Rheo-optical fourier transform infrared spectroscopy of polyurethanes and their blends with polyolefins

Rheo-optical Fourier transform infrared spectroscopy was used to analyze the orientational behavior of hard and soft segments of thermoplastic poly(ether urethane)s (TPU-Et) and poly(ester urethane)s (TPU-Es) and their blends with a 20 mass-% contribution of either polyethylene (PE) or polypropylene with an amorphous rubber phase (PP). The blends show a reduced stress level, lower elongation-to-break and a lower degree of orientation of the segments — especially for the TPU-Es blends — compared to those of pure TPU's when uniaxially elongated. Blends of TPU-Et with PP show reduced stress but increased strain compared to pure films of TPU-Et. This is caused by an improved adhesion of the rubber phase in the polypropylene and the polyether phase of TPU-Et. Optical micrographs visualize deformed polyolefin particles in elongated films of TPU-Et/PP blends. In the TPU-Et/PP blend we could achieve equivalent orientation for the polyolefin phase and the segments of TPU-Et caused by this higher phase adhesion compared to the other blends. Orientation functions (OF's) of absorption bands which specifically represent hard or soft polyurethane segments or which are characteristic of the polyolefin phase have been calculated to monitor the molecular alignment due to the mechanical treatment.     

Absence of relaxation to lactate in human placental vessels of pregnancies with severe preeclampsia

OBJECTIVE: Our objective was to determine whether the observed relaxation to lactate and other agents in placental vessels of normal pregnancies is altered in severe preeclampsia.STUDY DESIGN: Isolated placental arteries and veins from women with severe preeclampsia and uncomplicated term pregnancies were precontracted with prostaglandin F_2α under 5% oxygen and 5% carbon dioxide with the balance nitrogen (Po₂ 35 to 38 torr) and then exposed to lactate (1 to 10 mmol/L, pH 7.4, n = 8 to 15), arachidonic acid (0.01 to 10 μmol/L, n = 6 to 13), nitroglycerin (1 nmol to 1 μmol/L, n = 4 to 12), or forskolin (0.01 to 10 μmol/L, n = 6 to 9). The response to lactate was also examined in placental vessels from appropriate-for-gestational-age preterm deliveries (n = 8) for comparison with a similar group with severe preeclampsia (n = 8). The t test and analysis of variance statistics were used.RESULTS: Relaxation to lactate was markedly inhibited in both placental arteries and veins of women with severe preeclampsia compared with vessels from uncomplicated term or preterm pregnancies. Responses to the other relaxing agents were not altered in the severely preeclampsia vessels.CONCLUSIONS: In severe preeclampsia absence of lactate-induced dilatation of placental vessels may contribute to the fetal complications associated with impaired blood flow and vasospasm.     

Biomimetic porous scaffolds with high elasticity made from mineralized collagen--an animal study

Histological investigations of a new hydroxyapatite-collagen composite material were carried out to evaluate its possible suitability as a bone substitute. The three-dimensional scaffolds made from biomimetically mineralized collagen exhibit an interconnecting pore structure and elastic mechanical properties. They were implanted into the subcutaneous tissue and bone defects made in the femur of rats and harvested with the surrounding tissue at 1, 2, 4, 8, and 12 weeks after surgery. The materials implanted in the subcutaneous tissue were covered by fibrous connective tissue with a slight inflammatory response, and many foreign-body giant cells were observed on the surface of the scaffolds. Most of the material implanted in the subcutaneous tissue was resorbed at 8 weeks by phagocytosis. In the bone defects, new bone formation was observed on the surface of the material at 1 week. New bone increased with time, and osteoclasts were seen on the surface of the scaffolds at 2 weeks. Resorption and replacement by new bone of many parts of the materials implanted in the femur were observed by 12 weeks. These responses occurred faster than those of other hydroxyapatite-collagen composites. The results suggested that the new biomimetically mineralized collagen scaffolds were suitable as an implant material for bone-tissue reconstruction.     

Collagen type I increases bone remodelling around hydroxyapatite implants in the rat tibia

The early interface reaction of cancellous bone to a nanocrystalline hydroxyapatite (HA) cement containing 3 wt% collagen type I (HA/Coll) with a setting under physiological temperature and pH was observed using immunohistochemical techniques. Pure HA served as a control. Cylinders with a diameter of 2 mm were implanted into the proximal tibia of 72 adult Wistar rats. Histological sections of 6 animals were prepared after 1, 2, 4, 6, 14 and 28 days. First, osteoblast-like cells as well as a marked reaction for osteonectin, osteopontin and its ligand CD44 were observed as early as 2 days after implantation at the interface around HA/Coll implants. Further, reactivity for ED1 and cathepsin D, both markers for phagocytotic cells, appeared earlier and stronger around HA/Coll. In cell counts, a significantly higher average number of ED1- and cathepsin D-positive phagocytotic cells was observed around the HA/Coll implants on days 6 (p < 0.01), 14 and 28 (p < 0.05). The number of osteopontin-positive cells was significantly higher around HA/Coll implants at days 6 and 14 (p < 0.05). Two weeks after the implantation, first islands of newly formed woven bone were observed around the HA/Coll implant, but not around the control implant. The amount of direct bone contact after 28 days averaged 28% around pure HA and 51% around HA/Coll implants (p < 0.05). While both implants displayed a good osteoconductivity, a higher bone remodelling activity was observed around collagen-containing HA implants compared to pure HA implants. It appears that the addition of collagen to HA implants can enhance both phagocytotic and osteogenic processes. This may result in an earlier acceptance and better osseointegration of the HA/Coll implants into the surrounding tissue.     

A method for two dimensional multi-segmental kinematic and kinetic analysis of normal and pathological human gait

The application of an integrated gait analysis system in clinical research is described. With this system it is possible to analyse the walking pattern of various groups of patients with regard to foot-floor contact, kinematics and kinetics, using a Selspot system. In order to study various groups of patients an extensive body-segment model adapted to the variety in patient groups is dealt with and is related to data from the literature. Special attention has been paid to the analysis or errors in the quantities used in kinematics and kinetics. The various sources of errors leading to inaccuracy of the data describing the walking pattern are discussed.     

Increased muscle stiffness after anterior cruciate ligament reconstruction – memory on injury?

Residual impairment of knee function was tested in 25 patients 6 to 12 months after successful unilateral reconstruction of the anterior cruciate ligament. The control group comprised 25 healthy individuals. Jumping onto one foot from a height of 20 cm was taken as a prototype of similar everyday activities. We measured maximum flexion of the knee during the landing phase of the jump, and the degree of knee flexion at the time of maximum deceleration of the knee against gravity during jumping using the three-dimensional optical motion analysis system-ELITE. In the group of patients, measured parametres were significantly smaller on the operated side than on the unaffected side. These two measured values were significantly smaller on both legs in group of patients as compared to the values in the control group. The results of our study indicate that functional disturbance persisted for 6 to 12 months after anterior cruciate reconstruction. This may be due to the changed muscle activation pattern of the knee causing increased stiffness of knee muscles. It seems that re-programming of the central nervous system occurred in order to protect the injured lower extremities from another injury.     

Heart Failure Management in Nursing Homes: A Scoping Literature Review

Heart failure (HF) affects 20% of nursing home (NH) residents, causing high morbidity and mortality. The optimal approach to HF management in NHs remains elusive. We conducted a scoping review of published guidelines and HF management interventions in NHs. A search for English publications since 1990 was conducted using PubMed, EMBASE, CINAHL, and Scopus, for scientific statements, guidelines, recommendations, or intervention studies that addressed at least 1 principle of HF management. Of 2545 records retrieved, 19 articles were retained after screening, and 2 additional articles identified through reference list manual searches. Six articles represented 5 guidelines and 15 described interventions. All guidelines endorsed the applicability of general HF guidelines to NH residents, tailored to comorbidities, frailty, and advance care preferences. Four addressed quality assurance but not feasibility and sustainability. Methodological quality of the interventions was poor, although results suggest that guideline-based HF management in NHs can improve nursing staff knowledge and job satisfaction, prescribing, and reduce acute care utilization. Clinically-based education for staff, and access to specialist mentorship are important. NH physician involvement was limited, and resident/family education potentially ineffective. Concerns about feasibility, sustainability, and quality assurance were identified in most interventions, and advance care planning was rarely addressed. HF guidelines for NH support the applicability of general HF guidelines to the care of NH residents, and published interventions suggest that guideline-based HF management in NHs is effective. Future work should support greater physician and resident engagement, advance care planning, and provide robust guidelines on developing feasible and sustainable interventions.     

A multivariate hypothesis testing framework for tissue clustering and classification of DTI data

The primary aim of this work is to propose and investigate the effectiveness of a novel unsupervised tissue clustering and classification algorithm for diffusion tensor MRI (DTI) data. The proposed algorithm utilizes information about the degree of homogeneity of the distribution of diffusion tensors within voxels. We adapt frameworks proposed by Hext and Snedecor, where the null hypothesis of diffusion tensors belonging to the same distribution is assessed by an F‐test. Tissue type is classified according to one of the four possible diffusion models, the assignment of which is determined by a parsimonious model selection framework based on Schwarz Criterion. Both numerical phantoms and diffusion‐weighted imaging (DWI) data obtained from excised rat and pig spinal cords are used to test and validate these tissue clustering and classification approaches. The unsupervised clustering method effectively identifies distinct regions of interest (ROIs) in phantoms and real experimental DTI data. Copyright © 2009 John Wiley & Sons, Ltd.