Novel refractory phase, Ta7Si2(Si(x)B(1-x))2.

X-ray single crystal (XSC) and powder diffraction data (XPD) were used to elucidate the crystal structure of a new refractory silicon boride Ta7Si2(Si(x)B(1-x))2 (x = 0.12). Tetragonal Ta7Si2(Si(x)B(1-x))2 (space group P4/mbm; a = 0.62219(2) nm, c = 0.83283(3) nm) with B atoms randomly sharing the 4g site with Si atoms is isotypic with the boride structure of (Re,Co)7B4. The architecture of the structure of Ta7Si2(Si(x)B(1-x))2 combines layers of three-capped triangular metal prisms (Si,B)[Ta(6+2)(Si,B)] alternating with double layers of two-capped Si[Ta(8+1)Si] Archimedian metal antiprisms. Consequently, the metal framework contains (B/Si) pairs and Si-Si dumbbells. These two types of coordination figures around the nonmetal atoms are typical for the system-inherent structures of Ta2B (or Ta2Si) and Ta3B2. DFT calculations showed strong B(Si)-B(Si) and Si-Si bonding and represent Ta7Si2(Si(x)B(1-x))2 as a covalent-ionic compound. This bonding behavior is reflected in the high hardness value of 1750 HV. The Sommerfeld constant, γ = 7.58 mJ/mol K(2), as derived from the electronic density of states, calculated at the Fermi level, suggests typical metallic behavior.

Estudo da transmigração bacteriana na apendicite experimental em coelhos / Study about bacterial transmigration in experimental appendicitis in rabbits

Introdução: A queda extrínseca dos mecanismos de defesa de um hospedeiro é vista classicamente como uma infecção, que resulta na aquisição de um tecido normal, de um novo microorganismo, cuja virulência é fundamental para a sua patogenia.Na década de 50, estudos comprovaram que bactérias e endotoxinas podem ultrapassar a barreira intestinal e atingir a circulação, demonstrando ainda, que a flora intestinal representa uma importante fonte para o desenvolvimento da infecção sistêmica. Objetivo: o presente estudo visa avaliar a ocorrência de transmigração bacteriana em apendicite experimental induzida em coelhos, mediante a oclusão completa do apêndice vermiforme. Métodos: foram utilizados 24 coelhos brancos, da linhagem Nova Zelândia, com peso corporal variando de 2500 a 3000 gramas, sendo então divididos em 2 grupos. Os animais do Grupo I foram submetidos a laparotomia mediana e retirada de fragmentos do baço, rim esquerdo, pulmão direito, linfonodo abdominal, conteúdo da luz do apêndice vermiforme e sangue da veia porta para cultura. Os animais do Grupo II foram submetidos a laparotomia mediana e oclusão completa do apêndice vermiforme para a indução de apendicite e, após 24 horas, realizada a coleta do material nos moldes do Grupo I. Resultados: No Grupo controle (Grupo I), não se observou o crescimento de bactérias nas amostras analisadas. No Grupo experimento (Grupo II), observou-se o crescimento de Escherichia coli em todos os animais. Conclusão: Ocorreu transmigração bacteriana após 24 horas de observação em coelhos com apendicite experimental.

Comparison of Fe-HBED and Fe-EHPG as hepatobiliary MR contrast agents.

The authors studied the biodisposition and hepatobiliary transport of two potential magnetic resonance imaging contrast agents, the iron (III) chelates of N,N'-bis(2-hydroxybenzyl)ethylene-diamine-N,N'-diacetic acid (HBED) and diastereomeric N,N'-ethylenebis(2-hydroxyphenylglycine) (EHPG). Fecal and urinary excretion (mean +/- standard deviation), respectively, of FE-59 over 7 days in rats given tracer doses of the contrast agents were 67% +/- 2% and 22% +/- 1% for Fe-59-HBED and 22% +/- 2% and 26% +/- 5% for Fe-59-EHPG. In bile duct-cannulated rats given 0.05-mmol/kg doses labeled with Fe-59, 52% +/- 8% of Fe-59 from Fe-59-HBED but only 17% +/- 3% of that from Fe-59-EHPG was excreted into the bile within 90 minutes. Bromosulfophthalein, but not taurocholate or oxyphenonium, was shown to compete with both agents for hepatobiliary transport. Enterohepatic recirculation of both agents was less than 1%.

Hepatobiliary magnetic resonance contrast agents assessed by gadolinium-153 scintigraphy.

A simple method to test new gadolinium complexes potentially useful as enhancement agents for magnetic resonance imaging was developed. Healthy rats underwent scintigraphy with two potential hepatobiliary agents, diethyl IDA and diisopropyl IDA complexed with gadolinium-153. Control products included 153Gd DTPA, 153GdCl3 and technetium-99m diethyl IDA. As shown scintigraphically, 153Gd IDA complexes were partially excreted by urinary and hepatobiliary excretion early after administration. These findings paralleled significant reduction in 1H T1 values of excised livers. However, these agents exhibited prolonged 153Gd whole-body retention. The prolonged tissue distribution of 153Gd activity in animals given 153Gd diethyl IDA did not differ significantly from that observed in animals given GdCl3, and could be attributed to chemical instability or reticuloendothelial uptake. The scintigraphic method permits screening of gadolinium complexes in animals by showing mass balance, kinetics, distribution, and effective stability. Biologic effects of tracer or pharmacologic levels can be compared with those of carrier-free and carrier-added pharmaceuticals.

Improved immune-specificity in monoclonal radioimmunoimaging using dual radionuclide color functional maps.

Diagnostic radioimmunoimaging is potentially limited by tissue localization of radiolabeled antibody products through mechanisms other than antigen binding. Comparing the distributions of reactive and nonreactive products can distinguish tracer in targeted and nontargeted tissues. To achieve this in a single imaging procedure, dual photopeak scintigraphy was performed using 111In and 67Ga products. Melanoma-bearing athymic mice were coadministered intravenously subtype-matched 111In melanoma-reactive and 67Ga melanoma-nonreactive murine monoclonal antibodies. Paired images from 245 and 93 keV windows were processed with a unique dual parameter color display program. The display algorithm expresses pixel counts from paired photo-peak images in polar coordinates and color-encodes angle as hue and magnitude as intensity. The color functional maps permitted ready distinction of immune from nonimmune uptake. Compared with single tracer imaging methods, this technique better depicts antigen distribution.

Phase 1 immunolymphoscintigraphy with an In-111-labeled antimelanoma monoclonal antibody.

A phase 1 study was conducted using a monoclonal antimelanoma antibody-DTPA conjugate labeled with indium-111, for immunolymphoscintigraphy in patients with metastatic melanoma. The imaging agent, labeled with 1 mCi (37 MBq) In-111, was administered as an interstitial interdigital injection to six patients scheduled to undergo lymph node dissection for suspected metastatic malignant melanoma. No adverse effects were observed in any of the patients either during or after the infusion as determined by clinical and laboratory parameters. Antibodies to the murine immunoglobulin were produced in some patients. Regional lymph nodes were visualized whether tumor-bearing or not, and light microscopic autoradiography showed In-111 activity associated with histiocytes. One of two patients harboring both tumor-bearing and tumor-free lymph nodes exhibited preferential localization in tumor-bearing nodes. The authors conclude that this study demonstrates safety of the radiopharmaceutical and that further study is needed to improve its usefulness for diagnosis of lymph node metastases.