Biomedical subjects

J Chen

Publications and source records attributed to J Chen.

At least 991 records · Page 55Linked to original sources

PubMed2000

Interaction of nitric oxide and transforming growth factor-beta1 induced by angiotensin II and mechanical stretch in rat renal tubular epithelial cells.

PURPOSE: Changes in intrarenal pressure accompanying unilateral ureteral obstruction can result in tubular mechanical stretch and mediator release from renal tubules. Therefore, we examined the synthesis of nitric oxide and transforming growth factor-beta (TGF-beta), and their interaction in rat renal epithelial cells (NRK-52E) exposed to either angiotensin II or mechanical stretch. MATERIALS AND METHODS: NRK-52E were exposed to either angiotensin II or mechanical stretch. Nitrite and TGF-beta in the supernatant were assessed by the Greiss reaction and bioassay, respectively. The level of cell hypertrophy and intracellular TGF-beta protein was determined by flow cytometry. TGF-beta messenger RNA and inducible nitric oxide synthase protein were detected by reverse transcriptase polymerase chain reaction and Western blot, respectively. RESULTS: Angiotensin II stimulated TGF-beta1 and nitric oxide. The nitric oxide synthase inhibitor, N-nitro-L-arginine (L-NAME) or angiotensin II type I receptor blocker, losartan, inhibited nitric oxide and TGF-beta1 induced by angiotensin II. Flow cytometry showed that either L-NAME or losartan inhibited angiotensin II induced cell hypertrophy. TGF-beta1 inhibited iNOS protein and nitric oxide, whereas an anti-TGF-beta antibody enhanced iNOS. Mechanical stretch induced TGF-beta, inducible NOS protein and nitric oxide. However, TGF-beta expression was not affected by L-arginine or L-NAME when cells were exposed to mechanical stretch. CONCLUSIONS: These results demonstrate that nitric oxide is an intermediate in angiotensin II stimulated TGF-beta1 expression but not in stretch induced TGF-beta expression, and that TGF-beta1 is a negative regulator of nitric oxide in rat renal epithelial cells. The complex interaction of these cytokines may be a target for intervention in the fibrotic and apoptotic processes in the obstructed kidney.

Angiotensin II↗

PubMed2000

Screening a human population sample for DNA repair gene deficiencies utilizing the protein truncation test.

A significant fraction of human cancers are thought to have a genetic component and several lines of evidence suggest that deficiencies in DNA repair may be a contributing factor. Little is known, however, about the frequency and distribution of variants of DNA repair genes in the general human population. The protein truncation test (PTT) was used to screen 136 healthy volunteers for protein-truncating variants of 10 DNA repair genes: APE, CDK7, ERCC1, WAF1, HOGG1, MGMT, POLB, UNG, HAAG, and CCNH. This sample consisted of 41males (30%) and 95 females (70%) with an average age of 25.3 years, ranging from 17 to 60 years of age. No truncating mutations were found in the 10 genes examined in any of the subjects. The 95% confidence interval for a proportion of 0 over the 272 alleles examined per locus is 0-0.01. The calculated frequency of truncating mutations in each of these genes, among the general population, is thus less than 1%. Among the 10 genes tested in 136 people, a single sample had no PCR product for HAAG, even though PCR products were obtained on all other genes. Total RNA dot hybridization confirmed the presence of HAAG mRNA transcripts in this sample. Despite identification of this single DNA repair variant, these results indicate a low frequency of truncating mutations in DNA repair genes in the general population.

Base Sequence↗

PubMed2000

Nitric oxide stimulatory and endothelial protective effects of idoxifene, a selective estrogen receptor modulator, in the splanchnic artery of the ovariectomized rat.

Estrogen is known to stimulate endothelial nitric oxide production and attenuate endothelial dysfunction after ischemia and reperfusion. However, estrogen therapy increases the risk of breast and endometrial cancer. The present study was designed to determine whether idoxifene, a selective estrogen receptor modulator without adverse effects on reproductive organs, may stimulate nitric oxide release and protect endothelial function. In U-46619 precontracted superior mesenteric arterial (SMA) segments isolated from ovariectomized rats, idoxifene and 17 beta-estradiol resulted in a comparable dose-dependent vasorelaxation (maximal relaxation: 75.3 +/- 4.9 and 71 +/- 4.7%, respectively). Treatment of the rings with N(omega)-nitro-L-arginine methyl ester completely blocked idoxifene- and 17 beta-estradiol-induced vasorelaxation. In vitro incubation of SMA rings with TNF alpha significantly reduced vasorelaxation to an endothelium-dependent vasodilator, acetylcholine (maximal relaxation: 73 +/- 3.7 versus 95 +/- 2.9% pre-TNF alpha, P <.01). Idoxifene, but surprisingly not 17 beta-estradiol, prevented TNF alpha-induced endothelial dysfunction (maximal relaxation: 86 +/- 2.6% in idoxifene-treated rings and 77 +/- 5.1% in 17beta-estrogen-treated rings). In vivo ischemia and reperfusion resulted in significant endothelial dysfunction as evidenced by decreased vasorelaxation to acetylcholine (maximal relaxation: 48 +/- 5.5 versus 92 +/- 3.9% in normal SMA rings), but a normal relaxation response to an endothelium-independent vasodilator, acidified NaNO(2) (95 +/- 3.2%). Treatment with idoxifene at either 1 or 2 mg/kg/day, or 17beta-estrogen at 1 mg/kg/day for 4 days significantly preserved endothelial function (P <.01 versus vehicle). Taken together, these results demonstrate that idoxifene is an endothelium-dependent vasodilator and exerts significant endothelial protective effects against TNF alpha- and ischemia-reperfusion-induced endothelial injury. These results suggest that selective estrogen receptor modulators have therapeutic potential in diseases where endothelial dysfunction plays an important role.

Animals↗

PubMed2000

[Kinetics for terephthalic acid anaerobic degradation with easily biodegradable organic material co-existence].

The fact of preferential substrate utilization results in a sequence of substrate attack. As typically, the easily biodegradable substrates in TA-containing wastewater are degraded firstly through methane fermentation pathway, and just those intermediate metabolites have been proved to be inhibitors for TA biodegradation. Moreover, TA itself can inhibit the TA biodegradation, too. A kinetic model for the anaerobic digestion of wastewater containing both TA and easily biodegradable pollutants is constructed as q = qmax [formula: see text], The model parameters are estimated with non-linear regression method, the values are as follows: qmax = 1972.0 mgTA/gVSS.d; Ks = 20.2844 gTA/L; Ki,i = 2.041 gCOD/L; Ki,s = 0.0108 gTA/L. The experimental data verification for the model equation is satisfactory. According to the model analysis, a new strategy, a two-step anaerobic system, dealing with this kind of wastewater is suggested.

Anaerobiosis↗

PubMed2000

[Nutrition condition of hyaluronic acid fermentation with Streptococcus zooepidemicus].

Based on the analysis of metabolic pathway Streptococcous zooepidemicus for hyaluronic acid (HA) synthesis, nucleotide, especially uracil, was considered to be important to cell growth and metabolism. When 0.005 g.L-1 uracil added in the media in which yeast extract as complex nitrogen source, cell growth and HA production were increased by 32% and 34% respectively. From analysis of amino acid in fermentation process, it was show that arginine(Arg) was needed for cell metabolism, and concentration of free Arg maintained at 0 g.L-1 in fermentation process, which was proposed to limit cell growth and HA production. By shake-flask experiment HA concentration reached 0.510 g.L-1 when 0.06 g.L-1 Arg added, in the fermentation with 2.5 L fermentor, when uracil 0.005 g.L-1 and Arg 0.06 g.L-1 were added, the rate of cell growth increased, maximum of specific growth rate, concentration of HA and HA molecular weight reached 0.67 h-1, 5.2 g.L-1 and 2.15 x 10(6) Da from 0.54 h-1, 4.2 g.L-1, 2.0 x 10(6) Da, respectively.

Arginine↗

PubMed2000

[Study on the biocompatibility and toxicology of biomaterials--poly(epsilon-caprolactone)].

Four observation indexes were selected to evaluate the biocompatibility and toxicology of biodegradable materials poly(epsilon-caprolactone)(PCL), which is synthesized in our laboratory using Ti(OBu)4 as an initiator. The results showed that PCL films had a mild inflammatory reaction in the early days of planting and after 3 months the inflammation basically disappeared. We conclude that PCL material possesses good biocompatibility and has a good developmental prospect.

Animals↗

PubMed2000

[The research advance of brain derived neurotrophic factor].

Recent research advances in neuroscience show that neurotrophic factors are proteins that affect selectively various kinds of neurons of CNS and PNS. Brain derived neurotrophic factor (BDNF) is another neurotrophic factor that was first reported by Barde, a German chemist, thirty years later after the nerve growth factor had been found out. BDNF plays an important role in the growth, development, differentiation, maintenance and regeneration of various types of neurons in the CNS and has potential application to the treatment of brain injury and neurodegenerative diseases such as Alzheimer's disease, Parkinson's syndrome, Huntington's chorea and amyotrophic lateral sclerosis. In this paper, the structure, function and potential clinical application of BDNF were reviewed.

Animals↗

PubMed2000

Early and late long-term effects of vasectomy on Zn, Cd, and Cu levels in prostatic fluid and serum.

AIM: To evaluate the early and late long-term effects of vasectomy on the serum and prostatic fluid trace elements. METHODS: In 37 vasectomized and 25 non-vasectomized (control) men, the Zn, Cd and Cu levels in the serum and prostatic fluid were measured by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES). RESULTS: No significant difference was found in the prostatic Zn, Cd and Cu levels between the vasectomized and control group. The Zn level in the serum were significantly lower in the vasectomized men than in the controls (11.04 and 13.54 umol/L, respectively; P < 0.05), while the serum Cd and Cu levels were not significantly different between the two groups. CONCLUSION: Vasectomy may decrease the serum, but not the prostatic Zn levels. Its pathophysiological significance is worthy of further investigation.

Body Fluids↗

PubMed2000

[Preparation of biological bone carrier].

A series of studies on biological bone carrier (BBC), including preparation methods, components analysis, animal implantation test, biomechanical strength, ultrastructure, cross antigenicity and clinical application are reported in this article. Comprehensive process was adopted to reduce the antigen of BBC. As a substitute for bone, BBC has the following merits: (1) good biocompatibility; (2) suitable mechanical strength; (3) natural porous structure and porosity; (4) absorbability and replaceability in host; (5) unlimited sources, ready availability and simplicity in process and storage; (6) both functions of osteoconductability and osteoinductability can be developed after BBC combined with BMP.

Animals↗

PubMed2000

The research and development of noncontact 3-D laser dental model measuring and analyzing system.

OBJECTIVE: To research and develop a new laser scanning 3-dimensional digitization system for collecting, showing, and measuring the data of dental casts. MATERIAL AND METHODS: According to the 3-dimensional measuring method, by using 2 pulsate motors to make the synthetic movement of the dental cast, a special semiconductor laser, and 2 special line array CCD, the 3-D data could be found anywhere on the surface of the dental cast. The program, developed with Visual C++ language under the Windows (Windows tm) system, can control the scanner, rebuild the 3-D graphics and measure the data of the dental cast. RESULTS: The system offers 70 x 70 x 70 mm measurement scope, 0.01 mm resoling power, < 0.1 mm mean deviation, and 25 mins for single cast scanning. CONCLUSION: The advantages of this system are its precision, simplicity, high efficiency, and wide range of measurements with complete direct view. This system also supplied new information that cannot be found with traditional measurement methods.

Computer Graphics↗

PubMed2000

[Establishment of cisplatin-induced multidrug resistant human epithelial ovarian cancer cell line 3AO/cDDP and its expressions of multidrug resistance proteins].

OBJECTIVE: To establish multidrug resistant ovarian cancer cell line 3AO/cDDP by exposing parent cell line intervally and repeatedly to high-level concentration of cisplatin, and to detect expressions of lung resistance protein (LRP), multidrug resistance-associated protein(MRP) and P-glycoprotein (P-gp). METHODS: Using the corresponding dose calculated from clinical chemotherapy, we established 3AO/cDDP, with 3AO exposed intervally and repeatedly to high-level concentration of cisplatin at 10 micrograms/ml for 24 hours each time; LRP, MRP and P-gp expressions were detected with flow cytometry(FCM). RESULTS: 3AO/cDDP was established after 4.5 months with stable resistance and the drug resistant index was 1.62 which was similar to clinical resistance degree. Low expression levels of MRP and P-gp were found in both 3AO and 3AO/cDDP, and no statistical difference between the two lines (P > 0.05). However, LRP expression level in 3AO/cDDP was significantly higher than that in 3AO with FCM detection (P < 0.01). CONCLUSIONS: 3AO/cDDP, induced by exposing 3AO to high-level concentration of cisplatin intervally and repeatedly, is an ideal model for investigation of cisplatin resistance. Cisplatin resistance in 3AO/cDDP could be related to high LRP expression and be not associated with MRP or P-gp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

[A new signal receptor family--a review of the current progress of Toll/IL-1R family].

Toll receptor was first identified in studies of dorsalventral polarity formation of drosophila embryo. As its similarity in structure, function and signal transduction pathway to the IL-1 receptor, Toll becomes a member of a new signal receptor family--the Toll/IL-1R family. Besides participating in embryonic development, this signal receptor family also plays a key role in triggering innate defenses against pathogens, in which the function of human Toll protein in the pathogenesis of LPS is especially interested.

Amino Acid Sequence↗

PubMed2000

[Net photosynthetic rate of two species of wintering host mosses for gullaphids and its response to light, temperature and water content].

The net photosynthesis of Thuidium cymbifolium and Chrysocladium retrorsum, two species of wintering host mosses for gullaphids, and its response to light, temperature and water content were measured with CI-301PS(CID Inc. USA) both in winter and spring. The photosynthetic capacity of Thuidium cymbifolium and Chrysocladium retrorsum was about 141 and 117 mumolCO2kg-1dw.s-1, respectively, and trended to increase from winter to spring. The light saturation point of these two mosses at 800-900 mumol.m-2.s-1 was much higher than that of many other mosses, and the compensation point ranged from 40 to 50 mumol.m-2.s-1. The temperature response curves of these two mosses were similar, with optium temperature ranging from 25 to 36 degrees C in spring, and from 20 to 30 degrees C in winter. When the temperature was below the freezing point(-15 to 0 degree C), they both maintained a distinct net photosynthesis, with the optimum water content ranging from 200 to 300(400)% dw. The photosynthesis started to be restrained evidently, when the water content declined to about 150% dw. The gas exchange ceased or became negative, when the water content was as low as 40-50% dw. It can be inferred that these two species might be both poikilothermal and poikilohydric organisms, but the resistibility of T. cymbifolium to intense light and high temperature was higher than that of C. retrorsum.

Animals↗

PubMed2000

[Tolerance of various geographic populations of brown planthopper to adverse environmental stresses].

The populations of brown planthopper(BPH), Nilaparvata lugens, were collected from Zhejiang, Guangxi and Yunnan provinces to study their tolerance to various adverse environmental stresses. The results indicated that all of these three populations could adapt to the rice variety IR26 bearing resistant gene 1 (Bph1), and Guangxi and Yunnan populations could successfully infest rice varieties ASD7 bearing bph2 and Rathu Heenati bearing Bph3, implying that these two populations had a higher adaptability to resistant rice varieties. The significantly negative relationship between female brachypterous rate and nymphal density in Zhejiang population showed a lower tolerance to high nymphal density of Zhejiang population than that of Guangxi and Yunnan populations. A higher resistance to high temperature and a lower tolerance to starvation were obviously found in Guangxi and Yunnan populations. The resistance to insecticide (Omethoate) of Zhejiang population was little higher than that of Guangxi population. It was suggested that the tolerance of different geographic populations of BPH to various adverse environmental stresses be closely related to their habitat characteristics.

Animals↗

PubMed2000

[Environmental characteristic of walleye pollock fishing ground in high seas of the Okhotsk Sea in summer].

Based on the acoustic survey on the resource of walleye pollock (Theragra chalcogramma) in the high seas of the Okhotsk Sea, the distribution of walleye pollock and the environmental characteristics of its fishing ground were studied, and the relationship between them were analyzed. In August, the high schooling area of walleye pollock was situated in the waters with a depth of less than 500 meters and to the north of 55 degrees N. Walleye pollock mainly distributed in 150-300 m depth, and lived in groups. The main food was Euphausia pacifica, and the densely populated area of wall-eye pollock was roughly consistent with that of Euphausia pacifica. The thermocline was observed at 0-50 m depth, the temperature changed at a rate of 0.25 degree C per meter, and the cold water mass was roughly located in 50-150 m layer. The fish was mainly distributed in the layer below the cold water mass, because of the impeding effect of thermocline and the limiting action of fish food. It seldom inhabited the water below 400 m depth, partly because the dissolved oxygen there was rather low.

Animals↗

PubMed2000

[Effect of unsymmetrical cutting along both river slopes on rainstorm-runoff process].

A simulation experiment was conducted to compare the effect of cutting and no-cutting at both slopes along a river on the rainstorm run-off in catchment, and a model was constructed. The results showed that the appearance of outflow and peak flow of surface run-off was later on forest slope than on forest-cutting slope. On forest slope, the duration was prolonged, and the peak flow and surface runoff were lower. These effects were more obvious as the slope gradient was bigger. When rain intensity was 1.98 mm.min-1 and rainfall was 108.8 mm, the peak flow and the total runoff on both forested slopes of gradient 15 degrees was 5% and 4% less than that on the cutting slopes, respectively.

Rain↗

PubMed2000

[Hunger tolerance of Microvelia horvathi hibernating generation].

The experimental results showed that the hunger tolerance (HT) of different wing forms Microvelia horvathi adults had significant difference at 14-32 degrees C, and decreased with increasing temperature, which was 32.10 and 29.58 days at 14 degrees C, and 9.46 and 7.82 days at 32 degrees C, respectively for apterous and pterygote adults. The HT of apterous adults was higher than that of pterygote ones, and females was higher than males with the same wing form. The lower the temperature, the bigger the difference. The HT of M. horvathi adults differed obviously with densities. 1 female 1 male per bottle had a higher HT than 5 females 5 males per bottle and 10 females 10 males per bottle, while no difference was found between two latter densities. The HT of the 1st instar nymphs of M. horvathi had an obvious difference at different temperatures, which was significantly higher at 14 and 20 degrees C than at 26 and 32 degrees C.

Animals↗

PubMed2000

Effect of Q-switched alexandrite laser irradiation on dermal melanocytes of nevus of Ota.

OBJECTIVE: To investigate the effect of Q-switched alexandrite laser irradiation on dermal melanocytes of nevus of Ota. METHODS: Multiple biopsies were carried out on 4 patients with nevus of Ota before and after laser irradiation. Altogether 11 samples were examined under light microscope and 14 under transmission electron microscope. RESULTS: Immediately after laser irradiation, the dermal melanocytes were destroyed, the melanosomes were degenerated with central vesicle formation within most of them, and intradermal round vacuoles appeared. The epidermis remained intact. Three months to 1 year after irradiation, the degenerated melanosomes and cell debris were scavenged mainly by macrophages. Dermal melanocytes gradually decreased. No fibrosis was found. CONCLUSION: Q-switched alexandrite laser can selectively destroy dermal melanocytes of nevus of Ota and treat the disease safely.

Adolescent↗