Quantifying the heterogeneous heat response of Escherichia coli under dynamic temperatures

Aims: Non‐sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (T_max) were previously explained by the coexistence of two subpopulations, i.e. a stress‐sensitive and a stress‐resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing T_max, is studied. Methods and Results: Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h^?1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known T_max. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well. Conclusions: This study further confirms the existence of a stress‐resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than T_max. Significance and Impact of the Study: The growth of the small stress‐resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies.     

Cisplatin treatment of primary and metastatic epithelial ovarian carcinomas generates residual cells with mesenchymal stem cell-like profile

Epithelial mesenchymal transition (EMT) and cancer stem cells (CSC) have been associated with resistance to chemotherapy. Eighty percent of ovarian cancer patients initially respond to platinum-based combination therapy but most return with recurrence and ultimate demise. To better understand such chemoresistance we have assessed the potential role of EMT in tumor cells collected from advanced-stage ovarian cancer patients and the ovarian cancer cell line OVCA 433 in response to cisplatin in vitro. We demonstrate that cisplatin-induced transition from epithelial to mesenchymal morphology in residual cancer cells correlated with reduced E-cadherin, and increased N-cadherin and vimentin expression. The mRNA expression of Snail, Slug, Twist, and MMP-2 were significantly enhanced in response to cisplatin and correlated with increased migration. This coincided with increased cell surface expression of CSC-like markers such as CD44, α2 integrin subunit, CD117, CD133, EpCAM, and the expression of stem cell factors Nanog and Oct-4. EMT and CSC-like changes in response to cisplatin correlated with enhanced activation of extracellular signal-regulated kinase (ERK)1/2. The selective MEK inhibitor U0126 inhibited ERK2 activation and partially suppressed cisplatin-induced EMT and CSC markers. In vivo xenotransplantation of cisplatin-treated OVCA 433 cells in zebrafish embryos demonstrated significantly enhanced migration of cells compared to control untreated cells. U0126 inhibited cisplatin-induced migration of cells in vivo, suggesting that ERK2 signaling is critical to cisplatin-induced EMT and CSC phenotypes, and that targeting ERK2 in the presence of cisplatin may reduce the burden of residual tumor, the ultimate cause of recurrence in ovarian cancer patients.     

Shifts in Geographic Distribution and Antimicrobial Resistance during a Prolonged Typhoid Fever Outbreak — Bundibugyo and Kasese Districts,Uganda, 2009–2011

Background

Salmonella enterica serovar Typhi is transmitted by fecally contaminated food and water and causes approximately 22 million typhoid fever infections worldwide each year. Most cases occur in developing countries, where approximately 4% of patients develop intestinal perforation (IP). In Kasese District, Uganda, a typhoid fever outbreak notable for a high IP rate began in 2008. We report that this outbreak continued through 2011, when it spread to the neighboring district of Bundibugyo.

Methodology/Principal Findings

A suspected typhoid fever case was defined as IP or symptoms of fever, abdominal pain, and ≥1 of the following: gastrointestinal disruptions, body weakness, joint pain, headache, clinically suspected IP, or non-responsiveness to antimalarial medications. Cases were identified retrospectively via medical record reviews and prospectively through laboratory-enhanced case finding. Among Kasese residents, 709 cases were identified from August 1, 2009–December 31, 2011; of these, 149 were identified during the prospective period beginning November 1, 2011. Among Bundibugyo residents, 333 cases were identified from January 1–December 31, 2011, including 128 cases identified during the prospective period beginning October 28, 2011. IP was reported for 507 (82%) and 59 (20%) of Kasese and Bundibugyo cases, respectively. Blood and stool cultures performed for 154 patients during the prospective period yielded isolates from 24 (16%) patients. Three pulsed-field gel electrophoresis pattern combinations, including one observed in a Kasese isolate in 2009, were shared among Kasese and Bundibugyo isolates. Antimicrobial susceptibility was assessed for 18 isolates; among these 15 (83%) were multidrug-resistant (MDR), compared to 5% of 2009 isolates.

Conclusions/Significance

Molecular and epidemiological evidence suggest that during a prolonged outbreak, typhoid spread from Kasese to Bundibugyo. MDR strains became prevalent. Lasting interventions, such as typhoid vaccination and improvements in drinking water infrastructure, should be considered to minimize the risk of prolonged outbreaks in the future.     

Status and impact of rural aquaculture practice on Lake Victoria basin wetlands

Rural aquaculture in Lake Victoria basin is a fast increasing nontraditional farming activity which if not appropriately practised will lead to degradation of the wetlands. As part of a study to develop appropriate guidelines and model systems for wetlands‐based rural aquaculture in the basin a survey was conducted to assess the status and the ecological and socioeconomic impact of rural aquaculture on wetlands and wetlands communities. Aquaculture practice was found to be common but not as a major activity. Aquaculture in the wetlands can be described as a low input‐low output production activity and subsistence based on ponds under 400 m² using free seed from public agencies with hardly any supplementary feeding. Men owned most of the ponds and women only contributed to the management of the fishponds by feeding the fish. Poorly constructed ponds and loss during harvesting have led to the escape of cultured species into the wild. Introduction of nonnative species in the basin has already led to wide ranging ecological, environmental and socioeconomic changes whose impact and usefulness are still very much contentious. Repeat of such scenarios can be avoided if appropriate and science‐based models for rural aquaculture farming are developed, tested and disseminated to the communities.     

Comparative Morphology of Atalodera spp. and Thecavermiculatus spp. (Heteroderidae) with Scanning Electron Microscopy

SEM examination of second-stage juveniles (J2) and adults of Atalodera ucri, A. lonicerae (syn. Sherodera lonicerae), Thecavermiculatus sp. (undescribed new species), T. andinus, and T. crassicrustatus revealed new characters. A primitive en face pattern with six separate lips occurs in J2 of Thecavermiculatus spp. examined and in about half the polymorphic A. lonicerae. A derived en face pattern with fused adjacent submedial lips occurs in the other half of A. lonicerae and all A. ucri. Posteriorly, the J2 head of all species is annulated. The primitive en face pattern also occurs in males of A. lonicerae and Thecavermiculatus spp., and posteriorly the head of these species consists of plates. Fewer plates occur rarely in males of A. ucri. Males of A. ucri have a derived en face pattern where lips are fused and the head is annulated. Fusion of lips occurs rarely in males of A. lonicerae. Females of all species have similar derived en face patterns. En face patterns of J2 and males o f Atalodera and Thecavermiculatus may aid in species identification and to elucidate intergeneric relationships, but en face characters shared by the two genera are primitive and are not useful for demonstrating monophyly. Perineal region of females indicates the closeness of the vulval-anal distance, as a derived character, which is shared by Atalodera and most Thecavermiculatus spp. suggesting possible monophyly. T. andinus, while having a similar en face pattern to J2 of other Thecavermiculatus species, lacks the derived character of the perineal region. Phasmid openings were not observed in adults of any of the species examined.     

SEPARATING SOUTHERN BLUE WHALE SUBSPECIES BASED ON LENGTH FREQUENCIES OF SEXUALLY MATURE FEMALES

When sexually mature, Antarctic (true) blue whales are substantially longer than pygmy blue whales. To estimate the proportions of these two subspecies in various regions, Bayesian mixture models were fitted to catch length frequencies of sexually mature females. The extent of rounding to 5-ft intervals was also estimated. Antarctic blue whales dominated (99.2%) pelagic catches south of 52°S, whereas pygmy blue whales dominated (99.9%) north of 52°S and in 35°–180°E. South of 60°S, only 0.7% (95% credibility interval 0.5%–1.0%) were pygmy blue whales, lower than the 7% upper bound currently assumed. Shore-based catches from SW Africa and those before 1937 from South Georgia and the South Shetlands were estimated to contain 90%–92% Antarctic blue whales. Actual proportions were probably higher, but these data show evidence of rounding (up to 19% of records), poor length-estimation methods, and other problems. The mean length of sexually mature female Chilean blue whales (77.1 ft, 23.5 m) was intermediate between pygmy (68.9 ft, 21.0 m) and Antarctic blue whales (83.4–86.3 ft, 25.4–26.6 m). A good fit to these data was obtained only by assuming that the Chilean whales are a separate subspecies or distinctive population. This finding is also consistent with their discrete distribution, and genetic and call type differences, compared to Antarctic and pygmy blue whales.     

Evaluating effects of divided hemispheric processing on word recognition in foveal and extrafoveal displays: the evidence from Arabic

Background

Previous studies have claimed that a precise split at the vertical midline of each fovea causes all words to the left and right of fixation to project to the opposite, contralateral hemisphere, and this division in hemispheric processing has considerable consequences for foveal word recognition. However, research in this area is dominated by the use of stimuli from Latinate languages, which may induce specific effects on performance. Consequently, we report two experiments using stimuli from a fundamentally different, non-Latinate language (Arabic) that offers an alternative way of revealing effects of split-foveal processing, if they exist.

Methods and Findings

Words (and pseudowords) were presented to the left or right of fixation, either close to fixation and entirely within foveal vision, or further from fixation and entirely within extrafoveal vision. Fixation location and stimulus presentations were carefully controlled using an eye-tracker linked to a fixation-contingent display. To assess word recognition, Experiment 1 used the Reicher-Wheeler task and Experiment 2 used the lexical decision task.

Results

Performance in both experiments indicated a functional division in hemispheric processing for words in extrafoveal locations (in recognition accuracy in Experiment 1 and in reaction times and error rates in Experiment 2) but no such division for words in foveal locations.

Conclusions

These findings from a non-Latinate language provide new evidence that although a functional division in hemispheric processing exists for word recognition outside the fovea, this division does not extend up to the point of fixation. Some implications for word recognition and reading are discussed.     

CXCL10 contributes to p38-mediated apoptosis in primary T lymphocytes in vitro

CXCL10 is part of the group of interferon-stimulated genes and it plays an important role during different viral infections by inducing cell activation, chemotaxis and lymphocyte priming toward the Th1 phenotype. In this study, we investigated in vitro the effects of CXCL10 in activated human primary T lymphocytes in terms of apoptosis or survival, and delineated the signaling pathways that are involved. CXCL10, in combination with IL-2 and/or IFNα, induces apoptosis in T lymphocytes. Moreover, CXCL10-induced activation of CXCR3 also triggers pro-survival signals that can be blocked by pertussis toxin. The analysis of the downstream signaling kinases shows that apoptosis is p38 MAPK-dependent and the pro-survival signals rely on the sustained activation of PI3K and the transient activation of Akt. On the other hand, the transient activation of p44/p42 ERK did not have an impact on T lymphocyte survival. We propose an immunological model in which CXCL10, together with other co-stimulating cytokines, participates in the activation of T lymphocytes, promotes survival and expansion of certain lymphocyte subsets, and induces chemotaxis toward the infected tissues. On the other hand, CXCL10 might contribute to the triggering of apoptosis in other subsets of T lymphocytes, including those lymphocytes that were transiently activated but later lacked the appropriate sets of specific co-stimulating signals to ensure their survival.