Biomedical subjects

Yunsheng Li

Publications and source records attributed to Yunsheng Li.

6 recordsLinked to original sources

PubMed2005

Natural anti-diabetic compound 1,2,3,4,6-penta-O-galloyl-D-glucopyranose binds to insulin receptor and activates insulin-mediated glucose transport signaling pathway.

Insulin mimetics from natural sources are potential therapeutics that can act alone or supplement insulin and other anti-diabetic drugs in the prevention and treatment of diabetes. We recently reported the insulin-like glucose transport stimulatory activity of tannic acid (TA) in 3T3-L1 adipocytes. In this study, we find that chemically synthesized 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose (beta-PGG), one of the components of TA, as well as its natural anomer alpha-PGG possess activity. Mechanistic studies in adipocytes with alpha-PGG, the more potent of the two anomers, reveal that inhibitors that block the insulin-mediated glucose transport, including one that inhibits the insulin receptor (IR), also completely abolish the glucose transport activated by alpha-PGG. In addition, alpha-PGG induces phosphorylation of the IR and Akt, activates PI 3-kinase, and stimulates membrane translocation of GLUT 4. Receptor binding studies indicate that alpha-PGG binds to the IR and affects the binding between insulin and IR by reducing the maximum binding of insulin to IR without significantly altering the binding affinity of insulin to IR. Western blotting analysis of the products of a cross-linking reaction suggests that alpha-PGG may bind to IR at a site located on the alpha-subunit of the receptor. Animal studies demonstrate that PGG reduces blood glucose levels and improves glucose tolerance in diabetic and obese animals. Our results suggest that PGG may serve as a model for the development of new types of anti-diabetic and anti-metabolic syndrome therapeutics.

3T3-L1 Cells↗

PubMed2005

Tannic acid stimulates glucose transport and inhibits adipocyte differentiation in 3T3-L1 cells.

Obesity is a major risk factor for Syndrome X and type II diabetes (T2D). However, most antidiabetic drugs that are hypoglycemic also promote weight gain, thus alleviating one symptom of T2D while aggravating a major risk factor that leads to T2D. Adipogenesis, the differentiation and proliferation of adipocytes, is a major mechanism leading to weight gain and obesity. It is highly desirable to develop pharmaceuticals and treatments for T2D that reduce blood glucose levels without inducing adipogenesis in patients. Previously, we reported that an extract from Lagerstroemia speciosa L. (banaba) possessed activities that both stimulated glucose transport and inhibited adipocyte differentiation in 3T3-L1 cells. Using glucose uptake assays and Western/Northern blot analyses as major tools and 3T3-L1 cells as a model, we showed that the banaba extract (BE) with tannin removed was devoid of the 2 activities, and tannic acid (TA), a major component of tannins, had the same 2 activities as BE. Inhibitors known to abolish insulin-induced glucose transport also blocked TA-induced glucose transport. We further detected that TA induced phosphorylation of the insulin receptor (IR) and Akt, as well as translocation of glucose transporter 4 (GLUT 4), the protein factors involved in the signaling pathway of insulin-mediated glucose transport. We also demonstrated that TA inhibited the expression of key genes for adipogenesis. Differences between samples with or without TA in all of the quantitative assays were significant (P < 0.05). These results suggest that TA may be useful for the prevention and treatment of T2D and its associated obesity. TA may have the potential to become the lead compound in the development of new types of antidiabetic pharmaceuticals that are able to reduce blood glucose levels without increasing adiposity.

3T3 Cells↗

PubMed2002

Radiative ablation to low-Z matter.

Eight beams of 0.35-microm laser with pulse duration of about 1.0 ns and energy of 260 J per beam were injected into a cylindrical cavity to generate intense x-ray radiation on the Shengguang II high power laser facility. Plastic foils with a thickness in the range of about 3.0-45 microm were attached on the diagnostic hole of the cavity and ablated by the intense x-ray radiation. The radiative energy transport through plastic foils with different thicknesses has been studied experimentally. The burn-through time of the plastic foils has been obtained. For comparison, we also simulated the experimental results with Planckian and non-Planckian x-ray spectrum source, respectively. It is shown that for thick plastic foil the simulation with non-Planckian x-ray spectrum source is in good agreement with the experiment.

Journal Article↗

PubMed2002

Seryl-histidine as an alternative DNA nicking agent in nick translation yields superior DNA probes and hybridizations.

Nick translation is a commonly used method for labeling DNA to make DNA hybridization probes. In this approach, the use of DNase I to generate nicks in double-stranded DNA presents an inherent drawback, because the enzyme's high rate of reaction causes significant fragmentation and shortening of the hybridization probes. Based on our recent findings regarding the nucleolytic activity of the dipeptide seryl-histidine (Ser-His) and generation of free 3' hydroxyl and 5' phosphate groups at the cleavage sites of the substrate DNA by Ser-His, it was hypothesized that this disadvantage may be overcome by using Ser-His in place of DNase I as an alternative DNA nicking agent. In this study we demonstrate that like DNase I, Ser-His randomly nicks DNA, but the dipeptide has a much lower rate of reaction that enables more complete labeling of the DNA probes with less fragmentation. DNA probes labeled through nick translation using Ser-His as the DNA nicking agent were consistently larger in size and exhibited significantly higher specific activities, and enhanced hybridization signals in Southern blot analyses compared to control DNA probes that were made using DNase I as the nicking agent. Furthermore, the degree of nicking and consequently the quality of the probes could be easily controlled by adjusting the temperature and time of the Ser-His nicking reaction. These results affirm our hypothesis that Ser-His can serve as an alternative DNA nicking agent in nick translation to yield superior DNA probes and hybridization results and suggest the possible general utility of Ser-His for wide range of biological and biomedical applications that require more moderated nicking of nucleic acids. Based upon these and computer modeling results of Ser-His, a mechanism of action is proposed to explain how Ser-His may nick DNA.

Binding Sites↗

PubMed2002

[Microanatomy study on sinus triangle region].

OBJECTIVES: To explore shape and position relationship of the structures with in sinus triangle region, and provide the anatomic foundation for extended presigmoid operative approach. METHODS: Ten cadaveric heads and 15 skull-base specimens fixed with 10% formalin, with aid of operative microscope, the shape and relations of structures with in the sinus triangle region were observed and microphotographed. Four cadaveric heads were sectioned in different plane using collodion embedding process. RESULTS: Jugular blub (JB) had high -placed jugular blub (HJB), normal jugular blub (NJB) and low-placed jugular blub (LJB). The incidence of HJB was 8% and 18% for the left and right sides (P < 0.01). The JB dome can extend upward the hypotympanic cavity and the posterior wall of the internal acoustic meatus. The incidence of NJB and LJB was 36% and 30%, and 6% and 2% respectively. The level distance between the posterior semicircular canal and petrosal posterior surface was (4.1 +/- 1.1) mm. The distance between the JB and vertical part of the facial nerve was (3.2 +/- 0.5) mm and (2.0 +/- 0.4) mm. The distance between the JB and posterior margin of the internal acoustic port was (7.5 +/- 1.7) mm and (4.0 +/- 1.0) mm. CONCLUSIONS: Knowing the shape and position relationship of structures in the sinus triangle region is favorable for preserving the important structures in extended presigmoid operative approach.

Autopsy↗

PubMed2002

[Microsurgical anatomy of craniocervical junction region].

OBJECTIVES: To study the shape and the structures in the craniocervical junction region (CCJR) and the safety of far lateral approach. METHODS: Ten cadaveric heads and 20 skull-base specimens were fixed with 10% formalin, and 4 of the 10 cadaveric heads were sectioned in different plane with the aid of operative microscope. The shape and relation of structures in the CCJR were observed. RESULTS: The third segment of the vertebral artery(VA) was 21.6(15.3 31.9) mm. An incomplete bony canal was found to be 15% and complete bony canal surrounding the VA to be 5% on the VA groove. The distance of the left and right VA was 14.3a(c)(9.8 15.2) mm on the entry into the dura. The length of the occipital condyle was 26.8(25.1 28.2) mm, with the thickness of its anterior, middle and posterior one-third part was 9.9(9.6 10.6) mm, 11.2(9.2 13.1) mm and 8.6 (8.3 9.0) mm respectively. The distance between the posterior pole of the occipital condyle and the intracranial orifice of the hypoglossal canal was 9.9(8.6 11.4) mm, and between the posterior pole and the extracranial orifice was 16.1(13.5 17.1) mm. The transverse process of the atlas was the most important bony landmark for the approach. CONCLUSIONS: Knowing the shape and relationship of the VA and occipital condyle in the CCJR is helpful in preserving the important structures in far lateral approach to target region.

Humans↗