Hepatic superoxide dismutase activity in the mouse infected with Plasmodium berghei

The effects of malarial infection, induced by infecting the mouse with Plasmodium berghei (30-40% parasitemia), on hepatic superoxide dismutase (SODs) were studied. Total SOD and Cu-Zn SOD activities were found to be significantly reduced. Mn SOD activity, however, was not found to be altered.     

Humoral intestinal immunity against Encephalitozoon cuniculi (Microsporidia) infection in mice

Three strains of mice, BALB/c, IL-12 knock-out (KO) and INF-gamma knock-out, were chosen as an experimental model for the study of intestinal immunity induction against Encephalitozoon cuniculi Levaditi, Nicolau et Schoen, 1923 infection. Mice were infected perorally with 10(7) spores and re-infected with the same dose 70 days after the first infection. The anti-E. cuniculi IgA, IgG and IgM responses in sera and extracts of stool samples were determined by ELISA. Results have shown specific antibody production in the sera and intestinal secretions of all three strains of mice induced orally by E. ciniculi spores. BALB/c mice developed a stronger humoral immune response than IL-12 KO mice. The lowest antibody response developed in INF-gamma KO mice that succumbed to the infection within 28 days post infection.     

Leptin and leptin receptors during malaria infection in mice

Leptin, which is involved in a range of physiological processes, could be an important factor in the pathogenesis of malaria. We found that levels of leptin in serum and urine in Plasmodium berghei-infected mice increased progressively after infection, reaching a maximum value on day 6 post-infection. Serum values were approximately five-fold higher in infected mice than in non-infected controls. A similar relation was found for values of leptin in urine. Soluble leptin receptor levels also increased significantly in serum, more or less in line with the leptin increase. Our work represents the first report of visibly augmented leptin and soluble leptin receptor secretion in malarial infection.     

绿僵菌侵染对黏虫免疫反应的影响

为揭示黏虫被病原菌侵染后的免疫应答机制,本试验分析比较了黏虫幼虫被金龟子绿僵菌Metarhizium anisopliae侵染后不同时间其血淋巴蛋白含量、免疫关键酶系(酚氧化酶PO,溶菌酶)活性、抗菌活力以及血细胞数量等免疫相关指标的变化。结果表明:受绿僵菌侵染后,黏虫6龄幼虫血淋巴蛋白含量在侵染初期(6 h和24 h)显著高于对照,侵染48、72和96 h后幼虫血淋巴蛋白质含量显著低于对照。且侵染后幼虫血淋巴PO活性也呈现先升高后降低的趋势,侵染初期(6 h和24 h)显著高于对照,侵染后期除72 h外与对照组无显著差异。侵染初期(24 h)溶菌酶活性也显著升高,随后出现下降,并于48 h显著低于对照,但在化蛹时(96 h)再次上升。绿僵菌侵染后期,黏虫的抗菌活性下降,于侵染后72 h抗菌活性显著低于对照,而侵染初期抗菌活性与对照无显著差异。另外,绿僵菌侵染对幼虫血细胞数量以及浆血胞比率也有显著的影响,表现为:侵染后6 h和24 h血细胞总数、浆血胞比率均显著高于对照,随后与对照并无显著差异。综上,绿僵菌侵染黏虫幼虫初期会显著诱导其免疫反应的启动,体现在主要免疫指标升高,而后随着免疫系统的破坏与能量的消耗,其免疫反应能力降低,生理活动受到干扰。     

Attenuation of Schistosoma mansoni cercarial infectivity to albino mice by methanol extract of some plant species

This study elucidates the activity of certain plants’ methanol extract: Anagallis arvensis, Solanum nigrum (green fruits), Chenopodium ambrosioides, Calendula officinalis and Sesbania sesban, on the infectivity of S. mansoni cercariae to albino mice. Then, some parasitological parameters, e.g. the worm load/mouse, number of ova/g tissue in liver and intestine and the developmental stages of ova in the small intestinal wall (Oogram) of infected mice were determined. In addition, certain biochemical parameters of serum from infected mice (total protein, albumin, the activities of AlT, AsT, AcP and AkP enzymes) were, also, recorded.The results showed that exposure of S. mansoni cercariae for 30 min to the tested plants’ methanol extract before mice infection has a higher suppressive effect on their infectivity to albino mice then those exposed to this extract during mice infection. The number of worms recovered/infected mouse and the number of ova/g tissue from liver and intestine of mice groups infected with cercariae exposed to the tested plants’ methanol extract either pre- or during mice infection were less than those of infected control groups (e.g. the reduction rates of worm load/mouse and number of ova/g tissue in the intestine were 46.1% and 76.8%, respectively, for mice infected with cercariae exposed to 5 ppm of A. arvensis during mice infection).The results, also, indicated that exposing S. mansoni cercariae to methanol extract of the experimental plants either pre- or during mice infection reduced the activities of the enzymes AlT, AsT, AcP and AkP that were elevated in mice infected with untreated cercariae, meanwhile, the concentrations of total protein and albumin were increased in the serum of mice infected with these treated cercariae in comparison with those of mice group infected with untreated cercariae.     

Evaluation of pesticide effects on humoral response to sheep erythrocytes and mouse hepatitis virus 3 by immunosorbent analysis

Effect of selected organochlorine, organophosphorus, and carbamate pesticides on the humoral immune IgM response was examined upon immunization of inbred C57B1/6 mice with neutral, polyvalent, T-dependent sheep erythrocytes (SRBC) and T-independent lipopolysaccharide (LPS). In addition, a pathogenic antigen, mouse hepatitis virus 3 (MHV3) was used for determination for the interaction of selected pesticides on the primary IgG immune response in a model of viral infection, of the genetically resistant A/J mouse strain. Single, sublethal doses of dieldrin, carbofuran, and matacil induced a marked immunosuppression of the humoral responses to both neutral and pathogenic antigens. The data showed that single, sublethal doses (0.4 ≤ LD₅₀ ≤ 0.6) of dieldrin, carbofuran, and matacil inhibited the number of SRBC-primed cells without any direct cytotoxic effect on the activated plasmocyte, as the titer of specific antibody measured by an enzyme-linked immunosorbent assay (ELISA) per activated cell, was constant. In contrast, exposure to malathion at 10–14 days prior to the assay increased the number of plaque-forming cells (PFC) and the anti-SRBC IgM and anti-MHV3 IgG antibody titer, suggesting therefore an increase in the humoral response to neutral and pathogenic antigens in C57B1/6 and A/J mice. Immunomodulation of the humoral IgM response by selected pesticides was shown to take place at a stage prior to antibody secretion from the activated cell, as the ELISA/PFC index was similar to the control value. The data obtained for dieldrin-induced inhibition of the humoral response to SRBC and LPS antigens suggest a mechanism of immunosuppression common for both T-dependent and T-independent antigens. Good correlations were obtained for the immunomodulatory effects of selected pesticides, as measured by PFC and ELISA, which encourages support for the latter technique in the immunotoxicological screening of pesticides.     

Trypsin-sensitive plasmodia in the liver of post-infection rats and rhesus monkeys

Kupffer cells from the liver and erythrocytes from peripheral blood were collected at the post-patent period from albino rats infected earlier with Plasmodium berghei and rhesus monkeys infected earlier with P. cynomolgi var. bastianelli or P. knowlesi. The cells were subinoculated into individual normal recipients. These recipients subsequently showed parasitaemia in their circulation. The parasites present in Kupffer cell preparations were found to be sensitive to trypsin treatment, while those in erythrocytes were found to be resistant to trypsin treatment. This differential sensitivity of parasites to trypsin was observed in all the three species of plasmodia studied so far.     

Influence of thymic preparations on the result of experimental infection with Taenia crassiceps (Zeder, 1800) in ICR mice

Thymalin (Thymarin) and T-activin--thymic preparations of polypeptidic character--were used for influencing the parasitic infection in a model system mouse--Taenia crassiceps. A single subcutaneous application of 100 micrograms of Thymalin per mouse at the day of infection resulted in a decrease (by 54.9%) in the number of cysticerci in peritoneal cavity of experimental mice compared with the controls. Administration of Thymalin with T. crassiceps larval homogenate at various intervals before and after infection resulted in a statistically significant increase of the level of specific antibodies in the serum of infected mice, this increase, however, did not correlate with the corresponding protective effect. Immunosuppressant azathioprine, injected subcutaneously from 7th to 3rd day preceding infection at a dose of 100 micrograms resulted in a significant increase in the number of T. crassiceps larvae in the peritoneal cavity of experimental mice compared with the controls (by 48.7%). T-activin, injected subcutaneously to mice, immunosuppressed by azathioprine, led to a restoration of resistance of mice to T. crassiceps infection. Subcutaneous application of T-activin alone had a significant protective effect (decrease in cysticerci number by 53.7% in comparison with the controls). Correlation of the level of specific antibodies in the serum of infected mice, value of spleen index and number of T. crassiceps cysticerci in peritoneal cavity of mice was not detected.     

Experimental infection of immunocompetent and immunodeficient mice with Encephalitozoon cuniculi

An experimental infection with the microsporidian Encephalitozoon cuniculi Levaditi, Nicolau et Schoen, 1923 was studied using a model of immunocompetent BALB/c mice and immunodeficient SCID mice. The course of infection after intraperitoneal inoculation of E. cuniculi spores was evaluated using the presence of spores in peritoneal macrophages as a criterion. First significant decrease in the proportion of infected cells was recorded on day 9 post infection (p.i.) in BALB/c mice. From day 14 p.i. no spores were observed in macrophages from BALB/c mice, while the number of infected macrophages from SCID mice increased until the death of the mice. The natural killer (NK) cell activity of mouse splenocytes was compared with the production of interferon gamma (IFN-gamma) by these cells. While in BALB/c mice NK activity peaked on days 9 and 14 p.i., in SCID mice the marked increase of NK activity was recorded close before death of mice, on day 21 p.i. in correlation with the production of IFN-gamma. Production of specific antibodies was demonstrated from day 9 p.i. in sera from BALB/c mice. It is concluded that intraperitoneal infection of SCID mice with spores of E. cuniculi results in the marked increase in the number of peritoneal exudate cells and in the percentage of infected cells close before death of mice. Neither high activity of NK cells nor increased production of IFN-gamma are sufficient for the recovery of SCID mice from an E. cuniculi infection.     

DDT and inflammatory responses: 1. Influenza infection in mice fed DDT

Mice fed casein diets containing 100 and 200 ppm DDT for 20 days failed to exhibit any signs of DDT intoxication or an impairment of growth. When the mice were infected with influenza A₂ virus, the resulting disease was more severe in the DDT-fed groups as evidenced by increased inflammatory lung oedema and mortality rates. While DDT failed to affect viral replication in the lungs, the increased lung inflammatory oedema was evaluated in relationship to lung histamine content. Following the infection the lung histamine levels decreased; control group 30%; 100 ppm DDT 57%; and 200 ppm DDT 69%. The results indicate that DDT increases release of histamine that accelerates the inflammatory reaction and thus contributes to the mortality caused by influenza. The results suggest that DDT residues stored in tissues can affect inflammatory responses induced by infectious agents.     

Immune response of the long-tailed field mouse (Apodemus sylvaticus) to tick-borne encephalitis virus infection.

The immune response following infection with a virulent strain of Central European encephalitis (CEE) virus in a natural host, long-tailed field mouse (Apodemus sylvaticus L.) and white laboratory-bread ICR mouse, was compared. Viraemia was demonstrated in ICR mice after intraperitoneal infection with a dose of 10(5) LD50/0.5 ml. The virus titres were high in the spleen and, particularly, in the brain. In A. sylvaticus the virus was detected in the blood and spleen, but not in the brain. CEE virus multiplied in peritoneal macrophages from ICR mice, but not from A. sylvaticus. The infection induced a strong interferon response in both hosts. The natural killer (NK) cell activity increase was twice as high in A. sylvaticus compared to ICR mice. The neutralization antibodies appeared sooner in A. sylvaticus and reached higher titres in the early phases of infection.     

Accumulation of short interfering RNAs characteristic of RNA silencing precedes recovery of tomato plants from severe symptoms of <Emphasis Type="Italic">Potato spindle tuber viroid</Emphasis> infection

Tomato plants infected with Potato spindle tuber viroid (PSTVd) had severe leaf curling and vein necrosis. The disease symptoms began to diminish during the late stages of infection, however, and almost healthy-looking leaves began to appear on the upper portion of the plants. PSTVd concentrations reached their highest levels in leaves with severe symptoms and decreased in upper leaves recovering from severe symptoms. PSTVd-specific short interfering RNAs (siRNAs), characteristic of RNA silencing, accumulated in all leaves in which PSTVd reached a detectable level, suggesting that recovery from severe disease was induced by RNA silencing via sequence-specific degradation of PSTVd.     

The impact of co-infection by a nucleopolyhedrovirus and the endoparasitoid Microplitis pallidipes Szepligeti on the protective enzymes in hemolymph of Spodoptera exigua

We determined the effects of parasitism by Microplitis pallidipes and/or nucleopolyhedrovirus (NPV) infection on protective enzymes in the hemolymph of Spodoptera exigua larvae. We found that concentrations of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were constantly higher within the five observation days after treatment in parasitized/virus-infected than healthy (control) larvae. In parasitized + infected larvae, enzyme levels reduced from day 1 compared to parasitized larvae. Compared to enzyme levels in virus-infected larvae, in parasitized + infected larvae, CAT concentrations were generally lower, while SOD concentrations were significantly lower in the first two days and POD concentrations were lower in the first two days, but higher in following three days. We concluded that joint and separate parasitism and NPV infection promoted the activities of protective enzymes. Our findings also revealed that NPV infection inhibited the activities of protective enzymes induced by parasitism of M. pallidipes and that the parasitism inhibited the CAT activity induced by NPV infection.     

Immune response to rabbit coccidiosis: a comparison between infections with Eimeria flavescens and E. intestinalis

Seven- to eight-week-old rabbits were infected with Eimeria intestinalis Cheissin, 1948, a highly immunogenic coccidium, or Eimeria flavescens Marotel et Guilhon, 1941, which is weakly immunogenic. Immune response was investigated at 7, 14 and 21 days post inoculation (DPI). The level of serum immunoglobulins, lymphocyte proliferation stimulated by parasite antigens and weight of mesenteric lymph nodes (MLN) showed similar dynamics in rabbits inoculated with both coccidia species. The amount of serum IgG and IgM, but not IgA, was increased from 14 DPI. The lymphocytes from MLN of infected animals significantly reacted to stimulation with parasite antigen 14 and 21 DPI and MLN were enlarged at 14 DPI. Thus, both parasite species elicited immune response characterized by these parameters in a similar manner despite of their different immunogenicity. The only apparent difference in the responses was in the percentage of CD8+ lymphocytes in the specific site of parasite development (the last third of the small intestine in E. intestinalis, caecum in E. flavescens), which increased in rabbits infected with E. intestinalis but not with E. flavescens. This parameter reflects the status of local immunity and hence the results suggest that the local reaction plays an important role in induction of protective immunity to coccidia in rabbits.     

Involvement of kaempferol in the defence response of virus infected Arabidopsis thaliana

The roles of several phenolic compounds in plant defence response have been extensively studied, yet little is known about the role of flavonoids in plant-virus interaction. Quantitative and qualitative changes of selected phenolics in Arabidopsis thaliana induced by Cucumber mosaic virus containing satellite RNA (CMVsat) infection were analysed accompanied by plant hormone, chalcone synthase and pathogenesis-related gene expression analysis. Lower leaves of infected plants had a lower concentration of total phenolics compared to control plants. The concentration of kaempferol in upper leaves of all infected plants was significantly lower compared to control plants, while the expression of the chalcone synthase gene in those leaves was in most cases upregulated. All infected plants had a higher concentration of indole-3-acetic acid in lower leaves, which was accompanied with a lower concentration of kaempferol in upper leaves. Our research demonstrates a correlation between kaempferol and indole-3-acetic acid in response to CMVsat infection in Arabidopsis. We demonstrated two different metabolic patterns in infected plants suggesting the activation of two different defence responses. We also propose kaempferol to be an important part of the auxin-dependent defence response which limits systemic movement of CMVsat and that this defence response is activated prior to the well-known salicylic acid dependent defence response. Further research on kaempferol and its role in Arabidopsis-CMVsat interaction will improve our understanding on the role of flavonoids in plant defence.     

The influence of <Emphasis Type="Italic">Aphanomyces cochlioides</Emphasis> on selected physiological processes in sugar beet leaves and yield parameters

Alterations in some physiological processes in source leaves of sugar beet—such as chlorophyll and carbohydrate concentrations, stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants were infected at different times of their growth period: on the sowing day and 4 or 8 weeks after sowing. A variation treatment, with non-pelleted seeds infected on the sowing day, was also analyzed. The experiment showed that development of disease symptoms depends on the time of infection and seed protection. A significant root yield decrease was observed in case of late infection, as compared to the yield of plants infected on the sowing day. The fresh weight of leaves was significantly increased where there was late infection. The infected plants showed a lower content of K⁺, Na⁺ and α-amino-N than did the controls. Infection by A. cochlioides induced chlorophyll degradation mostly in older leaves with the occurrence of natural senescence processes. Chlorophyll fluorescence parameters indicated that the photosynthetic apparatus of younger leaves was more sensitive to pathogen infection, when compared to older ones. The photochemical efficiency of photosystem II was reduced in young leaves mainly due to disturbance of the water-splitting system. In plants grown from non-pelleted seeds a strong impairment of PSII was observed only in those leaves which developed during early pathogen infection. In young leaves of plants infected in the fourth week after sowing, inhibition of the rate of net photosynthesis was correlated with the increase in intercellular CO₂ concentration, indicating some disturbance in the carbon assimilation phase. In mature leaves of late infected plants the reduction of photosynthesis net rate was associated with a decrease of stomatal conductance and an increase of diffusion resistance to CO₂ and H₂O, which was also the cause of the transpiration rate inhibition. When the leaves developed during early infection, an increase of specific leaf weight and accumulation of carbohydrates was observed. In mature leaves of non-protected plants infected on the sowing day, the recovery of all physiological processes was observed together with a diminution of disease symptoms.     

The Effect of Endophytic Fusarium verticillioides on Infestation of Two Maize Varieties by Lepidopterous Stemborers and Coleopteran Grain Feeders

ABSTRACT A series of experiments were conducted to test the effect of the presence of Fusarium verticillioides in the maize plant on subsequent infestation by coleopteran and lepidopteran pests. The effect of percent internodes 1 to 5 infected with F. verticillioides, time after planting, and maize variety on attacks of stem and ears by lepidopterous and coleopteran pests was assessed in field experiments in early and late season 1998 and early season 1999 in Benin Republic. Artificial inoculation of the first internode with fungal-treated toothpicks was compared with a hot-water-fungicide seed treatment and a control. In 1998, two varieties that differed in husk tightness, the improved DMRLSR-W and the local Gbogbe, were used. Percentage of node 1 to 5 and plants infected was highest with the inoculation treatment but tended to be similar in the seed treatment and the control. The infection rate tended to increase with time and, within sampling date, decreased with node level. Ear infection was strongly correlated with percent infected nodes, indicating that F. verticillioides in the stem predisposed kernel infection. F. verticillioides incidence was higher in Gbogbe than in DMRLSR-W. Stem and ear infestations by the pyralid Eldana saccharina, the major pest in the area, tended to be highest in inoculation and lowest in the protection treatment. The same trends were found for the pyralid Chilo spp., the tortricid Cryptophlebia leucotreta, and beetles pooled across species. Significant positive correlations were found between ear/stem F. verticillioides infection and E. saccharina, Cryptophlebia leucotreta, Mussidia nigrivenella, and the noctuid Sesamia calamistis, but the latter three pest species were only significantly correlated with fungal infection of the upper nodes of the plant. Similar to disease incidence, E. saccharina numbers in stem and ear were higher in Gbogbe than DMRLSR-W in late 1998, whereas for the pyralid ear feeder M. nigrivenella, it was reversed. It was suggested that some lepidopterous and coleopteran pests are attracted by and survive longer (or have lower mortality) on plants infected with F. verticillioides.     

Comparison of virulence of Coxiella burnetii isolates from bovine milk and from ticks.

Laboratory animals (mice and guinea pigs) were infected with the isolates of Coxiella burnetii (Derrick, 1939) obtained from bovine milk (M18 and M35) and the ticks Ixodes ricinus (Linnaeus, 1758) and Dermacentor marginatus (Sulzer, 1776) (Kl3 and Kl6, respectively), and with the reference strain Nine Mile. Neither mortality nor lethality occurred with the mice. Antibody response in mice infected with isolates from milk was lower (1:16-512) than that from ticks (1:32-4096). Onset of seropositivity also occurred later - on the 10th day post-infection (p.i.) for M18 and M35 in comparison with the 7th day for Kl3 and Kl6. In guinea pigs, infection manifested by fever. The fever was less evident in guinea pigs infected with isolates from milk (39.5-40.1 degrees C) than in guinea pigs infected with isolates from ticks (39.5-40.6 degrees C). Partially engorged females of Dermacentor reticulatus (Fabricius, 1794) were inoculated with isolates M18 and Kl3. No differences in the multiplication of C. burnetii in haemocytes between these two isolates were ascertained.     

小麦凝集素类受体激酶TaLecRLK1的鉴定及抗锈病功能分析

凝集素类受体激酶(lectin receptor-like kinase, LecRLKs)是一类在植物应答多种生物/非生物胁迫中发挥重要作用的类受体激酶。本研究在小麦与条锈菌互作的转录组中筛选到1个在小麦与条锈菌非亲和互作中显著上调表达的LecRLKs基因TaLecRLK1。该基因全长2 292 bp,编码蛋白含有1个胞外信号肽、B-lectin结构域、PAN＿AP结构域、跨膜域和胞内酪氨酸激酶域。qRT-PCR分析表明：TaLecRLK1在小麦与条锈菌非亲和互作早期诱导表达,在烟草及小麦原生质体中瞬时表达,TaLecRLK1-GFP定位在细胞膜上。利用大麦条纹花叶病毒介导的基因沉默技术(BSMV-VIGS)沉默TaLecRLK1,接种无毒性条锈菌小种CYR23后,沉默叶片表面产生少量夏孢子堆,组织学观察发现沉默植株中条锈菌菌丝长度增长、侵染点附近活性氧积累面积减少;TaPR1、TaPR2、TaPR5的表达受到抑制,TaCAT和TaSOD则被迅速诱导表达。综上所述,TaLecRLK1对小麦抗条锈病起到正调控作用。