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Biomedical subjects

K K Lee

Publications and source records attributed to K K Lee.

At least 19 recordsLinked to original sources
PubMed2006

Temporal changes in cerebral tissue oxygenation with cerebrovascular pressure reactivity in severe traumatic brain injury.

OBJECTIVE: To investigate the temporal relationship between cerebrovascular pressure reactivity and brain tissue oxygenation in patients with severe head injury. METHODS: In 40 patients, brain tissue oxygenation and intracranial pressure were monitored. Time-averaged values for intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PtiO2) were computed. The pressure reactivity index (PRx) was calculated. The mean values of the variables were obtained at the 6-h and 72-h post-injury time points, and the difference between the two time points for each of the variables was denoted as delta (delta). RESULTS: Of the 40 patients, 32 were survivors and 8 were non-survivors. Statistically significant differences were present between these two groups with regard to deltaMAP (p = 0.013), ICP at 6 h (p = 0.027), CPP at 72 h (p = 0.018), deltaCPP (p = 0.033), PRx at 6 h (p = 0.029), PRx at 72 h (p = 0.002), PtiO2 at 72 h (p < 0.0005) and deltaPtiO2 (p = 0.023) values, reflecting an improvement with time in survivors and a deterioration with time in non-survivors. In non-survivors, the magnitude of change in PtiO2 and CPP with time correlated in a negative linear fashion (p = 0.042 and 0.029, respectively) with the change in PRx with time, whereas no such relationship was seen in survivors. CONCLUSION: The severity of brain tissue oxygenation derangement correlates with increasing cerebrovascular dysautoregulation in patients succumbing to severe head injury, supporting the utility of PRx as a monitoring variable and the rationale for a target-driven approach to head injury management.

Adult↗
PubMed2006

Demographical profiles of adult severe traumatic brain injury patients: implications for healthcare planning.

INTRODUCTION: In Singapore, severe traumatic brain injury (TBI) continues to be a major public health problem and devastating condition, with significant mortality and morbidity. By understanding the incidence, prevalence and implications of severe TBI in Singapore, strategic plans to meet the unique needs of these patients in the local context may be developed. METHODS: The demographical profiles of the adult severe TBI patients in Singapore were studied in this retrospective review of 528 patients admitted to the National Neuroscience Institute (NNI) from January 1999 to December 2003. RESULTS: There were 420 male and 108 female patients, age ranging from 15 to 96 years old, with a mean and standard deviation (SD) of 44.6 +/- 19.9 years, admitted to NNI during the study period. Motor vehicle and fall-related accidents were the leading causes of severe TBI. Three high-risk groups identified were young adults, elderly, and foreign workers. CONCLUSION: Preventive measures targeting at these high-risk groups are important to reduce the incidence of severe TBI.

Accidental Falls↗
PubMed2006

Premarital sexual intercourse among adolescents in Malaysia: a cross-sectional Malaysian school survey.

INTRODUCTION: Sexual intercourse among Malaysian adolescents is a major concern, especially with the worry of HIV/AIDS. This study was done to determine the prevalence of sexual intercourse among secondary school students aged 12 to 19 years in Negeri Sembilan, Malaysia. METHODS: This is a cross-sectional school survey conducted on 4,500 adolescent students based on a structured questionnaire. Data were collected using the self-administered questionnaire (translated version of the Youth Risk Behaviour Surveillance in Bahasa Malaysia). RESULTS: The study showed that 5.4 percent of the total sample were reported to have had sexual intercourse. The proportion among male students who had had sex was higher (8.3 percent) compared with female students (2.9 percent). The mean age at first sexual intercourse was 15 years. One percent of students reported that they had been pregnant or had made someone else pregnant. Adolescent sexual intercourse was significantly associated with (1) socio-demographical factors (age, gender); (2) environmental factors (staying with parents); and (3) substance use (alcohol use, cigarette smoking, drug use), even after adjustment for demographical factors. The survey showed that 20.8 percent of respondents had taken alcohol, 14.0 percent had smoked cigarettes, 2.5 percent had tried marijuana, 1.2 percent had tried ecstasy pills, 2.6 percent had tried glue sniffing, 0.7 percent had tried heroin, and 0.7 percent had intravenous drugs. CONCLUSION: Prevalence of sexual intercourse among Malaysian adolescents was relatively low compared to developed countries. However, certain groups of adolescents tend to be at higher risk of engaging in sexual intercourse. This problem should be addressed early by targeting these groups of high-risk adolescents.

Adolescent↗
PubMed2006

Menstruation among adolescent girls in Malaysia: a cross-sectional school survey.

INTRODUCTION: The onset of menstruation is part of the maturation process. However, variability in menstrual cycle characteristics and menstrual disorders are common. The purpose of this study was to determine the menstrual characteristics of adolescent females and factors associated with it. METHODS: This is a cross-sectional descriptive study carried out on 2,411 secondary school adolescent females in Negeri Sembilan, Malaysia. Data were collected using a self-administered structured questionnaire on menstruation in Bahasa Malaysia. RESULTS: Abnormal cycle length (menstrual cycle longer than 35 days or cycle length between 14 to 20 days or irregular pattern) was common and affected 37.2 percent of subjects. The majority (74.6 percent) experienced premenstrual syndrome and 69.4 percent had dysmenorrhoea. About 18 percent reported excessive menstrual loss (use two pads at a time to prevent blood from soaking through or confirmed by doctor to be anaemic due to heavy menstrual flow). Only 11.1 percent of schoolgirls seeked medical consultation for their menstrual disorders. Mothers remained the most important source of information (80 percent). Menstrual disorders were significantly more common in female adolescents who smoke and have suicidal behaviours (p-value is less than 0.05). CONCLUSION: Menstrual problems among adolescent female are common. They are influenced by certain modifiable factors.

Adolescent↗
PubMed2005

Brain tissue oxygenation monitoring in acute brain injury.

Cerebral ischemia is one of the most important causes of secondary insults following acute brain injury. While intracranial pressure monitoring in the intensive care unit constitutes the cornerstone of neurocritical care monitoring, it does not reflect the state of oxygenation of the injured brain. The holy grail of neuromonitoring is a modality that would reflect accurately real time the status of oxygenation in the tissue of interest, is robust, artefact free and that which provides information that can be used for therapeutic interventions and to improve outcome. Such a device could conceivably be used to augment the sensitivity of current multi-modality monitoring systems in the neurocritical management of brain injured patients. This article examines the availability of data in the literature to support clinical use of local tissue oxygen probes in intensive care.

Animals↗
PubMed2005

Effects of Qi therapy (external Qigong) on symptoms of advanced cancer: a single case study.

The aim of this study was to examine the effectiveness of Qi therapy (external Qigong) in the management of symptoms of advanced cancer in a man. We used a single case study design to evaluate the effectiveness of Qi therapy (external Qigong) in a 35-year-old man with advanced cancer (Stage IV) involving metastases in the stomach, lung and bone (Karnofsky performance scale: KPS, 40: requires special care and assistance, disabled). Treatment involved six days of pre-assessment, eight treatment sessions on alternate days over 16 days, and a two-week follow-up phase. A visual analogue scale (VAS) was used to assess the patient's self-reported symptoms of cancer over the intervention and follow-up periods. Following treatment, VAS scores' analysis revealed beneficial effects on pain, vomiting, dyspnoea, fatigue, anorexia, insomnia, daily activity and psychological calmness. These improvements were maintained over the two-week follow-up phase. After the first Qi therapy session, the patient discontinued medication and could sit by himself; after the fourth session, the patient was able to walk and use the toilet without assistance (improvement in KPS: 70: care for self, unable to perform normal activity or to do active work). Although limited by the single case study approach, our results support previous studies on this topic and provide reasons to conduct controlled clinical trials.

Adult↗
PubMed2004

Effects of laminectomy and facetectomy on the stability of the lumbar motion segment.

A ligamentous, nonlinear, sliding contact, three-dimensional finite element (FE) model of L2-L3 complex was developed to investigate the biomechanical effect of laminectomy with and without facetectomy. The L2-L3 FE model was validated against experimental study under various physiological loadings and found to match well with the experimental data. Four iatrogenic models (unilateral laminectomy, unilateral laminectomy with unilateral facetectomy, unilateral laminectomy with bilateral facetectomy and total bilateral laminectomy) were evaluated under flexion, extension, torsion, lateral bending, anterior and posterior shear load vectors to determine alterations in kinematics and annulus stress. Results show that total laminectomy with facetectomy induces considerable increase in motion and annulus stress, except for lateral bending, whereas unilateral laminectomy shows the least increases.

Biomechanical Phenomena↗
PubMed2004

Proteomic analysis of chromatin-modifying complexes in Saccharomyces cerevisiae identifies novel subunits.

Epigenetics is the alteration of phenotype without affecting the genotype. An underlying molecular mechanism of epigenetics is the changes of chromatin structure by covalent histone modifications and nucleosome reorganization. In the yeast, Saccharomyces cerevisiae, two of the most well-studied macromolecular complexes that perform these epigenetic changes are the ATP-dependent Swi/Snf chromatin-remodelling complex and the SAGA histone acetyltransferase complex. To understand fully the mechanism by which these large protein complexes perform their functions in the cell, it is crucial that all the subunits of these complexes are identified. In an attempt to identify new subunits associated with SAGA and Swi/Snf, we used tandem affinity purification, followed by a multidimensional protein identification technology to analyse the subunit composition. Our analysis identified two novel proteins, one associated with SAGA, YPL047W (Sgf11), and another associated with Swi/Snf, Rtt102.

Adenosine Triphosphate↗
PubMed2004

Poroelastic analysis of lumbar spinal stability in combined compression and anterior shear.

OBJECTIVE: A three-dimensional poroelastic finite element (FE) L2-L3 model was developed to study lumbar spinal instability and intrinsic parameters in the intervertebral disc (IVD). METHODS: The FE model took into consideration poroelasticity of the IVD and viscoelasticity of the annulus fibers and ligaments to predict the time-dependent behavior. To simulate a holding task, the motion segment was subjected to a combined loading of constant compressive load (1600 N) and anterior shear (200 N) for 2 hours, and the role of facet joints and ligaments in the biomechanical response was investigated by removal of unilateral/bilateral facets, posterior ligaments (supraspinous and interspinous), and facets and ligaments. RESULTS: The results show the stabilizing role of the facets and ligaments in resisting anterior shear and sagittal rotation under combined loading over time. The main pathway of fluid movement was found to permeate through the central region of the endplate, and the fluid diffusion occurred earlier at the posterior nucleus than the anterior nucleus. The fluid loss from the nucleus dictated the time-dependent motion under the sustained loading, whereas the intrinsic properties of ligaments/annulus fibers played a role only in the early stage of the loading. CONCLUSION: The predicted results using poroelastic elements provide new insight into the IVD in providing the spinal stiffness under combined loading.

Body Fluids↗
PubMed2004

Finite-element analysis for lumbar interbody fusion under axial loading.

A parametric study was conducted to evaluate axial stiffness of the interbody fusion, compressive stress, and bulging in the endplate due to changes in the spacer position with/without fusion bone using an anatomically accurate and validated L2-L3 finite-element model exercised under physiological axial compression. The results show that the spacer plays an important role in initial stability for fusion, and high compressive force is predicted at the ventral endplate for the models with the spacer and fusion bone together. By varying the positioning of the spacer anteriorly along anteroposterior axis, no significant change in terms of axial stiffness, compressive stress, and bulging of the endplate are predicted for the implant model. The findings suggest that varying the spacer position in surgical situations does not affect the mechanical behavior of the lumbar spine after interbody fusion.

Bone Transplantation↗
PubMed2004

The biomechanics of lumbar graded facetectomy under anterior-shear load.

In this paper, an anatomically accurate three-dimensional finite-element (FE) model of the human lumbar spine (L2-L3) was used to study the biomechanical effects of graded bilateral and unilateral facetectomies of L3 under anterior shear. The intact L2-L3 FE model was validated under compression, tension, and shear loading and the predicted responses matched well with experimental data. The gross external (translational and coupled) responses, flexibilities, and facet load were delineated for these iatrogenic changes. Results indicted that unilateral facetectomy of greater than 75% and bilateral facetectomy of 75% or more resection markedly alter the translational displacement and flexibilities of the motion segment. This study suggests that fixation or fusion to restore strength and stability of the lumbar spine may be required for surgical intervention of greater than 75% facetectomy.

Biomechanical Phenomena↗
PubMed2004

The effect of nitrogen supplementation on the efficiency of colour and COD removal by Malaysian white-rot fungi in textile dyeing effluent.

White-rot fungi, namely Coriolus versicolor and Schizophyllum commune, were studied for the biodecolorization of textile dyeing effluent in shaker-flask experiments. The results showed that C. versicolor was able to achieve 68% color removal after 5 days of treatment while that of S. commune was 88% in 9 days. Both fungi achieved the above results in non-sterile condition with diammonium hydrogen phosphate as the nutrient supplement. On the other hand, the best COD removal of 80% was obtained with C. versicolor in 9 days in sterile effluent with yeast extract as nutrient supplement, while S. commune was able to remove 85% COD within 8 days in non-sterile textile effluent supplemented with diammonium hydrogen phosphate.

Basidiomycota↗
PubMed2003

Lorenz number in high T(c) superconductors: evidence for bipolarons.

The strong electron-phonon interaction in cuprates has gathered support over the last decade in a number of experiments. While phonons remain almost unrenormalized, electrons are transformed into itinerant bipolarons and thermally excited polarons when the electron-phonon interaction is strong. We calculate the Lorenz number of the system to show that the Wiedemann-Franz law breaks down because of the interference of polaron and bipolaron contributions in the heat flow. The model fits numerically the experimental Hall Lorenz number, which provides direct evidence for bipolarons in the cuprates.

Journal Article↗
PubMed2003

Nuclear reprogramming of cloned embryos produced in vitro.

Despite the fact that cloned animals derived from somatic cells have been successfully generated in a variety of mammalian species, there are still many unsolved problems with current cloning technology. Somatic cell nuclear transfer has shown several developmental aberrancies, including a high rate of abortion during early gestation and increased perinatal death. One cause of these developmental failures of cloned embryos may reside in the epigenetic reprogramming of somatic donor genome. In mammals, DNA methylation is an essential process in the regulation of transcription during embryonic development and is generally associated with gene silencing. A genome-wide demethylation may be a prerequisite for the formation of pluripotent stem cells that are important for later development. We analyzed methylation patterns in cloned bovine embryos to monitor the epigenetic reprogramming process of donor genomic DNA. Aberrant methylation profiles of cloned bovine embryos were observed in various genomic regions, except in single-copy gene sequences. The overall genomic methylation status of cloned embryos was quite different from that of normal embryos produced in vitro or in vivo. These results suggest that the developmental failures of cloned embryos may be due to incomplete epigenetic reprogramming of donor genomic DNA. We expect that advances in understanding the molecular events for reprogramming of donor genome will contribute to clarify the developmental defects of cloned embryos.

Animals↗
PubMed2002

Pathogenesis of gastroenteritis caused by Vibrio carchariae in cultured marine fish.

Serious mortality among the cultured grouper Epinephelus coioides, characterized by a swollen intestine containing yellow fluid (gastroenteritis), occurred in 1993 in Taiwan. A bacterium isolated from the intestinal fluid and head kidney of moribund groupers was identified as Vibrio carchariae. Since then, the same Vibrio species has also been isolated from moribund black sea bream Acanthopagrus schlegeli, yellowfin sea bream A. latus, Japanese sea bass Lateolabrax japonicus, and red drum Sciaenops ocellatus suffering from the same syndrome. Each isolate was virulent to the respective fish. Recently, a similar syndrome, flounder infectious necrotizing enteritis, also caused by V. carchariae in summer flounder Paralichthys dentatus, was reported in Rhode Island. The extracellular products (ECPs) of V. carchariae strains EmI82KL (from grouper), Rd (from red drum), and SfUSA (from summer flounder, U.S.A.) were virulent to the grouper or red drum. A 33-kDa serine protease partially purified from the ECP of strain EmI82KL was lethal to the fish. All the moribund or killed fish exhibited gastroenteritis except those killed within 12 hours. This report is the first to show that intraperitoneal injection of the ECP or protease in the fish is virulent and can reproduce gastroenteritis. The serine protease was suggested as a major toxin in the grouper or red drum secreted by V. carchariae.

Journal Article↗
PubMed2002

Tattoo ink darkening of a yellow tattoo after Q-switched laser treatment.

The popularity of tattoos is burgeoning with 20-30 million tattooed individuals in the Western World. Requests for removal can be expected to rise concurrently with increased applications. Laser removal of tattoos is potentially a more cosmetically acceptable method of removing tattoos than surgical excision or dermabrasion. Nevertheless, complications and side-effects can result from laser treatment and include scarring, hypopigmentation, hyperpigmentation, partial removal, infection, bleeding and tattoo ink darkening. The latter has been reported for flesh-toned and red tattoos. Such a complication has never been reported for the laser treatment of a yellow tattoo in the dermatological literature. We describe a case of tattoo ink darkening of a yellow tattoo after treatment with the 532 nm quality-switched Neodymium : Ytrrium-Aluminium Garnet laser to highlight clinicopathological features. The mechanism by which some tattoos darken after laser treatment is not clearly understood. We review darkening of tattoos after laser treatment to raise awareness of this important complication. This paper will help to facilitate discussions with the patient and in obtaining informed consent prior to commencing treatment. Tattoo ink darkening of a yellow tattoo adds to the growing list of complications resulting from attempts at tattoo removal.

Color↗
PubMed2002

Application of the moving-actuator type pump as a ventricular assist device: in vitro and in vivo studies.

A moving actuator type pump has been developed as a multifunctional Korean artificial heart (AnyHeart). The pump consists of a moving actuator as an energy converter, right and left sacs, polymer (or mechanical) valves, and a rigid polyurethane housing. The actuator containing a brushless DC motor moves back and forth on an epicyclical gear train to produce a pendular motion, which compresses both sacs alternately. Of its versatile functions of ventricular assist device and total artificial heart use, we have evaluated the system performance as a single or biventricular assist device through in vitro and in vivo experiments. Pump performance and anatomical feasibility were tested using various animals of different sizes. In the case of single ventricular assist device (VAD) use, one of the sacs remained empty and a mini-compliance chamber was attached to either an outflow or inflow port of the unused sac. The in vitro and in vivo studies show acceptable performance and pump behavior. Further extensive study is required to proceed to human application.

Animals↗