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Biomedical subjects

L C Li

Publications and source records attributed to L C Li.

At least 37 records · Page 2Linked to original sources
PubMed2000

Particle size determination of a three-component suspension using a laser-scattering particle size distribution analyzer.

In this study, a rapid and accurate particle size determination method using a light-scattering particle size analyzer was developed to measure the particle size and size distribution of a suspension containing three solid components: clotrimazole, triamcinolone, and sarafloxacin, which have different refractive indices. To ensure that data represent the size distribution of the primary particles of the suspension, the optimal sonication prior to and during measurement was determined. It was found that the results obtained using the average relative refractive index (RRI) of the three components agreed with the results obtained using three individual RRIs. In addition, the results from two analysts demonstrated good reproducibility of this method. The size distribution data of the suspension were also compared to those of the bulk drugs. The results showed that the median particle size of this three-component suspension is relatively close to that of clotrimazole, which accounts for 80% of solid particles in the suspension. Furthermore, the results obtained using the light-scattering technique were comparable to those obtained using a polarized light microscope equipped with an image analyzer, indicating acceptable accuracy of this technique.

Anti-Infective Agents↗
PubMed2000

Effect of sodium dodecyl sulfate on iontophoresis of hydrocortisone across hairless mouse skin.

The purpose of the present work was to study the effect of sodium dodecyl sulfate (SDS), an anionic surfactant, on the iontophoretic transport of a neutral drug hydrocortisone (HC) across hairless mouse skin. The transport studies were conducted using Side-Bi-Side diffusion apparatus and drug concentration in the receptor cell was analyzed using reversed-phase HPLC. A theoretical model was described, tested, and found to agree well with experimental data (R2 = 0.9766). Anodal iontophoresis significantly enhanced the transport of HC compared to cathodal iontophoresis and passive diffusion, suggesting that the transport of the neutral solute occurs via the electro-osmotic flow. The effect of SDS on the transport of HC was highly concentration-dependent and driving mode-dependent. Below the critical micelle concentration (cmc), increasing the concentration of SDS increased both the passive and the iontophoretic fluxes of HC, but the increase was most significant with anodal iontophoresis. Above the cmc, passive transport of HC continued to increase with an increase in the SDS concentration. The transport after anodal iontophoresis, however, reached a plateau and then leveled off. Further increase in SDS concentration decreased flux, suggesting that the transport of micellar-solubilized drug is retarded by anodal iontophoresis, possibly due to electrostatic attraction.

Animals↗
PubMed2000

[Stable inheritance of hpt gene in transgenic rice plants mediated by biolistic bombardment].

Japonica rice cv 77170 was transformed with pBI222 carrying hygromycin phosphotransferase gene (hpt) by using biolistic bombardment and fertile transgenic rice plants were obtained. In T1 and most T2 generation the performance of hygromycin resistance was normal. Only in T2 progeny of SG-15 some lines showed decreased resistance. Mendelian inheritance of hygromycin resistance was showed as single dominant locus and proved by Southern blotting analysis in T1 and T2 generation of all transgenic plants. Multiple copies of hpt integrated into rice genome. These copies linked closely and inherited stablly. Msp I digested Southern blotting showed that methylation of hpt existed commonly in transgenic plants and their progeny, therefore uncomplete silencing of hpt in some T2 progeny of SG-15 was not associated with hpt methylation probably.

Biolistics↗
PubMed2000

[Comparison of genetic diversity among maize inbred lines based on RFLPs, SSRs, AFLPs and RAPDs].

RFLPs, SSRs, AFLPs and RAPDs were used to detect the genetic diversity among 15 maize inbred lines. A total of 56 probe enzyme combinations, 66 SSR primers, 20 RAPD primers and 9 AFLP primer combinations were identified with polymorphism among the entries, which produced 167, 201, 180 and 87 alleles respectively. SSR markers have the highest polymorphism information content (PIC, 0.47) and AFLP markers have the lowest value (0.36), while AFLP markers possess the highest assay efficiency index (Ai, 32.4). A comparison of genetic similarity matrices revealed that the estimates of correlation coefficients based on RFLPs, SSRs, AFLPs and RAPDs were significantly correlated, but the correlation of RAPD maker data with other markers was lower. These inbred lines were classified into five groups based on four molecular markers data, which are Tangsipingtou, Luda Red Cob, Lancaster, Reid, and PN group. They are consistent with the grouping based on the available pedigree data. Based on the results, we recommend RFLPs and SSRs for genetic diversity analysis among maize germplasm.

Genetic Variation↗
PubMed2000

[Repair on the traumatic defect of metacarpophalangeal joint by the cartilage transplantation of metatarsophalangeal joint].

OBJECTIVE: To present a simple and reliable method for the reconstruction of metacarpophalangeal joint by the cartilage transplantation of metatarsophalangeal joint. METHODS: From 1990, nine cases (11 sides) with traumatic metacarpophalangeal joint defect were treated by the autogenous cartilage transplantation of metatarsophalangeal joint followed by modified treatment. Appropriate biological mechanics was provided by internal fixation and collateral ligament repair. RESULTS: Followed up 6 months to 7 years, the range of joint motion was increased 35.1 degrees. The fusion of donor phalanges was fine, and the range of joint motion was decreased, even ankylosis after plastic operation, but no pain and no effect on walk. CONCLUSION: The key to successful operation is better matching of cartilage, reliable internal fixation, ligament reconstruction, thin cartilage and little bone of the donor, appropriate biological mechanical surroundings.

Adult↗
PubMed1999

High frequency of deletion on chromosome 9p21 may harbor several tumor-suppressor genes in human prostate cancer.

Chromosome 9p has been reported to be a critical region of loss in various cancers. Our present study was designed to determine the frequency of deletions at different loci of chromosome 9p in microdissected samples of normal prostatic epithelium and carcinoma from the same patients. For this purpose, DNA was extracted from the microdissected sections of normal and tumor cells of 40 prostate specimens, amplified by PCR and analyzed for loss of heterozygosity (LOH) on chromosome 9p using 15 microsatellite markers. Only 6 of 15 microsatellite markers exhibited LOH in prostate cancer specimens (D9S162, D9S1748, D9S171, D9S270, D9S273 and D9S153). LOH on chromosome 9p was identified in 29 of 40 cases (72.5%) with at least 1 marker. The main deletion was found on 9p21, at loci D9S1748 (50%), D9S171 (51.4%) and D9S270 (21.8%). There was also a deletion on 9p22 at locus D9S162 (8.3%), on 9p13 at locus D9S273 (13.8%) and on 9p11 at locus D9S153 (7.7%). LOH data were correlated with stage of prostate cancer and revealed a high frequency of LOH at 3 or more loci in samples with stage T(3)N(0)M(0) (46%) compared with stage T(2)N(0)M(0) (15%), which suggests a higher incidence of LOH in the advanced stage of prostate cancer. One of the candidate target tumor-suppressor genes, p16 (MTS-1/CDKN2), has been identified within the 9p21 deleted region in tumor cell lines. Expression of P16 protein was either absent or very low in prostate cancer samples, suggesting that loss of the p16 gene may be involved in prostatic carcinogenesis.

Chromosomes, Human, Pair 9↗
PubMed1999

A statistical experimental approach to cosolvent formulation of a water-insoluble drug.

19-Nor-1 alpha, 25-dihydroxyvitamin D2, an analog of vitamin D2, is a nonpolar compound with limited solubility in water. An injectable solution was formulated using a cosolvent system consisting of water, ethanol, and propylene glycol. A statistical response surface approach was used to evaluate the effect of these three solvents on the solubility of the drug (25 degrees C) in the ternary cosolvent system. The data generated from five selected formulations were used to develop a multiple linear regression model that quantitatively defines the solubility of the drug as a function of the cosolvent composition. Close agreement was found between the experimental data and data calculated using the model. The capability of this model to predict drug solubility in cosolvent systems with various combinations of the three solvents was also verified.

Chemistry, Pharmaceutical↗
PubMed1999

[Microdissection of M chromosome in Vicia faba and its library construction].

Microdissection and microcloning technique was employed to construct the library of M chromosome in Vicia faba. The M chromosomes were microdissected with a micromanipulator and were put into a 0.5 ml Eppendorf tube, then digested with Sau3A. Sau3A linker adaptors were ligated to the end of chromosome DNA fragments, and two rounds of PCR were carried out with one chain of linker adaptor as the primer. The PCR products ranged in size from 300 base pair (bp) to 3000 bp with predominant fragments from 500 bp to 1500 bp. Southern hybridization analysis confirmed that PCR products originated from Vicia faba genome. The second round PCR products were cloned and about 102,000 recombinants were obtained. 118 recombinants were selected randomly for analysis. The inserts ranged in size from 150 bp to 3000 bp with an average of 690 bp. Dot blot was carried out for 100 clones with DIG labeled Vicia faba genome DNA as probes. The result revealed that 51% were low and unique copy sequences, 49% were repetitive sequences. M chromosome DNA library has not been reported before.

Chromosome Mapping↗
PubMed1998

On-the-fly fluorescence lifetime detection of dye-labeled DNA primers for multiplex analysis.

Mixtures of dye-labeled, M13-forward DNA primers were separated by capillary gel electrophoresis and detected on-the-fly, using fluorescence lifetime measurements, to evaluate four-decay detection for multiplex DNA sequencing. Three different four-dye systems were used, two that were excited at 488 nm and one that was excited at 514 nm. Each dye-labeled primer was identified on the basis of the lifetime of the conjugated dye using nonlinear least squares or the maximum entropy method to analyze the lifetime data. Overlapping electrophoretic peaks were generated by making multiple injections of mixtures of the dye-labeled primers. The overlapping peaks were resolved by fitting the data to two-, three- or four-component lifetime models used in nonlinear least-squares analysis in which each lifetime component was fixed to the predetermined lifetime of the corresponding dye-labeled primer. In two of the dye systems, the lifetimes of the four dye-labeled primers were sufficiently different to allow peak resolution. In the other dye system, addition of 10% DMSO to the run buffer changed the lifetime of one dye-labeled primer, allowing it to be resolved from another dye-labeled primer with similar lifetime.

DNA Primers↗
PubMed1998

Moist-heat sterilization and the chemical stability of heat-labile parenteral solutions.

The impact of moist-heat sterilization (autoclaving) on the chemical stability of parenteral solutions was examined using two heat-labile products, clindamycin phosphate and succinylcholine chloride injections, as examples. A nonisothermal kinetic model was used to predict the extent of product degradation during autoclaving. The predicted results were found to be in close agreement with the experimental data. For the same peak temperature, a greater loss of product was shown by using a cycle with a higher F0. On the other hand, a higher peak-temperature cycle resulted in less product degradation for the same F0 value. The benefit of a high-temperature cycle was further illustrated by the fact that less chemical degradation for both products was produced by a 122 degrees C cycle with an F0 of 11 as compared to that which occurred during a 116.5 degrees C cycle with an F0 of 8. Although clindamycin phosphate was found to be highly unstable during a conventional autoclaving process, predicted data indicate that a UHT (Ultra-High Temperature) process may be used to sterilize this product with acceptable degradation.

Clindamycin↗
PubMed1998

Light-scattering method in particle size analysis of parenteral emulsions.

The use of a light-scattering particle size distribution analyzer has been shown to be a convenient method for characterizing the particle size distribution of parenteral emulsions. However, the concentrations of the samples used were found to have a major impact on the particle size distribution results, particularly for samples with a mean particle size smaller than 0.2 micron. An increase in sample concentration caused a shift to smaller particle sizes as a result of multiple scattering. The blue-light (tungsten lamp) intensity, instead of the He-Ne laser integrity, should be used to control sample concentration within the optimal range for measurement.

Emulsions↗
PubMed1998

Particle size determination of a flocculated suspension using a light-scattering particle size analyzer.

Microscopy is a useful and direct method for measuring the particle size of a suspension because, in addition to the particle size and size distribution, it provides visual detection of the shape and state of aggregation of the particles in the suspension. However, this method suffers from the shortcomings of being tedious and time consuming. In this study, a light-scattering particle size analyzer was used to determine the particle size and size distribution of a flocculated suspension. The sonication of the sample prior to and during measurement was found to be critical in ensuring that data are representative of the size distribution of the primary particles of the suspension. The light-scattering results were further confirmed by data generated using a polarized light microscope equipped with an image analyzer.

Benzocaine↗
PubMed1997

On-the-fly fluorescence lifetime detection of labeled DNA primers.

The first application of frequency-domain, on-the-fly fluorescence lifetime detection to the detection, identification and resolution of fluorescent labeled oligonucleotide primers in capillary electrophoresis is presented. These studies, which are directed towards the development of four-decay DNA sequencing, employed two common sequencing primers, SP6 and M13/pUC. The primers were each tagged by a derivative of either fluorescein or BODIPY. Fluorescence emission maxima and lifetimes of the free dyes and the labeled primers were determined both in batch mode and on-the-fly in capillary electrophoresis. Fluorescence intensity and lifetime electropherograms were extracted from dynamic lifetime data that were acquired at 0.1-s intervals during the CE separation. Lifetimes were recovered using either conventional non-linear least-squares analysis or the self-modeling maximum entropy method, which does not require prior knowledge of the system. Based on migration time and fluorescence lifetime, peaks could be detected and identified, and co-eluting peaks could be resolved. Interference from background impurities and scattered light was greatly reduced by the combination of physical separation and lifetime resolution.

DNA Primers↗
PubMed1997

Characterization of visible dyes for four-decay fluorescence detection in DNA sequencing.

Dyes of several classes were investigated as candidates for use in a multiplex, four-decay fluorescence detection scheme for DNA sequencing. The dyes include nitrobenzofuran dyes, rhodamine dyes, fluorescein dyes, cyanine dyes, Nile Red, and BODIPY dyes. Based on the results of fluorescence spectral and lifetime studies, an initial set of four dyes was selected for further study: NBD-aminohexanoic acid (NBD-HA, r = 1.1 ns), tetramethyl-rhodamine, methyl ester (r = 2.2 ns), rhodamine green (r = 4.3 ns), and BODIPY 505/515 (r = 5.9 ns). Limits of lifetime detection of the four dyes were investigated, and lifetime resolution was demonstrated for mixtures of the free dyes in batch solution. Lifetime of dye-labeled DNA primers also were determined in batch solution and detected on-the-fly in capillary electrophoresis (CE). Conjugation of the dyes to DNA improved the resolution of their individual lifetimes in mixtures in batch measurements. When attached to the primer, tetramethyl-rhodamine exhibited biexponential decay with a dominant lifetime of 3.8 ns, making it unsuitable for four-decay sequencing. Contact with the CE gel lengthened the lifetime of NBD-HA-labeled primer from 1.3 to 2.1 ns but did not affect the lifetimes of the other dyes. Lifetime detectability of labeled primers at individual points along an electrophoretic peak in the attomole range.

Evaluation Studies as Topic↗
PubMed1996

On-the-fly frequency-domain fluorescence lifetime detection in capillary electrophoresis.

On-the-fly fluorescence lifetime detection in capillary electrophoresis (CE) is demonstrated. Virtually continuous detection is achieved by interfacing a commercial CE instrument with a commercial, multiharmonic Fourier transform lifetime fluorometer (MHF). The CE capillary cartridge was modified to allow the capillary to pass through a specially constructed capillary column mount capable of micropositioning in the MHF sample chamber. Optimization of the CE/MHF interface was achieved through the incorporation of a focusing lens, appropriate alignment of the laser beam on the capillary, and use of appropriate optical filters in the emission beam. Both fluorescence intensity and lifetime are recovered from the dynamic MHF data, which is analyzed using either conventional nonlinear least-squares or the maximum entropy method, which allows for lifetime recovery without a priori knowledge of the system. Continuous, on-the-fly fluorescence lifetime detection using the MHF technology adds the dimension of fluorescence lifetime without sacrificing the resolution and speed of CE. Its application to the CE separation of a mixture of the fluorescent dyes NBD-hexanoic acid and fluorescein is demonstrated.

Electrophoresis, Capillary↗
PubMed1996

The efficacy of dexamethasone iontophoresis for the treatment of rheumatoid arthritic knees: a pilot study.

OBJECTIVE: To examine the efficacy of dexamethasone sodium phosphate (DEX) iontophoresis for the treatment of rheumatoid arthritis (RA) of the knee, and to obtain statistical information for a future randomized controlled trial (RCT). METHODS: Ten subjects with RA, ranging in age from 34-75, were randomly assigned to either the experimental or placebo group. Iontophoresis treatments were given to both groups on days 1, 3, and 5. Five subjects in the experimental group received a mixture of 1 ml of DEX (4 mg/ml) and 1 ml of injectable sterile water; those in the placebo group received 2 ml of saline solution. Pain on movement, at rest, and on pressure, active joint count, and active range of motion, were evaluated on days 1, 5, and 20. The patient's global assessment of treatment efficacy was also assessed on days 5 and 20. Mann-Whitney U tests and Friedman two-way analyses of variance were performed for statistical analyses. RESULTS: Pain at rest was found to be statistically different between the two groups (P = 0.0317). Statistical significance was also found over time for pain on movement within the experimental group (P = 0.0224). CONCLUSION: The results suggest that DEX iontophoresis is more effective than placebo in relieving pain at rest and on movement in the RA knee. Based on the study data, a total of 40 subjects will be required for an RCT of a similar nature.

Activities of Daily Living↗