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H Tang

Publications and source records attributed to H Tang.

At least 91 records · Page 5Linked to original sources
PubMed2000

Determination of threshold energy dose for ultrasound-induced transdermal drug transport.

Low-frequency (20 kHz) ultrasound has been shown to enhance transdermal transport of drugs, a phenomenon referred to as sonophoresis. In this paper, we report the threshold energy dose for ultrasound-induced transdermal drug transport. The threshold was determined by in vitro measurements of the dependence of sonophoretic enhancement on ultrasound parameters, including intensity, duty cycle, and exposure time. While the enhancement varies linearly with ultrasound intensity and exposure times, it is independent of the duty cycle in the range of parameters studied. The enhancement is also directly proportional to the ultrasound energy density once the threshold value is crossed. For full thickness pig skin, the threshold value is about 222 J/cm(2). The overall dependence of transport enhancement on ultrasound parameters is similar to that of cavitation measured in a model system, pitting of aluminum foil. Specifically, the extent of pitting is proportional to ultrasound intensity and exposure time and is independent of duty cycle. Furthermore, the extent of pitting is also proportional to the ultrasound energy density. The similarity between the parametric dependence of transport enhancement and cavitation is consistent with previous findings that cavitation plays the dominant role in sonophoresis.

Administration, Cutaneous↗
PubMed2000

Synergistic effect of low-frequency ultrasound and sodium lauryl sulfate on transdermal transport.

Application of low-frequency ultrasound has been shown to enhance transdermal transport of drugs (low-frequency sonophoresis). In this paper, we show that the efficacy of low-frequency ultrasound in enhancing transdermal transport can be further increased by its combination with sodium lauryl sulfate (SLS), a well-known surfactant. The dependence of the ultrasound-SLS-mediated transport on ultrasound parameters, including intensity, net exposure time, and duty cycle, is discussed. The transdermal transport enhancement is proportional to ultrasound intensity as well as to exposure time, and is independent of duty cycle as long as the net exposure time is the same. The synergistic effect of SLS and ultrasound on transdermal transport increases linearly with SLS concentration. The enhancement is also proportional to the ultrasound energy density beyond a threshold value, which suggests that a certain minimum amount of energy density is required before noticeable changes in skin permeability occur. A similar dependence of the transdermal transport enhancement on energy density is observed in the case of the enhancement induced by ultrasound alone. Although the threshold energy density value in the presence of SLS is about 10 times lower than that in the case of ultrasound alone, the relationship between enhancement and energy density in the presence and in the absence of SLS is otherwise similar. Possible mechanisms for the synergistic effect of ultrasound and SLS are also discussed.

Aluminum↗
PubMed2000

Identification and characterization of differentially expressed genes in denervated muscle.

Denervation results in a series of changes in skeletal muscle. To elucidate the molecular basis underlying these changes, it is important to identify the profile of altered gene expression in skeletal muscle following nerve injury. In the present study, we have examined the differentially expressed genes in denervated gastrocnemius muscle using RNA fingerprinting by arbitrarily primed PCR. Eight differentially expressed mRNA transcripts have been identified. A bilateral regulatory profile can be observed for the up-regulated genes in both denervated and contralateral control muscle following unilateral sciatic nerve injury. The temporal expression profiles of the denervation-regulated genes in muscle during development, together with their dependency on nerve activity, suggest potential functional roles following nerve injury in vivo. In particular, the identification of two apoptosis-related genes in denervated muscle provides molecular evidence that the apoptotic process is likely to be involved in the intricate changes that lead to muscle atrophy. Our findings not only allow the identification of novel genes, but also suggest possible functions for some known genes in muscle following nerve injury. Taken together, these findings provide important insights into our understanding of the molecular events in denervated muscle and suggest that the differentially expressed genes may play potential roles during muscle denervation and regeneration.

Animals↗
PubMed2000

Molecular regulation of constitutive expression of interleukin-8 in human pancreatic adenocarcinoma.

Recent studies have shown that interleukin-8 (IL-8) plays an important role in the growth and metastasis of human pancreatic cancer. In the present study, we determined the molecular regulation of constitutive IL-8 expression in human pancreatic cancer cells. Various human pancreatic cancer cell lines were incubated in vitro. Sixty-seven percent of the cell lines constitutively secreted high levels of IL-8, as determined using enzyme-linked immunosorbent assay. Consistently, these cells constitutively expressed high levels of IL-8 mRNA, as determined using Northern blot analysis. To determine the mechanisms of the high steady-state levels of IL-8 mRNA, the IL-8 half-life and transcription rate were measured. There was no significant difference in IL-8 half-life between cells expressing high and low levels of IL-8. However, higher transcription rates and increased IL-8 promoter activity were observed in the cells constitutively expressing high levels of IL-8. Detailed IL-8 promoter analysis using deletion mutation revealed that the region from -85 to -133 bp was essential for the constitutive IL-8 promoter activity. Also, point-mutation analysis indicated that mutation of NF-kappaB, AP-1, or NF-IL-6 binding sites significantly reduced or eliminated the constitutive IL-8 promoter activity. Consistent with the constitutive IL-8 transcription activity, high levels of constitutive NF-kappaB and AP-1 activity were detected in the cells overexpressing IL-8, as determined using electrophoretic mobility shift assay. In addition, transfection of a dominant-negative I-kappaBalpha expression vector (I-kappaBalphaM) inhibited constitutive NF-kappaB activity and IL-8 expression in pancreatic cancer cells. Collectively, our data demonstrated that constitutive NF-kappaB and AP-1 activation contributes to the overexpression of IL-8, which in turn plays an important role in tumor angiogenesis and contributes to the aggressive biology of human pancreatic cancer.

Adenocarcinoma↗
PubMed2000

Apoptosis of thyrocytes and effector cells during induction and resolution of granulomatous experimental autoimmune thyroiditis.

Experimental autoimmune thyroiditis (EAT) with granulomatous histopathology (G-EAT) can be induced by cells from mouse thyroglobulin (MTg)-immunized donors activated in vitro with MTg and IL-12. G-EAT lesions reach maximum severity 18-21 days after cell transfer and, if some thyroid follicles remain, lesions almost completely resolve by day 35. CD8(+) cells are required for G-EAT resolution. To begin to determine the mechanisms involved in G-EAT resolution, apoptosis in thyroids was analyzed by TUNEL staining. Apoptotic thyrocytes and inflammatory cells were present in the thyroids of both CD8(+) and CD8-depleted recipient mice at day 19-21. By day 35, apoptotic cells were rare in thyroids of mice whose lesions had resolved; the few apoptotic inflammatory cells were generally in close proximity to thyroid follicles. Thyroids of CD8-depleted mice had ongoing inflammation at day 35 and most apoptotic cells were thyroid follicular cells. The expression of Fas and Fas ligand (FasL) mRNA in thyroids was also determined by RT-PCR in both CD8(+) and CD8-depleted recipient mice. Fas was expressed in normal thyroids and its expression was relatively constant throughout the course of disease. FasL mRNA was not expressed in normal thyroids. FasL mRNA expression generally correlated with G-EAT severity, being maximal at day 21 and diminishing as lesions resolved. However, FasL mRNA expression in thyroids of CD8-depleted mice in which resolution was delayed was decreased compared to thyroids of CD8(+) mice with comparable disease severity, suggesting that FasL expressed by CD8(+) cells may play a role in G-EAT resolution.

Animals↗
PubMed2000

In vivo determination of body composition of rats using magnetic resonance imaging.

Magnetic resonance imaging (MRI) has potential as an instrument to measure body composition because it can discriminate various soft tissues in vivo. These soft tissues include adipose tissue, muscle, organs, and brain. We report on preliminary studies using a 4.2-tesla MRI for measuring body composition in the mouse and rat. We employed image segmentation methods that include an image correction method, a necessary requirement when the images are taken in the presence of nonuniform radio-frequency (RF) coil response. The software for 3-D data segmentation, quantification, correction, image manipulation, and visualization has been developed as a research tool. This method currently is being validated.

Animals↗
PubMed2000

Promoter-proximal pausing on the hsp70 promoter in Drosophila melanogaster depends on the upstream regulator.

RNA polymerase II pauses in the promoter-proximal region of many genes during transcription. In the case of the hsp70 promoter from Drosophila melanogaster, this pause is long-lived and occurs even when the gene is not induced. Paused polymerase escapes during heat shock when the transcriptional activator heat shock factor associates with the promoter. However, pausing is still evident, especially when induction is at an intermediate level. Yeast Gal4 protein (Gal4p) will induce transcription of the hsp70 promoter in Drosophila when binding sites for Gal4p are positioned upstream from the hsp70 TATA element. To further our understanding of promoter-proximal pausing, we have analyzed the effect of Gal4p on promoter-proximal pausing in salivary glands of Drosophila larvae. Using permanganate genomic footprinting, we observed that various levels of Gal4p induction resulted in an even distribution of RNA polymerase throughout the first 76 nucleotides of the transcribed region. In contrast, promoter-proximal pausing still occurs on endogenous and transgenic hsp70 promoters in salivary glands when these promoters are induced by heat shock. We also determined that mutations introduced into the region where the polymerase pauses do not inhibit pausing in a cell-free system. Taken together, these results indicate that promoter-proximal pausing is dictated by the regulatory proteins interacting upstream from the core promoter region.

Animals↗
PubMed2000

Additive antiviral effects of lamivudine and alpha-interferon in chronic hepatitis B infection.

alpha-Interferon has limited efficacy against chronic hepatitis B virus (HBV) infection. Nucleoside analogues may confer greater benefits, however, it is likely that combination therapies will be required for effective control of this infection. We investigated the antiviral effect of lamivudine and interferon therapy in eight patients with high HBV-DNA levels. Six patients received lamivudine/interferon combination therapy followed, after a 6-month drug-free period, with lamivudine monotherapy. Mean HBV viral load (copies/ml) reduction was significantly greater after 4 months of combination therapy (4.3 x 10(3)) compared to an equivalent period of lamivudine monotherapy (2.9 x 10(2)) (P=0.03). Two patients were given 6 months of lamivudine/interferon combination therapy followed immediately by lamivudine monotherapy. Cessation of interferon in these patients led to a rapid 1-2 log10 increase in HBV viral load. These findings suggest that alpha-interferon has a direct antiviral effect on chronic HBV infection, which may be additive to, or synergistic with lamivudine.

Antiviral Agents↗
PubMed2000

Addition of C-terminal histidyl tags to PsaL and PsaK1 proteins of cyanobacterial photosystem I.

In vitro mutagenesis was used to produce two photosystem I mutants of the cyanobacterium Synechocystis sp. PCC 6803. The mutant HK and HL contained hexahistidyl tags at the C-termini of the PsaK1 and PsaL subunits, respectively. The HK mutant contained wild-type amounts of trimeric PS I complexes, but the level of hexahistidine-tagged PsaK1 was found only ten per cent in the PS I complexes and membranes of the wild type level. Therefore, attachment of a tag at the C-terminus interferes with the expression or assembly of PsaK1. In contrast, the HL mutant contained a similar level of tagged PsaL as that in the wild type. However, trimeric PS I complexes could not be obtained from this strain, indicating that the C-terminus of PsaL is involved in the formation of PS I trimers. Hexahistidine-tagged complexes of the HL and HK strains could not be purified with Nickel-affinity chromatography, unless photosystem I was denatured with urea, demonstrating that tagged C-termini of PsaK1 and PsaL were embedded inside of the PS I complex. Protection of the C-terminus from trypsin cleavage further supported this conclusion. Thus, histidine tagging allowed us to demonstrate role of C-termini of two proteins of photosystem I.

Base Sequence↗
PubMed2000

[Plant functional type and its significance in ecological research].

In recent years, plant functional type is a new ecological concept introduced in the research of global change. This paper reviewed the definition, classification, ecological significance of plant functional type. The theories and methodologies of systematic biology were used to understand the concept of plant functional type. And finally, the significance of this term in ecological studies, especially its role in the study of global change and terrestrial ecosystem was explained.

Ecology↗
PubMed2000

[Serum lipoprotein(a) in woman with pregnancy induced hypertension].

OBJECTIVE: To examine lipoprotein(a) level in woman with Pregnancy induced hypertension (PIH) to elucidate the effect of it on the pathogenesis of the disease. METHODS: Serum lipoprotein (a) total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) levels were measured in 20 normal pregnant woman (control group) and 32 pregnant woman with PIH (PIH group). The PIH group was further divided into the following subgroup: mild, moderate, and severe PIH. We used a transmission turbidimetry method to measure serum lipoprotein(a). RESULTS: (1) The serum lipoprotein (a) levels were higher in PIH group than that in control group (228 +/- 187 mg/L vs 106 +/- 93 mg/L). (2) The serum lipoprotein (a) levels were higher in all PIH subgroups than that in control. (3) The serum levels of TC, TG, LDL-C in the PIH group were higher than those in control, while the level of HDL-C in the PIH group was lower than that in control (0.98 +/- 0.16 mmol/L vs 1.09 +/- 0.17 mmol/L). CONCLUSIONS: This study has demonstrated that lipoprotein (a) levels are elevated in pregnant woman with PIH and associated with severity of the disease. It may involved in the pathogenesis of PIH.

Adult↗
PubMed2000

[Expression in E. coli of protein encoded by human esophageal cancer related gene-1].

OBJECTIVE: To express esophageal cancer related gene-1 (ECRG-1)--in E. coli. METHODS: The human ECRG-1 was cloned by RT-PCR. Expression plasmid of the ECRG-1/GST pi fusion gene was constructed and introduced into E. Coli. The fusion protein was induced to express by ITPG. The recombinant protein was identified by Western blot. BALB/C mice were immunized with the protein purified by SDS-PAGE for the preparation of polyclonal antibody. RESULTS: DNA sequencing confirmed that the sequence of ECRG-1 was identical to that of the previously obtained by 5'-RACE technique. Expression of the protein in E. coli was verified by Western blot. The polyclonal antibody obtained from immunized BALB/C mice had a title of 1:3,200. CONCLUSION: The antibody available is useful for the further study of structure and function of the esophageal cancer related protein.

Animals↗
PubMed2000

[Evaluation of modified maze procedure by Doppler tissue imager].

Since 1998 the cardiac surgeons of WCUMS have performed modified maze procedure for treating the patients with rheumatic mitral valve disease accompanied with chronic atrial fibrillation (Af). In this study, echocardiography, especially Doppler Tissue Imager (DTI), was used to evaluate atria contraction and function of such patients before and after the operation. 14 rheumatic mitral disease patients, aged 27-60 years, were chosen; among them, 11 had mitral stenosis, 3 mitral regurgitation. The control group consisted of 16 cases, aged 24-67 years, with normal echocardiogram. Before and half-1 year after the operation, left atrium, left ventricle, right atrium and ventricle were measured, and cardiac function and posterior wall motion of left atrium were measured. Velocity of mitral valve annual and tricuspid valve annual was measured in DTI. The results showed: There was no age difference between the two groups. The motion of posterior wall of left atrium was 4.18 +/- 0.37 mm in the operation group, 4.09 +/- 0.29 mm in the control group (P > 0.05). No difference in velocity of mitral/tricuspid valve annual between the two groups was observed; 3 peaks of mitral valve annual were S 0.11 +/- 0.02, e 0.11 +/- 0.01, a 0.09 +/- 0.01 (m/s) in operation group, and S 0.08 +/- 0.00, e 0.10 +/- 0.01, a 0.08 +/- 0.01 (m/s) in control group, (P > 0.05, respectively); 3 peaks of tricuspid valve annual were S 0.10 +/- 0.01 vs 0.11 +/- 0.08, e 0.11 +/- 0.08 vs 0.10 +/- 0.01, a 0.10 +/- 0.10 vs 0.09 +/- 0.01 (m/s), (P > 0.05, respectively). The diameter of left atrium after operation in cases of mitral stenosis decreased significantly, compared with that before operation (P < 0.01). The diameter of right atrium after operation decreased significantly, compared with that before operation (P < 0.01). There was no significant change in right ventricle/left ventricle/EF and FS. The diameter of left atrium after operation in cases of mitral regurgitation decreased significantly, compared with that before operation (P < 0.01). The diameter of left ventricle after operation decreased significantly, compared with that before operation (P < 0.05). No significant change in right ventricle/right atrium/EF and FS was noted. The authors conclude the DTI, as a new diagnostic method in echocardiography, has high sensitivity and is less influenced when used to observe motion of atrium-ventricle annual influenced. It can avoid the error caused by deviation of blood displacement. In the rheumatic mitral valve disease patients who had mitral valve replacement and modified maze procedure, atrial contraction respores, the risk of thromboembolism decreases and prognosis improves. So the operation is worth doing.

Adult↗
PubMed2000

[Preliminary echocardiographic evaluation on prosthetic valve replacement of preserving the subvalvular apparatus with artificial chorade for mitral stenosis].

The purpose of this study was to evaluate the preliminary results after prosthetic valve replacement of preserving the subvalvular apparatus with artificial chorade for mitral stenosis. 20 patients had received operation with expanded polytetrafluoroethylene(e-PTFE) as artificial chordade. The patients were followed up by means of echocardiography. The time of follow-up study varied from 4 to 18 months with a mean of 6 months. The left atrial, ventricular dimension as well as ventricular function were assessed. In addition, the length of artificial chorade and obstruction of left ventricular outflow track were observed. The results showed that left atrial diameter (LAD, from 57.59 +/- 13.51 mm to 47.05 +/- 9.55 mm), left ventricular end-diastolic dimension (LVEDD, from 46.23 +/- 12.56 mm to 42.41 +/- 10.86 mm), left ventricular end-systolic dimension (LVESD, from 33.50 +/- 10.20 mm to 29.68 +/- 8.40 mm) decreased (P < 0.01), and ejection fraction (EF, from 52.59 +/- 11.89% to 58.36 +/- 8.03%) increased (P < 0.05) after operation. There were no significant changes of fractional shortening (FS, from 29.23 +/- 8.99% to 31.05 +/- 6.08%). The length of artificial chorade ranged from 2.6 cm to 4.3 cm (the mean, 3.2 cm). There was no case of obstruction of left ventricular outflow track. It is believed that the result of preliminary echocardiographic observation on prosthetic valve replacement of preserving the subvalvular apparatus with artificial chorade for mitral stenosis is satisfactory.

Adult↗
PubMed2000

[Study of spontaneous echo contrast in patients with rheumatic mitral stenosis by transesophageal echocardiography].

Spontaneous echo contrast (SEC) is common in the areas of slow blood flow. This study was conducted to examine the correlation of SEC and left atrial appendage function, atrial fibrillation (Af) and thrombus in patients with rheumatic mitral stenosis. The transthoracic and multiplane transesophageal echocardiograms were performed on 117 patients(mean age 42.22 +/- 10.79 years). Left atrial size, left atrial appendage area, mitral valve area, left atrial appendage flow peak emphatic velocity and full velocity were measured. The presence of SEC and thrombus in the left atrium and appendage was noted. The results showed that among the patients, 57 had normal sinus rhythm, 60 had Af; 19 had thrombus, 98 had no thrombus; 71 had SEC and 46 had no SEC. Compared with the patients without SEC, the patients with SEC showed greater incidence of thrombus (28.76% vs 0, P < 0.05), higher rate of Af (69.01% vs 23.91%, P < 0.05), larger LAD (46.93 +/- 0.85 mm vs. 41.76 +/- 1.05 mm, P < 0.05), larger LAA area (8.06 +/- 0.32 cm2 vs 6.92 +/- 0.31 cm2, P < 0.05), smaller MVA area (1.07 +/- 0.23 cm2 vs 1.32 +/- 0.35 cm2, P < 0.05), lower LAA flow peak emphatic velocity (0.17 +/- 0.01 m/s vs 0.32 +/- 0.02 m/s, P < 0.05), and lower LAA full velocity (0.18 +/- 0.01 m/s vs 0.31 +/- 0.03 m/s, P < 0.05). These findings indicate that the presence of SEC is associated with significantly greater incidence of thrombus, higher rate of Af, larger LAD and LAA area, smaller MVA area, lower LAA flow peak emphatic velocity and full velocity. Atrial fibrillation, the diameter of left atrium and the area of mitral valve are independent predictors of SEC. SEC is significantly associated with LAA function and thrombus formation.

Adolescent↗
PubMed2000

[Transthoracic three-dimensional echocardiography for determination of left ventricular mass in patients with dilated cardiomyopathy].

This study was performed to compare left ventricular mass (LVM) measurement by one- (1D), two- (2D) and 3D echocardiography with magnetic resonance imaging (MRI) in patients with dilated cardiomyopathy (DCM). 36 patients with DCM underwent imaging by conventional 1D and 2D echocardiography as well as transthoracic 3D echocardiographic data acquisition. Also patients were imaged with cardiac MRI. LVM was determined. There was no significant correlation (r = 0.42, P > 0.05) for measuring LVM between 1D echocardiography and MRI in patients with DCM. A significant correlation was obtained between 2D echocardiography and MRI (r = 0.64, P < 0.01) and between 3D and MRI (r = 0.78, P < 0.01) in determination of LVM. Compared with 1D and 2D echocardiography, the 3D analysis achieved a significantly higher agreement with the MRI results (1D; 399.2 g, 2D: 285.9 g, 3D: 172.6 g versus MRI: 199.1 g). Interobserver variability was 5.1% for measuring LVM by 3D echocardiography. These results suggest that LVM of patients with DCM can be accurately determined by transthoracic 3D echocardiography and this method could be used in clinical practice.

Adolescent↗