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1.
SEM evidence for a new species, Giardia psittaci 总被引:2,自引:0,他引:2
The genus Giardia has been subdivided by Filice (1952) into 3 species, G. agilis, G. muris, and G. duodenalis, based on the morphology of the median body and subtle variations in the dimensions of trophozoites. Giardia trophozoites were isolated from the small intestine of budgerigars (parakeets) and examined morphologically with light and scanning electron microscopy. These trophozoites, like other Giardia spp., possessed a flattened dorso-ventral shape, 8 flagella, and an adhesive disc on the ventral surface. The presence of a claw hammer-shaped median body suggested classification of these trophozoites as G. duodenalis. However, unlike any known members of G. duodenalis, the Giardia trophozoites from budgerigars were morphologically distinct in that they lacked the ventrolateral flange and therefore did not have a marginal groove bordering the anterior and lateral border of the adhesive disc. This distinct morphology clearly indicated that trophozoites from budgerigars should be considered as a separate species, G. psittaci. Our evidence has demonstrated that median body shape cannot serve as a sole criterion for speciation of Giardia. In addition, if other avian species of Giardia also resemble G. psittaci, then this would suggest that evolutionary divergence has occurred in the genus Giardia. 相似文献
2.
D P deRegnier L Cole D G Schupp S L Erlandsen 《Applied and environmental microbiology》1989,55(5):1223-1229
Numerous waterborne outbreaks of giardiasis have occurred since 1965, yet little or no information has been reported on the viability of Giardia cysts in different aquatic environments. We have studied the viability of Giardia muris cysts suspended in lake, river, and tap water, while also monitoring water temperature, dissolved oxygen, pH, and other water quality parameters. Fecal pellets containing G. muris cysts were placed in glass vials covered with filter paper and exposed to (i) lake water at 15 ft (ca. 4.6 m) and 30 ft (ca. 9.2 m), (ii) river water, (iii) tap water, and (iv) distilled water stored under laboratory conditions. At 3, 7, 14, 28, 56, and 84 days, two vials from each environment were removed, and cyst viability was determined by (i) fluorogenic dye exclusion, (ii) production of giardiasis in an animal, and (iii) cyst morphology by Nomarski microscopy. In the fall, the cysts suspended at 30 ft in lake water remained viable for up to 56 days whereas cysts stored at 15 ft were nonviable after day 28. The G. muris cysts exposed to river water remained viable up to 28 days as determined by the production of giardiasis in mice. G. muris cysts suspended in tap water showed no signs of viability after 14 days, while cysts serving as controls (exposed to refrigerated distilled water) remained viable for up to 56 days. In the winter, Giardia cysts suspended in either lake or river water were viable for 56 to 84 days whereas cysts exposed to tap water were nonviable by day 14.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
3.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
4.
High-resolution immunogold localization of Giardia cyst wall antigens using field emission SEM with secondary and backscatter electron imaging 总被引:4,自引:0,他引:4
S L Erlandsen W J Bemrick D E Schupp J M Shields E L Jarroll J F Sauch J B Pawley 《The journal of histochemistry and cytochemistry》1990,38(5):625-632
We describe here the ultrastructural localization of Giardia cyst antigens in the filaments associated with the outer portion of intact cysts and on developing cyst wall filaments in encysting trophozoites. Post-embedding immunogold labeling of thin sections of intact Giardia cysts with polyclonal and monoclonal antibodies specific for cyst wall antigens (major protein bands of approximately 29, 75, 88, and 102 KD on Western blots) showed strong labeling of the filamentous cyst wall, whereas no labeling was seen on the membranous portion. High-resolution field emission scanning electron microscopy (FESEM) of Giardia cysts revealed that the cyst wall-specific polyclonal rabbit antisera and monoclonal mouse antibody produced gold labeling of 20-nm filaments in the cyst wall as detected with secondary electron imaging (SEI) and backscatter electron imaging (BEI) at 10 kV, despite coating of the cells with platinum by ion sputtering. FESEM studies of encysting Giardia trophozoites demonstrated that immunostaining with antibodies to cyst wall antigens produced colloidal gold labeling of developing cyst wall filaments on the cell surface; however, the intervening membrane domains were unlabeled. Substitution of normal serum for cyst wall-specific antibodies, or preabsorption of specific antibodies with Giardia cysts, eliminated immunolabeling of the filaments. 相似文献
5.
G Wendelschafer-Crabb S L Erlandsen D H Walker 《The journal of histochemistry and cytochemistry》1976,24(3):517-526
Employing the unlabeled antibody enzyme method at the ultrastructural level, a comparison was made between preembedding staining and postembedding staining for the detection of viral antigens. The bacteriophage P1 absorbed to the surface of Shigella dysenteriae was used as a model system. Preembedding staining resulted in the specific deposition of peroxidase-antiperoxidase (PAP) complexes as an electron-dense coating around the viral heads. Disadvantages of the preembedding staining method included the agglutination of cells by the primary antiserum which produced a gradient of specific staining and the "bleeding" or migration of electron dense reaction product away from the sites of attached PAP complexes. The postembedding staining method had distinct advantages over the preembedding staining in that PAP complexes were deposited directly over exposed viral heads within the thin section. In addition, the specific immunostaining of viruses was uniform through the section and no artifactual migration of reaction product was observed. 相似文献
6.
Evidence for a complex life cycle and endospore formation in the attached, filamentous, segmented bacterium from murine ileum. 总被引:11,自引:2,他引:9 下载免费PDF全文
Light and electron microscope observations showed that the filamentous, segmented bacterium commonly found attached to the ileal epithelium of rats and mice undergoes a complex life cycle. Filaments comprising up to 90 segments were attached to the microvillous border of absorptive epithelial cells by a specialized terminal holdfast segment. Starting at the free end of the filament and progressing toward the attached end, undifferentiated segments were converted into reproductive or mother segments. Within each mother cell two new holdfast segments developed. As the holdfasts matured, their mother cells degenerated and released them into the intervillar space where they attached, grew, and divided to produce new segmented filaments. Alternately, in some filaments, newly formed but not yet released holdfasts were converted into endospores, which were released in the same manner as holdfasts, presumably to spread the bacterial colony to other members of the rodent population. 相似文献
7.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)
Background
Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.Methods
We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV1) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV1 in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV1 in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.Results
We found a positive cross-sectional association between 25(OH)D and FEV1 in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV1 in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV1 (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV1 in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).Conclusions
Serum 25(OH)D status was associated with cross-sectional FEV1, but not longitudinal change in FEV1. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV1 and is a promising candidate gene for further studies.Electronic supplementary material
The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users. 相似文献8.
Yan Lu Shulin/SL Li Shiguo/SG Zhu Yabin/YB Gong Jun/J Shi Ling/ L Xu 《Biological procedures online》2017,19(1):2
DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer. 相似文献
9.
Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
相似文献
10.
Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give Km of 200mM and 660mM and Vmax of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively. 相似文献