Distribuição das Tensões em Próteses Implantossuportadas com Diferentes Sistemas de Conexão e Comprimento de Cantilever

O presente estudo teve por objetivo avaliar, por meio de análise fotoelástica, o comportamento biomecânico de coroas duplas parafusadas implantossuportadas com diferentes tipos de sistemas de conexão e comprimento de cantilever. Para isso, foram confeccionados três modelos em resina fotoelástica PL-2 e divididos em 6 grupos, de acordo com o sistema de conexão do implante (hexágono externo (HE) e cone morse (CM)), intermediário (minipilar ou UCLA) e o número de coroas em cantilever (um ou dois elementos). O conjunto modelo fotoelástico-implante-prótese foi posicionado em um polariscópio circular e, em seguida, foram aplicadas cargas de 100 N, em direção axial e oblíqua (45°), em pontos fixos da superfície oclusal das coroas com ajuda de uma máquina ensaio universal (EMIC). As tensões geradas foram registradas fotograficamente e analisadas qualitativamente em programa gráfico (Adobe Photoshop). Os resultados mostraram que houve um maior número de franjas, quando da aplicação de carga oblíqua em todos os grupos. Sendo maiores no grupo (HE + minipilar). Concluiu-se que o tipo de sistema de conexão do implante não influenciou diretamente na distribuição das tensões para carga axial. E que a extensão do cantilever influenciou diretamente na distribuição das tensões. Sendo que os modelos com duas coroas em catilever apresentaram maior tensão.Palavras-chave: Implante Dentário. Força Mastigatória. Prótese.

Carboplatin plus weekly paclitaxel treatment in non-small cell lung cancer patients with interstitial lung disease

BACKGROUND

Since advanced non-small cell lung cancer (NSCLC) patients with the interstitial lung disease (ILD) have been excluded from clinical trials, it is uncertain whether chemotherapy really provides a benefit to these patients.

PATIENTS AND METHODS

Fifteen advanced NSCLC patients with ILD that was detected on the chest X-rays were enrolled in this study. Carboplatin plus paclitaxel was administered by two methods (method A or method B). Method A: Carboplatin (AUC 6, day 1) and paclitaxel (70 mg/m(2), days 1, 8, 15) were administered every four weeks. Method B: Carboplatin (AUC 2, day 1, 8, 15) and paclitaxel (60 mg/m(2), days 1, 8, 15) were administered every four weeks.

RESULTS

The response rate and the disease control rate were 33% and 53%. The median progression-free survival and the median overall survival time were 2.5 months and 7.0 months, respectively. The hematological toxicities were tolerable, but a grade 3 or higher pneumonitis was observed in 4 patients (27%).

CONCLUSION

Carboplatin plus weekly paclitaxel must be administered carefully to advanced NSCLC patients with ILD that is detected on chest X-rays after a sufficient evaluation of the risks and the benefits.

Ganglioside GD1a inhibits HGF-induced motility and scattering of cancer cells through suppression of tyrosine phosphorylation of c-Met

We previously reported that ganglioside GD1a, which is highly expressed in poorly metastatic FBJ-S1 cells, inhibits the serum-induced motility of FBJ-LL cells and that the metastatic potential of FBJ-LL cells is completely suppressed by enforced GD1a expression (Hyuga et al., Int J Cancer 1999;83:685-91). We recently discovered that hepatocyte growth factor (HGF) induces FBJ-LL cell motility. In the present study, the HGF-induced motility of FBJ-S1 cells was found to be one-thirtieth that of FBJ-LL cells. This motility of GD1a-expressing transfectants, which were produced by transfection of FBJ-LL cells with GM2/GD2 synthase cDNA, decreased with increases in their GD1a expression and HGF induced almost no motility in GD1a-pretreated FBJ-LL cells, indicating that GD1a inhibits the HGF-induced motility of FBJ-LL cells. The expression of the HGF receptor c-Met on FBJ-S1 cells, FBJ-LL cells, transfectants and a mock-transfectant was almost the same. The level of tyrosine phosphorylation of c-Met after HGF stimulation in FBJ-S1 cells, GD1a-pretreated FBJ-LL cells and a GD1a-expressing transfectant was significantly lower than in FBJ-LL cells and a mock-transfectant. These findings suggested that GD1a inhibits the HGF-induced motility of FBJ-LL cells through suppression of tyrosine phosphorylation of c-Met. HepG2 cells, a human hepatoma cell line, were used to investigate whether GD1a interferes with other cancer cells expressing c-Met. HepG2 cells did not express GD1a. HGF induced cell scattering of HepG2 cells and the scattering was inhibited by pretreating the cells with GD1a. The c-Met in the cells was autophosphorylated by stimulation with HGF, but after treating the cells with GD1a, the HGF-induced autophosphorylation of c-Met was suppressed. These results suggest that GD1a acts as a negative regulator of c-Met in cancer cells.

Effect of tributyltin chloride on the release of calcium ion from intracellular calcium stores in rat hepatocytes

The effects of tri-n-butyltin chloride (TBT), an environmental pollutant, on the release of Ca(2+) from intracellular stores were investigated in isolated rat hepatocytes. Isolated hepatocytes permeabilized with digitonin were suspended in solution, and the concentration of extracellular Ca(2+) was measured, using a fluorescent Ca(2+) dye, fura-2. In the solution containing permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min, the extracellular Ca(2+) concentration was high, but the inositol 1,4,5-trisphosphate (InsP(3))-induced increase in Ca(2+) concentration was suppressed, suggesting that the extracellular release of Ca(2+) in response to TBT treatment was from intracellular stores. Images of the Ca(2+) concentration in the intracellular stores of primary cultured hepatocytes loaded with fura-2 were obtained after digitonin-permeabilization, using digitalized fluorescence microscopy. The permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min had a very low fura-2 fluorescence ratio (340/380 nm), suggesting that stored Ca(2+) was released. When the hepatocytes were treated with 4.0 microM TBT after digitonin-permeabilization, the decrease in the fura-2 fluorescence ratio was very small. However, when the permeabilized hepatocytes were incubated with 4.0 microM TBT and 2.0 microM NADPH, the decrease was enhanced, raising the possibility that TBT might be metabolized to the active form(s), thus releasing Ca(2+) from intracellular stores. When the hepatocytes were preincubated with 0.1 microM TBT for 30 min and then were permeabilized, the fura-2 fluorescence ratio was almost the same as that in the control permeabilized hepatocytes. However, the InsP(3)-induced decrease in the fluorescence ratio was suppressed significantly in the permeabilized hepatocytes. These results suggest that TBT released Ca(2+) from the intracellular stores at high concentrations, and suppressed the InsP(3)-induced Ca(2+) release at non-toxic low concentrations. It is probable that the latter effect was responsible for the previously reported suppression of Ca(2+) response induced by hormonal stimulations (Kawanish et al., Toxicol Appl Pharmacol 1999;155:54-61).

Autoantibody against N(epsilon)-(carboxymethyl)lysine: an advanced glycation end product of the Maillard reaction

Prolonged incubation of proteins with reducing sugar produces advanced glycation end products (AGEs), which are implicated as factors for aging and diabetic complications. We previously demonstrated the presence of N(epsilon)-(carboxymethyl)lysine (CML), one of the main AGE structures, in human and animal tissues using a monoclonal anti-CML antibody (6D12). These findings suggest that CML structures present in vivo could serve as immunogens to generate autoantibodies. This suggestion was tested in the present study. First, plasma samples from diabetic rats reacted positively with AGE bovine serum albumin (BSA). These reactivities increased with the duration of diabetic states and were inhibited specifically by CML-BSA. Second, a fraction purified from plasma of diabetic patients, which bound to AGE-BSA, showed a positive reaction to CML-BSA and furthermore also to human lens proteins, which are known to undergo CML modification in vivo. Finally, patients with renal failure caused by diabetes or nondiabetic pathologies had a higher autoantibody activity against CML structure than that in normal subjects or diabetic patients without renal failure. These results indicate that CML accumulated in vivo serves as an immunological epitope to generate an autoantibody specific for CML that might be used as a potential marker for diabetic nephropathy or chronic renal failure.

Advanced glycation end products and their recognition by macrophage and macrophage-derived cells

Modification of proteins by long-term incubation with glucose leads to the formation of advanced glycation end products (AGEs). AGE proteins are taken up by macrophages via the AGE receptor, which is similar to the macrophage scavenger receptor (MSR). In the present study, we compared the ligand specificity of the AGE receptor with that of MSR by three different experiments. The endocytic uptake of 125I-acetyl-LDL by RAW cells was effectively inhibited by unlabeled AGE-bovine serum albumin (BSA), whereas the inhibitory effect of acetyl-LDL on 125I-AGE-BSA was partial. Polyanions showing an effective inhibition for endocytic uptake of AGE-BSA were not always inhibitory for endocytic degradation of acetyl-LDL. These data, together with those obtained by three-dimensional fluorescence-activated cell sorter analysis, indicate that AGE proteins are recognized by more than two receptors, of which MSR is at least one. Finally, we examined whether MSR could mediate the endocytic uptake of AGE proteins by Chinese hamster ovary cells overexpressing bovine type II MSR (CHO-SRII cells). 125I-AGE-BSA underwent endocytic degradation by CHO-SRII cells, and this was effectively inhibited by unlabeled acetyl-LDL. These results clearly show that MSR mediates the endocytic uptake of AGE proteins, suggesting a new role of MSR in biological recognition of AGE in vivo.

Macrophage scavenger receptor mediates the endocytic uptake and degradation of advanced glycation end products of the Maillard reaction

Modification of proteins by long-term incubation with glucose leads to the formation of advanced glycation end products (AGE). Recent immunological demonstration of the presence of AGE proteins in several human tissues suggests that they may be involved in aging, diabetic complications and atherosclerosis. AGE proteins are taken up by macrophages via the AGE receptor, which is similar to the macrophage scavenger receptor (MSR). In the present study, we examined whether MSR could mediate the endocytic uptake of AGE proteins by using Chinese hamster ovary (CHO) cells overexpressing bovine type II MSR (CHO-SRII). 125I-labelled AGE bovine serum albumin (125I-AGE-BSA) as well as 125I-acetylated low-density lipoprotein (125I-acetyl-LDL) underwent endocytic degradation by CHO-SRII cells, but not by control CHO cells. Endocytic degradation of 125I-acetyl-LDL and 125I-AGE-BSA by CHO-SRII cells was significantly inhibited by unlabeled AGE-BSA, as well as by acetyl-LDL. Immunoelectron microscopic studies using both AGE-BSA conjugated with gold particles and anti-(bovine MSR) antibody (D2) revealed co-localization of gold particles and the reactive sites for the antibody at coated pits of plasma membranes as well as in endosomes. These results clearly show that MSR mediates the endocytic uptake and degradation of AGE proteins, suggesting a new role of MSR in biological recognition of AGE in vivo.

Ultrastructural changes in glycerol-extracted skeletal muscle fibers after chemical modification of myosin heads with p-phenylenedimaleimide

We examined the structural changes in relaxed glycerinated rabbit psoas muscle fibers induced by modification of the myosin heads with p-phenylenedimaleimide (p-PDM), which reacts with sulfhydryls on the myosin head to cause its loss of ability to combine with actin and to hydrolyse ATP. In the longitudinal sections of both chemically fixed and quickly frozen muscle fibers, ladder-like structures, interpreted as the myosin heads extending nearly at right angles with the thick filaments, were more prominent in the p-PDM-modified fibers than in the control fibers. Fourier transform diffractograms of the longitudinal sections exhibited a distinct 14.3-nm meridional reflection, which arises from axial spacing of the myosin heads on the thick filament, in the p-PDM-modified fibers, but not in the control fibers. These results indicate that the p-PDM-modification of the myosin heads causes an increase in the regularity of myosin head arrangement on the thick filament.

Involvement of phosphoinositide turnover in ouabain inotropism

We examined whether ouabain activities phospholipases and reinforces contraction force of papillary muscles through resultant second messengers. 2-Nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC), the inhibitor of phospholipase C (PLC), abolished the ouabain inotropy in rabbit papillary muscles. Calphostin C, the specific inhibitor of protein kinase C (PKC), also depressed the ouabain inotropy. 12-O-Tetradecanoylphorbor-13-acetate (TPA), the specific activator of PKC, enhanced the beat-to-beat phasic contractility at low concentrations. Radioenzymatic assay revealed that ouabain treatment doubled diacylglycerol (DG) content in excised papillary muscles. We concluded that ouabain activates PLC, and the resultant second messenger, DG, augments the cardiac contraction force through activation of PKC.

Studies on metabolic pathways of cyanate in rats

Metabolic pathways of cyanate in rats were studied by means of measurements of cyanate, carbamyl phosphate and S-carbamyl group. Approximately 30-50% of cyanate administered to rats (0.5 mmol/kg body weight) was found in buffered gastric contents, and was also detected as ammonia liberated by acid hydrolysis. However, the gastric excretion of cyanate was a temporary phenomenon just after cyanate administration. Biliary and urinary excretion of cyanate and acid-soluble S-carbamyl group are minor metabolic pathways.

Circus movement tachycardia induced by a single premature stimulus on the ventricular sheet--evaluation of the leading circle hypothesis in the canine ventricular muscle

Mechanisms of ventricular tachycardia induced by local application of a properly timed premature stimulus were studied with routine microelectrode technique and extracellular recordings on a ventricular sheet. Thinly sliced preparations obtained from subepicardial muscle of the canine ventricle were used as an approximation of a two-dimensional model. On these preparations, spontaneously sustained tachycardia easily induced by a single premature stimulus. Since delayed after-depolarizations were never evoked by frequent stimulations even in the K+-free and high-Ca++ media, these tachycardias seemed to be induced by re-entrant and circus movement mechanisms. To analyse the re-entrant mechanisms, action potentials generated by normal driving stimuli were recorded from multiple points (40 approximately 50 points) and the spreads of the depolarization and repolarization phases of the action potentials were mapped. The depolarizing wave front on the map always showed a circular or elliptical pattern. Whenever the pattern of spread of the repolarizing wave was similar to that of the depolarizing wave, sustained tachycardia was never brought about by any premature stimulus. On the other hand, when the map of the spread of the repolarizing wave was very complicated and mixed with that of the depolarizing wave, sustained tachycardia was frequently induced. From the above results, it is suggested that the nonuniform recovery of excitability plays a role in the generation of sustained tachycardia. Moreover, a portion of the unidirectional block of the premature impulse was determined by calculated using the conduction velocity of the premature impulse and the effective refractory period in each cell; then a route of re-entry for the premature impulse was simulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on corticoid action on the toad tadpole tail in vitro

The effect of adrenal corticoids on the shrinkage of tail segments from Bufo bufo japonicus tadpoles was studied in vitro. Deoxycorticosterone acetate (DCA) was effective in accelerating the shrinkage of tail segments if thyroxine (T4) or triiodothyronine (T3) was present in the medium. The shrinkage caused by DCA was dose dependent. In the absence of thyroid hormone, DCA did not induce tail resorption. Shrinkage of tail segments induced by DCA and T4 was blocked by prolactin. Among the steroid hormones testes in vitro, aldosterone and corticosterone exhibited a potent activity in accelerating shrinkage of tail segments in the presence of T4. The nature of the corticoid action is discussed.