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Major Route (major + route)
Selected AbstractsBenzo[a]pyrene bioavailability from pristine soil and contaminated sediment assessed using two in vitro modelsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2007Luba Vasiluk Abstract A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane. [source] Can the high levels of human verocytotoxigenic Escherichia coli O157 infection in rural areas of NE Scotland be explained by consumption of contaminated meat?JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007O. Solecki Abstract Aims:, To determine if contamination levels of Escherichia coli O157 and generic E. coli in retail-minced meat products are greater in rural shops compared with urban shops in Grampian, NE Scotland. We also investigated whether meat from supermarkets and meat from local butcher shops had a similar bacteriological quality. Methods and Results:, Minced beef and minced lamb were tested from November 2004 to August 2006. Escheichia coli O157 was found at low levels in four samples out of 530 tested samples (0·75%). Generic E. coli were present in 11% of the samples tested, of which 67% came from supermarkets. We observed no significant difference in the prevalence of generic E. coli between rural and urban areas. Conclusions:, Low levels of contamination with E. coli O157 and generic E. coli in retail meat suggest that meat is not a major route of infection in NE Scotland. Significance and Impact of the Study:, The study does not suggest that the high incidence of E. coli O157 human infection in the rural areas of Grampian is because of meat consumption , this provides further evidence of contact with animals or water being the routes of infection. Hence, risk mitigation should be focussed more on environmental pathways of infection. [source] Evidences of high carbon catabolic enzyme activities during sporulation of Pleurotus ostreatus (Florida)JOURNAL OF BASIC MICROBIOLOGY, Issue 6 2003Tapas K. Chakraborty Measurements of the specific activities of the representative enzymes of different pathways linked to carbohydrate metabolism indicate that glycolysis and TCA cycles are the major route of carbohydrate catabolism in the sporulating phase of fruiting body development in Pleurotus ostreatus. Enzymes of the pentose phosphate pathway always showed lower specific activities as compared to those of the enzymes of the glycolytic pathway. The activity of NADP linked glutamate dehydrogenase which is known to be an anabolic enzyme decreased drastically in sporulating fruiting bodies and in spore containing gill tissue (spore bearing structure). Mannitol dehydrogenase activity declined significantly in the sporulating phase of P. ostreatus. The high rate of metabolism during sporulation was further supported by a lower rate of gluconeogenesis at this stage. Concentrations of all the major sugars of the fruiting body (mannitol, glucose and trehalose) decreased in the mature fruiting body and gill tissue. This indicated high catabolic activities at this stage of development. [source] Genetic diversity of HCV genotype 2 strains in South Western FranceJOURNAL OF MEDICAL VIROLOGY, Issue 1 2007Fabienne Thomas Abstract Hepatitis C virus (HCV) is a major cause of chronic hepatitis and liver disease worldwide. The genetic heterogeneity of HCV and its spread among infected patients can be examined accurately by nucleotide sequencing. The diversity of HCV genotype 2 strains (HCV-2) was studied in a large cohort of patients in the Midi Pyrénées area of southern France. Phylogenetic analysis was performed on 344 NS5B sequences from patients infected with HCV-2. These included 145 strains whose E2 region was also analyzed, and epidemiological data were collected for the corresponding patients. HCV-2 accounts for 11.3% of HCV infections in this area. Phylogenetic analysis of NS5B sequences revealed eight subtypes, while that of the E2 region provided congruent results for 100% of strains. The most frequent subtypes were 2i (24.7%), 2k (22.4%) 2c (17.4%), and 2a (10.8%). The mean age of HCV-2-infected patients was 55.5 years. Epidemiological data showed that blood transfusion is the major route of infection, but it was not associated with any particular subtype. By contrast, intravenous drug users were infected predominantly with genotype 2a. HCV-2a-infected patients were younger than patients infected with other subtypes (48 vs. 56.5 years, P,<,0.01). This study shows substantial genetic diversity of HCV-2 subtypes in the south of France and the spread of 2a strains via intravenous drug users. J. Med. Virol. 79:26,34, 2007. © 2006 Wiley-Liss, Inc. [source] The Role of the Vagus Nerve in Mediating the Long-Term Anorectic Effects of LeptinJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2007C. Sachot Leptin, the product of the obese (ob) gene, is mainly known for its regulatory role of energy balance by direct activation of hypothalamic receptors. Recently, its function in the acute control of food intake was additionally attributed to activation of the vagus nerve to regulate meal termination. Whether vagal afferent neurones are involved in longer term effects of leptin on food intake, however, remains undetermined. Using vagotomised (VGX) rats, we sought to clarify the contributions of vagal afferents in mediating the long-lasting effect of leptin on appetite suppression. Intraperitoneal (i.p.) injection of leptin (3.5 mg/kg) attenuated food intake at 4, 6, 8 and 24 h and body weight at 24 h postinjection in SHAM-operated rats; however, this response was not abrogated by vagotomy. In a separate study using immunohistochemistry, we observed leptin-induced Fos expression in the nucleus tractus solitarii, a brain structure where vagal afferent fibres terminate. This signal was not attenuated in VGX animals compared to the SHAM group. Moreover, leptin treatment led to a similar level of nuclear STAT3 translocation, a marker of leptin signalling, in the hypothalami of SHAM and VGX animals. In addition to the effects of leptin, vagotomy surgery itself resulted in a decrease of 24 h food intake. Analyses of brains from saline-treated VGX animals revealed a significant induction of Fos in the nucleus tractus solitarii and changes in agouti-related peptide and pro-opiomelanocortin mRNA expression in the hypothalamus compared to their SHAM counterparts, indicating that the vagotomy surgery itself induced a modification of brain activity in areas involved in regulating appetite. Collectively, our data suggest that vagal afferents do not constitute a major route of mediating the regulatory effect of leptin on food intake over a period of several hours. [source] Seedling regeneration, environment and management in a semi-deciduous African tropical rain forestJOURNAL OF VEGETATION SCIENCE, Issue 5 2009Edward N. Mwavu Abstract Questions: How is seedling regeneration of woody species of semi-deciduous rain forests affected by (a) historical management for combinations of logging, arboricide treatment or no treatment, (b) forest community type and (c) environmental gradients of topography, light and soil nutrients? Location: Budongo Forest Reserve, Uganda. Methods: Seedling regeneration patterns of trees and shrubs in relation to environmental factors and historical management types were studied using 32 0.5-ha plots laid out in transects along a topographic gradient. We compared seedling species diversity, composition and distribution patterns along topographic gradients and within types of historical management regimes and forest communities to test whether environmental factors contributed to differences in species composition of seedlings. Results: A total of 85 624 woody seedlings representing 237 species and 46 families were recorded in this rain forest. Cynometra alexandri C.H. Wright and Lasiodiscus mildbraedii Engl. had high seedling densities and were widely distributed throughout the plots. The most species-rich families were Euphorbiaceae, Fabaceae, Rubiaceae, Meliaceae, Moraceae and Rutaceae. Only total seedling density was significantly different between sites with different historical management, with densities highest in logged, intermediate in logged/arboricided and lowest in the nature reserve. Forest communities differed significantly in terms of seedling diversity and density. Seedling composition differed significantly between transects and forest communities, but not between topographic positions or historical management types. Both Chao-Jaccard and Chao-Sørensen abundance-based similarity estimators were relatively high in the plot, forest community and in terms of historical management levels, corroborating the lack of significant differences in species richness within these groups. The measured environmental variables explained 59.4% of variance in seedling species distributions, with the three most important being soil organic matter, total soil titanium and leaf area index (LAI). Total seedling density was positively correlated with LAI. Differences in diversity of >2.0 cm dbh plants (juveniles and adults) also explained variations in seedling species diversity. Conclusions: The seedling bank is the major route for regeneration in this semi-deciduous tropical rain forest, with the wide distribution of many species suggesting that these species regenerate continuously. Seedling diversity, density and distribution are largely a function of adult diversity, historical management type and environmental gradients in factors such as soil nutrient content and LAI. The species richness of seedlings was higher in soils both rich in titanium and with low exchangeable cations, as well as in logged areas that were more open and had a low LAI. [source] Limb morphogenesis in the branchiopod crustacean, Thamnocephalus platyurus, and the evolution of proximal limb lobes within AnostracaJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2007T. A. Williams Abstract Crustacean limbs exhibit highly diverse morphologies. One major route of diversification is in the number and position of branches arising from the proximal part of the limb. Here I describe development of larvae of the branchiopod crustacean, Thamnocephalus platyurus and describe in detail the development of the thoracic limbs. The thoracic limbs bear proximal branches both medially and laterally. The most proximal branches on either side (gnathobase and pre-epipod) show a similar developmental history: they develop via fusion of two rudiments into a single adult branch. However, phylogenetic analysis suggests that the developmental fusions have distinct evolutionary histories. In one case (gnathobase), the developmental rudiments reflect the ancestral adult morphology of two distinct branches. In the other (pre-epipod), the rudiments are an apparent novelty within the Anostraca and develop into two adult structures in only a single derived family. Zusammenfassung Die Extremitäten von Krebsen zeigen eine Vielfalt an unterschiedlichen Morphologien. Diversifikation findet zum Grossteil über Anzahl und Position der aus dem proximalen Anteil der Extremitäten entspringenden Äste statt. In dieser Studie wird die Larvalentwicklung von Thamnocephalus platyurus, einem branchiopoden Krebs, beschrieben, vor allem die Entwicklung der Extremitäten der Thoracalsegmente. Diese tragen proximale Äste, sowohl medial, als auch lateral. Die proximalsten Äste beider Seiten (Gnathobasis und Praeepipodit) zeigen ähnliche Entwicklungen: Beide entstehen durch Fusion zweier Rudimente zu einem einzigen Ast im Adultstadium. Phylogenetische Analysen lassen darauf schließen, dass diese Fusionen während der Entwicklung unabhängig entstanden sind. In einem Fall (Gnathobasis) spiegeln die Rudimente im Entwicklungsstadium die ancestrale adulte Morphologie zweier unterschiedlicher Äste wieder. Im anderen Fall (Praeepipodit) sind die Rudimente vermutlich Innovationen innerhalb der Anostraca und entwickeln sich zu zwei verschiedenen Strukturen in nur einer einzigen Familie. [source] Evaluation of ecotoxicity and fate of methylated butyltins in sediments and seawater from Tokyo Bay, JapanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2007Ryo Kurihara Abstract We analyzed the fate of organotins in seawater and sediments from Tokyo Bay, Japan, by gas chromatography/inductively coupled plasma mass spectrometry. We also measured the toxicity of methylated butyltins by in vitro bioassays, the retinoid × receptor (RXR) activation method, and the marine luminescent bacterium Vibrio fischeri. Concentrations of tributyltin (TBT) and tributylmonomethyltin (TBMMT) in seawater were 0.0636 to 0.419 and 0.0050 to 0.108 ng Sn/L and in sediment were 7.51 to 17.8 and 3.67 to 6.87 ng Sn/wet weight g, respectively. Methylated butyltins did not activate RXR and were not toxic to bacteria. Tributylmonomethyltin in seawater would elute from sediment since TBMMT-to-TBT ratios showed a positive correlation (r2 = 0.858) between sediment and deep seawater. Both methylation and debutylation of TBT seem to be major routes of decomposition of TBT in sediment. Methylation of TBT would not only cause subsequent volatilization but also decrease the toxicity of TBT species in the marine environment. [source] Use of deltamethrin ,pour-on' insecticide for the control of cattle trypanosomosis in the presence of high tsetse invasionMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2001G. J. Rowlands Summary A deltamethrin ,pour-on' insecticide was applied monthly to over 2000 cattle exposed to a high challenge of drug-resistant trypanosomes and high tsetse re-invasion pressure in the Ghibe valley, south-west Ethiopia. Blood samples were taken monthly from an average of 760 cattle for determination of PCV and presence of trypanosomes. The area of the valley is approximately 350 km2 and the cattle grazed in roughly four locations covering about a quarter to half of the area. Two years before the trial commenced, Glossina morsitans submorsitans Newstead (Diptera: Glossinidae) began to invade the valley. Despite the use of the pour-on the mean apparent density of G. m. submorsitans continued to rise, and, during the 4 years of tsetse control, was more than three-fold higher than that recorded during the previous 18 months. Over the same period there was little change in the apparent density of Glossina pallidipes Austen (Diptera: Glossinidae). By contrast, the mean monthly prevalence of trypanosome infections in cattle over 36 months of age decreased from 38.3 to 29.0%, the incidence of new infections decreased from 26.6 to 16.0% (a reduction of 40%), and packed cell volume in cattle increased from 21.7 to 24.1%. Evidence of a change in apparent parasite transmission rate was demonstrated by regression of infection incidence in cattle on the logarithm of apparent density of G. m. submorsitans. Before the trial started the regression coefficient was 45.8 ± 6.3 and this reduced to 9.2 ± 2.5% incidence per loge (flies/trap/day) during the period of tsetse control. It was concluded that this indicated reductions in tsetse numbers in the immediate vicinities of cattle in a way that was not reflected in overall tsetse catches. Nevertheless, the comparatively high levels of trypanosome prevalence that persisted in the cattle demonstrates that, where invasion prevalence is high, treatment of small pockets of cattle will not eradicate tsetse. To achieve more significant reduction in trypanosome prevalence in cattle, integrated methods of control utilizing target barriers in the major routes of invasion will be needed. [source] Development of the avian lymphatic system,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2001Jörg Wilting Abstract Recently, highly specific markers of the lymphatic endothelium have been found enabling us to reinvestigate the embryonic origin of the lymphatics. Here we present a review of our studies on the development of the lymphatic system in chick and quail embryos. We show that the lymphatic endothelium is derived from two sources: the embryonic lymph sacs and mesenchymal lymphangioblasts. Proliferation studies reveal a BrdU-labeling index of 11.5% of lymph sac endothelial cells by day 6.25, which drops to 3.5% by day 7. Lymphangioblasts are able to integrate into the lining of lymph sacs. Lymphatic endothelial cells express the vascular endothelial growth factor (VEGF) receptors-2 and -3. Their ligand, VEGF-C, is expressed almost ubiquitously in embryonic and fetal tissues. Elevated expression levels are found in the tunica media of large blood vessels, which usually serve as major routes for growing lymphatics. The homeobox gene, Prox1, is expressed in lymphatic but not in blood vascular endothelial cells throughout all stages examined, namely, in developing lymph sacs of day 6 embryos and in lymphatics at day 16. Experimental studies show the existence of lymphangioblasts in the mesoderm, a considerable time before the development of the lymph sacs. Lymphangioblasts migrate from the somites into the somatopleure and contribute to the lymphatics of the limbs. Our studies indicate that these lymphangioblasts already express Prox1. Microsc. Res. Tech. 55:81,91, 2001. © 2001 Wiley-Liss, Inc. [source] Homes for the orphans: utilization of multiple substrate-binding proteins by ABC transportersMOLECULAR MICROBIOLOGY, Issue 1 2010Gavin H. Thomas Summary Acquiring nutrients from the environment is essential for all microbes, and the ATP-binding cassette (ABC) transporters are one of the major routes by which bacteria achieve it. In this issue of Molecular Microbiology, Chen et al. describe their characterization of what appeared at first glance a simple ABC transporter for acquisition of quaternary ammonium compounds (QACs) in Pseudomonas sp., but their persistence in fully determining the properties of this system led to the experimental demonstration that QAC uptake utilizes three different substrate-binding proteins (SBPs), two of which are encoded at remote locations on the genome as ,orphan' SBPs that are each able to function with a single core ABC transporter. Building on the unusual nature of this system, in which multiple SBPs with non-overlapping substrate specificities compete for the same transporter binding site, they designed elegant in vivo experiments that suggest that only substrate-bound SBPs are able to form functional complexes with the membrane domains. This new finding provides an important piece of in vivo data leading to further insight into how this ubiquitous family of transporters operates. [source] Liposomes in investigative dermatologyPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 5 2001Daniel B. Yarosh Liposomes are microscopic spheres, usually composed of amphiphilic phospholipids. They may be useful without skin penetration if they simply protect or sequester compounds that would otherwise be unstable in the formulation. Liposomes that remain on the skin surface are useful as light-absorbers, agents to deliver color or sunscreens, or as depots for timed-release. Liposomes that penetrate the stratum corneum have the potential to interact with living tissue. Topically applied liposomes can either mix with the stratum corneum lipid matrix or penetrate the stratum corneum by exploiting the lipid-water interface of the intercellular matrix. There are at least four major routes of entry into the skin: pores, hair follicles, columnular spaces and the lipid:water matrix between squames. A major force driving liposome penetration is the water gradient, and flexible liposomes are best able to exploit these delivery opportunities. Some liposomes release their contents extracellularly. Topical application of photosensitizers may be enhanced by encapsulation in liposomes. Higher and longer-lasting drug concentrations may be produced in localized areas of skin, particularly at disease sites where the stratum corneum and the skin barrier function are disrupted. The liposome membrane should be designed to capture lipophilic drugs in the membrane or hydrophilic drugs in the interior. Other types of liposomes can be engineered to be taken up by cells. Once inside cells, the lysosomal sac and clatherin-coated pit are the dead-end destinations for liposomes unless an escape path has been engineered into the liposome. A novel method has been developed to allow delivery into cells of the skin, by escape from the lysosomal sac. These liposomes have been used to topical deliver active DNA repair enzymes from liposomes into epidermal cells and to enhance DNA repair of UV-irradiated skin. From these studies a tremendous amount has been learned about the relationship of DNA damage and skin cancer. Both mutations and immunosuppression appear to be essential to skin cancer and both are induced by DNA damage. DNA damage produces immediate effects by inducing the expression of cytokines, which means that DNA damage can induce signaling in neighboring, undamaged cells. The repair of only a fraction of the DNA damage has a disproportionate effect on the biological responses, clearly demonstrating that not all DNA damage is equivalent. This technology demonstrates that biologically active proteins can be delivered into the cells of skin, and opens up a new field of correcting or enhancing skin cell metabolism to improve human health. [source] Lactic acid bacteria vs. pathogens in the gastrointestinal tract of fish: a reviewAQUACULTURE RESEARCH, Issue 4 2010Einar Ringø Abstract Intensive fish production worldwide has increased the risk of infectious diseases. However, before any infection can be established, pathogens must penetrate the primary barrier. In fish, the three major routes of infection are the skin, gills and gastrointestinal (GI) tract. The GI tract is essentially a muscular tube lined by a mucous membrane of columnar epithelial cells that exhibit a regional variation in structure and function. In the last two decades, our understanding of the endocytosis and translocation of bacteria across this mucosa, and the sorts of cell damage caused by pathogenic bacteria, has increased. Electron microscopy has made a valuable contribution to this knowledge. In the fish-farming industry, severe economic losses are caused by furunculosis (agent, Aeromonas salmonicida spp. salmonicida) and vibriosis [agent, Vibrio (Listonella) anguillarum]. This article provides an overview of the GI tract of fish from an electron microscopical perspective focusing on cellular damage (specific attack on tight junctions and desmosomes) caused by pathogenic bacteria, and interactions between the ,good' intestinal bacteria [e.g. lactic acid bacteria (LAB)] and pathogens. Using different in vitro methods, several studies have demonstrated that co-incubation of Atlantic salmon (Salmo salar L.) foregut (proximal intestine) with LAB and pathogens can have beneficial effects, the cell damage caused by the pathogens being prevented, to some extent, by the LAB. However, there is uncertainty over whether or not similar effects are observed in other species such as Atlantic cod (Gadus morhua L.). When discussing cellular damage in the GI tract of fish caused by pathogenic bacteria, several important questions arise including: (1) Do different pathogenic bacteria use different mechanisms to infect the gut? (2) Does the gradual development of the GI tract from larva to adult affect infection? (3) Are there different infection patterns between different fish species? The present article addresses these and other questions. [source] Synthesis of a New Seleninic Acid Anhydride and Mechanistic Studies into Its Glutathione Peroxidase ActivityCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2008Sun-Chol Yu Dr. Abstract Starting from low toxic salicyloylglycine, a new seleninic acid anhydride 7 that lacks Se,,,N or Se,,,O non-bonded interactions was synthesized. This compound exhibits a fourfold higher glutathione peroxidase-like (GPx-like) activity than ebselen and inhibits plant and mammalian 12/15-lipoxygenases at lower micromolar concentrations. Because of these pharmacological properties, 7 may constitute a new lead compound for the development of anti-inflammatory low-molecular-weight seleno-organic compounds. Analyzing the redox products of 7 with glutathione (GSH) and tBuOOH, we identified three potential catalytic cycles (A, B, C) of GPx-like activity that are interconnected by key metabolites. To study the relative contribution of these cycles to the catalytic activity, we prepared selected reaction intermediates and found that the activity of seleninic acid anhydride 7 and of the corresponding diselenide 11 and selenol 14 compounds were in the same range. In contrast, the GPx-like activity of monoselenide 9 was more than one order of magnitude lower. These data suggested that cycles A and B may constitute the major routes of GPx-like activity of 7, whereas cycle C may not significantly contribute to catalysis. [source] | ||||||||||||||||