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Biomedical subjects

J H Ware

Publications and source records attributed to J H Ware.

99 records · Page 6Linked to original sources
PubMed1969

Regulation of the formation of acid phosphatases by inorganic phosphate in Aspergillus ficuum.

Two types of extracellular acid phosphatases are synthesized by Aspergillus ficuum NRRL 3135: a nonspecific orthophosphoric monoester phosphohydrolase (EC 3.1.3.2) with an optimum pH of 2.0, and an enzyme with restricted specificity, a mesoinositol-hexaphosphate phosphohydrolase (EC 3.1.3.8; phytase) with an optimum pH of 5.5. Although the pH 5.5 enzyme is termed a phytase, both enzymes hydrolyze phytin. Synthesis of the enzymes is repressed by high orthophosphate concentrations in the fermentation medium. The highest total level for each enzyme is synthesized in low orthophosphate medium. In high orthophosphate medium, more pH 5.5 enzyme is produced than pH 2.0 enzyme. In low orthophosphate medium, more pH 5.5 enzyme is produced than pH 2.0 enzyme during the early stages of growth, but the reverse occurs after 5 days. The enzymes are differentiated by heat denaturation at acid and alkaline pH levels. They are separated into two distinct fractions on Sephadex G-100 followed by carboxymethylcellulose column chromatography. This indicates that the two enzymes are structurally different. The K(m) for both enzymes is 1.25 mm when calcium phytate is the substrate. Orthophosphate competitively inhibits the pH 2.0 (K(i) = 1.1 x 10(-2)m) but not the pH 5.5 phosphatase. Neither enzyme is denatured by 50% (w/v) urea or inhibited by 0.01 m tartrate. Thus, they differ from human prostatic phosphatase.

6-Phytase↗
PubMed1968

Survey of microorganism for the production of extracellular phytase.

A culture enrichment technique was used to isolate phytase-producing microorganisms. Also, microorganisms from various culture collections were tested for their phytase-producing ability. A number of the Aspergillus niger group produced extracellular phytase which dephosphorylated calcium phytate in acidic solution. A soil isolate, A. ficuum NRRL 3135, produced the most active phytase in a cornstarch-based medium. Production of phytase was strongly repressed by inorganic phosphates and required a high carbon to phosphorus ratio in the medium.

6-Phytase↗
PubMedDate not supplied

Issues in the analysis of repeated categorical outcomes.

This paper discusses statistical methods for the analysis of repeated observations of categorical variables as they might arise in longitudinal studies. Two general types of models are described: marginal models that give representations for the marginal distribution of response at each occasion, and transitional models that give representations for the transition probabilities between outcome states at successive occasions. The conceptual and technical differences are discussed and recent work advancing both approaches is reviewed. The two approaches are illustrated through analysis of repeated observations on interval history of the respiratory symptom 'persistent wheeze' in preadolescent children.

Asthma↗
PubMedDate not supplied

A critical evaluation of acute ozone epidemiology results.

Evidence from controlled human exposure studies demonstrates transient pulmonary functional responses to ozone exposure concentrations near the U.S. primary air quality standard of 0.120 ppm. There have been several recent efforts to document low concentration ozone effects in the epidemiological setting. Quantification of ozone effects under natural conditions of exposure can provide valuable information for risk assessment. However, results of epidemiological studies on acute ozone effects have had a limited role in decisions for air quality standards. This reflects difficulties in the quantitative interpretation of results that are to some extent inherent in the epidemiological approach, such as the difficulty of assessing individual exposures, failure to account for varying activity levels, and confounding by temporal covariates, e.g., temperature and pollen. However, in spite of the limitations of individual studies, when viewed as a group the epidemiological studies are consistent among themselves and with results from chamber studies.

Adolescent↗