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At least 793 records · Page 44Linked to original sources
PubMed2006

Effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone consolidation on distraction osteogenesis: a preliminary study in rabbit mandibles.

AIM: To examine the effectiveness of administering recombinant human bone morphogenetic protein-2 (rhBMP-2) in distraction osteogenesis. MATERIAL AND METHODS: Twenty-one mature male Japanese white rabbits underwent unilateral mandibular osteotomy. After 5 days, the osteotomized mandibles were distracted 1mm/day for 10 days. On the first day (groups A-1 [n=4] and A-2 [n=4]) or on the last day (group B [n=5]) of distraction, rhBMP-2 mixed with collagen gel was injected into the distraction zone. In control groups (groups C-1 [n=4] and C-2 [n=4]), the mandibles were distracted without rhBMP-2 injection. At the end of the distraction period (groups A-1 and C-1) and after 2 weeks of consolidation (groups A-2, B, and C-2), the distracted mandibles were harvested and examined with soft radiographs, peripheral quantitative computed tomography (pQCT), and microscopy. RESULTS: Radioopacity was more marked in the distraction zone of the groups with rhBMP-2 than in control groups. The mineral density of the cortical bone (BMD) was higher in groups B and A-2 than in group C-2. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. The cortical BMD was higher in group A-1 than in group C-1. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. CONCLUSION: These results suggest that rhBMP-2 promotes bone formation in distraction osteogenesis.

Absorptiometry, Photon↗
PubMed2007

Fatigue effects on tracking performance and muscle activity.

It has been suggested that fatigue affects proprioception and consequently movement accuracy, the effects of which may be counteracted by increased muscle activity. To determine the effects of fatigue on tracking performance and muscle activity in the M. extensor carpi radialis (ECR), 11 female participants performed a 2-min tracking task with a computer mouse, before and immediately after a fatiguing wrist extension protocol. Tracking performance was significantly affected by fatigue. Percentage time on target was significantly lower in the first half of the task after the fatigue protocol, but was unaffected in the latter half of the task. Mean distance to target and the standard deviation of the distance to target were both increased after the fatigue protocol. The changed performance was accompanied by higher peak EMG amplitudes in the ECR, whereas the static and the median EMG levels were not affected. The results of this study showed that subjects changed tracking performance when fatigued in order to meet the task instruction to stay on target. Contrary to our expectations, this did not lead to an overall higher muscle activity, but to a selective increase in peak muscle activity levels of the ECR.

Adult↗
PubMed2004

A fast flexible ink-jet printing method for patterning dissociated neurons in culture.

We present a new technique that uses a custom-built ink-jet printer to fabricate precise micropatterns of cell adhesion materials for neural cell culture. Other work in neural cell patterning has employed photolithography or "soft lithographic" techniques such as micro-stamping, but such approaches are limited by their use of an un-alterable master pattern such as a mask or stamp master and can be resource-intensive. In contrast, ink-jet printing, used in low-cost desktop printers, patterns material by depositing microscopic droplets under robotic control in a programmable and inexpensive manner. We report the use of ink-jet printing to fabricate neuron-adhesive patterns such as islands and other shapes using poly(ethylene) glycol as the cell-repulsive material and a collagen/poly-D-lysine (PDL) mixture as the cell-adhesive material. We show that dissociated rat hippocampal neurons and glia grown at low densities on such patterns retain strong pattern adherence for over 25 days. The patterned neurons are comparable to control, un-patterned cells in electrophysiological properties and in immunocytochemical measurements of synaptic density and inhibitory cell distributions. We suggest that an inexpensive desktop printer may be an accessible tool for making micro-island cultures and other basic patterns. We also suggest that ink-jet printing may be extended to a range of developmental neuroscience studies, given its ability to more easily layer materials, build substrate-bound gradients, construct out-of-plane structure, and deposit sources of diffusible factors.

Animals↗
PubMed2006

Trabecular bone status in ultradistal tibia under habitual gait loading: a pQCT study in postmenopausal women.

This study investigated regional volumetric trabecular bone mineral density (tBMD) and bone area at the ultradistal tibia in Chinese women using peripheral quantitative computed tomography. Fifty-six postmenopausal women aged 47-62 yr participated in BMD measurements at baseline and 22 of them were followed at both 1-yr and 3-yr follow-up scans. Regional baseline tBMD, rate of annual bone loss, and trabecular bone area were determined. Baseline measurements showed that the tBMD of both the posterior (252.9+/-63.4 mg/cm(3)) and medial (226.6+/-68.9 mg/cm(3)) regions was significantly higher than that of the anterior (126.3+/-61.9 mg/cm(3)) and lateral regions (149.8+/-50.6 mg/cm(3)), respectively (p<0.001). Both the 1-yr and 3-yr follow-up measurements showed that there was significant physiological annual tBMD loss on an average of 1.61%, at the four regions. Inter-slice regional tBMD and trabecular bone area measurements demonstrated a significant linear decrease from the distal to proximal aspects (p<0.001). Findings suggest that dynamic compressive loading during the heel strike and the body weight vector shifting toward the medial aspect during the stance phase in a normal gait might account for the regional tBMD differences. Increased tBMD and bone area toward the distal tibial endplate may adapt to withstand the axial impact loading. However, the low-impact weight-bearing nature of a normal gait may not be osteogenic to prevent regional bone loss. An exercise program specific to the women at risk should be contemplated.

Adaptation, Physiological↗
PubMed2005

Effect of platelet-rich plasma with autogenous bone graft for maxillary sinus augmentation in a rabbit model.

PURPOSE: To evaluate the effect of platelet-rich plasma (PRP) on autogenous bone graft remodeling during sinus augmentation in a rabbit model. MATERIALS: Twelve New Zealand White rabbits were divided randomly into 3 groups based on their time of sacrifice (2, 4, and 8 weeks). All animals underwent a general anesthetic and harvesting of an autogenous bone graft from the right iliac crest with subsequent bilateral maxillary sinus augmentation. PRP was prepared via standard approved technique by acquiring 21 cc of autogenous blood and performing differential centrifugation to obtain PRP. One cc of PRP was produced that was mixed with bovine topical thrombin and calcium chloride. The left maxillary sinus received only autogenous bone, while the right maxillary sinus received a mixture of PRP mixed with autogenous bone, thus each animal acted as its own control. Equal volumes of bone were inserted in each maxillary sinus. Animals were sacrificed at 2, 4, and 8 weeks and all specimens were harvested for peripheral quantitative computed tomography (pQ-CT), static, and dynamic and histomorphometric analysis. RESULTS: Student t tests were performed comparing bone density via pQ-CT analysis, histomorphometric parameters of total bone area, and bone apposition rate. PRP had no statistically significant effect on bone graft healing in maxillary sinus augmentation when compared using standard pQ-CT, static, and dynamic histologic criteria. CONCLUSION: This study fails to find a direct stimulatory effect of PRP on healing of autogenous bone grafts using pQ-CT, static, and dynamic histomorphometric analyses.

Alveolar Ridge Augmentation↗
PubMed2004

Alterations in bone characteristics associated with glycemic control in adolescents with type 1 diabetes mellitus.

OBJECTIVE: To determine whether bone characteristics in adolescents with type 1 diabetes mellitus (DM) are influenced by blood glucose regulation and disease duration. The subjects were adolescents with type 1 DM (n=55) recruited from the University of Utah's Primary Children's Pediatric Diabetes Treatment Center. A reference database consisting of 95 healthy adolescents from the same geographic area was used for comparison.Study design Measurements of the tibia by peripheral quantitative computed tomography were made to assess cortical and trabecular bone characteristics. Hip, spine, and whole body characteristics were measured by dual-energy x-ray absorptiometry. Height, weight, health histories, Tanner stage, disease duration, insulin regimen, and glycosylated hemoglobin values were recorded. RESULTS: Age, maturation, and body size and composition values were similar between the subjects with type 1 DM and reference. Subjects with type 1 DM had lower tibia trabecular and femoral neck density and whole body mineral content and density. The mean glycosylated hemoglobin value was inversely related to tibia trabecular bone density (R(2)=-0.30) and whole body bone mineral content (R(2)=-0.25) and accounted for 3.0% to 8.9% of the variance. CONCLUSIONS: Altered bone mineral acquisition in adolescents with type 1 DM may limit peak bone mass acquisition and increase the risk of osteoporosis in later life.

Absorptiometry, Photon↗
PubMed2004

Bone mineral acquisition in adolescents with type 1 diabetes.

OBJECTIVE: To track bone mineral acquisition in adolescents with type 1 diabetes (DM). STUDY DESIGN: Subjects were adolescents, ages 12 to 18 years, with DM (n=42) and a healthy regional reference (n=199). Measurements of tibia bone characteristics by peripheral quantitative computed tomography (pQCT) and spine and whole body (WB) by dual-energy x-ray absorptiometry (DEXA), anthropometrics, and lifestyle questionnaires were obtained during a 12-month period. Disease duration, insulin dose, renal function, and glycosylated hemoglobin (HbA1c) values for the previous 12 months were recorded. RESULTS: Body size and maturation were similar between groups. DM had lower tibia, spine, and WB bone characteristics but greater muscle mass (LBM) and lower bone mineral content (BMC)/LBM at baseline and 12 months. Annual gains for tibia cortical bone and WB BMC/LBM were lower and inversely related to HbA1c levels (R=-0.36 to -0.51), whereas spine area and density and WBLBM were greater and were predicted by pubertal-driven growth. Overall, the DM cohort had 8.5% less WB BMC/LBM, suggesting that bone mineral deposition was not adequately adapted to muscle gains. CONCLUSIONS: Adolescents with type 1 diabetes continue to have smaller bone mass and bone size despite normal growth and maturation. Poor metabolic control appears to negatively influence bone mineral acquisition.

Absorptiometry, Photon↗
PubMed2005

Speed of sound: relation to geometric characteristics of bone in children, adolescents, and adults.

OBJECTIVES: To investigate the relation between volumetric bone mineral density (vBMD) and speed of sound (SOS). STUDY DESIGN: Total and trabecular vBMD were measured by peripheral quantitative computed tomography at the forearm in a population of 216 individuals of a pediatric outpatient clinic. Moreover, SOS was measured by a quantitative ultrasound device (QUS) at the thumb, patella, and os calcis. RESULTS: Linear regression analysis revealed that the prediction of SOS by vBMD is relatively weak (R2 < 0.1). Moreover, body height and measures of bone size have a stronger influence on SOS than vBMD. The influence of bone size on SOS also depends on the location of measurement (highest prediction of SOS by body height at patella with R2 = 0.56). Anthropometric characteristics have a stronger influence on SOS than measures of bone mineral density at the thumb and patella in comparison to os calcis (body height predicts SOS at os calcis, with R2 = 0.03). Conclusions QUS is not a suitable method to assess bone density. If QUS is applied for the assessment of bone development and of bone fracture risk, the measurement should be performed with consideration of anthropometric measurements.

Adolescent↗
PubMedDate not supplied

Total, trabecular, and cortical bone mineral density in different regions of the glenoid.

The purpose of this study was to analyze total, trabecular, and cortical bone mineral density (BMD) of different regions of the glenoid. Soft tissue was dissected from 20 cadaveric shoulders, and the glenoids were isolated. Axial peripheral quantitative computed tomography (pQCT) scans perpendicular to the articular surface were performed at the middle level of each (superior, middle, and inferior) horizontal third of the glenoid, and the total, trabecular, and cortical BMDs of the anterior and posterior half of each region were determined by use of pQCT software. The total BMDs of the posterior and superior glenoid were significantly higher than those of the anterior and inferior glenoid (P <.01). Trabecular BMD of the posterior glenoid was significantly higher than that of the anterior glenoid, and cortical BMD of the superior glenoid was significantly higher than that of the inferior glenoid (P <.01). These significant differences in distribution of the BMD explain previous findings of the mechanical properties of the glenoid. Future glenoid component design should provide maximal surface area for posterior and superior bone ingrowth to the component. Posteriorly and superiorly, the glenoid bone stock also provides stronger support for any kind of fixation on the bony surface.

Aged↗
PubMed2006

Proximal humeral fractures: regional differences in bone mineral density of the humeral head affect the fixation strength of cancellous screws.

The purpose of this study was to investigate the 3-dimensional trabecular bone mineral density (BMD) in the humeral head and determine the effects of trabecular BMD on the pullout strength of cancellous screws. Five regions of interest (ROIs) were defined in the humeral head (superior- anterior, superior-posterior, central, inferior-anterior, and inferior-posterior). The trabecular BMD of each ROI was determined by use of peripheral quantitative computed tomography. Cancellous screws were inserted in each ROI and cyclically loaded. The superior-anterior ROI had a lower trabecular BMD than all other ROIs (P < .001). The central ROI had a higher trabecular BMD than the inferior-anterior ROI (P < .01), whereas no differences were found between the inferior-posterior, superior-posterior, and central ROIs. Pullout strength was lower in the superior-anterior ROI compared with all other ROIs (P < .01). The trabecular BMD and pullout strength were significantly correlated (P < .01). Placement of screws in regions with a higher trabecular BMD may help to prevent implant loosening and may improve patient outcome.

Aged↗
PubMed2004

[Experimental increase in resistance of the osteoporotic distal radius with a calcium phosphate cement].

Diagnosis and treatment of osteoporosis are focused on demineralisation but bone mineral density is not directly correlated with bone strength. As with every material, the mechanical strength of bone depends upon its Young's modulus and its cross-sectional moment of inertia. In the clinical situation, bone strength can be quantified using peripheral quantitative computed tomography imaging (pQCT), a non-invasive imaging method, which allows calculation of a strength index. In this study, we tried to increase the fracture threshold of the distal radius by directly increasing bone strength rather than density. Twenty wrists in 10 cadavers were filled percutaneously with a calcium phosphate cement. Fluoroscopy and pQCT were performed twice, once before cementing and again 24 h after cement crystallisation to hydroxyapatite. We obtained measurements of trabecular and total bone density, and also stress strain index (SSI). Our results showed that trabecular bone density increased by a factor of 2.85, whereas total bone density increased by 1.61 and SSI by 1.99. Fluoroscopy showed two small leaks of cement at the point of injection. This study demonstrated that percutaneous injection of calcium phosphate cement increased distal radius strength, and consequently its fracture threshold. This technique could be employed in the future to prevent the occurrence of fractures in osteoporotic patients.

Aged↗
PubMed2005

The effect of a simultaneous dietary administration of xylitol and ethanol on bone resorption.

Our previous studies have shown that dietary xylitol supplementation diminishes bone resorption in rats, as well as protects against ovariectomy-induced increase of bone resorption during experimental osteoporosis. Interestingly, ethanol, when given simultaneously with xylitol, is known to increase blood concentration of xylitol. On the other hand, ethanol, when given alone, has been shown to increase bone resorption. The aim of the present study was to evaluate the effects of a simultaneous dietary administration of 10% xylitol and 10% ethanol on bone resorption. Bone resorption was determined using measurement of urinary excretion of hydrogen 3 (3H) radioactivity in 3H-tetracycline prelabeled rats. Already 4 days after the beginning of dietary supplementations, excretion of 3H was about 15% lower in the xylitol group (diet supplemented with 10% xylitol) and about 25% lower in the xylitol-ethanol group (diet supplemented with 10% xylitol and 10% ethanol) as compared to the controls. The excretion of 3H in these groups remained smaller than that of the controls throughout the entire study period of 40 days. The excretion of 3 H in the xylitol-ethanol group remained also smaller than that of the xylitol group. Bone mineral density and bone mineral content were determined with a peripheral quantitative computed tomography (pQCT) system from the rat tibiae at the end of the experiment. Trabecular bone mineral density and trabecular bone mineral content were significantly greater in the xylitol group and in the xylitol-ethanol group compared to the controls. They were also greater in the xylitol-ethanol group as compared to the xylitol group. Cortical bone mineral density and cortical bone mineral content did not differ significantly between the groups. In conclusion, a simultaneous dietary supplementation with 10% xylitol and 10% ethanol seems to diminish bone resorption and to increase trabecular bone mineral density and trabecular bone mineral content in rats. These effects seem to be stronger than the effects induced by 10% xylitol supplementation alone.

Animals↗
PubMed2005

Delayed repair of tendon to bone injuries leads to decreased biomechanical properties and bone loss.

INTRODUCTION: Repair of the torn rotator cuff tendon is a common procedure performed in the shoulder. In the clinical setting, a significant delay between rotator cuff tear and subsequent repair often exists. The purpose of this study was to investigate the biomechanical properties and bone density of the tendon to bone repair site after acute and delayed repair. METHODS: The supraspinatus tendons in bilateral shoulders of 60 rats were transected from the bone. In the acute group, the tendons were immediately repaired with suture. In the delayed group, the tendons were allowed to retract and repaired in a second procedure after a 3-week delay. Cross sectional area and biomechanical properties were evaluated. Bone density of the humeral head was assessed using peripheral quantitative computed tomography. Histologic sections were obtained and examined. RESULTS: At 10 days the repair tissue displayed vascular and fibroblast proliferation accompanied by predominantly mononuclear infiltrate. At 28 days the inflammatory process gradually decreased. No significant histologic differences were noted between the acute and delayed repair specimens. Cross-sectional area was higher in the delayed group at the early time points (44% at 10 days and 31% at 28 days). Viscoelastic properties were greater in the acute group at the early time points and significantly less at the latest time point, compared to the delayed group. Bone density was markedly decreased (8% and 12%, 28 and 56 days respectively) in the delay group. DISCUSSION: Inferior rotator cuff healing was demonstrated when there was a delay between injury and repair. Viscoelastic properties of the acute repairs were increased compared to the delayed group at 10 days, indicating tendon stiffening during the 3-week delay before repair. Viscoelastic properties of the acute repairs were decreased compared to the delayed group at 56 days indicating deterioration of properties over time in the delayed group. The deterioration in properties in the delayed group coincide with bone density decreases in the greater tuberosity. These results indicate that bone loss may a significant factor in poor healing.

Animals↗
PubMed2006

Development of the BITE Master II and its application to the study of cheese hardness.

Instrumental methods to assess food texture are often used without considering parameters relevant to the sensory perception of food texture and without considering conditions occurring in the mouth during chewing. The objective of this research was to develop a sensory robot capable of closely mimicking the human bite and to conduct its preliminary testing with various cheeses.

Cheese↗
PubMed2006

Perinatal exposure to PCB 153, but not PCB 126, alters bone tissue composition in female goat offspring.

The aim of this study was to investigate if environmentally relevant doses of the putative estrogenic non dioxin-like PCB 153 and the dioxin-like PCB 126 caused changes in bone tissue in female goat offspring following perinatal exposure. Goat dams were orally dosed with PCB 153 in corn oil (98 microg/kg body wt/day) or PCB 126 (49 ng/kg body wt/day) from day 60 of gestation until delivery. The offspring were exposed to PCB in utero and through mother's milk. The suckling period lasted for 6 weeks. Offspring metacarpal bones were analysed using peripheral quantitative computed tomography (pQCT) after euthanisation at 9 months of age. The diaphyseal bone was analysed at a distance of 18% and 50% of the total bone length, and the metaphyseal bone at a distance of 9%. Also, biomechanical three-point bending of the bones was conducted, with the load being applied to the mid-diaphyseal pQCT measure point (50%). PCB 153 exposure significantly decreased the total cross-sectional area (125 mm(2)+/-4) versus non-exposed (142 mm(2)+/-5), decreased the marrow cavity (38 mm(2)+/-4) versus non-exposed (50 mm(2)+/-3) and decreased the moment of resistance (318 mm(3)+/-10) versus non-exposed (371 mm(3)+/-20) at the diaphyseal 18% measure point. At the metaphyseal measure point, the trabecular bone mineral density (121 mg/cm(3)+/-5) was increased versus non-exposed (111 mg/cm(3)+/-3). PCB 126 exposure did not produce any observable changes in bone tissue. The biomechanical testing of the bones did not show any significant changes in bone strength after PCB 153 or PCB 126 exposure. In conclusion, perinatal exposure to PCB 153, but not PCB 126, resulted in altered bone composition in female goat offspring.

Administration, Oral↗
PubMed2004

Islet autotransplantation combined with pancreatectomy for treatment of pancreatic adenocarcinoma: a case report.

Extensive pancreatectomy (EP) may increase the resection rate of pancreatic adenocarcinoma (PA). Unfortunately, EP often results in unstable diabetes. Recently, islet autotransplantation (auto-Tx) has offered the potential to prevent this metabolic disorder. Because of the fear of contamination of prepared islets by malignant cells, this procedure has so far not been used as a treatment for PA. We herein report a case of a 63-year-old nondiabetic patient who underwent EP combined with islet auto-Tx in an emergency operation following histologically proved R(0)-resection for PA (pT(3)pN(1)G(2)). Islets were isolated from the excised pancreas using a continuous digestion filtration device. The resultant preparation was injected into the portal vein. Owing to the moderate fasting hyperglycemia, postoperative exogenous insulin therapy was necessary (26 U/d). After discharge, the patient's daily insulin dose was gradually reduced. At 1-year follow-up the fasting C-peptide level was 0.66 ng/mL, and an oral glucose tolerance test (oGTT) and an intravenous (IV) glucagon stimulation (GS) showed functioning engrafted islets. The K-ras mutations were detected in the paraffin-embedded PA, but not in the prepared islets or in the peripheral blood. Computed tomographic (CT) imaging revealed neither local tumor recurrence nor liver metastases. At 2-year follow-up, the patient was on a balanced food regimen and gaining weight. Although he remains insulin-dependent (16 U/d), he is metabolically stable (HbA(1)(c) 5.9%). The fasting C-peptide level is 0.68 ng/mL. The peak value of C-peptide in response to oGTT was 0.92 ng/mL and to GS 0.89 ng/mL. At this time Ca19-9 and CEA are increased to 35.3 U/mL and 19.2 ng/mL, respectively. The patient died 2.5 years after operation owing to tumor recurrence. There was no evidence for liver metastases. We postulate that histologic evaluation (R(0)-resection) and detection of K-ras mutations may be useful techniques. However, islet auto-Tx after EP for adenocarcinoma should only be regarded for rescue therapy. Studies on strategies to exclude possible contamination of islet tissue with carcinoma cells are critically important.

Adenocarcinoma↗
PubMed2005

Image quality of film transparency printer output of digital dental radiographs.

OBJECTIVE: The purpose of this study was to evaluate the physical properties of the film transparency output of a printer and its potential use in dental radiography. STUDY DESIGN: A color printer (Sony UP-D70XR) was used to produce film transparencies of digital radiographs. A physical evaluation for the image quality was conducted including measurements of the image density reproducibility, the dose response function, the root mean square (RMS) granularity and the modulation transfer function (MTF). RESULTS: The characteristic curve of the hard copy image produced a nonlinear, sigmoid response for pixel value or x-ray absorbed dose. The RMS of the scan parallel direction was greater than that of the scan perpendicular direction in low density areas, but it reversed beyond density 1.3. The MTF of the scan perpendicular direction was superior to that of the scan parallel direction. CONCLUSION: It was suggested that further examination of the image qualities of this printer is worthwhile.

Computer Peripherals↗
PubMed2006

Seasonal changes in bone metabolism in sheep.

There is a great need for animal models of osteoporosis and sheep are a suitable large animal that meets most requirements. Since it is known that bone mass in humans responds to seasonal changes, this study investigated natural bone metabolism in sheep in order to better define the sheep as a model for osteoporosis. Bone mineral density (BMD), trabecular structure, biochemical markers of bone formation and resorption and estrogen were analysed over a period of 18 months. The lowest BMDs, measured by peripheral quantitative computed tomography (pQCT), were observed during winter. Thereafter, a 5.1% increase in BMD was observed during spring and summer (P<0.05). Bone resorption markers showed a variable pattern, with higher values in spring compared to autumn (P<0.001). The physiological estrus phase during autumn was detected by serum estrogen levels. The findings show that it is necessary to take seasonal variations into account if sheep are used to establish an animal model for osteoporosis.

Amino Acids↗