Search PubMed⌕ Search

Biomedical subjects

S T Hung

Publications and source records attributed to S T Hung.

6 recordsLinked to original sources
PubMed2005

Resonant Raman spectra and first molecular hyperpolarizabilities of strongly charge-transfer molecules.

The effect of vibrational structure on the frequency dependence of the first molecular hyperpolarizability of two thiophene-based charge-transfer chromophores is investigated. A time domain formulation is used to express the polarizability. The new expression includes the solvent-induced inhomogeneous distribution of electronic transition frequencies as well as the effect of the motion of solvent molecules that modulates the vibrational and electronic transition frequencies of the nonlinear optical molecule on which the first molecular hyperpolarizability depends. Resonance Raman scattering and one-photon absorption spectra of the chromophores are measured. By simultaneously fitting the experimental one-photon absorption spectrum and Raman cross sections of vibrational lines derived from resonance Raman scattering to a theoretical model, important parameters needed for the calculation of the first molecular hyperpolarizability are obtained. The first molecular hyperpolarizability is calculated as a function of frequency covering both nonresonance and two-photon resonance regions. The calculated result is compared with the measured hyperpolarizability as a function of frequency of the excitation laser. The resonance Raman-based analysis is shown to account reasonably well for the dispersion of the hyperpolarizability of the two charge transfer chromophores.

Journal Article↗
PubMed2002

Protection of dopaminergic neurons in primary culture by lisuride.

Dopamine agonists play an important role in the treatment of Parkinson's disease by reducing the administration of L-3,4-dihydroxyphenylalanine (L-DOPA). The enzymatic and non-enzymatic conversion of L-DOPA is suspected to increase oxidative stress, which leads to the degeneration of dopaminergic neurons in Parkinson's disease. In primary mouse mesencephalic cultures we show that the dopamine D1/D2 receptor agonist lisuride, in a concentration range of 0.001-1 microM, enhances the survival of dopaminergic neurons, protects against toxicity induced by L-DOPA or 1-methyl-4-phenylpyridinium ion (MPP+) and stimulates 3H-dopamine uptake. Lisuride also reduces anaerobic metabolism during incubation with L-DOPA. The present findings suggest that lisuride may have trophic/survival-promoting properties and potentially reduces oxidative stress.

1-Methyl-4-phenylpyridinium↗
PubMed2000

PICCOLO: a tool for combinatorial library design via multicriterion optimization.

Combinatorial library design is by nature a multicriterion problem. These criteria often include reagent diversity, product similarity to lead compounds and product novelty with respect to a corporate compound bank. More recently, developability and druglikeness have also attracted much attention in library design practices. To address this multicriterion design problem, we have developed a computer program (PICCOLO) that simultaneously optimizes all the factors under consideration using a weighted sum optimization technique. In this paper, we describe the overall design of this program and the formulation of individual penalty functions that characterize the underlying design criteria. We also give an example to illustrate the process and the result of a library design using this program.

Algorithms↗
PubMed1989

Human immunodeficiency virus type 1 antigen in cerebrospinal fluid. Correlation with clinical neurologic status.

Human immunodeficiency virus type-1 (HIV-1) antigen was assayed in paired serum/cerebrospinal fluid (CSF) specimen from 85 adults and 58 children with acquired immunodeficiency syndrome and was compared with clinical neurological status. A quantitative comparison of HIV-1 antigen levels in matched serum and CSF specimens indicated that HIV-1 antigen expression in these compartments is independent and is correlated with acquired immunodeficiency syndrome dementia complex in adults and progressive encephalopathy in children. In a longitudinal study (n = 47), 16 patients tested positive for HIV-1 antigen in the CSF before (n = 2) or coincident (n = 14) with neurological deterioration. Six patients who tested positive for HIV-1 antigen in the CSF remained neurologically normal for a median duration of follow-up of 11 months. Six of 25 patients who tested negative for HIV-1 antigen in the CSF, subsequently showed neurological deterioration. These data indicate that HIV-1 antigen expression in the CSF is not useful in predicting neurological deterioration.

Acquired Immunodeficiency Syndrome↗
PubMed1976

The measurement of circulating red cell volume using nonradioactive cesium and fluorescent excitation analysis.

Nonradioactive cesium, as an analogue of potassium, has been used to label autologous red blood cells for determination of the red cell volume in man. The initial and the equilibration concentrations of cesium are assayed by fluorescent excitation analysis (FEA), using a 600 mCi 241Americium source and a Si(Li) detector with a 1024-channel analyzer. Comparative studies with 51Chromium in 13 rabbits showed good correlation, but the intracellular cesium concentration achieved by simple incubation with 2.6 per cent cesium chloride solution was too low to be of practical value in humans. Incubation of the human red blood cells with 50 mug per milliliter of Nystatin in 2.6 per cent cesium chloride opened reversible "pores" in the red cell membrane which permitted high intracellular cesium labeling without demonstrable red cell damage. The cesium red cell volumes in 11 random human subjects differed from the 51Chromium red cell volumes by only 0.2 +/- 4.5 per cent and 2.5 +/- 7.6 per cent at blood sampling times of 10 minutes and 40 minutes, respectively. Blood cesium levels fell with a clearance half-time of 31.5 hours in 4 rabbits, and 2.4 days in 1 normal human. Fluorescent excitation analysis of cesium-labeled autologous red blood cells permits accurate determination of the red cell volume in man without associated patient radiation, thus making the procedure much more acceptable for children, pregnant women, normal volunteers, and for repeated studies in the same individual.

Blood Volume Determination↗