CpG methylation of promoter region inactivates E-cadherin gene in renal cell carcinoma

CpG methylation in the promoter region has been shown to be important in the regulation of genes implicated in malignant transformation. The present study was designed to test the hypothesis that CpG methylation of the promoter region of the E-cadherin gene may inactivate its expression in renal cell carcinoma. To test this hypothesis, five kidney cancer cell lines and 34 microdissected renal cell carcinoma samples were analyzed for gene and protein expression by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. CpG methylation in the promoter regions of the E-cadherin gene was analyzed by the sodium bisulfite genome sequencing technique. Our results show that all normal renal tissue expressed the E-cadherin gene and protein. Of the renal cancer tissues analyzed, 67% (23 of 34) lacked E-cadherin expression, with an associated increase in methylation, compared with normal tissue. E-cadherin gene promoter was methylated in all renal cancer cell lines and was accompanied by a loss of E-cadherin gene and protein expression. The treatment of renal cancer cell lines with the demethylating agent 5-aza-2'-deoxycytidine restored E-cadherin mRNA expression in all renal cancer cell lines. This is the first report that shows inactivation of the E-cadherin gene and protein in renal cell carcinoma through CpG hypermethylation in the promoter region of this gene. The results of these experiments may contribute to an understanding of the role of E-cadherin inactivation in renal cell carcinoma.

Methylation of the E-cadherin gene promoter correlates with progression of prostate cancer

PURPOSE

We studied the methylation status of E-cadherin gene promoter in prostate cancer and its relationship with E-cadherin inactivation in prostate cancer.

MATERIALS AND METHODS

Seven human prostate cell lines and 35 microdissected prostate cancer specimens were analyzed for E-cadherin promoter methylation using the bisulfite genome sequencing technique. E-cadherin messenger (m)RNA expression and protein expression were also studied in prostate cell lines by reverse transcriptase-polymerase chain reaction and in prostate cancer specimens by immunostaining, respectively.

RESULTS

The overall methylation of E-cadherin promoter was evident in 14 of 20 grades III to V (70%) and in 5 of 15 grades I to II (33%) prostate cancer samples. It correlated with absent or reduced E-cadherin immunostaining. Methylation in low grade tumors was present mainly in the exon region, whereas in high grade tumors methylation was also present in the promoter region. Methylation was noted in 2 of 6 prostate cancer cell lines (33%) and correlated well with decreased E-cadherin mRNA in these cell lines. Treatment with the demethylating agent 5-aza-2'-deoxycytidine restored E-cadherin mRNA levels in the E-cadherin negative prostate cancer cell lines TSUPr1 and DuPro.

CONCLUSIONS

Methylation of the E-cadherin gene is common in prostate cancer and the severity of E-cadherin methylation correlates with tumor progression. This study implies that the invasion and metastasis suppressor function of E-cadherin may often be compromised in human prostate cancer by epigenetic rather than by mutational events.

Grass group I pollen allergens (beta-expansins) lack proteinase activity and do not cause wall loosening via proteolysis

Group I grass pollen allergens make up a subgroup of the beta-expansin family of cell wall loosening proteins in plants. A recent study reported that recombinant Phl p 1, the group I allergen from timothy grass pollen, was associated with papain-like proteinase activity and suggested that expansins loosen the plant cell wall via proteolysis. We tested this idea with three experimental approaches. First, we evaluated three purified native group I allergens from timothy grass, ryegrass and maize (Phl p 1, Lol p 1, Zea m 1) using five proteinase assays with a variety of substrates. The proteins had substantial wall loosening activity, but no detectable proteolytic activity. Thus we cannot confirm proteolytic activity in the pollen allergen class of beta-expansins. Second, we tested the ability of proteinases to induce cell wall extension in vitro. Tests included cysteine proteinases, serine proteinases, aspartic proteinases, metallo proteinases, and aggressive proteinase mixtures, none of which induced wall extension in vitro. Thus, wall proteins are unlikely to be important load-bearing components of the plant cell wall. Third, we tested the sensitivity of beta-expansin activity and native wall extension activity to proteinase inhibitors. The results show that a wide range of proteinase inhibitors (phenylmethanesulfonyl fluoride, N-ethylmaleimide, iodoacetic acid, Pefabloc SC, and others) inhibited neither activity. From these three sets of results we conclude proteolysis is not a likely mechanism of plant cell wall loosening and that the pollen allergen class of beta-expansins do not loosen cell walls via a proteolytic mechanism.

[Inhibitory effects of hydrocortisone on human polymorphonuclear leukocyte adhesion to human synovial cell]

AIM

To investigate the inhibitory effects of hydrocortisone on human polymorphonuclear leukocyte (PMN) adhesion to human synovial cell (HSC), and to explore its mechanism.

METHODS

MTT colorimetry was used to determine the adhesion effect of PMN to HSC. Cell-ELISA and RT-PCR methods were used to determine the expression of adhesion molecular ICAM-1 and VCAM-1. EMSA method was also used to observe the activity of nucleus transcription factor-kappa B (NF-kappa B).

RESULTS

Hydrocortisone inhibited TNF-alpha (50 U.mL-1 for 12 hours) and IL-1 beta (50 U.mL-1 for 12 hours)-induced adhesion of PMN to HSC (IC50 2.05 x 10(-6) mol.L-1 and 2.13 x 10(-7) mol.L-1, respectively) in a concentration-dependent manner. Adhesion molecular VCAM-1 and ICAM-1 protein and mRNA (rather than ICAM-1) expression in HSC induced by TNF-alpha (50 U.mL-1) were inhibited significantly by hydrocortisone at 1 x 10(-6)-10(-5) mol.L-1. The activity of NF-kappa B was also extensively inhibited by hydrocortisone at 1 x 10(-6)-10(-5) mol.L-1.

CONCLUSION

Hydrocortisone inhibited TNF-alpha-stimulated PMN-HSC adhesion, and expression of VCAM-1 by suppressing the activity of NF-kappa B.

[Inhibitory effects of isorhapotigenin on IL-8 production and mRNA expression induced with TNF alpha in normal human synovial cells]

AIM

To study the effects of isorhapotigenin (Iso) on interleukin-8 (IL-8) production and mRNA expression in normal human synovial cells (HSC) induced with TNF alpha.

METHODS

IL-8 were assayed with RIA method. The mRNA expression of IL-8 was detected by RT-PCR method.

RESULTS

It was shown that TNF alpha at concentrations of 0.05 to 0.5 U.mL-1 for 24 h significantly increased IL-8 production. The expression of IL-8 mRNA was also promoted by TNF alpha (0.25 U.mL-1) for 6 h. Iso at the concentrations of 1 x 10(-6) mol.L-1 to 1 x 10(-5) mol.L-1 showed inhibitory effects on IL-8 production induced with TNF alpha (0.25 U.mL-1). The further study indicated that Iso at the concentrations of 1 x 10(-6) mol.L-1 to 1 x 10(-5) mol.L-1 inhibited IL-8 mRNA expression in HSC induced with TNF alpha (0.25 U.mL-1).

CONCLUSION

TNF alpha promoted IL-8 production and mRNA expression in HSC. Iso inhibited IL-8 production and mRNA expression induced by TNF alpha (0.25 U.mL-1). This might be one of the anti-inflammatory mechanisms of Iso.

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.

Expression analysis of Y chromosome genes in human prostate cancer

PURPOSE

We hypothesized that alterations in Y chromosome gene expression may be associated with prostate cancer. To test this hypothesis we analyzed the expression of 19 Y chromosome genes in benign and malignant prostate tissue.

MATERIALS AND METHODS

To study the expression of Y chromosome genes RNA was extracted from prostate cancer and benign prostatic hyperplasia (BPH) tissue as well as from prostate cancer cell lines. RNA was reverse transcribed and polymerase chain reaction amplified using specific primers. These primers were designed for each gene sequence obtained from the gene data bank. We analyzed 19 Y chromosome genes using 6 cell lines, 7 BPH and 7 prostate cancer tissues. Normal testis RNA served as a positive control.

RESULTS

Of the 19 genes analyzed in cell lines BPH-1 cells expressed the RPS4Y, USP9Y, TMSB4Y and DBY genes; DUPro expressed RPS4Y, USP9Y, TMSB4Y, DBY and UTY; DU145 expressed DAZ, RPS4Y, USP9Y, TMSB4Y, DBY, EIAFIY, PRKY and SMCY; LNCaP expressed TSPY, SRY, BPY1, PRY, DAZ, RBMIH, RPS4Y, DBY, EIAFIY, PRKY and SMCY; ND1 expressed DAZ, RPS4Y, USP9Y, TMSB4Y, DBY, EIAFIY, PRKY and SMCY; and PC3 expressed RPS4Y, USP9Y and DBY. BPH tissue expressed the SRY, PRY, DBY, PRKY, RPS4Y, TMSB4Y, USP9Y and ZFY genes. Prostate cancer tissue expressed the PRY, TSPY, USP9Y, UTY, DBY, SMCY, ZFY, EIAFIY, TMSB4Y and RPS4Y genes.

CONCLUSIONS

The differential expression of Y chromosome genes in prostate cancer, BPH tissue and prostate cancer cell lines indicates that they may have a role in prostate cancer.

Shift of the gastric T-cell response in gastric carcinoma

BACKGROUND AND AIMS

The etiology and pathophysiology of stomach carcinoma is complex, and the mechanism whereby H. pylori directly or indirectly induces carcinoma remains unclear. In this study, interleukin (IL)-8, IL-4 and interferon (IFN)-gamma were measured in the tissue culture supernatant of gastric organ cultures from subjects with chronic gastritis with or without H. pylori infection, and with or without gastric cancer and gastric dysplasia.

RESULTS

Interleukin-8 levels were higher in cancer- and H. pylori-infected gastritis subjects than in H. pylori-negative subjects (12.95 +/- 3.16, 10.48 +/- 1.55 and 4.49 +/- 1.28 ng/mL, respectively). Elevated levels of IFN-gamma were detected in both H. pylori-infected and non-infected subjects with uncomplicated gastritis (72.23 +/- 19.0 and 34.61 +/- 5.30 pg/mL) and in non-infected dysplasia subjects (88 +/- 20.5 pg/mL). Background levels of IL-4 (< or = 9.4 pg/mL) in uncomplicated gastritis subjects and relatively high levels of IL-4 in dysplasia subjects (25.8 +/- 7.3 pg/mL) were detected. In contrast, trace amounts of IFN-gamma (16.01 +/- 0.35 pg/mL) and high levels of IL-4 (42.81 +/- 8.49 pg/mL) in gastric biopsy culture supernatants were found in cancer subjects. Mucosal IL-4 levels (but not IL-8 levels) correlated with infection and mucosal anti-H. pylori immunoglobulin G antibody.

CONCLUSIONS

The significant differences between gastritis with and without cancer and dysplasia indicated a shift from a Th1 to a Th2 helper cell pattern of cytokine secretion. This study has identified a local mucosal defect in gastric cancer. The near absence of IFN-gamma production from the mucosa at the margins of the tumor may be a critical factor in promoting growth of neoplastic cells.

Cloning and characterization of human estrogen receptor beta promoter

Estrogen receptors beta (ERbeta) belong to the nuclear receptor superfamily of ligand-dependent transcription factors that play critical roles in regulating genes involved in a wide array of biological processes. To investigate regulation of tissue-specific expression of ERbeta, we cloned and characterized a 2.1-kilobase 5'-flanking region of the human ERbeta gene. Two major transcription start sites were identified by primer extension and rapid amplification of 5'-cDNA end. The human ERbeta proximal promoter contains both TATA box and initiator element (Inr) and is GC-rich with a GC content of 65%. An Alu repeat sequence containing an ER-dependent transcription enhancer exists between -1416 and -1703. The full-length 5'-flanking sequence of ERbeta fused to a luciferase reporter exhibited functional promoter activity in ERbeta-positive TSUPr1 cell, but not in ERbeta-negative DU145 cells. In addition, DNase I protection assays of the proximal promoter showed unique protection patterns with nuclear extracts from TSUPr1 cells and ERbeta negative HeLa cells, suggesting presence of cell-specific trans-acting factors that mediate tissue/cell-specific ERbeta expression. Serial deletion analysis revealed that a 293-bp region encompassing the TATA box and Inr element possesses basal promoter activity.

Sustained-release butorphanol microparticles

Various butorphanol-loaded microparticles have been prepared with a biodegradable copolymer P(FAD-SA) of erucic acid dimer (FAD) and sebacic acid (SA) and a copolymer P(CPP-SA) of carboxyphenoxypropane (CPP) and SA using a melt compounding and milling method. Drug release was measured in vitro following incubation of drug-loaded microparticles in water for injection at 37 degrees C. It was found that butorphanol was released in a sustained manner, yielding a cumulative drug release of about 100% over a period of 48 hr. Also, drug release was affected by drug loading and the size of the microparticles; however, it was not significantly influenced by the copolymer composition. Scanning electron microscopic (SEM) results showed that most of the particles were irregular in shape with uneven surfaces. The molecular weights of the copolymers were not changed after this fabrication process. In addition, 20% butorphanol-encapsulated microspheres were prepared with copolymer P(FAD-SA) by spray-drying. The SEM micrograph shows that the particle sizes of the microspheres ranged from 2 to 10 microns, and the external surfaces appear smooth. Moreover, rapid drug release was observed for these microspheres, with more than 92% of the encapsulated drug released within the first 2 hr.

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.

[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.

Identification of a yellow impurity in aged samples of aqueous butamben suspension: evidence for the oxidative degradation of poly(ethylene glycol)

Butamben (butyl p-aminobenzoate) has been formulated to provide long-acting treatment for chronic pain. The suspension, which contains poly(ethylene glycol) and polysorbate 80, was found to yellow under ambient conditions if not adequately protected from oxygen. The impurity responsible for the color was isolated and identified on the basis of nuclear magnetic resonance spectroscopy and mass spectrometry. The compound is an oxalamidine, which is formally the condensation product of oxalic acid with four equivalents of butamben, and may be formed by the reaction of butamben with an oxidation product of poly(ethylene glycol).

A single nucleotide polymorphism in the E-cadherin gene promoter alters transcriptional activities

E-cadherin plays a critical role in many aspects of cell adhesion, epithelial development, and the establishment and maintenance of epithelial polarity. The loss of the adhesive function of E-cadherin is a critical step in the promotion of epithelial cells to a more malignant phenotype. We identified a C/A single nucleotide polymorphism at -160 from the transcriptional start site of the E-cadherin gene promoter. Transient transfection experiments showed that the A allele of this polymorphism decreased the transcriptional efficiency by 68% compared with the C allele (P<0.001). Electrophoretic mobility shift and footprinting assays revealed that the C allele had a stronger transcriptional factor binding strength than the A allele. These results indicate that the -160 C/A polymorphism has a direct effect on E-cadherin gene transcriptional regulation. This allelic variation may be a potential genetic marker that can help identify those individuals at higher risk for invasive/metastatic diseases.

Frequent methylation of estrogen receptor in prostate cancer: correlation with tumor progression

Prior studies have shown that the estrogen receptor (ER) gene is down-regulated in prostate cancer, but the mechanism of its inactivation is not known. We hypothesize that inactivation of the ER gene in prostate cancer is through promoter methylation. To test this hypothesis, we investigated the methylation status of the ER gene in prostate cancer cell lines, prostate cancer, and benign prostatic hyperplasia (BPH) tissues samples using the bisulfite genomic sequencing method. Our results show that the ER gene promoter was methylated in 100% (six of six) of the prostate cancer cell lines tested and all were accompanied by loss of ER mRNA expression. Treatment of these cell lines with demethylating agent 5-aza-2'-deoxycytidine restored ER mRNA expression in all of the ER-negative cell lines. In addition, elevated expression of DNA methyltransferase mRNA was found in all of the prostate cancer cell lines. Of the prostate tissue samples analyzed, 60% (6 of 10) in the BPH samples, 80% (8 of 10) in the low-grade cancer samples (grades I and II), and 95% (20 of 21) in the high-grade cancer samples (grades III-V) exhibited promoter methylation of the ER gene. The overall methylation levels in the cancer samples were higher than that in the BPH samples. The differences between the high-grade cancer samples and BPH samples were significant at all CpG sites. Only at three CpG sites were the differences significant between the low-grade cancer samples and BPH samples. This study presents the first evidence that ER gene is transcriptionally inactivated by DNA methylation in prostate cancer. Our data suggest that ER may be involved in the pathogenesis of prostate cancer, as well as BPH.

[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.

[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.

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.

[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.

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.

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.

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.

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.