Combined effect of grain refinement and surface modification of pure titanium on the attachment of mesenchymal stem cells and osteoblast-like SaOS-2 cells.

Surface modification is an important step in production of medical implants. Surface roughening creates additional surface area to enhance the bonding between the implant and the bone. Recent research provided a means to alter the microstructure of titanium by severe plastic deformation (SPD) in order to increase its strength, and thereby reduce the size of the implants (specifically, their diameter). The purpose of the present study was to examine the effect of bulk microstructure of commercially pure titanium with coarse-grained (CG) and ultrafine-grained (UFG) bulk structure on the surface state of these materials after surface modification by sand blasting and acid etching (SLA). It was shown that SLA-modified surface characteristics, in particular, roughness, chemistry, and wettability, were affected by prior SPD processing. Additionally, biocompatibility of UFG titanium was examined using osteosarcoma cell line SaOS-2 and primary human adipose-derived mesenchymal stem cell (adMSC) cultures. Enhanced cell viability as well as increased matrix mineralization during osteogenic differentiation of MSCs on the surface of ultrafine-grained titanium was shown.

Effect of bulk microstructure of commercially pure titanium on surface characteristics and fatigue properties after surface modification by sand blasting and acid-etching.

Surface modification techniques are widely used to enhance the biological response to the implant materials. These techniques generally create a roughened surface, effectively increasing the surface area thus promoting cell adhesion. However, a negative side effect is a higher susceptibility of a roughened surface to failure due to the presence of multiple stress concentrators. The purpose of the study reported here was to examine the effects of surface modification by sand blasting and acid-etching (SLA) on the microstructure and fatigue performance of coarse-grained and ultrafine-grained (UFG) commercially pure titanium. Finer grain sizes, produced by equal channel angular pressing, resulted in lower values of surface roughness in SLA-processed material. This effect was associated with greater resistance of the UFG structure to plastic deformation. The fatigue properties of UFG Ti were found to be superior to those of coarse-grained Ti and conventional Ti-6Al-4V, both before and after SLA-treatment.

Quantitative analysis of human masticatory muscles using magnetic resonance imaging.

OBJECTIVES: The objective of this study was to quantitatively evaluate the correlation between left and right masticatory muscle volumes in normal subjects. METHODS: Contiguous 1 mm MR scans were obtained of 12 normal adult subjects aged 20-25 years using a Siemens 1.5 T MR scanner. The volumes of the human masticatory muscles (masseter, lateral and medial pterygoid) were measured from the scans using our previously proposed method. To test for inter- and intraobserver reproducibility, measurements were performed by two users on two separate occasions, with a span of 2 weeks between them and with the previous results blinded. Good inter- and intraobserver reproducibility was achieved in our study. RESULTS: The mean volumes for left and right masseters, and lateral and medial pterygoids were 29.54 cm3, 29.65 cm3, 9.47 cm3, 10.23 cm3, 8.69 cm3 and 8.92 cm3, respectively. The Pearson correlation coefficients between the volumes of the left and right masseters, lateral and medial pterygoids are 0.969, 0.906 and 0.924, respectively. CONCLUSIONS: The computed volumes of the masticatory muscles show a strong correlation between the volumes of the left and right masseters, and lateral and medial pterygoids for normal adult subjects. The total masticatory muscle volume on the left and right sides of normal subjects is similar.

3D segmentation and quantification of a masticatory muscle from MR data using patient-specific models and matching distributions.

A method is proposed for 3D segmentation and quantification of the masseter muscle from magnetic resonance (MR) images, which is often performed in pre-surgical planning and diagnosis. Because of a lack of suitable automatic techniques, a common practice is for clinicians to manually trace out all relevant regions from the image slices which is extremely time-consuming. The proposed method allows significant time savings. In the proposed method, a patient-specific masseter model is built from a test dataset after determining the dominant slices that represent the salient features of the 3D muscle shape from training datasets. Segmentation is carried out only on these slices in the test dataset, with shape-based interpolation then applied to build the patient-specific model, which serves as a coarse segmentation of the masseter. This is first refined by matching the intensity distribution within the masseter volume against the distribution estimated from the segmentations in the dominant slices, and further refined through boundary analysis where the homogeneity of the intensities of the boundary pixels is analyzed and outliers removed. It was observed that the left and right masseter muscles' volumes in young adults (28.54 and 27.72 cm(3)) are higher than those of older (ethnic group removed) adults (23.16 and 22.13 cm(3)). Evaluation indicates good agreement between the segmentations and manual tracings, with average overlap indexes for the left and right masseters at 86.6% and 87.5% respectively.

Masseter segmentation using an improved watershed algorithm with unsupervised classification.

The watershed algorithm always produces a complete division of the image. However, it is susceptible to over-segmentation and sensitivity to false edges. In medical images this leads to unfavorable representations of the anatomy. We address these drawbacks by introducing automated thresholding and post-segmentation merging. The automated thresholding step is based on the histogram of the gradient magnitude map while post-segmentation merging is based on a criterion which measures the similarity in intensity values between two neighboring partitions. Our improved watershed algorithm is able to merge more than 90% of the initial partitions, which indicates that a large amount of over-segmentation has been reduced. To further improve the segmentation results, we make use of K-means clustering to provide an initial coarse segmentation of the highly textured image before the improved watershed algorithm is applied to it. When applied to the segmentation of the masseter from 60 magnetic resonance images of 10 subjects, the proposed algorithm achieved an overlap index (kappa) of 90.6%, and was able to merge 98% of the initial partitions on average. The segmentation results are comparable to those obtained using the gradient vector flow snake.

Medical image segmentation using watershed segmentation with texture-based region merging.

The use of the watershed algorithm for image segmentation is widespread because it is able to produce a complete division of the image. However, it is susceptible to over-segmentation and in medical image segmentation, this meant that that we do not have good representations of the anatomy. We address this issue by thresholding the gradient magnitude image and performing post-segmentation merging on the initial segmentation map. The automated thresholding technique is based on the histogram of the gradient magnitude map while the post-segmentation merging is based on the similarity in textural features (namely angular second moment, contrast, entropy and inverse difference moment) belonging to two neighboring partitions. When applied to the segmentation of various facial anatomical structures from magnetic resonance (MR) images, the proposed method achieved an overlap index of 92.6% compared to manual contour tracings. It is able to merge more than 80% of the initial partitions, which indicates that a large amount of over-segmentation has been reduced. Results produced using watershed algorithm with and without the proposed and proposed post-segmentation merging are presented for comparisons.

Estimation and presentation of blood flow and velocity from angiographic scans in the human cerebral arterial system.

This paper provides an overview of blood flow in the arterial system and aims to estimate the blood velocity from cerebral angiography scans without having acquired data on velocity by using Murray's Law. The estimation technique post-processes the scan and provides crucial 3D visual data for the development of a visualization program of the blood flow in the human brain.

Medical image segmentation using feature-based GVF snake.

We propose a feature-based GVF snake for medical image segmentation here. Feature-based criteria are introduced for the GVF snake to stop its iterations. Without these criteria, the GVF snake might continue its iterations even though it has converged at the targeted object and result in longer computational time. The feature here is the area of the targeted object. Our proposed method comprises of two stages, namely the training stage and the segmentation stage. In the training stage, we acquire prior knowledge on the relative area of the targeted object from training data. In the segmentation stage, the proposed feature-based GVF snake is applied to segment the object from the image after computing the estimated area of the targeted object. In our proposed method, the GVF snake stops its iterations when the area bounded by its propagation is approximately equal to the estimated area and when it undergoes little change over two consecutive iterations. To illustrate the effectiveness of our proposed method, we applied it to the segmentation of the masseter muscle, which is the strongest jaw muscle, from 2-D magnetic resonance (MR) images. Numerical evaluation done indicates good agreement between the computerized and manual segmentations, with mean overlap of 92%.

A study on shape determinative slices for the masseter muscle.

In this paper, we localize the shape-determinative slices of the masseter, which plays a critical role in the mastication system, from magnetic resonance (MR) data sets for clinical purposes. Shape-based criteria were used to locate the candidates for determinative slices from training data. The localization process involves tracking of the centroid and detecting the locations where the structure of the masseter undergoes an abrupt change in orientation. Having determined all the candidates which satisfy the criteria, fuzzy-c-means (FCM) clustering technique was used to establish the determinative slices. Localization of these slices will facilitate the building of more accurate models. It will also allow for more accurate computerized extraction of the masseter from MR data. In our work here, a hybrid method to shape-based interpolation is used to build the masseter model from magnetic resonance (MR) data sets, and the mean overlap index (¿) achieved is 87.7%. Extraction of the masseter was carried out using our earlier proposed method and the mean ¿ achieved is 8.9%. This indicates good agreement between the results obtained using computerized technique and those contained using manual contour tracing.

Induction of autoimmune thyroiditis and hypothyroidism by immunization of immunoactive T cell epitope of thyroid peroxidase.

Autoimmune thyroiditis (AT) is characterized by a continuous inflammatory self-destructive process that eventually leads to chronic progressive dysfunction of the thyroid. In a previously established experimental AT model, C57bl/6 mice immunized with recombinant mouse thyroid peroxidase (TPO) (rmTPO) developed lymphocytic thyroiditis and anti-TPO antibody but not chronic hypothyroidism. To determine the immunodominant epitope(s) of TPO, T cell proliferation assays were performed in which rmTPO-primed lymph nodes cells were reacted with recombinant mTPO fragments or short overlapping synthetic TPO peptides. Within residue 405-849, peptide 540-559 gave the maximum proliferation response with a stimulation index more than 12. Mice immunized with peptide 540-559 developed antibody against rmTPO and native mouse TPO protein, lymphocytic thyroiditis, and hypothyroidism. In conclusion, this study demonstrated that TPO is the autoantigen for the development of lymphocyte thyroiditis and thyroid dysfunction, and peptide 540-559 is the immunodominant T cell epitope of TPO. Identification of T cell epitopes of TPO may enable the development of immunotherapy to prevent chronic hypothyroidism in AT.

Knowledge-driven 3-D extraction of the masseter from MR data.

In this paper, we propose a knowledge-driven highly automatic methodology for extracting the masseter from magnetic resonance (MR) data sets for clinical purposes. The masseter is a muscle of mastication which acts to raise the jaw and clench the teeth. In our initial work, we designed a process which allowed us to perform 2-D segmentation of the masseter on 2-D MR images. In the methodology proposed here, we make use of ground truth to first determine the index of the MR slice in which we will carry out 2-D segmentation of the masseter. Having obtained the 2-D segmentation, we will make use of it to determine the region of interest (ROI) of the masseter in the other MR slices belonging to the same data set. The upper and lower thresholds applied to these MR slices, for extraction of the masseter, are determined through the histogram of the 2-D segmented masseter. Visualization of the 3-D masseter is achieved via volume rendering. Our methodology has been applied to five MR data sets. Validation was done by comparing the segmentation results obtained by using our proposed methodology against manual contour tracings, obtaining an average accuracy of 83.5%

In vitro effects of local anaesthetics on the thromboelastographic profile of parturients.

BACKGROUND: Post-dural puncture headache can be an incapacitating complication of obstetric epidural analgesia/anaesthesia and early or prophylactic epidural blood patch (EBP) is one of the treatment options. Although local anaesthetic (LA) agents have been shown to have anticoagulation effects in vitro, peri-partum women are known to be hypercoagulable. We postulated that the presence of residual LA might not result in impaired haemostasis of the EBP in parturients. METHODS: Blood samples from 10 healthy term parturients were subjected to thromboelastography after the addition of four different LA (lidocaine, bupivacaine, levobupivacaine, and ropivacaine) preparations. RESULTS: There was a significant reduction in reaction (R) and coagulation (K) time (P<0.001, P<0.05) and an increase in alpha degrees angle (P<0.01) when comparing undiluted blood with the saline control group. Maximum amplitude (MA) and clot lysis (Ly30) did not change significantly despite the 50% dilution. The thromboelastographic parameters of all four LA-treated groups were no different from their saline controls and from each other. CONCLUSION: At clinical dosages, LA did not cause any hypocoagulable changes on the thromboelastographic profile of healthy parturients.

Neonatal post-intubation subglottic stenosis.

Acquired subglottic stenosis is a compication or neonatal endotracheal intubation. Although it is rare, it contributes significantly to the morbidity and physical well being of post extubated neonates. A 20-day old neonate, ventilated for meconium aspiration syndrome and persistent fetal circulation, presented with marked stridor and respiratory embarrassment. A stenosed subglottic area was found on rigid bronchoscopy. Anterior cricoid split was performed to relieve the obstruction. He is asymptomatic post operatively.

Development of a murine model of autoimmune thyroiditis induced with homologous mouse thyroid peroxidase.

Autoimmune thyroid disease (AITD) is a common autoimmune disease. Thyroid peroxidase (TPO) is a well characterized autoantigen in AITD. Autoantibodies and autoreactive T lymphocytes to TPO are believed to play a major role in the pathogenesis of lymphocytic thyroiditis. To understand the pathogenic mechanisms of AITD and the role of TPO, we have established a mouse model of lymphocytic thyroiditis by immunizing C57Bl/6 (H-2(b)), CBA (H-2(k)), and C57Bl/6 x CBA F1 mice with recombinant murine TPO (rmTPO) ectodomain comprising amino acid residue 1-837 produced in Escherichia coli. Mice were immunized with 30 microg purified ectodomain in complete Freund's adjuvant. Antibodies against rmTPO were detected in the serum of all mice from day 21 onward. Draining lymph node cells from rmTPO-immunized animals showed dose-dependent proliferation to TPO stimulation. Mice killed at d 50 and 90 revealed variable degrees of thyroiditis with infiltration of mononuclear cells and destruction of thyroid follicles. C57Bl/6 and the F1 mice, in comparison with CBA mice, showed a greater degree of thyroiditis. There was a lack of correction between the intensity of thyroiditis and the anti-TPO response. Immunotyping of the thyroid cellular infiltrates showed predominantly CD4+ T cells and B220+ B cells but scanty CD8+ T cells. None of the control mice injected with the purified fusion partner developed anti-TPO antibodies and thyroiditis. In conclusion, a genuine autoimmune mouse model of lymphocytic thyroiditis was established using autologous mouse TPO. This new model induced with autologous TPO will lead to a better understanding of the mechanisms in destructive thyroiditis and will assist in the development of new strategies for modulating the pathogenic immune response.

The effects of hypertonic saline solution (7.5%) on coagulation and fibrinolysis: an in vitro assessment using thromboelastography.

We studied the effects of hypertonic (7.5%) and normal saline on coagulation and fibrinolysis in an in vitro model using thromboelastography of human whole blood. Reaction times increased and alpha angles decreased with hypertonic saline replacement at 7.5% blood volume compared with similar dilution with normal saline. At 10% blood volume replacement with hypertonic saline, reaction and coagulation times were significantly increased and alpha angles were decreased. Clot lysis at 30 min was also significantly reduced. We conclude that 7.5% hypertonic saline solution has anticoagulant effects if it replaces 7.5% or more of blood volume.

Intraoperative single-shot "3-in-1" femoral nerve block with ropivacaine 0.25%, ropivacaine 0.5% or bupivacaine 0.25% provides comparable 48-hr analgesia after unilateral total knee replacement.

PURPOSE: To compare analgesia after intraoperative single shot "3-in-1" femoral nerve block (FNB) in combination with general anesthesia using ropivacaine 0.25%, ropivacaine 0.5% with bupivacaine 0.25% for total knee replacement (TKR). METHODS: We performed a randomized, double-blind study in 48 patients for elective TKR under general anesthesia. Patients were randomized to one of four groups (C: sham block, R1: "3-in-1" FNB using 30 mL of ropivacaine 0.25%, R2: "3-in-1" FNB using 30 mL of ropivacaine 0.5%, B: "3-in-1" FNB using 30 mL of bupivacaine 0.25%). Verbal pain score (VPS) both at rest and movement were assessed for 48 hr after TKR (0=none; 1=mild; 2=moderate; 3=severe). Total morphine consumption and its associated side effects, duration of hospitalization after operation were also compared. RESULTS: There were no differences in patients' physical characteristics, intraoperative morphine usage, operation time, tourniquet time or length of hospitalization between the four groups. When compared with group C, the VPS was significantly lower in groups R1, R2 and B at one, four, eight, 24 and 48 hr after TKR (P <0.05). The morphine requirement of groups R1, R2 and B were also significantly lower when comparing with group C up to 48 hr postoperatively (P <0.05). There were no significant differences in VPS and postoperative morphine requirement at any time between groups R1, R2 and B. CONCLUSION: "3-in-1" FNB with ropivacaine provided analgesia that was clinically comparable to that of bupivacaine up to 48 hr after TKR. Increasing the concentration of ropivacaine from 0.25% to 0.5% failed to improve the postoperative analgesia of "3-in-1" FNB.

Effect of ondansetron pretreatment on pain after rocuronium and propofol injection: a randomised, double-blind controlled comparison with lidocaine.

In a randomised, controlled, double-blinded trial to study the effect of ondansetron pretreatment on the pain produced after intravenous injection of rocuronium and propofol in comparison with lidocaine, 60 patients were randomly assigned to one of three groups. Group 1 received 5 ml of intravenous 0.9% sodium chloride solution pretreatment, group 2 received ondansetron 4 mg (2 mg.ml-1 solution) diluted into a 5-ml solution, and group 3 received 50 mg lidocaine (5 ml 1% solution); this was followed 1 min later by rocuronium and propofol. Pain was reduced significantly in the ondansetron and lidocaine groups (p < 0.0001) compared with placebo, and significantly better with lidocaine than with ondansetron (p = 0.02). We conclude that ondansetron is effective in relieving the pain of rocuronium but is not as effective as lidocaine.

CCR1-specific non-peptide antagonist: efficacy in a rabbit allograft rejection model.

The classic signs of acute cellular rejection during organ transplantation include the infiltration of mononuclear cells into the interstitium. This recruitment of leukocytes into the transplanted tissue is promoted by chemokines like RANTES. Since RANTES is a potent agonist for the CC chemokine receptor CCR1, we examined whether the CCR1 antagonist BX 471 was efficacious in a rabbit kidney transplant rejection model. BX 471 was able to compete with high affinity with the CCR1 ligands MIP-1alpha and RANTES for binding to HEK 293 cells expressing rabbit CCR1. BX 471 was a competitive antagonist of rabbit CCR1 in Ca(2+) flux studies. Two separate studies in which animals were subcutaneously implanted with slow release pellets of BX 471 demonstrated that animals implanted with BX 471 had increased survival compared with untreated controls or animals implanted with placebo. The mean survival time for the placebo group was 12.33+/-1.7 days. The animals in the BX 471 treated group had mean survival times of 16.9+/-2.1 and 16.0+/-1.7 days, respectively, for the two studies. Analysis of the combined data by Student t-test gave a P value of 0.03 that is significant at the 0.05 level. In addition, there was a marked reduction in the urea and creatinine levels in the BX 471 treated animals compared with the control and placebo groups in both studies. Finally, pathologic analysis of the kidneys in the rabbit renal transplantation model from animals in the different groups showed that BX 471 was similar to cyclosporin in its ability to prevent extensive infarction of transplanted kidneys. Based on the data from these studies, BX 471 shows clear efficacy at the single dose tested compared with animals treated with placebo.

A non-peptide functional antagonist of the CCR1 chemokine receptor is effective in rat heart transplant rejection.

Chemokines like RANTES appear to play a role in organ transplant rejection. Because RANTES is a potent agonist for the chemokine receptor CCR1, we examined whether the CCR1 receptor antagonist BX471 is efficacious in a rat heterotopic heart transplant rejection model. Treatment of animals with BX471 and a subtherapeutic dose of cyclosporin (2.5 mg/kg), which is by itself ineffective in prolonging transplant rejection, is much more efficacious in prolonging transplantation rejection than animals treated with either cyclosporin or BX471 alone. We have examined the mechanism of action of the CCR1 antagonist in in vitro flow assays over microvascular endothelium and have discovered that the antagonist blocks the firm adhesion of monocytes triggered by RANTES on inflamed endothelium. Together, these data demonstrate a significant role for CCR1 in allograft rejection.