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Biomedical subjects

J P Hsu

Publications and source records attributed to J P Hsu.

17 recordsLinked to original sources
PubMed1992

A theoretical analysis of a new drug delivery system: a cylindrical device with a vertical opening on its surface.

A theoretical analysis of a proposed drug delivery device is presented. The device is of cylindrical shape with an opening on its side surface. Analytical expressions for the temporal variations in the amount of drug released and the size of the unreleased portion of the device are derived. The result of numerical simulation reveals that an approximately zero-order mechanism can be obtained, provided that the device is designed appropriately. The applicability of the analytical expressions derived is justified by examining the release of sodium salicylate embedded in polyethylene. The present work is a generalization of analyses suggested previously for some similar devices.

Drug Delivery Systems↗
PubMed1991

Modeling the repair of radiation-induced DNA double-strand breaks.

A problem often overlooked in the study of the repair of radiation-induced DNA double-strand breads (DSBs) is the question of what the status of a regular site is in the DNA duplex immediately after a radiation treatment. Here, we suggest a mixed repair mechanism which consists of a gradual process and an instantaneous process. A comparison of the present kinetic model with those which have appeared in the literature shows that the former is a generalization of the latter. We have shown that different repair mechanisms may lead to equivalent mathematical representations. Therefore, care must be taken in interpreting the repair mechanism on the basis of the experimentally observed transient number of DSBs.

DNA↗
PubMed1990

The effect of multivalent cations on adhesion time for cellular adhesion to solid surfaces.

The dynamic behavior of the adhesion of a charge-regulated cell to a solid surface of constant potential is investigated. In particular, the effect of the presence of multivalent cations in the suspension medium on adhesion time is discussed. By neglecting the effect of hydrodynamic retardation and assuming that the bulk liquid phase is stagnant, we show that the presence of multivalent cations has the effect of retarding cell adhesion. At a fixed level of ionic strength, the adhesion time increases with the increase of the concentration of multivalent cations in the suspension medium, and decreases with the increase in magnitude of the Hamaker constant. For a fixed concentration of cations, the adhesion time decreases with the increase of ionic strength. The effect of the magnitude of Hamaker constant on adhesion time is appreciable if both the ionic strength and the concentration of cations are high.

Animals↗
PubMed1990

A comparison of the parameter estimating procedures for the Michaelis-Menten model.

The performance of four parameter estimating procedures for the estimation of the adjustable parameters in the Michaelis-Menten model, the maximum initial rate Vmax, and the Michaelis-Menten constant Km, including Lineweaver & Burk transformation (L-B), Eadie & Hofstee transformation (E-H), Eisenthal & Cornish-Bowden transformation (ECB), and Hsu & Tseng random search (H-T) is compared. The analysis of the simulated data reveals the followings: (i) Vmax can be estimated more precisely than Km. (ii) The sum of square errors, from the smallest to the largest, follows the sequence H-T, E-H, ECB, L-B. (iii) Considering the sum of square errors, relative error, and computing time, the overall performance follows the sequence H-T, L-B, E-H, ECB, from the best to the worst. (iv) The performance of E-H and ECB are on the same level. (v) L-B and E-H are appropriate for pricesly measured data. H-T should be adopted for data whose error level are high. (vi) Increasing the number of data points has a positive effect on the performance of H-T, and a negative effect on the performance of L-B, E-H, and ECB.

Animals↗
PubMed1990

A stochastic analysis of the repair of radiation-induced DNA double-strand breaks.

A three-state stochastic model is described for the repair of radiation-induced double-strand breaks (DSBs) in DNA. If irradiated, a site or region in DNA is assumed to be in a potentially damaged state; this site may either become permanently damaged or be repaired after a certain period of time. The result of the analysis of the available experimental data reveals that the present two-parameter model is capable of interpreting the rapid decrease in the number of DSBs in the initial period, which cannot be predicted by previously proposed models. The stochastic analysis yields not only the temporal variation of the mean of the number of DSBs but also its variance, and therefore is a generalization of the conventional deterministic models.

DNA↗
PubMed1990

Dynamic modelling of the growth of a surface fungal colony.

The growth of a surface fungal colony in the three-dimensional space was modeled kinetically. The present analysis led to the conclusion that the radius of a fungal colony increases exponentially in the initial period followed by a constant increase in its radius at large times. This is justified by analyzing the available experimental data. The elevation of a fungal colony was limited by a balance of the transport of protoplasm inside a growing hyphae and a maintenance factor. A numerical simulation revealed that a typical fungal colony had a disk-shaped base with a flat top and a side face generated by rotating a concave upward curve about a vertical axis.

Fungi↗
PubMed1990

A kinetic analysis of the repair of radiation-induced DNA double-strand breaks.

The repair of radiation-induced DNA double-strand breaks (DSBs) is analyzed kinetically. It is assumed that a fraction of the damaged sites in the DNA duplex are irreparable. The kinetic model takes the effect of radiation dose into account. The analysis of the available experimental data reveals that, although the number of irreparable DSBs is a quadratic function of radiation dose, the normalized number of irreparable DSBs correlates linearly with this variable.

DNA↗
PubMed1990

A stochastic simulation of tumor growth.

The growth of a tumor is described by a nonlinear stochastic representation. A systematic approach based on Taylor series expansion is adopted to solve the nonlinear master equation governing the variation of tumor weight as a function of time. The analysis of the available experimental data reveals that the growth rate of a tumor has a power law dependence on its weight.

Animals↗
PubMed1988

Analytical methods for detection of nonoccupational exposure to pesticides.

An analytical protocol is developed to analyze for 33 compounds in ambient air around the household, drinking water, and from dermal contact while applying pesticides. Soxhlet extraction is used on both the polyurethane foam plugs, which were used as air sample trapping media, and the gloves reflecting dermal contact. The extraction procedure of U.S. Environmental Protection Agency (EPA) Method 608 is used for water samples. A stringent gas chromatography/electron capture detection (GC/ECD) and gas chromatography/mass spectroscopy/multiple ion detection (GC/MS/MID) analytical approach parallel to the procedures of the current EPA contract laboratory program is used for analysis.

Air Pollutants↗
PubMed1987

Kinetics of bacterial adhesion--a stochastic analysis.

In a previous work (Hsu & Wang, 1986), a birth-death type of stochastic model was proposed to analyze bacterial adhesion onto the substrate surface. The model is based upon the assumption that the number of available active sites on the substrate surface is relatively large compared to that of the cells in the system. This assumption is relaxed in the present study, and thus, the problem is considered in a more rigorous manner. The transient behavior of bacterial adhesion is examined through simulation studies. It is found that the present stochastic model should be employed when the number of available active sites is less than or on the same order of magnitude as that of the cells.

Bacterial Adhesion↗
PubMed1987

Stochastic modeling of bacterial adhesion: a two-step mechanism with linear adhesion rate.

Stochastic analysis of bacterial adhesion onto the surface of solid substrate is presented. Bacterial adhesion is assumed to occur in two steps: (i) a reversible adhesion between bacteria and solid surface; bacteria on the surface are weakly bound during this period, followed by (ii) an irreversible surface reaction which results in a strong binding force between bacteria and the surface; bacteria are considered to be in adhered form at this stage. The stochastic representation provides both the macroscopic and fluctuating information about the transient behavior of the phenomenon under consideration.

Bacterial Adhesion↗
PubMed1987

Ulcerogenicity of piroxicam: an analysis of spontaneously reported data.

Previous reports have suggested that piroxicam may be more ulcerogenic than other non-steroidal anti-inflammatory drugs (NSAIDs) in use. Critics have attributed this putative relation to flawed comparisons of spontaneously reported data. In this study cases of upper gastrointestinal bleeding, perforation, and ulcer reported to the Food and Drug Administration's spontaneous reporting system over 12 years were examined. Reporting rates for eight NSAIDs were compared over identical periods of their marketing life cycles. After adjustments were made for the heterogeneity in the underlying reporting rates the difference in rates between piroxicam and the other drugs was considerably reduced but piroxicam retained its top ranking among the drugs; however, large and clinically important differences in the frequency of cases of upper gastrointestinal bleeding, perforation, and ulcer between piroxicam and the rest of the NSAIDs compared probably do not exist.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

Bacterial adhesion onto particulate substrates.

The adhesion of anaerobic saccharolytic bacteria onto cellulose powder and raw starch granules through scanning electron microscope were observed. The adhering bacteria had a tendency to penetrate the granule surface; colonization was observed to occur on both the surface and inside the starch granule. The inner material of the starch granules was first digested, resulting in a shell type of structure at this stage. This implied that the surface of starch granules might have a different structure from its inner material. Bacterial adhesion and substrate digestion were found to be affected by operating temperature.

Bacterial Adhesion↗
PubMed1986

Solid state fermentation of swine manures.

A kinetic model for the solid state fermentation of swine manures under both aerobic and anaerobic conditions have been proposed. The rate of CO2 production is used as an indicator of the degree of stabilization of swine manures. Analysis of available experimental data suggests that the initial rate of stabilization, as measured by the product of the reaction constant and the initial activity of bacteria, increases with temperature and correlates with the initial moisture content of swine manures. The rate of deactivation of bacteria, as reflected by the deactivation rate constant, is relatively constant for low and medium temperatures (25-35 degrees C) and is fast for higher temperature (45 degrees C). The optimum operating scheme should adopt a medium high temperature (35 degrees C) and an appropriate amount of initial moisture.

Animals↗
PubMedDate not supplied

Fast turnaround multiresidue screen for pesticides in produce.

A rapid multiresidue screen for 110 pesticides was applied to 5628 produce samples. Samples were extracted, analyzed, and evaluated within 6 1/2 h of receipt. Analyses were confirmed within a 24 h period on those samples in which a potential residue was found above the U.S. Environmental Protection Agency's tolerance level. A thorough yet quick chromatographic interpretation program is also described.

Carbamates↗
PubMedDate not supplied

The impact of the addition of naloxone on the use and abuse of pentazocine.

An epidemic of abuse with "T's and blues" began in the late 1970's in which pentazocine-Talwin tablets ("T")--and the antihistamine tripelennamine (known as blues) were crushed, dissolved together, filtered, and injected intravenously. The resulting high was reported to be similar to that of heroin. In 1981, the manufacturer and the Food and Drug Administration met to discuss a possible solution. As a result, 0.5 mg of naloxone hydrochloride, a narcotic antagonist that is pharmacologically inactive at that dose orally but active if administered parenterally, was added to the tablet formulation. The reformulated product, Talwin Nx, was approved for marketing in late 1982 and introduced in the second quarter of 1983. Distribution of Talwin tablets in the United States was discontinued. The Drug Abuse Warning Network (DAWN) of the National Institute of Drug Abuse and IMS America's National Prescription Audit were used to review the use and abuse patterns of pentazocine before and after the naloxone intervention. The number of prescriptions dispensed quarterly for pentazocine products remained fairly stable from 1981 through the first quarter of 1983 and increased after the introduction of Talwin Nx. In contrast, DAWN emergency room and medical examiner mentions decreased after the product reformulation. The rates of both emergency room and medical examiner mentions per million prescriptions were substantially lower in the 2 years following the introduction of Talwin Nx (decreases of 70 percent by emergency rooms and 71 percent by medical examiners), indicating that the product reformulation successfully reduced pentazocine abuse.

Coroners and Medical Examiners↗