Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 217 records · Page 12Linked to original sources

PubMed1999

beta-adrenergic modulation of L-type Ca2+-channel currents in early-stage embryonic mouse heart.

Little information is available concerning the modulation of cardiac function by beta-adrenergic agonists in early-stage embryonic mammalian heart. We have examined the effects of isoproterenol (Iso) on the spontaneous beating rate and action potential (AP) configuration in embryonic mouse hearts at 9.5 days postcoitum (dpc), just 1 day after they started to beat. Iso (3 microM) increased the spontaneous beating rate in whole hearts, dissected ventricles, and isolated ventricular myocytes. In ventricular myocytes, Iso also increased the slope of the pacemaker potential and the action potential duration but decreased the maximum upstroke velocity. In whole cell voltage-clamp experiments, the Ca2+-channel currents were measured as Ba2+ currents (IBa). In 9.5-dpc myocytes, IBa was enhanced significantly from -4.7 +/- 0.9 to -6.7 +/- 1.2 pA/pF (by 52.4 +/- 14.8%, n = 10) after the application of Iso. Propranolol (3 microM) reversed the effect of Iso. Forskolin (For, 10 microM) produced an increase in IBa by 95.5 +/- 18.8% (n = 8). In ventricular myocytes at a late embryonic stage (18 dpc), 3 microM Iso caused an appreciably greater increase in IBa from -6.2 +/- 0.5 to -14.5 +/- 2.2 pA/pF (by 137.8 +/- 33.0%, n = 8), whereas the increase in IBa by 10 microM For (by 120.0 +/- 23.0%, n = 7) was comparable to that observed in the early stage (9.5 dpc). These results indicate that the L-type Ca2+-channel currents are modulated by beta-adrenergic receptors in the embryonic mouse heart as early as 9.5 dpc, probably via a cAMP-dependent pathway.

Action Potentials↗

PubMed1999

Changes of superoxide dismutase in cultured rat aortic smooth muscle cells (A7r5) by an incubation of vitamin E.

Supplementation of antioxidants such as vitamin E and vitamin C as health promotion food is popular recently. Epidemiological studies supported the beneficial effect of these antioxidants because oxygen free radicals have been linked to the process of diseases and aging. The present study evaluated the effect of alpha-tocopherol (vitamin E) on the changes of superoxide dismutase (SOD) in cultured rat aortic smooth muscle cells (A7r5) after a short-term (2 days) or long-term (7 days) incubation. Incubation of A7r5 cells with vitamin E at a concentration of 50 micromol/l for 2 days caused an increase of both the activity and mRNA level of SOD. At higher concentrations, such as 100 or 200 micromol/l, vitamin E failed to enhance SOD more effectively. However, after incubation for 7 days, vitamin E caused a decrease in both the activity and mRNA level of SOD in a concentration-dependent manner. Otherwise, the protein amount of SOD remained the same in these samples regardless of the concentration of vitamin E or the duration of incubation. The obtained results suggest that vitamin E can increase the effect of SOD to result in the beneficial influence of this antioxidant only at low concentration under a short-term supplementation because a down-regulation of SOD was observed in cells receiving a long-term incubation.

Animals↗

PubMed1999

Tuberculous pseudoaneurysm of the descending thoracic aorta: successful treatment by surgical excision and primary repair.

Tuberculous pseudoaneurysm of the aorta is a rare disease with a high mortality rate. We present the case of a 27-year-old woman who had a tuberculous pseudoaneurysm of the descending thoracic aorta. The patient underwent successful excision and primary repair of the lesion while under hypothermic circulatory arrest and partial femoral bypass. To the best of our knowledge, this is the youngest patient to be successfully treated with surgery for a tuberculous pseudoaneurysm of the descending thoracic aorta. The pathogenesis, diagnosis, and treatment of this disease are reviewed, and the need to include tuberculous pseudoaneurysm in the differential diagnosis of chest lesions is emphasized.

Adult↗

PubMed1999

Inhibition of DNA synthesis in isolated human endometrial cells by a levonorgestrel-releasing intrauterine device.

OBJECTIVE: To estimate the effect of an intrauterine device (IUD) releasing 20 micrograms levonorgestrel (LNG) per 24 hours on DNA synthesis in human endometrial cells before and after 12 months of use. STUDY DESIGN: Endometrial specimens were collected from the anterior or posterior wall of the miduterus from 6 females on cycle day 10-12 before insertion of the IUD and after 12 months of use. RESULTS: Previous results from our group did not reveal any influence on endometrial DNA cell content when a levonorgestrel IUD releasing 2 micrograms/24 h was used for 12 months in a group of fertile females. In this study, the IUD release rate, 20 micrograms LNG/24 h, was statistically significantly different from the results in the previous studies. The effect of the levonorgestrel IUD on endometrial proliferation was dose dependent, and a significant correlation could be found between continuous exposure to LNG and inhibition of DNA synthesis in endometrial cells. CONCLUSION: Inhibition of proliferative activity in endometrial cells seems to be reflected by a decrease in DNA synthesis per cell nucleus and contributes to the clinical performance of the LNG-releasing IUD.

Adult↗

PubMed1999

Effects of transient forebrain ischemia and radix Salviae miltiorrhizae (RSM) on extracellular levels of monoamine neurotransmitters and metabolites in the gerbil striatum--an in vivo microdialysis study.

The aim of this study was to investigate the effect of 30 min forebrain ischemia, followed by 120 min reperfusion on extracellular fluid (ECF) levels of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their metabolites, homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of gerbils, so as to obtain further information on the mechanism of Radix Salviae Miltiorrhizae (RSM)-induced neuroprotection. Microdialysis was used to sample the extracellular space. Dialysate was measured by high performance liquid chromatography with electrochemical detector (HPLC-ED). ECF DA, NE levels increased from basal levels by 282, 227 and 221 folds, by 9.14, 8.51 and 8.25 folds, respectively for the three ischemic duration (0-10; 11-20; 21-30 min). ECF DA, NE, 5-HT levels in the RSM-treated group were significantly decreased as compared with those in the control group during ischemia (P < 0.01). The results suggested that monoamine neurotransmitters were involved in ischemic neuron damage directly or indirectly; and that RSM plays a protective role during cerebral ischemia by attenuating the dysfunctions of monoamine neurotransmitters.

Animals↗

PubMed1999

Cloning and sequence analysis of an amastin coding gene from Leishmania major Abdou.

OBJECTIVE: To clone a surface protein encoding gene from Leishmania major Abdou parasites. METHODS: Using Trypanosotidae cruzi (T. cruzi) amastin DNA sequence as a reference, computer search was done on Genbank and dbEST data bases with BLASTN path. A Leishmania major Abdou DNA library has been established and screened by in situ colony hybridization. RESULTS: No homology sequence to T. cruzi amastin was found in Genbank, but a 309 nt DNA fragment from Leishmania major (L. major) existed in bEST. Leishmania major Abdou DNA library was screened using specific probes synthesized according to 309 nt DNA sequence of T. cruzi amastin gene, and full-length coding sequence for Leishmania major Abdou amastin was cloned. The coding sequence consisted of 552 nt, and translated into 183 amino acid residues. The homology is 23.5% at amino acid sequence level between Leishmania major Abdou and T. cruzi amastins. CONCLUSION: We have cloned the full length amastin coding DNA for Leishmania major Abdou.

Amino Acid Sequence↗

PubMed1999

[Apoptosis of human melanoma cell line WM-983A by p16 gene transduction].

OBJECTIVE: To further understand the mechanism of action of the tumor-suppressor gene p16. METHODS: An adenoviral expression vector with full length cDNA of p16 gene insert was constructed (Ad-p16) and transfected into WM-983A cells, the p16 gene of which was point mutated at codon 126. The effect of exogenous p16 gene on the growth of WM-983A cells was examined in vitro and in vivo. RESULTS: Expression of p16 gene in WM-983A cells was confirmed by Western blot. The in vitro growth of the Ad-p16 transfected WM-983A cells was significantly inhibited (inhibition rate: 78%) as compared to mock (Ad-LacZ) transfected WM-983A cells. Colony-forming activity in vitro of the Ad-p16 transfected WM-983A cells was completely inhibited. Morphologically, the Ad-p16 transfected cells appeared apoptotic which was confirmed by the appearance of pre-G1 on flow cytometry and DNA fragmentation. The growth of WM-983A xenografts in nude mice was retarded by intra-tumoral injection of Ad-p16. CONCLUSION: p16 gene participates in the induction of cell apoptosis. It is promising to use it for gene therapy of cancer, especially when combined with other apopptosis-inducing agents.

Animals↗

PubMed1999

[A case-control study on relationship between body mass index and lung cancer in non-smoking women].

OBJECTIVE: To investigate the relationship between body mass index (BMI) and lung cancer in non-smoking women. METHODS: A population-based case-control study on lung cancer in non-smoking women was conducted during February 1992 to December 1993 in Shanghai. Totally, 504 cases of lung cancer of non-smoking women and 601 population controls were studied. RESULTS: The risk of lung cancer increased with the decrease of BMI. The odds ratio of lung cancer in non-smoking women was 1.95, as compared to controls with the highest quartile of their BMI, with a dose-response pattern (P < 0.0002 with chi(2) test for trend), adjusted for age, schooling and income. Non-conditional logistic regression analysis was used to adjust for some main risk factors found in other studies carried out at home, such as passive smoking, tea drinking, eye irritation by cooking oil fume, kinds of cooking oils, pulmonary tuberculosis, family history of lung cancer, age of menarche, menstrual cycle and dietary nutrition (including intake of vitamins C and E, beta-carotene, total fat and calorie), was used to adjust. There still existed relationship between BMI and lung cancer in non-smoking women after adjustment for those factors. Stratification analysis showed that there was relationship mainly between BMI and lung adenocarcinoma. CONCLUSION: BMI may be a risk factor for lung cancer in non-smoking women.

Adult↗

PubMed1999

[Rapid determination of cefazolin in porcine serum by high performance capillary electrophoresis].

A rapid high performance capillary electrophoretic method was established to assay cefazolin in porcine blood serum. Porcine serum was deproteined by 60% acetonitrile and superlants were injected with 10 s pressure load. The final assay condition was: 40 cm x 75 microns silica capillary, 50 mmol/L bicarbonate buffer at pH10, 20 kV for 5 min, 254 nm UV detection. The assay was linear within the range of 5-320 micrograms/ml, the intra-day and inter-day relative standard deviations ranged from 1.7% to 8.0%. Analytical recovery of cefazolin was 107.9%, the limit of detection was 1.5 micrograms/ml, the limit of quantitation was 3.6 micrograms/ml. To investigate the pharmacokinetic profile of cefazolin in pig, six adult pigs were injected with 16 mg/kg cefazolin and all data was analyzed by pharmacokinetic software 3P87. Cefazolin metabolism in adult pigs appeared to be a typical two-compartment model with a clearance of 8.43 ml/(kg.min).

Animals↗

PubMed1999

[Wavelet application to reduction of stimulus artifact in transient evoked otoacoustic emissions testing].

Otoacoustic emissions(OAEs) are presently considered as an objective clinical test for assessing the integraity of peripheral hearing. Owing to the adding of the reflex waves of the stimuli, recordings of emissions evoked in response to transient stimuli are contaminated by an initial artifact, which inhibits the examination of high frequency cochlear responses that have short latencies. So OAEs testing is of serious limitation in most clinical environments. We propose an artifact reduction technique based on discrete wavelet transform pre-processing method and demonstrate empirically that the method not only improves artifact reduction but also enhances signal-to-noise ratio in the response region.

Acoustic Stimulation↗

PubMed1999

[Registration and fusion of multimodality medical images].

This paper introduces the present situation of research and methods of multimodality medical images fusion. Some algorithms and relative techniques are given in detail. A summary of the clinical application of multimodality medical images fusion is also presented.

Algorithms↗

PubMed1999

[Texture analysis of B-scan image using fractal dimension].

Based on the texture analysis of B-Scan image fractal model, this paper presents the liver clinical B-Scan images and their fractal characteristics. It describes the semi-fractal characteristics of B-Scan images and calculates the fractal dimension(D) of the liver B-scan images of 10 normal persons, 3 patients with cancer of the liver, and 3 patients with cirrhosis of the liver. The results indicate that Fractal Dimension (D) is an important parameter in differentiating some diseases. On the basis of the influence of Fractal Dimension (D) and scale (epsilon), this paper suggests the texture classified parameter S. The experiment results indicate that the parameter S can be used to differentiate diseases efficiently.

Algorithms↗

PubMed1999

[Recognition and classification of heart sounds].

This paper reviews the methods and research advances of recognition and classification of heart sounds. The methods include the statistical techniques and artificial neural network. It also discusses the main problems in the methods.

Algorithms↗

PubMed1999

[Influence of sample dilution on separation and detection of DNA fragments by capillary electrophoresis].

Capillary electrophoresis has become an important and useful method to separate and determine DNA fragments. In molecular biochemistry, the volume of DNA sample is very small (microL level) and DNA sample is liable to be contaminated and degraded. According to theoretical inference and experiments, we propose that dilution of DNA sample solution can increase separation efficiency and resolution without evidently reducing height of peaks. By this method, the usage efficiency of DNA sample can be improved. It is also demonstrated the separation and detection of DNA fragments by capillary electrophoresis with hydroxyethyl cellulose non-gel sieving matrix and with laser-induced fluorescence charge-coupled device as detector. By using lower concentration non-gel matrix (0.4%), all 8 larger size fragments of lambda DNA/Hind III (125 bp-23 130 bp) can be completely separated. Twenty smaller size fragments of pBR322-Hae III DNA (18 bp-587 bp) can be separated by higher concentration (1.6%) non-gel matrix. As ratio of sample dilution is 10, two adjacent fragment (123 bp and 124 bp) of pBR322-Hae III DNA can be separated.

DNA↗

PubMed1999

[Quantitative backscatter imaging].

Some methods for producing quantitative backscatter images are presented. As a basis, the data reduction method calculates absolute coefficient. The reference phantom method is easier to implement for clinical application. An application method is also presented which separates the contributions of scatter size and scattering strength to backscatter signal and displays Size image and Strength image separately. This method is generally accepted by the medical community. At last, the recent development of ultrasonic backscatter imaging is reviewed.

Algorithms↗

PubMed1999

[Research highlight of image reconstruction today].

In today's image processing researches, image reconstruction is a highlight. It includes the following several aspects: (1) reducing noise before reconstruction or after reconstruction under time-frequency constraints; (2) researches for reconstruction of motion organ; (3) image reconstruction from incomplete projection data; (4) direct volume reconstruction and 3-D image rendering; (5) researches for non-X-ray CT; (6) researches for parallel processing system of CT. In this paper, an introduction to these aspects is given.

Algorithms↗

PubMed1999

[Limited diffraction beams and its application].

Limited diffraction beams have a large depth of field and thus have many applications such as medical imaging, tissue characterization, material flaw detection and blood flow detection by Doppler method. Nondiffraction beams colud be produced only by transducer with an infinity large aperture in theory. The experimental results show that limited diffraction beams produced by a limited aperture have desirable large depth of field also. The theory of this kind of beams and their applications in field of medical imaging and blood flow estimation are introduced.

Acoustics↗

PubMed1999

[Study of HSP70 gene upstream regulation element on expression efficiency of GST gene in M. smegmatis].

Four different expression vectors were constructed by cloning foreign gene which encode Schistosoma japonicum 26 kD antigen (Sj26GST) into Escherichia coli-Mycobacteria shuttle plasmid pBCG-2000 and investigated their expression efficiency in mycobacteria smegmatis. The plasmid which contains promoter of human mycobacterial tuberculosis heat shock protein 70 was firstly digested with Nco I and modified with two different ways to lead to two kinds of SD sequences, and ligated with Sj26GST encoding gene. Then, the DNA fragment contained HSP70 promoter and Sj26GST gene was obtained and cloned into E. coil-mycobacteria shuttle plasmid pBCG-2000, and finally four recombinant mycobacterial expression vectors that differenciated in SD sequence, orientation and copy number were selected. The expressed native recombinant Sj26GST(rSj26GST) was soluble and could be observed on SDS-PAGE about at the molecular weight of 26 kD obviously. Analysis with protein density scanning indicated: the expression efficiency that containing double-copy promoter-foreign gene vector was the highest and the expressed protein which was about 1.6 times than others was 28% of total protein of Mycobacteria smegmatis. The cloned direction and SD sequence had no significant effect on expression efficiency.

Animals↗