Reducing methylmercury accumulation in the food webs of San Francisco Bay and its local watersheds.

San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts. Concern for human exposure to MeHg in the region has led to advisories for consumption of sport fish. Striped bass from the Bay have the highest average Hg concentration measured for this species in USA estuaries, and this degree of contamination has been constant for the past 40 years. Similarly, largemouth bass in some Bay Area reservoirs have some of the highest Hg concentrations observed in the entire US. Bay Area wildlife, particularly birds, face potential impacts to reproduction based on Hg concentrations in the tissues of several Bay species. Source control of Hg is one of the primary possible approaches for reducing MeHg accumulation in Bay Area aquatic food webs. Recent findings (particularly Hg isotope measurements) indicate that the decades-long residence time of particle-associated Hg in the Bay is sufficient to allow significant conversion of even the insoluble forms of Hg into MeHg. Past inputs have been thoroughly mixed throughout this shallow and dynamic estuary. The large pool of Hg already present in the ecosystem dominates the fraction converted to MeHg and accumulating in the food web. Consequently, decreasing external Hg inputs can be expected to reduce MeHg in the food web, but it will likely take many decades to centuries before those reductions are achieved. Extensive efforts to reduce loads from the largest Hg mining source (the historic New Almaden mining district) are underway. Hg is spread widely across the urban landscape, but there are a number of key sources, source areas, and pathways that provide opportunities to capture larger quantities of Hg and reduce loads from urban runoff. Atmospheric deposition is a lower priority for source control in the Bay Area due to a combination of a lack of major local sources. Internal net production of MeHg is the dominant source of MeHg that enters the food web. Controlling internal net production is the second primary management approach, and has the potential to reduce food web MeHg in some habitats more effectively and within a much shorter time-frame. Controlling net MeHg production and accumulation in the food web of upstream reservoirs and ponds is very promising due to the many features of these ecosystems that can be manipulated. The most feasible control options in tidal marshes relate to the design of flow patterns and subhabitats in restoration projects. Options for controlling MeHg production in open Bay habitat are limited due primarily to the highly dispersed distribution of Hg throughout the ecosystem. Other changes in these habitats may also have a large influence on food web MeHg, including temperature changes due to global warming, sea level rise, food web alterations due to introduced species and other causes, and changes in sediment supply. Other options for reducing or mitigating exposure and risk include controlling bioaccumulation, cleanup of contaminated sites, and reducing other factors (e.g., habitat availability) that limit at-risk wildlife populations.

Acanthamoeba castellanii capping protein: properties, mechanism of action, immunologic cross-reactivity, and localization.

We report further characterization of the physical and immunologic properties, mechanism of action, and intracellular localization of Acanthamoeba castellanii capping protein, an actin regulatory protein discovered by Isenberg (Isenberg, G., U. Aebi, and T. D. Pollard, 1980, Nature (Lond.) 288:455-459). The native molecular weight calculated from measurements of Stokes' radius (3.8 nm by gel filtration chromatography) and sedimentation coefficient (4.8 S by sucrose gradient velocity sedimentation) was 74,000 daltons. The subunit molecular weights were 31,000 and 28,000 daltons, so the native molecule is a heterodimer. The two subunits did not immunologically cross-react with each other or with any other proteins from Acanthamoeba or several other organisms. In studies of the mechanism of action, Isenberg (see above reference) found that capping protein blocked polymerization from the barbed end of actin filaments and sedimented with actin filaments. We confirmed that capping protein binds to actin filaments with a gel filtration assay. Capping protein decreased the length distribution and high shear viscosity of actin filaments. Capping protein did not bundle or cross-link actin filaments. Low concentrations of capping protein increased the critical concentration for muscle and ameba actin polymerization from 0.1 to 0.6 microM in Mg++ and EGTA. Increasing amounts of capping protein did not increase the critical concentration further. In Ca++ capping protein did not change the critical concentration for muscle actin, but did increase the critical concentration for ameba actin. Ca++ had no effect on the ability of capping protein to decrease the low or high shear viscosity of actin filaments. By indirect fluorescent antibody staining, capping protein was localized to the cell cortex, an area rich in actin filaments. During subcellular fractionation of homogenates, about 1/3 of cellular capping protein banded with a crude membrane fraction. The other 2/3 of cellular capping protein was soluble, with a Stokes' radius equal to that of the purified protein. The molar ratio of capping protein to actin in the cell was 1:150.

Oxygen isotope constraints on the origin of impact glasses from the cretaceous-tertiary boundary.

Laser-extraction oxygen isotope and major element analyses of individual glass spherules from Haitian Cretaceous-Tertiary boundary sediments demonstrate that the glasses fall on a mixing line between an isotopically heavy (delta(18)O = 14 per mil) high-calcium composition and an isotopically light (delta(18)O = 6 per mil) high-silicon composition. This trend can be explained by melting of heterogeneous source rocks during the impact of an asteroid (or comet) approximately 65 million years ago. The data indicate that the glasses are a mixture of carbonate and silicate rocks and exclude derivation of the glasses either by volcanic processes or as mixtures of sulfate-rich evaporate and silicate rocks.

Distributive justice and global health: a call for a global corporate tax.

Significant efforts have been directed toward addressing the financial needs of the developing world for assistance with public health and related development problems. Both public and private organizations have made considerable economic contributions to assist with immediate and long term health challenges, and there is growing international support for programs of national debit relief. Still, there is a need for additional resources to combat international health problems, which go beyond largesse. This paper calls for the creation of a legally rooted, global tax as a mechanism for consistent long term funding. Specifically, the paper proposes engagement of the World Trade Organization as a vehicle to sponsor a global tax on multinational corporations who have benefited most from the international trading scheme.

Mental health practitioners. Old stereotypes and new realities.

Changes in the patterns of mental health care have led to shifts in the treatment roles of types of mental health personnel. The current contributions of mental health personnel in one geographic region were identified. Over 500 psychiatrists, clinical psychologists, psychiatric social workers, psychiatric nurses, and mental health workers responded to questionnaires covering their personal background, training and education, treatment roles, salary, and attitudes. Unexpected findings about these groups included their overall youthfulness, differences in religion, the high proportions of nurses and mental health workers with advanced degrees; and occupational ratings for families of origin. Despite differences in the types of psychotherapy provided, almost half of each group provided some formal psychotherapy. An important factor in the mental health field's "identity crisis" may be that these groups can no longer define themselves in terms of psychotherapy.

The use of isotope tracers for identifying populations of migratory birds.

To determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we examined the isotopic composition of hydrogen (deuterium, δD), carbon (δ13C), and strontium (δ87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. δD and δ13C values in feathers, which are grown in the breeding area, varied systematically along a latitudinal gradient, being highest in samples from the southern end of the species' breeding range in Georgia and lowest in southern Canada. In addition, δD decreased from east to west across the northern part of the breeding range, from New Brunswick to Michigan. δ87Sr ratios were highest in the Appalachian Mountains, and decreased towards the west. These patterns are consistent with geographical variation in the isotopic composition of the natural environment, i.e., with that of precipitation, plants, and soils for δD, δ13C, and δ87Sr, respectively. Preliminary analyses of the δD and δ13C composition of feathers collected from warblers in their Caribbean winter grounds indicate that these individuals were mostly from northern breeding populations. Furthermore, variances in isotope ratios in samples from local areas in winter tended to be larger than those in summer, suggesting that individuals from different breeding localities may mix in winter habitats. These isotope markers, therefore, have the potential for locating the breeding origins of migratory species on their winter areas, for quantifying the degree of mixing of breeding populations on migratory and wintering sites, and for documenting other aspects of the population structure migratory animals - information needed for studies of year-round ecology of these species as well as for their conservation. Combining information from several stable isotopes will help to increase the resolution for determining the geographic origins of individuals in such highly vagile populations.

Economic credentialing moves from the hospital to managed care.

This article deals with the application of economic measures to the appointment, reappointment, and delineation of medical staff privileges, the so-called practice of economic credentialing. The concept of economic credentialing is first explored in the hospital context with a focus on legal and political issues. The second part of the article examines how economic credentialing will evolve in new managed care practice settings. Emphasis is placed on how the law and legislation will be utilized by organized medicine to protect physician interests in the process of selective contracting. Specific discussion focuses on the American Medical Association's Patient Protection Act and the implications of "any willing provider" provisions.

Withdrawing life support: a legal assessment and a possible response.

How to deal with terminally ill incompetent patients is a painful dilemma for for hospital medical staffs and administrators, not to mention families of these patients. Case law on the removal of life support is emerging, and physicians and administrators may find the hospital-based ethics committee one means to guide them in making difficult decisions without involving the courts.

Federalism and managed care: introductory comments to the American Association of Law Schools' Section on Law, Medicine and Health Care on the role of the states in managed care regulation.

This section of the Annals of Health Law represents a compilation of materials concerning the state regulation of managed care. The following materials were first presented at the annual meeting of the American Association of Law Schools ("AALS"), Section on Law, Medicine and Health Care in January 1999. Chairman John Blum introduces the subject and questions the dual role assumed by state and federal authorities in regulating managed care.

Physician economic efficiency--a new factor in credentialing.

"Economic credentialing"--the use of economic indicators in evaluating physicians for the purposes of staff appointment and reappointment--is a controversial new development in the ongoing struggle to control hospital costs while maintaining quality patient care. This article describes the concept of economic credentialing, discusses some of the legal considerations raised by the use of economic criteria in the credentialing process, and presents the findings of a recent study of the utilization of economic credentialing in hospitals today.