Development of vascular substitutes for low-flow peripheral bypass grafting - a review.

The development of a low-flow vascular prosthesis is a very topical issue. The authors present a pathway for the development of a prosthesis with optimal properties based on the idea of mimicking the characteristics of a biological model (saphenous vein graft) and programming these properties in the model of the prosthetic substitute. The vascular prosthesis presented consists of three layers - a non-absorbable scaffold representing vascular “media”, and two absorbable collagen layers - pseudointima and pseudoadventitia. The basic methods of physical testing are presented - the single axis stretch test and inflation-extension test, as well as other procedures that affect the final properties. These include collagen curing, antithrombotic treatment of the inner layer and the use of sterilization methods. The designed new graft was successfully implanted in an ovine model.

Constitutive modeling of human saphenous veins at overloading pressures.

In the present study, inflation tests with free axial extension of 15 human vena saphena magna were conducted ex vivo to obtain data suitable for multi-axial constitutive modeling at overloading conditions (pressures up to approximately 15kPa). Subsequently the data were fitted with a hyperelastic, nonlinear and anisotropic constitutive model based on the theory of the closed thick-walled tube. It was observed that initial highly deformable behavior (up to approximately 2.5kPa) in the pressure-circumferential stretch response is followed by progressive large strain stiffening. Contrary to that, samples were much stiffer in longitudinal direction, where the observed stretches were in the range 0.98-1.03 during the entire pressurization in most cases. The effect of possible residual stress was evaluated in a simulation of the intramural stress distribution with the opening angle prescribed to 0°, 10°, 20°, 30°, 40°, and 50°. The result suggests that the optimal opening angle making the stress distribution through the wall thickness uniform is about 40°. The material parameters presented here are suitable for use in mechanobiological simulations describing the adaptation of the autologous vein wall after bypass surgery.

Mucoadhesive polymers as platforms for peroral peptide delivery and absorption: synthesis and evaluation of different chitosan-EDTA conjugates.

The purpose of the present study was to synthesize and evaluate mucoadhesive polymers, exhibiting a high capacity to bind bivalent cations which are essential co-factors for intestinal proteolytic enzymes. Under the formation of amide bonds, the complexing agent EDTA was covalently bound to the primary amino groups of chitosan. One gram of the resulting conjugate with the lowest amount of remaining free amino groups (0.1 +/- 0.03%; mean +/- SD, n = 3) based on free chitosan as 1.0 was capable of binding 1.4 +/- 0.1 mM calcium, 2.0 +/- 0.1 mM zinc and 1.9 +/- 0.03 mM cobalt (mean +/- SD, n = 3) under intestinal pH-conditions, respectively. Whereas proteolytic activity of the serine proteases trypsin (EC 3.4.21.4), alpha-chymotrypsin (EC 3.4.21.1) and elastase (EC 3.4.21.36) could not be inhibited, proteolytic activity of the zinc proteases carboxypeptidase A (EC 3.4.17.1) and aminopeptidase N (EC 3.4.11.2) was strongly inhibited by the chitosan-EDTA conjugate. Moreover, it displays quick swelling properties in water and basic aqueous solutions. The adhesive force of the conjugate was even higher than of chitosan HCl. However, lowering the percentage of covalently attached EDTA on the polymer, leads to a significantly reduced adhesive force. According to these results, chitosan-EDTA conjugates exhibiting the lowest amount of remaining free amino groups, seem to be a useful tool in overcoming the enzymatic barrier for perorally administered therapeutic peptides.

Hearing loss in Down's syndrome. A treatable handicap more common than generally recognized.

Significant hearing loss was found in about two-thirds of a series of 107 individuals with Down's syndrome. Hearing loss of that degree causes retardation of speech, language and intellectual development in normal children. Down's children are presumably affected even more by this sensory deprivation and without correction are prevented from reaching their full potential.

PNP roles and interventions with children with special needs and their families.

Pediatric nurse practitioners (PNPs) can create excellent professional roles caring for children with special health care needs (CSHCN) and their families. Children with chronic conditions represent an estimated 31% of the US population younger than 18 years (approximately 20 million children in 1988). Five percent of all children who have multiple special needs account for approximately 40% of all pediatric health care expenditures. Skill building is needed for PNPs who have traditionally focused on wellness and common acute illnesses in primary care settings. Role theory and research can guide PNPs in creating roles and interventions to improve the health, safety, and developmental outcomes for CSHCN and their families. Two roles are described, with examples of specific nursing interventions. Assisting child care centers to serve children and families with special needs is an ideal role for PNPs who have knowledge of health and regulatory issues. Another important PNP role is working with adolescents with special health care needs as they transition from pediatric to adult care. Many resources (such as those from the Maternal and Child Health Bureau) are available to assist PNPs to create new roles and interventions for CSHCN and their families.

First Start: specially trained child care providers.

Child care programs that serve infants and toddlers with disabilities and chronic illnesses and that have staffs with specially trained caretakers can greatly improve the quality of life of these children. First Start is an interdisciplinary program that provides special training for these caretakers.