Biomedical subjects

Chin-Chung Lin

Publications and source records attributed to Chin-Chung Lin.

26 records · Page 2Linked to original sources

PubMed2002

The use of in vitro metabolic stability for rapid selection of compounds in early discovery based on their expected hepatic extraction ratios.

PURPOSE: The in vivo hepatic extraction ratio of cynomolgus monkeys was correlated with the corresponding in vitro extraction ratios that were determined in monkey microsomal incubations. METHOD: For compounds that are eliminated mainly through liver phase I metabolism, the extraction ratio calculated from liver microsomal stability studies should correlate with their in vivo hepatic extraction ratios and also with their oral bioavailability in monkey. We used both well-stirred and parallel tube models of intrinsic clearance for the correlation. We also calculated extraction ratios for compounds within a given therapeutic area from fraction absorbed values that were estimated from the Caco-2 absorption model. RESULT: The present data show that in vitro extraction ratios in monkey microsomes are predictive of the in vivo hepatic extraction ratios in monkeys. All compounds with high extraction ratio (>70%) in vivo were successfully classified as high-extraction-ratio compounds based on the in vitro monkey microsomal stability data. From the results of this study, it appears that the parallel tube model provided a slightly better classification than the well-stirred model. CONCULUSIONS: The present method appears to be a valuable tool to rapidly screen and prioritize compounds with respect to liver first-pass metabolism in monkeys at an early phase of drug discovery.

Animals↗

PubMed1995

Pharmacokinetics of Loratadine in Pediatric Subjects.

The pharmacokinetics of loratadine, a new nonsedating antihistamine, was studied in 14 pediatric volunteers between the ages of 8 to 12 years. In an open-label design, one volunteer (with body weight less than 30 kg) received 5 mg of loratadine syrup and 13 volunteers (with body weights greater than 30 kg) received 10 mg of loratadine syrup. Blood samples were collected up to 72 h after dosing. Plasma concentrations of loratadine and its metabolite, descarboethoxyloratadine, were determined by a specific and sensitive gas-liquid chromatographic method. Following a 10-mg dose as a syrup, plasma concentrations of loratadine and descarboethoxyloratadine could be determined up to 8 and 48 h, respectively. The maximum concentration (C(max)) of loratadine and descarboethoxyloratadine were approximately 4 ng ml(minus sign1) each. However, the AUC of the metabolite was about six times that of loratadine. The elimination phase half-life of descarboethoxyloratadine averaged about 13.8 hr. The pharmacokinetics of loratadine in pediatric subjects was similar to that in healthy adult volunteers.

Journal Article↗

PubMed1994

Multiple-Dose Pharmacokinetics of Ceftibuten in Healthy Adults and Geriatric Volunteers.

The steady-state pharmacokinetics of ceftibuten, an orally active cephalosporin were investigated in 12 healthy male volunteers (19--38 years) and in 12 geriatric volunteers (65--76 years). Each received one 200-mg ceftibuten capsule every 12 h on days 1--3 and one capsule in the morning on day 4. Plasma and urine samples were collected at various times on days 1--4 and assayed by high-pressure liquid chromatographic method for ceftibuten and ceftibuten-trans, a conversion product. The T(max) for ceftibuten and ceftibuten-trans occurred at about 2 and 3 h, respectively, in both populations. The C(max) and AUC((0--12 h)) ranged from 10.8 to 12.4 &mgr;g ml(minus sign1) and from 47.5 to 55.1 &mgr;g h ml(minus sign1), respectively, for normal volunteers compared to 12.9--17.5 &mgr;g ml(minus sign1) and 62.3--87.1 &mgr;g h ml(minus sign1), respectively, for geriatric volunteers. The respective values for ceftibuten-trans in normal and geriatric volunteers were 1.3 and 1.3 &mgr;g ml(minus sign1), respectively, and 6.9--8.2 and 5.9--9.8 &mgr;g h ml(minus sign1). At steady state, the C(max) and AUC((0--12 h)) of ceftibuten-trans were about 10--11% and 13--16% those of ceftibuten in normal volunteers and about 8--9% and 9--11% those of ceftibuten, respectively, in geriatric volunteers. The accumulation factor of ceftibuten in normal volunteers was 1.1 as compared to 1.3 in geriatric volunteers. The terminal phase half-life was 2.5 h in healthy volunteers and 3.2 h in geriatric volunteers. Urinary excretion appeared to be the major route of elimination in both populations accounting for more than 90% of the dose recovered in the urine during the dosing interval. The results of this study demonstrate that ceftibuten, 200 mg given twice a day, is safe and well tolerated, is well absorbed, and that steady-state is achieved on days 3 and 4. There is some accumulation in the elderly, but dosage regimen based on age is not warranted.

Journal Article↗

PubMedDate not supplied

A sensitive and specific method for the determination of total ribavirin in human red blood cells by liquid chromatography-tandem mass spectrometry.

A sensitive and specific method using high-performance liquid chromatography (LC)-tandem mass spectrometry (MS) for the analysis of total ribavirin in human red blood cells (RBC) is developed and validated. The method involves the addition of an internal standard and perchloric acid, the conversion of ribavirin phosphorylated metabolites to ribavirin, purification with a solid-phase exchange cartridge, and LC-MS-MS analysis. The MS-MS is selected to monitor m/z 245-113 for ribavirin and m/z 250-113 for [13C]ribavirin using positive electrospray ionization. The calibration curve is linear over a concentration of 100-10,000 ng/mL with a limit of quantitation of 100 ng/mL. Mean interassay accuracy for quality control (QC) at 100, 1000, and 10,000 ng/mL are 101.8%, 99.4%, and 98.8%, respectively. Mean interassay precision (%CV) for QC at 100, 1000, and 10,000 ng/mL are 5.0%, 5.0%, and 2.5%, respectively. Extractibility of total ribavirin from RBC is confirmed with RBC obtained from a [(14)C]ribavirin-dosed monkey. The method is used to determine the free and total ribavirin concentration in human RBC obtained from hepatitis C patients treated with ribavirin.

Antiviral Agents↗

PubMedDate not supplied

Berberine decreased N-acetylation of 2-aminofluorene through inhibition of N-acetyltransferase gene expression in human leukemia HL-60 cells.

Previous studies have demonstrated that berberine decreases N-acetyltransferase (NAT) activity in human leukemia HL-60 cells, however, NAT gene expression has not been investigated. In this study, berberine was selected for testing the inhibition of N-acetylation of 2-aminofluorene (AF) and NAT gene expression in human HL-60 cells. The N-acetylation of AF was determined and quantitated by high performance liquid chromatography (HPLC). The data showed that a 24-hour berberine treatment decreased the amount of N-acetylation of AF in HL-60 cells. The NAT enzymes were stained and examined by Western blotting and flow cytometry. The results indicated that berberine decreased the levels of NAT protein in HL-60 cells. The expression of NAT gene (mRNAT NAT1) was determined by polymerase chain reaction (PCR), and it was found that berberine had inhibited the expression of mRNA NAT1 in human HL-60 cells.

Acetylation↗

PubMedDate not supplied

Diallyl disulfide inhibits WEHI-3 leukemia cells in vivo.

Enhanced garlic (Allium sativum) consumption is closely related to reduced cancer incidence, as shown in epidemiological studies. Diallyl disulfide (DADS), a component of garlic, inhibits the proliferation of human blood, colon, lung and skin cancer cells. Although DADS had been reported to induce apoptosis in human leukemia HL-60 cells, there are no reports regarding whether or not it affects leukemia cells in vivo. Therefore, the present study is focused on the in vivo effects of DADS on WEHI-3 leukemia cells. The effects of DADS on murine WEHI-3 cells were initially examined, and the results indicated that DADS induced cytotoxicity and that this effect was dose-dependent. The effects of DADS on WEHI-3 in BALBIc mice were also examined, and the results indicated that DADS decreased the percentage of MAC-3 marker, indicating that differentiation of the precursor of macrophage and T cells was inhibited. The weights of liver and spleen were also measured, and the results indicated that DADS decreased the weight of these organs. An important characteristic of WEHI-3 leukemia is the enlarged spleen in mice after i.p. injection of WEHI-3 cells. Based on pathological examination, the function of DADS was observed in the liver and spleen of mice previously injected with WEHI-3 cells. Apparently, DADS affects WEHI-3 cells both in vitro and in vivo.

Allyl Compounds↗

PubMedDate not supplied

Apoptosis of human leukemia HL-60 cells and murine leukemia WEHI-3 cells induced by berberine through the activation of caspase-3.

The aim of this study was to clarify the mechanisms of apoptosis, cytotoxicity, DNA damage and fragmentation, as well as the production of reactive oxygen species (ROS) and Ca+2, induced by berberine in human promyelocytic leukemia HL-60 and murine myelomonocytic leukemia WEHI-3 cells. The levels of Bcl-2 and Bax, the changes of mitochondria membrane potential (MMP), cytochrome c release and activation of caspase-3 were also investigated in both cell lines. The flow cytometry and DAPI staining assays indicated that berberine induced cytotoxicity in both cell lines examined. Flow cytometry assay also showed that berberine induced ROS and Ca+2 production, decreased the levels of MMP and increased the activity of caspase-3 in both cell lines examined. Berberine-induced apoptosis was accompanied by increased levels of Ca+2 and a decrease in the mitochondrial membrane potential, leading to the release of cytochrome c and the cleavage of pro-caspase-3. Western blotting also showed that berberine increased the levels of Bax and cytochrome c and decreased the levels of Bcl-2 in both cell lines. Inhibition of caspase-3 activation (z-VAD-fmk: cell-permeable broad-spectrum caspase inhibitor) completely blocked berberine-induced apoptosis in both HL-60 and WEHI-3 cells. Therefore, berberine induced apoptosis in both examined cell lines through the activation of caspase-3.

Animals↗

PubMedDate not supplied

Down-regulation of cyclin B1 and up-regulation of Wee1 by berberine promotes entry of leukemia cells into the G2/M-phase of the cell cycle.

Berberine has a wide range of biological actions that suggest it may be of use in cancer prevention. It was previously reported that berberine induced cell cycle arrest, not only at the G0/G1-phase, but also at the G2/M-phase in a dose-dependent manner. However, the mechanism of berberine-induced G2/M-phase arrest in leukemia cells is not fully understood. In the present study, the effects of the naturally occurring berberine (the major constituent of Coptis chinensis) on the cell cycle, as well as on CDK1, cyclin B1, 14-3-3sigma, Wee1 and Cdc25c expressions, were investigated in the human promyelocytic leukemia HL-60 cells and in the murine myelomonocytic leukemia WEHI-3 cells. The flow cytometry assays indicated that berberine induced G2/M-phase arrest in both examined cell lines. The berberine-induced G2/M-phase arrest in both examined cell lines was accompanied by increased levels of Wee1 and 14-3-3sigma, but decreased levels of Cdc25c, CDK1 and cyclin B1. However, CDK2 expression was not affected as revealed by Western blotting assay. Berberine induced G2/M arrest in both the examined cells via the inhibition of cyclin B1 and the promotion of Wee1.

14-3-3 Proteins↗