Publications by authors named "I Bing Tan"

659 Publications

Multistationarity in Cyclic Sequestration-Transmutation Networks.

Bull Math Biol 2022 May 11;84(6):65. Epub 2022 May 11.

Department of Mathematics, University of Michigan, Ann Arbor, MI, USA.

We consider a natural class of reaction networks which consist of reactions where either two species can inactivate each other (i.e., sequestration), or some species can be transformed into another (i.e., transmutation), in a way that gives rise to a feedback cycle. We completely characterize the capacity of multistationarity of these networks. This is especially interesting because such networks provide simple examples of "atoms of multistationarity", i.e., minimal networks that can give rise to multiple positive steady states.
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http://dx.doi.org/10.1007/s11538-022-01021-7DOI Listing
May 2022

R-wave amplitude changes with posture and physical activity over time in an insertable cardiac monitor.

Cardiovasc Digit Health J 2022 Apr 30;3(2):80-88. Epub 2021 Dec 30.

The Wesley Hospital, Auchenflower, Queensland, Australia.

Background: Insertable cardiac monitors (ICMs) are accepted tools in cardiac arrhythmia management. Consistent R-wave amplitude (RWA) is essential for optimal detection.

Objectives: Assess RWAs with posture/activities at insertion and at 30 days.

Methods: Participants (n = 90) with Confirm Rx™ ICM had RWAs measured in different postures (supine, right-side [RS], left-side [LS], sitting, and standing) and defined physical activities (including isometric push [IPUSH] and pull) at 2 time points. ICMs were inserted in 45° to sternum and parasternal orientations.

Results: There were significant reductions at insertion with RS, LS, sitting, or standing vs supine (reference position) (all < .05). At 30 days, significant changes only occurred with LS and sitting ( < .05). Sex had an effect on RWAs, with females having significant variability at insertion (supine vs RS, LS, sitting, standing, and IPUSH; all < .05). Males showed large RWA interpatient variabilities but minimal differences between positions vs supine. At 30 days, RS, LS, and sitting positions remained significant for females ( < .05), while in males RWAs were higher than at insertion for most postures and activities. The orientation 45° to sternum had consistently higher RWAs vs parasternal orientation at both time points ( < .0001). In females, ICM orientation had no significant effect on RWAs; however, in males the 45° to sternum produced higher RWAs. ICM movement from the insertion site showed no correlation with RWA changes.

Conclusion: The mean RWAs were higher at 30 days with less interparticipant and interpostural variability; males had higher RWAs compared to females; 45° to sternum orientation had higher RWAs; and ICM migration from the insertion site did not affect RWAs.
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http://dx.doi.org/10.1016/j.cvdhj.2021.12.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9043368PMC
April 2022

Effects of dietary interventions on telomere dynamics.

Mutat Res Genet Toxicol Environ Mutagen 2022 Apr-May;876-877:503472. Epub 2022 Feb 10.

Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Vellore Institute of Technology, Vellore, India; Mangalore University, Mangalore, India. Electronic address:

Telomeres play a critical role in maintaining cellular fate through tight regulation of cell division and DNA damage or repair. Over the years, it is established that biological ageing is defined by a gradual derangement in functionality, productivity, and robustness of biological processes. The link between telomeres and ageing is highlighted when derangement in telomere biology often leads to premature ageing and concomitant accompaniment of numerous age-associated diseases. Unfortunately, given that ageing is a biologically complicated intricacy, measures to reduce morbidity and improve longevity are still largely in the infancy stage. Recently, it was discovered that dietary habits and interventions might play a role in promoting successful healthy ageing. The intricate relationship between dietary components and its potential to protect the integrity of telomeres may provide unprecedented health benefits and protection against age-related pathologies. However, more focused prospective and follow-up studies with and without interventions are needed to unequivocally link dietary interventions with telomere maintenance in humans. This review aims to summarise recent findings that investigate the roles of nutrition on telomere biology and provide enough evidence for further studies to consider the topic of nutrigenomics and its contributions toward healthy ageing and concomitant strategy against age-associated diseases.
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http://dx.doi.org/10.1016/j.mrgentox.2022.503472DOI Listing
May 2022

A Nonexercise Estimate of Cardiorespiratory Fitness Using a Symptom Questionnaire and Clinical Variables.

J Cardiopulm Rehabil Prev 2022 Apr 26. Epub 2022 Apr 26.

Cardiology Division, Veterans Affairs Palo Alto Health Care System, Palo Alto, California (Dr Myers, Chan, Kamil-Rosenberg, Waheed, and Mathew, Ms Tan, and Messrs Bail and Zell); and Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California, and Healthy Living for Pandemic Event Protection (HL-PIVOT) Network, Chicago, Illinois (Dr Myers).

Purpose: Cardiorespiratory fitness (CRF) has recently been recognized as a risk factor for mortality, but it is not routinely measured in clinical settings. The purpose of this study was to assess a nonexercise method to estimate CRF (eCRF) and its association with mortality in a clinically referred population.

Methods: A symptom tool, termed the Veterans Specific Activity Questionnaire (VSAQ), and nonexercise clinical variables were obtained from 1545 clinically referred subjects (60 ± 13 yr), and followed for a mean of 5.6 ± 4.2 yr. The VSAQ along with nonexercise clinical and historical variables was used to develop a multivariate model to predict achieved CRF from maximal exercise testing. Proportional hazards analysis was used to assess the association between measured and eCRF and all-cause mortality.

Results: The eCRF model was significantly associated with achieved CRF (multiple R= 0.67, P< .001). Mean achieved CRF from maximal treadmill testing and eCRF were similar (8.6 ± 5.0 metabolic equivalents [METs] vs 8.7 ± 4.7 METs respectively, P= .27). Achieved CRF and eCRF performed similarly for predicting mortality. After full adjustment, each 1 MET higher increment in achieved CRF and eCRF was associated with 19% and 26% reductions in mortality risk, respectively. Compared with the lowest fit group (<5 METs), the highest CRF groups (>11 METs) had 88% and 87% lower risks for mortality for achieved CRF and eCRF, respectively.

Conclusions: A multivariable nonexercise model featuring a symptom questionnaire combined with clinical variables that are readily available during a typical clinical encounter had a reasonably strong association with achieved CRF and exhibited prognostic characteristics that were similar to achieved CRF.
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http://dx.doi.org/10.1097/HCR.0000000000000695DOI Listing
April 2022

Pharmacological venous thromboembolism prophylaxis in elective cranial surgery: a systematic review of time of initiation, regimen and duration.

Br J Neurosurg 2022 Apr 21:1-8. Epub 2022 Apr 21.

Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London, UK.

Introduction: Pharmacological prophylaxis of venous thromboembolism (VTE) requires nuanced decision-making to balance the risk of VTE against haemorrhage. This problem is compounded in neurosurgical patients, in whom postoperative intracranial haemorrhage (ICH) may be catastrophic, compared to non-neuraxial bleeding in other types of surgery. Current major guidelines recommend caution when using pharmacological prophylaxis in elective cranial surgery, but incorporate low-quality evidence and lack precise guidance on timing and duration of anticoagulation.

Methods: We aimed to answer the following questions for patients undergoing elective cranial surgery: (1) when is the optimal time to initiate postoperative anticoagulation, and (2) how long should postoperative anticoagulation be continued for? In this systematic review, we screened randomised and non-randomised studies reporting original data on pharmacological VTE prophylaxis in elective cranial surgery. Outcomes of interest were VTE and ICH.

Results: Three retrospective, single-centre observational studies met eligibility criteria, with a total of 923 participants. Meta-analysis was not performed due to a high risk of bias across all studies. Through narrative synthesis, we found that patients who developed VTE were significantly more likely to receive their first postoperative dose at a later time (mean: 144 vs. 29 h,  = .04). Shorter courses of anticoagulation (<7 days) were associated with significantly lower ICH rates ( = .03) compared to longer courses (>21 days).

Conclusion: The limited evidence favours earlier initiation and shorter courses of thromboprophylactic anticoagulation. These findings are specific to patients undergoing surgery for meningioma or glioma and may not apply to other populations. Randomised controlled trials or robustly designed observational studies are necessary to establish a clearer evidence base.
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http://dx.doi.org/10.1080/02688697.2022.2064429DOI Listing
April 2022
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