Polyethylene/phospholipid polymer alloy as an alternative to poly(vinylchloride)-based materials

To develop new biomaterials for making medical devices, polymer alloys composed of a phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and polyethylene (PE) were prepared. The PE/PMPC alloy membrane could be obtained by a combination of solution mixing and solvent evaporation methods using xylene and n-butanol mixture as a solvent. Moreover, thermal treatment was applied to improve the mechanical properties of the PE/PMPC alloy membrane. In the PE/PMPC alloy membrane, the PMPC domains were located not only inside the membrane but also at the surface. Surface analysis of the PE/PMPC alloy membrane with X-ray photoelectron spectroscopy, wettability evaluation, and dynamic contact angle measurements revealed that the phospholipid polar groups in the PMPC covered the surface even after thermal treatment. Blood compatibility tests with attention to platelet adhesion and change in morphology of adhered platelets showed that the PE/PMPC alloy membrane had excellent platelet adhesion resistance. We finally concluded that the PE/PMPC alloy could be used as biomaterials instead of poly(vinyl chloride)-based materials.     

Effects of magnesium on prostacyclin synthesis and intracellular free calcium concentration in vascular cells.

This study investigated the effects of extracellular magnesium concentration ([Mg2+]e; 0.3-3 mM) on intracellular free calcium concentration ([Ca2+]i) and prostacyclin (PGI2) production in cultured human umbilical vein endothelial cells (HUVEC) and vascular smooth muscle cells from rats (VSMC) under basal and agonist-stimulated conditions. We used histamine as agonist which increases [Ca2+]i and PGI2 production in HUVEC, norepinephrine in VSMC. [Mg2+]e dose-dependently increased basal and agonist-stimulated PGI2 production in both cells. [Mg2+]e dose-dependently reduced basal [Ca2+]i in VSMC, but did not influence in HUVEC. In both cells, increasing [Mg2+]e reduced agonist-stimulated [Ca2+]i responses. Furthermore, [Mg2+]e dose-dependently reduced agonist-stimulated [Ca2+]i in Ca(2+)-free buffer, indicating intracellular Ca2+ release. In VSMC, 10(-6) M diltiazem and 10(-7) M nifedipine, Ca2+ channel blockers, reduced agonist-stimulated [Ca2+]i as well as 3 mM Mg2+, but did not affect PGI2 production. [Mg2+]e amplified dose-dependently arachidonic acid-induced PGI2 production in both cells, suggesting the activation of cyclooxygenase and/or PGI2 synthetase. Our results suggest that [Mg2+]e influences intracellular Ca2+ mobilization of not only vascular smooth muscle cells but also endothelial cells by inhibiting both Ca2+ influx and intracellular Ca2+ release. [Mg2+]e enhances PGI2 production in both types of cells, although the mechanism is likely to be independent from Ca2+ mobilization.     

Nano-scale surface modification of a segmented polyurethane with a phospholipid polymer

Nano-scale modification of a segmented polyurethane (SPU) with cross-linked 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was performed to obtain a biocompatible elastomer. To control the domain size and the depth of the modified layer, various compositions of monomers, including MPC, 2-ethylhexyl methacrylate (EHMA), and glycerol 1,3-diglycerolate diacrylate, were examined. SPU film was immersed in the monomer solution and visible light irradiation was applied to initiate polymerization to the SPU film that was held by mica to condense MPC units at the surface. The surfaces of the obtained film were analyzed by X-ray photoelectron spectroscopy and water contact angle measurement. The surface density of MPC units changed with the monomer concentration, and the density was the highest when the ratio between MPC and EHMA was 7:3. In modified SPU films, 6- to 25-nm MPC unit-enriched domains were observed and the density of these domains gradually decreased with depth. The sizes of the domains depended on the MPC composition in the monomer solution. The mechanical properties of the modified films as evaluated by tensile strength measurement under wet conditions were not significantly different from those of SPU. With increase in the existence of MPC unit-enriched domains on the MEG film surface, platelet adhesion and activation were remarkably reduced compared to the SPU film. This nano-scale surface modification may be a useful technique for applying elastic polymer biomaterials.     

Renal primitive neuroectodermal tumor: An immunohistochemical and cytogenetic analysis

The cytogenetic and morphologic characteristics of a case with a primitive neuroectodermal tumor (PNET) arising from the left kidney in a 22 year old man are presented. The patient was detected as having a left renal mass with a tumor embolus In the inferior vena cava and multiple pulmonary metastases. A radical nephrectomy with tumor embolectomy of the Inferior vena cava, along with a resection of the pulmonary nodules were performed. Histologic examination revealed a dense proliferation of small round cells with many Homer-Wright type rosettes and perlvascular pseudo-rosettes. Immunohlstochemically, the tumor cells stained strongly positive for HBA71(p30/32^{M IC2}), a surface glycopro-teln specific to PNET and Ewlng's sarcoma. In addition, the tumor cells expressed several neural markers (neuron specific enolase, neurofilament, synaptophysin, and Leu-7) and vimentin, while the epithelial, muscular, and lymphocytlc markers were negative in the tumor cells. Cytogenetic analysis of cultured tumor cells showed a reciprocal translocation t(11; 22)(q24; q12) that is considered to be specific to PNET and Ewing's sarcoma. In conclusion, this case suggested that a karyotyping analysis is a useful diagnostic tool for renal PNET, and it may therefore be utilized to help distinguish between difficult cases of small round cell tumors and Wilms' tumor of the kidney.     

Significance of broad distribution of electron-dense deposits in patients with IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is characterized by mesangial cell proliferation and mesangial expansion with mesangial depositions of IgA. We have found that electron-dense deposits (EDD) are often observed in areas other than paramesangial areas in glomeruli. To compare electron microscopic findings with light microscopic findings and clinical data, we examined the biopsies from 178 patients with IgAN. Patients were divided into two groups: group A had only paramesangial deposits and group B had deposits not only in paramesangial areas but also in other areas. All patients examined in this study had EDD in glomerular paramesangial areas. Thirty-six patients were included in group B. Cellular crescent formation in glomeruli and urinary protein in group B were significantly higher than those in group A (P < 0.01). Serum albumin and estimated glomerular filtration rate (eGFR) in group B were significantly lower than those in group A (P < 0.05). Group B showed a significant positive correlation with histological severity, which is defined in the Japanese Clinical Guidelines on IgAN. In patients with broad distribution of EDD, urinary protein was significantly increased (P < 0.05). Detailed observation of EDD distribution has an impact on evaluation of the disease activity of IgAN.     

Enhanced angiogenesis by multiple release of platelet-rich plasma contents and basic fibroblast growth factor from gelatin hydrogels

The objective of this study is to evaluate the angiogenic effects induced by biodegradable gelatin hydrogel granules incorporating mixed platelet-rich plasma (PRP) growth factor mixture (PGFM) and bioactive basic fibroblast growth factor (bFGF). The PRP was prepared by a double-spinning technique for isolating animal bloods, followed by treatment with different concentrations of calcium chloride (CaCl(2)) solution. The CaCl(2) solution treatment activated the platelets of PRP, allowing the release of various growth factors, such as platelet-derived growth factor (PDGF)-BB, vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β(1), and epithelial growth factor (EGF). In the PRP treated with different CaCl(2) solutions, high amounts of representative platelet growth factor, PDGF-BB, VEGF, EGF, and TGF-β(1) were detected in the CaCl(2) concentrations of 1, 2, and 4 wt.% compared with higher or lower ones. The PRP treated was impregnated into gelatin hydrogel granules freeze-dried at 37°C for 1h, and then the percentage of PGFM desorbed from the gelatin hydrogel granules was evaluated. The percentages of PDGF-BB, VEGF, EGF, and TGF-β(1) desorbed tended to decrease with decreasing CaCl(2) concentration. Taken together, the CaCl(2) concentration to activate PRP for PGFM release was fixed at 2 wt.%. In vitro release tests demonstrated that the PGFM was released from the gelatin hydrogel granules with time. For the gelatin hydrogels incorporating PGFM and bFGF, the time profile of PDGF-BB or bFGF release was in good correspondence with that of gelatin hydrogel degradation. The gelatin hydrogel granules incorporating mixed PGFM and bFGF were prepared and intramuscularly injected to a mouse leg ischemia model to evaluate the angiogenic effects in terms of histological and laser Doppler perfusion imaging examinations. As controls, hydrogel granules incorporating bFGF, PGFM, and platelet-poor plasma were used for the angiogenic evaluation. The number of blood vessels newly formed and the percentage of anti-α-smooth muscle actin antibody-positive cells increased around ischemic sites injected with the gelatin hydrogel granules incorporating mixed PGFM and bFGF, in marked contrast to other control groups. The blood reperfusion level of ischemic tissues was enhanced by the hydrogel granules incorporating mixed PGFM and bFGF, whereas no enhancement was observed for other groups. It is concluded that the dual-release system of PGFM and bFGF from gelatin hydrogel granules shows promise as a method to enhance angiogenic effects.     

Allelic alterations in well-differentiated neuroendocrine tumors (carcinoid tumors) identified by genome-wide single nucleotide polymorphism analysis and comparison with pancreatic endocrine tumors

Well-differentiated neuroendocrine tumors (WDNT, carcinoid tumors) are uncommon indolent neoplasms. The genetic alterations of these tumors are not well characterized. We used genome-wide high-density single nucleotide polymorphism (SNP) array analysis to detect copy number alterations in 29 WDNTs, including seven lung, seven nonileal gastrointestinal, and 15 ileal tumors, and compared with allelic imbalances in 15 pancreatic endocrine tumors (PETs). Most frequent allelic imbalances in WDNTs were losses of chromosome 18 in 10 tumors (34%), chromosome 21 or 21q in six (21%), chromosome 13 or 13q in five (17%) and chromosome 16 or 16q in four (14%) tumors, and amplification of chromosome 20 or 20p in seven (24%) tumors. We also found one tumor with loss of heterozygosity of chromosomes 10 and 15 without copy number loss. These allelic imbalances were associated with primary site of tumor: loss of chromosome 18 was present exclusively in ileal WDNTs (P = 0.001), and loss of chromosome 21 or 21q was more frequent in nonileal gastrointestinal WDNTs (P = 0.02). The tumors with loss of chromosome 21 were larger compared to tumors without loss (P = 0.03). Chromosomal aberrations were less common in WDNTs from lung and gastrointestinal tract compared to PETs (P = 0.001). Our study shows that genome-wide allelotyping using SNP array is a powerful new tool for the analysis of allelic imbalances in WDNTs, and some of these alterations are tumor site-dependent and are different than in PETs.