Vertebrate sex determination: a new player in the field

Sex-determining genes have been identified in flies, worms and mammals but not, until recently, in non-mammalian vertebrates. Now, a gene has been isolated from the Y chromosome of the teleost fish medaka that is functionally comparable to the mammalian testis-determining gene, Sry.     

Cis-4-hydroxypipecolic acid and 2,4-cis-4,5-trans-4,5-dihydroxypipecolic acid from Calliandra

cis-4-Hydroxypipecolic acid and 2,4-cis-4,5-trans-4,5-dihydroxypipecolic acid were isolated from leaves of Calliandra pittieri. A system for resolving the eight imino acids isolated from Calliandra is described.     

Analytical validation of quantitative immunohistochemical assays of tumor infiltrating lymphocyte biomarkers

Tumor infiltrating lymphocytes (TIL), especially T-cells, have both prognostic and therapeutic applications. The presence of CD8+ effector T-cells and the ratio of CD8+ cells to FOXP3+ regulatory T-cells have been used as biomarkers of disease prognosis to predict response to various immunotherapies. Blocking the interaction between inhibitory receptors on T-cells and their ligands with therapeutic antibodies including atezolizumab, nivolumab, pembrolizumab and tremelimumab increases the immune response against cancer cells and has shown significant improvement in clinical benefits and survival in several different tumor types. The improved clinical outcome is presumed to be associated with a higher tumor infiltration; therefore, it is thought that more accurate methods for measuring the amount of TIL could assist prognosis and predict treatment response. We have developed and validated quantitative immunohistochemistry (IHC) assays for CD3, CD8 and FOXP3 for immunophenotyping T-lymphocytes in tumor tissue. Various types of formalin fixed, paraffin embedded (FFPE) tumor tissues were immunolabeled with anti-CD3, anti-CD8 and anti-FOXP3 antibodies using an IHC autostainer. The tumor area of stained tissues, including the invasive margin of the tumor, was scored by a pathologist (visual scoring) and by computer-based quantitative image analysis. Two image analysis scores were obtained for the staining of each biomarker: the percent positive cells in the tumor area and positive cells/mm² tumor area. Comparison of visual vs. image analysis scoring methods using regression analysis showed high correlation and indicated that quantitative image analysis can be used to score the number of positive cells in IHC stained slides. To demonstrate that the IHC assays produce consistent results in normal daily testing, we evaluated the specificity, sensitivity and reproducibility of the IHC assays using both visual and image analysis scoring methods. We found that CD3, CD8 and FOXP3 IHC assays met the fit-for-purpose analytical acceptance validation criteria and that they can be used to support clinical studies.     

Stable germ line transformation of a leafy vegetable crop amaranth (Amaranthus tricolor L.) mediated by Agrobacterium tumefaciens

We have optimized a procedure for genetic transformation of a major leafy vegetable crop, Amaranthus tricolor L., using epicotyl explant co-cultivation with Agrobacterium tumefaciens. Two disarmed A. tumefaciens strains EHA 105 and LBA 4404, both carrying the binary plasmid p35SGUSINT harboring the neomycin phosphotransferase II gene (nptII) and the β-glucuronidase gene (gus), were evaluated as vector systems. The former displayed a higher transforming efficiency. Several key factors influencing the transformation events were optimized. The highest percentage of transformed shoots (24.24%) was achieved using hand-pricked epicotyl explants, a 10-min infection period, with 100 μM acetosyringone-pretreated Agrobacterium culture corresponding to OD₆₀₀???0.6 and diluted to 10⁹ cells ml^?1, followed by 4 d co-cultivation in the regeneration medium. Putative transformed explants capable of forming shoots were selected on medium supplemented with 75 μg?ml^?1 kanamycin, and transient as well as stable glucuronidase expression was determined by histochemical analysis. From a total of 48 selected shoot lines derived from independent transformation events with epicotyl explants co-cultivated with EHA 105, 32 showed positive PCR amplification for both the nptII and gus genes. Germ line transformation and transgene stability were evident in progeny of primary transformed plants (T₀). Among T₁ seedlings of 12 selected transgenic plant lines, kanamycin-resistant and kanamycin-sensitive seedlings segregated in a ratio typical of the Mendelian monohybrid pattern (3:1) as verified by the chi-square (χ ²) test. Southern hybridization of genomic DNA from kanamycin-resistant T₁ transgenic segregants to an nptII probe substantiated stable integration of the transgene. Neomycin phosphotransferase (NPTII) activity was detected in leaf protein extracts of selected T₁ transgenic plants, thereby confirming stable expression of the nptII gene.     

A secreted splice variant of the Xenopus frizzled-4 receptor is a biphasic modulator of Wnt signalling

Background

Activation of the Wnt signalling cascade is primarily based on the interplay between Wnt ligands, their receptors and extracellular modulators. One prominent family of extracellular modulators is represented by the SFRP (secreted Frizzled-related protein) family. These proteins have significant similarity to the extracellular domain of Frizzled receptors, suggesting that they bind Wnt ligands and inhibit signalling. The SFRP-type protein Fz4-v1, a splice variant of the Frizzled-4 receptor found in humans and Xenopus, was shown to augment Wnt/β-catenin signalling, and also interacts with those Wnt ligands that act on β-catenin-independent Wnt pathways.

Findings

Here we show that Xenopus Fz4-v1 can activate and inhibit the β-catenin-dependent Wnt pathway. Gain-of-function experiments revealed that high Wnt/β-catenin activity is inhibited by low and high concentrations of Fz4-v1. In contrast, signals generated by low amounts of Wnt ligands were enhanced by low concentrations of Fz4-v1 but were repressed by high concentrations. This biphasic activity of Fz4-v1 was not observed in non-canonical Wnt signalling. Fz4-v1 enhanced β-catenin-independent Wnt signalling triggered by either low or high doses of Wnt11. Antisense morpholino-mediated knock-down experiments demonstrated that in early Xenopus embryos Fz4-v1 is required for the migration of cranial neural crest cells and for the development of the dorsal fin.

Conclusions

For the first time, we show that a splice variant of the Frizzled-4 receptor modulates Wnt signalling in a dose-dependent, biphasic manner. These results also demonstrate that the cystein-rich domain (CRD), which is shared by Fz4-v1 and SFRPs, is sufficient for the biphasic activity of these secreted Wnt modulators.

     

Ultrasensitivity in Phosphorylation-Dephosphorylation Cycles with Little Substrate

Cellular decision-making is driven by dynamic behaviours, such as the preparations for sunrise enabled by circadian rhythms and the choice of cell fates enabled by positive feedback. Such behaviours are often built upon ultrasensitive responses where a linear change in input generates a sigmoidal change in output. Phosphorylation-dephosphorylation cycles are one means to generate ultrasensitivity. Using bioinformatics, we show that in vivo levels of kinases and phosphatases frequently exceed the levels of their corresponding substrates in budding yeast. This result is in contrast to the conditions often required by zero-order ultrasensitivity, perhaps the most well known means for how such cycles become ultrasensitive. We therefore introduce a mechanism to generate ultrasensitivity when numbers of enzymes are higher than numbers of substrates. Our model combines distributive and non-distributive actions of the enzymes with two-stage binding and concerted allosteric transitions of the substrate. We use analytical and numerical methods to calculate the Hill number of the response. For a substrate with phosphosites, we find an upper bound of the Hill number of , and so even systems with a single phosphosite can be ultrasensitive. Two-stage binding, where an enzyme must first bind to a binding site on the substrate before it can access the substrate''s phosphosites, allows the enzymes to sequester the substrate. Such sequestration combined with competition for each phosphosite provides an intuitive explanation for the sigmoidal shifts in levels of phosphorylated substrate. Additionally, we find cases for which the response is not monotonic, but shows instead a peak at intermediate levels of input. Given its generality, we expect the mechanism described by our model to often underlay decision-making circuits in eukaryotic cells.

Authors Summary

Dose-response curves are said to be ultrasensitive when they are sigmoidal rather than hyperbolic and often underlay cellular decision-making circuits. Zero-order ultrasensitivity is a well-known mechanism to generate sigmoidal curves in phosphorylation cycles, but one of its assumptions often implies that the substrate is more abundant than the modifying enzymes. We show that this assumption is unlikely to always hold in vivo, and we present a general model that generates ultrasensitivity when the enzymes are in excess of their substrate. The model combines conformational allosteric transitions of the substrate with two-stage binding of the enzymes: the enzymes bind first to a docking site on the substrate and then to the substrate''s phosphosites. Ultrasensitivity is generated because the kinase can bind to the fully phosphorylated form of the substrate (at its docking site) and sequester the substrate away from the phosphatase and, similarly, the phosphatase can bind to the fully dephosphorylated form of the substrate and sequester the substrate away from the kinase. The number of kinase-phosphatase competitions for the substrate determines the degree of ultrasensitivity. Finally, we show that this model can generate non-monotonic responses that peak at intermediate levels of input.     

Two silicone nontoxic fouling release coatings: Hydrosilation cured PDMS and CaCO3 filled,ethoxysiloxane cured RTV11

Two silicone coatings have been evaluated for barnacle adhesion. One coating is an unfilled hydrosilation cured polydimethylsiloxane (PDMS) network, while the other is a room temperature vulcanized (RTV), filled, ethoxysiloxane cured PDMS elastomer, RTV11^?. The adhesion strength of one species of barnacle, Balanus eburneus, to the hydrosilation coatings is in the range of 0.37–0.60 kg cm^‐2 while the corresponding range for RTV11 is 0.64–0.90 kg cm^‐2. The easier release of B. eburneus from the hydrosilation cured network compared to RTV11 is discussed in relationship to differences in bulk and surface properties. Preliminary results suggest bulk modulus may be the most important parameter in determining barnacle adhesion strength. In light or mechanical property analysis, a re‐evaluation of surface properties and chemical stability is presented.     

Incest versus abstinence: reproductive trade‐offs between mate limitation and progeny fitness in a self‐incompatible invasive plant

Plant mating systems represent an evolutionary and ecological trade‐off between reproductive assurance through selfing and maximizing progeny fitness through outbreeding. However, many plants with sporophytic self‐incompatibility systems exhibit dominance interactions at the S‐locus that allow biparental inbreeding, thereby facilitating mating between individuals that share alleles at the S‐locus. We investigated this trade‐off by estimating mate availability and biparental inbreeding depression in wild radish from five different populations across Australia. We found dominance interactions among S‐alleles increased mate availability relative to estimates based on individuals that did not share S‐alleles. Twelve of the sixteen fitness variables were significantly reduced by inbreeding. For all the three life‐history phases evaluated, self‐fertilized offspring suffered a greater than 50% reduction in fitness, while full‐sib and half‐sib offspring suffered a less than 50% reduction in fitness. Theory indicates that fitness costs greater than 50% can result in an evolutionary trajectory toward a stable state of self‐incompatibility (SI). This study suggests that dominance interactions at the S‐locus provide a possible third stable state between SI and SC where biparental inbreeding increases mate availability with relatively minor fitness costs. This strategy allows weeds to establish in new environments while maintaining a functional SI system.     

Effects of Diet Composition on Postprandial Energy Availability during Weight Loss Maintenance

Background

The major circulating metabolic fuels regulate hunger, and each is affected by dietary composition. An integrated measure of postprandial energy availability from circulating metabolic fuels may help inform dietary recommendations for weight maintenance after weight loss.

Aim

We examined the effect of low-fat (LF, 60% of energy from carbohydrate, 20% fat, 20% protein), low-glycemic index (LGI, 40%–40%-20%), and very low-carbohydrate (VLC, 10%–60%-30%) diets on total postprandial metabolic fuel energy availability (EA) during weight loss maintenance.

Methods

Eight obese young adults were fed a standard hypocaloric diet to produce 10–15% weight loss. They were then provided isocaloric LF, LGI, and VLC diets in a randomized crossover design, each for a 4-week period of weight loss maintenance. At the end of each dietary period, a test meal representing the respective diet was provided, and blood samples were obtained every 30 minutes for 5 hours. The primary outcome was EA, defined as the combined energy density (circulating level×relative energy content) of glucose, free fatty acids, and β-hydroxybutyrate. Secondary outcomes were individual metabolic fuels, metabolic rate, insulin, glucagon, cortisol, epinephrine, and hunger ratings. Respiratory quotient was a process measure. Data were analyzed by repeated-measures analysis of variance, with outcomes compared in the early (30 to 150 min) and late (180 to 300 min) postprandial periods.

Results

EA did not differ between the test meals during the early postprandial period (p = 0.99). However, EA in the late postprandial period was significantly lower after the LF test meal than the LGI (p<0.0001) and VLC (p<0.0001) test meals. Metabolic rate also differed in the late postprandial period (p = 0.0074), with higher values on the VLC than LF (p = 0.0064) and LGI (p = 0.0066) diets.

Conclusion

These findings suggest that an LF diet may adversely affect postprandial EA and risk for weight regain during weight loss maintenance.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00315354","term_id":"NCT00315354"}}NCT00315354