scholarly journals Detection of Salmonella in the intestine of Hypostomus plecostomus from the upper San Marcos River, Texas

2018 ◽  
Vol 16 (3) ◽  
pp. 460-471
Author(s):  
Anna Y. Gates ◽  
Trina M. Guerra ◽  
Fritzina B. Morrison ◽  
Michael R. J. Forstner ◽  
Thomas B. Hardy ◽  
...  
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Sampling Period ◽  
Selective Enrichment ◽  
Fish Intestine ◽  
San Marcos ◽  
Element Sequence ◽  
Sampling Event ◽  
Sampling Times ◽  
Precipitation Events

Abstract The prevalence of salmonellae in the intestines of the invasive suckermouth catfish Hypostomus plecostomus was assessed in the San Marcos River, just down-stream of its spring-fed headwaters. In 2014, H. plecostomus, sediment, and water samples were collected during 15 sampling events. A combination of semi-selective enrichment and quantitative polymerase chain reaction (qPCR) revealed the presence of salmonellae in 45% of the fish intestines across the entire year, with a prevalence range of 13–100% per sampling event. Repetitive element sequence-based PCR (rep-PCR) and multi-locus sequence typing (MLST) revealed a high diversity of salmonellae from fish intestine samples at individual sampling times, single or multiple presence of rep-PCR patterns and serotypes within individual fish, and identical rep-PCR patterns and serotypes for different fish within and across sampling events. Overall, 15 serotypes were identified by MLST, with a diversity range between one and seven serotypes per sampling event. Some serotypes were retrieved only once, while others were detected more frequently. A few serotypes were retrieved at several sampling times, nearly evenly distributed over the entire sampling period. Prevalence and diversity were independent of precipitation events, indicating the potential presence of environmental strains that are capable of long-term persistence in the environment.

scholarly journals Recovery of Salmonella from biofilms in a headwater spring ecosystem

2011 ◽  
Vol 9 (3) ◽  
pp. 458-466 ◽  
Author(s):  
James P. Gaertner ◽  
Joseph A. Mendoza ◽  
Michael R. J. Forstner ◽  
Dittmar Hahn
Keyword(s):  
Pathogenic Bacteria ◽  
Chain Reaction ◽  
Selective Enrichment ◽  
Animal Wastes ◽  
San Marcos ◽  
Polymerase Chain ◽  
Spring Lake ◽  
Precipitation Events

Salmonellae are pathogenic bacteria often detected in waters impacted by human or animal wastes. In order to assess the fate of salmonellae in supposedly pristine environments, water and natural biofilm samples along with snails (Tarebia granifera) and crayfish (Procambarus clarkia) were collected before and up to 7 days following four precipitation events from sites within the headwater springs of Spring Lake, San Marcos, TX. The samples were analyzed for the presence of salmonellae by polymerase chain reaction (PCR) after semi-selective enrichment. Salmonellae were detected in one water sample directly after precipitation only, while detection in ten biofilm and two crayfish samples was not related to precipitation. Salmonellae were not detected in snails. Characterization of isolates by rep-PCR revealed shared profiles in water and biofilm samples, biofilm and crayfish samples, and biofilm samples collected 23 days apart. These results suggest that salmonellae are infrequently washed into this aquatic ecosystem during precipitation runoff and can potentially take up residency in biofilms which can help facilitate subsequent long-term persistence and eventual transfer through the food chain.

scholarly journals Temporal analyses of Salmonellae in a headwater spring ecosystem reveals the effects of precipitation and runoff events

2008 ◽  
Vol 7 (1) ◽  
pp. 115-121 ◽  
Author(s):  
James P. Gaertner ◽  
Tiffany Garres ◽  
Jesse C. Becker ◽  
Maria L. Jimenez ◽  
Michael R. J. Forstner ◽  
...  
Keyword(s):  
Molecular Techniques ◽  
Precipitation Event ◽  
Rainfall Events ◽  
Before And After ◽  
San Marcos ◽  
Polymerase Chain ◽  
Spring Lake ◽  
Events Detection ◽  
Precipitation Events

Sediments and water from the spring and slough arm of Spring Lake, the pristine headwaters of the San Marcos River, Texas, were analyzed for Salmonellae by culture and molecular techniques before and after three major precipitation events, each with intermediate dry periods. Polymerase chain reaction (PCR)-assisted analyses of enrichment cultures detected Salmonellae in samples after all three precipitation events, but failed to detect them immediately prior to the rainfall events. Detection among individual locations differed with respect to the precipitation event analyzed, and strains isolated were highly variable with respect to serovars. These results demonstrate that rainwater associated effects, most likely surface runoff, provide an avenue for short-term pollution of aquatic systems with Salmonellae that do not, however, appear to establish for the long-term in water nor sediments.

scholarly journals Thunderstorms and thunderstorm precipitations in southern Poland

2014 ◽  
Vol 2 (3) ◽  
pp. 33-46
Author(s):  
Zuzanna Bielec-Bąkowska
Keyword(s):  
Temporal Variability ◽  
Daily Precipitation ◽  
Overwhelming Majority ◽  
Spatial And Temporal Variability ◽  
Southern Poland ◽  
Clear Cut ◽  
Term Change ◽  
Atmospheric Fronts ◽  
Precipitation Events

AbstractThis paper addresses spatial and temporal variability in the occurrence of thunderstorms and related precipitation in southern Poland between 1951 and 2010. The analysis was based on thunderstorm observations and daily precipitation totals (broken down into the few ranges) from 15 meteorological stations. It was found that precipitation accompanied an overwhelming majority of thunderstorms. The most frequent range of thunderstorm precipitation totals was 0.1–10.0 mm which accounted for 60% of all values while precipitation higher than 20.0 mm accounted only for ca. 8%. During the study period, long-term change in the number of days with thunderstorm precipitation within a certain range displayed no clear-cut trends. Exceptions included: 1) an increase in the number of days with thunderstorm precipitation in the lowest range of totals (0.1–10.0 mm) at Katowice, Tarnów, Rzeszów and Lesko and decrease at Mt. Kasprowy Wierch, 2) an increase in the range 10.1–20.0 mm at Zakopane and 20.1–30.0 mm at Opole, 3) a decrease of the top range (more than 30.0 mm) at Mt. Śnieżka. It was found that the heaviest thunderstorm precipitation events, i.e. totalling more than 30 mm, and those events that covered all or most of the study area, occurred at the time of air advection from the southern or eastern sectors and a passage of atmospheric fronts.

Probabilistic model predictive control for extended prediction horizons

2021 ◽  
Vol 69 (9) ◽  
pp. 759-770
Author(s):  
Tim Brüdigam ◽  
Johannes Teutsch ◽  
Dirk Wollherr ◽  
Marion Leibold ◽  
Martin Buss
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Prediction Models ◽  
Computational Effort ◽  
Probabilistic Constraints ◽  
Detailed Model ◽  
Control Approach ◽  
Proposed Model ◽  
Sampling Times

Abstract Detailed prediction models with robust constraints and small sampling times in Model Predictive Control yield conservative behavior and large computational effort, especially for longer prediction horizons. Here, we extend and combine previous Model Predictive Control methods that account for prediction uncertainty and reduce computational complexity. The proposed method uses robust constraints on a detailed model for short-term predictions, while probabilistic constraints are employed on a simplified model with increased sampling time for long-term predictions. The underlying methods are introduced before presenting the proposed Model Predictive Control approach. The advantages of the proposed method are shown in a mobile robot simulation example.

scholarly journals Impact of Open-Market Share Repurchases on Long-Term Stock Returns

SAGE Open ◽  
2016 ◽  
Vol 6 (4) ◽  
pp. 215824401667019 ◽  
Author(s):  
Mohamed Albaity ◽  
Diana Syafiza Said
Keyword(s):  
Stock Returns ◽  
Abnormal Returns ◽  
Sampling Period ◽  
Share Repurchases ◽  
Open Market ◽  
Calendar Time ◽  
Price Performance ◽  
Long Run ◽  
Portfolio Approach

After the Asian financial crisis in 1997, firms listed on Bursa Malaysia were allowed to repurchase their shares on the open market. The number of companies engaged in share buyback is increasing and has become a tool to stabilize price by signaling undervaluation of the share. However, studies on share buyback in Malaysia are limited to the price performance surrounding the buyback events. This study aims to fill this gap by examining long-run price performance after the actual share buyback event over a sampling period of 2 years from 2009 to 2010 for Malaysian firms listed on FTSE Bursa Malaysia. There is no evidence to conclude that there exist long-term abnormal returns using the calendar-time portfolio approach that support the inefficient market hypothesis. On the contrary, buy-and-hold method was found to be significant supporting that the Malaysian stock market is semi-strong efficient.

Roles of gonad-inhibiting hormone in the protandric simultaneous hermaphrodite peppermint shrimp†

2020 ◽  
Vol 103 (4) ◽  
pp. 817-827
Author(s):  
Wenyuan Shi ◽  
Fang Liu ◽  
An Liu ◽  
Huiyang Huang ◽  
Qi Lin ◽  
...  
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Gonadal Development ◽  
Simultaneous Hermaphrodite ◽  
Secondary Sexual Characteristic ◽  
Significant Difference ◽  
Peppermint Shrimp ◽  
Gonad Inhibiting Hormone ◽  
Sexual Characteristic ◽  
Secondary Sexual

Abstract To date, the molecular mechanisms of the unique gonadal development mode known as protandric simultaneous hermaphroditism (PSH) are unclear in crustaceans. In this study, cDNA of a gonad-inhibiting hormone (Lv-GIH1) was isolated from the PSH peppermint shrimp Lysmata vittata, and its expression was exclusively found in the eyestalk ganglion. Real-time quantitative polymerase chain reaction (qRT-PCR) revealed that the expression of Lv-GIH1 increased during gonadal development of the functional male stages but decreased significantly at subsequent simultaneous hermaphroditism stage. Further in vitro experiment showed that recombinant GIH1 protein (rGIH1) effectively inhibited Vg expression in the cultured hepatopancreas tissues while the short-term injection of GIH1-dsRNA resulted in reduced expression of Lv-GIH1 and upregulated expression of Vg in the hepatopancreas. Moreover, long-term rGIH1 injection led to significantly reduced expression of Lv-Vg, Lv-VgR, and Lv-CFSH1, subdued growth of oocytes, and feathery setae as a secondary sexual characteristic in females. Interestingly, while germ cells in testicular part were suppressed by rGIH1 injection, the expression of Lv-IAGs showed no significant difference; and long-term GIH1-dsRNA injection results were contrary to those of rGIH1 injection. Taken together, the results of this study indicate that Lv-GIH1 is involved in gonadal development and might also participate in controlling secondary sexual characteristic development in L. vittata by inhibiting Lv-CFSH1 expression.

scholarly journals Snow-accumulation variability from seasonal surface observations and firn-core stratigraphy, eastern Wilkes Land, Antarctica

1991 ◽  
Vol 37 (127) ◽  
pp. 383-387 ◽  
Author(s):  
Ian D. Goodwin
Keyword(s):  
Circulation Pattern ◽  
Snow Accumulation ◽  
Atmospheric Circulation Pattern ◽  
Oxygen Isotope Ratios ◽  
Stratigraphic Model ◽  
Wilkes Land ◽  
Annual Frequency ◽  
Terre Adélie ◽  
Precipitation Events

AbstractAnnual accumulation records were derived from two firn cores drilled at GD03 (69° 00’S, 115° 30’E, 1835m) and GD15 (69° 00’S, 130° 48’E, 2155m), which are separated by 750 km along the 2000 m contour in eastern Wilkes Land. The accumulation records, spanning the period 1930–85, show that annual accumulation has increased by 25% from 1960 to 1985, resulting in the highest accumulation rates in the 55 year records. Annual accumulation layers were identified in the firn cores using a firn-stratigraphic model (based on the observed characteristics and variability of the seasonal snow-surface layer) together with seasonal oxygen-isotope ratios. The accumulation records support other evidence for a similar recent increase across Antarctica. The greater increase over the long-term mean for 1930–85 in eastern Wilkes Land was observed at GD15 which is located on a northeast aspect slope near Terre Adèlie. It is suggested that the increase is the result of changes in the general atmospheric circulation pattern which have produced a higher annual frequency of precipitation events.

The short- and long-term inhibitory effects of Fe (II) on anaerobic ammonium oxidizing (anammox) process

2019 ◽  
Vol 79 (10) ◽  
pp. 1860-1867 ◽  
Author(s):  
Cherh Yih Mak ◽  
Jih Gaw Lin ◽  
Wen Hsing Chen ◽  
Choon Aun Ng ◽  
Mohammed J. K. Bashir
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Substrate Inhibition ◽  
Optimum Concentration ◽  
Anammox Bacteria ◽  
Batch Test ◽  
Short Term ◽  
Anammox Activity ◽  
Study Results ◽  
Anammox Process

Abstract The application of the anammox process has great potential in treating nitrogen-rich wastewater. The presence of Fe (II) is expected to affect the growth and activity of anammox bacteria. Short-term (acute) and long-term effects (chronic) of Fe (II) on anammox activity were investigated. In the short-term study, results demonstrated that the optimum concentration of Fe (II) that could be added to anammox is 0.08 mM, at which specific anammox activity (SAA) improved by 60% compared to the control assay, 0.00 mM. The inhibition concentration, IC50, of Fe (II) was found to be 0.192 mM. Kinetics of anammox specific growth rate were estimated based on results of the batch test and evaluated with Han-Levenspiel's substrate inhibition kinetics model. The optimum concentration and IC50 of Fe (II) predicted by the Han-Levenspiel model was similar to the batch test, with values of 0.07 mM and 0.20 mM, respectively. The long-term effect of Fe (II) on the performance of a sequencing batch reactor (SBR) was evaluated. Results showed that an appropriate Fe (II) addition enhanced anammox activity, achieving 85% NH4+-N and 96% NO2−-N removal efficiency when 0.08 mM of Fe (II) was added. Quantitative polymerase chain reaction (qPCR) was adopted to detect and identify the anammox bacteria.

Promoter Methylation and Decreased Expression of Mir-124 In Myelodysplastic Syndromes

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4014-4014
Author(s):  
Yuesheng Meng ◽  
Qiao Xia ◽  
Jun Hu
Keyword(s):  
Myelodysplastic Syndromes ◽  
Promoter Methylation ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Quantitative Polymerase Chain Reaction ◽  
Methylation Status ◽  
Polymerase Chain Reaction Analysis ◽  
Promoter Regions ◽  
Hematopoietic Stem

Abstract Abstract 4014 The myelodysplastic syndromes (MDS) are a heterogeneous group of clonal disorders of hematopoietic stem/progenitor cells. Although demethylating agents such azacytidine and decitabine have been widely used to treat MDS, the underlying molecular mechanisms remain obscure. Abnormalities of microRNAs (miRNA) have been recently associated with hematological malignancies including MDS. The miR-124 was initially demonstrated to modulate neurogenesis. It was recently shown that EVI1-induced methylation and silencing of miR-124 were present in murine MDS cells. In the retrospective study we evaluated methylation status and expression levels of miR-124 in fifteen MDS patients (subtypes included RCUD, RCMD, RAEB-1, RAEB-2 and CMML). Genomic DNA samples were modified with bisulfite and methylation at three promoter regions of miR-124 was examined with methylation-specific real time quantitative polymerase chain reaction analysis (MQPCR). In general, we observed an increased methylation levels of miR-124 in MDS patients than that in normal bone marrow (NBM, P<0.01). In accordance with this, marked depression of miR-124 was seen in six patients when compared with NBM (more than 2 times lower), as determined with quantitative reverse-transcriptive PCR assay. Moreover, there were higher degrees of promoter methylation in cases with depressed miR-124 than that in remaining cases. A negative correlation between the expression and methylation levels was statistically significant (R= -0.498, P<0.01). The change of miR-124 was not directly related to short-term clinical response or prognosis, possibly due to limited size of the sample. However, the miR-124 amount returned to basal levels in two cases (RCMD and CMML subtypes respectively) after low-dose decitabine therapy and DNA methylation of all three loci disappeared. Continued work is underway to accumulate more cases and make long-term clinical follow-up. In conclusion, this primary work suggested a possible role of the methylation-mediated silencing of miR-124 in the pathogenesis or disease progression of MDS. Disclosures: No relevant conflicts of interest to declare.

scholarly journals DNA from lake sediments reveals the long-term dynamics and diversity of <i>Synechococcus</i> assemblages

2013 ◽  
Vol 10 (6) ◽  
pp. 3817-3838 ◽  
Author(s):  
I. Domaizon ◽  
O. Savichtcheva ◽  
D. Debroas ◽  
F. Arnaud ◽  
C. Villar ◽  
...  
Keyword(s):  
16S Rrna ◽  
Environmental Conditions ◽  
Trophic Status ◽  
Community Dynamics ◽  
Environmental Changes ◽  
Quantitative Polymerase Chain Reaction ◽  
Additive Models ◽  
Phosphorus Concentration ◽  
Rrna Gene

Abstract. While picocyanobacteria (PC) are important actors in carbon and nutrient cycles in aquatic systems, factors controlling their interannual dynamics and diversity are poorly known due to the general lack of long-term monitoring surveys. This study intended to fill this gap by applying a DNA-based paleolimnological approach to sediment records from a deep subalpine lake that has experienced dramatic changes in environmental conditions during the last century (eutrophication, re-oligotrophication and large-scale climate changes). In particular, we investigated the long-term (100 yr) diversity and dynamics of Synechococcus,, PC that have presumably been affected by both the lake trophic status changes and global warming. The lake's morphological and environmental conditions provided the ideal conditions for DNA preservation in the sediment archives. Generalised additive models applied to quantitative PCR (qPCR; quantitative Polymerase Chain Reaction) results highlighted that an increase in summer temperature could have a significant positive impact on the relative abundance of Synechococcus, (fraction of Synechococcus, in total cyanobacteria). The diversity of Synechococcus, in Lake Bourget was studied by phylogenetic analyses of the 16S rRNA gene and the following internally transcribed spacer (ITS). Up to 23 different OTUs (based on 16S rRNA), which fell into various cosmopolitan or endemic clusters, were identified in samples from the past 100 yr. Moreover, the study of ITS revealed a higher diversity within the major 16S rRNA-defined OTUs. Changes in PC diversity were related to the lake's trophic status. Overall, qPCR and sequencing results showed that environmental changes (in temperature and phosphorus concentration) affected Synechococcus, community dynamics and structure, translating into changes in genotype composition. These results also helped to re-evaluate the geographical distribution of some Synechococcus, clusters. Providing such novel insights into the long-term history of an important group of primary producers, this study illustrates the promising approach that consists in coupling molecular tools and paleolimnology to reconstruct a lake's biodiversity history.

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