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Biomedical subjects

D Song

Publications and source records attributed to D Song.

At least 127 records · Page 7Linked to original sources
PubMed1996

Recent developments in pharmacokinetic modeling of perfluorocarbon emulsions.

Perfluorocarbon (PFC) emulsions are potential oxygen carriers. This study is to investigate pharmacokinetic compartment models and physiologically based models, which correlate the distribution of PFC emulsion in the blood, reticuloendothelial system (RES) tissues and non-RES tissues with the excretion data. The models are evaluated by nonlinear regression analysis (using PCNONLIN software) with expiration data from animal following an i.v. injection of a concentrated perflubron emulsion. One model with four compartments (representing PFC emulsion in blood, RES tissues, non-RES tissues, and PFC solubilized in blood) meets the mathematical and physical criteria. The physiological modeling provides insight of physiological mechanisms. The relationship between the compartment model parameters (rate constants) and physiological parameters (tissue volumes, flow rates, etc.) is presented. An advantage of physiological model is that prediction may be made in interspecies scaling. The above two kinds of modeling are useful in many applications, e.g. to describe and predict the time course of PFC disposition throughout the body.

Animals↗
PubMed1995

Mapping of linear epitopes recognized by monoclonal antibodies with gene-fragment phage display libraries.

Epitope mapping with mono- or polyclonal antibodies has so far been done either by dissecting the antigens into overlapping polypeptides in the form of recombinantly expressed fusion proteins, or by synthesizing overlapping short peptides, or by a combination of both methods. Here, we report an alternative method which involves the generation of random gene fragments of approximately 50-200 bp in length and cloning these into the 5' terminus of the protein III gene of fd phages. Selection for phages that bind a given monoclonal antibody and sequencing the DNA inserts of immunopositive phages yields derived amino acid sequences containing the desired epitope. A monoclonal antibody (mAb 215) directed against the largest subunit of Drosophila RNA polymerase II (RPB215) was used to map the corresponding epitope in a fUSE5 phage display library made of random DNA fragments from plasmid DNA containing the entire gene. After a single round of panning with this phage library, bacterial colonies were obtained which produced fd phages displaying the mAb 215 epitope. Sequencing of single-stranded phage DNA from a number of positive colonies (recognized by the antibody on colony immunoblots) resulted in overlapping sequences all containing the 15mer epitope determined by mapping with synthetic peptides. Similarly, we have localized the epitopes recognized by a mouse monoclonal antibody directed against the human p53 protein, and by a mouse monoclonal antibody directed against the human cytokeratin 19 protein. Identification of positive colonies after the panning procedure depends on the detection system used (colony immunoblot or ELISA) and there appear to be some restrictions to the use of linker-encoded amino acids for optimal presentation of epitopes. A comparison with epitope mapping by synthetic peptides shows that the phage display method allows one to map linear epitopes down to a size only slightly larger than the true epitope. In general, our phage display method is faster, easier, and cheaper than the construction of overlapping fusion proteins or the use of synthetic peptides, especially in cases where the antigen is a large polypeptide such as the 215 kDa subunit of eukaryotic RNA polymerase II.

Amino Acid Sequence↗
PubMed1995

Determination of flumazenil in plasma by gas chromatography-negative ion chemical ionization mass spectrometry.

A gas chromatographic-negative ion chemical ionization mass spectrometric (GC-NCI-MS) method for the determination of flumazenil in plasma is described. The GC of flumazenil (M(r) 303) is considered to be difficult as it is readily adsorbed in the GC column. Therefore, preconditioning the GC column with reconstituted extract from plasma and Silyl-8 was required to cover the active sites on the column. Monitoring the maximum mass peak (m/z 275) of the flumazenil resulted in a tenfold enhancement of sensitivity and signal-to-noise ratio (concentration = 1 ng/ml). Isotopically labeled flumazenil-d3 (M(r) 306, m/z 278) was used as the internal standard. The detection limit for flumazenil was found to be 0.1 ng/ml with an injection volume of 2 microliters. The signal-to-noise ratio was about 10. The routine quantification limit was set at 2 ng/ml for dog plasma and 1 ng/ml for human plasma. The sample volumes in both instances were 1 ml.

Animals↗
PubMed1995

Isocratic high-performance liquid chromatographic assay of taxol in biological fluids and tissues using automated column switching.

This report describes the analysis of taxol in human plasma, cell culture medium, and dog bladder tissue by isocratic high-performance liquid chromatography (HPLC) with automated column switching. Cephalomannine was used as the internal standard. Biological samples were extracted with ethyl acetate, with a recovery of > 80%. Sample extracts reconstituted in 37.5% acetonitrile were stable in polypropylene tubes at room temperature for 22 h. The HPLC stationary phase consisted of a clean-up column (Nova-Pak C8, 75 x 3.9 mm I.D., 4 microns particle size) and an analytical column (Bakerbond octadecyl, 250 x 4.6 mm I.D., 5 microns particle size). Taxol and cephalomannine were monitored at 229 nm. Samples were injected onto the clean-up column and eluted with the clean-up mobile phase (37.5% acetonitrile in distilled water) at 1 ml/min. Concurrently, the analytical mobile phase (49% acetonitrile in distilled water) was directed through the analytical column at a flow-rate of 1.2 ml/min. A heart-cut fraction from 8 to 15 min was transferred from the clean-up column onto the analytical column. Loading of a second sample onto the clean up column while the first sample was eluting from the analytical column reduced the HPLC analysis time to about 15 min per sample. This method has a lower detection limit of 5 ng/ml and intra- and inter-day variations of < 5%.

Animals↗
PubMed1995

Activation-induced apoptosis in human macrophages: developmental regulation of a novel cell death pathway by macrophage colony-stimulating factor and interferon gamma.

Activated macrophages (M phi s) are important participants in host defense, but their uncontrolled activation leads rapidly to septic shock and death. One mechanism for regulating other dangerous cells in the immune system is programmed cell death, or apoptosis. Monocytes are known to undergo spontaneous apoptosis upon leaving the circulation unless provided with specific survival signals, but mature tissue M phi s are more robust cells, and it was not clear that they could be similarly regulated by apoptosis. We now show that during differentiation monocytes rapidly lose their sensitivity to apoptosis triggered by passive cytokine withdrawal, but they may retain a novel pathway which initiates apoptosis after activation with specific stimuli (zymosan and phorbol esters). Sensitivity to activation-induced apoptosis was developmentally determined, being downregulated by the maturation-promoting cytokine macrophage colony-stimulating factor but stably upregulated by even transient exposure to the proinflammatory cytokine interferon gamma (IFN-gamma). Apoptosis began within 2-4 h of activation, occurred in > 95% of susceptible cells, and in mixed cocultures selectively affected only those M phi s with a history of IFN-gamma priming. Consistent with a possible role for protein kinase C in the signaling pathway leading to cell death, the kinase inhibitor staurosporine was protective against both phorbol ester- and zymosan-induced apoptosis. Our studies describe a novel form of activation-induced M phi apoptosis which is developmentally regulated by two physiologically relevant cytokines. We speculate that apoptosis may serve to restrict the destructive potential of inflammatory M phi s.

Apoptosis↗
PubMed1995

Relationships of dopamine, cortical oxygen pressure, and hydroxyl radicals in brain of newborn piglets during hypoxia and posthypoxic recovery.

The present study describes the relationships of extracellular striatal dopamine, cortical oxygen pressure, and striatal hydroxyl radicals in brain of newborn piglets during hypoxia and posthypoxic reoxygenation. Hypoxia was induced by reducing the fraction of inspired oxygen (FiO2) from 22% (control) to 7% for 1 h. The FiO2 was then returned to the control value and measurements were continued for 2 h. Cerebral oxygen pressure was measured by the oxygen dependent quenching of phosphorescence and extracellular levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and hydroxy radicals in the striatum were determined by in vivo microdialysis. Hypoxia decreased the cortical oxygen pressure from 47 +/- 2 to 9 +/- 1.3 torr (p < 0.001); the levels of extracellular dopamine in the striatum increased to 16,000 +/- 3,270% of control (p < 0.01), whereas the levels of DOPAC and HVA decreased to 25.3 +/- 6% (p < 0.001) and 36 +/- 5% (p < 0.01) of control, respectively. Compared with control, the hydroxyl radical levels at each time point were not significantly increased during hypoxia, although the sum of the measured values was significantly increased (p < 0.05). During the first 5 min after FiO2 was returned to 22%, the cortical oxygen pressure increased to control values and stayed at this level for the remainder of the measurement period. The extracellular level of dopamine declined to values not statistically different from control during 40 min of reoxygenation. During the first 10 min of reoxygenation, DOPAC and HVA further decreased and then began to slowly increase. By 70 min of reoxygenation, the values were not significantly different from control.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Comparison of the efficacy of blood and polyethylene glycol-hemoglobin in recovery of newborn piglets from hemorrhagic hypotension: effect on blood pressure, cortical oxygen, and extracellular dopamine in the brain.

BACKGROUND: Successful blood substitutes, when infused in place of an equal volume of whole blood, provide similar delivery of oxygen to the tissues without introducing abnormalities in cellular metabolism. STUDY DESIGN AND METHODS: Equal volumes of whole blood (control), polyethylene glycol-hemoglobin solution at 6 g per dL, dextran solution, and physiologic saline were compared for their ability to reverse the effects of hemorrhagic hypotension on oxygenation and dopamine metabolism in the brain of newborn piglets. The decrease in mean arterial blood pressure was used as a measure of the hemorrhagic insult. Cerebral oxygen pressure was determined optically by the oxygen-dependent quenching of phosphorescence, and the extracellular level of dopamine in the corpus striatum was determined by in vivo microdialysis. RESULTS: Following a 2-hour stabilization after implantation of the microdialysis probe in the corpus striatum, the mean arterial blood pressure was decreased from 88 +/- 7 torr (control) to 42 +/- 5 torr by the removal of blood in a stepwise manner, over a period of 60 minutes. Decrease in mean arterial blood pressure caused a progressive stepwise decrease in cortical oxygen pressure from 48 +/- 5 torr to 16 +/- 4 torr at the end of bleeding. As a consequence of the decrease in oxygen pressure, extracellular dopamine increased progressively to about 2300 percent of the control value. When a volume of blood equal to that removed was returned and bicarbonate was injected to help correct arterial pH, blood pressure, cortical oxygen pressure, and extracellular dopamine all returned within the 20- to 30-minute recovery period to values not significantly different from control values. An equal volume of polyethylene glycol-hemoglobin solution, even with significantly lower hemoglobin content than whole blood, gave results comparable to those with whole blood. CONCLUSION: Polyethylene glycol-hemoglobin solution, like whole blood but in contrast to physiologic saline or dextran solution, was capable of returning the mean arterial blood pressure, cortical oxygen pressures, and extracellular dopamine nearly to control levels after acute blood loss in newborn piglets.

Animals↗
PubMed1995

Tree structured wavelet transform segmentation of microcalcifications in digital mammography.

A novel multistage algorithm is proposed for the automatic segmentation of microcalcification clusters (MCCs) in digital mammography. First, a previously reported tree structured nonlinear filter is proposed for suppressing image noise, while preserving image details, to potentially reduce the false positive (FP) detection rate for MCCs. Second, a tree structured wavelet transform (TSWT) is applied to the images for microcalcification segmentation. The TSWT employs quadrature mirror filters as basic subunits for both multiresolution decomposition and reconstruction processes, where selective reconstruction of subimages is used to segment MCCs. Third, automatic linear scaling is then used to display the image of the segmented MCCs on a computer monitor for interpretation. The proposed algorithms were applied to an image database of 100 single view mammograms at a resolution of 105 microns and 12 bits deep (4096 gray levels). The database contained 50 cases of biopsy proven malignant MCCs, 8 benign cases, and 42 normal cases. The measured sensitivity (true positive detection rate) was 94% with a low FP detection rate of 1.6 MCCs/image. The image details of the segmented MCCs were reasonably well preserved, for microcalcification of less than 500 microns, with good delineation of the extent of the microcalcification clusters for each case based on visual criteria.

Calcinosis↗
PubMed1995

Kinetic models of batch and fed-batch culture of single-cell protein with double carbon sources.

Unstructured logistic models were applied to simulate the kinetic process of the SCP batch culture with two species of yeast, in which glucose, xylose, or a mixture of the two were used as carbon sources. A modified logistic growth model was used to describe the fed-batch process of using mixed carbon sources. The model parameters were determined by the simulated model with the experimental data. The simulated curves of the models were in agreement with the experimental data.

Candida↗
PubMed1994

The LIM/double zinc-finger motif functions as a protein dimerization domain.

Protein-protein interactions resulting in dimerization and heterodimerization are of central importance in the control of gene expression and cell function. Proteins that share the 52-residue LIM/double zinc-finger domain are involved in a wide range of developmental and cellular controls. Some of these functions have been hypothesized to involve protein dimerization. In the present report we demonstrate, using both in vitro and cell-based studies, that a representative LIM protein, human cysteine-rich protein (hCRP), can efficiently homodimerize. The dimerization ability of hCRP is mapped to the LIM domains, can be transferred to an unrelated protein by fusion of a single minimal LIM/double zinc-finger segment, occurs in the absence as well as the presence of DNA, and appears to depend on coordination of two zinc atoms in the finger doublet. These observations support a specific role for protein dimerization in the function of proteins containing the LIM/double zinc-finger domain and expand the general spectrum of potential interactions mediated by zinc-finger motifs.

Amino Acid Sequence↗
PubMed1994

Determination of chlordiazepoxide in mouse plasma by gas chromatography-negative-ion chemical ionization mass spectrometry.

A gas chromatographic-negative-ion chemical ionization mass spectrometric (GC-NCIMS) method for the determination of chlordiazepoxide (Librium) in mouse plasma is described. Chlordiazepoxide was not suitable for GC analysis because of its thermal instability. The specific derivatization technique described permits the analysis using GC-MS with high sensitivity and selectivity. The use of halazepam as an internal standard instead of an isotopic internal standard decreases the cost and time of the analysis. The detection limit for chlordiazepoxide was 0.1 ng/ml with an injection volume of 1 microliter at a signal-to-noise ratio > 5. The limit of quantification was 5 ng/ml.

Animals↗
PubMed1994

Gas chromatographic-mass spectrometric method for the determination of flurazepam and its major metabolites in mouse and rat plasma.

A capillary gas chromatographic-negative chemical ionization (NCI) mass spectrometric method for the determination of flurazepam and its metabolites N-1-hydroxyethyl-flurazepam and N-1-desalkyl-flurazepam in mouse and rat plasma was described. Derivatization of the metabolites of flurazepam with BSTFA allowed a highly stable, accurate, and sensitive GC-MS analysis. The use of a single internal standard (halazepam) for the quantification of all compounds saved cost and time. The detection limits were 0.1 ng/ml for N-hydroxyethyl-flurazepam-TMS (M(r) = 404), 0.5 ng/ml for desalkyl-flurazepam-TMS (M(r) = 360), and 0.5 ng/ml for flurazepam (M(r) = 387) with an injection volume of 1 microliter at a signal-to-noise ratio greater than 5. The quantitation limit was set to 10 ng/ml for all compounds.

Animals↗
PubMed1994

Effects of buffer pH and phosphate concentration on the droplet size and EYP hydrolysis of perflubron/EYP emulsions.

Oil-in-water emulsions containing perflubron (perfluorooctyl bromide; PFOB) and stabilized with egg yolk phospholipid (EYP) have potential applications as contrast agents and oxygen carriers. In this study, the effects of buffer pH and total phosphate concentration on the emulsion droplet size and EYP hydrolysis were evaluated. 90% w/v perflubron emulsions with NaH2PO4-Na2HPO4 buffers of different pH (4.7-8.7) and phosphate concentrations (30 and 60 mM) were prepared with a high-pressure homogenizer. Emulsions were stored at 40 degrees C and tested at 0, 1, 2 and 3 months. The pH dropped quickly in emulsions with pH 8.7 buffer whereas acidic and neutral buffered emulsions exhibited minor pH drops. The concentration of free fatty acids (FFA) vs emulsion pH can be fitted to a parabolic curve with a minimum at about pH 6.0. The droplet growth rates in emulsions with the pH 4.7 buffer were about 2.5 times of those in emulsions with the pH 8.7 buffer. Total phosphate concentration had only a minor effect. This study emphasizes the importance of the careful selection of buffer pH and capacity to control EYP hydrolysis and possibly emulsion droplet size.

Buffers↗
PubMed1994

Effects of formulation, processing and storage parameters on the characteristics and stability of perflubron emulsion.

In this study, the effects of formulation, processing and storage parameters on perflubron (perfluorooctyl bromide; PFOB) emulsions were investigated. Emulsions with varying concentrations of perflubron and egg yolk phospholipid (EYP) were prepared with different processing parameters and placed at different storage temperatures. Their characteristics and stability were compared. The emulsion droplet growth rate was nearly proportional to the perflubron percentage in the range of 15-110% w/v. The initial droplet size of perflubron emulsions was inversely proportional to the concentration of EYP until a certain lower limit of droplet size was reached. The initial droplet size and droplet growth rate of perflubron emulsion were strongly dependent upon the processing parameters. The logarithmic value of the droplet growth rate decreased linearly with l/T in the range of 5-40 degrees C. The formulation and processing parameters are the key variables to be optimized to achieve better emulsion characteristics and stability.

Drug Stability↗
PubMed1992

Molecular cloning and expression of Bacillus subtilis bglS gene in Saccharomyces cerevisiae.

A 2.7-kb EcoRI DNA fragment carrying a Bacillus subtilis endo-beta-1,3-1, 4-glucanase gene (bglS) from the E. coli plasmid pFG1 was cloned into an Escherichia coli/yeast shuttle vector to construct a hybrid plasmid YCSH. The hybrid plasmid was used to transform Saccharomyces cerevisiae, and the bglS gene was expressed. Variation between levels of bglS gene expression in S. cerevisiae was about 2.3-fold, depending on the orientation of the 2.7-kb DNA fragment. Assay of substrate specificity and optimal pH of the enzyme demonstrated that the enzyme encoded by YCSH (bglS) was identical with that found in B. subtilis, but the expression level of bglS gene in S. cerevisiae (YCSH) was much lower than that in E. coli (YCSH).

Bacillus subtilis↗
PubMed1992

Aging Koreans' perceived conflicts in relationships with their offspring as a function of age, gender, cohabitation status, and marital status.

The Youn Scale was used to assess aging Koreans' perceived conflicts in relationships with their adult offspring. The sample consisted of 623 elderly Koreans between the ages of 55 and 84 years. Results indicated that aging Koreans experienced significantly more conflicts in their relationships as they grew older. There were also differences in the perceptions of problems in relationships with their offspring between those who lived together with their adult children and the those who did not, and also between those who were married and those who were single. The findings imply that aging Koreans want to have qualitatively better (i.e., warmer and closer) relationships with their offspring, regardless of their bereavement status and cohabitation status.

Age Factors↗