bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical coding and electrophysiology of enteric neurons expressing neurofilament 145 in guinea pig gastrointestinal tract
Authors: Hu Hong‐Zhen , Gao Na , Lin Zhong , Gao Chuanyun , Liu Sumei , Ren Jun , Xia Yun , Wood Jackie D.
Published: October 2004

Electrophysiologic recording and indirect immunofluorescence were combined to study localization of the medium‐sized neurofilament 145 (NF145) component of the cytoskeleton in morphologically identified neurons in the myenteric and submucosal plexuses of the guinea pig enteric nervous system. Neuronal localization of chemical markers, including calbindin DK28, calretinin, nitric oxide synthase, choline‐acetyltransferase, neuropeptide Y, serotonin, neurokinin 1 receptor protein, and somatostatin, was integrated with electrophysiologic and morphologic results for a more complete assessment. NF145 immunoreactivity (‐IR) was present in ganglion cells with Dogiel type I morphology in the myenteric plexus of the stomach and small and large intestine. NF145‐IR was not found in myenteric ganglion cells with Dogiel type II morphology. NF145‐IR was not present in any of the ganglion cells in the submucosal plexus. NF145 was expressed in nerve fibers in both myenteric and submucosal plexuses. The majority of these fibers were identified as sympathetic postganglionic axons based on their disappearance in organotypic culture and on their expression of tyrosine hydroxylase. The myenteric ganglion cells with NF145‐IR had electrophysiologic properties of S‐type enteric neurons. NF145‐IR was found in neurons with vasoactive intestinal peptide, serotonin, nitric oxide synthase, somatostatin, and neurokinin 1 receptor but not with neuropeptide Y or calbindin. The results in general suggest that NF145 is localized to distinct subsets of myenteric motor neurons and interneurons. Absence of NF145 from ganglion cells in the submucosal plexus is an example of differences between myenteric and submucosal components of the enteric nervous system. J. Comp. Neurol. 442:189–203, 2002. © 2001 Wiley‐Liss, Inc.
Dysembrioplastic neuroepithelial tumor: Cytological diagnosis by intraoperative smear preparation
Authors: Bleggi‐Torres Luiz F. , Netto Mário Rodrigues Montemór , Gasparetto Emerson Leandro , Gonçalves e Silva Adriano , Moro Marlus
Published: October 2004

The dysembrioplastic neuroepithelial tumor (DNT) is a benign and slow‐growing temporal lobe cortical lesion that presents with clinically unresponsive partial and complex seizures, with onset before age 20 yr. DNT shows a multinodular architecture and the presence of mixed glioneural elements. The authors report on a case of DNT diagnosed by the intraoperative smear cytological technique. We describe the cytological characteristics of smear preparations of DNT, with emphasis on the differential diagnosis. The authors present a 5‐yr‐old male with partial seizures for the preceding 3 yr. The patient showed no other neurological deficits. Magnetic resonance identified a lesion in the cortical area of the right temporal lobe. The smear cytology showed small, round, oligodendroglial‐like cells arranged in lobules, with microcystic spaces containing ganglion cells floating in a fine fibrillary background. Histology confirmed the diagnosis of DNT. This report shows that the smear preparation can be trustworthy for the intraoperative diagnosis of DNTs, helping to determine the appropriate neurosurgical procedure and thus avoiding extensive and unnecessary resections. Diagn. Cytopathol. 2002;26:92–94; DOI 10.1002/dc.10042 © 2002 Wiley‐Liss, Inc.
Understanding the online consumer: A typology of online relational norms and behavior
Authors: Mathwick Charla
Published: October 2004

Relational norms governing Web-based interaction provide the basis for a typology of relationship orientation manifested by consumers online. Clustering techniques are applied to survey data collected online to identify four groups: Transactional Community Members, Socializers, Personal Connectors, and Lurkers. Cluster assignment is validated by examination of segment means, under volitional versus constraint-based marketing contexts. Relational profiles are developed, differentiated by the strength of relational norms and exhibited interactive behavior. Results suggest investment in community-building infrastructure (i.e., chat rooms, bulletin boards, interactive events), has a positive effect on the future loyalty intentions of highly relational patrons. Implications and future research directions are discussed.
A design theory of ferroelectric liquid crystal polarization control device for tilted incident light angle
Authors: Ogawa Noriyuki , Machida Kosuke , Nakagami Takakiyo
Published: October 2004

As a form of free‐space‐type optical switch, the authors have proposed a planar polarization control‐type optical switch. The present paper reports the design theory for a liquid crystal polarization control device with a tilted incidence angle as a key device for this switch. Since the switching of the optical paths by the polarization control of a liquid crystal is used as the operating principle, it is necessary to develop a device that can accurately change the direction of polarization of the beam incidence tilted from the crystal plane by 90° by an applied voltage. It has been known experimentally that a device with a characteristic close to this requirement can exist. A general design method has not been reported. In this paper, for the device made of ferroelectric liquid crystal, the polarization control characteristic is theoretically analyzed by the Jones matrix so that the condition for changing the polarization direction of the output light exactly by 90° is derived. Based on this finding, the optimum design values of the layer thickness and optical axis of the liquid crystal are numerically obtained. The polarization control characteristics of the fabricated device for a wavelength of 0.85 µm are measured and the validity of the present design method is demonstrated. © 2002 Scripta Technica, Electron Comm Jpn Pt 2, 85(3): 30–39, 2002
Transient power characteristics of balanced three‐phase variable inductance
Authors: Funato Hirohito , Kamiyama Kenzo , Kawamura Atsuo
Published: October 2004

Inductance has a particularly important role in power circuits. The authors have proposed the Variable Active–Passive Reactance (VAPAR), which can produce a virtual variable inductance. In this paper, the transient power characteristics of a balanced three‐phase variable inductance are analyzed using the instantaneous active and reactive power theorem. With an ideal voltage source or an ideal current source connected to a balanced three‐phase variable inductance, the transient power characteristics are analyzed theoretically, and then the results are verified through simulations. In the other cases, it is difficult to solve for the transient power, but it is shown that the transient power characteristics can easily be estimated from the results of simulations in which an ideal voltage source or an ideal current source is connected to a balanced three‐phase variable inductance. Experiments are also carried out to verify the theoretical analysis and simulations. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 49–57, 2001
Compensation of stator iron loss of vector‐controlled induction motor using robust flux observer
Authors: Hasegawa Masaru , Yamasaki Hisanori , Doki Shinji , Okuma Shigeru
Published: October 2004

A new vector control system of an induction motor is proposed in this paper to reduce the influence of iron loss, which has been difficult to deal with. Recently, many methods have been proposed to improve the accuracy of torque control, concentrating on the identification of parameters and the adjustment of the controllers. But, it is necessary for experts to tune parameters initially in those methods. The new method can reduce the influence of iron loss by using a robust flux observer. By adding current decoupling control for compensation of the iron loss, a vector control system with high torque linearity can be constructed. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 59–66, 2001
Transition Metal Chemistry of Low Valent Group 13 Organyls
Authors: Gemel Christian , Steinke Tobias , Cokoja Mirza , Kempter Andreas , Fischer Roland A.
Published: October 2004

The coordination of low‐valent group 13 organyls EIR [E = Al, Ga, In; R = Cp*, C(SiMe3)3] to transition metals has attracted increasing interest over the past decade. Complexes and cluster compounds of these new ligands with a number of transition metals have been isolated and characterised. The EIR moiety is formally isolobal with CO and PR3 (R = alkyl, Cp*) or carbenes (R = chelating group) with varying σ‐donor and π‐acceptor properties depending on the organic group R as well as the group 13 metal E. In this review, different ways of forming M−E bonds such as substitution reactions of labile ligands or insertion of EIR into transition metal halide bonds are described. Furthermore, the reactivity of homoleptic complexes Ma(EIR)b is discussed, outlining the use of these new complex types in bond activation reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Interleukin‐13 and ‐4 induce death of activated microglia
Authors: Yang Myung‐Soon , Park Eun Jung , Sohn Seonghyang , Kwon Hyuk Jae , Shin Won‐Ho , Pyo Han Kyung , Jin Byungkwan , Choi Kyeong Sook , Jou Ilo , Joe Eun‐Hye
Published: October 2004

When the brain suffers injury, microglia migrate to the damaged sites and become activated. These activated microglia are not detected several days later and the mechanisms underlying their disappearance are not well characterized. In this study, we demonstrate that interleukin (IL)‐13, an anti‐inflammatory cytokine, selectively induces cell death of activated microglia in vitro. Cell death was detected 4 days after the coaddition of IL‐13 with any one of the microglial activators, lipopolysaccharide (LPS), ganglioside, or thrombin. This cell death occurred in a time‐dependent manner. LPS, ganglioside, thrombin, or IL‐13 alone did not induce cell death. Among anti‐inflammatory cytokines, IL‐4 mimicked the effect of IL‐13, while TGF‐β did not. Cells treated with IL‐13 plus LPS, or IL‐13 plus ganglioside, showed the characteristics of apoptosis when analyzed by electron microscopy and terminal deoxynucleotidyl transferase‐mediated dUTP nick end labeling staining. Electron micrographs also showed microglia engulfing neighboring dead cells. We propose that IL‐13 and IL‐4 induce death of activated microglia, and that this process is important for prevention of chronic inflammation that can cause tissue damage. GLIA 38:273–280, 2002. © 2002 Wiley‐Liss, Inc.
Platelet‐derived growth factor‐b expression induced after rat peripheral nerve injuries
Authors: Oya Takeshi , Zhao Ying‐Luan , Takagawa Kiyoshi , Kawaguchi Makoto , Shirakawa Kamon , Yamauchi Tadakazu , Sasahara Masakiyo
Published: October 2004

Schwann cells are crucially important for peripheral nerve regeneration. These cells synthesize several factors that are supposed to enhance axonal regeneration when injured. Platelet‐derived growth factor (PDGF) B‐chain and its β‐receptor are expressed in Schwann cells in both normal peripheral nerves and culture. To elucidate the role of PDGF‐B in peripheral nerve regeneration, we investigated its expression in cut or crush‐injured rat sciatic nerves for up to 28 days. Northern blotting identified substantial increase of PDGF B‐chain transcripts in injured nerves. Immunohistochemistry demonstrated that protein products of the transcripts were augmented at the distal tip of swollen axons in proximal nerve segments and in regenerating axons. Soon after both types of injury, considerable amounts of PDGF‐B accumulated in numerous Schwann cells in distal segments of both models. With restoration of the axon–Schwann cell relationship in the crush model, levels of PDGF‐B tended to decrease, eventually returning to normal. In the cut model in which the relationship cannot be restored, the PDGF‐B was depleted to a very low level. The spatiotemporal correlation between PDGF‐B and cell proliferation was very close throughout the study. These results differed strikingly from those of our previous study of rat optic nerve transection, in which PDGF‐B was expressed only in a few recruited macrophages and glial cells. Augmented PDGF‐B expression after sciatic nerve injury might contribute to peripheral nerve regeneration because PDGF‐B is a mitogen and survival factor for Schwann cells and because it has trophic activity on neurons. GLIA 38:303–312, 2002. © 2002 Wiley‐Liss, Inc.
Exact multivariate tests for brain imaging data
Authors: Almeida Rita , Ledberg Anders
Published: October 2004

In positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) data sets, the number of variables is larger than the number of observations. This fact makes application of multivariate linear model analysis difficult, except if a reduction of the data matrix dimension is performed prior to the analysis. The reduced data set, however, will in general not be normally distributed and therefore, the usual multivariate tests will not be necessarily applicable. This problem has not been adequately discussed in the literature concerning multivariate linear analysis of brain imaging data. No theoretical foundation has been given to support that the null distributions of the tests are as claimed. Our study addresses this issue by introducing a method of constructing test statistics that follow the same distributions as when the data matrix is normally distributed. The method is based on the invariance of certain tests over a large class of distributions of the data matrix. This implies that the method is very general and can be applied for different reductions of the data matrix. As an illustration we apply a test statistic constructed by the method now presented to test a multivariate hypothesis on a PET data set. The test rejects the null hypothesis of no significant differences in measured brain activity between two conditions. The effect responsible for the rejection of the hypothesis is characterized using canonical variate analysis (CVA) and compared with the result obtained by using univariate regression analysis for each voxel and statistical inference based on size of activations. The results obtained from CVA and the univariate method are similar. Hum. Brain Mapping 16:24–35, 2002. © 2002 Wiley‐Liss, Inc.
Carcinoma of the supraglottic larynx: Treatment results with radiotherapy alone or with planned neck dissection
Authors: Hinerman Russell W. , Mendenhall William M. , Amdur Robert J. , Stringer Scott P. , Villaret Douglas B. , Robbins K. Thomas
Published: October 2004

Purpose

To present the results of radiotherapy with or without neck dissection for squamous cell carcinoma of the supraglottic larynx treated at the University of Florida and to compare these data with those obtained after conservation surgery.

Methods and Materials

Continuous‐course radiotherapy alone or combined with a planned neck dissection was used to treat 274 patients with squamous cell carcinoma of the supraglottic larynx between 1964 and 1998. All patients had follow‐up for a minimum of 2 years, and 250 (91%) had follow‐up for 5 years or more.

Results

At 5 years, the actuarial probability of local control after radiotherapy according to T stage was as follows: T1, 100%; T2, 86%; T3, 62%; and T4, 62%. The probability of cause‐specific survival at 5 years by AJCC stage was as follows: stage I, 100%; II, 93%; III, 81% IVA, 50%; and IVB, 13%. The risk of severe late complications was 4%. Of 57 patients undergoing planned postradiotherapy neck dissection, 7% experienced a severe complication.

Conclusions

On the basis of our data and the literature, early or moderately advanced supraglottic carcinomas may be treated successfully with either supraglottic laryngectomy or radiotherapy. Supraglottic laryngectomy probably produces a higher initial local control rate but, based on anatomic and coexisting medical constraints, is suitable for a smaller subset of patients and has a higher risk of complications compared with radiotherapy. © 2002 Wiley Periodicals, Inc.
Anaerobic thyroid abscess from a thyroid cyst after fine‐needle aspiration
Authors: Sun Jui‐Hung , Chang Hung‐Yu , Chen Kwang‐Wen , Lin Koan‐Day , Lin Jen‐Der , Hsueh Chuen
Published: October 2004

Background

Anaerobic abscess formation within a thyroid cyst is rare but still possible, although aerobic thyroid abscess formation in the thyroid gland after fine‐needle aspiration (FNA) has been observed in immunocompromised patients.

Methods

This study describes the clinical manifestations, thyroid echography, cytologic finding, culture outcome, and treatment course of an anaerobic abscess formation within a thyroid cyst after FNA in a healthy subject.

Results

A 53‐year‐old male subject had rapid enlargement of a left thyroid cyst develop after second FNA. Frank pus was obtained through third FNA. The culture outcome was Propionibacterium acnes, which was rich in saliva and one of the pathogens causing periodontitis and gingivitis. After adequate antimicrobial therapy, the abscess gradually diminished.

Conclusions

This article reported, for the first time, on the formation of an anaerobic thyroid abscess after FNA in a healthy subject. We recommended careful aseptic procedure and adequate isolation processes, such as wearing a mask to avoid an unfavorable outcome as a result of a bacterial infection. © 2002 John Wiley & Sons, Inc. Head Neck 24: 84–86, 2002.
Effect of perforations in burr hole covers on cranial bone regeneration in rabbits
Authors: Leiggener Christoph S. , Curtis Raymond , Pfluger Dominik , Rahn Berton A.
Published: October 2004

The reconstruction of bone defects is a significant problem in cranio‐maxillofacial surgery. In an effort to avoid the known disadvantages of autogenous bone grafting, alternatives have been investigated. Bone substitute materials, degradable or nondegradable, aim at facilitating bone regeneration, while they take over load‐bearing functions for a period of time. In this study, the healing of cranial defects in rabbits was assessed using polylactide guiding covers with and without perforations. Bilateral circular cranial defects were produced in 16 New Zealand white rabbits. The defects were covered with extruded and laser cut polylactide burr hole covers, each animal receiving a perforated burr hole cover on one side and a nonperforated one on the contralateral side. Bone seeking fluorochromes were administered at regular intervals. After an observation period of 8 weeks the amount of bone regeneration in the area of the defects was quantified from contact radiographs, and the dynamics of bone formation were assessed by fluorescence microscopy. Stained sections were used to analyze morphologic differences. No signs of adverse tissue reactions or osteolysis were observed. A bone‐guiding function was observed for both covers with or without perforations. Intracranial tissue herniation into the defect hindered the regeneration process. Wide intraindividual and interindividual variation became apparent and average defect filling was only 40% within the 8‐week observation period. In this model the perforated covers offered no advantage over nonperforated covers. It can be concluded from this study, that the use of external burr hole covers alone does not guarantee a full thickness regeneration of the cranial defect, but it provides a guiding function for promotion of structured bone regeneration. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 131–137, 2002
In vitro and in vivo dissolution behavior of a dysprosium lithium borate glass designed for the radiation synovectomy treatment of rheumatoid arthritis
Authors: Conzone Samuel D. , Brown Roger F. , Day Delbert E. , Ehrhardt Gary J.
Published: October 2004

Dysprosium lithium borate (DyLB) glass microspheres were investigated for use in the radiation synovectomy treatment of rheumatoid arthritis. In vitro testing focused on weight loss and cation dissolution from glass microspheres immersed in simulated synovial fluid (SSF) at 37°C for up to 64 days. In vivo testing was performed by injecting glass microspheres into the stifle joints of Sprague‐Dawley rats and monitoring the biodegradability of the microspheres and the tissue response within the joints. The DyLB microspheres reacted nonuniformly in SSF with the majority of lithium and boron being dissolved, whereas nearly all of the dysprosium (>99.7%) remained in the reacted microspheres. Because the DyLB glasses released negligible amounts of dysprosium while reacting with SSF, they are considered safe for radiation synovectomy from the standpoint of unwanted radiation release from the joint capsule. Furthermore, the DyLB microspheres fragmented, degraded, and reacted with body fluids while in the joints of rats without histologic evidence of joint damage. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 260–268, 2002; DOI 10.1002/jbm.10047
Resorbability and solubility of zinc‐containing tricalcium phosphate
Authors: Ito Atsuo , Kawamura Haruo , Miyakawa Shunpei , Layrolle Pierre , Kanzaki Noriko , Treboux Gabin , Onuma Kazuo , Tsutsumi Sadao
Published: October 2004

Using zinc‐containing tricalcium phosphate (ZnTCP) as the zinc carrier for zinc‐releasing calcium phosphate ceramic implants promoted bone formation around the implants. Because no quantitative information was available on the equilibrium solubility and resorbability of ZnTCP,in vitroequilibrium solubility andin vivoresorbability of ZnTCP were determined and compared quantitatively in this study. The solubility of ZnTCP decreased with increasing zinc content. The negative logarithm of the solubility product (Ksp) of ZnTCP was expressed as pKsp= 28.686 + 1.7414C− 0.42239C2+ 0.063911C3− 0.0051037C4+ 0.0001595C5in air, whereCis the zinc content in ZnTCP (mol %). The solubility of ZnTCP containing a nontoxic level of zinc (<0.63 wt %) decreased to 52–92% of the solubility of pure tricalcium phosphate (TCP) in the pH range 5.0–7.4. However, thein vivoresorbed volume of ZnTCP containing the same amount of zinc was much lower than that expected from thein vitrosolubility, becoming as low as 26–20% of that of TCP. Cellular resorption of TCP is substantially a process of dissolution in a fluid with an acidic pH that is maintained by the activities of cells. Therefore, the reduction of the resorbability of ZnTCP could be attributable principally to its lowered cellular activation property relative to that associated with pure TCP. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res 60: 224–231, 2002; DOI 10.1002/jbm.10068
Degradation characteristics of α and β tri‐calcium‐phosphate (TCP) in minipigs
Authors: Wiltfang J. , Merten H. A. , Schlegel K. A. , Schultze‐Mosgau S. , Kloss F. R. , Rupprecht S. , Kessler P.
Published: October 2004

In seven Goettingen minipigs 3.5–4.7‐ml cancellous bone defects were created in the area of the tibial head on both sides. The defects were filled with α‐TCP or β‐TCP (tricalciumphosphate). ITI implants (Straumann, Freiburg, Germany) of 3.2 × 12‐mm length were inserted into the underlying ceramic substitutes. Two additional pigs were used as control. Within the periods of observation (4, 16, 20, 28, 46, 68, and 86 weeks) fluorescent dyes were applied. Nondecalcified thin‐sliced sections were examined by means of light and fluorescence microscopy. In addition microangiography and microradiography were performed. Bony regeneration occurred basally and on the sides of the defect according the angiogenetic reossification pattern. Resorption was due to a hydrolytic and cellular degradation process. After 46 weeks histomorphological evaluation showed an incomplete osseointegration of the simultaneously implanted dental implants. The bone contact surface ratio was lower than 25%. After 86 weeks 95–97% of both α‐ and β‐TCP were resorbed. Ceramic residuals stayed within the newly formed trabeculae thus resisting further degradation until remodeling occurred. Both α‐ and β‐TCP show a comparable degradation process. At the 86‐week postoperative point only small residuals of the ceramic can be found. These residuals stay within the newly formed trabeculae, which show a functional orientation. In comparison control defects showed only sparse reossification. The β‐TCP material shows an accelerated degradation mode and has an optimal reactivity with the surrounding tissues. According to the results of this animal experiment both materials can be classified as bone‐rebuilding materials. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 115–121, 2002; DOI 10.1002/jbm.10084
Fixation strength of tapered versus bicylindrical hydroxyapatite‐coated external fixation pins: An animal study
Authors: Moroni Antonio , Faldini Cesare , Pegreffi Francesco , Giannini Sandro
Published: October 2004

The purpose of this study was to comparatively measure the bone–pin interface strength in two types of hydroxyapatite‐coated pins that differed in shape, diameter, and implantation technique. Both pin types are commonly used for tibia fixation. Thirty bicylindrical 5/4‐mm stainless‐steel pins (Group A) and 30 tapered 6/5‐mm stainless‐steel pins (Group B) were implanted in the left tibiae of 10 adult sheep. A monolateral fixator was mounted on the pins after implantation. A 5‐mm‐long bone segment was removed from the tibial mid‐diaphysis to ensure high load at the bone–pin interface. Pin insertion torque was 830 ± 446 N/mm in Group A and 3415 ± 743 N/mm in Group B (p<0.0001, one‐way ANOVA). Six weeks after surgery, the sheep were euthanized and pin extraction torque measured. Pin extraction torque was 1237 ± 499 N/mm in Group A and 3367 ± 1512 N/mm in Group B (p<0.0001, Mann‐Whitney test). Morphological analysis performed at 60× magnification showed a direct bone–pin contact in both groups. Despite challenging biomechanical conditions, this study showed both pin types to be well‐fixed and osteointegrated. Therefore, both pin types are recommended for tibial fixation. However, the tapered pins showed higher extraction torque, an important result for external fixation treatments. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 61–64, 2002
Characterization of damage modes in dental ceramic bilayer structures
Authors: Deng Yan , Lawn Brian R. , Lloyd Isabel K.
Published: October 2004

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic‐layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all‐ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture‐mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime‐threatening damage is discussed. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 137–145, 2002; DOI 10.1002/jbm.10091
Characterization of new acrylic bone cements prepared with oleic acid derivatives
Authors: Vázquez Blanca , Deb Sanjukta , Bonfield William , Román Julio San
Published: October 2004

Acrylic bone‐cement formulations were prepared with the use of a new tertiary aromatic amine derived from oleic acid, and also by incorporating an acrylic monomer derived from the same acid with the aim of reducing the leaching of toxic residuals and improving mechanical properties. 4‐N,N dimethylaminobenzyl oleate (DMAO) was used as an activator in the benzoyl‐peroxide radical cold curing of polymethyl methacrylate. Cements that contained DMAO exhibited much lower polymerization exotherm values, ranging between 55 and 62 °C, with a setting time around 16–17 min, depending on the amine/BPO molar ratio of the formulation. On curing a commercial bone cement, Palacos® R with DMAO, a decrease of 20 °C in peak temperature and an increase in setting time of 7 min were obtained, the curing parameters remaining well within limits permitted by the standards. In a second stage, partial substitution of MMA by oleyloxyethyl methacrylate (OMA) in the acrylic formulations was performed, the polymerization being initiated with the DMAO/BPO redox system. These formulations exhibited longer setting times and lower peak temperatures with respect to those based on PMMA. The glass transition temperature of the experimental cements were lower than that of PMMA cement because of the presence of long aliphatic chains of both activator and monomer in the cement matrix. Number average molecular weights of the cured cements were in the range of 1.2×105. PMMA cements cured with DMAO/BPO revealed a significant (p<0.001) increase in the strain to failure and a significant (p<0.001) decrease in Young's modulus in comparison to Palacos® R, whereas ultimate tensile strength remained unchanged. When the monomer OMA was incorporated, low concentrations of OMA provided a significant increase in tensile strength and elastic modulus without impairing the strain to failure. The results demonstrate that the experimental cements based on DMAO and OMA have excellent promise for use as orthopaedic and/or dental grouting materials. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 88–97, 2002; DOI 10.1002/jbm.10092
Deposition of 90YPO4 and 144CePO4 radioisotopes on polymer surfaces for radiation delivery devices
Authors: Qu Xin , Weinberger Judah
Published: October 2004

Intravascular irradiation with β emitters inhibits restenosis in arteries after balloon angioplasty or stent implantation. Yttrium‐90 (90Y, T1/2=64 h) and cerium‐144 (144Ce, T1/2=286 d) emit beta particles (Emax=2.28–3.50 MeV) having an ideal energy range for brachytherapy delivery system. In this article, a previously reported method for depositing 32P on poly(ethylene terephtalate) (PET) surfaces is generalized and modifications that allow deposition of other β‐emitting radioisotopes, such as 90Y and 144Ce, are demonstrated. PET films were first coated with chitosan hydrogel and then adsorbed different amounts of phosphoric acid (PA) in aqueous solutions. Yttrium was deposited onto the surface as YPO4 after the films were immersed in YCl3 solutions. 1 μCi 90YCl3 (2×10−9 g) was used in each sample as a tracer for measuring the deposition efficiency, which is defined as the percentage of YCl3 deposited on the surface compared to the amount of YCl3 in solutions before the deposition. In order to improve the safety of brachytherapy treatments, polyurethanes were used to seal the deposited radioisotopes on the surface to minimize the leakage of the isotopes into the patients. The generality of this method presented here for a wide variety of particular radioisotopic components allows design of a broad range of versatile radioisotope sources. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 98–105, 2002; DOI 10.1002/jbm.10095
The effect of processing conditions on the properties of poly(methyl methacrylate) fibers
Authors: Wright Debra D. , Lautenschlager Eugene P. , Gilbert Jeremy L.
Published: October 2004

Brittle failure of bone cement remains a problem for the long‐term stability of hip prostheses. Fibers have been developed from poly(methyl methacrylate) (PMMA) that retain the chemistry of bone cement, but improve the mechanical properties greatly. To fabricate the fibers, a polymer melt is extruded out of a small die (spinneret) and pulled onto a take‐up wheel. Varying the speed of extrusion and temperature of the melt can control the viscosity of the molten polymer. This study examines the effect of melt viscosity on the resultant properties of fibers fabricated from PMMA. The goals are to optimize fiber processing and determine processing‐structure–property relationships. Resultant fibers had moderate to high levels of retained molecular orientation, and ultimate tensile strengths (UTS) ranging from 60 to 225 MPa, moduli from 1.5 to 3.5 GPa, and strain to failure from 10 to 40%. Fibers fabricated at a constant viscosity and draw velocity had identical properties, whereas decreasing the viscosity generally increased the mechanical properties and retained orientation. Linear regression models were constructed to predict how the processing variables affect the structure (orientation) of the fiber and how the structure affects the UTS. This can be used to design efficient processing methods for PMMA fibers. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 152–160, 2002
Permeation of protein from porous poly(ϵ‐caprolactone) films
Authors: Lu Chia‐Hui , Lin Wen‐Jen
Published: October 2004

The objective of this study was designed to extend the application of poly(ϵ‐caprolactone) (PCL) in delivery of macromolecular proteins. The strategy applied here is to create a porous structure in PCL films in order to control the diffusion rate of protein. Various amounts of both high‐molecular‐weight and low‐molecular‐weight poly(ethylene glycol) (PEG) were used as pore‐forming agents. The porous films were prepared by a solvent‐casting‐leaching method. The thicknesses of the prepared films were controlled to be in the range of 75.3 ± 0.6 ∼ 81.7 ± 0.6 μm. The pore fraction of films was determined to be 27.7 ± 1.0% ∼ 52.5 ± 0.8% for PEG10000 and 26.6 ± 1.8% ∼ 48.8 ± 1.4% for PEG4000. The pore fraction initially increased with increasing amounts of PEG, independent of the molecular weight of PEG. In the permeation study, lysozyme was used as a model diffuser. The permeation rate of protein increased as the pore fraction of films increased, especially when 30 ∼ 40% of PEG was added initially, and this phenomenon was more prominent when low‐molecular‐weight PEG was used. This result was probably due to the highly porous structure creating interconnected channels in the films, further enhancing protein diffusion. In addition, the size of micropores formed by PEG4000 was observed to be larger than by PEG10000, which also accounted for faster permeation rate of lysozyme through PCL‐PEG4000 porous films. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 220–225, 2002; DOI 10.1002/jbm.10120
Macroporous poly(L‐lactide) scaffold 1. Preparation of a macroporous scaffold by liquid–liquid phase separation of a PLLA–dioxane–water system
Authors: Hua Feng Jun , Kim Go Eun , Lee Jong Doo , Son Yong Keun , Lee Doo Sung
Published: October 2004

A biodegradable poly(L‐lactic acid) (PLLA) macroporous scaffold with a regular and highly interconnected structure in the size range from 50 to 150 μ m was fabricated from a PLLA–dioxane–water ternary system with the use of the thermally induced phase separation (TIPS) process. The phase diagram of PLLA with molecular weight above 200,000 was measured. It was found that a small change in the water content in the solvent caused a large shift in the cloud‐point temperature. The porous morphology of the scaffold was closely related to the quenching route and formulation parameters, including polymer concentration, quenching temperature, aging time, and solvent composition of the ternary system. The porous morphology development in the scaffold was recorded as a function of aging time by scanning electronic microscopy (SEM). For systems with lower polymer concentrations (<4.5 wt%), polymer sedimentation occurred in the later stages of phase separation. A slight increase in the water content of the solvent mixture caused the sedimentation boundary to expand to higher polymer concentration. For systems with higher polymer concentrations (≥4.5 wt%), the development of phase separation was restricted by gelation that resulted from the crystallization of the PLLA chains. This gelation effect was greater at high polymer concentrations and low quenching temperatures. The macroporous expected scaffold could be optimized from the slow development of phase separation during the long coarsening process. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 161–167, 2002
Effect of additives on the microstructure and thermal properties of a mica‐based glass‐ceramic
Authors: Denry I. L. , Holloway J. A.
Published: October 2004

Previous work has shown that lithium mica glass‐ceramics were excellent potential candidates as dental ceramics. The purpose of this study was to evaluate the effect of various additives on the microstructure and thermal properties of a mica glass‐ceramic in the system Li2O‐K2O‐SiO2‐MgO‐F. Five glass compositions were prepared: a base composition and four compositions with various additives. The compositions were melted at 1400 °C for 2 h and cast into 50 × 8 mm ingots. Differential thermal analyses were performed on the glasses up to 1400 °C. Bars (4 × 8 × 25 mm) were cut from the ingots and heat treated at various temperatures. The crystalline phases were analyzed by x‐ray diffraction. The microstructure was investigated by scanning electron microscopy. The percent crystallinity, crystal density, and average particle size were calculated from stereology measurements. X‐ray diffraction revealed that the major crystalline phase was taeniolite for all glass‐ceramics. Differential thermal analyses showed that the crystallization exotherm occurred in the temperature range 600–700 °C. The addition of calcium fluoride was most efficient in promoting the growth of mica crystals. Larger mica plate diameter could be beneficial to the crack‐propagation resistance of the glass‐ceramic. The addition of aluminum phosphate promoted nucleation rather than crystal growth and led to a significantly lower glass transition temperature and crystallization exotherm temperature. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 146–151, 2002; DOI 10.1002/jbm.10122
Healing process induced by three composite prostheses in the repair of abdominal wall defects
Authors: Bellón Juan M. , Jurado Francisca , García‐Moreno Francisca , Corrales Celia , Carrera‐San Martín Antonio , Buján Julia
Published: October 2004

The present study compared the performance of three composite prostheses used to repair abdominal wall defects in rabbits. Two of them [Parietex Composite® (PC) and Composix® (CS)] are commonly used in clinical practice and one was designed by the present team (PL‐PU99). At 14 and 90 days postimplant, specimens were obtained for morphological, macrophage response (RAM‐11) and morphometric and biomechanical analysis. The prosthetic area covered by adhesions was significantly greater (p < 0.05) in the CS group (6.83 ± 2.31 cm2) than in PC (0.11 ± 0.02 cm2) or PL‐PU99 (0.10 ± 0.07 cm2). At 14 days, it was observed a homogeneous, organized, well‐vascularized neoperitoneum that was significantly thicker (p < 0.05) in PL‐PU99. Except in the CS implants, this layer was covered by a continuous mesothelium. All three composites achieved good recipient tissue integration. Highest macrophage levels were recorded at 14 days with significantly higher values in the PL‐PU99 prosthesis. Biomechanical strength was significantly greater (p < 0.05) in CS at two weeks postimplant, but it was similar at 90 days. These findings suggest that the three composites show ideal integration with host tissue, along with similar biomechanical strength at 90 days, and significantly higher adhesion formation is induced by the CS prosthesis, possibly due to incomplete mesothelialization of the lower prosthetic surface. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 182–190, 2002; DOI 10.002/jbm.10123
Cytotoxicity of precious and nonprecious alloys—experimental comparison of in vitro data from two laboratories
Authors: Bumgardner Joel D. , Gerard Patrick D. , Geurtsen Werner , Leyhausen Gabriele
Published: October 2004

The aim of this investigation was to evaluate and compare the reproducibility of cytotoxicity data generated in two different laboratories using the same testing protocols. A series of dental alloys that are widely used in both countries were chosen. These alloys (five precious, two nonprecious) were wet ground up to 1200 grit SiC, sterilized in 70% ethanol, and extracted in sterile culture medium for 7 days. Pure copper was used as a positive control and Teflon® and media only were used as negative controls. Test and control samples were randomized and blinded to each laboratory. Cells, primary human gingival fibroblasts, and immortalized 3T3 fibroblasts, were exposed to the extracts for 24 h. Extract cytotoxicity was evaluated spectrophotometrically with the use of a mitochondrial enzyme activity assay. Data were collected from both laboratories, combined, and subjected to a mixed‐model analysis of variance. No statistical difference was obtained for the immortalized 3T3 cells, except for two extracts in which differences between the two labs were significant but were still not cytotoxic. Furthermore, no statistical differences were found for the primary cells. These data strongly suggest that cytotoxicity tests performed in different laboratories with the use of the same test materials may lead to comparable results if sample preparation, cells, test procedures, and data analyses are carefully considered. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 214–219, 2002; DOI 10.1002/jbm.10124
Mechanical properties of newly developed loop ligament for connection between the endobutton and hamstring tendons: Comparison with Ethibond sutures and Endobutton tape
Authors: Uchio Yuji , Ochi Mitsuo , Sumen Yoshio , Adachi Nobuo , Kawasaki Kenzo , Iwasa Junji , Katsube Kenichi
Published: October 2004

A new artificial loop ligament (LL) without mechanical weak points, such as a knot, has been developed to connect the EndoButton and hamstring tendons for anterior or posterior cruciate ligament (CL) reconstruction. This study assessed the mechanical properties of the LL and sutures (No. 5 Ethibond thread, EndoButton tape) and those of the different CL constructs with these materials and fixation devices commonly used in CL reconstruction. The LL had a significantly higher ultimate tensile load (UTL) and stiffness value (p < 0.001) than No. 5 Ethibond thread or EndoButton tape in static and fatigue tests (50–500 N, 1.08 million cycles). The LL‐tendons‐Leeds‐Keio artificial ligament‐staple construct complex also had significantly higher UTL and stiffness value than the Ethibond loops or EndoButton tape loop‐tendons‐Ethibond sutures‐postscrew‐fixed construct complex. Furthermore, the LL construct complex elongated the least after cyclic loading (50–150 N, 90,000 cycles). These findings suggested that using the LL construct complex might avoid a bungee cord effect and elongation before biological healing between the construct and bony socket. The LL construct complex could be a safe substitute for use during the postoperative period. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 173–181, 2002; DOI 10.002/jbm.10125
Thermal analysis of dental resins cured with blue light‐emitting diodes (LEDs)
Authors: Nomura Y. , Teshima W. , Tanaka N. , Yoshida Y. , Nahara Y. , Okazaki M.
Published: October 2004

Thermal analysis was used to measure the characteristics of dental resins cured with the use of a new light‐activation unit equipped with high illuminant blue light‐emitting diodes (LEDs). The characteristics were compared with those of resins cured with the use of two conventional halogen lamp units. The prepared base monomer consisted of a mixture of Bis‐GMA and TEGDMA (60:40 by weight), with 0.5 wt% CQ/DMPT or CQ/DMAEMA. The two experimental visible‐light‐cured resins were polymerized for 40 s. Differential scanning calorimetry (DSC) was used to examine the thermal characteristics of the cured resins. The activation energy for the decomposition of the dental resin was calculated from the peaks of the endothermic curves obtained when the specimens were heated at three different rates (5, 10, and 15 °C/min) during DSC. The activation energies calculated for the LED‐cured specimens were more than 220 kJ/mol; specimens cured with the use of the halogen units had activation energies of less than 192 kJ/mol. The Knoop hardness number (KHN) of the same specimens was measured, and was higher with the blue LED units than with halogen lamp units. Therefore, dental resins cured using blue LEDs have a higher degree of polymerization and more stable three‐dimensional structures than those cured with halogen lamps. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 209–213, 2002; DOI 10.1002/jbm.10126
Rheological properties of acrylic bone cement during curing and the role of the size of the powder particles
Authors: Lewis Gladius , Carroll Michael
Published: October 2004

A dynamic compressive rheometric technique was used to determine the true or complex viscosity (η*) of three poly (methyl methacrylate), PMMA‐based bone cement formulations (one commercially available and two experimental), as a function of the time that elapsed from commencement of hand mixing of the cement constituents (t). For each cement, two rheological parameters [namely, the time of onset of cure (tons) and the critical cure rate (CCR), which is herein defined as the complex viscosity rate computed at tons] were determined from the η*−t data. For each cement, particle analysis was used to obtain the powder particle size distribution, from which the following parameters were obtained: (a) the overall mean particle diameter Dm, and (b) the relative amounts of small‐sized PMMA beads (mean diameter d between 0 and 40 μm) (α) and large‐sized PMMA beads (d > 75 μm) (β). It is seen that the key particle parameter is not Dm per se but α and β. Thus, the highest values of tons and CCR were obtained from a cement with the highest values of α and β. An explanation for these trends is given, and two areas for further research work in this field are outlined. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 191–199, 2002; DOI 10.1002/jbm.10127
Bioactivity and osseointegration study of calcium phosphate ceramic of different chemical composition
Authors: Manjubala I. , Sivakumar M. , Sureshkumar R. V. , Sastry T. P.
Published: October 2004

Synthetic hydroxyapatite (HA) and tricalcium phosphate (TCP) are promising bone‐substitute materials in the orthopaedic and dental fields, as their chemical composition is similar to that of bone. This study investigated the osseointegration performance of carbonated biphasic calcium phosphate (CBCP) ceramics containing carbonated hydroxyapatite and tricalcium phosphate prepared by microwave irradiation, in femoral defects of dogs. The defects were created as 3‐mm holes on the lateral aspect of femur and filled with the implant material. The serum was collected postoperatively and biochemical assays for alkaline phosphatase activity levels were carried out. The animals' defective sites were radiographed at 4, 8, and 12 weeks. The radiographic results showed that the process of ossification started after 4 weeks and the defect was completely filled with new bone after 8 weeks. Histological examination of the tissue showed the osteoblastic activity inducing the osteogenesis in the defect. The complete haversian system with osteoblastic and osteoclastic activity and bone remodelling process were observed after 12 weeks. The alkaline phosphatase activity levels also correlated with the formation of osteoblast cells. This calcium phosphate ceramic has proved to work well as a biocompatible implant and as an osteoconductive and osteoinductive material for the filling of bone defects. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 200–208, 2002; DOI 10.1002/jbm.10128