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M Woo

Publications and source records attributed to M Woo.

At least 19 recordsLinked to original sources
PubMed2003

Commissioning, evaluation, quality assurance and clinical application of a virtual micro MLC technique.

Multileaf collimators (MLCs) are a valuable tool in modern radiation therapy, offering flexible and convenient field shaping. One disadvantage, however, is the undulation of the dose distribution at the edge shaped by the leaves due to the finite leaf width. An attempt to reduce the effect of this undulation is the objective of the commercial linear accelerator package HD270, which incorporates three-dimensional couch translation together with leaf adjustment to emulate finer leaf widths. In this paper we report on the commissioning and evaluation of this feature, together with the development of a process for quality assurance, as well as description of a clinical application of this technique. It is concluded that this technique could be applied reliably to situations currently utilizing MLC for shielding, with little added cost in treatment time, provided that a comprehensive quality assurance program is in place to monitor the performance of this complicated procedure.

Algorithms↗
PubMed2002

The sexual profile of rapists in Singapore.

To our knowledge, this is the first paper that examines the sexual profile of rapists in Singapore. A semi-structured interview based on a questionnaire about sexual habits was conducted on 62 convicted rapists and a control group of 63 prisoners comprising 32 convicted for violent non-sexual offences and 31 for non-violent non-sexual offences. Significantly more rapists masturbated at least once a month and were exposed to pornography within six months before the offence when compared to non-violent controls. Violent controls did not differ significantly from rapists in any aspect of the sexual history. The greater similarity between rapists and violent controls lends support to the concept of rape as a violent rather than sexual offence. A subgroup of 17 'hypersexual' rapists were identified who were either having sex or masturbating very frequently but had still resorted to rape. Compared to the other 46 rapists, the 'hypersexual' rapists were more likely to have fantasised predominantly about rape or bondage and to cite domination, aggression or hostility as reasons for committing rape, suggesting an even stronger element of power and aggression than in their less sexually active counterparts.

Adult↗
PubMed2001

Acquired subglottic stenosis caused by methicillin resistant Staphylococcus aureus that produce epidermal cell differentiation inhibitor.

Local infection of the trachea in intubated neonates is one of the main risk factors for development of acquired subglottic stenosis, although its role in the pathogenesis is unclear. Methicillin resistant Staphylococcus aureus (MRSA) is often the cause of critical illness in neonatal patients. Two cases are reported of acquired subglottic stenosis following bacterial infection of the trachea, suggesting an association with the staphylococcal exotoxin, epidermal cell differentiation inhibitor (EDIN). EDIN-producing MRSA were isolated from purulent tracheal secretions from both infants. Acquired subglottic stenosis in both cases was probably caused by delayed wound healing as the result of EDIN inhibition of epithelial cell migration.

Epidermal Growth Factor↗
PubMed2001

Men who commit statutory rape: how are they different from other rapists?

From an original cohort of 63 rapists serving prison sentences for rape in Singapore, two subgroups were identified, one subgroup who raped females 14 years and younger (an offence that is termed 'statutory rape' or 'SR') and another who raped females 14 years and above (which we term 'non-statutory rape' or 'NSR'). The two subgroups were compared across a broad range of variables. Those who committed SR tended to be older, married, Malay men who were more likely to commit rape in their home or in the home of their victims, and who rated the quality of their sexual relationships more unfavourably than the NSRs. The NSRs were more likely to be single men but with concurrent relationships with different females. NSRs were more likely to report dysfunctional family backgrounds, early conduct problems and were more likely to rape their victims outdoors and late into the night. Although in both subgroups the majority of the victims were known to the rapists, relatives (i.e. step-daughters or daughters) were by far the most common victims of the SR rapists.

Adolescent↗
PubMed2001

A phase I dose-ranging trial of monthly infusions of zoledronic acid for the treatment of osteolytic bone metastases.

Bisphosphonates are potent inhibitors of bone resorption and provide a therapeutic benefit for patients with bone metastases. Zoledronic acid is a highly potent, nitrogen-containing bisphosphonate. In the present trial, we assessed the safety and tolerability of increasing doses of zoledronic acid and its effects on urinary markers of bone resorption in cancer patients with bone metastases. Fifty-nine cancer patients with bone metastases were enrolled sequentially into one of 8 treatment groups in the core protocol. Each patient received a 5-min i.v. infusion of 0.1, 0.2, 0.4, 0.8, 1.5, 2, 4, or 8 mg zoledronic acid monthly for 3 months. Patients were monitored for clinical findings, adverse events, electrocardiograms, markers of bone resorption, as well as routine hematology, blood chemistries, and urinalysis. Thirty patients who demonstrated a radiographic response to treatment or stable disease in the core protocol were enrolled in a humanitarian extension protocol and continued to receive monthly infusions. Zoledronic acid was well tolerated at all dose levels. Adverse events reported by >10% of patients included skeletal pain, nausea, fatigue, upper respiratory tract infection, constipation, headache, diarrhea, and fever. Three patients in the core protocol and one patient in the extension protocol experienced grade 3 skeletal pain, "flu-like" symptoms, or hypophosphatemia, which were possibly related to treatment; all recovered completely. Adverse events were reported with similar frequency across all of the dosage groups. Zoledronic acid resulted in sustained, dose-dependent decreases in urinary markers of bone resorption. Zoledronic acid was safe and well tolerated and demonstrated potent inhibition of bone resorption.

Adult↗
PubMed2001

Men who commit rape in Singapore.

INTRODUCTION: Rape is regarded as one of the most serious forms of sexual assault, yet there has been a lack of clinical information on convicted rapists in Singapore. This paper attempts to confirm the hypotheses that rapists come from disordered backgrounds, from large families and are poorly educated. We further hypothesize that they are more likely to have a history of antisocial behaviour and to have had recent exposure to pornography. METHODS: Rapists serving sentence in a Singapore prison were compared with 2 control groups, one consisting of violent non-sexual offenders and another comprising non-violent non-sexual offenders. RESULTS: Rapists tended to be men in their late thirties who rape women in their early twenties. A large majority of the rapists and their victims are known to each other. Rapists are more likely to come from large, disordered families, attaining low educational levels but seemingly less antisocial when compared with the controls. More rapists and violent controls reported recent viewing of pornography before committing their offenses. CONCLUSION: The demonstrated similarities between rapists and violent controls lend support to the view that rape is an act of violence carried out in a sexual manner rather than a sexual act violently expressed.

Adult↗
PubMed2000

A novel mutation detected by temporal temperature gradient gel electrophoresis led to the confirmative prenatal diagnosis of a Hispanic CF family.

Mutational analysis of 30 recurrent known mutations detects only about 58% of Hispanic cystic fibrosis (CF) chromosomes. The low mutation detection rate has greatly hindered prenatal diagnosis and carrier testing of Hispanic families who have multiple affected children with unidentified cystic fibrosis transmembrane conductance regulator (CFTR) mutations. We recently employed a temporal temperature gradient gel electrophoresis (TTGE) method to effectively scan unknown mutations in the entire CFTR gene. A novel mutation, 2105-2117 del13insAGAAA was identified in a Hispanic family heterozygous for delta F508. The discovery of the devastating mutation facilitated the prenatal diagnosis for this family who already had two severely affected children. The fetus was found to be a compound heterozygote of delta F508/2105-2117 del13insAGAAA. This case emphasizes the importance of whole gene mutational analysis in patients with a clinical diagnosis of CF, but without the identifiable DNA mutations by routine mutation analysis. Finding of CF mutations in the patient would allow proper genetic counselling and prenatal and carrier detection of at-risk family members.

Adolescent↗
PubMed2000

Executionary pathway for apoptosis: lessons from mutant mice.

Apoptosis or programmed cell death (PCD) is an evolutionarily conserved cellular process that is essential for normal development and homeostasis of multicellular organisms. Defects in the apoptosis signaling result in many diseases including autoimmune diseases and cancer. The apoptosis signaling pathway was first described genetically in the nematode Caenorhabditis elegans which serves as a framework for the more complex apoptotic pathways that exist in mammals. In this review, we will discuss the apoptotic pathways that are emerging in mammals as elucidated by studies of gene-targeted mutant mice.

Animals↗
PubMed1999

In vivo evidence that caspase-3 is required for Fas-mediated apoptosis of hepatocytes.

Caspase-3 is essential for Fas-mediated apoptosis in vitro. We investigated the role of caspase-3 in Fas-mediated cell death in vivo by injecting caspase-3-deficient mice with agonistic anti-Fas Ab. Wild-type controls died rapidly of fulminant hepatitis, whereas the survival of caspase-3-/- mice was increased due to a delay in hepatocyte cell death. Bcl-2 expression in the liver was dramatically decreased in wild-type mice following anti-Fas injection, but was unchanged in caspase-3-/- mice. Hepatocytes from anti-Fas-injected wild-type, but not caspase-3-/-, mice released cytochrome c into the cytoplasm. Western blotting confirmed the lack of caspase-3-mediated cleavage of Bcl-2. Presumably the presence of intact Bcl-2 in caspase-3-/- hepatocytes prevents the release of cytochrome c from the mitochondria, a required step for the mitochondrial death pathway. We also show by Western blot that Bcl-xL, caspase-9, caspase-8, and Bid are processed by caspase-3 in injected wild-type mice but that this processing does not occur in caspase-3-/- mice. This study thus provides novel in vivo evidence that caspase-3, conventionally known for its downstream effector function in apoptosis, also modifies Bcl-2 and other upstream proteins involved in the regulation of Fas-mediated apoptosis.

Animals↗
PubMed1999

Gene targeting in the analysis of mammalian apoptosis and TNF receptor superfamily signaling.

Apoptosis, or programmed cell death (PCD), is the subject of much current investigative interest. Developing embryos and many adult organ systems require the tight coupling of cellular proliferation and PCD to ensure proper organogenesis and optimal tissue function. Over the past decade, our knowledge of the genetic basis underlying the execution of apoptosis in mammals has progressed enormously, thanks largely to groundbreaking studies performed in the nematode Caenorhabditis elegans. In contrast, the components of the signaling apparatus that links the various death stimuli and the receptors they stimulate to the execution mechanism remain relatively unknown. It is only in the past 4 years that studies of signal transduction via members of the tumor necrosis factor (TNF) receptor superfamily have identified a plethora of novel signaling proteins, including molecules that are directly involved in apoptosis signaling, and others that regulate the induction of cell death. This two-part review focuses on the biology of apoptosis and signaling through members of the TNF receptor superfamily as revealed by the study of gene-targeted "knockout" mice. These genetic mutant animals are invaluable tools not only for confirming or refuting a proposed function of a particular gene in an in vivo setting, but also for uncovering novel functions for a gene that were not anticipated from conventional in vitro experiments. In the field of apoptosis, as for many other areas of biomedical research, knockout mice and cell lines can be used as models for studying human disease, with the ultimate goal of developing therapeutic strategies.

Adaptor Proteins, Signal Transducing↗
PubMed1999

The relationship between stress and absenteeism.

UNLABELLED: BACKGROUND OF STUDY: Three hundred and sixty three subjects from various civil service organisations were administered the SCOPE-i (Stress, Coping and Personality Inventory) as part of the Institute of Mental Health's efforts to promote mental health in the workplace. AIM OF STUDY: This study examines the relationship between stress-related factors and absenteeism. Absenteeism is measured by the number of days of medical leave taken (MC) and self-report of minor illnesses (MI) which are not severe enough to warrant the coverage of a medical certificate. RESULTS: In this study, we are interested in the differences between MI and MC, and their respective relationships with stress-related factors. We hypothesised that MI, rather than MC, is more related to poor workplace conditions. The findings of this study support this hypothesis. Thus if workplace environment is stressful, people are still likely to come to work despite their illness. An interesting observation in this study is the different ways in which environmental stressors and psychosocial aspects of the workplace environment affect the MC variable. Individuals are more likely to take MC when the environmental stressors are high (i.e., poor lighting, uncomfortable temperatures, etc) as compared to poor psychosocial environmental conditions (e.g., work overload, high organisational tension, career limitations and high personal constraints). On the other hand, when faced with poor psychosocial environmental conditions, MI increases instead of MC. CONCLUSION: These findings have implications on the types of changes in a workplace which employers should make in order to decrease MC and improve physical well-being. In addition, the study shows the usefulness of MI in future studies as a dependent variable.

Absenteeism↗
PubMed1998

Differential requirement for caspase 9 in apoptotic pathways in vivo.

Mutation of Caspase 9 (Casp9) results in embryonic lethality and defective brain development associated with decreased apoptosis. Casp9-/- embryonic stem cells and embryonic fibroblasts are resistant to several apoptotic stimuli, including UV and gamma irradiation. Casp9-/- thymocytes are also resistant to dexamethasone- and gamma irradiation-induced apoptosis, but are surprisingly sensitive to apoptosis induced by UV irradiation or anti-CD95. Resistance to apoptosis is accompanied by retention of the mitochondrial membrane potential in mutant cells. In addition, cytochrome c is translocated to the cytosol of Casp9-/- ES cells upon UV stimulation, suggesting that Casp9 acts downstream of cytochrome c. Caspase processing is inhibited in Casp9-/- ES cells but not in thymocytes or splenocytes. Comparison of the requirement for Casp9 and Casp3 in different apoptotic settings indicates the existence of at least four different apoptotic pathways in mammalian cells.

Animals↗
PubMed1998

Essential contribution of caspase 3/CPP32 to apoptosis and its associated nuclear changes.

Caspases are fundamental components of the mammalian apoptotic machinery, but the precise contribution of individual caspases is controversial. CPP32 (caspase 3) is a prototypical caspase that becomes activated during apoptosis. In this study, we took a comprehensive approach to examining the role of CPP32 in apoptosis using mice, embryonic stem (ES) cells, and mouse embryonic fibroblasts (MEFs) deficient for CPP32. CPP32(ex3-/-) mice have reduced viability and, consistent with an earlier report, display defective neuronal apoptosis and neurological defects. Inactivation of CPP32 dramatically reduces apoptosis in diverse settings, including activation-induced cell death (AICD) of peripheral T cells, as well as chemotherapy-induced apoptosis of oncogenically transformed CPP32(-/-) MEFs. As well, the requirement for CPP32 can be remarkably stimulus-dependent: In ES cells, CPP32 is necessary for efficient apoptosis following UV- but not gamma-irradiation. Conversely, the same stimulus can show a tissue-specific dependence on CPP32: Hence, TNFalpha treatment induces normal levels of apoptosis in CPP32 deficient thymocytes, but defective apoptosis in oncogenically transformed MEFs. Finally, in some settings, CPP32 is required for certain apoptotic events but not others: Select CPP32(ex3-/-) cell types undergoing cell death are incapable of chromatin condensation and DNA degradation, but display other hallmarks of apoptosis. Together, these results indicate that CPP32 is an essential component in apoptotic events that is remarkably system- and stimulus-dependent. Consequently, drugs that inhibit CPP32 may preferentially disrupt specific forms of cell death.

Animals↗
PubMed1998

Undergraduate pediatric surgery objectives: goal and reality.

BACKGROUND/PURPOSE: Educational objectives can be used both in the standardization of curricula and in their evaluation. Surveys of subspecialty objectives can clarify educational priorities and identify areas of proficiency and deficiency. METHODS: Fifty-one third-year and 56 fourth-year medical students were surveyed on their perceived mastery level of 60 pediatric surgery cognitive objectives. The same objectives were also used to survey 34 pediatric surgeons and 126 practicing family physicians. Physicians' expected and students' self-reported proficiency was scored for each objective from 0 (not required/unaware of condition) to 3 (confident with diagnosis and management of condition). Information regarding pediatric surgery instruction was also obtained from the undergraduate deans of 12 Canadian medical schools. Data were analyzed using descriptive methods and one-way analysis of variance (ANOVA) and were compared with existing objectives listings in the subspecialty. RESULTS: Students' familiarity scores increased significantly from third-year to fourth-year (P < .05), and approximated in fourth year the expected proficiency levels. Family physicians' and pediatric surgeons' expectations were remarkably similar. Eleven items were identified by both physician groups as nonessential (mean score < 1.5), whereas 29 were perceived as essential (score > 2.0). The fourth-year students' perceived knowledge of all but 3 of these 29 objectives was adequate. Comparison of the data with previous objectives listings showed similar expected competencies. Deans' data showed varied but mostly limited exposure to pediatric surgery in the undergraduate curriculum. CONCLUSIONS: The current study has allowed a revision of undergraduate objectives in pediatric surgery based on broad stakeholder input. It has also clarified both the expected and the perceived student mastery of these objectives, and identified areas of specific stress required. The results can be used toward establishing a unified, reliable, undergraduate curriculum for pediatric general surgery.

Adult↗