bluuebunny/crossref_metadata_2025 huggingface dataset:
A Retrospective Analysis of Placentas From Twin Pregnancies Derived From Assisted Reproductive Technology
Authors: Chan Owen T. M. , Mannino Frank L. , Benirschke Kurt
Published: April 2007

There are conflicting studies associating twin pregnancies derived from assisted reproductive technology (ART) with preterm birth, low birthweight, and other negative outcomes. This work investigates whether ART is linked with any placental pathology, given that placentation significantly influences fetal development. A 5-year, retrospective cohort study was conducted on placentas from twin pregnancies. The placental information from 417 patients was divided into two groups: placentas derived from ART and placentas derived from spontaneous pregnancies (non-ART). Available clinical information and pathologic findings from both groups then were compared. There was no statistical difference in the prevalence of placental pathology between the non-ART and ART cohorts (i.e., cord insertion, single umbilical artery, cord knot, retroplacental hemorrhage, infarction, vasculopathy, vascular anastomoses, chorangiosis, villitis, deciduitis, chorioamnionitis, meconium staining). However, 8% of ART multiple pregnancies were monochorionic. While monochorionicity is a known risk factor for adverse obstetric and neonatal outcomes, the rate of monochorionic placentation did not increase as a result of ART. Nevertheless, it is interesting to note that this small percentage of monochorionic placentation occurred in the ART cohort despite the implantation of individual embryos. Overall, the data suggests that ART does not have a role in the pathologic placentation of twin pregnancies.
On the Possible Cause of Monozygotic Twinning: Lessons From the 9-Banded Armadillo and From Assisted Reproduction
Authors: Blickstein Isaac , Keith Louis G.
Published: April 2007

Available hypotheses proposed to explain the mechanism of zygotic splitting fail to explain why monozygotic twins are more prevalent after all methods of assisted reproduction and which structure is likely to control this phenomenon. Arguably, a small proportion of oocytes might have an inborn propensity to undergo splitting upon fertilization leading to the constant prevalence of spontaneous monozygotic conceptions among different populations. Ovarian stimulation would then predictably increase the number of available splitting-prone oocytes and consequently would increase the chance for such oocytes to develop into monozygotic twins, leading to a ‘dose’-dependent relationship between monozygosity rates and the combined effect of infertility treatment. Embryonic division into 2 distinct cell lines begins and accommodates within an intact zona pellucida that controls the process by preventing ill-timed hatching. Human fertilized oocytes are able to undergo 2 binary fissions, just as is the case for the 9-banded armadillo (the only other mammal that produces monozygotic quadruplets) and to give rise to a variety of combinations of monozygotic pregnancies. This hypothetical explanation does not negate the already existing and genetically sound hypotheses, but places them into a broader perspective that respects recent observations from modern infertility treatment.
Parenting Stress and Psychosocial Health in Mothers with Twin–Twin Transfusion Syndrome Managed with Laser Surgery: A Preliminary Study
Authors: Edwards Dawn M. , Gray Peter H. , Soong Barbara , Chan Fung-Yee , Cincotta Robert
Published: April 2007

Twin–twin transfusion syndrome (TTTS) is a severe complication of twin pregnancies with high risk for perinatal mortality and long-term morbidity. This cross-sectional cohort study aimed to determine parenting stress and psychosocial health in mothers with a pregnancy complicated by TTTS that had been managed with laser ablation of communicating placental vessels. Questionnaires were sent to the mothers for completion: Parenting Stress Index (PSI), Edinburgh Postnatal Depression Scale (EPDS) and a semi-structured questionnaire related to mental health problems and support received from health professionals. Thirty-seven mothers were sent questionnaires with 32 being returned. The results showed that 47% of women had total scores equal to or greater than the 85th percentile on the PSI, which is considered abnormally high. Twenty-six per cent of mothers had evidence of depression on the EPDS. Mothers of children with prolonged medical conditions or neurological problems had significantly higher scores (p=.011). Parenting stress was not associated with high scores on the EPDS. Medical and midwifery staff were considered to provide high levels of support, with social work providing none or low levels of support. In conclusion, women whose TTTS pregnancy was managed by laser surgery have high levels of parenting stress. As the results showed that parenting stress cannot be predicted at the time of hospitalization, it is suggested that more support should be provided in hospital with further follow-up after discharge.
Mechanical properties and creep behavior of lyocell fibers by nanoindentation and nano-tensile testing
Authors: Lee Seung-Hwan , Wang Siqun , Pharr George M. , Kant Matthew , Penumadu Dayakar
Published: April 2007

Mechanical and time-dependent mechanical properties of lyocell fibers have been investigated as a function of depth at a nano-scale level in longitudinal and transverse directions. The nanoindentation technique was applied and extended to continuous stiffness measurement. Lyo10 and Lyo13 lyocell fibers were investigated. The individual fiber properties were measured using a nano-tensile testing system to obtain reference data for mechanical properties. The hardness and elastic modulus obtained from nanoindentation test are described using two different approaches. The first uses mean values for a depth of 150–300 nm, while the second uses unloading values at the final indentation depth. There is no significant difference between modulus values inferred from nanoindentation and those obtained from single fiber tensile testing. Hardness and elastic modulus values were higher in the longitudinal direction than those in the transverse direction and Lyo13 values were higher than those for Lyo10 in both directions. The time-dependent mechanical properties were also investigated as a function of the holding time. Increasing the holding time led to an increase in indentation displacement and a decrease in hardness. Stress exponents were calculated from the linear relationship between contact stress and contact strain using a power-law creep equation.
Changes in physical, mechanical and chemical properties of wood during sterilisation by gamma radiation
Authors: Despot Radovan , Hasan Marin , Brischke Christian , Welzbacher Christian Robert , Rapp Andreas Otto
Published: April 2007

Gamma irradiation, which is an easy, fast and effective method for wood sterilisation, changes molecular structures not only in pest cells, but also in wood cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness, as demonstrated by experimental data. The influence of gamma radiation on maximum swelling (αMAX), resistance to impact milling (RIM), and the total amount of water-soluble carbohydrates (TSC) was investigated. Cobalt (60Co) was used as a gamma source and Scots pine wood (Pinus sylvestris L.) was irradiated at doses of 30, 90 and 150 kGy. A strong linear correlation was found between TSC and radiation dosage. Leached irradiated specimens showed significantly greater TSC content than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters improved. Gamma radiation had no significant effect on αMAX and the time elapsed after irradiation did not influence αMAX, RIM or TSC.
Editorial
Authors: Spranger Tade M
Published: April 2007

Both the confidence of the international scientific community and the public hopes risen by stem cell technology were shaken one year ago by what is called the Korean stem cell scandal. The forgery conducted by one of Korea's major scientists led to several fundamental questions. Some of them refer to ethical aspects, while others concern legal facets: Are law and ethics really able to control scientific research in the field of biotechnology and biomedicine ? Which effects are exerted by the ”publish or perish” policy as well as the commercialisation of basic research on the quality of scientific work ? Is the practical relevance of stem cell research overestimated ? Has the relationship between principal researchers and their staff to be reviewed or even controlled according to tightened ethical and legal standards ?
Enhancement as a Legal Challenge
Authors: Beck Susanne
Published: April 2007

“What better way to start the new year than with a new you?” comments Liz Dale, Transform's commercial manager, on the recent British fashion to give away cosmetic surgeries for Christmas. Creating a “new you” has become a remarkable development in the western world. In 2005, around 1 500 000 surgical cosmetic procedures have taken place among Americans, and almost 3 300 000 were treated with Botox. In many countries cosmetic surgery is one of the few medical areas which is still profitable. But beauty is just one human characteristic amenable perfecting: the enhancement of mental abilities with drugs has already become a serious problem in universities across the U.S., and the progress of genetic technology might pave the way to create a perfect next generation.
Biotechnology Investment in Vietnam
Authors: Hilmer Sarah E
Published: April 2007

On 11 January 2007 Vietnam became the World Trade Organisation's (WTO) 150th member. WTO members completed their task on 26 October 2006 by accepting the documents indicating Vietnam's obligations and rights. The documents reached General Council which approved Vietnam's membership on the 7 November 2006. Vietnam informed the WTO on 12 December 2006 that it has ratified its membership agreement, and it thereby became a full member after 30 days of ratifying the agreement, which was on the 11 January 2007.
Turbidity Tolerances of Great Lakes Coastal Wetland Fishes
Authors: Trebitz Anett S. , Brazner John C. , Brady Valerie J. , Axler Richard , Tanner Danny K.
Published: April 2007

Despite recent interest in assessing the condition of fish assemblages in Great Lakes coastal wetlands and a concern for increasing turbidity as a major stressor pathway influencing these ecosystems, there is little information on fish tolerance or intolerance to turbidity on which to base wetland assessment metrics. Existing studies have borrowed tolerance designations from the stream literature, but they have not confirmed that the designations apply to Great Lakes wetlands or that designations based on tolerance to degradation in general apply to turbidity in particular. We used a published graphical method to determine turbidity tolerances of Great Lakes fishes based on their pattern of occurrence and relative abundance across coastal wetlands spanning a turbidity gradient. Fish composition data were obtained from fyke-net and electrofishing surveys of 75 wetlands along the U.S. shoreline of the Laurentian Great Lakes, representing a turbidity range of approximately 0–110 nephelometric turbidity units (NTU). Turbidity levels of 10, 25, and 50 NTU (corresponding to the thresholds in use for state water quality criteria) were used to separate fish into tolerance classes. We found that the turbidity tolerances of many species in Great Lakes wetlands differed from the published tolerances to general degradation in streams. Also, the tolerance levels for many species were unclear owing to the species' infrequent occurrence. Although many of the wetlands sampled had quite low turbidity, a large proportion of the fish species were tolerant or moderately tolerant to turbidity and very few were intolerant, suggesting that enumerating intolerant species may not be a useful metric or that the metric should be expanded to include moderately intolerant species. Our study lays the foundation for additional turbidity indicator development efforts for Great Lakes coastal wetlands.
An Improved Sibling Model for Forecasting Chum Salmon and Sockeye Salmon Abundance
Authors: Haeseker Steven L. , Dorner Brigitte , Peterman Randall M. , Su Zhenming
Published: April 2007

The sibling model is often one of the best methods for calculating preseason forecasts of adult return abundance (recruits) for populations of Pacific salmon Oncorhynchus spp. This model forecasts abundance of a given age-class for a given year based on the abundance of the previous age-class in the previous year. When sibling relations fit historical data well, the sibling model generally performs better than other forecasting methods, such as stock–recruitment models. However, when sibling relations are weak, better forecasts are obtained by other models, such as naïve models that simply use an historical average. We evaluated the performance of a hybrid model that used quantitative criteria for switching between a sibling model and a naïve model when generating forecasts for 21 stocks of chum salmon O. keta and 37 stocks of sockeye salmon O. nerka in the northeastern Pacific Ocean. Compared with the standard sibling model, the hybrid model reduced the root mean square error (RMSE) of forecasts by an average of 27% for chum salmon stocks and 28% for sockeye salmon stocks. Compared with a naïve model, the hybrid model reduced the RMSE of forecasts by an average of 16% for chum salmon stocks and 15% for sockeye salmon stocks. Our results suggest that hybrid models can improve preseason forecasts and management of these two species.
Effect of Omega‐3 Fatty Acid Supplementation on the Arachidonic Acid: Eicosapentaenoic Acid Ratio
Authors: Burns Tammy , Maciejewski Stephanie R. , Hamilton William R. , Zheng Margaret , Mooss Aryan N. , Hilleman Daniel E.
Published: April 2007

Study Objectives. To determine the baseline arachidonic acid: eicosapentaenoic acid (AA:EPA) ratio in patients with coronary artery disease and healthy subjects, and whether supplementation of omega‐3 fatty acids, administered as fish oil capsules, affects this ratio.

Design. Prospective, open‐label trial.

Setting. University‐affiliated cardiology clinic.

Subjects. Thirty patients with stable coronary artery disease (CAD) and 30 healthy subjects.

Intervention. All participants received omega‐3 fatty acids 1.5 g/day for 4 weeks, followed by 3 g/day for an additional 4 weeks.

Measurements and Main Results. For each participant, a lipid profile was determined at baseline and after 4 weeks of treatment with each dose. Other laboratory results analyzed were serum AA:EPA ratios, high‐sensitivity C‐reactive protein (hs‐CRP) levels, and blood glucose levels. Mean ± SD baseline AA:EPA ratios were 39.6 ± 19.0 in healthy subjects and 23.7 ± 12.5 in patients with CAD. These ratios decreased significantly in both groups after treatment with 1.5 g/day of omega‐3 fatty acids: 9.0 ± 4.2 in healthy subjects and 10.3 ± 8.8 in patients with CAD. After treatment with 3 g/day, the ratios were further reduced: 5.1 ± 3.2 in healthy subjects and 4.9 ± 2.6 in patients with CAD. Supplementation with omega‐3 fatty acids did not significantly affect hs‐CRP, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol, or blood glucose levels. Triglyceride levels were not reduced in patients with CAD but were significantly decreased in healthy subjects (by 20% decrease with omega‐3 fatty acids 1.5 g/day and by 32% decrease with 3 g/day).

Conclusion. Treatment with omega‐3 fatty acids significantly reduced AA:EPA ratios in both healthy subjects and in patients with stable CAD. The treatment had no effect on hs‐CRP levels in either group, and it reduced triglyceride levels in healthy subjects but not in patients with CAD.
Role of Prescription Omega‐3 Fatty Acids in the Treatment of Hypertriglyceridemia
Authors: McKenney James M. , Sica Domenic
Published: April 2007

A prescription form of omega‐3 fatty acids has been approved by the United States Food and Drug Administration as an adjunct to diet for the treatment of very high triglyceride levels. The active ingredients of omega‐3 fatty acids are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are responsible for the triglyceride lowering. The prescription product contains a total of 0.84 g of these two active ingredients in every 1‐g capsule of omega‐3 fatty acids. The total EPA and DHA dose recommended for triglyceride lowering is approximately 2–4 g/day Fish oil products containing EPA and DHA are available without a prescription, but the American Heart Association advises that therapy with EPA and DHA to lower very high triglyceride levels should be used only under a physician's care. In patients with triglyceride levels above 500 mg/dl, approximately 4 g/day of EPA and DHA reduces triglyceride levels 45% and very low‐density lipoprotein cholesterol levels by more than 50%. Low‐density lipoprotein cholesterol levels may increase depending on the baseline triglyceride level, but the net effect of EPA and DHA therapy is a reduction in non–high‐density lipoprotein cholesterol level. Alternatively, patients may receive one of the fibrates (gemfibrozil or fenofibrate) or niacin for triglyceride lowering if their triglyceride levels are higher than 500 mg/dl. In controlled trials, prescription omega‐3 fatty acids were well tolerated, with a low rate of both adverse events and treatment‐associated discontinuations. The availability of prescription omega‐3 fatty acids, which ensures consistent quality and purity, should prove to be valuable for the medical management of hypertriglyceridemia.
Reengineering Clinical Operations in a Medical Practice to Optimizethe Management of Anemia of Chronic Kidney Disease
Authors: Joy Melanie S. , Candiani Corina , Vaillancourt Beverly A. , Chin Hyunsook , Hogan Susan L. , Falk Ronald J.
Published: April 2007

Objectives. To describe the clinic design, clinical evaluations, and treatment approaches used in a multidisciplinary clinic for management of anemia of chronic kidney disease (CKD), and to evaluate several selected clinical outcomes associated with this approach to anemia management.

Setting. University‐affiliated, division of nephrology, outpatient multidisciplinary model CKD clinic headed by a clinical pharmacist.

Patients. One hundred sixty‐six patients with anemia of CKD who were referred by nephrologists and primary care providers to the multidisciplinary clinic from March 1, 2002–July 31, 2004.

Measurements and Main Results. Patients received darbepoetin alfa dosed on an every‐other‐week basis. If patients were already receiving once‐weekly recombinant human erythropoietin (r‐HuEPO), the darbepoetin alfa dose was calculated by using the darbepoetin alfa package insert conversion table. If patients were naïve to previous erythropoietic therapy, the darbepoetin alfa dose was either 60 μg or 0.7 μg/kg. The dose and frequency of darbepoetin alfa and oral iron supplements were adjusted to achieve the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) targets for hemoglobin levels and iron measures. The primary outcome analyzed was the proportion of patients with at least 30 days of treatment who achieved a target hemoglobin level of 11.0 g/dl or greater. Of 128 patients who received at least 30 days of treatment, 100 (78%) attained the hemoglobin level (mean ± SD 11.7 ± 7 g/dl). Ninety‐nine of 128 patients were originally naïve to erythropoietic therapy; 77 (78%) of these 99 patients achieved the hemoglobin target in a mean ± SD of 7.9 ± 7.5 weeks. These data contrast with the data of 29 patients seen in the year previous to the reengineered clinic process, whereby only 12 (41%) of these comparable patients reached hemoglobin target with r‐HuEPO therapy. Of the 77 previously erythropoietic‐naïve patients, 82% were receiving darbepoetin alfa every other week, 14% every 3 weeks, and 4% every 4 weeks at the time the hemoglobin target was achieved. Oral iron administration significantly increased the chance of achieving the K/DOQI targets for hemoglobin and iron.

Conclusion. Redefining roles and practices of members of a clinical practice and reengineering processes for anemia management were effective in achieving and maintaining target hemoglobin and iron levels.
Iontophoretic Drug Delivery System: Focus on Fentanyl
Authors: Herndon Chris M.
Published: April 2007

Fentanyl iontophoretic transdermal system (ITS) is a novel, patient‐activated drug delivery device used for the management of acute postoperative pain in the hospital setting. This credit‐card–sized device uses an imperceptible current of 170 milliampere to actively deliver a fentanyl hydrochloride 40‐μg dose into the vasculature over a 10‐minute interval. The unit is programmed to lock out further doses after either 80 doses or 24 hours, whichever is reached first. When comparing fentanyl ITS with intravenously administered fentanyl, serum concentrations differ significantly at 10 minutes after the initial dose is administered: 0.1 ng/ml for fentanyl ITS versus 0.7 ng/ml for intravenous fentanyl. Fentanyl ITS absorption increases in a time‐dependent fashion over the first 10 hours of dosing. Other pharmacokinetic parameters of fentanyl ITS are comparable to those of intravenous fentanyl after 24 hours (maximum concentration 1.37 and 1.82 μg/ml, time to maximum concentration 0.65 and 0.58 hr, and area under the concentration‐time curve at 23–24 hrs 1.23 and 1.34 μg•hr/ml for fentanyl ITS and intravenous fentanyl, respectively). This new technology exhibited superior analgesia compared with placebo in two placebo‐controlled studies that used time to exit as a primary end point. In addition, fentanyl ITS proved equivalent to patient‐controlled analgesia with intravenous morphine. Although adverse effects were congruent with those expected from pure‐agonist opioids, subjects assigned to the ITS group did experience a higher rate of mild, clinically nonsignificant erythema at the system placement site. Judicious monitoring for opioid‐induced respiratory depression is recommended for fentanyl ITS, although this adverse effect has not been observed in clinical trials. Fentanyl ITS may provide another useful alternative in the management of acute postoperative pain.
Leuconostoc Species—Associated Endocarditis
Authors: Starr Jessica A.
Published: April 2007

Leuconostoc species are gram‐positive cocci belonging to the Streptococcaceae family. The species were generally regarded as nonpathogenic and of little importance in clinical microbiology until several occurrences of Leuconostoc infections were reported in the literature. Unlike many gram‐positive bacteria, Leuconostoc species commonly demonstrate high‐level resistance to vancomycin, with preserved sensitivity to most other antibacterial agents. We describe a 55‐year‐old man who developed endocarditis caused by Leuconostoc species sensitive to vancomycin. The patient received an aortic valve replacement and was treated with penicillin G and gentamicin; he experienced no further complications.
Indolyl substituted 4-oxobut-2-enoic acids. Synthesis and aza-Michael additions
Authors: Berkeš Dušan , Koren̆ová Anna , Šafár̆ Peter , Horváthová Helena , Prónayová Nadežda
Published: April 2007

The synthesis of three new substituted 4-hetereoaryl-4-oxobut-2-enoic acids with indole ring substitutedin positions 3-, 5- and 7- is described. The addition of these Michael acceptors to 4-(1-phenylsulphonylpyrrol-3-yl)-4-oxobut-2-enoic acid in conjugate addition was explored using both racemic and chiral amines. In tandem with the crystallization-induced asymmetric transformation (CIAT) protocol the effective methodology for the synthesis of enantiomerically highly enriched substituted 2-amino-4-heteroaryl-4-oxobutanoic acids as multifunctional homotryptophan analogues was developed.
Glycoproteomics Using Chemical Immobilization
Authors: Zhang Hui
Published: April 2007

Protein glycosylation is prevalent in proteins destined for extracellular environments, e.g., transmembrane proteins, cell surface proteins, and secreted proteins in tissues and body fluids. These also are the proteins that are most easily accessible for diagnostic and therapeutic purposes. This unit describes methods for solid‐phase extraction of glycopeptides and subsequent identification of glycopeptides as well as glycosylation sites. The extraction is based on the conjugation of glycopeptides to a solid support, using hydrazide chemistry, and the specific release of formerly glycosylated peptides. The recovered peptides are then identified by tandem mass spectrometry. The methods are applied to the analysis of proteins from cells, body fluids, and tissues.
Histochemical Methods for the Detection of Apoptosis in the Nervous System
Authors: Oo Tinmarla Frances , Burke Robert E.
Published: April 2007

Neuroscientists often need to detect neuron death at the light microscope level in tissue sections derived from animal models of neurological disease. In many instances there is a need to detect apoptosis, the most common morphology of programmed cell death. This unit provides two protocols for the detection of apoptosis by immunostaining for either activated forms of caspases or their cleavage products. When used in conjunction with nuclear dyes, these protocols permit visualization not only of caspase activation, but also the nuclear chromatin clumps characteristic of apoptosis. The first protocol utilizes peroxidase‐mediated chromogen deposition to visualize antibodies by brightfield microscopy. The second protocol utilizes fluorophores to visualize antibodies by epifluorescence. Double immunofluorescence labeling can be performed to identify the phenotype of cells in which caspases are activated. Not all cell death is apoptotic. Therefore, a third protocol is presented for suppressed silver staining, a useful method to screen for all morphologic forms of cell death.
Lentiviral Strategies for RNAi Knockdown of Neuronal Genes
Authors: Crittenden Jill R. , Heidersbach Amy , McManus Michael T.
Published: April 2007

RNA interference (RNAi) refers to the process by which 21‐ to 23‐nucleotide short interfering RNAs (siRNAs) mediate post‐transcriptional degradation of homologous mRNA transcripts. This process is carried out by an endogenous pathway that centers on the use of endogenously encoded small RNAs, and can be hijacked to knock down the expression of any target protein by introducing a specific siRNA into a cell. Stable knockdown can be obtained by constitutive expression of the siRNA from the host chromosome. Retroviruses, such as lentivirus, provide a convenient vector by which to integrate RNAi expression constructs. Lentiviruses can infect nondividing cells, thereby allowing knockdown in cells such as mature neurons. This unit provides methods to design and clone siRNAs into a lentiviral vector. Additional protocols describe production and titering of the lentivirus, as well as safety testing. Finally, methods are provided for infecting neurons in culture and in vivo with RNAi lentivirus.
Overview of Animal Models of Schizophrenia
Authors: Powell Susan B. , Geyer Mark A.
Published: April 2007

Animal models of schizophrenia may increase the understanding of the neurological abnormalities associated with the disorder and aid in the development of rational pharmacological treatments. Rather than attempting to model the entire syndrome of schizophrenia, a more biologically oriented approach to animal models has been to focus on specific symptoms of schizophrenia that are more objectively measured in the clinical population and more directly translatable to animals (e.g., observables or endophenotypes). This overview focuses on behavioral measures that have been investigated in rodent models of schizophrenia with varying degrees of predictive, etiological, and construct validity. Because of the severity of cognitive deficits in schizophrenia and their resistance to current treatments, there is a need to develop animal models specific to the cognitive symptoms of schizophrenia. In light of this need, this overview discusses rodent models of cognition with relevance to the core cognitive deficits observed in schizophrenia.
Production of Recombinant Adeno‐Associated Viral Vectors for In Vitro and In Vivo Use
Authors: Choi Vivian W. , Asokan Aravind , Haberman Rebecca A. , Samulski Richard Jude
Published: April 2007

Adeno‐associated virus is a nonpathogenic human virus that has been developed into a gene‐delivery vector due to its high efficiency of infection in many different cell types and its ability to persist and lead to long‐term gene expression. The vector is also a valuable tool in molecular biology experiments. This unit describes efficient methods to generate high‐titer, research‐grade, adenovirus‐free, recombinant single‐stranded and self‐complementary adeno‐associated virus in various serotypes, along with methods to quantify the viral vectors.
Histopathology in Mouse Metabolic Investigations
Authors: Mark Manuel , Teletin Marius , Antal Cristina , Wendling Olivia , Auwerx Johan , Heikkinen Sami , Khetchoumian Konstantin , Argmann Carmen A. , Dgheem Mounzer
Published: April 2007

Due to the small size of the mouse, evaluating its clinical phenotype is sometimes problematic. In contrast, mouse models are readily accessible to post‐mortem analyses at any time during the course of a disease and prior to its clinical onset. RNA, protein, and histological analyses following sacrifice represent a powerful means to identify affected cell types and molecular events underlying the altered phenotype, and therefore to understanding the signaling or metabolic pathways involved. In this unit, an overview of post‐mortem analyses is provided with a strong emphasis on the principles of routine histology, including tissue fixation, processing, embedding, and staining with hematoxylin and eosin. There are also several protocols for staining with specialized histological stains used in the metabolic field to detect intracellular lipids, intracellular lipid “ghosts”, cholesterol esters, polysaccharides, mitochondria, pathological collagen deposits, and atherosclerotic plaques.
Assessment of Cell Proliferation by 5‐Bromodeoxyuridine (BrdU) Labeling for Multicolor Flow Cytometry
Authors: Rothaeusler Kristina , Baumgarth Nicole
Published: April 2007

Cell proliferation assays are used for a large variety of applications in the life sciences. This unit describes a flow‐cytometry‐based method that uses BrdU labeling in conjunction with multiple fluorescently labeled cell surface markers, allowing extensive phenotypic characterization of dividing cells in addition to assessment of their frequency. BrdU labeling has the advantage of constituting a nonradioactive technique that, when combined with additional fluorescent‐based reagents, avoids time‐consuming and often costly cell isolation procedures. Moreover, because BrdU is stably integrated into the DNA, it can be measured in a cell for many months. The method presented in this unit is based on paraformaldehyde fixation and reversible saponin‐based cell membrane permeabilization, which maintains cell integrity as well as fluorescent labeling with a large number of different fluorochromes, allowing 10‐ to 12‐color flow cytometric analysis of proliferating cells.
Viral clearance using surfactant‐aided size‐exclusion chromatography
Authors: Horneman D. A. , Ottens M. , van der Wielen L. A. M. , Keurentjes J. T. F.
Published: April 2007

Surfactant‐aided size‐exclusion chromatography (SASEC) is applied to the viral clearance of blood proteins, taking BSA as an example. Fixed bed systems as well as simulated moving bed (SMB) systems are examined. SASEC shows a better performance of this separation in terms of log reduction value (LRV), productivity of BSA, yield on BSA and solvent consumption compared to normal size‐exclusion chromatography (SEC) in fixed bed as well as in SMB systems. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Minimalist Active‐Site Redesign: Teaching Old Enzymes New Tricks
Authors: Toscano Miguel D. , Woycechowsky Kenneth J. , Hilvert Donald
Published: April 2007

Although nature evolves its catalysts over millions of years, enzyme engineers try to do it a bit faster. Enzyme active sites provide highly optimized microenvironments for the catalysis of biologically useful chemical transformations. Consequently, changes at these centers can have large effects on enzyme activity. The prediction and control of these effects provides a promising way to access new functions. The development of methods and strategies to explore the untapped catalytic potential of natural enzyme scaffolds has been pushed by the increasing demand for industrial biocatalysts. This Review describes the use of minimal modifications at enzyme active sites to expand their catalytic repertoires, including targeted mutagenesis and the addition of new reactive functionalities. Often, a novel activity can be obtained with only a single point mutation. The many successful examples of active‐site engineering through minimal mutations give useful insights into enzyme evolution and open new avenues in biocatalyst research.
Effect of in situ synthesized macroactivator on morphology of PA6/PS blends via successive polymerization
Authors: Pei Aihua , Liu Andong , Xie Tingxiu , Yang Guisheng
Published: April 2007

In situ polymerization and in situ compatibilization was adopted for preparation of ternary PA6/PS‐g‐PA6/PS blends by means of successive polymerization of styrene, with TMI and ε‐caprolactam, via free radical copolymerization and anionic ring‐opening polymerization, respectively. Copolymer poly(St‐g‐TMI), the chain of which bears isocyanate (NCO), acts as a macroactivator to initiate PA6 chain growth from the PS chain and graft copolymer of PS‐g‐PA6 and pure PA6 form, simultaneously. The effect of the macroactivator poly(St‐g‐TMI) on the phase morphology was investigated in detail, using scanning electron microscopy. In case of blends with higher content of PS‐g‐PA6 copolymer, copolymer nanoparticles coexisting with the PS formed the matrix, in which PA6 microspheres were dispersed evenly as minor phase. The content of the compositions (homopolystyrene, homopolyamide 6, and PS‐g‐PA6) of the blends were determined by selective solvent extraction technique. The mechanical properties of PA6/PS‐g‐PA6/PS blends were better than that of PA6/PS blends. Especially for the blends T10 with lower PS‐g‐PA6 copolymer content, both the flexural strength and flexural modulus showed significantly improving because of the improved interfacial adhesion between PS and PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and magnetic properties of Fe/Si/C/N ceramics derived from a polymeric precursor
Authors: Li Junping , Zhang Zhijie , Zheng Zhimin , Guo Li , Xu Guiyun , Xie Zemin
Published: April 2007

Iron‐containing polysilazanes (PSZI) were prepared by the amine displacement reaction along with heat‐induced vinyl crosslinking reactions between Fe[N(SiMe2Vi)2]3 (Vi = CHCH2) and polysilazane containing SiVi (PVSZ). The PSZIs were converted into magnetic ceramics by the pyrolysis in N2. The ceramics produced were investigated by X‐ray diffraction, transmission electron microscope and vibrating sample magnetometer at room temperature. It was indicated that α‐Fe is the only magnetic crystalline embedded in the amorphous Si/C/N‐based matrix from 500 to 900°C. Moreover, the sample prepared at 500°C showed few hysteresis at room temperature, consistent with the behavior of superparamagnetic particles, which was confirmed by the zero‐field‐cooled and field‐cooled magnetization measurement. Additionally, the results indicated that the magnetic properties of the ceramics could be tuned by controlling the content of iron and the pyrolysis temperature. This flexibility may be advantageous for some particular magnetic materials applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Synthesis and liquid‐crystal‐aligning properties of novel aromatic poly(amide imide)s bearing n‐alkyloxy side chains
Authors: Sarkar Anjana , More Arvind S. , Wadgaonkar Prakash P. , Jic Shin Gyo , Chul Jung Jin
Published: April 2007

Novel aromatic poly(amide imide)s (m‐PAIs, m = 8, 12, 16) containing preformed isophthalamide unit and pendent n‐alkyloxy (‐O‐n‐CmH2m+1, m = 8, 12, 16) side chains were prepared in thin films by polymerization of pyromellitic dianhydride (PMDA) with N,N′‐bis(4‐aminophenyl)‐5‐(n‐alkyloxy)isophthalamides (m‐DAs) obtained from N,N′‐bis(4‐nitrophenyl)‐5‐(n‐alkyloxy)isophthalamides (m‐DNs). The m‐PAI films were tough, flexible and transparent with inherent viscosities in the 1.25–1.67 dL/g range in DMAc and soluble in DMAc and NMP on heating. In TGA m‐PAIs began to degrade around 440°C and in DSC no phase transitions were detected. In X‐ray diffractometry the m‐PAIs appeared amorphous with loosely developed layered crystalline structure. In liquid crystal (LC)‐aligning performance measured using 4‐n‐pentyl‐4′‐cyanobiphenyl (5CB) on thin film surfaces rubbed with standard velvet fibers, the m‐PAIs showed homogeneous LC alignment parallel to the rubbing direction with 2.5–17.5° pretilt angles, depending on the rubbing density and n‐alkyloxy side chain length. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Radiation‐induced graft copolymerization of cellulosic fabric waste and its application in the removal of cyanide and dichromate from aqueous solution
Authors: El‐Kelesh N. A. , Abd Elaal S. E. , Hashem A. , Sokker H. H.
Published: April 2007

Graft polymerization and crosslinking in radiation processing are attractive techniques for modification of the chemical and physical properties of the conventional polymer. The graft polymerization and subsequent chemical treatment can introduce a chelate agent function into a conventional polymer such as cellulosic fabric. Cellulosic graft copolymers were prepared by the reaction of the fiber with acrylonitrile (AN) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in DMF initiated by γ‐radiation 60Co. The grafted fabric was chemically treated with hydroxyl amine to obtain amidoxime from. Factors affecting the grafting such as radiation dose, monomer concentration and solvent concentration as well as monomer composition was investigated. The chemically modified graft fabric was applied for recovery of cyanide and dichromate from aqueous solution. CN− shows 89% removal, whereas dichromate has 65% removal. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Influence of organic modification on mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites
Authors: Tiwari Rajkiran R. , Natarajan Upendra
Published: April 2007

The influence of organic modifiers on intercalation extent, structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)–clay nanocomposites were studied. Two different organic modifiers with varying hydrophobicity (single tallow versus ditallow) were investigated. The nanocomposites were prepared from melt processing method and characterized using wide angle X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. Mechanical properties such as tensile modulus (E), break stress (σbrk), and % break strain (εbrk) were determined for nanocomposites at various clay loadings. Extent of PMMA intercalation is sufficient and in the range 9–15 Å depending on organoclay and filler loading. Overall thermal stability of nanocomposites increases by 16–30°C. The enhancement in Tg of nanocomposite is merely by 2–4°C. With increase in clay loading, tensile modulus increases linearly while % break strain decreases. Break stress is found to increase till 4 wt % and further decreases at higher clay loadings. The overall improvement in thermal and mechanical properties was higher for the organoclay containing organic modifier with lower hydrophobicity and single tallow amine chemical structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effect of a chiral dopant on the electro‐optical properties of polymer‐dispersed liquid‐crystal films
Authors: Li Wenbo , Zhang Hongxue , Wang Liping , Ouyang Canbin , Ding Xiaokang , Cao Hui , Yang Huai
Published: April 2007

Polymer‐dispersed liquid crystal (PDLC) films were prepared by the ultraviolet‐light‐induced polymerization of photopolymerizable monomers in nematic liquid crystal/monomer/chiral dopant composites, and the effect of the chiral dopant on the electro‐optical properties of the PDLC films was studied. It was demonstrated that the addition of a small amount of the chiral dopant increased the driving voltage somewhat but decreased the turn‐off time significantly. Furthermore, the transmittance of ultraviolet, visible, and near‐infrared light of the off state of PDLC films showing light scattering increased with increasing content of the chiral dopant, and the optimum electro‐optical properties of the PDLC films were obtained when the content of the chiral dopant was not more than 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Noncovalent imprinted microspheres: Preparation, evaluation and selectivity of DBU template
Authors: Del Sole Roberta , De Luca Agnese , Catalano Massimo , Mele Giuseppe , Vasapollo Giuseppe
Published: April 2007

1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) imprinted polymer was prepared as microspheres by precipitation polymerization method to obtain molecular recognition systems based on the noncovalent interactions between DBU template, methacrylic acid (MAA), and ethylene .glycol dimethacrylate (EDMA) in acetonitrile. 1H NMR analysis of DBU/MAA mixture has been performed and hydrogen bonding interactions have been established. Microspheres have been characterized by FTIR studies with evidence of DBU linkage in polymer particles and by Scanning Electron Microscopy (SEM) to study their morphological properties. How pH values affect the binding capacity of imprinted polymer during the binding stage has been also discussed and results suggest that imprinted poly‐(MAA‐EDMA) behavior is related to the influence of DBU basicity during rebinding processes and the optimum pH value for binding has been found around neutral range. Binding ability of the imprinted polymer towards different concentration of DBU buffered solutions has been evaluated and compared with binding ability of the non‐imprinted polymer. A more sensitive response to the template in the imprinted system suggests that a reasonable number of specific binding sites is formed. Finally, differential selectivity towards other less strong than DBU nitrogen bases, such as pyridine, imidazole, and 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) has been also discussed. Our results indicate that both specific sites and basic properties are involved in the rebinding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Sesbania gum xanthate supported palladium complex as an efficient catalyst for heck reaction
Authors: Zhang Lei , Zhang Puyu , Li Xiang , Cui Yuanchen
Published: April 2007

Sesbania gum xanthate supported palladium complex (SG‐CS2‐Pd) was synthesized and characterized by XPS, TGA, DTA, etc. The complex exhibits high activity and stereoseletivity for Heck reaction under atmospheric condition and can be easily recovered and reused. Heck reaction of styrene with iodobenzene can be carried out efficiently by using SG‐CS2‐Pd as catalyst even at the low temperature (70°C) or with tiny amount of the catalyst (0.1 mol % Pd). SG‐CS2‐Pd has high catalytic activity for arylation of acrylic acid or styrene with iodobenzene under the condition of NMP as solvent and the yield of cinnamic or trans‐stilbene exceeded 90%. The Heck arylation of substituted iodobenzene with acrylic acid or styrene with iodobenzene can also be efficiently catalyzed by using SG‐CS2‐Pd as catalyst under the conditions of 90°C, NMP as solvent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Conductivity relaxation in zirconia nanoparticles dispersed in conducting polymer
Authors: Dey Ashis , De S. K.
Published: April 2007

Zirconia‐polyaniline (ZrO2‐PANI) nanocomposites have been synthesized using the colloidal stability of ZrO2 sol. Complex impedance and dielectric permittivity of ZrO2‐PANI nanocomposites have been investigated as a function of frequency and temperature for different compositions. Grain conductivity is about two orders of magnitude higher than the grain boundary conductivity. A very large dielectric permittivity of about 2500 at room temperature has been observed for the composite with highest content of ZrO2. The high dielectric permittivity is mainly dominated by interfacial polarization because of Maxwell‐Wagner relaxation effect. The electric modulus spectra reveal two types of conductivity relaxation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Alternate method for grafting thermoresponsive polymer for transferring in vitro cell sheet structures
Authors: Kumar P. R. Anil , Sreenivasan K. , Kumary T. V.
Published: April 2007

Retrieval of cells for various applications involves enzymatic or mechanical methods that hamper the cell–cell and cell–extracellular matrix (ECM) binding. Poly(N‐isopropylacrylamide) (PIPAAm) is a known temperature‐sensitive polymer that exhibits a lower critical solution temperature (LCST) around 32°C and is hydrophobic over LCST and hydrophilic below LCST. PIPAAm‐grafted culture surface can be used for detaching adhered cells by lowering the temperature below LCST. In this study, polymerization and grafting of PIPPAm was done by gamma (γ) ray irradiation instead of the conventional method of electron beam irradiation. The efficacy of the grafted surface was confirmed by the successful growth of different cell lines such as L‐929, NRK‐49F, HOS, and SIRC. The cell sheet structures with intact cell–cell and cell–ECM contact was detached by lowering incubation temperature below 20°C. Live–dead staining of cells before and after transfer showed that cell sheet structures maintained viability. This approach of synthesizing thermoresponsive surface by γ‐ray irradiation method can be used to culture many other cell types and could be utilized to prepare in vitro tissue constructs for bioengineering. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Hierarchy structure in injection molded polypropylene/ethylene–octane copolymer blends
Authors: Li Jiang , Zhang Xiaoqing , Qu Cheng , Zhang Qin , Du RongNi , Fu Qiang
Published: April 2007

In this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene–octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin‐core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007