Biomedical subjects

T Jämsä

Publications and source records attributed to T Jämsä.

At least 19 recordsLinked to original sources

PubMed2007

The effect of oxide thickness on osteoblast attachment and survival on NiTi alloy.

NiTi alloy is used in various medical applications and the surface titanium oxide layer produced naturally or enhanced artificially has been thought to offer a protecting film against allergic and toxic effects of nickel (Ni). In this study, we investigated the effect of different oxide layer thicknesses on the survival and attachment of osteoblastic cells (ROS-17/2.8). AFM, X-ray diffraction and electrical resistance measurements were used to analyze the surface properties of oxidized NiTi samples and the effect of oxidation on material properties. The results clearly showed that straight correlation between oxide thickness and cellular well-being cannot be maid. However, the different thicknesses of oxide layer on NiTi had surprising impacts on cellular responses and also to the properties of the metal alloy.

Alloys↗

PubMed2006

Intensity of exercise is associated with bone density change in premenopausal women.

INTRODUCTION: High-impact exercise is known to be beneficial for bones. However, the optimal amount of exercise is not known. The aim of the present study was to evaluate the association between the intensity of exercise and bone mineral density (BMD). METHODS: We performed a 12-month population-based trial with 120 women (aged 35-40 years) randomly assigned to an exercise group or to a control group. The intensity of the physical activity of 64 women was assessed with an accelerometer-based body movement monitor. The daily activity was analyzed at five acceleration levels (0.3-1.0 g, 1.1-2.4 g, 2.5-3.8 g, 3.9-5.3 g, and 5.4-9.2 g). BMD was measured at the hip, spine (L1-L4), and radius by dual-energy x-ray absorptiometry. The calcaneus was measured using quantitative ultrasound. RESULTS: Physical activity that induced acceleration levels exceeding 3.9 g correlated positively with the BMD change in the hip area (p<0.05-0.001). L1 BMD change correlated positively with activity exceeding 5.4 g (p<0.05) and calcaneal speed of sound with the level of 1.1-2.4 g (p< 0.05). Baseline BMD was negatively associated with the BMD change at the hip. CONCLUSION: The intensity of exercise, measured as the acceleration level of physical activity, was significantly correlated with BMD changes. Bone stimulation is reached during normal physical exercise in healthy premenopausal women. In the hip area, the threshold level for improving BMD is less than 100 accelerations per day at levels exceeding 3.9 g.

Adult↗

PubMed2005

The phase state of NiTi implant material affects osteoclastic attachment.

In the present work, the responses of mature osteoclasts cultured on austenite and martensite phases of NiTi shape memory implant material were studied. We used the sensitivity of osteoclasts to the underlying substrate and actin ring formation as an indicator of the adequacy of the implant surface. The results showed osteoclasts with actin ring on both NiTi phases. However, significantly more osteoclasts were present on the austenitic NiTi than on the martensitic NiTi. We also analyzed the surface free energy of the samples but found no significant difference between austenite and martensite phases. The results revealed that osteoclasts tolerated well the austenite phase of NiTi. The chemically identical martensitic NiTi was not as well tolerated by osteoclasts (e.g., indicated by diminished actin ring formation). This leads to the conclusion that certain physical properties specific to the martensitic NiTi have an adverse effect to the surviving of osteoclasts on this NiTi phase. These results confirm that mature, authentic osteoclasts can act as cell probes in experiments concerning aspects of biocompatibility of bone implant materials.

Bone and Bones↗

PubMed2005

Abnormal response to physical activity in femurs after heterozygous inactivation of one allele of the Col2a1 gene for type II collagen in mice.

The objective of this study was to evaluate the influence of heterozygous inactivation of one allele of the type II collagen gene (Col2a1) on biomechanical properties and mineral density of bone under physical loading conditions. C57BL/6-TGN mice with heterozygous knockout (HZK) inactivation of Col2a1 gene and their nontransgenic littermate controls were housed in individual cages with running wheels for 9 and 15 months. The running activity of each mouse was monitored continuously throughout the experiment. Bone mineral density (BMD) of mice femora was measured using dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT). Biomechanical properties were determined using three-point bending tests. Vertebral bone samples were prepared for quantitative polarized light microscopy and digital densitometry of proteoglycans. The concentration of total collagen and collagen cross-links were analyzed using high-performance liquid chromatograpy (HPLC). The average daily running distance was shorter for the HZK mice between the age of 4 and 15 months as compared with normal runners (P < 0.05). The ultimate breaking force was 14.8% and 23.6% (9 vs. 15 months) lower in HZK-runners than in wild-type runners. BMD of the femur was 6.1% lower in HZK-runners at the age of 9 months (P < 0.05). Physical activity increased cortical BMD in wild-type runners but not in the HZK runners at the age of 9 months. The collagen network of the HZK mice was less organized. There were only minor changes in BMD and mechanical and structural properties between sedentary HZK mice and their wild-type controls. Increased physical activity induced significantly lower bone density, mechanical properties, and organization of collagen fibers in male HZK mice. However, there were no major differences in biomechanical parameters between sedentary HZK and wild-type male mice. This suggests an important guiding role of collagen type II in bone remodelling and maturation.

Animals↗

PubMed2005

Headache children with temporomandibular disorders have several types of pain and other symptoms.

The aim was to investigate the association between temporomandibular disorders (TMD) and overall muscle tenderness, depressive symptoms, sleep difficulties, headache frequency and related symptoms in children with primary headache in comparison with controls. Based on an unselected population sample of 1135 Finnish schoolchildren classified according to the type of headache at age 12, altogether 297 children aged 13-14 from different headache groups and healthy controls were randomly selected for an interview and clinical examinations. Children with migraine had more TMD signs than children with nonmigrainous headaches or healthy controls. High TMD total scores were associated with palpation tenderness in other parts of the body and with frequent headache attacks. We conclude that children with overall headache, migraine in particular, and high total TMD scores showed an increased overall tenderness to muscle palpation and multiply manifested hypersensitivity pain.

Adolescent↗

PubMed2005

Gamma irradiation and ethylene oxide in the sterilization of native reindeer bone morphogenetic protein extract.

BACKGROUND AND AIMS: For human use, it is necessary to sterilize bone morphogenetic proteins (BMPs), in order to reduce the risk of infections and associated complications. We compared the effects of ethylene oxide and gamma irradiation in the sterilization of native reindeer BMP extract with regard to bone induction in the Balb/C mouse thigh muscle pouch model. MATERIALS AND METHODS: BMP extract, sterilized with ethylene oxide gas (Steri-Vac 4XL, temperature 29 degrees C, exposure time 4 h, ethylene oxide concentration 860 mg/l), or gamma irradiation at doses of 3.15 MRad was administered in implants containing 5 or 10 mg of BMP extract with collagen carrier. Non-sterilized collagen implants served as controls. New bone formation was evaluated based on the incorporation of Ca45 and radiographically three weeks after implantation. RESULTS: The collagen was not able to induce new bone visible in radiographs. The mean Ca45 incorporation in the gamma sterilized group containing 5 mg of BMP extract was 30% (p = 0.04) and that containing 10 mg of BMP extract was 60% (p = 0.02) higher than seen in the corresponding ethylene oxide sterilized groups. The mean new bone areas were 45% higher in the gamma sterilized groups than in the corresponding ethylene oxide sterilized groups, but the differences were not significant. The mean optical density of new bone in the gamma sterilized group containing 5 mg of BMP extract was 75% (p = 0.00) and in that containing 10 mg of BMP extract was 70% (p = 0.00) higher than seen in the corresponding ethylene oxide sterilized groups. CONCLUSION: Native reindeer BMP extract is more sensitive to the effects of ethylene oxide gas sterilization than gamma irradiation. These results suggest that gamma irradiation is recommendable for the sterilization of BMP extracts.

Animals↗

PubMed2003

Long-term administration of clodronate does not prevent fracture healing in rats.

Clinicians have been concerned that fractures do not heal properly in individuals exposed to bisphosphonate treatment, a treatment that strongly affects bone metabolism. The current study attempted to clarify the long-term effects of clodronate (dichloromethylene bisphosphonate) treatment on fracture healing in growing rats. Clodronate was administered subcutaneously twice a week in a dose of 2 mg/kg or 10 mg/kg. Physiologic saline served as a control. After 24 weeks of treatment, the tibiae were fractured, and the treatment was continued for another 4 weeks and 8 weeks. At both end points the cross-sectional areas of the callus, measured by peripheral quantitative computed tomography, were greater in the clodronate-treated rats than in controls, but there were no significant differences in bone mineral density. There were no significant differences between treatments in radiologic healing, histomorphometry, or in mechanical failure load of the callus with the exception of increased tensile stiffness at a dose of 2 mg/kg at 4 weeks. Clodronate treatment does not seem to prolong the fracture healing process, even when administered on a long-term basis before the fracture. Clodronate increases the size of the callus, but has only a minor effect on its biomechanical properties. The current results suggest that long-term clodronate treatment does not inhibit fracture healing.

Animals↗

PubMed2002

Comparison of the bone modeling effects caused by curved and straight nickel-titanium intramedullary nails.

Nitinol (NiTi) shape memory metal alloy makes it possible to prepare functional implants. A curved intramedullary NiTi nail has been shown to cause bending of the bone, bone thickening, increase in cortical area, and reduction in bone longitudinal growth. The purpose of the present study was to find out whether these changes are caused by the bending force of the curved nail or by the intramedullary nailing itself. Pre-shaped intramedullary NiTi nails were implanted in the cooled martensitic form into the medullary cavity of the right femur in 12 rats, where they started to restore their austenitic form, causing a bending force. Straight nails were used as controls in another 12 rats. After 12 weeks, the operated femurs were compared with their non-operated contralateral counterparts and the differences were compared between the groups. Anteroposterior radiographs demonstrated bone bowing only in the curved nail group. Retardation of longitudinal growth was observed in both groups, showing that the growth effect seems to be due to the intramedullary nailing itself. Increase in bone cross-sectional area and cortical thickness were found in both groups. However, this increase was more evident with the curved nail, indicating that the bending force of the functional nail seems to induce these changes.

Journal Article↗

PubMed2002

Improved bone biomechanical properties in xylitol-fed aged rats.

Our previous studies have shown that dietary xylitol protects against weakening of bone biomechanical properties in experimental postmenopausal osteoporosis. To study whether xylitol preserves bone biomechanics also during aging, a long-term experimental study was performed with rats. Twenty-four male Sprague-Dawley rats were divided into 2 groups. The rats in the control group (NON-XYL group) were fed a basal rat and mouse no. 1 maintenance (RM1) diet, while the rats in the experimental group (XYL group) were continuously fed the same diet supplemented with 10% xylitol (wt/wt). The rats were killed after 20 months. Their femurs were prepared for biomechanical analyses and scanning analyses with peripheral quantitative computed tomography (pQCT). In 3-point bending of the femoral diaphysis, maximum load, maximum elastic load, stiffness, energy absorption, elastic energy absorption, ultimate stress, and yield stress were significantly greater in the XYL group than in the NON-XYL group. This indicates a xylitol-induced improvement of both structural and material strength properties of cortical bone. Accordingly, the maximum load of femoral neck was significantly greater in the XYL group. In the pQCT analysis of femoral diaphysis, cortical bone area, cortical thickness (CtTh) periosteal circumference, and cross-sectional moment of inertia were greater in the XYL group. The endosteal circumference was smaller in the XYL group. In the pQCT analysis of the femoral neck cortical area of the midneck was significantly greater in the XYL group. This data indicates that xylitol exerted beneficial effects on the cross-sectional architecture of the bones. In conclusion, continuous moderate dietary xylitol supplementation leads to improved bone biomechanical properties in aged rats concerning both bone structural and material strength properties.

Aging↗

PubMed2001

Bovine bone implant with bovine bone morphogenetic protein in healing a canine ulnar defect.

Xenograft is considered an alternative material for bone transplantation, but its bone healing capacity is inferior compared to that of autografts and allografts. Here, we tested whether bone morphogenetic protein (BMP) addition enhances the suitability of demineralized xenogeneic bovine bone for bone grafting in dogs, and whether xenogeneic bone is a suitable carrier material for BMPs. The capacity of demineralized bovine bone implants, with and without native partially purified bovine BMP, to heal a 2-cm ulnar defect was determined in six dogs over a follow-up time of 20 weeks. No instances of bone union were seen, but there was slightly more bone formation in the xenografts with BMP, though the difference was not statistically significant. The ulnas treated with an implant with BMP were also mechanically stronger, but the difference was not significant. Computed tomography scans showed no differences in the implant area in bone density, bone mineral content, or bone cross-sectional area. It is concluded that native, partially purified BMP does not sufficiently improve the suitability of bovine demineralized xenografts as a bone substitute material for dog. Demineralized xenogeneic bone does not seem to be a feasible carrier material for BMP.

Animals↗

PubMed2001

A metaphyseal defect model of the femur for studies of murine bone healing.

A bone defect model was developed in the distal metaphysis of the femur for studies on bone healing in the mouse. The circular defect involving 20% of the bone circumference resulted in a 34% reduction in the bending moment compared to intact bone. The healing process was followed using histomorphometry, peripheral quantitative computed tomography (pQCT), biomechanical testing, and molecular biological analyses. Histologically, healing of the defect was characterized by filling of the medullary cavity with trabecular new bone during the first week of healing, and by closing of the cortical window by 6 weeks. Small areas of periosteal chondrogenesis were frequently observed during defect healing. In pQCT, bone mineral content (BMC) of the defect area approached that of intact control bone already by 3 weeks, reflecting the production of trabecular bone. Similarly, the bending strength and stiffness of the healing femur reached the level of intact control femur already at 3 weeks. Bone formation and remodeling was followed by Northern analyses, which demonstrated elevated mRNA levels for bone components (type I collagen and osteocalcin), and for osteoclastic enzymes (cathepsin K, matrix metalloproteinase-9, and tartrate-resistant acid phosphatase) throughout the healing period. Finally, the applicability of the defect model for gene therapy experiments was tested using adenovirus-mediated transfer of the LacZ reporter gene. Both histochemistry and mRNA analyses demonstrated that the gene was expressed in the repair tissue with the highest expression during the first week of healing. The present model thus provides a standardized environment for studies on induction and remodeling of trabecular new bone in normal and genetically engineered mice.

Animals↗

PubMed2001

Coping with the onset of cancer: coping strategies and resources of young people with cancer.

A chronic illness, such as cancer, causes permanent changes in a person's way of life and their way of adapting to changes. The purpose of this study was to describe the coping strategies and resources of adolescents and young adults with cancer. The data were collected by interviewing adolescents and young adults aged 16-22 (n = 14) who had had cancer for more than 2 months and who came to a university hospital for treatment or control check ups. The interview material was analysed by content analysis. Emotion-focused, appraisal-focused and problem-focused coping strategies were used. The major coping strategies were social support, belief in recovery and getting back to normal life as soon as possible. The subjects discussed with health care providers their disease, its treatment and how they could cope with everyday life as well as their energy and will-power to cope. The family was the most important source of emotional support. Also, gaining knowledge about cancer and its treatment was a good coping strategy. Moreover, a positive life attitude, belief in one's own resources, belief in God, earlier life experiences and willingness to fight against the disease were resources for coping with cancer.

Adaptation, Psychological↗

PubMed2001

Computerized in-situ test for bone conduction hearing aids.

Conventionally, bone-conduction (BC) hearing aids are tested with skull simulator devices and the individual adjustments are reliant on psychoacoustic free-field audiometry. Here we present a novel PC-based system for in situ measurements of BC hearing aids. With the presented system, we are able to measure the hearing aid induced skull vibrations in relation to the individual BC hearing threshold at given frequencies. According to the preliminary measurements, the vibration levels are relatively low but the system is sensitive enough for relevant measurements.

Acoustic Stimulation↗

PubMed2001

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on bone in two rat strains with different aryl hydrocarbon receptor structures.

Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic environmental contaminants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent dioxin. Here, we studied the effects of TCDD on bone. Two rat strains, Han/Wistar (H/W) and Long-Evans (L-E), were used because they exhibit a 1000-fold sensitivity difference in acute lethality of TCDD, which difference is related to the aryl hydrocarbon receptor (AHR). TCDD inhibited the tibial growth dose dependently, the effect being manifested at lower doses in the more sensitive L-E strain. In H/W rats the effect of TCDD was seen only at the high dose of 170 microg/kg (p < 0.05), whereas in the sensitive L-E rats a significant reduction of bone growth was already seen at 1.7 microg/kg (p < 0.01). This reduction was caused by the smaller tibial size because the diaphyseal bone mineral density (BMD) did not change. The three-point bending breaking force of the tibia was significantly reduced in H/W rats at 170 microg/kg (p < 0.05), but tibial stiffness was lower already at the dose of 17 microg/kg (p < 0.05). In the sensitive L-E strain, both breaking force and stiffness were reduced at the dose of 17 microg/kg (p < 0.001). These results indicate that TCDD dose-dependently interferes with bone growth, modeling, and mechanical strength. The altered transactivation domain of AHR is associated with a lower sensitivity of bone to TCDD in H/W rats, suggesting that AHR plays a role in modulating the effects of dioxins on bone.

Alkaline Phosphatase↗

PubMed2001

Influence of the upper femur and pelvic geometry on the risk and type of hip fractures.

The geometry of the upper femur has been reported to associate with the hip fracture risk in postmenopausal women. However, these associations seem to be partly conflicting, probably because of differences in measurement setup. Here, we compared the upper femur and pelvic geometries of 70 hip fracture patients (46 cervical and 24 trochanteric fractures) and 40 age-adjusted controls based on plain anteroposterior radiographs, eliminating the possible sources of inaccuracy as far as possible by using a standardized patient position and calibrated dimension measurements by digital image analysis. The femoral neck/shaft angle (NSA) was larger in the fracture patients compared with the controls (p < 0.001). The fracture group had thinner cortices in the upper femur than the controls (p < 0.001). The femoral shaft diameter (FSD; p < 0.001), trochanter width (TW; p < 0.01), and the pelvic dimensions, that is, the smallest outer pelvic diameter (SOPD; p < 0.01) and the largest inner pelvic diameter (LIPD; p < 0.05) were smaller in the fracture group. Comparing the fracture types, we found NSA larger in the cervical hip fracture patients than in the patients with a trochanteric fracture (p < 0.01). The femoral neck/shaft cortex ratio was lower and the FSD was smaller in the cervical hip fracture group (p < 0.05). Acetabular width (AW) was greater and the SOPD was wider in the cervical fracture patients (p < 0.01). We concluded that the upper femur and pelvic dimensions as defined from calibrated and position-standardized plain radiographs are useful in the evaluation of hip fracture risk and fracture type.

Aged↗

PubMed2001

Composite implant composed of hydroxyapatite and bone morphogenetic protein in the healing of a canine ulnar defect.

BACKGROUND AND AIMS: Hydroxyapatite (HA) has been considered as a carrier material for bone morphogenetic proteins (BMP). The aim of this study was to evaluate the capacity of a composite implant of HA and native bovine BMP to heal a 2 cm segmental defect in the canine ulna. MATERIALS AND METHODS: A composite HA+BMP implant was compared with plain HA implants and cortical autografts. The fixation was accomplished with an intramedullary Kirschner wire. The bone union was evaluated by X-rays taken at operation and after 3, 6, 9, 12, 16, 25, 35 weeks and by histology and mechanical torsion tests. RESULTS: HA implants were not able to produce complete bone union even with BMP. There was some bridging between the implant and the bone in the defects treated with either plain HA or HA+BMP implant, the bridging being slightly more pronounced with HA+BMP. The autografts showed a significantly better capacity to heal the defect. The HA implant did not resorb markedly during the study. There was no significant difference in mechanical strength between the HA and HA+BMP groups. CONCLUSIONS: HA was not an adequate bone substitute material in this study model, and BMP was not able to enhance sufficiently the poor capacity of HA to heal canine ulnar defects.

Animals↗

PubMed2000

Comparison of radiographic and pQCT analyses of healing rat tibial fractures.

Fracture healing and callus formation have traditionally been evaluated by using X-ray radiography. Here we compared X-ray radiography and peripheral quantitative computed tomography (pQCT) in evaluating the healing callus of standardized tibial fractures in 141 female rats after a 4- or 8-week follow-up. The results were compared with the tensile (4-week) and compressive (8-week) failure load of the callus. The projectional size of callus, as defined from lateral ex vivo radiographs, correlated significantly with the pQCT-defined cross-sectional area (CSA) of midcallus. This relationship was dependent on the pQCT attenuation threshold, being higher for the CSA of compact bone (r = 0.85, P < 0.0001) than for the total bone CSA (r = 0.68, P < 0.0001). Radiographically defined callus projectional area also correlated strongly with bone mineral content (BMC) (r = 0.84-0.86, P < 0.0001). The mean optical density of the callus analyzed from the radiographs had only a weak correlation with the pQCT-defined bone mineral density (BMD) of callus. A weak negative relationship was found between CSA and BMD. The optical density analyzed from lateral radiographs did not correlate with the tensile or compressive failure load of callus. Callus size, BMC, and BMD were associated with the compressive failure load, whereas both radiographs and pQCT were poor in explaining the failure load in tension.

Animals↗

PubMed2000

Native bovine bone morphogenetic protein improves the potential of biocoral to heal segmental canine ulnar defects.

We studied the effect of a composite implant consisting of coral and native bovine bone morphogenetic protein (BMP) on the healing of 2 cm segmental defects in the canine ulna. Plain coral and cortical autograft bone implants were used as controls. The fixation was temporary for 9 weeks with an intramedullary Kirschner wire (6 ulnas with a composite implant of coral and BMP, 6 with plain coral and 6 with an autograft) or a plate and screws (3 ulnas with a composite implant and 3 with plain coral). X-rays were taken at 3, 6, 9, 12, 16, 26 and 36 weeks, and mechanical torsion tests were performed at the end of the study. The score for bone formation and bone union evaluated from radiographs was significantly higher in the composite implant group than in the plain coral group at 16 weeks, but the score was even higher with autografts. BMP accelerated the resorption of the coral implant. The mechanical strength of the composite implants was higher than that of the bones with a plain coral implant (P < 0.05), while the mechanical strength of the coral implants, even with BMP, was significantly lower than the strength of autografts (P < 0.01). In conclusion, BMP enhanced the capacity of a coral implant to heal a segmental ulnar defect by increasing bone formation, but the effect of this combination was not as good as that of a cortico-cancellous autograft.

Animals↗