PubMed Health⌕ Search

Biomedical subjects

C Cheung

Publications and source records attributed to C Cheung.

36 records · Page 2Linked to original sources
PubMed1998

Carbohydrate deficient transferrin in the assessment of alcohol misuse: absolute or relative measurements? A comparison of two methods with regard to total transferrin concentration.

Carbohydrate deficient transferrin (CDT) is now accepted as a potentially useful marker for the detection of alcohol misuse. It is not clear whether absolute values or values expressed relative to the total transferrin concentration provide the same diagnostic efficiency. CDT was measured in 35 patients with alcohol related liver disease, 35 subjects abusing alcohol without evidence of liver disease and 35 patients with chronic viral hepatitis using two commercial methods (CDTect and %CDT). To compare the methods, results were normalised by dividing the actual result by the upper limit of the reference range. Subtracting normalised %CDT results from the normalised CDTect results demonstrated a linear relationship between CDTect and total transferrin. This linear relationship could be abolished by calculating the CDTect/total transferrin ratio. The sensitivity of the methods was similar with CDTect (43 and 57%) being slightly superior to %CDT (40 and 46%). Specificity was similar (78%) for both methods. Calculation of the CDTect/total transferrin ratio improved the sensitivity and specificity slightly. The linear relationship between CDTect and total transferrin may produce misleading results in populations with a high prevalence of abnormal total transferrin concentrations and could cause difficulties in method comparisons unless taken into account.

Adolescent↗
PubMed1998

Expression of cytokine mRNA transcripts in renal cell carcinoma.

Renal cell carcinoma (RCC) is a solid tumour of the kidney and is the most common renal neoplasm. Despite the presence of tumour infiltrating lymphocytes (TIL) in RCC, these tumours continue to progress in vivo suggesting a poor host immune response to the tumour, and the suppression of TIL effector function. Cytokines are key molecules that modulate the function of T cells. The possibility is investigated that the local production of cytokines in RCC contributes to immunosuppression of TIL. The expression of pro-inflammatory (IFN-gamma/IL-2) and immunosuppressive (IL-10/TGF-beta) cytokine mRNA transcripts was determined in RCC, normal kidney and peripheral blood of RCC patients using a semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) with cytokine-specific primers. Following Southern blot hybridization of the PCR products with internal radiolabelled oligonucleotide probes, cytokine transcript levels were measured by densitometry and expressed relative to the glyceraldehyde-3-phosphate dehydrogenase densitometry score. With the exception of IL-10, there were no differences in expression of cytokine mRNA transcripts between the peripheral blood of patients and normal healthy individuals. It was found that TGF-beta transcripts were well represented in normal kidney and RCC. In contrast, the expression of IFN-gamma transcripts, while low in the majority of samples, was significantly increased in RCC when compared to normal kidney (P=0.05). The IL-2 and IL-10 transcripts showed a more variable expression in normal kidney and RCC, with no significant differences in expression between the sample groups. The data demonstrating pro-inflammatory and immunosuppressive cytokine expression in RCC do not support a prominent immunosuppressive cytokine profile in these tumours.

Adult↗
PubMed1998

T cell engraftment in lymphoid tissues of human peripheral blood lymphocyte reconstituted SCID mice with or without prior activation of cells.

The reconstitution of severe combined immunodeficiency (SCID) mice with human PBL (Hu-PBL-SCID) was assessed using fresh unstimulated PBL and anti-CD3-stimulated PBL. Mice were reconstituted with PBL by intraperitoneal injection of 1-2.5 x 107 PBL in PBS; controls received PBS. Successful engraftment of human PBL in SCID mice was determined by measurement of human IgG in mouse sera, polymerase chain reaction (PCR) detection of human-specific HLA-DRbeta DNA in SCID periphery, and immunohistochemical staining of mouse tissues (spleen, lymph nodes, thymus, liver and lung) with antibodies specific for human CD45 and CD3. Human IgG was detected 1 week after reconstitution in sera of all animals that received at least 1 x 107 PBL and continued to increase for 8 weeks. Human-specific HLA-DRbeta DNA was detected in the majority of mice 3 weeks after reconstitution but not in controls. Moreover, immunohistochemical analysis of Hu-PBL-SCID mouse tissues revealed the presence of human CD45+ cells in all tissues examined. CD3+ T cell engraftment was observed in lymphoid tissues irrespective of whether PBL had been activated prior to transfer or not.

Animals↗
PubMed1997

The diagnostic value of the diatom test for drowning, I. Utility: a retrospective analysis of 771 cases of drowning in Ontario, Canada.

The utility and validity of the diatom test for drowning was studied using a retrospective analysis of 771 cases of drowning mostly from Ontario, Canada, over the period 1977 to 1993. In this article (part one), the utility of the test was assessed using an analysis of test outcomes. In the companion article (part two), the validity of the test was assessed by analyzing the relationship between test outcome and characteristics of diatoms in the bone marrow and samples of putative drowning medium. In the present study, freshwater drownings accounted for 738 of the cases and 33 cases were drownings in bathtubs, pools, or toilets. Diatoms were recovered from the femoral bone marrow of 205 cases (28%) of freshwater drowning and four cases (12%) of domestic water drowning. There was a monthly variation in the frequency of positive test outcomes that could not be explained by seasonal differences in the total number of drownings. However, the monthly variation was strongly correlated with the periodic cycle of diatom blooms that occurs in freshwater. Positive diatom tests were characterized by a limited number of distinctive diatom species per case, and a restricted quantity and size range of diatom frustules. These results indicate that the diatom test for drowning will identify approximately one in three victims of freshwater drowning and may be useful in the assessment of deaths occurring in bathtubs. The correlation of the outcome of the diatom test for drowning with diatom blooms provides further evidence for the reliability of the test.

Bone Marrow↗
PubMed1996

E-cadherin cell-adhesion molecule expression as a diagnostic adjunct in urothelial cytology.

E-cadherin (E-CD) is a cell-adhesion molecule that has been associated with invasion and metastasis in a wide variety of human neoplasms. We have recently shown that, although decreased E-CD expression is associated with increased bladder-wall invasion and higher tumor grade of infiltrating transitional cell carcinomas (TCC), E-CD expression in the exophytic portion of pure papillary and papillary-infiltrating TCC is increased over that of normal transitional cells. To evaluate whether E-CD levels could serve as a diagnostic adjunct in urinary cytology specimens, we stained 40 alcohol-fixed bladder-washing cytospin preparations with an avidin-biotin-peroxidase method using a monoclonal antibody to E-CD (Sigma Chemical Co., St. Louis, MO). E-CD expression level was defined as a high-intensity or low-intensity staining increase over background squamous cell staining for the transitional cells in 21 biopsy-proven transitional cell carcinomas with papillary components, and in 19 benign or reactive control specimens. Twenty-one of 21 TCC (100%) showed an increased E-CD level over background, with 13 low-intensity and 8 highintensity cases. Ten of 19 benign cases (53%) showed increased E-CD staining over background, with 8 low-intensity and 2 highintensity cases. This difference between malignant and benign specimens was statistically significant (chi-square test. P approximately 0.001). We conclude that increased E-CD expression in the papillary components of TCC can be identified in urinary cytology specimens, may reflect the physical and chemical structural makeup of papillary architecture, and warrants further study as a diagnostic adjunct in the interpretation of urine cytology specimens.

Aged↗
PubMed1996

Visual evoked potentials with crossed asymmetry in incomplete congenital stationary night blindness.

PURPOSE: To investigate a proposed postretinal defect in patients with the incomplete form of congenital stationary night blindness (CSNB2) and to compare visual evoked potential (VEP) results with those found in various forms of albinism. METHODS: Visual evoked potentials were performed in 10 patients with a diagnosis of CSNB2, 10 subjects with albinism, and 17 normal subjects. Visual evoked potentials were elicited monocularly with diffuse flash stimulation. Scalp electrodes were placed over each hemisphere and referred to the forehead. Interhemispheric bipolar recordings were derived, and the correlation coefficient (CC) was calculated for various segments of the interhemispheric responses. RESULTS: A crossed visual evoked potential asymmetry pattern could be demonstrated in 9 of 10 patients with CSNB2. All subjects with albinism and none of the normal subjects showed the crossed asymmetry pattern. Statistical comparison of the CC computed for various segments of the interhemispheric response shows that the pattern of inversion in CSNB2 is more prominent in the 25 to 100 msec range (median CC, -0.37) and in the 175 to 250 msec range (CC, -0.27). In subjects with albinism, all segments show a negative CC (range, -0.46 to -0.60). In normal subjects, all segments are positively correlated (range, 0.36 to 0.66). CONCLUSIONS: Crossed visual evoked potential asymmetry was found in patients with CSNB2; therefore, excessive decussation, as demonstrated by this testing procedure, should not be considered as pathognomonic for albinism.

Adolescent↗
PubMed1989

Effect of adenosine triphosphate depletion in vivo on renal function in the rat with and without ischemia.

To investigate the importance of renal tissue concentrations of adenosine triphosphate (ATP) in maintaining normal renal functions as well in the recovery from ischemic injury in vivo, fructose was administered without ischemia as well as in the setting of an ischemic insult. In nonischemic as well as kidneys recovering from 30 min of clamp ischemia, fructose caused a 50% reduction in the tissue concentration of ATP which persisted for over 1 h. In nonischemic animals, fructose had no effect on renal function as assessed by inulin clearance and sodium reabsorption and showed no evidence of histologic injury 24 h after administration. In animals subjected to 30 min of ischemia, animals given fructose showed no worsening of functional or histologic injury as compared to controls. We conclude from these data that reductions in the tissue concentration of ATP in the range observed does not adversely affect normal renal functions or recovery from a reversible ischemic insult.

Adenine Nucleotides↗
PubMed1987

Comparison of the natriuretic response to atriopeptin III and loop diuretic in the isolated perfused rat kidney.

1. Isolated rat kidneys were perfused at a constant perfusion pressure of 90 mmHg to study the natriuretic effects of atriopeptin III (AP-III) and to compare these effects with those of frusemide. AP-III (1 microgram) or frusemide (1 mg) were added to the perfusate (100 ml) after two 15 min control collection periods. 2. Compared with the control group, AP-III and frusemide increased urinary sodium excretion (UNa V, 5.6 +/- 1.1 and 4.6 +/- 0.6 vs control 1.8 +/- 0.3 mumol min-1 g-1, mean +/- SEM, P less than 0.01 and P less than 0.05, respectively), fractional sodium excretion (FENa, 4.8 +/- 1.1 and 6.7 +/- 0.8 vs control 2.0 +/- 0.2%, P less than 0.05 and P less than 0.001, respectively) and potassium excretion (UKV, 3.2 +/- 0.3 and 3.0 +/- 0.3 vs control 1.5 +/- 0.3 mumol min-1 g-1, both P less than 0.01). However, AP-III, but not frusemide, increased glomerular filtration rate (820 +/- 55 vs 590 +/- 24 microliter min-1 g-1, P less than 0.01) and urine flow rate (V 97.5 +/- 8.0 vs 44.1 +/- 5.2 microliter min-1 g-1, P less than 0.001). Calculated distal delivery of sodium (CNa +/- CH2O, 76.6 +/- 6.8 vs 30.7 +/- 3.8 microliter min-1 g-1, P less than 0.005) as well as fractional distal delivery of sodium [(CNa +/- CH2O)/CIn, 9.4 +/- 0.9 vs 5.1 +/- 0.6%, P less than 0.01] were increased by AP-III, but not frusemide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of adenosine triphosphate depletion in the isolated perfused rat kidney.

Glycerol or fructose (40 mM) was added to the control perfusate and renal function was observed in the isolated perfused rat kidney during nonischemic perfusions or perfusions following 30 min of clamp ischemia. Addition of glycerol or fructose resulted in lowering adenosine triphosphate (ATP) levels to 62 and 35%, respectively, of levels achieved with control perfusate under nonischemic conditions (p less than 0.01). Total adenine nucleotides (TAN) were also lowered to 67% with glycerol and 61% with fructose of control values under nonischemic conditions (p less than 0.05). However, physiologic parameters of renal plasma flow and inulin clearance were essentially unaffected by either glycerol or fructose. Following ischemia, glycerol and fructose reduced ATP levels to 51 and 37% and TAN levels to 67 and 65%, respectively, of values seen with control perfusate. However, recovery of renal plasma flow and inulin clearance were uneffected by the addition of either glycerol or fructose. Thus, a 33-65% reduction in renal tissue ATP by glycerol or fructose does not appear to have a deleterious effect on organ function in the basal state or during recovery from an ischemic insult in the isolated perfused rat kidney.

Adenine Nucleotides↗
PubMed1985

The effect of verapamil on renal function after warm and cold ischemia in the isolated perfused rat kidney.

The potential usefulness of verapamil, a calcium channel blocker to renal allograft preservation, was investigated using the isolated perfused rat kidney. Two models of ischemic injury were used. In the first model, rat kidneys were exposed to 40 min of 37 degrees C ischemia on the perfusion circuit. Addition of verapamil in doses of 2.5, 5, and 100 microM concentration to the perfusate significantly improved inulin clearance (Cin) and total sodium absorption (TNa) in the hour of reperfusion following ischemia. Regeneration of adenosine triphosphate (ATP) and total adenine nucleotide TAN levels during reperfusion following warm ischemia were also significantly higher in verapamil-treated kidneys. In the second model, rat kidneys were flushed in situ with Collins C2 solution and stored at 0 degrees C for 8 hr. After this period of cold ischemia, they were perfused on a perfusion circuit with perfusion media. Verapamil 2.5 microM was absent from both flush and perfusate (control), or added to just the flush, both the flush and perfusate, or just the perfusate. Addition of verapamil to the flush or the flush and perfusate significantly improved Cin, urine flow rate (V) and TNa during reperfusion, compared with control. Addition of verapamil to just the perfusate did not effect Cin, TNa, or V but did significantly increase RPF. These findings suggest the verapamil may protect against organ damage occurring during both warm and cold ischemia in the absence of any systemic effects and thus may be useful for renal allograft preservation.

Adenine Nucleotides↗
PubMed1985

Isozyme relative mobility (Rm) changes related to leaf position; apparently smooth Rm trends and some implications.

Relative mobilities (Rm's) of peroxidase and acid phosphatase isozymes were examined in leaves of flax (Linum usitatissimum L.). The leaves were sampled from four equidistantly spaced positions from main stem base to apex in various genotypes. Rm's for the two slowest-migrating isozymes of each enzyme system changed in a simple, coherent fashion in leaves from stem bases toward apices. The Rm trends up the stem seen in two highly branched flax types were somewhat different from those in two sparsely branched types. The coherent Rm trends in the four types, suggesting a smooth continuum and a potentially large number of slightly different forms of these isozymes, are discussed in relation to other data for such Rm trends. In the study reported here, both enzyme systems behaved similarly. This fact and the simple Mendelian genetical system with no codominance controlling Rm's in flax peroxidases and acid phosphatases suggest posttranscriptional or posttranslational modifications as plausible mechanisms underlying the numerous, presumably small molecular changes generating the small, consistent changes in Rm's.

Acid Phosphatase↗
PubMed1983

A microcomputer-based system for measuring temporal asymmetry in amputee gait.

This paper reports the development of a microcomputer-based system for measuring the temporal factors of amputee gait. The system has been designed for possible use in a standard clinical environment. It consists of a simple walkway, two photoelectric beam relays, a control unit and an APPLE II Plus microcomputer. Preliminary clinical assessment of the system has been conducted. The gait characteristics of eight amputees during their ambulation training were investigated with the use of the new system. A comparison of the results from different groups of subjects, selected primarily on level of amputation, is presented.

Aged↗
PubMedDate not supplied

Supervised interpretation of echocardiograms with a psychological model of expert supervision.

We have developed a collaborative scheme that facilitates active human supervision of the binary segmentation of an echocardiogram. The scheme complements the reliability of a human expert with the precision of segmentation algorithms. In the developed system, an expert user compares the computer generated segmentation with the original image in a user friendly graphics environment, and interactively indicates the incorrectly classified regions either by pointing or by circling. The precise boundaries of the indicated regions are computed by studying original image properties at that region, and a human visual attention distribution map obtained from the published psychological and psychophysical research. We use the developed system to extract contours of heart chambers from a sequence of two dimensional echocardiograms. We are currently extending this method to incorporate a richer set of inputs from the human supervisor, to facilitate multi-classification of image regions depending on their functionality. We are integrating into our system the knowledge related constraints that cardiologists use, to improve the capabilities of our existing system. This extension involves developing a psychological model of expert reasoning, functional and relational models of typical views in echocardiograms, and corresponding interface modifications to map the suggested actions to image processing algorithms.

Algorithms↗
PubMedDate not supplied

Long-term results of voice rehabilitation after total laryngectomy using primary tracheoesophageal puncture in Chinese patients.

PURPOSE: Prosthetic voice restoration is an increasingly popular method of postlaryngectomy voice rehabilitation. Despite its success in non-tonal languages, the efficacy of tracheoesophageal speech in tonal languages was largely unknown. The aim of the present study was to evaluate the long-term results of voice rehabilitation using a Blom-Singer valve (BSV) in the tonal language of Cantonese. PATIENTS AND METHODS: The records of 159 patients who underwent total laryngectomy and primary tracheoesophageal puncture (TEP) between May 1985 and December 1994 were retrospectively reviewed. Tracheoesophageal speech was regarded as functional if effective communication could be made during face-to-face conversation and telephone conversation. Any TEP-related complications were noted. Perioperative factors that might contribute to nonfunctional speech were subjected to statistical analysis. RESULTS: Six hospital mortalities were excluded from speech analysis. Of the remaining 153 patients, the median follow-up was 25 months, ranging from 3 to 113 months. Seventy-three patients had closure of tracheosophageal fistulae (TEF), and the main causes were ineffective voice production, dislodgment, and tracheostomal stenosis. Only 15 of them acquired functional speech before closure. The other 80 patients used a BSV as the chief modality of voice rehabilitation, with functional results achieved in 64 patients. None of the perioperative factors were found to be statistically significant in relation to nonfunctional speech. CONCLUSION: Primary TEP is an established method of voice rehabilitation after total laryngectomy. In our series, 52% patients achieved functional tracheoesophageal speech using a BSV.

Esophagus↗