RESUMO
The remodeling mechanisms of transseptal fibers during and after tooth movement were investigated histologically. An autoradiographic study was conducted to assess the synthetic response. One hundred fifty male Wistar strain growing rats were divided into three groups--one control and two experimental groups. Animals in the experimental groups were subjected to tooth movement with 25 g and 150 g of force. Maxillary first and second molars were separated and retained mechanically. Transseptal fibers were stretched in proportion to the amount of force applied for up to 2 days. Dynamic remodeling with proliferation of fibroblasts during tooth movement and slow rearrangement during retention periods occurred in both experimental groups. Collagen phagocytosis within the fibroblasts was observed ultrastructurally during the experimental periods. The number of silver grains in fibroblasts in the collagen fibers increased 160% the first day and 206% during the first 3 days. Proliferating fibroblasts remodeled the transseptal fibers through the synthesization and degradation of collagen fibers.
Assuntos
Processo Alveolar/fisiologia , Remodelação Óssea , Técnicas de Movimentação Dentária , Processo Alveolar/metabolismo , Animais , Colágeno/biossíntese , Análise do Estresse Dentário , Fibroblastos/metabolismo , Fibroblastos/ultraestrutura , Masculino , Microscopia Eletrônica , Ligamento Periodontal/fisiologia , Ratos , Ratos WistarRESUMO
Retinoic acid inhibited the contraction of collagen gel containing fibroblasts. Moreover, in its presence fibroblasts extensions were shorter, fewer collagen fibers were recognized, cell adhesiveness was inhibited concentration-dependently, and microfilaments appeared to be disrupted, resulting in morphological changes including loss of multipolar cell processes due to changes in cytoskeletal linkages.
Assuntos
Colágeno , Fibroblastos/efeitos dos fármacos , Tretinoína/farmacologia , Adesão Celular , Células Cultivadas , Criança , Feminino , Fibroblastos/citologia , Gengiva/citologia , HumanosRESUMO
Most reinforced concrete (RC) frame structures in the mid-western and eastern regions of the UNited States are built mainly for gravity loads without proper seismic desgn, and thus are vulnerable to severe damage in the event of a major earthquake in these regions (AU)
Assuntos
Terremotos , Indústria da Construção , Materiais de Construção , Engenharia , Medição de Risco , 34661Assuntos
Velocidade do Fluxo Sanguíneo , Capilares , Eritrócitos , Microcirculação , Oscilometria , Artérias , Pressão Sanguínea , Resistência Capilar , Hematócrito , Humanos , Matemática , Modelos BiológicosRESUMO
As an idealized problem of the motion of blood in small capillary blood vessels, the low Reynolds number flow of plasma (a newtonian fluid) in a circular cylindrical tube involving a series of circular disks is studied. It is assumed in this study that the suspended disks are equally spaced along the axis of the tube, and that their centers remain on the axis of the tube and that their faces are perpendicular to the tube axis. The inertial force of the fluid due to the convective acceleration is neglected on the basis of the smallness of the Reynolds number. The solution of the problem is derived for a quasi-steady flow involving infinitesimally thin disks. The numerical calculation is carried out for a set of different combinations of the interdisk distance and the ratio of the disk radius to the tube radius. The ratio of the velocity of the disk to the average velocity of the fluid is calculated. The different rates of transport of red blood cells and of plasma in capillary blood vessels are discussed. The average pressure gradient along the axis of the tube is computed, and the dependence of the effective viscosity of the blood on the hematocrit and the diameter of the capillary vessel is discussed.
Assuntos
Velocidade do Fluxo Sanguíneo , Capilares , Eritrócitos , Modelos Biológicos , Reologia , ViscosidadeRESUMO
A general form of the statistical equation of motion of the blood is derived by averaging the motion of individual elements of the blood over a small volume in space. This equation can be transformed into an explicit form to find the constitutive equations of the blood provided the detailed motion of the plasma in some neighborhood of a suspended particle is known. As a demonstration of such transformation, the general form of the statistical equation of motion is applied to the suspension of sphere with a very low concentration to find the effective viscosity.
Assuntos
Viscosidade Sanguínea , Hemodinâmica , Determinação do Volume Sanguíneo , Hematócrito , Modelos Teóricos , Reologia , Estatística como AssuntoRESUMO
To have a better understanding of the flow of blood in arteries a theoretical analysis of the pressure wave propagation through a viscous incompressible fluid contained in an initially stressed tube is considered. The fluid is assumed to be Newtonian. The tube is taken to be elastic and isotropic. The analysis is restricted to tubes with thin walls and to waves whose wavelengths are very large compared with the radius of the tube. It is further assumed that the amplitude of the pressure disturbance is sufficiently small so that nonlinear terms of the inertia of the fluid are negligible compared with linear ones. Both circumferential and longitudinal initial stresses are considered; however, their origins are not specified. Initial stresses enter equations as independent parameters. A frequency equation, which is quadratic in the square of the propagation velocity is obtained. Two out of four roots of this equation give the velocity of propagation of two distinct outgoing waves. The remaining two roots represent incoming waves corresponding to the first two waves. One of the waves propagates more slowly than the other. As the circumferential and/or longitudinal stress of the wall increases, the velocity of propagation and transmission per wavelength of the slower wave decreases. The response of the fast wave to a change in the initial stress is on the opposite direction.
