bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of grafting materials on osseointegration of dental implants surrounded by circumferential bone defects. An experimental study in the dog
Authors: Abushahba Faleh , Renvert Stefan , Polyzois Ioannis , Claffey Noel
Published: February 2008

Aims: This study was designed to evaluate the effect of gap width and graft placement on bone healing around implants placed into simulated extraction sockets in the mandibles of four beagle dogs.

Materials and methods: Four Ti‐Unite® implants (13 mm × 3.3 mm) were placed on each side of the mandible. Three implants were surrounded by a 1.35 mm circumferential and a 5 mm deep gap around the coronal portion of the implants. A fourth implant was inserted conventionally into both sides of the mandibles as a positive control. The gaps were filled with either Bio‐Oss®, autogenous bone or with a blood clot alone. The study design was balanced for animal, side and modality. Ground sections were prepared from biopsies taken at 3 months, and computer‐aided histometric measurements of bone/implant contact and area of bone within threads were made for the coronal 5 mm. Data were analysed using analysis of variance.

Results: The mean bone/implant contact was 9.8 mm for the control and ranged from 9.3 to 11.3 mm for the three test modalities. The corresponding values for area within threads were 1 mm2 and 1–1.2 mm2. Modality had a significant effect on both bone/implant contact (F=16.9; P<0.0001) and area within threads (F=16.7; P<0.0001).

Conclusion: The results of this study suggest that both autogenous bone graft and Bio‐Oss® played an important role in the amount of hard tissue fill and osseointegration occurring within marginal bone defects around implants.
Adjunctive effect of chlorhexidine in ultrasonic instrumentation of aggressive periodontitis patients: a pilot study
Authors: Guarnelli Maria Elena , Franceschetti Giovanni , Manfrini Roberta , Trombelli Leonardo
Published: February 2008

Aim: The aim of the present pilot randomized clinical trial was to evaluate the effects of ultrasonic mechanical instrumentation (UMI) associated with the professional use of chlorhexidine (CHX) formulations compared with UMI alone during periodontal supportive therapy in patients with generalized aggressive periodontis (G‐AgP).

Material and Methods: Nine patients (test group) received a single session of UMI associated with subgingival irrigation under cavitation with CHX 0.02%. A 0.2% CHX solution was used for professional tongue brushing and mouthrinsing. Ten patients (control group) received a similar session of UMI associated with subgingival irrigation and professional tongue brushing and mouthrinsing with a control formulation. Clinical and microbiological parameters were assessed pre‐treatment at 3, 6 and 12 weeks post‐treatment.

Results: UMI either with or without additional CHX use determined a significant reduction of supragingival plaque and gingival inflammation as well as a significant reduction of subgingival bacterial pathogens. The additional use of CHX did not result in any additional clinical and microbiological benefit with respect to mere UMI.

Conclusions: The adjunctive professional use of CHX formulations to UMI seems to produce no additional effects over UMI alone during supportive therapy in G‐AgP patients.
Selective estrogen enzyme modulator actions of melatonin in human breast cancer cells
Authors: Gonzalez A. , Cos S. , Martinez‐Campa C. , Alonso‐Gonzalez C. , Sanchez‐Mateos S. , Mediavilla M. D. , Sanchez‐Barcelo E. J.
Published: February 2008

Abstract:  Melatonin exerts oncostatic effects on different kinds of neoplasias, especially on estrogen‐dependent mammary tumors. Current knowledge about the mechanisms by which melatonin inhibits the growth of breast cancer cells point to an interaction of melatonin with estrogen‐responsive pathways. The intratumoral production of estrogens in breast carcinoma tissue plays a pivotal role in the proliferation of mammary tumoral cells and its blockade is one of the main objectives of the treatment of breast cancer. The aim of the present work is centered on the study of the role of melatonin in the control of some enzymes involved in the formation and transformation of estrogens in human breast cancer cells. The present study demonstrates that melatonin, at physiologic concentrations, modulates the synthesis and transformation of biologically active estrogens in MCF‐7 cells, through the inhibition of sulfatase (STS) and 17β‐hydroxysteroid dehydrogenase type 1 (17β‐HSD1) activity and expression, enzymes involved in the estradiol formation in breast cancer cells. Physiologic concentrations of melatonin also stimulate the activity and expression of estrogen sulfotransferase (EST), the enzyme responsible for the formation of the biologically inactive estrogen sulfates. The level of EST mRNA steady‐state of cells treated with melatonin was three times higher than that in control cells. These findings which document that melatonin has an inhibitory effect on STS and 17β‐HSD1 and a stimulatory effect on EST, in combination with its previously described antiaromatase effect, can open up new and interesting possibilities in clinical applications of melatonin in breast cancer.
Melatonin regulates matrix metalloproteinases after traumatic experimental spinal cord injury
Authors: Esposito Emanuela , Genovese Tiziana , Caminiti Rocco , Bramanti Placido , Meli Rosaria , Cuzzocrea Salvatore
Published: February 2008

Abstract:  The matrix metalloproteinases (MMPs) are important enzymes that regulate developmental processes, maintain normal physiology in adulthood and have reparative roles at specific stages after an insult to the nervous system. MMPs, particularly MMP‐9/gelatinase B, promote early inflammation and barrier disruption after spinal cord injury (SCI). Recently, we have reported that the pineal secretory product melatonin exerts important anti‐inflammatory effects in an experimental model of SCI induced by the application of vascular clips (force of 24 g) to the dura after a four‐level T5–T8 laminectomy. However, no reports are available on the relationship between the activity of MMPs and melatonin’s anti‐inflammatory effects. The aim of the present study was to evaluate whether the protective effect of melatonin observed in SCI is related to the regulation of MMP‐9 and MMP‐2 in mice. Biochemical and zymographic methods were used to analyze MMP‐9 and ‐2 expression and activities in spinal cord tissue from SCI‐treated mice at 24 hr after the trauma. Our studies reveal that melatonin reduced SCI and lipid peroxidation in spinal cord at 24 hr after SCI. Melatonin also diminished proMMP‐9 and ‐2 activities that were induced in the spinal cord tissues at 24 hr after SCI. The reduced activities of MMP‐9 and ‐2 were associated with depressed expression of TNF‐α. We propose that melatonin’s ability to reduce SCI in mice is also related to a reduction in MMP‐9 and MMP‐2 activity and expression.
Dynamic physiological and molecular changes in gastric ulcer healing achieved by melatonin and its precursor L‐tryptophan in rats
Authors: Konturek Peter C. , Konturek Stanislaw J. , Burnat Grzegorz , Brzozowski Tomasz , Brzozowska Iwona , Reiter Russel J.
Published: February 2008

Abstract:  Following induction of gastric ulcer in rats by serosal application of acetic acid, local mucosal necrosis ensues accompanied by a reduction in mucosal microcirculation and by almost immediate expression of inducible nitric oxide (NO) synthase (iNOS) and proinflammatory cytokines. Daily application of melatonin (20 mg/kg) or l‐tryptophan (100 mg/kg) accelerates ulcer healing by affecting the cyclooxygenase‐2 (COX‐2)–prostaglandin (PG) system with excessive production of protective PG, especially in later period of ulcer healing. Furthermore, expression of hypoxia inducible factor, vascular‐endothelial growth factor, an activation of cNOS–NO system and the stimulation of sensory nerves with the expression and release of calcitonin gene related peptide (CGRP) appear to aid the restoration of mucosal repair and microcirculation in the ulcer bed. The enhanced expression of the melatonin MT2 receptors (MT2‐R) combined with overexpression of key enzymes involved in biosynthesis of melatonin such as N‐acetyltransferase and hydroxyindole‐O‐methyltransferase contribute to the acceleration of ulcer healing by this indole. Melatonin‐induced acceleration of ulcer healing is also mediated by release of gastrin and ghrelin, the most potent stimulants of gastric mucosal cell proliferation and mucosal repair. These sequential steps in ulcer healing accelerated by melatonin can be interfered with by the blockade of MT2R, COX‐2/PG and cNOS/NO systems, and by reduction in the inflammatory iNOS/NO system. Thus, melatonin and its precursor l‐tryptophan, trigger the cascade of molecular events leading to the functional improvement in ulcer healing.
Thermogravimetric evaluation of perennial ryegrass (Lolium perenne) for the prediction of in vitro dry matter digestibility
Authors: Sharma H.S.S. , Mellon R.M. , Johnston D. , Fletcher H.
Published: February 2008

Thermogravimetry (TG) can be used for assessing the compositional differences in grasses that relate to dry matter digestibility (DMD) determined by pepsin–cellulase assay. This investigation developed regression models for predicting DMD of herbage grass during one growing season using TG results. The calibration samples were obtained from a field trial of eight cultivars and two breeding lines. The harvested materials from five cuts were analysed by TG to identify differences in the combustion patterns within the range of 30–600°C. The discrete results including weight loss, peak height, area, temperature, widths and residue of three decomposition peaks were regressed against the measured DMD values of the calibration samples. Similarly, continuous weight loss results of the same samples were also utilised to generate DMD models. The r2 for validation of the discrete and the best continuous models were 0.90 and 0.95, respectively, and the two calibrations were validated using independent samples from 24 plots from a trial carried out in 2004. The standard error for prediction of the 24 samples by the discrete model (4.14%) was higher than that by the continuous model (2.98%). This study has shown that DMD of grass could be predicted from the TG results. The benefit of thermal analysis is the ability to detect and show changes in composition of cell wall fractions of grasses during different cuts in a year.
Interaction between plant resistance and predation of Aphis fabae (Homoptera: Aphididae) by Coccinella septempunctata (Coleoptera: Coccinellidae)
Authors: Shannag H.K. , Obeidat W.M.
Published: February 2008

We investigated the compatibility of host plant resistance to the black bean aphid in the faba bean crop with the use of the predatory ladybird beetle for biological control under laboratory and greenhouse conditions. Greenhouse experiments indicated that apteriform Aphis fabae reproduced on Vicia faba major (susceptible) and on 79S4 (partially resistant) cultivars at different rates. During the entire experimental period, aphids built up higher populations on V. faba major than on 79S4 cultivar. Aphid numbers on 79S4 were about 37% of those on V. faba major after 14 days. Release of a newly hatched Coccinella septempunctata larva onto each plant significantly reduced aphid density to 32.8% and 57.2% on V. faba major and 79S4 on day 14, respectively. Partial resistance combined with predation was more effective in lessening aphid numbers on faba bean than either the predator or the plant resistance alone. Laboratory tests showed that prey, A. fabae, raised on susceptible cultivar was more suitable for the predator as food source, enhancing the development rate and fecundity than aphids fed on the partially resistant cultivar. Consumption of aphids reared on susceptible cultivar significantly increased the female fecundity and fertility of C. septempunctata by 37.7% and 33.2%, respectively, more than those fed with aphids from partially resistant cultivar. Pre‐oviposition time was shortened by 4.5 days, and oviposition period was extended by 11.4 days. Feeding the predator on aphids from the partially resistant cultivar prolonged the embryonic larval developmental time and the time required from egg laying to adult emergence by 19.8, 10.1 and 32.5 h, respectively. Adult longevity was not influenced by the aphid source. The results are discussed in relation to the compatible utilisation of host plant resistance and biological control in the integrated management of aphids.
Locomotory behaviour of the seven‐spotted ladybird, Coccinella septempunctata, in response to five commonly used insecticides
Authors: Thornham D.G. , Blackwell A. , Evans K.A. , Wakefield M. , Walters K.F.A.
Published: February 2008

Coccinella septempunctata is known to actively avoid substrates treated with an insecticide containing the organophosphate dimethoate. This study examines the responses of C. septempunctata to a range of different insecticide products from three chemical classes, carbamates, organophosphates and pyrethroids. Five formulated product insecticides were compared with the active ingredients (AIs) at two different application rates and using two different spray patterns (conferring choice or no‐choice designs) in a randomised block design. Coccinellids’ responses differed between insecticide classes. Pyrethoid treatments significantly reduced locomotion. Organophosphates effected mixed locomotory responses, as found in previous studies. Carbamate treatments effected very few changes in locomotory activity. Similar results were found at both application rates tested and under different test designs. The results of the AI tests indicated that different components of the products were responsible for the different reactions, with the AIs being responsible for some responses but the carriers being responsible for others. Results are discussed in relation to the insecticides’ modes of action and to their potential to increase the efficiency of integrated aphid control.
Genetic variation, pathogenicity and mycelial growth rate differentiation betweenGaeumannomyces graminisvar.triticiisolates derived from winter and spring wheat
Authors: Irzykowska L. , Bocianowski J.
Published: February 2008

The variability ofGaeumannomyces graminisvar.tritici(Ggt) isolates was evaluated at an intravarietal level using non‐molecular and molecular methods. Pathogenicity and linear growth rate of the pathogen were estimated. Very high pathogenicity was found in 44% of the isolates, medium in 20% and low only in 8%. Significant differences in mycelial growth rate were observed. The quickest linear growth rate ofGgtmycelium was observed at 25°C. Isolates derived from winter wheat grew faster than those obtained from spring wheat. The correlation between growth rates and pathogenicity was not significant. DNA polymorphism determined by random amplified polymorphic DNA (RAPD)–PCR was used to assess genetic variation among isolates. Thirty‐two RAPD markers revealed DNA polymorphism suitable for assessing variability among isolates examined. Cluster analysis of RAPD data identified a few groups of isolates. RAPD markers associated with pathogenicity as well as mycelium growth rate were found.
Relationship between baseline cerebral blood flow and vascular responses to changes in PaCO2 measured by positron emission tomography in humans: implication of inter‐individual variations of cerebral vascular tone
Authors: Ito H. , Kanno I. , Ibaraki M. , Suhara T. , Miura S.
Published: February 2008

Aim:  Inter‐individual variations in normal human cerebral blood flow (CBF) at rest condition have been reported. Inter‐individual variation of cerebral vascular tone is considered to contribute to this, and several determinants of cerebral vascular tone have been proposed. In the present study, the relationship between CBF and cerebral vascular tone to inter‐individual variation at rest condition was investigated using positron emission tomography (PET).

Methods:  CBF was measured using PET with H215O in each of 20 healthy subjects (20–28 years) under three conditions: at rest (baseline), during hypercapnia and during hypocapnia. The vascular response to change in PaCO2 was calculated as the percentage changes in CBF per absolute change in PaCO2 in response to hypercapnia and hypocapnia.

Results:  A significant negative correlation between baseline CBF and the vascular response to hypocapnia was observed in the thalamus, temporal cortex, parietal cortex, occipital cortex and cerebral cortex (P < 0.05). A trend towards negative correlation between baseline CBF and the vascular response to hypocapnia was observed in the cerebellum and putamen (P < 0.1). A significant negative correlation between baseline CBF and the vascular response to hypercapnia was observed in the occipital cortex (P < 0.05). No significant correlation was observed between baseline CBF and haemoglobin concentration, and PaCO2.

Conclusion:  These findings support the assumption that cerebral vascular tone might incline towards vasoconstriction and vasodilatation when baseline CBF is low and high between individuals respectively. Although several determinants of cerebral vascular tone have been proposed, the mechanism of such inter‐individual differences in cerebral vascular tone is unknown.
Comparison of Physical and Chemical Properties of Medium‐Grain Rice Cultivars Grown in California and Arkansas
Authors: Cameron D.K. , Wang Y.‐J. , Moldenhauer K.A.
Published: February 2008

ABSTRACT:  The physical attributes, chemical composition, and physicochemical properties of 2 medium‐grain rice cultivars from Arkansas (Bengal, Medark) and from California (M202, M204) were compared when grown in their respective locations and grown together in Arkansas to better understand the impacts of heredity and environment on medium‐grain rice quality. Variations existed in grain dimensions, particularly length distribution, among cultivars and between crop years. When grown separately, the Arkansas cultivars tended to have higher protein and lipid contents but lower amylose contents than the California cultivars. M204 contained a significantly higher apparent amylose content (21.0%) compared with the other 3 cultivars (14.3% to 16.4%). The Arkansas rice cultivars exhibited higher pasting and gelatinization temperatures and produced harder gels and less sticky cooked rice. However, when the 4 cultivars were grown together in Arkansas, differences in protein and amylose contents, gelatinization and pasting properties, and cooked rice texture decreased. This study demonstrated that genetics, location, and crop year all contributed to variations in rice chemical and physical characteristics.
Control of Listeria monocytogenes and Salmonella anatum on the Surface of Smoked Salmon Coated with Calcium Alginate Coating containing Oyster Lysozyme and Nisin
Authors: Datta S. , Janes M.E. , Xue Q.‐G. , Losso J. , La Peyre J.F.
Published: February 2008

ABSTRACT:  This study investigated the antimicrobial effect of oyster lysozyme with or without nisin added to calcium alginate (CaAlg) coated on the surface of smoked salmon against Listeria monocytogenes and Salmonella anatum. L. monocytogenes or S. anatum inoculated smoked salmon samples (1 g) were dipped into CaAlg with either oyster lysozyme (OysL) or hen egg white lysozyme (HEWL), with or without added nisin (N), then stored at 4 °C for 35 d. Our results indicated that the effectiveness of oyster lysozyme or hen egg white lysozyme was enhanced when added to calcium alginate coatings. After 35 d at 4 °C the growth of L. monocytogenes and S. anatum was suppressed in the range of 2.2 to 2.8 log CFU/g with CaAlgNOysL or CaAlgNHEWL coatings compared to the control nontreated samples. There was no significant difference between oyster lysozyme and hen egg white lysozyme treatments against L. monocytogenes or S. anatum inoculated on the surface of salmon. Calcium alginate coatings containing lysozyme with nisin or without could be used to reduce the growth of L. monocytogenes and S. anatum on the surface of ready‐to‐eat smoked salmon at refrigerated temperatures.
Polyphenols and Antioxidant Properties of Almond Skins: Influence of Industrial Processing
Authors: Garrido I. , Monagas M. , Gómez‐Cordovés C. , Bartolomé B.
Published: February 2008

ABSTRACT:  Almond (Prunus dulcis[Mill.] D.A. Webb) skins have been proposed as a source of bioactive polyphenols. In this article, the phenolic composition and antioxidant activity of almond skins obtained from different processes (blanching [freeze‐drying], blanching + drying, and roasting) were studied. A total of 31 phenolic compounds corresponding to flavan‐3‐ols (33% to 56% of the total of phenolic compounds identified), flavonol glycosides (9% to 36%), hydroxybenzoic acids and aldehydes (6% to 26%), flavonol aglycones (1.7% to 18%), flavanone glycosides (3% to 7.7%), flavanone aglycones (0.69% to 5.4%), hydroxycinnamic acids (0.65% to 2.6%), and dihydroflavonol aglycones (0% to 2.8%) were determined in the skins from 3 different varieties of almonds. The total contents of phenolic compounds identified were significantly (P < 0.05) higher (around 2‐fold) in the roasted samples than in the blanched almonds (freeze‐dried). Industrial drying (oven drying) of the blanched almond skins produced an increase (< 2‐fold) in the contents of phenolic compounds, although the results were only statistically significant (P < 0.05) for some samples. The antioxidant activity (ORAC values) was higher for the roasted samples (0.803 to 1.08 mmol Trolox/g), followed by the samples subjected to blanching + drying (0.398 to 0.575 mmol Trolox/g) and then the blanched (freeze‐dried) samples (0.331 to 0.451 mmol Trolox/g). Roasting is the most suitable type of industrial processing of almonds to obtain almond skin extracts with the greatest antioxidant capacity.
The Use of a Universal Force-Moment Sensor to Determine In-Situ Forces in Ligaments: A New Methodology
Authors: Fujie Hiromichi , Livesay Glen A. , Woo Savio L-Y. , Kashiwaguchi Shinji , Blomstrom Gail
Published: February 2008

Determination of ligament forces is an integral part of understanding their contribution during motion and external loading of an intact joint. While almost all previous investigations have reported only the magnitude of tension, this alone cannot adequately describe the function of a particular ligament. An alternative approach to determine the in-situ forces in ligaments has been developed which utilizes a universal force-moment sensor in conjunction with a force transformation scheme. In addition to providing the magnitude of ligament force, the direction and point of application of this in-situ force can also be determined. Further, the approach does not require mechanical contact with the ligament. Application of this new methodology is demonstrated for the human anterior cruciate ligament in the present study (n = 7) although it may be similarly applied to other ligaments at the knee or in other synovial joints of the human body.
Thoracic Deformation and Velocity Analysis in Frontal Impact
Authors: Yoganandan N. , Morgan R. M. , Eppinger R. H. , Pintar F. A. , Skrade D. A. , Sances A.
Published: February 2008

The objective of the present study was to measure dynamic chest deformations and compute chest velocity and viscous criterion during real world frontal impacts conducted on a horizontal sled. Four unembalmed human cadavers were restrained using a three-point belt restraint in the driver seat of a sled buck. Two chest bands (each with a 24 gauge capability) were placed on the thorax to record the temporal deformation patterns during impact. All tests were conducted at a velocity of approximately 50 kph. Biomechanical data were gathered digitally at a sampling rate of 12,500 Hz. Multiple rib fractures were identified in all specimens at autopsy. Analysis of approximately 800 temporal deformation contours of the thorax demonstrated regional differences. The overall mean maximum normalized chest deflections, maximum chest compression velocities, and peak viscous response variables ranged from 0.15 to 0.51, 1.79 to 4.87 m/s, and 0.15 to 1.95 m/s, respectively. These findings clearly illustrate the potential use of the chest band output to correlate injury with biomechanical variables and establish thoracic impact tolerance.
An Experimental Model Investigation of the Opening of a Collapsed Untethered Pulmonary Airway
Authors: Perun Matthew L. , Gaver Donald P.
Published: February 2008

We developed an essentially two-dimensional planar benchtop model of an untethered collapsed airway to investigate the influence of fluid properties (viscosity, μ and surface tension, γ) and the structural characteristics (effective diameter, D, longitudinal tension, T, and fluid film thickness, H) on airway reopening. This simplified model was used to quantify the relationship between wall deformation and meniscus curvature during reopening. We measured the pressure (P) required to move the meniscus at a constant velocity (U), and found the dimensionless post-startup pressure (PD/γ) increased monotonically with the capillary number (Ca = μU/γ). Startup pressures depend on the fluid viscosity and piston acceleration, and may significantly increase reopening pressures. Consistently stable steady-state pressures existed when Ca > 0.5. D was the most dominant structural characteristic, which caused an increase in the post-startup pressure (P) for a decrease in D. An increase in H caused a slight decrease in the reopening pressure, but a spatial variation in H resulted in only a transient increase in pressure. T did not significantly affect the reopening pressure. From our planar two-dimensional experiments an effective yield pressure of 3.69 γ/D was extrapolated from the steady-state pressures. Based on these results, we predicted airway pressures and reopening times for axisymmetrically collapsed airways under various disease states. These predictions indicate that increasing surface tension (as occurs in Respiratory Distress Syndrome) increases the yield pressure necessary to reopen the airways, and increasing viscosity (as in cystic fibrosis) increases the time to reopen once the yield pressure has been exceeded.
Axial Strain Measurements in Skeletal Muscle at Various Strain Rates
Authors: Best T. M. , McElhaney J. H. , Garrett W. E. , Myers B. S.
Published: February 2008

A noncontact optical system using high speed image analysis to measure local tissue deformations and axial strains along skeletal muscle is described. The spatial resolution of the system was 20 pixels/cm and the accuracy was ±0.125mm. In order to minimize the error associated with discrete data used to characterize a continuous strain field, the displacement data were fitted with a third order polynomial and the fitted data differentiated to measure surface strains using a Lagrangian finite strain formulation. The distribution of axial strain along the muscle-tendon unit was nonuniform and rate dependent. Despite a variation in local strain distribution with strain rate, the maximum axial strain, Exx = 0.614 ± 0.045 mm/mm, was rate insensitive and occurred at the failure site for all tests. The frequency response of the video system (1000 Hz) and the measurement of a continuous strain field along the entire length of the structure improve upon previous noncontact optical systems for measurement of surface strains in soft tissues.
Development and Validation of a Three-Dimensional Finite Element Model of the Pelvic Bone
Authors: Dalstra M. , Huiskes R. , van Erning L.
Published: February 2008

Due to both its shape and its structural architecture, the mechanics of the pelvic bone are complex. In Finite Element (FE) models, these aspects have often been (over) simplified, sometimes leading to conclusions which did not bear out in reality. The purpose of this study was to develop a more realistic FE model of the pelvic bone. This not only implies that the model has to be three-dimensional, but also that the thickness of the cortical shell and the density distribution of the trabecular bone throughout the pelvic bone have to be incorporated in the model in a realistic way. For this purpose, quantitative measurements were performed on computer tomography scans of several pelvic bones, after which the measured quantities were allocated to each element of the mesh individually. To validate this FE model, two fresh pelvic bones were fitted with strain gages and loaded in a testing machine. Stresses calculated from the strain data of this experiment were compared to the results of a simulation with the developed pelvic FE model.
Finite Element Model Study of Head Impact Based on Hybrid III Head Acceleration: The Effects of Rotational and Translational Acceleration
Authors: Ueno Kazunari , Melvin John W.
Published: February 2008

The translational and rotational components of acceleration measured at the center of gravity of a Hybrid III dummy head were used to investigate their individual and combined effects on a two-dimensional finite element model of the human brain. Each component of acceleration generated distinct patterns of deformation. Although translational acceleration is related to pressure and rotational acceleration has a dominant effect on shear deformations, complete acceleration (combination of translation and rotation) yielded the highest values in all stresses and produced a maximum shear stress at the top of the brain.
Implementation of Strain Rate as a Bone Remodeling Stimulus
Authors: Luo Gangming , Cowin Stephen C. , Sadegh Ali M. , Arramon Yves P.
Published: February 2008

Strain rate is implemented as a stimulus for surface bone remodeling. Using idealized models of trabecular bone structures, the surface remodeling predictions using the strain rate as the stimulus are compared with the predictions using the peak strain magnitude as the stimulus. For a uniaxially loaded cruciform shape, the comparison shows that the two surface remodeling stimuli predict the same final shape under a periodic compressive load, but the two evolutionary paths to final shapes are different. Two biaxially loaded regular grid models of trabecular structure were considered, one a grid of square diamond shaped elements and the other a brick wall patterned grid. For both of these idealized trabecular structures, the comparison shows that the two surface remodeling stimuli predict the same final shape under a periodic compressive load, even from these distinctly different initial grid patterns, and the evolutionary paths to final shapes are quite different. In general the two stimuli do not predict the same remodeling and the conditions under which they do are derived. The models developed are also applied to the data from the animal experiments reported in Goldstein et al. (1991), and it is shown that the strain rate stimulus predicts bone remodeling similar to what was experimentally observed.
Fabrication of Vascular Replicas From Magnetic Resonance Images
Authors: Friedman M. H. , Kuban B. D. , Schmalbrock P. , Smith K. , Altan T.
Published: February 2008

Image processing and Computer Numerical Controlled (CNC) machining techniques have been used to prepare a larger-than-life investment cast of an aortic bifurcation from magnetic resonance images of a replica of the vessel. The technique will facilitate experimental studies of vascular fluid dynamics and permit the in vitro reproduction of flows in living subjects.
A New Load Application System for In Vitro Study of Ligamentous Injuries to the Human Knee Joint
Authors: Bach J. M. , Hull M. L.
Published: February 2008

This paper describes the design and accuracy evaluation of a new six degree of freedom load application system for in vitro testing of the human knee joint. External loads of both polarity in all six degrees of freedom can be applied either individually or in any combination while the knee is permitted to move unconstrained in response to applied loads. The flexion/extension degree of freedom permits the full physiological range of motion. In addition to external loads, forces of the three major muscle groups (quadriceps, hamstrings, gastrocnemius) crossing the joint can be developed. Full automation and rapid convergence of loads to programmed values are achieved through a computer which feeds command signals to servo controller/electro-pneumatic servo valves. The servo valves regulate pressure to pneumatic actuators which develop the various loads. Experiments undertaken to quantify the accuracy of both load and displacement measurements reveal that errors particularly in load measurement are effectively controlled through the apparatus design.
Confined Compression of Canine Annulus Fibrosus Under Chemical and Mechanical Loading
Authors: Drost M. R. , Willems P. , Snijders H. , Huyghe J. M. , Janssen J. D. , Huson A.
Published: February 2008

Uniaxial confined compression and swelling experiments on cylindrical specimens taken either in an axial or in a radial direction from a canine lumbar annulus fibrosus are presented. The loading protocol consisted of a combination of stepwise mechanical and chemical loading. Swelling and consolidation curves of normalized displacement versus square root of normalized time did not show a dependence on site or orientation of the specimen. All stages in which height increases, namely, conditioning, swelling, and desolidation show only slight differences in these normalized curves. Consolidation is initially faster, and later slower. The transport coefficient for axial specimens is higher than for radial specimens, for consolidation e.g., 3.14 ± 1.56 10−10 m2s−1 and 1.11 ± 0.33 10−10 m2s−1 respectively, the biphasic aggregate moduli are 1.01 ± 0.31 MPa and 0.66 ± 0.30 MPa, respectively.
Mechanical Responses of the Rabbit Patello-Femoral Joint to Blunt Impact
Authors: Haut R. C. , Ide T. M. , De Camp C. E.
Published: February 2008

Various studies suggest impact trauma may initially soften cartilage, damage subchondral bone, or a combination thereof. The initial damages are commonly thought due to excessive contact pressures generated on cartilage and the underlying bone. The objective of this research was to develop a small animal model for studying post-traumatic OA and to correlate contact pressures with tissue damage. Blunt insult was graded by dropping a rigid mass onto the hyperflexed hind limb of rabbits. Contact pressure in the patello-femoral joint was measured with pressure sensitive film. One, 3, 6, and 14 days later the animals were euthanized. Damage to cartilage and the underlying bone was assessed visually and in microscopic sections. Indentation experiments were performed on the patellar cartilage with a rigid, flat probe. Contact pressures were nonuniform over the articular surfaces and a high frequency of surface fissures were generated on the lateral facet in severe insults. The appearance of surface fissures correlated better with the magnitude of contact pressure gradients in the damage zone than the magnitude of contact pressures on the facet, per se. Blunt trauma causing surface fissures resulted in a measurable degree of softening in the patellar cartilage, especially close to the defects. Surgical intervention of the joint to insert pressure sensitive film, however, also resulted in significant softening of the cartilage.
Numerical Simulation of Airflow in the Human Nasal Cavity
Authors: Keyhani K. , Scherer P. W. , Mozell M. M.
Published: February 2008

An anatomically correct finite element mesh of the right human nasal cavity was constructed from CAT scans of a healthy adult nose. The steady-state Navier-Stokes and continuity equations were solved numerically to determine the laminar airflow patterns in the nasal cavity at quiet breathing flow rates. In the main nasal passages, the highest inspiratory air speed occurred along the nasal floor (below the inferior turbinate), and a second lower peak occurred in the middle of the airway (between the inferior and middle turbinates and the septum). Nearly 30 percent of the inspired volumetric flow passed below the inferior turbinate and about 10 percent passed through the olfactory airway. Secondary flows were induced by curvature and rapid changes in cross-sectional area of the airways, but the secondary velocities were small in comparison with the axial velocity through most of the main nasal passages. The flow patterns changed very little as total half-nasal flow rate varied between resting breathing rates of 125 m/s and 200 ml/s. During expiration, the peaks in velocity were smaller than inspiration, and the flow was more uniform in the turbinate region. Inspiratory streamline patterns in the model were determined by introducing neutrally buoyant point particles at various locations on the external naris plane, and tracking their path based on the computed flow field. Only the stream from the ventral tip of the naris reached the olfactory airway. The numerically computed velocity field was compared with the experimentally measured velocity field in a large scale (20×) physical model, which was built by scaling up from the same CAT scans. The numerical results showed good agreement with the experimental measurements at different locations in the airways, and confirmed that at resting breathing flow rates, airflow through the nasal cavity is laminar.
Energy Comparison Between Trot, Bound, and Gallop Using a Simple Model
Authors: Nanua P. , Waldron K. J.
Published: February 2008

In this paper, the dynamics of quadruped trot, gallop, and bound will be examined using a simple model for the quadruped. The body of the quadruped is modeled as a uniform bar and the legs are modeled by massless springs. It will be shown that symmetry can be used to study the locomotion of this system. Using symmetry, a technique will be developed to obtain periodic solutions for each of the gaits of the quadruped model. These periodic solutions will be computed at various speeds. The energy levels will be compared for each of the gaits. The exchange of energy between its different forms will be shown for different gaits. It will be shown that even without body flexibility, there are significant savings in energy due to gait transition from trot to gallop. The energy levels will be used to predict the trot-gallop transition speed. These results will be compared with the experimental results for horses and dogs.
Cervical Vertebral Strain Measurements Under Axial and Eccentric Loading
Authors: Pintar F. A. , Yoganandan N. , Pesigan M. , Reinartz J. , Sances A. , Cusick J. F.
Published: February 2008

The mid to lower cervical spine is a common site for compression related injury. In the present study, we determined the patterns of localized strain distribution in the anterior aspect of the vertebral body and in the lateral masses of lower cervical three-segment units. Miniature strain gages were mounted to human cadaveric vertebrae. Each preparation was line-loaded using a knife-edge oriented in the coronal plane that was moved incrementally from anterior to posterior to induce compression-flexion or compression-extension loading. Uniform compressive loading and failure runs were also conducted. Failure tests indicated strain shifting to “restabilize” the preparation after failure of a component. Under these various compressive loading vectors, the location which resulted in the least amount of deformation for a given force application (i.e., stiffest axis) was quantified to be in the region between 0.5–1.0 cm anterior to the posterior longitudinal ligament. The location in which line-loading produced no rotation (i.e., balance point) was in this region; it was also close to where the vertebral body strains change from compressive to tensile. Strain values from line loading in this region produced similar strains as recorded under uniform compressive loading, and this was also the region of minimum strain. The region of minimum strain was also more pronounced under higher magnitudes of loading, suggesting that as the maximum load carrying capacity is reached the stiffest axis becomes more well defined.
A Technique for Calibrating Measurements From Photographs of Sliced Specimens
Authors: Han JungSoo , Wang Huicong , Ryu Jaiyoung , Rowen Bruce
Published: February 2008

Determining the geometry of articular joint surfaces is critical to the study of human joint mechanics. Photographs of sliced specimens (PSS) is currently one of the most popular methods used to determine surface geometry. This study sought to improve the photographs of sliced specimens method through a new calibration technique that includes a mathematical model and a precise plastic grating (calibration grid). Simulations showed that calibration results for x and y coordinates using the new technique attained a high degree of accuracy that was independent of camera and projector lens quality, degree of parallelity between the projector and digitizing table and selection of the area to be calibrated.
Membrane Model of Endothelial Cells and Leukocytes. A Proposal for the Origin of a Cortical Stress
Authors: Schmid-Scho¨nbein Geert W. , Kosawada Tadashi , Skalak Richard , Chien Shu
Published: February 2008

Previous models of the erythrocyte membrane have been based on the assumption that the resting curvature of the membrane is either flat or has a small curvature relative to the overall cell dimension. In contrast, several recent experimental observations, both in leukocytes and in endothelial cells, suggest that local regions of the membrane may have high membrane curvature in the resting state. The resting curvature may be of the order of plasmalemmal vesicles in endothelial cells or surface membrane folds on leukocytes. A tension is required to unfold the membrane with strain energy which depends largely on mean curvature. It is proposed that the tendency of endothelial or leukocyte membranes to wrinkle in the unstressed state may provide a restoring force, i.e. a cortical tension.
A Molecular Model of Proteoglycan-Associated Electrostatic Forces in Cartilage Mechanics
Authors: Buschmann M. D. , Grodzinsky A. J.
Published: February 2008

Measured values of the swelling pressure of charged proteoglycans (PG) in solution (Williams RPW, and Comper WD; Biophysical Chemistry 36:223, 1990) and the ionic strength dependence of the equilibrium modulus of PG-rich articular cartilage (Eisenberg SR, and Grodzinsky AJ; J Orthop Res 3: 148, 1985) are compared to the predictions of two models. Each model is a representation of electrostatic forces arising from charge present on spatially fixed macromolecules and spatially mobile micro-ions. The first is a macroscopic continuum model based on Donnan equilibrium that includes no molecular-level structure and assumes that the electrical potential is spatially invariant within the polyelectrolyte medium (i.e. zero electric field). The second model is based on a microstructural, molecular-level solution of the Poisson-Boltzmann (PB) equation within a unit cell containing a charged glycosaminoglycan (GAG) molecule and its surrounding atmosphere of mobile ions. This latter approach accounts for the space-varying electrical potential and electrical field between the GAG constituents of the PG. In computations involving no adjustable parameters, the PB-cell model agrees with the measured pressure of PG solutions to within experimental error (10%), whereas the ideal Donnan model overestimates the pressure by up to 3-fold. In computations involving one adjustable parameter for each model, the PB-cell model predicts the ionic strength dependence of the equilibrium modulus of articular cartilage. Near physiological ionic strength, the Donnan model overpredicts the modulus data by 2-fold, but the two models coincide for low ionic strengths (C0 < 0.025M) where the spatially invariant Donnan potential is a closer approximation to the PB potential distribution. The PB-cell model result indicates that electrostatic forces between adjacent GAGs predominate in determining the swelling pressure of PG in the concentration range found in articular cartilage (20–80 mg/ml). The PB-cell model is also consistent with data (Eisenberg and Grodzinsky, 1985, Lai WM, Hou JS, and Mow VC; J Biomech Eng 113: 245, 1991) showing that these electrostatic forces account for ˜ 1/2 (290kPa) the equilibrium modulus of cartilage at physiological ionic strength while absolute swelling pressures may be as low as ˜ 25 – 100kPa. This important property of electrostatic repulsion between GAGs that are highly charged but spaced a few Debye lengths apart allows cartilage to resist compression (high modulus) without generating excessive intratissue swelling pressures.
The Effect of Pulsatile Frequency on Wall Shear in a Compliant Cast of a Human Aortic Bifurcation
Authors: Kuban Barry D. , Friedman Morton H.
Published: February 2008

A realistically compliant flow-through cast of a human aortic bifurcation was perfused with two almost identical physiological flow waves differing in pulsatile frequency. Near-wall fluid velocities were measured with a laser Doppler velocimeter at 14 sites along the flow divider and the lateral walls of the aorta and iliac arteries. The wall position at each site was tracked using a linescan camera. The temporal wall shear rate at each site was then calculated from the near-wall velocity profile and the instantaneous wall position. Increasing the frequency reduced the oscillatory component of shear rate at sites where it was greater than average, and increased it at sites where it was less, effectively reducing its site to site variability. Pulsatile frequency had no significant effect on mean shear rate at most sites. The phase shift between wall shear and radial strain was governed by the phase of the shear, and was linearly related to the extent of site dependent shear reversal The mean shear rate was inversely related to the extent of shear reversal. If atherosclerotic development depends chiefly on mean shear rate, heart rate would not be expected to affect susceptibility, however, if only the wall sites experiencing the lowest maximum shears are vulnerable, then the effect of increasing the heart rate would seem to be beneficial.
Flow Structures at the Proximal Side-to-End Anastomosis. Influence of Geometry and Flow Division
Authors: Hughes P. E. , How T. V.
Published: February 2008

Flow structures were visualized in transparent polyurethane models of proximal side-to-end vascular anastomoses, using planar illumination of suspended tracer particles. Both the effects of geometry and flow division were determined under steady and pulsatile flow conditions, for anastomosis angles of 15, 30, and 45 degrees. The flow patterns were highly three-dimensional and were characterized by a series of vortices in the fully occluded distal artery and two helical vortices aligned with the axis of the graft. In steady flow, above a critical Reynolds number, the flow changed from a laminar regime to one displaying time-dependent behavior. In particular, significant fluctuating velocity components were observed in the distal artery and particles were shed periodically from the occluded artery into the graft. Pairs of asymmetric flow patterns were also observed in the graft, before the onset of the time-dependent flow regime. The critical Reynolds number ranged from 427 to 473 and appeared to be independent of anastomosis angle. The presence of a patent distal artery had a significant effect on the overall flow pattern and led to the formation of a large recirculation region at the toe of the anastomosis. The main structures observed in steady flow, such as vortices in the distal artery and helical flow in the graft, were also seen during the pulsatile cycle. However, the secondary flow components in the graft were more pronounced in pulsatile flow particularly during deceleration of the flow waveform. At higher mean Reynolds numbers, there was also a greater mixing between fluid in the occluded arterial section and that in the graft.