Interactions between marine megafauna and plastic pollution in Southeast Asia.

Southeast (SE) Asia is a highly biodiverse region, yet it is also estimated to cumulatively contribute a third of the total global marine plastic pollution. This threat is known to have adverse impacts on marine megafauna, however, understanding of its impacts has recently been highlighted as a priority for research in the region. To address this knowledge gap, a structured literature review was conducted for species of cartilaginous fishes, marine mammals, marine reptiles, and seabirds present in SE Asia, collating cases on a global scale to allow for comparison, coupled with a regional expert elicitation to gather additional published and grey literature cases which would have been omitted during the structured literature review. Of the 380 marine megafauna species present in SE Asia, but also studied elsewhere, we found that 9.1 % and 4.5 % of all publications documenting plastic entanglement (n = 55) and ingestion (n = 291) were conducted in SE Asian countries. At the species level, published cases of entanglement from SE Asian countries were available for 10 % or less of species within each taxonomic group. Additionally, published ingestion cases were available primarily for marine mammals and were lacking entirely for seabirds in the region. The regional expert elicitation led to entanglement and ingestion cases from SE Asian countries being documented in 10 and 15 additional species respectively, highlighting the utility of a broader approach to data synthesis. While the scale of the plastic pollution in SE Asia is of particular concern for marine ecosystems, knowledge of its interactions and impacts on marine megafauna lags behind other areas of the world, even after the inclusion of a regional expert elicitation. Additional funding to help collate baseline data are critically needed to inform policy and solutions towards limiting the interactions of marine megafauna and plastic pollution in SE Asia.

Mitogenomic phylogeny of the Asian colobine genus Trachypithecus with special focus on Trachypithecus phayrei (Blyth, 1847) and description of a new species.

Trachypithecus, which currently contains 20 species divided into four groups, is the most speciose and geographically dispersed genus among Asian colobines. Despite several morphological and molecular studies, however, its evolutionary history and phylogeography remain poorly understood. Phayre's langur ( Trachypithecus phayrei) is one of the most widespread members of the genus, but details on its actual distribution and intraspecific taxonomy are limited and controversial. Thus, to elucidate the evolutionary history of Trachypithecus and to clarify the intraspecific taxonomy and distribution of T. phayrei, we sequenced 41 mitochondrial genomes from georeferenced fecal samples and museum specimens, including two holotypes. Phylogenetic analyses revealed a robustly supported phylogeny of Trachypithecus, suggesting that the T. pileatus group branched first, followed by the T. francoisi group, and the T. cristatus and T. obscurus groups most recently. The four species groups diverged from each other 4.5-3.1 million years ago (Ma), while speciation events within these groups occurred much more recently (1.6-0.3 Ma). Within T. phayrei, we found three clades that diverged 1.0-0.9 Ma, indicating the existence of three rather than two taxa. Following the phylogenetic species concept and based on genetic, morphological, and ecological differences, we elevate the T. phayrei subspecies to species level, describe a new species from central Myanmar, and refine the distribution of the three taxa. Overall, our study highlights the importance of museum specimens and provides new insights not only into the evolutionary history of T. phayrei but the entire Trachypithecus genus as well.

Diet and mitochondrial DNA haplotype of a sperm whale (Physeter macrocephalus) found dead off Jurong Island, Singapore.

Despite numerous studies across the large geographic range of the sperm whale (Physeter macrocephalus), little is known about the diet and mitochondrial DNA haplotypes of this strongly female philopatric species in waters off Southeast Asia. A female sperm whale found dead in Singapore waters provided the opportunity to study her diet and mitochondrial DNA haplotype. Here we report on the identification of stomach contents and mitochondrial DNA haplotype of this individual, and we include coastal hydrodynamic modelling to determine the possible geographic origin of the whale. At least 28 species of prey were eaten by this adult female whale, most of which were cephalopods. The mesopelagic squids Taonius pavo, Histioteuthis pacifica, Chiroteuthis imperator,and Ancistrocheirus lesueurii made up over 65% of the whale's stomach contents. Plastic debris was also found in the whale's stomach. Based on the diet, genetics, and coastal hydrodynamic modelling that suggest an easterly drift of the whale carcass over several days, the dead sperm whale in Singapore probably originated from a pod in the Southern Indian Ocean. This study provides an increase in the understanding the diet and natural history of the sperm whale in Southeast Asia. The combined analyses of stomach contents, DNA, and hydrodynamic modeling could provide a context to future studies on the sperm whale strandings, and have broader applicability for other marine mammals in the region.

Confounding in air pollution epidemiology: when does two-stage regression identify the problem?

A two-stage approach has recently been proposed to assess confounding by copollutants or other variables in time-series epidemiology studies for airborne particulate matter (PM), using independent series from different cities. In the first stage of the proposed method, two regression models are fitted for each city in the analysis. The first relates the health effect to the putative causal variable such as PM without including any copollutant or confounder. The other first-stage model relates a putative confounding variable to PM. In the second stage of the analysis, the estimated city-specific regression slopes for the health-effect-versus-PM model are regressed against the estimated city-specific regression slopes for the confounder-versus-PM model. Under the proposed method, a nonzero intercept estimate in the second-stage regression would be interpreted as indicating a direct pathway from PM to the health effect, and a nonzero slope estimate would be interpreted as indicating at least partial confounding of PM with the putative confounder. A simple counterexample using an additional copollutant variable shows that inferences based on this method could be misleading.

Dynamics of the mitochondrial reticulum in live cells using Fourier imaging correlation spectroscopy and digital video microscopy.

We report detailed studies of the dynamics of the mitochondrial reticulum in live cells using two independent experimental techniques: Fourier imaging correlation spectroscopy and digital video fluorescence microscopy. When both methods are used to study the same system, it is possible to directly compare measurements of preaveraged statistical dynamical quantities with their microscopic counterparts. This approach allows the underlying mechanism of the observed rates to be determined. Our results indicate that the dynamics of the reticulum structure is composed of two independent contributions, each important on very different time and length scales. During short time intervals (1-15 sec), local regions of the reticulum primarily undergo constrained thermally activated motion. During long time intervals (>15 sec), local regions of the reticulum undergo long-range "jump" motions that are associated with the action of cytoskeletal filaments. Although the frequency of the jumps depend on the physiological state of the cells, the average jump distance ( approximately 0.8 microm) is unaffected by metabolic activity. During short time intervals, the dynamics appear to be spatially heterogeneous, whereas the cumulative effect of the infrequent jumps leads to the appearance of diffusive motion in the limit of long time intervals.

Experimental observations of non-Gaussian behavior and stringlike cooperative dynamics in concentrated quasi-two-dimensional colloidal liquids.

We report, from direct observation of particle trajectories as a function of time, the presence of stringlike cooperative motion in a quasi-two-dimensional liquid. We have used digital video microscopy to study the equilibrium dynamics of suspensions of sterically stabilized uncharged poly(methylmethacrylate) spheres confined in a thin glass cell. Our experiments reveal the existence, in semidilute and dense liquid states, of a transition in the qualitative dynamical behavior of the system. At short times particles undergo unhindered Brownian motion, at intermediate times they undergo uncorrelated binary collisions, and at long times these one-particle self-diffusive modes are coupled to collective longitudinal acoustic modes of the fluid, the signature of which is local fluctuating domains of enhanced particle mobility. We study the properties of these domains by examining the density dependence of the van Hove self-correlation function and its deviation from Gaussian behavior. We observe that periods of non-Gaussian behavior correlate precisely with the timing of events involved in the relaxation of "caged" particles and their nearest neighbors. In contrast with relaxation processes in supercooled liquids, the lifetime of dynamical heterogeneities in a dissipative colloidal suspension is found to shift towards shorter time scales with increasing particle density. During time periods for which a quasi-two-dimensional system follows Gaussian behavior, we observe that, as predicted by Cichocki and Felderhof [J. Phys. Condens. Matter 6, 7287 (1994)], the time dependence of the evolution of the effective diffusion coefficient from its short time to its long time value has the form (ln t)/t. This last finding is true for all observed particle densities. To our knowledge, these results are the first experimental verification of the existence of microscopic cooperativity and the predicted temporal evolution of the diffusion coefficient for Brownian motion in concentrated quasi-two-dimensional liquids.

The conceptual structure of the integrated exposure uptake biokinetic model for lead in children.

The integrated exposure uptake biokinetic model for lead in children was developed to provide plausible blood lead distributions corresponding to particular combinations of multimedia lead exposure. The model is based on a set of equations that convert lead exposure (expressed as micrograms per day) to blood lead concentration (expressed as micrograms per deciliter) by quantitatively mimicking the physiologic processes that determine blood lead concentration. The exposures from air, food, water, soil, and dust are modeled independently by several routes. Amounts of lead absorbed are modeled independently for air, food, water, and soil/dust, then combined as a single input to the blood plasma reservoir of the body. Lead in the blood plasma reservoir, which includes extracellular fluids, is mathematically allocated to all tissues of the body using age-specific biokinetic parameters. The model calculation provides the estimate for blood lead concentration for that age. This value is treated as the geometric mean of possible values for a single child, or the geometric mean of expected values for a population of children exposed to the same lead concentrations. The distribution of blood lead concentrations about this geometric mean is estimated using a geometric standard deviation, typically 1.6, derived from the analysis of well-conducted community blood studies.

Some useful statistical methods for model validation.

Although formal hypothesis tests provide a convenient framework for displaying the statistical results of empirical comparisons, standard tests should not be used without consideration of underlying measurement error structure. As part of the validation process, predictions of individual blood lead concentrations from models with site-specific input parameters are often compared with blood lead concentrations measured in field studies that also report lead concentrations in environmental media (soil, dust, water, paint) as surrogates for exposure. Measurements of these environmental media are subject to several sources of variability, including temporal and spatial sampling, sample preparation and chemical analysis, and data entry or recording. Adjustments for measurement error must be made before statistical tests can be used to empirically compare environmental data with model predictions. This report illustrates the effect of measurement error correction using a real dataset of child blood lead concentrations for an undisclosed midwestern community. We illustrate both the apparent failure of some standard regression tests and the success of adjustment of such tests for measurement error using the SIMEX (simulation-extrapolation) procedure. This procedure adds simulated measurement error to model predictions and then subtracts the total measurement error, analogous to the method of standard additions used by analytical chemists.

Nickel absorption and kinetics in human volunteers.

Mathematical modeling of the kinetics of nickel absorption, distribution, and elimination was performed in healthy human volunteers who ingested NiSO4 drinking water (Experiment 1) or added to food (Experiment 2). Nickel was analyzed by electrothermal atomic absorption spectrophotometry in serum, urine, and feces collected during 2 days before and 4 days after a specified NiSO4 dose (12 micrograms of nickel/kg, n = 4; 18 micrograms of nickel/kg, n = 4; or 50 micrograms of nickel/kg, n = 1). In Experiment 1, each of the subjects fasted 12 hr before and 3 hr after drinking one of the specified NiSO4 doses dissolved in water; in Experiment 2, the respective subjects fasted 12 hr before consuming a standard American breakfast that contained the identical dose of NiSO4 added to scrambled eggs. Kinetic analyses, using a compartmental model, provided excellent goodness-of-fit for paired data sets from all subjects. Absorbed nickel averaged 27 +/- 17% (mean +/- SD) of the dose ingested in water vs 0.7 +/- 0.4% of the same dose ingested in food (a 40-fold difference); rate constants for nickel absorption, transfer, and elimination were not significantly influenced by the oral vehicle. The elimination half-time for absorbed nickel averaged 28 +/- 9 hr. Renal clearance of nickel averaged 8.3 +/- 2.0 ml/min/1.73 m2 in Experiment 1 and 5.8 +/- 4.3 ml/min/1.73 m2 in Experiment 2. This study confirms that dietary constituents profoundly reduce the bioavailability of Ni2+ for alimentary absorption; approximately one-quarter of nickel ingested in drinking water after an over-night fast is absorbed from the human intestine and excreted in urine, compared with only 1% of nickel ingested in food. The compartmental model and kinetic parameters provided by this study will reduce the uncertainty of toxicologic risk assessments of human exposures to nickel in drinking water and food.

Dose-response curves for erythrocyte protoporphyrin vs blood lead: effects of iron status.

An increase in erythrocyte protoporphyrin (EP) is one of the most useful indicators of adverse biological response to lead exposure. A nonlinear mathematical model relating EP to blood lead concentration (PbB) was fitted to data in a sample of 1677 U.S. children (ages 2-6 years) in the Second National Health and Nutrition Examination Survey (NHANES II). Iron status was defined by percentage transferrin saturation (PTS). The dose-response curves for EP vs PbB increased systematically with decreasing PTS, largely due to decrease of a parameter proportional to red cell lead-holding capacity with decreasing PTS.

Sexual differences in the distribution and retention of organic and inorganic mercury in methyl mercury-treated rats.

At 56 days of age, male and female Long-Evans rats received 1 mumole of 203Hg-labeled methyl mercuric chloride per kilogram sc and total, organic, and inorganic mercury contents and concentrations in tissues were determined for up to 98 days postdosing. Whole body clearance of mercury was faster in females than in males, and females attained higher peak percentages of the methyl mercury dose in kidney and brain than did males. Females had significantly higher mean percentages of the mercury dose present in the kidney and brain as organic or total mercury and in brain as inorganic mercury than did males. Males had significantly higher mean percentages of the dose present as organic or total mercury in pelt and whole body than did females. When expressed on a concentration basis, the only significant sexual difference was in the higher average concentration of organic mercury in the kidneys of females. When expressed on a tissue content basis, significant male-female differences in the kinetics (sex X time interactions) of organic mercury retention were found in kidney, brain, skeletal muscle, pelt, and whole body. Significant sex X time interactions in the concentrations of organic mercury were found in kidney, skeletal muscle, and whole body. Kinetics of retention and concentration of inorganic Hg in the pelt differed significantly for males and females. Discordance in degree of statistical significance of differences in mercury contents and concentrations reflected in part differences in relative body composition of males and females. Integrated exposures of tissues of males and females to organic or inorganic mercury were determined by fitting multiexponential retention functions to retention data. Differences in integrated exposure were estimated by the female-to-male ratio of areas under retention curves. Reconstruction of whole body organic and inorganic mercury burdens from constituent tissues indicated that integrated exposures of males and females to inorganic mercury were equal but females had a lower integrated exposure to organic mercury. Integrated exposure of liver to either form of mercury was about equal in males and females. However, the integrated exposure of the brain of females to inorganic mercury was 2.19 times that of males suggesting a sexual difference in accumulation or retention of inorganic mercury in the nervous system. These sexual differences in distribution and retention of organic and inorganic mercury after methyl mercury exposure may underlie reported sexual differences in sensitivity to the toxic effects of methyl mercury.

Multicompartment kinetic models for lead. I. Bone diffusion models for long-term retention.

The long-term retention of lead in bone poses a number of difficulties for the usual multicompartment models. The use of diffusion models based on exchange of lead between blood in canaliculi and the crystalline bone of the osteon allows a linear compartmental approximation suitable for statistical estimation of kinetic parameters in peripheral compartments. The model is applied to lead retention by beagle dogs.

Multicompartment kinetic models for lead. II. Linear kinetics and variable absorption in humans without excessive lead exposures.

Multicompartment models with constant fractional transfer rates have been fitted to experimental data on lead metabolism in four subjects studied by M. B. Rabinowitz, G. W. Wetherill, and J. D. Kopple (Science 182, 725-727, 1973; Environ. Health Perspect. 7, 145-153, 1974; Arch. Environ. Health 31, 220-223, 1976; J. Clin. Invest. 58, 260-270, 1976; J. Lab. Clin. Med. 90, 238-248, 1977). Long-term retention is estimated for blood, soft tissue, cortical and trabecular bone pools, and for facial hair. The absorption of lead from diet is shown to change with time, but no evidence was found for other variable or nonlinear kinetic mechanisms of lead metabolism in humans without excessive lead exposure.

Multicompartment kinetic model for lead. III. Lead in blood plasma and erythrocytes.

Multicompartment models have been fitted to experimental data on plasma lead and blood lead concentrations of subjects studied by P. E. deSilva (Brit. J. Ind. Med. 38, 209-217, 1981) and one subject studied by W.I. Manton and C.R. Malloy (Brit. J. Ind. Med. 40, 51-57, 1983). Nonlinear models for plasma lead vs blood lead in populations provide significantly better descriptions than does a linear model. Short-term kinetic data do not clearly resolve the precise nonlinear mechanism, however, Parameters of plasma and erythrocyte distribution in a single subject were significantly different on two occasions.

Compartmental models for trace metals in mammals.

Kinetic models for the distribution and elimination of certain trace metals in mammals allow evaluation of metal burdens in critical target organs under time-variables exposure patterns, and thus may assist in formulating exposure standards. The linear compartmental model is described and some of its implications for conceptual models of trace metal metabolism are developed. The model is then applied to data on multiple doses of cadmium in mice. Many trace metals do not follow simple linear kinetic models because exposure to more than one metal simultaneously often results in synergistic effects.

Ontogeny of the barley plant as related to mutation expression and detection of pollen mutations.

Clustering of mutant pollen grains in a population of normal pollen due to premeiotic mutational events complicates translating mutation frequencies into rates. Embryo ontogeny in barley will be described and used to illustrate the formation of such mutant clusters. The nature of the statistics for mutation frequency will be described from a study of the reversion frequencies of various waxy mutants in barley. Computer analysis by a "jackknife" method of the reversion frequencies of a waxy mutant treated with the mutagen sodium azide showed a significantly higher reversion frequency than untreated material. Problems of the computer analysis suggest a better experimental design for pollen mutation experiments. Preliminary work on computer modeling for pollen development and mutation will be described.