Randomized controlled trial of the Medifast 5 & 1 Plan for weight loss.

OBJECTIVE: The Medifast 5 & 1 Plan (MD) is a portion-controlled, nutritionally-balanced, low-fat weight-loss plan. We studied the effects of MD compared with a reduced-energy, food-based diet (FB) on body weight, waist circumference, fat mass and other measures in adults. DESIGN: We conducted a two-parallel-arm, randomized, controlled trial comparing MD to FB over 52 weeks. A total of 120 men and women aged 19-65 years with BMI 35 and 50 kg m(-2) were randomized to MD (n=60) or FB (n=60). Follow-up included a 26-week weight-loss phase and 26-week weight-maintenance phase. Anthropometric, body composition, biochemical and appetite/satiety measures were performed at baseline and at 26 and 52 weeks. An intention-to-treat, linear mixed models analysis was the primary analysis. RESULTS: Fifty MD subjects (83.3%) and 45 FB subjects (75.0%) completed the study on assigned treatment. At 26 weeks, race-adjusted mean weight loss was 7.5 kg in MD subjects vs 3.8 kg in FB subjects (P=0.0002 for difference); reduction in waist circumference was 5.7 cm in MD vs 3.7 cm in FB (P=0.0064); and fat mass loss was 6.4 kg in MD vs 3.7 kg in FB (P=0.0011). At 52 weeks, the corresponding reductions were 4.7 vs 1.9 kg (P=0.0004); 5.0 vs 3.6 cm (P=0.0082); and 4.1 vs 1.9 kg (P=0.0019) in MD and FB subjects, respectively. CONCLUSION: In obese adults, MD resulted in significantly greater reductions in body weight and fat compared with an FB diet for 1 year after randomization.

Getting carried away: a note showing baseline observation carried forward (BOCF) results can be calculated from published complete-cases results.

OBJECTIVE: Randomized controlled trials (RCTs) in obesity are plagued by missing data due to participant dropouts. Most methodologists and regulatory bodies agree that the primary analysis of such RCTs should be based on the intent-to-treat (ITT) principle, such that all randomized subjects are included in the analysis, even those who dropped out. Unfortunately, some authors do not include an ITT analysis in their published reports. Here we show that one form of ITT analysis, baseline observation carried forward (BOCF), can be performed utilizing only information available in a published complete-case (CC) analysis, permitting readers, editors, meta-analysts and regulators to easily conduct their own ITT analyses when the original authors do not report one. METHOD: We mathematically derive a simple method for estimating and testing treatment effects using the BOCF to allow a more conservative comparison of treatment effects when there are dropouts in a clinical trial. We provide two examples of this method using available CC analysis data from reported obesity trials to illustrate the application for readers who wish to determine a range of treatment effects based on published summary statistics. CONCLUSION: Commonly used CC analyses may lead to inflated type I error rates and/or treatment effect estimates. The method described herein can be useful for researchers who wish to estimate a conservative range of plausible treatment effects based on limited reported data. Limitations of this method are discussed.

Influence of CYP2C9 and VKORC1 on warfarin response during initiation of therapy.

BACKGROUND: Although multiple reports have documented the influence of CYP2C9 and VKORC1 variants on warfarin dose, risk of over-anticoagulation and hemorrhage, their influence on anticoagulation maintenance and individual proportion of time spent in target INR range (PPTR) is limited. Moreover the potential benefit of genotype-guided dosing implemented after initiation of therapy in a racially diverse population has not been explored. Herein we present the influence of CYP2C9 and VKORC1 C1173T on warfarin response during the first 30 days of therapy. METHODS: Warfarin dose was empirically determined in 250 African Americans 271 European Americans. The influence of CYP2C9 and VKORC1 on rate of INR increase, anticoagulation maintenance, risk of over-anticoagulation, and change in dose over 30 days was evaluated after adjustment for socio-demographic, lifestyle and clinical factors. Possession of variant VKORC1 (+/- variant CYP2C9) genotype was associated with a more rapid attainment of target INR and higher frequency of dose adjustments. Patients possessing variant genotypes spent less time in target range. However adjustment for rate of INR increase rendered the association non-significant. European Americans (but not African Americans) possessing variant VKORC1 (+/- variant CYP2C9) genotype had a higher risk of over-anticoagulation. Neither CYP2C9 nor VKORC1 influenced the risk of minor hemorrhage. CYP2C9 and VKORC1 explained 6.3% of the variance in dose change over the first 30 days of therapy demonstrating that the usefulness of genotype-guided dosing may extend beyond first day of therapy. CONCLUSION: The benefit of genotype-based dose prediction may extend beyond first few days of therapy. Whether genotype-guided dosing will decrease the risk of over-anticoagulation, improve anticoagulation control and most importantly improve outcomes for chronic warfarin users remains to be proven.

Influence of CYP2C9 and VKORC1 1173C/T genotype on the risk of hemorrhagic complications in African-American and European-American patients on warfarin.

The association of CYP2C9 and VKORC1 1173C/T genotype and risk of hemorrhage among African Americans and European Americans is presented. This association was evaluated using Cox proportional hazard regression with adjustment for demographics, comorbidity, and time-varying covariates. Forty-four major and 203 minor hemorrhages occurred over 555 person-years among 446 patients (60.6+/-15.6 years, 50% men, 227 African Americans). The variant CYP2C9 genotype conferred an increased risk for major (hazard ratio (HR) 3.0; 95% confidence interval (CI): 1.1-8.0) but not minor (HR 1.3; 95% CI: 0.8-2.1) hemorrhage. The risk of major hemorrhage was 5.3-fold (95% CI: 0.4-64.0) higher before stabilization of therapy, 2.2-fold (95% CI: 0.7-6.5) after stabilization, and 2.4-fold (95% CI: 0.8-7.4) during all periods when anticoagulation was not stable. The variant VKORC1 1173C/T genotype did not confer a significant increase in risk for major (HR 1.7; 95% CI: 0.7-4.4) or minor (HR 0.8; 95% CI: 0.5-1.3) hemorrhage. The variant CYP2C9 genotype is associated with an increased risk of major hemorrhage, which persists even after stabilization of therapy.

Racial differences in the prevalence of Factor V Leiden mutation among patients on chronic warfarin therapy.

We report the prevalence of Factor V Leiden (FVL) in European American and African American patients on warfarin therapy residing in Alabama. METHODS.: Detailed history was obtained and FVL genotype was determined for 288 patients enrolled in a prospective cohort: Pharmacogenetic Optimization of Anticoagulation Therapy. Racial differences in genotype frequency were assessed by the Chi-square statistics and HWE assumptions by G-statistics. Race-specific analysis for the association between site of thromboembolism and the presence of FVL mutation was assessed using logistic regression. RESULTS.: The overall heterozygote (GA genotype) frequency was 4.9%. No patient was found to be homozygous (AA) for the variant allele. The prevalence of GA was higher in European American (8.6%) compared to African American (1.4%) patients (p=0.004). The FVL genotype frequency was significantly different across race for venous thromboembolic events (p=0.014) but not for arterial thromboembolic events (p=0.20). Multivariable race-specific analysis highlights the contribution of FVL mutation to the risk of venous thromboembolic events in European American (p=0.03) but not in African American patients (p=0.95). European American patients with the GA mutation were approximately 6.3 times more likely to have experienced a venous, rather than arterial thromboembolic event. CONCLUSION.: In Alabama, among patients on warfarin, the GA genotype is more prevalent in European Americans compared to African Americans. In European Americans, but not in African Americans, the GA genotype was more prevalent in patients with venous compared to arterial thromboembolic events.

Systemic lupus erythematosus in a multi-ethnic cohort (LUMINA) XXXII: [corrected] contributions of admixture and socioeconomic status to renal involvement.

Renal involvement in systemic lupus erythematosus (SLE) is more frequent in minorities. We examined whether genetic or socioeconomic status (SES) explain these disparities in a large multiethnic (Hispanics from Texas and Puerto Rico, African Americans and Caucasians) SLE cohort. Renal involvement was defined as WHO Class II-V and/or proteinuria (> 0.5 g/24 h or 3+) attributable to SLE and/or abnormal urinary sediment, proteinuria 2+, elevated serum creatinine/ decreased creatinine clearance twice, 6 months apart present any time over the course of the disease. Ancestry informative markers (AIMS) were used to define the admixture proportions in each patient and group. Logistic regression models were examined to determine the percentage variance (R2) in renal involvement related to ethnicity that is explained by socio-economic status (SES) and admixture (adjusting for age, gender and disease duration, basic model). Four-hundred and fifty-nine (out of 575) patients were included; renal involvement occurred in 44.6% Texas Hispanics, 11.3% Puerto Rico Hispanics, 45.8% African Americans, 18.3% Caucasians. SES accounted for 14.5% of the variance due to ethnicity (after adjusting for basic model variables), admixture 36.8% and both, 12.2%; 45.9% of the variance remained unexplained. Alternative models for decreased glomerula filtration rate and end-stage renal disease were comparable in the distribution of the explanatory variables. Our data indicate that genetic factors appear to be more important than SES in explaining the ethnic disparities in the occurrence of renal involvement.

Racial or ethnic differences in allele frequencies of single-nucleotide polymorphisms in the methylenetetrahydrofolate reductase gene and their influence on response to methotrexate in rheumatoid arthritis.

BACKGROUND: The anti-folate drug methotrexate (MTX) is commonly used to treat rheumatoid arthritis. OBJECTIVE: To determine the allele frequencies of five common coding single-nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene in African-Americans and Caucasians with rheumatoid arthritis and controls to assess whether there are differences in allele frequencies among these ethnic or racial groups and whether these SNPs differentially affect the efficacy or toxicity of MTX. METHODS: Allele frequencies in the 677, 1298 and 3 additional SNPs in the MTHFR coding region in 223 (193 Caucasians and 30 African-Americans) patients with rheumatoid arthritis who previously participated in one of two prospective clinical trials were characterised, and genotypes were correlated with the efficacy and toxicity of MTX. Another 308 subjects with rheumatoid arthritis who participated in observational studies, one group predominantly Caucasian and the other African-American, as well as 103 normal controls (53 African-Americans and 50 Caucasians) were used to characterise allele frequencies of these SNPs and their associated haplotypes. RESULTS: Significantly different allele frequencies were seen in three of the five SNPs and haplotype frequencies between Caucasians and African-Americans. Allele frequencies were similar between patients with rheumatoid arthritis and controls of the same racial or ethnic group. Frequencies of the rs4846051C, 677T and 1298C alleles were 0.33, 0.11 and 0.13, respectively, among African-Americans with rheumatoid arthritis. Among Caucasians with rheumatoid arthritis, these allele frequencies were 0.08 (p<0.001 compared with African-Americans with rheumatoid arthritis), 0.30 (p = 0.002) and 0.34 (p<0.001), respectively. There was no association between SNP alleles or haplotypes and response to MTX as measured by the mean change in the 28-joint Disease Activity Score from baseline values. In Caucasians, the 1298 A (major) allele was associated with a significant increase in MTX-related adverse events characteristic of a recessive genetic effect (odds ratio 15.86, 95% confidence interval 1.51 to 167.01; p = 0.021), confirming previous reports. There was an association between scores of MTX toxicity and the rs4846051 C allele, and haplotypes containing this allele, in African-Americans, but not in Caucasians. CONCLUSIONS: : These results, although preliminary, highlight racial or ethnic differences in frequencies of common MTHFR SNPs. The MTHFR 1298 A and the rs4846051 C alleles were associated with MTX-related adverse events in Caucasians and African-Americans, respectively, but these findings should be replicated in larger studies. The rs4846051 SNP, which is far more common in African-Americans than in Caucasians, can also be proved to be a useful ancestry informative marker in future studies on genetic admixture.

Genetic risk factors for infection in patients with early rheumatoid arthritis.

We analyzed clinical and genetic factors contributing to infections in 457 subjects with early rheumatoid arthritis (RA) enrolled in a prospective, 1-year clinical trial of methotrexate and the TNF inhibitor etanercept. Subjects were genotyped for the following single nucleotide polymorphisms (SNPs): (TNF -308, -238, and + 488); lymphotoxin-alpha (LTA) (LTA + 249, + 365, and + 720); and Fc gamma receptors FCGR2A 131 H/R; FCGR3A 176 F/V; and FCGR3B NA 1/2 and genotypes were correlated with infections. At least one URI was noted in 52% of subjects (99/191) with the NA2/NA2 genotype of the neutrophil-specific FCGR3B gene, compared to 42% (77/181) of those with the NA1/NA2 genotype and 39% (23/59) of those with the NA1/NA1 genotype (P = 0.038). Urinary tract infection (UTI) was associated with the TNF -238 A (odds ratio(OR) 2.56, 95% confidence interval (CI) 1.05-6.25) and LTA +365 C (OR 1.73, 95% CI 1.07-2.79) alleles, and marginally with the FCGR3A F allele (OR 1.72, 95% CI 0.99-3.00). There was a striking linear correlation between UTI and the number of risk alleles defined by these three SNPs (P < 0.001), suggesting an additive effect on susceptibility. These findings have important implications for the role of genetics in susceptibility to bacterial and viral infections.

Effects of outcome-driven insurance reimbursement on short-term weight control.

CONTEXT: Although most health insurers exclude coverage of weight control therapy, one local insurer offered partial reimbursement of the cost of a weight control program, using an incentive plan. OBJECTIVE: To determine whether outcome-driven insurer-based reimbursement improves participation in a weight control program and short-term weight loss outcomes. DESIGN: Cohort follow-up study between January 1998 and February 2001. SETTING: Community weight management program operated by an academic medical center. SUBJECTS: Obese participants who had the potential for reimbursement (Group A, n=25) and participants in the same program classes (Group B, n=100) who had no possibility for reimbursement. Subjects in Group B were selected from among 206 potential participants using a propensity score to match them with subjects in Group A on age, gender, ethnicity, starting BMI, starting weight, and educational, economic, and demographic variables. INTERVENTION: Group lifestyle-based weight management program. The insurer reimbursed half the cost of the program to obese participants who met minimum weight criteria, paid the program fee at enrollment, attended > or =10 of the 12 classes, and lost > or =6% of initial body weight after 12 weeks. MAIN OUTCOME MEASURES: Participation rates and weight loss outcomes. RESULTS: Group A subjects attended significantly more classes (mean+/-s.d.: 10.1+/-1.8 vs 8.2+/-2.5, P<0.001) and lost more weight than Group B subjects (6.1+/-3.1 vs 3.7+/-3.6%, P=0.002). While 84% of Group A subjects attended > or =10 classes, only 37% of Group B subjects did so (P<0.001); 56% of Group A subjects lost > or =6% of body weight, but only 20% of Group B subjects did so (P<0.001); 56% of Group A subjects achieved both the class attendance and weight loss goals, but only 14% of Group B subjects did so (P<0.001). Logistic regression estimated that Group A subjects had 8.2 times the odds of attending > or =10 classes and 4.5 times the odds of losing > or =6% of body weight of Group B subjects, after controlling for class attendance. CONCLUSIONS: Insurer-based reimbursement that is contingent upon initial financial commitment on the part of the patient, consistent program participation, and successful weight loss is associated with significantly better short-term weight control outcomes.

Effect of Box-Cox transformation on power of Haseman-Elston and maximum-likelihood variance components tests to detect quantitative trait Loci.

Non-normality of the phenotypic distribution can affect power to detect quantitative trait loci in sib pair studies. Previously, we observed that Winsorizing the sib pair phenotypes increased the power of quantitative trait locus (QTL) detection for both Haseman-Elston (HE) least-squares tests [Hum Hered 2002;53:59-67] and maximum likelihood-based variance components (MLVC) analysis [Behav Genet (in press)]. Winsorizing the phenotypes led to a slight increase in type 1 error in H-E tests and a slight decrease in type I error for MLVC analysis. Herein, we considered transforming the sib pair phenotypes using the Box-Cox family of transformations. Data were simulated for normal and non-normal (skewed and kurtic) distributions. Phenotypic values were replaced by Box-Cox transformed values. Twenty thousand replications were performed for three H-E tests of linkage and the likelihood ratio test (LRT), the Wald test and other robust versions based on the MLVC method. We calculated the relative nominal inflation rate as the ratio of observed empirical type 1 error divided by the set alpha level (5, 1 and 0.1% alpha levels). MLVC tests applied to non-normal data had inflated type I errors (rate ratio greater than 1.0), which were controlled best by Box-Cox transformation and to a lesser degree by Winsorizing. For example, for non-transformed, skewed phenotypes (derived from a chi2 distribution with 2 degrees of freedom), the rates of empirical type 1 error with respect to set alpha level=0.01 were 0.80, 4.35 and 7.33 for the original H-E test, LRT and Wald test, respectively. For the same alpha level=0.01, these rates were 1.12, 3.095 and 4.088 after Winsorizing and 0.723, 1.195 and 1.905 after Box-Cox transformation. Winsorizing reduced inflated error rates for the leptokurtic distribution (derived from a Laplace distribution with mean 0 and variance 8). Further, power (adjusted for empirical type 1 error) at the 0.01 alpha level ranged from 4.7 to 17.3% across all tests using the non-transformed, skewed phenotypes, from 7.5 to 20.1% after Winsorizing and from 12.6 to 33.2% after Box-Cox transformation. Likewise, power (adjusted for empirical type 1 error) using leptokurtic phenotypes at the 0.01 alpha level ranged from 4.4 to 12.5% across all tests with no transformation, from 7 to 19.2% after Winsorizing and from 4.5 to 13.8% after Box-Cox transformation. Thus the Box-Cox transformation apparently provided the best type 1 error control and maximal power among the procedures we considered for analyzing a non-normal, skewed distribution (chi2) while Winzorizing worked best for the non-normal, kurtic distribution (Laplace). We repeated the same simulations using a larger sample size (200 sib pairs) and found similar results.

Iodine-129 concentrations in marginal seas of the north Pacific and Pacific-influenced waters of the Arctic Ocean.

Water sampling during the 1993 IV Russian-US Joint Expedition to the Bering and Chukchi Seas (BERPAC) indicates that Pacific Ocean burdens of the long-lived radionuclide 129I are relatively low in the Pacific-influenced Arctic, particularly compared to high latitude waters influenced by the North Atlantic. These low concentrations occur despite the presence of potential submerged anthropogenic sources in the East Sea (Sea of Japan), and in the northwest Pacific Ocean, east of the Kamchatka Peninsula. The concentration of 129I entering the Arctic Ocean through Bering Strait, approximately 0.7 x 10(8) atoms kg(-1), is only slightly higher than observed in deep Pacific waters. Similar concentrations (0.44-0.76 x 10(8) atoms kg(-1)) measured in Long Strait indicate no significant transfer of 129I eastward into the Chukchi Sea in the Siberian Coastal Current from the Siberian marginal seas to the west. However, the concentrations reported here are more than an order of magnitude higher than the Bering Strait input concentration estimated (1.0 x 10(6) atoms kg(-1)) from bomb fallout mass balances, which supports other existing evidence for a significant atmospheric deposition term for this radionuclide in surface ocean waters. Near-bottom water samples collected in productive waters of the Bering and Chukchi Seas also suggest that sediment regeneration may locally elevate 129I concentrations, and impact its utility as a water mass tracer. As part of this study, two deep 129I profiles were also measured in the East Sea in 1993-1994. The near-surface concentration of 129I ranged from 0.12 to 0.31 x 10(8) atoms kg(-1). The 129I concentration showed a steady decrease with depth, although because of active deep water ventilation, the entire 3000 m water column exceeded natural concentrations of the radionuclide. Atom ratios of 129I/137Cs in the East Sea also suggest an excess of 129I above bomb fallout estimates, also possibly resulting from atmospheric deposition ultimately originating from nuclear facilities.

Testing the robustness of the new Haseman-Elston quantitative-trait loci-mapping procedure.

Variance components (VC) techniques have emerged as among the more powerful methods for detection of quantitative-trait loci (QTL) in linkage analysis. Allison et al. found that, with particularly marked leptokurtosis in the phenotypic distribution and moderate-to-high residual sibling correlation, maximum likelihood (ML) VC methods may produce a severe excess of type I errors. The new Haseman-Elston (NHE) method is a least-squares-based VC method for mapping of QTL in sib pairs (Elston et al.). Using simulation, we investigate the robustness of the NHE to marked nonnormality, by means of the same distributions and worst-case conditions identified by Allison et al. for the ML approach (i.e., 100 pairs; high residual sibling correlation). Results showed that, when marked nonnormality is present, the NHE can be used without severe type I error-rate inflation, even at very small alpha levels.

Global distribution of Pu isotopes and 237Np.

Inventories and compositions of Pu isotopes and 237Np in archived soil samples collected in the 1970s from 54 locations around the world were determined to provide regional baselines for recognizing possible future environmental inputs of non-fallout Pu and Np. As sample sizes used in this work were small (typically 1 g), inhomogeneities in Pu and Np concentrations were easily recognizable and, as a result, we were able to determine that atypical debris in South America, from French testing in the South Pacific, is more widely and uniformly distributed than previously supposed. From our results we conclude that fallout 237Np/239Pu atom ratios are generally lower in the Southern Hemisphere (approximately 0.35) than in the Northern Hemisphere (approximately 0.47.) Moreover, 237Np/239Pu atom ratios are more device-dependent, hence more variable, than counterpart 240Pu/239Pu atom ratios. Given predictable trends caused by sample inhomogeneities, with only two exceptions, the Pu results of this work are entirely consistent with (and in several instances improve on) results previously reported for these same samples. However, unlike earlier interpretations used to explain these results, we recommend that fallout isotopic signatures be represented by mixing lines, rather than averages, to better reflect regional variations of stratospheric fallout inventories relative to tropospheric fallout inventories, and provide the theoretical basis for doing so. Finally, the Np results of this work constitute one of the largest single compilations of such data reported to date.

Factors that influence health risk behaviors among tanning salon patrons.

A principal components analysis identified the immediate convenience of indoor tanning (i.e., relaxation, perceived attractiveness of tans) as a major factor that motivates people to visit commercial tanning salons frequently and continually. Long-term considerations, such as price, socializing, and perceived health, also emerged as a motivating factor that was related to tanning frequency. Furthermore, almost half of the participants mentioned that regulations restricting indoor tanning would not make them more cautious in their tanning behavior. Findings confirm several other studies indicating that knowledge of the danger of UV exposure may have little influence on actual tanning behavior. Suggestions for alternative approaches that focus on the perceived attractiveness of tanned skin rather than the susceptibility of frequent tanners to skin cancer are discussed.

Chronic self-destructive behavior in normative and delinquent adolescents.

The Chronic Self-Destructiveness Scale (CSDS) and the Psychopathic Deviate and Hypomania scales of the MMPI were administered to 112 delinquent adolescents and to 141 high-school students. Both male and female delinquents reported significantly higher levels of chronic self-destructiveness. Significant positive correlations between the CSDS and the MMPI scales were found for all groups. The results indicate that delinquent males have high levels of chronic self-destructiveness attributable to these personality variables; however, other cultural variables may intervene. The results for delinquent females were similar to those of high-school males. Thus, these findings raise questions about societal influences and the definitions of delinquent behavior.

Effects of lesion laterality on the Satz-Mogel WAIS-R short form.

Effects of lateralized brain damage on the Satz-Mogel (1962) WAIS-R short form were examined. Patients (N = 65) were assigned to groups based on diffuse, predominantly left, or predominantly right brain damage. Overall, results supported the validity of the Satz-Mogel short-form IQs with neurological patients, although there were significant ANOVA results for various subtests when original scores were compared to short-form scores. A comparison of groups in regard to the number of deviations (i.e., +/- 3) from original WAIS-R subtests raised questions with regard to the effects of lesion laterality on certain short-form subtest scores. Criteria for evaluating short forms and issues for further research are discussed.

Radiochemical determination of cobalt-60 in environmental samples.

A procedure for the radiochemical determination of (60)Co in low-activity samples of sediment and biological material is described. Cobalt recovery is high and decontamination from tervalent lanthanides and naturally-occurring radionuclides is complete. Cobalt is precipitated with 1-nitroso-2-naphthol, decontaminated from iron by precipitation of the iron as ferric phosphate, extracted into methyl isobutyl ketone, and finally precipitated as cobalt mercury(II) thiocyanate for yield determination and beta-counting.

Biokinetic behavior of technetium in the red abalone, Haliotis rufescens: a re-assessment.

The biokinetic behavior of 95mTc in the red abalone, Haliotis rufescens, is reviewed in light of recent experiments with other molluscs. Additional experimentation has confirmed that, when uptake is directly from labeled seawater, abalones exhibit concentration factors in excess of 100. Bivalve molluscs under the same experimental conditions have concentration factors that do not exceed 2. However, uptake and loss kinetics in the abalone cannot be described by a single compartment model as had been previously advanced. Assimilation of 95mTc by abalones following a single feeding of labeled macroalga, Nereocystis luetkeana, is approximately 45% and loss kinetics are similar to those observed following direct uptake from seawater.