Estudo prospectivo de um novo substituto ósseo em Odontologia / Prospective study of a new bone substitute in Dentistry

Os avanços recentes da Odontologia, aliados ao aprimoramento dos materiais obtidos através das técnicas de bioengenharia, impulsionaram o desenvolvimento de um novo substituto ósseo, composto por colágeno bovino tipo I e hidroxiapatita. Os autores acompanharam 15 pacientes com diferentes diagnósticos e nos quais foi utilizado o material em questão. Os resultados favoráveis encontrados estiveram de acordo com os resultados de estudo histopatológico e foram atribuídos às características de biocompatibilidade, osteocondução e osteoindução e correlacionados com dados da literatura científica.

Differential scanning calorimetry and optical properties of collagen-dichroic azo ponceau ss complexes

The purpose of this research was to find correlations between thermocalorimetric properties, linear dichroism and birefringence of collagen-Ponceaus SS complex as compared to pure collagen fibers. In this work, we show that the binding of the dichroic sulfo-azo dye Ponceau SS to highly oriented collagen fibers results in increased crystallinity, as measured by differential scanning calorimetry and optical anisotropy. Collagen fibers formed a complex with Ponceau SS that showed higher crystallinity and molecular order than the fibers alone. Differential scanning calorimetry revealed that the denaturation (peak) temperatures (Tm) of the complex were higher than for the pure collagen fibers. In addition, the dye-collagen complex showed high linear dichroism and stark interference colors in birefringence dispersion. These photo-optical properties are caused by periodic differences in the refractive indices along the molecules in the ordered collagen-dye complex, and indicate that this complex is a non-linear optical supramolecular chiral object.

Naturally supraorganized collagen increases axonal regeneration after tubulization repair

After axotomy, regeneration can be enhanced by bridging the transected nerve with a biocompatible tube, and the effect of trophic substances or molecules from the extracellular matrix can be investigated by filling the prosthesis. In this study, we assessed the importance of the molecular organization and aggregational state of collagen type I in axonal regeneration and guidance. Two types of collagen were used, namely, a collagen gel derived from bovine tendon that displays supraorganization after extrusion, and collagen from rat tail which does not self-organize under such conditions. Adult male Wistar rats were divided into four groups. In the first group (n=3), the polyethylene tube was filled with bovine collagen, while in the second (n=3), the prosthesis was filled with rat-derived collagen. In the third group (n=3), the tube was left empty, and the fourth group (n=3), consisted of unoperated rats. Six weeks after tubulization, the number of axons was significantly higher with bovine collagen than with rat collagen (7,661 ± 1,018 versus 4,110 ± 1,027, p<0.05), as was the degree of implant absorption. These results support the hypothesis that the use of extracellular matrix substances that self-assembly in an organized pattern can enhance nerve regeneration.

Incresead DNA content and nuclear phenotypic alterations associated with mechanical load in wrap-around joint chiken tendons*

Tendons are highly superstructures with a capacity to respond to variation in load. Fibroblasts in tendon cartilage respond to mechanical stimuli through metaplasia and the expression of new synthetic activities fallowing gene activation. In study we examined the changes in the nuclear phenotypes of calcaneus communis and flexor digitorum superficiales tendons in 21-and 41-day-old chickens. Video image analysis was used to examine fibroblasts in Feugen-stained tendon sections. The parameters studient included integrated optical desnsity, optical density, nuclear area, feret-ratio, gray average. standard deviation of the gray average per nucleus, and entropy. Compared to diploid chicken erythocytes, fibroblasts had larger amounts of DNA in the G2 phase and showed polyploidy. The DNA content of the fibroblasts incresead with age. In both tendons, the nuclei of 41-day-old chickens had a higher DNA content and optical density, i.e. more packed chromatin, than in 21-day-old chickens. The linear correlation of nuclear area vs integrated optical density (R2 por cento) was greater in flexor digitorum superficialis than in calcaneus communis nuclei. The latter showed a marked dispersion around the fitted line, with R2=0,44 por cento for 41-day-old chickens. The high feret-ratios of calcaneus communis nuclei indicated more spherical nuclei. These results show that fibroblast nuclei in both types of tendon respond to a compressive load around the articulation type involved. Molecular order and collagen fiber crystallinity apparently contribute to signaling by the extracellular matrix to the cells analized here.

Feulgen staining in malpighian tubules of meliponid bees: a methodological contribution

Whole-mounted Malpighian tubules of larvae from two meliponid bee species fixed in acetic acid-ethanol showed apositive cytoplasmic staining with Schiff reagent when submitted to the Feulgen reaction in which acid hydrolysiswas done in 4 M HCl at room temperature. The ability of various treatments applied before the Feulgen acid hydrolysisto abolish this cytoplasmic staining was examined. The aldehyde groups of phospholipids present in the cytoplasm ofthe Malpighian tubules were blocked or removed by sequential treatment with 5% sodium borohydride and acetonechloroform(1:1, v/v) for 15 min each prior to HCl hydrolysis. This treatment is recommended in order to abolish thecytoplasmic (plasmal) reaction and to allow the reliable quantification of DNA by the Feulgen reaction and thediscrimination of nuclear phenotypes in the Malpighian tubules of meliponid bees.

Reticulin morphometry and collagen fibers optical anisotropy as assessed by image analysis after silver impregnation

A new method for the impregnation of tissue sections with ammoniacal silver carbonate in terms of single-step reaction, no gold toning, no oxidation step and silver impregnation after treatment with pancreatic (alfa)-amylase is described. This method yields silver nanocrystalloids with 18.40 nm in average diameter [16]. Natural carbohydrate radicals probably acting as natural reducing agents for silver are assumed to occur. Despite the fact that the method is not specific, reticulin fibers (type III colagen) were clearly distinguished from other collagen fibers types and easily and accurately segmented by image analysis (IA) systems, when using this procedure. Data from myocardial reticulin fibers are presented. Collagen bundles (type I collagen rich structures) exhibited intense linear dichroism (LD) interms of gray averages measured by IA (non-impregnated, natural, collagen fibers do not show LD) Anomalous dispersion of birefringence was also detected, highlighting typical morphologies, including crimp, which allow us to propose the methodo for molecular order studies and to assess collagen bundles as chiral objects, especially together with LD data.

A biochemical histochemical analysis of the efficiency of a low ionic strength solution in extracting cartilage extracellular matrix components

The extracellular matrix of cartilage is composed of collagen, proteoglycans and non-collagenous proteins. These components may interact sufficiently strongly with each other, so that they can only be extracted using chaotropic agents such as 4 M quanidine chloride. Extraction in this normally preceded by homogenization in phosphate buffered saline (PBS) solution (0.15 NaCl, 5mM phosphate buffer, pH 7.4) followed by centrifugation to obtain a precipitate which is then extracted with guanidine chloride. In this work, the suitability of PBS alone for extracting the components of chicken xiphoid cartilage was compared with that of guanidine chloride. The stability of the matrix components obtained was also analyzed. Proteins with molecular masses of 30, 40, 52, 58 and 110 kDa were identified in the PBS extract. Small proteoglycans were detected in guanidine chloride extracts, but not in PBS extracts, suggesting that these molecules were strongly bound to other components of the matrix. The examination of cartilage sections stained with toluidine blue and Ponceau S after exposure to saline and guanidine chloride, showed that although saline did not remove substantial amounts of glycosaminoglycans it caused structural changes in the organization of the extracellular matrix. However, this effect was much less than with guanidine chloride.

Ensaio uniaxial de tração dos tendões dos músculos grácil e semitendinoso humanos / Uniaxial traction test on human gracilis and semitendinous tendon

O uso de tendões humanos, de forma isolada ou associada, em reconstruções ligamentares do joelho é uma prática usual. A utilização desses enxertos (tendão patelar, duplo semitendinoso associado ao duplo grácil) apresenta evolução pós-operatória diferente, quando analisados os parâmetros: perda mínima da extensão, deslocamento ântero-posterior (artrômetro KT-2000), retorno as atividades esportivas. A presente pesquisa tem por objetivo analisar o comportamento mecânico de tendões humanos (grácil e semitendinoso), quando submetidos a ensaios uniaxiais de tração, até a ruptura. Como parâmetros mecânicos para análise e confronto foram considerados: tensão de ruptura (MPa), deformação relativa, módulo de elasticidade (MPa), energia de ruptura (N.mm) e velocidade de carregamento (mm/s). Os resultados permitiram concluir que: 1) o tendão do músculo semitendinoso é mais resistente que o tendão do músculo grácil; apresenta menores deformações relativas; acumula maior energia de ruptura; 2) a utilização destes tendões como enxerto único, impõe uma análise mecânica mais detalhada, pois apresentam comportamento mecânico distinto e são materiais história e tempo - dependentes (viscoelásticos).

Action of chemical agents in the process of in Vitro cell differentiation induced by microcrystalline collagen felt

The collagen used in the work as substratum has been divided into 3 groups: one under glutaraldehyde treatment, the second under periodate acid treatment, while the third remained non treated. The samples were removed after 1, 5, 10 and 15 days of growth to morphological analysis. The results led to the conclusion that both treated and non treated collagen felt induce a differentiation process distinguished by alterations in shape and size of cells and modifications in the protein-DNA complex, observed by Toluidine blue staining. The periodate acid acts on glicosidic portion of the collagen molecule and the cells that grow on this substratum have attachment and spreading changed, indicating that the lateral chains of carbohydrates of the collagen molecule exert influence on the attachment and spreading process of VERO cells, causing a partially changed cell proliferation

Reposicionamento cirúrgico de um segundo molar inferior direito impactado com cárie: relato de caso / Surgical repositioning in impacted permanent mandibular second molar with caries: case report

Segundos molares inferiores impactados näo ocorrem freqüentemente. Por diferentes motivos, podem ficar impactados nos primeiros molares, näo fazendo sua erupçäo na época normal. Diversos säo os fatores etiológicos, porém o mais comum é a falta de espaço no arco dental, devida ao inadequado crescimento mandibular. Quando isto ocorre e o tratamento ortodôntico näo dispöe de meios para levar este dente à oclusäo, nós sugerimos que esta técnica seja considerada para o tratamento de segundos molares mal posicionados. O objetivo deste artigo foi relatar um caso de reposicionamento cirúrgico de um segundo molar inferior direito com cárie. Na radiografia panorâmica da paciente M.S.S., de 17 anos e 10 meses, foi detectada a impactaçäo do segundo molar inferior direito no primeiro molar. Após o reposicionamento cirúrgico, o dente foi, na mesma sessäo, restaurado provisoriamente, aguardando a troca por material definitivo

Image analysis and definition of nuclear phenotypes

Alguns tópicos básicos relativos à extraçäo de informaçöes texturais e geométricas de núcleos celulares, bem como a descriçäo e a categorizaçäo da supraorganizaçäo cromatínica e conseqüente classificaçäo de fenótipos nucleares, säo aqui apresentados.

Human renal carcinoma: Feulgen-DNA, area and chromatin condesation determined by scanning cytometry

Säo reportadas neste trabalho as variaçöes em conteúdo de DNA, as correspondentes variaçöes das áreas cobertas por cromatina-Feulgen reativa e o grau de empacotamento (condensaçäo) cromatínica em núcleos de células de carcinomas renais. O método eleito, para levar a efeito o trabalho, foi o de análise de imagem a partir de dados obtidos com microespectrofotometria de varredura. Controles de muita precisäo foram levados a efeito usando-se núcleos de eritrócitos de frango, neutrófilos humanos e núcleos epiteliais de rim humano normal. Os núcleos tumorais apresentaram uma populaçäo poliplóide, tendo como origem provável uma populaçäo hipodiplóide ("stem cell"). Detectou-se nos núcleos tumorais, um aumento de área coberta por material Feulgen-positivo, tal fato correspondendo a um fenômeno geral de descondensaçäo cromatínica. Este achado, contudo, foi acompanhado por um aumento dos valores da razäo das absorbâncias médias (AAR) significando que as regiöes de cromatina condensada, nos casos de tumores renais, säo mais condensadas do que as correspondentes das células normais

Interaction of concanavalin A with sugar residues of collagen from different tissues

Particularidades topoquímicas da reaçäo de diferentes tipos de estruturas contendo colágeno, com Cancanavalina A (Con A) näo tem sido considerados até agora. A presença de disponibilidade de resíduos de glicose em moléculas de colágeno de intestino, fígado, cartilagem e tendäo säo verificados usando Con A e peroxidase de rábano silvestre (HRP). Em cortes de intestino, cartilagem e tendäo, o método usando Con A-HRP só foi significativamente positivo quando os cortes eram submetidos a um tratamento prévio com papaína sugerindo a presença de glicoproteínas e proteoglicanas da matriz extracelular (ECM), interagindo com resíduos laterais de carboidratos das moléculas de colágeno ou causando algum bloqueio estérico como ocorre em regiöes com alto estado de compactaçäo

Emprego experimental do bisturi eletrico nas anastomoses do intestino grosso / Experimental employment of the electric bistoury in anastomosis of the large intestine

O presente trabalho analisa na anastomose em um plano de sutura a tecnica de preparo das bocas anastomoticas que emprega o bisturi eletrico tanto na secçao das tunicas quanto na hemostasia dos vasos da submucosa e aquela em que se pratica a secçao das tunicas com o bisturi frio, efetuando-se laqueadura dos vasos da submucosa com fio de categute 5-0. Estas duas tecnicas foram comparadas a classica sutura em dois planos. Foram operados 30 caes, 10 com cada variedade de sutura a ser analisada. Metade dos caes de cada grupo foi sacrificada no 5.(quinto) dia e a outra metade no 15. (decimo quinto) dia. Os resultados histologicos foram analisados a microscopia otica e de polarizaçao. A microscopia otica procurou-se analisar o grau de necrose tecidual, a reaçao inflamatoria, a proliferaçao de fibroblastos e a formaçao de fibras colagenas. O exame a mcroscopia de polarizaçao tem como objetivo a demonstraçao da lise e da formaçao do tecido colageno durante o processo de cicatrizaçao, o que e possivel pela birrefringencia dos feixes de colageno, demonstraveis pelo seu brilho contra o campo escuro dos demais tecidos. A analise do presente trabalho permite as seguintes conclusoes: 1- A analise de birrefringencia a microscopia de polarizaçao mostrou ser um excelente metodo de estudo, tendo em vista a possibilidade de identificaçao direta das fibras de colageno. 2- A analise a macroscopia e a microscopia (otica e de polarizaçao) mostra haver vantagens das suturas em um plano sobre a classica sutura em dois planos. Ocorreu necrose tecidual e reaçao inflamatoria exsudativa mais intensas nas suturas em dois planos. 3- Os resultados verificados pelo estudo da birrefringencia nas suturas em dois planos evidenciou a ausencia de formaçao de tecido colageno no 5. (quinto) dia de evoluçao e minima formaçao de tecido colageno no 15. (decimo quinto) dia de pos-operatorio. 4- Os resultados obtidos pelo estudo da birrefringencia nas suturas em um plano mostraram a presença de tecido colageno no 5.(quinto) e 15.(decimo quinto) dias. 5- A analise da birrefringencia demonstrou que a formaçao de tecido colageno e mais intensa e melhor orientada quando as bocas anastomoticas foram preparadas com o bisturi eletrico