Biomedical subjects

Yun Hu

Publications and source records attributed to Yun Hu.

27 records · Page 2Linked to original sources

PubMed2003

Effect of selenium on increasing the antioxidant activity of tea leaves harvested during the early spring tea producing season.

This research was to determine the effect of foliar application of selenium on increasing the antioxidant activity of tea harvested during the early spring tea producing season using a alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical scavenging method and the linoleic acid system. The results showed that the radical scavenging ability of the tea extracts followed this order during the first 60 min: selenium-enriched tea obtained by fertilization with selenate > BHT > selenium-enriched tea obtained by fertilization with selenite > alpha-tocopherol > regular tea. Se-enriched tea obtained by fertilization with selenate exhibited the highest inhibition percentage of 84.29% at 30 min. Se-enriched tea extracts provided higher hydrogen-donating capabilities than regular tea and contrasts with BHT and alpha-tocopherol at the concentration of 100 microg of solids/mL of ethanol. There was a little change in the sequence of radical scavenging ability during the later 60 min: Se-enriched tea obtained by fertilization with selenate > Se-enriched tea obtained by fertilization with selenite > BHT > regular tea > alpha-tocopherol. The individual activity of tea extracts and references measured by the linoleic acid system showed that the tea extracts, BHT, and alpha-tocopherol manifested almost the same patterns of activity as the DPPH method. Tea enriched in selenium by fertilization with selenate still exhibited the highest inhibition activity of lipid oxidation, whereas alpha-tocopherol showed the lowest inhibition. The antioxidant activity of Se-enriched green tea harvested during the early spring tea producing season is enhanced compared to regular tea.

Antioxidants↗

PubMed2003

Involvement of beta 1,4 galactosyltransferase 1 and Gal beta1-->4GlcNAc groups in human hepatocarcinoma cell apoptosis.

Beta 1,4 galactosyltransferase 1 (beta 1,4GT1) synthesizes Gal beta 1-->4GlcNAc groups in N-linked sugar chains of animal glycoproteins, which have been demonstrated to play an important role in many biological events, including sperm-egg interaction, cell migration and mammalian embryonic development. In this study, the mRNA level of beta 1,4GT1 was found to increase greatly during the 7721 hepatocarcinoma cells apoptosis induced by cycloheximide. Ricinus Communis Agglutinin-I staining indicated generous increase of Gal beta 1-->4GlcNAc groups during apoptosis. Further study showed that the 7721 hepatocarcinoma cells transiently transfected with beta 1,4GT1 were more susceptible to the apoptosis induced by cycloheximide. The increased susceptibility was in accordance to the transfection concentration of beta 1,4GT1, which also led to the increased Gal beta 1-->4GlcNAc groups on the transfected cell surface. All the observations suggested that beta 1,4GT1 and Gal beta 1-->4GlcNAc groups might be associated with the apoptosis of human hepatocarcinoma cells.

Apoptosis↗

PubMed2002

Determination of selenium concentration of rice in china and effect of fertilization of selenite and selenate on selenium content of rice.

A method of hydride generation atomic fluorescence spectrometry was applied to the determination of the selenium concentration of regular polished rice in China and selenium-enriched polished rice obtained by foliar application of selenium-enriched fertilizer in the forms of selenite and selenate. The average selenium content of regular rice was 0.025 +/- 0.011 microg g(-)(1). On the basis of a daily dietary rice intake of 300-500 g suggested by the China Nutrition Society, the total selenium intake from regular rice was calculated to be 7.5-12.5 microg per person per day for an adult. The selenium contents of rice were significantly increased to 0.471-0.640 microg g(-)(1) by foliar application of selenium-enriched fertilizer at rate of 20 g of Se ha(-)(1) in the forms of sodium selenite and sodium selenate. The selenium content of rice by application of a fertilizer of selenate was 35.9% higher than that by a fertilizer of selenite, which showed that Se-enriched fertilizer in selenate exhibited greater efficiency in increasing Se content in rice products. The Se-enriched rice products can increase daily Se intake on average by 100-200 microg of Se per day by the consumption of 400 g of rice products if the Se level of rice products is controlled at 0.3-0.5 microg of Se g(-)(1). Because rice is a staple food in China, selenium-enriched rice obtained by bioenrichment of selenium to increase the Se content of rice could be a good selenium source for the population in selenium-deficient regions.

China↗

PubMed2002

Identification of interaction between MEK2 and A-Raf-1.

Mitogen-activated protein (MAP) kinases are activated by dual-specificity kinases, termed MEKs. Using MEK2 as bait in yeast two-hybrid screening, besides c-Raf and KSR, A-Raf was identified as a novel partner that interacts with MEK2. This interaction was confirmed by in vitro binding assay. Further investigation indicates that regions critical for this interaction were located between residues 255 and 606 that represent the kinase domain of A-Raf.

Binding Sites↗

PubMed2002

Development of a melanoma-specific adenovirus.

Concerns regarding the hepatotoxicity of adenovirus for cancer gene therapy have led to attempts to engineer viruses for tissue-specific gene expression and tissue-specific replication. The Tyrex2 (a tandem murine melanocyte-specific enhancer) system was used to express luciferase, purine nucleoside phosphorylase (PNP), and the essential adenoviral gene E1A. In nonmelanoma cell lines, the CMV promoter/enhancer (CMV p/e) was 969 times stronger than the Tyrex2 construct, whereas in melanoma cells it was only 2.6 times stronger. An adenovirus with Tyrex2 regulating PNP (Ad2Tyr2-PNP) was tested for cytotoxicity. In melanoma cells, treatment with Ad2Tyr2-PNP plus the prodrug 6-methylpurine deoxyriboside (6-MPDR) resulted in 90% cytotoxicity by day 4. In non-melanoma cell lines, only the CMV p/e resulted in significant cytotoxicity. We compared the intrinsic E1A promoter/enhancer (E1A p/e) system with the melanoma-specific constructs and found that the Tyrex2 system achieved higher levels of luciferase than the E1A p/e in all melanoma lines tested. In non-melanoma cell lines, the E1A p/e is 12.4 times stronger than the Tyrex2 construct. Tyrex2 was then used to regulate adenoviral E1A expression to construct a melanoma-specific replicating adenovirus. We were unable to achieve selective replication. As E1A is a known transactivator of the adenovirus major late promoter (MLP), we studied the ability of the MLP to express a transgene in the context of tissue-selective E1A expression. We were able to demonstrate high levels of luciferase activity with this construct; however, selectivity was lost. Melanoma-specific adenovirus expression was achieved with the Tyrex2 construct, and this led to melanoma-specific cytotoxicity by the potent PNP suicide gene. Selective melanoma-specific replication was not successful. The MLP may be a useful promoter in the context of a tissue-specific replicating adenovirus.

Adenoviridae↗

PubMed2002

Different effects of p58PITSLRE on the apoptosis induced by etoposide, cycloheximide and serum-withdrawal in human hepatocarcinoma cells.

Minimal overexpression of the p58PITSLRE protein kinase in Chinese hamster ovary cells induces telephase delay, abnormal cytokinesis, retarded cell growth and apoptosis. Fas mediated T cell death is correlated with p58PITSLRE proteolysis and an increase in its histone H1 kinase activity. In this study, it was found that p58PITSLRE had different effects on the apoptosis induced by etoposide, cycloheximide and serum-withdrawal in human hepatocarcinoma cells. The ectopic expression of p58PITSLRE in human hepatocarcinoma cells suppressed apoptosis induced by etoposide, while enhancing the apoptosis induced by cycloheximide and serum-withdrawal respectively. Elevated expression of p58PITSLRE was found during the apoptosis induced by etoposide, whereas most of p58PITSLRE was proteolytically processed during apoptosis induced by cycloheximide and serum-withdrawal. Furthermore, transient transfection of p50PITSLRE resembling the proteolytic form of p58PITSLRE enhanced the 7,721 cells susceptibility to apoptosis induced by all the three stimuli. These findings suggest that the full-length p58PITSLRE might protect the cells from the apoptosis induced by etoposide and its proteolysis might contribute to and enhance the apoptosis induced by cycloheximide and serum-withdrawal respectively.

Apoptosis↗

PubMed2002

Hypothalamic regulation of cyclic ovulation: evidence that the increase in gonadotropin-releasing hormone pulse frequency during the follicular phase reflects the gradual loss of the restraining effects of progesterone.

The luteal-follicular transition is characterized by decreasing plasma levels of E(2), progesterone (P), and inhibin A, with concomitant increases in FSH and LH levels. LH (and by inference GnRH) pulse frequency increases from 1 pulse every 3-4 h during the luteal phase to approximately 1 pulse/h at the midcycle LH surge. To examine the regulation of GnRH pulse frequency, we gave 10 normally cycling women transdermal E(2) and oral P to produce midluteal levels [364 +/- 65.0 pmol/liter (99 +/- 18 pg/ml) and 29.7 +/- 6.8 nmol/liter (9.3 +/- 2.1 ng/ml), respectively] for 10 d after the LH surge (d 0). P was then discontinued, and E(2) was given alone for 3 additional wk. Pulsatile LH secretion and follicular size were assessed on d 10, 17, 24, and 31. Results are presented as the mean +/- SEM. LH pulse frequency was 3.1 +/- 0.5 pulses/12 h after 10 d of E(2) and P, and remained low on d 17 when P had fallen below 1.6 nmol/liter (<0.5 ng/ml). In the continued presence of midluteal levels of E(2) [ approximately 360 pmol/liter (100 pg/ml)], LH pulse frequency increased on d 24 and 31 to 5.5 +/- 0.9 and 5.8 +/- 0.5 pulses/12 h, respectively, whereas pulse amplitude remained unchanged. FSH increased 2-fold, but follicular size did not change. These results are consistent with E(2) potentiating the effects of low concentrations of P on the GnRH pulse generator for at least 7 d, after which pulse frequency increases despite maintenance of E(2) levels. This supports the hypothesis that the increasing GnRH pulse frequency throughout the follicular phase reflects the gradual loss of the inhibitory actions of low concentrations of P.

Adult↗

PubMed2002

[Cell apoptosis in closed cerebellar contusion in rat].

OBJECTIVE: To observe the cell apoptosis explore closed cerebellar contusion in rat. METHODS: SD rats model of contusion was established and apototic cells were detected by TUNEL method at 5, 10, 30, 45, 60 min and 2, 4, 6, 8, 12 h, after injury. RESULTS: Apototic cells in contusion area appeared at 1 h after closed cerebellar contusion, reached the peak at 4-6 h, then decreased and so as marginal area where the peak was in 6-8 h. CONCLUSION: The apoptotic index of closed contusion of cerebellum in different injury time may provide a new sensitive and objective method for the forensic early injury time estimation.

Animals↗

PubMed1996

The Expression of Human alpha(1,3) Fucosyltransferase in Human Liver Cancer by in situ Hybridization.

The increase of Lewis x and Sialyl Lewis x epitopes on the surface of cancer cells was known for decades. alpha(1,3) FuT is the key enzyme in the biosynthesis of these epitopes. The increase of the activity of this enzyme was actually found in many cancer tissues, cancer cell lines and the serum of the cancer patients. The recent cloning of the enzyme led to the possibility of the application of the sensitive methods with small amount of tissues to detect the expression of the gene. In this paper, probes for alpha(1,3) FuT type III, V and VI were prepared, and they are 447, 486 and 443 bp in length respectively. The DIG-labeled probe (type V) was used to detect the mRNA of the enzyme by in situ hybridization. Surgical samples from five patients with metastatic lesions, five cases without metastasis and two normal liver tissues from liver angioma patients were examined. The alpha(1,3) FuT mRNA level was highest in samples with the metasitatic lesion, and lowest in normal tissues and those of the original tumor lesion in them. The difference is very distinct. The possibility of the method to be used in evaluation the prognosis of the disease is discussed.

Journal Article↗