Publications by authors named "Kleiman D"

Background: For patients with recurrent diverticulitis, the trigger to proceed to elective sigmoid colectomy is unclear. Current clinical practice guidelines suggest this is an individualized decision between surgeon and patient.

Objective: To assess long-term risk of diverticulitis recurrence and determine predictors of recurrent disease.

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Objective: Bariatric surgery is an effective treatment to obesity, leading to weight loss and improvement in glycemia, that is characterized by hypersecretion of gastrointestinal hormones. However, weight regain and relapse of hyperglycemia are not uncommon. We set to identify mechanisms that can enhance gastrointestinal hormonal secretion following surgery to sustain weight loss.

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Molecular dynamics (MD) simulations are fundamental computational tools for the study of proteins and their free energy landscapes. However, sampling protein conformational changes through MD simulations is challenging due to the relatively long time scales of these processes. Many enhanced sampling approaches have emerged to tackle this problem, including biased sampling and path-sampling methods.

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Background: The benefit of primary tumor resection in distant metastatic small bowel neuroendocrine tumors (SBNETs) is controversial, with treatment-based morbidity not well-defined. We aimed to determine the impact of primary tumor resection on development of disease-specific complications in patients with metastatic well-differentiated SBNETs.

Patients And Methods: A retrospective analysis was performed of patients diagnosed with metastatic well-differentiated jejunal/ileal SBNETs at a single tertiary care cancer center from 1980 to 2016.

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Plant hormones are small molecules that regulate plant growth, development, and responses to biotic and abiotic stresses. They are specifically recognized by the binding site of their receptors. In this work, we resolved the binding pathways for eight classes of phytohormones (auxin, jasmonate, gibberellin, strigolactone, brassinosteroid, cytokinin, salicylic acid, and abscisic acid) to their canonical receptors using extensive molecular dynamics simulations.

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Introduction: Nonoperative management (NOM) of locally advanced rectal cancer was described as early as 2004. Initial national data demonstrated increase in utilization of NOM from 1998 to 2010, but newer national utilization data are not available.

Methods: We performed a retrospective cohort study using the National Cancer Database to assess utilization and 5-y overall survival (OS) of NOM of locally advanced rectal cancer.

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Weight loss interventions, including dietary changes, pharmacotherapy, or bariatric surgery, prevent many of the adverse consequences of obesity, and may also confer intervention-specific benefits beyond those seen with decreased weight alone. We compared the molecular effects of different interventions on liver metabolism to understand the mechanisms underlying these benefits. Male rats on a high-fat, high-sucrose diet underwent sleeve gastrectomy (SG) or intermittent fasting with caloric restriction (IF-CR), achieving equivalent weight loss.

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Rapid computational exploration of the free energy landscape of biological molecules remains an active area of research due to the difficulty of sampling rare state transitions in molecular dynamics (MD) simulations. In recent years, an increasing number of studies have exploited machine learning (ML) models to enhance and analyze MD simulations. Notably, unsupervised models that extract kinetic information from a set of parallel trajectories have been proposed including the variational approach for Markov processes (VAMP), VAMPNets, and time-lagged variational autoencoders (TVAE).

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Mice are a common model organism used to study metabolic diseases such as diabetes mellitus. Glucose levels are typically measured by tail-bleeding, which requires handling the mice, causes stress, and does not provide data on freely behaving mice during the dark cycle. State-of-the-art continuous glucose measurement in mice requires inserting a probe into the aortic arch of the mouse, as well as a specialized telemetry system.

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Background Ond Objectives: Complete cytoreductive surgery (CRS) may prolong survival for selected patients with peritoneal carcinomatosis from colorectal cancer (CRC). However, there is a paucity of data on outcomes following incomplete procedures.

Methods: Patients with incomplete CRS for well-differentiated (WD) and moderate/poorly-differentiated (M/PD) appendiceal cancer, right and left CRC were identified at a single tertiary center (2008-2021).

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Diabetes is associated with increased risk for kidney disease, heart failure, and mortality. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) prevent these adverse outcomes; however, the mechanisms involved are not clear. We generated a roadmap of the metabolic alterations that occur in different organs in diabetes and in response to SGLT2i.

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Introduction: During the first surge of the COVID-19 pandemic, healthcare utilization changed. We sought to examine the impact of the first COVID-19 surge on the outcomes of patients whose elective surgeries for diverticulitis were postponed and those who underwent urgent surgery during the surge.

Materials And Methods: This was a retrospective study from a single tertiary center in the Northeast of the US.

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Machine learning is increasingly applied to improve the efficiency and accuracy of molecular dynamics (MD) simulations. Although the growth of distributed computer clusters has allowed researchers to obtain higher amounts of data, unbiased MD simulations have difficulty sampling rare states, even under massively parallel adaptive sampling schemes. To address this issue, several algorithms inspired by reinforcement learning (RL) have arisen to promote exploration of the slow collective variables (CVs) of complex systems.

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The growing recognition of the functional and therapeutic roles played by RNA and the difficulties in gaining atomic-level insights by experiments are paving the way for all-atom simulations of RNA. One of the main impediments to the use of all-atom simulations is the imbalance between the energy terms of the RNA force fields. Through exhaustive sampling of an RNA helix-junction-helix (HJH) model using enhanced sampling, we critically assessed the select Amber force fields against small-angle X-ray scattering (SAXS) experiments.

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Mothers that underwent bariatric surgery are at higher risk for delivering a small-for-gestational age (SGA) infant. This phenomenon is attributed to malabsorption and rapid weight loss following surgery. We compared pregnancy outcomes in lean mice that underwent sham surgery or sleeve gastrectomy (SG).

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One anastomosis gastric bypass (OAGB) surgery became a common bariatric procedure in recent years. In this surgery, the distal stomach, duodenum, and proximal jejunum are bypassed, leading to weight loss, improvement in metabolic parameters, and a change in hormonal secretion. We sought to generate and characterize a mouse model for OAGB.

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Background: Horseshoe fistula is a challenging benign anorectal condition to treat. The aim of this study was to assess the utilization and success of different definitive fistula repair techniques in the treatment of horseshoe fistula.

Methods: This was a retrospective case series which included all patients who were treated for horseshoe fistula from 2006 to 2019 at a single, tertiary care center and whom had at least one follow-up visit.

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Background: Little is known about the long-term functional outcomes of restorative proctocolectomy.

Objective: The aim of this study was to examine ileoanal pouch outcomes 20 and 30 years postoperatively.

Design: This is a retrospective case series.

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Objective: To identify strategies and barriers to career progression in early-career colorectal surgeons.

Design: Qualitative research study performed via semi-structured interviews with early-career, board-certified colon, and rectal surgeons. Responses were analyzed, coded, and categorized to understand strategies towards career progression, perceived barriers to career progression, beliefs about case mix, and referral patterns.

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Background: The optimal strategy for colonic polyps not amenable to traditional endoscopic polypectomy is unknown. Endoscopic step up is a promising strategy for definitive treatment.

Objective: The purpose of this study was to determine whether endoscopic step up leads to improved outcomes and decreased costs compared with planned colectomy for endoscopically unresectable colon polyps.

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Background: National Colorectal Cancer Awareness Month occurs each March to promote awareness and screening for colorectal cancer. The effectiveness of this public health campaign is unknown. The aim of this study was to determine the impact of National Colorectal Cancer Awareness Month on rates of screening endoscopies and on public interest in colorectal cancer.

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Objective: Colorectal surgery (CRS) training has seen many changes over the years. This study sought to identify aspects of CRS residency curriculum that were most valued by recent graduates and what changes could be made to improve training.

Design: Semistructured interviews were performed with board-certified colorectal surgeons 2 to 7years removed from their CRS residency.

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