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At least 145 records · Page 8Linked to original sources
PubMed1989

Development of resistance in calves to nymphs of Rhipicephalus appendiculatus (Acarina:Ixodidae) during test feeds.

A test of host resistance to infestation by the tick Rhipicephalus appendiculatus was repeated 5 times, at weekly intervals, on 2 initially susceptible calves. One hundred nymphs (NN) were used each time. Pairs of tick-susceptible rabbits served as controls. The engorged NN were weighed, then allowed to moult individually, and the sex of each was noted after emergence of the adult. During the course of the experiment there was a significant reduction in mean engorged weight (especially in the pre-male NN) and also in the length of the feeding period, and a downward trend in the percentage of NN which engorged. There was a significant increase in the percentage of engorged NN that moulted. Pre-male NN were significantly heavier than pre-female NN after feeding on susceptible hosts, but though mean feeding times were the same, they took 1-2 days longer to moult than pre-females at 28 degrees C. It was concluded that the test itself could induce resistance if applied to fully susceptible calves.

Analysis of Variance↗
PubMed2000

Cytokines (IL-4 and IFN-gamma) and antibodies (IgE and IgG2a) produced in mice infected with Borrelia burgdorferi sensu stricto via nymphs of Ixodes ricinus ticks or syringe inoculations.

Mice were tolerant to tick bites during three infestations with nymphs of Ixodes ricinus infected with Borrelia burgdorferi sensu stricto. To determine whether tick bites influence the immune response against B. burgdorferi, we examined the production of cytokines IL-4 and IFN-gamma by lymph node cells of BALB/c mice and IL-4 deficient BALB/c mice after tick inoculation versus syringe inoculation of B. burgdorferi. We also measured IgG2a anti-borrelial antibodies and total IgE in these mice. Results showed that BALB/c mice developed a Th2 immune response against B. burgdorferi after tick inoculation and a mixed Th1/Th2 response after syringe inoculation of B. burgdorferi. IL-4 deficient mice produced a Th1 immune response in both cases. IL-4 produced following tick bites greatly decreased the production of anti-borrelial IgG2a antibodies by comparison with the production of anti-borrelial IgG2a antibodies produced following syringe injection of B. burgdorferi.

Animals↗
PubMed1991

Ultrastructural changes of the midgut epithelial cells in feeding and moulting nymphs of the tick Haemaphysalis longicornis.

The midgut epithelial cells in nymphs fed on laboratory rabbits were examined during feeding and after detachment. The midgut epithelium at the unfed stage consisted of digestive cells of lower activity, containing such nutritive substances as protein, lipid and glycogen. As feeding proceeded, the cells became active in intracellular digestion. At the middle of the feeding stage, the spent digestive cells derived from the active digestive cells began to be replaced by the new digestive cells of lower activity. After detachment, the pinocytotic activity of the above cells increased greatly, and the digestive activity increased to some extent. As a result, many large endosomes were formed by fusion of numerous pinosomes. Thereafter, endosomes decreased in size as digestion proceeded and there was an increase of haematin granules. On day 7 after detachment, the new digestive cells of lower activity, belonging to the 'nutritional reserve' type, appeared adjacent to the spent digestive cells which had almost exhausted all endosomes, and these new cells had completely replaced the spent cells by day 3 after moulting.

Animals↗
PubMed1994

Humoral and cellular immune response of BALB/c mice to repeated infestations with Ixodes ricinus nymphs.

The capacity of female BALB/c mice to mount an immune response and effective resistance to repeated infestations with I. ricinus nymphs was studied. An anamnestic antibody response and transient in vitro responsiveness of spleen lymphocytes to tick antigens were demonstrated in repeatedly infested mice. On the other hand, the response to concanavalin A--a T-cell mitogen, was suppressed at the same time. In the presented experiment, BALB/c mice did not manifest tick resistance after three successive infestations (with a reinfestation period of 2 weeks). The possibility of an infestation-dependent modulation of immune response in BALB/c mice is discussed.

Animals↗
PubMed1978

Flight muscle differentiation in nymphs of a dragonfly Anax imperator.

Flight muscle fibers of Anax imperator nymphs, in different developmental stages are analyzed for several morphological features, such as the arragnement and numerical ratio of actin and myosin filaments, the pattern of the T system and sarcoplasmic reticulum, the number of microtubules and the fractional volume of mitochondria in each fiber. The T system is initially represented by longitudinal grooves on the cell surface, joined with vesicles of the sarcoplasmic reticulum; this pattern rapidly changes and the grooves start to break up into longitudinal segments. The thin to thick filament ratio is at first quite high (about 4-4.5:1) but rapidly falls to the final (3:1) when the myofibrils are well developed at the fiber periphery. Statistical analyses show that the measured values are significantly different in the various stages of development, also indicating a progressive reduction of the ratio variability. The reduction of thin to thick filament ratio and the variance decrease fit quite well with the hypothesis that the synthesis of actin and myosin depends on independently regulated messenger RNA molecules.

Animals↗
PubMed2005

Contaminated sediments and bioassay responses of three macroinvertebrates, the midge larva Chironomus riparius, the water louse Asellus aquaticus and the mayfly nymph Ephoron virgo.

Bioassays are widely used to estimate ecological risks of contaminated sediments. We compared the results of three whole sediment bioassays, using the midge larva Chironomus riparius, the water louse Asellus aquaticus, and the mayfly nymph Ephoron virgo. We used sediments from sixteen locations in the Dutch Rhine-Meuse Delta that differed in level of contamination. Previously developed protocols for each bioassay were followed, which differed in sediment pretreatment, replication, and food availability. The Chironomus bioassay was conducted in situ, whereas the other two were conducted in the laboratory. The measured endpoints, survival and growth, were related to contaminant levels in the sediment and to food quantity in water and sediment. Only the response of A. aquaticus in the bioassay was correlated with sediment contamination. Food availability in overlying water was much more important for C. riparius and E. virgo, thereby masking potential sediment contaminant effects. We conclude that growth of A. aquaticus was depressed by sediment contamination, whereas growth of E. virgo and C. riparius was stimulated by seston food quantity. We discuss that the trophic state of the ecosystem largely affects the ecological risks of contaminated sediments.

Animals↗
PubMed2005

Dissecting the variance-covariance structure in insect physiology: the multivariate association between metabolism and morphology in the nymphs of the sand cricket (Gryllus firmus).

Energy metabolism in animals has been largely studied in relation to exogenous sources of variation. However, because they give insight into the relationship between whole metabolism and lower organizational levels such as organs and tissues, examination of endogenous determinants of metabolism other than body mass is itself very important. We studied the multivariate association of body parts and several aspects of energy metabolism in an insect, the nymphs of the sand cricket, Gryllus firmus. By using a variety of both univariate and multivariate techniques, we explored the resultant variance-covariance matrix to build a path diagram with latent variables. After controlling for body mass, we found a significant canonical correlation between metabolism and morphology. According to the factor loadings and path coefficients, the most important contributions of morphology to the correlation were thorax and abdomen size measures, whereas the most important metabolic contribution was resting metabolism. Activity metabolism was mostly explained by body mass rather than body parts, which could be a result of resting rates being chronic consequences of the functioning of the metabolic machinery that the insect must maintain.

Animals↗
PubMed2005

Acaricidal properties of the essential oil of Melaleuca alternifolia Cheel (tea tree oil) against nymphs of Ixodes ricinus.

The aim of the study was to examine the acaricidal effect of essential oil of Melaleuca alternifolia (tea tree oil, TTO) at different doses (4, 6, 8 and 10 microl) and for different exposure times (30, 60, 90 and 120 min) on nymphs of Ixodes ricinus. A dose of 8 microl TTO was lethal for more than 70% of ticks when inhaled and this effect was enhanced when the dose was increased to 10 microl (> 80%). The effect was correlated with the duration of exposure of ticks to TTO, with a significant effect being observed after 90 min exposure. The findings show that TTO has acaricidal properties and could be extremely useful in controlling ticks that are efficient vectors of pathogens.

Animals↗
PubMed2003

To be or not to be a locust? A comparative analysis of behavioral phase change in nymphs of Schistocerca americana and S. gregaria.

Phenotypic plasticity in behavior induced by high rearing density is often part of a migratory syndrome in insects called phase polyphenism. Among locust species, swarming and the expression of phase polyphenism are highly correlated. The american grasshopper, Schistocerca americana, rarely swarms even though it is closely related to the swarming Old World desert locust, S. gregaria, as well as two swarming New World locusts. Anecdotal field observations of locust-like behavior in S. americana indicate that it may express behavioral phase polyphenism, but empirical investigations are lacking. In this study, I tested the hypothesis that S. americana expresses locust-like density-dependent changes in behavior during both the first and final nymphal instars. I then compared the expression of behavioral phase change between S. americana and S. gregaria. First instar S. americana exhibited significant geographic variation in behavior with grasshoppers from a North Carolina population expressing more pronounced density-dependent changes relative to grasshoppers from a Texas population. The behavior of final instar S. americana was only slightly affected by rearing density and there was no evidence for a difference between populations. Comparison with S. gregaria revealed that the magnitude of density-dependent behavioral change, particularly among final instar nymphs, was much reduced in S. americana.

Analysis of Variance↗
PubMed2000

Interaction of hemocytes and prophenoloxidase system of fifth instar nymphs of Acheta domesticus with bacteria.

The hemocytes to which bacteria adhere were defined and the contribution of the prophenoloxidase system of fifth instar nymphs of Acheta domesticus to adhesion were examined. The physicochemical parameters affecting hemocyte and phenoloxidase activity were determined. Both plasmatocytes and granular cells responded to bacteria, the latter cells entrapping the microorganisms on filopodial extensions. The optimum pH for hemocyte adhesion to glass slides was 6.5, the granular cells being the most sensitive hemocyte type. Although hydrophobic resin beads and positively-charged beads favoured hemocyte attachment, these parameters did not contribute to differential bacterial adhesion to hemocytes. Activation of phenoloxidase was neither enhanced nor inhibited by 0.1 and 1 mg/ml of laminarin or zymosan nor by dead Bacillus subtilis. However, live B. subtilis activated the enzyme and dead Xenorhabdus nematophilus inhibited enzyme activation. Serine protease components of the prophenoloxidase system had opsonic properties for B. subtilis but not for X. nematophilus. Phenoloxidase activity was enhanced by Ca(2+) and Mg(2+) and inhibited by SO(2-)(4).

Animals↗
PubMed2001

Factor Xa (FXa) inhibitor from the nymphs of the camel tick Hyalomma dromedarii.

An inhibitor of factor Xa (FXa) was isolated from the nymphs of the camel tick Hyalomma dromedarii by a combination of chromatography on DEAE-cellulose and Sephacryl S-300 columns. The isolated nymphal FXa inhibitor turned out to be a homogenous preparation of a single polypeptide chain (15 kDa) as judged by both the native and denatured SDS-PAGE. Its pI value ranged from 7.7 to 7.9. The inhibitor is a potent anticoagulant since it prolonged both the activated partial thromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma in a concentration-dependent manner. Its activity was threefold lower toward thrombin than FXa, but it did not inhibit any of the proteases; trypsin, alpha-chymotrypsin, papain, pepsin and subtilisin. The inhibitor binds at two sites on FXa uncompetitively with an inhibition constant (K(i)) value of 134 nM.

Animals↗
PubMed2000

Collection of free-living nymphs and adults of Amblyomma hebraeum (Acari: Ixodidae) with pheromone/carbon dioxide traps at 5 different ecological sites in heartwater endemic regions of South Africa.

The capture of free-living adults and nymphs of Amblyomma hebraeum, the main vector of heartwater in domestic and wild ruminants in South Africa, by means of attraction-aggregation-attachment-pheromone/carbon dioxide traps at five endemic localities in South Africa is described. Although the traps were used successfully at each of the localities, no determination of their efficiency in relation to the actual abundance of ticks at a particular site was made. This study confirmed that the traps could be used in a variety of ecological areas to locate populations of free-living adult A. hebraeum.

Animals↗
PubMed1994

Transmission of Anaplasma marginale with adult Boophilus microplus ticks fed as nymphs on calves with different levels of rickettsaemia.

Nine splenectomised calves were infested with dissimilar numbers of adult Boophilus microplus ticks 72 h after collection as engorged nymphs from three non splenectomised calves with different levels of Anaplasma marginale rickettsaemia. Successful transmission of A. marginale appeared to be more dependent on the level of rickettsaemia of the donor calves than on the number of ticks attaching to the splenectomised calves, since infection was transmitted only when the rickettsaemia was 0.3% or greater. Field transmission would thus depend on the rate of tick migration amongst susceptible hosts and the rickettsaemia level of cattle on which the ticks fed previously.

Anaplasma↗
PubMed2001

Effect of tick removal on transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis nymphs.

The effect of feeding duration on pathogen transmission was studied for individual ticks infected with either laboratory or field strains of the Lyme disease spirochete Borrelia burgdorferi and field strains of Ehrlichia phagocytophila, an agent of human granulocytic ehrlichiosis. Infected nymphal Ixodes scapularis were allowed to feed individually on mice, and equal numbers were removed at 24-h intervals for < or =96 h. Mice were assayed for infection by culture, serologic testing, and polymerase chain reaction (PCR) analysis. Fed ticks were assayed by culture or PCR analysis. Transmission of B. burgdorferi did not occur during the first 24 h among 66 attempts, with maximum transmission occurring between 48 and 72 h. A model estimating the probability of infection from individual ticks removed by patients in a Lyme disease-endemic area yielded an overall probability of 4.6%. Infected I. scapularis nymphs transmitted E. phagocytophila within 24 h in 2 of 3 attempts, which indicates that daily tick removal may not be adequate to prevent human infection with this agent.

Animals↗
PubMed1994

Correlation between ecdysteroids and cuticulogenesis in nymphs of the tick Ornithodoros parkeri (Acari: Argasidae).

Ecdysteroids and cuticulogenesis were studied in third-instar nymphs of the tick Ornithodoros parkeri Cooley. Ecdysteroid titer increases slightly during the postfeeding intermolt period, which correlates with the deposition of additional procuticle lamellae. The titer increases at the time of apolysis, peaks at the time of epicuticle deposition, and then drops to a low but detectable level from the time of procuticle deposition until after ecdysis. Ecdysone and 20-hydroxyecdysone are the two major ecdysteroids present during the postfeeding intermolt period and the period of epicuticle deposition. After ecdysis, the ecdysteroid immunoreactive material is composed principally of an unknown compound more polar than 20,26-dihydroxyecdysone and is found only in the midgut. This compound is possibly a metabolite of ecdysteroids left over from the previous instar.

Animals↗
PubMed1995

Application of desiccant and insecticidal soap treatments to control Ixodes scapularis (Acari: Ixodidae) nymphs and adults in a hyperendemic woodland site.

The desiccant Drione (1% pyrethrin) and Safer's insecticidal soap (0.2% pyrethrin) formulated with and without isopropyl alcohol (ROH) were field tested against nymphal and adult populations of Ixodes scapularis Say in a hyperendemic woodlot in Westchester County, New York. Drione, insecticidal soap, and insecticidal soap with ROH provided equivalent levels of control for nymphs and adults. Compared with untreated plots, nymphal populations were significantly reduced 1 (93.3-100%) and 2 (66.4-85.7%) wk following treatment, and adult populations were significantly reduced 1 wk (53.5-62.9%) following treatment. Factors possibly contributing to the moderate and shorter period of adult control are discussed. Drione and insecticidal soap are effective alternatives to residual insecticides and could be an important component of an integrated tick management program on residential properties in areas where Lyme disease is endemic. Both products lack residual activity and would require repeated applications to maintain sufficient levels of control throughout the tick season.

1-Propanol↗
PubMed1998

Illustrated key to nymphs of the tick genus Amblyomma (Acari: Ixodidae) found in the United States.

A dichotomous identification key, with important characters illustrated by scanning electron micrographs, is provided for nymphs of the 9 species of the genus Amblyomma occurring in the United States. Species included are A. americanum (L.), A. cajennense (F.), A. dissimile Koch, A. imitator Kohls, A. inornatum (Banks), A. longirostre (Koch), A maculatum Koch, A. rotundatum Koch, and A. tuberculatum Marx. Notes on the geographical distributions, medical and veterinary importance, and nymphal stage hosts are included for each species.

Animals↗
PubMed1998

Air temperature and relative humidity effects on behavioral activity of blacklegged tick (Acari: Ixodidae) nymphs in New Jersey.

Air-temperature and relative humidity data were used to explain variation in behavioral activity of Ixodes scapularis Say nymphs. We estimated behavioral activity as the residual variation in drag-sample data after seasonal changes in population density were removed by regression. The seasonal decline in drag samples between June and August 1995 on field plots at Morristown National Historical Park, NJ, can be described by a simple negative exponential function. Residuals around a fitted exponential were significantly correlated with temperature and with relative humidity measured at the leaf-litter surface, and explained 34 and 44% of the variance, respectively. Multiple regression on temperature and relative humidity explained 51% of the variance. These regressions estimated the explanatory power of microclimate, independent of seasonal correlations, and might provide a basis for day-to-day prediction of human exposure to Lyme disease.

Animals↗