The sheep antibody response to repeated infection with Lucilia cuprina.

, , and 1992. The sheep antibody response to repeated infection with Lucilia cuprina. International Journal for Parasitology 22: 1169–1174. The specific serum antibody responses of sheep exposed to 10 consecutive infections of L. cuprina have been analysed by enzyme-linked immuno-sorbent assay and immunoblotting using monoclonal antibodies specific for sheep immunoglobulin isotypes. Recognition of a number of larval excretory-secretory products by IgM antibodies appeared to be non-specific. IgG₁ was the major antibody class stimulated by the infection protocol and marked increases in antibody to specific excretory-secretory antigens were observed. Three molecules of 35, 30 and 25 kDa were particularly recognized although the extent of recognition of these molecules varied considerably between individual sheep serum. A pooled serum composed of sera collected after five to seven infections significantly inhibited larval growth in in vitro cultures when compared to a sera pool consisting of sera collected both prior to infection and after infections 1 and 2. The degree of inhibition was greater when serum with high specific antibody titre was used.     

Use of a monoclonal antibody to ovine IgE for fly strike studies in sheep

A new monoclonal raised against sheep IgE was used to examine sera and wound exudates from sheep which had been struck by Lucilia cuprina in the field. The antibody was also used to detect the presence of IgE in sera and skin sections from sheep which had been artificially infected with fly larvae 3 times. Neither total, nor L. cuprina specific circulating IgE could be detected in serum or wound exudates from struck sheep. Cell bound IgE was, however, identified by the monoclonal in skin sections from struck sheep and from a control sheep which had not been struck. No difference in the number of IgE positive cells was observed between the control and 2 of the 3 artificially infected sheep, and none of the latter showed an increase in IgE positive cells even after 3 infections. One sheep showed twice as many IgE positive cells as the other treated sheep and the third larval infection was difficult to establish and limited in size and severity. This suggests a relationship between innate resistance to strike and the number of IgE positive cells present in skin.     

Proteases released by Lucilia cuprina during egg hatch

Products released by Luclia cuprina (sheep blowfly) during egg hatch and early larval development were found to contain a variable number of proteases, probably reflecting their different functions during these developmental phases. Moreover, a number of the developmentally regulated proteases produced only during egg hatch appeared to be strongly egg shell associated, indicating the egg shell proteins to be their specific substrates. Several proteases were tested for their ability to enhance the rate of egg hatch. The commercial proteases chymotrypsin and trypsin were able to significantly enhance (p≤0.01) egg hatch by 36% and 44%, respectively, when compared to an untreated control. Interestingly, fluids containing the egg shell associated proteases were able to significantly (p≤0.001) enhance L. cuprina egg hatch by up to 70%. This hatch enhancement activity could be significantly (p≤0.001) reversed by the addition of Phenylmethylsulphonyl fluoride (PMSF). Fractionation of the egg-associated proteases by gelatin affinity chromatography suggested that gelatin-binding molecules were responsible for the majority of the egg hatch enhancement activity in this preparation.     

Experimental American leishmaniasis and Chagas'' disease in the Brazilian squirrel monkey: cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi

, and 1988. Experimental American leishmaniasis and Chagas' disease in the Brazilian squirrel monkey: cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi. International Journal for Parasitology 18: 1053–1059. Adult, laboratory-bred squirrel monkeys (Saimiri sciureus) previously infected with either Leishmania braziliensis braziliensis or L. b. panamensis were challenge infected with blood-form trypomastigotes of Trypanosoma cruzi (Brazil strain). Monkeys previously infected with T. cruzi were challenged with stationary phase promastigote forms of L. b. braziliensis. Monkeys were examined during the course of challenge for evidence of infection, electrocardiographic alterations and parasite-specific antibody responses. T. cruzi epimastigotes were cultured from the blood of monkeys up to 3 months after challenge with this parasite. Unulcerated cutaneous lesions appeared and persisted in monkeys challenged with L. b. braziliensis. The formation of satellite lesions was observed in one monkey. Increased QRS intervals were not observed in T. cruzi challenged monkeys without prior cardiac irregularities and QRS left axis shifts were observed in only two of these monkeys. Elevated titers of parasite binding IgM and IgG specific for both T. cruzi and L. braziliensis were observed in all monkeys following challenge. These results indicate that prior infection with T. cruzi or L. braziliensis does not protect against heterologous challenge infection with these organisms. However, prior infection with Leishmania parasites may provide some protection against chagasic cardiopathies.     

Shell and hinge morphology of juvenile Limopsis (Bivalvia: Arcoida) - implications for limopsid evolution

Early ontogenetic shells of Limopsis angusta, L. aurita, L. cristata, L. friedbergi and L. minuta are described in detail and their morphogenetic traits discussed in a phylogenetic context. Prodissoconch length is found to range from 170-370 µm discounting the so-called prodissoconch 2 stage of authors. Reports of such a stage refer to the early postlarval 'interdissoconch'. Prodissoconch sizes are indicative of lecithotrophy but not of brooding. Limopsid-like prodissoconchs are rather common among pteriomorphs and at present of little use for phylogenetic interpretations, therefore. The early postlarval hinge is characterized by two tooth generations: an early one, (G1), representing the postlarval continuation of provincular teeth, and a late one, (G2), representing the independent adult dentition. This is a plesiomorphic trait for Pteriomorphia. The postlarval ligament is continuous with the larval resilium; it is neither co-functional with nor is it substituted by the typical duplivincular ligament as in other arcoids. Occasionally developed ridges, gutters or multiplication of ligament sublayers remain restricted to the primordial resilifer. It is concluded that the limopsid adult ligament represents a fusion of adult sublayer repetition within a retained larval resilium, a phenomenon best described as a heterochronic process. Comparisons with homologous characters of other arcoids support the view that Limopsidae evolved from parallelodontid arcoids and that they gave rise to Philobryidae but not to Glycymerididae.     

Initial characterisation of the sheep immune response to infections of Lucilia cuprina

Assays for total serum antibody, histamine sensitivity and the presence of reaginic antibodies were carried out on sheep repeatedly infected with first stage larvae of Lucilia cuprina. Effects of the sheep response on the larvae were monitored at the final infection and compared with control animals by the recovery of larvae and measurement of the wound caused by the larvae. Overall larval survival was not significantly different in the pre-infected group though wound sizes were smaller. Histamine sensitivity appeared to correlate with wound size only in the control group. Thus recent infection experience may lead to immune responses which override non-specific inflammatory events and cause smaller wound sizes. A sub-group of the pre-infected sheep had lower larval survival and smaller wound sizes than the other animals and this correlated with increased levels of reaginic antibody and lower total antibody levels. The results suggest a genetic basis for resistance to fly strike and the possible involvement of reaginic antibody in protective responses.     

Survival of larvae of the ragwort flea beetle, Longitarsus flavicornis (Coleoptera: Chrysomelidae), in water-logged soil

Water-logged soil could be a major factor affecting populations of the ragwort biological control agent, Longitarsus flavicornis, in Australia. Survival of L. flavicornis larvae in potted ragwort plants after inundation with water for up to 264h (11days) was compared to larval survival in control plants not exposed to inundation. Probit analysis indicated that 35.6% mortality of the larval population occurred after 24h inundation and 50.4% after 72h. As high mortality was recorded at periods of inundation known to occur in the field, it is concluded that winter flooding is likely to be detrimental to populations of L. flavicornis.     

Expression of heat shock protein in host macrophages correlates with a protective potential against infection with Leishmania major in mice

We studied the relationship between the expression of 65-kDa heat shock protein (HSP65) and resistance of mice to infection with Leishmania major (L. major), an obligate intracellular protozoan. C57BL/6 (B6) mice, a strain genetically resistant to L. major infection, expressed high level of HSP65 in their peritoneal and draining lymph node macrophages after infection, whereas susceptible BALB/c mice expressed only slightly at the early stage of infection. This protein was not expressed in the parasite itself and macrophages of non-infected mice. We examined the role of T cells in the expression of HSP65 by using SCID mice grafted with the fetal thymus from B6 or BALB/c mice (B6-TG or BALB-TG mice, respectively). Either BALB-TG or B6-TG mice were reconstituted with T cells derived from each grafted fetal thymus. B6-TG mice were markedly resistant against infection with L. major, compared with BALB-TG mice. Furthermore, the HSP65 expression in macrophages of thymus-grafted mice was similar to that of the thymus-donor type. That is, B6-TG mice expressed a high level of this protein, whereas BALB-TG mice did in lower level than B6-TG mice. These results show that T cells are necessary to express HSP65 and the expression correlates with a protective potential of T cells against infection with L. major.     

Selection and characterization of somatic hybrids between Lycopersicon esculentum and Lycopersicon peruvianum

Somatic hybrids of the cultivated tomato, Lycopersicon esculentum, and a wild species, L. peruvianum, were obtained by fusion of leaf protoplasts from both species in the presence of poly-ethylene-glycol (PEG) or in an electric field. The somatic hybrids were selected on the basis of kanamycin resistance of L. esculentum and the plant regeneration capacity of L. peruvainum. Chromosome counts in root tips and the determination of the number of chloroplasts in guard cell pairs revealed that the majority of these hybrids was tetraploid (2n = 4x = 48). The remaining hybrids were at the hexaploid level with chromosome numbers between 64 and 72. The hybrid nature of the regenerated plants was confirmed by analysis of isozyme markers and by their morphology. Most hybrids did flower and set fruits and seeds after selfing. According to RFLP analysis 6 out of the 10 hexaploid hybrids contained two genomes of L. esculentum and four genomes of L. peruvianum. One of these hexaploids had genomes of two different L. peruvianum genotypes and was therefore considered to be derived from a triple protoplast fusion. The hexaploid plants were less fertile than the tetraploids and more resembled L. peruvianum.     

The Common Black Ant, Lasius niger (Hymenoptera: Formicidae), as a Vector of the Entomopathogen Lecanicillium longisporum to Rosy Apple Aphid, Dysaphis plantaginea (Homoptera: Aphididae)

The potential for common black ant Lasius niger workers to vector conidia of the entomopathogenic fungus Lecanicillium longisporum to colonies of the rosy apple aphid Dysaphis plantaginea was assessed in laboratory and field experiments. Scanning electron microscope studies showed that L. niger workers which were artificially contaminated with L. longisporum conidia, carried conidia primarily on their tarsae but also on antennae and mandibles. Neither L. niger workers nor larvae were susceptible to infection with L. longisporum. Workers which were artificially contaminated with conidia of L. longisporum initiated infection in colonies of healthy D. plantaginea on apple. Mortality due to L. longisporum was recorded as 68.3, 30.8 and 3.7% of aphids under laboratory, semi-field and field conditions, respectively.     

Comparison between a native and exotic adelgid as hosts for Laricobius rubidus (Coleoptera: Derodontidae)

Laricobius rubidus LeConte, native to eastern North America whose primary host is Pineus strobi Hartig, has been observed in association with Adelges tsugae, an exotic and lethal pest of hemlock trees in eastern North America. Pineus strobi and A. tsugae were used to evaluate host preference and suitability of this predatory beetle to determine in part its suitability as a potential biological control agent of A. tsugae. In a paired-choice oviposition test, L. rubidus preferred to oviposit in P. strobi ovisacs over those of A. tsugae. However, in the no-choice oviposition test, there was no significant difference in the mean number of eggs laid by L. rubidus females in P. strobi or A. tsugae ovisacs. There were no significant differences in larval developmental time or survivorship for L. rubidus reared on a diet of either P. strobi or A. tsugae. Laricobius rubidus completed development to the adult stage on A. tsugae indicating that it is a suitable host and therefore has the potential to contribute to biological control of A. tsugae in the eastern United States. The introduction of a congener, Laricobius nigrinus to eastern North America may result in competition with L. rubidus on A. tsugae, but the inability of L. nigrinus to complete development on P. strobi suggests that the two congeners will not compete on the primary host of L. rubidus.     

Acquired resistance in sheep to infection with larvae of the blowfly, Lucilia cuprina

Acquired resistance in sheep to infection with larvae of the blowfly, Lucilia cuprina. International Journal for Parasitology16: 69–75. Resistance to blowfly larvae infections developed in sheep exposed to at least four consecutive infections. Half of the sheep treated showed significant levels of resistance, the others remained susceptible. This resistance took the form of a decreased yield of third instar larvae in comparison to controls and sheep which remained susceptible. In addition an increased sensitivity to larvae developed, as shown by the area of wound obtained per maggot recovered, by the early appearance in resistant sheep of exudate from the infection site and by skin reactions to larval products. Radioimmunoassays demonstrated high levels of serum antibody against larval excretory/secretory antigens, though the response did not peak until after four infections. Resistant animals showed somewhat lower antibody titres than susceptible sheep. Consecutive infections of only 50 larvae failed to induce resistance to larger challenge infections. It is suggested that consecutive infections of larger numbers of maggots induce a hypersensitivity response which may effect larval survival especially of first and second instar maggots.     

宁夏枸杞对枸杞瘿螨为害的内源激素响应及外源水杨酸对枸杞瘿螨的影响

为探索宁夏枸杞对枸杞瘿螨致瘿过程诱导的激素响应及外源水杨酸对枸杞瘿螨的影响,利用LC-MS/MS技术对枸杞瘿螨为害后宁夏枸杞叶片中水杨酸(SA)、茉莉酸(JA)、生长素(Auxin)和脱落酸(ABA)4种内源激素进行测定,并通过浸叶法研究外源SA对枸杞瘿螨侵染过程、虫瘿生长和种群增长的影响。结果表明:枸杞瘿螨的致瘿行为可引发枸杞叶片中多种内源激素产生变化,其中SA和JA的变化最显著,分别是对照组含量的4.0和13.0倍,而Auxin和ABA的变化不显著;外源SA对枸杞瘿螨虫瘿生长有显著抑制作用,且随时间的延长,抑制作用增强,同时虫瘿内瘿螨种群数量受到显著抑制。枸杞瘿螨能够同时诱导枸杞产生SA和JA抗性,外源SA对枸杞瘿螨虫瘿生长和瘿螨种群数量均具有显著抑制作用,利用外源SA防治枸杞瘿螨具有一定的应用前景。     

基于Vaganov-Shashkin模型的太白红杉径向生长对气候要素的响应

利用采自太白山南坡药王殿、北坡上板寺的太白红杉树芯样品分别建立树轮宽度年表,运用Vaganov-Shashkin模型揭示秦岭太白红杉径向生长对各气候要素的响应.结果表明: 生长季(4—8月)的温度、生长初期的降水量以及7、8月的降水量是限制秦岭地区太白红杉生长的主要气候因子.良好的温度条件有利于太白红杉的生长,但生长初期的降水量会抑制太白红杉的生长;7、8月的降水量对秦岭南坡和北坡太白红杉的影响差异明显,该时段内丰富的降水量对北坡太白红杉的生长具有促进作用,而对南坡太白红杉的生长产生一定的限制作用;同一坡向、不同海拔采样点树木径向生长与气候因子的响应结果同样存在差异,高海拔采样点太白红杉的生长需要的温度条件低于低海拔采样点,但对土壤湿度的需求大于低海拔采样点.生长开始日的早晚对太白红杉树轮宽度的形成影响很大,而生长结束日仅与南坡采样点树轮宽度之间呈显著相关.     

Responses of NFR/N inbred mice to very low-dose infections with Ascaris suum

Mice were evaluated for immunological responses and resistance to challenge infections after single infections. When given infections simultaneously with thiabendazole, larval migration to the liver and lungs was blocked but not when mice were given infections only. Enlargement of Peyer's patches was observed after infection followed by increased numbers of IgA-containing cells in the lamina propria of the intestines and increased levels of hepatobiliary IgA. Ig-containing cells were variable in the spleens during the early phase of infection. The observed changes quickly returned to normal control levels and did not change throughout the rest of the experiment. Serum Ig levels did not change dramatically. Challenge with high doses of eggs indicated that mice given single very low-dose infections became highly resistant.     

樟子松和落叶松径向生长对气候变化的响应

在全球变暖的背景下,升温可能会影响树木的生长,导致森林生态系统的平衡受到干扰。本研究利用树轮年代学方法中的生长-气候响应函数、滑动相关分析,探讨大兴安岭漠河地区樟子松和落叶松径向生长的限制因子,以及二者径向生长对快速升温的响应。结果表明: 樟子松和落叶松的径向生长受温度和降水的共同作用,樟子松对气候变化的响应比落叶松更为敏感,对气候因子的敏感性比落叶松更稳定。樟子松径向生长与当年生长季月均温及月均最低温呈显著正相关,而落叶松与冬季月均温及月均最高温呈显著正相关。冬季降水促进樟子松生长,前一年生长季后期降水抑制落叶松的径向生长。1990年快速升温后,降水对樟子松的限制作用由升温前的负相关转变为升温后的显著正相关,高温对樟子松的抑制作用大于促进作用;高温对落叶松的抑制作用增强,降水对落叶松的限制作用也在升温后增强,生长速率显著下降,二者生长速率与温度和降水的相关性变化存在明显差异。本研究可为大兴安岭森林生态系统管理与保护提供科学依据。     

滇西北白马雪山长苞冷杉和大果红杉年内径向生长动态及其对环境因子的响应

以滇西北白马雪山亚高山寒温性针叶林的常绿树种长苞冷杉和落叶树种大果红杉为对象,采用高精度生长仪监测了2个树种的年内径向生长动态,分析其径向生长的季节动态特征及其对环境因子的响应。结果表明: 大果红杉和长苞冷杉的径向生长主要发生在4—8月,6月是生长最快的时期。与长苞冷杉相比,大果红杉径向生长的开始时间较早,停止生长时间稍晚,其生长季持续时间明显长于长苞冷杉。大果红杉最大生长速率和年生长量均略高于长苞冷杉。长苞冷杉日生长量与降水量呈显著正相关,与饱和水汽压亏缺、空气温度呈显著负相关;而大果红杉的日径向生长量与降水量呈显著正相关,与土壤体积含水量和饱和水汽压亏缺呈显著负相关。长苞冷杉和大果红杉的径向生长均受到水分的限制,大果红杉对水分条件更敏感。在全球变暖的背景下,植物蒸腾作用和土壤蒸发散的增加,可能进一步加剧土壤水分丧失和植物可利用水分下降,进而导致长苞冷杉和大果红杉更易受到干旱胁迫。     

The interaction of Trypanosoma congolense and Haemonchus contortus in Djallonké sheep

The interaction between Trypanosoma congolense and Haemonchus contortus was studied in 5 groups of 8 Djallonké sheep. Two groups received a single infection with either H. contortus or T. congolense, and 2 groups were infected with T. congolense followed by H. contortus (TH) or vice versa (HT). One group was kept as uninfected controls. Mortality due to infection was observed only in the dual infection groups. In the TH group, the effects were more acute whereas in the HT group they were more chronic. No significant differences in weight gain could be demonstrated between infected and control groups. Djallonké sheep are able to withstand a single infection with either T. congolense or H. contortus, which confirms their trypanotolerant nature and provides preliminary indication of resistance against helminth infections. However, when exposed to successive infections with both parasites, some of the animals lose this tolerance.     

Morphological and morphometric study of crustacean parasites within the genus Lernaeocera

Two species of Lernaeocera are present in the southeastern North Sea. Lernaeocera lusci infects bib Trisopterus luscus, dragonet Callionymus lyra and sand goby Pomatoschistus minutus. L. Minuta is a junior synonym of L. lusci. The second valid species, L. branchialis, infects whiting Merlangius merlangus. The two species can be morphologically separated by the antennary processes, which are present in L. lusci and absent in L. branchialis. Discriminant functions allow complete separation between L. lusci and L. branchialis. There is high intraspecific, host-dependent variability within L. lusci. Length of L. lusci is significantly influenced by host size, and body form is influenced by the site of attachment of L. lusci on at least one host (bib). It is suggested that L. lusci consists of 3 forms: f. lusci, f. minuta and f. lyra.