Controlled Release of Vanadium from a Composite Scaffold Stimulates Mesenchymal Stem Cell Osteochondrogenesis.

Large bone defects often require the use of autograft, allograft, or synthetic bone graft augmentation; however, these treatments can result in delayed osseous integration. A tissue engineering strategy would be the use of a scaffold that could promote the normal fracture healing process of endochondral ossification, where an intermediate cartilage phase is later transformed to bone. This study investigated vanadyl acetylacetonate (VAC), an insulin mimetic, combined with a fibrous composite scaffold, consisting of polycaprolactone with nanoparticles of hydroxyapatite and beta-tricalcium phosphate, as a potential bone tissue engineering scaffold. The differentiation of human mesenchymal stem cells (MSCs) was evaluated on 0.05 and 0.025 wt% VAC containing composite scaffolds (VAC composites) in vitro using three different induction media: osteogenic (OS), chondrogenic (CCM), and chondrogenic/osteogenic (C/O) media, which mimics endochondral ossification. The controlled release of VAC was achieved over 28 days for the VAC composites, where approximately 30% of the VAC was released over this period. MSCs cultured on the VAC composites in C/O media had increased alkaline phosphatase activity, osteocalcin production, and collagen synthesis over the composite scaffold without VAC. In addition, gene expressions for chondrogenesis (Sox9) and hypertrophic markers (VEGF, MMP-13, and collagen X) were the highest on VAC composites. Almost a 1000-fold increase in VEGF gene expression and VEGF formation, as indicated by immunostaining, was achieved for cells cultured on VAC composites in C/O media, suggesting VAC will promote angiogenesis in vivo. These results demonstrate the potential of VAC composite scaffolds in supporting endochondral ossification as a bone tissue engineering strategy.

Influence of zinc on immunity in the elderly.

There is compelling evidence that demonstrates that severe zinc deficiency can cause substantial impairment of cellular immunity which can result in infection and even death. The effects on immunity of mild to moderate zinc deficiency are considerably less severe and may be subtle. Zinc supplementation, especially in combination with other micronutrients, can enhance immunity if an underlying deficiency is present. Supplementation with zinc as a single nutrient, especially at high doses, can have adverse effects that include interfering with copper nutriture and impairment of immune functions.

Administration of the oral antibiotic frenolicin-B selectively alters copper nutriture in male rats.

The polyketide antibiotic Frenolicin-B (FB) produces anorexia and esophageal epithelial hyperplasia (EH) in rats, findings that are characteristic of zinc deficiency. Because FB also chelates divalent cations in vitro, we conducted studies to determine whether FB modifies blood and organ concentrations of zinc and other essential metals (calcium, copper, iron and magnesium). Groups of male Sprague-Dawley rats ( approximately 250g; n = 20/group) consumed diets with adequate (40 microg/g), deficient (<2 microg/g) or fortified (100 microg/g) zinc concentrations ad libitum for 28 d. Two groups fed either Zn-adequate or Zn-fortified diets also were given 100 mg/(kg. d) of FB in diet, and 2 groups were pair-fed controls. Histopathology or metal analyses were performed on tissues from 10 rats/group. FB caused EH of the nonglandular stomach but not of other tissues. Of the metals evaluated, only copper concentrations were significantly reduced in all tissues examined except kidney. A broad range of kidney copper concentrations was found; these concentrations were associated with plasma copper and proteinaceous deposits within tubules. In rats, FB substantially and selectively depletes Cu in vivo, suggesting that drugs with structures that permit metal chelation should be evaluated for their potential to alter trace metal nutriture.

Status of selected nutrients and progression of human immunodeficiency virus type 1 infection.

BACKGROUND: Immune function is highly dependent on nutritional status because the large mass and high rate of cellular turnover of the immune system make it a major user of nutrients. Furthermore, nutrient requirements may be increased during acute and chronic infections, including HIV-1 infection. OBJECTIVE: The current study was designed to assess relations among HIV-1 progression and 11 nutritional and demographic variables. DESIGN: The participants were 106 HIV-infected outpatients and 29 uninfected control subjects (n = 89 men and 46 women; age range: 35-57 y). The HIV-infected subjects represented a broad range of disease progression. RESULTS: We found lower concentrations of plasma and erythrocyte magnesium and of erythrocyte reduced glutathione beginning early in the course of HIV-1 infection. Significantly decreased hematocrit and increased serum copper concentration developed only late in the course of the disease. Statistically significant univariate associations were found between the CD4(+) T lymphocyte count and hematocrit, plasma magnesium concentration, and plasma zinc concentration. The lowest erythrocyte magnesium concentrations occurred in HIV-infected subjects who consumed alcoholic beverages. Independent variables that were significant joint predictors of CD4(+) cell count in multiple regression analyses were hematocrit and plasma free choline and zinc concentrations. These 3 factors together explained 43% of the variability in CD4(+) cell counts. CONCLUSION: The results provide evidence that compromised nutritional and antioxidant status begin early in the course of HIV-1 infection and may contribute to disease progression.

Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Millions of women of child-bearing age have substantial bone lead stores due to lead exposure as children. Dietary calcium ingested simultaneously with lead exposure can reduce lead absorption and accumulation. However, the effects of dietary calcium on previously accumulated maternal lead stores and transfer to the fetus have not been investigated. We studied the effects of lead exposure of female rats at an early age on fetal development during a subsequent pregnancy. We gave 5-week-old female Sprague-Dawley rats lead as the acetate in their drinking water for 5 weeks; controls received equimolar sodium acetate. This was followed by a 1-month period without lead exposure before mating. We randomly assigned pregnant rats (n = 39) to diets with a deficient (0.1%) or normal (0.5%) calcium content during pregnancy. A total of 345 pups were delivered alive. Lead-exposed dams and their pups had significantly higher blood lead concentrations than controls, but the concentrations were in the range of those found in many pregnant women. Pups born to dams fed the calcium-deficient diet during pregnancy had higher blood and organ lead concentrations than pups born to dams fed the 0. 5% calcium diet. Pups born to lead-exposed dams had significantly (p<0.0001) lower mean birth weights and birth lengths than controls. There were significant inverse univariate associations between dam or pup organ lead concentrations and birth weight or length. The 0.5% calcium diet did not increase in utero growth. Stepwise regression analysis demonstrated that greater litter size and female sex were significantly associated with reduced pup birth weight and length. However, lead exposure that ended well before pregnancy was significantly (p<0.0001) associated with reduced birth weight and length, even after litter size, pup sex, and dam weight gain during pregnancy were included in the regression analysis. The data demonstrate that an increase in dietary calcium during pregnancy can reduce fetal lead accumulation but cannot prevent lead-induced decreases in birth weight and length. The results provide evidence that dietary nutrients can influence the transfer of toxins to the fetus during pregnancy. If these results are applicable to women, an increase in diet calcium during pregnancy could reduce the transfer of lead from prepregnancy maternal exposures to the fetus.

HIV heterosexual transmission: a hypothesis about an additional potential determinant.

Transmission rates of human immunodeficiency virus (HIV) during heterosexual intercourse vary dramatically around the world. In Asia and South America, they are extraordinarily high, whereas in the United States and Europe, rates are much lower even after a large number of unprotected contacts. The transmission rates in Africa also probably are high, but the available studies unfortunately are weak. In Thailand, female-to-male transmission rates per contact were estimated at.056 (l in 18) compared to.0002 to.0015 (1/5000-1. 5/1000) for male-to-female transmission in the United States and Europe. Male-to-female transmission in Thailand appears to show, as expected, even greater transmission likelihood compared to female-to-male rates. In general, in the United States and Europe, transmission rates within heterosexual couples range from less than 10% to 22%, whereas in Thailand and Brazil, the rates exceed 40%. The much lower transmission rate per contact in the United States and Europe is based on an assumption that HIV transmitters are a homogeneous group. Wiley and colleagues argue that transmitters are likely to be a heterogeneous group with a large percentage of very low frequency transmitters and a small percentage of high frequency transmitters. That hypothesis is given some support by a cluster of cases in rural New York State in which one man appeared to infect 31% of his many contacts.

Effects of weight loss and exercise on the distribution of lead and essential trace elements in rats with prior lead exposure.

We studied the effects of weight loss and non-weight-bearing exercise (swimming) on blood and organ lead and essential metal concentrations in rats with prior lead exposure. Nine-week-old female Sprague-Dawley rats (n = 37) received lead acetate in their drinking water for 2 weeks, followed by a 4-day latency period without lead exposure. Rats were then randomly assigned to one of six treatment groups: weight maintenance with ad libitum feeding, moderate weight loss with 20% food restriction, and substantial weight loss with 40% food restriction, either with or without swimming. Blood lead concentrations were measured weekly. The rats were euthanized after a 4-week period of food restriction, and the brain, liver, kidneys, quadriceps muscle, lumbar spinal column bones, and femur were harvested for analysis for lead, calcium, copper, iron, magnesium, and zinc using atomic absorption spectrophotometry. Both swimming and nonswimming rats fed restricted diets had consistently higher blood lead concentrations than the ad libitum controls. Rats in the substantial weight loss group had higher organ lead concentrations than rats in the weight maintenance group. Rats in the moderate weight loss group had intermediate values. There were no significant differences in blood and organ lead concentrations between the swimming and nonswimming groups. Organ iron concentrations increased with weight loss, but those of the other metals studied did not. Weight loss also increased hematocrits and decreased bone density of the nonswimming rats. The response of lead stores to weight loss was similar to that of iron stores because both were conserved during food restriction in contrast to decreased stores of the other metals studied. It is possible that weight loss, especially rapid weight loss, could result in lead toxicity in people with a history of prior excessive lead exposure.

Dietary calcium intakes of urban children at risk of lead poisoning.

Dietary calcium is well known to decrease gastrointestinal lead absorption and thereby reduce the risk for lead poisoning. Because children in economically deprived urban centers are especially likely to have excessive lead exposure, we surveyed dietary calcium intakes of 314 children from the greater Newark, New Jersey, area. The areas of Newark and adjacent communities studied had been previously identified as containing significant sources of environmental lead by geographic information systems technology. An abbreviated National Cancer Institute Health Habits and History Questionnaire, modified to focus on foods high in calcium, was used to determine dietary calcium. Calcium intakes were then compared to the new Dietary Reference Intake (DRI) guidelines. The respondents were primarily the parents of African-American and Hispanic children ranging in age from 1 to 8 years, with a mean age of 3.5 years. The most recent blood lead concentration was 11.4 +/- 0.8 microg/dL (mean +/- standard error), and 48.6% had concentrations at or above the current guideline of 10 microg/dL. Quintiles of calcium intake were: 221 +/- 13; 488 +/- 9; 720 +/- 6; 885 +/- 6; and 1,389 +/- 49 mg/day. Fifty-five of 175 (31.4%) children aged 1-3 years had calcium intakes below the DRI, as did 82 of 139 (59.0%) children aged 4-8 years. The percentage of mothers reporting lactose intolerance in their children was 2.5%. The observation that the children in the highest quintile easily exceeded the DRIs for calcium suggests that urban parents who include dairy foods in their childrens' meals can provide a diet that meets the DRI guidelines. Children in the lowest quintiles are at risk of increased absorption of the environmental lead to which they are inevitably exposed, as well as other problems associated with a low intake of dietary calcium. The data suggest that both lead exposure and low dietary calcium continue to pose significant health risks to urban minority children.

Lead exposure at an early age substantially increases lead retention in the rat.

It has been hypothesized that the high rate of bone remodeling during childhood and the consequent high calcium and lead turnover result in a substantial reduction in bone lead stores so that much of the lead incorporated in bone during childhood does not persist into adulthood. We studied the effect of age at lead exposure on blood and organ concentrations of lead, calcium, and zinc 1-5 months after termination of lead ingestion. Blood and organ lead concentrations and contents 4 weeks after lead exposure ceased were significantly higher in the rats exposed beginning at 5 weeks of age than in those exposed beginning at 10 or 15 weeks old. Bone lead declined as the time since exposure increased. Despite this trend, the rats exposed when youngest had bone lead concentrations at 20 weeks after the termination of lead exposure that were higher than those of the other rats only 4 weeks after cessation of lead ingestion. Multiple regression analysis demonstrated that age at lead exposure remained a significant predictor of blood and organ lead concentrations and contents even after the inclusion of total lead consumed, body weight, and age at organ harvesting in the regression analysis. There were only small differences in organ calcium and zinc concentrations among treatment groups except for kidney calcium. The results do not support the hypothesis of rapid depletion of bone lead stores in young animals, but rather suggest that younger age at lead exposure is associated with greater lead retention and toxicity even in the absence of continued lead exposure.

Lead poisoning--one approach to a problem that won't go away.

A reduction in sources of environmental lead exposure has resulted in substantial declines in mean blood lead concentrations of all age groups in the United States. However, some segments of the population continue to have unacceptable levels of lead exposure and elevated blood lead concentrations. In addition, virtually all residents of industrialized countries have bone lead stores that are several orders of magnitude greater than those of our preindustrial ancestors. Recent studies suggest that these skeletal lead stores adversely affect health and can contribute to reduced birth weights, aggressive behavior in children, and anemia, hypertension, and kidney disease in adults. Evidence is described that demonstrates that an increase in dietary calcium consumption can reduce lead absorption and toxicity from exogenous and endogenous lead exposure. A relatively inexpensive and effective way to reduce the substantial morbidity that will result from widespread lead exposure is by fortification of a variety of foods with low levels of calcium. This approach can complement other efforts to prevent lead exposure and reduce lead toxicity.

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.

Calcification of bovine pericardium: glutaraldehyde versus No-React biomodification.

BACKGROUND: Calcific degeneration is the most frequent cause of clinical dysfunction of glutaraldehyde (GA)-pretreated bioprosthetic heart valves. The No-React (NR) process has been shown to be a promising anticalcification treatment. In this comparative study, our objective was to delineate the advantages of the NR treatment over GA. METHODS: Bovine pericardial strips pretreated with GA and NR were individually incubated in calcium phosphate solution for 21 days at 37 degrees C. The pretreated bovine pericardium then was implanted subcutaneously in rats and retrieved at 14, 21, and 35 days after-implantation. Mineral and morphologic analyses were performed on each specimen. RESULTS: The NR-treated pericardium revealed significantly reduced in vitro calcification compared with the GA-treated tissue (mean tissue calcium content 1.3 +/- 0.2 versus 5.9 +/- 0.7 micrograms/mg; p < 0.001). Mineral analysis showed progressive calcification of the GA-pretreated pericardium over the period of implantation (calcium content increasing from 49.6 +/- 9.6 micrograms/mg after 2 weeks to 134.3 +/- 9.1 micrograms/mg at 5 weeks after-implantation). The NR-treated implants had calcified significantly less (p < 0.05) at each corresponding interval. Moreover, morphologic examinations demonstrated a protracted inflammatory response in the form of giant cell and mononuclear cell infiltration associated with intrinsic collagen disruption in the GA-treated tissue; the NR-treated pericardium maintained morphologic integrity with a mild inflammatory response. CONCLUSIONS: The NR biochemical process appears not only to attenuate pericardial calcification, but also to abort the host's destructive inflammatory response to the xenograft.

Micronutrient profiles in HIV-1-infected heterosexual adults.

There is compelling evidence that micronutrients can profoundly affect immunity. We surveyed vitamin supplement use and circulating concentrations of 22 nutrients and glutathione in 64 HIV-1 seropositive men and women and 33 seronegative controls participating in a study of heterosexual HIV-1 transmission. We assayed antioxidants (vitamins A, C, and E; total carotenes), vitamins B6 and B12, folate, thiamin, niacin, biotin, riboflavin, pantothenic acid, free and total choline and carnitine, biopterin, inositol, copper, zinc, selenium, and magnesium. HIV-infected patients had lower mean circulating concentrations of magnesium (p < 0.0001), total carotenes (p = 0.009), total choline (p = 0.002), and glutathione (p = 0.045), and higher concentrations of niacin (p < 0.0001) than controls. Fifty-nine percent of HIV+ patients had low concentrations of magnesium, compared with 9% of controls (p < 0.0001). These abnormal concentrations were unrelated to stage of disease. Participants who took vitamin supplements had consistently fewer low concentrations of antioxidants, across HIV infection status and disease stage strata (p = 0.0006). Nevertheless, 29% of the HIV+ patients taking supplemental vitamins had subnormal levels of one or more antioxidants. The frequent occurrence of abnormal micronutrient nutriture, as found in these HIV+ subjects, may contribute to disease pathogenesis. The low magnesium concentrations may be particularly relevant to HIV-related symptoms of fatigue, lethargy, and impaired mentation.

Weight loss alters organ concentrations and contents of lead and some essential divalent metals in rats previously exposed to lead.

The loss of adipose tissue during energy restriction may be accompanied by a loss of lean body mass, including bone mass. Because most of the body lead burden is in the skeleton, we studied the effects of weight loss on the concentrations of lead in bone, blood and several organs in rats with prior but not current lead exposure. Concentrations of the essential divalent metals calcium, copper, iron, magnesium and zinc were also determined for comparison with lead. Lead-exposed rats (n = 25) were randomly assigned to one of three treatment groups: weight maintenance (WM), moderate weight loss (MWL) or substantial weight loss (SWL). For the two last-named groups, food intake was restricted for 4 wk to 70 and 40% of that of the WM group. Lead concentrations did not differ significantly (ANOVA, P > 0.05) among the three groups for blood, brain and bone. Significantly higher liver lead concentrations were observed in the SWL rats than in the WM and MWL groups. In general, organ concentrations of calcium, copper, magnesium and zinc were either lower or did not differ in the groups losing weight compared with the WM group. In contrast, organ Iron concentrations of the SWL group were higher than those of the other groups except in brain where there were no significant differences. The total liver content of lead was highest in the SWL group, but the lead content of other organs did not differ among the treatment groups. The contents of calcium, copper, magnesium and zinc generally were lower in the MWL and SWL groups than in the WM group in the liver and some of the other organs. The results demonstrate that weight loss can increase the quantity and concentration of lead in the liver, even in the absence of continued lead exposure. The data also demonstrate considerable differences among organ divalent metals in response to weight loss.

Dietary calcium and lead interact to modify maternal blood pressure, erythropoiesis, and fetal and neonatal growth in rats during pregnancy and lactation.

We studied the effects of dietary calcium and lead exposure on lead toxicity, fetal and neonatal growth, erythropoiesis and blood pressure during pregnancy and lactation in rats. Pregnant Sprague-Dawley rats (n = 43) were randomly assigned to one of six treatment groups of 7-8 rats each. Half of the rats were fed diets of low (0.1%), normal (0.5%) or high (2.5%) calcium as calcium carbonate and exposed to 250 mg/L of lead in their drinking water for the duration of the pregnancy and for 1 wk of lactation. Three control groups were fed the same diets without lead exposure. Pups were studied at 1 d and 1 wk of age. Maternal and fetal blood and organ samples from the groups fed the low calcium diet had the highest lead concentrations, whereas the lowest lead concentrations were found in the groups fed the high calcium diet. Dam and pup hemoglobin concentrations, hematocrits, and body weights and lengths were reduced by lead exposure and by the high calcium diet. The latter also reduced organ iron concentrations and prevented lead-induced increases in free erythrocyte protoporphyrin. Dam systolic blood pressures during the third trimester of gestation were significantly higher in rats exposed to lead and fed the low calcium diet than in rats in the other five treatment groups. The results demonstrate that dietary calcium and lead exposure interact in rats to influence maternal blood pressure, erythropoiesis, and fetal and neonatal growth during pregnancy and lactation.

Daily micronutrient supplements enhance delayed-hypersensitivity skin test responses in older people.

A placebo-controlled double-blind trial of the effects of daily micronutrient supplements on circulating vitamin and trace metal concentrations and delayed-hypersensitivity skin test (DHST) responses was conducted. Subjects, aged 59-85 y, were randomly assigned to placebo (n = 27) or micronutrient (n = 29) treatment groups. DHST and circulating concentrations of nine micronutrients were measured before and after 6 and 12 mo of micronutrient ingestion. For the micronutrient group, there were statistically significant increases at 6 and/or 12 mo in the mean serum concentrations of ascorbate, beta-carotene, folate, vitamin B-6, and alpha-tocopherol. There was a significant increase at 12 mo in the number of subjects in the placebo group with one or more low concentrations. DHST responses to a panel of seven recall antigens were significantly increased at 12 mo in the micronutrient group but not the placebo group. This study demonstrates that daily supplementation with low-to-moderate doses of micronutrients can prevent low concentrations of some micronutrients and can improve DHST responses in healthy, independently living older adults.