Publications by authors named "Norman Chan"

Introduction: Heterotopic pancreas (HP) is a relatively rare entity occurring in approximately 5% of the general population. It most commonly presents as an asymptomatic mass incidentally picked up on unrelated scans. HP most commonly occurs intra-abdominally, but has been known to occur in extra-abdominal sites such as the lung and brain.

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Growing tumour syndrome (GTS) is a rare event in which germ cell tumours treated with chemotherapy undergo maturation, acquire resistance to chemotherapy and regrow. The optimum treatment strategy is complete surgical excision. We report on a case of GTS with malignant metastases to the liver presenting 22 years after completion of treatment for immature teratoma, successfully managed with surgical resection alone.

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OBJECTIVE Temporal lobe encephaloceles and cerebrospinal fluid otorrhea from temporal bone defects that involve the tegmen tympani and mastoideum are generally repaired using middle fossa craniotomy, mastoidectomy, or combined approaches. Standard middle fossa craniotomy exposes patients to dural retraction, which can lead to postoperative neurological complications. Endoscopic and minimally invasive techniques have been used in other surgeries to minimize brain retraction, and so these methods were applied to repair the lateral skull base.

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Purpose: Release of the orbicularis retaining ligament (ORL) has been advocated as a technique to address tear trough deformities. This study sought to compare the effectiveness and morbidity of lower blepharoplasty with and without ORL release.

Methods: Retrospective chart review of 53 lower blepharoplasty patients.

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Objective: To elucidate the progression of angioedema of the head and neck with routine management and to assess the utility of serial physical exams and fiberoptic laryngoscopy in its management.

Methods: This study was a prospective observational research. From 2013 to 2014, a prospective observational study was conducted at a tertiary referral center.

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Objective: This study aimed to determine the duration of use, presentation, and management of angiotensin converting enzyme (ACE) inhibitor-related angioedema patients at an urban academic medical center.

Methods: Retrospective chart review.

Results: Eighty-eight patients who presented with ACE inhibitor-related angioedema between January 1, 2012, and December 31, 2012, were identified.

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Unlabelled: Regions of acute and chronic hypoxia exist within solid tumors and can lead to increased rates of mutagenesis and/or altered DNA damage and repair protein expression. Base excision repair (BER) is responsible for resolving small, non-helix-distorting lesions from the genome that potentially cause mutations by mispairing or promoting DNA breaks during replication. Germline and somatic mutations in BER genes, such as MutY Homolog (MUTYH/MYH) and DNA-directed polymerase (POLB), are associated with increased risk of colorectal cancer.

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Background: Vibration anesthesia is an effective pain-reduction technique for facial cosmetic injections. The analgesic effect of this method was tested in this study during facial dermal filler injections. The study aimed to evaluate the safety and efficacy of vibration anesthesia for these facial injections.

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Purpose The sphenoid sinus is a complex structure with key variations that are important for endoscopic parasellar approaches. In this study, high-resolution computed tomography (HRCT) scans were analyzed for the frequency of these variations. Methods A retrospective radiographic analysis was conducted on patients undergoing HRCT between July 2008 and September 2010.

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Purpose: Radiation therapy (RT) is one of the primary modalities for treatment of non-small cell lung cancer (NSCLC). However, due to the intrinsic radiation resistance of these tumors, many patients experience RT failure, which leads to considerable tumor progression including regional lymph node and distant metastasis. This preclinical study evaluated the efficacy of a new-generation cyclin-dependent kinase (Cdk) inhibitor, AZD5438, as a radiosensitizer in several NSCLC models that are specifically resistant to conventional fractionated RT.

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Objectives/hypothesis: Onodi cells are the posterior-most ethmoid air cells that lie superior to the sphenoid sinus. Identification of these cells is essential prior to endoscopic sinus and skull base surgery due to their intricate relationship with the optic nerves and carotid arteries, which may lead to deleterious complications. In this study, high-resolution computed tomography (HRCT) scans from 170 adult-patients were analyzed by two independent observers for the presence of Onodi cells.

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Epistaxis is a common clinical complaint with a spectrum of severity ranging from spontaneous cessation to unrelenting, life threatening hemorrhage requiring surgical treatment. Both otolaryngologic and neurointerventional techniques are discussed to provide a comprehensive paradigm to treat patients with epistaxis. An exhaustive review of the anatomic basis for the two main subtypes of epistaxis is provided as well as a graduated approach to appropriate clinical management.

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Purpose: PTEN deletions in prostate cancer are associated with tumor aggression and poor outcome. Recent studies have implicated PTEN as a determinant of homologous recombination (HR) through defective RAD51 function. Similar to BRCA1/2-defective tumor cells, PTEN-null prostate and other cancer cells have been reported to be sensitive to PARP inhibitors (PARPi).

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Background: We sought to identify the prevalence of and risk factors associated with cervical abnormalities among Chinese women in Hong Kong.

Methods: A community-based cervical screening program was offered free of charge in Hong Kong. Information on the demographics, sexual experience, and obstetrical history of women who attended the Cervical Screening Clinic were collected and tabulated with their Pap smear results to establish the risk factors associated with cervical abnormalities among Hong Kong Chinese women.

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Acute and chronic hypoxia exists within the three-dimensional microenvironment of solid tumors and drives therapy resistance, genetic instability, and metastasis. Replicating cells exposed to either severe acute hypoxia (16 hours with 0.02% O(2)) followed by reoxygenation or moderate chronic hypoxia (72 hours with 0.

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DNA double-strand breaks (DSBs) induced during clinical radiotherapy are potent inducers of cell death. Poly(ADP-ribose) polymerase (PARP)-1 is a 113-kD nuclear protein that binds to both single- and double-strand DNA breaks and is actively involved in DNA single-strand break repair and base excision repair. Recently, potent and specific chemical inhibitors of PARP activity have been developed that are effective tumor cell radiosensitizers in vitro and in vivo.

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Hypoxia exists in every solid tumor and is associated with poor prognosis because of both local and systemic therapeutic resistance. Recent studies have focused on the interaction between tumor cell genetics and the dynamic state of oxygenation and metabolism. Hypoxia generates aggressive tumor cell phenotypes in part owing to ongoing genetic instability and a "mutator" phenotype.

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Signaling and repair of DNA double-strand breaks (DSBs) are critical for preventing immunodeficiency and cancer. These DNA breaks result from exogenous and endogenous DNA insults but are also programmed to occur during physiological processes such as meiosis and immunoglobulin heavy chain (IgH) class switch recombination (CSR). Recent studies reported that the E3 ligase RNF8 plays important roles in propagating DNA DSB signals and thereby facilitating the recruitment of various DNA damage response proteins, such as 53BP1 and BRCA1, to sites of damage.

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Purpose: Rapidly metabolizing tumor cells have elevated levels of nicotinamide phosphoribosyltransferase, an enzyme involved in NAD(+) biosynthesis, which serves as an important substrate for proteins involved in DNA repair. GMX1777, which inhibits nicotinamide phosphoribosyltransferase, was evaluated in two human head and neck cancer models in combination with radiotherapy.

Experimental Design: Effects of GMX1777-mediated radiosensitization were examined via metabolic and cytotoxicity assays in vitro; mechanism of action, in vivo antitumor efficacy, and radiosensitization were also investigated.

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Hypoxia is a common characteristic of many solid tumors and is associated with poor prognosis. Cells with low oxygen levels can have altered sensitivity to radiotherapy and chemotherapy secondary to changes in the incidence of DNA single- and double-strand breaks (DNA-ssb, DNA-dsb), DNA base damage, DNA-DNA cross-links and DNA-protein cross-links. Recent evidence also supports that cells exposed to chronic hypoxia have a decreased capacity of DNA-dsb repair.

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Quantification of two types of nucleic acids [double-stranded (ds-) and single-stranded (ss-) DNA] was performed to understand the distribution of DNA within the epidermal strata and to examine the effects of DNA structure on gene expression, viz., apoptosis and terminal differentiation. In addition, we examined the precise starting point of cell death within the epidermis (suprabasal layer); examined how DNA structure affects gene expression of melanocytes; and characterized the "transitional cells" located between the stratum granulosum and stratum corneum, viz.

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Aims: Elderly breast cancers are associated with a more favourable biological marker profile and higher proportion of specific subtypes, some of which are of low histological grade. We reviewed the fine needle aspiration cytology (FNAC) to assess the cytological characteristics and any clues to assist in the diagnosis.

Methods: The aspirates of 140 cancers of various histological types and grades and 39 benign lesions were evaluated for 13 cytological parameters including cellularity of the direct and cytospin smears, epithelial cell clusters, cellular atypism, cytoplasmic features, vacuoles, mitotic figures, presence of myoepithelial cells, single background epithelial cells, the presence of naked nuclei, stromal fragments and necrosis.

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The chemo- and radioresponse of tumor cells can be determined by genetic factors (e.g., those that modify cell cycle arrest, DNA damage repair or cell death) and microenvironmental factors, such as hypoxia.

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