Search PubMed⌕ Search

Biomedical subjects

T S Lin

Publications and source records attributed to T S Lin.

At least 109 records · Page 6Linked to original sources
PubMed1991

Effects of environmental exposure on carbon polysulphone composites.

In vivo and in vitro studies were designed to characterize the material degradation associated with implantation of carbon fibre-reinforced polysulphone (C/PS). Composite plates were compression moulded for both studies, and a fibre orientation of 0 degrees with the long axis and a fibre volume fraction of approximately 55% were used. The in vitro experiment involved soaking three groups of four plates each at 4, 12 and 26 wk in 0.9% saline solution at 37 degrees C. The plates were measured for weight gain after each time period and mechanically tested non-destructively in four-point bending to determine modulus. The in vivo experiment involved implanting three groups of eight composite plates (24 total) subcutaneously in the abdomens of 12 rabbits (two implants/animal). Implants were harvested at 4, 12 and 26 wk after implantation and evaluated for changes in weight or modulus of elasticity. In vitro results showed a statistically significant (P less than 0.05 paired t-test) increase in weight for all time periods: 0.41, 1.25 and 0.93% weight gain for the 4, 12 and 26 wk periods respectively. In vivo results were similar to those in vitro: 0.66, 1.06 and 1.15% weight gain for the 4, 12 and 26 wk periods respectively (P less than 0.05 paired t-test). There was no statistically significant difference between the pre- and post-implantation modulus of elasticity for any time period in vivo or in vitro. However, in both studies, on average, the modulus tended to increase with environmental exposure.

Animals↗
PubMed1991

Synthesis and anticancer activity of various 3'-deoxy pyrimidine nucleoside analogues and crystal structure of 1-(3-deoxy-beta-D-threo-pentofuranosyl)cytosine.

Various 3'-deoxy pyrimidine nucleoside analogues have been synthesized for evaluation as potential anticancer and antiviral agents. Among these compounds, 1-(3-deoxy-beta-D-threo-pentofuranosyl)cytosine (10, 3'-deoxy-ara-C) and 3'-deoxycytidine (22) had significant anticancer activity against CCRF-CEM, L1210, P388, and S-180 cancer cell lines in vitro, producing ED50 values of 2, 10, 5, and 34 microM, respectively, for 3'-deoxy-ara-C (10); and 25, 5, 2.5, and 15 microM, respectively, for 3'-deoxycytidine (22). Thus, 3'-deoxy-ara-C (10) was 12.5 times more active against CCRF-CEM cells than 3'-deoxycytidine (22). The 2'-O-acetyl, 5'-O-acetyl, and 2',5'-di-O-acetyl derivatives of 3'-deoxy-ara-C (10), compounds 34, 31, and 30, demonstrated anticancer activity in the same range as 3'-deoxy-ara-C (10) against CCRF-CEM, L1210, P388, and S-180 cells. The 5'-O-acetyl derivative (31) had significantly greater activity against CCRF-CEM with an ED50 value of 0.4, but this compound also showed similar activity, as did 3'-deoxy-ara-C, against L1210, P388, and S-180 with ED50 values of 3, 3, and 13 microM, respectively. 3'-Deoxy-ara-C was also evaluated in vitro against HSV-2, HCMV, and GPCMV viruses and was found to be not very active with respective IC50 values of 110, 220, and 1000 microM. The single-crystal structure of 3'-deoxy-ara-C (10) was determined by X-ray crystallography. There are two molecules of the nucleoside and one molecule of water in the asymmetric unit. The sugar moieties of the two nucleoside molecules adopt different conformations. In molecule A, the ring pucker is C3'-endo with P = 18.7 degrees and tau m = 37.3 degrees, while the CH2OH side chain is gauche+. In molecule B, the ring pucker is C2'-endo with P = 156.8 degrees and tau m = 37.8 degrees and the side chain is trans.

Animals↗
PubMed1991

Synthesis and antimalarial activity of 2-aziridinyl- and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives.

A series of 2-aziridinyl- and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives has been synthesized and evaluated for antimalarial activity in vitro against the human malaria parasite, Plasmodium falciparum (Vietnam Smith strain, chloroquine-resistant at the R3 level). The most active compounds, 2-aziridinyl-1,4-naphthoquinon-5-yl p-ethylbenzenesulfonate (13), 2-aziridinyl-1,4-naphthoquinon-5-yl p-tert-butylbenzenesulfonate (48), and 2-aziridinyl-5-hydroxy-1,4-naphthoquinone (5) produced 50% inhibition of the growth of P. falciparum at 9.6 x 10(-8), 2.4 x 10(-8), and 8.8 x 10(-8) M, respectively.

Animals↗
PubMed1991

Synthesis and anticancer and antiviral activities of various 2'- and 3'-methylidene-substituted nucleoside analogues and crystal structure of 2'-deoxy-2'-methylidenecytidine hydrochloride.

Various 2'- and 3'-methylidene-substituted nucleoside analogues have been synthesized and evaluated as potential anticancer and/or antiviral agents. Among these compounds, 2'-deoxy-2'-methylidene-5-fluorocytidine (22) and 2'-deoxy-2'-methylidenecytidine (23) not only demonstrated potent anticancer activity in culture against murine L1210 and P388 leukemias, Sarcoma 180, and human CCRF-CEM lymphoblastic leukemia, producing ED50 values of 1.2 and 0.3 microM, 0.6 and 0.4 microM, 1.5 and 1.5 microM, and 0.05 and 0.03 microM, respectively, but also were active in mice against murine L1210 leukemia. Of all the tested drug dosage levels (25, 50, and 75 mg/kg, respectively) compound 23 had no toxic deaths and compound 22 yielded only one toxic death at the highest dosage level. On the contrary, in the same study, 1-beta-D-arabinofuranosylcytosine (ara-C) resulted in 2/5, 5/5, and 5/5 toxic deaths, respectively. Both compounds 22 and 23 have shown better anticancer activity than ara-C, yielding higher T/C x 100 values and some long-term survivors (greater than 60 days). In addition, compounds 22 and 23 were found to have, respectively, approximately 130 and 40 times lower binding affinity for cytidine/deoxycytidine deaminase derived from human KB cells compared to ara-C, suggesting that the two 2'-methylidene-substituted analogues may be more resistant to deamination. Cytoplasmic deoxycytidine kinase (dCK) was required for compounds 22 and 23 action. Furthermore, compounds 14, 22, 23, and 24 also have antiherpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) activity in cell culture. In addition, the crystal structure of 2'-deoxy-2'-methylidenecytidine hydrochloride (23-HCl) was determined by X-ray crystallography.

Animals↗
PubMed1991

Alteration of cellular oncogene expression in L1210 cells by a nitrosourea analog of thymidine.

3'[3-(2-Chloroethyl)-3'nitrosoureido]-3'-deoxythymidine (3'-CTNU), a chloroethylnitrosourea analog of thymidine, is a potent antineoplastic agent against murine leukemia L1210. In this study, we have examined the effects of 3'-CTNU on cellular oncogene (proto-oncogene) expression. We found that the expression of the c-myb proto-oncogene was dramatically enhanced in a concentration- and time-dependent manner by 3'-CTNU in murine leukemia L1210 cells, whereas the expression of the c-myc proto-oncogene was suppressed. The enhancement of c-myb gene expression was found to be cell type-specific and to involve an increase of the c-myb transcription rate rather than an alteration of c-myb gene structure or increased stability of c-myb mRNA. Further analysis demonstrated that the altered c-myb gene expression was largely due to the presence of 3'-amino-3'-deoxythymidine, a decomposition product of 3'-CNTU. The expression of five other proto-oncogenes was unaffected by 3'-CTNU treatment. Our study showed that an antineoplastic agent can increase or decrease the expression of proto-oncogenes.

Actins↗
PubMed1991

Metabolism of carbamazepine: evidence of autoinduction in Chinese.

To investigate the autoinduction of carbamazepine (CBZ) metabolism in Chinese, eleven healthy male volunteers joined in this study. There were two phases of drug administration with a wash-out interval of one month, 400 mg CBZ was taken orally in single-dose phase, and 200 mg three times per day were given for seven days in multiple-dose phase. Plasma samples were obtained in series of time after the last dose of drug in each phase. CBZ concentrations were determined by a high pressure liquid chromatography method. A non-linear regression program was applied in a personal computer to estimate the pharmacokinetic parameters. The average CBZ half-lives in single- and multiple-dose phases were 50.1 +/- 12.1 (mean +/- SD) hours and 26.1 +/- 4.2 hours and the clearances were 16.4 +/- 3.3 ml/kg/h and 45.3 +/- 23.4 ml/kg/h respectively, both with significant differences (p less than 0.005). There is evidence to support the presumption of autoinduction in Chinese.

Adult↗
PubMed1990

VirD2 gene product from the nopaline plasmid pTiC58 has at least two activities required for virulence.

Virulence genes virD1 and virD2 are required for T-DNA processing in Agrobacterium tumefaciens. The regions within virD2 contributing to T-DNA processing and virulence were investigated. Some insertional mutations in virD2 prevented T-DNA border endonucleolytic cleavage and produced an avirulent phenotype. However, a non-polar insertion immediately after bp 684 of the 1344 bp open reading frame of virD2 did not inhibit endonucleolytic cleavage but still caused a loss of virulence. This suggested that in addition to T-DNA border cleaving activity, the VirD2 protein has another virulence function which resides in the C-terminal half of the protein. Comparative nucleotide sequence analyses of virD2 showed that the first 684 bp were 81% homologous to virD2 of an octopine Ti plasmid whereas the remaining 660 bp were only 44% homologous. A plasmid containing the virD region from octopine Ti plasmid could restore both virulence and processing to a nopaline virD2 mutant. No complementation resulted when a nopaline virD2 clone containing a region similar to eukaryotic nuclear envelope transport sequences was deleted from the 3' end. These results suggest that virD1 and only the first half of virD2 are required to encode for the T-DNA processing endonuclease, and that the 3'-half of virD2 encodes a function separate from endonuclease activity that is required for virulence.

Amino Acid Sequence↗
PubMed1990

Platelet-fibrin interaction in the suspension and under flow conditions.

Interactions between platelets and fibrin are important in hemostasis but often confused with platelet-fibrinogen interactions. A stirred mixture of solubilized fibrin and washed platelets at neutral pH range showed drastic reduction in turbidity and concomitant platelet adhesion onto newly formed fibrin strands. This platelet-fibrin interaction did not require platelet activation nor did it cause platelet aggregation. A device consisting of a parallel-plate flow chamber mounted on a fluorescence microscope has been constructed to allow direct visualization and recording of platelet-fibrin interaction under flow conditions. Platelets in whole blood adhered to the fibrin-coated portion but not to the uncoated portion of the flow chamber. Slow motion playback of video tapes indicated that the adhesion phenomenon was a dynamic process that involved attaching, detaching, relocation and transient contact. The fibrin coating influenced platelet adhesion both by increasing the number of cells making short-term attachments to the surface and by increasing the duration of cells attached to the surface. These observations provided basic characteristics of platelet-fibrin interaction.

Blood Platelets↗
PubMed1990

Molecular characterization of the vir regulon of Agrobacterium tumefaciens: complete nucleotide sequence and gene organization of the 28.63-kbp regulon cloned as a single unit.

The entire vir regulon of Agrobacterium tumefaciens was subcloned and the complete 28.6-kbp nucleotide sequence was determined. The regulon was cloned as a single unit into two replicons, one of which replicates at a high copy number in this bacterium, and a second which has broad-host-range features to replicate in other Gram-negative bacteria. These vir region plasmids are able to confer in trans the processing and transfer activities on a second plasmid containing the T-DNA. In the high copy number vir region plasmid pUCD2614, a moderate increase in basal vir gene expression was observed as judged by virE::cat fusion expression assays relative to the wild-type control plasmid. Furthermore, higher efficiencies of tobacco leaf disk transformation were observed than with the widely used vir helper plasmid pAL4404. The nucleotide sequence studies showed that the vir region consists of 28,631 bp comprising 24 open reading frames which encode proteins involved in tumorigenicity. Two open reading frames not previously characterized, virH and ORF5, were uncovered within the virD/virE intervening spacer region. Together these studies more completely characterize the structure and function of the vir regulon.

Base Sequence↗
PubMed1989

Adjuvant chemotherapy after radical hysterectomy for cervical carcinoma.

Three hundred and sixty-eight cases of invasive cervical cancer (stage IB through early stage IIB) were treated with radical abdominal hysterectomy and bilateral pelvic lymphadenectomy at Chang Gung Memorial Hospital. Of these patients, 172 were classified postoperatively as a high-risk group after surgical-pathological assessment of tumor extent. Among these high-risk patients, 40 received adjuvant chemotherapy with cisplatin, vinblastine, and bleomycin (PVB), 38 received adjuvant radiotherapy, and 79 refused adjuvant treatment. The 3-year cumulative disease-free survival rate was 91.6% for the low-risk group and 59.7% for those at high risk. Among patients in the high-risk group, the 3-year survival rate was 75.0% for patients treated with adjuvant chemotherapy and 46.8% for those not treated with adjuvant therapy (P less than 0.05). The preliminary results of this pilot study showed a significant activity of adjuvant chemotherapy, which warrants further investigation of its role in the treatment of cervical cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

1-(2,3-Dideoxy-beta-D-glycero-pent-2-enofuranosyl)thymine. A highly potent and selective anti-HIV agent.

The nucleoside analogue 1-(2,3-dideoxy-beta-D-glycero-pent-2-enofuranosyl)thymine (d4T, 1) was prepared by ring opening of the 3',5'-anhydro compound 5. This method has been refined such that it can be used to prepare d4T on a large scale. The triphosphate of d4T was also synthesized from 1 in order to examine the mode of action. The in vitro inhibitory activity of d4T was found to be comparable to that of AZT in HIV-infected CEM cells. The triphosphate of d4T (8) and that of AZT inhibited the HIV reverse transcriptase with poly(rA):oligo(dT) as the template:primer with Ki values of 0.032 and 0.007 microM, respectively. The in vitro toxicity of d4T against normal human hematopoietic progenitor cells (CFU-GM) was measured in comparison to AZT. While d4T reduces colony-forming units by 50% at a concentration of 100 microM, it takes only 1 microM AZT to have a similar toxic effect. With erythrocyte burst forming units (BFU-E) the in vitro toxicities for d4T and AZT have comparable ID50 values of 10 and 6.7 microM, respectively.

Antiviral Agents↗
PubMed1989

Synthesis of 2,3-diaziridinyl-1,4-naphthoquinone sulfonate derivatives as potential antineoplastic agents.

A new class of 2,3-diaziridinyl-1,4-naphthoquinone sulfonates (27 compounds) has been synthesized and evaluated as potential antineoplastic agents. The most active compounds, benzenesulfonate 4, p-toluenesulfonate 5, p-methoxybenzenesulfonate 7,8-quinolinesulfonate 17, and 2-thiophenesulfonate 20, in the aromatic sulfonate series, at their optimum daily dosage level of 25 mg/kg X 6, produced 100%, 90%, 75%, 80%, and 100% 50-day survivors, respectively, of L1210 tumor-bearing mice. At a lower optimum daily dosage level of 20 mg/kg X 6, treatments with p-fluorobenzenesulfonate 11 and p-nitrobenzenesulfonate 15 resulted in 100% and 80% 50-day survivors. In the aliphatic sulfonate series, methanesulfonate 21 produced 80% 50-day survivors at a 10 mg/kg daily dosage level X 6. Benzenesulfonate 4, p-fluorobenzenesulfonate 11, 8-quinolinesulfonate 17, and 2-thiophenesulfonate 20 derivatives were also tested in mice bearing the B16 melanoma; these agents gave T/C X 100 values of 180, 182, 219, and 161, respectively, in this neoplastic cell system. Structure-activity relationships of compounds of this class are discussed.

Animals↗
PubMed1989

Synthesis and antiviral activity of several 2,5'-anhydro analogues of 3'-azido-3'-deoxythymidine, 3'-azido-2',3'-dideoxyuridine, 3'-azido-2',3'-dideoxy-5-halouridines, and 3'-deoxythymidine against human immunodeficiency virus and Rauscher-murine leukemia virus.

Several 2,5'-anhydro analogues of 3'-azido-3'-deoxythymidine (AZT), 3'-azido-2'3'-dideoxyuridine (AZU), 3'-azido-2'3'-dideoxy-5-bromouridine, 3'-azido-2',3'-dideoxy-5-iodouridine, and 3'-deoxythymidine and the 3'-azido derivative of 5-methyl-2'-deoxyisocytidine have been synthesized for evaluation as potential anti-HIV (human immunodeficiency virus) agents. These 2,5'-anhydro derivatives, compounds 13-17, demonstrated significant anti-HIV-1 activity with IC50 values of 0.56, 4.95, 26.5, 27.1, and 48 microM, respectively. Compared to that of the parent compounds AZT and AZU, the respective 2,5'-anhydro analogues, compounds 13 and 14, were somewhat less active. Whereas AZT was cytotoxic with a TCID50 of 29 microM, the toxicity of the 2,5'-anhydro derivative of AZT, compound 13, was reduced considerably to a TCID50 value of greater than 100 microM. The 2,5'-anhydro analogue of 5-methyl-2'-deoxyisocytidine also demonstrated anti-HIV-1 activity with an IC50 value of 12 microM. These compounds were also evaluated against Rauscher-Murine leukemia virus (R-MuLV) in cell culture. Among them, AZT, 3'-azido-2',3'-dideoxy-5-iodouridine, 3'-azido-2',3'-dideoxy-5-bromouridine, and 2,5'-anhydro-3'-azido-3'-deoxythymidine (13) were found to be most active, with IC50 values of 0.023, 0.21, 0.23, and 0.27 microM, respectively.

Antiviral Agents↗
PubMed1989

Selective inhibition of human immunodeficiency virus type 1 replication by the (-) but not the (+) enantiomer of gossypol.

The (-) enantiomer of gossypol but not the (+) enantiomer had good antiviral activity in peripheral blood mononuclear cells against human immunodeficiency virus type 1 at a concentration more than 20-fold lower than that required for cytotoxicity; however, in H9 cells the (-) enantiomer, although more potent as an antiviral agent, was more cytotoxic.

Cells, Cultured↗
PubMed1989

Prevention of hypothermia during abdominal surgery: comparison of thermal tube and blanket.

Twenty patients who received elective abdominal surgery for more than two hours were randomly assigned into two groups. Group 1 was warmed by using "EXACON" thermal therapy system model TT8200. Group 2 was warmed by using a thermal blanket of aquamatic K-thermia (electronic control), model PK-600 of American Hamilton medical systems. Other variables were kept constant, and the theater temperature was maintained at 24 degrees C. Core temperature was recorded every five minutes in a two hour period. There were statistically significant differences between these two groups intra-operatively. Decrease of temperature between these two groups had significant changes from 30 minutes to 2 hours (p less than 0.05). The warming effect of esophageal thermal tube was well controlled by directly warming the central compartment. However, the effect of blanket was unpredictable due to wet dressing and superficial warming of surgical fields. There were no side effects during the study.

Abdomen↗
PubMed1989

The effect of low dose intravenous lidocaine in tracheal intubation with atracurium.

This study investigated the effect of low dose intravenous lidocaine during tracheal intubation with atracurium. Forty patients were studied in double blind, randomized groups. Intravenous lidocaine, 1 mg/kg, or saline was given to the patients three minutes before induction. This result showed there is no difference about the intubation condition between these groups. The changes in mean arterial blood pressure and heart rate after laryngoscopy and intubation were similar in both groups. However, the lidocaine group had a shorter time to have 75% twitch depression (when the first twitch of train of four equals 25% of the original height) than the control group (p less than 0.05). The addition of intravenous lidocaine 1 mg/kg during induction has no significant advantage although it can shorten the intubation time.

Adult↗