Ultraporous poly(l-lactide) scaffolds prepared with quaternary immiscible polymer blends modified by copolymer brushes at the interface

The activity of polystyrene-block-poly(l-lactide) (PS-b-PLLA) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer brushes located at a PS/PLLA interface were employed as a route to control the final microstructure of 95% void volume, ultraporous PLLA scaffolds. The latter were initially prepared from melt-processed quaternary blends of ethylene propylene diene rubber/poly(?-caprolactone)/polystyrene/poly(l-lactide) (EPDM/PCL/PS/PLLA) 45/45/5/5%vol. modified with the diblock copolymers. The blends display a layer comprised of the PS and PLLA phases located at the interface of the co-continuous EPDM and PCL phases. When the PS-b-PLLA copolymer is added, sub-micrometric PLLA droplets are encapsulated within the PS continuous layer phase. In comparison, both the PS and PLLA phases compete for the encapsulation process when the PS-b-PMMA is used, indicating that the microstructure of the PLLA phase can be fine-tuned with an adequate choice of interfacial modifier. These effects were investigated by analyzing the microstructure of ternary high-density polyethylene (HDPE)/PS/PMMA 80/10/10%vol. blends displaying PS/PMMA shell/core composite droplets in a HDPE matrix. An inversion of the shell/core structure is observed when the PS-b-PLLA copolymer is used to compatibilize the PS/PMMA interface, whereas no such restructuring occurs with the PS-b-PMMA. These effects are explained by the activity and swelling powers of the copolymer brushes. For the EPDM/PCL/PS/PLLA quaternary systems modified with the PS-b-PMMA, the PLLA homopolymer phase significantly penetrates and swells the PMMA blocks due to their mutual high affinity, as compared to the classical like-prefers-like compatibilization approach. The swelling of the blocks will tend to bend the interface toward the PS phase in order to minimize the lateral compression of the PMMA blocks. A similar effect explains the reversal of the PS/PMMA shell/core structure in the HDPE/PS/PMMA ternary system. This level of control ultimately leads to quite significant differences in microstructures and surface textures for the PLLA scaffolds.     

Structural Investigations on the Anti‐HIV G‐Quadruplex‐Forming Oligonucleotide TGGGAG and Its Analogues: Evidence for the Presence of an A‐Tetrad

Several anti‐HIV aptamers adopt DNA quadruplex structures. Among these, “Hotoda's aptamer” (base sequence TGGGAG) was one of the first to be discovered. Although it has been the topic of some recent research, no detailed structural investigations have been reported. Here we report structural investigations on this aptamer and analogues with related sequences, by using UV, CD, and NMR spectroscopy as well as electrophoretic techniques. The addition of a 3′‐end thymine has allowed us to obtain a single, investigable quadruplex structure. Data clearly point to the presence of an A‐tetrad. Furthermore, the effects of the incorporation of an 8‐methyl‐2′‐deoxyguanosine at the 5′‐end of the G‐run were investigated.     

Expanding the Potential of G‐Quadruplex Structures: Formation of a Heterochiral TBA Analogue

In order to expand the potential applications of G‐quadruplex structures, we explored the ability of heterochiral oligodeoxynucleotides based on the thrombin‐binding aptamer (TBA) sequence to fold into similar complexes, with particular focus on their resistance in biological environments. A combination of CD and NMR techniques was used. Similarly to TBA, the ODN ggTTggtgtggTTgg (lower case letters indicate L residues) is able to fold into a chair‐like antiparallel G‐quadruplex structure, but has a slightly higher thermal stability. The discovery that heterochiral ODNs are able to form stable G‐quadruplex structures opens up new possibilities for their development in several fields, as aptamers, sensors and, as recently shown, as catalysts for enantioselective reactions.     

Rule-based Adaptation of Web Information Systems

Mobile devices provide a variety of ways to access information resources available on the Web and a high level of adaptability to different aspects of the context (such as the device capabilities, the network QoS, the user preferences, and the location) is strongly required in this scenario. In this paper, we present a rule-based approach supporting the automatic adaptation of content delivery in Web Information Systems. The approach relies on the general notions of profile and configuration. The former is used to model a variety of context characteristics in a uniform way. The latter describes, in abstract terms, how to build the various levels of a suitable Web interface (content, navigation and presentation). We propose an original notion of adaptation rule that can be used to specify, in a declarative way, how to build a configuration that satisfies the requirements of adaptation for a profile. The evaluation process defined for these rules supports: (1) the handling of many separately specified adaptation requirements according to different aspects of the context, possibly not fixed in advance, and (2) their integration into one coherent recipe for adaptation. We also describe the architecture and functionality of a prototype implementing the proposed approach and illustrate experimental results supporting its flexibility and efficiency. A preliminary version of this paper appears in the Proceedings of Seventh International Conference on Mobile Data Management (MDM’06) Nara, Japan, May 10–12, 2006.     

Is brown adipose tissue a store of long chain polyunsaturated fatty acids during postnatal developing brain?

Mammals along their early postnatal period develop a substantial amount of a very active brown adipose tissue (BAT). Through this work we explored the possibility that BAT may function as a long chain polyunsaturated fatty acids reservoir (LC-PUFA) during the rapid growth of brain structures. In new born rats 1, 6, 12 and 20 days old, we analyzed fatty acid percentage of triglycerides (TG) and phospholipid fractions, and the absolute amount of TG. In 6 day old rats we also evaluated the extend of further desaturation of 1-14C linoleic acid administered by intraperitoneal injection. Results demonstrated a drastic increase of TG concentration during experimental period (1,5; 40; 118; 120 mg/g wet weight) and LC-PUFA percentage was higher in "1 and 6" than "12 and 20" days old rats (16-17% vs 5%). Our results showed that BAT stored important amounts of LC-PUFA. On the other hand, 1-14C linoleic acid incorporation was higher in liver than BAT. In contrast, the desaturated products of 1-14C linoleic acid /1-14C linoleic acid ratio was greater in BAT than liver (>4). This could indicate that BAT synthesizes LC-PUFA in addition to store it. In summary we demonstrated than BAT is an important reservoir of LC-PUFA during postnatal brain growth.     

Development of a multiplex PCR for rapid detection of verocytotoxin-producing Escherichia coli O26 in raw milk and ground beef

Verocytotoxin-producing Escherichia coli (VTEC) O26 is an emergent pathotype that has caused an increasing number of sporadic cases and outbreaks of gastroenteritis, hemorrhagic colitis, and hemolytic uremic syndrome in the United States and Europe. Many cases are associated with the consumption of milk and undercooked or fermented meats. The stx(2) strains of VTEC O26 seem to be more likely to cause human infections than isolates expressing only stx(1). The isolation and identification of VTEC O26 from foods is labor intensive and time-consuming. We developed a multiplex PCR (M-PCR) assay for the identification and characterization of E. coli O26 VTEC and its detection in raw milk and ground beef. The method is based on the amplification of the wzx, stx(1), and stx(2) genes for the simultaneous detection of the O26 antigen and verocytotoxin types 1 and 2. This M-PCR assay had a sensitivity of 10(8) CFU/ml when applied to a bacterial suspension and of 10(6) CFU/ml or g when applied to both inoculated milk and minced beef samples. This M-PCR assay also was highly specific, and results were consistently negative for negative controls (nonpathogenic E. coli strains, uninoculated milk and beef samples, and samples inoculated with the nontarget microorganisms). This method could be used for the rapid detection of E. coli O26 VTEC from foods and for the rapid identification and characterization of clinical and environmental isolates.     

Short-Term Stability of Whole Blood Polyunsaturated Fatty Acid Content on Filter Paper During Storage at −28 °C

Finger or heel‐pricked blood sampling for fatty acid analysis is suitable especially in newborn infants where blood sampling is difficult and phlebotomy for research can be unethical. The aim of this study was to evaluate dried blood long chain polyunsaturated fatty acids (LC‐PUFA) stability during storage at ?28 °C. We collected 12 blood cord samples that were analyzed immediately after blood drawing, with and without drying the blood on filter paper. Dried samples were then analyzed 7 days and 1, 3, and 6 months after collection. Butylated hydroxytoluene was added to all samples. Fatty acid composition and ¹³C enrichment were measured by gas chromatography and by gas chromatography‐isotope ratio mass spectrometry, respectively. The fatty acid composition, expressed in mol%, of the major LC‐PUFA at day 7 was not statistically different from time 0, however lower values were found by the first month of storage. The ¹³C enrichment of 20:4n‐6 and 22:6n‐3 did not differ during the whole study period. LC‐PUFA analysis from dried umbilical cord blood in neonates should be performed within a week, major losses of LC‐PUFA occur afterwards. However, fatty acids obtained from dried blood maintain their ¹³C enrichment value for up to 6 months and thus these samples are suitable for natural abundance isotopic studies.