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Biomedical subjects

H Yu

Publications and source records attributed to H Yu.

At least 91 records · Page 5Linked to original sources
PubMed2001

Linkage analysis of angiotensin-converting enzyme (ACE) insertion/deletion polymorphism and systemic lupus erythematosus.

Previous studies have suggested an association between systemic lupus erythematosus (SLE) and an insertion/deletion polymorphism in the angiotensin-converting enzyme gene (ACE). This polymorphism consists of a 250-bp insertion/deletion of an alu repeat in the 16th intron of the ACE gene. Individuals homozygous for the deletion have a higher level of circulating enzyme. Due to the important role of this enzyme in regulating the renin--angiotensin and kallikrein--kininogen systems, it is possible that the ACE insertion/deletion may play a role in SLE, which can include vasculitis and vascular changes. Using primers flanking the insertion/deletion site, we have examined the ACE gene in lupus patients and family members using genomic DNA obtained from the Lupus Multiplex Registry and Repository (LMRR). We were unable to detect significant linkage or genetic association between the ACE gene and SLE.

Family Health↗
PubMed2001

Constitutive activation of Stat3 by the Src and JAK tyrosine kinases participates in growth regulation of human breast carcinoma cells.

Constitutive activation of signal transducer and activator of transcription (STAT) proteins has been detected in a wide variety of human primary tumor specimens and tumor cell lines including blood malignancies, head and neck cancer, and breast cancer. We have previously demonstrated a high frequency of Stat3 DNA-binding activity that is constitutively-induced by an unknown mechanism in human breast cancer cell lines possessing elevated EGF receptor (EGF-R) and c-Src kinase activities. Using tyrosine kinase selective inhibitors, we show here that Src and JAK family tyrosine kinases cooperate to mediate constitutive Stat3 activation in the absence of EGF stimulation in model human breast cancer cell lines. Inhibition of Src or JAKs results in dose-dependent suppression of Stat3 DNA-binding activity, which is accompanied by growth inhibition and induction of programmed cell death. In addition, transfection of a dominant-negative form of Stat3 leads to growth inhibition involving apoptosis of breast cancer cells. These results indicate that the biological effects of the Src and JAK tyrosine kinase inhibitors are at least partially mediated by blocking Stat3 signaling. While EGF-R kinase activity is not required for constitutive Stat3 activation in breast cancer cells, EGF stimulation further increases STAT DNA-binding activity, consistent with an important role for EGF-R in STAT signaling and malignant progression. Analysis of primary breast tumor specimens from patients with advanced disease revealed that the majority exhibit elevated STAT DNA-binding activity compared to adjacent non-tumor tissues. Our findings, taken together, suggest that tyrosine kinases transduce signals through Stat3 protein that contribute to the growth and survival of human breast cancer cells in culture and potentially in vivo.

Animals↗
PubMed2001

Ribozyme-mediated inhibition of caspase-3 activity reduces apoptosis induced by 6-hydroxydopamine in PC12 cells.

6-Hydroxydopamine (6-OHDA) is a neurotoxin used in the induction of experimental Parkinson's disease in both animals and PC12 cells, which are derived from rat pheochromocytoma tumors and have many properties similar to dopamine neurons. Biochemical and molecular approaches have shown that low doses of 6-OHDA induce apoptosis in PC12 cells and, in the processing of apoptosis, caspases are crucial mediators, and caspase inhibition is sufficient to rescue PC12 cells from apoptosis induced by 6-OHDA. However, because this caspase inhibition targets multiple caspases, it is not known whether a single caspase is primarily responsible for effecting cell death in this model. To assess the particular member (caspase-3) of the ced-3 family relevant to cell death and to position their activation within the apoptotic pathway, we constructed a hammerhead ribozyme directed against rat caspase-3, which could downregulate the expression of caspase-3 in vitro and in vivo, and transfer to PC12 cells. The results show that the ribozymes against caspase-3 could protect PC12 cells from apoptosis induced by low doses of 6-OHDA. The PC12 cell transfected with the ribozymes shows a significant decrease in caspase-3 activity compared with control cells at various time points. Parallel to the reduced caspase-3 protease activity, similar decreased levels of apoptotic cells and DNA fragmentation were also assessed by staining with Hoechst 33258 and ELISA, respectively. Overexpression of p35, a general caspase inhibitor, also protected PC12 cells from apoptosis. These results confirm that caspases play an important role in 6-OHDA-induced PC12 cell apoptosis and indicate that caspase-3 itself is one of the crucial mediators of neurotoxin-induced PC12 cell apoptosis.

Adrenergic Agents↗
PubMed2001

Levels of insulin-like growth factor after stem cell transplantation.

Some cytokines, i.e. tumor necrosis factor-, interleukin-6 and soluble interleukin-2 receptors are associated with complications of stem cell transplantation. Insulin-like growth factors (IGFs) are a family of peptides essential for the proliferation of normal and malignant cells. Recently increased levels of IGFs have been associated with the development of malignant tumors. In this communication we report on 96 measurements of insulin-like growth factor-I (IGF-1), insulin-like growth factor-II (IGF-2), and insulin-like growth factor-binding protein-3 (IGFBP-3) performed in 19 patients following stem cell transplants. Seventeen patients had allogeneic and 2 patients autologous transplants. Most IGF determinations were made at days 0, 7, 14, 21 and 28, some at other time points. The baseline values (day 0) of IGF-1 and IGFBP-3 were not different from controls. IGF-2 values were slightly lower than controls. Following transplantation, a consistent increase of IGF-1 was observed in 9/16 patients at days 7 and 14. Later the values decreased again. IGF-2 and IGFBP-3 did not change significantly after transplantation. No direct correlation could be established with the severity of graft-versus-host disease, levels of interleukin-6 and the time to hematopoietic recovery. A potential relevance of IGFs following stem cell transplantation may be the early diagnosis of liver damage and the development of second malignancies. More studies are necessary to investigate the pathophysiology and the clinical relevance of the increase of IGF-1 following stem cell transplantation.

Adolescent↗
PubMed2001

PartsList: a web-based system for dynamically ranking protein folds based on disparate attributes, including whole-genome expression and interaction information.

As the number of protein folds is quite limited, a mode of analysis that will be increasingly common in the future, especially with the advent of structural genomics, is to survey and re-survey the finite parts list of folds from an expanding number of perspectives. We have developed a new resource, called PartsList, that lets one dynamically perform these comparative fold surveys. It is available on the web at http://bioinfo.mbb.yale.edu/partslist and http://www.partslist.org. The system is based on the existing fold classifications and functions as a form of companion annotation for them, providing 'global views' of many already completed fold surveys. The central idea in the system is that of comparison through ranking; PartsList will rank the approximately 420 folds based on more than 180 attributes. These include: (i) occurrence in a number of completely sequenced genomes (e.g. it will show the most common folds in the worm versus yeast); (ii) occurrence in the structure databank (e.g. most common folds in the PDB); (iii) both absolute and relative gene expression information (e.g. most changing folds in expression over the cell cycle); (iv) protein-protein interactions, based on experimental data in yeast and comprehensive PDB surveys (e.g. most interacting fold); (v) sensitivity to inserted transposons; (vi) the number of functions associated with the fold (e.g. most multi-functional folds); (vii) amino acid composition (e.g. most Cys-rich folds); (viii) protein motions (e.g. most mobile folds); and (ix) the level of similarity based on a comprehensive set of structural alignments (e.g. most structurally variable folds). The integration of whole-genome expression and protein-protein interaction data with structural information is a particularly novel feature of our system. We provide three ways of visualizing the rankings: a profiler emphasizing the progression of high and low ranks across many pre-selected attributes, a dynamic comparer for custom comparisons and a numerical rankings correlator. These allow one to directly compare very different attributes of a fold (e.g. expression level, genome occurrence and maximum motion) in the uniform numerical format of ranks. This uniform framework, in turn, highlights the way that the frequency of many of the attributes falls off with approximate power-law behavior (i.e. according to V(-b), for attribute value V and constant exponent b), with a few folds having large values and most having small values.

Cysteine↗
PubMed2001

Overexpression of a dominant-negative signal transducer and activator of transcription 3 variant in tumor cells leads to production of soluble factors that induce apoptosis and cell cycle arrest.

Gene therapy of B16 tumors with a dominant-negative signal transducer and activator of transcription (Stat3) variant, designated Stat3beta, results in inhibition of tumor growth and tumor regression. Although only 10-15% of the tumor cells are transfected in vivo, the Stat3beta-induced antitumor effect is associated with massive apoptosis of B16 tumor cells, indicative of a potent bystander effect. Here, we provide evidence that blocking Stat3 signaling in B16 cells results in release of soluble factors that are capable of inducing apoptosis and cell cycle arrest of nontransfected B16 cells. RNase protection assays using multi-template probes specific for key physiological regulators of apoptosis reveal that overexpression of Stat3beta in B16 tumor cells induces the expression of the apoptotic effector, tumor necrosis factor-related apoptosis-inducing ligand. These in vitro results suggest that the observed in vivo bystander effect leading to tumor cell growth inhibition is mediated, at least in part, by soluble factors produced as a result of overexpression of Stat3beta in tumor cells.

3T3 Cells↗
PubMed2001

Dexamethasone inhibits the antigen presentation of dendritic cells in MHC class II pathway.

Glucocorticoids (GC) are physiological inhibitors of inflammatory responses and are widely used as anti-inflammatory and immunosuppressive agents in treatment of many autoimmune and allergic diseases. In the present study, we demonstrated that one of the mechanisms by which GC can suppress the immune responses is to inhibit the differentiation and antigen presentation of dendritic cells (DC). DC were differentiated from murine bone marrow hematopoietic progenitor cells by culture with GM-CSF and IL-4 with or without dexamethasone (Dex). Our data showed that Dex, in a dose dependent manner, down-regulated surface expression of CD86, CD40, CD54 and MHC class II molecules by DC, but the expression of MHC class I, CD80, CD95 and CD95L were not affected. In addition, Dex-treated DC showed an impaired function to activate alloreactive T cells and to secrete IL-Ibeta and IL-12p70. Moreover, Dex inhibited DC to present antigen by MHC class II pathway. However, the endocytotic activity of DC was not affected. The inhibitory effect of Dex on the expression of costimulatory molecules and the antigen-presenting capacity of DC could be blocked by the addition of RU486, a potent steroid hormone antagonist, suggesting the requirement of binding to cytosolic receptors in the above-described action of Dex. Since DC have the unique property to present antigen to responding naive T cells and are required in the induction of a primary response, the functional suppression of DC by Dex may be one of the mechanisms by which GC regulate immune responses in vivo.

Animals↗
PubMed2001

Free insulin-like growth factor-I and breast cancer risk.

Insulin-like growth factor-I (IGF-I) has mitogenic and anti-apoptotic effects on breast cancer cells. Epidemiologic studies have shown that high plasma levels of IGF-I and low levels of IGF binding protein (BP)-3 are associated with increased risk of breast cancer in premenopausal women. The actions of IGF-I are mediated through the IGF-I receptor (IGF-IR) and are regulated by IGFBPs. In circulation, most of the IGF-I binds to IGFBP-3, and binding of IGF-I to IGFBP-3 inhibits the actions of IGF-I. Since free IGF-I, which does not bind to IGFBPs, can readily cross the endothelial barrier to interact with IGF-IR, circulating free IGF-I is thought to be more relevant to the biologic activity of IGF-I. To examine the association of free IGF-I with breast cancer, we compared free IGF-I levels between 40 newly diagnosed breast cancer patients and 40 age- and race-matched healthy controls. Plasma levels of free IGF-I, total IGF-I and IGF-II, as well as total, intact and fragment IGFBP-3, were measured using commercial immunoassay kits. The association between IGF-I and breast cancer was examined using the conditional logistic regression analysis. Analysis of correlation (Spearman) showed that free IGF-I was correlated with total IGF-I and IGFBP-3 but not with IGF-II. The odds ratios for breast cancer patients having high plasma IGF-I (> or = median) after adjusting for menopausal status and IGFBP-3 were 2.00 (p < o r = 0.376) for total IGF-I and 6.31 (p < or = 0.047) for free IGF-I. A high ratio of IGF-I to IGFBP-3 was also associated with breast cancer (p < 0.05). No association was found for IGF-II, nor for total, intact and fragment IGFBP-3. The findings of this study suggest that measuring free IGF-I in circulation is more useful than measuring total IGF-I with respect to evaluation of an association between IGF-I and breast cancer risk.

Adult↗
PubMed2001

[High efficiency gene transfer into breast cancer cells by pseudotyped retroviral vector].

OBJECTIVE: To investigate the efficiency of gene transfer mediated by pseudotyped retroviral vector in breast cancer, and to provide an useful vector for breast cancer gene therapy. METHODS: We used a MuLV vector pseudotyped with the vesicular stomatitis virus glycoprotein(VSV-G) envelope to transduce breast cancer cells MDA-MB-435, To compare the transfer efficiency with MuLV. RESULTS: The transfer efficiency is (92 +/- 12)% by using MuLV/VSV-G vector, (24 +/- 5)% by MuLV vector. The transfer efficiency of MuLV/VSV-G is 3.8 times that of MuLV vector. CONCLUSION: Our results suggest that pseudotyped retroviral vector MuLV/VSV-G is a kind of high efficiency gene transfer vector in breast cancer cells.

Breast Neoplasms↗
PubMed2001

Association of a 27-bp repeat polymorphism in ecNOS gene with ischemic stroke in Chinese patients.

OBJECTIVE: To investigate the association between a 27-bp repeat polymorphism of the ecNOS gene in 364 patients with ischemic stroke and 516 control subjects. BACKGROUND: The incidence of stroke in China is higher than that of coronary artery disease. Furthermore, ischemic stroke is more prevalent than hemorrhagic stroke. A 27-bp repeat polymorphism in intron 4 of the endothelial constitutive nitric oxide synthase (ecNOS) gene has been reported to associate with coronary artery disease in an Australian population, but no association was found between this polymorphism and ischemic stroke in a Japanese population. METHODS: All patients and unrelated control subjects were screened by CT. All participants lived in central China. Multivariate logistic regression analysis was used to determine the independent roles of this ecNOS gene polymorphism and covariates in ischemic stroke. RESULTS: These results indicated an association between the ecNOS a allele and ischemic stroke in the Chinese patients studied (7.8 versus 17.0%; OR = 2.44; 95% CI = 1.60 to 3.71, p < 0.0001). CONCLUSION: The ecNOS a allele in intron 4 may be an independent risk factor for ischemic stroke in the Chinese population studied, especially in those lacking other conventional risk factors.

Aged↗
PubMed2001

Enhanced retroviral transduction of 293 cells cultured on liquid-liquid interfaces.

In clinical research, retrovirus-mediated gene therapy is one of the most commonly used methods to deliver and express the gene of interest due its ability to allow for stable gene integration into the chromosomes of target cells. To elevate the efficiency of viral transduction, several restrictions, such as low virus-cell encounters and the necessity for cell division, must be improved. In this study, we focused on the possibility of accelerating cell division and the ensuing increment of viral transduction on flexible substrata. Perfluorocarbon FC-40 was harnessed to form a liquid-liquid interface with culture medium. Enhanced green fluorescence protein (EGFP) was employed as the marker gene to quickly illustrate the percentage of viral infection. The results indicate that the gene transfer efficiency to 293 cells cultured on protein-precoated liquid-liquid interfaces was higher than in cells cultured on rigid polystyrene surfaces. This increased transduction rate on the liquid-liquid interface is consistent with the acceleration of division of 293 cells on a flexible interface, which exhibited less adhesiveness. The effect of cell-cell contact inhibition on the rate of gene transduction is also addressed in this study.

Cell Adhesion↗
PubMed2001

Structure-activity studies of 5-substituted pyridopyrimidines as adenosine kinase inhibitors.

The synthesis and SAR of a novel series of non-nucleoside pyridopyrimidine inhibitors of the enzyme adenosine kinase (AK) are described. It was found that pyridopyrimidines with a broad range of medium and large non-polar substituents at the 5-position potently inhibited AK activity. A narrower range of analogues was capable of potently inhibiting adenosine phosphorylation in intact cells indicating an enhanced ability of these analogues to penetrate cell membranes. Potent AK inhibitors were found to effectively reduce nociception in animal models of thermal hyperalgesia and persistent pain.

Adenosine Kinase↗
PubMed2001

1,2,5-Thiadiazolidin-3-one 1,1 dioxide: a powerful scaffold for probing the S' subsites of (chymo)trypsin-like serine proteases.

The 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold (I) embodies a motif that allows it to dock to the active site of (chymo)trypsin-like proteases in a predictable and substrate-like fashion. Consequently, inhibitors derived from this heterocyclic scaffold interact with both the S and S' subsites of an enzyme. Exploitation of binding interactions with both the S and S' subsites of a target enzyme may lead to compounds with greatly enhanced enzyme selectivity and inhibitory potency. This preliminary report describes the use of a series of compounds having the heterocyclic scaffold linked to various amino acids to probe the S' subsites of human leukocyte elastase (HLE), proteinase 3 (PR 3), and cathepsin G (Cat G). For comparative purposes, a series of compounds derived from a related scaffold, isothiazolidin-3-one 1,1 dioxide (II), was also generated. Several of the compounds were found to be highly potent and selective time-dependent inhibitors of HLE, PR 3, and Cat G.

Cathepsin G↗
PubMed2001

Anti-CD40 antibody induces antitumor and antimetastatic effects: the role of NK cells.

We assessed the effect of the stimulatory anti-CD40 Ab on NK cell activation in vivo and the therapeutic potential of activated NK cells in tumor-bearing mice. Single-dose i.p. injection of the anti-CD40 Ab resulted in production of IL-12 and IFN-gamma in vivo, followed by a dramatic increase in NK cell cytolytic activity in PBLs. NK cell activation by anti-CD40 Ab was also observed in CD40 ligand knockout mice. Because NK cells express CD40 ligand but not CD40, our results suggest that NK activation is mediated by increased cytokine production upon CD40 ligation of APCs. Treatment of tumor-bearing mice with anti-CD40 Ab resulted in substantial antitumor and antimetastatic effects in three tumor models. Depletion of NK cells with anti-asialo GM1 Ab reduced or abrogated the observed antitumor effects in all the tested models. These results indicate that a stimulatory CD40 Ab indirectly activates NK cells, which can produce significant antitumor and antimetastatic effects.

Animals↗
PubMed2001

Quantitative model for the interecho time dependence of the CPMG relaxation rate in iron-rich gray matter.

A quantitative model is proposed for computing the dependence on the interecho time of the NMR relaxation rate in iron-rich gray matter obtained with a Carr-Purcell-Meiboom-Gill sequence. The model consists of representing oligodendrocytes as identical magnetic spheres arranged in a spatially random pattern, and in approximating water diffusion as isotropic and unrestricted. Predictions of the model are calculated numerically using a Monte Carlo technique and, for the weak field limit, using an analytic formula. The model is shown to provide a good fit to experimental measurements of in vitro samples of monkey brain at field levels of 1.0 T and 1.5 T. These field levels are not sufficient to fully determine the model parameters, but it is argued that this may be possible at 3.0 T. The model is potentially of value for multiple-spin-echo MRI studies of iron-related neurodegenerative disorders, such as Parkinson's disease. In particular, the model can be applied to correlate MRI data with the cellular distribution of iron in gray matter. Magn Reson Med 46:159-165, 2001.

Animals↗
PubMed2001

Transgene expression in the brain stem effected by intramuscular injection of polyethylenimine/DNA complexes.

Gene delivery into the CNS without tissue destruction is challenging. As neurons are capable of taking up exogenous particulates from the muscles that they innervate, we investigated the feasibility of achieving gene transfer in CNS neurons by peripheral intramuscular injection of plasmid DNA complexed with the cationic polymer polyethylenimine (PEI) in the rat hypoglossal system. Using the luciferase reporter gene driven by a Rous sarcoma virus promoter, transgene expression of up to 4 x 10(6) RLU per brain stem at 20 microg of plasmid DNA was achieved after tongue injection. Using lacZ as a reporter gene, transgene expression in the brain stem was detected in hypoglossal motor neurons, a group of neurons that innervate tongue muscles. The plasmid DNA was detected by PCR analysis in the brain-stem samples, demonstrating that the PEI/DNA complexes had migrated by retrograde axonal transport to neuronal cell bodies in the brain stem after being internalized by nerve terminals in the tongue muscle. Using a therapeutic bcl-2 gene driven by a cytomegalovirus promoter and Western blotting, transgene expression was detectable in the brain stem as early as 18 h after tongue injection and lasted for at least 2 weeks. Two lipid transfection agents, GenePORTER and TransFast, mediated a weak gene expression in the hypoglossal system, but not two polymers, poly-l-lysine and chitosan. The nonviral neuronal gene delivery method established in this study bypasses the blood-brain barrier and suggests a possible therapeutic strategy for noninvasive CNS gene transfer.

Animals↗
PubMed2001

A complex adenovirus vector that delivers FASL-GFP with combined prostate-specific and tetracycline-regulated expression.

Cell-type-restricted transgene expression delivered by adenovirus vectors is highly desirable for gene therapy of cancer, as it can limit cytotoxic gene expression to tumor cells. However, many tumor- and tissue-specific promoters are weaker than the constitutively active promoters and are thus less effective. To combine cell-type specificity with high-level regulated transgene expression, we have developed a complex adenoviral vector. We have placed the tetracycline transactivator gene under the control of a prostate-specific ARR2PB promoter, and a mouse Tnfsf6 (encoding FASL)-GFP fusion gene under the control of the tetracycline responsive promoter. We have incorporated both expression cassettes into a single construct. We show that FASL-GFP expression from this vector is essentially restricted to prostate cancer cells, in which it can be regulated by doxycycline. Higher levels of prostate-specific FASL-GFP expression were generated by this approach than by driving the FASL-GFP expression directly with ARR2PB. More FASL-GFP expression correlated with greater induction of apoptosis in prostate cancer LNCaP cells. Mouse studies confirmed that systemic delivery of both the prostate-specific and the prostate-specific/tet-regulated vectors was well tolerated at doses that were lethal for FASL-GFP vector with CMV promoter. This strategy should be able to improve the safety and efficacy of cancer gene therapy using other cytotoxic genes as well.

Adenoviridae↗