Biomedical subjects

Ping Yan

Publications and source records attributed to Ping Yan.

25 records · Page 2Linked to original sources

PubMed2004

Studying and switching electron transfer: from the ensemble to the single molecule.

We report here on the systematic investigation of photoinduced intramolecular electron transfer (IET) in a series of donor-bridge-acceptor molecules as a means of understanding electron transport through the bridge. Perylenebisimide chromophores connected by various oligophenylene bridges are studied because their electron-transfer behavior can readily be monitored by following changes in the fluorescence intensity. We find dramatic switching of the IET behavior as the solvent polarity (dielectric constant) is increased. By combining steady-state and time-resolved fluorescence spectroscopy in a variety of solvents at multiple temperatures with standard theories of electron transfer, we determine parameters governing the IET behavior of these dimers, such as the electronic coupling through the bridges. We also deploy available ab initio quantum chemical methods to calculate the through-space component of the electronic coupling matrix element. Single-molecule investigations of the electron-transfer behavior also show that IET can be switched reversibly by a similar mechanism in an isolated individual molecule.

Journal Article↗

PubMed2004

[Follow-up surveying the clinical effects after the endoscopic sinus surgery].

OBJECTIVE: To explore the follow-up time and the effect of intranasal glucocorticoid for chronic sinusitis and nasal polyps after endoscopic sinus surgery. METHOD: After the endoscopic sinus surgery, 30 cases of sinusitis and nasal polyps accepted the postsurgical care for the cavity, sinus washing, and intranasal local glucocorticoid rhinocort, then the clinical effects was follow-up surveyed. RESULT: Intranasal local glucocorticoid could evidently reduce the courses of dry and the epithelial metaplasia of nasal cavity and sinus. CONCLUSION: After the endoscopic sinus surgery, follow-up of endoscopic sinus, postsurgical care for the cavity and intranasal local glucocorticoid played equally important roles in treating sinusitis and nasal polyps.

Adolescent↗

PubMed2003

Expression of the type 1 and type 2 receptors for tumor necrosis factor after traumatic spinal cord injury in adult rats.

Posttraumatic inflammation has been implicated in secondary tissue damage after spinal cord injury (SCI). Tumor necrosis factor-alpha (TNF-alpha) is a key inflammatory mediator that is increasingly expressed after SCI. The effect of TNF-alpha is mediated through its receptors TNFR1 (p55) and TNFR2 (p75). However, whether these two receptors are expressed after SCI has not been demonstrated. In the present study, the temporo-spatial expression of TNFR1 and TNFR2 was examined in rats that had received a 10 g impact injury dropped at a height of 12.5 mm using the New York University impact device. In sham operates, no detectable TNFR1 or TNFR2 immunoreactivity (IR) was observed. In contused spinal cord, TNFR1 protein expression and immunoreactivity (IR) were detected as early as 15 min postinjury, reached its peak at 8 h, and declined markedly after 1 and 3 days postinjury. The temporal pattern of TNFR2 expression was similar to that of TNFR1 but its expression peaked at 4 h postinjury. During peak expression, TNFR1- and TNFR2-IR were most intense at the site of injury and decreased gradually from the injury epicenter. TNFR1- and TNFR2-positive cells included neurons, astrocytes, and oligodendrocytes. Methylprednisolone (MP), a synthetic glucocorticoid, partially inhibited the injury-induced expression of TNFR1 and TNFR2, an effect which could be reversed by RU486, an antagonist of glucocorticoid receptors. We suggest that the expression of TNFR1 and TNFR2 after SCI may contribute to posttraumatic inflammatory responses of TNF-alpha.

Animals↗

PubMed2003

Glial cell line-derived neurotrophic factor-enriched bridging transplants promote propriospinal axonal regeneration and enhance myelination after spinal cord injury.

Glial cell line-derived neurotrophic factor (GDNF), a distant member of the transforming growth factor-beta (TGF-beta) family, is widely expressed in the developing and adult central nervous system (CNS). At present, limited information is available regarding the effects of GDNF in the repair of spinal cord injury (SCI). In the present study, mini-guidance channels containing either: (1) Matrigel (MG, a basement membrane component), (2) Schwann cells (SCs, 120 x 10(6)/ml) in MG (SC-MG), (3) recombinant human GDNF (rhGDNF, 3 microg/microl) in MG (GDNF-MG), and (4) a combination of all three components (GDNF-SC-MG) were grafted into a T9 hemisection-gap lesion in adult rats to examine the effects of GDNF on axonal regeneration and myelination following SCI. Thirty days post-transplantation, limited axonal growth was observed within guidance channels containing MG-alone (MG). When SCs were added to the channels (SC-MG group), consistent axonal ingrowth containing both myelinated and unmyelinated axons was observed, confirming our previous findings. The addition of GDNF-alone without SCs (GDNF-MG) resulted in substantial ingrowth of unmyelinated axons, suggesting that GDNF has a direct neurite-growth promoting effect on these axons. Implantation of channels containing both GDNF and SCs (GDNF-SC-MG) produced a significant and synergistic increase in axonal regeneration and myelination. In addition, GDNF reduced the extent of reactive gliosis, infiltration of activated macrophages/microglia, and cystic cavitation at the graft-host interfaces. Retrograde tracing revealed that grafts of SC-seeded channels containing GDNF promoted a significant increase in the number of propriospinal neurons which had regenerated their axons into the grafts, as compared to SC-MG-seeded channels. These results indicate that GDNF may play a novel therapeutic role in promoting propriospinal axonal regeneration, enhancing myelin formation, and improving graft-host interfaces after SCI.

Animals↗

PubMed2003

Combining data sources to monitor the HIV epidemic in Canada.

This article describes the methods, results and future perspectives of four information sources used to monitor the HIV epidemic in Canada: AIDS case surveillance, HIV case surveillance, HIV sentinel serosurveillance, and behavioral surveillance. Synthesizing data from these multiple sources provides a more comprehensive picture of the HIV epidemic than any one source alone could provide. In Canada, there has been a shift over time from an epidemic dominated by men who have sex with men to one where more than half of new infections are attributed to other groups, such as injection drug users and non-injecting heterosexuals. The available evidence also suggests increasing HIV infections among Aboriginal persons and among women. Surveillance data have been used in Canada to guide prevention and care programs and to formulate policy. In particular, these data have been used to support the development of an HIV testing program in pregnancy, to re-direct community work toward injection drug users and the young, and to demonstrate the effectiveness of new treatments for HIV. The main challenge now is to continue to improve the monitoring of the shifting HIV epidemic with more accurate data and to use the resulting information to inform appropriate prevention and care responses.

AIDS Serodiagnosis↗

PubMed2002

Designing an optical disk lens without analytical definition of aspheric surfaces.

We have developed a new method to design aspheric lenses. The conventional technique is usually based on analytic definition of optical surfaces; in the new method discretely defined aspheres are used, and the final design is attained point by point with an iterative algorithm. Simulation results are compared with results obtained with conventional optical design software to prove that this new method is more effective and reliable for designing aspheric lenses, especially when the aspheric order is high.

Journal Article↗

PubMed2002

[Clinical observation on treatment of ankylosing spondylitis with huatan zhuyu jiedu decoction].

OBJECTIVE: To observe the clinical effect of Huatan Zhuyu Jiedu Decoction (HZJD) in treating ankylosing spondylitis (AS). METHODS: One hundred AS patients were randomly divided into two groups, the 60 patients in the treated group were treated with HZJD, the 40 patients in the control group were treated with Duhuo Jisheng Decoction. Treatment for both groups was orally given 1 dose per day in decoction form for 1 month as a treatment course. The efficacy of treatment was evaluated after 1-3 treatment courses. RESULTS: The effect of treatment in the treated group was short-term controlled in 12 patients, markedly effective in 29, improved in 16 and ineffective in 3, the total effective rate was 95% (57 cases), while in the control group, the corresponding figure was 2, 8, 20, 10 and 75% (30 cases), comparison between the two groups showed significant difference (chi 2 = 20.85, P < 0.01). The manifestation of symptoms of patients in both groups improved obviously, the pain in loin and back alleviated, spinal motion (flexion forward, extension backward and lateral inclination) improved and thoracic expansion increased. Laboratory indices such as ESR, C3, IgA and CRP reduced obviously after treatment (P < 0.01 or P < 0.05), and better effect was shown in the treated group (P < 0.05). X-ray film after treatment showed improvement in 11 cases in the treated group and 4 in the control group, inter-group comparison showed significant difference (chi 2 = 7.99, P < 0.01), the effect of HZJD was better than that of the control. CONCLUSION: HZJD has definite therapeutic effect in treating AS.

Adolescent↗