun challenge. The results indicate that the oxime HI-6 in combination with atropine was not able to protect the rats from the lethal effects of tabun. Two non-treated tabun-poisoned rats and one tabun-poisoned rat treated with atropine combined with HI-6 died within 2 h. On the other hand, all other tested oximes combined with atropine allowed all the tabun-poisoned rats to survive 7 days following tabun challenge. Both newly developed oximes combined with atropine seem to be sufficiently effective antidotes for a decrease in tabun-induced neurotoxicity in the case of sublethal poisoning although they are not able to eliminate tabun-induced neurotoxicity completely. The neuroprotective efficacy of obidoxime in combination with atropine approached the potency of newly developed oximes but the ability of the oxime HI-6 to counteract tabun-induced acute neurotoxicity was significantly lower, especially at 24 h after tabun poisoning. Due to their neuroprotective effects, both newly developed oximes appear to be suitable oximes for the antidotal treatment of acute tabun poisoning. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Ionizing radiation-induced long-term expression of senescence markers in mice is independent of p53 and immune status

AGING CELL, Issue 3 2010
Oanh N. L. Le
Summary Exposure to IR has been shown to induce the formation of senescence markers, a phenotype that coincides with lifelong delayed repair and regeneration of irradiated tissues. We hypothesized that IR-induced senescence markers could persist long-term in vivo, possibly contributing to the permanent reduction in tissue functionality. Here, we show that mouse tissues exposed to a sublethal dose of IR display persistent (up to 45 weeks, the maximum time analyzed) DNA damage foci and increased p16INK4a expression, two hallmarks of cellular senescence and aging. BrdU-labeling experiments revealed that IR-induced damaged cells are preferentially eliminated, at least partially, in a tissue-dependent manner. Unexpectedly, the accumulation of damaged cells was found to occur independent from the DNA damage response modulator p53, and from an intact immune system, as their levels were similar in wild-type and Rag2,/, ,C,/, mice, the latter being deficient in T, B, and NK cells. Together, our results provide compelling evidence that exposure to IR induces long-term expression of senescence markers in vivo, an effect that may contribute to the reduced tissue functionality observed in cancer survivors. [source]

Systemic action of novel neonicotinoid insecticide IPP-10 and its effect on the feeding behaviour of Rhopalosiphum padi on wheat

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2010
Li Cui
Abstract BACKGROUND: IPP-10 is a novel neonicotinoid insecticide recently developed in China and has good activity against sucking insects. Studies were carried out to investigate the activity of IPP-10 against Rhopalosiphum padi L. RESULTS: The results demonstrated that IPP-10 had both contact and systemic activity, including acropetal and basipetal translocation in wheat vascular bundles. Starved R. padi were allowed to stay on wheat treated with a sublethal dose of IPP-10. The results of studying their feeding behaviour from an electrical penetration graph (EPG) revealed a decrease in total time and bout duration of xylem and phloem ingestion, but the total time and bout duration of phloem salivation were significantly prolonged. The frequency (7.03 ± 0.49 Hz) of the xylem ingestion waveform produced by aphids on wheat treated with IPP-10 was significantly lower than that of blank control aphids (8.20 ± 0.30 Hz). Consequently, aphids born on wheat treated with IPP-10 were obviously lighter and less fecund than the control aphids. CONCLUSION: These tests indicated that IPP-10 had both contact and systemic activity, with sublethal effects resulting in reduction in R. padi feeding behaviour, growth rate and fecundity. Copyright © 2010 Society of Chemical Industry [source]

Effects of sublethal dose of chlorfluazuron on testicular development and spermatogenesis in the common cutworm, Spodoptera litura

Survivin as a Radioresistance Factor in Pancreatic Cancer

CANCER SCIENCE, Issue 11 2000
Koichi Asanuma
We examined whether survivin acts as a constitutive and inducible radioresistance factor in pancreatic cancer cells. Using a quantitative TaqMan reverse transcription-polymerase chain reaction for survivin mRNA in five pancreatic cancer cell lines, we found an inverse relationship between survivin mRNA expression and radiosensitivity. PANC-1 cells, which had the highest survivin mRNA levels, were most resistant to X-irradiation; MIAPaCa-2 cells, which showed the least survivin mRNA expression, were the most sensitive to X-irradiation. Our results suggested that survivin could act as a constitutive radioresistance factor in pancreatic cancer cells. To determine whether radioresistance is enhanced by induction of survivin expression by irradiation, PANC-1 and MIAPaCa-2 cells were subjected to sublethal doses of X-irradiation followed by a lethal dose. Survivin mRNA expression was increased significantly in both PANC-1 and MIAPaCa-2 cell lines by pretreatment with a sublethal dose of X-irradiation, as was cell survival after exposure to the lethal dose. In this system, enzymatic caspase-3 activity was significantly suppressed in cells with acquired resistance. These results suggest that survivin also acts as an inducible radioresistance factor in pancreatic cancer cells. Survivin, then, appears to enhance radioresistance in pancreatic cancer cells; inhibition of survivin mRNA expression may improve the effectiveness of radiotherapy. [source]

Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)

Sublethal effects of chlorfluazuron on reproductivity and viability of Spodoptera litura (F. ) (Lep., Noctuidae)

Oxidative stress increases levels of endogenous amyloid-, peptides secreted from primary chick brain neurons

AGING CELL, Issue 5 2008
Claire Goldsbury
Summary Oxidative damage is associated with Alzheimer's disease and mild cognitive impairment, but its relationship to the development of neuropathological lesions involving accumulation of amyloid-, (A,) peptides and hyperphosphorylated tau protein remains poorly understood. We show that inducing oxidative stress in primary chick brain neurons by exposure to sublethal doses of H2O2 increases levels of total secreted endogenous A, by 2.4-fold after 20 h. This occurs in the absence of changes to intracellular amyloid precursor protein or tau protein levels, while heat-shock protein 90 is elevated 2.5-fold. These results are consistent with the hypothesis that aging-associated oxidative stress contributes to increasing A, generation and up-regulation of molecular chaperones in Alzheimer's disease. [source]

Effects of sublethal dose of chlorfluazuron on testicular development and spermatogenesis in the common cutworm, Spodoptera litura

Neutrophils in a mouse model of autoantibody-mediated arthritis: Critical producers of Fc receptor ,, the receptor for C5a, and lymphocyte function,associated antigen 1

ARTHRITIS & RHEUMATISM, Issue 3 2010
Paul A. Monach
Objective Neutrophils represent a prominent component of inflammatory joint effusions and are required for synovial inflammation in mouse models, but the mechanisms are poorly understood. In this study, we developed a system with which to test the importance of the production of specific factors by neutrophils in a mouse model of arthritis. Methods Neutrophil-deficient Gfi-1,/, mice were administered sublethal doses of radiation and were then engrafted with donor bone marrow cells (BMCs), which resulted in the production of mature neutrophils within 2 weeks. By reconstituting with BMCs from mice lacking selected proinflammatory factors, we generated mice that specifically lacked these factors on their neutrophils. Arthritis was initiated by transfer of K/BxN serum to identify the role of defined neutrophil factors on the incidence and severity of arthritis. Results Neutrophils lacking the signaling chain of stimulatory Fc receptors (FcR,,/,) were unable to elicit arthritis, but neutrophils lacking Fc,RIII still did so. Neutrophils lacking the chemotactic or adhesion receptor C5a receptor (C5aR) or CD11a/lymphocyte function,associated antigen 1 (LFA-1) also failed to initiate arthritis but could enter joints in which inflammation had been initiated by wild-type neutrophils. Neutrophils unable to produce interleukin-1, (IL-1,) and IL-1, (IL-1,/,,/,) or leukotrienes (5-lipoxygenase [5-LOX,/,]) produced arthritis of intermediate severity. The inability of neutrophils to make tumor necrosis factor or to express receptors for tumor necrosis factor or IL-1 had no effect on arthritis. Conclusion A novel transfer system was developed to identify neutrophil production of FcR,, C5aR, and CD11a/LFA-1 as critical components of autoantibody-mediated arthritis. Neutrophil production of IL-1 and leukotriene B4 likely contributes to inflammation but is not essential. Molecular requirements for neutrophil influx into joints become more permissive after inflammation is initiated. [source]