Clinical Measurements of Force Exerted on Anterior Teeth in Partial Edentulous Distal Extension.

Purpose: To determine the influence of partial edentulous distal extension and the use of removable partial dental prostheses in partially edentulous areas on the force exerted on the anterior teeth.

Materials And Methods: A total of 83 volunteer patients participated in this study. The occlusal force was measured using an occlusal force measuring sheet in the patient's mouth.

Force exerted on maxillary anterior teeth in mandibular unilateral and bilateral distal extension partial edentulous situation.

The purpose of this study was to determine the influence of mandibular unilateral and bilateral distal extension partial edentulous situation and the use of removable partial dental prostheses on the force exerted on maxillary anterior teeth. A commercially available jaw model with exchangeable teeth was used. Seven experimental conditions of mandibular distal extension edentulous situation were prepared and a distal extension removable partial dental prosthesis to replace missing posterior teeth was fabricated.

Flow Behavior and Distribution of Embolus-Model Particles at the Terminal Bifurcation of the Human Internal Carotid Artery.

Background: To investigate the possible role of fluid mechanical factors in thromboembolism that occurs at a high rate in the human middle cerebral artery (MCA).

Methods: Isolated transparent cerebral arterial trees containing the terminal bifurcation of the internal carotid artery (ICA), where the ICA bifurcated into the MCA and the anterior cerebral artery, were prepared from human cadavers. The flow behavior and distribution of embolus-model polystyrene particles in dilute suspensions at the bifurcation were studied in detail by means of flow visualization and high-speed cinemicrographic techniques.

Flow patterns and preferred sites of atherosclerotic lesions in the human aorta - II. Abdominal aorta.

Objective: As in Part I, to elucidate the role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in man, here in the abdominal aorta.

Methods: Flow patterns and preferred sites of atherosclerotic lesions in the aorta were studied in detail using the same isolated transparent aortic trees prepared from humans postmortem and the flow visualization and cinemicrographic techniques as in Part I.

Results: Under steady flow simulating mid-systole, the flow was found to be disturbed at the aorto-celiac and aorto-superior mesenteric artery junctions by the formation of complex secondary and adverse flows along the lateral and posterior walls of the abdominal aorta.

Flow patterns and preferred sites of atherosclerotic lesions in the human aorta - I. Aortic arch.

Objectives: To elucidate the role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in man.

Methods: Flow patterns and preferred sites of atherosclerotic lesions in the human aortic arch were studied in detail using isolated transparent aortic trees prepared from humans postmortem and by means of flow visualization of tracer polystyrene microspheres, using cinemicrographic techniques.

Results: Under the condition of steady flow that simulated mid-systole, the flow in the aortic arch consisted of three major components; (i) a straight flow to the brachio-cephalic artery located close to the right dorsal wall of the ascending aorta; (ii) a quasi-parallel undisturbed flow located close to the common median plane of the aortic arch and its side branches, and (iii) a clockwise slow, spiral secondary flow located dominantly near the left ventral wall of the aortic arch.

Flow patterns and distributions of fluid velocity and wall shear stress in the human internal carotid and middle cerebral arteries.

Background: The aim of this study is to elucidate the relationship between the flow patterns and the preferred sites of the development of atherosclerotic lesions and cerebral aneurysms in the human ICA and MCA.

Methods: Five isolated transparent arterial trees containing the ICA and MCA with a sufficient length of the carotid siphon were prepared from humans postmortem, and flow patterns and distributions of fluid velocity and wall shear stress in these vessels were studied in detail using flow visualization and high-speed cinemicrographic techniques.

Results: In the carotid siphon that contained several acute bends, due to the impingement and deflection of the flow at the bends, a strong and complex helicoidal flow formed.

Effect of a disturbed flow on proliferation of the cells of a hybrid vascular graft.

Atherosclerotic lesions and intimal hyperplasia develop preferentially in regions where blood flow is disturbed by the formation of secondary and recirculation flows. Hence, to investigate the mechanism of the localization of these vascular diseases, we constructed a sudden tubular expansion consisting of a 0.92 mm i.

Effect of a disturbed flow on adhesion of monocytes to a model of an arterial wall.

Monocytes are involved in the pathogenesis and localization of intimal hyperplasia and atherosclerosis in regions of disturbed flow in man. Hence, to investigate the mechanism of the localization of these vascular diseases, we created a state of disturbed flow distal to a 0.92 mm into 3.

Flow patterns and velocity distributions in the human vertebrobasilar arterial system. Laboratory investigation.

Object: The authors conducted a study to elucidate the relationship between the flow patterns and the formation of aneurysms at the bifurcation of the basilar artery (BA).

Methods: Six isolated, transparent vertebrobasilar arterial systems were prepared from humans postmortem, and flow patterns and velocity distributions were studied in detail using flow visualization and cinemicrographic techniques.

Results: The authors found that if the diameters of 2 vertebral arteries (VAs) were nearly equal and they formed a symmetrical inverted Y-shaped junction with the BA, the BA flow was also symmetrical.

Effect of serum concentration on adhesion of monocytic THP-1 cells onto cultured EC monolayer and EC-SMC co-culture.

Background: The adhesion of monocytes to the endothelium following accumulation of low-density lipoprotein (LDL) in subendothelial spaces is an important step in the development of intimal hyperplasia in arterially implanted vein grafts and atherosclerosis in both animals and humans. However, it is not well known how serum factors affect the adhesion of monocytes.

Methods: We have studied the effect of fetal calf serum (FCS), which we considered a source of LDL, on the adhesion of monocytes to endothelial cells (ECs) by using human monocytic THP-1 cells and both a monolayer of cultured bovine aortic endothelial cells (EC monoculture) and a co-culture with bovine aortic smooth muscle cells (EC-SMC co-culture).

Flow-dependent accumulation of LDL in co-cultures of endothelial and smooth muscle cells in the presence of filtration flow through the cell layer.

To elucidate the roles of blood flow and transmural filtration flow in localized LDL accumulation in vascular walls, we studied the effects of flow velocity on LDL concentration at the cell surface and LDL uptake by co-cultures of vascular endothelial cells (ECs) and smooth muscle cells using a parallel-plate flow cell with or without filtration flow. Co-cultures were prepared on porous membranes. In the presence of filtration flow through the cell layer, the LDL concentration at the cell surface increased when the perfusion velocity was decreased (shear stress was decreased from 1.

Measurement of rheologic property of blood by a falling-ball blood viscometer.

The viscosity of blood obtained by using a rotational viscometer decreases with the time elapsed from the beginning of measurement until it reaches a constant value determined by the magnitude of shear rate. It is not possible to obtain an initial value of viscosity at time t = 0 that is considered to exhibit an intrinsic property of the fluid by this method. Therefore, we devised a new method by which one can obtain the viscosity of various fluids that are not affected by both the time elapsed from the beginning of measurement and the magnitude of shear rate by considering the balance of the forces acting on a solid spherical particle freely falling in a quiescent viscous fluid.

Improved arterial wall model by coculturing vascular endothelial and smooth muscle cells.

We have constructed an in vitro arterial wall model by coculturing bovine arterial endothelial cells (ECs) and smooth muscle cells (SMCs). When ECs were seeded directly over SMCs and cocultured in an ordinary culture medium, ECs grew sparsely and did not form a confluent monolayer. Addition of ascorbic acid to the culture medium at concentrations greater than 50 mug/ml increased the production of type IV collagen by the SMCs, and ECs formed a confluent monolayer covering the entire surface of SMCs.

Flow patterns and preferred sites of intimal thickening in diameter-mismatched vein graft interpositions.

Background: It is suspected that blood flow and flow-induced shear stress play an important role in the pathogenesis and localization of intimal hyperplasia in anastomosed vessels. However, experimental data that demonstrate the correlation between the flow and the sites of intimal thickening obtained in the same vessel are scarce. For this reason, we have studied the relationship between the flow and precise locations of wall thickening specific to the particular vessel by performing diameter-mismatched vein graft interpositions.

Molecular basis of the shish-kebab morphology in polymer crystallization.

In the rich and long-standing literature on the flow-induced formation of oriented precursors to polymer crystallization, it is often asserted that the longest, most extended chains are the dominant molecular species in the "shish" of the "shish-kebab" formation. We performed a critical examination of this widely held view, using deuterium labeling to distinguish different chain lengths within an overall distribution. Small-angle neutron-scattering patterns of the differently labeled materials showed that long chains are not overrepresented in the shish relative to their concentration in the material as a whole.

Difference in lower critical solution temperature behavior between random copolymers and a homopolymer having solvatophilic and solvatophobic structures in an ionic liquid.

The solubility and phase behavior of poly(benzyl methacrylate) (PBzMA) and poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) in a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfone)imide ([C(2)mim][NTf(2)]), have been explored as a function of temperature. Although both polymers have solvatophobic phenyl groups and solvatophilic methacrylate groups in the structure, their distribution on the polymer chains is quite different. In PBzMA, both structures are incorporated in each monomer unit, whereas in P(St-co-MMA)s the distribution is statistically determined by the monomer reactivity ratio of St and MMA.

Nonuniformity in natural rubber as revealed by small-angle neutron scattering, small-angle X-ray scattering, and atomic force microscopy.

The microscopic structures of natural rubber (NR) and deproteinized NR (DPNR) were investigated by means of small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM). They were compared to those of isoprene rubber (IR), which is a synthetic analogue of NR in terms of chemical structure without any non-rubber components like proteins. Comparisons of the structure and mechanical properties of NR, DPNR, and IR lead to the following conclusions.

Reactive oxygen species mediate shear stress-induced fluid-phase endocytosis in vascular endothelial cells.

To elucidate the role of shear stress in fluid-phase endocytosis of vascular endothelial cells (EC), we used a rotating-disk shearing apparatus to investigate the effects of shear stress on the uptake of lucifer yellow (LY) by cultured bovine aortic endothelial cells (BAEC). Exposure of EC to shear stress (area-mean value of 10 dynes/cm2) caused an increase in LY uptake that was abrogated by the antioxidant, N-acetyl-L-cysteine (NAC), the NADPH oxidase inhibitor, acetovanillone, and two inhibitors of protein kinase C (PKC), calphostin C and GF109203X. These results suggest that fluid-phase endocytosis is regulated by both reactive oxygen species (ROS) and PKC.

Effects of a ventricular untwisting on intraventricular diastolic flow and color M-mode Doppler echocardiograms.

Intraventricular hemodynamics during diastole was numerically analyzed in order to investigate effects of a ventricular untwisting on flow and a pattern of a color M-mode Doppler echocardiogram. Results showed that the ventricular untwisting affected secondary flows by inducing spiral flows in the ventricular cavity especially in the apical region. On the other hand, flows in the long-axis plane were not affected.

Cellular growth under hydrostatic pressure using bovine aortic EC-SMC co-cultured ePTFE vascular graft.

High blood pressure (hypertension) is implicated in the development of atherosclerosis. Blood vessels are constantly subjected to stretch due to blood pressure and changes in stretch usually instigate adaptive vascular remodeling, including abnormal growth and proliferation of vascular smooth muscle cells (VSMCs) as well as extracellular matrix (ECM). In this experiment, we used bovine aortic endothelial cells and smooth muscle cells (EC-SMC) co-cultured ePTFE vascular grafts subjected to normal atmospheric pressure (as a control), and 100 mmHg hydrostatic pressure for 7 d.

Effect of ionization on the temperature- and pressure-induced phase transitions of poly(N-isopropylacrylamide) gels.

The ionization effects on the pressure-induced phase transition of weakly charged poly(N-isopropylacrylamide-co-acrylic acid) (PNIPA-AAc) gels have been investigated by small-angle neutron scattering. At low temperature, T, and pressure, P, the structure factor of PNIPA-AAc gels was well represented by a Lorentzian (L) function, which was similar to noncharged PNIPA gels. However, at high Ps, the contribution of inhomogeneities became large and a squared-Lorentzian term had to be added in addition to the L term.

The effects of a shear flow on the uptake of LDL and acetylated LDL by an EC monoculture and an EC-SMC coculture.

To elucidate the mechanisms of localized genesis and development of atherosclerosis and anastomotic intimal hyperplasia in man, a coculture of bovine aortic endothelial cells (ECs) and smooth muscle cells (SMCs) was prepared, and the effects of a shear flow on the uptake of lipoproteins by the cells was studied by incubating the EC-SMC coculture as well as an EC monoculture with a culture medium containing either DiI-LDL or DiI-Ac-LDL and subjecting to a laminar shear flow. It was found that in both the presence and absence of a shear flow that imposed the ECs an area mean shear stress of 13.3 dynes/cm2, the uptake of LDL by an EC-SMC coculture was much greater than that by an EC monoculture, whereas that of Ac-LDL was almost the same.

Roles of protein kinase C delta in the accumulation of P53 and the induction of apoptosis in H2O2-treated bovine endothelial cells.

To clarify the signaling pathways of oxidative stress-induced apoptosis in bovine aortic endothelial cells (BAEC), we treated cells with 1 mM H2O2 and investigated the roles of protein kinase C delta (PKC delta) and Ca2+ in the accumulation of p53 associated with apoptosis. The treatment of cells with H2O2 caused the accumulation of p53, which was inhibited by rottlerin (a PKC delta inhibitor) but not by BAPTA-AM (an intracellular Ca2+ chelator). PKC delta itself was activated through the phosphorylation at tyrosine residues.

Theoretical prediction of low-density lipoproteins concentration at the luminal surface of an artery with a multiple bend.

To elucidate the mechanisms of localization of atherosclerotic lesions in man, the effects of various physical and hemodynamic factors on transport of atherogenic low-density lipoproteins (LDL) from flowing blood to the wall of an artery with a multiple bend were studied theoretically by means of a computer simulation under the conditions of a steady flow. It was found that due to a semipermeable nature of an arterial wall to plasma, flow-dependent concentration polarization of LDL occurred at the luminal surface of the vessel, creating a region of high LDL concentration distal to the apex of the inner wall of each bend where the flow was locally disturbed by the formation of secondary and recirculation flows and where wall shear stresses were low. The highest surface concentration of LDL occurred distal to the acute second bend where atherosclerotic intimal thickening developed.

Prediction of LDL concentration at the luminal surface of a vascular endothelium.

To find out whether concentration polarization of low-density lipoprotein (LDL) occurs at the surface of a vascular endothelium or not, transport of LDL in flowing blood to an water-permeable endothelium was studied theoretically by means of CFD. Calculations were carried out for an endothelium exposed to a Couette flow by assuming that the surface geometry of the endothelium could be expressed by a cosine function. Two typical cases were considered for the permeability of endothelium to water; one was uniform permeability everywhere in the endothelium, and the other was uneven permeability which was augmented at the intercellular junction.