Fiber reinforced hydrated networks recapitulate the poroelastic mechanics of articular cartilage

The role of poroelasticity on the functional performance of articular cartilage has been established in the scientific literature since the 1960s. Despite the extensive knowledge on this topic there remain few attempts to design for poroelasticity and to our knowledge no demonstration of an engineered poroelastic material that approaches the physiological performance. In this paper, we report on the development of an engineered material that begins to approach physiological poroelasticity. We quantify poroelasticity using the fluid load fraction, apply mixture theory to model the material system, and determine cytocompatibility using primary human mesenchymal stem cells. The design approach is based on a fiber reinforced hydrated network and uses routine fabrication methods (electrohydrodynamic deposition) and materials (poly[ɛ-caprolactone] and gelatin) to develop the engineered poroelastic material. This composite material achieved a mean peak fluid load fraction of 68%, displayed consistency with mixture theory, and demonstrated cytocompatibility. This work creates a foundation for designing poroelastic cartilage implants and developing scaffold systems to study chondrocyte mechanobiology and tissue engineering. STATEMENT OF SIGNIFICANCE: Poroelasticity drives the functional mechanics of articular cartilage (load bearing and lubrication). In this work we develop the design rationale and approach to produce a poroelastic material, known as a fiber reinforced hydrated network (FiHy™), that begins to approach the native performance of articular cartilage. This is the first engineered material system capable of exceeding isotropic linear poroelastic theory. The framework developed here enables fundamental studies of poroelasticity and the development of translational materials for cartilage repair.

Intrinsic cell rheology drives junction maturation

A fundamental property of higher eukaryotes that underpins their evolutionary success is stable cell-cell cohesion. Yet, how intrinsic cell rheology and stiffness contributes to junction stabilization and maturation is poorly understood. We demonstrate that localized modulation of cell rheology governs the transition of a slack, undulated cell-cell contact (weak adhesion) to a mature, straight junction (optimal adhesion). Cell pairs confined on different geometries have heterogeneous elasticity maps and control their own intrinsic rheology co-ordinately. More compliant cell pairs grown on circles have slack contacts, while stiffer triangular cell pairs favour straight junctions with flanking contractile thin bundles. Counter-intuitively, straighter cell-cell contacts have reduced receptor density and less dynamic junctional actin, suggesting an unusual adaptive mechano-response to stabilize cell-cell adhesion. Our modelling informs that slack junctions arise from failure of circular cell pairs to increase their own intrinsic stiffness and resist the pressures from the neighbouring cell. The inability to form a straight junction can be reversed by increasing mechanical stress artificially on stiffer substrates. Our data inform on the minimal intrinsic rheology to generate a mature junction and provide a springboard towards understanding elements governing tissue-level mechanics.

Polymer formulated self-amplifying RNA vaccine is partially protective against influenza virus infection in ferrets

COVID-19 has demonstrated the power of RNA vaccines as part of a pandemic response toolkit. Another virus with pandemic potential is influenza. Further development of RNA vaccines in advance of a future influenza pandemic will save time and lives. As RNA vaccines require formulation to enter cells and induce antigen expression, the aim of this study was to investigate the impact of a recently developed bioreducible cationic polymer, pABOL for the delivery of a self-amplifying RNA (saRNA) vaccine for seasonal influenza virus in mice and ferrets. Mice and ferrets were immunized with pABOL formulated saRNA vaccines expressing either haemagglutinin (HA) from H1N1 or H3N2 influenza virus in a prime boost regime. Antibody responses, both binding and functional were measured in serum after immunization. Animals were then challenged with a matched influenza virus either directly by intranasal inoculation or in a contact transmission model. While highly immunogenic in mice, pABOL-formulated saRNA led to variable responses in ferrets. Animals that responded to the vaccine with higher levels of influenza virus-specific neutralizing antibodies were more protected against influenza virus infection. pABOL-formulated saRNA is immunogenic in ferrets, but further optimization of RNA vaccine formulation and constructs is required to increase the quality and quantity of the antibody response to the vaccine.

Fitness of Isidorella newcombi Following Multi-generational Cu Exposures: Mortality, Cellular Biomarkers and Life History Responses

The effects of multigenerational Cu exposure on the freshwater gastropod Isidorella newcombi were investigated. Snails were exposed to a range of treatment-specific Cu concentrations in the parental to F₂ generations, and a common Cu concentration in the F₃ generation. In the parental to F₂ generations, some general responses to 3 days Cu exposures included reduced survival and feeding in snails exposed to higher Cu concentrations. This suggested that the snails exposed to the high Cu concentration were experiencing Cu-induced stress that may apply selection pressure. In the F₃ generation, when all treatments were exposed to a common Cu concentration, increased survival was correlated with the pre-exposure Cu concentration history. Snails that had been pre-exposed to Cu also displayed reduced stress at a sub-lethal level, indicated by lower lysosomal destabilisation (LD). Mortality and LD responses in the F₃ generation were not related to Cu tissue concentrations, indicating increased tolerance and reduced stress were not related to changes in Cu bioaccumulation. Total antioxidant capacity increased in the higher Cu concentration pre-exposure treatments which could be associated with lower Cu-induced stress, however, this is not supported by the oxidative damage marker lipid peroxidation, which also increased. While Cu tissue concentrations and oxidative stress markers were assessed to determine underlying reasons for increased tolerance in snails from a population with a multi-generational exposure history to Cu, the results were not conclusive. Despite this, it was demonstrated through increased survival and reduced LD that Cu tolerance can develop over a short evolutionary time scale.

The Response of the Planorbid Snail Isidorella newcombi to Chronic Copper Exposure Over a 28-Day Period: Linking Mortality, Cellular Biomarkers, and Reproductive Responses

The native freshwater gastropod Isidorella newcombi attacks the roots of developing rice plants in southern Australia and is controlled using copper sulphate. The apparent tolerance of this species to moderate levels of copper (Cu) exposure led us to investigate its potential usefulness as a biomonitor species. To assess its response to chronic Cu exposure, adult I. newcombi were exposed to 0-120 µg L^-1 of Cu for 28 days. Lethal and sublethal responses were investigated. The relationships between subcellular biomarkers and life history traits also were explored. At exposure concentrations of 60 µg L^-1 Cu and above, 100% mortality was observed during the 28-day exposure period. In these treatments, there was an exposure concentration dependent decrease in the time that the snails survived. In the surviving snails, there was an exposure concentration-dependent increase in tissue Cu concentration. In the snails exposed to Cu concentrations above 15 µg L^-1, no eggs were produced during the final week of copper exposure, indicating that populations would not persist at Cu concentrations above 15 µg L^-1. The general stress biomarker lysosomal membrane destabilisation (LD) indicated organisms exposed to 10 µg L^-1 Cu and above were experiencing Cu induced stress. This suggests that LD could act as an early warning system for responses at higher levels of biological organisation in I. newcombi exposed to copper.

Multiscale analyses reveal native-like lamellar bone repair and near perfect bone-contact with porous strontium-loaded bioactive glass

The efficient healing of critical-sized bone defects using synthetic biomaterial-based strategies is promising but remains challenging as it requires the development of biomaterials that combine a 3D porous architecture and a robust biological activity. Bioactive glasses (BGs) are attractive candidates as they stimulate a biological response that favors osteogenesis and vascularization, but amorphous 3D porous BGs are difficult to produce because conventional compositions crystallize during processing. Here, we rationally designed a porous, strontium-releasing, bioactive glass-based scaffold (pSrBG) whose composition was tailored to deliver strontium and whose properties were optimized to retain an amorphous phase, induce tissue infiltration and encourage bone formation. The hypothesis was that it would allow the repair of a critical-sized defect in an ovine model with newly-formed bone exhibiting physiological matrix composition and structural architecture. Histological and histomorphometric analyses combined with indentation testing showed pSrBG encouraged near perfect bone-to-material contact and the formation of well-organized lamellar bone. Analysis of bone quality by a combination of Raman spectral imaging, small-angle X-ray scattering, X-ray fluorescence and focused ion beam-scanning electron microscopy demonstrated that the repaired tissue was akin to that of normal, healthy bone, and incorporated small amounts of strontium in the newly formed bone mineral. These data show the potential of pSrBG to induce an efficient repair of critical-sized bone defects and establish the importance of thorough multi-scale characterization in assessing biomaterial outcomes in large animal models.

Raman spectroscopic imaging for quantification of depth-dependent and local heterogeneities in native and engineered cartilage

Articular cartilage possesses a remarkable, mechanically-robust extracellular matrix (ECM) that is organized and distributed throughout the tissue to resist physiologic strains and provide low friction during articulation. The ability to characterize the make-up and distribution of the cartilage ECM is critical to both understand the process by which articular cartilage undergoes disease-related degeneration and to develop novel tissue repair strategies to restore tissue functionality. However, the ability to quantitatively measure the spatial distribution of cartilage ECM constituents throughout the tissue has remained a major challenge. In this experimental investigation, we assessed the analytical ability of Raman micro-spectroscopic imaging to semi-quantitatively measure the distribution of the major ECM constituents in cartilage tissues. Raman spectroscopic images were acquired of two distinct cartilage tissue types that possess large spatial ECM gradients throughout their depth: native articular cartilage explants and large engineered cartilage tissue constructs. Spectral acquisitions were processed via multivariate curve resolution to decompose the "fingerprint" range spectra (800-1800 cm-1) to the component spectra of GAG, collagen, and water, giving rise to the depth dependent concentration profile of each constituent throughout the tissues. These Raman spectroscopic acquired-profiles exhibited strong agreement with profiles independently acquired via direct biochemical assaying of spatial tissue sections. Further, we harness this spectroscopic technique to evaluate local heterogeneities through the depth of cartilage. This work represents a powerful analytical validation of the accuracy of Raman spectroscopic imaging measurements of the spatial distribution of biochemical components in a biological tissue and shows that it can be used as a valuable tool for quantitatively measuring the distribution and organization of ECM constituents in native and engineered cartilage tissue specimens.

A nucleic acid strand displacement system for the multiplexed detection of tuberculosis-specific mRNA using quantum dots

The development of rapid, robust and high performance point-of-care diagnostics relies on the advancement and combination of various areas of research. We have developed an assay for the detection of multiple mRNA molecules that combines DNA nanotechnology with fluorescent nanomaterials. The core switching mechanism is toehold-mediated strand displacement. We have used fluorescent quantum dots (QDs) as signal transducers in this assay, as they bring many benefits including bright fluorescence and multiplexing abilities. The resulting assay is capable of multiplexed detection of long RNA targets against a high concentration of background non-target RNA, with high sensitivity and specificity and limits of detection in the nanomolar range using only a standard laboratory plate reader. We demonstrate the utility of our QD-based system for the detection of two genes selected from a microarray-derived tuberculosis-specific gene expression signature. Levels of up- and downregulated gene transcripts comprising this signature can be combined to give a disease risk score, making the signature more amenable for use as a diagnostic marker. Our QD-based approach to detect these transcripts could pave the way for novel diagnostic assays for tuberculosis.

Biodegradable silicon nanoneedles delivering nucleic acids intracellularly induce localized in vivo neovascularization

The controlled delivery of nucleic acids to selected tissues remains an inefficient process mired by low transfection efficacy, poor scalability because of varying efficiency with cell type and location, and questionable safety as a result of toxicity issues arising from the typical materials and procedures employed. High efficiency and minimal toxicity in vitro has been shown for intracellular delivery of nuclei acids by using nanoneedles, yet extending these characteristics to in vivo delivery has been difficult, as current interfacing strategies rely on complex equipment or active cell internalization through prolonged interfacing. Here, we show that a tunable array of biodegradable nanoneedles fabricated by metal-assisted chemical etching of silicon can access the cytosol to co-deliver DNA and siRNA with an efficiency greater than 90%, and that in vivo the nanoneedles transfect the VEGF-165 gene, inducing sustained neovascularization and a localized sixfold increase in blood perfusion in a target region of the muscle.

Evaluation of skeletal tissue repair, part 2: enhancement of skeletal tissue repair through dual-growth-factor-releasing hydrogels within an ex vivo chick femur defect model

There is an unmet need for improved, effective tissue engineering strategies to replace or repair bone damaged through disease or injury. Recent research has focused on developing biomaterial scaffolds capable of spatially and temporally releasing combinations of bioactive growth factors, rather than individual molecules, to recapitulate repair pathways present in vivo. We have developed an ex vivo embryonic chick femur critical size defect model and applied the model in the study of novel extracellular matrix (ECM) hydrogel scaffolds containing spatio-temporal combinatorial growth factor-releasing microparticles and skeletal stem cells for bone regeneration. Alginate/bovine bone ECM (bECM) hydrogels combined with poly(d,l-lactic-co-glycolic acid) (PDLLGA)/triblock copolymer (10-30% PDLLGA-PEG-PLDLGA) microparticles releasing dual combinations of vascular endothelial growth factor (VEGF), chondrogenic transforming growth factor beta 3 (TGF-β3) and the bone morphogenetic protein BMP2, with human adult Stro-1+bone marrow stromal cells (HBMSCs), were placed into 2mm central segmental defects in embryonic day 11 chick femurs and organotypically cultured. Hydrogels loaded with VEGF combinations induced host cell migration and type I collagen deposition. Combinations of TGF-β3/BMP2, particularly with Stro-1+HBMSCs, induced significant formation of structured bone matrix, evidenced by increased Sirius red-stained matrix together with collagen expression demonstrating birefringent alignment within hydrogels. This study demonstrates the successful use of the chick femur organotypic culture system as a high-throughput test model for scaffold/cell/growth factor therapies in regenerative medicine. Temporal release of dual growth factors, combined with enriched Stro-1+HBMSCs, improved the formation of a highly structured bone matrix compared to single release modalities. These studies highlight the potential of a unique alginate/bECM hydrogel dual growth factor release platform for bone repair.

Plasmonic ELISA for the detection of gp120 at ultralow concentrations with the naked eye

The technique of plasmonic ELISA is utilised here to detect the HIV-1 protein gp120 with the ultralow limit of detection of 8 × 10(-20) M (10(-17) g mL(-1)) in an independent laboratory. It was corroborated that changes in the concentration of hydrogen peroxide as small as 0.05 μM could lead to nanoparticle solutions of completely different tonality.

Cotton-wool-like bioactive glasses for bone regeneration

Inorganic sol-gel solutions were electrospun to produce the first bioactive three-dimensional (3-D) scaffolds for bone tissue regeneration with a structure like cotton-wool (or cotton candy). This flexible 3-D fibrous structure is ideal for packing into complex defects. It also has large inter-fiber spaces to promote vascularization, penetration of cells and transport of nutrients throughout the scaffold. The 3-D fibrous structure was obtained by electrospinning, where the applied electric field and the instabilities exert tremendous force on the spinning jet, which is required to be viscoelastic to prevent jet break up. Previously, polymer binding agents were used with inorganic solutions to produce electrospun composite two-dimensional fibermats, requiring calcination to remove the polymer. This study presents novel reaction and processing conditions for producing a viscoelastic inorganic sol-gel solution that results in fibers by the entanglement of the intermolecularly overlapped nanosilica species in the solution, eliminating the need for a binder. Three-dimensional cotton-wool-like structures were only produced when solutions containing calcium nitrate were used, suggesting that the charge of the Ca(2+) ions had a significant effect. The resulting bioactive silica fibers had a narrow diameter range of 0.5-2μm and were nanoporous. A hydroxycarbonate apatite layer was formed on the fibers within the first 12h of soaking in simulated body fluid. MC3T3-E1 preosteoblast cells cultured on the fibers showed no adverse cytotoxic effect and they were observed to attach to and spread in the material.

Surface properties and ion release from fluoride-containing bioactive glasses promote osteoblast differentiation and mineralization in vitro

Bioactive glasses (BG) are suitable for bone regeneration applications as they bond with bone and can be tailored to release therapeutic ions. Fluoride, which is widely recognized to prevent dental caries, is efficacious in promoting bone formation and preventing osteoporosis-related fractures when administered at appropriate doses. To take advantage of these properties, we created BG incorporating increasing levels of fluoride whilst holding their silicate structure constant, and tested their effects on human osteoblasts in vitro. Our results demonstrate that, whilst cell proliferation was highest on low-fluoride-containing BG, markers for differentiation and mineralization were highest on BG with the highest fluoride contents, a likely effect of a combination of surface effects and ion release. Furthermore, osteoblasts exposed to the dissolution products of fluoride-containing BG or early doses of sodium fluoride showed increased alkaline phosphatase activity, a marker for bone mineralization, suggesting that fluoride can direct osteoblast differentiation. Taken together, these results suggest that BG that can release therapeutic levels of fluoride may find use in a range of bone regeneration applications.

Changes in embryonic stem cell colony morphology and early differentiation markers driven by colloidal crystal topographical cues

The use of materials properties to guide cell behaviour is an attractive option for regenerative medicine, where controlling stem cell behaviour is important for the establishment of a functioning cell population. A wide range of materials properties have been shown to influence many types of cells but little is known about the effects of topography on embryonic stem cells (ESCs). In order to advance this knowledge, we synthesised and characterised substrates formed of silica colloidal crystal (SCC) microspheres to present highly ordered and reproducible topographical features from 120-600 nm in diameter. We found that, compared to cells cultured on flat glass, cells cultured on the SCC substrates retained transcription of stem cell (Dppa5a, Nanog, and Pou5f1) and endoderm (Afp, Gata4, Sox17, and Foxa2) markers more similar to undifferentiated ESCs, suggesting the substrates are restricting differentiation, particularly towards the endoderm lineage. Additionally, five days after seeding, we observed strikingly different colony morphology, with cells on the SCC substrates growing in spherical colonies approximately ten cells thick, while cells on glass were growing in flat monolayers. Colonies on the SCC substrates developed a central pit, which was never observed in cells cultured on glass, and expressed proteins related to epithelialisation. Together, these data demonstrate the potential of using topographical cues to control stem cell behaviour in vitro.

Growth and growth hormone therapy of children treated for leukaemia

A total of 37 children (24 male, 13 female) who had been treated for leukaemia with chemotherapy and 24 Gy cranial irradiation, and who were disease free for at least 18 months, were commenced on somatrem at a mean of 7.6 years (range, 4.8-12.1 years) after leukaemia diagnosis because of growth rate below the 25th centile for bone age. Peak GH response to provocation (exercise, arginine, insulin hypoglycaemia) was less than 20 milliunits/litre in 27 children (deficient group) and 20 milliunits/litre or more in 10 children (non-deficient group). The mean height SD decrease from diagnosis of leukaemia to commencement of somatrem was 1.98, 86% of the children decreasing by more than 1 SD. Those who were tall for age at leukaemia diagnosis and females were more severely affected. Mean (+/- SD) height velocity increased on somatrem from 2.7 +/- 1.1 to 6.6 +/- 2.2 cm/year during the first 6 months (n = 25), and to 6.0 +/- 1.7 cm/year during the first 12 months (n = 19). No difference in growth response was seen between the sexes or between the deficient and non-deficient groups. Catch-up growth occurred for the first 6 months only. It is concluded that children with a low growth rate after treatment of leukaemia should be considered for GH therapy irrespective of the results of GH provocative tests.

Raman microspectroscopy for non-invasive biochemical analysis of single cells

Recent developments in biomedical vibrational spectroscopy now permit the non-invasive imaging of cells and tissues within both the laboratory and clinical settings. The rapid nature and diagnostic potential of both Raman and FTIR (Fourier-transform IR) spectroscopy have resulted in their widespread application to a number of biological fields including fundamental cell biology, medical imaging, tissue engineering and pharmacology. In particular, Raman microspectroscopy shows tremendous promise for the analysis of biological processes within living cells, such as cell cycle dynamics, cell differentiation and cell death. Unlike conventional biological assays, laser-based Raman spectroscopy enables rapid and non-invasive biochemical analysis of cells in the absence of fixatives or labels. The low Raman signal of cell culture buffer/media permits the rapid monitoring of living cells growing under standard cell culture conditions. The Raman spectrum of a cell is a biochemical ‘fingerprint’, containing molecular-level information about all biopolymers contained within the cell. The high information content of Raman spectra can be used to characterize the distribution of multiple cellular components, and to study the dynamics of subcellular reactions, with excellent spatial resolution. This review highlights recent developments in Raman microspectroscopy, with a focus on non-invasive biochemical analysis of single living cells.

Gene activation by bioactive glasses

Bioactive glasses have been shown to regulate gene expression in both hard and soft tissue repair. New resorbable bioactive glass constructs are now being developed that can influence gene expression in the local environment by manipulating material properties such as the surface chemistry, topography and the release of dissolution ions. The success of these scaffolds, however, may depend upon a greater understanding of the bioactive glass stimulated gene expression pathways. This will allow the construction of tissue specific scaffolds with tailored surface chemistry, topography and ion release rates. This paper summarises the advances made in understanding gene expression in response to bioactive glasses and discusses the future steps required for further insights into these molecular mechanisms.

Enhanced differentiation and mineralization of human fetal osteoblasts on PDLLA containing Bioglass® composite films in the absence of osteogenic supplements

This study investigates the cellular response of fetal osteoblasts to bioactive resorbable composite films consisting of a poly-D,L-lactide (PDLLA) matrix and bioactive glass 45S5 Bioglass (BG) particles at three different concentrations (0% (PDLLA), 5% (P/BG5), and 40% (P/BG40)). Using scanning electron microscopy (SEM) we observed that cells were less spread and elongated on PDLLA and P/BG5, whereas cells on P/BG40 were elongated but with multiple protrusions spreading over the BG particles. Vinculin immunostaining revealed similar distribution of focal adhesion contacts on all cells independent of substratum, indicating that all materials permitted cell adhesion. However, when differentiation and maturation of fetal osteoblasts was examined, incorporation of 45S5 BG within the PDLLA matrix was found to significantly (p < 0.05) enhance alkaline phosphatase enzymatic activity and osteocalcin protein synthesis compared to tissue culture polystyrene controls and PDLLA alone. Alizarin red staining indicated extracellular matrix mineralization on both P/BG5 and P/BG40, with significantly more bone nodules formed than on PDLLA. Real time RT-PCR revealed that expression of bone sialoprotein was also affected by the BG containing films compared to controls, whereas expression of Collagen Type I was not influenced. By performing these investigations in the absence of osteogenic factors it appears that the incorporation of BG stimulates osteoblast differentiation and mineralization of the extracellular matrix, demonstrating the osteoinductive capacity of the composite.

Toxicity of Bacillus thuringiensis var. israelensis formulations, spinosad, and selected synthetic insecticides to Chironomus tepperi larvae

Three Bacillus thuringiensis var. israelensis (BTi) formulations, the bacterial metabolite spinosad, and 7 synthetic insecticides were bioassayed against 4th instars of Chironomus tepperi, a serious pest of rice in southern Australia. The BTi formulations returned 48-h product median lethal concentration (LC50) values (25 < or = 1 degrees C) of between 0.59 mg/liter (VectoBac water-dispersible granule [WDG], 3,000 international toxic units [ITU]/mg) and 2.15 mg/liter (Teknar suspension concentrate [SC], 1,200 ITU/mg). When LC50 values were adjusted to reflect nominal ITU values of the 3 products, there was still substantial variation, with LC50 values ranging from 1,770 ITU/liter (VectoBac WDG) to 2,580 ITU/liter (Teknar SC). Aquabac SC (1,200 ITU/mg) showed intermediate activity. Differential activity between formulations may reflect faster settling rates in the more active formulations, which may be a beneficial characteristic when controlling benthic species such as C. tepperi. Spinosad (24-h LC50 = 28.9 microg active ingredient [AI]/liter) and the synthetic insecticides we evaluated were all substantially more active than BTi. The highest activity was shown by the neonicotinoid compounds thiacloprid, acetamiprid, and clothianidin, which all returned 24-h LC50 values between 1 and 3 microg AI/liter. Indoxacarb and thiomethoxam showed the lowest activity of the synthetic compounds evaluated.

Factors affecting the toxicity of Bacillus thuringiensis var. israelensis and Bacillus sphaericus to fourth instar larvae of Chironomus tepperi (Diptera: Chironomidae)

Laboratory bioassays (48h duration, 25+/-1 degrees C) were used to determine the toxicity of Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus to fourth instar larvae of Chironomus tepperi, a major pest of rice in southern Australia. Bioassays were conducted using different combinations of larval ages and densities to determine if these factors affected toxicity. The effects of temperature and substrate type on B.t.i. toxicity were also investigated. Tests were conducted using a commercial B.t.i. formulation (VectoBac WDG, 3000ITU/mg), a spore/crystal mixture derived from the VectoBac WDG strain, and VectoLex WDG, a commercial B. sphaericus formulation (650ITU/mg). VectoBac WDG was highly toxic to fourth instar C. tepperi in bioassays using a sand substrate (LC(50) 0.46mg/L, older larvae); younger fourth instar larvae were more susceptible (LC(50) 0.20mg/L). Increasing larval densities (from 10 to 30 per bioassay cup) increased LC(50) values for both age groups, significantly so in the case of older larvae (higher density LC(50) 0.80mg/L). Use of a soil substrate increased the LC(50) value (older larvae, 10 per cup) to 0.99mg/L. Similar differences in toxicity relative to larval age and substrate type were found in bioassays using the B.t.i. spore/crystal mixture. VectoBac WDG and the spore/crystal mixture both showed similar (approximately 6-fold) declines in activity between 30 and 17.5 degrees C. At lower temperatures (between 17.5 and 15 degrees C), activity of the spore/crystal mixture declined much more rapidly than that of VectoBac WDG. VectoLex WDG showed very low toxicity to C. tepperi larvae, and the overall impact of larval age and density was relatively minor (LC(50) values 1062-1340mg/L). Autoclaving VectoLex WDG did not substantially reduce its toxicity (LC(50) 1426mg/L), suggesting that formulation additives (i.e., surfactants and other adjuvants) are responsible for much of the toxicity occurring at the high product concentrations required to cause C. tepperi mortality. Whilst VectoLex WDG was ineffective against C. tepperi, VectoBac WDG has the potential to provide selective control of this rice pest at economically viable application rates.

Oviposition response of Chironomus tepperi to nitrogenous compounds and bioextracts in two-choice laboratory tests

Two-choice laboratory tests were used to investigate the oviposition response of Chironomus tepperi to a range of nitrogenous compounds and crude bioextracts. Responses to nitrogenous compounds varied in response to concentration. Ammonium nitrate did not influence oviposition at concentrations from 2 to 12 mg/liter. Hydroxylamine hydrochloride increased oviposition at 6 mg/liter, but had no effect at either 2 or 12 mg/liter. Sodium nitrate reduced oviposition at 2 mg/liter relative to the controls, but had no significant effect at 6 or 12 mg/liter. C. tepperi responded to many of the crude bioextracts, strongly avoiding oviposition in solutions containing homogenized chironomid larvae ( 1 final instar/100 ml; C. tepperi or Polypedilum nubiferum), and avoiding solutions conditioned by conspecific larvae at concentrations down to the equivalent of 1 final instar/100 ml over 24 hr. Homogenates of adult conspecifics had no effect on oviposition site selection. Homogenates of larval Culex annulirostris (Culicidae) deterred oviposition, but only at high concentrations (3 final instars/100 ml). Our results demonstrate that chemical cues from larval populations deter oviposition by C. tepperi females searching for newly flooded habitats where larval competition will be minimized.

Comparison of two bioassay techniques for assessing the acute toxicity of pesticides to chironomid larvae (Diptera: Chironomidae)

Two container and substrate combinations were compared to determine which provided optimal survival of larvae of Chironomus tepperi and Glyptotendipes paripes in the absence of toxicants. Unfed final-stage larvae of G. paripes survived significantly (P < 0.05) better in waxed paper cups with sand substrate (92.8% after 3 days) than in glass tubes with a shredded paper substrate (85.3%). Survival of larvae of C. tepperi over the same period did not differ significantly in the 2 systems. Larvae of C. tepperi were bioassayed against 3 insecticides (technical and formulated imidacloprid, chlorpyrifos, and betacypermethrin) with both container and substrate combinations. Median lethal concentration values (24 h) obtained with waxed cups with sand were 1.8 times higher on average than those obtained with glass tubes with shredded paper (range 1.13-2.65 times). To determine the cause of this variability, solid-phase microextraction was used to measure changes in chlorpyrifos availability over time in the 2 bioassay systems. Chlorpyrifos concentrations in the waxed cups and sand system fell from 7.50 to 3.36 microg/liter over 24 h, probably as a consequence of chemical adsorption to the waxed surfaces. Chlorpyrifos concentrations in the glass tubes and paper system remained unchanged over this period. Excluding substrates from the containers had only a minor effect on chlorpyrifos availability. These results demonstrate that the behaviors of both test organisms and toxicants within bioassay systems need to be understood if the data generated with different systems are to be compared. Understanding how toxicant availability is affected by different container and substrate types is particularly important where bioassays are conducted with nominal concentration values rather than analytically determined exposure concentrations.

The measurement of symptoms in young children with cancer: the validation of the Memorial Symptom Assessment Scale in children aged 7-12

Few studies have attempted to describe the experience of symptoms in young children with cancer. This is due, in part, to the lack of validated symptom assessment scales for this patient population. The objective of this study was to evaluate the reliability and validity of a revised Memorial Symptom Assessment Scale (MSAS) in patients aged 7-12 as an instrument for the assessment of symptoms in young children with cancer. The MSAS (7-12) was administered to 149 children (inpatients and outpatients) who were undergoing treatment at either the Royal Marsden NHS Trust, London, United Kingdom or The Children's Hospital at Westmead, Sydney, Australia. Validity was evaluated by comparison with the medical record, parental report, and concurrent assessment on visual analogue scales for selected symptoms. The data provide evidence of the reliability and validity of MSAS (7-12) and demonstrate that children with cancer as young as 7 years can report clinically relevant and consistent information about their symptom experience. Young children with cancer experience multiple symptoms. Approximately one-third had experienced lethargy and/or pain and/or insomnia during the 48 hours prior to the completion of MSAS (7-12). The completion rate for MSAS (7-12) was high and the majority of children completed the instrument in a short period of time and with little difficulty. The instrument appears to be age appropriate and may be helpful to older children unable to independently complete MSAS (10-18). Systematic symptom assessment may be useful in future epidemiological studies of symptoms and in cancer chemotherapy drug trials.

Laboratory and field studies on the effect of molinate, clomazone, and thiobencarb on nontarget aquatic invertebrates

The midge Chironomus tepperi was used in laboratory experiments to assess the relative toxicity of formulated molinate, clomazone, and thiobencarb, three herbicides used in Australian rice crops. Static bioassays were initiated with first-instar larvae at herbicide concentrations between 0.0625 and 2 times the anticipated field concentrations (AFCs) expected from the registered application rates. Adult emergence success, development time, and wing length were used as indices of the effect of each herbicide. Clomazone had no effect on any parameters at concentrations up to 0.288 mg/L (p > 0.05). Molinate significantly increased development time at concentrations equivalent to the AFC (3.6 mg/L) and above (p < 0.05). Thiobencarb reduced emergence success of adult C. tepperi at 0.0625 times the AFC (0.1875 mg/L) as well as decreasing male adult size and increasing development time for males and females at 0.125 times the AFC (p < 0.05). Nontarget effects of the herbicides on aquatic invertebrate communities were assessed in shallow experimental ponds using commercial application rates. One week after treatment, only thiobencarb had a significant effect, suppressing populations of chironomids, calanoids, and cyclopoids (p < 0.05). Four weeks later, all populations had recovered, equaling or exceeding control densities.

Children and guns in a well child cohort

BACKGROUND

The purpose of this study was to estimate the extent of and to identify predictors of preadolescent gun use in a well child cohort with matched parent and child data.

METHODS

We analyzed self-report questionnaires from children and their parents using conditional logistic regression models. Questionnaires were given to 3,145 ten- to twelve-year-old children and 3,145 parents enrolled by their pediatricians in a prevention cohort study.

RESULTS

Thirty-two percent of the children lived in households with guns. Children and parents generally agreed about the presence of guns in their homes; 17% had access to unlocked guns in their homes; 22% had fired guns. In this preadolescent cohort, firing guns was associated with being male, having guns in the home, having friends who use guns, and initiation of alcohol use.

CONCLUSIONS

In this well child cohort, significant numbers of preadolescent, healthy boys in white, middle-class U.S. homes have access to guns, are using guns, and have friends who use guns. These children are also early alcohol adopters. Safety interventions with parents of preadolescents about the risks for accidental injury, death, and suicide due to child gun use may prove beneficial.

E-mail communication between medical students and schoolchildren: A model for medical education

OBJECTIVE

To examine e-mail communication between student physicians and schoolchildren, in the context of a school-based tobacco prevention program, as a way to teach communication skills and model physician-patient interactions.

DESIGN

Twenty medical students and pediatric residents were partnered with groups of children as part of HealthQuest, a tobacco prevention program implemented in 2 kindergarten through grade 12 Vermont schools. Medical students and residents acted as mentors for their group and provided support to the schoolchildren through e-mail and occasional site visits. E-mail messages were transmitted and stored in a Web server and monitored by preceptors. Content analysis of the messages was performed to identify emerging themes.

RESULTS

During the 2-year intervention period, 1187 messages were exchanged between children, teachers, and the student physicians. Thirty-two percent (n = 383) of the messages involved tobacco, of which 54% addressed health effects; 23% were related to social influences of tobacco use, 15% to cessation by parents and others, and 7% to cessation by students. Other categories included nontobacco health issues (n = 135), personal questions (n = 294), and classroom information (n = 735). Many inquiries required medical students and residents to research their answers, and several required collaboration with preceptors, because the questions raised serious medical or psychosocial issues. With feedback, medical students and residents adjusted their responses so that they were appropriate for the developmental level of the children.

CONCLUSIONS

The e-mail component of this program provided important learning opportunities for student physicians in tobacco control, child development, communication skills, and developing a physician-patient relationship. This model also offers potential benefits for medically underserved pediatric populations. Arch Pediatr Adolesc Med. 2000;154:1258-1262.

Mammography in New Hampshire: characteristics of the women and the exams they receive

New Hampshire (NH) is one of two states that has developed a population-based mammography registry. The purpose of this paper is to describe what we have learned about mammography use in New Hampshire. After collecting data for 20 months, the database contains almost 110,000 mammographic encounters representing 101,679 NH women, who range in age from 18 to 97 with a mean of 56.7 years (SD=10.91). Education levels are high with 92% having a high school education and 59% with some college. Forty-six percent report their primary insurance is private, 29% report HMO/PPO coverage, and 25% receive federal health care assistance. Risk factors represented in the database include (categories not mutually exclusive) advancing age (60% over age 50), hormone replacement therapy use by menopausal women (40.6%), and a family history of breast cancer (29%). Penetration of mammography relative to the NH population is higher for younger age groups (40-48% for those aged 44-64) than older age groups (34-39% for those aged 65-84). The majority of mammographic encounters are routine screening exams (86%), often interpreted as negative or normal with benign findings (88%). Use of comparison films to interpret either diagnostic or screening mammography occurred in 86% of encounters. We have matched 3,877 breast pathology records to these mammographic encounters. The distribution of pathology outcomes for diagnostic exams was very similar to that for screening exams (approximately 65% benign, 17% invasive breast cancer, and 6% noninvasive breast cancer). Overall, we have designed a system that is well accepted by the NH community. Challenges include careful monitoring of data for coding errors, and a limitation of linking variables in mammography and pathology data. Data represented in this registry are a critical resource for research in mammographic screening and breast cancer early detection.

Acute and chronic toxicity of the herbicide benzofenap (Taipan 300) to Chironomus tepperi Skuse (Diptera: Chironomidae) and Isidorella newcombi (Adams and Angas) (Gastropoda: Planorbidae)

Acute and chronic toxicity tests were conducted on the herbicide benzofenap (Taipan 300) using two Australian freshwater invertebrates. The commercial formulation of benzofenap and a blank formulation containing only the adjuvants of Taipan 300 were tested against final instar larvae of the midge Chironomus tepperi and adults of the aquatic snail Isidorella newcombi. In 24-h acute bioassays the midge larvae did not show significant mortality at a nominal concentration of 1.2 mg/L active ingredient (AI), double the maximum notional concentration expected in rice fields after application of Taipan 300 at the permit rate of 2 L/ha. No significant snail mortality was recorded in acute bioassays (24-h exposure, 48-h recovery) at nominal concentrations up to 76 mg/L AI, which is over 120 times the maximum notional field concentration. In chronic assays, the pupation and emergence of C. tepperi was monitored after a 4-h pulse exposure of final instar larvae to Taipan 300 (nominal concentrations 0.001 to 0.1 mg/L AI) and adjuvant-only (0.1 mg/L equivalent) treatments. No statistically significant effects were observed, although emergence appeared to be delayed by higher benzofenap concentrations and by the adjuvant-only treatment. During snail bioassays, egg and feces production were monitored for 21 days after 24-h exposure to Taipan 300 (nominal concentrations 1.2 mg/L to 60 mg/L AI) and adjuvant-only treatments (60 mg/L equivalent). No significant chronic effects were proven against I. newcombi, despite a decline in egg mass production following exposure to all treatments and a reduction in the total numbers of eggs produced at the highest nominal concentrations tested (60 mg/L AI and adjuvant-only treatments). Similarly, feces production by snail pairs exposed to the majority of treatments declined, but these differences were not statistically significant. It is concluded that Taipan 300 does not represent a significant risk to mature C. tepperi larvae or adult I. newcombi in downstream environments when applied to rice fields at the permit rate of 2 L/ha.

Probing protein-peptide-protein molecular architecture by atomic force microscopy and surface plasmon resonance

We demonstrate the creation of a protein multilayer which utilises the high affinity interaction between streptavidin and biotin and incorporates a peptidic spacer. Surface plasmon resonance measurements enabled us to monitor the construction of the multilayer in real time. Atomic force microscopy was utilised to determine surface functionality at each stage of the multilayer construction, allowing us to investigate the associated mechanical properties. In this context we observed an increase in biomolecular stretching on the formation of the multilayer. We demonstrate, utilising circular dichroism, that variations in the solvent can affect the secondary structure of the peptide linker and hence its mechanical properties. Trifluoroethanol titrations on the assembled system indicate that the multilayer properties are also stimuli responsive with regard to solvent conditions. These results indicate that the multilayer stretch before cleavage is increased in the presence of trifluoroethanol. This was not expected from the study of the individual linker alone, indicating the need to study the system as a whole as opposed to the isolated components.

Promoting sun protection in elementary schools and child care settings: the SunSafe Project

Elementary schools and child care settings in rural New Hampshire participated in a sun protection program that reached more than 4,200 children. The program was part of a successful multifaceted community intervention targeting children ages 2-9. Program components included curricular materials, training and support for school/child care staff, and parent outreach. Evaluation showed good uptake of the curriculum by teachers and child care providers, improvements in sun protection policy in participating schools and child care settings, and significant knowledge and attitude improvements in fourth grade children tested, as well as actual behavior change. The study highlighted the importance of flexible, developmentally appropriate curricular materials and active engagement of principals and directors in policy review. In addition, for parent outreach programs to be successful, children needed to participate.

Home care for the dying child. A parent's perception

OBJECTIVES

To identify the benefits and difficulties of families caring for a dying child at home and to assess the parents' adjustment following their child's death.

METHOD

Semi-structured interview and questionnaire.

RESULTS

The benefits of home versus hospital care included greater freedom, more privacy and less disruption to family life, and that caring for the child was a positive experience for most families. Despite this experience many families expressed many fears and concerns about the symptomatic care of their children and requested more support.

DISCUSSION

Hospital-based treatment teams have a responsibility to ensure adequate support can be provided before home care is recommended for dying children. The experience of home-based palliative care reported by these parents and their suggestions for change will assist all who care for dying children and to improve services supporting home-based palliative care.

Seasonal variations in foraging by ants (Hymenoptera : Formicidae) in two New South Wales citrus orchards

Summary. Pitfall traps were used to monitor the seasonal activity of ants in 2 citrus orchards in the Murrumbidgee Irrigation Area of south-western New South Wales for 22–24 months (November 1992–August/October 1994). Twenty-four species were recorded (22 species at Yanco and 18 species at Cudgel), with Iridomyrmex rufoniger group species being numerically dominant at both sites (63 and 59% of total captures at Yanco and Cudgel respectively). Meat ants, Iridomyrmex purpureus (F.Smith), were a significant (9%) component of trap captures at Yanco where regular soil cultivation was practised, but were less common (<1% of captures) at Cudgel. Sample species richness was generally greater at the Yanco site (mean 9.3 species per trapping interval compared with 6.6 at Cudgel). Total ant captures and sample species richness showed a positive correlation with mean daily temperatures over trapping intervals. Variations in seasonal activity were shown by the numerically dominant species, with 2 distinct patterns being evident. Whilst all taxa were less active during winter, some species [I. rufoniger group sp. 2, Pheidole sp., Rhytidoponera metallica (F.Smith)] continued to forage, albeit at reduced levels. Other species of Iridomyrmex including I. rufoniger group sp. 1 and I. purpureus ceased foraging almost entirely during June–September. Iridomyrmex species are known to interfere with the biological control of honeydew-producing insects in citrus orchards, and our results indicate that ant control programs in southern New South Wales should be initiated in late August–early September to achieve optimal results.

Solar protection of children at the beach

BACKGROUND

Excessive sun exposure during childhood has been associated with subsequent development of skin cancers. Children have been advised to avoid sun exposure, use protective clothing, and apply sunscreen lotions, but how completely these recommendations are followed has not been studied.

OBJECTIVE

To determine the extent of sun protection among children visiting lake beaches, the methods used, and the characteristics associated with more protection.

DESIGN

Direct observations of children were linked with concurrent care giver/parent interviews.

SUBJECTS/SETTING

A total of 871 children 2 to 9 years of age and their parents/care givers at freshwater beaches in 10 small New Hampshire towns during July and August 1995.

OUTCOME MEASURES

Protection of the head, torso, and legs according to method used (hats, shirts, pants, sunscreen, or shade).

RESULTS

Fifty-four percent of children were protected by at least one method for all three body surface regions, although 17% had no protection for any region. Sunscreen was used either alone or in combination with clothing for at least one region in 79%. Hats were used by 3%, shirts by 22%, and pants to the knee by 49%. Only 12% of observed children were in the shade. The region that was protected most often was the legs for boys (due to swim suit styles) followed by the torso for both sexes. The region most often unprotected was the legs for girls followed closely by the face for both boys and girls. Girls were significantly more likely to have no protection (31.2% female vs 7% male, chi2 83.3) due to better leg protection from swim trunks to the knees popular with boys. Full protection of all three regions was more common for children younger than 5 (odds ratio [OR] = 1.8, 95% confidence interval, [CI] 1.3-2.5), for children perceived to usually or always burn (OR = 2.0, 95% CI 1.4-2.7), for children whose parents had more than a high school education (OR = 1.8, 95% CI 1.3-2.5), and if the parents indicated receiving sun protection information from a school or clinician during the previous year (OR = 1.7, 95% CI 1.2-2.3). Approximately 51.6% of parents recalled receiving childhood solar protection advice in the past year from either their physician, a nurse, or a school/day care setting.

CONCLUSIONS

Sunscreen provided the most common form of solar protection. Hats and shade were used rarely, and shirts were also underused. Although the sun protection of these children visiting the beach was substantial, nearly half were still not fully protected. Clinician advice within the past year was associated with better protection. Clinicians could increase their influence by providing more specific counseling about how to achieve full protection. Use of multiple methods of protection rather than just sunscreen and full protection rather than protection for just one or two body regions should be emphasized. It is helpful to remind families to protect the regions most frequently omitted from protection: girls' legs and boys' and girls' faces. Advice can be enhanced with patient education materials such as included in the "Slip" (on a shirt), "Slop" (on sunscreen), and "Slap" (on a hat) program developed in Australia and available through the American Cancer Society.

Risk of squamous cell carcinoma of the skin in relation to plasma selenium, alpha-tocopherol, beta-carotene, and retinol: a nested case-control study

We conducted a nested case-control study of squamous cell skin cancer (SCC) to determine whether risk was related to plasma concentrations of selenium, alpha-tocopherol, beta-carotene, and retinol. We derived the study sample from participants in our Skin Cancer Prevention Study, all of whom had at least one basal cell or squamous cell skin cancer before study entry. Those who developed a new squamous cell skin cancer during the 3-5-year follow-up period were selected as cases (n = 132). Controls (n = 264) were chosen at random, with matching by age, sex, and study center, from among those who did not develop SCC but were being followed actively at the time the SCC case was diagnosed. Prediagnostic plasma samples were analyzed for alpha-tocopherol, beta-carotene, and retinol using high-performance liquid chromatography. Selenium determinations were made using instrumental neutron activation analysis. Odds ratios were computed using conditional logistic regression for matched samples. We found no consistent pattern of SCC risk associated with any of the nutrients examined. The odds ratios (95% confidence intervals) for the highest versus the lowest quartiles of beta-carotene, retinol, alpha-tocopherol, and selenium were 0.73 (0.38-1.41), 1.43 (0.77-2.64), 0.89 (0.43-1.85), and 0.86 (0.47-1.58), respectively. Thus, our data add to the growing body of evidence that these nutrients, at the concentrations we evaluated, are not related strongly to SCC risk.

Risk of basal cell and squamous cell skin cancers after ionizing radiation therapy. For The Skin Cancer Prevention Study Group

BACKGROUND

Human evidence that ionizing radiation is carcinogenic first came from reports of nonmelanoma skin cancers (NMSCs) on the hands of workers using early radiation devices. An increased risk of NMSC has been observed among uranium miners, radiologists, and individuals treated with x rays in childhood for tinea capitis (ringworm of the scalp) or for thymic enlargement; NMSC is one of the cancers most strongly associated with the atomic bombing of Hiroshima and Nagasaki. Although exposure to ionizing radiation is a known cause of NMSC, it is not yet clear whether therapeutic radiation causes both major histologic types of NMSC, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Additionally, the potentially modifying effects, such as latency, age when treated, and type of treatment, are not well understood.

PURPOSE

We investigated the relative risks of BCC and SCC associated with previous radiation therapy and evaluated these risks in relation to age and time since initial treatment and the medical condition for which radiation therapy was given.

METHODS

The study group comprised individual diagnosed with at least one BCC or SCC from January 1980 through February 1986, who were recruited to participate in a skin cancer prevention trial designed to test whether oral beta-carotene supplementation would reduce the risk of new NMSCs. Patients were identified through the dermatology and pathology records of academic medical centers in Hanover, NH; Los Angeles, CA; San Francisco, CA; and Minneapolis, MN. Each participant completed a questionnaire detailing lifetime residence, pigmentary characteristics, occupational and recreational sun exposure, and history of radiation therapy. At enrollment, a study dermatologist assessed skin type (tendency to burn or tan) and extent of actinic skin damage. Participants were followed with an annual dermatologic examination for an average of 4 years. Of the 5232 potentially eligible individuals, 1805 were enrolled in the trial. We excluded 112 patients who reported previous radiation therapy for skin cancer only and three with missing information on whether they were ever treated with radiation therapy, leaving 1690 patients for the analysis. Approximately 4% of the patients died or discontinued participation for other reasons during each study year. We examined time to occurrence of first new histopathologically confirmed BCC and SCC during the follow-up period in relation to history of radiation therapy (for reasons other than NMSC) using a proportional hazards model. A multiple end points survival model was used to compare the rate ratios (RRs) for BCC and SCC. We also used a longitudinal method of analysis to compute the RR of total new BCC and SCC tumors per person per study year associated with radiation therapy. Using this method, we additionally assessed the potential modifying effects of age at treatment, latency, and type of therapy. All P values were derived from two-sided statistical tests of significance.

RESULTS

Among the participants we studied, 597 developed a new BCC (n = 1553 tumors) and 118 developed a new SCC (n = 179 tumors). The time to first new BCC, but not SCC, was associated with prior radiation therapy (RR = 1.7; 95% confidence interval [CI] = 1.4-2.0 and RR = 1.0; 95% CI = 0.6-1.7, respectively; P = .03 for the difference between the RRs). The RR of total BCC tumors was slightly higher (RR = 2.3; 95% CI = 1.7-3.1), but it was still unity for SCC (RR = 1.0; 95% CI = 0.5-1.9). BCC risk appeared to increase with younger age at exposure and time since initially treated, although these effects were only marginally statistically significant (P for trend = .06 and .07, respectively). Also, risk of BCC was more strongly related to treatment for acne (RR = 3.3; 95% CI = 2.1-5.2) than other conditions.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that exposure to therapeutic radiation is associated with BCC but not with SCC.

Improving employee health and wellness: a pilot study of the employee-driven Perfect Health Program

These preliminary findings suggest that participation in the account may have modified participant behaviors associated with risk for death from heart attack and lung cancer. Although further research and development is needed before stronger conclusions about the impact of the program can be made, these findings suggest positive effects of participation in an innovative employee-driven health and wellness program.

Rural adolescent drinking behavior: three year follow-up in the New Hampshire substance abuse prevention study

A three-year follow-up study of alcohol prevention among 4,406 children showed that neither a comprehensive school curriculum nor a community intervention was successful in preventing adolescent drinking. Predictor variables for drinking are examined and the importance of tolerance and encouragement of drinking by adult role models are noted.

Mortality associated with low plasma concentration of beta carotene and the effect of oral supplementation

OBJECTIVE

To examine the relationship between beta carotene plasma concentration and beta carotene supplementation and risk of death from major disease causes.

DESIGN

Cohort study of plasma concentrations; randomized, controlled clinical trial of supplementation.

SETTING

Medical school-affiliated dermatology practices.

PATIENTS

A total of 1188 men and 532 women with mean age of 63.2 years, who had enrolled in a randomized clinical trial of beta carotene supplementation to prevent nonmelanoma skin cancer.

INTERVENTION

Oral beta carotene, 50 mg per day for a median of 4.3 years.

MAIN OUTCOME MEASURES

All-cause mortality and mortality from cardiovascular disease and cancer.

RESULTS

During a median follow-up period of 8.2 years, there were 285 deaths. Persons whose initial plasma beta carotene concentrations were in the highest quartile (>0.52 micromol/L [27.7 microg/dL]) had a lower risk of death from all causes (adjusted relative rate [RR], 0.52; 95% confidence interval [CI] 0.44 to 0.87) and from cardiovascular diseases (adjusted RR, 0.57; 95% CI, 0.34 to 0.95) compared with persons with initial concentrations in the lowest quartile (<0.21 micromol/L [11.2 microg/dL]). Patients randomly assigned to beta carotene supplementation showed no reduction in relative mortality rates from all causes (adjusted RR, 1.03; 95% CI, 0.82 to 1.30) or from cardiovascular disease (adjusted RR, 1.16; 95% CI, 0.82 to 1.64). There was no evidence of lower mortality following supplementation among patients with initial beta carotene concentrations below the median for the study group.

CONCLUSIONS

These analyses provide no support for a strong effect of supplemental beta carotene in reducing mortality from cardiovascular disease or other causes. Although the possibility exists that beta carotene supplementation produces benefits that are too small or too delayed to have been detected in this study, noncausal explanations should be sought for the association between plasma concentrations of beta carotene and diminished risk of death.