Shenggao Han

No-React Detoxification Process: A Superior Anticalcification Method for Bioprostheses

BACKGROUND Glutaraldehyde pretreatment of bioprosthetic heart valves is the major pathogenic factor in their calcific degeneration. This comparative study investigates the merit of the No-React aldehyde detoxification process as an alternative modifier of xenograft tissues. METHODS Glutaraldehyde- and No-React-pretreated porcine aortic valve cusps were implanted subcutaneously in 6-week-old rats (n = 20). At 3, 6, and 14 weeks, randomly selected animals were sacrificed and the explants underwent mineral and morphologic analyses. Glutaraldehyde- and No-React-treated bovine pericardium and porcine aortic valve cusp were incubated in fibroblast cell culture plates. Cell viability was observed under reversed microscope at 6, 24, 48, and 96 hours. Erythrosin B dye exclusion test was used to validate percent cell death. RESULTS Pretreatment with No-React significantly inhibited calcification of aortic cusp subcutaneous implants throughout the 14-week period (mean tissue Ca2+ content = 1.3 +/- 0.7 micrograms/mg at 14 weeks.) Glutaraldehyde-treated cusps underwent protracted calcification (Ca2+ content = 190.6 +/- 89.5 micrograms/mg; p < 0.01). Morphologic findings correlated with mineral analyses. One-hundred percent of fibroblast cells survived in the presence of No-React-treated tissue, with a growth pattern indistinguishable from control cell culture (ie, in the presence of no tissue). The cells incubated with glutaraldehyde-treated tissue showed signs of nonviability by 6 hours, with 100% cell death by 48 hours. Dye exclusion tests validated these findings. CONCLUSIONS The No-React detoxification process completely abolishes the cytotoxicity of the xenograft tissue and inhibits calcific degeneration.

Effects of Weight Loss and Weight-Bearing Exercise on Blood and Organ Concentrations of Lead and Some Essential Metals

Thousands of years of human evolution have resulted in the selection of genes that enhance the ability to survive during extended periods of starvation or reduced energy intake. However, this has occurred in the absence of extensive exposure to environmental pollutants. Adults cur-rently living in industrialized countries have body lead burdens about 500 times greater than those who lived prior to widespread lead dissemination in the environment. Most (>95%) of the lead burden is stored in the skeleton. During rapid weight loss, there is a decline in bone mass in addition to soft tissue mass. This bone mass loss may mobilize skeletal lead. However, weight-bearing exercise during weight loss may prevent or reduce bone lead mobilization and redistribu-tion to other organs. The objective was to determine the effects of weight loss, with and without weight-bearing exercise, on lead and essential metal stores in rats with prior lead exposure. Fifty-five, 12-week-old, female, Sprague-Dawley rats were exposed to 400 ppm lead as the acetate in drinking water for 4 weeks, followed by a one-week period without lead exposure. The rats were randomly assigned to seven groups before the start of food restriction. The seven groups were weight maintenance (WM) with ad lib feeding, moderate weight loss (MWL) with 25% food restriction and substantial weight loss (SWL) with 50% food restriction, with or without treadmill running, and one background group euthanized before food restriction. Tread-mill running speed was gradually increased to

RELATIONSHIPS BETWEEN TRACE ELEMENT NUTRITURE AND PROGRESSION OF HUMAN IMMUNODEFICIENCY VIRUS INFECTION

Immune function is highly dependent on nutritional status, since its large mass and high rate of cellular turnover make the immune system a major user of nutrients. Furthermore, there is enhanced nutrient utilization during acute and chronic infections, including HIV-1 infection. Glutathione (GSH), magnesium (Mg), copper (Cu), zinc (Zn), and choline are among the nutrients required to support cellular immune function; we have found reduced intra and/or extracellular concentrations of GSH, Mg, and choline in patients with HIV-1 infection in a prior study (Skurnick et al., 1996). The current study assessed relationships among HIV-1 progression and several nutritional/biochemical variables including three essential elements—magnesium, copper and zinc.

Age at Lead Exposure Influences Lead Retention in Bone

More than 90% of the body lead burden in rats and people is in the skeleton (1–3). The half-life of bone lead is long, 5–20 years or more, with lead in cortical bone having a longer biological residence time than lead in trabecular bone (1–3). The long half-life suggests that environmental exposure of children to lead can result in bone lead accumulation that may persist for many years. However, it has been hypothesized that the high rate of bone remodeling during childhood and the related high turnover of calcium and lead results in a substantial reduction in bone lead stores, so that much of the lead incorporated into bone during childhood does not persist into adulthood (4). We tested the alternative hypothesis that younger age at lead exposure results in a greater accumulation of lead stored in the skeleton as well as in soft tissues. The objective of this study was to determine the effect of age during lead exposure on blood and organ lead concentrations one month later. Organ concentrations of the essential divalent metals calcium, copper, iron, magnesium, and zinc were also measured for comparison to lead.