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Biomedical subjects

Zhen Yang

Publications and source records attributed to Zhen Yang.

At least 91 records · Page 5Linked to original sources
PubMed2003

Measurement of ammonia volatilization from a field, in upland Japan, spread with cattle slurry.

Ammonia volatilization from livestock manure is one of the most important pathways of nitrogen loss from agricultural cultivated fields. In this paper, we report the measurement of ammonia emission from cattle slurry manure applied to upland in Miyazaki, Japan. It has been determined that after the cattle slurry was sprayed on the upland surface, the emission flux of the first day was 110 microg N ha(-1) s(-1). The loss of NH4(+) -N in the applied slurry was 60% after 5 days following the spraying of cattle slurry.

Agriculture↗
PubMed2003

Diversity oriented synthesis and branching reaction pathway to generate natural product-like compounds.

Combinatorial chemistry can be used to synthesize diversified molecules on a large scale. As with all large-scale experiments, this process requires a major investment in equipment, consumables and time. Therefore, careful design is critical. As the complexity of the libraries to be generated increases, additional considerations become important. What are the issues that should be considered when planning combinatorial chemistry projects? Which features in the design strategy are critical to consider ensuring that all of the potential products will be synthesized? How are the reactants selected to optimize product synthesis and yield? Over the last several years, through an experimental process, we have successfully developed and optimized our synthetic strategy. Our approach incorporates a number of critical components into a tightly controlled process that generates molecules with maximal structural complexity. This complexity emanates from carbon-carbon bond formation, which is extremely stable and it is reminiscent of complex natural product molecules. Our studies have illustrated that transition metal catalysts are powerful reagents that can be used to drive the synthesis of diverse small molecules from less complex starting materials. In this review, we will describe some of our recent efforts to synthesize natural product-like molecules and their derivative structures to successfully create libraries of complex molecules for drug discovery applications. Our diversity-oriented synthesis methods incorporate transition metal catalysts, as a versatile tool for creating carbon-carbon bonds and structural complexity, and the branched reaction pathway, as a method for incorporating diversity into the molecular scaffolds. We will review our combinatorial chemistry program, focusing on the decisions that we made for (1) the scaffold selection; (2) the design of a diversity oriented approach for library synthesis; (3) the incorporation of the branched reaction pathway to generate natural product-like molecules from the same starting material; and (4) the process steps that we selected for chemistry development and library generation.

Biological Factors↗
PubMed2003

Heat shock protein 90 is responsible for hyperdynamic circulation in portal hypertensive rats.

AIM: To examine the participation of HSP90 in portal hypertensive rat mesentery in vitro. METHODS: Immunohistochemistry and Western-blot were used to examine the expression of HSP90 in mesenteric vasculature. HSP90 mRNA was detected by RT-PCR, and the role of HSP90 in hyperdynamic circulation was examined by in vitro mesenteric perfusion studies. RESULTS: HSP90 was overexpressed in endothelium of mesentery vasculature in animals with experimental portal hypertension induced by partial portal vein ligation (PVL) compared with normal animals. Geldanamycin (GA), a special inhibitor of HSP90 signaling, attenuated ACh-dependent vasodilation but did not affect vasodilation in response to sodium nitroprusside in normal rats. In PVL animals, the perfused mesentery was hyporesponsive to vasoconstrictor methoxamine. GA significantly potentiated methoxamine-induced vasoconstrictor after PVL. CONCLUSION: HSP90 plays a key role in NO-dependent hyperdynamic circulation in portal hypertension and provides a novel method for future treatment of portal hypertension.

Acetylcholine↗
PubMed2003

Angiogenesis effect on rat liver after administration of expression vector encoding vascular endothelial growth factor D.

AIM: To verify the expressing efficiency and angiogenesis effect after administration of expression vector encoding for vascular endothelial growth factor D in normal and ischemic rat liver. METHODS: Ten female S-D rats were administrated with liver tissue dot injection of naked PCHO/hVEGF-D, 50 microg/dot, three dots for each. The same amount of physiological saline was used as control in the neighboring lobe. Fourteen S-D rats, using inflow occlusion of left lateral lobe, were divided into two groups, seven rats in each group. One was ischemic plasmid group, which received naked plasmid PCHO/hVEGF-D injection of 150 microg. The other received the equal amount of natural saline injection and designed as control. The expressions of hVEGF-D in mRNA and protein levels were identified by in situ hybridization and immunohistochemistry, respectively. Endothelial cells were labeled by the factor VIII immunohistochemistrically. The average number of peri-sinusoidal capillaries of each group was calculated and compared statistically 8 days after injection. RESULTS: A large amount of hVEGF-D in mRNA level was found in both normal and ischemic plasmid groups and but none in their corresponding control groups. The protein of hVEGF was also highly expressed in both normal and ischemic plasmid groups than in the controls. The mean number of capillaries under microscopy (X200) of the plasmid group and control was 10.2+/-2.78 vs 7.1+/-2.02 (P<0.05), and those of ischemic plasmid group and ischemic control were 7.43+/-1.72 vs 4.71+/-1.11 with statistical difference (P<0.05). CONCLUSION: The naked PCHO/hVEGF-D dot injection to normal, ischemic rat liver can produce comparatively high expression of hVEGF in both protein and mRNA levels, and prominently increase the number of new capillaries around hepatic sinuses. Therefore, it could be another ideal choice for the treatment of ischemic liver diseases.

Animals↗
PubMed2003

Expression of local renin and angiotensinogen mRNA in cirrhotic portal hypertensive patient.

AIM: To investigate the expression of local renin and angiotensinogen mRNA in cirrhotic portal hypertensive patients. METHODS: The expression of local renin and angiotensinogen mRNA in the liver, splenic artery and vein of PH patients was detected by RT-PCR analysis. RESULTS: Expression of local renin mRNA in the liver of control group was (0.19+/-0.11), significantly lower than that in splenic artery (0.45+/-0.17) or splenic vein(0.39+/-0.12) respectively, (P<0.05). Expression of local angiotensinogen mRNA in the liver was (0.64+/-0.21), significantly higher than that in splenic artery(0.41+/-0.15) or in splenic vein (0.35+/-0.18) respectively, (P<0.05). Expression of local renin mRNA in the liver, splenic artery and vein of PH group was (0.78+/-0.28), (0.86+/-0.35) and (0.81+/-0.22) respectively, significantly higher than that in the control group, (P<0.05). Expression of local angiotensinogen mRNA in the liver, splenic artery and vein of PH group was (0.96+/-0.25), (0.83+/-0.18) and (0.79+/-0.23) respectively, significantly higher than that in the control group, (P<0.05). There was no significant difference between the liver, splenic artery and vein in the expression of local renin or local angiotensinogen mRNA in PH group, (P<0.05). CONCLUSION: In normal subjects the expression of local renin and angiotensinogen mRNA was organ specific, but with increase of the expression of LRAS, the organ-specificity became lost in cirrhotic patients. LRAS may contribute to increased resistance of portal vein with liver and formation of splanchnic vasculopathy.

Adult↗
PubMed2003

In vivo adaptive response of the peripheral conduit artery in patients with borderline systolic hypertension.

OBJECTIVE: To investigate elastic changes of the radial artery, a medium-sized muscular peripheral conduit artery, in patients with borderline systolic hypertension. METHODS: Using a non-invasive high-resolution echo-tracking device coupled to a photoplethysmography (Finapres system) allowing simultaneous arterial diameter and finger blood pressure monitoring, we measured radial artery elastic parameters of 20 patients with borderline systolic hypertension and 20 normal subjects according to Langewouters model. RESULTS: The diameter of the radial artery of control subjects and those with borderline systolic hypertension at the isobaric level of 100 mmHg and mean arterial pressure was similar, but the compliance and distensibility at similar conditions in patients with borderline systolic hypertension did not further reduced and even increased. CONCLUSION: In patients with borderline systolic hypertension, the adaptive responses of the radial artery compliance and distensibility to increased pressure were directed to maintain its elasticity, contributing to the homeostasis of the cardiovascular system.

Adaptation, Physiological↗
PubMed2003

NF-kappaB/I-kappaB pathway during ischemia reperfusion injury of rat liver.

OBJECTIVE: To determine the role of the NF-kappaB/I-kappaB pathway during ischemia reperfusion (I/R) injury to rat liver. METHODS: A group of rats underwent partial hepatic ischemia and reperfusion. The left and median lobe of the liver was subjected to ischemia for 90 minutes followed by reperfusion for previously specified periods. NF-kappaB activity was analyzed by electrophoretic mobility shift assay (EMSA). The protein level of I-kappaB was assessed using Western blot analysis. A semiquantitative reverse transcriptase polymerase chain reaction was used to analyze TNF-alpha and ICAM-1 mRNA levels. RESULTS: During liver I/R injury, NF-kappaB activation was induced in a time-dependent fashion. NF-kappaB was activated within 1 hour and 2 hours after the initiation of reperfusion and decreased afer 4 hours. The I-kappaB protein level was decreased in the cytoplasm after 2 hours, and the messenger RNA expression of TNF-alpha and ICAM-1 were increased simultaneously. CONCLUSIONS: The data suggest that I-kappaB protein was degraded during hepatic I/R injury, NF kappaB was released and bound to special sequence in the promoters of budget genes, which regulated the expression of TNF-alpha and ICAM-1 mRNA. This provides evidence that the NF-kappaB/I-kappaB pathway plays an important modulating role in the expression of proinflammatory genes relevant to the development of ischemia reperfusion injury.

Animals↗
PubMed2003

[Effects of short-term treatment of somatostatin on angiogenesis of gastric carcinoma].

BACKGROUND & OBJECTIVE: It is a hot spot in tumor therapies to inhibit the angiogenesis of carcinoma. Our current study was designed to investigate the inhibitory effect of somatostatin analogue on the angiogenesis of gastric carcinoma by hypodermic injection. METHODS: Twenty-five patients who have positive expression of vascular endothelial growth factor(VEGF) and somatostatin receptor 2(SSTR2)were selected by gastroscopic biopsy and immunohistochemical staining before surgical operation. After 7 days of Sandostatin administration (10 microg/kg, hypodermic injection, twice a day), the tumor extirpations were made. During the Sandostatin treatment, the serum levels of VEGF and the basic fibroblast growth factor(bFGF)were measured by enzyme-linked immunosorbant assay (ELISA) (d1,d3,d7, separately). Before and after operation,the expression levels of VEGF and bFGF were examined by Western blot analysis and the density of micro-vessels was determined by immunohistochemical staining. RESULTS: After a week of Sandostatin therapy,the concentration of VEGF and bFGF in serum was drastically diminished (VEGF:1.02+/-0.41 microg /L vs 1.88+/-0.87 microg/L, P< 0.05;bFGF:0.88+/-0.32 ng/L vs 2.12+/-1.06 ng/L,P< 0.05). The expression levels of VEGF(absorbance:1.306 vs 488,P< 0.01) and bFGF(absorbance:1.287 vs 512,P< 0.01) were obviously decreased after the remedy. The density of micro-vessels turn to the less, but there was no statistical difference before and after operation(P >0.05). CONCLUSION: By the short-term therapy of sandostatin, the expression of VEGF and bFGF can be inhibited. There is a tendency that the serum levels of VEGF and bFGF decrease with the increase of therapy time.

Adult↗
PubMed2003

[The effect of pinyangmycin, dexamethasonum and sodium morrhuate injected concomitantly to treat cavernous hemangioma].

OBJECTIVE: The effect of Pinyangmycin, Dexamethasonum and Sodium Morrhuate injected concomitantly to treat cavernous hemangioma in oral and maxillofacial regions was evaluated. METHODS: The medical records of 350 patients with cavernous hemangioma in oral and maxillofacial regions between January 1998 and January 2002 were reviewed. One hundred and sixty-five of the patients were men, and 185 were women, the sex ratio was 1:1.12. The patients' ages were between 4 months and 55 years. Two hundred and Twenty-six hemangiomas were located in the maxillofacial regions, and 124 located in the oral cavity. The size of the lesions varied from 1 cm x 1 cm to 6 cm x 9 cm. Pinyangmycin, Dexamethasonum and Sodium Morrhuate were injected simultaneously into the lesions or in the vicinity of the cavernous hemangiomas, and the injection might be repeated every 5 to 7 days when necessary, and this process could be repeated 3 to 5 times. RESULTS: Three hundred and fifty patients were followed up for 6-48 months. The cure and essentially cured rates were 95.48%, the total efficiency rate was 100%. CONCLUSION: This method was a safe, simple and effective therapy to manage cavernous hemangioma in the oral and maxillofacial regions.

Adolescent↗
PubMed2002

Phenyliodonium zwitterion as an efficient electrophile in the palladium-catalyzed suzuki-type reaction: a novel method for the synthesis of 3-aryl-4-hydroxycoumarins.

[reaction: see text] A palladium-catalyzed coupling reaction of phenyliodonium zwitterions with aryl boronic acids has been developed. The unique characteristics of the mild reaction conditions and convenient synthetic accessibility of phenyliodonium zwitterions make this method a valuable tool for generating diversified 3-aryl-4-hydroxycoumarins.

Journal Article↗
PubMed2002

Palladium-catalyzed carbonylative annulation of o-alkynylphenols: syntheses of 2-substituted-3-aroyl-benzo[b]furans.

We report here a general synthetic methodology for palladium-catalyzed carbonylative annulation of o-alkynylphenol to construct 2-substituted-3-aroyl-benzo[b]furan. On the basis of the results, this methodology could be applied to a wider selection of iodide substrates to generate desired products. In accordance with mechanistic studies, this process involves coordination of cationic and less hindered acyl palladium complexes with o-alkynylphenols to create a desired cascade triad (coordination, nucleophilic addition, and reductive elimination). Consistent with this mechanism, addition of 1 equiv of AgBF(4) to palladium catalyst Pd(Ph(3)P)(4) generates an ideal candidate for this unique transformation.

Benzofurans↗
PubMed2002

A world-to-chip socket for microfluidic prototype development.

We report a prototype for a standard connector between a microfluidic chip and the macroworld. This prototype is the first to demonstrate a fully functioning socket for a microchip to access the outside world by means of fluids, data, and energy supply, as well as providing process visibility. It has 20 channels for the input and output of liquids or gases, as well as compressed air or vacuum lines for pneumatic power lines. It also contains 42 pins for electrical signals and power. All these connections were designed in a planar configuration with linear orthogonal arrays. The vertical space was opened for optical measurement and evaluation. The die (29.1 mm x 27.5 mm x 0.9 mm) can be easily mounted and dismounted from the socket. No adhesives or solders are used at any contact points. The pressure limit for the connection of working fluids was 0.2 MPa and the current limit for the electrical connections was 1 A. This socket supports both serial and parallel processing applications. It exhibits great potential for developing microfluidic systems efficiently.

Electrochemistry↗
PubMed2002

Increased expression of endothelin receptors in human cirrhosis--relationship with splanchnic hemodynamics.

The purpose of the present study was to assess the correlation that likely exists among increased portal pressure (Pp), portal blood flow quantity (Qp) and ETA and ETB receptor mRNA expression in human cirrhosis. In situ hybridization and reverse-transcription polymerase chain reactions (RT-PCR) were performed to determined the expression of ETA and ETB receptor mRNA in liver tissues from traumatic subjects (n = 10) and cirrhotic patients (n = 15) in whom hepatic hemodynamic values were measured. The expression of the two transcripts was significantly higher in liver samples of cirrhotic patients than in those obtained from traumatic subjects. It has shown that ETA receptor mRNA predominantly located in hepatic stellate cells (HSCs) and vascular smooth muscle cells of intrahepatic arteries and portal veins, ETB receptor mRNA in HSCs, sinusoidal endothelial cells and Kuppfer cells. There was a highly significant direct relationship between ETA and ETB receptor mRNA and Pp and Qp in cirrhotic patients. It suggests that liver paracrine endothelin system may be overactivated in human cirrhosis accompanied with increased expression of ETA and ETB receptor mRNA which may play an important role in the pathogenesis and maintenance of splanchnic hyperdynamics.

Female↗
PubMed2002

Pathological morphology alteration of the splanchnic vascular wall in portal hypertensive patients.

OBJECTIVE: To investigate the pathological morphology alteration of the splanchnic vascular wall in portal hypertensive patients. METHODS: Splenic arteries, veins and gastric coronary veins from portal hypertensive patients (n = 50) were removed during esophagogastric devascularization with splenectomy and were observed under optic and electron microscopes. The expression of iNOS in the splenic artery wall was analysed with immunohistochemistry. RESULTS: The internal elastic membrane and medial elastic fibers of the splenic artery wall were broken and degenerated. Atrophy, apoptosis and phenotypic changes were seen in smooth muscle cells of splenic arteries. Positive staining for iNOS was seen in the cytoplasm of smooth muscle cells and iNOS activity was elevated compared with the non-cirrhotic patients (P < 0.01). In the splenic and gastric coronary veins of cirrhotic patients, we found proliferative intima, extensive thrombi adhering to the venous wall, mimicked arteriosclerosis plaques accompanied with hypertrophy of smooth muscle cells, and thickened muscle fibers of veins with increase in extracellular matrix. CONCLUSION: Portal hypertension may be complicated by splanchnic arterial and venous vasculopathy. There may be an interactive relationship among portal hypertension, splanchnic hyperdynamic disturbances and splanchnic vasculopathy in the pathogenesis of portal hypertension.

Adult↗
PubMed2002

Expressions of vascular endothelial growth factor in cirrhotic tissues and their relations to proto-oncogene c-fos, c-myc.

OBJECTIVE: To investigate the significance of vascular endothelial growth factor (VEGF) in the pathogenesis of liver cirrhosis and the correlation between VEGF and proto-oncogene c-fos and c-myc in cirrhotic liver. METHODS: The proteins of VEGF, c-fos, and c-myc were identified immunohistochemically in each tissue section of 53 cases of liver cirrhosis. The correlations between VEGF, c-fos and c-myc were analyzed. The levels of VEGF protein in different Child gradings were also compared. RESULTS: The proteins of VEGF were more highly expressed in Child A and B patients than in Child C patients and controls. The expressions of both c-fos and c-myc were not statistically significant between VEGF positive and negative patients. CONCLUSIONS: The protein level of VEGF can reflect the compensation status of cirrhosis patients and may act as an anti-cirrhotic factor. The proto-oncogene c-fos, c-myc and VEGF may have different mechanisms in the course of cirrhosis or hepatic tumorigenesis.

Adolescent↗