Analysis of the influence of two different milling processes on the properties of beta-TCP precursor powder and cement

There are several characteristics that put calcium phosphate cements in evidence, like its bioactivity and in vivo resorption. The influence of two milling processes on the morphological properties of the [beta]-tricalcium phosphate powder, [beta]-TCP, and in the mechanical properties of the cement were analyzed. The powder was obtained by solid state reaction of CaCO3 and CaHPO4 at 1050 ºC. It showed high phase purity and absence of toxic elements. The powder was processed in ball mill (A) and high-energy vibratory mill (B), with posterior analysis by SEM and particle size distribution. The powders showed different average and distribution of grain size. Finally, the cement prepared with powder submitted to process (B) showed values of axial tensile strength significantly greater than that prepared with powder submitted to process (A). The milling process (B) is much more efficient than the process (A).São várias as características que tem colocado os cimentos de fosfato de cálcio em evidência na área dos biomateriais, como sua bioatividade e reabsorção in vivo. Neste trabalho, analisou-se a influência de dois processos de moagem nas propriedades morfológicas do pó de [beta]-fosfato tricálcico, [beta]-TCP, e na resistência mecânica do cimento. O pó foi obtido via reação no estado sólido de CaCO3 e CaHPO4 a 1050 ºC, apresentando pureza de fase e ausência de elementos tóxicos. O pó foi moído em: (A) moinho de bolas e (B) moinho vibratório de alta energia; sendo analisado por MEV e distribuição granulométrica. Os pós apresentaram propriedades diferentes com relação à distribuição e tamanho médio de grão. Finalmente, o cimento preparado com o pó submetido ao processo (B) apresentou valores de resistência mecânica significativamente maiores que o preparado com o pó submetido ao processo (A). Conclui-se que o processo de moagem (B) é muito mais eficiente que o processo (A).Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNICAMP FEM DEMAUNIFESP Instituto de Ciência e TecnologiaUNIFESP, Instituto de Ciência e TecnologiaSciEL

Biomechanical And Histological Evaluation Of Hydrogel Implants In Articular Cartilage.

We evaluated the mechanical behavior of the repaired surfaces of defective articular cartilage in the intercondylar region of the rat femur after a hydrogel graft implant. The results were compared to those for the adjacent normal articular cartilage and for control surfaces where the defects remained empty. Hydrogel synthesized by blending poly(2-hydroxyethyl methacrylate) and poly(methyl methacrylate-co-acrylic acid) was implanted in male Wistar rats. The animals were divided into five groups with postoperative follow-up periods of 3, 5, 8, 12 and 16 weeks. Indentation tests were performed on the neoformed surfaces in the knee joint (with or without a hydrogel implant) and on adjacent articular cartilage in order to assess the mechanical properties of the newly formed surface. Kruskal-Wallis analysis indicated that the mechanical behavior of the neoformed surfaces was significantly different from that of normal cartilage. Histological analysis of the repaired defects showed that the hydrogel implant filled the defect with no signs of inflammation as it was well anchored to the surrounding tissues, resulting in a newly formed articular surface. In the case of empty control defects, osseous tissue grew inside the defects and fibrous tissue formed on the articular surface of the defects. The repaired surface of the hydrogel implant was more compliant than normal articular cartilage throughout the 16 weeks following the operation, whereas the fibrous tissue that formed postoperatively over the empty defect was stiffer than normal articular cartilage after 5 weeks. This stiffness started to decrease 16 weeks after the operation, probably due to tissue degeneration. Thus, from the biomechanical and histological point of view, the hydrogel implant improved the articular surface repair.33307-1

Physical-mechanical characterization of hydroxyapatite-titanium oxide composites prepared by the polymeric sponge method

Bioceramics have been used as bone reconstruction materials in the last decades, hydroxyapatite being one of the most used for this purpose. However, the hydroxyapatite mechanical strength is not so high when compared to other bioceramics. This work aimed on characterizing physically and mechanically HA-TiO2 composites. Samples were prepared by the polymeric sponge method with 70% - 30% wt., 60% - 40% wt. and 50% - 50% wt. of HA - TiO2, calcined at 550ºC for sponge burning out and sintered at 1250 ºC, 1300 ºC and 1350 ºC. The samples were submitted to mechanical essays of compression and Vickers hardness and to physical essays of water absorption, apparent density, burning linear retraction and apparent density. Results showed relatively better than those of pure hydroxyapatite and they are in agreement with the literature.Ao longo das últimas décadas as biocerâmicas vem sendo utilizadas como materiais para reconstrução óssea, na qual a hidroxiapatita é uma das biocerâmicas mais utilizadas. Entretanto, a resistência mecânica da hidroxiapatita não é tão alta quando comparada com outras biocerâmicas. Este trabalho teve como objetivo fazer a caracterização físico-mecânica de compósitos de HA-TiO2 porosos. As amostras de HA-TiO2 foram confeccionadas pelo método da esponja polimérica nas proporções de 70% - 30%, 60% - 40% e 50% - 50% HA - TiO2, calcinadas a 550 ºC para retirada da esponja polimérica e sinterizadas a 1250 ºC, 1300 ºC e 1350 ºC. As amostras foram submetidas a ensaios mecânicos de compressão e dureza Vickers e a ensaios físicos de absorção de água, densidade aparente, retração linear de queima e porosidade aparente. Os resultados mostraram ser relativamente melhores quando comparados com os da hidroxiapatita, e estão de acordo com os encontrados na literatura.388392Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Unsaturated polyester resins: influence of the styrene concentration on the miscibility and mechanical properties

Abstract Styrene is frequently used as comonomer for unsaturated polyester (UP) resins. Variations in the styrene content in the polyester affect the resulting properties. Dynamic mechanical tests show the phase separation in the cured resin with an increase of styrene concentration. The dependence of the glass transition temperature of the UP resin on the styrene content is complex and reflects a balance of elastic forces of the network and the immiscibility of polystyrene and UP. The thermal stability and the mechanical properties are governed by the phase behaviour of the mixture and therefore can be controlled by the styrene content.

Use of a novel coaxial guide needle-wire (GNW) combination system for computed tomography guided radiofrequency tumor ablation

We developed a novel coaxial system using a fine guide needle wire (GNW) to safely and easily place the radiofrequency needle under CT-guidance. The GNW consists of a fine needle (diameter, 21-gauge; length, 150 mm) and a wire (0.018 inch, 250 mm). An exclusive radiofrequency cannula (14-gauge; 160 mm) was also used. This system was used for the treatment of six hepatocellular carcinomas in six patients. All lesions were located deeper than 10 cm from the needle entry site. This system was useful in performing CT-guided RF ablation for deeply or precariously located liver lesions particularly in patients who are unable to hold their breath

A mouse mammary tumor virus env-like exogenous sequence is strictly related to progression of human sporadic breast carcinoma

A viral etiology of human breast cancer (HBC) has been postulated for decades since the identification of mouse mammary tumor virus (MMTV). The detection of MMTV env-like exogenous sequences (MMTVels) in 30% to 40% of invasive HBCs increased attention to this hypothesis. Looking for MMTVels during cancer progression may contribute to a better understanding of their role in HBC. Herein, we analyzed HBC preinvasive lesions for the presence of MMTVels. Samples were obtained by laser microdissection of FFPE tissues: 20 usual-type ductal hyperplasias, 22 atypical ductal hyperplasias (ADHs), 49 ductal carcinomas in situ (DCISs), 20 infiltrating ductal carcinomas (IDCs), and 26 normal epithelial cells collateral to a DCIS or an IDC. Controls included reductive mammoplastic tissue, thyroid and colon carcinoma, and blood samples from healthy donors. MMTVels were detected by fluorescence-nested PCR. DNA samples from the tissues of nine patients were analyzed by real-time quantitative PCR, revealing a different viral load correlated with stage of progression. Furthermore, as never previously described, the presence of MMTVels was investigated by chromogenic in situ hybridization. MMTVels were found in 19% of normal epithelial cells collateral to a DCIS or an IDC, 27% of ADHs, 82% of DCISs, and 35% of IDCs. No MMTVels were found in the control samples. Quantitative PCR and chromogenic in situ hybridization confirmed these results. These data could contribute to our understanding of the role of MMTVels in HBC. (Am J Pathol 2011, 179:2083-2090; DOI: 10.1016/j.ajpath.2011.06.046

Melanoma-restricted genes

Human metastatic cutaneous melanoma has gained a well deserved reputation for its immune responsiveness. The reason(s) remain(s) unknown. We attempted previously to characterize several variables that may affect the relationship between tumor and host immune cells but, taken one at the time, none yielded a convincing explanation. With explorative purposes, high-throughput technology was applied here to portray transcriptional characteristics unique to metastatic cutaneous melanoma that may or may not be relevant to its immunogenic potential. Several functional signatures could be identified descriptive of immune or other biological functions. In addition, the transcriptional profile of metastatic melanoma was compared with that of primary renal cell cancers (RCC) identifying several genes co-coordinately expressed by the two tumor types. Since RCC is another immune responsive tumor, commonalities between RCC and melanoma may help untangle the enigma of their potential immune responsiveness. This purely descriptive study provides, therefore, a map for the investigation of metastatic melanoma in future clinical trials and at the same time may invite consideration of novel therapeutic targets

Carbenic nitrile imines: Properties and reactivity

Structures and properties of nitrile imines were investigated computationally at B3LYP and CCSD(T) levels. Whereas NBO analysis at the B3LYP DFT level invariably predicts a propargylic electronic structure, CCSD(T) calculations permit a clear distinction between propargylic, allenic, and carbenic structures. Nitrile imines with strong IR absorptions above ca. 2150 cm-1 have propargylic structures with a CN triple bond (RCNNSiMe 3 and R2BCNNBR2), and those with IR absorptions below ca. 2150 cm-1 are allenic (HCNNH, PhCNNH, and HCNNPh). Nitrile imines lacking significant cumulenic IR absorptions at 1900-2200 cm -1 are carbenic (R-(C:)-N=N-R′). Electronegative but lone pair-donating groups NR2, OR, and F stabilize the carbenic form of nitrile imines in the same way they stabilize "normal" singlet carbenes, including N-heterocyclic carbenes. NBO analyses at the CCSD(T) level confirm the classification into propargylic, allenic, and carbenic reactivity types. Carbenic nitrile imines are predicted to form azoketenes 21 with CO, to form [2+2] and [2+4] cycloadducts and borane adducts, and to cyclize to 1H-diazirenes of the type 24 in mildly exothermic reactions with activation energies in the range 29-38 kcal/mol. Such reactions will be readily accessible photochemically and thermally, e.g., under the conditions of matrix photolysis and flash vacuum thermolysis