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Biomedical subjects

N Weng

Publications and source records attributed to N Weng.

13 recordsLinked to original sources
PubMed2001

Interplay between telomere length and telomerase in human leukocyte differentiation and aging.

Blood leukocytes derive from bone marrow hematopoietic stem cells and differentiate into multiple types of mature cells that include granulocytes, monocytes, mast cells of myeloid lineage, and T and B lymphocytes of lymphoid lineage. Their distinctive paths of differentiation and unique roles in immune response provide a model for comparative analysis of biological parameters, such as telomere length and telomerase activity, in different types of leukocytes. Age has also been associated with the decline in immune functions and with the attrition of telomere length in leukocytes. This review will summarize recent progress in the study of telomere length and telomerase expression in leukocytes during differentiation and aging. In addition, I will attempt to shed new light on the roles of telomere and telomerase in leukocyte function and potential clinical interventions.

Cell Differentiation↗
PubMed2001

[The morphologic structure of vitreous hemorrhage and posterior vitreous detachment].

OBJECTIVE: To investigate the morphologic structures of vitreous hemorrhage that may be beneficial to its treatment. METHODS: The clinical data of 74 cases (79 eyes) with vitreous hemorrhage resulting from proliferative diabetic retinopathy, retinal vasculitis and retinal vein occlusion in December 1995 to January 2000 and having undergone vitrectomy were studied retrospectively, which focused on the morphologic characteristics of vitreous body by B-scan, surgical microscopy and surgical manipulation, to evaluate the relation of retina and vitreous body in order to discern the relationships among the retina, neovascular fibromembrane and the posterior hyaloid surface. RESULTS: Posterior vitreous detachment (PVD) in various degrees was observed in all the cases. The morphologic character was classified as the complete and partial vitreous detachment. The latter one can be subdivided into "V", "L" types and posterior vitreoschisis that was not rarely seen in the proliferative phase of ischemic retinopathy. CONCLUSIONS: To evaluate the characteristics of posterior vitreous detachment and vitreoschisis may provide valuable information for vitreoretinal surgery, elevate the rate of success and improve the prognosis of the surgery.

Adult↗
PubMed2000

Lineage-specific telomere shortening and unaltered capacity for telomerase expression in human T and B lymphocytes with age.

Age effects on telomere length and telomerase expression in peripheral blood lymphocytes were analyzed from 121 normal individuals age newborn to 94 years and revealed several new findings. 1) Telomere shortening was observed in CD4+ and CD8+ T and B cells with age. However, the rate of telomere loss was significantly different in these populations, 35 +/- 8, 26 +/- 7, and 19 +/- 7 bp/year for CD4+ and CD8+ T and B cells, respectively. In addition, CD4+ T cells had the longest average telomeres at all ages, followed by B cells, with CD8+ T cell telomeres the shortest, suggesting that these lymphocyte populations may have different replicative histories in vivo. 2) Telomerase activity in freshly isolated T and B cells was indistinguishably low to undetectable at all ages but was markedly increased after Ag and costimulatory receptors mediated stimulation in vitro. Furthermore, age did not alter the magnitude of telomerase activity induced after stimulation of T or B lymphocytes through Ag and costimulatory receptors or in response to PMA plus ionomycin treatment. 3) The levels of telomerase activity induced by in vitro stimulation varied among individual donors but were highly correlated with the outcome of telomere length change in CD4+ T cells after Ag receptor-mediated activation. Together, these results indicate that rates of age-associated loss of telomere length in vivo in peripheral blood lymphocytes is specific to T and B cell subsets and that age does not significantly alter the capacity for telomerase induction in lymphocytes.

Adolescent↗
PubMed1998

[The clinical features of retinal detachment with congenital choroidal coloboma].

OBJECTIVE: To approach the clinical features of retinal detachment with congenital choroidal coloboma and seek better surgical methods to improve the effect of treatment. METHODS: Vitreoretinal surgery was performed on eight patients of retinal detachment with choroidal coloboma. During surgery by using an operating microscope with high magnification and endoillumination, we searched for retinal break(s) located in the colobomatous area, looked into the condition of posterior hyaloid area, status of coloboma, treatment was given accordingly, and finally silicone oil tamponade was performed. RESULTS: Retina was reattached anatomically after operation in all cases, and their visual acuities improved. CONCLUSIONS: The type of retinal detachment is caused by the retinal break inside the coloboma. The breaks located at the edge of the detachment within the coloboma, ectatic sclera at the colobomatous region, without posterior vitreous detachment are the features of the retinal detachment with congenital choroidal coloboma. Complete vitrectomy with method to create chorioretinal adhesion around the coloboma and silicone oil tamponade provide an effective treatment for this complicated type of retinal detachment.

Adolescent↗
PubMed1998

[A preliminary investigation on causes of failure of vitreoretinal surgery for complicated rhegmatogenic retinal detachments].

OBJECTIVE: To evaluate the failure causes of vitreoretinal surgery for complicated rhegmatogenic retinal detachment. METHODS: Vitreoretinal (VR) surgery was performed on 477 cases (479 eyes) with complicated rhegmatogenic retinal detachment, the operative procedures including vitrectomy, peeling of pre-retinal membrane, fluid-air exchange, inert gas (SF(6) or C(3)F(8)) or silicone tamponade. RESULTS: On discharge, the operation was effective in 349 eyes (72.87%) and failed in 130 (27.13%) eyes. CONCLUSION: The multiple stepwise multivariate regression shows that the factors significantly influencing VR surgery are silicone tamponade, giant retinal tears, SF(6) tamponade, iatrogenic tear, anterior proliferative vitreoretinopathy (PVR), subretinal proliferation, PVR, C(3)F(8) tamponade, operative frequency and choroidal detachments.

Adolescent↗
PubMed1997

Telomere length, telomerase activity, and replicative potential in HIV infection: analysis of CD4+ and CD8+ T cells from HIV-discordant monozygotic twins.

To address the possible role of replicative senescence in human immunodeficiency virus (HIV) infection, telomere length, telomerase activity, and in vitro replicative capacity were assessed in peripheral blood T cells from HIV+ and HIV- donors. Genetic and age-specific effects on these parameters were controlled by studying HIV-discordant pairs of monozygotic twins. Telomere terminal restriction fragment (TRF) lengths from CD4+ T cells of HIV+ donors were significantly greater than those from HIV- twins. In contrast, telomere lengths in CD8+ T cells from HIV+ donors were shorter than in HIV- donors. The in vitro replicative capacity of CD4+ cells from HIV+ donors was equivalent to that of HIV- donors in response to stimulation through T cell receptor CD3 and CD28. Little or no telomerase activity was detected in freshly isolated CD4+ or CD8+ lymphocytes from HIV+ or HIV- donors, but was induced by in vitro stimulation of both HIV+ and HIV- donor cells. These results suggest that HIV infection is associated with alterations in the population dynamics of both CD4+ and CD8+ T cells, but fail to provide evidence for clonal exhaustion or replicative senescence as a mechanism underlying the decline in CD4+ T cells of HIV-infected donors.

Adult↗
PubMed1997

Regulation of telomerase RNA template expression in human T lymphocyte development and activation.

Telomeres are unique DNA-protein complexes at the terminals of chromosomes that appear to play a critical role in protecting chromosomal integrity and in maintaining cellular replicative potential. Telomerase is a ribonuclear protein that is capable of elongating telomeres by the addition of telomeric hexanucleotide repeats and therefore contributing to the capacity for cell replication. Telomerase activity is expressed in human germline cells and malignant cells, and it has recently been demonstrated that telomerase activity is highly regulated in normal lymphocytes at specific stages of development and activation. However, these studies have not elucidated whether telomerase activity is regulated at the level of specific gene expression or whether the regulation of telomerase RNA template (hTR) and/or protein components contributes to the regulation of telomerase activity in normal somatic cells. To characterize at a molecular level the regulation of telomerase expression in human T lymphocytes, we analyzed the expression of hTR during lineage development and after in vitro activation. It was found that hTR is expressed in subsets of thymocytes with strong telomerase activity at levels that are consistently higher (1.5 times; p < 0.01) than those found in peripheral blood resting T cells. In addition, hTR is up-regulated two- to fivefold in peripheral blood naive and memory CD4+ T cells after in vitro activation with anti-CD3 plus anti-CD28. These results establish that hTR expression is regulated in normal human T cells during lineage development and after activation, and indicate that regulation of hTR expression may contribute to the regulation of telomerase activity in normal lymphoid cells.

Adolescent↗
PubMed1997

Three-dimensional surface reconstruction using optical flow for medical imaging.

The recovery of a three-dimensional (3-D) model from a sequence of two-dimensional (2-D) images is very useful in medical image analysis. Image sequences obtained from the relative motion between the object and the camera or the scanner contain more 3-D information than a single image. Methods to visualize the computed tomograms can be divided into two approaches: the surface rendering approach and the volume rendering approach. In this paper, a new surface rendering method using optical flow is proposed. Optical flow is the apparent motion in the image plane produced by the projection of the real 3-D motion onto 2-D image. The 3-D motion of an object can be recovered from the optical-flow field using additional constraints. By extracting the surface information from 3-D motion, it is possible to get an accurate 3-D model of the object. Both synthetic and real image sequences have been used to illustrate the feasibility of the proposed method. The experimental results suggest that the proposed method is suitable for the reconstruction of 3-D models from ultrasound medical images as well as other computed tomograms.

Algorithms↗
PubMed1995

Clinical and pathologic studies on idiopathic uveal effusion.

In order to investigate the clinical features, pathology and treatment of idiopathic uveal effusion syndrome, ten eyes of seven patients with the syndrome had been studied. In addition to general clinical examinations, indirect opthalmoscopy, fundus fluorescein angiography and (FFA) ultrasonography were used to make definite diagnoses. The findings of these examinations indicate four key features of the idiopathic uveal effusion syndrome. They are: annular cilio-choroidal detachment, shifting non-rhegmatogenous retinal detachment, unremarkable inflammation in the anterior segment, and normal intraocular pressure. The fundus change is characterized by the "leopard-spot". All patients were treated by sclerectomy and sclerotomy, ciliochoroidal detachments disappeared soon after surgery, and retinal detachments resolved later on. Patients' visual acuity recovered well. The histochemical and electron microscopic examinations of excised tissues from five eyes showed thickened sclera, a general increase of the scleral fibril width compared to normal scleral, the disruption of normal lamellar arrangement of the scleral fibers and the deposition of glycosaminoglycans in the interfibrillar spaces. All these indicate that a congenital scleral abnormality seems to be the basic pathophysiology of the idiopathic uveal effusion syndrome.

Adult↗
PubMed1994

Development and validation of a high-performance liquid chromatographic method for the determination of methocarbamol in human plasma.

An isocratic HPLC method was developed and validated for the quantitation of methocarbamol in human plasma. Methocarbamol and internal standard in 200 microliters of human plasma were extracted with ethyl acetate, evaporated to dryness and reconstituted in water. Separation was achieved on a reversed-phase C18 column with a mobile phase of methanol-0.1 M potassium phosphate monobasic-water (35:10:55, v/v/v). The detection was by ultraviolet at 272 nm. Linearity was established at 1-100 micrograms/ml (r > 0.999). The limit of quantitation was designed as 1 microgram/ml to suit pharmacokinetic studies. Inter-day precision and accuracy of the calibration standards were 1.0 to 3.6% coefficients of variance (C.V.) and -2.0 to +1.6% relative error (R.E.). Quality controls of 3, 20 and 70 micrograms/ml showed inter-day precision and accuracy of 2.5 to 3.6% C.V. and -0.9 to -0.4% R.E. Recovery of methocarbamol was 91.4-100.3% in five different lots of plasma. The method was shown to be applicable on different brands of C18 columns.

Chromatography, High Pressure Liquid↗
PubMed1990

Heavy and light chain sequences of four monoclonal antibodies that bind galactosylgloboside (GalGb4).

We recently described IgM monoclonal antibodies directed against the glycospingolipid galactosylgloboside (GalGb4; Marcus, M. D. et al., Arch. Biochem. Biophys, 1988.262: 620). We now present the nucleotide and deduced amino acid sequences of the heavy and light chains of these antibodies. The antibodies were generated in a single fusion, their heavy as well as their light chains are almost identical, and they appear to be clonally related. The light chains were encoded by J kappa 5 and a V kappa gene belonging to the Ox1 family, but they are only 93% homologous to the most closely related germ-line gene, and they are probably encoded by a germ-line gene that has not yet been identified. The heavy chains were all encoded by VH441 and JH2, and have identical N segments. The VH441 germ-line gene encodes a potential glycosylation site at Asn58 in the complementarity-determining region 2. This site, which has been retained in all VH441-encoded monoclonal antibodies sequenced previously, was mutated out by a single base change in all four anti-GalGb4 antibodies.

Amino Acid Sequence↗