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91.
The Spiral Plater System used for enumeration of bacteria was evaluated for the titration of Carnpylobacter phages. Twelve phages of C. jejuni were titrated using the conventional surface droplet technique, soft agar overlay-pour plate technique, and the Spiral Plater System. Phage counts obtained by the three methods were similar but the Spiral Plater System showed greater precision than the other methods. 相似文献
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No significant differences in electrical conductance parameters were observed when multiple portions of animal proteins were examined for salmonella on three Malthus 2000 analysers. No differences were noted in the isolation rates from conductance tubes on the three analysers. Results also indicates the importance of examining multiple samples due to uneven distribution of organisms in a dry matrix. 相似文献
95.
Acetylcholine, the principal neurotransmitter of the parasympathetic nervous system, evokes smooth muscle excitation and contraction by acting at the muscarinic receptors which, in many tissues, including the gastrointestinal tract, are comprised of the M2 and M3 subtypes. The opening of ion channels selective for monovalent cations (e.g., Na+ and K+) is the major mechanism of cholinergic excitation. We have studied signal transduction pathways and single cationic channel properties using patch-clamp recording and Ca2+ imaging techniques in guinea-pig single ileal myocytes. Cationic channels were found to couple to both M2 and M3 receptors via the GTP-bound Goα and phospholipase C activation, respectively. When these primarily signaling links are established, cationic channel opening can be further potentiated by membrane depolarization and an increase in the intracellular Ca2+ concentration. A strong synergism exists between the receptor occupancy by the agonist and intrinsic voltage dependence of the current as the former can effectively modulate the voltage range of cationic channel activation, while membrane depolarization produces a strong sensitizing effect. However, at potentials close to 0 mV ion flux is terminated by channel flickery block, while further depolarization induces long-lasting channel inactivation. Channel flicker is not caused by intracellular Mg2+, polyamines, or any other freely diffusible molecule and is confined to potentials around 0 mV irrespective of the driving force. Thus, it appears to be an intrinsic channel property of physiological importance as it improves conditions for the action potential discharge and propagation. Similarly, intracellular Ca2+-dependent facilitation of channel opening is counteracted by a slower desensitization. Further, the most intriguing negative control was discovered in the experiments whereby all cellular G proteins were non-selectively and persistently activated by GTPγS infusion, in which case, over time, carbachol instead of activation caused strong and almost irreversible inhibition of the cationic current. In cell-attached and outside-out membrane patches exposed to 50 μM carbachol or 200 μM internal GTPγS, the activity of three types of cationic channels was observed. They had dissimilar conductances (10, 50, and 130 pS), voltage dependence, and kinetics. The properties of the 50 pS channel are consistent with the whole-cell current behavior, at least when [Ca2+] i is “clamped” at 100 nM. The voltage-independent component of the cationic conductance, which appears at higher levels of [Ca2+] i , is likely mediated by the 130 pS channel, while the role of the 10 pS channel at present is unclear. Thus, smooth muscle cationic channels can uniquely detect and integrate many of the most important physiological signals such as the active conformation of two different muscarinic receptors, their associated G proteins and enzymes, as well as membrane potential and [Ca2+] i levels. Moreover, some signals act in synergy, while most of them, depending on the intensity, can be either stimulatory or inhibitory. 相似文献
96.
Peri E. Bolton Lee A. Rollins James Brazill-Boast Kimberley L. Maute Sarah Legge Jeremy J. Austin Simon C. Griffith 《Conservation Genetics》2018,19(3):737-754
Declines in population size can compromise the viability of populations by reducing the effective population size (Ne), which may result in loss of genetic diversity and inbreeding. Temporal population genetic data can be a powerful tool for testing the presence and severity of reductions in Ne. The Gouldian finch (Erythrura gouldiae) is a flagship for conservation of Australian monsoonal savanna species. This species underwent severe population declines in the twentieth century due to land use changes associated with European colonization. Microsatellite and mitochondrial genetic data from Gouldian finch samples sourced from natural history collections prior to land use changes were compared with contemporary samples to estimate the severity of decline in effective population size and to detect changes in gene flow. These data show that Gouldian finch decline was not as severe as some sources suggest, and that population genetic connectivity has not changed following land use changes in the twentieth century. Multiple estimators of current Ne using genetic data from consecutive years suggest the Gouldian finch Ne is likely between a few hundred and a few thousand individuals, with some estimates within the range considered of conservation concern. This work has identified the need to genetically characterize populations in Queensland, and to understand critical demographic parameters (e.g. lifespan) in the Gouldian finch. Understanding these factors is vital to further improve genetic estimates of population size, key to the formation of appropriate conservation management of this species. 相似文献
97.
Nicholas C. Coops Gregory J. M. Rickbeil Douglas K. Bolton Margaret E. Andrew Niels C. Brouwers 《Ecography》2018,41(7):1147-1160
Determining drivers of species richness is recognised as highly complex, involving many synergies and interactions. We examine the utility of newly available remote sensing representations of vegetation productivity and vegetation structure to examine drivers of species richness at continental and regional scales. We related richness estimates derived from stacked species distribution models for birds, mammals, amphibians, and reptiles to estimates of actual and potential evapotranspiration (AET and PET), forest structure, and forest productivity across Australia as a whole as well as by bioclimatic zones. We used structural equation modeling to partition correlations between climate energy and vegetation attributes and their subsequent associations with species richness. Continentally, vertebrate richness patterns were strongly related to patterns of energy availability. Richness of amphibians, mammals, and birds were positively associated with AET. However, reptile richness was most strongly associated with PET. Regionally, forest structure and productivity associations with bird, mammal, and amphibian richness were strongest. Again, reptile richness associated most strongly with PET. Our results suggest that a hierarchy of drivers of broad‐scale vertebrate richness patterns exist (reptiles excluded): 1) climate energy is most important at the continental scale; next, 2) vegetation productivity and vegetation structure are most important at the regional scale; except 3) at low extremes of climate energy when energy becomes limiting. 相似文献
98.
Mina?AryaEmail authorView authors OrcID profile Ali?Akbar?Mirzaei Abdol?Mahmood?Davarpanah Seyed?Masoud?Barakati Hossein?Atashi Abas?Mohsenzadeh Kim?Bolton 《Journal of molecular modeling》2018,24(2):47
Catalytic combustion of hydrocarbons is an important technology to produce energy. Compared to conventional flame combustion, the catalyst enables this process to operate at lower temperatures; hence, reducing the energy required for efficient combustion. The reaction and activation energies of direct combustion of hydrocarbons (CH?→?C?+?H) on a series of metal surfaces were investigated using density functional theory (DFT). The data obtained for the Ag, Au, Al, Cu, Rh, Pt, and Pd surfaces were used to investigate the validity of the Brønsted-Evans-Polanyi (BEP) and transition state scaling (TSS) relations for this reaction on these surfaces. These relations were found to be valid (R2?=?0.94 for the BEP correlation and R2?=?1.0 for the TSS correlation) and were therefore used to estimate the energetics of the combustion reaction on Ni, Co, and Fe surfaces. It was found that the estimated transition state and activation energies (ETS?=??69.70 eV and Ea?=?1.20 eV for Ni, ETS?=??87.93 eV and Ea?=?1.08 eV for Co and ETS?=??92.45 eV and Ea?=?0.83 eV for Fe) are in agreement with those obtained by DFT calculations (ETS?=??69.98 eV and Ea?=?1.23 eV for Ni, ETS?=??87.88 eV and Ea?=?1.08 eV for Co and ETS?=??92.57 eV and Ea?=?0.79 eV for Fe). Therefore, these relations can be used to predict energetics of this reaction on these surfaces without doing the time consuming transition state calculations. Also, the calculations show that the activation barrier for CH dissociation decreases in the order Ag ? Au ? Al ? Cu ? Pt ? Pd ? Ni?>?Co?>?Rh?>?Fe. 相似文献
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100.
Detection of Campylobacter jejuni and Campylobacter coli in Environmental Waters by PCR Enzyme-Linked Immunosorbent Assay 下载免费PDF全文
A. D. Sails F. J. Bolton A. J. Fox D. R. A. Wareing D. L. A. Greenway 《Applied microbiology》2002,68(3):1319-1324
A PCR enzyme-linked immunosorbent assay (ELISA) assay was applied to the detection of Campylobacter jejuni and Campylobacter coli in environmental water samples after enrichment culture. Bacterial cells were concentrated from 69 environmental water samples by using filtration, and the filtrates were cultured in Campylobacter blood-free broth. After enrichment culture, DNA was extracted from the samples by using a rapid-boiling method, and the DNA extracts were used as a template in a PCR ELISA assay. A total of 51 samples were positive by either PCR ELISA or culture; of these, 43 were found to be positive by PCR ELISA and 43 were found to be positive by culture. Overall, including positive and negative results, 59 samples were concordant in both methods. Several samples were positive in the PCR ELISA assay but were culture negative; therefore, this assay may be able to detect sublethally damaged or viable nonculturable forms of campylobacters. The method is rapid and sensitive, and it significantly reduces the time needed for the detection of these important pathogens by 2 to 3 days. 相似文献