Coarsening Dynamics of Domains in Lipid Membranes

We investigate isothermal diffusion and growth of micron-scale liquid domains within membranes of free-floating giant unilamellar vesicles with diameters between 80 and 250 μm. Domains appear after a rapid temperature quench, when the membrane is cooled through a miscibility phase transition such that coexisting liquid phases form. In membranes quenched far from a miscibility critical point, circular domains nucleate and then progress within seconds to late stage coarsening in which domains grow via two mechanisms 1), collision and coalescence of liquid domains, and 2), Ostwald ripening. Both mechanisms are expected to yield the same growth exponent, α = 1/3, where domain radius grows as time^α. We measure α = 0.28 ± 0.05, in excellent agreement. In membranes close to a miscibility critical point, the two liquid phases in the membrane are bicontinuous. A quench near the critical composition results in rapid changes in morphology of elongated domains. In this case, we measure α = 0.50 ± 0.16, consistent with theory and simulation.     

Site-dependent angiogenic cytokine production in human tumor xenografts

Tumor microenvironment plays a critical role in tumor growth, angiogenesis, and metastasis. Differences in site of tumor implantation result in differences in tumor growth, metastasis, as well as response to chemotherapy. We hypothesized that tumor-induced angiogenic growth factor production into the plasma will also be influenced by site of tumor implantation. We evaluated the site-dependent production of angiogenic growth factors in the plasma of tumor bearing animals at two different sites of implantation. Plasma levels of tumor necrosis factor-alpha (TNF-alpha), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were evaluated in nude mice bearing A2780, SKOV-3, or OVCAR-3 human ovarian tumors, as well as Panc-1, AsPC-1, or BxPC-3 human pancreatic tumors grown as subcutaneous (SC) xenografts or in the intraperitoneal (IP) cavity. Plasma VEGF and bFGF levels produced by two ovarian tumor lines and two pancreatic tumor lines were substantially higher when the tumors were implanted in the IP cavity than in the SC space. These studies indicated that the site of tumor implantation was an important determinant in the production of plasma VEGF and bFGF levels. As more and more anti-angiogenic agents are developed, the need for appropriate animal models becomes apparent. These results suggest the demand for an appropriate model for the in vivo evaluation of anti-angiogenesis.     

Circulating radioimmunoassayable inhibin during periods of transient follicle-stimulating hormone rise: secondary surge and unilateral ovariectomy

We have measured changes in circulating immunoreactive (ir-) inhibin in male and female rats using an RIA with an antiserum raised against porcine inhibin alpha (1-26)-Gly-Tyr. The same synthetic peptide was used for standards and for the preparation of tracer. Serum ir-inhibin levels were significantly higher in intact female than in intact male rats (p less than 0.001). Immunoreactive inhibin was significantly reduced in both sexes 24 h after bilateral gonadectomy (p less than 0.0001). Unilateral ovariectomy (ULO) of female rats on metestrus caused a transient decrease in serum inhibin 8 h after surgery, but levels were not significantly different from those of sham-operated controls at later times after surgery. Increases in serum FSH and LH were observed for 8-18 h after ULO. Serum ir-inhibin levels were also measured on the early morning of estrus during the secondary FSH surge. At this time, ir-inhibin levels were low, while FSH levels were high and LH levels were low. These results show that serum ir-inhibin levels in rats are decreased at times when serum FSH levels are high.     

Quality and quantity of genetic relatedness data affect the analysis of social structure

Kinship plays a fundamental role in the evolution of social systems and is considered a key driver of group living. To understand the role of kinship in the formation and maintenance of social bonds, accurate measures of genetic relatedness are critical. Genotype‐by‐sequencing technologies are rapidly advancing the accuracy and precision of genetic relatedness estimates for wild populations. The ability to assign kinship from genetic data varies depending on a species’ or population's mating system and pattern of dispersal, and empirical data from longitudinal studies are crucial to validate these methods. We use data from a long‐term behavioural study of a polygynandrous, bisexually philopatric marine mammal to measure accuracy and precision of parentage and genetic relatedness estimation against a known partial pedigree. We show that with moderate but obtainable sample sizes of approximately 4,235 SNPs and 272 individuals, highly accurate parentage assignments and genetic relatedness coefficients can be obtained. Additionally, we subsample our data to quantify how data availability affects relatedness estimation and kinship assignment. Lastly, we conduct a social network analysis to investigate the extent to which accuracy and precision of relatedness estimation improve statistical power to detect an effect of relatedness on social structure. Our results provide practical guidance for minimum sample sizes and sequencing depth for future studies, as well as thresholds for post hoc interpretation of previous analyses.     

Chemotherapy in patients with progressive, undifferentiated neuroendocrine tumors: a single-center experience

Treatment of patients with undifferentiated and histologically confirmed neuroendocrine tumors (NET) usually includes chemotherapeutic intervention. This retrospective study evaluated the outcome of 2 such chemotherapies. 18 patients (11 males; age 56.2 ± 2.5) with proven progressive disease were enrolled (mean Ki-67 34 ± 5%). Patients were treated from 2005 to 2007 with regimen A (carboplatin, etoposide, paclitaxel), and from 2007 to 2009 with regimen B (cisplatin, etoposide). This change was due to low tolerability of regimen A. The standard imaging procedure was computed tomography. 8 patients underwent treatment with regimen A (mean 3.3 ± 0.7 courses). Due to severe side effects, 3 patients had their therapy prematurely discontinued. The treatment responses of 6 patients who received more than 1 course were: 0% complete response (CR), 17% partial response (PR), 50% stable disease (SD), and 33% progressive disease (PD). The median progression free survival (PFS) was 6.7 months (range 3.2-10.0). In contrast, 12 patients received regimen B (mean 3.8 ± 0.4 courses), and none of them dropped out because of side effects. The overall responses were: 0% CR, 17% PR, 42% SD, and 42% PD. The median PFS was 6.3 months (range 2.8-26.4). The response rates of both regimes were not statistically different. Patients who were treated with regimen B demonstrated comparable PFS and less severe side effects than patients who received regimen A. However, patients need to be aware of the relatively short PFS time. In order to improve therapeutic outcome of patients with progressive undifferentiated NET, new therapeutic approaches and larger multi-center studies are needed.     

Detailed analysis of the microdiversity of Prochlorococcus populations along a North-South Atlantic Ocean transect

In order to understand how environmental factors shape the diversity of Prochlorococcus in the Atlantic Ocean, we have elucidated the microdiversity along a north–south transect. The polymerase chain reaction-restriction fragment length polymorphism analysis of the genetic diversity of rpoC1 gene fragments of Prochlorococcus at 12 sampling sites revealed a latitudinal pattern in Prochlorococcus RFLP-type diversity in the samples collected from two depths. At the depth to which 14% of surface irradiance penetrated, HLII clones dominated the stations closest to the equator. The percentage of HLI clones increased with distance from the equator and LL clones were found only at the most northern and southern stations. In contrast, deeper (1% light depth) water samples did not show any overall trend in Prochlorococcus diversity or clade dominance. Multivariate statistical analyses indicated that Prochlorococcus diversity was linked to water temperature (partially an effect of latitude) and depth (which was linked to light penetration and turbidity). Phylogenetic analysis of the sequences obtained from the 423 different environmental RFLP-types detected in this study indicated that the HLII and HLI populations were composed of a wide range of genetically different clones, while the LL Prochlorococcus clade was less diverse, although half of the samples screened in this study derived from the 1% light depth.     

Identification of a Residue Affecting Fatty Alcohol Selectivity in Wax Ester Synthase

The terminal enzyme in the bacterial wax ester biosynthetic pathway is the bifunctional wax ester synthase/acyl-coenzyme A:diacylglycerol acyltransferase (WS/DGAT), which utilizes a fatty alcohol and a fatty acyl-coenzyme A (CoA) to synthesize the corresponding wax ester. In this report, we identify a specific residue in WS/DGAT enzymes obtained from Marinobacter aquaeolei VT8 and Acinetobacter baylyi that alters fatty alcohol selectivity and kinetic parameters when modified to alternative residues.     

Changing Dietary Calcium-Phosphorus Level and Cereal Source Selectively Alters Abundance of Bacteria and Metabolites in the Upper Gastrointestinal Tracts of Weaned Pigs

Several dietary ingredients may affect the bacterial community structure and metabolism in the porcine gut and may therefore influence animals'' health and performance. This study investigated the effects of cereal source and calcium-phosphorus (CaP) level in the diet on bacterial microbiota and metabolites, nutrient intake, and gut environment in weaned pigs. Pigs (n = 8/treatment) were fed wheat-barley- or corn-based diets with an adequate or high CaP level for 14 days. Effects on microbiota in the stomach, ileum, and midcolon were assessed using quantitative PCR. Data showed that Enterobacteriaceae, Campylobacter spp., and Helicobacter spp., which all contain highly immune reactive lipopolysaccharide (LPS), were abundant at all gut sites. Diet effects on bacteria and metabolites were moderate and occurred mainly in the upper gut, whereas no effects on bacteria, fermentation products, and LPS could be observed in the colon. Differences in carbohydrate intake with corn versus wheat-barley diets selectively stimulated Bifidobacterium in the stomach and ileum. There was a growth advantage for a few bacterial groups in the stomach and ileum of pigs fed the high versus adequate CaP level (i.e., gastric Enterobacteriaceae and ileal Enterococcus, Bacteroides-Prevotella-Porphyromonas, and Campylobacter). Interestingly, gastrointestinal pH was not affected by dietary CaP level. The present findings demonstrate the stability of the bacterial community and gut environment toward dietary changes even in young pigs. The results on stimulation of gastric and ileal Bifidobacterium by corn diets may be employed in nutritional strategies to support gut health after weaning.     

Resolution of the fluorescence equilibrium unfolding profile of trp aporepressor using single tryptophan mutants.

Single tryptophan mutants of the trp aporepressor, tryptophan 19-->phenylalanine (W19F) and tryptophan 99-->phenylalanine (W99F), were used in this study to resolve the individual steady-state and time-resolved fluorescence urea unfolding profiles of the two tryptophan residues in this highly intertwined, dimeric protein. The wild-type protein exhibits a large increase in fluorescence intensity and lifetime, as well as a large red shift in the steady-state fluorescence emission spectrum, upon unfolding by urea (Lane, A.N. & Jardetsky, O., 1987, Eur. J. Biochem. 164, 389-396; Gittelman, M.S. & Matthews, C.R., 1990, Biochemistry 29, 7011-7020; Fernando, T. & Royer, C.A., 1992, Biochemistry 31, 6683-6691). Unfolding of the W19F mutant demonstrated that Trp 99 undergoes a large increase in intensity and a red shift upon exposure to solvent. Lifetime studies revealed that the contribution of the dominant 0.5-ns component of this tryptophan tends toward zero with increasing urea, whereas the longer lifetime components increase in importance. This lifting of the quenching of Trp 99 may be due to disruption of the interaction between the two subunits upon denaturation, which abolishes the interaction of Trp 99 on one subunit with the amide quenching group of Asn 32 on the other subunit (Royer, C.A., 1992, Biophys. J. 63, 741-750). On the other hand, Trp 19 is quenched in response to unfolding in the W99F mutant. Exposure to solvent of Trp 19, which is buried at the hydrophobic dimer interface in the native protein, results in a large red shift of the average steady-state emission.(ABSTRACT TRUNCATED AT 250 WORDS)