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Raymond Chan

Publications and source records attributed to Raymond Chan.

9 recordsLinked to original sources
PubMed2006

Reaction time of the Continuous Performance Test is an endophenotypic marker for schizophrenia: a study of first-episode neuroleptic-naive schizophrenia, their non-psychotic first-degree relatives and healthy population controls.

Sustained attention has been proposed as an endophenotype of schizophrenia, and consequently may be useful as a quantitative trait in genetic studies. In the present study, we used the continuous performance test (CPT) to measure sustained attention in 112 first-episode and neuroleptic-naive schizophrenic patients, 296 of their non-psychotic first-degree relatives, and 452 normal controls. Compared with controls, probands with schizophrenia showed worse performance on all measures of CPT. Parents, siblings and offspring of probands were also impaired on 'hit reaction time', an index of psychomotor processing speed of the correct response. Hit reaction time was also independent of the acute clinical features of the disease, indicating it is a trait rather than a state marker. Our findings supported the use of the hit reaction time measure of the CPT as an endophenotype marker for schizophrenia.

Adolescent↗
PubMed2005

Characterization of atherosclerotic plaques by laser speckle imaging.

BACKGROUND: A method capable of determining atherosclerotic plaque composition and measuring plaque viscoelasticity can provide valuable insight into intrinsic features associated with plaque rupture and can enable the identification of high-risk lesions. In this article, we describe a new optical technique, laser speckle imaging (LSI), that measures an index of plaque viscoelasticity. We evaluate the potential of LSI for characterizing atherosclerotic plaque. METHODS AND RESULTS: Time-varying helium-neon laser speckle images were acquired from 118 aortic plaque specimens from 14 human cadavers under static and deforming conditions (0 to 200 microm/s). Temporal fluctuations in the speckle patterns were quantified by exponential fitting of the normalized cross-correlation of sequential frames in each image series of speckle patterns to obtain the exponential decay time constant, tau. The decorrelation time constants of thin-cap fibroatheromas (TCFA) (tau=47.5+/-19.2 ms) were significantly lower than those of other atherosclerotic lesions (P<0.001), and the sensitivity and specificity of the LSI technique for identifying TCFAs were >90%. Speckle decorrelation time constants demonstrated strong correlation with histological measurements of plaque collagen (R=0.73, P<0.0001), fibrous cap thickness (R=0.87, P<0.0001), and necrotic core area (R=-0.81, P<0.0001). Under deforming conditions (10 to 200 microm/s), tau correlated well with cap thickness in necrotic core fibroatheromas (P>0.05). CONCLUSIONS: The measurement of speckle decorrelation time constant from laser speckle images provides an index of plaque viscoelasticity and facilitates the characterization of plaque type. Our results demonstrate that LSI is a highly sensitive technique for characterizing plaque and identifying thin-cap fibroatheromas.

Analysis of Variance↗
PubMed2005

Outcome of anterior resection for stage II rectal cancer without radiation: the role of adjuvant chemotherapy.

BACKGROUND: This study aimed to evaluate the oncological outcome of patients who had Stage II rectal cancer and underwent curative nonsphincter-ablation surgery without adjuvant radiation. PATIENTS AND METHODS: During the study period from August 1993 to December 2002, 224 patients (141 men) with Stage II cancer underwent curative anterior resection or Hartmann's procedure without adjuvant radiation. Data were collected prospectively. The oncologic outcomes of these patients were studied and the risk factors for recurrence and survival were analyzed. RESULTS: The median age of the patients was 69 (range, 27-89) years and the median level of the tumor from the anal verge was 8 (range, 3-20) cm. Four patients (1.8 percent) died in the postoperative period and postoperative complications occurred in 74 patients (33 percent). The median follow-up time of the surviving patients was 43.6 months. The actuarial five-year recurrence rate was 25.4 percent, whereas the five-year actuarial local and systemic recurrence rates were 6.1 percent and 20 percent, respectively. On multivariate analysis, independent factors associated with a higher recurrence rate included lymphovascular invasion, perineural invasion, and absence of chemotherapy. The overall and cancer-specific survival rates of the patients were 71.1 percent and 81.1 percent, respectively. On multivariate analysis, only adjuvant chemotherapy (P = 0.024; hazard ratio = 6.04; 95 percent confidence interval, 1.27-28.74) and the absence of lymphovascular invasion (P = 0.002; hazard ratio = 3.77; 95 percent confidence interval, 1.63-8.77) were independent factors associated with significantly better cancer-specific survival. CONCLUSION: A low local recurrence rate can be achieved in patients with Stage II rectal cancer treated with nonsphincter-ablation surgery without adjuvant radiation. Postoperative chemotherapy is associated with a lower recurrence rate and higher survival rates. Further study is warranted to define the role of adjuvant chemotherapy in patients with rectal cancer.

Adult↗
PubMed2004

Gonadotropin-releasing hormone (GnRH) antagonists promote proapoptotic signaling in peripheral reproductive tumor cells by activating a Galphai-coupling state of the type I GnRH receptor.

Gonadotropin-releasing hormone (GnRH) receptor agonists are extensively used in the treatment of sex hormone-dependent cancers via the desensitization of pituitary gonadotropes and consequent decrease in steroid sex hormone secretion. However, evidence now points to a direct inhibitory effect of GnRH analogs on cancer cells. These effects appear to be mediated via the Galpha(i)-type G protein, in contrast to the predominant Galpha(q) coupling in gonadotropes. Unlike Galpha(q) coupling, Galpha(i) coupling of the GnRH receptor can be activated by both agonists and antagonists. This unusual pharmacology suggested that the receptor involved in the cancer cells may not be the classical gonadotrope type I GnRH receptor. However, we have previously shown that a functional type II GnRH receptor is not present in man. In the present study, we show that GnRH agonists and selective GnRH antagonists exert potent antiproliferative effects on JEG-3 choriocarcinoma, benign prostate hyperplasia (BPH-1), and HEK293 cells stably expressing the type I GnRH receptor. This antiproliferative action occurs through a Galpha(i)-mediated activation of stress-activated protein kinase pathways, resulting in caspase activation and transmembrane transfer of phosphatidlyserine to the outer membrane envelope. Structurally related antagonistic GnRH analogs displayed divergent antiproliferative efficacies but demonstrated equal efficacies in inhibiting GnRH-induced Galpha(q)-based signaling. Therefore the ability of GnRH receptor antagonists to exert an antiproliferative effect on reproductive tumors may be dependent on ligand-selective activation of the Galpha(i)-coupled form of the type I GnRH receptor.

Apoptosis↗
PubMed2003

Vascular calcification in ex vivo carotid specimens: precision and accuracy of measurements with multi-detector row CT.

PURPOSE: To test the accuracy and precision of multi-detector row computed tomography (CT)-derived measurements of vascular calcification in ex vivo human carotid endarterectomy (CEA) specimens. MATERIALS AND METHODS: Sixteen ex vivo CEA specimens were imaged with multi-detector row CT. Multi-detector row CT-derived calcium scoring algorithms (ie, mineral mass and volume score) were compared with the mass and volume of ashed remnants of the CEA specimens. Bland-Altman analysis was performed to assess the mean (ie, bias) and SD (ie, precision) of differences between multi-detector row CT- and ashing-derived measurements. In addition, conventional Agatston score, volume score, mineral mass, and modified Agatston score were calculated for each specimen by using a number of scanning protocols. Images were obtained at a section thickness of 1.25 mm by using different tube energy settings and tube currents. Specimens were also imaged at different section thicknesses with fixed combinations of tube energy and tube current. To compare measurement variability of scoring methods, coefficients of variation for all protocols were calculated. RESULTS: Both mean multi-detector row CT-derived mineral mass and mean ashing-derived mineral mass were 0.129 g +/- 0.173 (r = 0.99, P <.001). Mean multi-detector row CT- and ashing-derived volumes were 339.94 mm3 +/- 395.4 and 39.48 mm3 +/- 55.76, respectively (r = 0.95, P <.001). Measurement bias relative to the reference ashing values was high (2,800.0%) for volume score and low (2.58%) for mineral mass. Measurement precision was 0.6% for volume score and greater than 0.0005% for mineral mass. Mean coefficients of variation for all CT protocols were 5.0% +/- 4.2 and 4.9% +/- 4.2 for mineral mass and modified Agatston score, respectively, and 16.0% +/- 9.2 and 14.5% +/- 3.9 for conventional Agatston and volume scores, respectively (P <.001). CONCLUSION: Compared with the conventional volume score, multi-detector row CT-derived mineral mass is a less biased and more precise measurement of the mineral content of nonmoving ex vivo CEA specimens. Mineral mass and modified Agatston score are more reproducible than conventional volume and Agatston scores.

Calcinosis↗
PubMed2002

Response of Ceriodaphnia dubia to ionic silver: discrepancies among model predictions, measured concentrations and mortality.

Silver thiosulfate, often a waste product of photoprocessing, is less bioavailable or toxic to aquatic organisms than is ionic silver. We conducted duplicate 48-h Ceriodaphnia dubia tests in reconstituted laboratory water using treatments of 92.7 nM Ag+ with various concentrations of thiosulfate. Expected Ag+ concentrations were generated for thiosulfate treatment levels using MINEQL + chemical equilibrium modeling. Ag+ concentrations in treatments were determined using a novel silicon-based sensor. Based on predicted Ag+ and published 48-h LC50 values for C. dubia, we did not expect to observe adverse effects. Yet, 100% mortality was observed at low thiosulfate treatments, whereas > 85% and > 95% survival was observed at higher thiosulfate treatment levels, respectively. Our results indicate that biotic responses match the sensor-based Ag+ concentrations. However, there is a discrepancy between these empirical results and responses expected to occur with Ag+ concentrations as predicted by MINEQL + chemical modeling. By correlating silicon sensor data with toxicity results obtained from our laboratory, our work clearly relates a specific chemical form (Ag+) to toxicity results.

Animals↗
PubMed2002

Use of the Chinese version of the Beck Depression Inventory for screening depression in primary care.

Many Asian-Americans are unfamiliar with depression and its treatment. When depressed, they generally seek treatment from their primary care physicians and complain about their physical symptoms, resulting in under-recognition and under-treatment of depression. This study evaluates the effectiveness of the Chinese version of the Beck Depression Inventory (CBDI) for screening depression among Chinese-Americans in primary care. A total of 503 Chinese-Americans in the primary care clinic of a community health center were administered the CBDI for depression screening. Patients who screened positive (CBDI > or = 16) were interviewed by a psychiatrist using the Structured Clinical Interview for DSM-III-R, patient version (SCID-I/P) for confirmation of the diagnosis. Patients who screened negative (CBDI < 16) were randomly selected to be interviewed using the depression module of the SCID-I/P. The results of the SCID-I/P interview were used as the standard for evaluating the sensitivity and specificity of the CBDI. A total of 815 Chinese-Americans in a primary care clinic were approached, and 503 completed the CBDI. Seventy-six (15%) screened positive (CBDI > or = 16), and the prevalence of major depression was 19.6% by using extrapolated results from SCID-I/P interviews. When administered by a native-speaking research assistant, the CBDI has good sensitivity (.79), specificity (.91), positive predictive value (.79), and negative predictive value (.91). Despite the commonly believed tendency to focus on physical symptoms rather than depressed mood, Chinese-Americans are able to report symptoms of depression in response to a questionnaire. The CBDI, when administered by research assistants, has good sensitivity and specificity in recognizing major depression in this population. Lack of interest among Chinese-American patients in using the CBDI as a self-rating instrument has limited its use for depression screening in primary care settings.

Adolescent↗
PubMedDate not supplied

Prevalence of major depressive disorder among Chinese-Americans in primary care.

An epidemiological study in Los Angeles showed that Chinese Americans had lower rates of depression compared to the U.S. national estimates. This study surveys the prevalence of major depressive disorder (MDD) among Asian-Americans in the primary care setting. A two-phase epidemiological survey was performed in the primary care clinic of a community health center in Boston, MA, which provides treatment to under-served Asian-Americans. Participants were Chinese Americans in the waiting area of the primary care clinic, 18 years of age or older, who spoke any one the four commonly used Chinese dialects. The Chinese version of the Beck Depression Inventory (CBDI) was used for initial screening. All consenting patients who screened positive (CBDI >/= 16) and a fraction of those who screened negative (CBDI < 16) were interviewed by a bilingual and bicultural psychiatrist with the Structured Clinical Interview for DSM-III-R, patient version, for confirmation of the diagnosis of MDD. There were 815 in the primary care clinic that were approached, of which 503 patients (62% female, mean age 50 +/- 17 years) filled out the CBDI in the initial phase of depression screening. Extrapolating the results from the SCID-P interviews, the prevalence of MDD among Asian-Americans in the primary care setting was estimated to be 19.6% +/- 0.06. MDD is common among Asian-Americans in primary care settings. The prevalence of MDD is comparable to or higher than those found in the U.S. nonminority populations.

Adolescent↗