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101.
You J Xu Y He M McAllister TA Thacker PA Li X Wang T Jin L 《Applied microbiology and biotechnology》2011,89(6):1885-1893
Currently available enterotoxigenic Escherichia coli (ETEC) vaccines are based on colonization factors and/or the heat-labile enterotoxin B subunit (LTB). However, the induction
of antitoxic responses against heat-stable enterotoxin a (STa) and b (STb) has merit as these two poorly immunogenic toxins
are frequently associated with ETEC strains. In this study, we genetically constructed a trivalent enterotoxin fusion protein
(STa–LTB–STb, abbreviated to SLS) in an effort to develop a single toxoid containing these three enterotoxins for vaccination
against ETEC. Mutagenesis at one disulfide-bridge-forming cysteine in STa led to a dramatic reduction in the STa toxicity
of SLS; however, the fusion peptide retained the STb-associated toxicity. Immunization of mice with SLS protein elicited significant
antibody responses to LTB, STa, and STb. Significantly, the mice antisera were able to neutralize the biological activity
of both STa and STb. In the experiment to assess the protective effect of SLS immunization, the mortality of mice receiving
SLS was significantly lower than their control cohorts (P < 0.01) after intraperitoneal challenge with ETEC. These results show that the trivalent fusion enterotoxin SLS has the potential
to serve as a useful toxin-based vaccine against ETEC-induced diarrheal disease via a single immunogen. 相似文献
102.
Pontell L Sharma P Rivera LR Thacker M Tan YH Brock JA Furness JB 《Cell and tissue research》2011,343(2):411-419
Periods of ischemia followed by restoration of blood flow cause ischemia/reperfusion (I/R) injury. In the intestine, I/R damage
to the mucosa and neurons is prominent. Functionally, abnormalities occur in motility, most conspicuously a slowing of transit,
possibly as a consequence of damage to neurons and/or muscle. Here, we describe degenerative and regenerative changes that
have not been previously reported in intestinal muscle. The mouse small intestine was made ischemic for 1 h, followed by re-perfusion
for 1 h to 7 days. The tissues were examined histologically, after hematoxylin/eosin and Masson’s trichrome staining, and
by myeloperoxidase histochemistry to detect inflammatory reactions to I/R. Histological analysis revealed changes in the mucosa,
muscle, and neurons. The mucosa was severely but transiently damaged. The mucosal surface was sloughed off at 1–3 h, but re-epithelialization
occurred by 12 h, and the epithelium appeared healthy by 1–2 days. Longitudinal muscle degeneration was followed by regeneration,
but little effect on the circular muscle was noted. The first signs of muscle change were apparent at 3–12 h, and by 1 and
2 days, extensive degeneration within the muscle was observed, which included clear cytoplasm, pyknotic nuclei, and apoptotic
bodies. The muscle recovered quickly and appeared normal at 7 days. Histological evidence of neuronal damage was apparent
at 1–7 days. Neutrophils were not present in the muscle layers and were infrequent in the mucosa. However, they were often
seen in the longitudinal muscle at 1–3 days and were also present in the circular muscle. Neutrophil numbers increased in
the mucosa in both I/R and sham-operated animals and remained elevated from 1 h to 7 days. We conclude that I/R causes severe
longitudinal muscle damage, which might contribute to the long-term motility deficits observed after I/R injury to the intestine. 相似文献
103.
Lei Zhang Ling Liu Defa Li Quanfeng Li Xiangshu Piao Philip A. Thacker 《Archives of animal nutrition》2017,71(1):67-80
The objective of this research was to determine the effects of variety and storage duration on the nutrient digestibility and the digestible (DE) and metabolisable (ME) energy content in maize when fed to growing pigs. Four maize varieties (LS1, LS2, LS3 and LS4) were hand-harvested from the same growing area in China in early October of 2012. The samples were sun dried to about 14% moisture content and then stored in the warehouse of the Fengning Pig Experiment Base at China Agricultural University for 0, 3 or 10 months. Twenty-four barrows of about 33 kg body weight were used and allotted to a completely randomised block design with four diets and six replicate pigs per diet. Pigs were individually housed in metabolic crates. The four experimental diets were formulated by mixing 96.8% of each variety of maize with 3.2% vitamins and minerals. A 5-day collection period followed a 7-day diet acclimation period. The results indicated that the DE and ME contents of maize and the apparent total tract digestibility (ATTD) of organic matter (OM), dry matter, gross energy (GE), neutral detergent fibre, acid detergent fibre (ADF), crude protein (CP) and ether extract (EE) were significantly (p < 0.05) influenced by maize variety and storage duration. With an extension of storage duration from 0 to 10 months, the DE and ME of maize and the ATTD of OM, GE, ADF, CP and EE changed in a quadratic manner (p < 0.05), and 3 months of storage exceeded 0 months of storage by 1.84%, 1.43%, 0.31%, 0.32%, 15.37%, 2.11% and 5.02%, respectively. The DE, ME of maize and the ATTD of OM, GE, ADF, CP and EE decreased by 3.67%, 6.00%, 0.97%, 1.40%, 30.54%, 3.92% and 20.93%, respectively, at 10 months of storage compared to 3 months of storage. No interaction was observed between maize variety and storage duration in DE and ME contents in maize. In conclusion, under the conditions of this study, most of the nutrient digestibility and the DE and ME contents of maize increased from 0 to 3 months and decreased from 3 to 10 months. 相似文献
104.
Abstract. Because the taxonomy of marine sponges is based primarily on morphological characters that can display a high degree of phenotypic plasticity, current classifications may not always reflect evolutionary relationships. To assess phylogenetic relationships among sponges in the order Verongida, we examined 11 verongid species, representing six genera and four families. We compared the utility of morphological and molecular data in verongid sponge systematics by comparing a phylogeny constructed from a morphological character matrix with a phylogeny based on nuclear ribosomal DNA sequences. The morphological phylogeny was not well resolved below the ordinal level, likely hindered by the paucity of characters available for analysis, and the potential plasticity of these characters. The molecular phylogeny was well resolved and robust from the ordinal to the species level. We also examined the morphology of spongin fibers to assess their reliability in verongid sponge taxonomy. Fiber diameter and pith content were highly variable within and among species. Despite this variability, spongin fiber comparisons were useful at lower taxonomic levels (i.e., among congeneric species); however, these characters are potentially homoplasic at higher taxonomic levels (i.e., between families). Our molecular data provide good support for the current classification of verongid sponges, but suggest a re-examination and potential reclassification of the genera Aiolochroia and Pseudoceratina . The placements of these genera highlight two current issues in morphology-based sponge taxonomy: intermediate character states and undetermined character polarity. 相似文献
105.
The effect of insulin and insulin-like growth factor-1 (IGF-1) on progesterone secretion by porcine granulosa cells and their modulatory effect on follicle-stimulating hormone (FSH)-induced responses were examined. For comparative purposes, growth hormone (GH), previously shown to stimulate IGF-1 secretion, was also included. Granulosa cells from ovarian follicles (3 to 5 mm) were cultured in multiwell plates for the first 48 hours, either in the presence or absence of 1% fetal bovine serum (FBS). Following plating, all cultures were maintained in serum-free media. The addition of only insulin, but not IGF-1 or GH, enhanced progesterone secretion under both culture conditions. When low-density lipoprotein was provided as steroid substrate, a stimulatory effect of insulin on progesterone accumulation was observed with a minimum dose of 10 ng/ml. Granulosa cells cultured in serum-free media from the time of plating secreted less progesterone and were less responsive to FSH compared with cultures plated with 1% FBS. Only insulin, but not IGF-1, enhanced FSH responses to threefold in cells cultured with 1% FBS. However, when cells were cultured in serum-free media from the time of plating, both insulin and IGF-1, but not GH, potentiated the responses to FSH, but insulin was more potent than IGF-1. Insulin-like growth-factor-1 binding studies with granulosa cells indicate the presence of specific high-affinity binding sites (Kd 3.96 nM). A dose of 100 ng/ml of insulin had negligible cross-reactivity with IGF-1 receptors. 相似文献
106.
The effect of three-dimensional shape optimization on the probabilistic response of a cemented femoral hip prosthesis 总被引:2,自引:0,他引:2
Probabilistic analyses allow the effect of uncertainty in system parameters on predicted model performance measures to be determined. Furthermore, using performance functions to describe a failure event, the probability of failure can be quantified. The effect of three-dimensional prosthesis shape optimization on the probabilistic response and failure probability of a cemented hip prosthesis system is investigated. Random variables include joint and muscle loading, cortical and cancellous bone and PMMA bone cement elastic properties, and strength parameters describing failure of the bone cement and the prosthesis-bone cement interface. Several performance functions describing the bone cement and prosthesis-cement interface are used to compute the probability of failure. When evaluated deterministically, most performance functions indicated a safe design, with the exception of interface tensile failure. However, when evaluated probabilistically, finite probabilities of failure were computed, some significant. The most likely mode of failure before shape optimization was prosthesis-bone cement interface tensile failure with a predicted probability of failure of 97.9%. Deterministic prosthesis shape optimization reduced the probability of failure for all performance functions and reduced prosthesis-bone cement interface tensile failure by 31.7%. Probability sensitivity factors indicate that the uncertainty in the joint loading, cement strength, and implant-cement interface strength have the greatest effect on the computed probability of failure. Implant shape optimization results in a more robust implant design that is less sensitive to uncertainties in joint loading, which cannot be easily controlled, and more sensitive to cement and interface properties, which are easier to modify. 相似文献
107.
Cole G. Easson Marc Slattery Henrique G. Momm Julie B. Olson Robert W. Thacker Deborah J. Gochfeld 《PloS one》2013,8(11)
Background
Marine diseases are of increasing concern for coral reef ecosystems, but often their causes, dynamics and impacts are unknown. The current study investigated the epidemiology of Aplysina Red Band Syndrome (ARBS), a disease affecting the Caribbean sponge Aplysina cauliformis, at both the individual and population levels. The fates of marked healthy and ARBS-infected sponges were examined over the course of a year. Population-level impacts and transmission mechanisms of ARBS were investigated by monitoring two populations of A. cauliformis over a three year period using digital photography and diver-collected data, and analyzing these data with GIS techniques of spatial analysis. In this study, three commonly used spatial statistics (Ripley’s K, Getis-Ord General G, and Moran’s Index) were compared to each other and with direct measurements of individual interactions using join-counts, to determine the ideal method for investigating disease dynamics and transmission mechanisms in this system. During the study period, Hurricane Irene directly impacted these populations, providing an opportunity to assess potential storm effects on A. cauliformis and ARBS.Results
Infection with ARBS caused increased loss of healthy sponge tissue over time and a higher likelihood of individual mortality. Hurricane Irene had a dramatic effect on A. cauliformis populations by greatly reducing sponge biomass on the reef, especially among diseased individuals. Spatial analysis showed that direct contact between A. cauliformis individuals was the likely transmission mechanism for ARBS within a population, evidenced by a significantly higher number of contact-joins between diseased sponges compared to random. Of the spatial statistics compared, the Moran’s Index best represented true connections between diseased sponges in the survey area. This study showed that spatial analysis can be a powerful tool for investigating disease dynamics and transmission in a coral reef ecosystem. 相似文献108.
Darmon E Lopez-Vernaza MA Helness AC Borking A Wilson E Thacker Z Wardrope L Leach DR 《Journal of bacteriology》2007,189(18):6686-6694
109.
R. R. Facklam J. F. Padula L. G. Thacker E. C. Wortham B. J. Sconyers 《Applied microbiology》1974,27(1):107-113
A battery of five tests was used for presumptive identification of the pathogenic streptococci. The non-serological methods included determination of hemolysis for all strains, bacitracin susceptibility for group A streptococci, hippurate hydrolysis by group B streptococci, and bile-esculin reaction for group D streptococci. Enterococcal group D streptococci were differentiated from non-enterococcal group D streptococci by 6.5% NaCl tolerance. Two other categories of streptococci resulted: beta-hemolytic streptococci non-groups A, B, or D; and alpha- or nonhemolytic streptococci, not enterococci, not further identified (viridans streptococci). The tests were used as a battery and not as single entities. In this manner more than 99% of the group A, 99% of the group B, 81% of the beta-hemolytic streptococci non-group A, B, or D, 99% of the group D enterococci, 97% of the group D non-enterococci, and 94% of the viridans streptococci were correctly identified. 相似文献
110.