Biomedical subjects

Yan Luo

Publications and source records attributed to Yan Luo.

70 records · Page 4Linked to original sources

PubMed2003

[Subretinal transplantation of retinal cells by outer approach].

OBJECTIVE: To investigate the approaches and effect of pure retinal photoreceptor cells and mixed retinal cells subretinal transplantation on retinal degenerative diseases. METHODS: 16 Kunming mice were divided into two groups: group A and group B (n = 8). Through sclera and choroid, mixed retinal cells were injected into the subretinal space of mice eyes of group A and pure retinal photoreceptors were injected into the subretinal space of mice eyes of group B by using a specific micro-syringe under operative microscopy. 30, 90 and 180 d after transplantation, experimental eyes were enucleated, stained with HE and analyzed by light microscopy. RESULTS: Most transplants (13/15) were exactly in host subretinal space without the infiltration of inflammatory cells and interfere of retina. The infiltration of inflammatory cells and damage of retina were only found in few eyes (2/15). The transplanted retinal cells survived well at 180 days after transplantation. The mixed retinal cells all formed rosette, but the pure retinal photoreceptors formed an orderly layer of photoreceptors. CONCLUSIONS: This specific technique of subretinal microinjection is an easy, safe and optimal technique to meet the need of subretinal drug administration and retinal cells transplantation for retinal degenerative diseases. It is easier for the transplanted pure retinal photoreceptor cells to establish functional connection with host cells through subretinal microinjection.

Animals↗

PubMed2003

[Construction,identification and amplification of a yeast two-hybrid random cycle peptide library].

AIM: To construct a cycle peptide library composed of 16 random amino acids with yeast two-hybrid system. METHODS: Random oligonucleotides encoding 16-mer peptides were designed and synthesized artificially, and then were amplified by PCR. The amplified products were digested with BamH I and EcoR I and cloned into yeast expression plasmid pGADT(7) GH to construct the cycle library plasmids pGADT(7) GH-RP Then the number of different recombinants and the randomness of the library were tested, and the cycle peptide library plasmids were amplified, extracted and purified. RESULTS: A random cycle peptide library with 1.28 x10(7) different recombinant clones was obtained. No significant difference was found between amino acid distribution in the cycle peptide library and the expected frequency. CONCLUSION: The random cycle peptide library has been successfully constructed. And a lot of cycle peptide library plasmids with high purity were obtained.

Amino Acid Sequence↗

PubMed2002

OcaB is required for normal transcription and V(D)J recombination of a subset of immunoglobulin kappa genes.

OcaB, a transcriptional coactivator also known as Bob-1 or OBF-1, was isolated on the basis of its ability to enhance transcription of immunoglobulin (Ig) genes in vitro. Paradoxically, OcaB(-/-) mice showed no apparent deficiency in Ig gene transcription, only cellular immune defects including absence of germinal centers (GC) and decreased numbers of immature B cells; the genes targeted by OcaB were not determined. Here we report that OcaB is essential for V(D)J recombination of a subset of Igkappa genes. We show that OcaB modulates recombination by directly enhancing Igkappa gene transcription in vivo.

Animals↗

PubMed2002

Relations of transcription expression of IL-2 with nuclear factor of activated T cells as well as changes of C-Fos and C-Jun after trauma.

OBJECTIVE: To observe the relations among expression of interleukin-2 (IL-2) in spleen lymphocytes, DNA binding activity of nuclear factor of activated T cells (NFAT) and expression of the partly family members C-Fos, C-Jun after trauma. METHODS: A murine closed trauma model was used, animals were sacrificed 6, 12 hours and 1, 4, 7, 10, 14 days, respectively after injury. Spleen lymphocytes were isolated from injured mice and stimulated with concanavalin-A. The culture supernatants were harvested and assayed for IL-2 activity. Total RNA was extracted from spleen lymphocytes and assayed for IL-2 mRNA. Nuclear protein was extracted, and the DNA binding activity of NFAT was measured using an electrophoretic mobility shift assay (EMSA), the expressions of C-Fos, C-Jun protein determined by Western blot analysis. RESULTS: The expressions of IL-2 activity and IL-2 mRNA in spleen lymphocytes were decreased in injured mice compared with those in control mice, and the most obvious decrease appeared on the 4th day after injury. The DNA binding activity of NFAT decreased gradually and reached the minimum that was only 41% of the control on the 4th day after injury, which was closely associated with the decline of IL-2 activity and IL-2 mRNA. An decrease in the expression of C-Fos on the 1st and 4th day after injury, trauma had no significant effect on the C-Jun expression. CONCLUSIONS: These results suggest that the inhibition of IL-2 expression is partly due to the impairment in the activation of NFAT in injured mice; and the decline in the DNA binding activity of NFAT is partly due to trauma block in the C-Fos expression.

Animals↗

PubMed2002

Decline in the expression of IL-2 after trauma and changes in the nuclear transcription factors NFAT and AP-1.

OBJECTIVE: To investigate whether the decrease in expression of interleukin-2 (IL-2) after trauma is associated with changes in DNA binding activity of nuclear factor of activated T cells (NFAT) and activator protein-1 (AP-1). METHODS: Mice with closed impact injury with fracture in both hind limbs were adopted as the trauma model. Spleen lymphocytes were isolated from traumatized mice and stimulated with Con-A. Culture supernatants were assayed for IL-2 activity, and total RNA was extracted from spleen lymphocytes and assayed for IL-2 mRNA. DNA binding activity of NFAT and AP-1 were measured by electrophoretic mobility shift assay (EMSA). The expression of c-Fos, c-Jun and JunB proteins was determined by the Western blot analysis. RESULTS: DNA binding activity of NFAT and AP-1 gradually decreased to a minimum of 41% and 49%, respectively, of the control on the 4th day after injury, which was closely followed by the decline in IL-2 activity and IL-2 mRNA. A decrease in the expression of c-Fos on the 1st and 4th day after trauma had no significant effect on c-Jun expression; the increase in expression of JunB was only on the 1st day after injury. CONCLUSION: Decreased IL-2 expression is, at least in part, due to a decline in the activation of NFAT and AP-1 in traumatized mice. The decline in DNA binding activity of NFAT and AP-1 is partly due to a trauma-induced block in the expression of c-Fos.

Animals↗

PubMed2002

Clinical evaluation of Dyract AP restorative in permanent molars: 2-year results.

PURPOSE: To evaluate the clinical behavior of a compomer restorative system, Dyract AP, placed in combination with Non-Rinse Conditioner and Prime&Bond NT in permanent posterior teeth. MATERIALS AND METHODS: Fifty Class II and 41 Class I restorations were placed in 39 patients in a dental teaching hospital. The restorations were evaluated directly at baseline and after 6, 12 and 24 months using the modified USPHS-Ryge criteria. Clinical photographs, polyvinylsiloxane impressions and bitewing radiographs of each restoration were taken for indirect assessment. RESULTS: After 2 years, all 76 restorations were evaluated in situ. Color matching ability and surface characteristics were excellent. A gradual deterioration in marginal discoloration and marginal integrity was noted. The percentages of Alfa scores for each criterion at the 24-month evaluation were: color match 96%, marginal discoloration 50%, marginal integrity 26%, anatomic form 97% and surface texture 95%. Five of the restorations (6%) had experienced partial fracture or recurrent caries. After 6, 12 and 24 months, the net mean occlusal wear values were 18.5 microm, 35.7 microm and 55.9 microm, respectively. There was no statistically significant difference between Class I and II restorations for each criterion (Fisher's exact test, P > 0.05).

Adult↗

PubMed2002

[Study on relationship between leukocytes and early diabetic retinopathy].

PURPOSE: To explore the leukocytic functions in adhesion, stacking and causing microcirculatory disorder in retinal microvessels in early diabetic rats. METHODS: Sixteen healthy adult male Wistar rats were randomly divided into normal control group and 3 months group of diabetes (STZ) . We carried out morphological observations and CD45 (Leukocyte Common Antigen) monoclonal antibody immunohistochemical studies of the retinal digest preparations. RESULTS: Morphological changes including capillary varix, irregularity of capillary caliber, was found in the retinal blood capillaries in diabetic rats at 3 months. Further more, the expression of CD45 was significantly increased in the diabetic retinal microvessels, which were found leukocytes adhering and stacking. CONCLUSION: Changes of retinal microvessels can be found in STZ diabetic rats at 3 months. The leukocytes were important in the onset and development of diabetic retinopathy (DR).

Animals↗

PubMed2002

The preliminary report of pathological changes of epiretinal membranes and internal limiting membrane removed during idiopathic macular hole surgery.

PURPOSE: To investigate the pathological changes of epiretinal membranes (ERM) and internal limiting membrane (ILM) removed during idiopathic macular hole surgery. METHODS: Ten consecutive patients with a unilateral idiopathic macular hole underwent pars plana vitrectomy (PPV) with the surgical removal of the ERMs overlying the hole and ILM surrounding the hole. The pathological features of the excised tissues were examined under the microscope. RESULTS: According to the morphological changes, four ERMs showed cellular elements which looked like glia cells, macrophages, plasma cells, lymphocytes and fibroblast cells. Two of the ILM appeared as transparent membranes without cellular elements. The other eight ILM showed cellular elements on the transparent membranes. CONCLUSION: Our study supports the hypothesis that the tangential traction of vitreous and proliferative cellular elements on the inner surface of ILM causes idiopathic macular holes. Removal of the posterior cortical vitreous, ILM and proliferative cellular tissue is a valid treatment for IMH.

Adult↗

PubMed2000

The effect of macrophages posttrauma on T cell functions.

OBJECTIVE: To study molecular mechanism of suppressive effect of macrophages posttrauma on T cell functions. METHODS: A murine closed trauma model was used, macrophages were harvested from the abdominal cavity and added into the culture system of T cells, which were separated from splenocytes in normal mice using nylon column. T cell functions and intracellular messenger molecules were determined. In addition, the effect of macrophages' removal from splenocytes of traumatized mice on T cell functions and intracellular messenger molecules was investigated. RESULTS: Macrophages posttrauma in vitro could obviously suppress ConA stimulated normal T cell functions such as T lymphocyte transformation, interleukin 2 (IL-2) production, IL-2 receptor alpha (IL-2Ralpha) expression, IL-2 mRNA and IL-2Ralpha mRNA levels, and elevate cAMP contents of activated normal T cells while decreasing cGMP contents, intracellular free calcium ([Ca(2+)]i) concentration and protein kinase C (PKC) activity. Removal of macrophages from splenocytes of traumatized mice could at certain degree reverse the suppression of T cell functions, decrease cAMP contents while increasing cGMP contents, [Ca(2+)]i concentration and PKC activity. CONCLUSIONS: Macrophages posttrauma may suppress T cell functions via altering messenger molecule levels in activated T cells.

Journal Article↗

PubMed1998

Inhibition of T cells by direct contact with macrophages after murine-amputation injury.

OBJECTIVE: To determine whether macrophages post trauma have inhibitory effect on normal T cells via direct cell to cell contact. METHODS: A murine amputation injury model was used, macrophages were harvested from abdominal cavity and treated with mitomycin-C to abrogate the secretion of cytokines. Separation of T cells from splenocytes in normal mice was performed using nylon column method. Mitomycin-C treated macrophages from control and traumatized mice were added into the normal T cell culture systems, then various parameters of T cell functions were determined. RESULTS: The production and secretion of interleukin 1 (IL-1), interleukin 6 (IL-6), tumor necrosis factor (TNF) and prostaglandin E-2 (PGE-2) could be abrogated after macrophages were treated with 25 &mgr;g/mL mitomycin-C for 30 minutes. Mitomycin-C treated macrophages from traumatized mice could obviously suppress T lymphocyte transformation, IL-2 mRNA and IL-2Ralpha mRNA levels, IL-2 production, IL-2Ralpha expression, IL-2 mediated lymphocyte proliferation response of normal T cells, could not affect IL-2-IL-2R interaction but elevated suppressive action of Ts cells. Removal of Ts cells from T cells could almost abolish the inhibition of macrophages. CONCLUSIONS: Macrophages post trauma can suppress T cell functions by depressing IL-2 and IL-2Ralpha gene expression via direct cell to cell contact, and this effect may be mediated mainly by increasing the action of Ts cells.

Journal Article↗

PubMedDate not supplied

Active antitumor immunity elicited by vaccine based on recombinant form of epidermal growth factor receptor.

Active immunotherapy targeting epidermal growth factor receptor (EGFR) should be another attractive approach to the treatment of EGFR-positive tumors. To test this concept, the authors evaluated the potential immune responses and antitumor activities elicited by dendritic cells pulsed with recombinant ectodomain of mouse EGFR (DC-edMER). Spleen cells isolated from DC-edMER-vaccinated mice showed a high quantity of EGFR-specific antibody-producing cells. EGFR-reactive antibody in sera isolated from vaccinated mice was identified and shown to be effective against tumors in vitro and in vivo by adoptive transfer. DC-edMER vaccine also elicited cytotoxic T-lymphocyte responses that could mediate antitumor effects in vitro and adoptive transfer in vivo. In addition, EGFR-specific cytokines responses were elicited by DC-edMER vaccine. Immunization with DC-edMER resulted in tumor regression and prolonged survival in mice challenged with Lewis lung carcinomas and mammary cancer models. Depletion of CD4+ T lymphocytes could completely abrogate the antitumor activity and EGFR-specific antibody responses, whereas the depletion of CD8+ T lymphocytes showed partial abrogation of the antitumor activity but antibody was still detected. Furthermore, tumor-induced angiogenesis was suppressed in DC-edMER-vaccinated mice or mice treated with antibody adoptive transfer. Taken together, these findings suggest the antitumor immunity could be induced by DC-edMER, which may involve both humoral and cellular immunity, and may provide insight into the treatment of EGFR-positive tumors through the induction of active immunity against EGFR.

Animals↗

PubMedDate not supplied

Outreach dental service for persons with special needs in Hong Kong.

The authors describe the acceptance and efficiency of an outreach dental service, which provided oral health care to persons with special needs in Hong Kong. Portable dental equipment was transported to various institutions. Basic dental care including prevention, scaling, restoration, extraction, and denture repair was provided free of charge. Elderly adults living in institutions were the main service recipients, but other people with special needs, including physically disabled and persons with mental retardation were also reached. One-third of the patients had dental pain or sensitivity, and 70% had not visited a dentist for more than three years. Dental care was provided to 6,867 patients over four years. Feedback from the patients showed that more than 90% of them were satisfied with the service. These findings indicate that patients with special needs in Hong Kong are in great need of dental care. An outreach dental service appears to be both appropriate and efficient in providing care to these persons.

Adolescent↗

PubMedDate not supplied

Oral health status of homeless people in Hong Kong.

The authors report on an oral health survey among Hong Kong Chinese homeless people. A total of 140 homeless men underwent clinical examination and were interviewed with a structured questionnaire. More than 90% had evidence of caries experience; most (75%) were related to untreated caries. The mean DMFT score was 9.0 (DT = 3.2, MT = 5.2, FT = 0.6). Periodontal disease was highly prevalent, with 96% having periodontal pockets. The dental problems most frequently reported by the homeless were: bleeding gums or drifting teeth (62%), dental pain (52%) and tooth trauma (38%). More than 70% of the study's participants perceived a need for dental care. The population surveyed had poorer oral health compared to the general population. High levels of dental needs, both normative and perceived, were found. There is a need to provide more accessible and affordable oral health services to this group of people.

Adult↗

PubMedDate not supplied

Rapamycin inhibits Akt-mediated oncogenic transformation and tumor growth.

Akt is a serine/threonine kinase that plays a critical role in cell survival and proliferation. Three isoforms of Akt have been identified and have been shown to be up-regulated in human malignancies. We examined the requirement of these pathways for Akt transformation. We generated NIH-3T3 cells over-expressing constitutively active Myr-Akt1 (3T3-Akt1 cells) or Myr-Akt2 (3T3-Akt2 cells). These cells are able to form colonies in soft-agar and 3T3-Akt1 cells formed tumors in SCID mice. Rapamycin efficiently inhibited the activation of the mTOR-p70S6K pathway and the anchorage-independent growth of both 3T3-Akt cells, demonstrating the importance of the mTOR-p70S6K pathway for transformation by Akt1 as well as by Akt2. Moreover, rapamycin dramatically inhibited the tumor formation by 3T3-Akt1 cells in SCID mice. Thus, we demonstrated the importance of mTOR-p70S6 kinase pathway in the transformation by Akt, both in tissue-cultured cells and in animal tumor models. In contrast, neither the MAPK pathway nor the p38 MAPK pathway is required for Akt-dependent transformation of NIH3T3 cells.

Amino Acid Sequence↗

PubMedDate not supplied

Functional analysis of focal adhesion kinase (FAK) reduction by small inhibitory RNAs.

The focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that localizes to the points of cell contact with the extracellular matrix, called focal adhesions. Many factors induce tyrosine phosphorylation of FAK including growth factors, neuropeptides and integrin-dependent adhesion to the extracellular matrix. FAK has been implicated in several cellular processes such as invasion, motility, proliferation and apoptosis. In addition, FAK expression was shown to be elevated in a number of different human cancers, suggesting a role in the development of malignancy. We examined the biological functions of FAK using small inhibitory RNAs (siRNA) in cancer cells. Although FAK siRNA reduced the FAK protein levels by approximately 70% in several cancer cell lines, there was no clear evidence of apoptosis. However, in clonogenic and soft-agar assays in H1299, a lung cancer cell line, FAK siRNA treatment led to a 43% to 55% decrease in colony formation. Furthermore, FAK siRNA-treated cells displayed a decrease in migration when serum or EGF (epidermal growth factor) were used as chemo-attractants. Our results demonstrated that inhibition of FAK protein leads to alterations in cell growth and migration.

Cell Line, Tumor↗

PubMedDate not supplied

Regulation of LDL receptor expression by the effect of curcumin on sterol regulatory element pathway.

To investigate the molecular mechanisms of the effect of curcumin on up-regulation of LDL receptor expression, a sterol regulatory report system was established in Xenopus laevis oocytes by microinjection of a plasmid pLXRN-4SRE-fPA, in which green fluorescence protein (GFP) gene was constructed downstream from the sterol regulatory element-1 (SRE-1), in the nucleus of the oocytes. The oocytes were treated with different kinds of natural medicines: curcumin, tea polyphenols, tanshinone, ligustrazine, ginkgolide, astragalosides. The expression of GFP was induced only by curcumin. In addition, it was also proved that the curcumin can increase the expression of functional LDL receptors in human liver hepatoma cell line HepG2. In conclusion, curcumin may up-regulate the expression of LDL receptor by its effect on SRE pathway.

Animals↗