bluuebunny/crossref_metadata_2025 huggingface dataset:
Adult-born granule cells modulate CA2 network activity during retrieval of developmental memories of the mother
Authors: Laham Blake J. , Gore Isha R. , Brown Casey J. , Gould Elizabeth
Published: March 2024

Adult-born granule cells (abGCs) project to the CA2 region of the hippocampus, but it remains unknown how this circuit affects behavioral function. Here we show that abGC input to the CA2 of adult mice is involved in the retrieval of remote developmental memories of the mother. Ablation of abGCs impaired the ability to discriminate between a caregiving mother and a novel mother, and this ability returned after new neurons were regenerated. Chemogenetic inhibition of projections from abGCs to the CA2 also temporarily prevented the retrieval of remote mother memories. These findings were observed when abGCs were inhibited at 4-6 weeks old, but not when they were inhibited at 10-12 weeks old. We also found that abGCs are necessary for differentiating features of CA2 network activity, including theta-gamma coupling and sharp wave-ripples, in response to novel versus familiar social stimuli. Taken together, these findings suggest that abGCs are necessary for neuronal oscillations associated with discriminating between social stimuli, thus enabling retrieval of remote developmental memories of the mother by their adult offspring.
Synaptotagmin 7 docks synaptic vesicles to support facilitation and Doc2α-triggered asynchronous release
Authors: Wu Zhenyong , Kusick Grant F , Berns Manon MM , Raychaudhuri Sumana , Itoh Kie , Walter Alexander M , Chapman Edwin R , Watanabe Shigeki
Published: March 2024

Despite decades of intense study, the molecular basis of asynchronous neurotransmitter release remains enigmatic. Synaptotagmin (syt) 7 and Doc2 have both been proposed as Ca2+ sensors that trigger this mode of exocytosis, but conflicting findings have led to controversy. Here, we demonstrate that at excitatory mouse hippocampal synapses, Doc2α is the major Ca2+ sensor for asynchronous release, while syt7 supports this process through activity-dependent docking of synaptic vesicles. In synapses lacking Doc2α, asynchronous release after single action potentials is strongly reduced, while deleting syt7 has no effect. However, in the absence of syt7, docked vesicles cannot be replenished on millisecond timescales. Consequently, both synchronous and asynchronous release depress from the second pulse onward during repetitive activity. By contrast, synapses lacking Doc2α have normal activity-dependent docking, but continue to exhibit decreased asynchronous release after multiple stimuli. Moreover, disruption of both Ca2+ sensors is non-additive. These findings result in a new model whereby syt7 drives activity-dependent docking, thus providing synaptic vesicles for synchronous (syt1) and asynchronous (Doc2 and other unidentified sensors) release during ongoing transmission.
Conformation selection by ATP-competitive inhibitors and allosteric communication in ERK2
Authors: Anderson Jake W , Vaisar David , Jones David N , Pegram Laurel M , Vigers Guy P , Chen Huifen , Moffat John G , Ahn Natalie G
Published: March 2024

Activation of the extracellular signal-regulated kinase-2 (ERK2) by phosphorylation has been shown to involve changes in protein dynamics, as determined by hydrogen-deuterium exchange mass spectrometry (HDX-MS) and NMR relaxation dispersion measurements. These can be described by a global exchange between two conformational states of the active kinase, named ‘L’ and ‘R,’ where R is associated with a catalytically productive ATP-binding mode. An ATP-competitive ERK1/2 inhibitor, Vertex-11e, has properties of conformation selection for the R-state, revealing movements of the activation loop that are allosterically coupled to the kinase active site. However, the features of inhibitors important for R-state selection are unknown. Here, we survey a panel of ATP-competitive ERK inhibitors using HDX-MS and NMR and identify 14 new molecules with properties of R-state selection. They reveal effects propagated to distal regions in the P+1 and helix αF segments surrounding the activation loop, as well as helix αL16. Crystal structures of inhibitor complexes with ERK2 reveal systematic shifts in the Gly loop and helix αC, mediated by a Tyr-Tyr ring stacking interaction and the conserved Lys-Glu salt bridge. The findings suggest a model for the R-state involving small movements in the N-lobe that promote compactness within the kinase active site and alter mobility surrounding the activation loop. Such properties of conformation selection might be exploited to modulate the protein docking interface used by ERK substrates and effectors.
Wound-Induced Syncytia Outpace Mononucleate Neighbors during Drosophila Wound Repair
Authors: White James S. , Su Jasmine J. , Ruark Elizabeth M. , Hua Junmin , Shane Hutson M. , Page-McCaw Andrea
Published: March 2024

All organisms have evolved to respond to injury. Cell behaviors like proliferation, migration, and invasion replace missing cells and close wounds. However, the role of other wound-induced cell behaviors is not understood, including the formation of syncytia (multinucleated cells). Wound-induced epithelial syncytia were first reported around puncture wounds in post-mitotic
Drosophila
epidermal tissues, but have more recently been reported in mitotically competent tissues such as the
Drosophila
pupal epidermis and zebrafish epicardium. The presence of wound-induced syncytia in mitotically active tissues suggests that syncytia offer adaptive benefits, but it is unknown what those benefits are. Here, we use
in vivo
live imaging to analyze wound-induced syncytia in mitotically competent
Drosophila
pupae. We find that almost half the epithelial cells near a wound fuse to form large syncytia. These syncytia use several routes to speed wound repair: they outpace diploid cells to complete wound closure; they reduce cell intercalation during wound closure; and they pool the resources of their component cells to concentrate them toward the wound. In addition to wound healing, these properties of syncytia are likely to contribute to their roles in development and pathology.
Plastic vasomotion entrainment
Authors: Sasaki Daichi , Imai Ken , Ikoma Yoko , Matsui Ko
Published: March 2024

The presence of global synchronization of vasomotion induced by oscillating visual stimuli was identified in the mouse brain. Endogenous autofluorescence was used and the vessel “shadow” was quantified to evaluate the magnitude of the frequency-locked vasomotion. This method allows vasomotion to be easily quantified in non-transgenic wild-type mice using either the wide-field macro-zoom microscopy or the deep-brain fiber photometry methods. Vertical stripes horizontally oscillating at a low temporal frequency (0.25 Hz) were presented to the awake mouse and oscillatory vasomotion locked to the temporal frequency of the visual stimulation was induced not only in the primary visual cortex but across a wide surface area of the cortex and the cerebellum. The visually induced vasomotion adapted to a wide range of stimulation parameters. Repeated trials of the visual stimulus presentations resulted in the entrainment of the amplitude of the vasomotion. Horizontally oscillating visual stimulus is known to induce horizontal optokinetic response (HOKR). The amplitude of the eye movement is known to increase with repeated training sessions and the flocculus region of the cerebellum is known to be essential for this learning to occur. Here, we show a strong correlation between the average HOKR performance gain and the vasomotion entrainment magnitude in the cerebellar flocculus. Therefore, the plasticity of vasomotion and neuronal circuits appeared to occur in parallel. Efficient energy delivery by the entrained vasomotion may contribute to meeting the energy demand for increased coordinated neuronal activity and the subsequent neuronal circuit reorganization.
High frequency spike inference with particle Gibbs sampling
Authors: Diana Giovanni , Sermet B. Semihcan , DiGregorio David A.
Published: March 2024

Fluorescent calcium indicators are indispensable tools for monitoring the spiking activity of large neuronal populations in animal models. However, despite the plethora of algorithms developed over the last decades, accurate spike time inference methods for spike rates greater than 20 Hz are lacking. More importantly, little attention has been devoted to the quantification of statistical uncertainties in spike time estimation, which is essential for assigning confidence levels to inferred spike patterns. To address these challenges, we introduce (1) a statistical model that accounts for bursting neuronal activity and baseline fluorescence modulation and (2) apply a Monte Carlo strategy (particle Gibbs with ancestor sampling) to estimate the joint posterior distribution of spike times and model parameters. Our method is competitive with state-of-the-art supervised and unsupervised algorithms by analyzing the CASCADE benchmark datasets. The analysis of fluorescence transients recorded using an ultrafast genetically encoded calcium indicator, GCaMP8f, demonstrates the ability of our method to infer spike time intervals as short as five milliseconds. Overall, our study describes a Bayesian inference method to detect neuronal spiking patterns and their uncertainty. The use of particle Gibbs samplers allows for unbiased estimates of spike times and all model parameters, and it provides a flexible statistical framework to test more specific models of calcium indicators.
Role of N343 glycosylation on the SARS-CoV-2 S RBD structure and co-receptor binding across variants of concern
Authors: Ives Callum M , Nguyen Linh , Fogarty Carl A , Harbison Aoife M , Durocher Yves , Klassen John , Fadda Elisa
Published: March 2024

Glycosylation of the SARS-CoV-2 spike (S) protein represents a key target for viral evolution because it affects both viral evasion and fitness. Successful variations in the glycan shield are difficult to achieve though, as protein glycosylation is also critical to folding and structural stability. Within this framework, the identification of glycosylation sites that are structurally dispensable can provide insight into the evolutionary mechanisms of the shield and inform immune surveillance. In this work, we show through over 45 μs of cumulative sampling from conventional and enhanced molecular dynamics (MD) simulations, how the structure of the immunodominant S receptor binding domain (RBD) is regulated by N-glycosylation at N343 and how this glycan’s structural role changes from WHu-1, alpha (B.1.1.7), and beta (B.1.351), to the delta (B.1.617.2), and omicron (BA.1 and BA.2.86) variants. More specifically, we find that the amphipathic nature of the N-glycan is instrumental to preserve the structural integrity of the RBD hydrophobic core and that loss of glycosylation at N343 triggers a specific and consistent conformational change. We show how this change allosterically regulates the conformation of the receptor binding motif (RBM) in the WHu-1, alpha, and beta RBDs, but not in the delta and omicron variants, due to mutations that reinforce the RBD architecture. In support of these findings, we show that the binding of the RBD to monosialylated ganglioside co-receptors is highly dependent on N343 glycosylation in the WHu-1, but not in the delta RBD, and that affinity changes significantly across VoCs. Ultimately, the molecular and functional insight we provide in this work reinforces our understanding of the role of glycosylation in protein structure and function and it also allows us to identify the structural constraints within which the glycosylation site at N343 can become a hotspot for mutations in the SARS-CoV-2 S glycan shield.
#GotGlycans: Role of N343 Glycosylation on the SARS-CoV-2 S RBD Structure and Co-Receptor Binding Across Variants of Concern
Authors: Ives Callum M. , Nguyen Linh , Fogarty Carl A. , Harbison Aoife M. , Durocher Yves , Klassen John S. , Fadda Elisa
Published: March 2024

Glycosylation of the SARS-CoV-2 spike (S) protein represents a key target for viral evolution because it affects both viral evasion and fitness. Successful variations in the glycan shield are difficult to achieve though, as protein glycosylation is also critical to folding and to structural stability. Within this framework, the identification of glycosylation sites that are structurally dispensable can provide insight into the evolutionary mechanisms of the shield and inform immune surveillance. In this work we show through over 45 μs of cumulative sampling from conventional and enhanced molecular dynamics (MD) simulations, how the structure of the immunodominant S receptor binding domain (RBD) is regulated by
N
-glycosylation at N343 and how this glycan’s structural role changes from WHu-1, alpha (B.1.1.7), and beta (B.1.351), to the delta (B.1.617.2) and omicron (BA.1 and BA.2.86) variants. More specifically, we find that the amphipathic nature of the
N
-glycan is instrumental to preserve the structural integrity of the RBD hydrophobic core and that loss of glycosylation at N343 triggers a specific and consistent conformational change. We show how this change allosterically regulates the conformation of the receptor binding motif (RBM) in the WHu-1, alpha and beta RBDs, but not in the delta and omicron variants, due to mutations that reinforce the RBD architecture. In support of these findings, we show that the binding of the RBD to monosialylated ganglioside co-receptors is highly dependent on N343 glycosylation in the WHu-1, but not in the delta RBD, and that affinity changes significantly across VoCs. Ultimately, the molecular and functional insight we provide in this work reinforces our understanding of the role of glycosylation in protein structure and function and it also allows us to identify the structural constraints within which the glycosylation site at N343 can become a hotspot for mutations in the SARS-CoV-2 S glycan shield.
Complementary cognitive roles for D2-MSNs and D1-MSNs in interval timing
Authors: Bruce R. Austin , Weber Matthew A. , Bova Alexandra S. , Volkman Rachael A. , Jacobs Casey E. , Sivakumar Kartik , Stutt Hannah R , Kim Young-cho , Curtu Rodica , Narayanan Nandakumar S.
Published: March 2024

The role of striatal pathways in cognitive processing is unclear. We studied dorsomedial striatal cognitive processing during interval timing, an elementary cognitive task that requires mice to estimate intervals of several seconds, which involves working memory for temporal rules as well as attention to the passage of time. We harnessed optogenetic tagging to record from striatal D2-dopamine receptor-expressing medium spiny neurons (D2-MSNs) in the indirect pathway and from D1-dopamine receptor-expressing MSNs (D1-MSNs) in the direct pathway. We found that D2-MSNs and D1-MSNs exhibited opposing dynamics over temporal intervals as quantified by principal component analyses and trial-by-trial generalized linear models. MSN recordings helped construct and constrain a four-parameter drift-diffusion computational model. This model predicted that disrupting either D2-MSN or D1-MSNs would increase interval timing response times and alter MSN firing. In line with this prediction, we found that optogenetic inhibition or pharmacological disruption of either D2-MSNs or D1-MSNs increased response times. Pharmacologically disrupting D2-MSNs or D1-MSNs also increased response times, shifted MSN dynamics, and degraded trial-by-trial temporal decoding. Together, our findings demonstrate that D2-MSNs and D1-MSNs make complementary contributions to interval timing despite opposing dynamics, implying that striatal direct and indirect pathways work together to shape temporal control of action. These data provide novel insight into basal ganglia cognitive operations beyond movement and have implications for a broad range of human striatal diseases and for therapies targeting striatal pathways.
Communication Skills Inventory-Short Form: Validity and Reliability Study
Authors: BALCI ÇELİK Seher , ERSANLI Kurtman
Published: March 2024

Bu araştırmada; Ersanlı ve Balcı (1997) tarafından geliştirilen iletişim becerileri envanterinin kısa formu, geçerlik ve güvenilirlik çalışmasının yapılması amaçlanmıştır. Araştırmada üç farklı bölgede öğrenim gören üniversite öğrencilerinden
veriler toplanmıştır. 614 öğrenciden oluşan ilk gruptan toplanan veriler ile açımlayıcı faktör analizi, 583 öğrenciden oluşan ikinci gruptan toplanan veriler ile doğrulayıcı faktör analizi, 148 öğrenciden toplanan üçüncü veri seti
de ölçüt geçerliği analizi için kullanılmıştır. Toplam 1345 üniversite öğrencisinden veri toplanmıştır. Öğrencilere İletişim Becerileri Envanteri (İBE), Topluluk Önünde Konuşma Kaygısı Ölçeği (TÖKKÖ), İletişim Becerileri Ölçeği
(İBÖ) ve Kişisel Bilgi Formu uygulanmıştır. Ölçeğin yapı geçerliliğini test etmek için Açımlayıcı (AFA) ve Doğrulayıcı Faktör Analizi (DFA) yapılmıştır. Açımlayıcı faktör analizi ile elde edilen yapı, doğrulayıcı faktör analizi
ile model uyumu açısından test edilmiştir. 1. düzey ve 2. düzey doğrulayıcı faktör analizleri sonucunda 16 maddelik üç faktörlü modelin uyum iyiliği indekslerinin iyi uyum gösterdiği ortaya çıkmıştır. Analizler sonucunda, İletişim
Becerileri Envanteri kısa formunun 16 maddeden ve üç faktörden oluşan bir yapıya sahip olduğu bulunmuştur. Envanterin iç tutarlılığa, benzer ölçek geçerliğine ve üç faktörlü bir yapıya sahip olduğu görülmüştür. Cinsiyete göre fark
olup olmadığını test etmek için Tek yönlü MANOVA analizi yapılmış olup anlamlı farklılık olmadığı bulunmuştur. Sonuç olarak, yapılan analizler İletişim Becerileri Envanteri kısa formunun üniversite öğrencilerinin iletişim becerilerini
belirlemek için kullanılabilecek geçerli ve güvenilir bir ölçme aracı olduğu bulgulanmıştır. Bulgular ilgili alanyazın ışığında tartışılmıştır.
Narrative Review on Osteoporosis: A Silent Killer
Authors: Kulkarni Shrihari L , Kour Harpreet
Published: March 2024

Osteoporosis is a common condition affecting the elderly population. Most of the time, it is diagnosed only after an individual suffers from a fracture. In addition to the fracture and its complications, the patients and their families must also bear the psychological and financial consequences of the disease. There are multiple risk factors associated with osteoporosis, hence it requires a multimodal approach in management as well. This narrative review aims to provide a comprehensive insight into the classification, prevalence, pathophysiology, signs and symptoms, risk factors, screening tools, management, differential diagnosis, prognosis, complications, and recent advances in osteoporosis.
Efficient Tariff System in the Electricity Distribution: Evidence from Uganda
Authors: Mutumba Geoffrey Ssebabi , Amerit Bosco , Kaddu Milly , Mubiinzi Geoffrey , Bashir Hassan , Birungi Felister , Nakajubi Florence , Jaza Muhamood , Senyonga Livingstone
Published: March 2024

This study investigates incentive regulation to foster an efficient tariff system in the electricity distribution subsector in Uganda. This study seeks to find empirical evidence to support the argument that regulation is associated with efficiency among distributors. It seeks to design an appropriate model of incentive regulation within the distribution subsector. It assesses the efficiency of existing tariff setting system with a view of guiding policy on how best incentives should be appropriated.
 It uses the data envelopment analysis and stochastic frontier analysis to investigate how distribution firms use input costs to come up with an efficient end user tariffs. Quarterly data used is from Electricity Regulatory Authority (ERA) covering the period 2013-2019.
 The findings are that distribution firms cost inputs are inconsistent with the way they their operational and maintenance costs are generated and transmitted to end user tariff. The regulator should be keen on the way tariff is set such that it is fair to all players in the electricity markets.
Incentive regulation has a positive influence on cost efficiency and end user tariff. A reduction in energy losses and energy purchases from transmitter makes up the most efficient cost drivers. Lastly, tariff regulation has increased efficiency in operations through in improved quality and reliability of power distribution. First and foremost is reduced load shedding, secondly is more reliable power distribution to end users. Appropriate Incentive regulation has a direct effect on cost of utility and in increasing access of vulnerable groups.
Undesirable complication after transradial coronary angiography: A case report
Authors:   Gaziantep University, Vocational School of Health Services, Department of Operating Room Services, Gaziantep, Türkiye, Altinbas Ozgur , Isik Mehmet ,   Necmettin Erbakan University, Faculty of Medicine, Department of Cardiovascular Surgery, Konya, Türkiye
Published: March 2024

Radial artery is one of the intervention cites for coronary angiography and has an increased tendency according to the successful results in the literature. However, some undesirable clinical situations may occur by using this route as with every invasive intervention. In this study, we presented a patient who had left upper limb ischemia following transradial angiography. An intimal flap with an approximate length of 15 cm was removed during embolectomy from the brachial artery. After multiple embolectomy procedures, axillo-brachial bypass was performed using the saphenous vein. However, ischemia in the forearm did not improve and limb loss occurred.
Investigation of factors affecting reintervention after type A aortic dissection
Authors:   Mehmet Akif Ersoy Thoracic and Cardiovascular Surgey Training Research Hospital, Department of Cardiovascular Surgery, Istanbul, Türkiye, Kaplan Mustafa Can , Kadirogulları Ersin ,   Department of Cardiovascular Surgery, University of Health Sciences, Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Training and Research Hospital, Istanbul, Turkey, Guler Salih ,   Departments of Cardiovascular Surgery, İstanbul Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Training and Research Hospital, İstanbul, Timur Baris ,   University of Health Sciences Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital, Cardiovascular Surgery Clinic, İstanbul, Türkiye, Kutanis Kemal ,   Mehmet Aki̇f Ersoy Thoraci̇c and Cardi̇ovascular Surgery Trai̇ni̇ng Research Hospital, Cardiovascular Surgery Clinic, İstanbul, Türkiye, Yasar Emre ,   Department of Cardiovascular Surgery, İstanbul Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Training and Research Hospital, Istanbul, Turkey, Yazici Batuhan ,   Mehmet Aki̇f Ersoy Thoraci̇c And Cardi̇ovascular Surgery Trai̇ni̇ng Research Hospital, Cardiovascular Surgery Clinic, İstanbul, Türkiye, Aydin Unal ,   Mehmet Akif Ersoy Chest Cardiovascular Surgery Training and Research Hospital, İstanbul, Türkiye
Published: March 2024

Aim: Our study aims to share the reintervention results of patients who were operated with the diagnosis of Type A aortic dissection and to examine the factors that cause reintervention. Material and Methods: In our single-center retrospective study, 244 patients who underwent surgery due to Type A aortic dissection between November 2010 and June 2021 were included. Results for patients who underwent reintervention and factors which caused reintervention were compared with demographic data, preoperative, intraoperative and postoperative variables. Results: A total of 142 patients were included in the study and 15.5% of them underwent reintervention. Reoperation was performed in 8 (36.4%) of 22 patients who underwent reintervention, while thoracic aortic endovascular repair was performed in 14 (63.6%) patients. Post-procedure mortality was observed in 5 (22.7%) of the patients who underwent reintervention. The mean age of the patients who underwent reintervention was 46.6±13.2 and there was a statistically significant (p<0.05) difference between the groups (p: 0.026). Results that were significant for reintervention were multivariate analysis with cox regression and it was shown that the persistence of postoperative hypertension with total arch surgery was a risk factor for reintervention (p: 0.03, p: 0.008). Conclusion: Type A aortic dissection is not considered to be completely cured after the first operation. It is necessary to evaluate the patients in terms of reintervention with close follow-up. We propose that patients who underwent total arch surgery during the first operation and hypertension in the postoperative period are risk factors for reintervention.
Cover Picture: Functionalization of Crystalline Colloidal Arrays through Click Chemistry (Adv. Mater. 21/2007)
Authors: Evanoff D. D. , Hayes S. E. , Ying Y. , Shim G. H. , Lawrence J. R. , Carroll J. B. , Roeder R. D. , Houchins J. M. , Huebner C. F. , Foulger S. H.
Published: November 2007

Photonic crystals based on electrostatically‐stabilized colloidal arrays dispersed in a liquid medium are of interest to materials scientists partly because of the optical tuning afforded to theses systems with a variation in interparticle distance. On p. 3507, Stephen Foulger and co‐workers from Clemson University, USA report on a general strategy for the preparation of well‐defined and regioselectively functionalized ordered colloidal particles through the exploitation of “click” chemistry. Click transformations have found utility in the synthesis and/or functionalization of a range of systems. In addition, the solvochromic tuning of the ordered arrays is employed to modify the emission spectra of the surface‐attached photoluminescent dyes.
Preparation and properties of melt‐processable polyimides based on fluorinated aromatic diamines and aromatic dianhydrides
Authors: Wang Kai , Fan Lin , Liu Jin‐Gang , Zhan Mao‐Sheng , Yang Shi‐Yong
Published: November 2007

Two series of melt‐processable polyimides were prepared from 4,4′‐bis(3‐amino‐5‐trifluoromethylphenoxy)biphenyl (m‐6FBAB) and 4,4′‐bis(4‐amino‐5‐trifluoromethylphenoxy) biphenyl (p‐6FBAB) with various aromatic dianhydrides. The effects of the chemical structures of the polyimides on their properties, especially the melt processability and organic solubility, were investigated. The experimental results demonstrate that some of the fluorinated aromatic polyimides showed good melt processability at elevated temperatures (250–360°C) with relatively low melt viscosities and could be melt‐molded to produce strong and tough polyimide sheets. Meanwhile, the polyimides showed excellent organic solubility in both polar aprotic solvents and common solvents to give stable polyimide solutions with high polymer concentrations and relatively low viscosities. Thus, we prepared high‐quality polyimide films by casting the polyimide solutions on glass plates followed by baking at relatively low temperatures. The polyimides derived from m‐6FBAB showed better melt processability and solubility than the p‐6FBAB based polymers. The melt‐processable polyimides showed a good combination of thermal stability and mechanical properties, with decomposition temperatures of 547–597°C, glass‐transition temperatures in the range 205–264°C, tensile strengths of 81.3–104.9 MPa, and elongations at break as high as 19.6%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation of hydrogels composed of poly(vinyl alcohol) and polyethyleneimine and their electrical response
Authors: Kie Shim Jin , Ryong Oh Seng , Bong Lee Sang , Cho Kye Min
Published: November 2007

Semi‐ and full‐interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) and polyethyleneimine (PEI) were prepared to investigate the bending behavior under the electric response. To find out the characteristics of the hydrogel in the medium, swelling ratio, and rate and water state of the hydrogels were measured. The swelling ratio of the semi‐IPN hydrogels increased with PEI content in the matrix, whereas that of full‐IPN hydrogels dramatically decrease with increase of PEI contents in the hydrogels. In the water state of hydrogel, the bound water and free water of semi‐IPN hydrogels increased with PEI weight ratio. The full‐IPN hydrogels show the lower free water content in comparison with the semi‐IPN hydrogel. The IPN hydrogels exhibited bending angle change in response to external stimulus such as voltage, the bending angle increased with PEI concentration. In addition, the repeated bending behaviors according to the magnitude of the applied electric field revealed that the bending angle is reversible without collapse of formation of hydrogel in all samples. Thus, the hydrogels will be useful as novel modulation systems in the field of artificial organ and matrix for drug delivery. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) membranes using amphiphilic urethane acrylate nonionomers as an reactive compatibilizer
Authors: Kim Ju‐Young , Mulmi Suresh , Lee Chang‐Hyun , Lee Young‐Moo , Ihn Kyo‐Jin
Published: November 2007

Microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) random copolymer (PSSU) membranes were fabricated through a new copolymerization process. Two immiscible monomers, styrene and sodium styrene sulfonate were dissolved in a single solvent and formed homogeneous solutions, which were directly converted to wall‐to‐wall membranes via radical copolymerization process with microphase separation. Since urethane acrylate nonionomer (UAN) chain has amphiphilicity as well as reactivity with vinyl monomers, UAN chain could act not only as compatibilizer for polystyrene and poly(sodium styrene sulfonate), but also as macrocrosslinker, which makes it possible for the formation of crosslinked copolymer of two immiscible polymers without macrophase separation. TEM image of the PSSU membranes showed that nanosized hydrophilic domains formed by hydrophilic/hydrophobic microphase separation were dispersed at hydrophobic matrix phase. PSSU membranes fabricated using UAN chain having longer chain length of polyethylene oxide showed bigger size of hydrophilic domains, which was also confirmed by TEM images. Fabricated PSSU membranes showed proton conductivity higher than 10−2 S/cm and methanol permeability lower than 10−7 cm2/s of Nafion® 117 membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Consistent model predictions for isothermal cure kinetics investigation of high performance epoxy prepregs
Authors: Zhang Jin , Fox Bronwyn , Guo Qipeng
Published: November 2007

An accurate kinetics model is essential for understanding the curing mechanism and predicting the end properties of polymer materials. Graphite/epoxy AS4/8552 prepreg is a recent high‐performance thermosetting composite modified with thermoplastic, which is being used in the manufacture of aircraft and military structures. The isothermal cures of this system along with another thermoplastic toughened high‐performance prepreg, the T800H/3900‐2 system, were investigated by real‐time Fourier transform infrared (FTIR) spectroscopy. The cure rate was quantitatively analyzed based on the concentration profiles of both the epoxy and primary amine groups. Three autocatalytic models were used to determine kinetics parameters for both composite systems. The model which utilizes an empirical term, the final relative conversion (at different isothermal curing temperatures), describes the experimental data of both systems more satisfactorily than the model which applies a diffusion factor. The modeling results suggest that the curing of epoxy within both prepregs can be assumed to be a second order process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
A Zeolite‐Like Zinc Phosphonocarboxylate Framework and Its Transformation into Two‐ and Three‐Dimensional Structures
Authors: Chen Zhenxia , Zhou Yaming , Weng Linhong , Yuan Chao , Zhao Dongyuan
Published: November 2007

Three zinc phosphonocarboxylates, Zn2(pbc)2⋅Hdma⋅H3O⋅2H2O (1), Zn(pbc)⋅Hdma (2), and Zn4.5(pbc)3(OH)(H2O)0.5⋅Hdma (3) (H3pbc=4‐phosphonobenzoic acid, dma=dimethylamine) were synthesized by the mixed solvothermal reaction of Zn(Ac)2⋅2H2O and 4‐phosphonobenzoic acid in N,N‐dimethylformamide (DMF) and water. The zigzag and ladderlike chains completely constructed by triply fused 4‐membered rings (denoted SBU‐1) are linked by the organic moieties to form the 3D zeolite‐like structure 1 and the layered structure 2, respectively. As for structure 3, a new second building unit (SBU‐2) formed by the inset of the [Zn3O12] trimer into the 4‐membered ring as well as SBU‐1 is observed. The connections between the two types of SBUs lead to a “zinc phosphate” layer, which is linked by the organic groups to generate a 3D pillar‐layered structure. Both solution‐mediated and solid‐state transformations of 1 to 2 and 3 were observed. A possible mechanism for the transformation is proposed. Gas sorption studies show that 1 has accessible pores for methanol and water and exhibits size selectivity for alcohols.
Highly Diastereoselective Friedel–Crafts Alkylation Reactions via Chiral α‐Functionalized Benzylic Carbocations
Authors: Stadler Daniel , Bach Thorsten
Published: November 2007

A series of chiral 1‐aryl‐1‐alkanols, which carry different functional groups (FGs) at the 2‐position, were subjected to an acid (HBF4)‐catalyzed reaction with various arenes. An SN1 substitution reaction was observed, in the course of which 1,1‐diarylalkanes were formed. In most cases (40 out of 51 reactions), yields were very good to excellent (75–99 %). The diastereoselectivity of the reaction was heavily dependent on the FG at the 2‐position. If the FG was methoxycarbonyl, nitro, hydroxy, cyano, trimethylsilylethynyl, or chloro, the corresponding anti products were favored and with a decreasing preference in this order. The methoxycarbonyl‐substituted substrates gave the anti products with diastereomer ratios (d.r.) that exceeded 92:8 (16 examples). Nitro‐ and hydroxy‐substituted products were obtained in most instances with d.r.≥90:10, whereas cyano‐, trimethylsilylalkynyl‐, or chloro‐substituted substrates delivered only with certain arenes products with high selectivity (d.r.≥90:10). The sterically more demanding FGs ethylsulfonyl, ethoxysulfonyl, and diethoxyphosphonyl induced diastereofacial selectivity in favor of the corresponding syn products, with diethoxyphosphonyl being the most effective. The substrate with FG=PO(OEt)2 delivered, with eight different arenes, the corresponding syn substitution products (d.r.=80:20 – >95:5). The relative configuration of the products was elucidated by spectroscopic and synthetic methods. On selected examples, the reactions were shown to proceed stereoconvergently, under kinetic control, and without racemization. Depending on the functional group, the onset of the reactions between 2‐methylthiophene and some representative alcohols was found to occur at a temperature Θ between −78 and −40 °C. There was no correlation between the selectivity and Θ. A model is suggested to explain the facial diastereoselectivity based on a preferred conformation of the putative intermediate carbocation.
A Note on P ‐values for Two‐sided Tests
Authors: Finner Helmut , Strassburger Klaus
Published: November 2007

Based on uniformly most powerful unbiased (UMPU) tests for two‐sided hypotheses and a short note in Lehmann (1959) on critical levels for randomized tests, Meulepas (1998, 1999) proposed (two‐tailed) P ‐values taking into account the randomization constant(s) of the UMPU‐tests. While UMPU‐tests need an extra uniform observation if randomization is required, the P ‐values proposed by Meulepas need no extra uniform observation. At first glance, his idea looks very promising in order to define a suitable and powerful P ‐value. Unfortunately, such P ‐values are generally too conservative. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Atlanta Classification of acute pancreatitis revisited
Authors: Bollen T L , van Santvoort H C , Besselink M G , van Leeuwen M S , Horvath K D , Freeny P C , Gooszen H G
Published: November 2007

Background

In a complex disease such as acute pancreatitis, correct terminology and clear definitions are important. The clinically based Atlanta Classification was formulated in 1992, but in recent years it has been increasingly criticized. No formal evaluation of the use of the Atlanta definitions in the literature has ever been performed.

Methods

A Medline literature search sought studies published after 1993. Guidelines, review articles and their cross-references were reviewed to assess whether the Atlanta or alternative definitions were used.

Results

A total of 447 articles was assessed, including 12 guidelines and 82 reviews. Alternative definitions of predicted severity of acute pancreatitis, actual severity and organ failure were used in more than half of the studies. There was a large variation in the interpretation of the Atlanta definitions of local complications, especially relating to the content of peripancreatic collections.

Conclusion

The Atlanta definitions for acute pancreatitis are often used inappropriately, and alternative definitions are frequently applied. Such lack of consensus illustrates the need for a revision of the Atlanta Classification.
Transcatheter closure of atrial septal defect without balloon sizing
Authors: Wang Jou‐Kou , Tsai Shen‐Kou , Lin Shu‐Man , Chiu Shuenn‐Nan , Lin Ming‐Tai , Wu Mei‐Hwan
Published: November 2007

Objective: To evaluate the safety and feasibility of transcatheter closure of atrial septal defect (ASD) without balloon sizing. Methods: A total of 243 patients (group I), aged 2.1–76 years (median 22 years), underwent transcatheter closure of ASD without balloon sizing. The maximal diameter of the defect was measured on transesophageal echocardiographic (TEE) images. The size of device selected was generally 4–6 mm and 5–8 mm larger than the maximal diameter, if the defect was <14 mm and ≥14 mm, respectively. The results of ASD closure in group I were compared with those of 271 patients (group II, median age 11 years) who underwent ASD closure with balloon sizing prior to the study period. Results: Of the 243 patients in group I, the maximal defect diameter ranged from 5.2 to 37 mm (mean 17.5 ± 6.6 mm, median 17 mm). A total of 247 Amplatzer septal occluders were deployed in 240 patients. Two patients were found to develop distal embolization of a device the next day. Therefore, failure occurred in five patients. Comparing the results between group I and group II, there was no significant difference in success rate (238/243 vs. 263/271), incidence of embolization (2/243 vs. 2/271) and complete closure rate at 3‐month follow‐up (94.1% vs. 95.8%). There is significant difference in mean age (26.6 ± 20.2 vs. 19.1 ± 17.6), maximal defect diameter (17.5 ± 6.6 vs. 14.1 ± 5.9 mm) and Qp/Qs ratio (2.77 ± 1.11 vs. 2.48 ± 0.97) between group I and II. The mean diameter of device used was significantly larger in group I than in group II (23.1 ± 8.1 vs. 19.6 ± 7 mm, P < 0.001). Conclusions: Balloon sizing may not be necessary in transcatheter closure of ASD. © 2008 Wiley‐Liss, Inc.
Classification of coronary artery bifurcation lesions and treatments: Time for a consensus!
Authors: Louvard Yves , Thomas Martyn , Dzavik Vladimir , Hildick‐Smith David , Galassi Alfredo R. , Pan Manuel , Burzotta Francisco , Zelizko Michael , Dudek Darius , Ludman Peter , Sheiban Imad , Lassen Jens F. , Darremont Olivier , Kastrati Adnan , Ludwig Josef , Iakovou Ioannis , Brunel Philippe , Lansky Alexandra , Meerkin David , Legrand Victor , Medina Alfonso , Lefèvre Thierry
Published: November 2007

Background: Percutaneous coronary intervention (PCI) of coronary bifurcation lesions remains a subject of debate. Many studies have been published in this setting. They are often small scale and display methodological flaws and other shortcomings such as inaccurate designation of lesions, heterogeneity, and inadequate description of techniques implemented. Methods: The aim is to propose a consensus established by the European Bifurcation Club (EBC), on the definition and classification of bifurcation lesions and treatments implemented with the purpose of allowing comparisons between techniques in various anatomical and clinical settings. Results: A bifurcation lesion is a coronary artery narrowing occurring adjacent to, and/or involving, the origin of a significant side branch. The simple lesion classification proposed by Medina has been adopted. To analyze the outcomes of different techniques by intention to treat, it is necessary to clearly define which vessel is the distal main branch and which is (are) the side branche(s) and give each branch a distinct name. Each segment of the bifurcation has been named following the same pattern as the Medina classification. The classification of the techniques (MADS: Main, Across, Distal, Side) is based on the manner in which the first stent has been implanted. A visual presentation of PCI techniques and devices used should allow the development of a software describing quickly and accurately the procedure performed. Conclusion: The EBC proposes a new classification of bifurcation lesions and their treatments to permit accurate comparisons of well described techniques in homogeneous lesion groups. © 2008 Wiley‐Liss, Inc.
An analysis of door‐to‐balloon time in a single center to determine causes of delay and possibilities for improvement
Authors: Wu Eugene B. , Arora Nipun , Eisenhauer Andrew C. , Resnic Frederic S.
Published: November 2007

Objectives: We analyzed door‐to‐balloon times in our institution to identify those factors which significantly prolong time to treatment in ST elevation myocardial infarction (STEMI). Background: Recent data have shown that patients with myocardial infarction transferred from one institution to another for PCI and those presenting outside of normal working hours suffer considerably prolonged door‐to‐balloon times. Methods: We analyzed the door‐to‐balloon time and its components from January 2005 to March 2006 in 167 consecutive patients presenting with STEMI to determine which variables were associated with delays. Results: The median door to balloon (DTB) time of all patients was 127 min. DTB was 62 min (P = 0.001) for patients presenting directly during working hours, 111.5 min for patients presenting directly during on‐call hours, 157.5 min for patients presenting to outside hospitals during working hours and 149 min for patients transferred from outside hospitals during on‐call hours. Factors that significantly lengthened DTB time included presentation during on‐call hours (P = 0.007), outside hospital presentation (<0.001), prolonged time from chest pain onset to presentation (P = 0.004), absence of chest pain on presentation (P = 0.01), and cardiac arrest before PCI (P = 0.05). Conclusion: In our center, transport time and on‐call hour delays account for the majority of reperfusion delay. Other factors that influenced delay were atypical presentation without chest pain, borderline ST changes, or delayed presentation. Thus, transfer from an outside facility, presentation after working hours, and having a difficult diagnosis all influence the rapidity of treatment. The implementation of an in‐house STEMI response team may reduce the process induced delays and improve door‐to‐balloon times. © 2008 Wiley‐Liss, Inc.
Different strategies of retrograde approach in coronary angioplasty for chronic total occlusion
Authors: Saito Shigeru
Published: November 2007

Background:

Retrograde approach through the collateral channels has been recently proposed and has the potential to improve the success rate of percutaneous coronary intervention (PCI) in chronic total occlusion (CTO) lesions of the coronary arteries.

Methods:

The author performed retrograde approach for CTO lesions in 45 patients from January 2006 to January 2007 at different medical institutions worldwide. The details of the techniques were examined retrospectively.

Results:

The septal branch route was used in 93% of the cases. The author classified the strategies into six types after the successful crossing of a guidewire into the target artery distal to the CTO lesion through the collateral channels. Among them, “Just landmark,” “Controlled antegrade and retrograde subintimal tracking,” and “Proximal true lumen puncture” strategies were used most frequently (32, 27, and 30%, respectively). The retrograde guidewires could be successfully passed distal to the CTO lesion in 37 patients (82%), among them the final PCI success was achieved in 31 patients, yielding the PCI success by pure retrograde approach of 69%. The final success rate among 45 patients including 42 patients with previous failed attempts was 84% (38 patients). There were no serious complications related to the retrograde approach.

Conclusions:

Retrograde approach with different strategies, mainly through septal arteries, can provide a high success rate with PCI, as shown in 83% of patients with previous failed attempts at traditional PCI for CTO lesions, with there being no serious complications. More experience of this technique and its refinement are required for further improvement of PCI techniques for CTO lesions. © 2008 Wiley‐Liss, Inc.
Late target lesion revascularization after implantation of sirolimus‐eluting stent
Authors: Hong Myeong‐Ki , Mintz Gary S. , Lee Cheol Whan , Park Duk‐Woo , Lee Seung‐Whan , Kim Young‐Hak , Jung In‐Hyun , Kim Sang‐Hyun , Cheong Sang‐Sig , Kim Jae‐Joong , Park Seong‐Wook , Park Seung‐Jung
Published: November 2007

Objectives: We evaluated the incidence, clinical presentation, and angiographic in‐stent restenosis (ISR) pattern of late target lesion revascularization (TLR) after sirolimus‐eluting stent (SES) implantation. Background: Late TLR is an unusual finding beyond 6–9 months after bare‐metal stent implantation. However, late TLR after SES implantation has not been sufficiently evaluated. Methods: The study population consisted of 804 patients with 1,020 native lesions that were patent at 6‐month follow‐up angiogram after SES implantation. Results: Late TLR was performed in 18 patients with 18 lesions (1.8%) at 24.1 ± 2.6 months (range; 18–30 months) after SES implantation. Clinical presentation of late TLR patients was silent ischemia in eight patients and recurrent angina in 10 patients, but none had an acute coronary syndrome. Angiographic ISR pattern of late TLR lesions were focal ISR in 12 lesions (67%) and diffuse ISR in six lesions (33%). Serial quantitative coronary angiographic analysis of these lesions showed a minimal lumen diameter of 2.6 ± 0.5 mm immediately after SES implantation, 2.4 ± 0.4 mm at 6‐month follow‐up and 0.7 ± 0.6 mm at 24‐month follow‐up (ANOVA P < 0.001). By stepwise multiple logistic regression analysis, the only independent predictor of late TLR was stent length (P < 0.001, OR = 1.040, 95% CI = 1.019–1.061). Conclusions: Late TLR was performed in 1.8% of 1,020 native lesions that were patent at 6‐month follow‐up angiogram. Clinical presentations of late TLR was either silent ischemia or recurrent angina, but not acute coronary syndrome. Two‐thirds of late TLR lesions had a focal angiographic ISR pattern. © 2007 Wiley‐Liss, Inc.