Synthesis of a folate functionalized PEGylated poly(propylene imine) dendrimer as prospective targeted drug delivery system

Based on fourth generation diaminobutane poly(propylene imine) dendrimer, a novel targeted drug nanocarrier was prepared, bearing protective PEG chains and a folate targeting ligand. As a control a PEGylated derivative without folate was also synthesized. The encapsulation and release properties of these PEGylated derivatives were investigated employing etoposide, an anticancer hydrophobic drug. Enhanced solubility of etoposide was achieved inside the dendrimeric scaffold which was subsequently released in a controlled manner. These properties coupled with specificity towards the folate receptor and the low toxicity render folate functionalized PEGylated poly(propylene imine) dendrimer promising candidate for targeted drug delivery.     

Genetically distinct pathways guide effector export through the type VI secretion system

Bacterial secretion systems often employ molecular chaperones to recognize and facilitate export of their substrates. Recent work demonstrated that a secreted component of the type VI secretion system (T6SS), haemolysin co‐regulated protein (Hcp), binds directly to effectors, enhancing their stability in the bacterial cytoplasm. Herein, we describe a quantitative cellular proteomics screen for T6S substrates that exploits this chaperone‐like quality of Hcp. Application of this approach to the Hcp secretion island I‐encoded T6SS (H1‐T6SS) of Pseudomonas aeruginosa led to the identification of a novel effector protein, termed Tse4 (t ype VI s ecretion e xported 4), subsequently shown to act as a potent intra‐specific H1‐T6SS‐delivered antibacterial toxin. Interestingly, our screen failed to identify two predicted H1‐T6SS effectors, Tse5 and Tse6, which differ from Hcp‐stabilized substrates by the presence of toxin‐associated PAAR‐repeat motifs and genetic linkage to members of the valine‐glycine repeat protein G (vgrG) genes. Genetic studies further distinguished these two groups of effectors: Hcp‐stabilized effectors were found to display redundancy in interbacterial competition with respect to the requirement for the two H1‐T6SS‐exported VgrG proteins, whereas Tse5 and Tse6 delivery strictly required a cognate VgrG. Together, we propose that interaction with either VgrG or Hcp defines distinct pathways for T6S effector export.     

The role of nocturnal vision in mate choice: females prefer conspicuous males in the European tree frog (Hyla arborea)

Nocturnal frog species rely extensively on vocalization for reproduction. But recent studies provide evidence for an important, though long overlooked, role of visual communication. In many species, calling males exhibit a conspicuous pulsing vocal sac, a signal bearing visually important dynamic components. Here, we investigate female preference for male vocal sac coloration—a question hitherto unexplored—and male colour pattern in the European tree frog (Hyla arborea). Under nocturnal conditions, we conducted two-choice experiments involving video playbacks of calling males with identical calls and showing various naturally encountered colour signals, differing in their chromatic and brightness components. We adjusted video colours to match the frogs'' visual perception, a crucial aspect not considered in previous experiments. Females prefer males with a colourful sac and a pronounced flank stripe. Both signals probably enhance male conspicuousness and facilitate detection and localization by females. This study provides the first experimental evidence of a preference for specific vocal sac spectral properties in a nocturnal anuran species. Vocal sac coloration is based on carotenoids and may convey information about male quality worthwhile for females to assess. The informative content of the flank stripe remains to be demonstrated.     

Characterizing the role of the microtubule binding protein Bim1 in Cryptococcus neoformans

During sexual development the human fungal pathogen Cryptococcus neoformans undergoes a developmental transition from yeast-form growth to filamentous growth. This transition requires cellular restructuring to form a filamentous dikaryon. Dikaryotic growth also requires tightly controlled nuclear migration to ensure faithful replication and dissemination of genetic material to spore progeny. Although the gross morphological changes that take place during dikaryotic growth are largely known, the molecular underpinnings that control this process are uncharacterized. Here we identify and characterize a C. neoformans homolog of the Saccharomyces cerevisiae BIM1 gene, and establish the importance of BIM1 for proper filamentous growth of C. neoformans. Deletion of BIM1 leads to truncated sexual development filaments, a severe defect in diploid formation, and a block in monokaryotic fruiting. Our findings lead to a model consistent with a critical role for BIM1 in both filament integrity and nuclear congression that is mediated through the microtubule cytoskeleton.     

High-throughput RNAi screening to dissect cellular pathways: A how-to guide

RNA interference (RNAi) has become a powerful tool to dissect cellular pathways and characterize gene functions. The availability of genome-wide RNAi libraries for various model organisms and mammalian cells has enabled high-throughput RNAi screenings. These RNAi screens successfully identified key components that had previously been missed in classical forward genetic screening approaches and allowed the assessment of combined loss-of-function phenotypes. Crucially, the quality of RNAi screening results depends on quantitative assays and the choice of the right biological context. In this review, we provide an overview on the design and application of high-throughput RNAi screens as well as data analysis and candidate validation strategies.     

Lower extremity fat mass is associated with insulin resistance in overweight and obese individuals: the CARDIA study

Lower extremity fat mass (LEFM) has been shown to be favorably associated with glucose metabolism. However, it is not clear whether this relationship is similar across varying levels of obesity. We hypothesized that lower amounts of LEFM is associated with higher insulin resistance (IR) and this association may vary according to weight status. Participants with available measures were examined from the Coronary Artery Risk Development in Young Adults study (CARDIA), a multi-center longitudinal study of the etiology of atherosclerosis in black and white men and women aged 38-50 years old in 2005-2006 (n = 1,579). The homeostasis model assessment of IR (HOMA(IR)) was calculated to estimate IR, regional adiposity was measured using dual energy X-ray absorptiometry (DXA), and weight status was defined according to BMI categories. Obese and overweight participants exhibited higher IR, total fat mass (FM), trunk FM (TFM), and LEFM compared to normal weight participants. After controlling for age, height, race, study center, education, smoking, and cardiorespiratory fitness (CRF), greater LEFM was significantly associated with higher IR only in normal weight men and women. Further adjustment for TFM revealed that lower LEFM was significantly associated with higher IR in overweight and obese men and women and the positive association in normal weight individuals was attenuated. These results suggest that excess adiposity in the lower extremities may attenuate the metabolic risk observed at a given level of abdominal adiposity in overweight and obese individuals. Weight status presents additional complexity since the metabolic influence of adipose tissue may not be homogenous across anatomic regions or level of obesity.