Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 487 records · Page 27Linked to original sources

PubMed1999

[An investigation of immunoprotecting mechanism of macroencapsulated pancreatic islet xenograft].

Macroencapsulated islet xenografts in agarose are able to prevent rejection. This study was conducted to shed light on the immunoprotecting mechanism of macroencapsulated islet xenografts in agarose. There were four groups (n = 5 in each group): (1) macroencapsulated islet xenografts in agarose; (2) nonencapsulated islet xenografts; (3) agarose macroeencapsule without islet; (4) syngenic pancreatic islets. Mixed lymphocyte islet culture (MLIC) was used in the experiment. The results showed that stimulating index (SI) of MLIC and IL-2 level in the macroencapsulated islet xenografts in agarose group were similar to those of syngenic pancreatic islets group. The SI and IL-2 levels of nonencapsulated islet xenograft group were significant higher than those in macroencapsulated islet xenografts in agarose group and syngenic pancreatic islets group. These indicate that macroencapsulation is capable of reducing the immunogenicity of islet xenograft, and it is presumable that macroencapsulated islet xenografts in agarose be not recognized by the recipient's immune system because of being separated by the selectively permeable membrane made with agarose.

Animals↗

PubMed1999

[Study on cross-sections at the plane of the aortic arch and its adjacent structures].

The purpose of this study was to describe and explain the normal appearances of aortic arch and its adjacent structures on the transaxial sections and to provide anatomical data for the diagnosis of CT and MR images. Dissections were performed on 1.2 cm interval cross-sections of the thorax of 30 embalmed cadavers. The results showed 20.00 +/- 7.30% of the aortic arch and arch of the azygos vein at the same plane and 40.00 +/- 8.94% of the arch of the azygos vein at the level of concavity of the aortic arch. 80.00 +/- 7.30% of the top of the superior aortic recess extended to the level of the aortic arch from which the branchiocephalic trunk arises. At the level of the aortic arch, 100% of the lymph nodes of superior vena cava were located among the aortic arch, superior vena cava and trachea. At the level of azygos vein, 100% of the lymph nodes of azygos vein and the superior aortic recess were located among the superior vena cava, arch of azygos vein, trachea and concavity of aortic arch. These data suggest that aortic arch and arch of azygos vein are the key structures to identify the superior aortic recess and lymph nodes. They are essential for understanding the related pathologic changes depicted on CT and MR images.

Adult↗

PubMed1999

[Effects of reperfusion on neuronal changes and macrophagic response after transient focal ischemia--reperfusion of brain in rats].

Male SD rats(n = 29) were subjected to 2 hours' middle cerebral artery occlusion and were killed at various times of reperfusion (0.5-48 hours). The histological features of neuronal changes, the macrophagic response and the relationship between them were investigated. The neurons underwent acute changes(shrinking or swollen), and the pyknotic apoptotic neurons were occasionally seen within 3 hours. The number of apoptotic neurons increased with recirculation time. The scattered red neurons and ghost cells were first found at 6 hours of reperfusion. Many apoptotic neurons, apoptotic bodies were detected in the penumbra of ischemic core at 48 hours. Lectin histochemistry with GSI-B4 was performed to observe the macrophage. The results showed the active microglia and macrophage from meninges presented at 12 hours. The macrophages from parenchyma vessels appeared at 24 hours. Reactive microglia and extrinsic macrophage aggregated into the band of macrophage which phagocytized the apoptotic neurons. The results indicate that, firstly, it is important to prevent the neuronal apoptosis and reduce the volume of infarct in stroke patients; secondly, irreversible neuronal lesions simultaneously stimulate microglial activation and the presence of extrinsic macrophages from meninges was earlier than the appearance of the macrophages from parenchyma blood-monocytes. The authors also suggest that the data on the neuronal changes over time after ischemia and reperfusion be useful reference materials for selecting the most timely medication to treat cerebral infarction.

Animals↗

PubMed1999

[The expression of IGF-I, TGF beta and Fas-L in granulosa cells of ovarian follicle with relation to the onset of atresia in rats].

This study was designed to investigate the effects of IGF-I, TGF beta and Fas-L on the sustaining of granulosa cells of ovarian follicle and the modulation of apoptosis of those cells, and to understand the molecular mechanisms of ovarian follicle atresia. Paraffin-embedded sections of SD rat ovary were made. Both TUNEL method and PCNA immunohistochemistry were employed to recognize atretic and healthy follicles. The expression of IGF-I, TGF beta, Fas-L and their receptors was displayed by immunostaining. The results showed that most of the granulosa cells within the healthy preantral and antral follicles were PCNA(+). At the early stage of atretic antral follicle, more than 5 granulosa cells were labelled by TUNEL method, and some granulosa cells were PCNA(+). At the late stage of atretic antral follicle, were labelled by TUNEL method. The immunoreactive products of IGF-I, IGF-IR, TGF beta, TGF beta R, Fas and Fas-L could be seen in the granulosa cells of healthy antral follicles. But, Granulosa cells were only TGF beta, TGF beta R and Fas immunopositive in all atretic antral follicles. In conclusion, combination of TUNEL method and PCNA immunochemistry is of benefit for distinguishing atretic follicles from healthy follicles. IGF-I might play an important role in stimulating proliferation of the granulosa cells and sustaining them. The lower expression or disappearance of IGF-I in the antral follicle might cause the onset of atresia. TGF beta, Fas-L and Fas might mediate apoptosis of the granulosa cells in antral follicles, causing follicle atresia. But, their effects of mediation could be inhibited as IGF-I exists in the follicles.

Animals↗

PubMed1999

[A study on hemostatic and immunological actions of fresh and dry Dihuang].

OBJECTIVE: To investigate the difference between fresh and dry Dihuang (Radix Rehmanniae) in hemostatic and immunological actions. METHODS: The hemostatic action was assessed in aspirin-treated mice; immunological action was assessed by phagocytosis of macrophages in dexamethasone-treated mice; and Con A-induced mitogenesis and LPS-induced alkaline phosphatase activity of splenocytes were determined in thyroxin-treated mice. RESULT: The blood clotting in mice induced by aspirin was inhibited by oral administrations of juice decoction of fresh Dihuang or decoction of dry Dihuang alike. The action of fresh Dihuang juice was stronger than that of dry Dihuang decoction. Oral administrarion of fresh Dihuang juice or decoction for 10 days enhanced LPS-induced alkaline phosphatase activity of splenocytes in thyroxin-treated mice. The juice also enhanced Con A-induced splenocyte mitogenesis. The action of dry Dihuang decoction was weaker than that of fresh juice in increasing LPS-induced alkaline phosphatase activity. CONCLUSION: It is recommended to follow the tradition of using fresh Dihuang juice or decoction to treat some diseases such as hemorrhagenic troubles.

Animals↗

PubMed1999

[Effect of transforming growth factor-beta on proliferation cycle of epiphyseal chondrocyte].

In order to investigate the effect of transforming growth factor-beta (TGF-beta) on chondrocyte proliferation cycle, we used flow-cytometry to assess the epiphyseal chondrocyte of embryonic chick femora which was cultured in free-serum media and treated with TGF-beta. The results showed that after treated with TGF-beta for 24 h, the proliferation indexes(PIs) of experimental groups(0.11 ng, 0.33 ng, 1.00 ng/ml) were lower than the PIs of the control groups, but the PI of 3.00 ng/ml group was higher than that of the control group (P < 0.001). After treated for 48 h, except the 0.11 ng/ml group, the PIs of experimental groups were lower than those of the control (P < 0.001). And after treated for 96 h, the PIs of all groups were higher than those of the control; the PI of the 0.33 ng/ml group was the highest (P < 0.001). These suggest that after treated in varied time and dosage, the effect of TGF-beta on epiphyseal chondrocyte is obvious, and TGF-beta on epiphyseal chondrocyte is obvious, and TGF-beta can inhibit chondrocyte proliferation first, and then its effect on chondrocyte can transform from inhibition into proliferation.

Animals↗

PubMed1999

[Calcium and chronic diseases].

Calcium plays a role in physiological functions in our body. Many diseases are associated with physiological dysfunction caused by abnormal calcium homeostasis. In this review, we discussed the relationships between calcium and some common chronic diseases including cardiovascular diseases. Here we put emphasis on hypertension and atherosclerosis, tumor, osteoporosis and osseous hyperostosis. The most appropriate daily calcium intake and adverse effects of high-calcium diets are also mentioned in this article.

Animals↗

PubMed1999

[Investigation of aluminum oxide matrix of the machinable infiltrated ceramic(MIC)].

OBJECTIVE: To explore the effects of different powder/liquid ratio during the procedure of aluminum oxide slip preparation on the properties and microstructure of the machinable infiltrated ceramic(MIC) aluminum matrice. METHODS: PI alpha-Al2O3 powder was employed in this study. Aluminum slip with different powder/liquid ratios of 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5 and 10.5 was prepared separately. Specimens were slip-casted and pre-fired, and whose physical properties were determined and morphology of specimens was examined under scanning electromicroscope. RESULTS: The packing density increased while the linear shrinkage decreased, when the powder/liquid ratio increased. Elevated pre-firing temperature resulted in higher flexural strength of the matrice. The matrice demonstrated porous morphology under electromicroscope, and neck-fusion between Al2O3 particles was observed and increased with elevated prefiring temperature. CONCLUSION: MIC is a kind of easy-manipulated material with high packing density, optimum porosity and lower linear shrinkage, so it may be an ideal aluminum matrix for infiltrated ceramic.

Aluminum Oxide↗

PubMed1999

[Study on mechanical compression regulating the proliferation of rat mandibular condylar chondrocytes in vitro].

OBJECTIVE: To study the proliferative changes of cultured rat mandibular condylar chondrocytes effected by mechanical compression. METHODS: Using flow cytometry(FCM) to explore the changes of cellular DNA content and cell cycles of passaged condylar chondrocytes. RESULTS: During certain force range (0-207 g/cm2), the proliferation of rat mandibular condylar chondrocytes rose, reaching the maximum after 6-hour application of force. The cellular proliferation went down when the chondrocytes were cultured under continuous pressure for 24 hours. CONCLUSION: The proliferation of rat mandibular condylar chondrocytes increase under certain force and certain period of time, but decreased if the applied pressure is beyond the magnitude.

Animals↗

PubMed1999

[Color comparison of VITA shade guide and metal ceramic restoration].

OBJECTIVE: To understand color distribution of Vita shade guide and metal ceramic restoration and make Vita shade guide more reasonable in clinical applying. METHODS: The international standard CIE1976L*a*b* color system and Minolta CR-100 spectrocolorimeter were selected to measure and compare the characteristics of the shade guide and metal ceramic restoration. RESULTS: Color differences were noted between the shade guide and ceramic restorations. The value of metal ceramic restoration was brighter than that of VITA shade guide tab. There was different chroma between metal ceramic restoration and Vita shade guide. Metal ceramic restorations were yellower and redder. But no saturation differences were found between ceramic restorations and D2, D3 tabs. CONCLUSION: During clinical color-matching of metal ceramic porcelains, it is suggested that a VITA shape guide tab with lower brightness and paler color than that of adjacent teeth should be selected.

Colorimetry↗

PubMed1999

[Effects of human thorax tissues on conduction of electrocardiogram and body surface potential].

In this paper, the forward problem of electrocardiogram(ECG) has been calculated by means of numerical simulating techniques. Firstly, It is focused on the effects of organs and tissues within the thorax on the body surface potentials under a 2-D cross section of thorax in terms of finite element method (FEM). To check the effect of skeletal muscle layers on ECG, the simulating computation of ECG, by a method combining FEM with boundary element method (BEM), has been carried out in terms of a 3-D thorax model.

Algorithms↗

PubMed1999

[Direct determination of purine bases in tea by reversed-phase high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic(RP-HPLC) method for the direct determination of three purine bases(theobromin, theophyllin and caffeine) in tea was developed. An ODS column with Zorbax SB-C18(4.6 mm i.d. x 250 mm, 5 microns) was employed. The aqueous solution of methanol containing 0.05% of acetic acid and 0.25% of N,N-dimethylformamide(DMF) was used as eluent with a flow rate of 0.8 mL/min. In this method, the aqueous extract of tea can be injected into HPLC directly, but in current HPLC methods for purine bases the coexisted tea polyphenols must be pre-separated. The three purine bases in tea were separated without any interference from the coexisted tea polyphenols. This method is simple (without any special sample pretreatment) and sensitive with detection limits (S/N = 3) of 0.7, 0.9 and 1.8 mg/L for theobromin, theophyllin and caffeine respectively. The linear range of the calibration curve of peak area for the three purine bases were from 6 mg/L to 1,000 mg/L with a correlation coefficient (r) of 0.998-0.999.

Caffeine↗

PubMed1999

[Studies on the metabolism pathway of aniline degradation by Comamonas acidovorans AN3].

All of the enzymes relating to aniline degradation in C. acidovorans AN3 were inducible ones. When growing on aniline as sole carbon, nitrogen and energy sources, the cells of C. acidovorans AN3 contained aniline dioxygenase, catechol-2, 3-dioxygenase, 2-hydromuconic semialdehyde dehydrogenase, 4-oxalocrotonic acid decarboxylase and 4-hydroxy-2-oxovalerate acid aldolase. The Km and Vmax of aniline dioxygenase were 292 mumol/L and 3.57 mumol.mg-1. min-1, respectively. The Km and Vmax of catechol-2, 3-dioxygenase were 16.4 mumol/L and 15.2 mumol.mg-1.min-1, respectively. According to these results, the degradation metabolism pathway of aniline by C. acidovorans AN3 was hypothesised.

Aniline Compounds↗

PubMed1999

[Effect of promoter-PTH4 on Streptomyces sporulation].

233 bp of promoter--PTH4 was subcloned into Streptomyces plasmid pIJ4083. pIJ4470 was obtained after recombinant plasmid was introduced into Streptomyces coelicolor J1501. Both Streptomyces coelicolor J1501/pIJ4083 and J1501/pIJ4470 were grown on minimal medium (MM) agar containing mannitol and 10 micrograms/mL thiostrepton for 6 days, and then ultrathin sections of colonies were prepared and stained with silver proteinate to observe glycogen biosynthesis in cell by the electron microscope. Result showed that the glycogen was produced by J1501/pIJ4083, whereas little glycogen was produced by J1501/pIJ4471. The dark color spores were not observed in J1501/pIJ4470 with lead stain in contrast with dark color spores which were produced by J1501/pIJ4083, indicating that promoter PTH4 may play an important role in physiological and morphological differentiation of Streptomyces.

Gene Expression Regulation, Bacterial↗

PubMed1999

[Anti-Toxoplasma effect of activated mouse macrophages induced by interferon-gamma combined with TNF-alpha].

AIM: To compare the inhibitory effect of the macrophages activated by IFN-gamma combined with TNF-alpha against RH strain and Fukaya strain. METHODS: The average parasite proliferation rates of the two strains within the cytokine-activated M phi s were calculated at different times post-challenge, the nitric oxide (NO) levels in the medium supernatant were simultaneously determined. RESULTS: In the macrophages activated by 100 U each of IFN-gamma and TNF-alpha, the invaded tachyzoites of RH strain were completely killed, while the invaded tachyzoites of Fukaya strain remained slow proliferation with significantly lower levels of NO detected at 24 h post challenge. CONCLUSION: The difference in the anti-Toxoplasma effect of the activated macrophages against RH and Fukaya strains might be attributed to the different amount of NO produced by the macrophages.

Animals↗

PubMed1999

[Comparison of sensitivity of artesunate-sensitive and artesunate-resistant Plasmodium falciparum to chloroquine and amodiaquine].

AIM: To explore the in vitro sensitivity of artesunate-sensitive and -resistant Plasmodium falciparum to chloroquine and amodiaquine and to observe the effect of artesunate combined with chloroquine and artesunate combined with amodiaquine on artesunate-resistant P. falciparum. METHODS: The sensitivity of the artesunate-sensitive and -resistant P. falciparum to chloroquine and amodiaquine and their combination with artesunate was compared by using Rieckmann's in vitro micro-technique. RESULTS: The ID50 and ID95 values of chloroquine, amodiaquine and artesunete were 90.9, 50.9, 9.6 nmol/L and 320.0, 320.0, 40.0 nmol/L to the artesunate-sensitive P. falciparum respectively and were 112.0, 133.5, 85.1 nmol/L and 320.0, 320.0, 400.0 nmol/L to artesunate-resistant P. falciparum, respectively. When artesunate was combined with chloroquine, the ID50 values of the 2 drugs were 3.2 and 20.0 nmol/L to the artesunate-resistant P. falciparum. When artesunate was combined with amodiaquine, the ID95 values of the 2 drugs were 3.2 and 5.0 nmol/L to the artesunate-resistant P. falciparum, respectively. CONCLUSION: The artesunate-resistant P. falciparum has no cross resistance to chloroquine and amodiaquine, however, artesunate combined with chloroquine or amodiaquine exhibit an apparent synergistic effect in vitro.

Amodiaquine↗

PubMed1999

[Detecton of circulating antigen in sera from mice infected with Toxoplasma tachyzoites].

AIM: To explore an assay method for the early diagnosis of Toxoplasma infection. METHODS: Serum samples collected from three groups of mice infected experimentally with different doses of Toxoplasma trophozoites were detected for the presence of Toxoplasma circulating antigen by using fast ELISA. RESULTS: Toxoplasma circulating antigen was detected on days 4, 4 and 3 after infection in light, moderate and heavy infection groups, respectively. CONCLUSION: The level of circulating antigen was in parallel with the duration of infection. The determination of circulating antigen is useful in the early diagnosis of Toxoplasma infection.

Animals↗

PubMed1999

[Assay of sensitivity of Plasmodium falciparum to chloroquine, amodiaquine, piperaquine, mefloquine and quinine in Yunnan province].

AIM: To determine the sensitivity of P. falciparum to chloroquine, amodiaquine, piperaquine, mefloquine and quinine in Yunnan Province of China in 1992-1995. METHODS: Rieckmann's in vitro microtechnigue was used. The sensitivity of P. falciparum was tested to the above-mentioned antimalarials. RESULTS: The resistance rates of isolates of P. falciparum from the south, southeast and the west part of Yunnan to chloroquine and amodiaquine were 96.7% (29/30), 78.9% (30/38), 95.7% (22/23) and 100% (30/30), 85.3% (29/34), 8/9, respectively, with their corresponding ID50 of 125 nmol/L, 136 nmol/L and 176 nmol/L, and 52 nmol/L, 64 nmol/L and 72 nmol/L, respectively. All the isolates were sensitive to quinine and their ID50 were 480 nmol/L, 352 nmol/L, 608 nmol/L, respectively. The resistance rates of P. falciparum from the south part and southeast part of Yunnan to piperaquine were 96.4% (27/29), 72.9 (27/37), respectively, their ID50 were 320 nmol/L and 228 nmol/L; all the cases were sensitive to mefloqine, their ID50 were 68 nmol/L and 88 nmol/L. CONCLUSION: P. falciparum generally produces resistance to chloroquine, amodiaquine and piperaquine in Yunnan Province; the degree of resistance to chloroquine of P. falciparum from the west part of Yunnan were higher than the P. falciparum from the southeast part of Yunnan; all the isolates were sensitive to mefloquine and quinine in this region.

Amodiaquine↗