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1.
M L Eberhard M N Njenga A J DaSilva D Owino E K Nace K Y Won J M Mwenda 《The Journal of parasitology》2001,87(6):1394-1397
From March 1999 through August 2000, 511 stool samples collected from 11 different primate species in 10 geographically distinct locations in Kenya, East Africa, were screened for the presence of Cyclospora spp. oocysts. Positive samples (43/102, 42%) were identified in vervet monkeys (Cercopithecus aethiops) in 4 of 4 locations; 19/206 (9%) in yellow and olive baboons (Papio cynocephalus, P. anubis, respectively) in 5 of 5 locations; and 19/76 (25%) in black and white colobus monkeys (Colobus angolensis, C. guereza, respectively) from 2 of 3 locations. DNA sequences obtained from 18 S rRNA coding regions from respective subsets of these positive samples were typed as Cyclospora cercopitheci (samples from Cercopithecus aethiops). Cyclospora papionis (samples from Papio cynocephalus and P. anubis), and Cyclospora colobi (samples from Colobus angolensis and C. guereza). Cyclospora oocysts were not detected in samples collected from patas, highland sykes, lowland sykes, blue sykes, DeBrazza, or red-tailed monkeys. A coded map showing the geographic location of the collected samples is given. Stool samples from 1 troop of vervet monkeys were collected over a 12-mo period. Positive samples ranged between 21 and 63%. These results suggest that there is no strongly marked seasonality evident in Cyclospora infection in monkeys as has been noted in human infection. This is further confirmed by the recovery of positive samples collected from vervet monkeys, baboons, and colobus monkeys at all times of the year during this survey. This absence of seasonality in infection is especially notable because of the extreme weather patterns typical of Kenya, where marked rainy and dry seasons occur. A second noteworthy observation is that the striking host specificity of the Cyclospora species initially described was confirmed in this survey. Baboons were only infected with C. papionis, vervet monkeys with C. cercopitheci, and colobus monkeys with C. colobi, despite geographic overlaps of both the monkey and parasite species and wide geographic distribution of each parasite and monkey host. 相似文献
2.
Classification and distribution of large intestinal bacteria in nonhibernating and hibernating leopard frogs (Rana pipiens). 总被引:1,自引:1,他引:0
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The large intestinal flora of the leopard frog, Rana pipiens, was examined to determine whether differences existed between the nonhibernating and hibernating states of the animal and to determine the relative concentrations and proportions of potential frog pathogens. Hibernators had a logarithmic decrease of bacteria per milligram of intestine averaging one, and significantly greater proportions of facultative bacteria and psychrophiles relative to nonhibernators. The predominant anaerobic bacteria were gram-positive Clostridium species and gram-negative Bacteroides and Fusobacterium species. The predominant facultative bacteria were enterobacteria in nonhibernators but Pseudomonas species in hibernators. Many species of Pseudomonas are pathogenic for frogs, and thus the intestinal flora in hibernators may be a potential source of infectious disease. 相似文献
3.
4.
Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life. 相似文献
5.
Individuals from natural populations of the leopard frog, Rana pipiens, were analyzed for electrophoretic differences in blood proteins and enzymes from an amputated digit. The proteins examined represent products of 72 loci. Presumptive heterozygotes at multiple loci were selected for experimental crosses. Mendelian inheritance of 18 protein variations were demonstrated in the offspring. Tests for linkage or independent assortment were performed for 75 locus pairs. Three linkage groups were established. Linkage group 1 contains two loci, aconitase-1 (Acon1) and serum albumin (Alb), with a 19% recombination frequency between them. Linkage group 2 contains four loci, glyoxalase (Gly), acid phosphatase-1 (Ap1), acid phosphatase-2 (AP2), and esterase-5 (Est5). The data show the relationships Gly-21.1%-AP1-0%-AP2-6.3%-Est5, and Gly-25.6%-Est5. Linkage group 3 consists of four closely linked esterase loci. The data, Est1-5.1%-Est6, Est6-1.8%-Est10-1.9%-Est4 and Est6-3.0%-Est4, do not establish a complete order but suggest that Est10 is between Est4 and Est6. These results, with data demonstrating apparent independent assortment of 67 other locus pairs, provide a foundation for establishing the frog genetic map.The project was supported by Grant No. RR-00572 from the Division of Research Resources, National Institutes of Health. This paper is contribution No. C-87 from the Amphibian Facility, George W. Nace, Director. 相似文献
6.
Alain Gagnon Matthew S. Miller Stacey A. Hallman Robert Bourbeau D. Ann Herring David JD. Earn Joaquín Madrenas 《PloS one》2013,8(8)
The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.
“The war is over – and I must go” Egon Schiele, 1890–1918.相似文献
7.
PJ?MumbyEmail author JD?Hedley JRM?Chisholm CD?Clark H?Ripley J?Jaubert 《Coral reefs (Online)》2004,23(2):171-183
Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m2 pixels and 6 spectral bands with 0.25-m2 pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral resolution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead
Porites (total colony mortality within 6 months), old dead (>6 months) Porites,
Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562–580 nm. However, partially dead and recently dead Porites
colonies could not be distinguished from an airborne platform. Spectral differences among substrata are then exploited to predict the cover of reef substrata in ten 25-m2 plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01-m2 grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m2 quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of
Porites spp.). At the scale of the reef (all ten 25-m2 quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living
Porites, recently dead Porites
and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods required 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Remote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m2 of reef, which represents 3,700 plots of 25 m2 each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m2 and 0.25-m2 image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6–1.8 times greater in 0.25-m2 pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, providing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey). 相似文献
8.
A protocol was developed using 96-well plates and multichannel pipettes for serial dilutions, followed by drop plating on agar in a 6 x 6 format. This protocol permits simultaneous plating of six dilutions which greatly decreases the number of plates utilized thereby saving incubator space for organisms such as Campylobacter which require unique environmental conditions. 相似文献
9.
Sébastien JD Giroux Celmar Alves-Leiva Yann Lécluse Patrick Martin Olivier Albagli Isabelle Godin 《BMC developmental biology》2007,7(1):79
Background
Hematopoietic development in vertebrate embryos results from the sequential contribution of two pools of precursors independently generated. While intra-embryonic precursors harbour the features of hematopoietic stem cells (HSC), precursors formed earlier in the yolk sac (YS) display limited differentiation and self-renewal potentials. The mechanisms leading to the generation of the precursors in both sites are still largely unknown, as are the molecular basis underlying their different potential. A possible approach to assess the role of candidate genes is to transfer or modulate their expression/activity in both sites. We thus designed and compared transduction protocols to target either native extra-embryonic precursors, or hematopoietic precursors. 相似文献10.
Peter JD Andrews Helen Louise Sinclair Claire G Battison Kees H Polderman Giuseppe Citerio Luciana Mascia Bridget A Harris Gordon D Murray Nino Stocchetti David K Menon Haleema Shakur Daniel De Backer 《Trials》2011,12(1):1-13