Real-time monitoring of intracellular mRNA hybridization inside single living cells

A molecular beacon, an oligonucleotide probe with inherent signal transduction mechanisms, is an optimal tool for visualizing real-time mRNA hybridization in single living cells. Each molecular beacon (MB) consists of a single-stranded DNA molecule in a stem-loop conformation with a fluorophore linked to the 5' end and a quencher at the 3' end. In this study, we demonstrate real-time monitoring of mRNA-DNA hybridization inside living cells using molecular beacons. A MB specific for beta-actin mRNA has been designed and synthesized. After microinjection into the cytoplasm of single living kangaroo rat kidney cells (PtK2 cells), the MB hybridizes with beta-actin mRNA as shown by fluorescence measurements over time. Hybridization dynamics have been followed. Strict control experiments have been carried out to confirm that the fluorescence signal increase is indeed due to the hybridization of mRNA inside single living cells. Variation in the MB/mRNA hybridization fluorescent signal has been observed for different PtK2 cells, which indicates the amount of mRNA in different cells is different. We have also monitored the beta-1 andrenergic receptor mRNA inside the PtK2 cells. These studies demonstrate the feasibility of using MBs and the ultrasensitivity achieved in our fluorescence imaging system for real-time detection of mRNA hybridization and for the visualization of oligonucleotide/mRNA interactions inside single living cells.

[Detection of malondialdehyde-DNA adduct level by 32P-postlabeling assay in normal human esophageal epithelium and esophageal squamous cell carcinoma]

OBJECTIVE

To study whether the main malondialdehyde-DNA adduct (M1-dG) produced by lipid peroxidation is involved in the carcinogenesis of esophagus.

METHODS

DNA samples were isolated from normal esophageal epithelium (n = 32) obtained by biopsy and esophageal squamous cell carcinoma specimens (n = 30) obtained by surgery. All tissue samples came from individuals living in Linxian, Henan, a high-risk area of esophageal cancer. Contents of M1-dG adducts were detected by 32P-postlabeling method.

RESULTS

M1-dG adducts were detectable both in the normal and cancerous tissue samples. However, normal esophageal epithelial tissues exhibited significantly lower levels of M1-dG adducts (median 3.4, range 1.7/10(8)-55.4/10(8) nucleotides) than those found in esophageal cancer tissues (median 14.1, range 1.4/10(8)-59.0/10(8) nucleotides, P < 0.0001). The adduct levels were neither associated with gender, age, tobacco smoking status or genetic polymorphism in the CYP2E1, an enzyme participating in the oxidation of ethanol to form reactive free radicals.

CONCLUSIONS

Our findings provide evidence that DNA damage, resulted from lipid peroxidation, can accumulate in the normal human esophageal tissue and reach relatively high level in cancer tissue which suggests that M1-dG adducts may be involved in the initiation and progression of cancer with its mutagenic and carcinogenic effects.

Conjugation of biomolecules with luminophore-doped silica nanoparticles for photostable biomarkers

A new molecular conjugation method has been developed to label biomolecules with optically stable metalorganic luminophores, such as tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), which are otherwise not possible for direct linking with the biomolecules. Unique biochemical properties of the biomolecule can, thus, be associated with photostable luminophores. This opens a general way to conjugate desired biomolecules using a sensitive signal transduction method. It also promotes the application of excellent luminescent materials, especially those based on photostable metalorganic luminophores, in biochemical analysis and biomolecular interaction studies. The conjugation method is based on uniform luminophore-doped silica (LDS) nanoparticles (63 +/- 4 nm). These nanoparticles have been prepared using a water-in-oil (W/O) microemulsion method. The controlled hydrolysis of tetraethyl orthosilicate (TEOS) in W/O microemulsion leads to the formation of monodisperse LDS nanoparticles. The luminophores are doped inside the nanoparticles, and the particle's silica surfaces can be used to covalently bind with biomolecules. The luminophores are well-protected from the environmental oxygen when they are doped inside the silica network. As an example, we used an antibody for leukemia cell recognition. The antibody was first immobilized onto the luminophore-doped nanoparticle through silica chemistry and then was used for leukemia cell identification by an optical microscopy imaging technique. The leukemia cells were identified easily, clearly, and with high efficiency using these antibody-coated nanoparticles. The advantages of using small, uniform luminophore-doped nanoparticles are discussed.

Conjugation of biomolecules with luminophore-doped silica nanoparticles for photostable biomarkers

A new molecular conjugation method has been developed to label biomolecules with optically stable metalorganic luminophores, such as tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), which are otherwise not possible for direct linking with the biomolecules. Unique biochemical properties of the biomolecule can, thus, be associated with photostable luminophores. This opens a general way to conjugate desired biomolecules using a sensitive signal transduction method. It also promotes the application of excellent luminescent materials, especially those based on photostable metalorganic luminophores, in biochemical analysis and biomolecular interaction studies. The conjugation method is based on uniform luminophore-doped silica (LDS) nanoparticles (63 +/- 4 nm). These nanoparticles have been prepared using a water-in-oil (W/O) microemulsion method. The controlled hydrolysis of tetraethyl orthosilicate (TEOS) in W/O microemulsion leads to the formation of monodisperse LDS nanoparticles. The luminophores are doped inside the nanoparticles, and the particle's silica surfaces can be used to covalently bind with biomolecules. The luminophores are well-protected from the environmental oxygen when they are doped inside the silica network. As an example, we used an antibody for leukemia cell recognition. The antibody was first immobilized onto the luminophore-doped nanoparticle through silica chemistry and then was used for leukemia cell identification by an optical microscopy imaging technique. The leukemia cells were identified easily, clearly, and with high efficiency using these antibody-coated nanoparticles. The advantages of using small, uniform luminophore-doped nanoparticles are discussed.

Ultrasensitive optical DNA biosensor based on surface immobilization of molecular beacon by a bridge structure

A novel biotinylated molecular beacon (MB) probe was developed to prepare a DNA biosensor using a bridge structure. MB was biotinylated at the quencher side of the stem and linked on a biotinylated glass cover slip through streptavidin, which acted as a bridge between MB and glass matrix. An efficient fluorescence microscope system was constructed to detect the fluorescence change caused by the conformation change of MB in the presence of complementary DNA target. The proposed biosensor was used to directly detect, in real-time, the target DNA molecules. The bridge immobilization method caused the proposed DNA biosensor to have a faster and more stable response. Under the optimal conditions, the newly developed DNA biosensor showed a linear response toward ssDNA in the range of 5-100 nM with a detection limit of 2 nM. It was interesting to note that the described biosensor was reproducible after being regenerated by urea.

Antiangiogenic potential of 10-hydroxycamptothecin

To investigate the antiangiogenic potential of 10-hydroxycamptothecin (HCPT), the proliferation of human microvascular endothelial cells (HMEC) and seven human tumor cell lines were detected by SRB assay, and the endothelial cell migration and tube formation were assessed using two in vitro model systems. Also, inhibition of angiogenesis was determined with a modification of the chick embryo chorioallantoic membrane (CAM) assay in vivo. Morphological assessment of apoptosis was performed by fluorescence microscope. HCPT 0.313-5 micromol x L(-1) treatment resulted in a dose-dependent inhibition of proliferation, migration and tube formation in HMEC cells, and HCPT 6.25-25 nmol x egg(-1) inhibited angiogenesis in CAM assay. HCPT 1.25-5 micromol x L(-1) elicited typical morphological changes of apoptosis including condensed chromatin, nuclear fragmentation, and reduction in volume in HMEC cells. HCPT significantly inhibited angiogenesis both in vitro and in vivo at relatively low concentrations, and this effect was related with induction of apoptosis in HMEC cells. These results taken collectively suggest that HCPT may be a potent antiangiogenetic and cytotoxic drug and further investigation is warranted.

Relationship between dopamine-stimulated phospholipid methylation and the single-carbon folate pathway

In a previous study we demonstrated the ability of dopamine (DA) to stimulate phospholipid methylation (PLM) via a novel mechanism involving the D4 dopamine receptor (D4R) in which single-carbon folates appeared to be the primary source of methyl groups. To further understand the relationship between D4R-mediated PLM and folate metabolism, we examined the effect of several folate pathway interventions on the level of basal and DA-stimulated incorporation of [14C]-labeled formate into phospholipids in cultured SH-SY5Y neuroblastoma cells. These interventions included: (i) Overexpression of methenyltetrahydrofolate synthetase (MTHFS). (ii) Treatment with 5-formylTHF. (iii) Treatment with the MTHFS inhibitor 5-formyltetrahydrohomofolic acid (5-formylTHHF). (iv) Growth in nucleoside-free media. 31P-NMR was also used to follow DA-induced changes in cell phospholipid composition. MTHFS overexpression and 5-formylTHHF treatment, both of which lower 5-methylTHF levels, each reduced basal PLM and its stimulation by DA. In contrast, 5-formylTHF, which increases 5-methylTHF, caused a dose-dependent increase in both basal and DA-stimulated PLM. Growth in nucleoside-free media caused time-dependent changes in PLM, which were due to the absence of purine nucleosides. While basal PLM was maintained at a reduced level, DA-stimulated PLM was initially increased followed by a later decrease. Together, these findings indicate a close functional relationship between single-carbon folate metabolism and DA-stimulated PLM, consistent with a role for 5-methylTHF as the methyl donor for the D4R-mediated process.

Biochemically functionalized silica nanoparticles

In this report, we demonstrate the biochemical modification of silica based nanoparticles. Both pure and dye-doped silica nanoparticles were prepared, and their surfaces were modified with enzymes and biocompatible chemical reagents that allow them to function as biosensors and biomarkers. The nanoparticles produced in this work are uniform in size with a 1.6% relative standard deviation. They have a pure silica surface and can thus be modified easily with many biomolecules for added biochemical functionality. Specifically, we have modified the nanoparticle surfaces with enzyme molecules (glutamate dehydrogenase (GDH) and lactate dehydrogenase (LDH)) and a biocompatible reagent for cell membrane staining. Experimental results show that the silica nanoparticles are a good biocompatible solid support for enzyme immobilization. The immobilized enzyme molecules on the nanoparticle surface have shown excellent enzymatic activity in their respective enzymatic reactions. The nanoparticle surface biochemical functionalization demonstrates the feasibility of using nanoparticles for biosensing and biomarking applications.

Localized exocytosis detected by spatially resolved amperometry in single pancreatic beta-cells

Spatially resolved measurements of exocytosis in pancreatic beta-cells were made using amperometry with 1-microm radius electrodes. These measurements revealed that certain portions of a cell actively undergo exocytosis following stimulation with depolarizing agents, but other regions are inactive. The amperometric measurements were compared to measurements made with the membrane indicator dye, FM1-43, which showed uneven increases in fluorescence around the surface of the cell, with amperometric secretion being detected only at the brightest regions. In some instances, a large number of exocytotic events were detected from one electrode position. The number of events was larger than what would be expected based on the number of vesicles that could fit under an electrode of the dimensions used. These results suggest a mechanism of vesicle traffic that allows multiple fusions at a small membrane area.

Ser326Cys polymorphism in hOGG1 gene and risk of esophageal cancer in a Chinese population

Ser326Cys polymorphism in the hOGG1 gene, which is involved in the repair of 8-hydroxyguanine in oxidatively damaged DNA, has been identified and the variant genotype appears to be related to susceptibility to certain cancers. We investigated the association between Ser326Cys polymorphism and squamous-cell carcinoma of the esophagus among a Chinese population. hOGG1 gene polymorphism was detected by PCR-based single-strand conformation polymorphism and DNA sequencing among 201 normal controls and 196 patients with esophageal cancer from Linxian, China, a high-risk area for the disease. The association between this genetic polymorphism and risk of the cancer was examined by a multivariate analysis. We found that the distribution of hOGG1 Ser326Cys genotypes among controls (Ser/Ser, 33.8%; Ser/Cys, 52.8%; and Cys/Cys, 13.4%) was significantly different from that among esophageal cancer cases (39.8%, 38.8% and 21.4%, respectively) (p < 0.05). Homozygosity for the Cys/Cys genotype significantly increased the risk of developing esophageal squamous-cell carcinoma, with the odds ratio (OR) adjusted for age, sex and smoking being 1.9 (95% confidence interval [CI] = 1.3-2.6). Although smoking alone also significantly increased esophageal cancer risk in this case-control study (adjusted OR = 2.6; 95% CI = 1.7-3.9), no significant interaction between smoking and the Cys/Cys genotype was observed in terms of risk. Our results suggest that the hOGG1 326Cys allele might play a role in the carcinogenesis of the esophagus.

Ser326Cys polymorphism in hOGG1 gene and risk of esophageal cancer in a Chinese population

Ser326Cys polymorphism in the hOGG1 gene, which is involved in the repair of 8-hydroxyguanine in oxidatively damaged DNA, has been identified and the variant genotype appears to be related to susceptibility to certain cancers. We investigated the association between Ser326Cys polymorphism and squamous-cell carcinoma of the esophagus among a Chinese population. hOGG1 gene polymorphism was detected by PCR-based single-strand conformation polymorphism and DNA sequencing among 201 normal controls and 196 patients with esophageal cancer from Linxian, China, a high-risk area for the disease. The association between this genetic polymorphism and risk of the cancer was examined by a multivariate analysis. We found that the distribution of hOGG1 Ser326Cys genotypes among controls (Ser/Ser, 33.8%; Ser/Cys, 52.8%; and Cys/Cys, 13.4%) was significantly different from that among esophageal cancer cases (39.8%, 38.8% and 21.4%, respectively) (p < 0.05). Homozygosity for the Cys/Cys genotype significantly increased the risk of developing esophageal squamous-cell carcinoma, with the odds ratio (OR) adjusted for age, sex and smoking being 1.9 (95% confidence interval [CI] = 1.3-2.6). Although smoking alone also significantly increased esophageal cancer risk in this case-control study (adjusted OR = 2.6; 95% CI = 1.7-3.9), no significant interaction between smoking and the Cys/Cys genotype was observed in terms of risk. Our results suggest that the hOGG1 326Cys allele might play a role in the carcinogenesis of the esophagus.

Methylenetetrahydrofolate reductase polymorphisms increase risk of esophageal squamous cell carcinoma in a Chinese population

Methylenetetrahydrofolate reductase (MTHFR) plays a central role in folate metabolism that affects DNA methylation and synthesis. Because germ-line mutations at nucleotides 677 (C-->T) and 1298 (A-->C) in the MTHFR gene cause diminished enzyme activity, and aberrant DNA methylation is oncogenic, we examined the relationship between these two MTHFR polymorphisms and susceptibility to esophageal squamous cell carcinoma (ESCC) in 240 ESCC cases and 360 age- and sex-matched controls in northern CHINA: We found that the allele frequency of MTHFR 677T was significantly higher among cases than among controls (63% versus 41%, P < 0.001). Subjects with the 677TT genotype had a more than 6-fold increased risk of developing ESCC [adjusted odds ratio (OR), 6.18; 95% confidence interval (CI), 3.32-11.51] compared with those who had the 677CC genotype. Furthermore, the elevated ESCC risk associated with the 677 polymorphism was in an allele-dose relationship (trend test, P = 0.0001) with ORs of 1.00, 3.14 (95% CI, 1.94-5.08), and 6.18 (95% CI, 3.32-11.51) for the CC, CT, and TT genotype, respectively, after adjustment for age, sex, smoking status, and the MTHFR 1298 polymorphism. The allele frequency for the MTHFR 1298C was 14% among cases and 17% among controls. The 1298CC genotype was extremely rare in both controls (1.4%) and cases (2.9%) and was also associated with an elevated risk of ESCC (adjusted OR, 4.43; 95% CI, 1.23-16.02) compared with the 1298AA genotype, whereas the 1298AC genotype had no effect on the risk of ESCC. Thus, our findings support the hypothesis that genetic polymorphisms in the MTHFR gene may contribute to susceptibility to carcinogenesis of the esophagus in the at-risk Chinese population.

Frequency of CYP2A6 gene deletion and its relation to risk of lung and esophageal cancer in the Chinese population

Cytochrome P450 2A6 (CYP2A6) plays an important role in the oxidation of nicotine and in the activation of tobacco-related carcinogens, such as N-nitrosodimethylamine, N-nitrosodiethylamine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. It has been suggested that individuals with defective CYP2A6 alleles are at a lower risk of becoming smokers and of developing lung and other tobacco-related cancers. We examined the relationship between the CYP2A6 gene deletion and susceptibility to lung and esophageal cancer in a Chinese population via a hospital-based case-control study. The CYP2A6 gene deletion was determined by a PCR-based approach in 326 healthy controls, 149 patients with esophageal squamous-cell carcinoma and 151 patients with lung cancer. The allele frequency of the CYP2A6*4 deletion was 8.6% among controls compared with 8.4% among cases with esophageal squamous-cell carcinoma (p = 0.29) or 13.2% among cases with lung cancer (p < 0.01). Individuals who harbored at least one CYP2A6*4 deletion allele were at a 2-fold increased risk of developing lung cancer (95% confidence interval [CI] = 1.2-3.2) compared with those without a defective CYP2A6 allele. This effect was mainly limited to squamous-cell carcinoma and to non-smokers, although a joint effect of CYP2A6 deletion and tobacco smoking on lung cancer risk was observed among heavy smokers. The overall risk of esophageal cancer did not appear to be associated with this CYP2A6 genetic polymorphism (odds ratio [OR] = 1.2, 95% CI = 0.7-2.1). However, stratified analysis suggested an excess risk with borderline significance (OR = 2.1; 95% CI = 1.0-4.5) related to the CYP2A6*4 allele among non-smokers. The distribution of CYP2A6 genotype frequency was not significantly different (p = 0.40) between smokers (n = 174) and non-smokers (n = 152) in this study population. Our results demonstrate that the CYP2A6 gene deletion is associated with an increased risk of lung and esophageal cancer but not with a reduced tendency to smoke.

Development of novel dye-doped silica nanoparticles for biomarker application

We report the development of novel luminescent nanoparticles composed of inorganic luminescent dye, Tris(2,2'-bipyridyl) dichlororuthenium (II) hexahydrate, doped inside a silica network. These dye doped silica (DDS) nanoparticles have been synthesized using a water-in-oil microemulsion technique in which controlled hydrolysis of the tetraethyl orthosilicate leads to the formation of monodispersed nanoparticles. They are prepared with a variety of sizes: small (5+/-1 nm), medium (63+/-4 nm), and large (400+/-10 nm), which shows the efficiency of the microemulsion technique for the synthesis of uniform nanoparticles. All these nanoparticles are suitable for biomarker application since they are much smaller than cellular dimension. These nanoparticles are highly photostable in comparison to most commonly used organic dyes. These nanoparticles have been characterized by various microscopic and spectroscopic techniques. The amount of dye content in these nanoparticles has been optimized to eliminate self-quenching. It has been observed that maximum luminescence intensity is achieved when the dye content is around 20 wt%. Silica surface of DDS nanoparticles is available for surface modification and bioconjunction. For demonstration as a biomarker, the DDS nanoparticle's surface has been biochemically modified to attach membrane-anchoring groups and applied successfully to stain human leukemia cells.

Evaluation of nanostructured composite collagen--chitosan matrices for tissue engineering

The development of suitable three-dimensional matrices for the maintenance of cellular viability and differentiation is critical for applications in tissue engineering and cell biology. The structure and composition of the extracellular matrix (ECM) has been shown to modulate cell behavior with respect to shape, movement, proliferation, and differentiation. Although collagen and chitosan have separately been proposed as in vitro ECM materials, the influence of chitosan--collagen composite matrices on cell morphology, differentiation, and function is not well studied. To this end, gel matrices of different proportions of collagen and chitosan were examined ultrastructurally and characterized for their ability to regulate cellular activity. A three-chamber system with circulating hydraulic fluids was used to evaluate the gel stability under fluid force. Results indicated that overall matrix integrity increased with the proportion of chitosan. Scanning electron microscopy indicated that the addition of chitosan greatly influences ultrastructure and changes collagen fiber cross-linking, reinforcing the structure and increasing pore size. K562 cells cultured in three-dimensional gels were examined for cell proliferation and differentiation. Although cell proliferation was inhibited with an increasing proportion of chitosan, cell function based on cytokine-release was greatly augmented. Results suggest that a hybrid chitosan--collagen matrix may have potential biological and mechanical benefits for use as a cellular scaffold.

Frequency of CYP2A6 gene deletion and its relation to risk of lung and esophageal cancer in the Chinese population

Cytochrome P450 2A6 (CYP2A6) plays an important role in the oxidation of nicotine and in the activation of tobacco-related carcinogens, such as N-nitrosodimethylamine, N-nitrosodiethylamine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. It has been suggested that individuals with defective CYP2A6 alleles are at a lower risk of becoming smokers and of developing lung and other tobacco-related cancers. We examined the relationship between the CYP2A6 gene deletion and susceptibility to lung and esophageal cancer in a Chinese population via a hospital-based case-control study. The CYP2A6 gene deletion was determined by a PCR-based approach in 326 healthy controls, 149 patients with esophageal squamous-cell carcinoma and 151 patients with lung cancer. The allele frequency of the CYP2A6*4 deletion was 8.6% among controls compared with 8.4% among cases with esophageal squamous-cell carcinoma (p = 0.29) or 13.2% among cases with lung cancer (p < 0.01). Individuals who harbored at least one CYP2A6*4 deletion allele were at a 2-fold increased risk of developing lung cancer (95% confidence interval [CI] = 1.2-3.2) compared with those without a defective CYP2A6 allele. This effect was mainly limited to squamous-cell carcinoma and to non-smokers, although a joint effect of CYP2A6 deletion and tobacco smoking on lung cancer risk was observed among heavy smokers. The overall risk of esophageal cancer did not appear to be associated with this CYP2A6 genetic polymorphism (odds ratio [OR] = 1.2, 95% CI = 0.7-2.1). However, stratified analysis suggested an excess risk with borderline significance (OR = 2.1; 95% CI = 1.0-4.5) related to the CYP2A6*4 allele among non-smokers. The distribution of CYP2A6 genotype frequency was not significantly different (p = 0.40) between smokers (n = 174) and non-smokers (n = 152) in this study population. Our results demonstrate that the CYP2A6 gene deletion is associated with an increased risk of lung and esophageal cancer but not with a reduced tendency to smoke.

A facile synthetic approach to prenylated flavanones: first total syntheses of (+/-)-bonannione A and (+/-)-sophoraflavanone A

A facile and efficient approach for the syntheses of both C-8 and C-6 prenylated flavonoids has been developed that features a highly regioselective prenylation of 2,4,6-trihydroxyacetophenone and regioselective cyclization of prenylated polyhydroxy chalcones. Thus, the first efficient total syntheses of (+/-)-sophoraflavanone A (1) and (+/-)-bonannione A (2), two naturally occurring geranylated flavanones with antibacterial activities, have been achieved starting from the key intermediate 3 via regioselective cyclization of geranylated tetrahydroxychalcone 4.

Atomic force microscopy for the characterization of immobilized enzyme molecules on biosensor surfaces

The development of biosensors has been one of the key areas in biotechnology and biomedical studies. Often it is difficult to investigate the immobilized biomolecules on the surfaces for biosensor optimization. Atomic force microscopy (AFM) should provide an ideal means for the visualization of biosensor surface and for the investigation of biomolecule activities. Therefore, AFM has been employed to study the surface topography of immobilized glutamate dehydrogenase (GDH) on two-dimensional glutamate biosensor surfaces. Correlation between the surface topography and the activity of the biosensor was investigated. Surface analysis has revealed that the enzymatic activity of the immobilized GDH molecules on the biosensor surface is linked to surface roughness, as measured by the peak-to-valley distance. Fractal dimension of the immobilization sensor surface was found to be a good parameter for judging the quality of the immobilized biosensors. As enzyme immobilization time increases, the biosensor has its maximum activity with around 18 h of immobilization in 10(-6) M GDH solution. Various biosensors prepared under different experimental conditions have been studied by AFM. This technique is shown to be an effective tool to characterize biosensor surfaces.

CYP 1A1 polymorphism and risk of lung cancer in relation to tobacco smoking: a case-control study in China

The impact of genetic polymorphisms in CYP1A1 on susceptibility to lung cancer has received particular interest in recent years since this enzyme plays a central role in activation of major classes of tobacco carcinogens. Several polymorphisms in the CYP1A1 locus have been identified and their genotypes appear to exhibit population frequencies that depend on ethnicity. We have assessed the role of CYP1A1 genotype in lung cancer risk in the Chinese population via a case-control study. Three polymorphisms, m1 (MSP:I), m2 (exon 7 Ile-->Val) and m4 (exon 7 Thr-->Asn), were determined by PCR-RFLP in 404 controls and 217 lung cancer cases. While no polymorphic alleles were detectable in the m4 site among our study subjects, the allele frequencies for CYP1A1 m1 and CYP1A1 m2 were found to be 35.6 and 25.6% among controls, compared with 42.6 and 34.2% among cases. Multivariate analysis showed an elevated risk for lung cancer in subjects having at least one m1 allele [odds ratio (OR) = 2.0, 95% confidence interval (CI) = 1.4-2.8] or having at least one m2 allele (OR = 1.9, 95% CI = 1.3-2.7). However, this increased risk was limited to squamous cell carcinoma (SCC), but not adenocarcinoma or other histological types of lung cancer. Stratified analysis indicated a multiplicative interaction between tobacco smoking and variant CYP1A1 m1 genotypes on the risk of SCC. The ORs of SCC for the variant CYP1A1 m1 genotype, tobacco smoking and both factors combined were 2.8, 9.1 and 29.9, respectively. When the data was stratified by the pack-year values, this joint effect was consistent and stronger among the heaviest smokers. The interaction between tobacco smoking and the variant CYP1A1 m2 genotypes followed the same pattern. Our findings support the conclusion that CYP1A1 m1 and CYP1A1 m2 polymorphisms are associated with smoking-related lung cancer risk in Chinese.

[Genetic polymorphism in hOGG1 and susceptibility to esophageal cancer in Chinese]

OBJECTIVE

To examine the association between Ser326Cys polymorphism in hOGG1 gene, which is involved in the repair of 8-hydroxyguanine in damaged DNA, and investigate the risk of squamous cell carcinoma of the esophagus in Chinese.

METHODS

Ser326Cys polymorphism in hOGG1 gene was determined by PCR-SSCP approach among 201 normal controls and 196 patients with squamous cell carcinoma of the esophagus. The association between this genetic polymorphism and the risk of the cancer was examined by a multivariate analysis.

RESULTS

The Cys/Cys genotype of hOGG1 was found in 21.4% of patients with the cancer and in 13.4% of controls (P<0.05). Homozygosity for the Cys/Cys genotype significantly increased the risk of developing esophageal cancer, with the odds ratio adjusted for age, sex and smoking being 1.9(95% CI 1.3-2.6). Smoking also significantly increased esophageal cancer risk in this case-control study (adjusted OR 2.6; 95% CI 1.7- 3.9). No interaction between smoking and Cys/Cys genotype was observed for the risk of esophageal cancer.

CONCLUSION

Polymorphism of hOGG1 Ser326Cys may play a role in esophageal carcinogenesis.

The mRNA export in Caenorhabditis elegans is mediated by Ce-NXF-1, an ortholog of human TAP/NXF and Saccharomyces cerevisiae Mex67p

Human TAP and Saccharomyces cerevisiae Mex67p belong to a family of proteins that mediate mRNA export. Computer searches identified previously two Caenorhabditis elegans genes, C15H11.3 and C115H11.6, that encode putative homologs of hTAP and Mex67p (Segref et al., EMBO J, 1997, 16:3256-3271). Using RNA interference experiments in C. elegans, we found that functional knockout of C15H11.3 resulted in nuclear accumulation of poly(A)-containing RNAs and was lethal for both embryos and adult nematodes. No embryonic or progeny abnormality was observed in functional knockout of C15H11.6. Taken together, these data established that the C15H11.3 gene product is an ortholog of hTAP and Mex67p; thus, it was named Ce-NXF-1. Ce-NXF-1 binds RNA directly and is a nucleocytoplasmic shuttle protein accumulating in the nucleoplasm and at the nuclear rim. The rim association is mediated via unique signals present in the C-terminal portion of all TAP/NXF and Mex67p proteins. This region was shown to interact with the FG-repeat domains of nucleoporins Nup98, Nup153, and Nup214, indicating that the rim association occurs through components of the nuclear pore complex. In summary, Ce-NXF-1 belongs together with hTAP and Mex67p to a family of proteins that participate in mRNA export and can provide a direct molecular link between mRNAs and components of the nuclear pore complex. Therefore, despite differences in mRNA metabolism between these species, they utilize a conserved mRNA transport mechanism.

Human CYP1B1 Leu432Val gene polymorphism: ethnic distribution in African-Americans, Caucasians and Chinese; oestradiol hydroxylase activity; and distribution in prostate cancer cases and controls

Cytochrome P4501B1 (CYP1B1) is involved in the activation of many carcinogens and in the metabolism of steroid hormones, including 17beta-oestradiol (E2) and testosterone. We report a significant difference in the allele frequencies of two point mutations in the coding region of the CYP1B1 gene among Caucasian (n = 189), African-American (n = 52) and Chinese (Linxian) (n = 109) populations. A (C to G) transversion at position 1666 in exon 3, which results in an amino acid substitution of Leu432 to Val, was present in African-Americans with an allele frequency for Va1432 of 0.75, in Caucasians of 0.43, and in Chinese of 0.17. A (C to T) transition at position 1719 in exon 3, with no amino acid change (Asp449), appeared to be closely linked with the Val432 variant. Results using human lung microsomal preparations from individuals with the CYP1B1Val/Val and CYP1B1Leu/Leu genotypes indicate that Val432 variant may be a high activity allele and thus may contribute to the interindividual differences in CYP1B1 activity. Because CYP1B1 is involved in hormone and carcinogen metabolism, and given the disparate rates of prostate cancer among ethnic groups, we also evaluated the association of the CYP1B1 Leu432Val polymorphism with prostate cancer risk in a pilot case-control study. Among Caucasians, 34% of men with cancer (n = 50) were homozygous for the Val432 polymorphism, while only 12% of matched control subjects (n = 50) had this genotype. These preliminary data indicate that genetic polymorphisms in CYP1B1 might play an important role in human prostate carcinogenesis.

Influence of the thermal effect on the TEM00 mode output power of a laser-diode side-pumped solid-state laser

A fraction of pump power has been converted to TEM00 mode laser power for a side-pumped solid-state laser by use of a space-dependent rate equation. We investigated the pump-to-mode (TEM00) ratio when scaling laser-diode side-pumped solid-state lasers to high-power levels by including the thermal effect in the space-dependent rate equation. Based on the assumption that Gaussian pump power is the same at any cross section of a laser rod, we resolved the output power with a space-dependent rate equation; temperature distribution in the laser rod was obtained; the optical path difference distribution was derived, and we estimated the diffraction losses that result from thermally induced spherical aberration by use of the Strehl intensity ratio. We determined that thermally induced diffraction losses are strongly dependent on pump power and on the pump-to-mode ratio.

Influence of FL on ex vivo expansion of hematopoietic cells from cord blood in long-term liquid cultures

The use of umbilical cord blood for stem cell transplantation has numerous advantages, but a major deficiency is the rather low cell number available. Therefore, ex vivo expansion were proposed to overcome this limitation. In this paper the effects of flt-3 ligand (FL), stem cell factor (SCF), interleukin(IL)-3, IL-6, granulocyte colony-stimulating factor (G-CSF) and granulocyte- monocyte colony-stimulating factor (GM-CSF) on long-term ex vivo expansion and differentiation of cord blood hematopoietic cells were investigated. In the culture containing FL + SCF + G-CSF + GM-CSF, the total cell expansion ratio reached the maximum (385.30 +/- 163.51-fold) at 28 days, whereas in the culture with FL + SCF + IL-3 + IL-6, CFU-GMs expansion ratio reached a plateau (409.52 +/- 189.50-fold) at 28 days. FL synergized with SCF and other cytokines. In all the conditions investigated, cultures with FL obtained an increase of fold expansion in both total cells and CFU-GMs. The combination of FL + SCF does not benefit the proliferation of the total cells, however, the expansion of CFU-GM was kept at a high level. Apparently, both cytokines maintained the activities of stem/progenitor cells and hampered differentiation. In the presence of G-CSF and GM-CSF, total cells enhanced quickly, and had the most expansion of total cells in comparison with other combinations. However, CFU-GM output peaked at 18 days and subsequently dropped to 0 promptly, suggesting that G-CSF and GM-CSF inspired differentiation.

Natural animal coloration can Be determined by a nonfluorescent green fluorescent protein homolog

It is generally accepted that the colors displayed by living organisms are determined by low molecular weight pigments or chromoproteins that require a prosthetic group. The exception to this rule is green fluorescent protein (GFP) from Aequorea victoria that forms a fluorophore by self-catalyzed protein backbone modification. Here we found a naturally nonfluorescent homolog of GFP to determine strong purple coloration of tentacles in the sea anemone Anemonia sulcata. Under certain conditions, this novel chromoprotein produces a trace amount of red fluorescence (emission lambda(max) = 595 nm). The fluorescence demonstrates unique behavior: its intensity increases in the presence of green light but is inhibited by blue light. The quantum yield of fluorescence can be enhanced dramatically by single amino acid replacement, which probably restores the ancestral fluorescent state of the protein. Other fluorescent variants of the novel protein have emission peaks that are red-shifted up to 610 nm. They demonstrate that long wavelength fluorescence is attainable in GFP-like fluorescent proteins.

Molecular beacons for DNA biosensors with micrometer to submicrometer dimensions

Ultrasensitive molecular beacon (MB) DNA biosensors, with micrometer to submicrometer sizes, have been developed for DNA/RNA analysis. The fluorescence-based biosensors have been applied in DNA/ RNA detection without the need for a dye-labeled target molecule or an intercalation reagent in the testing solution. Molecular beacons are hairpin-shaped oligonucleotides that report the presence of specific nucleic acids. We have designed a surface-immobilizable biotinylated ssDNA molecular beacon for DNA hybridization at a liquid-solid interface. The MBs have been immobilized onto ultrasmall optical fiber probes through avidin-biotin binding. The MB DNA biosensor has been used directly to detect, in real time, its target DNA molecules without the need for a competitive assay. The biosensor is stable and reproducible. The MB DNA biosensor has selectivity with single base-pair mismatch identification capability. The concentration detection limits and mass detection limits are 0.3 nM and 15 amol for a 105-microm biosensor, and 10 nM and 0.27 amol for a submicrometer biosensor, respectively. We have also prepared molecular beacon DNA biosensor arrays for simultaneous analysis of multiple DNA sequences in the same solution. The newly developed DNA biosensors have been used for the precise quantification of a specific rat gamma-actin mRNA sequence amplified by the polymerase chain reaction.

Using molecular beacons to probe molecular interactions between lactate dehydrogenase and single-stranded DNA

The interactions between two key macromolecular species, nucleic acids and proteins, control many important biological processes. There have been limited effective methodologies to study these interactions in real time. In this work, we have applied a newly developed molecular beacon (MB) DNA probe for the analysis of an enzyme, lactate dehydrogenase (LDH), and for the investigation of its properties of binding with single-stranded DNA. Molecular beacons are single-stranded oligonucleotide probes designed to report the presence of specific complementary nucleic acids by fluorescence detection. The interaction between LDH and MB has resulted in a significant fluorescence signal enhancement, which is used for the elucidation of MB/LDH binding properties. The processes of binding between MB and different isoenzymes of LDH have been studied. The results show that the stoichiometry of LDH-5/MB binding is 1:1, and the binding constant is 1.9 x 10(-7) M(-1). We have also studied salt effects, binding sites, temperature effects, pH effects, and the binding specificities for different isoenzymes. Our results demonstrate that MB can be effectively used for sensitive protein quantitation and for efficient protein-DNA interaction studies. MB has a signal transduction mechanism built within the molecule and can thus be used for the development of rapid protein assays and for real-time measurements.

[Effects of IFN-alpha combined with IL-6 on cell growth and related genes expression and apoptosis of bone marrow cells from CGL patients]

OBJECTIVE

To investigate the effects of interferon-alpha (IFN-alpha) and IFN-alpha combined with interleukin-6 (IL-6) on cell growth and bcr/abl, bcl-2 and c-myc genes expression in the bone marrow mononuclear cells (MNC) from chronic granulocytic leukemia (CGL) patients.

METHODS

MNCs were cultured in liquid medium at the presence of IFN-alpha (200 U/ml) or IFN-alpha (200 U/ml) plus IL-6 (100 ng/ml). The viable cells were counted and the expression levels of beta-actin, bcr/abl, bcl-2 and c-myc genes were quantitatively detected by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

The cell growth was markedly inhibited by IFN-alpha, but the extent of the inhibition was slightly decreased when IFN-alpha combined with IL-6. The expression levels of bcr/abl and bcl-2 gene were reduced by IFN-alpha or IFN-alpha plus IL-6. The expression of c-myc gene was inhibited by IFN-alpha but promoted by IL-6.

CONCLUSIONS

Both IFN-alpha and IFN-alpha plus IL-6 can inhibit the expression of anti-apoptosis genes, and modulate the expression of c-myc. It is the possible mechanism of IFN-alpha therapy for CGL in chronic phase.

Using molecular beacons as a sensitive fluorescence assay for enzymatic cleavage of single-stranded DNA

Traditional methods to assay enzymatic cleavage of DNA are discontinuous and time consuming. In contrast, recently developed fluorescence methods are continuous and convenient. However, no fluorescence method has been developed for single-stranded DNA digestion. Here we introduce a novel method, based on molecular beacons, to assay single-stranded DNA cleavage by single strand-specific nucleases. A molecular beacon, a hairpin-shaped DNA probe labeled with a fluorophore and a quencher, is used as the substrate and enzymatic cleavage leads to fluorescence enhancement in the molecular beacon. This method permits real time detection of DNA cleavage and makes it easy to characterize the activity of DNA nucleases and to study the steady-state cleavage reaction kinetics. The excellent sensitivity, reproducibility and convenience will enable molecular beacons to be widely useful for the study of single-stranded DNA cleaving reactions.

Impact of genetic polymorphisms in cytochrome P450 2E1 and glutathione S-transferases M1, T1, and P1 on susceptibility to esophageal cancer among high-risk individuals in China

Esophageal cancer, which is prevalent in China, is believed to be induced by environmental carcinogens such as nitrosamines and other agents. The disproportionate geographical distribution of this cancer among individuals suggests a role for gene-environment interactions in developing the disease. We have shown in our preliminary study that a genetic polymorphism in cytochrome P450 2E1 (CYP2E1) that is known to activate nitrosamines may be a susceptibility factor involved in the early events leading to the development of esophageal cancer (Lin et al., Cancer Epidemiol. Biomark. Prev., 7: 1013-1018, 1998). This relatively larger study was conducted to compare the results with our previous findings. One hundred and fifty cases with esophageal cancer, 146 cases with esophageal dysplasia, and 150 normal controls were residents of Linxian, China, a high-risk area. Genomic DNA samples were assayed for restriction fragment length polymorphisms in the CYP2E1 and GSTP1 loci by PCR amplification followed by digestion with RsaI and Alw26I, respectively. Deletion of the GSTM1 and GSTT1 genes was detected by multiplex PCR. The distribution of CYP2E1 c1/c1 allele frequency was found to be significantly different between controls (44.0%) and cases with cancer (71.3%) or cases with dysplasia (70.6%; P < 0.0001). Individuals having the c1/c1 genotype were at a 3.1-fold [95% confidence interval (CI), 2.4-3.9] increased risk of developing dysplasia and a 3.2-fold (95% CI, 2.5-4.1) increased risk of developing squamous cell carcinoma of the esophagus. Although polymorphisms in the GSTT1 and GSTP1 were not significantly different between cases with cancer or cases with dysplasia and controls, the frequency of the GSTM1 non-null (+/+ and +/0) genotypes appeared to be overrepresented in cases with cancer compared with controls (odds ratio, 2.3; 95% CI, 1.8-3.0). Furthermore, a joint effect of the CYP2E1 c1/c1 genotype and GSTM1 non-null genotype on the cancer risk was observed, showing an odds ratio of 8.5 (95% CI, 3.7-19.9). These results demonstrate that CYP2E1 and perhaps GSTM1 are genetic determinants in the development of squamous cell carcinoma of the esophagus.

Herpes simplex viral and amplicon vector-mediated gene transfer into glia and neurons in organotypic spinal cord and dorsal root ganglion cultures

The progression of neurodegenerative diseases and secondary consequences of spinal cord injury may be diminished by introducing transgenes to glia, spinal neurons, and/or sensory neurons. Organotypic cultures of spinal cord slices and dorsal root ganglia proved to be an excellent system in which to compare the relative neurotropism of a replication-defective recombinant herpes simplex virus and herpes virus-derived amplicon vectors. Hundreds of beta-galactosidase-expressing cells, transduced by the viral vectors, were observed in spinal cord slices 3 and 8 days postinfection. Immunostaining to identify the infected cell type indicated that oligodendrocytes were permissive for viral vector transduction of beta-galactosidase in the spinal cord slice, whereas neurons were not. Heparan sulfate proteoglycan, the initial receptor for herpes contact with cells, was highly expressed in the white matter of the spinal cord slice, but was negligible in the gray matter. In contrast to the spinal cord, many fewer cells were infected in the dorsal root ganglia (DRG) by these vectors, but a majority of infected cells were identified as sensory neurons. Heparan sulfate proteoglycan expression was abundant in the sensory fibers emanating from the DRG and also surrounded each neuron within the ganglion. Our results demonstrate HSV-induced transgene expression that is amenable to ex vivo assessment of its physiological impact.

[Study on the effects of hyaluronic acid-streptomycin perfusion through the round window on the function and morphology in guinea pig inner ears]

To investigate the effects of the hyaluronic acid-streptomycin (HA-SM) perfusion through round window on the function and morphology of the inner ear in guinea pig, membrous labyrinth mapping, temporal bone section after celloidin embedding, transmission electron microscopy, electrocochlegraphy (ECochG) and electronystagmography (ENG) were examined. The nystagmus duration induced by caloric test was obviously reduced in comparison with that of the preoperation (P< 0.01), while the action potential(AP) by ECochG was not obviously changed. The sensory cells of estibular organs were severely damaged, while the morphology of corti's organs were significantly damaged after HA-SM perfusion. The results suggest that the HA-SM perfusion through the round window may selectively destroy the vestibular function, whereas the auditory function is not obviously damaged.

Molecular beacons: a novel DNA probe for nucleic acid and protein studies

A new concept has been introduced for molecular beacon DNA molecules. Molecular beacons are a new class of oligonucleotides that can report the presence of specific nucleic acids in both homogeneous solutions and at the liquid-solid interface. They emit an intense fluorescent signal only when hybridized to their target DNA or RNA molecules. Biotinylated molecular beacons have been designed and used for the development of ultrasensitive DNA sensors and for DNA molecular interaction studies at a solid-liquid interface. Molecular beacons have also been used to study protein-DNA interactions. They have provided a variety of exciting opportunities in DNA/RNA/protein studies.

Direct observation of single-molecule generation at a solid-liquid interface

Direct observation of single-molecule generation from a chemical reaction was achieved at a solid-liquid interface. The reaction between fluorescamine and immobilized N'-(3-trimethoxysilylpropyl)diethylenetriamine (DETA) was studied at the single-molecule level. Time-lapse fluorescence images of single-molecule products, excited by the evanescent field generated at a quartz-liquid interface, were recorded to follow the chemical reaction to its completion. The reactions were restricted to the approximately 1 nm thick layer nearest to the interface. Analysis of the photoelectron intensity of the fluorescent product of the reaction and its distribution shows that the reaction kinetics goes through a transition from zeroth-order to first-order as the reaction proceeds. This approach offered a novel means to study single-molecule reactions at the solid-liquid interface. It also enabled the investigation of reaction kinetics and chemical mapping of surface heterogeneity at the single-molecule level.

The prevalence of BRCA1 mutations in Chinese patients with early onset breast cancer and affected relatives

The purpose of this study was to determine the prevalence of BRCA1 mutations in Chinese breast cancer patients in Singapore. BRCA1 analysis was conducted in consecutive patients with breast cancer before the age of 40 years (76 women), or whose relatives had breast or ovarian cancer (16 women). Ten patients had both early onset breast cancer and affected relatives. Genomic DNA from peripheral mononuclear blood cells was studied by using the protein transcription-translation assay (exon 11) and single-strand conformational polymorphism, with subsequent DNA sequencing. All six disease-causing mutations occurred in women under 40 years (8.6%) with three occurring in patients under 35 years (three out of 22 patients, 13.6%). Mis-sense mutations of unknown significance were found in three patients. Two of the ten women with affected relatives under 40 years had BRCA1 mutations. The prevalence of BRCA1 mutations in Chinese patients with early onset breast cancer is similar to that observed in Caucasian women. Most Chinese patients with affected relatives were not carriers of BRCA1 mutations.

Attachment kinetics of vero cells onto CT-3 microcarriers

The effects of cell seeding density, microcarrier concentration, agitation speed and age of seeding cells on the rate of cell attachment to the surface of CT-3 microcarriers were investigated. It was shown that the attachment followed first-order kinetics. When either the cell seeding density or the microcarrier concentration was increased, the kinetic constant increased due to an increase in the probability of collision between cells and microcarriers. However, at higher microcarrier concentrations, the increase in the kinetic constant with increasing microcarrier concentration was not significant. Cell attachment was decelerated upon increasing the agitation speed because of the shorter cell-microcarrier contact time. In addition, it was also demonstrated that cell attachment occurred more efficiently when seeding cells from the middle or early exponential growth phase were used. The process of cell attachment onto CT-3 microcarriers was investigated, and our results showed that the attachment stage was the rate-limiting step. These results will facilitate the optimization of the Vero cell culture process.

[Susceptibility to lung cancer in Chinese is associated with genetic polymorphism in cytochrome P4502E1]

OBJECTIVE

To investigate the genetic polymorphism of cytochrome P4502E1 (CYP2E1) as a susceptibility factor for lung cancer in Chinese population.

METHODS

The genotype frequencies of RsaI restriction fragment length polymorphisms were analyzed in 92 lung cancer cases and 137 frequency-matched normal controls.

RESULTS

The CYP2E1 c1/c1 genotype was found in 72.8% of lung cancer cases, which was significantly higher (P < 0.01) than that in controls (54.7%). By multivariate analysis, this genotype was found to be associated with a 2.5-fold increased risk of lung cancer (adjusted OR 2.5, 95% CI 1.8-3.8). Stratified analysis suggested an interaction between CYP2E1 c1/c1 genotype and cigarette smoking. The odds ratio (OR) for the CYP2E1 c1/c1 genotype, cigarette smoking and both factors combined was 3.9 (95% CI 1.1-15.2), 4.1 (95% CI 1.1-15.9) and 7.9 (95% CI 2.4-29.4), respectively. The interaction between CYP2E1 c1/c1 genotype and pack-years of cigarette smoking followed the same pattern, with a markedly increased risk in the heaviest smokers.

CONCLUSION

The CYP2E1 c1/c1 genotype is a susceptibility factor for development of lung cancer in Chinese and there is an apparent gene-environment interaction between the susceptible genotype and cigarette smoking.

[A mutation specific polymerase chain reaction for detecting hepatitis B virus genome with A-to-C mutation at nt585]

OBJECTIVE

To investigate the prevalence of hepatitis B virus (HBV) nt585 A-to-C mutants in China.

METHODS

A mutation specific polymerase chain reaction (msPCR) was established for amplifying HBV DNAs with A-to-C mutation at nt585. Two sets of primer pairs with same sequences except for one base at 3' terminus were designed and synthesized according to 48 of the known HBV genome sequences and the popular HBV subtypes, adr and adw, in China.

RESULTS

57 of HBV S gene fragments amplified by a nested PCR from different and child adult hepatitis B patients were characterized by using the msPCR. It was shown that HBV mutants with A-to-C mutation at nt585 could be confirmed.

CONCLUSION

The msPCR is a specific and sensitive method for detecting the HBV nt585 A-to-C mutants.

A fiber-optic evanescent wave DNA biosensor based on novel molecular beacons

We have prepared a novel optical fiber evanescent wave DNA biosensor using a newly developed molecular beacon DNA probe. The molecular beacons (MB) are oligonucleotide probes that become fluorescent upon hybridization with target DNA/RNA molecules. Biotinylated MBs have been designed and immobilized on an optical fiber core surface via biotin-avidin or biotin-streptavidin interactions. The DNA sensor based on a MB does not need labeled analyte or intercalation reagents. It can be used to directly detect, in real-time, target DNA/RNA molecules without using competitive assays. The sensor is rapid, stable, highly selective, and reproducible. We have studied the hybridization kinetics of the immobilized MB by changing the ionic strength of the hybridization solution and target DNA concentration. Our result shows divalent cations play a more important role than monovalent cations in stabilizing the MB stem hybrids and in accelerating the hybridization reaction with target DNA/RNA molecules. The concentration detection limit of the MB evanescent wave biosensor is 1.1 nM. The MB DNA biosensor has been applied to the analysis of specific gamma-actin mRNA sequences amplified by polymerase chain reaction.

Identification of novel import and export signals of human TAP, the protein that binds to the constitutive transport element of the type D retrovirus mRNAs

The nuclear export of the unspliced type D retrovirus mRNA depends on the cis-acting constitutive transport RNA element (CTE) that has been shown to interact with the human TAP (hTAP) protein promoting the export of the CTE-containing mRNAs. We report here that hTAP is a 619-amino-acid protein extending the previously identified protein by another 60 residues at the N terminus and that hTAP shares high homology with the predicted rat and mouse TAP proteins. We found that hTAP is a nuclear protein that accumulates in the nuclear rim and the nucleoplasm. We further demonstrated that hTAP is able to shuttle between the nucleus and the cytoplasm. Identification of the signals responsible for nuclear import (NLS) and export (NES) revealed that they are distinct but partially overlapping. NLS and NES of hTAP are active transferable signals that do not share similarities with known elements. The C-terminal portion contributes further to hTAP's nuclear retention and contains a signal(s) for nuclear rim association. Taken together, our data show that hTAP is a dynamic protein capable of bidirectional trafficking across the nuclear envelope. These data further support hTAP's role as an export factor of the CTE-containing mRNAs.

Expression and purification of a secreted functional mouse/human chimaeric antibody against bacterial endotoxin in baculovirus-infected insect cells

We have created a mouse/human chimaeric antibody by taking antigen-binding fragment (Fab) genes of a mouse antibody-producing hybridoma with specificity for bacterial endotoxin and joining them to human Ig crystallizing-fragment (Fc) genes using recombinant DNA techniques. This chimaeric antibody has been expressed in Sf21 and High Fivetrade mark (BTI-TN-5B1-4) insect cells using the baculovirus expression system, which may allow the mass production of secretory recombinant antibodies. This was achieved by using infection with a double-recombinant virus containing cDNAs of both the Ig heavy-chain (HC) and light-chain (LC) genes. Prior to recombination, each gene was cloned into the dual-expression baculovirus transfer vector pPLSP2, which permitted the insertion of the LC gene in-frame with the signal peptide of honey bee melittin downstream of the polyhedrin promoter, and of the HC gene in-frame with the signal peptide of Bombyx mori larval serum protein downstream of the p10 promoter. Our results showed that the polypeptide chains were secreted by insect cells and correctly assembled into H(2)L(2) heterodimers containing N-linked carbohydrate at the heavy chain. Furthermore, the recombinant chimaeric antibody exhibited a similar antigen specificity to that of the monoclonal antibody. More importantly, it provides a generic method for the high-level expression of antibodies.

cDNA cloning and sequence analysis of hepatitis G virus genome isolated from a Chinese blood donor

OBJECTIVE

To obtain full-length sequence of a Chinese hepatitis G virus (HGV) strain (HGVch) and investigate the genetic characteristic of HGVch and its identity to other isolates.

METHODS

Reverse transcription (RT) and nested-PCR were used to screen HGV RNA positive serum and amplify cDNA fragments. A positive serum without known hepatitis virus markers was selected for isolating HGV RNA template. The HGV genome was divided into 12 overlapping fragments and directly cloned into pGEM-T vector. Sequences were determined by dideoxy terminus-end method of DNA sequencing and then analyzed by computer.

RESULTS

The twelve fragments of HGVch cover 9213 nucleotides in length, containing a large open reading frame (ORF) encoding 2873 animo acids polyprotein that began with a methonine residue and ended at termination codon. HGVch is about 86.5%-89.5% identical to other known HGV isolates at the nucleotide level and about 93.9%-96.2% at the deduced animo acid level.

CONCLUSION

HGV is a non-A-E hepatitis causal agent, proved to be related with posttransfusion hepatitis in all over the world. Chinese HGV isolate has very close relationship to other isolates from Africa, Europe, Japan, without significant difference across the entire genome. It is suggested that the sequences of HGV isolates are very conservative and the evolution is very slow.

Automated detection of Salmonella spp. in foods

An automated method to detect salmonellae in foods was developed and tested in food samples intentionally contaminated with the test organisms. Liquid eggs, shell eggs, dry eggs, skim milk and chicken were spiked with Salmonella enteritidis, S. typhimurium or S. newport to yield 2 to 25 CFU per 25 g or ml of sample. Following pre-enrichment in universal pre-enrichment broth at 42 degrees C for 6 h (eggs and milk) or 16 h (chicken), Salmonella cells were captured by immunomagnetic beads coated with Salmonella antibody (Vicam, Watertown, MA). The beads were transferred to selective liquid media containing carbohydrate (dulcitol or xylose), amino acid (lysine or ornithine), and H2S indicator, and incubated at 42 degrees C in the BioSys instrument (MicroSys, Ann Arbor, MI). Salmonella positive samples were identified by black discoloration of the media during incubation, while negative samples remained colorless. These color changes were recorded by the instrument. All the artificially contaminated samples tested positive within 15-18 h, while control samples remained negative during 24 h incubation. The results agreed with standard identification procedures. A total of 24 h was required to detect 2 to 25 CFU of the pathogen in 25 g or ml of eggs and milk, and up to 36 h in chicken, compared to 72 h in the standard methods.

[Recovery of gastrointestinal motility following laparoscopic versus open cholecystectomy]

OBJECTIVE

To investigate the recovery of gastrointestinal motility after laparoscopic cholecystectomy (LC) and open cholecystectomy (OC).

METHODS

Motilin (MOT), gastrin (GAS), electrogastrogram (EGG), the peristaltic sound recovery timing (PSRT) and the anorectum exhaust timing (AET) were determined in 30 patients having LC and 18 patients having OC.

RESULTS

MOT, GAS, EGG frequency and EGG amplitude on the first, second and third day after operation in LC group were not significantly different in comparison with preoperative data (P > 0.05), but significant difference on the first and second postoperative day compared with preoperative data and data of the the LC group (P < 0.05). The PSRT and AET in the LC group were much shorter in comparison with the OC group (P < 0.05).

CONCLUSIONS

The recovery of gastrointestinal motility after LC is earlier than OC, which justifies early feeding for patients after LC.

Probing intracellular dynamics in living cells with near-field optics

Near-field optics (NFO) overcomes the diffraction limit of light microscopes and permits visualization of single molecules. However, despite numerous applications of NFO in the physical sciences, there is still a paucity of applications in the neurosciences. In this work, the authors have developed NFO probes to image intracellular dynamic processes in living cells. This is the first time a NFO probe has been inserted inside a living cell to deliver light to a spatially controlled region for optical measurements and to record cellular responses to external stimuli. Two different optical detection systems (CCD camera and avalanche photon detection) were developed to monitor cellular responses to drug administration in two different cell types. NG108-15 neuroblastoma cells and vascular smooth muscle cells (VSMC) were penetrated with NFO probes. Intracellular Ca2+ increases post drug stimulation were detected by NFO probes. The cells were loaded with either fura-2/AM or fluo-3/AM calcium dyes. VSMC were stimulated with angiotensin II, resulting in a precise area of intracellular Ca2+ increase. Different response profiles of Ca2+ increases were observed after ionomycin and bradykinin administration in NG108-15 cells. Responsive heterogeneities due to ionomycin among different cells of the same type were recorded. The results show that NFO probes make possible real-time visualization of intracellular events. With refinement, intracellular NFO probes offer the potential of probing cell function with fast temporal and excellent spatial resolutions.

D4 dopamine receptor-mediated phospholipid methylation and its implications for mental illnesses such as schizophrenia

Previous studies have shown D2-like dopamine receptor involvement in the regulation of phospholipid methylation (PLM), while others have documented impaired methionine and folate metabolism in schizophrenia. Utilizing [14C]formate labeling in cultured neuroblastoma cell lines, we now show that D4 dopamine receptors (D4R) mediate the stimulatory effect of dopamine (DA) on PLM. The effect of DA was potently blocked by highly D4R-selective antagonists and stimulated by the D4R-selective agonist CP-226269. DA-stimulated PLM was dependent upon the activity of methionine cycle enzymes, but DA failed to increase PLM in [3H]methionine labeling studies, indicating that a methionine residue in the D4R might be involved in mediating PLM. A direct role for MET313, located on transmembrane helix No. 6 immediately adjacent to phospholipid headgroups, was further suggested from adenosylation, site-directed mutagenesis and GTP-binding results. A comparison of PLM in lymphocytes from schizophrenia patients vs control samples showed a four-fold lower activity in the schizophrenia group. These findings reveal a novel mechanism by which the D4R can regulate membrane composition. Abnormalities in D4R-mediated PLM may be important in psychiatric illnesses such as schizophrenia.

Single cell studies of enzymatic hydrolysis of a tetramethylrhodamine labeled triglucoside in yeast

Several hundred molecules of enzyme reaction products were detected in a single spheroplast from yeast cells incubated with a tetramethylrhodamine (TMR) labeled triglucoside, alpha-d-Glc(1-->2)alpha-d-Glc(1-->3)alpha-d-Glc-O(CH2)8CONHCH2- CH2NH- COTMR. Product detection was accomplished using capillary electrophoresis and laser induced fluorescence following the introduction of a single spheroplast into the separation capillary. The in vivo enzymatic hydrolysis of the TMR-trisaccharide involves at least two enzymes, limited by processing alpha-glucosidase I, producing TMR-disaccharide, TMR-monosaccharide, and the free TMR-linking arm. Hydrolysis was reduced by preincubation of the cells with the processing enzyme inhibitor castanospermine. Confocal laser scanning microscopy studies confirmed the uptake and internalization of fluorescent substrate. This single cell analysis methodology can be applied for the in vivo assay of any enzyme with a fluorescent substrate.