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Biomedical subjects

David Chan

Publications and source records attributed to David Chan.

11 recordsLinked to original sources
PubMed2006

Interactive effects of situational judgment effectiveness and proactive personality on work perceptions and work outcomes.

This study was based on a sample of 139 employees. The results support the hypothesis that proactive personality (PAP) predicts work perceptions (procedural justice perception, perceived supervisor support, and social integration) and work outcomes (job satisfaction, affective organizational commitment, and job performance) positively among individuals with high situational judgment effectiveness (SJE) but negatively among those with low SJE. The findings on the disordinal SJE = PAP interaction effects show that high levels of PAP may be either adaptive or maladaptive, depending on the individual's level of SJE, and these findings caution against direct interpretations of bivariate associations between PAP and work-relevant criteria. Limitations and implications of the study as well as future research directions on the study of PAP and situational judgment are discussed.

Adult↗
PubMed2006

A mutant deleted for most of the herpes simplex virus type 1 (HSV-1) UOL gene does not affect the spontaneous reactivation phenotype in rabbits.

The mechanisms involved in the herpes simplex virus type 1 (HSV-1) latency-reactivation cycle are not fully understood. The latency-associated transcript (LAT) is the only HSV-1 RNA abundantly detected during neuronal latency. LAT plays a significant role in latency because LAT(-) mutants have a reduced reactivation phenotype. Several novel viral transcripts have been identified within the LAT locus, including UOL, which is located just upstream of LAT. The authors report here on a mutant, DeltaUOL, which has a 437-nucleotide deletion that deletes most of UOL. DeltaUOL replicated similarly to its wild-type parental McKrae HSV-1 strain in infected cells, the eyes, trigeminal ganglia, and brains of mice and rabbits. It was indistinguishable from wild-type virus as regards explant-induced reactivation in mice, and spontaneous reactivation in rabbits. In contrast, DeltaUOL was significantly less virulent in mice. Thus, UOL appears to be dispensable for the wild-type reactivation phenotype while appearing to play a role in neurovirulence in ocularly infected animals.

Animals↗
PubMed2005

Extracardiac Fontan conversion, cryoablation, and pacemaker placement for patients with a failed Fontan.

OBJECTIVE: We review our experience with Fontan conversion and cryoablation in patients with an atriopulmonary Fontan in low cardiac output from arrhythmia or venous obstruction, including two patients with protein losing enteropathy. METHODS: Fifteen patients (mean age 25.0 +/- 8.4 years) underwent extracardiac Fontan conversion, cryoablation, and pacemaker placement between November 1999 and December 2004. Twelve patients were in NYHA class III and three were in NYHA class IV. Twelve had clinically important intraatrial reentry tachycardia refractory to medical therapy. RESULTS: Follow-up was between 2 and 62 months (mean 38.4 +/- 17.7). One death occurred at seven days after surgery due to sepsis and multisystem organ failure. The second death occurred at five days from myocardial depression following surgery. One patient with PLE preoperatively died to malnutrition and sepsis on POD number 52. The second patient with protein losing enteropathy had improved NYHA classification, cessation of albumin transfusions, and a normal stool alpha antitrypsin level (down from 4.1 mg/g preoperatively). All surviving patients improved NYHA classification to class I or II. Sustained arrhythmias could not be induced in any patient. One patient had recurrence of intraatrial reentrant tachycardia eleven months postoperatively that required electrical cardioversion and is currently well controlled on one medication. The other patients are not on any antiarrhythmic medical therapy. CONCLUSION: Extracardiac Fontan, cryoablation, and pacemaker placement reduced atrial arrhythmias and improved NYHA classification. In selected patients, this operation offers improvement in clinical outcome and is an alternative to transplantation. Protein losing enteropathy may not be a contraindication to performing Fontan conversion with cryoablation.

Arrhythmias, Cardiac↗
PubMed2005

Family medicine obstetrics. Collaborative interdisciplinary program for a declining resource.

PROBLEM BEING ADDRESSED: A continuing decline in the number of family physicians in Canada providing obstetric, and particularly intrapartum, care. OBJECTIVE OF PROGRAM: The Maternity Centre of Hamilton in Ontario was a pilot project initiated to help family physicians provide full obstetric care through a collaborative interdisciplinary model and shared call. PROGRAM DESCRIPTION: Eleven family physicians provided care in collaboration with a nurse practitioner and other health professionals. Women came from the Maternity Centre's own practices, community physicians, or agencies, or through self-referral. More than a quarter of the women were considered psychosocially high-risk patients. Key features of the program included interdisciplinary collaboration and information technology that supported prenatal and birth documentation. CONCLUSION: The program has helped family physicians, and even recruited some, to practise full obstetric care and has provided high-quality, accessible services to pregnant women. Physicians experienced increased jab and personal satisfaction, and patients were highly satisfied with the service.

Cooperative Behavior↗
PubMed2004

Fueling synapses.

The transmission of information across neuronal synapses is an energetically taxing business. Sheng and colleagues monitored the localization of mitochondria following different levels of synaptic activation and discovered that these organelles change their distribution in interesting ways, stalling near synapses when neurons are activated and increasing their movement when neurons are silent (Li et al., 2004 [this issue of Cell]).

Animals↗
PubMed2003

Outcome of symptomatic patients undergoing extracardiac Fontan conversion and cryoablation.

OBJECTIVE: We review our experience with Fontan conversion and cryoablation in patients with an atriopulmonary Fontan in low cardiac output from arrhythmia or venous obstruction, including 2 patients with protein-losing enteropathy. METHODS: Ten patients (mean age 21.1 +/- 7.0 years) underwent extracardiac Fontan conversion, cryoablation, and pacemaker placement between November 1999 and April 2002 (13.1 +/- 4.1 years after the original atriopulmonary connection). Eight patients were in New York Heart Association class III and 2 were in New York Heart Association class IV. Nine patients had clinically important intra-atrial reentry tachycardia refractory to medical therapy. RESULTS: Follow-up was between 3.1 and 32.6 months (16.8 +/- 9). One death occurred at 7 days after surgery due to sepsis and multisystem organ failure. The second death occurred at 48 days from complications of protein-losing enteropathy. The second patient with protein-losing enteropathy had improved New York Heart Association classification, cessation of albumin transfusions, and a normal stool alpha antitrypsin level (down from 4.1 mg/g preoperatively). Five patients improved to New York Heart Association class I and 3 patients to New York Heart Association class II. Sustained arrhythmias could not be induced in any patient. Seven patients are on no antiarrhythmics. One patient had recurrence of intra-atrial reentrant tachycardia 11 months postoperatively, which required electrical cardioversion; this patient's symptoms are currently well controlled on 1 medication. CONCLUSION: Extracardiac Fontan, cryoablation, and pacemaker placement reduced atrial arrhythmias and improved New York Heart Association classification in all surviving patients. In selected patients, this operation offers improvement in clinical outcome and is an alternative to transplantation. Protein-losing enteropathy may not be a contraindication to performing Fontan conversion with cryoablation.

Adolescent↗
PubMed2003

Investigation of the effects of peppermint oil and valerian on rat liver and cultured human liver cells.

1. The aim of the present study was to investigate the effects of peppermint oil and valerian on rat liver and cultured human hepatoma cells. 2. Rats received a single oral dose of peppermint oil (8.3-830 microL/kg) or valerian (0.31-18.6 g/kg), or daily oral doses of 83 microL/kg peppermint oil or 3.1 g/kg valerian for 28 days. After 24 h, rats were anaesthetized and measurements made of bile flow, liver function and in vivo sinusoidal area. Livers were then removed for histology. 3. Bile flow was unaffected by any treatment, except acute high-dose peppermint oil (830 microL/kg; 70% increase in flow). No change in liver enzyme activity was found, except for a 45% increase in alkaline phosphatase after chronic peppermint oil. No change in sinusoidal area in vivo or in histology was found following any treatment, although pretreatment with carbon tetrachloride reduced sinusoidal bed area and produced histological damage. Incubation of human hepatoma cells with 0.5 microL/mL (but not 0.05 microL/mL) peppermint oil or 20 mg/mL (but not 2 mg/mL) valerian resulted in increased cell death. 4. In conclusion, the present study demonstrated in vitro toxicity of high doses of valerian and peppermint oil in cultured human hepatoma cells and, at doses 2-3 orders of magnitude greater than those recommended for human use, an increase in rat bile flow after acute peppermint oil and an increase in alkaline phosphatase after chronic peppermint oil.

Animals↗
PubMed2002

Ets1 is required for p53 transcriptional activity in UV-induced apoptosis in embryonic stem cells.

Embryonic stem (ES) cells contain a p53-dependent apoptosis mechanism to avoid the continued proliferation and differentiation of damaged cells. We show that mouse ES cells lacking Ets1 are deficient in their ability to undergo UV-induced apoptosis, similar to p53 null ES cells. In Ets1(-/-) ES cells, UV induction of the p53 regulated genes mdm2, perp, cyclin G and bax was decreased both at mRNA and protein levels. While p53 protein levels were unaltered in Ets1(-/-) cells, its ability to transactivate genes such as mdm2 and cyclin G was reduced. Furthermore, electrophoretic mobility shift assays and immunoprecipitations demonstrated that the presence of Ets1 was necessary for a CBP/p53 complex to be formed. Chromatin immunoprecipitations demonstrated that Ets1 was required for the formation of a stable p53-DNA complex under physiological conditions and activation of histone acetyltransferase activity. These data demonstrate that Ets1 is an essential component of a UV-responsive p53 transcriptional activation complex in ES cells and suggests that Ets1 may contribute to the specificity of p53-dependent gene transactivation in distinct cellular compartments.

Acetylation↗