The use of polyurethane as an elastomer in thermoplastic microfluidic devices and the study of its creep properties

We report using polyurethane (PU) as an elastomer in microvalves integrated with thermoplastic microfluidic devices. Elastomer-based microvalves have been used in a number of applications and the elastomer often used is PDMS. Although it is a convenient material for prototyping, PDMS has been recognized to possess shortcomings such as solvent incompatibility and unfavorable manufacturability. We investigated the use of PU as an elastomer to address the challenges. A reliable method was developed to bond hybrid materials such as PU and cyclic olefin copolymer. The film thickness from 3.5 to 24.5 μm was studied to identify an appropriate thickness of PU films for desirable elasticity in microvalves. We integrated PU with thermally actuated, elastomer-based microvalves in thermoplastic devices. Valve actuations were demonstrated, and the relationship between the valve actuation time and heater power was studied. We compared PU with PDMS in terms of their microvalve performance. Valves with PDMS failed to function after two weeks since the thermal-sensitive solution evaporated through porous PDMS membrane, whereas the same valve with PU functioned properly after eight months. In addition, we evaluated the creep and creep recovery of PU, which is a common phenomenon of viscoelastic materials and is related to the long-term elastic property of PU after prolonged use.

Induction of retinal ganglion-like cells from fibroblasts by adenoviral gene delivery

Central nervous system neurons fail to regenerate after birth, which greatly hampers the effective treatment of many neurodegenerative diseases. Neurons differentiated from induced pluripotent stem cells have been considered a possible option for cell-based therapies. Recent discoveries have revealed that fibroblasts can be directly converted into neurons without a transition through a pluripotent state. This approach might serve as a more efficient and convenient method for the cellular therapy of neurodegenerative diseases. Currently, several types of neurons have been directly generated from fibroblasts, including dopamine neurons, motor neurons and neural progenitor cells. In our study, by screening a series of candidate genes, we found that the adenovirus-mediated transduction of Ascl1, Brn3b and Ngn2 can directly convert mouse fibroblasts to retinal ganglion-like cells. The induced retinal ganglion-like cells co-express multiple retinal ganglion cell markers, and exhibit membrane properties of functional neurons. The reprogramming mediated by adenoviruses occurs much sooner than that mediated by lentiviruses. Furthermore, the induced retinal ganglion-like cells that are produced via adenoviral gene delivery are free of exogenous gene integration. Retinal ganglion-like cells that are induced by adenoviruses demonstrate great potential applicability in clinical therapy and provide a novel platform for the research of retinal degenerative diseases.

β-Catenin overexpression is associated with gefitinib resistance in non-small cell lung cancer cells

BACKGROUND

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) presents great challenges in the treatment of non-small cell lung cancer (NSCLC) patients, while the mechanisms are still not well understood. The β-catenin signaling pathway has been found to be associated with chemoresistance and can activate the EGFR and its downstream pathways. This study aimed to investigate the role of β-catenin in acquired resistance to EGFR-TKIs in NSCLC cell lines.

METHODS

The expression and transcriptional activity of β-catenin were measured in both the NSCLC cell line PC9 and its sub-line PC9/AB(2) which has acquired resistance to gefitinib. Knockdown and overexpression of β-catenin in the PC9/AB(2) and PC9 cells were performed. The cell survival rate and the activation of the EGFR and its downstream pathways were detected in the two cell lines after transfection.

RESULTS

Nuclear translocation of β-catenin was increased in the PC9/AB(2) cells and the baseline expression of members of the β-catenin signaling pathway was also higher in the PC9/AB(2) cells. Knocking down the expression of β-catenin increased the sensitivity of the PC9/AB(2) cells to gefitinib by blocking the activation of the EGFR downstream pathways, while β-catenin overexpression improved PC9 cells resistance to gefitinib by enhancing the activation of the EGFR and its downstream signaling.

CONCLUSION

β-catenin plays an important role in acquired resistance to EGFR-TKIs in NSCLC cell lines and may be a potential therapeutic target for NSCLC patients who have failed to respond to targeted therapy.

Usual interstitial pneumonia coexisted with nonspecific interstitial pneumonia, What's the diagnosis?

The differential diagnosis between idiopathic nonspecific interstitial pneumonia(INSIP) and idiopathic pulmonary fibrosis(IPF)/usual interstitial pneumonia(UIP)is tough in both clinicians and pathologists. In this study, we analyzed the lesions of right lung removed from a 58-year-old patient by gross and microscopy. The results showed that the pathological appearance of nonspecific interstitial pneumonia (NSIP) and UIP coexisted in his upper lobe. Besides, because of severe fibrosis in middle and lower lobes, it was hard to distinguish the lesions of NSIP fibrotic pattern (NSIP-F) or UIP. Based on clinic-radiologic-pathological data, the diagnosis of INSIP-F was made for this patient finally. Our study suggests that UIP is not always an accurate diagnosis when the NSIP and UIP coexist, and NSIP can have regions of UIP.

Association of leptin receptor gene polymorphisms and essential hypertension in a Chinese population

BACKGROUND

The leptin receptor (LEPR) is an important regulator of leptin activity and resistance. Several single nucleotide polymorphisms (SNP) of LEPR have been linked to diseases accompanying obesity and/or obesity-related diseases in different populations. However, the results from published studies remain inconsistent rather than conclusive.

AIM

To investigate whether LEPR SNP are associated with essential hypertension and related metabolic traits in Chinese subjects.

MATERIALS AND METHODS

A total of 544 Chinese patients with hypertension and 357 non-hypertensive subjects were screened. The genotypes of LEPR polymorphisms were determined by PCR-restriction fragment length polymorphism methods. Demographic and biochemical characteristics including waist circumference, waist-to-hip ratio, body mass index (BMI), lipids profiles, glucose metabolism, and leptin levels were obtained for analysis.

RESULTS

This case-control study showed associations between the frequencies of AA genotype and A allele of Gln223Arg and hypertension (p=0.029, p=0.002, respectively). Furthermore, the Gln223Arg polymorphism was significantly associated with plasma leptin levels (p<0.001), while no correlations between Lys109Arg SNP and hypertension were found. Multivariate logistic regression analysis evidenced that A allele carriers of Gln223Arg (AA+AG) showed higher risks of hypertension than GG carriers after adjustment of age and sex (adjusted odds ratio: 1.549, 95% confidence interval: 1.031- 2.036, p=0.035). BMI, fasting serum insulin, oral glucose tolernace test (OGTT)-2h glucose, serum leptin, as well as LDL-cholesterol (LDL-C) levels were also independent risk factors of hypertension in this population. In addition, significant associations were observed between the Gln223Arg and Lys109Arg SNP and serum total cholesterol, LDL-C, and fasting plasma glucose levels in hypertensive patients. Besides, A allele of Gln223Arg had raised diastolic blood pressure, compared with GG carriers (p=0.001). While variance of Lys109Arg was associated with waist-to-hip ratio, OGTT-2h glucose, and homeostasis model assessment of insulin resistance (p<0.05).

CONCLUSIONS

LEPR polymorphisms may be a marker for susceptibility to essential hypertension in Chinese subjects, and be involved in the development of several features including dyslipidemia and impaired glucose regulation in hypertension subjects.

Improvement of glucose tolerance by rhein with restored early-phase insulin secretion in db/db mice

AIMS

In the present study, we investigated whether rhein exerted hypoglycemic action and rhein's effect on the pancreatic β cell in db/db mice.

MATERIALS AND METHODS

Thirty 4-week-old db/db mice were randomized to treatment with rhein (120 mg/kg) (no.=15) and placebo (1% natrium cellulose solution) (no.=15) for 8 weeks, respectively. Fifteen age-matched non-diabetic littermates db/m mice treated with placebo were studied as non-diabetic control. After an 8-week treatment, ip glucose tolerance test (IPGTT) and arginine tolerance test were performed. Area under curve (AUC) of insulin levels in IPGTT was calculated to evaluate insulin secretory function. Immunohistochemical staining of insulin was performed to estimate β cell mass. TUNEL assay was performed to determine β cell apoptosis. Islet isolation and perifusion were performed to evaluate kinetics of insulin release in vitro, especially first-phase insulin.

RESULTS

Compared with control group, AUC of glucose concentrations significantly decreased in the rhein-treated group (p<0.05). Simultaneously, AUC of insulin levels increased in the rhein-treated group (p<0.05), especially in the first 30 min after glucose load. Perifusion showed that the rhein-treated group manifested a significantly increase of first-phase insulin secretion. Immunohistochemical study and TUNEL assay showed that rhein treatment greatly preserved β cell mass and inhibited β cell apoptosis.

CONCLUSIONS

Rhein treatment significantly improved glucose- dependent and independent insulin secretion by preservation of β cell mass and inhibition of β cell apoptosis in db/db mice. The characteristics of rhein may make it a novel therapeutic means for preventing from or curing diabetes in the near future.

Cord ghrelin levels are decreased in large-for-gestational-age neonates

Ghrelin is a growth hormone secretagogue peptide and has been recognized as an orexigenic factor. To investigate relationship between cord ghrelin and anthropometric and metabolic indices, we measured cord ghrelin in large-for-gestational-age (LGA) and appropriate-for-gestational-age (AGA) neonates and examined whether cord ghrelin levels were correlated to concentrations of cord blood glucose, insulin, lipid and maternal ghrelin. Fifty-five singletons born at term and their mothers were investigated in this study. Maternal venous blood samples were collected before delivery. Plasma concentrations of ghrelin, insulin, glucose, total cholesterol, triacylglycerol (TG), low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol were measured in cord blood sampled at birth. The results show that the concentrations of cord ghrelin are significantly lower in LGA neonates. There is a positive correlation between cord ghrelin levels and maternal ghrelin levels. Negative correlations are found between cord ghrelin levels and gestational age, the concentrations of cord glucose, insulin, TG and LDL. Multivariate regression analyses show that birth weight (r(2)  = 0.674, β = -0.548, P < 0.001) was the predictor correlating with ghrelin levels. In conclusion, LGA neonates have lower cord ghrelin concentrations than AGA neonates.

Improved glucose-stimulated insulin secretion by intra-islet inhibition of protein-tyrosine phosphatase 1B expression in rats fed a high-fat diet

BACKGROUND

Insulin resistance of pancreatic β-cell itself may be a potential link between systemic insulin resistance and impaired insulin secretion in Type 2 diabetes. Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates tyrosine residues in insulin receptors (IR) and IR substrate (IRS) proteins, and thereby inhibits insulin signaling. Thus the impact of PTP1B expression on β-cell insulin pathway may affect insulin secretory function.

AIM

The aim of the present study was to investigate the effects of intra-islet inhibition of PTP1B expression on glucose-stimulated insulin secretion and potential mechanisms in rats fed a high-fat diet (HFD).

MATERIALS AND METHODS

Twenty 10-week-old Sprague Dawley rats were randomly assigned to a regular diet (RD) or a HFD for 8 weeks. At the end of the 8th week, fasting glucose, fasting insulin concentration and lipid profile were measured and an oral glucose tolerance test was done after 12-h fast. Then islet isolation was performed for static incubation and perifusion. Recombinant adenoviruses containing siPTP1B (Ad-siPTP1B), or siControl (Ad-siControl) sequences were constructed using AdEasy™ system. Islets were transfected and then assigned to the Ad-siPTP1B group, the Ad-siControl group, and mock control group. Real-time RT-PCR and Western blot were used to evaluate the expression level of PTP1B. Western blot of glucose transporter 2 (GLUT-2) and glucokinsase were also done to investigate the β-cell glucose-sensing apparatus. Islets were incubated with Krebs-Ringer bicarbonate containing 2.8 mmol/l glucose then 16.7 mmol/l glucose to evaluate glucose-stimulated insulin secretion (GSIS). Islet perifusion was also performed to evaluate kinetics of insulin release in vitro.

RESULTS

HFD rats manifested modest glucose intolerance compared with RD group. And PTP1B expression in isolated islets of rats in the HFD group was higher than that of the RD group. GSIS was impaired in islets of HFD rats (2.3±0.5-fold as basal for HFD vs 8.1±1.3-fold for RD; p<0.05). Ad-siPTP1B treatment resulted in 73% decrease in PTP1B mRNA levels and 61% decrease in PTP1B protein compared with islets treated with Ad-siControl (p<0.05). Simultaneously, PTP1B inhibition resulted in 4.7±0.8-fold increase of GSIS from basal (vs 1.9±0.1-fold for Ad-siControl, p<0.05). Perifusion showed notable improvement of first-phase insulin secretion by AdsiPTP1B treatment. Significant decrease of both GLUT-2 (by 49.8%) and glucokinase (GCK, by 43.7%) were found in the HFD group when compared with the RD group, while up-regulation of both GLUT-2 (by 98%) and GCK (by 62%) was achieved after PTP1B inhibiton by Ad-siPTP1B.

CONCLUSIONS

Intra-islet PTP1B is an important physiological regulator of glucose-induced insulin release and the characteristics of PTP1B inhibitors in insulin secretion could make it a potential novel therapeutics for protection of β-cell secretory function in Type 2 diabetes.

Characterization of bonding between poly(dimethylsiloxane) and cyclic olefin copolymer using corona discharge induced grafting polymerization

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated.

Chemical-assisted bonding of thermoplastics/elastomer for fabricating microfluidic valves

Thermoplastics such as cyclic olefin copolymer (COC) and polymethylmethacrylate (PMMA) have been increasingly used in fabricating microfluidic devices. However, the state-of-the-art microvalve technology is a polydimethylsiloxane (PDMS)-based three-layer structure. In order to integrate such a valve with a thermoplastics-based microfluidic device, a bonding method for thermoplastics/PDMS must be developed. We report here a method to bond COC with PDMS through surface activation by corona discharge, surface modification using 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), and thermal annealing. The method is also applicable to PMMA. The bonding strength between thermoplastics and PDMS was represented by the peeling force, which was measured using a method established by the International Organization for Standardization (ISO). The bonding strength measurement offered an objective and quantitative indicator for protocol optimization, as well as comparison with other PDMS-associated bonding methods. Using optimized bonding conditions, two valve arrays were fabricated in a COC/PDMS/COC device and cyclic operations of valve closing/opening were successfully demonstrated. The valve-containing devices withstood 100 psi (∼689 KPa) without delamination. Further, we integrated such valve arrays in a device for protein separation and demonstrated isoelectric focusing in the presence of valves.

Metabolic syndrome: prevalence and risk factors in southern China

This was a cross-sectional study to investigate the epidemiology of metabolic syndrome and the distribution of inter-related metabolic abnormalities in different population groups in Guangdong, southern China. Individuals were recruited according to the percentage of different occupational populations in southern China. The study cohort included 1206 subjects, and the prevalence and distribution of the components of metabolic syndrome were assessed using the National Cholesterol Education Program Adult Treatment Panel III 2005 criteria. The unadjusted rate of metabolic syndrome was 26.7%, and the prevalences of hypertension and diabetes were 38.0% and 4.3% respectively. Hypertension, diabetes, metabolic syndrome, abdominal obesity, elevated blood glucose and elevated blood pressure decreased significantly with increasing levels of life stress and anxiety. The prevalence of hypertension and metabolic syndrome in southern China is very high, and early identification and treatment of at-risk individuals may help target intervention to improve future cardiovascular health.

Protein tyrosine phosphatase 1B gene polymorphisms and essential hypertension: a case-control study in Chinese population

BACKGROUND

Protein tyrosine phosphatase (PTP)- 1B, encoded by the PTPN1 gene, negatively regulates insulin signaling by dephosphorylating the phosphotyrosine residues of the insulin receptor kinase activation segment. Several rare single nucleotide polymorphisms (SNP) have been linked to diseases accompanying insulin resistance such as Type 2 diabetes, obesity, and dyslipidemia in different populations.

AIM

To investigate whether PTP-1B SNP are associated with hypertension and hypertension-related metabolic traits in Chinese subjects.

MATERIALS AND METHODS

A total of 239 Chinese patients with hypertension and 141 non-hypertensive subjects were screened. The genotypes of PTP-1B gene polymorphisms were determined by PCR-restriction fragment length polymorphism methods.

RESULTS

The case-control study showed associations between the frequencies of T allelic g54281 T>A and A allele of I5/37C>A and hypertension (p<0.0001, p=0.0371, respectively). In addition, significant associations were observed between the IVS6+G82A polymorphism and waist circumference, total cholesterol, and LDL-cholesterol levels in hypertensive patients (p=0.0005 approximately 0.0260). And g54281 T allele was associated with higher plasma triglyceride (p=0.0390) and LDL-cholesterol concentration (p=0.0141), while g58585 T>C was associated with body mass index (BMI) (p=0.0308), waist circumference (p=0.0216), and homeostasis model assessment of insulin resistance (p=0.047). Multivariate logistic regression analysis showed that T allele carriers of g54281T>A and A allele carriers of I5/37C>A had higher risks of hypertension independent of age, gender, BMI, glucose levels, and lipids profiles [odds ratio (OR): 1.79, 95% confidence interval (CI): 1.09- 2.96, p=0.02; OR: 1.66, 95% CI: 1.13-2.44, p=0.01, respectively].

CONCLUSIONS

PTP-1B polymorphisms contribute to pathogenesis of hypertension in Chinese subjects and PTP-1B SNP may be involved in the development of several features including dyslipidemia and obesity in hypertensive subjects.

Inhibition of metastasis to lung of a human nasopharyngeal carcinoma cell line CNE- 2L2 transfected with pRc/ CMV-antisense 6A8 cDNA in nude mice

The growth of CNE-2L2 cell, a cloned line of human nasopharyngeal carcinoma with a high potentiality of metastasis to lung was inhibited to a certain extent after transfection with a recombinant antisense expression vector of a cDNA encoding a human alpha-mannosidase (pRc/CMV-antisense 6A8 cDNA) (the Genbank accession number of 6A8 cDNA is U37248) in comparison with that of the cell transfected with the Mock and of the wild cell. Two months after a subcutaneous inoculation of CNE-2L2 cell into the axilla of nude mice metastatic lesions in the lung were observed in 9/10 mice (90%) with grade III in 8 mice and grade II in one mouse in the wild cell group, in 6/8 mice (75 %) with grade III in one mouse, grade II in 2 mice and grade I in 3 mice in the Mock-transfection group, in only 3/10 mice (30%) with all grade I in pRc/CMV-antisense 6A8 cDNA-transfection group.

The Long-term Effect of Autologous Endothelial Progenitor Cells from Peripheral Blood Implantation on Infarcted Myocardial Contractile Force

This study was designed to evaluate the long-term effect of endothelial progenitor cell (EPC) implantation in acute myocardial infarction in Sprague-Dawley rats after ligation of the left anterior descending coronary artery. Autologous EPCs from peripheral blood were purified and implanted into an acute myocardial infarct site. Specimens and muscle strip were harvested at 3 and 6 weeks, and at 6, 8 and 12 months for contractile force assessment and, by immunohistology, for expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and factor VIII. Expression of VEGF and bFGF, and microvessel counts and contractile force in the cell implantation group were significantly higher than in the control group up to 8 months after implantation. Beyond 8 months following implantation, however, no further improvement occurred. The EPCs showed an ability to improve contractile performance in infarcted myocardium by means of angiogenesis and vasculogenesis, and the results seemed to persist long-term.

Search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-)

A sensitive search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-) has been performed using a sample of approximately 10(9) Xi(-) hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Xi(-)-->pmu(-)mu(-))<4.0x10(-8) at 90% confidence, improving on the best previous limit by 4 orders of magnitude.

Search for DeltaS = 2 nonleptonic hyperon decays

A sensitive search for the rare decays Omega(-)--> Lambdapi(-) and Xi(0)--> ppi(-) has been performed using data from the 1997 run of the HyperCP (Fermilab E871) experiment. Limits on other such processes do not exclude the possibility of observable rates for |DeltaS| = 2 nonleptonic hyperon decays, provided the decays occur through parity-odd operators. We obtain the branching-fraction limits B(Omega(-)-->Lambdapi(-)) < 2.9 x 10(-6) and B(Xi(0)--> ppi(-)) < 8.2 x 10(-6), both at 90% confidence level.

Search for CP violation in charged-Xi and Lambda hyperon decays

We have compared the p and p angular distributions in 117 x 10(6) Xi- -->Lambdapi- -->ppi-pi- and 41 x 10(6) Xi+ -->Lambda pi+ -->p pi+pi+ decays using a subset of the data from the HyperCP experiment (E871) at Fermilab. We find no evidence of CP violation, with the direct-CP-violating parameter AXiLambda identical with (alphaXialphaLambda-alpha Xialpha Lambda)/(alphaXialphaLambda+alphaXialphaLambda)=[0.0+/-5.1(stat)+/-4.4(syst)] x 10(-4).

Observation of the decay K- --> pi(-)mu(+)mu(-) and measurements of the branching ratios for K+/- --> pi(+/-)mu(+)mu(-)

Using data collected with the HyperCP (E871) spectrometer during the 1997 fixed-target run at Fermilab, we report the first observation of the decay K--->pi(-)mu(+)mu(-) and new measurements of the branching ratios for K+/--->pi(+/-)mu(+)mu(-). By combining the branching ratios for the decays K+-->pi(+)mu(+)mu(-) and K--->pi(-)mu(+)mu(-), we measure Gamma(K+/--->pi(+/-)mu(+)mu(-))/Gamma(K+/--->all) = (9.8+/-1.0+/-0.5)x10(-8). The CP asymmetry between the rates of the two decay modes is [Gamma(K+-->pi(+)mu(+)mu(-))-Gamma(K--->pi(-)mu(+)mu(-))]/[Gamma(K+-->pi(+)mu(+)mu(-))+Gamma(K--->pi(-)mu(+)mu(-))] = -0.02+/-0.11+/-0.04.

Mutagenesis of the regulatory domain of phenylalanine hydroxylase

The regulatory domain of phenylalanine hydroxylase (PAH, EC ) consists of more than 100 amino acids at the N terminus, the removal of which significantly activates the enzyme. To study the regulatory properties controlled by the N terminus, a series of truncations and site-specific mutations were made in this region of rat PAH. These enzymes were expressed highly in Escherichia coli and purified through a pterin-conjugated Sepharose affinity column. The removal of the first 26 amino acids of the N terminus increased the activity by about 20-fold, but removal of the first 15 amino acids increased the activity by only 2-fold. Replacing serine-29 of rat PAH with cysteine from the same site of human PAH increased the activity by more than 4-fold. Mutation of serine to other amino acids with varying side chains: alanine, methionine, leucine, aspartic acid, asparagine, and arginine also resulted in significant activation, indicating a serine-specific inhibitory effect. But these site-specific mutants showed 30--40% lower activity when assayed with 6-methyl-5,6,7,8-tetrahydropterin. Stimulation of hydroxylase activity by preincubation of the enzyme with phenylalanine was inversely proportional to the activation state of all these mutants. Combined with recent crystal structures of PAH [Kobe, B. et al. (1999) Nat. Struct. Biol. 6, 442-448; and Erlandsen, H., Bjorgo, E., Flatmark, T. & Stevens, R. C. (2000) Biochemistry 39, 2208-2217], these data suggest that residues 16-26 have a controlling regulatory effect on the activity by interaction with the dihydroxypropyl side chain of (6R)-5,6,7,8-tetrahydrobiopterin. The serine/cysteine switch explains the difference in regulatory properties between human and rat PAH. The N terminus as a whole is important for maintaining rat PAH in an optimum catalytic conformation.

Detection of genetic alterations in mouse lung adenocarcinomas by two-dimensional gel electrophoresis

DNA from 14 mouse lung adenocarcinomas and 7 normal lungs were examined by 2-dimensional gel electrophoresis (2-DGE) for genetic alterations. 2-DGE profiles from tumor samples were compared with those profiles from normal lung tissues through a computer-assisted color overlay system. Compared to the profiles in normal lung DNA, 6 spots were amplified and 16 spots were partially reduced in their intensity in tumors. Two spots were detectable only in tumor tissues. These altered spots indicate genetic changes in mouse lung tumor development. The identification of these genetic alterations is probably important in understanding mouse lung carcinogenesis.

[Expression of proteolytic enzymes of metastatic tumor cells and the effects of some influencing factors]

OBJECTIVE

To elucidate the types of proteolytic enzymes the dendritic cell sarcoma (DCS) cell expressed in vitro and the effects of modulating factors.

METHODS

The proteolytic spots of DCS cells were examined, with ten different proteinase inhibitors, various antibodies and matrix.

RESULTS

Aprotinin, EDTA-Na2 and pepstatin could inhibit the proteolysis of DCS cells respectively. Anti-ubiquitin antibody and anti-DCS antibody (1:200-1:100) showed no obvious inhibitory effects. DCS cells spread out fairly well but with no proteolysis.

CONCLUSIONS

Under the conditions of our experiments the DCS cells had serine proteinase, metalloproteinase and aspartate proteinase activities. Antiubiquitin antibodies and anti-DCS antibodies showed no obvious influence on the proteolysis of DCS cells. DCS cells displayed different proteolysis status on different matrix.

[The effects of 6A8 cDNA transfection on biological behavior of tumor cells]

OBJECTIVE

To investigate the effects of antisense 6A8 cDNA on the malignant behavior of tumor.

METHODS

Highly metastatic clonal variant CNE-2L2 from nasopharygeal carcinoma cell line(CNE-2Z) was transfected with antisense 6A8 cDNA or mock plasmid. Their adhesion, locomotion, proteolytic ability, in vitro invasion, in vivo growth and metastasis were comparatively studied with the wild CNE-2L2 cells.

RESULTS

Antisense 6A8 cDNA transfected CNE-2L2 showed less adhesion to FN and LN, weakened locomotive ability and proteolytic ability, retarded in vivo growth and much less metastasis.

CONCLUSION

Transfection of antisense 6A8 cDNA obviously decreased the malignant behavior of tumor cells.

Function-structure studies and identification of three enzyme domains involved in the catalytic activity in rat hepatic squalene synthase

Rat hepatic squalene synthase (RSS, EC 2.5.1.21) contains three conserved sections, A, B, and C, that were proposed to be involved in catalysis (McKenzie, T. L., Jiang, G., Straubhaar, J. R., Conrad, D., and Shechter, I. (1992) J. Biol. Chem. 267, 21368-21374). Here we use the high expression vector pTrxRSS and site-directed mutagenesis to determine the specific residues in these sections that are essential for the two reactions catalyzed by RSS. Section C mutants F288Y, F288L, F286Y, F286W, F286L, Q293N, and Q283E accumulate presqualene diphosphate (PSPP) from trans-farnesyl diphosphate (FPP) with reduced production of squalene. F288L, which retains approximately 50% first step activity, displays only residual activity (0.2%) in the production of squalene from either FPP or PSPP. Substitution of either Phe288 or Phe286 with charged residues completely abolishes the enzyme activity. Thus, F288W, F288D, F288R, F286D, and F286R cannot produce squalene from either FPP or PSPP. All single residue mutants in Section A, except Tyr171, retain most of the RSS activity, with no detectable accumulation of PSPP in an assay mixture complete with NADPH. Y171F, Y171S, and Y171W are all inactive. Section B, which binds the diphosphate moieties of the allylic diphosphate subtrates, contains four negatively charged residues: Glu222, Glu226, Asp219, and Asp223. The two Glu residues can be replaced with neutral or with positively charged residues without signficantly affecting enzyme activity. However, replacement of either Asp residues with Asn eliminates all but a residual level of activity, and substitution with Glu abolishes all activity. These results indicate that 1) Section C, in particular Phe288, may be involved in the second step of catalysis, 2) Tyr171 of Section A is essential for catalysis, most likely for the first reaction, 3) the two Asp residues in Section B are essential for the activity and most likely bind the substrate via magnesium salt bridges. Based on these results, a mechanism for the first reaction is proposed.

[Peripheral artery blood flow measurements using pulsed Doppler and electromagnetic flowmetry in dogs: a comparative study]

To investigate the accuracy of blood flow parameters in peripheral artery by Doppler ultrasound, the intermal diameter(D), peak velocity(Vp), mean velocity (Vm) and flow volume (Q) of dog's femoral artery were measured by using either a pulsed Doppler (PD) system or electromagnetic flowmeters(EMFM). The results showed that the D measured by B-mode ultrasound values significantly smaller than that by callipers but it correlated very well with the D by callipers. When the values of Vp, Vm and Q measured by pulsed Doppler and EMFM were compared, the Vp had the most highly significant correlation between the data obtained by the two techniques (r: 0.91, 0.79, 0.83 respectively). When Vp, Vm and Q were measured by angle correction of PD, the correlations between the data determined by the two techniques were still significant(r: 0.88, 0.82, 0.78).

Characterization of a novel microsomal fatty acid synthetase (FAS) compared to a cytosolic FAS in the housefly, Musca domestica

A novel membrane-bound fatty acid synthetase (FAS) associated with the microsomal fraction from the housefly, Musca domestica, was solubilized and purified to homogeneity. The microsomal FAS was solubilized by 0.75 M KCl in phosphate buffer and was purified to homogeneity by the sequential use of ammonium sulfate precipitation followed by Sepharose CL-6B, DEAE Sephacel and Red Agarose (dye ligand affinity) chromatography. The specific activity of the microsomal FAS was increased 1,440-fold to 6,522 U/mg during purification. The cytosolic FAS from the housefly was also purified by similar methods and the specific activity increased 183-fold to 7,533 U/mg. The relative molecular mass of the microsomal and cytosolic FAS are 419 +/- 22 kDa and 405 +/- 18 kDa, respectively, for the dimers as determined by gel permeation chromatography. The microsomal and the cytosolic FAS yield different tryptic digestion maps and have slightly different amino acid compositions, which demonstrate structural differences between the two FASs. In addition, there are differences between the two FASs in their kinetic characteristics and their ability to incorporate methylmalonylCoA into the growing fatty acyl chain.

Detection of genomic alterations in human cervical cancer by two-dimensional gel electrophoresis

Two-dimensional gel electrophoresis was used to comprehensively scan the whole genome of 6 cervical intraepithelial neoplasia (CIN) lesions, 7 cervical squamous cell carcinomas, 1 cervical adenosquamous cell carcinoma, and 2 cervical adenocarcinomas for multiple genetic alterations, such as DNA amplification, chromosome deletion, loss of heterozygosity, and chromosome translocation, as compared with the paired normal tissues. DNA spot analysis of the genomic 2-dimensional gels was performed by a computer color overlay system and by spot recognition software allowing for objective spot comparison and quantitation. Nine spots were found to be amplified in the cervical carcinomas while two amplified spots were detected in the CIN III lesions. Fourteen DNA spots were either reduced in their intensity or absent in cervical carcinomas as compared to their normal paired tissues. Reduction of intensity in 6 spots was observed in the 5 CIN III lesions. These genetic alterations may represent changes in cancer genes that are associated with human cervical carcinogenesis. Further characterization of these alterations may be significant to the understanding of cervical tumorigenesis and to the development of biomarkers for clinical trials in cancer chemoprevention.

Regulation of enzymatic activity involved in sex pheromone production in the housefly, Musca domestica

Ovarian produced ecdysteroids regulate sex pheromone production in the female housefly, inducing the synthesis of (Z)-9-tricosene (Z9-23:Hy), cis-9,10-epoxytricosane, (Z)-14-tricosen-10-one and methylalkanes. Experiments were performed to gain a detailed understanding of the processes affected by 20-hydroxyecdysone (20-HE) that result in sex pheromone production as the female becomes reproductively mature. A novel microsomal fatty acid synthetase (FAS) is present in the epidermal tissue and plays a role in producing the methyl-branched fatty acid precursors to the methylalkanes. This FAS is released from the microsomes in the presence of 3 M KCl. A major enzyme activity influenced by 20-HE is the fatty acyl-CoA elongation system. A shift in the chain length specificity of the products of the elongation system causes the change in the chain lengths of the alkenes produced to switch from C27 and longer in the previtellogenic female to C23 in the mature female. Data is presented indicating that it is the condensation activity of the elongation system that is affected. Z9-23:Hy arises from a 24 carbon acyl group which is reduced to an aldehyde, and then converted to the hydrocarbon. Data is presented demonstrating that it is the fatty acyl-CoA derivative and not the free fatty acid that is the substrate. There does not appear to be a chain length specificity which regulates the conversion of fatty acyl-CoAs to hydrocarbons as both 24 and 28 carbon fatty acyl-CoAs are converted to hydrocarbon by both males and females of all ages.

Spectrophotometer for measuring spectral reflectance and transmittance

The development of a computer-controlled spectrophotometer that enables measurement of spectral transmittance, reflectance, and optical loss of thin-film specimens is discussed. We also describe the design and testing procedure of the spectrophotometer, incorporating test sample performance data. In the visible region the overall photometric accuracy is verified to be 0.1% and 0.2% for transmittance and reflectance, respectively. The wavelength scale is accurate to within 0.5 nm with a reproducibility of 0.1 nm.

[Chemosensitivity testing of fresh human gastrointestinal cancers using AgNOR assay]

The argyrophilic staining of nucleolar onganizer region (AgNOR), a simple colorimetric test, has been adapted for chemosensitivity testing of human gastric and colorectal cancers. Seven different chemotherapeutic agents were tested. The drug sensitivity was measured and compared according to the decrease rate of AgNOR granules between control tumor cells and tumor cells treated with antitumor drugs. Only 3 of 10 cases of advanced gastric carcinoma were sensitive to one antitumor agent. Most colorectal carcinoma cases (18/20) were sensitive to at least one antitumor agent. The sensitive sequence of antitumor agents we have had in this study was relative to clinic. The method and characteristics of AgNOR assay as a chemosensitivity test was introduced. It's value is being observed.