bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutron Diffraction
Authors: Yousufuddin Muhammed , Bau Robert
Published: March 2008

The following article reviews the technique of neutron diffraction and its effectiveness in probing materials of chemical interest. The main advantage of neutrons is their ability to detect hydrogen atoms. We describe in this article several examples where neutrons offered additional information that was otherwise unavailable from X‐rays. We have summarized a number of structures studied using neutron diffraction. Most of these structures showed the precise location of chemically interesting hydrogen atoms. We have also summarized structures where neutron diffraction allowed for the assignment of absolute stereochemistry in deuterated systems. Lastly, we have discussed the usefulness of neutron diffraction in protein crystallography.

One of the major disadvantages of neutron diffraction is the immensely low number of neutron sources available as compared to X‐ray sources. We have detailed the neutron sources around the world capable of neutron diffraction experiments, including sources that are currently under construction such as the Spallation Neutron Source in Oak Ridge, TN and J‐PARC in Tokyo, Japan. In addition, a number of neutron diffraction instruments and their sample requirements are illustrated.

In the past, neutron diffraction has been overlooked by most practicing chemists as an efficient analytical tool. However, with the newer more powerful facilities and instrumentation in development, chemical systems studied with neutrons should become more common.
Vibrational Spectroscopy
Authors: Dyer R. Brian , Woodruff William H.
Published: March 2008

The application of vibrational spectroscopy to the study of inorganic and bioinorganic structures and dynamics has a rich history. Recent advances in vibrational spectroscopic techniques have increased the utility of these methods. Time‐resolved methods in particular have benefited from advances in lasers and other enabling technologies. In this chapter we describe the application of both Raman and infrared methods to problems in inorganic chemistry, with a focus on bioinorganic systems. We also describe difference vibrational spectroscopy methods for the analysis of metal active sites within complex protein structures. We develop quantitative rules for the relationships between force constants and bond distances. Such relationships are useful for predicting bond distances for cases where it is difficult to measure them otherwise, such as for excited states of molecules. Finally, we review time‐resolved Raman and IR methods and their application to the study of the structures and dynamics of excited states and chemical reactions of inorganic systems.
Electron Paramagnetic Resonance (
EPR
) Spectroscopy
Authors: Hales Brian J.
Published: March 2008

Electron‐Paramagnetic Resonance (EPR) spectroscopy, also know as Electron‐Spin Resonance (ESR) spectroscopy, monitors the energy levels of paramagnetic molecules. The major energy interaction (Zeeman Interaction) is between the magnetic moment of the electron and the field of a large uniform magnet. This interaction splits the normally degenerate spin levels of the electron and the electron‐paramagnetic resonance (EPR) spectrometer measures the energy of this interaction. The EPR spectrometer is described along with a discussion of spectral optimization techniques. Additionally, energy interaction terms are described and include hyperfine coupling (the interaction of the magnetic moments of the unpaired electron and magnetic nuclei) and spin‐orbit coupling, which influences the magnitude of the spectroscopic
g
‐factor and the energy levels of
S
 > 1/2 systems. The general features of half‐integer and integer high‐spin systems are further described, including examples.
Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy
Authors: McCracken John
Published: March 2008

In the 46 years since its discovery in Ce(III)‐doped CaWO4single crystals, electron spin echo envelope modulation (ESEEM) spectroscopy has developed into an important method for the characterization of paramagnetic centers. The capability of ESEEM to resolve ligand hyperfine couplings to paramagnetic transition metal ions in powder or frozen solution samples, and its sensitivity to the orientation and number of coupled nuclei, make it a valuable tool for structural biology and materials chemistry. This article presents a brief history of the method from its discovery to the development of commercial instrumentation that has provided an opportunity for scientists to address difficult questions regarding coordination chemistry in paramagnetic systems. The technical background section presents the three most basic ESEEM experiments: the one‐dimensional primary echo (two‐pulse) and stimulated echo (three‐pulse) experiments and the two‐dimensional, four‐pulse hyperfine sublevel correlation (HYSCORE) experiment. The mathematical expressions developed for these experiments and the simpleS = 1/2,I = 1/2 coupled spin system, will be used together with sample ESEEM data from Cu(II) centers in a model complex and an enzyme to illustrate the strengths and weaknesses of these pulse schemes. The article will conclude with a case study of the nonheme Fe(II) site in taurine/α‐ketoglutarate dioxygenase (TauD) that will feature some of the strengths of one‐dimensional and two‐dimensional ESEEM spectroscopy and show that the method has matured into a powerful technique for elucidating the coordination chemistry of this important class of enzymes as well as many other systems.
Prediction of the development of reading comprehension: a longitudinal study
Authors: Verhoeven Ludo , van Leeuwe Jan
Published: March 2008

Specific effects of word decoding, vocabulary and listening comprehension abilities on the development of reading comprehension were longitudinally examined for a representative sample of 2143 Dutch children throughout the elementary school period. An attempt was made to test two theoretical frameworks for the prediction of the development of reading comprehension: the lexical quality hypothesis in which word decoding and vocabulary are assumed to be critical determinants of reading comprehension and the simple reading view in which reading comprehension is assumed to be the product of word decoding and listening comprehension. The results showed significant progress across grades on all of the predictor and criterion measures. The stability of the measures was also high across time, which shows the individual differences between students to remain across grades. Word decoding exerted a substantial effect on early reading comprehension and a small effect on later sixth grade reading comprehension. The data provide empirical support for the lexical quality hypothesis as they show knowledge of word forms and word meanings (i.e. vocabulary) to predict the development of reading comprehension. Support for the simple reading view was also found in that word decoding and listening comprehension significantly predicted reading comprehension as well. A combined structural model with word decoding, vocabulary and listening comprehension as predictors of reading comprehension showed a substantial impact of the three predictors on reading comprehension at first grade. In subsequent grades, vocabulary is still predicting reading comprehension directly whereas listening comprehension shows a reciprocal relationship with vocabulary. Copyright © 2008 John Wiley & Sons, Ltd.
Advances in text comprehension: commentary and final perspective
Authors: Graesser Arthur C.
Published: March 2008

The articles in this special issue present data, theory and applications of the field of Discourse Processes. This commentary identifies some of the challenges this field has faced in its attempt to understand the mechanisms of discourse comprehension and production to scale up the research to applications. The prevailing models emphasize the interaction between data‐driven and conceptually driven processes and the importance of representational constraints in guiding discourse processing. The field embraces a wide range of methodologies that are illustrated in this special issue, including brain imaging, eye tracking, thing aloud protocols, reading times, recall, summarization and question answering. The tasks include text comprehension, search through large repositories of electronic texts and learning from advanced multimedia environments. The major claim in the commentary is that researchers need to conduct deeper analyses of the information in the materials (texts, tasks) and world knowledge before they can offer defensible generalizations about cognitive processes and real world applications. Copyright © 2008 John Wiley & Sons, Ltd.
Comprehension skill and word‐to‐text integration processes
Authors: Perfetti Charles , Yang Chin‐Lung , Schmalhofer Franz
Published: March 2008

We examine comprehension skill differences in the processes of word‐to‐text integration, the connection of the meaning of a word, as it is read, to a representation of the text. We review two ‘on‐line’ integration studies using event related potentials (ERPs) to provide fine‐grain temporal data on the word‐to‐text processes of adult readers. The studies demonstrate indicators for word‐to‐text integration and show differences in these indicators as a function of adult reading comprehension skill. For skilled comprehenders, integration processes were reflected in N400 indicators when a critical word had an explicit link to a word in the prior text and by both N400 and P300 indicators when its meaning was a paraphrase of a prior word. When forward inferences were required for subsequent word‐to‐text integration, effects for skilled comprehenders were not reliable. Less skilled comprehenders showed delayed and less robust ERP effects, especially when meaning paraphrase was the basis of the integration. We discuss the significance of skill differences in integration processes with a focus on the use of context‐dependent word meaning as a possible source of these differences. Copyright © 2008 John Wiley & Sons, Ltd.
An internet database for the classification and dissemination of information about hazardous chemicals and occupational diseases
Authors: Brown J.A.
Published: March 2008

Background

The amount of information about hazardous agents in the workplace exceeds the capacity of human memory. There is a need to accurately represent or map this scientific knowledge for digital storage and retrieval.

Methods

A relational database of hazardous chemicals and occupational diseases was constructed by first collecting and sifting through the large volume of information. The information was indexed with a controlled vocabulary and documented with references to the scientific literature.

Results

The evolving database is available on the website of the National Library of Medicine. It enables users to browse categories and query by pick lists. Users can drill down to find specific information that may be useful for intervention and prevention.

Conclusions

The large amount of information needed to support decisions concerning occupational exposures and diseases can be distilled, classified, and summarized in a relational database and disseminated by means of the World Wide Web to assist in the prevention of work‐related diseases. Am. J. Ind. Med. 51:428–435, 2008. © 2008 Wiley‐Liss, Inc.
Save the date: Honors for Microsoft and its GC, Brad Smith
Authors: Bleemer Russ
Published: March 2008

Microsoft and its general counsel, Brad Smith, will be the 2008 CPR Corporate Leadership Award honorees this fall. Also, complicated registration features have been wiped out, and CPR members now need only one click to get full advance and archive electronic access to Alternatives.
Update: Despite mediation‐related incarceration, Girls Gone Wild founder is headed for more ADR
Authors: Bleemer Russ
Published: March 2008

A Florida federal court judge rejects a recusal motion from the Girls Gone Wild founder, dismissing contentions–including some from a 2007 Alternatives article–that the judge's mediation rulings stepped over the line. Also, a New York state case is sounding alarms about a potential loss of mediation confidentiality.
Methane production in an UASB reactor operated under periodic mesophilic–thermophilic conditions
Authors: Bourque J.‐S. , Guiot S.R. , Tartakovsky B.
Published: March 2008

Methane production was studied in a laboratory‐scale 10 L anaerobic upflow sludge bed (UASB) reactor with periodic variations of the reactor temperature. On a daily basis the temperature was varied between 35 and 45°C or 35 and 55°C with a heating period of 6 h. Each temperature increase was accompanied by an increase in methane production and a decrease in the concentration of soluble organic matter in the effluent. In comparison to a reactor operated at 35°C, a net increase in methane production of up to 22% was observed. Batch activity tests demonstrated a tolerance of mesophilic methanogenic populations to short‐term, 2–6 h, temperature increases, although activity of acetoclastic methanogens decreased after 6 h exposure to a temperature of 55°C. 16S sequencing of DGGE bands revealed proliferation of temperature‐tolerant Methanospirillum hungatii sp. in the reactor. Biotechnol. Bioeng. 2008;100: 1115–1121. © 2008 Wiley Periodicals, Inc.
A dual CT‐MR dendrimer contrast agent as a surrogate marker for convection‐enhanced delivery of intracerebral macromolecular therapeutic agents
Authors: Regino Celeste Aida S. , Walbridge Stuart , Bernardo Marcelino , Wong Karen J. , Johnson Dennis , Lonser Russell , Oldfield Edward H. , Choyke Peter L. , Brechbiel Martin W.
Published: March 2008

The feasibility of using Gd dendrimer‐based macromolecules (Gd‐G8 dendrimer) as a dual CT and MR contrast agent for monitoring convection‐enhanced delivery of therapy in the brain is evaluated both in vitro and in vivo with optimal dosing established. In vitro CT attenuation values of the Gd‐based agents (∼6.0 HU mM−1) were ∼1.6 times greater than iodine‐based agents and the attenuation of the Gd‐DTPA was comparable to Gd‐G8 dendrimer. Visible enhancement was observed on both CT and MR using Gd‐G8 dendrimer over a range of 23–78 mM; however, a concentration of at least 47 mM in Gd was required for adequate delineation of the injection site on both CT and MR. MR offers greater sensitivity than CT in estimating the volume of distribution (Vd) and effectively quantified the agent's concentration and diffusion using T1 mapping at much lower concentrations of Gd (<10 mM in [Gd]). Copyright © 2008 John Wiley & Sons, Ltd.
Imaging of angiogenesis using Cadence™ contrast pulse sequencing and targeted contrast agents
Authors: Stieger Susanne M. , Dayton Paul A. , Borden Mark A. , Caskey Charles F. , Griffey Stephen M. , Wisner Erik R. , Ferrara Katherine W.
Published: March 2008

Objectives

Low‐power multipulse contrast ultrasound imaging provides a promising tool to quantify angiogenesis noninvasively when used with contrast agents targeted to vascular markers expressed by the angiogenic endothelium. Targeted ultrasound contrast agents, with a diameter on the order of micrometers, cannot extravasate and therefore are targeted solely to receptors expressed by the vascular endothelium. The aim of this study was to evaluate the potential of a low‐power multipulse imaging sequence, CadenceTMcontrast pulse sequencing (CPS), combined with targeted contrast agents to quantify angiogenesis.

Material and Methods

Targeted microbubbles were prepared by conjugating echistatin via biotin–avidin linkage to the surface of a phospholipid microbubble shell. The density of echistatin present on the shell was confirmed with flow‐cytometry and quantified by total fluorescence. The binding of targeted microbubbles was evaluatedin vitroby quantifying the adherence of targeted microbubbles to rat aortic endothelial cells, compared with control (nontargeted) microbubbles. The circulation time and adherence of targeted microbubbles was evaluatedin vivoin a Matrigel model in rats and compared with control microbubbles using CPS in addition to a destructive ultrasound pulse.

Results

Using only the low‐power CPS pulse, the echo intensity produced in the neovasculature of the Matrigel pellet was significantly greater with targeted microbubbles than with the control contrast agent (p < 0.001). Combining CPS with the destructive pulse, the processed image was significantly different in intensity (p < 0.001) and spatial extent between targeted and control agents (p < 0.001). When the morphology of the histological sample and ultrasound image correlated, the microvessel density count and the percentage of the circular area enhanced by ultrasound were correlated (p < 0.05).

Conclusion

Low‐power multipulse imaging in combination with targeted echistatin‐bearing microbubbles facilitated a noninvasive, quantitative evaluation of early angiogenesis during real‐time imaging. The addition of high‐intensity destructive pulses facilitated estimation of the spatial extent of angiogenesis. Copyright © 2008 John Wiley & Sons, Ltd.
Morphology and physiology of vibratory interneurons in the thoracic ganglia of the southern green stinkbugNezara viridula(L.)
Authors: Zorović Maja , Prešern Janez , Čokl Andrej
Published: March 2008

The central processing mechanisms of vibratory signals in small plant‐dwelling insects that rely primarily on substrate‐borne vibratory communication are still largely unknown. To elucidate the neural mechanisms involved in vibratory signaling, the vibration‐sensitive interneurons in thoracic ganglia of the southern green stinkbug,Nezara viridula, were investigated electrophysiologically by single‐cell recordings and staining. Ten types of interneurons were described and divided into four categories, based on their gross morphology. The cell body of the L‐shaped CG‐AC neurons is located in the metathoracic neuromere of the central ganglion, and the axon ascends contralaterally. This group comprises five types of neurons differing in their fine structure and functional properties. CG‐AB neurons are dorsal unpaired median (DUM) neurons with cell bodies in the mesothoracic neuromere of the central ganglion and two axons that ascend bilaterally into the prothoracic ganglion. Group CG‐L includes three types of local neurons limited to the central ganglion. With ipsilateral dendritic arborizations and contralateral axonal branching, their gross morphology is similar to that of cricket omega cells. Interneuron PTG‐DC, with the cell body in the prothoracic ganglion (PTG) and a contralaterally descending axon, conveys information received by the sensory organs of the front contralateral leg to the neuropil regions of the ipsilateral middle and hind legs. Based on their frequency tuning and acceleration sensitivity, the vibratory interneurons fall into two groups: the low‐frequency units are tuned to 50 Hz and the middle frequency units to 200 Hz, with their acceleration thresholds at 10−1m/s2and 5 × 10−3m/s2, respectively. Their function is discussed with relevance to the vibratory communication ofN. viridula. J. Comp. Neurol. 508:365–381, 2008. © 2008 Wiley‐Liss, Inc.
Activation of phenotypically distinct neuronal subpopulations in the anterior subdivision of the rat basolateral amygdala following acute and repeated stress
Authors: Reznikov Leah R. , Reagan Lawrence P. , Fadel Jim R.
Published: March 2008

The effects of acute and repeated stress on expression of the early immediate gene c‐fos in the basolateral amygdala have previously been reported; however, characterization of which neuronal subpopulations are activated by these stimuli has not been investigated. This question is of considerable relevance, insofar as the basolateral amygdala houses a heterogeneous population of neurons, including those of γ‐aminobutyric acid (GABA)‐ergic and glutamatergic phenotypes that may be subcategorized based on their expression of various calcium‐binding proteins, including parvalbumin, calbindin, calretinin, and the calcium‐sensitive enzyme calcium/calmodulin‐dependent kinase II. Characterization of these subpopulations has revealed unique differences in their physiology, synaptology, and morphology, suggesting that each distinct phenotype may have profound effects on the local circuitry of the amygdala. Therefore, we examined the effects of acute and repeated restraint stress on expression of the immediate early gene c‐fos in neurons containing parvalbumin, calbindin, calretinin, or calcium/calmodulin‐dependent kinase II in the basolateral amygdala. Double‐label immunohistochemistry revealed that acute restraint stress activated a proportion of parvalbumin‐, calbindin‐, or calcium/calmodulin‐dependent kinase II‐positive neurons. Prior exposure to repeated restraint stress markedly attenuated acute‐stress mediated activation of these neuronal populations, although not equally. Expression of c‐Fos protein was not detected in calretinin‐positive neurons in any experimental group. These results demonstrate that distinct neuronal phenotypes in the basolateral amygdala are activated by acute restraint stress and that prior repeated restraint stress differentially affects this response. J. Comp. Neurol. 508:458–472, 2008. © 2008 Wiley‐Liss, Inc.
Bulbospinal neurons implicated in mesopontine‐induced anesthesia are substantially collateralized
Authors: Reiner K. , Sukhotinsky I. , Devor M.
Published: March 2008

Microinjection of pentobarbital or other γ‐aminobutyric acid type A receptor (GABAA‐R) active anesthetics into a brainstem region in the rat that we have called the mesopontine tegmental anesthesia area (MPTA) induces a general anesthesia‐like state that includes suppression of locomotor activity, loss of the righting reflex, atonia, antinociception, and apparent loss of consciousness. The suppression of muscle tone and of nocifensive spinal reflexes suggests a direct or indirect effect at the level of the spinal cord itself, an inference supported by anterograde tracing from the MPTA area. We have now used single and double retrograde tracing to characterize this bulbospinal pathway further. The MPTA contains the majority of all bulbospinal neurons present at mesopontine levels (65.8%). Many of these neurons, although not all, appear to have a highly collateralized projection pattern within the spinal cord. About 40% of the MPTA neurons that project to the lumbar spinal cord also have collaterals at cervical levels, and about 60% of those with projections to the ventral horn also have projections to the dorsal horn (at cervical levels). However, the large majority projects either ipsilaterally or contralaterally. Relatively few (∼13%) send collaterals to both sides of the spinal cord. The pattern of connectivity revealed appears to be consistent with a system designed primarily to modulate motor and sensory functions globally, over the entire neuraxis, rather than regionally or segmentally. J. Comp. Neurol. 508:418–436, 2008. © 2008 Wiley‐Liss, Inc.
Photochromic, Thermochromic, and Fluorescent Spirooxazines and Naphthopyrans: A Spectrokinetic and Thermodynamic Study
Authors: di Nunzio Maria R. , Gentili Pier L. , Romani Aldo , Favaro Gianna
Published: March 2008

The photochromic and thermochromic behavior of four commercially available Reversacol dyes are presented. The compounds studied belong to the class of spirooxazines and naphthopyrans, which are typically thermoreversible photochromic molecules. On stimulation with UV light, these compounds become colored and exhibit spectra which extend over the whole visible region. Increasing the temperature causes spontaneous coloration (thermochromism). Herein, absorption and fluorescence spectra, molar absorption coefficients of the colorless and colored forms, fluorescence and photochemical quantum yields, and kinetic parameters of thermal bleaching (rate constant, frequency factor, and activation energy) are determined in acetonitrile solution. The thermal ground‐state reaction is exhaustively described in terms of thermodynamic parameters (equilibrium constant, free energy, enthalpy, and entropy). Temperature effects on photochemical and thermal colorabilities are evaluated. The results indicate that the two spirooxazines are good photochromes below room temperature, whereas they are efficient thermochromic compounds above room temperature. Naphthopyrans are better photochromes but worse thermochromic compounds than spirooxazines.
Plasmablastic lymphoma involving breast: A case diagnosed by fine‐needle aspiration and core needle biopsy
Authors: Wang Jun , Hernandez Osvaldo J. , Şen Filiz
Published: March 2008

Plasmablastic lymphoma (PBL) is a rare lymphoma originating from B‐cells with terminal differentiation. Most common anatomic site involved by PBL is the oral cavity. Involvement of other body sites has only rarely been reported. Herein, we report a rare case of EBV‐negative PBL involving the breast of an HIV positive 47‐year‐old woman. The patient presented with decreased vision and photophobia. During physical examination, she was found to have bilateral breast masses and multiple lymphadenopathy. Fine‐needle aspiration of one of the breast masses showed large malignant cells with plasmacytoid features. Immunohistochemical studies performed on the core biopsy showed that the tumor cells were positive for common leukocyte antigen CD45 and plasma cell marker CD138, but negative for the pan‐B cell markers CD20 and CD79a. Molecular genetic studies showed clonal rearrangement of the immunoglobulin kappa light chain gene. This is the first case of PBL involving the breast reported in English cytological literature. Diagn. Cytopathol. 2008;36:257–261. © 2008 Wiley‐Liss, Inc.
Giant‐cell containing neoplasms of the pancreas: An aspiration cytology study
Authors: Layfield Lester J. , Bentz Joel
Published: March 2008

Giant‐cell containing neoplasms of the pancreas are rare with few reports documenting their cytologic appearance. Giant‐cell containing neoplasms of the pancreas have been divided into two subtypes corresponding to the osteoclastic giant‐cell tumor of the pancreas and the pleomorphic giant‐cell carcinoma of the pancreas. Despite the better prognosis reported in some series for osteoclastic giant‐cell tumors, the most recent edition of the World Health Organization classification lumps the two entities into a single category designated as undifferentiated carcinoma with osteoclast‐like giant cells. Smears obtained from osteoclastic giant‐cell tumors show numerous giant‐cells with clustered overlapping, bland appearing nuclei containing prominent nucleoli consistent with an osteoclast‐type multinucleated giant‐cell. These neoplasms contain a second population of mononuclear cells showing more marked nuclear atypia. Pleomorphic giant‐cell carcinomas are characterized by anaplastic giant‐cells displaying marked nuclear pleomorphism. The mononuclear component is also pleomorphic with markedly atypical epithelioid and spindle shaped cells. In three reported cases, a tumor contained a mixture of the two cell patterns. Thus, undifferentiated carcinoma with osteoclast‐like giant cells and pleomorphic giant cell carcinoma may represent a morphologic spectrum with pure osteoclast‐like giant‐cell tumors at one end and pleomorphic giant‐cell carcinoma at the other. Fine‐needle aspiration specimens from pure osteoclast‐like giant‐cell tumors will contain a population of bland multinucleated osteoclastic‐like giant‐cells that differ markedly from the anaplastic giant‐cells of pleomorphic giant‐cell carcinoma. The difference in the appearance of the giant‐cells aids in distinction of the two neoplasms. When in pure form, the two neoplasms may follow different clinical courses. Diagn. Cytopathol. 2008;36:238–244. © 2008 Wiley‐Liss, Inc.
Weak hand preference in children with down syndrome is associated with language deficits
Authors: Groen M. A. , Yasin I. , Laws G. , Barry J. G. , Bishop D. V. M.
Published: March 2008

This study explores associations between language ability and hand preference in children with Down syndrome. Compared to typically developing children of the same age, children with Down syndrome showed weaker hand preference, were less consistent in the hand they used and also less willing to reach to extreme positions in contralateral space. Within the group of children with Down syndrome, those who showed a stronger or more consistent hand preference had better language and memory skills. This association could not be explained by differences in non‐verbal cognitive ability or hearing loss. These findings are discussed within the theory of neurolinguistic development proposed by Locke [Locke (1997). Brain & Language, 58, 265–326]. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 242–250, 2008.
Proper expression of the Gcn5 histone acetyltransferase is required for neural tube closure in mouse embryos
Authors: Lin Wenchu , Zhang Zhijing , Srajer Geraldine , Chen Yi Chun , Huang Maosheng , Phan Huy M. , Dent Sharon Y.R.
Published: March 2008

Histone acetyltransferases (HATs) are important to gene activation, altering chromatin structures to facilitate association of transcription proteins with gene promoters. The functions of individual HATs in mammalian developmental are not well defined. Our previous studies demonstrated that Gcn5, a prototypical HAT, is required for mesodermal maintenance in early embryos. Homozygous Gcn5 null embryos die soon after gastrulation, preventing determination of Gcn5 functions later during development. We report here the creation of a Gcn5flox(neo) allele, which is only partially functional and gives rise to a hypomorphic phenotype. Mice homozygous for this allele had an increased risk of cranial neural tube closure defects (NTDs) and exencephaly. These defects were found at an even greater penetrance in Gcn5flox(neo)/Δ embryos. These results indicate that normal levels of Gcn5 expression are critical for neural tube closure in mice and predict that mutations in this HAT may be associated with increased risk of NTDs in humans. Developmental Dynamics 237:928–940, 2008. © 2008 Wiley‐Liss, Inc.
Different effects of anti‐sonic hedgehog antibodies and the hedgehog pathway inhibitor cyclopamine on generation of dopaminergic neurons from neurospheres of mesencephalic precursors
Authors: Parga J.A. , Rodriguez‐Pallares J. , Blanco V. , Guerra M. J. , Labandeira‐Garcia J. L.
Published: March 2008

Production of dopaminergic neurons from stem/precursor cells for transplantation in Parkinson's disease has become a major focus of research. However, the inductive signals mediating this process have not been clarified. Reported data on the effects of Sonic hedgehog on differentiation of dopaminergic and serotonergic neurons from cultures of neural precursors are controversial. In the present study, cultures of proliferating neurospheres of mesencephalic precursors treated with anti–sonic hedgehog antibodies showed significantly less serotonergic and GABAergic cells and a markedly higher number of dopaminergic neurons generated from the neurospheres than control cultures. Treatment of the neurospheres with cyclopamine, which selectively inhibits sonic hedgehog signaling by preventing Smoothened activation, did not induce significant changes in generation of serotonergic and dopaminergic neurons. This suggests that Smoothened activation is not significantly involved in the above‐mentioned effects and that sonic hedgehog may exert effects on the mesencephalic precursors that do not involve the canonical Patched‐Smoothened‐Gli signaling. Developmental Dynamics 237:909–917, 2008. © 2008 Wiley‐Liss, Inc.
RNA expression microarray analysis in mouse prospermatogonia: Identification of candidate epigenetic modifiers
Authors: Lefèvre Christophe , Mann Jeffrey R.
Published: March 2008

The mammalian totipotent and pluripotent lineage exhibits genome‐wide dynamics with respect to DNA methylation content. The first phase of global DNA demethylation and de novo remethylation occurs during preimplantation development and gastrulation, respectively, while the second phase occurs in primordial germ cells and primary oocytes/prospermatogonia, respectively. These dynamics are indicative of a comprehensive epigenetic resetting or reprogramming of the genome in preparation for major differentiation events. To gain further insight into the mechanisms driving DNA methylation dynamics and other types of epigenetic modification, we performed an RNA expression microarray analysis of fetal prospermatogonia at the stage when they are undergoing rapid de novo DNA remethylation. We have identified a number of highly or specifically expressed genes that could be important for determining epigenetic change in prospermatogonia. These data provide a useful resource in the discovery of molecular pathways involved in epigenetic reprogramming in the mammalian germ line. Developmental Dynamics 237:1082–1089, 2008. © 2008 Wiley‐Liss, Inc.
High‐resolution in vivo imaging of the cross‐sectional deformations of contracting embryonic heart loops using optical coherence tomography
Authors: Männer Jörg , Thrane Lars , Norozi Kambiz , Yelbuz T. Mesud
Published: March 2008

The embryonic heart tube consists of an outer myocardial tube, a middle layer of cardiac jelly, and an inner endocardial tube. It is said that tubular hearts pump the blood by peristaltoid contractions. The traditional concept of cardiac peristalsis sees the cyclic deformations of pulsating heart tubes as concentric narrowing and widening of tubes of circular cross‐section. We have visualized the cross‐sectional deformations of contracting embryonic hearts in chick embryos (HH‐stages 9–17) using real‐time high‐resolution optical coherence tomography. Cardiac contractions are detected from HH‐stage 10 onward. During the cardiac cycle, the myocardial tube undergoes concentric narrowing and widening while the endocardial tube undergoes eccentric narrowing and widening, having an elliptic cross‐section at end‐diastole and a slit‐shaped cross‐section at end‐systole. The eccentric deformation of the endocardial tube is the consequence of an uneven distribution of the cardiac jelly. Our data show that the cyclic deformations of pulsating embryonic heart tubes run other than originally thought. There is evidence that heart tubes of elliptic cross‐section might pump blood with a higher mechanical efficiency than those of circular‐cross section. The uneven distribution of cardiac jelly seems to prefigure the future AV and cono‐truncal endocardial cushions. Developmental Dynamics 237:953–961, 2008. © 2008 Wiley‐Liss, Inc.
Current perspectives in zebrafish reverse genetics: Moving forward
Authors: Skromne Isaac , Prince Victoria E.
Published: March 2008

Use of the zebrafish as a model of vertebrate development and disease has expanded dramatically over the past decade. While many articles have discussed the strengths of zebrafish forward genetics (the phenotype‐driven approach), there has been less emphasis on equally important and frequently used reverse genetics (the candidate gene‐driven approach). Here we review both current and prospective reverse genetic techniques that are applicable to the zebrafish model. We include discussion of pharmacological approaches, popular gain‐of‐function and knockdown approaches, and gene targeting strategies. We consider the need for temporal and spatial control over gain/loss of gene function, and discuss available and developing techniques to achieve this end. Our goal is both to reveal the current technical advantages of the zebrafish and to highlight those areas where work is still required to allow this system to be exploited to full advantage. Developmental Dynamics 237:861–882, 2008. © 2008 Wiley‐Liss, Inc.
Kinetics and mechanism of the reaction between maleic anhydride and fatty acid esters and the structure of the products
Authors: Stefanoiu Florina , Candy Laure , Vaca‐Garcia Carlos , Borredon Elisabeth
Published: March 2008

Alkenyl succinic anhydrides (ASA) were obtained by reaction between maleic anhydride and high‐oleic sunflower oil (HOSO) esters. A kinetics study of the maleinization of alkyl esters indicated that the maleinization reaction was second order overall and first order with respect to the individual reactants, and the activation energy was 77.2 ± 3.3 kJ/mol in the investigated temperature range (185–225 °C). These results showed that the cis configuration and the central position of the double bond in HOSO esters facilitate the maleinization of the latter. On the contrary, the length of the linear ester moiety had no influence on the course of the maleinization reaction. Moreover, new evidence demonstrates that there are two different reaction mechanisms: ene‐reaction and addition in allylic position with a 2 : 1 ratio, respectively. This ratio was constant throughout the reaction, thus indicating that these mechanisms are independent.
Simplification of separation of the reaction mixture after transesterification of vegetable oil
Authors: Hájek Martin , Skopal František , Machek Jaroslav
Published: March 2008

A heterogeneous reaction mixture is formed by transesterification of vegetable oils. The reaction mixture contains mainly methyl esters of higher fatty acids and glycerol. From this mixture, biodiesel is gained by spontaneous sedimentation in the gravitational field. The sedimentation can be considerably accelerated by controlled addition of water. It was found that addition of small amounts of water to the crude reaction mixture significantly affected the mixture, and substantial changes in the speed of the separation took place. Considerable differences in the composition and quality of the ester and glycerol phases occurred. The optical properties (transmittance and refractive indices) of the heterogeneous reaction mixture are changed after addition of water; this change can be observed spectrophotometrically. This method is applicable to all types of vegetable oils including waste frying oils.
A new min‐cut problem with application to electric power network partitioning
Authors: Sen Arunabha , Ghosh Pavel , Vittal Vijay , Yang Bo
Published: March 2008

The problem of partitioning a graph into two or more subgraphs that satisfies certain conditions is encountered in many different domains. Accordingly, graph partitioning problem has been studied extensively in the last 50 years. The most celebrated result among this class of problems is the max flow = min cut theorem due to Ford and Fulkerson. Utilizing the modifications suggested by Edmonds and Karp, it is well known that the minimum capacity cut in the directed graph with edge weights can be computed in polynomial time. If the partition divides the node setVinto subsetsV1andV2, whereV1contains one of the specified nodessandV2contains the other specified nodet, the capacity of a cut is defined as the sum of the edge weights going fromV1toV2. In electrical power distribution networks, a slow‐coherency‐based islanding strategy is used as a prevention against the cascading failures. In this paper, we concentrate on the graph partition problems which are encountered in electric power distribution networks. In this environment, two different definitions of capacity of a cut are used. In the first definition, capacity of a cut is taken to be the difference of the edge weights going fromV1toV2and fromV2toV1. In the second definition, the capacity of a cut is taken to be the maximum of sum of the edge weights going fromV1toV2and fromV2toV1. Surprisingly, with slight change of the definition of the capacity of a cut, the computational complexity of the problem changes significantly. In this paper, we show that with the new definitions of the capacity of a cut, the minimum cut computation problem becomes NP‐complete. We provide an optimal solution to the problems using mathematical programming techniques. In addition, we also provide heuristic solutions and compare the performance with that of the optimal solution. Copyright © 2008 John Wiley & Sons, Ltd.
Influences of climate, terrain and land cover on stream salinity in southeastern Australia, and implications for management through reforestation
Authors: van Dijk A. I. J. M. , Gilfedder M. , Austin J.
Published: March 2008

Reforestation of cleared land has the potential to reduce groundwater recharge, salt mobilization and streamflow. Stream salinity change is the net result of changes in stream salt load and streamflow. The net effect of these changes varies spatially as a function of climate, terrain and land cover. Successful natural resource management requires methods to map the spatial variability of reforestation impacts. We investigated salinity data from 2000 bores and streamflow and salinity measurements from 27 catchments in the Goulburn–Broken region in southeast Australia to assess the main factors determining stream salinity and opportunities for management through reforestation. For groundwater systems of similar geology, relationships were found between average annual rainfall and groundwater salinity and between groundwater salinity and low‐flow salinity. Despite its simplicity, we found that the steady‐state component of a simple conceptual coupled water–salt mass balance model (BC2C) adequately explained the spatial variation in streamflow and salinity. The model results suggest the efficiency of afforestation to reduce stream salinity could be increased by more than an order of magnitude through spatial planning. However, appreciable reductions in stream salinity in large rivers through land cover change alone would still require reforestation on an unprecedented scale. Copyright © 2008 John Wiley & Sons, Ltd.
p53 reaction to apoptosis induced by hydroxyapatite nanoparticles in rat macrophages
Authors: Sun Jiao , Ding Tingting
Published: March 2008

The effects and mechanism of hydroxyapatite (HAP) nanoparticles (NPs) on the induction of cytotoxicity and apoptosis in rat macrophages was evaluated by testing the antiproliferative effect of HAP NPs with agar overlay and direct contact methods. The apoptotic phenotype of the macrophages was observed by transmission electron microscopy (TEM), and the variation of transcription and expression of a cell apoptosis related gene (p53) was determined by semiquantitative RT‐PCR and western blotting. The results showed that a dose‐dependent proliferative inhibition of macrophages was induced by HAP NPs (30–80 nm) at concentrations between 20 and 200 μg/mL. The characteristic morphological changes of apoptosis were observed in macrophages after treatment with HAP NPs for 24 h. Furthermore, p53 mRNA levels significantly increased when macrophages were incubated with 200 μg/mL HAP NPs (p < 0.01). Western blot analysis showed that 100 μg/mL HAP NPs upregulated p53. The conclusion is that HAP NPs can induce p53 expression through phosphorylation, which promotes downstream genes and finally results in cell apoptosis. Moreover, p53 may be one of the ideal indictors to evaluate the biological safety of ceramic nanoparticles. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Surface‐initiated atom‐transfer radical polymerization of 3‐O‐methacryloyl‐1,2:5,6‐di‐ O‐isopropylidene‐α‐ D‐glucofuranoside onto gold surface
Authors: Yoon Kuk Ro , Ramaraj B. , Lee Seungho , Yu Jong‐Sung , Choi Insung S.
Published: March 2008

A sugar‐containing polymer was grown on gold surface by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) of methacrylate monomer, 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranoside (MAIpGIc), using 1,4,8,11‐tetraaza‐1,4,8,11‐tetramethylcyclotetradecane (Me4Cyclam) as ligand, 2‐bromopropionyl moiety attached on the gold surface as initiator, and Copper(I) bromide as catalyst, respectively, in tetrahydrofuran (THF) medium. The resultant sugar film was characterized by polarized infrared external reflectance spectroscopy (PIERS), X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE‐SEM), ellipsometry, and contact angle goniometry. The IR peaks characteristics of poly(3‐O‐methacryloyl‐α,β‐D‐glucopyranoside) (PMAGlc), broad OH stretch at ∼3400 cm−1, and CO ester stretch at ∼1748 cm−1 observed in PIERS spectra demonstrate the formation of PMAGlc on the gold surface. The AFM and SEM images show the polymer growth away from the gold surface without visible domain boundaries, and it further confirms the formation of sugar coating. The method described in the article would be beneficial in many areas, such as pathogen detection and biosensors, considering the biological importance of carbohydrate polymers. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Histopathology of the three implanted degradable biopolymers in rabbit eye
Authors: Rönkkö Seppo , Rekonen Petri , Sihvola Roope , Kaarniranta Kai , Puustjärvi Tuomo , Teräsvirta Markku , Uusitalo Hannu
Published: March 2008

New straightforward applications of new biopolymers are needed in glaucoma surgery. The aim of this study was to compare biocompatibility of three biomaterials in rabbit eyes after deep sclerectomy; a collagen implant (AquaFlow™) represented the “gold standard”. A blend of 85:15 poly(L‐lactide‐co‐glycolide) and 70:30 poly(L‐lactide‐co‐1,3‐trimethylene carbonate) copolymers in a molar ratio of 70:30 (Bio‐1 = Inion GTR™ membrane) and poly(DL‐lactide‐co‐glycolide with molar compositions of 50:50 (Bio‐2) and 85:15 (Bio‐3) were inserted into rabbits eyes. Bio‐1, Bio‐2 or Bio‐3 caused very mild eye irritation or tissue response which was comparable to that of the collagen implant. The biodegradation time of Bio‐1, Bio‐2, and Bio‐3 implants was over one year, 3 months and 6 months, respectively. Implant mapping by Fourier transform infrared (FTIR) microscopy revealed a heterogeneous distribution of degradation products throughout Bio‐1, Bio‐2, and Bio‐3. All implants were surrounded by a very fine tissue capsule which was not visible after total degradation of the implants. The FTIR spectrum of tissue capsule around Bio‐1 was almost identical to that around Bio‐2 whereas significant differences were observed in the spectrum of the tissue capsule around Bio‐3. Despite some differences in tissue response, all tested implants represent biologically acceptable materials for drainage devices in glaucoma surgery. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Nanophase separation of polymers exposed to simulated bonding conditions
Authors: Ye Qiang , Wang Yong , Spencer Paulette
Published: March 2008

Under in vivo conditions, there is little control over the amount of water left on the tooth during dentin bonding. As a result, it is possible to leave the dentin surface so wet that the adhesive actually undergoes physical separation into hydrophobic‐ and hydrophilic‐rich phases. Using tapping mode atomic force microscopy/PhaseImaging technique, nanosized phases with worm‐like features were found on the surface of model HEMA/BisGMA dentin adhesives cured in the presence of varying concentrations of water. The phase contrast became evident with the increase of water concentration in the initial adhesive formulation and varied with the ratio of hydrophilic/hydrophobic composition. Oversaturated water droplets of variable sizes may accumulate as micro‐voids within the hydrophilic and hydrophobic polymer phases. The phase domains were also identified following ethanol‐etching in combination with SEM/AFM techniques. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009