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31.
The intracellular parasite Toxoplasma has an indirect life cycle, in which felids are the definitive host. It has been suggested that this parasite developed mechanisms for enhancing its transmission rate to felids by inducing behavioral modifications in the intermediate rodent host. For example, Toxoplasma-infected rodents display a reduction in the innate fear of predator odor. However, animals with Toxoplasma infection acquired in the wild are more often caught in traps, suggesting that there are manipulations of intermediate host behavior beyond those that increase predation by felids. We investigated the behavioral modifications of Toxoplasma-infected mice in environments with exposed versus non-exposed areas, and found that chronically infected mice with brain cysts display a plethora of behavioral alterations. Using principal component analysis, we discovered that most of the behavioral differences observed in cyst-containing animals reflected changes in the microstructure of exploratory behavior and risk/unconditioned fear. We next examined whether these behavioral changes were related to the presence and distribution of parasitic cysts in the brain of chronically infected mice. We found no strong cyst tropism for any particular brain area but found that the distribution of Toxoplasma cysts in the brain of infected animals was not random, and that particular combinations of cyst localizations changed risk/unconditioned fear in the host. These results suggest that brain cysts in animals chronically infected with Toxoplasma alter the fine structure of exploratory behavior and risk/unconditioned fear, which may result in greater capture probability of infected rodents. These data also raise the possibility that selective pressures acted on Toxoplasma to broaden its transmission between intermediate predator hosts, in addition to felid definitive hosts. 相似文献
32.
Balinsky CA Delhon G Afonso CL Risatti GR Borca MV French RA Tulman ER Geary SJ Rock DL 《Journal of virology》2007,81(20):11392-11401
Sheeppox virus (SPPV), a member of the Capripoxvirus genus of the Poxviridae, is the etiologic agent of a significant disease of sheep in the developing world. Genomic analysis of pathogenic and vaccine capripoxviruses identified genes with potential roles in virulence and host range, including three genes with similarity to kelch-like genes of other poxviruses and eukaryotes. Here, a mutant SPPV with a deletion in the SPPV-019 kelch-like gene, DeltaKLP, was derived from the pathogenic strain SPPV-SA. DeltaKLP exhibited in vitro growth characteristics similar to those of SPPV-SA and revertant virus (RvKLP). DeltaKLP-infected cells exhibited a reduction in Ca(2+)-independent cell adhesion, suggesting that SPPV-019 may modulate cellular adhesion. When inoculated in sheep by the intranasal or intradermal routes, DeltaKLP was markedly attenuated, since all DeltaKLP-infected lambs survived infection. In contrast, SPPV-SA and RvKLP induced mortality approaching 100%. Lambs inoculated with DeltaKLP exhibited marked reduction or delay in fever response, gross lesions, viremia, and virus shedding compared to parental and revertant viruses. Together, these findings indicate that SPPV-019 is a significant SPPV virulence determinant in sheep. 相似文献
33.
34.
The aim of this study was to establish the requirements for macrophage activating factor (MAF) production by sea bass head-kidney leucocytes and the kinetics of macrophage activation when exposed to MAF-containing supernatants and/or lipopolysaccharide (LPS), a known macrophage stimulant. MAF activity was found in culture supernatants of total head-kidney leucocytes pulsed with 5 microg ml(-1)Con A, 5 or 10 ng ml(-1)PMA and 100 ng ml(-1)calcium ionophore, or 10 microg ml(-1)Con A alone, as assessed by the capacity to prime macrophages for enhanced production of reactive oxygen intermediates (ROI). Mixed leucocyte cultures from two or eight fish showed higher MAF activity after stimulation, indicating that a mixed leucocyte reaction was also important for MAF production. MAF-induced activation of macrophage cultures was highest at 18 h of exposure and was lost by 72 h except for MAF induced by Con A-stimulation alone. LPS primed macrophages for increased ROI production at early incubation times and down-regulated ROI production after 24 h. LPS had no effect in further stimulating the MAF-induced priming effect on production of ROI and down-regulated the MAF-priming by 48 h. Sea bass head-kidney macrophages did not show increased nitrite production when exposed to MAF and/or LPS, which may be related to their differentiation status. 相似文献
35.
Afonso LO Wassermann GJ Terezinha de Oliveira R 《The Journal of experimental zoology》2001,290(2):177-181
Several studies have demonstrated that steroid hormones can influence sex differentiation in nonmammalian vertebrates and it has been hypothesized that male and female sex differentiation are driven by androgen and estrogen hormones, respectively. Estrogen biosynthesis is mediated by the steroidogenic enzyme cytochrome P450 aromatase, which converts androgens to estrogens. In the present study we examined the efficacy of a potent nonsteroidal aromatase inhibitor incorporated into the food, on sex reversal of Nile tilapia (Oreochromis niloticus) larvae. Nile tilapia larvae were divided in seven groups, which were fed with diets containing different amounts of the aromatase inhibitor Fadrozole (0, 50, 75 and 100 mg/kg) during 15 and 30 days, starting 9 days after hatching. Independent of the period, the proportion of males was significantly higher in the treated groups. Treatment with the highest doses (75 and 100 mg/kg) for 30 days produced 100% males. Histological examination revealed no differences in gonadal tissues between control males and treated fish. Furthermore, one intersex fish was identified in the group treated with 50 mg Fadrozole/kg for 30 days. This study reports that a 100% Nile tilapia male population can be obtained by suppressing aromatase activity and suggests that besides steroid hormones, nonsteroidal compounds, such as aromatase inhibitors, have potential for production of monosex population in tilapia. J. Exp. Zool. 290:177-181, 2001. 相似文献
36.
Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae 总被引:8,自引:2,他引:8
Arginine decarboxylase (ADC) is an important enzyme in the production of
putrescine and polyamines in plants. It is encoded by a single or low-copy
nuclear gene that lacks introns in sequences studied to date. The rate of
Adc amino acid sequence evolution is similar to that of ndhF for the
angiosperm family studied. Highly conserved regions provide several target
sites for PCR priming and sequencing and aid in nucleotide and amino acid
sequence alignment across a range of taxonomic levels, while a variable
region provides an increased number of potentially informative characters
relative to ndhF for the taxa surveyed. The utility of the Adc gene in
plant molecular systematic studies is demonstrated by analysis of its
partial nucleotide sequences obtained from 13 representatives of
Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order
Capparales) and 1 from the related order Malvales. Two copies of the Adc
gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied
to data except the basal genus Aethionema. The resulting Adc gene tree
provides robust phylogenetic data regarding relationships within the
complex mustard family, as well as independent support for proposed tribal
realignments based on other molecular data sets such as those from
chloroplast DNA.
相似文献
37.
Analytical HPLC methods using carbamate chiral stationary phases of polysaccharide derivatives were developed for the enantiomeric resolution of five racemic mixtures of xanthonolignoids: rac-trans-kielcorin C, rac-cis-kielcorin C, rac-trans-kielcorin D, rac-trans-isokielcorin D, and rac-trans-kielcorin E. The separations were evaluated with the stationary phases cellulose tris-3,5-dimethylphenylcarbamate, amylose tris-3,5-dimethylphenylcarbamate, amylose tris-(S)-1-phenylethylcarbamate, and amylose tris-3,5-dimethoxyphenylcarbamate under normal, reversed-phase, and polar organic elution conditions. Chiral recognition of those chiral stationary phases, the influence of mobile phases on the enantiomers separation, and the effects of structural features of the solutes on the chiral discrimination observed are discussed. The best performance was achieved on an amylose tris-3,5-dimethylphenylcarbamate phase. Polar organic conditions gave shorter retention factors and better resolutions and were a valuable alternative to the alcohol-hexane or reversed-phase conditions. 相似文献
38.
39.
We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
相似文献
40.
Pauline M. Leite Rodrigo S. Gomes Amanda B. Figueiredo Tiago D. Serafim Wagner L. Tafuri Carolina C. de Souza Sandra A. L. Moura Juliana L. R. Fietto Maria N. Melo Fátima Ribeiro-Dias Milton A. P. Oliveira Ana Rabello Luís C. C. Afonso 《PLoS neglected tropical diseases》2012,6(10)