Peizhang Zhou | Singapore University of Technology and Design (SUTD) (original) (raw)

Papers by Peizhang Zhou

arXiv (Cornell University), Aug 2, 2020

Determining whether two graphs are isomorphic is an important and difficult problem in graph theo... more Determining whether two graphs are isomorphic is an important and difficult problem in graph theory. One way to make progress towards this problem is by finding and studying graph invariants that distinguish large classes of graphs. Stanley conjectured that his chromatic symmetric function distinguishes all trees, which has remained unresolved. Recently, Hasebe and Tsujie introduced an analogue of Stanley's function for posets, called the strict order quasisymmetric function, and proved that it distinguishes all rooted trees. In this paper, we devise a procedure to explicitly reconstruct a rooted tree from its strict order quasisymmetric function by sampling a finite number of terms. The procedure not only provides a combinatorial proof of the result of Hasebe and Tsujie, but also tracks down the representative terms of each rooted tree that distinguish it from other rooted trees.

arXiv: Combinatorics, 2020

Determining whether two graphs are isomorphic is a very important and difficult problem in graph ... more Determining whether two graphs are isomorphic is a very important and difficult problem in graph theory, with applications in image recognition. One way to make progress towards this problem is by finding graph invariants that distinguish large classes of graphs. In 1995, Richard Stanley conjectured that his chromatic symmetric function distinguishes all trees, which has remained unresolved. In 2017, Takahiro Hasebe and Shuhei Tsujie proved a version of Stanley's conjecture for posets: their strict order quasisymmetric function distinguishes all rooted trees. However, the strict order quasisymmetric function has an infinite number of terms, and it's not clear which terms need to be computed to distinguish two rooted trees. To resolve this, we use an original combinatorial framework to devise a procedure that explicitly reconstructs a rooted tree from its strict order quasisymmetric function. This procedure takes us one step closer to a concrete implementation of the strict o...

The chromatic symmetric function defined by Stanley is a power series that is symmetric in an inf... more The chromatic symmetric function defined by Stanley is a power series that is symmetric in an infinite number of variables and generalizes the chromatic polynomial. Shareshian and Wachs defined the chromatic quasisymmetric function, and Awan and Bernardi defined an analog of it for digraphs. Three decades ago, Stanley posed a question equivalent to “Does the chromatic symmetric function distinguish between all trees?” A similar question can be raised for rooted trees: “Does the chromatic quasisymmetric function distinguish between all rooted trees?”. Hasebe and Tsujie showed algebraically the stronger statement that the order quasisymmetric function distinguishes rooted trees. Here, we aim to directly extract useful statistics about a tree given only its order quasisymmetric function. This approach emphasizes the combinatorics of trees over the the algebraic properties of quasisymmetric functions. We show that a rooted-tree-statistic we name the “co-height profile profile” is extrac...

Neuropsychiatric Disease and Treatment, 2019

Epidemiology research has demonstrated that magnesium (Mg) deficiency is associated with a high i... more Epidemiology research has demonstrated that magnesium (Mg) deficiency is associated with a high incidence of Parkinson's disease (PD). It is known that the systemic administration of MgSO 4 is not able to elevate the Mg concentration in cerebrospinal fluid (CSF). This study aims to verify the protective effect of magnesium-L-threonate (MgT) in 1methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model. Methods: C57BL/6J mice were orally administered MgT or MgSO 4 for 4 weeks, and received MPTP in the third week. After analysis of open-field and rotarod tests on the last day, tyrosine hydroxylase (TH) immunopositive cells and protein levels were quantified in the substantia nigra pars compacta (SNpc) and striatum. The expression of inducible nitric oxide synthase (iNOS) level was evaluated. Mg concentration in serum and CSF was measured after oral administration of MgSO 4 or MgT in normal mice. Mg concentration in the CSF was increased in the mice treated with MgT but not MgSO 4. Results: The total distance and mean speed in open-field tests, and the time spent on rotarod in the MgT group were increased, compared with MPTP group. The MgT treatment but not MgSO 4 dose-dependently attenuated the loss of TH-positive neurons, and the reduction of the TH expression in the SNpc. The MgT treatment also inhibited the expression of iNOS as measured by immunohistochemistry and Western blots. Double-immunofluorescence staining of TH and iNOS showed iNOS-positive cells were collocalized for TH-positive cells. Conclusion: The treatment with MgT is associated with an increase of Mg in the CSF. MgT, rather than MgSO4, can significantly attenuate MPTP-induced motor deficits and dopamine (DA) neuron loss.

Children and Youth Services Review, 2017

Caregivers of children in the child welfare system (CWS) often need more support in their parenti... more Caregivers of children in the child welfare system (CWS) often need more support in their parenting efforts. Some of these caregivers only need parenting related advices, whereas others may need more intensive training to prevent recurrence of maltreatment. Few parenting interventions can be delivered to both groups of caregivers with satisfying results. This study investigated the treatment change associated with Positive Parenting Programme (Triple P) on 83 caregivers who completed either the Level 4 version or the Level 5 (Pathways) version of the programme (mean age = 40.6 years). Repeated measure analysis showed significant improvement in common outcomes such as parenting practices, children's behaviour problems, parental satisfaction, and parents' psychological adjustment for both groups of caregivers. However, changes on Level 5 (Pathways) specific outcomes were not statistically significant. Further analysis suggested this lack of change may be due to the distinct profiles of dropouts in Level 5 Triple P. Study limitation and its implication for future research as well as programme development was also discussed.

Journal of Hypertension, 2011

Conclusion: The responsiveness of baPWV relative to acute BP reduction (ΔbaPWV/ΔBP) was correlate... more Conclusion: The responsiveness of baPWV relative to acute BP reduction (ΔbaPWV/ΔBP) was correlated with tissue Doppler imaging-detected left ventricular diastolic function. The ΔbaPWV/ΔBP was more correlated with E/E' ratio than baPWV itself, but not with E' wave velocity in male.

Molecular Cancer Therapeutics

Camptothecin and Adriamycin are clinically important inhibitors for topoisomerase (Topo) I and To... more Camptothecin and Adriamycin are clinically important inhibitors for topoisomerase (Topo) I and Topo II, respectively. The ataxia-telangiectasia mutated (ATM) product is essential for ionizing radiation-induced DNA damage responses, but the role of ATM in Topo poisons-induced checkpoints remains unresolved. We found that distinct mechanisms are involved in the activation of different cell cycle checkpoints at different concentrations of Adriamycin and camptothecin. Adriamycin promotes the G1 checkpoint through activation of the p53-p21CIP1/WAF1 pathway and decrease of pRb phosphorylation. Phosphorylation of p53(Ser20) after Adriamycin treatment is ATM dependent, but is not required for the full activation of p53. The G1 checkpoint is dependent on ATM at low doses but not at high doses of Adriamycin. In contrast, the Adriamycin-induced G2 checkpoint is independent on ATM but sensitive to caffeine. Adriamycin inhibits histone H3(Ser10) phosphorylation through inhibitory phosphorylation...

JAIDS Journal of Acquired Immune Deficiency Syndromes, 2021

Background: It is unknown whether gaining inpatient healthcare coverage had an effect on hospital... more Background: It is unknown whether gaining inpatient healthcare coverage had an effect on hospitalization rates among persons with HIV (PWH) following implementation of the Affordable Care Act (ACA) in 2014. Methods: Hospitalization data from 2015 were obtained on 1634 adults receiving longitudinal HIV care at 3 U.S. HIV clinics within the HIV Research Network. All patients were engaged in care and previously uninsured and supported by the Ryan White HIV/AIDS Program (RWHAP) in

PLOS ONE, 2020

Arginine deprivation cancer therapy targets certain types of malignancies with positive result in... more Arginine deprivation cancer therapy targets certain types of malignancies with positive result in many studies and clinical trials. NEI-01 was designed as a novel arginine-depleting enzyme comprising an albumin binding domain capable of binding to human serum albumin to lengthen its half-life. In the present work, NEI-01 is shown to bind to serum albumin from various species, including mice, rat and human. Single intraperitoneal administration of NEI-01 to mice reduced plasma arginine to undetectable level for at least 9 days. Treatment of NEI-01 specifically inhibited cell viability of MIA PaCa-2 and PANC-1 cancer cell lines, which were ASS1 negative. Using a human pancreatic mouse xenograft model, NEI-01 treatment significantly reduced tumor volume and weight. Our data provides proof of principle for a cancer treatment strategy using NEI-01.

AIDS Care, 2018

Federally Qualified Health Centers (FQHCs) have long been important sources of care for publicly ... more Federally Qualified Health Centers (FQHCs) have long been important sources of care for publicly insured people living with HIV. FQHC users have historically used emergency departments (EDs) at a higher-than-average rate. This paper examines whether this greater use relates to access difficulties in FQHCs or to characteristics of FQHC users. Zeroinflated Poisson models were used to estimate how FQHC use related to the odds of being an ED user and annual number of ED visits, using claims data on 6,284 HIV-infected California Medicaid beneficiaries in 2008-2009. FQHC users averaged significantly greater numbers of annual ED visits than non-FQHC users and those with no outpatient usage (1.89, 1.59, and 1.70, respectively; P=0.043). FQHC users had higher odds of being ED users (OR=1.14; 95%CI 1.02-1.27). In multivariable analyses, FQHC clients had higher odds of ED usage controlling for demographic and service characteristics (OR=1.15; 95%CI 1.02-1.30) but not when medical characteristics were included (OR=1.08; 95%CI 0.95-1.24). Among ED users, FQHC use was not significantly associated with the number of ED visits in our models (rate ratio (RR)=1.00; 95%CI 0.87-1.15). The overall difference in mean annual ED visits observed between FQHC and non-FQHC groups was reduced to insignificance (1.75; 95% CI 1.59-1.92 vs 1.70; 95%CI 1.54-1.85) after adjusting for demographic, service, and medical characteristics. Overall, FQHC users had higher ED utilization than non-FQHC users, but the disparity was largely driven by differences in underlying medical characteristics.

Open Forum Infectious Diseases, 2018

Background. The Ryan White Program (RWP), which provides safety net outpatient healthcare coverag... more Background. The Ryan White Program (RWP), which provides safety net outpatient healthcare coverage to thousands of low-income persons with HIV (PWH), does not pay for inpatient care. Many PWH who relied on RWP transitioned to either Medicaid or private insurance (private) with the Affordable Care Act in 2014. It is unknown whether such transitions affected hospitalization rates. Methods. We included patients from three HIV Research Network sites (two in Medicaid expansion states, one in a nonexpansion state) who relied solely on RWP in 2013. Patients either stayed in RWP through 2015, or changed to Medicaid or private in 2014. 2015 hospitalization rate ratios were modeled using negative binomial regression, adjusting for demographics, CD4 count, HIV viral load (VL), clinic site, and number of 2013 hospitalizations. Results. Our sample of 1,634 patients was 73% male, 46% Black, 36% Hispanic; median age was 45 years (IQR 37,52) and median CD4 count 526 cells/μL (356, 716); 85% had a VL ≤400 copies/mL. Ninety-five patients were hospitalized in 2015. Unadjusted hospitalization rates (per 100 person years) were 8.4, 21.3, and 7.4 in 2013 and 6.3, 20.2, and 3.7 in 2015 for those who remained in RWP, switched to Medicaid, or switched to private, respectively. Switching to Medicaid or private was not associated with 2015 hospitalization rates (IRR 1.26 (95% CI 0.71-2.23) and 0.48 (0.18-1.28), table). Older age, CD4 <200, VL >400, and number of 2013 hospitalizations were associated with higher rates. Conclusion. Among PWH relying on RWP in 2013, changing to either Medicaid or private insurance was not associated with a change in hospitalization rate. Among PWH, gaining inpatient coverage does not appear to increase inpatient utilization.

Sexually transmitted diseases, Mar 1, 2017

Men who have sex with men (MSM) and transgender women (TW) in Peru bear a disproportionate burden... more Men who have sex with men (MSM) and transgender women (TW) in Peru bear a disproportionate burden of human immunodeficiency virus (HIV) and sexually transmitted infections (STIs). In a context of quickly expanding communication technology, increasing numbers of MSM and TW are using social media applications to seek sex partners. Understanding social media users and their sex partnering practices is needed to update HIV and STI prevention programming. In Lima, Peru, 312 MSM and 89 TW from 2 STI clinics underwent HIV and STI testing and participated in a survey of demographics, behaviors, sexual health, and social media practices. χ, t tests, and Wilcoxon Mann-Whitney tests were used to compare those with and without recent social media sex partners. Men who have sex with men with social media sex partners were younger, more educated, and more likely to identify as gay. They were significantly more likely to report greater numbers of sex partners, including anonymous sex partners; sex...

Sexually Transmitted Infections, 2015

Circulation, Nov 22, 2011

Introduction: With the ever-increasing number of acutely ill patients with cardiac disease that n... more Introduction: With the ever-increasing number of acutely ill patients with cardiac disease that need intensive monitoring and limited resources in coronary care unit (CCU), there is a need to ensure appropriate admission to CCU. TIMI risk index (TRI) was a robust predictor (for STEMI patients on first arrival in hospital) and high discriminatory capacity of in-hospital events. TRI was divided into five risk groups with the higher the index score, the higher the mortality. We attempt to study TIMI risk index {TRI = [heart rate X (age/10)2]/systolic blood pressure} in determining the need of admission to CCU for STEMI patient after successful primary percutaneous coronary intervention (PPCI). Methods: This was a retrospective study over 12 months period. Inclusion criterias including patient presented with STEMI at emergency department and underwent successful PPCI which defined as achieving TIMI 3 flow. Exclusion criterias include no documentation of blood pressure and/or heart rate at presentation at emergency department. Study end point was in-hospital major adverse cardiovascular events (MACE) that include all cause death including cardiac death, target lesion revascularization, recurrent myocardial infarction, stroke, in-stent thrombosis. Results: A total of 275 patients had STEMI and underwent PPCI. 16 patients were excluded (13 patients did not have heart rate and/or blood pressure documented at presentation and 3 patients had unsuccessful PPCI). Majority was male (85.3%) and had anterior STEMI (51.0%). In the first two groups (risk group 1 and risk group 2), there was no in-hospital MACE as compare to the last two groups (risk group 4 and risk group 5), in which the in-hospital MACE was >10% (12.2% and 17.0% respectively, p=0.001). The in-hospital mortality was high in the last two groups (9.8% and 13.2% respectively) as compare to no in-hospital mortality in the first two groups, p=0.004. Non of the patients in risk group 1 and 2 required intra-aortic balloon counterpulsation. Conclusions: Patients presented with acute STEMI with TRI

Oncotarget, Jan 20, 2015

Mitosis is choreographed by a number of protein kinases including polo-like kinases and Aurora ki... more Mitosis is choreographed by a number of protein kinases including polo-like kinases and Aurora kinases. As these kinases are frequently dysregulated in cancers, small-molecule inhibitors have been developed for targeted anticancer therapies. Given that PLK1 and Aurora kinases possess both unique functions as well as co-regulate multiple mitotic events, whether pharmacological inhibition of these kinases together can enhance mitotic catastrophe remains an outstanding issue to be determined. Using concentrations of inhibitors that did not induce severe mitotic defects on their own, we found that both the metaphase arrest and mitotic slippage induced by inhibitors targeting Aurora A and Aurora B (MK-5108 and Barasertib respectively) were enhanced by a PLK1 inhibitor (BI 2536). We found that PLK1 is overexpressed in cells from nasopharyngeal carcinoma, a highly invasive cancer with poor prognosis, in comparison to normal nasopharyngeal epithelial cells. Nasopharyngeal carcinoma cells we...

Molecular cancer therapeutics, 2013

Nasopharyngeal carcinoma is a rare but highly invasive cancer. As options of agents for effective... more Nasopharyngeal carcinoma is a rare but highly invasive cancer. As options of agents for effective combination chemoradiotherapy for advanced nasopharyngeal carcinoma are limited, novel therapeutic approaches are desperately needed. The ubiquitin ligase CHFR is known to target PARP1 for degradation and is epigenetically inactivated in nasopharyngeal carcinoma. We present evidence that PARP1 protein is indeed overexpressed in nasopharyngeal carcinoma cells in comparison with immortalized normal nasopharyngeal epithelial cells. Tissue microarray analysis also indicated that PARP1 protein is significantly elevated in primary nasopharyngeal carcinoma tissues, with strong correlation with all stages of nasopharyngeal carcinoma development. We found that the PARP inhibitor AZD2281 (olaparib) increased DNA damage, cell-cycle arrest, and apoptosis in nasopharyngeal carcinoma cells challenged with ionizing radiation or temozolomide. Isobologram analysis confirmed that the cytotoxicity trigger...

Transplantation, 2008

Background. Currently, hepatocellular carcinoma (HCC) patients are selected for liver transplanta... more Background. Currently, hepatocellular carcinoma (HCC) patients are selected for liver transplantation based on radiological assessment (size and number of tumor nodules) and/or pathological features (tumor grade and vascular invasion). The former criteria have limited power on prognosis, whereas the latter do not provide complete information until explant is available. Methods. This study aims to investigate whether quantitative measurement of plasma mRNA derived from cancer can provide preoperative prognostic information. Preoperative plasma samples obtained from 72 HCC patients who had undergone liver transplantation were studied. The patients were selected for liver transplantation largely based on the Milan criteria before 2002 and UCSF criteria after 2002. Real-time quantitative reverse transcriptase polymerase chain reaction with Taqman system was used to measure the albumin mRNA levels in plasma. Results. Fifteen patients (21%) had HCC recurrences. Patients with a high plasma albumin mRNA level (Ͼ14.6) had a significantly higher recurrence rate (log-rank test, Pϭ0.001). High plasma albumin mRNA level predicted 2-year HCC recurrence with sensitivity and specificity of 73% and 70%, respectively. By multivariate analysis, plasma albumin mRNA level (adjusted hazard ratioϭ5.9, Pϭ0.002) and vascular invasion (adjusted hazard ratioϭ6.0, Pϭ0.001) were the only independent risk factors for prediction of HCC recurrence. Conclusions. Plasma albumin mRNA quantification predicts posttransplant HCC recurrence. It may supplement the current selection criteria of HCC patients for liver transplantation.

Oncogene, 2012

Inhibition of cyclin-dependent kinase 1 (CDK1) by phosphorylation is a key regulatory mechanism f... more Inhibition of cyclin-dependent kinase 1 (CDK1) by phosphorylation is a key regulatory mechanism for both the unperturbed cell cycle and the DNA damage checkpoint. Although both WEE1 and MYT1 can phosphorylate CDK1, little is known about the contribution of MYT1. We found that in contrast to WEE1, MYT1 was not important for the normal cell cycle or checkpoint activation. Time-lapse microscopy indicated that MYT1 did, however, have a rate-determining role during checkpoint recovery. Depletion of MYT1 induced precocious mitotic entry when the checkpoint was abrogated with inhibitors of either CHK1 or WEE1, indicating that MYT1 contributes to checkpoint recovery independently of WEE1. The acceleration of checkpoint recovery in MYT1-depleted cells was due to a lowering of threshold for CDK1 activation. The kinase activity of MYT1 was high during checkpoint activation and reduced during checkpoint recovery. Importantly, although depletion of MYT1 alone did not affect longterm cell growth, it potentiated with DNA damage to inhibit cell growth in clonogenic survival and tumor xenograft models. These results reveal the functions of MYT1 in checkpoint recovery and highlight the potential of MYT1 as a target for anti-cancer therapies.

Neuroscience Letters, 2008

Protein tyrosine phosphatase receptor type Z (Ptprz, also known as PTP or RPTP␤) is preferentiall... more Protein tyrosine phosphatase receptor type Z (Ptprz, also known as PTP or RPTP␤) is preferentially expressed in the CNS as a major chondroitin sulfate proteoglycan (CSPG). Ptprz interacts with the PSD95 family through its intracellular carboxyl-terminal PDZ-binding motif in the postsynaptic density. Ptprzdeficient adult mice display impairments in spatial and contextual learning. Here, we identified the proteolytic processing of Ptprz by plasmin in the mouse brain, which is markedly enhanced after kainic acid (KA)-induced seizures. We mapped plasmin cleavage sites in the extracellular region of Ptprz by cellbased assays and in vitro digestion experiments with recombinant proteins. These findings indicate that Ptprz is a physiological target for activity-dependent proteolytic processing by the tPA/plasmin system, and suggest that the proteolytic cleavage is involved in the functional processes of the synapses during learning and memory.

Molecular Cancer Therapeutics, 2011

Genotoxic stress such as ionizing radiation halts entry into mitosis by activation of the G2 DNA ... more Genotoxic stress such as ionizing radiation halts entry into mitosis by activation of the G2 DNA damage checkpoint. The CHK1 inhibitor 7-hydroxystaurosporine (UCN-01) can bypass the checkpoint and induce unscheduled mitosis in irradiated cells. Precisely, how cells behave following checkpoint abrogation remains to be defined. In this study, we tracked the fates of individual cells after checkpoint abrogation, focusing in particular on whether they undergo mitotic catastrophe. Surprisingly, while a subset of UCN-01–treated cells were immediately eliminated during the first mitosis after checkpoint abrogation, about half remained viable and progressed into G1. Both the delay of mitotic entry and the level of mitotic catastrophe were dependent on the dose of radiation. Although the level of mitotic catastrophe was specific for different cell lines, it could be promoted by extending the mitosis. In supporting this idea, weakening of the spindle-assembly checkpoint, by either depleting M...