Biomedical subjects
Publications and source records attributed to Yan Zhang.
We propose a new method based on in-line digital holography for the reconstruction of a wave front from only two intensity recordings. The simulation result shows that this method works well when the object wave is weak compared with the reference wave. This technique can be employed for real-time imaging.
We propose a method for the digital reconstruction of an object whose diffraction pattern has been recorded on a hologram. The fractional Fourier transform is used for the object reconstruction. To determine the position of the object, the fractional order is scanned. The fractional cosine and fractional Hartley transforms are also employed for object reconstruction. These two transforms are real valued and allow the reconstruction to be done with lower computing complexity. Simulations and experimental results are presented.
The age-associated decline in immunocompetence is paralleled by changes in the proportions of PBL subpopulations. In turn, the size and composition of the peripheral lymphocyte pool is determined by input from the thymus and bone marrow and by the balance of proliferation and death in each lymphocyte subpopulation. We compared the kinetics of lymphocyte subtypes in young (seven of eight CMV seronegative) and healthy elderly human subjects (six of seven CMV seropositive), using deuterated glucose DNA labeling in vivo to measure rates of T cell proliferation and disappearance. For CD45RO(+) cells of both CD4(+) and CD8(+) subtypes and for CD4(+)CD45RA(+) cells the kinetics of proliferation and disappearance were remarkably similar between elderly and young subjects. In the young, the kinetics of CD8(+)CD45RA(+) cells with a naive phenotype resembled those of CD4(+)CD45RA(+) cells. However, CD8(+)CD45RA(+) T cells from the elderly exhibited a predominantly primed phenotype, and for this subset, although the proliferation rate was similar to that of other CD45RA(+) cells, the disappearance rate of labeled cells was greatly decreased compared with that of all other T cell subsets. Our data provide a direct demonstration that there are no substantial changes in in vivo kinetics for most T cell populations in healthy elderly compared with young subjects. However, primed CD8(+)CD45RA(+) cells show unusual kinetic properties, indicating the persistence of these cells in the blood and dissociation of proliferation from disappearance.
Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo.
Previous studies have suggested more than 20 genetic intervals that are associated with susceptibility to type 1 diabetes (T1D), but identification of specific genes has been challenging and largely limited to known candidate genes. Here, we report evidence for an association between T1D and multiple single-nucleotide polymorphisms in 197 kb of genomic DNA in the IDDM5 interval. We cloned a new gene (SUMO4), encoding small ubiquitin-like modifier 4 protein, in the interval. A substitution (M55V) at an evolutionarily conserved residue of the crucial CUE domain of SUMO4 was strongly associated with T1D (P = 1.9 x 10(-7)). SUMO4 conjugates to I kappa B alpha and negatively regulates NF kappa B transcriptional activity. The M55V substitution resulted in 5.5 times greater NF kappa B transcriptional activity and approximately 2 times greater expression of IL12B, an NF kappa B-dependent gene. These findings suggest a new pathway that may be implicated in the pathogenesis of T1D.
The tumor suppressor p53 regulates the expression of various genes that promote apoptosis. PIG11 (P53-induced gene 11), also referred to as TP53I11 (tumor protein p53 inducible protein 11), is a direct p53 target gene. Recent data demonstrated that PIG11 was up-regulated markedly in arsenic trioxide induced apoptosis by DDRT-PCR, suggesting a new class of p53 target genes that sensitize cells to the effects of chemotherapeutic agents. In this study, through the construction of a recombinant GFP-PIG11 expression vector and transfection of HEK293 cells with GFP or GFP-PIG11, the role of PIG11 in apoptosis was analyzed. Results demonstrated that the percentage (11.38%) of apoptotic cells with GFP-PIG11 transfection was higher than that (7.28%) of with only GFP transfection (P<0.05). At 24 h after 1 microM of arsenic trioxide treatment, apoptotic cells exhibited a significant increase in the expression of GFP-PIG11 (36.67%+/-2.78), in contrast, 10.50%+/-2.03 only GFP and 5.25%+/-0.96 vehicle control (P<0.01). In addition, we showed that intracellular content of reactive oxygen species (ROS) was 9.66+/-0.52 in GFP-PIG11 transfection, higher than 5.21+/-0.08 in GFP only and 5.99+/-0.45 in vehicle control (P<0.01). The above results suggest that overexpression of PIG11 could induce cell apoptosis in the low levels and enhanced the apoptotic effects of arsenic trioxide. The process could be involved in intracellular generation of ROS.
Several multidrug resistance-associated protein (MRP) homologs are expressed in brain microvessel endothelial cells forming the blood-brain barrier (BBB). The influence of these MRP transporters on BBB permeability will be dependent on their localization within the brain microvessel endothelial cells. Using two different and complementary approaches, the localization of various MPR homologs (MRP1, MRP4, and MRP5) was examined in primary cultured bovine brain microvessel endothelial cells (BBMECs). The first approach involved centrifugal separation of apical and basolateral plasma membranes of cultured BBMECs. The membrane fractions were then subjected to Western blot analysis for MRPs. The second approach used confocal laser scanning microscopy to determine membrane localization of MRPs in BBMECs. Results show a predominantly apical plasma membrane distribution for MRP1 and MRP5, and an almost equal distribution of MRP4 on the apical and basolateral plasma membrane of BBMECs. These studies provide the first demonstration of the localization of MRP1, MRP4, and MRP5 homologs in brain microvessel endothelial cells. The present studies also indicate that the localization of MRPs in the endothelial cells forming the BBB is different from that observed in polarized epithelial cells and thus may contribute to the reduced entry and enhanced elimination of organic anions and nucleotides in the brain.
BACKGROUND: A number of noninvasive techniques have been used to predict the effectiveness of cardiac resynchronization therapy (CRT) in heart failure patients, in particular left ventricular (LV) reverse remodeling. This study compared the relative predictive values of tissue Doppler imaging (TDI) and strain-rate imaging (SRI) parameters for LV reverse remodeling in patients who received CRT and examined for potential differences in ischemic (n=22) and nonischemic (n=32) heart failure. METHODS AND RESULTS: TDI and SRI were performed at baseline and 3-month follow-up. Eighteen parameters of intraventricular and interventricular asynchrony based on the time to peak myocardial contraction (Ts) and time to peak strain rate (Tsr) were compared, along with postsystolic shortening (PSS). Reverse remodeling with reduction of LV end-diastolic and end-systolic volumes and gain in ejection fraction (all P<0.001) was observed in the whole study population. The standard deviation of Ts of 12 LV segments (Ts-SD) is the most powerful predictor of reverse remodeling in both the ischemic (r=-0.65, P<0.001) and nonischemic (r=-0.79, P<0.001) groups. The PSS of 12 LV segments was a good predictor only for the nonischemic (r=-0.64, P<0.001) but not the ischemic (r=0.32, P=NS) group. However, parameters of SRI and interventricular asynchrony failed to predict reverse remodeling. By multiple regression analysis, independent parameters included Ts-SD in both groups (P<0.005) and PSS of 12 LV segments in the nonischemic group (P=0.03). The area of the receiver operating characteristic curve was largest for Ts-SD (0.94; CI=0.88 to 1.00). CONCLUSIONS: Ts-SD is the most powerful predictor of LV reverse remodeling and was consistently useful for ischemic and nonischemic heart failure. However, PSS is useful only for nonischemic pathogenesis, whereas the role of SRI parameters was not supported by the present study.
Intracellular amyloidbeta peptide (iAbeta1-42) accumulates in the Alzheimer's disease brain before plaque and tangle formation (Gouras et al., 2000) and is extremely toxic to human neurons (Zhang et al., 2002). Here, we investigated whether androgen and estrogen could prevent iAbeta1-4) toxicity, because both these hormones have a wide range of neuroprotective actions. At physiological concentrations, 17-beta-estradiol, testosterone, and methyl testosterone reduce iAbeta1-42-induced cell death by 50% in neurons treated after the injection and by 80-90% in neurons treated 1 hr before the injection. The neuroprotective action of the hormones is mediated by receptors, because the estrogen receptor (ER) antagonist tamoxifen and the androgen receptor (AR) antagonist flutamide completely block the estrogen- and androgen-mediated neuroprotection, respectively. Transcriptional activity is required for the neuroprotective action, because dominant negative forms of the receptors that block the transcriptional activity of the ER and AR prevent estrogen- and androgen-mediated neuroprotection. Proteomics followed by Western blot analyses identified increased levels of heat shock protein 70 (Hsp70) in testosterone- and estrogen-treated human neurons. Comicroinjection of Hsp70 with the iAbeta1-42 blocks the toxicity of iAbeta1-42. We conclude that estrogen and androgens protect human neurons against iAbeta1-42 toxicity by increasing the levels of Hsp70 in the neurons.
BACKGROUND: Although tobacco products with reportedly reduced carcinogen content are being marketed, carcinogen uptake in people who use these products has not been assessed systematically. METHODS: Between June 2001 and November 2002, 54 users of smokeless tobacco and 51 cigarette smokers were randomly assigned to one of two groups. One used test products (Swedish snus for users of smokeless tobacco or OMNI cigarettes for smokers), while the other quit and used medicinal nicotine (the nicotine patch). All participants were assessed for urinary levels of total NNAL [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronide], metabolites of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Smokers were also assessed for levels of 1-hydroxypyrene (1-HOP), a biomarker of polycyclic aromatic hydrocarbon uptake. Assessments were made weekly during 2 weeks of baseline normal tobacco use and 4 weeks of treatment. Statistical tests were two-sided. RESULTS: Primary data analyses were conducted on 41 users of smokeless tobacco and 38 cigarette smokers who met the inclusion criteria. Total NNAL levels were statistically significantly lower in users of smokeless tobacco after they switched to snus or to nicotine patch (P<.001 for both groups) than they were before the switch, although the overall mean total NNAL level among subjects who used the nicotine patch was statistically significantly lower than that among those who used snus (mean = 1.2 and 2.0 pmol of NNAL/mg of creatinine, respectively; mean difference = 0.9 pmol of NNAL/mg of creatinine, 95% confidence interval [CI] = 0.2 to 1.5; P =.008). Compared with baseline levels, total NNAL levels (P =.003), but not 1-HOP levels, were statistically significantly reduced in cigarette smokers who switched to the OMNI cigarette, although both total NNAL levels and 1-HOP levels were statistically significantly reduced in smokers who switched to the nicotine patch (P<.001 for both). The overall mean total NNAL levels among smokers who used the nicotine patch was statistically significantly lower than that among smokers who used the OMNI cigarette (mean = 1.2 and 1.9 pmol of NNAL/mg of creatinine, respectively; mean difference = 0.6 pmol of NNAL/mg of creatinine, 95% CI = 0.1 to 1.1; P =.022). CONCLUSION: Switching to reduced-exposure tobacco products or medicinal nicotine can decrease levels of tobacco-associated carcinogens, with greater reductions being observed with medicinal nicotine. Medicinal nicotine is a safer alternative than modified tobacco products.
We have cloned, expressed and characterized a novel member of the human UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (pp-GalNAc-T) family, pp-GalNAc-T15. The pp-GalNAc-T15 transcript was ubiquitously expressed in human tissues. Recombinant pp-GalNAc-T15 transferred N-acetylgalactosamine (GalNAc) toward a panel of mucin-derived peptide substrates in vitro. Although pp-GalNAc-T15 showed significantly less catalytic activity than pp-GalNAc-T2, T15 transferred up to seven GalNAcs to the Muc5AC peptide, while T2 transferred up to five GalNAcs. These results clearly indicated that pp-GalNAc-T15 is a novel member of the human pp-GalNAc-T family with unique catalytic activity.
Individual variation in drug response is considered to have multiple origins arising from interactions among susceptible genes and environmental factors. A total of 726 hypertensive patients who took benazepril 10 mg once a day for 15 days and their families from Huoqiu county of Anhui Province, China, were used to study the association between D919G polymorphism of methionine synthase (MTR) gene and the antihypertensive effect of this angiotensin-converting enzyme inhibitor. Compared to the 919D allele, both population-based ( P=0.010) and family-based association tests (additive model P=0.018, dominant model P=0.025) demonstrated that the 919G allele was associated with a significantly less diastolic blood pressure reduction. No significant association was found between the extent of systolic blood pressure reduction and benazepril therapy. Our finding suggests that the D919G polymorphism of the MTR gene may be a useful genetic marker to predict the antihypertensive effect of short-term benazepril therapy in hypertensive patients of Anhui Province, China.
The high-affinity heparin-binding domain and the V region of fibronectin (FN) mediate invasion and migration of human oral squamous cell carcinoma (SCC) cells. We investigated the role of the alpha4, alpha5, and alphav integrin receptors--which are central to mediating interactions with these domains of FN--in regulating SCC cell migration. SCC cells expressed the alpha4, alpha5, and alphav integrin subunits on their surface, although alpha4 expression was low. Treatment with recombinant FN proteins containing an alternatively spliced V region (V+) and either an unmutated (H+) or a mutated, nonfunctional high-affinity heparin-binding domain (H-) increased expression of alpha5 and alphav and cell motility. Antisense alpha5 or alphav oligonucleotides inhibited cell motility stimulated by FN proteins, as did blocking antibodies to alpha5 or alphav. Blocking antibodies to alpha5 increased alphav and alpha4 levels, and blocking antibodies to alphav increased the levels of alpha5 and alpha4, without increasing cell motility. In contrast, an antisense alpha4 oligonucleotide and alpha4-blocking antibodies increased cell motility, especially migration stimulated by V+H+ and V+H- FN proteins. alpha4-Blocking antibodies alone increased motility, probably by inducing alpha5 and alphav expression. Transfection with alpha4 cDNA decreased cell motility and alpha5 and alphav expression. Thus, the increased motility induced by the FN protein is probably mediated by alphav and alpha5, whereas alpha4 downregulates this process in a transdominant fashion.
MOTIVATION: Expression profiling in diverse tissues is fundamental to understanding gene function as well as therapeutic target identification. The vast collection of expressed sequence tags (ESTs) and the associated tissue source information provides an attractive opportunity for studying gene expression. RESULTS: To facilitate EST-based expression analysis, we developed GEPIS (gene expression profiling in silico), a tool that integrates EST and tissue source information to compute gene expression patterns in a large panel of normal and tumor samples. We found EST-based expression patterns to be consistent with published papers as well as our own experimental results. We also built a GEPIS Regional Atlas that depicts expression characteristics of all genes in a selected genomic region. This program can be adapted for large-scale screening for genes with desirable expression patterns, as illustrated by our large-scale mining for tissue- and tumor-specific genes. AVAILABILITY: The email server version of the GEPIS application is freely available at http://share.gene.com/share/gepis. An interactive version of GEPIS will soon be freely available at http://www.cgl.ucsf.edu/Research/genentech/gepis/. The source code, modules, data and gene lists can be downloaded at http://share.gene.com/share/gepis.
Mammalian phospholipase D (PLD), a multifunctional signaling enzyme, has been reported to facilitate neurite outgrowth in cultured neurons. However, two mammalian isoforms have been found, PLD1 and PLD2, and it has not been determined which isoform is involved, or whether this in vitro phenomenon is relevant to neurite extension in vivo. Using confocal microscopy, we demonstrate that the PLDs are expressed by different cell types in the mouse brain: PLD1 by neurons, and PLD2 by astrocytes. Moreover, using a model of experimentally induced hippocampal mossy fiber sprouting, both isoforms were observed to increase dramatically in expression level along tracts of mossy fiber spouting, supporting the proposal that PLD plays a role in this process. Given that the two isoforms undertake unique molecular functions in cultured cells, our findings suggest that in vivo PLD1 and PLD2 may modulate neuronal plasticity via different pathways and cell types.
In this paper, we employ the time-dependent quantum wave packet method to study the reaction of F((2)P(3/2), (2)P(1/2)) with HD on the Alexander-Stark-Werner potential energy surface. The reaction probabilities and total integral cross sections of the spin-orbit ground and excited states for the two possible products of the system are calculated. Because the reaction channel of the excited spin-orbit state is closed at the resonance energy, the resonance feature does not appear in the reaction probabilities and cross section for the F((2)P(1/2))+HD(v=j=0)-->HF+D reaction, in contrast with that found for the ground spin--orbit state. We also compare the average cross sections of the two possible products with the experimental measurement. The resonance peak in the present average cross section for the HF+D product is slightly larger than the experimental result, but much smaller than that of the single-state calculations on the potential energy surface of Stark and Werner. It seems that the spin--orbit coupling would play a relatively important role in this reaction. Moreover, the isotope effects of the ground and excited spin--orbit states and the reactivity of the two product channels from the excited spin--orbit state are presented.
Cells are programmed to die when critical signaling and metabolic pathways are disrupted. Inhibiting the type 2 ryanodine receptor (RyR2) in human and mouse pancreatic beta-cells markedly increased apoptosis. This mode of programmed cell death was not associated with robust caspase-3 activation prompting a search for an alternative mechanism. Increased calpain activity and calpain gene expression suggested a role for a calpain-dependent death pathway. Using a combination of pharmacological and genetic approaches, we demonstrated that the calpain-10 isoform mediated ryanodine-induced apoptosis. Apoptosis induced by the fatty acid palmitate and by low glucose also required calpain-10. Ryanodine-induced calpain activation and apoptosis were reversed by glucagon-like peptide or short-term exposure to high glucose. Thus RyR2 activity seems to play an essential role in beta-cell survival in vitro by suppressing a death pathway mediated by calpain-10, a type 2 diabetes susceptibility gene with previously unknown function.
AIM: To improve the technique of tissue microarray (tissue chip). METHODS: A new tissue microarraying method was invented with a common microscope installed with a special holing needle, a sampling needle, and a special box fixing paraffin blocks on the microscope slide carrier. With the movement of microscope tube and objective stage on vertical and cross dimensions respectively, the holing procedure on the recipient paraffin blocks and sampling procedure of core tissue biopsies taken from the donor blocks were performed with the refitted microscope on the same platform. The precise observation and localization of representative regions in the donor blocks were also performed with the microscope equipped with a stereoscope. RESULTS: Highly-qualified tissue chips of colorectal tumors were produced by a new method, which simplified the conventional microarraying procedure, and was more convenient and accurate than that employing the existing tissue microarraying instruments. CONCLUSION: Using the refitted common microscope to produce tissue microarray is a simple, reliable, cost-effective and well-applicable technique.