Maternal insulin resistance, triglycerides and cord blood insulin in relation to post-natal weight trajectories and body composition in the offspring up to 2 years.

AIMS: The intrauterine metabolic environment might have a programming effect on offspring body composition. We aimed to explore associations of maternal variables of glucose and lipid metabolism during pregnancy, as well as cord blood insulin, with infant growth and body composition up to 2 years post-partum. METHODS: Data of pregnant women and their infants came from a randomized controlled trial designed to investigate the impact of nutritional fatty acids on adipose tissue development in the offspring. Of the 208 pregnant women enrolled, 118 infants were examined at 2 years. In the present analysis, maternal fasting plasma insulin, homeostasis model assessment of insulin resistance and serum triglycerides measured during pregnancy, as well as insulin in umbilical cord plasma, were related to infant growth and body composition assessed by skinfold thickness measurements and abdominal ultrasonography up to 2 years of age. RESULTS: Maternal homeostasis model assessment of insulin resistance at the 32nd week of gestation was significantly inversely associated with infant lean body mass at birth, whereas the change in serum triglycerides during pregnancy was positively associated with ponderal index at 4 months, but not at later time points. Cord plasma insulin correlated positively with birthweight and neonatal fat mass and was inversely associated with body weight gain up to 2 years after multiple adjustments. Subsequent stratification by gender revealed that this relationship with weight gain was stronger, and significant only in girls. CONCLUSIONS: Cord blood insulin is inversely associated with subsequent infant weight gain up to 2 years and this seems to be more pronounced in girls.

Influence of surface chemistry of the substrate on the adsorption of Escherichia coli.

The adsorption of Escherichia coli as influenced by the surface chemistry of different absorbents was studied with microbeads of (1) polystyrene, hydroxymethylated, chloromethylated and aminomethylated polystyrene, (2) cation and anion exchange resins, (3) glass and siliconized glass using a shake test. The adsorption kinetics can be described by a first order rate law for all materials. The specific surface free energy is not even a rough correlation parameter for the adsorption effect. Polar groups with the exception of those with a negative charge (cation exchange resin) favour adsorption of Escherichia coli, but the type of the polar surface group plays a dominating role. Adsorption was maximum with protonated aminomethylated polystyrene which is attributed to the interaction of the positive charge with the negatively charged bacterial surface.

Carbon, a promising material in endoprosthetics. Part 1: the carbon materials and their mechanical properties.

Progress in endoprosthetics depends to a large extent on the availability of materials. Carbon is known for its excellent biocompatibility. Carbon materials can also be manufactured with a great variety of properties. The application of carbon materials has been restricted to some special cases like heart valves or tooth roots. Construction of high-loaded endoprosthetic joints has been impossible due to insufficient mechanical strength or manufacturable size of the materials. Three new carbon materials have been developed which seem to offer new possibilities: (1) a high strength isotropic carbon, (2) a silicon carbide/carbon composite (SiC/C) and (3) a carbon fibre reinforced carbon (CFRC). The mechanical properties of these materials were investigated including size effects (length / to thickness d ratio of samples) and manufactured parameters (final heat treatment temperature, fibre volume content and fibre orientation). Flexural strength of the first two materials, which are both isotropic, increases with decreasing l/d ratio, whereas the CFRC behaves contrarily. In the latter case, failure at low l/d ratios is caused by shear failure. The Wöhler diagram of all three materials demonstrates limits of fatigue even after only 10(3) to 10(4) cycles. The fatigue strength of the isotropic C and the SiC/C is between 70 and 80% of the static strength, even in Ringer's solution. The Young's modulus of the isotropic C is comparable to that of femoral bone. The modulus of the SiC/C is still appreciably low. It follows that both isotropic materials are applicable for sliding parts like ball and socket. Their tribological properties are described in a following paper. The CFRC finally combines high fatigue strength (approximately 400 MN/m2) with a moderate Young's modulus (approximately 150 X 10(3) MN/m2). These properties indicate application for shafts and pins.

Carbon, a promising material in endoprosthetics. part 2: tribological properties.

In a previous three types of carbon materials were presented. A basic study of their mechanical properties showed that two of these materials might be applicable for sliding parts of artificial joints such as ball and acetabular cup of a hip joint endoprosthesis. The materials are: (1) a high strength isotropic carbon and (2) a silicon carbide/carbon composite material. The results of relevant tribological investigations are given in this paper. Experimental methods applied consisted of ring-on-disc and ball-in-socket tests. Ring-on-disc tests were performed with specific loads of 10, 20 and 30 MN/m2. In the ball-in-socket tests the gap width was 0.075 and 0.1 mm but the load was adjusted in such a way that the compression stress in the contact area was constant at 6.6 MN/m2. The latter was experimentally measured and theoretically calculated with good accordance. Ringer's solution was used as a lubricant. In ring-on-disc tests the ring was made of the SiC/C and the disc of the isotropic carbon. In ball-in-socket tests balls of SiC/C and sockets os isotropic carbon were chosen. For comparison the combination CoCrMo alloy or Al2O3 as ball, and HDPE as socket, were tested under corresponding conditions. It is shown, that the special carbon materials can withstand the extreme tribological conditions of high specific load and low sliding velocity. Neither material suffers from fatigue wear. The coefficient of friction is below 0.1 even at a specific load of 30 MN/m2. The wear rate as determined with ring-on-disc test is lower than those of all known and proposed material combinations. The data with the carbon materials combination indicate a penetration of the ball into the acetabular cup of only 1 micrometer per year.

Carbon as an implant material in orthopaedic surgery.

Carbon is a material of proven value in many fields of medicine. It has only minor reactions compared with other materials, but does have unfavourable mechanical characteristics. New kinds of carbon with similar physical characteristics to other materials, e.g. steel and ceramic, have now been developed.

[Mechanical properties of carbon as implant material in orthopedic surgery (author's transl)]. / Mechanische Aspekte des Kohlenstoffes als Mehrzweck-Implantatwerkstoff in der orthopädischen Chirurgie.

Among others material problems are come to the fore in endoprothetic with growing biochemical knowledge, also because of the realisation that in different parts of the same prothesis functionally different mechanical demands must be set. Technological progress in carbon production has lead to the development of a spectrum of different carbon specialities with various mechanical properties. In orthopaedic surgery of endoprothetic high strengh isotropic carbon, impregnated carbon and fibrereinforced carbon-carbon-composites are of particular interest, because of their physical properties and unchanged favourable chemical and biological properties of carbon. Thereby it is on one side a question of carbon material with extraordinary tribological qualities, on the other side of carbons with nearly isoelastic behaviour towards the bone, respectively with equal quotient of breaking strength and young's modulus. Therefore in future the manufacture of components with functional approbiate material using the same basic material carbon seems to be possible for the production of endoprothesis with different working parts.