Why are triploid quaking aspen (Populus tremuloides) common?

PREMISE: Quaking aspen is a clonal tree species that has mixed ploidy, often with high relative abundance of both diploids and triploids but no haploids or tetraploids. Triploids typically have low fertility, leaving their occurrence apparently unlikely from an evolutionary perspective, unless they provide a "triploid bridge" to generating higher-fitness tetraploids-which are not observed in this species. This study focused on how triploidy can be maintained in quaking aspen. METHODS: A computational model was used to simulate gamete production, sexual reproduction, asexual reproduction, parent survival, and offspring survival in a population. All parameters were assumed to be cytotype-dependent and environment-independent. Sampling methods were used to identify parameter combinations consistent with observed cytotype frequencies. RESULTS: Many processes and parameter values were sufficient to yield a moderate frequency of triploids, and very few were necessary. The most plausible route involved higher triploid survival at the parent or offspring stage and limited unreduced gamete production by either diploid or triploid parents. Triploid fertility was helpful but not necessary. CONCLUSIONS: The coexistence of diploids and triploids in quaking aspen is statistically likely and promoted by the existence of commonly observed, long-lived triploid clones. However, other mechanisms not captured by the model related to environmental variation could also occur. Further empirical data or more complex but difficult-to-parameterize models are needed to gain further insight.

Negative allometry of leaf xylem conduit diameter and double-wall thickness: implications for implosion safety.

Xylem conduits have lignified walls to resist crushing pressures. The thicker the double-wall (T) relative to its diameter (D), the greater the implosion safety. Having safer conduits may incur higher costs and reduced flow, while having less resistant xylem may lead to catastrophic collapse under drought. Although recent studies have shown that conduit implosion commonly occurs in leaves, little is known about how leaf xylem scales T vs D to trade off safety, flow efficiency, mechanical support, and cost. We measured T and D in > 7000 conduits of 122 species to investigate how T vs D scaling varies across clades, habitats, growth forms, leaf, and vein sizes. As conduits become wider, their double-cell walls become proportionally thinner, resulting in a negative allometry between T and D. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e. higher T/D ratios) was found in asterids, arid habitats, shrubs, small leaves, and minor veins. Despite the strong allometry, implosion safety does not clearly trade off with other measured leaf functions, suggesting that implosion safety at whole-leaf level cannot be easily predicted solely by individual conduits' anatomy.

Plant water use theory should incorporate hypotheses about extreme environments, population ecology, and community ecology.

Plant water use theory has largely been developed within a plant-performance paradigm that conceptualizes water use in terms of value for carbon gain and that sits within a neoclassical economic framework. This theory works very well in many contexts but does not consider other values of water to plants that could impact their fitness. Here, we survey a range of alternative hypotheses for drivers of water use and stomatal regulation. These hypotheses are organized around relevance to extreme environments, population ecology, and community ecology. Most of these hypotheses are not yet empirically tested and some are controversial (e.g. requiring more agency and behavior than is commonly believed possible for plants). Some hypotheses, especially those focused around using water to avoid thermal stress, using water to promote reproduction instead of growth, and using water to hoard it, may be useful to incorporate into theory or to implement in Earth System Models.

Characterization of dengue virus 3'UTR RNA binding proteins in mosquitoes reveals that AeStaufen reduces subgenomic flaviviral RNA in saliva.

Dengue viruses (DENV) are expanding global pathogens that are transmitted through the bite of mosquitoes, mostly Aedes aegypti. As RNA viruses, DENV rely on RNA-binding proteins (RBPs) to complete their life cycle. Alternatively, RBPs can act as restriction factors that prevent DENV multiplication. While the importance of RBPs is well-supported in humans, there is a dearth of information about their influence on DENV transmission by mosquitoes. Such knowledge could be harnessed to design novel, effective interventions against DENV. Here, we successfully adapted RNA-affinity chromatography coupled with mass spectrometry-a technique initially developed in mammalian cells-to identify RBPs in Ae. aegypti cells. We identified fourteen RBPs interacting with DENV serotype 2 3'UTR, which is involved in the viral multiplication and produces subgenomic flaviviral RNA (sfRNA). We validated the RNA affinity results for two RBPs by confirming that AePur binds the 3'UTR, whereas AeStaufen interacts with both 3'UTR and sfRNA. Using in vivo functional evaluation, we determined that RBPs like AeRan, AeExoRNase, and AeRNase have pro-viral functions, whereas AeGTPase, AeAtu, and AePur have anti-viral functions in mosquitoes. Furthermore, we showed that human and mosquito Pur homologs have a shared affinity to DENV2 RNA, although the anti-viral effect is specific to the mosquito protein. Importantly, we revealed that AeStaufen mediates a reduction of gRNA and sfRNA copies in several mosquito tissues, including the salivary glands and that AeStaufen-mediated sfRNA reduction diminishes the concentration of transmission-enhancing sfRNA in saliva, thereby revealing AeStaufen's role in DENV transmission. By characterizing the first RBPs that associate with DENV2 3'UTR in mosquitoes, our study unravels new pro- and anti-viral targets for the design of novel therapeutic interventions as well as provides foundation for studying the role of RBPs in virus-vector interactions.

Dengue virus infection modifies mosquito blood-feeding behavior to increase transmission to the host.

Mosquito blood-feeding behavior is a key determinant of the epidemiology of dengue viruses (DENV), the most-prevalent mosquito-borne viruses. However, despite its importance, how DENV infection influences mosquito blood-feeding and, consequently, transmission remains unclear. Here, we developed a high-resolution, video-based assay to observe the blood-feeding behavior of Aedes aegypti mosquitoes on mice. We then applied multivariate analysis on the high-throughput, unbiased data generated from the assay to ordinate behavioral parameters into complex behaviors. We showed that DENV infection increases mosquito attraction to the host and hinders its biting efficiency, the latter resulting in the infected mosquitoes biting more to reach similar blood repletion as uninfected mosquitoes. To examine how increased biting influences DENV transmission to the host, we established an in vivo transmission model with immuno-competent mice and demonstrated that successive short probes result in multiple transmissions. Finally, to determine how DENV-induced alterations of host-seeking and biting behaviors influence dengue epidemiology, we integrated the behavioral data within a mathematical model. We calculated that the number of infected hosts per infected mosquito, as determined by the reproduction rate, tripled when mosquito behavior was influenced by DENV infection. Taken together, this multidisciplinary study details how DENV infection modulates mosquito blood-feeding behavior to increase vector capacity, proportionally aggravating DENV epidemiology. By elucidating the contribution of mosquito behavioral alterations on DENV transmission to the host, these results will inform epidemiological modeling to tailor improved interventions against dengue.

Perforated Early Gastric Cancer: Uncommon and Easily Missed a Case Report and Review of Literature

Gastric carcinoma rarely presents as a perforation, but when it does, is perceived as advanced disease. The majority of such perforations are Stage III/IV disease. A T1 gastric carcinoma has never been reported to perforate spontaneously in English literature. We present a 56 year-old Chinese male who presented with a perforated gastric ulcer. Intra-operatively, there was no suspicion of malignancy. At operation, an open omental patch repair was performed. Post-operative endoscopy revealed a macroscopic Type 0~III tumour and from the ulcer edge biopsy was reported as adenocarcinoma. Subsequently, the patient underwent open subtotal gastrectomy and formal D2 lymphadenectomy. The final histopathology report confirms T1b N0 disease. The occurrence of a perforated early gastric cancer re-emphasises the need for vigilance, including intra-operative frozen section and/or biopsy, as well as routine post-operative endoscopy for all patients.

The use of nocturnal home hemodialysis as salvage therapy for patients experiencing peritoneal dialysis failure.

BACKGROUND: Failure of peritoneal dialysis (PD) results in poor quality of life and worsening morbidity in patients with end-stage renal disease (ESRD). Traditionally, hospital-based conventional hemodialysis has been the only option for this patient population. We hypothesized that nocturnal home hemodialysis (NHD), 3-6 sessions per week, 6-8 hours per session, is a suitable alternative salvage therapy for this vulnerable patient group. METHODS: This is a descriptive cohort study of all consecutive ESRD patients failing PD that were converted to NHD at the University Health Network and Humber River Regional Hospital from 2003 to 2005. Our primary objective was to describe the changes in clinical and biochemical indices before and after conversion from PD to NHD. RESULTS: 69 patients required transfer from PD to another form of renal replacement therapy during the period of interest. Our pilot cohort included 8 ESRD patients (5 males, 3 females; age 53 +/- 7 years). Mean duration on PD was 4.8 +/- 4.6 years. NHD delivered a higher dose of dialysis, as reflected by lower plasma creatinine concentration 1 year after beginning NHD (from 1107 +/- 312 micromol/L with PD to 649 +/- 309 micromol/L, p = 0.01) and a rise in standardized Kt/V (from 2.21 +/- 0.73 with PD to 4.49 +/- 1.92 after 6 months of NHD, to 4.51 +/- 1.77 after 1 year of NHD; p < 0.001). There was a progressive and sustained rise in plasma albumin after conversion to NHD (from 31 +/- 4 g/L with PD to 36 +/- 4 g/L after 6 months of NHD, to 39 +/- 2 g/L after 1 year of NHD; p = 0.001). Hemoglobin concentrations increased (from 102 +/- 13 to 125 +/- 7 g/L, p = 0.03), while erythropoietin requirement tended to fall (from 17500 +/- 8669 to 9197 +/- 7573 U/week). Plasma phosphate fell (from 2.1 +/- 0.6 to 1.1 +/- 0.3 mmol/L, p = 0.01) despite a decrease in phosphate binder requirement. Blood pressure profile also tended to improve after conversion to NHD. CONCLUSION: Nocturnal HD represents a promising, viable, alternative renal replacement therapy for patients experiencing PD failure. The clinical impact of transferring ESRD patients failing PD to NHD deserves further investigation.

Effects of octreotide on expression of L-type voltage-operated calcium channels and on intracellular Ca2+ in activated hepatic stellate cells / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The contractility of hepatic stellate cells (HSCs) may play an important role in the pathogenesis of cirrhosis with portal hypertension. The aim of this study was to research the effects of octreotide, an analogue of somatostatin, on intracellular Ca2+ and on the expression of L-type voltage-operated calcium channels (L-VOCCs) in activated HSCs, and to try to survey the use of octreotide in treatment and prevention of cirrhosis with portal hypertension complications.</p><p><b>METHODS</b>HSC-T6, an activated HSCs line, was plated on small glass coverslips in 35-mm culture dishes at a density of 1 x 10(5)/ml, and incubated in DMEM media for 24 hours. After the cells were loaded with Fluo-3/AM, intracellular Ca2+ was measured by Laser Scanning Confocal Microscopy (LSCM). The dynamic changes in activated HSCs of intracellular Ca2+, stimulated by octreotide, endothelin-1, and KCl, respectively, were also determined by LSCM. Each experiment was repeated six times. L-VOCC expression in HSCs was estimated by immunocytochemistry.</p><p><b>RESULTS</b>After octreotide stimulation, a significant decrease in the intracellular Ca2+ of activated HSCs was observed. However, octreotide did not inhibit the increases in intracellular Ca2+ after stimulation by KCl and endothelin-1. Moreover, octreotide did not significantly affect L-VOCC expression. These results suggest that neither L-VOCC nor endothelin-1 receptors in activated HSCs are inhibited by octreotide.</p><p><b>CONCLUSIONS</b>Octreotide may decrease portal hypertension and intrahepatic vascular tension by inhibiting activated HSCs contractility through decreases in intracellular Ca2+. The somatostatin receptors in activated HSCs may be inhibited by octreotide.</p>