PubMed Health⌕ Search

Biomedical subjects

T Chan

Publications and source records attributed to T Chan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Cytogenetic investigation of fetuses and infants conceived through intracytoplasmic sperm injection.

OBJECTIVE: To determine the incidence of aneuploidy among fetuses and infants conceived through intracytoplasmic sperm injection (ICSI) in our clinic using umbilical cord blood samples. DESIGN: Follow-up study of the cytogenetic outcome of ICSI pregnancies. SETTING: University-based IVF clinic. PATIENT(S): Forty-six couples who underwent ICSI and conceived. INTERVENTION(S): Umbilical cord blood was taken after delivery of the infant for analysis. Samples of chorionic villi and chorion were taken for studies on the spontaneous abortuses. Amniocentesis was performed for couples that chose prenatal diagnosis. MAIN OUTCOME MEASURE(S): The cytogenetic chromosomal status of the pregnancy outcome. RESULT(S): Fifty pregnancies and 55 live births were recorded, with nine spontaneous abortions. Of 43 separate umbilical cord blood samples analyzed, 1 abnormality (2%) was found, 45, XX,+21. Nine births went through prenatal diagnosis alone, with four accepting both forms of analysis-no abnormalities were found. Origin of abnormality was established in two spontaneous abortion cases (45, XO and 45, XY,-21), and the maternal chromosome was lost in both cases. CONCLUSION(S): Using umbilical cord blood obtained after birth, we obtained karyotype results from 78% of the ICSI population in our clinic. Combined with results from five additional cases that underwent prenatal diagnosis but not umbilical cord blood sampling, a chromosomal result was obtained in 87% of our ICSI population. The use of umbilical cord blood for cytogenetic analysis substantially improves the ability to determine rates of chromosomal abnormalities in newborns produced via ICSI clinics.

Adult↗
PubMed2001

Prognostic assessment of nonmetastatic renal cell carcinoma: a clinically based model.

OBJECTIVES: Determining the recurrence risk in patients treated for renal cell carcinoma (RCC) is important for providing prognostic information and planning potential surveillance strategies. The pathologic stage has been the most widely used single prognostic variable. However, with minimally invasive treatment modalities, the pathologic stage may not be readily available. We developed a biostatistical prognostic model for postoperative RCC that is independent of the pathologic stage. METHODS: The records of 296 patients who underwent open nephrectomy for RCC at Johns Hopkins Hospital between 1990 and 1999 were reviewed. Cox proportional hazards regression analysis was used to generate a prognostic model. RESULTS: The recurrence risk (R(rec)) was determined from this model: R(rec)=1.55 x presentation (0-1)+0.19 x clinical size (in centimeters). Using this equation, 79% of patients were identified as low risk compared with 45% of patients considered low risk by pathologic stage (pT1). Moreover, the separation between the high and low-risk survival curves increased. CONCLUSIONS: This model is the first to our knowledge that uses purely clinical variables to assess the postoperative prognosis in patients with RCC. These results, although not validated, provide substantial evidence that preoperative clinical variables may be used instead of the pathologic stage to determine the risk of recurrence. Uncoupling the reliance on pathologic stage for prognostic information removes a potential barrier to novel minimally invasive treatments for renal malignancy and provides a standard to which observation protocols can be compared. In the future, this model may facilitate selection of appropriate patients for less toxic adjuvant or neoadjuvant therapies.

Aged↗
PubMed2001

Electrocardiographic diagnosis of acute myocardial infarction.

The widely recognized benefits of early diagnosis and treatment of acute myocardial infarction (AMI) have only emphasized the importance of emergency physician (EP) competence in electrocardiographic interpretation. As such, the EP must be an expert in the interpretation of the electrocardiogram (ECG) in the emergency department chest pain center patient. The ECG is a powerful clinical tool used in the evaluation of patients, assisting in making the diagnosis of AMI and other syndromes, selecting appropriate therapies (including thrombolysis and primary angioplasty), securing the location of an adequate inpatient disposition, and predicting the risk of cardiovascular complications and death. This article will discuss the appropriate uses of the ECG in the patient with possible or confirmed AMI and review the typical electrocardiographic findings of AMI, diagnostically confounding patterns, mimickers of infarction, and new techniques.

Arrhythmias, Cardiac↗
PubMed2001

Mapping residents' perceptions of neighborhood boundaries: a methodological note.

Neighborhood influences on children and youth are the subjects of increasing numbers of studies, but there is concern that these investigations may be biased, because they typically rely on census-based units as proxies for neighborhoods. This pilot study tested several methods of defining neighborhood units based on maps drawn by residents, and compared the results with census definitions of neighborhoods. When residents' maps were used to create neighborhood boundary definitions, the resulting units covered different space and produced different social indicator values than did census-defined units. Residents' agreement about their neighborhoods' boundaries differed among the neighborhoods studied. This pilot study suggests that discrepancies between researcher and resident-defined neighborhoods are a possible source of bias in studies of neighborhood effects.

Adult↗
PubMed2001

A comparison of the intubating and standard laryngeal mask airways for airway management by inexperienced personnel.

Twenty-four inexperienced participants were timed inserting the intubating laryngeal mask airway and the laryngeal mask airway in 75 anaesthetised subjects. Adequacy of ventilation was assessed on a three-point scale. The pressure at which a leak first developed around the device's cuff was also measured. There was no significant difference in insertion time or the likelihood of achieving adequate ventilation between devices. However, the intubating laryngeal mask airway was better at providing adequate ventilation without audible leak (58/75 (77%) vs. 42/75 (56%); p = 0.009). The median (range [IQR]) pressure at which an audible leak developed was higher for the intubating laryngeal mask airway, 34.5 (14-40 [29-40]) cmH2O, than for the laryngeal mask airway, 27.5 (14-40 [22-33]) cmH2O (p < 0.001). The intubating laryngeal mask airway is worthy of further consideration as a tool for emergency airway management for inexperienced personnel.

Adolescent↗
PubMed2001

Electrocardiographic manifestations of pulmonary embolism.

The electrocardiogram (ECG) may be entirely normal in the patient with pulmonary embolism (P/E); alternatively, any number of rhythm and/or morphologic abnormalities may be observed in such a patient. The abnormal ECG may deviate from the norm with alterations in rhythm, in conduction, in axis of the QRS complex, and in the morphology of the P wave, QRS complex, and ST segment/T wave. The electrocardiographic findings associated with PE are numerous, including arrhythmias (sinus tachycardia, atrial flutter, atrial fibrillation, atrial tachycardia, and atrial premature contractions), nonspecific ST segment/T wave changes, T wave inversions in the right precordial leads, rightward QRS complex axis shift and other axis changes, S1Q3 or S1Q3T3 pattern, right bundle branch block, and acute cor pulomnale. This review focuses on the ECG and the various abnormalities seen in the patient with PE.

Adult↗
PubMed2001

Clinical significance of cell proliferation, microvessel density, and CD44 adhesion molecule expression in renal cell carcinoma.

Renal cell carcinoma (RCC) is known to have a wide variation in clinical outcome despite the use of conventional prognostic factors, such as staging or grading. A better knowledge of the biologic aggressiveness of RCC could facilitate the selection of patients at high risk of tumor progression. The aim of this study was to determine if use of measurements of vascular density, cell proliferation, and cell adhesion could better predict the biologic behavior of RCC. We immunohistochemically analyzed CD34, Ki-67, and CD44H expression on formalin-fixed, paraffin-embedded tissues from 73 RCCs for quantifying microvessel density (MVD), Ki-67 labeling index (LI), and CD44H LI, respectively. Univariate cancer-specific survival analysis showed that tumor stage (P < .01), tumor size (P < .001), nuclear grade (P < .01), metastasis (P < .001), MVD (P < .03), Ki-67 LI (P < .001), and CD44H LI (P < .0001) were predictors of tumor-related death. There was a statistical correlation between CD44H LI and both Ki-67 LI (r' = .3) and MVD (r' = -44). Ki-67 LI (P < .04) and CD44H LI (P < .02), as well as metastasis (P < .008), emerged as independent predictors of cancer-specific survival in multivariate analysis in patients with metastases (P < .04 and P < .02, respectively) and in patients without metastases (P < .006 and P < .00001, respectively). Our study suggests that vascular density, cell proliferation, and cell adhesion represent a complex tumor-host interaction that may favor progression of RCC. Cell proliferation and CD44H expression appear to be powerful markers to identify patients with an adverse prognosis.

Adult↗
PubMed2001

Electrocardiographic ST-segment elevation: correct identification of acute myocardial infarction (AMI) and non-AMI syndromes by emergency physicians.

OBJECTIVE: To determine the emergency physician's (EP's) ability to identify the cause of ST-segment elevation (STE) in a hypothetical chest pain patient. METHODS: Eleven electrocardiograms (ECGs) with STE were given to EPs; the patient in each instance was a 45-year-old male with a medical history of hypertension and diabetes mellitus with the chief complaint of chest pain. The EP was asked to determine the cause of the STE and, if due to acute myocardial infarction (AMI), to decide whether thrombolytic therapy (TT) would be administered (the patient had no contraindication to such treatment). Rates of TT administration were determined; appropriate TT administration was defined as that occurring in an AMI patient, while inappropriate TT administration was defined as that in the non-AMI patient. RESULTS: Four hundred fifty-eight EPs completed the questionnaire; levels of medical experience included the following: postgraduate year 2-3, 193 (42%); and attending, 265 (58%). The overall rate of correct interpretation of the study ECGs was 94.9% (4,782 correct interpretations out of 5,038 instances). Acute myocardial infarction with typical STE, ventricular paced rhythm, and right bundle branch block were never misinterpreted. The remaining conditions were misinterpreted with rates ranging between 9% (left bundle branch block, LBBB) and 72% (left ventricular aneurysm, LVA). The overall rate of appropriate thrombolytic agent administration was 83% (1,525 correct administrations out of 1,832 indicated administrations). The leading diagnosis for which thrombolytic agent was given inappropriately was LVA (28%), followed by benign early repolarization (23%), pericarditis (21%), and LBBB without electrocardiographic AMI (5%). Thrombolytic agent was appropriately given in all cases of AMI except when associated with atypical STE, where it was inappropriately withheld 67% of the time. CONCLUSIONS: In this survey, EPs were asked whether they would give TT based on limited information (ECG). Certain syndromes with STE were frequently misdiagnosed. Emergency physician electrocardiographic education must focus on the proper identification of these syndromes so that TT may be appropriately utilized.

Bundle-Branch Block↗
PubMed2001

Centrifugation of salvaged pump blood is useful in reducing the amount of heparin re-infused into the patient.

Conservation of blood and blood products are of major concern in clinical practice today. All blood salvaged from the extracorporeal circuit at the end of cardiopulmonary bypass should be returned to the patient. We propose the use of a simple and inexpensive centrifuge machine to reduce the amount of heparin from the residual pump blood re-infused to the patient. At the same time, the re-infused blood is concentrated. Sixteen patients were prospectively included in this study. The residual pump blood was collected from the bypass circuit and spun at 4,000 rpm for 7 min on the Jouan GR 4.22 machine. The clear upper supernatant was discarded and the remaining concentrated red cells re-infused back to the patient. The heparin concentration and full blood counts of both layers were measured. We found that this method was useful in removing excessive heparin and avoiding the need for additional protamine.

Adult↗
PubMed2000

Dietary fibre intake and constipation in children with severe developmental disabilities.

OBJECTIVE: Constipation is a common problem in children with severe developmental disabilities (DD). This study aimed to evaluate fibre intake of severe DD children living in a residential institution, and the possibility of reducing the use of laxatives by increasing their fibre intake. METHODOLOGY: A baseline study was performed to evaluate the fibre and macronutrient intake in a group of severe DD children. Nutrients including fibre for a standard serving in each meal were calculated and daily macronutrients and fibre intake were estimated. An intervention study was then carried out to evaluate whether increasing fibre intake could relieve constipation. A total of 20 children aged between 3 and 17 years were assessed over a 4-month period. In a residential unit for severe DD children, laxatives were routinely prescribed if there was no spontaneous bowel motion for two consecutive days. Fibre intake was increased in stages by adding All-Bran(R) (Kellogg Company, Battle Creek, MI, USA) and desserts. The mean number of laxative usage per week per child in the different stages were then compared. RESULTS: The baseline fibre intake was found to be approximately 2 g/day. The mean number of laxatives required per week per child decreased significantly from a baseline value of 1.22 (about 5 laxatives/month) (standard deviation (SD) = 0.36)) to 0.90 (about 3. 5 laxatives/month) (SD = 0.75) in the first stage, and 0.71 (about 3 laxatives/month) (SD = 0.40) in the second stage. Using paired t-test, the difference was statistically significant when compared with the baseline: P < 0.05 for the first, and P < 0.01 for the second stage of fibre supplementation. CONCLUSION: Very low daily intake of fibre of 2 g/day was documented. Relief of constipation and a significant reduction in the usage of laxatives was demonstrated by increasing fibre intake to 17 g/day (stage 1). Increasing fibre intake further to 21 g/day (stage 2), showed a further reduction in the use of laxatives. There was, however, no statistical significance between stage 1 and stage 2 of fibre supplementation. Alternative ways to further relieve constipation in severe DD children require further studies.

Adolescent↗
PubMed2000

Protein carbonyls and lipid peroxidation products as oxidation markers in preterm infant plasma: associations with chronic lung disease and retinopathy and effects of selenium supplementation.

The purpose of this study was to determine whether protein carbonyls and the lipid peroxidation product malondialdehyde (MDA) are elevated in plasma from very low birth weight (<1500 g) infants, whether they are affected by selenium supplementation, and whether they are associated with poor respiratory outcome or retinopathy. The study group comprised 173 infants enrolled in a randomized controlled trial of selenium supplementation. Plasma samples, collected before randomization, at 7 and 28 d after birth, and at 36 wk postmenstrual age, were analyzed for protein carbonyls and total MDA. Respiratory outcome was assessed as oxygen requirement at 28 d of age or 36 wk postmenstrual age and as number of days on oxygen. Protein carbonyl concentrations in very low birth weight infants were significantly higher than for adults but lower than for cord blood from term infants. Median values decreased significantly by 28 d, and there was no relationship with birth weight. MDA concentrations in very low birth weight infants overlapped the ranges for healthy adults and cord blood from term infants. They correlated positively with birth weight at 28 d but not at other times. Supplementation almost doubled plasma selenium concentrations, but carbonyls and MDA did not differ between the supplemented and unsupplemented groups. There were no significant differences in oxidant marker levels in infants who did or did not develop chronic lung disease or retinopathy. Protein carbonyls and MDA measurements in plasma do not show evidence of systemic oxidative stress in <1500-g infants and are not affected by selenium supplementation. Oxidative injury at sites such as the lung may be important in prematurity, but markers from such sites must be measured to relate to outcome and antioxidant supplementation.

Adult↗
PubMed2000

An investigation of finger and manual dexterity.

In ergonomics, handgrip has been perceived as one of the most important hand functions; however, other types of functions of the hand are also important to the ergonomist, such as finger and manual dexterity, on which few ergonomic studies have been done. This experiment involved 60 male and female college students whose performance (number of pegs placed into a board in 30 sec.) of finger dexterity were statistically significantly different between the right and left hands and between women and men. The interaction of hand and sex was significant.

Biomechanical Phenomena↗
PubMed1999

Oxygen activation during peroxidase catalysed metabolism of flavones or flavanones.

Flavonoids containing phenol B rings, e.g. naringenin, naringin, hesperetin and apigenin, formed prooxidant metabolites that oxidised NADH upon oxidation by peroxidase/H2O2. Extensive oxygen uptake occurred which was proportional to the NADH oxidised and was increased up to twofold by superoxide dismutase. Only catalytic amounts of flavonoids and H2O2 were required indicating a redox cycling mechanism that activates oxygen and generates H2O2. NADH also prevented the oxidative destruction of flavonoids by peroxidase/H2O2 until the NADH was depleted. These results suggest that prooxidant phenoxyl radicals formed by these flavonoids cooxidise NADH to form NAD radicals which then activated oxygen. Similar oxygen activation mechanisms by other phenoxyl radicals have been implicated in the initiation of atherosclerosis and carcinogenesis by xenobiotic phenolic metabolites. This is the first time that a group of flavonoids have been identified as prooxidants independent of transition metal catalysed autoxidation reactions.

Catalysis↗
PubMed1999

Antiglucocorticoid treatment of depression: double-blind ketoconazole.

BACKGROUND: Hypercortisolemia is frequently observed in major depression but its pathophysiologic significance is unknown. In patients in whom hypercortisolism contributes to depressive symptomatology, antiglucocorticoid agents should have antidepressant effects. METHODS: Twenty medication-free depressed patients (eight of whom were hypercortisolemic and twelve of whom were not) received either the cortisol biosynthesis inhibitor, ketoconazole (400-800 mg/d p.o.) or placebo for 4 weeks in a double-blind manner, and behavioral ratings were performed weekly. RESULTS: Ketoconazole, compared to placebo, was associated with improvements in depression ratings in the hypercortisolemic, but not in the non-hypercortisolemic patients. The hormonal changes seen (decreased dehydroepiandrosterone and testosterone levels and increased pregnenolone and pregnenolone-sulfate levels) are consistent with enzymatic blockade of C17,20-lyase, 11-hydroxylase, and 17-hydroxylase. Ketoconazole was generally well tolerated with no occurrence of significant side effects or laboratory abnormalities. CONCLUSIONS: This small-scale double-blind study suggests that antiglucocorticoids have antidepressant activity in hypercortisolemic depressed patients. The data are consistent with a causal role of adrenocortical dysfunction in some depressed patients and suggest the need for larger-scale trials.

Adult↗
PubMed1999

Germline hMSH2 and differential somatic mutations in patients with Turcot's syndrome. Genes Chromosomes Cancer 25:75-81, 1999.

Chan TL, Yuen ST, Chung LP, Ho JWC, Kwan K, Fan YW, Chan ASY, Leung SY. 1999. Germline hMSH2 and differential somatic mutations in patients with Turcot's syndrome. Genes Chromosomes Cancer 25:75-81, 1999. It has come to our attention that the three patients described in the article above, were also included in a report by Leung et al., American Journal of Pathology, 153:1181-1189, 1998. Reference to the American Journal of Pathology article was inadvertently omitted

Journal Article↗
PubMed1999

Glutathione-dependent generation of reactive oxygen species by the peroxidase-catalyzed redox cycling of flavonoids.

Catalytic concentrations of apigenin (a flavone containing a phenol B ring) and naringin or naringenin (flavanones containing a phenol B ring) caused extensive GSH oxidation at a physiological pH in the presence of peroxidase. Only catalytic H2O2 concentrations were required, indicating a redox cycling mechanism that generated H2O2 was involved. Extensive oxygen uptake ensued, the extent of which was proportional to the extent of GSH oxidation to GSSG and was markedly increased by superoxide dismutase. These results suggest that prooxidant phenoxyl radicals formed by these flavonoids co-oxidized GSH to form thiyl radicals which activated oxygen. GSH also prevented the peroxidase-catalyzed oxidative destruction of these flavonoids which suggests that phenoxyl radicals initiated the oxidative destruction. This is the first time that a group of flavonoids have been identified as prooxidants independent of autoxidation reactions catalyzed by the transition metal ions Fe3+, Fe2+, Mn2+, and Cu2+.

Catalysis↗
PubMed1999

Does lesion size affect the outcome in avascular necrosis?

The size of the necrotic lesion may be a significant factor in predicting outcome and determining treatment in hips with avascular necrosis. However, to date most reports on the treatment of this condition have not attempted to correlate outcome with lesion size. Seventy-three hips with avascular necrosis were evaluated, 11 in Stage I and 62 in Stage II. All were treated with core decompression and bone grafting. Patients were followed up 2 to 6 years (mean, 39 months). The results were determined by change in Harris hip score, degree of radiographic progression, and the need for total hip replacement. Outcome was correlated with the lesion size, stage, etiology, and other factors. In Stage I, the true three-dimensional size of the lesion was measured with a new technique of quantitative magnetic resonance imaging. In Stage II, measurements were obtained from radiographs using a modular system for quantitative digital analysis. Hips were divided into three groups based on lesion size: Group A, less than 15% of femoral head involvement; Group B, 15% to 30%; and Group C, greater than 30%. There were no significant differences in outcome between Stages I and II and no relationship to etiology or other demographic factors. When correlated with lesion size, radiographs on a 21-point scale showed progression by 1.1, 4.2, and 4.3 points; the Harris hip score showed an improvement of 10.6 and 3.3 points and a loss of 3.6 points; and total hip replacement was required in 7%, 31%, and 33% of Group A, B, and C lesions, respectively. The difference in outcome between small lesions and large or medium lesions was statistically significant, but no significant differences were seen between medium and large lesions. These observations emphasize the importance of lesion size in predicting outcome after core decompression and grafting and possibly after other surgical and nonsurgical methods of managing hips with avascular necrosis. They also encourage the use of methods of evaluation and staging that include a determination of lesion size and stage.

Arthroplasty, Replacement, Hip↗