Biomedical subjects
Publications and source records attributed to Hong Chen.
A bisdesmosidic steroidal saponins library, composed of 16 novel kryptogenin glycosides, was set up via six random glycosylation procedures, wherein two compounds showed their antitumor activity against HeLa cell in the preliminary pharmacological research.
RanBPM as a novel binding protein can interact with neurotrophin receptor p75NTR and tyrosine kinase receptor Met which has a similar tyrosine kinase structure as receptor TrkA has. Whether RanBPM interacts with neurotrophin receptor TrkA has not been established to date. In this study, using yeast two-hybrid system, it was identified that RanBPM bound to the intracellular domain (ICD) of neurotrophin receptor TrkA through its SPRY motif. We confirmed the formation of complexes between RanBPM and TrkA by co-immunoprecipitation studies and GST pull-down assays. The region of TrkA interacted with the SPRY domain of RanBPM was located in its tyrosine kinase domain. Furthermore, coimmunoprecipitaiton revealed endogenous RanBPM and receptors TrkA did interact in several mammalian cell lines. It was found that the overexpression of RanBPM could inhibit NGF-induced increase of nuclear factor of activated T cells (NFAT) dependent luciferase expression through its interaction with receptor TrkA, and NFAT transcriptional activity plays an important role in neuronal signal transduction. These data suggested that RanBPM could participate in neurotrophin-mediated gene transcription and expression by its binding to TrkA.
Two Y chromosome specific microsatellites UMN2404 and UMN0103 were genotyped and assessed for polymorphisms in a total of 423 unrelated males from 25 indigenous Chinese cattle breeds. Consistently, both microsatellites displayed specific indicine and taurine alleles in each bull examined. The indicine and taurine alleles were detected in 248 males (58.6%), and 175 males (41.4%), respectively, although these frequencies varied amongst different breeds examined. The indicine alleles dominated in the southern group (92.4%), while the taurine alleles dominated in the northern group (95.5%). Hainan Island was possibly the site for the origin of Chinese zebu, and Tibetan cattle were probably independently domesticated from another strain of Bos primigenius. The geographical distribution of these frequencies reveals a pattern of male indicine introgression and a hybrid zone of indicine and taurine cattle in China. The declining south-to-north and east-to-west gradient of male indicine introgression in China could be explained by historical data, geographical segregation and temperature and weather conditions.
A series of bamboo-like CN(x)() nanotubes have been synthesized from pyridine precursor by chemical vapor deposition with bimetallic Fe-Co/gamma-Al(2)O(3) catalyst in the range of 550 approximately 950 degrees C. An unusual predomination of pyridinic nitrogen over graphitic nitrogen has been observed for the CN(x)() nanotubes with reaction temperature below 750 degrees C. The pyridinic nitrogen decreases and the graphitic nitrogen increases with rising reaction temperature. A synergism mechanism of C(5)N-six-membered-ring-based growth through surface diffusion and vapor-liquid-solid growth through bulk diffusion was accordingly deduced and schematically presented. This mechanism could not only explain our own experimental results, but also understand the CN(x)()-nanotube-related experimental phenomena in the literature, as well as be in accordance with the basic principle of diffusion kinetics. A promising route to the challenging topic for synthesizing regularly arranged C(5)N or high-N-content CN(x)() nanotubes has also been suggested.
OBJECTIVE: To investigate the changes of vessel function, vessel injury, blood viscosity and vessel regeneration in steroid-induced osteonecrosis of femoral head. METHODS: Forty Chinese white rabbits were randomly divided into 2 equal groups to be injected with: horse serum intravenously twice with an interval of 3 weeks and than prednisone intraperitoneally once a day for 5 days (Group A), or injected with prednisone once a day for 5 days (Group B). Whole blood samples were collected by intracordal puncture before intravenous injection in group A and B, 24 hr after injection of horse serum in group A, and 3, 7, and 21 days after prednisone administration. Radioimmunological methods were used to detect the plasma endothelin (ET) and thrombomodulin (TM), and ELISA was used to detect the plasma intercellular adhesion molecule-1 (ICAM-1. Some rabbits were killed before intravenous administration, 24 hrs after injection of horse serum in group A, and 3, 7, 21, 35, and 49 days after the first treatment with prednisone respectively and their bilateral femoral heads were taken out to undergo HE staining and microscopy and SP-VEGF immunohistochemistry. RESULTS: The levels of plasma TM, ET, and ICAM-1 gradually increased in comparison with those before treatment in both group, however, not significantly (all P > 0.05). The levels of plasma TM 1 week and 3 weeks after the initial prednisone administration inn Group A were significantly higher than those in Group B (both P < 0.05). 3 weeks after the initial prednisone administration the levels of plasma ICAM-1 and TM began to decrease and were lower than those 1 week after, however, not significantly (both P > 0.05). Pathological changes could be seen 1 and 3 weeks after in both groups and then recovered by the 7th week after the treatment. The level of VEGF expression in the osteocytes, osteoblasts, and cells of bone matrix and endothelial cells increased first 1 week after and then decreased after the prednisone administration in Group A, and decreased after the prednisone administration in Group B, however, without significant differences between these 2 groups. CONCLUSION: After prednisone treatment, a pre-necrosis status occurs in femoral head with a potential to restore which can be affected by many factors. Long-term observation on this status is necessary.
Ginseng, the root of Panax ginseng C.A. Meyer (Araliaceae), has been extensively used in traditional oriental medicine for the prevention and treatment of aging-related disorders for over 2000 years. Accumulating evidence suggests that ginsenosides such as Rg1 and Rb1, which are the pharmacologically active ingredients of ginseng, modulate neurotransmission. Synapsins are abundant phosphoproteins essential for regulating neurotransmitter release. All synapsins contain a short amino-terminal domain A that is highly conserved and phosphorylated by cAMP-dependent protein kinase (PKA), which plays a key role in regulating neurotransmitter release. In the present study, we demonstrated that both Rg1 and Rb1 increased neurotransmitter release in undifferentiated and differentiated PC12 cells. However, in the presence of the PKA inhibitor H89, Rg1, but not Rb1, still induced neurotransmitter release. Moreover, Rb1, but not Rg1, enhanced the phosphorylation of synapsins via PKA pathway. In summary, Rb1 promotes neurotransmitter release by increasing the phosphorylation of synapsins through the PKA pathway, whereas the similar effects observed with Rg1 are independent of the phosphorylation of synapsins.
Two natural triterpenoid saponins bearing N-acetylglucosamine, lotoidoside D and lotoidoside E, which had been available only from Glinus lotoides growing in Egyptian desert, were facilely synthesized from readily available oleanolic acid. Preliminary pharmacological research showed their antitumor activity against HeLa cell.
In many therapeutic applications of high-intensity focused ultrasound (HIFU) the appearance of cavitation bubbles is unavoidable, whereas the dynamics of the bubbles induced by HIFU have not been clarified. The objective of the present work is to observe the inception process of cavitation bubble clouds generated by HIFU transducer in water using high-speed photography. Sequential images captured within 600 micros after the onset of ultrasound transmission show the dynamics of cavitation bubbles' generation, growth, deformation, expansion and collapse in the focal region. However, when the observation time is narrowed to the initial 145 micros, both the still and streak images reveal that the cavitation bubbles astonishingly stay stable in the focal region for at least 60 micros. The results imply that through adjusting the HIFU exposure time while other physical parameters are appropriately chosen, it might be possible to control the generation of stable cavitation bubbles locally in the focal region.
The major active constituent of Astragalus membranaceus, astragaloside IV, has been found to have properties of increasing coronary flow and cardioprotection. In this study, we examined the direct effects of astragaloside IV on vessel dilatation and contraction in isolated aortic rings from both normal and stroke-prone spontaneously hypertensive rats (SHR-SP) in vitro. The results demonstrated that astragaloside IV could antagonize vessel contractions induced by phenylephrine and potassium chloride in a concentration-dependent way. Astragaloside IV reduced CaCl2-induced contractions in Ca2+-free solution. Astragaloside IV also dilated aortic vessels in a dose-dependent manner, which was partially endothelium-dependent through the nitric oxide (NO) and cGMP pathways. The aorta from 6-month-old SHR-SP rats showed impaired endothelium function, and astragaloside IV dilated the vessels from the hypertensive rats to a lesser extent as compared with normal control rats. In the presence of perivascular fat tissue, the contractile responses induced by angiotensin II and phenylephrine were also attenuated by astragaloside IV. Collectively, this study provides functional evidence that astragaloside IV exerts vessel dilatation properties through the endothelium-dependent NO-cGMP pathway in normal and hypertensive rats. It blocks extracellular calcium influx and participates in vessel relaxation partly through phenylephrine and angiotensin II inhibition when perivascular fat is present.
The yellow fever mosquito Aedes aegypti has been the subject of extensive genetic research due to its medical importance and the ease with which it can be manipulated in the laboratory. A molecular genetic linkage map was constructed using 148 amplified fragment length polymorphism (AFLP) and six single-strand conformation polymorphism (SSCP) markers. Eighteen AFLP primer combinations were used to genotype two reciprocal F2 segregating populations. Each primer combination generated an average of 8.2 AFLP markers eligible for linkage mapping. The length of the integrated map was 180.9 cM, giving an average marker resolution of 1.2 cM. Composite interval mapping revealed a total of six QTL significantly affecting Plasmodium susceptibility in the two reciprocal crosses of Ae. aegypti. Two common QTL on linkage group 2 were identified in both crosses that had similar effects on the phenotype, and four QTL were unique to each cross. In one cross, the four main QTL accounted for 64% of the total phenotypic variance, and digenic epistasis explained 11.8% of the variance. In the second cross, the four main QTL explained 66% of the variance, and digenic epistasis accounted for 16% of the variance. The actions of these QTL were either dominance or underdominance. Our results indicated that at least three new QTL were mapped on chromosomes 1 and 3. The polygenic nature of susceptibility to P. gallinaceum and epistasis are important factors for significant variation within or among mosquito strains. The new map provides additional information useful for further genetic investigation, such as identification of new genes and positional cloning.
Integrins are heterodimeric adhesion receptors associated with bidirectional signaling. In vitro studies support a role for the binding of evolutionarily conserved tyrosine motifs (NPxY) in the beta integrin cytoplasmic tail to phosphotyrosine-binding (PTB) domain-containing proteins, an interaction proposed to be dynamically regulated by tyrosine phosphorylation. Here we show that replacement of both beta1 integrin cytoplasmic tyrosines with alanines, resulting in the loss of all PTB domain interaction, causes complete loss of beta1 integrin function in vivo. In contrast, replacement of beta1 integrin cytoplasmic tyrosines with phenylalanines, a mutation that prevents tyrosine phosphorylation, conserves in vivo integrin function. These results have important implications for the molecular mechanism and regulation of integrin function.
We consider the lateral shift (LS) of a light beam reflecting from a dielectric slab backed by a metal. It is found that the LS of the reflected beam can be negative while the intensity of reflected beam is almost equal to the incident one under a certain condition. The explanation for the negativity of the LS is given in terms of the interference of the reflected waves from the two interfaces. It is also shown that the LS can be enhanced or suppressed under some other conditions. The numerical calculation on the LS for a realistic Gaussian-shaped beam confirms our theoretical prediction.
The average length of genes in a eukaryote is larger than in a prokaryote, implying that evolution of complexity is related to change of gene lengths. Here, we show that although the average lengths of genes in prokaryotes and eukaryotes are much different, the average lengths of genes are highly conserved within either of the two kingdoms. This suggests that natural selection has clearly set a strong limitation on gene elongation within the kingdom. Furthermore, the average gene size adds another distinct characteristic for the discrimination between the two kingdoms of organisms.
We study the properties of one-dimensional photonic crystals with an epsilon-negative and a mu-negative defect. With suitable parameters, the pair defect is equivalent to a transparent material with zero effective refractive index. This special pair defect has no influence on the spectral gap formed by the interference of propagating waves in positive-refractive-index materials. However, the field distribution is modified noticeably by the decaying wave in the pair defect. Particularly, the gap-edge field can be a highly localized wave instead of the usual standing wave as the size of the pair defect increases. The localized gap-edge field can reduce the switching thresholds for bistability greatly when Kerr-type nonlinear mu-negative material is involved. A nonideal model when the epsilon-negative and mu-negative materials are dispersive and lossy is used to verify the unusual properties.
Cavitation bubbles have been recognized as being essential to many applications of ultrasound. Temporal evolution and spatial distribution of cavitation bubble clouds induced by a focused ultrasound transducer of 1.2 MHz center frequency are investigated by high-speed photography. It is revealed that at a total acoustic power of 72 W the cavitation bubble cloud first emerges in the focal region where cavitation bubbles are observed to generate, grow, merge and collapse during the initial 600 micros. The bubble cloud then grows upward to the post-focal region, and finally becomes visible in the pre-focal region. The structure of the final bubble cloud is characterized by regional distribution of cavitation bubbles in the ultrasound field. The cavitation bubble cloud structure remains stable when the acoustic power is increased from 25 W to 107 W, but it changes to a more violent form when the acoustic power is further increased to 175 W.
Type 2 diabetes is rapidly becoming a worldwide epidemic. Obesity and sedentary lifestyle are the main environmental causes for the development of insulin resistance and type 2 diabetes. In the past decade, it has been increasingly recognized that obesity and insulin resistance are associated with chronic, low-grade systemic inflammation. This review will cover the recent advances in this field and provide a working model explaining how cellular inflammatory responses arise to cope with obesity-induced metabolic stresses and how these inflammatory responses underlie insulin resistance.
There is growing recognition that white matter pathology is a common feature in Alzheimer's disease. We have previously reported that the amyloid beta peptide (Abeta) induces apoptosis in oligodendrocytes (OLG), via activation of neutral sphingomyelinase (nSMase) and resultant generation of ceramide. In the current study, we report that both Abeta and ceramide increased expression of the proapoptotic protein DP5/Hrk (DP5), and release of cytochrome C from mitochondria to cytoplasm in OLGs. We provide evidence that the Jun N-terminal kinase (JNK) signaling pathway mediates Abeta- and ceramide-induced apoptosis: Both Abeta and ceramide activated JNK phosphorylation, and subsequent AP-1 DNA binding activity; JNK siRNA decreased AP-1 DNA binding, DP5 expression and reduced cell death. Furthermore, inhibition of nSMase attenuated Abeta-induced JNK phosphorylation, AP-1 DNA binding activity, DP5 expression, and cytochrome C release. Collectively, these results suggest that Abeta-induced apoptosis involves the sequential activation of nSMase with ceramide generation, JNK activation, AP-1 DNA binding, and DP5 expression.
BACKGROUND: Malaria cases on the highlands west of Mount Kenya have been noticed since 10-20 years ago. It was not clear whether these cases were introduced from the nearby lowland or resulted from local transmission because of no record of vector mosquitoes on the highlands. Determination of presence and abundance of malaria vector is vital for effective control and epidemic risk assessment of malaria among both local residents and tourists. METHODS: A survey on 31 aquatic sites for the malaria-vector mosquitoes was carried out along the primary road on the highlands around Mount Kenya and the nearby Mwea lowland during April 13 to June 28, 2005. Anopheline larvae were collected and reared into adults for morphological and molecular species identification. In addition, 31 families at three locations of the highlands were surveyed using a questionnaire about their history of malaria cases during the past five to 20 years. RESULTS: Specimens of Anopheles arabiensis were molecularly identified in Karatina and Naro Moru on the highlands at elevations of 1,720-1,921 m above sea level. This species was also the only malaria vector found in the Mwea lowland. Malaria cases were recorded in the two highland locations in the past 10 years with a trend of increasing. CONCLUSION: Local malaria transmission on the Mount Kenya highlands is possible due to the presence of An. arabiensis. Land use pattern and land cover might be the key factors affecting the vector population dynamics and the highland malaria transmission in the region.