bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro degradation and biocompatibility of poly(DL‐lactide‐ϵ‐caprolactone) nerve guides
Authors: Meek Marcel F. , Jansen Koen , Steendam Rob , Oeveren Wim. van , van Wachem Pauline B. , van Luyn Marja J.A. 
Published: December 2003

AbstractBridging nerve gaps by means of autologous nerve grafts involves donor nerve graft harvesting. Recent studies have focused on the use of alternative methods, and one of these is the use of biodegradable nerve guides. After serving their function, nerve guides should degrade to avoid a chronic foreign body reaction. The in vitro degradation, in vitro cytotoxicity, hemocompatibility, and short‐term in vivo foreign body reaction of poly(65/35 (85/15L/D) lactide‐ϵ‐caprolactone) nerve guides was studied. The in vitro degradation characteristics of poly(DLLA‐ϵ‐CL) nerve guides were monitored at 2‐week time intervals during a period of 22 weeks. Weight loss, degree of swelling of the tube wall, mechanical strength, thermal properties, and the intrinsic viscosity of the nerve guides were determined. Cytotoxicity was studied by measuring the cell proliferation inhibition index (CPII) on mouse fibroblasts in vitro. Cell growth was evaluated by cell counting, while morphology was assessed by light microscopy. Hemocompatibility was evaluated using a thrombin generation assay and a complement convertase assay. The foreign body reaction against poly(DLLA‐ϵ‐CL) nerve guides was investigated by examining toluidine blue stained sections. The in vitro degradation data showed that poly(DLLA‐ϵ‐CL) nerve guides do not swell, maintain their mechanical strength and flexibility for a period of about 8–10 weeks, and start to lose mass after about 10 weeks. Poly(DLLA‐ϵ‐CL) nerve guides were classified as noncytotoxic, as cytotoxicity tests demonstrated that cell morphology was not affected (CPII 0%). The thrombin generation assay and complement convertase assay indicated that the material is highly hemocompatible. The foreign body reaction against the biomaterial was mild with a light priming of the immunesystem. The results presented in this study demonstrate that poly(65/35 (85/15L/D) lactide‐ϵ‐caprolactone) nerve guides are biocompatible, and show good in vitro degradation characteristics, making these biodegradable nerve guides promising candidates for bridging peripheral nerve defects up to several centimeters. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 43–51, 2004
Neovascularization of poly(ether ester) block‐copolymer scaffolds in vivo: Long‐term investigations using intravital fluorescent microscopy
Authors: Druecke Daniel , Langer Stefan , Lamme Evert , Pieper Jeroen , Ugarkovic Marija , Steinau Hans Ulrich , Homann Heinz Herbert 
Published: December 2003

AbstractPoly(ether ester) block‐copolymer scaffolds of different pore size were implanted into the dorsal skinfold chamber of balb/c mice. Using intravital fluorescent microscopy, the temporal course of neovascularization into these scaffolds was quantitatively analyzed. Three scaffold groups (diameter, 5 mm; 220–260 thickness, μm; n = 30) were implanted. Different pore sizes were evaluated: small (20–75 μm), medium (75–212 μm) and large pores (250–300 μm). Measurements were performed on days 8, 12, 16, and 20 in the surrounding normal tissue, in the border zone, and in the center of the scaffold. Standard microcirculatory parameters were assessed (plasma leakage, vessel diameter, red blood cell velocity, and functional vessel density). The large‐pored scaffolds showed significantly higher functional vessel density in the border zone and in the center (days 8 and 12) compared with the scaffold with the small and medium‐sized pores. These data correlated with a larger vessel diameter and a higher red blood cell velocity in the large‐pored scaffold group. Interestingly, during the evaluation period the microcirculatory parameters on the edge of the scaffolds returned to values similar to those found in the surrounding tissue. In the center of the scaffold, however, neovascularization was still active 20 days after implantation. Plasma leakage and vessel diameter were higher in the center of the scaffold. Red blood cell velocity and functional vessel density were 50% lower than in the surrounding tissue. In conclusion, the dorsal skinfold chamber model in mice allows long‐term study of blood vessel growth and remodeling in porous biomedical materials. The rate of vessel ingrowth into poly(ether ester) block‐copolymer scaffolds is influenced by pore size and was highest in the scaffold with the largest pores. The data generated with this model contribute to knowledge about the development of functional vessels and tissue ingrowth into biomaterials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 10–18, 2004
Novel bioactive and biodegradable glass ceramics with high mechanical strength in the CaOSiO2B2O3 system
Authors: Ryu Hyun‐Seung , Lee Jung‐Kun , Seo Jun‐Hyuk , Kim Hwan , Hong Kug Sun , Kim Deug Joong , Lee Jae Hyup , Lee Dong‐Ho , Chang Bong‐Soon , Lee Choon‐Ki , Chung Sung‐Soo 
Published: December 2003

AbstractNovel bioactive and biodegradable glass ceramics with high mechanical strength in the (50‐x/2)CaO · SiO2xB2O3 (4.2 ≤ x ≤ 17.2) system were investigated. The systems consisted of three phases: monoclinic wollastonite, calcium metaborate, and amorphous borosilicate matrix. The glass ceramics containing 4.2 mol% and 8.4 mol% B2O3 showed high bulk density and a dense microstructure. Mechanical strengths of the glass ceramics were higher than those of other bioactive ceramics: high compressive strength (2813 MPa), bending strength of 212 MPa, and fracture toughness of 3.12 MPa · m1/2. The glass‐ceramic formed apatite layer on their surface in the simulated body fluid and showed significant biodegradation. The degree of apatite formation in the glass ceramics depended on the calcium metaborate content and borosilicate glassy matrix. Additional calcium metaborate and borosilicate glassy matrix increased the apatite formation rate on the surface. It might be likely that calcium metaborate causes supersaturation of Ca ions, for its high solubility in SBF and the water‐reactive borosilicate glassy matrix formed SiOH groups on the surface to provide nucleation sites for apatite formation. Also, through in vitro test for the biocompatibility of the CaOSiO2B2O3 glass ceramics, no cytotoxicity of the glass ceramics were found. The results on bioactivity and noncytotoxicity indicated that glass ceramics in the (50‐x/2)CaO · SiO2xB2O3 (4.2 ≤ x ≤ 17.2) system could be useful as a biodegradable bone replacement material. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 79–89, 2004
Ultrasound degradation of novel polymer contrast agents
Authors: El‐Sherif Dalia M. , Lathia Justin D. , Le Ngocyen T. , Wheatley Margaret A. 
Published: December 2003

AbstractThis report describes an investigation into factors affecting the degradation of novel poly(lactic‐co‐glycolic acid) (PLGA) contrast agents. Contrast agents fabricated by two different methods and varying in acoustic properties were compared. The effect of ultrasound frequency (5 and 10 MHz) on degradation of the microcapsules was also studied. High‐performance liquid chromatography was used to quantify the production of lactic and glycolic acid to monitor agent degradation. The degradation pattern from the microcapsules was found to be closely related to capsule morphology; the more acoustically efficient capsules (maximum enhancement of 25 dB at 5 MHz with 0.004 mg/mL) degraded at a faster rate than those with lower acoustical efficiency (maximum enhancement of 25 dB at 5 MHz only achieved with 0.6 mg/mL). The capsules also degraded fastest when insonated at the frequency at which they gave highest backscatter. In addition, despite the use of a 50:50 PLGA copolymer, more glycolic than lactic acid was released at early time points, which reflects the greater hydrophilicity of the glycolic acid residues, and greater degradation rate of glycolic acid repeat units. The results from this study provided unique insight into the degradation behavior of hollow PLGA microcapsules, and their potential in ultrasound diagnosis and therapy. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 71–78, 2004
Fracture associated with hydrogen absorption of sustained tensile‐loaded titanium in acid and neutral fluoride solutions
Authors: Yokoyama Ken'ichi , Kaneko Kazuyuki , Miyamoto Youji , Asaoka Kenzo , Sakai Jun'ichi , Nagumo Michihiko 
Published: December 2003

AbstractThe fracture of commercial pure titanium in acid and neutral fluoride solutions has been examined by a sustained tensile‐loading test and hydrogen thermal desorption analysis. It was found that the fracture of titanium occurred in neutral 2.0% NaF solution as well as in 2.0% acidulated phosphate fluoride (APF) solution. The time to fracture decreased with increasing applied stress in both 2.0% APF and 2.0% NaF solutions. In the case of the same applied stress, the time to fracture in the 2.0% APF solution was shorter than that in the 2.0% NaF solution. General corrosion was exhibited on the side surface of the tested specimens. The formation of sodium titanium fluoride was observed on the surface of the immersed specimens in the 2.0% APF solution. Hydrogen desorption of the tested specimen in the 2.0% APF solution was observed with a peak at approximately 600°C. The amount of absorbed hydrogen was >300 mass ppm in the 2.0% APF solution under an applied stress for 24 h. The results of the present study imply that applying stress to titanium by immersing in fluoride solutions leads to the degradation of its mechanical properties. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 150–158, 2004
Protein Synthesis Is Required for the Transition to Ca2+‐Dependent Regulated Secretion in Progesterone‐Matured Xenopus Oocytes
Authors: Kohan Sirus A. , Gundersen Cameron B. 
Published: December 2003

AbstractCalcium (Ca) ionophores trigger cortical granule exocytosis in progesterone‐matured Xenopus oocytes (eggs), but not in immature oocytes. Prior work suggested that this secretory transition involved a Ca‐dependent isoform of protein kinase C (PKC). To address this possibility, we treated eggs with several different inhibitors of Ca‐dependent PKCs. Although these agents (eg., staurosporine, Ro31–8220) completely blocked cortical granule exocytosis that is triggered in eggs by phorbol esters, they had no impact on ionomycin‐evoked secretion of cortical granule lectin. These data suggest that Ca‐dependent PKCs do not mediate secretory triggering in eggs. Instead, further investigation revealed that protein synthesis (but not RNA synthesis) was required for eggs to secrete in response to ionomycin. Moreover, we observed that when oocytes were matured by injection of maturation promoting factor (MPF), they failed to secrete in response to ionomycin. Collectively, these results suggest that the progesterone‐dependent maturation pathway induces these cells either to synthesize de novo, a protein that mediates Ca‐dependent secretory triggering, or that intrinsic Ca‐sensing machinery is modified in a protein‐synthesis‐dependent fashion. Initial efforts to distinguish between these possibilities (using Ca overlay, pharmacological and immunoblot strategies) revealed that such Ca‐binding proteins as calmodulin, synaptotagmin1, CAPS, rabphilin–3A and calcineurin were unlikely to transduce the secretory effects of ionomycin in eggs. Thus, the cortical reaction in these cells may rely on a novel mechanism for initiating Ca‐dependent exocytosis. J. Exp. Zool. 300A:113–125, 2003. © 2003 Wiley‐Liss, Inc.
Development of the adenohypophysis in the lamprey: Evolution of epigenetic patterning programs in organogenesis
Authors: Uchida Katsuhisa , Murakami Yasunori , Kuraku Shigehiro , Hirano Shigeki , Kuratani Shigeru 
Published: December 2003

AbstractIn gnathostomes, the adenohypophysis, a component of the hypothalamo‐hypophysial complex, is believed to develop through hierarchically organized epigenetic interactions based primarily on the topographical relationships between tissues. From a comparison of developmental processes and gene expression patterns of pituitary‐related genes between the agnathan species, lampreys and gnathostomes, we speculate on the evolutionary pathway of the vertebrate adenohypophysis. In the lamprey, this is derived from the nasohypophysial placode (NHP) that develops anterior to the oral ectoderm. The NHP can be identified by the expression of LjPitxA, before actual histogenesis, but it is initially distant from the future hypothalamic region. Subsequently, the NHP expresses both LjFgf8/17 and LjBmp2/4a gene transcripts, and grows caudally to establish a de novo contact with the hypothalamic region by the mid‐pharyngula stage. Later, the NHP gives rise to both the adenohypophysis and an unpaired nasal organ. Thus, the topographical relationship between the NHP and the hypothalamic region is established secondarily in the lamprey, unlike gnathostomes in which the equivalent relationship appears early in development. Comparing the developmental pattern of the amphioxus homologue of the adenohypophysis, we hypothesize that a modification of the regulation of the growth factor encoding gene lies behind the evolutionary changes recognized as heterochrony and heterotopy, which leads to the gnathostome hypophysial developmental pattern. J. Exp. Zool. (Mol. Dev. Evol.) 300B:32–47, 2003. © 2003 Wiley‐Liss, Inc.
K‐linked graphs with girth condition
Authors: Kawarabayashi Ken‐ichi 
Published: December 2003

AbstractRecently, Mader [7] proved that every 2k‐connected graph with girth g(G) sufficiently large is k‐linked. We show here that g(G ≥ 11 will do unless k = 4,5. If k = 4,5, then g(G) ≥ 19 will do. © 2003 Wiley Periodicals, Inc. J Graph Theory 45: 48–50, 2004
Defective choosability of graphs with no edge‐plus‐independent‐set minor
Authors: Woodall Douglas R. 
Published: December 2003

AbstractIt is proved that, if s ≥ 2, a graph that does not have K2 + Ks = K1 + K1, s as a minor is (s, 1)*‐choosable. This completes the proof that such a graph is (s + 1 − d,d)*‐choosable whenever 0 ≤ d ≤ s −1 © 2003 Wiley Periodicals, Inc. J Graph Theory 45: 51–56, 2004
Intramolecular electrophilic aromatic substitution in gas‐phase‐protonated difunctional compounds containing one or two arylmethyl groups
Authors: Edelson‐Averbukh M. , Mandelbaum A. 
Published: December 2003

AbstractA variety of dibenzyl esters and ethers undergo a rearrangement process upon isobutane chemical ionization and collision‐induced dissociation of their MH+ ions, whereby a new bond is formed between the two benzyl groups, giving rise to abundant [C14H13]+ (m/z 181) ions. This rearrangement has been explained as an intramolecular electrophilic substitution in the gas phase occurring in an ion–neutral complex formed by the cleavage of one of the benzyl–oxygen bonds. A similar highly efficient intramolecular electrophilic substitution takes place in di‐α‐ and β‐naphthylmethyl adipates affording m/z 281 [C22H17]+ ions, but not in the sterically hindered di‐9‐anthracylmethyl adipate. An analogous efficient rearrangement occurs in benzyl α‐ and β‐naphthylmethylcyclohexane‐1,4‐dicarboxylates and in benzyl α‐ and β‐phenylethylcyclohexane‐1,4‐dimethanol ethers. The analogous rearrangement is much less efficient in benzylallyl, benzylpropargyl and benzyl‐9‐anthracylmethyl derivatives, even less in benzylisopropyl and benzylacetyl analogs, and it is absent in benzyltetrahydropyranyl derivatives. The distinctive behavior of the protonated difunctional benzyl derivatives is interpreted in terms of the energy requirements of the O—R bond heterolysis of the protonated functionalities, the ability of the neutral R′ groups (non‐dissociated from the oxygen atom) to play the role of the nucleophile in the intramolecular electrophilic substitution processes and the electrophilicity of the R+ ions. Copyright © 2003 John Wiley & Sons, Ltd.
Liquid chromatography/electrospray ionization tandem mass spectrometric screening and confirmation methods for β2‐agonists in human or equine urine
Authors: Thevis Mario , Opfermann Georg , Schänzer Wilhelm 
Published: December 2003

AbstractElectrospray ionization (ESI) mass spectra of 19 common β2‐agonists were investigated in terms of fragmentation pattern and dissociation behavior of the analytes, proving the origin of fragment ions and indicating mechanisms of charge‐driven and charge‐remote fragmentation. Based on these data, liquid chromatographic/ESI tandem mass spectrometric (LC/ESI‐MS/MS) screening and confirmation methods were developed for doping control purposes. These procedures employ established sample preparation steps including either acidic or enzymatic hydrolysis, alkaline extraction and, in the case of equine urine specimens, acidic re‐extraction of the analytes. In addition, a degradation product of formoterol caused by acidic hydrolysis during sample preparation could be identified and utilized as target compound in screening and also confirmation methods. The screening procedures cover 18 or 19β2‐agonists, the estimated limits of detection of which for equine and human urine samples vary between 2 and 100 ng ml−1 and between 2 and 50 ng ml−1, respectively. A single LC/MS/MS analysis can be performed in 9 min. Copyright © 2003 John Wiley & Sons, Ltd.
Two types of VIP neuronal components in rat suprachiasmatic nucleus
Authors: Kawamoto Kunihiko , Nagano Mamoru , Kanda Fumio , Chihara Kazuo , Shigeyoshi Yasufumi , Okamura Hitoshi 
Published: December 2003

AbstractVasoactive intestinal peptide (VIP) neurons constitute a large group in the suprachiasmatic nucleus (SCN) and it is thought that they are involved in the generation and entrainment of circadian rhythm. We have characterized these VIP‐expressing neurons in rat SCN by their ability to induce the mammalian Period1 (Per1) gene in response to light exposure, innervation of retinal afferents, day‐night variations in VIP mRNA, and coexpression of gastrin releasing peptide (GRP). VIP neurons in the ventrolateral SCN (SCNVL) were subdivided into two groups, light‐evoked Per1‐inducible main SCNVL (SCNVLmain) and non‐Per1‐inducible medially located SCNVL (SCNVLmed). Retinal innervation was abundant in the SCNVLmain but nearly absent in the SCNVLmed. Day‐night variation in VIP mRNA expression level was observed in the SCNVLmain but not in the SCNVLmed. GRP mRNA was seen in rarely SCNVLmed but abundant in SCNVLmain, where some neurons coexpressed VIP mRNA. These findings indicate that VIP neurons in the SCN can be divided into two topographically and functionally distinct groups. © 2003 Wiley‐Liss, Inc.
Glutamate uptake inhibitor L‐trans‐pyrrolidine 2,4‐dicarboxylate becomes neurotoxic in the presence of subthreshold concentrations of mitochondrial toxin 3‐nitropropionate: Involvement of mitochondrial reducing activity and ATP production
Authors: García Octavio , Massieu Lourdes 
Published: December 2003

AbstractAn increased concentration of extracellular glutamate is associated with neuronal damage induced by cerebral ischemia. We have demonstrated previously that exposure of cultured cerebellar granule neurons to L‐trans‐pyrrolidine‐2,4‐dicarboxylate (PDC), a glutamate uptake inhibitor, increases extracellular glutamate levels but does not induce neuronal damage. Coincubation of PDC, however, with a subthreshold concentration of the mitochondrial toxin, 3‐nitropropionic acid (3‐NP), results in severe damage to these neurons. We have investigated the time course of changes in mitochondrial reducing capacity and ATP levels in cerebellar granule cells after simultaneous exposure to 3‐NP and PDC, and its relation to cell viability and nuclear condensation. Although individually, 3‐NP and PDC treatments are not harmful to neurons, the simultaneous exposure to both compounds results in a progressive decline in mitochondrial reducing capacity during the first 4 hr, and a rapid decrease in ATP levels. At 4 hr, cells lose plasma membrane integrity and show condensed nuclei. In the presence of the energy substrates pyruvate and acetoacetate, the N‐methyl‐D‐apartate (NMDA) receptor antagonist, MK‐801, and the spin trapper α‐phenyl‐N‐tert‐butylnitrone (PBN), the decline in mitochondrial activity and ATP levels is prevented, the number of condensed nuclei is reduced, and plasma membrane integrity is preserved. In contrast, the broad‐spectrum caspase inhibitor Z‐Asp‐DCB (Z‐Asp‐CH2‐DCB) prevents nuclear condensation but has no effect on mitochondrial reducing capacity or cell survival. Our results show that glutamate uptake impairment rapidly induces neuronal death during inhibition of succinate dehydrogenase by a mechanism involving mitochondrial dysfunction that, if not prevented, leads to cell death. © 2003 Wiley‐Liss, Inc.
Tissue inhibitor of metalloproteinase (TIMP)‐1: The TIMPed balance of matrix metalloproteinases in the central nervous system
Authors: Gardner Jessica , Ghorpade Anuja 
Published: December 2003

AbstractAstrocytes are intimately involved in the mechanisms of neural injury and repair. They participate in a variety of homeostatic functions and elicit repair responses as balance mechanisms. Currently, there is a growing appreciation of a more active role of astrocytes in neuronal signaling and function. One key homeostatic mechanism of astrocytes in tissue repair is maintained through their production of tissue inhibitors of metalloproteinases (TIMPs). The family of TIMPs (1–4) plays a central regulatory role as inhibitors of matrix metalloproteinases (MMPs), enzymes involved in extracellular matrix maintenance and remodeling. Recently, TIMP‐1, the inducible form, has been identified as a multifunctional molecule with divergent functions. It participates in wound healing and regeneration, cell morphology and survival, tumor metastasis, angiogenesis, and inflammatory responses. An imbalance of MMP/TIMP regulation has been implicated in several inflammatory diseases of the central nervous system (CNS). Here we review the conundrums of TIMP‐1 regulation in CNS pathophysiology. We propose that astrocyte‐TIMP‐1 may play an important role in CNS homeostasis and disease. Astrocyte TIMP‐1 expression is differentially regulated in inflammatory neurodegenerative diseases and may have significant therapeutic relevance. © 2003 Wiley‐Liss, Inc.
Constitutive expression of p21H‐Rasval12 in neurons induces increased axonal size and dendritic microtubule density in vivo
Authors: Seeger Gudrun , Gärtner Ulrich , Holzer Max , Arendt Thomas 
Published: December 2003

AbstractThe small G protein p21Ras is a key signal transducer mediating cellular growth and proliferation responses to extracellular stimuli. We investigated by electron microscopy the effects of augmented p21Ras activity on neuronal processes and microtubule arrangement in vivo. We used transgenic mice with a neuron‐specific overexpression of p21H‐RasVal12, which starts postnatally around Day 15. Axonal and dendritic diameters and the numerical density of dendritic microtubules were analyzed at postnatal Day 12 before the onset of transgene expression and in adult mice. In adult transgenic mice, calibers of both axons (corpus callosum) and dendrites (layers II/III of somatosensory cortex) were enlarged by about 57% and 79%, respectively. The increase in dendritic calibers was associated with an increment in the amount of microtubules. Even in dendrites of equivalent diameters, the number of microtubules was higher in transgenic mice compared to that in wild‐type mice suggesting an elevated microtubule density. Changes in process diameters or microtubule density were not observed at postnatal Day 12 before relevant transcription of transgenic p21H‐RasVal12. The present results extend previous findings on neuronal hypertrophy as a consequence of p21H‐RasVal12 expression and suggest a profound influence on the dendritic microtubule network. © 2003 Wiley‐Liss, Inc.