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Biomedical subjects

R D Sjoblad

Publications and source records attributed to R D Sjoblad.

11 recordsLinked to original sources
PubMed1994

Regulatory oversight of biochemical pesticides by the U.S. Environmental Protection Agency: health effects considerations.

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) enables the Office of Pesticide Programs (OPP) of the U.S. Environmental Protection Agency to ensure that pesticide use in commerce will not result in unreasonable adverse effects to humans and the environment. Currently, two classes of pesticides are recognized: conventional chemical pesticides and biological pesticides. The latter group is divided into biochemical and microbial pesticides. The recent resurgence of biochemical pesticides as effective pest control agents has increased the number of applications for experimental use permits and for product registration. The fundamental information and data necessary to evaluate such products by the Health Effects Division (HED) of OPP are discussed, as well as the criteria for the classification of a pesticide as a biochemical versus a conventional chemical pesticide. In accordance with the Agency's effort to encourage the development of pesticides less toxic to humans and the environment, the scientific basis for providing future regulatory relief and reduced data requirements for biochemical pesticides is discussed.

Animals↗
PubMed1992

Toxicological considerations for protein components of biological pesticide products.

The toxicity of protein components of microbial pesticide products is evaluated at EPA by requiring that pesticide manufacturers conduct a thorough taxonomic evaluation of the active microbial ingredient. The requirement for acute toxicity testing by dosing laboratory animals with the active microbial ingredient and with fermentation growth medium materials provides additional information on the toxicity of protein components of microbial pesticides. The potential for toxicity from proteins associated with contaminating organisms is addressed by use of appropriate quality control procedures to minimize or prevent growth of contaminants and by screening of fermentation batches for known human/mammalian pathogens. These considerations also would apply to any biochemical pesticide that is formed via the growth of a microorganism. If a protein itself is intended for commercial use as an active pesticide ingredient, acute exposure studies and in vitro digestibility studies could be done to answer potential concerns regarding toxicity.

Animals↗
PubMed1988

Potential future requirements for immunotoxicology testing of pesticides.

The thoughts presented above comprise a possible approach for revising Subdivision F guidelines with respect to testing of chemical pesticides as immunotoxicants. The main points of this report can be summarized as follows: 1. The tier system approach to Subdivision M guidelines allows for an effective screen (Tier I), and for in-depth (Tier II) evaluation of biochemical pesticides as immunotoxic agents. 2. Subchronic and chronic studies in Subdivision F guidelines can be modified to provide a more effective screen for evaluating the immunotoxic potential of chemical pesticides. 3. Addition to Subdivision F of studies to measure certain specific and non-specific cell-mediated immune responses might be considered appropriate for an immunotoxicity screen and, if included, would render Subdivision F data requirements analogous to those of Subdivision M. 4. When considered necessary, further studies can be done with chemical pesticides to provide sufficient data for an in-depth immunotoxicological risk evaluation. These studies would not necessarily be performed routinely (i.e., would not be included as data requirements in Subdivision F), but rather would be reserved for pesticides for which the immune system is shown to be a sensitive target of toxicity.

Animals↗
PubMed1983

Invited review: bacterial flagellar sheaths: structures in search of a function.

Although bacterial flagellar sheaths were observed over 30 years ago, they may still be characterized as structures in search of a function. In addition to true sheaths, bacterial flagella may possess other adornments that cause an increase in the organelle's cross-sectional diameter. These "complex flagella" are sharply differentiated from sheathed flagella. Immunological and chemical distinctions have been found between flagellar sheaths, flagellar cores, and LPS layers inferred to be the sheath sensu stricto. Although complex flagella may serve as specific receptors for flagellotropic phages or in allowing for more efficient swimming in viscous environments, similar functions have not yet been attributed to true sheaths. It is postulated that flagellar sheaths may allow for specific interaction between a bacterium and a surface. In addition, there is a problem as to the relationship between a rapidly rotating flagellum and the sheath.

Antigens, Bacterial↗
PubMed1981

Chemotactic responses of Chlamydomonas reinhardtii.

A capillary chemotaxis assay revealed that among a wide range of inorganic and organic chemicals, only ammonium ion (NH4+) could serve as an attractant of Chlamydomonas reinhardtii. NH4+ (10(-2) M) gave the maximum response, with up to a 15-fold increase in accumulated algae being measured. No repellents for the chlorophyte were detected. The response to NH4+ was influenced by exogenous levels of calcium, but not by L-methionine. The optimal pH for positive chemotaxis was 7.0; however, attraction was measurable from pH 4.0 to 9.0. Positive chemotaxis was stimulated by performing the assay under fluorescent illumination rather than in the dark.

Ammonium Chloride↗
PubMed1979

Characterization of an enzyme from Rhizoctonia praticola which polymerizes phenolic compounds.

An extracellular phenol oxidase from the fungus Rhizoctonia praticola which polymerizes various xenobiotic phenols was isolated and characterized. The enzyme was purified by DEAE-cellulose and Sephadex G-200 chromatography followed by preparative polyacrylamide gel electrophoresis. Atomic absorption and EPR spectroscopy indicated the presence of copper, and SDS gel electrophoresis revealed a molecular weight of 78,000. With 2,6-dimethoxyphenol as substrate, the enzyme showed a pH optimum of 6.7--6.9, and a temperature optimum of 40 degrees C. According to these and additional characteristics it appears that the enzyme belongs to the class of laccases.

Catechol Oxidase↗
PubMed1979

Chemotactic responses of Vibrio alginolyticus to algal extracellular products.

A capillary assay was used to evaluate the chemotactic responses of Vibrio alginolyticus to three common algal extracellular products. Acrylate and glycolate attracted the motile marine bacterium. The peak response occurred with 10(-2) M of each chemical. Acrylic and glycolic acid also attracted V. alginolyticus, with the peak response occurring at 5 x 10(-4) M of each chemical. Higher concentrations of the organic acids resulted in a decreased response. The bacteria also displayed positive chemotaxis to dimethyl sulfide.

Acrylates↗
PubMed1978

Quantitative assay for algal chemotaxis.

A quantitative capillary assay is described for measuring chemoreception in the neritic and littoral unicellular alga Dunaliella tertiolecta. Lucite chemotaxis plates were used in the assay with 3-microliter capillaries. A Coulter Counter was employed to determine algal cell numbers. D. tertiolecta is attracted to ammonium ion with a maximum positive response at 10(-3) M. Inclusion of calcium and L-methionine in the chemotaxis medium stimulates algal chemoreception, although neither chemical is essential for motility. Attraction of the chlorophyte to ammonium is dependent on time of incubation, cell density, and pH. The optimum pH for attraction was found to be 6.25.

Ammonium Chloride↗
PubMed1977

Polymerization of phenolic intermediates of pesticides by a fungal enzyme.

The fungus Rhizoctonia praticola produces an extracellular phenol oxidase (laccase) which polymerizes phenolic intermediates of various pesticides. The enzyme catalyzes the formation of oligomeric products from halogenated phenolic intermediates of phenoxyalkanoate herbicides and from naphtholic products derived from carbamate insecticides. These findings permit further investigations into the mechanism and role of oxidative coupling leading to the incorporation of xenobiotic compounds into soil organic matter.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1977

Oxidative coupling of aromatic pesticide intermediates by a fungal phenol oxidase.

The soil fungus Rhizoctonia praticola produced an enzyme that accumulated in the growth medium and caused the polymerization of phenolic and naphtholic intermediates of various pesticides. The dialyzed crude enzyme was purified by ion-exhange column chromatography with diethylaminoethyl-cellulose, followed by gel filtration with Sephadex G-200. The enzyme, a phenol oxidase, was capable of polymerizing 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, and 4-bromo-2-chlorophenol. 1-Naphthol, 2-naphthol, and some of their derivatives formed oligomers or polymers when incubated with the enzyme, but 4-nitrophenol and 2,4-dinitriphenol were not oxidized. Chlorinated and brominated anilines, which are derivatives of herbicides, were not altered by the phenol oxidase from R. praticola, but 4-methoxyaniline was transformed by the enzyme to 2-amino-5-p-anisidinobenzoquinone-di-p-methoxyphenylimine. The formation of polymeric products was determined by mass spectrometric analysis.

Aniline Compounds↗