Solvent stimulated actuation of polyurethane-based shape memory polymer foams using dimethyl sulfoxide and ethanol.

Solvent exposure has been investigated to trigger actuation of shape memory polymers (SMPs) as an alternative to direct heating. This study aimed to investigate the feasibility of using dimethyl sulfoxide (DMSO) and ethanol (EtOH) to stimulate polyurethane-based SMP foam actuation and the required solvent concentrations in water for rapid actuation of hydrophobic SMP foams. SMP foams exhibited decreased Tg when submerged in DMSO and EtOH when compared to water submersion. Kinetic DMA experiments showed minimal or no relaxation for all SMP foams in water within 30 min, while SMP foams submerged in EtOH exhibited rapid relaxation within 1 min of submersion. SMP foams expanded rapidly in high concentrations of DMSO and EtOH solutions, where complete recovery over 30 min was observed in DMSO concentrations greater than 90% and in EtOH concentrations greater than 20%. This study demonstrates that both DMSO and EtOH are effective at triggering volume recovery of polyurethane-based SMP foams, including in aqueous environments, and provides promise for use of this actuation technique in various applications.

Effect of pendant group structure on the hydrolytic stability of polyaspartamide polymers under physiological conditions.

We describe the synthesis of metal chelating polymers based on polyaspartamide and polyglutamide backbones as carriers for (111)In in radioimmunoconjugates. These polymers [PAsp(DTPA), PGlu(DTPA)] have a biotin end group and diethylenetriaminepentaacetic acid (DTPA) chelators attached to the primary amines of the diethylenetriamine (DET) pendant groups of biotin-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)] and of biotin-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]glutamide} [PGlu(DET)]. Like Asn-containing proteins and polypeptides, polyaspartamides undergo uncatalyzed degradation under model physiological conditions (10 mM phosphate buffer, pH 7.4, 150 mM NaCl). We studied the uncatalyzed degradation of the polyaspartamide polymers by size exclusion chromatography and found that the degradation rate was sensitive to the nature of the pendant groups. The metal-free polymer underwent somewhat slower degradation than the corresponding polymers in which the DTPA groups were saturated with Eu(3+) or In(3+), but even after 14 days, substantial fractions of the polymers survived. We conclude that these polymers undergo negligible degradation on the time scale (24-48 h) of radioimmunotherapy treatment of tumors with (111)In. From a mechanistic perspective, we note that these degradation rates are on the order of the deamidation rates reported [J. Peptide Res. 2004, 63, 426] for Asn-containing pentapeptides, with half-times on the order of 10 days, but much slower than the rapid decay (hours) reported recently [Biomaterials 2010, 31, 3707] for poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} itself. This variation in degradation rate can be explained in terms of the influence of positive charges on the pendant group enhancing the acidity of the side-chain amide nitrogen of the aspartamide repeat unit. The DET pendant group is positively charged at pH 7, but in indium-loaded PAsp(DTPA) this charge is offset by the net negative charge of the DTPA-In complex.

Angiotensin II and the cardiac complications of diabetes mellitus.

The prevalence of diabetes has reached epidemic proportions in the developed world and is expect to increase to 5.4% by 2025. This has resulted in an unprecedented number of patients experiencing the macro- and micro-vascular complications of diabetes, such as renal, retinal, neurological and cardiac dysfunction. Premature coronary artery disease and cardiac failure are vastly over-represented in the diabetic population, with significant morbidity and mortality. In fact, the rate of cardiac events in patients with diabetes is equivalent to non-diabetic patients with a previous myocardial infarction. Epidemiological evidence, combined with the results of large scale trials blocking the renin-angiotensin system (RAS) have provided data to support the hypothesis that angiotensin II and its interaction with the metabolic changes associated with diabetes mellitus is responsible for the pathogenesis of many of these complications. This review focuses on the role of the RAS and the development of diabetic cardiac disease.

Mesenchymal stem cells for cardiac regenerative therapy.

Until recently, the concept of treating the injured or failing heart by generating new functional myocardium was considered physiologically impossible. Major scientific strides in the past few years have challenged the concept that the heart is a post-mitotic organ, leading to the hypothesis that cardiac regeneration could be therapeutically achieved. Bone marrow-derived adult stem cells were among the first cell populations that were used to test this hypothesis. Animal studies and early clinical experience support the concept that therapeutically delivered mesenchymal stem cells (MSCs) safely improve heart function after an acute myocardial infarction (MI). MSCs produce a variety of cardio-protective signalling molecules, and have the ability to differentiate into both myocyte and vascular lineages. Additionally, MSCs are attractive as a cellular vehicle for gene delivery, cell transplantation or for tissue engineering because they offer several practical advantages. They can be obtained in relatively large numbers through standard clinical procedures, and they are easily expanded in culture. The multi-lineage potential of MSC, in combination with their immunoprivileged status, make MSCs a promising source for cell therapy in cardiac diseases. Here we provide an overview of biological characteristics of MSCs, experimental animal studies and early clinical trials with MSCs. In addition, we discuss the routes of cell delivery, cell tracking experiments and current knowledge of the mechanistic underpinnings of their action.

Management of ischaemic heart disease in women of child-bearing age.

Ischaemic heart disease is rare in young women but is expected to increase with increasing average age of child bearing. Diagnosis of myocardial ischaemia in this group is complicated by limited data about maternal and fetal safety of the standard diagnostic tests routinely used in other patients. Management of these patients remains difficult, as many standard treatments, such as beta-blockers and angiotensin converting enzyme inhibitors are pregnancy category C or D, and there is little experience with many of the newer treatments such as coronary artery stenting, clopidogrel and glycoprotein IIb/IIIa inhibitors in pregnancy. An interesting case of a woman, who had an acute myocardial infarction treated with thrombolysis and coronary artery stenting, and who subsequently became pregnant, is reported here, and other published reports regarding the management of coronary artery disease, both acute and chronic, in pregnant women are explored.

Mural endocarditis caused by Salmonella virchow: survival with conservative treatment.

We describe a case of endocarditis caused by Salmonella enterica serotype virchow, which was treated conservatively with antibiotics alone. It is the only reported case of survival from salmonella endocarditis with conservative treatment, and the first reported case of endocarditis caused by Salmonella virchow. The changing prevalence, virulence patterns and importance of salmonella species in endocarditis are discussed.

Hypothalamic-pituitary-adrenal axis activity during exercise in African American and Caucasian women.

African American women have a greater prevalence of obesity than Caucasian women, but the reasons for this difference are not known. We have investigated whether activity of the hypothalamic-pituitary adrenal axis plays a role in this phenomenon. Previous studies have shown that plasma ACTH immunoreactivity (ACTH-IR) of African American women, measured after ovine CRH (oCRH) stimulation, is significantly greater than ACTH-IR of Caucasian women, but is not accompanied by greater plasma cortisol concentrations. Analysis by high pressure liquid chromatography has demonstrated that after oCRH stimulation, the plasma ACTH-IR of African American women contains many nonintact ACTH fragments not found in Caucasians. To determine whether these racial differences in ACTH-IR secretion are an artifact of exogenous oCRH administration or are also found after a physiological stimulus for ACTH secretion, we measured hormones of the hypothalamic-pituitary adrenal axis before and after a standardized, maximal exercise treadmill test in 16 African American and 19 Caucasian healthy women matched for age, socioeconomic status, and body mass index. The intensity of exercise performed was similar in the two groups, as determined by duration of exercise, perceived intensity of exertion, plasma lactate, maximal heart rate, and maximum oxygen uptake. Basal ACTH-IR measured by RIA or immunoradiometric assay and cortisol were similar in African Americans and Caucasians. Plasma ACTH-IR, measured 10 min after completion of exercise, was significantly greater in African Americans than in Caucasians [by RIA: mean +/- SD ACTH-IR, 47.1 +/- 30.9 vs. 25.4 +/- 16.7 pmol/L (P < 0.01); by immunoradiometric assay: ACTH-IR, 45.9 +/- 43.2 vs. 21.1 +/- 14.6 pmol/L (P < 0.05)]. However, plasma cortisol after exercise was not different (450.2 +/- 157.7 vs. 483.6 +/- 180.4 nmol/L; P = 0.57). We conclude that ACTH-IR is significantly greater in African American than in Caucasian women after intense exercise. The ACTH-IR of African Americans and Caucasians does not appear to be equipotent at adrenal melanocortin-2 receptors, because the greater ACTH-IR of African Americans does not lead to greater cortisol secretion. Whether some components of the ACTH-IR detected in African Americans affect signal transduction of the hypothalamic melanocortin-4 receptors implicated in body weight regulation and thus predispose African American women to weight gain without altering plasma cortisol remains to be determined.

The maritime environment: a comparison with land-based remote area health care.

The sea is not often considered when discussing remote area health care; however, when a comparison is made of the challenges posed by this and land-based remote areas and the experiences of people providing health care in both settings, the similarities are striking. Like people living in land-based remote areas, seafarers live in isolated communities, are often in remote geographical locations, and are required to be self-sufficient in the provision of health care, utilising limited medical resources and training in conjunction with radio medical advice. Given the large numbers of small, isolated floating communities that characterise the world shipping industry, some consideration of the quality of and access to health care needs to be made. This paper introduces the marine environment as a remote area, drawing comparisons between it and land-based environments. Issues pertinent to the people providing health care in both environments are discussed. These issues include limited educational preparation, sparse resources and the problems related to distance, isolation, communication, accessibility and weather.

Resting metabolic rate in African-American and Caucasian girls.

Recent studies have found a lower resting metabolic rate (RMR) in African-American (AA) women with obesity as compared with Caucasian (C) women with obesity. It is unknown if this difference in RMR is seen in prepubertal girls or in those of average body weight. Therefore, we studied RMR in 21 AA and 24 C girls, ages 7-10, who were well matched for age, weight, body mass index (BMI), and pubertal status. All had BMI between 15% and 85% for age and race, based on data from the First National Health and Nutrition Examination Survey. Fat free mass (FFM) was measured by dual-energy X-ray absorptiometry. RMR was measured with a Deltatrac indirect calorimeter under controlled conditions after the subjects underwent an overnight fast. The slopes of the regression equations were similar for both groups (p = 0.7). After adjustment for FEM, the AA girls had a significantly lower RMR than did the C girls (-92 +/- 32 kcal/d, p = 0.007 by analysis of covariance). This significance was maintained after exclusion of total body bone mineral content. These data suggest that normal-weight prepubertal AA girls may have reduced resting energy expenditure compared with C girls.

Molecular typing and haplotypic associations of HLA-B*44 subtypes.

The heterogeneity of HLA-B44 is confirmed and the sequence difference between the two major subtypes, B*4402, *4403, is attributed to one polymorphic site in the third exon. A method is described to discriminate B*4402 and B*4403, and the occurrence and linkage disequilibrium of B*44 subtypes is discussed. No example of B*4401 polymorphism in exon 2 was observed.

The role of magnesium in myocardial preservation.

The purpose of this review is to look at the role of magnesium in the formation of preservation and reperfusion solutions for the ischaemic heart. Preservation of the heart during cardiac surgery procedures, including cardiac transplantation, can be divided into distinct phases: arrest, cold storage in the case of transplantation, global ischaemia during implantation or cardiac surgery procedures, followed by reperfusion when the heart is rewarmed and restarted. Although the magnesium ion can play a significant role in myocardial protection, it is important to recognize the different types of protection required during these different phases of surgical procedures. The rationale for the inclusion of magnesium in cardioplegic solutions is threefold: (i) for its negative inotropic effect; (ii) to prevent ischaemia-induced magnesium loss; (iii) to influence cellular ionic movements. Preservation temperature as well as the concentration of other ionic constituents present in the preservation solution alter the effects of magnesium. Results obtained from animal models suggest that elevated magnesium (16 mM) is beneficial to the hypothermic preservation of hearts with extracellular type solutions, especially when calcium is elevated in the solution formulation. Research has shown that the amplitude of the inotropic effect of magnesium varies from one species to another so that the beneficial effect of magnesium is inferior in the less sensitive species. Using the human atrial trabecular preparation as a model for myocardial preservation, we have assessed the effects of elevated magnesium on the recovery of developed force, both for long-term preservation (24 h) during hypothermic arrest (4 degrees C) and for reperfusion during rewarming of the trabeculae. No clear pattern emerged when the ratio of calcium to magnesium was altered in St Thomas' I and II solutions used for the storage. However, when the atrial trabecular preparation was rewarmed in a Krebs Henseleit buffer containing an elevated level of magnesium (16 mM), a greater number of trabeculae reached a greater developed force and had higher levels of energetic metabolites than when the magnesium in the Krebs Henseleit buffer was 1.2 mM. Several studies have suggested that an elevated magnesium prevents calcium overload by competing with this ion at the membrane, and reduces the workload, while ATP reserves and ion homoeostasis are re-established. The role of the magnesium ion in hypothermic preservation of the human myocardium is still not clear after many clinical and experimental studies and requires further investigation.(ABSTRACT TRUNCATED AT 400 WORDS)

Methods for assessing drivers' perception of specific hazards on the road.

The purpose of this research was to test a number of techniques for assessing drivers' perception of hazards. The techniques included three types of interview methods, the Q-sort method, and several variants of the repertory grid method. The techniques were judged largely on their ability to differentiate between old and young drivers, two groups with known differences in accident frequency. None of the interview techniques produced useful information regarding drivers' perception of hazards, and neither these techniques nor the Q-sort discriminated between old and young drivers. All the variants of the repertory grid differentiated between old and young drivers, in the sense that old drivers used extremes of the rating scale more often than young drivers. This phenomenon was most apparent with the fixed repertory grid. Further work on this technique revealed further differences between the age groups in terms of the correlational structure of the responses, which point to a number of hypotheses about risk perception in old and young drivers.

DR4 and susceptibility to type I diabetes mellitus: discrimination of high risk and low risk DR4 haplotypes on the basis of TA10 typing.

DR4 related serological heterogeneity differences between type I diabetic and normal individuals previously observed appear to be due to differences in the DQ subregion. An Australasian sera study has identified two subsets of DQw3, the DQ allele in linkage disequilibrium with DR4, one of which (DQw3S) is present in 95.2% of diabetic DR4 compared with 58.1% of normal DR4 individuals (p less than 0.0005). The DQw3 subset showing a negative association with diabetes, DQw3L, appears to be closely related to or identical to TA10 a DQ subregion product previously described and studied in the 9th International Workshop. Analysis of the Workshop data showed a strong association of TA10- in type I diabetic DR4 individuals (93.5% v 69.1% in DR4 + normals) (p less than 0.0005). B44 appears to show an association with the presence of TA10 in DR4 positive individuals. This observation is suggestive of positive linkage disequilibrium and may explain the decreased frequency of the B44-DR4 haplotype in type I diabetes.

Mossbauer spectra of bicarbonate-free ferric-transferrin complex.

The bicarbonate-free ferric-transferrin complex was investigated by Mossbauer Spectroscopy under anaerobic conditions. No evidence of specific binding was found. The spectral results indicates that the apparent binding is due to the formation of antiferromagnetic ferric hydroxide polymers which are firmly attached to the transferrin molecule. Specific binding would only occur in the presence of bicarbonate or other low molecular weight chelators.

Basilar membrane vibration examined with the Mössbauer technique.

The tuning curve has been measured, in vivo, at a point approximately 1.5 millimeters from the stapes in the first turn of the guinea pig cochlea. Curves for constant stapes movement and constant sound pressure were obtained over the range 350 hertz to 30 kilohertz, with an amplitude peak at about 18 kilohertz.