Long-term in vivo biostability of poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol-based polyurethane elastomers

The long-term biostability of a novel thermoplastic polyurethane elastomer (Elast-Eon 2 80A) synthesized using poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS) macrodiols has been studied using an in vivo ovine model. The material's biostability was compared with that of three commercially available control materials, Pellethane 2363-80A, Pellethane 2363-55D and Bionate 55D, after subcutaneous implantation of strained compression moulded flat sheet dumbbells in sheep for periods ranging from 3 to 24 months. Scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to assess changes in the surface chemical structure and morphology of the materials. Gel permeation chromatography, differential scanning calorimetry and tensile testing were used to examine changes in bulk characteristics of the materials. The results showed that the biostability of the soft flexible PDMS-based test polyurethane was significantly better than the control material of similar softness, Pellethane 80A, and as good as or better than both of the harder commercially available negative control polyurethanes, Pellethane 55D and Bionate 55D. Changes observed in the surface of the Pellethane materials were consistent with oxidation of the aliphatic polyether soft segment and hydrolysis of the urethane bonds joining hard to soft segment with degradation in Pellethane 80A significantly more severe than that observed in Pellethane 55D. Very minor changes were seen on the surfaces of the Elast-Eon 2 80A and Bionate 55D materials. There was a general trend of molecular weight decreasing with time across all polymers and the molecular weights of all materials decreased at a similar relative rate. The polydispersity ratio, Mw/Mn, increased with time for all materials. Tensile tests indicated that UTS increased in Elast-Eon 2 80A and Bionate 55D following implantation under strained conditions. However, ultimate strain decreased and elastic modulus increased in the explanted specimens of all three materials when compared with their unimplanted unstrained counterparts. The results indicate that a soft, flexible PDMS-based polyurethane synthesized using 20% PHMO and 80% PDMS macrodiols has excellent long-term biostability compared with commercially available polyurethanes.     

The relationship between muscle kinetic parameters and kinematic variables in a complex movement

Summary Kinematic variables of the vertical jump (jumping height, jump phase durations and joint angles) were measured on 39 male physical education students. In addition, kinetic parameters of the hip and knee extensors, and of the plantar flexors (maxima voluntary force and its rate of development) were recorded on the same subjects, in isometric conditions. The results demonstrated significant positive correlations between kinetic parameters of the active muscle groups and jumping height (r=0.217−0.464). The dominant effect on these correlations was due to the knee extensors. Correlations between these parameters and the duration of the jump phases were much weaker. Correlation coefficients between kinetic parameters and limb angles in the lowest body position showed that fast force production in one muscle group was related to a significant decrease in the joint angles of distant body segments. Multiple correlation coefficients between leg extensor parameters and kinematic variables (ranging between 0.256 for the duration of the counter-movement phase and 0.616 for jump height) suggested that kinetic parameters could explain more than a quarter of the variability of this complex human movement. Therefore, the conclusion was drawn that an extended set of measurements of the relevant musculo-skeletal system parameters could predict a considerable amount of the variability of human movement. However, high correlation coefficients between the same kinetic parameters of different muscle groups suggest that not all active muscle groups have to be included in the measurements.     

Analysis of the seasonal pattern in suicide

BACKGROUND: Suicide has been attributed to social and psychological factors but also to geophysical effects. Of the latter, changes in solar radiation and geomagnetic activities may contribute to the frequency and the seasonal pattern of suicides. METHODS: We studied with a population-based, nationwide analysis all the individuals who committed suicide (n=27,469) in Finland during the period of 1979 to 1999. The daily data on the number of suicides, and the mean and maximum levels of geomagnetic activity were compiled and modelled with Poisson regression using the number of inhabitants in each province as the denominator. Time series analysis of monthly numbers of suicides was carried out using a seasonal-trend decomposition procedure. RESULTS: There was a strong seasonal effect on suicide occurrence (P<0.00001), the risk of suicide being greatest in spring. The seasonal effect was most pronounced when the number of suicides was relatively low. High levels of solar radiation activity were associated with the increased risk of suicide (P=0.00001), but the effect of geomagnetic activity was weak. LIMITATIONS: No individual data on alcohol consumption or mental disorders were available. CONCLUSIONS: Suicide occurrence varies markedly by season and needs attention where prevention is concerned.     

Dopamine transporter and D2-receptor density in late-onset alcoholism

Rationale: Late onset type 1 alcoholism has been suggested to be associated with an underlying dopaminergic defect. Therefore, it is relevant to study both postsynaptic D₂-receptor and presynaptic dopamine transporter (DAT) densities among alcoholics. Objective: We investigated DAT densities, along with striatal and extrastriatal dopamine D₂-receptor densities, in nine non-violent late-onset male alcoholics, who had no major mental disorder nor antisocial personality disorder (ASPD), and nine healthy controls. Methods: [¹²³I]PE2I and [¹²³I]epidepride were used in SPECT imaging. Results: DAT occupancy ratios (striatum/cerebellum) were significantly lower among alcoholics than in controls. Extrastriatal D₂-receptor occupancy ratios (temporal pole/cerebellum) were not significantly different between the groups. Conclusions: Striatal presynaptic DAT densities are decreased among type 1 alcoholics, and this finding is not associated with recent alcohol abuse. Received: 22 March 1999 / Final version: 25 June 1999     

Striatal dopamine transporter density in major depression

Rationale: There are no previous data available regarding [¹²³I]β-CIT binding to the dopamine transporter sites in the basal ganglia in depressed patients. Objective: The present study tested the hypothesis that the brain DAT density in depressed patients is lower than that in matched healthy controls. Methods: Fifteen drug-naive outpatients with major depression and 18 healthy controls were investigated using single photon emission computerized tomography (SPECT) with a high-affinity dopamine transporter specific radioligand, ¹²³I-labeled β-CIT (2β-carbomethoxy-3β-(4-iodophenyl)-tropane). Results: We found a significantly higher [¹²³I]β-CIT uptake in both sides of the basal ganglia in patients with major depression than in the controls (Mann-Whitney U-test, P = 0.002 on the right and P = 0.003 on the left). Conclusions: The radioligand uptake reflecting the DAT density was significantly higher among the patients than in the controls. This finding is unexpected, since it is generally believed that monoaminergic neurotransmission is lower in depression, and therefore it could be assumed that a reduction in dopamine transmission would lead to secondary down-regulation of DAT density. However, it is possible that up-regulation of the DAT may be the primary alteration, which leads to lower intrasynaptic dopamine concentration and to lower dopamine neural transmission. Received: 20 October 1998/Final version: 25 January 1999     

Temporomandibular joint related painless symptoms,orofacial pain,neck pain,headache, and psychosocial factors among non-patients

The aims of this study were to assess the prevalence of temporomandibular joint related (TMJ) painless symptoms, orofacial pain, neck pain, and headache in a Finnish working population and to evaluate the association of the symptoms with psychosocial factors. A self-administered postal questionnaire concerning items on demographic background, employment details, perceived general state of health, medication, psychosocial status, and use of health-care services, was mailed to all employees with at least 5 years at their current job. The questionnaire was completed by 1339 subjects (75%). Frequent (often or continual) TMJ-related painless symptoms were found in 10%, orofacial pain in 7%, neck pain in 39%, and headache in 15% of subjects. Females reported all pain symptoms significantly more often than men (P < 0.001). Frequent pain and TMJ-related symptoms were significantly associated with self-reported stress, depression, and somatization (P < 0.001). Perceived poor general state of health (P < 0.001), health care visits (P < 0.001), overload at work (P < 0.001), life satisfaction (P < 0.05), and work satisfaction (P < 0.05) were also significantly associated with pain symptoms, but the work duty was not (P > 0.05). Our findings are in accordance with earlier studies and confirm the strong relationship between neck pain, headache, orofacial pain, TMJ-related painless symptoms, and psychosocial factors. Furthermore, TMJ-related symptoms and painful conditions seem to be more associated with work-related psychosocial factors than with type of work itself.     

Transmission of Streptococcus equi Subspecies zooepidemicus Infection from Horses to Humans

Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) is a zoonotic pathogen for persons in contact with horses. In horses, S. zooepidemicus is an opportunistic pathogen, but human infections associated with S. zooepidemicus are often severe. Within 6 months in 2011, 3 unrelated cases of severe, disseminated S. zooepidemicus infection occurred in men working with horses in eastern Finland. To clarify the pathogen’s epidemiology, we describe the clinical features of the infection in 3 patients and compare the S. zooepidemicus isolates from the human cases with S. zooepidemicus isolates from horses. The isolates were analyzed by using pulsed-field gel electrophoresis, multilocus sequence typing, and sequencing of the szP gene. Molecular typing methods showed that human and equine isolates were identical or closely related. These results emphasize that S. zooepidemicus transmitted from horses can lead to severe infections in humans. As leisure and professional equine sports continue to grow, this infection should be recognized as an emerging zoonosis.     

Low serum magnesium levels are associated with increased risk of fractures: a long-term prospective cohort study

Magnesium, which is an essential trace element that plays a key role in several cellular processes, is a major component of bone; however, its relationship with risk of major bone fractures is uncertain. We aimed to investigate the association of baseline serum magnesium concentrations with risk of incident fractures. We analyzed data on 2245 men aged 42–61 years in the Kuopio Ischemic Heart Disease prospective cohort study, with the assessment of serum magnesium measurements and dietary intakes made at baseline. Hazard ratios [95% confidence intervals (CI)] for incident total (femoral, humeral, and forearm) and femoral fractures were assessed. During a median follow-up of 25.6 years, 123 total fractures were recorded. Serum magnesium was non-linearly associated with risk of total fractures. In age-adjusted Cox regression analysis, the hazard ratio (HR) (95% CIs) for total fractures in a comparison of the bottom quartile versus top quartile of magnesium concentrations was 2.10 (1.30–3.41), which persisted on adjustment for several established risk factors 1.99 (1.23–3.24). The association remained consistent on further adjustment for renal function, socioeconomic status, total energy intake, and several trace elements 1.80 (1.10–2.94). The corresponding adjusted HRs for femoral fractures were 2.56 (1.38–4.76), 2.43 (1.30–4.53) and 2.13 (1.13–3.99) respectively. There was no evidence of an association of dietary magnesium intake with risk of any fractures. In middle-aged Caucasian men, low serum magnesium is strongly and independently associated with an increased risk of fractures. Further research is needed to assess the potential relevance of serum magnesium in the prevention of fractures.