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1.
Investigation of the effect of combined variations in temperature, pH, and NaCl concentration on nisin inhibition of Listeria monocytogenes and Staphylococcus aureus.
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Gradient plates were used to investigate the effects of varying temperature, pH, and sodium chloride (NaCl) concentration on nisin inhibition of Staphylococcus aureus and Listeria monocytogenes, Nisin was incorporated into the plates of 0, 50, 100, 250, and 500 IU ml -1. Gradients of pH (3.7 to 7.92) at right angles to NaCl concentration (2.1 to 7% [wt/vol]) were used for the plates, which were incubated at 20, 25, 30 and 35 degrees C. Growth on the plates were recorded by eye and by image analysis. The presence of viable but nongrowing cells was revealed by transfer to nongradient plates. Lower temperatures and greater NaCl concentrations increased the nisin inhibition of S. aureus synergistically. Increasing the NaCl concentration potentiated the nisin action against L. monocytogenes; the effect of temperature difference was not so apparent. Between pH 7.92 and ca. pH 5, a fall pH appeared to increase nisin's effectiveness against both organisms. At more acid pH values (ca. pH 4.5 to 5), the organisms showed resistance to both nisin and NaCl at 20 and 25 degrees C. Similar results were obtained with one-dimensional liquid cultures. 相似文献
2.
Wimpenny J 《Biofouling》1996,10(1-3):43-63
Biofilm formation is discussed in terms of the ecological processes involved in their formation. It is emphasised that any cell responds to its environment i.e. to the composition of a liquid layer a few microns thick adjacent to the cell surface. The concept of multidimensional habitat domains defining the growth limits to every species is introduced, and put into the context of competition between different organisms. Activity domains of organisms are discussed and a definition for the niche of an organism introduced. The development of a biofilm on a clean surface is described. The constant depth film fermenter is introduced as an appropriate tool for investigating spatial and temporal sequence in biofilm formation. Finally, nutrient concentration is considered and the effects of diffusion limitation on film structure explored with the aid of a cellular automaton model. 相似文献
3.
Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study 总被引:3,自引:1,他引:2
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The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions. 相似文献
4.
This study was conducted to examine the psycho-emotional effects of repeated oral exposure to capsaicin, the principal active component of chili peppers. Each rat received 1 mL of 0.02% capsaicin into its oral cavity daily, and was subjected to behavioural tests following 10 daily administrations of capsaicin. Stereotypy counts and rostral grooming were significantly increased, and caudal grooming decreased, in capsaicin-treated rats during the ambulatory activity test. In elevated plus maze test, not only the time spent in open arms but also the percent arm entry into open arms was reduced in capsaicin-treated rats compared with control rats. In forced swim test, although swimming duration was decreased, struggling increased in the capsaicin group, immobility duration did not differ between the groups. Repeated oral capsaicin did not affect the basal levels of plasma corticosterone; however, the stress-induced elevation of plasma corticosterone was prolonged in capsaicin treated rats. Oral capsaicin exposure significantly increased c-Fos expression not only in the nucleus tractus of solitarius but also in the paraventricular nucleus. Results suggest that repeated oral exposure to capsaicin increases anxiety-like behaviours in rats, and dysfunction of the hypothalamic-pituitary-adrenal axis may play a role in its pathophysiology. 相似文献
5.
Tyler JW Robinson Melody Pai Jeff C Liu Frederick Vizeacoumar Thomas Sun Sean E Egan Alessandro Datti Jing Huang Eldad Zacksenhaus 《Cell cycle (Georgetown, Tex.)》2013,12(18):3013-3024
Triple-negative breast cancer (TNBC) represents an aggressive subtype, for which radiation and chemotherapy are the only options. Here we describe the identification of disulfiram, an FDA-approved drug used to treat alcoholism, as well as the related compound thiram, as the most potent growth inhibitors following high-throughput screens of 3185 compounds against multiple TNBC cell lines. The average IC50 for disulfiram was ~300 nM. Drug affinity responsive target stability (DARTS) analysis identified IQ motif-containing factors IQGAP1 and MYH9 as direct binding targets of disulfiram. Indeed, knockdown of these factors reduced, though did not completely abolish, cell growth. Combination treatment with 4 different drugs commonly used to treat TNBC revealed that disulfiram synergizes most effectively with doxorubicin to inhibit cell growth of TNBC cells. Disulfiram and doxorubicin cooperated to induce cell death as well as cellular senescence, and targeted the ESA+/CD24-/low/CD44+ cancer stem cell population. Our results suggest that disulfiram may be repurposed to treat TNBC in combination with doxorubicin. 相似文献
6.
Fife MS Gutierrez A Ogilvie EM Stock CJ Samuel JM Thomson W Mack LF Lewis CM Woo P 《Arthritis research & therapy》2006,8(5):R148-5
Juvenile idiopathic arthritis (JIA) is the most common cause of chronic childhood disability and encompasses a number of disease
subgroups. In this study we have focused on systemic JIA (sJIA), which accounts for approximately 11% of UK JIA cases. This
study reports the investigation of three members of the IL10 gene family as candidate susceptibility loci in children with
sJIA. DNA from 473 unaffected controls and 172 patients with sJIA was genotyped for a single nucleotide polymorphism (SNP)
in IL19 and IL20 and two SNPs in IL10. We examined evidence for association of the four SNPs by single marker and haplotype
analysis. Significant differences in allele frequency were observed between cases and controls, for both IL10-1082 (p = 0.031)
and IL20-468 (p = 0.028). Furthermore, examination of the haplotypes of IL10-1082 and IL20-468 revealed greater evidence for
association (global p = 0.0006). This study demonstrates a significant increased prevalence of the low expressing IL10-1082
genotype in patients with sJIA. In addition, we show a separate association with an IL20 polymorphism, and the IL10-1082A/IL20-468T
haplotype. The two marker 'A-T' haplotype confers an odds ratio of 2.24 for sJIA. This positive association suggests an important
role for these cytokines in sJIA pathogenesis. 相似文献
7.
Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland
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The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
8.
During 2009, while we were celebrating Charles Darwin and his The origin of species, sadly, little was said about the critical contribution of Alfred Russel Wallace (1823–1913) to the development of the theory
of evolution. Like Darwin, he was a truly remarkable nineteenth century intellect and polymath and, according to a recent
book by Roy Davies (The Darwin conspiracy: origins of a scientific crime), he has a stronger claim to the Theory of Evolution by Natural Selection than has Darwin. Here we present a critical comparison
between the contributions of the two scientists. Sometimes referred to as ‘The other beetle-hunter’ and largely neglected
for many decades, Wallace had a far greater experience of collecting and investigating animals and plants from their native
habitats than had Darwin. He was furthermore much more than a pioneer biogeographer and evolutionary theorist, and also made
contributions to anthropology, ethnography, geology, land reform and social issues. However, being a more modest, self-deprecating
man than Darwin, and lacking the latter’s establishment connections, Wallace’s contribution to the theory of evolution was
not given the recognition it deserved and he was undoubtedly shabbily treated at the time. It is time that Wallace’s relationship
with Darwin is reconsidered in preparation for 2013, the centenary of Wallace’s death, and he should be recognized as at least
an equal in the Wallace-Darwin theory of evolution. 相似文献
9.
To help to understand the modelling process that occurs when a scaffold is implanted it is vital to understand the rather complex bone remodelling process prevalent in native bone. We have formulated a mathematical model that predicts osteoactivity both in scaffolds, as well as in bone in vivo and could set a basis for the more detailed allosteric models. The model is extended towards a bio-cybernetic vision of basic multicellular unit (BMU) action, when some of the regulation loops have been modified to reflect the allosteric control mechanisms, developed by Michaels-Menten, Hill, Koshland-Nemethy-Filmer, Monod-Wyman-Changeux. By implementation of this approach a four-dimensional system was obtained that shows steady cyclic behaviour using a wide range of constants with clear biological meaning. We have observed that a local steady state appears as a limiting cycle in multi-dimensional phase space and this is discussed in this paper. Physiological interpretation of this limiting four-dimension cycle possibly related to a conservative-like value has been proposed. Analysis and simulation of the model has shown an analogy between this conservative value, as a kind of substrate-energy regenerative potential of the bone remodelling system with a molecular nature, and to the classical physical value--energy. This dynamic recovery potential is directed against both mechanical and biomechanical damage to the bone. Furthermore, the current model has credibility when compared to the normal bone remodelling process. In the framework of widely recognised Hill mechanisms of allosteric regulation the cyclic attractor, described formerly for a pure cellular model, prevails for different forms of feedback control. This result indicates the viability of the proposed existence of a conservative value (analogous to energy) that characterises the recovery potential of the bone remodelling cycle. Linear stability analysis has been performed in order to determine the robustness of the basic state, however, additional work is required to study a wider range of constants. 相似文献
10.
Kan Chen Wanlu Cao Juan Li Dave Sprengers Pratika Y Hernanda Xiangdong Kong Luc JW van der Laan Kwan Man Jaap Kwekkeboom Herold J Metselaar Maikel P Peppelenbosch Qiuwei Pan 《Molecular medicine (Cambridge, Mass.)》2015,21(1):792-802
As uncontrolled cell proliferation requires nucleotide biosynthesis, inhibiting enzymes that mediate nucleotide biosynthesis constitutes a rational approach to the management of oncological diseases. In practice, however, results of this strategy are mixed and thus elucidation of the mechanisms by which cancer cells evade the effect of nucleotide biosynthesis restriction is urgently needed. Here we explored the notion that intrinsic differences in cancer cell cycle velocity are important in the resistance toward inhibition of inosine monophosphate dehydrogenase (IMPDH) by mycophenolic acid (MPA). In short-term experiments, MPA treatment of fast-growing cancer cells effectively elicited G0/G1 arrest and provoked apoptosis, thus inhibiting cell proliferation and colony formation. Forced expression of a mutated IMPDH2, lacking a binding site for MPA but retaining enzymatic activity, resulted in complete resistance of cancer cells to MPA. In nude mice subcutaneously engrafted with HeLa cells, MPA moderately delayed tumor formation by inhibiting cell proliferation and inducing apoptosis. Importantly, we developed a lentiviral vector–based Tet-on label-retaining system that enables to identify, isolate and functionally characterize slow-cycling or so-called label-retaining cells (LRCs) in vitro and in vivo. We surprisingly found the presence of LRCs in fast-growing tumors. LRCs were superior in colony formation, tumor initiation and resistance to MPA as compared with fast-cycling cells. Thus, the slow-cycling compartment of cancer seems predominantly responsible for resistance to MPA. 相似文献