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Biomedical subjects

J D Blum

Publications and source records attributed to J D Blum.

At least 19 recordsLinked to original sources
PubMed1999

Trace analyses of arsenic in drinking water by inductively coupled plasma mass spectrometry: high resolution versus hydride generation.

A magnetic sector inductively coupled plasma mass spectrometer (ICPMS) was applied to the determination of arsenic in drinking water samples using standard liquid sample introduction in the high-resolution mode (M/delta M = 7800) and hydride generation in the low-resolution mode (M/delta M = 300). Although high mass resolution ICPMS allowed the spectral separation of the argon chloride interference, the accompanying reduction in sensitivity at high resolution compromised detection and determination limits to 0.3 and 0.7 microgram/L, respectively. Therefore, a hydride generation sample introduction method, utilizing a new membrane gas-liquid separator design, was developed to overcome the chloride interference. Due to the high transport efficiency and the 50-100 times higher sensitivity at M/delta M = 300, the HG-ICPMS method resulted in an over 2000-fold increase in relative sensitivity. The routine detection and quantification limits were 0.3 and 0.5 ng/L, respectively. The results for both methods applied to the analysis of over 400 drinking water samples showed very good agreement at concentrations above 1 microgram/L. For concentrations between 0.01 and 1 microgram/L, only HG-ICPMS provided accurate quantitative results. Membrane desolvation, mixed-gas plasmas, and the addition of organic solvents for the reduction of the ArCl+ interference were also investigated and evaluated for trace As determination.

Arsenic↗
PubMed1999

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.

Facility Regulation and Control↗
PubMed1995

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.

American Medical Association↗
PubMed1991

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.

Antitrust Laws↗
PubMed1986

Purification and characterization of actophorin, a new 15,000-dalton actin-binding protein from Acanthamoeba castellanii.

Actophorin is a new actin-binding protein from Acanthamoeba castellanii that consists of a single polypeptide with a molecular weight of 15,000. The isoelectric point is 6.1, and amino acid analysis shows an excess of acidic residues over basic residues. The phosphate content is less than 0.2 mol/mol. There is 0.4 +/- 0.1 mg of actophorin/g of cells, so that the molar ratio of actin to actophorin is about 10:1 in the cell. Unique two-dimensional maps of tryptic and chymotryptic peptides and complete absence of antibody cross-reactivity show that Acanthamoeba actophorin, profilin, capping protein, and actin are separate gene products with minimal homology. Actophorin has features of both an actin monomer-binding protein and an actin filament-severing protein. Actophorin reduces the extent of actin polymerization at steady state in a concentration-dependent fashion and forms a complex with pyrene-labeled actin that has spectral properties of unpolymerized actin. During ultracentrifugation a complex of actophorin and actin sediments more rapidly than either actin monomers or actophorin. Although actophorin inhibits elongation at both ends of actin filaments, it accelerates the late stage of spontaneous polymerization like mechanical shearing and theoretical predictions of polymer fragmentation. Low concentrations of actophorin decrease the length and the low shear viscosity of actin filaments. High concentrations cause preformed filaments to shorten rapidly. Ca2+ is not required for any of these effects. Muscle and amoeba actin are equally sensitive to actophorin.

Actin Depolymerizing Factors↗
PubMed1984

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.

Actin Depolymerizing Factors↗
PubMed1984

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.

Ethics, Institutional↗