Valuable Technique (valuable + technique)

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Selected Abstracts

An investigation into the swelling properties, dimensional changes, and gel layer evolution in chitosan tablets undergoing hydration

Manuel Efentakis
Abstract The purpose of this research is to determine several characteristics of chitosan lactate in tablet form such as dimensional changes, gel evolution, swelling (liquid uptake), and erosion using an image analysis method. The examination of these characteristics will be helpful in the design of oral drug delivery systems with this polymer. It has been demonstrated that image analysis is a valuable technique, allowing the study of quantitative measurements of dimensional and core changes and gel evolution. The dimensional expansion changes of the chitosan lactate tablets were greater in water, and the crushing strength and the stirring effect affected these attributes to a limited extent. The fastest and greatest liquid uptake was observed in water, whereas the greatest erosion was observed in HCl. The thickness of the gel layer increased considerably with time up to the eighth hour, indicating the formation and development of a thick and durable gel, particularly in water. This is an essential characteristic for potential sustained drug release delivery. Consequently, this polymer appears to be a versatile material and a promising vehicle for the preparation of various oral sustained release medications and relevant devices. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:32,39, 2009; Published online in Wiley InterScience ( DOI 10.1002/adv.20147 [source]

Genome scan of Diabrotica virgifera virgifera for genetic variation associated with crop rotation tolerance

N. J. Miller
Abstract:, Crop rotation has been a valuable technique for control of Diabrotica virgifera virgifera for almost a century. However, during the last two decades, crop rotation has ceased to be effective in an expanding area of the US corn belt. This failure appears to be due to a change in the insect's oviposition behaviour, which, in all probability, has an underlying genetic basis. A preliminary genome scan using 253 amplified fragment-length polymorphism (AFLP) markers sought to identify genetic variation associated with the circumvention of crop rotation. Samples of D. v. virgifera from east-central Illinois, where crop rotation is ineffective, were compared with samples from Iowa at locations that the behavioural variant has yet to reach. A single AFLP marker showed signs of having been influenced by selection for the circumvention of crop rotation. However, this marker was not diagnostic. The lack of markers strongly associated with the trait may be due to an insufficient density of marker coverage throughout the genome. A weak but significant general heterogeneity was observed between the Illinois and Iowa samples at microsatellite loci and AFLP markers. This has not been detected in previous population genetic studies of D. v. virgifera and may indicate a reduction in gene flow between variant and wild-type beetles. [source]

A review of acoustic playback techniques for studying avian vocal duets

Sarah B. Douglas
ABSTRACT Playback experiments involve the broadcast of natural or synthetic sound stimuli and provide a powerful tool for studying acoustic communication in birds. Playback is a valuable technique for exploring vocal duetting behavior because it allows investigators to test predictions of the various hypotheses for duet function. Here, we adopt a methodological perspective by considering various challenges specific to studying duetting behavior, and highlighting the utility of different playback designs for testing duet function. Single-speaker playback experiments allow investigators to determine how duetting birds react to different stimuli, but do not simulate duets in a spatially realistic manner. Multi-speaker playback experiments are superior to single-speaker designs because duet stimuli are broadcast with spatial realism and unique and additional predictions can be generated for testing duet function. In particular, multi-speaker playback allows investigators to evaluate how birds respond to male versus female duet contributions separately, based on reactions to the different loudspeakers. Interactive playback allows investigators to ask questions about the time- and pattern-specific singing behavior of birds, and to understand how singing strategies correspond to physical behavior during vocal interactions. Although logistically challenging, interactive playback provides a powerful tool for examining specific elements of duets (such as the degree of coordination) and may permit greater insight into their functions from an operational perspective. Interactive playback designs where the investigator simulates half of a duet may be used to describe and investigate the function of pair-specific and population-wide duet codes. Regardless of experimental design, all playback experiments should be based on a sound understanding of the natural duetting behavior of the species of interest, and should aim to produce realistic and carefully controlled duet simulations. Future studies that couple playback techniques with other experimental procedures, such as Acoustic Location System recordings for monitoring the position of birds in dense vegetation or multimodal techniques that combine acoustic with visual stimuli, are expected to provide an even better understanding of these highly complex vocal displays. RESUMEN Los experimentos de reproducción de sonidos grabados involucran el uso de sonido natural o sintético y proveen una herramienta poderosa para el estudio de la comunicación acústica de las aves. La reproducción de sonidos grabados es una técnica valiosa para explorar las duetas vocales porque permite probar las predicciones de varios hipótesis sobre la función de duetas. Aquí, adoptamos una perspectiva metodológica, considerando los varios retos específicos al estudio del comportamiento de duetas y resaltando la utilidad de diferentes diseños de reproducción de sonidos grabados para probar la función de las duetas. Experimentos de reproducción de sonidos grabados hechas con un parlante permiten una determinación de como las aves que realizan duetas reaccionan a diferentes estímulos, pero no simulan las duetas de una manera espacialmente realística. Experimentos de reproducción de sonidos grabados hechas con múltiples parlantes son superiores a diseños con un solo parlante porque transmiten el sonido de una manera espacialmente realística y generan predicciones únicas y adicionales para probar la función de la dueta. En particular, la reproducción de sonidos grabados con múltiples parlantes permite una evaluación de cómo las aves responden a las contribuciones del macho y de la hembra separadamente, basado en sus reacciones a los diferentes parlantes. La reproducción de sonidos grabados interactiva permite hacer preguntas temporalmente especificas y en relación a patrones especificas sobre el comportamiento de canto. También permite entender como las estrategias de canto corresponden al comportamiento físico durante las interacciones vocales. Aunque es un reto logístico, la reproducción de sonidos grabados interactiva provee una herramienta poderosa para examinar elementos específicos de las duetas (como el grado de coordinación) y podría permitir un mayor conocimiento sobre sus funciones de una perspectiva operacional. Los diseños de la reproducción de sonidos grabados interactivas, en la cual el investigador simula la mitad de una dueta, podrían ser usadas para describir e investigar la función de los códigos de dueta específicos a una pareja y a una población. Sin importar el tipo de diseño experimental, todos los experimentos de reproducción de sonidos grabados deberían ser basadas en una buena comprensión del comportamiento natural de las duetas en la especie de interés, y deberían tener la meta de producir simulaciones de duetas realísticas y cuidadosamente controladas. Se espera que los estudios futuros cuales combinan técnicas de la reproducción de sonidos grabados con otros procedimientos experimentales, como grabaciones del Sistema de Ubicación Acústica para monitorear la posición de aves en vegetación densa, o técnicas multimodales que combinan estímulos acústicos con estímulos visuales, provean un mejor entendimiento de estos despliegues vocales altamente complejos. [source]

Rotating three-dimensional dynamic culture of adult human bone marrow-derived cells for tissue engineering of hyaline cartilage

Shinsuke Sakai
Abstract The method of constructing cartilage tissue from bone marrow-derived cells in vitro is considered a valuable technique for hyaline cartilage regenerative medicine. Using a rotating wall vessel (RWV) bioreactor developed in a NASA space experiment, we attempted to efficiently construct hyaline cartilage tissue from human bone marrow-derived cells without using a scaffold. Bone marrow aspirates were obtained from the iliac crest of nine patients during orthopedic operation. After their proliferation in monolayer culture, the adherent cells were cultured in the RWV bioreactor with chondrogenic medium for 2 weeks. Cells from the same source were cultured in pellet culture as controls. Histological and immunohistological evaluations (collagen type I and II) and quantification of glycosaminoglycan were performed on formed tissues and compared. The engineered constructs obtained using the RWV bioreactor showed strong features of hyaline cartilage in terms of their morphology as determined by histological and immunohistological evaluations. The glycosaminoglycan contents per µg DNA of the tissues were 10.01,±,3.49 µg/µg DNA in the case of the RWV bioreactor and 6.27,±,3.41 µg/µg DNA in the case of the pellet culture, and their difference was significant. The RWV bioreactor could provide an excellent environment for three-dimensional cartilage tissue architecture that can promote the chondrogenic differentiation of adult human bone marrow-derived cells. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 517,521, 2009 [source]

Determination of particle heterogeneity and stability of recombinant adenovirus by analytical ultracentrifugation in CsCl gradients

Xiaoyu Yang
Abstract Recombinant adenoviruses (rAd), widely used as vectors for gene therapy, are generally purified by column chromatography and frequently contain empty capsids and other aberrant forms of virus particles. To determine particle heterogeneity we utilized analytical ultracentrifugation (AUC) in CsCl density gradients. Preparations of three different rAd vectors were assessed. AUC was able to resolve multiple density forms including two empty capsid types in various virus preparations. One unusual density form (form V), was noninfectious and lacked protein VI. AUC was able to quantify empty capsids and monitor their removal during process development. Their relative concentrations were reduced by either addition of an immobilized zinc affinity chromatography (IZAC) step or by extension of the infection time. The Adenovirus Reference Material (ARM), a wild-type Ad5, had 2.2% empty capsids and no other detectable minor particle forms. Finally, AUC was utilized to monitor the thermal instability of the three rAd vectors via the transformations of different density forms. The vector and empty capsids containing protein IX were more stable than those without IX. Together, these results exemplify AUC in CsCl density gradients as a valuable technique for evaluating product particle heterogeneity and stability. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:746,763, 2008 [source]

Protein glycosylation analysis by HILIC-LC-MS of Proteinase K-generated N - and O -glycopeptides

Gerhild Zauner
Abstract Analysis of protein glycosylation is essential in order to correlate certain disease types with oligosaccharide structures on proteins. Here, a method for the MS characterization of site-specific protein glycosylation is presented. Using asialofetuin and fetuin as model substances, a protocol for glycopeptide dissection was developed based on unspecific proteolysis by Proteinase K. The resulting glycopeptides were then resolved by nanoscale hydrophilic interaction liquid chromatography-electrospray multistage MS. The early elution range of O -glycopeptides was clearly separated from the late elution range of N -glycopeptides. Glycopeptides were analyzed by ion trap-MS/MS, which revealed fragmentations of glycosidic linkages and some peptide backbone cleavages; MS3 spectra predominantly exhibited cleavages of the peptide backbone and provided essential information on the peptide sequence. The previously reported N - and O -glycan attachment sites of fetuin could be confirmed; moreover using our method, the occupation of a new, additional O -glycosylation site serine 296 was found. In conclusion, this approach appears to be a valuable technique for in-depth analysis of the site-specific N -glycosylation and O -glycosylation of individual glycoproteins. [source]

The value of microsurgery in liver research

Maria-Angeles Aller
Abstract The use of an operating microscope in rat liver surgery makes it possible to obtain new experimental models and improve the already existing macrosurgical models. Thus, microsurgery could be a very valuable technique to improve experimental models of hepatic insufficiency. In the current review, we present the microsurgical techniques most frequently used in the rat, such as the portacaval shunt, the extrahepatic biliary tract resection, partial and total hepatectomies and heterotopic and orthotopic liver transplantation. Hence, reducing surgical complications allows for perfecting the resulting experimental models. Thus, liver atrophy related to portacaval shunt, prehepatic portal hypertension secondary to partial portal vein ligation, cholestasis by resection of the extrahepatic biliary tract, hepatic regeneration after partial hepatectomies, acute liver failure associated with subtotal or total hepatectomy and finally complications derived from preservation or rejection in orthotopic and heterotopic liver transplantation can be studied in more standardized experimental models. The results obtained are therefore more reliable and facilitates the flow of knowledge from the bench to the bedside. Some of these microsurgical techniques, because of their simplicity, can be performed by researchers without any prior surgical training. Other more complex microsurgical techniques require in-depth surgical training. These techniques are ideal for achieving a complete surgical training and more select microsurgical models for hepatology research. [source]

Effect of maturation stage at cryopreservation on post-thaw cytoskeleton quality and fertilizability of equine oocytes

T. Tharasanit
Abstract Oocyte cryopreservation is a potentially valuable technique for salvaging the germ-line when a valuable mare dies, but facilities for in vitro embryo production or oocyte transfer are not immediately available. This study examined the influence of maturation stage and freezing technique on the cryopreservability of equine oocytes. Cumulus oocyte complexes were frozen at the immature stage (GV) or after maturation in vitro for 30 hr (MII), using either conventional slow freezing (CF) or open pulled straw vitrification (OPS); cryoprotectant-exposed and untreated nonfrozen oocytes served as controls. After thawing, GV oocytes were matured in vitro, and MII oocytes were incubated for 0 or 6 hr, before staining to examine meiotic spindle quality by confocal microscopy. To assess fertilizability, CF MII oocytes were subjected to intracytoplasmic sperm injection (ICSI) and cultured in vitro. At 12, 24, and 48 hr after ICSI, injected oocytes were fixed to examine their progression through fertilization. Both maturation stage and freezing technique affected oocyte survival. The meiosis resumption rate was higher for OPS than CF for GV oocytes (28% vs. 1.2%; P,<,0.05), but still much lower than for controls (66%). Cryopreserving oocytes at either stage induced meiotic spindle disruption (37%,67% normal spindles vs. 99% in controls; P,<,0.05). Among frozen oocytes, however, spindle quality was best for oocytes frozen by CF at the MII stage and incubated for 6 hr post-thaw (67% normal); since this combination of cryopreservation/IVM yielded the highest proportion of oocytes reaching MII with a normal spindle (35% compared to <20% for other groups), it was used when examining the effects of cryopreservation on fertilizability. In this respect, the rate of normal fertilization for CF MII oocytes after ICSI was much lower than for controls (total oocyte activation rate, 26% vs. 56%; cleavage rate at 48 hr, 8% vs. 42%: P,<,0.05). Thus, although IVM followed by CF yields a respectable percentage of normal-looking MII oocytes (35%), their ability to support fertilization is severely compromised. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source]

Metabonomic profiling of liver metabolites by gas chromatography,mass spectrometry and its application to characterizing hyperlipidemia

Shenghua Gu
Abstract The measurement of metabolites in tissues is of great importance in metabonomic research in the biomedical sciences, providing more relevant information than is available from systemic biofluids. The liver is the most important organ/tissue for most biochemical reactions, and the metabolites in the liver are of great interest to scientists. To develop an optimized extraction method and comprehensive profiling technique for liver metabolites, organic solvents of various compositions were designed using design of experiments to extract metabolites from the liver, and the metabolites were profiled by gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS). The resolved peak areas were processed by principle components analysis, partial least-squares projections to latent structures, and discriminant analysis. The results suggest the highest extraction efficiency was for methanol,water, which maximized the majority of GC/TOF-MS responses. The optimal solvent was applied to extract metabolites in liver of hyperlipidemia hamster and the control. The GC/TOF-MS profiles of liver metabolites showed obvious differences between hyperlipidemic hamsters and controls. A comparison of liver and serum data from the same animals identified common biomarkers and presented complementary information. Our results suggest that liver metabonomics is a valuable technique and that the combined analysis of systematic biofluids and local tissues is meaningful and complementary, recovering more comprehensive metabonomic data than either analysis alone. Copyright © 2009 John Wiley & Sons, Ltd. [source]