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T T Lee

Publications and source records attributed to T T Lee.

86 records · Page 5Linked to original sources
PubMed1972

Changes in indoleacetic Acid oxidase isoenzymes in tobacco tissues after treatment with 2,4-dichlorophenoxyacetic Acid.

2,4-Dichlorophenoxyacetic acid had a multiple effect on the development of indoleacetic acid oxidase isoenzymes in tobacco callus tissues (Nicotiana tabacum, cv. White Gold) cultured in vitro, and the development of these isoenzymes was differentially associated with growth promotion or inhibition depending on the concentration of 2,4-dichlorophenoxyacetic acid. At low concentrations (0.1 to 1 mum) it promoted the development of a fast migrating isoenzyme A(5) accompanied by stimulation of a tumor-type growth. At high concentrations (10 to 100 mum), it inhibited the development of the fast migrating isoenzymes but promoted a sharp rise in others with slower electrophoretic mobilities, which was accompanied by growth inhibition. The implications are that 2,4-dichlorophenoxyacetic acid might alter the level of endogenous auxins through its dual effects on the oxidase isoenzyme system.

Journal Article↗
PubMed1971

Cytokinin-controlled Indoleacetic Acid Oxidase Isoenzymes in Tobacco Callus Cultures.

Indoleacetic acid oxidase in tobacco callus tissues (Nicotiana tabacum L., cultivar White Gold) was resolved into seven anionic isoenzymes by polyacrylamide gel disc electrophoresis. Different concentrations of kinetin and zeatin in the presence of indoleacetic acid affected the level of this enzyme, particularly two fast-moving isoenzymes, A(5) and A(6). The optimal concentration of kinetin was 0.2 mum; increasing concentrations above this level progressively lowered the total activity of indoleacetic acid oxidase and repressed the development of isoenzymes A(5) and A(6). Actinomycin D and cycloheximide inhibited the development of these two isoenzymes under the influence of 0.2 mum kinetin, suggesting a requirement for RNA and protein synthesis. The cytokinin-promoted indoleacetic acid oxidase isoenzymes A(5) and A(6) increased with time and paralleled the dry weight increase of tobacco callus tissues, but the total activity of indoleacetic acid oxidase per unit dry weight of tobacco callus varied with time depending on the stage of plant growth.

Journal Article↗
PubMed1971

Promotion of indoleacetic Acid oxidase isoenzymes in tobacco callus cultures by indoleacetic Acid.

Indoleacetic acid oxidase in tobacco callus cultures (Nicotiana tabacum L., cv. White Gold) was composed of at least two groups of isoenzymes, which were distinctly different in electrophoretic mobilities and in responses to growth substances. Indoleacetic acid had dual effects; at low concentrations it promoted the development of two fast-migrating indoleacetic acid oxidase isoenzymes, but at high concentrations it increased the level of other indoleacetic acid oxidase isoenzymes with low and moderate electrophoretic mobilities. However, indoleacetic acid was not unique in such effects; 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid were effective at concentrations lower than that of indoleacetic acid.A correlation was apparent between the relative levels of the two groups of indoleacetic acid oxidase isoenzymes and the rate and type of growth, as affected by auxins. The development of the fast-migrating anionic indoleacetic acid oxidase isoenzymes was accompanied by a type of growth characterized by rapid growth rate, high water content, and friable tissues. On the other hand, a further increase in the isoenzymes of slower migrating rate was associated with growth retardation.The indoleacetic acid-mediated increase of the fast-migrating indoleacetic acid oxidase isoenzymes was dependent on the level of kinetin, suggesting a multiple control by different types of growth substances. The inhibition of the formation of the fast-migrating isoenzymes by actinomycin D and cycloheximide suggests a requirement for both RNA and protein synthesis.

Journal Article↗
PubMed1968

Effect of ozone on swelling of tobacco mitochondria.

The swelling of mitochondria isolated from leaves, roots, and callus tissues of Nicotiana tabacum, L, var. White Gold, was measured by following changes in optical density at 520 mmu in buffered 0.25 m sucrose or 0.125 m KCl. Ozone induced rapid swelling of the isolated mitochondria and increased the permeability of mitochondrial membranes. The extent of mitochondrial swelling and the amount of soluble proteins and other substances absorbing at 260 and 280 mmu released from mitochondria into the suspending medium were positively correlated with the length of exposure to O(3). The correlation between the extent of mitochondrial swelling and the loss of intramitochondrial materials was also highly significant.Protocatechuic acid, when initially present in the suspending medium, completely prevented O(3)-induced swelling. Reduced glutathione, ascorbate, and l-cysteine partially prevented O(3)-induced swelling. But these reducing substances failed to reverse mitochondrial swelling when added after O(3) treatment.Polyvinylpyrrolidone (PVP) and bovine serum albumin (BSA) induced contraction of tobacco mitochondria in the absence of O(3), but did not reverse swelling of O(3)-treated mitochondria. PVP and BSA only stopped O(3)-induced swelling. Evidently O(3)-induced swelling was osmotically irreversible. Hypertonic solutions of sucrose neither induced contraction of tobacco mitochondria nor prevented O(3)-induced swelling.Contraction of tobacco mitochondria occurred rapidly at acid pH, but the contracting state affected by acid pH did not protect mitochondria from O(3)-induced swelling. Although O(3) induced greater swelling at acid pH, the O(3)-treated mitochondria were still responsive to acid-induced contraction.

Journal Article↗
PubMed1967

Inhibition of oxidative phosphorylation and respiration by ozone in tobacco mitochondria.

Ozone was found to inhibit oxidative phosphorylation and oxygen uptake in mitochondria of tobacco leaves (Nicotiana tabacum, L. var. White Gold). The inhibition appeared to occur at both substrate and electron-transport chain levels. The inhibition increased with the length of exposure to ozone, however, the phosphorylative system was more sensitive to ozone than the respiratory system. With mitochondria from detached leaves after being treated with ozone at 1 ppm for 1 hour, uncoupling of phosphorylation was demonstrated without any detectable change in the rate of respiration in the early stage of ozone effect. Inhibition of phosphorylation by ozone was also demonstrated in isolated mitochondria without apparent change in optical density of the mitochondrial suspension at 520 mmu. Therefore, mitochondrial swelling appears not to be a necessary first step for ozone-induced uncoupling of phosphorylation. The evidence suggests that inhibition of oxidative phosphorylation in mitochondria may be a primary effect of ozone in tobacco leaves.Sucrose and glucose, when fed to the detached tobacco leaves before ozone treatment, tended to raise the phosphorylative activity of mitochondria. Mannitol and lactose were less effective.

Journal Article↗
PubMedDate not supplied

Screening and characterization of biopharmaceuticals by high-performance capillary electrophoresis with laser-induced native fluorescence detection.

High-performance capillary electrophoresis (HPCE) with laser-induced native fluorescence (LIF) detection is used to address significant problems in the quality control of biopharmaceuticals. All of the biopharmaceuticals studied can be detected at subnanomolar levels with linear dynamic ranges of at least 3 orders of magnitude. HPCE/LIF can determine impurities in "purified" biopharmaceuticals present in amounts less than 0.01% (i.e., at 4 x 10(-11) M) that of the major component. With HPCE/LIF, detection sensitivity is thus no longer a concern in the assaying of active ingredients in biopharmaceutical dosage formulations. The peptide mapping of biopharmaceuticals present at 1 x 10(-7) M (or an injected limit of detection of 60 amol) is presented. Also, kinetic information on the reaction of a recombinant enzyme-drug with its substrate present at the micromolar level has been extracted from electropherograms acquired in real-time.

Biopharmaceutics↗
PubMedDate not supplied

Comparison of preferences for health outcomes in schizophrenia among stakeholder groups.

BACKGROUND: To determine the effectiveness of psychiatric interventions for use in cost-effectiveness analysis, we assessed the feasibility of using a multimedia computer survey to study preferences (utilities) for health outcomes among persons with schizophrenia, family members of persons with schizophrenia, health professionals, and the public. METHODS: We developed videos depicting two patterns of mental health impairment in schizophrenia, both with and without pseudo-parkinsonism side-effects. These descriptions were integrated into a computer program that measured preferences using two psychometric methods: (1) standard gamble and (2) a visual analog scale. This program was used to compare preferences among potential stakeholder groups. RESULTS: 20 persons with schizophrenia, 11 family members, 20 healthy volunteers and 14 health professionals participated in the computerized interview. All but one subject completed the survey. The correlation among ratings of various states was high (r=0.7-0.95) and ratings were internally consistent in 89% of participants. There were significant differences in values between groups for health states (p=0.024) and in values for the effects of pseudo-parkinsonism on quality of life (p<0.001). Persons with schizophrenia valued the disease states more highly and placed more significance than did other groups on the effects of pseudo-parkinsonism on quality of life. CONCLUSIONS: Computer-based multimedia techniques can offer a feasible and valid approach to measure preferences for outcomes in schizophrenia. The study found significant differences in preferences among stakeholder groups for schizophrenia outcomes. Further work is needed to clarify how these differences affect clinical decision-making and policies for health resource allocation.

Adult↗
PubMedDate not supplied

What a physician needs to know about cost-effectiveness.

The cost of medical care in the United States continues to spiral upward, partly as a result of new technological breakthroughs that promise improved length of life and quality of life for patients. But how good are these treatments in everyday practice? How do we make policies for adopting innovations that improve outcome but also increase costs? Cost-effectiveness studies are designed to answer these questions. They reveal important aspects of a particular medical decision and inform treatment choices by systematically analyzing the relationships between the costs and outcomes of alternative health care interventions. This article provides an introduction to the field of cost-effectiveness analysis and describes an approach to interpreting the rapidly proliferating cost-effectiveness literature.

Cost-Benefit Analysis↗