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Biomedical subjects

W H Sun

Publications and source records attributed to W H Sun.

32 records · Page 2Linked to original sources
PubMed1996

Developing particle-mediated gene-transfer technology for research into gene therapy of cancer.

Gene therapy aims to (1) introduce specific genes into a host to replace defective ones (replacement therapy); (2) suppress expression of certain undesirable genes (antisense therapy); or (3) provide additional biological activities (supplement therapy). Naked DNA and viral or non-viral vectors containing candidate genes for human gene therapy are being actively pursued by researchers in molecular medicine. New gene transfer technologies are rapidly developing and some have proved to be powerful tools for medical research. This review discusses the development and application of particle-mediated gene transfer technology in experimental systems and its potential clinical utilities.

Animals↗
PubMed1996

Case report: rupture and growth of adrenal myelolipoma in two patients.

Two cases of pathologically confirmed adrenal myelolipoma are described in Chinese patients. The first patient presented with tumour rupture and perinephric haemorrhage. The second patient was operated on 18 months after the incidental discovery of the tumour, due to its large size and the interval growth.

Adrenal Gland Neoplasms↗
PubMed1995

In vivo cytokine gene transfer by gene gun reduces tumor growth in mice.

Implantation of tumor cells modified by in vitro cytokine gene transfer has been shown by many investigators to result in potent in vivo antitumor activities in mice. Here we describe an approach to tumor immunotherapy utilizing direct transfection of cytokine genes into tumor-bearing animals by particle-mediated gene transfer. In vivo transfection of the human interleukin 6 gene into the tumor site reduced methylcholanthrene-induced fibrosarcoma growth, and a combination of murine tumor necrosis factor alpha and interferon gamma genes inhibited growth of a renal carcinoma tumor model (Renca). In addition, treatment with murine interleukin 2 and interferon gamma genes prolonged the survival of Renca tumor-bearing mice and resulted in tumor eradication in 25% of the test animals. Transgene expression was demonstrated in treated tissues by ELISA and immunohistochemical analysis. Significant serum levels of interleukin 6 and interferon gamma were detected, demonstrating effective secretion of transgenic proteins from treated skin into the bloodstream. This in vivo cytokine gene therapy approach provides a system for evaluating the antitumor properties of various cytokines in different tumor models and has potential utility for human cancer gene therapy.

Animals↗
PubMed1995

Interleukin-6 causes hypocholesterolemia in middle-aged and old rhesus monkeys.

BACKGROUND: Hypocholesterolemia is a risk factor for morbidity and mortality in older people. We have hypothesized that hypocholesterolemia in older people is due to the chronic effect of proinflammatory cytokines on lipoprotein metabolism. METHODS: To test the effects of the chronic administration of interleukin-6 (IL-6) on lipoprotein levels in middle-aged and old rhesus monkeys, five middle-aged and five old rhesus monkeys received a subcutaneous injection of recombinant human IL-6 (15 micrograms/kg) for 28 days. Lipid, apolipoprotein, and albumin levels were measured at 0, 28, and 42 days after injection. RESULTS: Total and HDL cholesterol levels fell by 16 and 23%, respectively, after IL-6 injections. The concentrations of apolipoproteins A1 and B also decreased. The changes in lipoprotein levels were accompanied by a decrease in albumin levels and body weight. Levels of lipids and plasma proteins returned toward normal 2 weeks after injections were stopped. There was no difference in response between middle-aged and older animals. CONCLUSIONS: Chronic IL-6 injections cause acquired hypocholesterolemia, hypoalbuminemia, and weight loss in nonhuman primates. These changes are similar to those seen in older persons with acquired hypocholesterolemia.

Aging↗
PubMed1994

The role of interleukin-6 in certain age-related diseases.

Interleukin-6 (IL-6) is a pro-inflammatory cytokine with a wide range of functions. Perhaps the most important physiologically is its role as a mediator of the acute phase inflammatory response. Normally, there is little measurable IL-6 in the circulation, but levels increase abruptly to nanogram amounts during an inflammatory process. During aging, it has been proposed that the tight regulation of IL-6 gene expression becomes less effective and levels are measurable even when there is no evidence for inflammation. Several investigators have identified this cytokine as being involved in the pathogenesis of various disease processes and we have suggested that certain age-associated diseases are directly related. Among these are late-life lymphoma and myeloma, osteoporosis and possibly Alzheimer's disease.

Aging↗
PubMed1994

Effects of recombinant human interleukin-6 administration on bone in rhesus monkeys.

The role of interleukin-6 in the bone microenvironment is controversial. We studied the effect of recombinant human interleukin-6 (rhIL-6) administration on bone metabolism in 10 adult female rhesus monkeys (age 12-27 years). Monkeys received rhIL-6 (15 micrograms/kg/day) daily by subcutaneous injection for 28 days. Serum alkaline phosphatase, osteocalcin, and 24 h urinary calcium excretion were determined before, during (at weeks 2 and 4), and after (at week 6) treatment. Transilial biopsies (right and left) were obtained before treatment was initiated and just after the final (28th) dose at week 4. The serum alkaline phosphatase significantly increased at 2 and 4 weeks of rhIL-6 administration. Osteocalcin and urinary calcium excretion significantly decreased at week 2. Upon treatment with rhIL-6 significant reductions in OS/BS and Ob.S/BS were observed without changes in other static histomorphometry parameters. The reductions in urinary calcium excretion, serum osteocalcin, and the static bone parameters are consistent with an IL-6 induced reduction in bone formation or turnover. Whether this pharmacologic effect is relevant at the physiologic level remains to be determined.

Alkaline Phosphatase↗
PubMed1993

The influence of recombinant human interleukin-6 on blood and immune parameters in middle-aged and old rhesus monkeys.

IL-6 is a 26-kDa protein cytokine with pleiotropic activities in both hematopoietic and immune systems. It is one of the major mediators of the acute phase inflammatory response. Recently it has been demonstrated that pharmacological doses of human recombinant IL-6 (rhIL-6) inhibit certain murine tumors as well as stimulate thrombopoiesis in mice, dogs, nonhuman primates, and humans. The purpose of our study was to evaluate the effects and toxicity of rhIL-6 administration in nonhuman primates with particular reference to subject age. We treated 10 female monkeys of two age groups (midle-aged and old) with rhIL-6 (15 micrograms/kg/day) for 28 days. The monkeys were observed to be somewhat lethargic and lost an average of 10% of their body weights. The white blood cell count rose transiently whereas the levels of hemoglobin and hematocrit fell significantly and remained depressed for the same period. Importantly, platelet count rose and remained elevated for the duration of treatments. Serum alkaline phosphatase levels increase significantly and certain parameters of clinical immune competence were altered by IL-6 treatment. Treatment effects were similar in both age groups, but the changes in immune functions were different between the midle-aged and old monkeys. We observed a pattern in which the middle-aged group had a significant decrease in immune functions as a result of IL-6 administration and recovered to pretreatment level despite continuous treatment, whereas the old monkeys had a more protracted but less significant decline in these same immune functions during the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Interleukin-6 and aging: blood levels and mononuclear cell production increase with advancing age and in vitro production is modifiable by dietary restriction.

Interleukin-6 (IL-6) is a multifunctional cytokine that is proving to be a major contributor to the acute phase inflammatory response. IL-6 expression is normally low and serum levels are usually nondetectable in the absence of inflammation. With advancing age, however, serum levels become detectable and it is proposed that this reflects an age-associated loss in the normal regulation of gene expression for this molecule. There is also speculation that IL-6 may contribute to the pathogenesis of several diseases that are common in late-life including lymphoma, osteoporosis, and Alzheimer's disease. In this report we demonstrate that plasma levels of IL-6 rise with advancing age in well-selected healthy elderly people and comparably in old rhesus monkeys. That this change reflects a primary aging process is suggested by our findings in C57BL/6 mice in which the age-associated increase in the in vitro synthesis of IL-6 is largely prevented by life span-extending dietary restriction.

Adult↗
PubMed1992

In vivo and in vitro characteristics of interleukin 6-transfected B16 melanoma cells.

Interleukin 6 (IL-6) is a multifunctional cytokine important in the inflammatory response. Its potential role as an antitumor agent has been suggested by its demonstrated activity in a variety of tumor models. The mechanism of antitumor activity has been proposed to be its enhancement of cytotoxic T-cell function. In the current work we demonstrate clear antitumor activity for this cytokine in a nonimmunogenic tumor system. B16 melanoma cells transfected with the human IL-6 complementary DNA demonstrated slower tumor growth in vivo. Tumors that developed from these cells had a prominent stromal matrix, an easily recognized infiltration of inflammatory cells, fewer mitotic figures, and fewer blood vessels. These in vivo findings corresponded with a greater adhesion of the IL-6-transfected B16 cells to stromal matrix proteins (laminin, fibronectin, and vitronectin) and a less prominent vascular response in an intradermal angiogenesis assay. Therefore, we propose that with weakly antigenic tumors, such as B16 melanoma, IL-6 may mediate important antitumor responses by nonspecific proinflammatory mechanisms.

Animals↗
PubMed1991

Initial description of a tumor enhancing activity produced by murine splenocytes.

We have shown that certain murine tumors grow more slowly and spread less readily in immune deficient animals. We have also demonstrated that immunologic factors explain certain aspects of this difference. In the work presented we demonstrate that a subpopulation of splenocytes produce a factor(s) that enhances tumor cell proliferation in vitro. We also describe an in vitro model to determine the level of tumor stimulatory activity. We found that the tumor cell growth-enhancing activity (TEA) is heat stable but sensitive to trypsin digestion, low pH and beta-mercaptoethanol. TEA production is found to be insensitive to mitogen stimulation such as concanavalin A, lipopolysaccharide, and phytohemagglutinin. Among the known growth factors and interleukins we have tested (interleukin 1-7, basic FGF, EGF, TGF-beta PDGF, GM-CSF, and MCSF), none appear to account for TEA activity.

Animals↗
PubMed1989

Bootstrapped confidence intervals for the Cox model using a linear relative risk form.

A linear relative risk form for the Cox model is sometimes more appropriate than the usual exponential form. The usual asymptotic confidence interval may not have the appropriate coverage, however, due to flatness of the likelihood in the neighbourhood of beta. For a single continuous covariate, we derive bootstrapped confidence intervals with use of two resampling methods. The first resamples the original data and yields both one-step and fully iterated estimates of beta. The second resamples the score and information quantities at each failure time to yield a one-step estimate. We computed the bootstrapped confidence intervals by three different methods and compared these intervals to one based on the asymptotic standard error and to a likelihood-based interval. The bootstrapped intervals did not perform well and underestimated the true coverage in most cases.

Computer Simulation↗