bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutation and Overexpression of the Transgene in Ethylnitrosourea-Induced Tumors in Mice Carrying a Human Prototype c-Ha-ras Gene
Authors: Toyosawa Kaoru , Tanaka Kohji , Imai Toshio , Yasuhara Kazuo , Koujitani Takatoshi , Hirose Masao , Mitsumori Kunitoshi
Published: July 2008

To investigate mechanisms underlying accelerated carcinogenesis in mice carrying a human prototype c-Ha- ras gene (rasH2 mouse), mutations and the expression profile of the transgene were evaluated in 14 tumors induced by a single injection of ethylnitrosourea (ENU), with or without additional beta-estradiol 3-benzoate (EB) treatment. Although no codon 12 mutations were detected, changes in codon 61 were evident in all lung adenocarcinomas, skin squamous cell carcinomas and forestomach squamous cell carcinomas examined. The mRNA levels of the transgene in these lesions were also elevated 1.71- to 4.77-fold, 3.04- to 5.18-fold, and 3.00- to 5.67-fold, respectively, in comparison with those in the normal livers of rasH2 mice. The results obtained in this study suggest that mutations in codon 61 and amplification of the transgene play key roles in the carcinogenesis induced by ENU in rasH2 mice.
Comments on R. Karbe and R. L. Kerlin (2002). Cystic Degeneration/Spongiosis Hepatis (Toxicol Pathol 30 (2), 216—227) PETER BANNASCH
Authors: Bannasch Peter
Published: July 2008

Karbe and Kerlin have questioned the classification of spongiosis hepatis as a preneoplastic lesion or even a benign neoplasm, designated as spongiotic pericytoma, and have proposed to use the term cystic degeneration for this lesion in rats and fish. However, the reclassification of spongiosis as cystic degeneration is unwarranted for several reasons. In the rat, spongiosis hepatis represents a specific pathomorphologic entity, originating from the perisinusoidal (Ito) cells; it may occur spontaneously in aged animals but its number and size increases significantly after exposure to various (hepato)carcinogens. Comparative morphological, immunohistochemical, and autoradiographic studies in rats exposed to N-nitrosomorpholine revealed that spongiosis hepatis is an integral part of larger proliferative Ito-cell aggregates showing an autonomous, progressive growth. The classification of spongiosis hepatis as a benign neoplasm is based on these findings that endorse and extend previous considerations on the preneoplastic or neoplastic nature of this lesion. Irrespective of the classification of spongiosis hepatis as a benign neoplastic or a preneoplastic lesion, there is compelling evidence for its reliability as a sensitive marker for (hepato)carcinogenic effects in rats and fish. The data collected by Karbe and Kerlin support rather than contradict the reliability of spongiosis hepatis as an effect marker for carcinogens.
Inhibition by Ethinylestradiol of N-Ethyl-N-Nitrosourea-Initiated Uterine Carcinogenesis in Transgenic Mice Carrying a Human Prototype C-Ha-ras Gene (rasH2 Mice)
Authors: Watanabe Takao , Kashida Yoko , Ueda Makoto , Onodera Hiroshi , Takizawa Tamotsu , Hirose Masao , Mitsumori Kunitoshi
Published: July 2008

In order to demonstrate the tumor promoting effect of ethinylestradiol (EE) in our uterine carcinogenesis model, rasH2 or ICR mice given an intraperitoneal injection of 120 mg/kg body weight of N-ethyl- N-nitrosourea (ENU) or an intra-uterine injection of 50 mg/kg body weight of ENU, respectively, followed by 2.5 or 0 ppm EE in the diet for 24 weeks in experiment 1 and 6 weeks in experiment 2. In experiment 1, in ICR mice, the incidences of adenocarcinomas in the ENU alone and the ENU+EE groups were 0% and 37.5%, respectively, the difference being statistically significant. The incidences of atypical hyperplasias and endometrial hyperplasias in the ENU+EE group were also significantly higher than those in the ENU alone group. In rasH2 mice, on the other hand, no endometrial proliferative lesions were induced in the uterus of the ENU+EE group, although uterine adenocarcinomas (55.6%), atypical hyperplasias (33.3%), and endometrial hyperplasias (22.2%) were observed in the ENU alone group. Proliferating cell nuclear antigen (PCNA) positive indices for uterine adenocarcinomas and atypical hyperplasias in ICR mice treated with ENU+EE showed high values, but those in rasH2 mice given ENU alone were comparable to data for intact epithelium. In experiment 2, the immunohistochemical expression of estrogen receptor α (ER α) in the uterine luminal and glandular epithelium in the ENU+EE group of ICR mice was moderate to marked, but that in the ENU alone group was slight. There was no consistent difference in ER α expression in the uterine luminal and glandular epithelium between ENU+EE and ENU alone groups of rasH2 mice. These results suggest that 2.5 ppm EE paradoxically inhibits the uterine carcinogenesis in rasH2 mice initiated with ENU.
The Expression and Significance of Metallothioneins in Murine Organs and Tissues Following Mercury Vapour Exposure
Authors: Stankovic Roger Kevin , Lee Victor , Kekic Murat , Harper Clive
Published: July 2008

The fate of inspired mercury vapour (Hg0) is critical in the central nervous system (CNS) where it can circumvent the blood—brain barrier (BBB) at the neuromuscular junction (NMJ) and accumulate indefinitely in motor neurons by retrograde transport. The detoxification of systemic Hg0 by lung and liver requires investigation. We exposed 129/Sv wild-type (Wt) and 129/Sv MT-I, II double knockout (KO) mice to 500 μg Hg0/m3 for 4 hours to investigate the expression of MT in the lung, liver, and spinal cord following Hg0 exposure using unexposed groups as controls. There were congestive changes in liver and lung of both Wt and MT-KO groups of Hg0-treated mice; these changes appeared more pronounced in the MT-KO group. Motor neurons in the spinal cord did not show any pathological changes. Based on expression of MT, liver appears to have a major role in trapping and stabilising mercury. In the spinal cord, MT was expressed in all white matter astrocytes and in some grey matter astrocytes. Notably, motor neurons did not express MT, and the presence of MT could not be demonstrated in the axons of the ventral root. The absence of MT expression in motor neurons and their axons suggests the dependence of the motor system on the detoxifying capacity of liver MTs.
Preclinical Safety of Recombinant Human Interleukin-18
Authors: Herzyk Danuta J. , Bugelski Peter J. , Hart Timothy K. , Wier Patrick J.
Published: July 2008

Recombinant human interleukin-18 (rHuIL-18) is currently in clinical trials for treatment of cancer. This report presents results of preclinical toxicity studies with rHuIL-18 in cynomolgus monkeys and recombinant murine IL-18 (rMuIL-18) in mice. The rHuIL-18 was administered intravenously in 1 or 2 different 5-day cycles at doses 0.3 to 75 mg/kg/day in monkeys. Decreases in red cell mass, neutrophil, and platelet counts, increases in monocyte and large unstained cell counts, and lymphoid hyperplasia in spleen and lymph nodes were mild, reversible, and likely related to the pharmacologic activity of IL-18. The only toxic effect was protein cast nephropathy, secondary to coprecipitation of administered IL-18 and Tamm-Horsfall protein in the distal nephron, that only occurred at 75 mg/kg/day. Other adverse effects of rHuIL-18 were related to strong immunogenicity in monkeys and were manifest only during a second dosing cycle. The rMuIL-18, at similar dosing levels and cycles in mice, resulted in reduced red cell mass, increased white blood cell counts, spleen and lymph node hyperplasia, and mild, reversible changes in intestine, liver, and lungs. Protein cast nephropathy occurred in mice at doses ≥30 mg/kg/day. In conclusion, preclinical safety studies showed that rIL-18 was well tolerated at pharmacologically active doses in both monkeys and mice.
Safety of Aquaflor (Florfenicol, 50% Type A Medicated Article), Administered in Feed to Channel Catfish, Ictalurus punctatus
Authors: Gaikowski Mark P. , Wolf Jeffrey C. , Endris Richard G. , Gingerich William H.
Published: July 2008

Aquaflor, a feed premix containing the broad spectrum antibacterial agent florfenicol (50% w/w), is being developed for use to control enteric septicemia (ESC) in channel catfish Ictalurus punctatus caused by the gram-negative enterobacterium Edwardsiella ictaluri. The recommended dose of Aquaflor to control ESC is 10 mg/kg body weight (BW)/day for 10 days. The study objective was to determine the safety of Aquaflor administered in feed to channel catfish at doses of 0 (control), 10, 30, and 50 mg/kg BW/day for 20 consecutive days. Parameters evaluated included daily mortality, behavioral (appetite, distribution, flight/fright response), and water chemistry observations, initial and terminal weight measurements, and gross and microscopic pathology. Medicated feed consumption was 67—86% of target with group mean doses of 8.5 mg/kg BW/day, 24.6 mg/kg BW/day, and 34.9 mg/kg BW/day. There were no mortalities or clinically observable changes noted at any of the dose levels tested. Aquaflor-related changes were limited to the food consumption and histopathology data. Although Aquaflor-related decreased feed consumption was noted in the 30 and 50 mg/kg BW/day groups, there were no differences in fish growth among the treatment groups. Aquaflor-related histopathology findings were limited to a histomorphologically evident dose-dependent decrease in hematopoietic/lymphopoietic tissue in the anterior kidneys, posterior kidneys, and spleens of channel catfish.
Rapid Emergence of Mammary Preneoplastic and Malignant Lesions in Human c-Ha-ras Proto-Oncogene Transgenic Rats: Possible Application for Screening of Chemopreventive Agents
Authors: Matsuoka Yoichiro , Fukamachi Katsumi , Hamaguchi Tetsuya , Toriyama-Baba Hiroyasu , Kawaguchi Hiroaki , Kusunoki Masato , Yoshida Hiroki , Tsuda Hiroyuki
Published: July 2008

For comparison of mammary gland whole mounts with examination of 2 histologic sections of mammary gland, 56 Hras128 rats were intravenously injected with 50 mg/kg body weight of N-methyl- N-nitrosourea at 50 days of age and then sacrificed at days 5, 10, 15, 20, 25, and 56. Comparison of detection sensitivity between the whole mounts and histologic sections revealed no lesions apparent in whole mounts on day 10, although intraductal proliferation was clearly detected in histologic sections in 44% of treated rats. Proliferative lesions were first detected in whole mounts at a 44% incidence on day 15, while intraductal proliferations and atypical hyperplasias were apparent in the sections at 89% and 44% incidences, respectively. On day 20, atypical hyperplasias and small adenocarcinomas in histologic sections were found in almost all animals. In conclusion, examination of 2 histologic sections from mammary tissues was found to be practical for detection of small malignant lesions as early as 15 days after MNU injection, and suppressive effects of soy isoflavones were clearly evident within 20 days after carcinogen exposure. These results suggest that this model has practical utility for short-term screening of chemopreventive agents for mammary carcinogenesis.
Effect of Diet and Animal Care/Housing Protocols on Body Weight, Survival, Tumor Incidences, and Nephropathy Severity of F344 Rats in Chronic Studies
Authors: Haseman Joseph K. , Ney Elizabeth , Nyska Abraham , Rao Ghanta N.
Published: July 2008

Diet is an important environmental factor affecting body weight, survival, and age-related diseases of rodents. The NIH-07 open formula diet was the diet used in the National Toxicology Program's (NTPs) rodent carcinogenicity studies from 1980 to 1994. In 1994 the NTP began using a new diet designated the NTP-2000 diet. This paper compares body weight, survival, tumor incidence, and nephropathy severity in untreated control groups of Fischer 344 (F344) rats fed the NTP-2000 or NIH-07 diets, using data from 22 separate 2-year feed and inhalation studies. The feed studies were conducted in 3 different facilities, and all the inhalation studies were conducted in a single facility. During feed studies, rats were group housed in polycarbonate cages and fed diets in powder (mash) form, while in inhalation studies, rats were housed individually in wire mesh cages, and fed diets in pelleted form. Survival was significantly ( p < 0 .05) higher in groups fed NTP-2000 diet compared to the corresponding groups fed NIH-07 diet, irrespective of sex or housing conditions. Use of the NTP-2000 diet was also associated with a decreased incidence of pituitary gland tumors in both sexes and decreased incidences of adrenal pheochromocytoma and preputial gland tumors in males. The incidence and severity of nephropathy was also decreased in animals receiving the NTP-2000 diet, especially males. The decreased nephropathy severity and the decreased incidence of pituitary gland tumors are likely the major factors contributing to the improved survival of rats receiving the NTP-2000 diet relative to those given the NIH-07 diet. These data also support earlier findings that decreased incidences of adrenal pheochromocytoma are associated with reduced nephropathy severity in male F344 rats. Throughout the two-year study female rats receiving the NTP-2000 diet were significantly ( p < 0 .05) lighter than those receiving the NIH-07 diet. However, it is uncertain if this difference can be attributed to the NTP-2000 diet, since implementation of this diet by the NTP approximately coincided with changes in the F344 rat production colony that resulted in somewhat lighter animals being provided to the NTP. Controls from inhalation studies and feed studies differed significantly ( p < 0 .01) in the incidence of a variety of tumors, irrespective of diet. This suggests that differences in animal care and housing protocols may impact tumor incidence in F344 rats, most notably pituitary gland and testis tumors.
Apoptosis and Nitrative Stress Associated with Phosphodiesterase Inhibitor-Induced Mesenteric Vasculitis in Rats
Authors: Slim Rabih M. , Yunling Song  , Albassam Mudher , Dethloff Lloyd A.
Published: July 2008

Nitric oxide may play a role in phosphodiesterase (PDE) inhibitor-induced rat mesenteric vasculitis. The present study was conducted to identify cellular sources of iNOS, determine the distribution of nitrotyrosine (NT) residues as a footprint of peroxynitrite (ONOO-) production, and evaluate their association with vascular apoptosis. To dissociate primary events from secondary changes associated with the inflammatory response, rats were given the PDE IV inhibitor CI-1018 orally at 750 mg/kg alone or concurrently with dexamethasone (DEX) intraperitoneally at 1 mg/kg for 4—5 days. Neutrophil (PMN) involvement in apoptosis was investigated in CI-1018 treated rats dosed with rabbit anti-rat PMN serum (APS). iNOS expression, NT residues, and caspase-3 were detected by immuno-histochemistry. Apoptosis was evaluated by TUNEL assay. CI-1018 induced vascular lesions were associated with iNOS expression in endothelial cells and inflammatory infiltrates; NT was evident only in the latter. Caspase-3 and TUNEL-positive staining were prominent only in medial smooth muscle cells (SMC) from CI-1018-treated rats and only when associated with active inflammation. iNOS- and NT-positive inflammatory cells were present in close proximity to SMC with caspase-3 staining. Inflammatory infiltrates were absent in rats given DEX with minimal SMC necrosis and hemorrhage remained. DEX eliminated apoptosis and immunoreactivity associated with caspase-3, iNOS, and NT. APS depletion of PMNs decreased the incidence and severity of vasculitis but failed to abolish completely caspase-3 immunoreactivity. Expression patterns for caspase-3, iNOS, and NT demonstrated that nitrative stress is a prominent feature of PDE inhibitor-induced vasculitis, with a possible role in medial SMC apoptosis. Further, medial SMC apoptosis may not be a primary event, but instead may be secondary to the inflammatory response.
Morphogenesis of Postmortem Hepatocyte Vacuolation and Liver Weight Increases in Sprague-Dawley Rats
Authors: Xiantang Li  , Elwell Michael R. , Ryan Anne M. , Ochoa Ricardo
Published: July 2008

Accurate interpretation of microscopic changes in tissues is critical in hazard identification and risk assessment. To address a possible confounder, the effects of postmortem interval on hepatocyte vacuolation and liver weight were studied in fasted and nonfasted Sprague-Dawley rats. Male and female rats (5/sex/interval) were euthanized with CO2, weighed, and necropsied either immediately or after remaining in the closed CO2 chamber for 5, 10, or 25 minutes after respirations ceased. The liver was removed, weighed, and fixed for light microscopy, immunohistochemistry, and electron microscopy. The liver weight and liver to body weight ratio increased significantly in both male and female rats. Postmortem hepatocellular vacuolation was more prominent in males than in females. Both fasted and nonfasted males were similarly affected, however, fasted females were affected more than nonfasted females at the 25-minute interval. Ultrastructurally, intracytoplasmic vacuoles in hepatocytes and/or endothelial cells contained electron-lucent material that was morphologically similar to plasma in sinusoidal spaces. Results of our study suggest that hepatocyte vacuoles were formed in a postmortem time-dependent manner as a result of plasma influx into the cytoplasm. This change was associated with hepatic sinusoidal congestion and increases in liver weight. Males were more sensitive than females to postmortem hepatocyte vacuolation.
Morphology of Nasal Lesions in F344/N Rats Following Chronic Inhalation Exposure to Naphthalene Vapors
Authors: Long Philip H. , Herbert Ronald A. , Peckham John C. , Grumbein Sondra L. , Shackelford Cynthia C. , Abdo Kamal
Published: July 2008

Naphthalene (CAS No. 91-20-3) administered by inhalation at concentrations of 10, 30, or 60 ppm for 6 hours per day, 5 days per week for 105 weeks caused nonneoplastic and neoplastic effects in nasal respiratory and olfactory regions of male and female F344/N rats. Non-neoplastic nasal effects were characterized by an increase in the incidence and severity of a complex group of lesions, including atypical hyperplasia, atrophy, chronic inflammation, and hyaline degeneration of olfactory epithelium; hyperplasia, squamous metaplasia, hyaline degeneration, and goblet cell hyperplasia of the respiratory epithelium; and hyperplasia and squamous metaplasia of mucosal glands. Neoplastic effects were characterized by the induction of two types of rare primary nasal tumors, olfactory neuroblastomas and respiratory epithelial adenomas. The incidences of olfactory neuroblastomas in males at 0 ppm, 10 ppm, 30 ppm, and 60 ppm were, respectively, 0%, 0%, 8%, and 6%, whereas in females they were 0%, 4%, 6%, and 24%. The incidences of respiratory epithelial adenomas in males at 0 ppm, 10 ppm, 30 ppm, and 60 ppm were, respectively, 0%, 12%, 17%, and 31% and in females 0%, 0%, 8%, and 4%. The olfactory neuroblastomas and respiratory epithelial adenomas were considered carcinogenic effects related to naphthalene exposure based on their relatively high incidence in exposed rats, their absence in concurrent control rats and NTP historical controls, and their rare spontaneous occurrence in rats of any strain.
Repulsion by Slit and Roundabout prevents Shotgun/E-cadherin–mediated cell adhesion during Drosophila heart tube lumen formation
Authors: Santiago-Martínez Edgardo , Soplop Nadine H. , Patel Rajesh , Kramer Sunita G.
Published: July 2008

During Drosophila melanogaster heart development, a lumen forms between apical surfaces of contralateral cardioblasts (CBs). We show that Slit and its receptor Roundabout (Robo) are required at CB apical domains for lumen formation. Mislocalization of Slit outside the apical domain causes ectopic lumen formation and the mislocalization of cell junction proteins, E-cadherin (E-Cad) and Enabled, without disrupting overall CB cell polarity. Ectopic lumen formation is suppressed in robo mutants, which indicates robo's requirement for this process. Genetic evidence suggests that Robo and Shotgun (Shg)/E-Cad function together in modulating CB adhesion. robo and shg/E-Cad transheterozygotes have lumen defects. In robo loss-of-function or shg/E-Cad gain-of-function embryos, lumen formation is blocked because of inappropriate CB adhesion and an accumulation of E-Cad at the apical membrane. In contrast, shg/E-Cad loss-of-function or robo gain-of-function blocks lumen formation due to a loss of CB adhesion. Our data show that Slit and Robo pathways function in lumen formation as a repulsive signal to antagonize E-Cad–mediated cell adhesion.
Permeation and Gating in CaV3.1 (α1G) T-type Calcium Channels Effects of Ca2+, Ba2+, Mg2+, and Na+
Authors: Khan Nilofar , Gray I. Patrick , Obejero-Paz Carlos A. , Jones Stephen W.
Published: July 2008

We examined the concentration dependence of currents through CaV3.1 T-type calcium channels, varying Ca2+ and Ba2+ over a wide concentration range (100 nM to 110 mM) while recording whole-cell currents over a wide voltage range from channels stably expressed in HEK 293 cells. To isolate effects on permeation, instantaneous current–voltage relationships (IIV) were obtained following strong, brief depolarizations to activate channels with minimal inactivation. Reversal potentials were described by PCa/PNa = 87 and PCa/PBa = 2, based on Goldman-Hodgkin-Katz theory. However, analysis of chord conductances found that apparent Kd values were similar for Ca2+ and Ba2+, both for block of currents carried by Na+ (3 μM for Ca2+ vs. 4 μM for Ba2+, at −30 mV; weaker at more positive or negative voltages) and for permeation (3.3 mM for Ca2+ vs. 2.5 mM for Ba2+; nearly voltage independent). Block by 3–10 μM Ca2+ was time dependent, described by bimolecular kinetics with binding at ∼3 × 108 M−1s−1 and voltage-dependent exit. Ca2+o, Ba2+o, and Mg2+o also affected channel gating, primarily by shifting channel activation, consistent with screening a surface charge of 1 e− per 98 Å2 from Gouy-Chapman theory. Additionally, inward currents inactivated ∼35% faster in Ba2+o (vs. Ca2+o or Na+o). The accelerated inactivation in Ba2+o correlated with the transition from Na+ to Ba2+ permeation, suggesting that Ba2+o speeds inactivation by occupying the pore. We conclude that the selectivity of the “surface charge” among divalent cations differs between calcium channel families, implying that the surface charge is channel specific. Voltage strongly affects the concentration dependence of block, but not of permeation, for Ca2+ or Ba2+.
Damping Characterization of Magnesium Based Composites Using a New Circle-Fit Approach
Authors: Srikanth Narasimalu , Lim Samuel Chao Voon , Gupta Manoj
Published: July 2008

In the present study, a new methodology of using free–free beam method coupled with circle-fit approach is used to determine damping of ceramic reinforced magnesium composites. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency is predicted accurately for the test specimen. An attempt is made to rationalize the increase in damping capability of the MMC when compared against the monolithic specimen in terms of increase in dislocation density and presence of plastic zone at the matrix–particulate interface.
Dispersed Particle Size Distribution in Impact Modified Polypropylene
Authors: Pieroni Paula , Ercoli Daniel , Goizueta Graciela , Capiati Numa
Published: July 2008

In this work ternary polypropylene (PP) rich blends with ethylene propylene terpolymers (EPDM) and LLDPE are studied. Attention is focused on the effect of different viscosity ratios (β1/4 viscosity of dispersed phase/viscosity of PP matrix) on the particles sizes and particle size distribution of the dispersed phase. The incidence of the elastomer viscosity and dispersed phase content are also analyzed. A reduction in the viscosity ratio mainly affects the weight average particle diameter (Dw) rather than the number average particle diameter (Dn).
Electromagnetic Interference Shielding Effectiveness of Hybrid Conductive Polymer Composite
Authors: Das N. C. , Khastgir D. , Chaki T. K. , Chakraborty A.
Published: July 2008

Electromagnetic interference (EMI) shielding characteristics of ethylene vinyl acetate (EVA) and ethylene propylene diene (EPDM) and their 50: 50 blend filled with conductive carbon black and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100-2000 MHz and 8-12 GHz (X-band range). The return loss and the loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with increasing frequency. The SE also increases with the increase in filler loading. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composites. The SCF-filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results suggest that the fibre-filled (20 phr) composites can be used for the EMI shielding, as well as for some microwave applications.
Evaluation of Sulfonated Rubber Powder as Ion Exchange Resin
Authors: Yehia A. A. , Ismail M. N. , Hefny Y. A. , Abdel-Bary E. M. , Mull M. A.
Published: July 2008

Ground rubber powder was treated with both concentrated sulfuric acid and chlorosulfonic acid. The treatment conditions as well as the parameters affecting the degree of sulfonation were investigated. It is assumed that the sulfonation reaction occurs on the benzene ring as well as on the double bond of the butadiene unit in styrene butadiene rubber (SBR). Evaluation of the ion exchange capacity of both the acidic form and the neutralized form was carried out. It was found that the ion exchange capacity of the neutralized form is higher than that of its corresponding acidic form.
Mechanical Properties of Nylon6 Cord-Rubber Composite Subjected to Biaxial Tensile Loads
Authors: Zhang Fengfa , Wan Zhimin , Du Xinwen
Published: July 2008

Effects of perpendicular tensile loads on the mechanical behavior and biaxial tensile load ratios on stress-strain behaviors of single ply of nylon cord-rubber composite are studied respectively under biaxial tensile conditions employing a cruciform specimen. Experimental results indicate that transverse mechanical properties of nylon cord-rubber composite with longitudinal constant tensile loads are distinct from its uniaxial transverse tensile mechanical properties. This can be attributed to the action of longitudinal tension that makes the material rigidify in the direction perpendicular to the fiber. The mode of failure is representative of matrix-dominated failure. However, effects of transverse constant tensile load on longitudinal tensile mechanical properties are indistinctive compared with corresponding uniaxial longitudinal tensile mechanical properties. This could be due to a larger difference between longitudinal and transverse mechanical properties. Its dominating failure mode is typical fiber-dominated mode. Effects on biaxial tensile load ratios on its transverse stress-strain behaviors are obvious; whereas, longitudinal stress-strain behaviors under different biaxial tensile load ratios are almost identical. Large differences between longitudinal and transverse tensile properties can be direct reasons resulting in dissimilarities between longitudinal and transverse tensile mechanical behaviors of cord-rubber composite under biaxial tensile loading.
Compatibilized Blends of Low Density Polyethylene and Poly Dimethyl Siloxane Rubber: Part I: Acid and Alkali Resistance Properties
Authors: Jana R. N. , Nando G. B.
Published: July 2008

Acid and alkali resistance properties of cross linked blends of low-density polyethylene (LDPE) and polydimethyl siloxane rubber (PDMS) have been studied. Ethylene methyl acrylate (EMA) copolymer acts as a compatibilizer and dicumyl peroxide (DCP) acts as the crosslinking agent for the blend systems. Tensile properties of the individual components and the blends before and after treatment with different acids and two various concentrations of alkali are reported. Treatment with nitric acid has resulted in severe deterioration of tensile properties of all samples compared to all other acids studied. Retention of tensile properties of all the blends is found to improve significantly as compared to the reference sample, the PDMS rubber. This has been further supported by the scanning electron microscopic (SEM) studies.
GF/PP Tape Winding with On-Line Consolidation
Authors: Dai Shao-Cong , Ye Lin
Published: July 2008

In the tape winding/laying process, the quality of on-line consolidated thermoplastic composite parts is highly dependent on processing conditions, such as winding speed, local processing temperature and compaction pressure. Composite rings were manufactured using glass fibre (GF)/polypropylene (PP) tape with hot air as the heating source. Effects of processing conditions on consolidation quality were studied, and the upper bound for good consolidation and the lower bound for overheating were established for winding speed as a function of processing temperature, when the compaction pressure was kept constant. A simple consolidation model, based on heat transfer and intimate contact, was applied to correlate winding speed with processing temperature, and good correlation was obtained with experimental data.
Forward to Better Understanding of Optical Characterization and Development of Colored Polyamides for the Infra-Red/Laser Welding: Part I - Efficiency of Polyamides for Infra-Red Welding
Authors: Kagan Val , Bray Robert , Chambers Al
Published: July 2008

The influence of a wide range of the infrared (IR) wavelengths (from 830 to 1064 nm) on the optical properties of welded thermoplastics was evaluated for unfilled, filled and reinforced polyamide 666 and amorphous grades. Presented results and developed recommendations will help, designers, technologists and materials scientists in welded parts design, materials selection and new materials development for various laser welding (LW) applications.
An Investigation on the Polymer Composite Medical Device - External Fixator
Authors: Baidya K. P. , Ramakrishna S. , Rahman M. , Ritchie A. , Huang Zheng-Ming
Published: July 2008

Primary impetus for the development of composite materials for medical usage came from orthopedic implant application. In case of metal alloys stiffness mismatch causes stress shielding in applications such as bone plates, total hip replacement, and total knee replacement. Moreover, the metal alloys and ceramics are radio opaque, and in some cases they result in undesirable artifacts in X-ray radiography. In the case of polymer composite materials the radio transparency can be adjusted by adding contrast medium to the polymer. More over the polymer composite materials are fully compatible with the modern diagnostic methods such as computed tomography (CT) and magnetic resonance imaging (MRI) as they are non-magnetic.

The current study reports the development of a radiolucent fiber reinforced polymer composite material for a biomedical device, Ilizarov external fixator. Material fabrication and characterization are described. Quantitative X-ray radiographic analysis was carried out to choose the best from the probable materials.

The Finite Element Method (FEM) was employed to determine the worst possible in service loading condition, and the ring dimensions were modified accordingly. Half ring prototypes were produced using two types of composite materials: knitted aramid fiber fabric reinforced epoxy and random short carbon (RSC) fiber reinforced epoxy. The in-plane compressive strength and axial stiffness of the complete frame were measured according to ASTM specifications. The performance was evaluated and compared to an existing system in simulated in-service conditions.
The Effect of Molecular Weight of Biodegradable Hydrogel Components on Indomethacin Release from Dextran and Poly(DL)lactic Acid Based Hydrogels
Authors: Zhang Yeli , Chu Chih-Chang
Published: July 2008

Biodegradable hybrid hydrogels from chemically modified dextran and poly(DL)lactic acid (PDLLA) were prepared by UV photocrosslinking of different molecular weights (MWs) of these precursors. A series biodegradable hybrid hydrogels were obtained by changing the composition ratio of hydrogels and MWs of dextran and PDLLA. These hydrogels were characterized by swelling and in vitro biodegradation-induced morphological structure changes. Indomethacin (IDM) was entrapped in these hydrogels and the release kinetics were investigated in a pH 7.4 phosphate buffer solution. The relationship between hydrogel swelling and biodegradation, IDM release from the network hydrogels and the molecular weights of dextran and PDLLA were studied. It was found that the swelling and biodegradation of these hybrid hydrogels were affected by both the MWs of the polymer component and the composition ratio of the hydrogels. IDM release from the hybrid hydrogel networks depended on the structure and hydrophobicity of the hydrogels; the MW effect on IDM release profiles was smaller than on hydrogel properties.
Partitioning of Ganglioside-Reconstituted Liposomes in Aqueous Two-Phase Systems
Authors: Kang Eui-Chul , Miyahara Tomoo , Akiyoshi Kazunari , Sunamoto Junzo
Published: July 2008

The partitioning of ganglioside (GM3,GD1a, GD1b or GT1b)-reconstituted liposomes was investigated in an aqueous poly(ethylene oxide)/dextran two-phase system to evaluate the carbohydrate–carbohydrate interactions in water. The partitioning of the ganglioside-reconstituted liposome was strongly affected by the buffer employed. As the concentration of sodium phosphate decreased, the ganglioside-reconstituted liposomes were partitioned to the bottom, dextran-rich, phase. In 10 mM sodium phosphate containing 150 mM sodium chloride, the conventional liposome without ganglioside were located mostly at the interface between the two phases. On the other hand, the ganglioside-reconstituted liposomes were significantly partitioned to the bottom dextran-rich phase, which was related to the ganglioside density on the liposomal surface. This partitioningto the dextran-rich phase also depended on the chemical structure of the ganglioside on the liposomal surface. The affinity of liposomal ganglioside being on the liposomal surface to dextran was the following sequence; GT1b>GD1a>GD1b>GM3. Partitioning of liposomes to the top poly(ethylene oxide)-rich phase was negligible irrespective of the characteristics of the liposomal surface.
Tumor-Selective Macromolecular MRI Contrast Agents
Authors: Yan Guo-Ping , Zhuo Ren-Xi , Yang Yun-Huang , Li Li-Yun , Liu Mai-Li , Ye Chao-Hui
Published: July 2008

Tumor-selective macromolecular ligands containing 5-(p-Carbonyloxyphenyl)-10,15,20-triphenylporphyrin (HPTP) moiety (PHEA-DTPAHPTP and PAEA-DTPA-HPTP) were prepared by the incorporation of diethylenetriaminepentaacetic acid (DTPA) and 5-(p-hydroxylphenyl)-10,15, 20-triphenylporphyrin (HPTP) as the tumor-selective group in poly [α,β-(N-(2-hydroxyethyl)-L-aspartamide)] (PHEA) and poly-[α-β-(N-(2-aminoethy1)-L-aspartamide)] (PAEA). These ligands were further complexed with gadolinium chloride to form two tumor-selective macromolecular MRI contrast agents PHEA-Gd-DTPA-HPTP and PAEA-Gd-DTPA-HPTP. Relaxivity studies showed that both the polyaspartamide-gadolinium complexes possess higher relaxation effectiveness than that of the clinically used Gd-DTPA. Magnetic resonance imaging of tumors in mice indicated that these two polyaspartamide MRI contrast agents containing 5-(p-Carbonlyoxyphenyl)-10,15,20-triphenylporphyrin moiety can significantly enhance the contrast MRIs of Hepatoma (H22) and Ehrlich ascites carcinoma after injection and are taken up selectively by these cancers in mice.
Separation of Chitosan from Penicillium Chrysogenum Mycelium and its Applications
Authors: Tianwei Tan , Binwu Wang , Xinyuan Shi
Published: July 2008

A process to separate chitosan from Penicillium chrysogenum mycelium was developed. Alkaline treatment and acetic acid extraction were used for deacetylating chitin to chitosan. The molecular weight of the chitosan was 3.6 × 104 and the degree of deacetylation was 84%. Analysis indicated that the chitosan from Penicillium chrysogenum mycelium was similar to that obtained from shrimp. The chitosan from the mycelium was used to prepare microcapsules for controlled drug release. The chitosan microcapsules reached maximum release of vitamin D2 after 10 h which avoided the problem of instability in gastric juice; the chitosan microcapsules are suitable for adsorption of vitamin D2 in intestines.
New Biodegradable Polymers from Renewable Sources – Segmented Copolyesters of Poly(1,3-Propanediol Succinate) and Poly(Ethylene Glycol)
Authors: Liu Yan , Ranucci Elisabetta , Lindblad Margaretha Söderqvist , Albertsson Ann-Christine
Published: July 2008

New high-molecular-weight hydrophobic/hydrophilic segmented copolymers of poly(ester-ether-carbonate) structure, containing poly(1,3-propylene succinate) (SP) and poly(ethylene glycol) (PEG) segments in the main chain, were synthesized and characterized. These copolymers were obtained by a two-step chain-extension reaction performed by the thermal polycondensation of αω-dihydroxy-oligo(1,3-propylene succinate) with PEG1000 and PEG2000, respectively. The molecular structure of all the synthesized materials was characterized by 1H-NMR, by SEC for molecular weights, and by DSC for thermal properties. The molecular characterizations were in agreement with the proposed structures. Solubility and swellability tests indicated that the introduction of hydrophilic PEG segments into the high molecular weight poly(1,3-propylene succinate)s imparted amphiphilic character to the new materials. This is expected to influence the biocompatibility and biodegradability of these materials. The new polymers, besides having a degradable backbone, were derived from the monomers, 1,3-propanediol and succinic acid, which are both obtainable from renewable sources. Therefore, they have a potential as environmental friendly materials.
Model Protein BSA Adsorption and Covalent Coupling onto Methyl Methacrylate Based Latex Particles with Different Surface Properties
Authors: Ayhan Hakan
Published: July 2008

The adsorption and covalent coupling of bovine serum albumin (BSA) onto methylmethacrylate (MMA) based monodisperse latex particles with different hydrophylic surfaces were investigated. P(MMA) and P(MMA/HEMA) microbeads in the size range of 1.5–2.0 mm were prepared by a dispersion homopolymerization method in the presence of poly(vinylpyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) as steric stabilizer and by copolymerization of MMA and 2-hydroxethyl methacrylate (HEMA) where PVP was used as steric stabilizers. Surface properties of these particles were characterized in terms of contact angle measurements and FTIR-DRS spectra. Additionally, hydroxyl groups of PMMAPVA and P(MMA/HEMA) particles were activated to provide aldehyde groups on surfaces. Adsorption of the BSA onto these five types of latex particles was examined as a function of initial albumin concentration, pH and ionic strength of the various cations (Na+,Ca+ and Mg− and anions (Cl− and SCN−). The maximum adsorption capacities for all latex particles were obtained in solutions with 0.01μ m ionic strength and 1 mg/mL BSA concentration. When using PMMAPVA, P(MMA/HEMA) and PMMAPVP, the adsorption increased as hydrophobicity increased. Aldehyde activation of the two most hydrophobic particles elevated the coupling (immobilization) significantly in ionic strength of 0.01μ m. The adsorption and/or immobilization were maximum in the presence of monovalent cation, Na+ or anion, Cl−B for all types of latex particles.
Novel Betulin-Containing Polyelectrolyte Conjugates
Authors: Mustafaev Mamed , Mustafaeva Zeynep , Ergen Erhan , Uraki Yasumitsu , Sano Yoshihiro
Published: July 2008

Conjugates ofanionic polyelectrolytes (PE) with betulin (PE–B) were synthesized by cross-linking the carboxyl groups oftemperature responsive poly(N-isopropylacrylamide-co-acrylic acid) (CP1) and poly(N-vinylpyrrolidoneco-acrylic acid) (CP2) copolymers, to the hydroxyl groups ofbetulin using thionyl chloride as the coupling agent. Water-insoluble CP1–B and poorly soluble CP2–B covalent conjugates were formed in a single step by mixing solutions of the selected components. Water-soluble bovine serum albumin (BSA)–betulin covalent conjugates (BSA*B) were synthesized by carbodiimide coupling. Betulin-containing polyelectrolyte conjugates (PEC–B) were prepared by complexing BSA*B conjugates with synthetic polycations – poly(N-alkyl-4-vinylpyridinium bromide). A single immunization ofmice with CP1–B and CP2–B, covalent conjugated with protein containing PEC–B and BSA*B systems without traditional adjuvants increased the specific immune response to betulin. CP2–B, as a soft and wet biocompatible delivery system, in contrast to the CP1–B conjugates, displayed an essentially higher betulin-specific immunogenic activity. The immunogenicity of BSA*B conjugates decreased rapidly with time while the PE–BSA*B complexes generated betulin-specific antibodies for 160 days.
125I-Labeled PLA/PEO Block Copolymer: Biodistribution Studies in Rats
Authors: Novakova K. , Laznicek M. , Rypacek F. , Machova L.
Published: July 2008

Block copolymers have a potential utility as drug carriers. In order to study their in vivo fate, the biodegradable block copolymer poly(D,L- lactide ethylene oxide) (PLA/PEO) (Mw 5000/5000) with a p-methoxyphenyl moiety was radio labeled with 125I. The copolymer was [125I] iodinated in the organic medium by a chloramine T method. The labeling efficiency was about 5%, and the agent was freed from [125I] iodide by dialysis. The tissue distribution of radioactivity was determined at 5 min, 1, 2 and 24 hrs after intravenous injection of male rats with 125I-labeled copolymer in the dose 4.5–5.5 mg/kg. After administration of the labeled copolymer, a high concentration of radioactivity in the liver during the initial time intervals was found. At the subsequent intervals after dosing, an increase in 125I activity in the bowels was determined. The distribution of radioactivity into inflamed areas was evaluated as well. The inflammatory-to-non-inflammatory muscle tissue ratios increased with time from 2.18 (5 min), 3.63 (1 h) to 3.68 (2 hrs); after 24 hrs, this ratio was significantly lower (1.70).

The PLA/PEO copolymer exhibits along residence time in the blood stream and, therefore, it could be employed as a drug delivery system for inflammatory and cancer treatment.
Recent Progress in Developing Durable and Permanent Impeller Pump
Authors: Qian K. X. , Zeng P. , Ru W. M. , Yuan H. Y.
Published: July 2008

Since 1980s, the author’s impeller pump has successively achieved the device implantability, blood compatibility and flow pulsatility. In order to realize a performance durability, the author has concentrated in past years on solving the bearing problems of the impeller pump. Recent progress has been obtained in developing durable and permanent impeller blood pumps. At first, a durable impeller pump withrolling bearing and purge system has been developed, in which the wear-less rollers made of super-high-molecular weight polythene make the pump to work for years without mechanical wear; and the purge system enables the bearing to work in saline and heparin, and no thrombus therefore could be formed. Secondly, a durable centrifugal pump withrolling bearing and axially reciprocating impeller has been developed, the axial reciprocation of rotating impeller makes the fresh blood inand out of the bearing and to wash the rollers once a circle; in suchway, no thrombus could be formed and no fluid infusion is necessary, which may bring inconvenience and discomfort to the receptors. Finally, a permanent maglev impeller pump has been developed, its rotor is suspended and floating in the blood under the action of permanent magnetic force and nonmagnetic forces, without need for position measurement and feed-back control. In conclusion, an implantable, pulsatile, and blood compatible impeller pump withdurability may have more extensive applications than ever before and could replace the donor heart for transplantation in the future.
Change in a Maxillo-Facial Prosthesis Material Effecting from Environmental Factors: A Clinical Report
Authors: Keyf Filiz
Published: July 2008

The purpose of this study was to indicate change in an auricular prosthesis resulting from environmental factors. An auricular prosthesis was made from a commercially maxillo-facial dental materials. The patient used this prosthesis. After one year, the auricular prosthesis was changed, it was nonesthetic. The prosthesis was made over againfrom the beginning. The prosthesis was changed from environmental factors such as sunlight, wetting and drying, cleaning and secretions. Facial prosthesis was fabricated anew because of color changes and surface changes.
Nonporous Polyurethane Membranes as Islet Immunoisolation Matrices – Biocompatibility Studies
Authors: George Sheela , Nair Prabha D. , Risbud Makarand V. , Bhonde Ramesh R.
Published: July 2008

Novel elastomeric nonporous polyurethane membranes were synthesised with differing hard segment contents for evaluation as possible islet encapsulation matrices. Physico-chemical properties of these membranes were reported earlier by authors and have been found suitable for immunoisolation. In the present study, membranes were evaluated fortheir in vitro biocompatibility. Membranes T1, T4, T5 and T6 did not show toxicity in direct cell contact study towards L929 fibroblasts. However, T2 and T3 were found cytotoxic and were excluded from further testing. NIH3T3 cells when exposed to leach out productsof T4, T5 and T6 showed no cytotoxicity, while T1 decreased cellular viability as confirmed by MTT assay. T4 and T5 alone were seen to be compatible with mouse islets while T6 was incompatible to the mouse islets. Digital image analysis (DIA) studies showed intact morphology of islets cultured on the T4 and T5 with viability (88.4 and 91% respectively) comparable to islets on tissue culture polystyrene (TCPS) control. Islets on T4 and T5 also retained their functionality, as judged by insulin secretion in response to in vitro glucose challenge (16.0 mM). These studies point out the crucial role of surface free energy and hydrophilicity in deciding compatibility of polyurethane membranes with islets of Langerhans. Studies indicate that polyurethane membranes T4 and T5 could be potential candidates for islet immunoisolation.
Stimuli Sensitive Polymethacrylic Acid Microparticles (PMAA) – Oral Insulin Delivery
Authors: Victor Sunita Prem , Sharma Chandra P.
Published: July 2008

This study investigated polymethacrylic acid (PMAA) microparticles for controlled release of Insulin in oral administration. The microparticles were characterised by scanning electron microscopy (SEM) for morphological studies.The swelling behaviour and drug release profile in various pH media were studied. The% swelling of gels was found to be inversely related to the amount of crosslinker added. Inclusion complex of βCD and Insulin was studied using polyacrylamide gel electrophoresis (PAGE). Optimum complexation was obtained in the ratio 100mg βCD: 200IU Insulin. The release pattern of Insulin from Insulin–βCD complex encapsulated PMAA microparticles showed release of Insulin for more than seven hours.