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Biomedical subjects

H Cheung

Publications and source records attributed to H Cheung.

At least 19 recordsLinked to original sources
PubMed2001

The development of phonological awareness: effects of spoken language experience and orthography.

Phonological awareness, the ability to analyze spoken language into small sound units, has been shown to be affected by the individual's early orthographic experience (alphabetic vs. non-alphabetic). Past studies, however, have not differentiated the effect of script alphabeticity from that of spoken language experience, which covaries strongly with the phonological properties of the language. The present study compares younger, pre-reading to older, literate children from different linguistic backgrounds on their phonological awareness. Hong Kong and Guangzhou subjects both spoke Cantonese. The latter subjects had early experience with Pinyin (alphabetic) in addition to their logographic Chinese reading; the former read only logographic Chinese. New Zealand subjects spoke English and read the Roman alphabet. Results showed that: (1) the Hong Kong and Guangzhou pre-readers performed very similarly at all levels of phonological awareness; (2) the New Zealand pre-readers outperformed their Hong Kong and Guangzhou counterparts on onset, rime, and coda analyses; (3) the Guangzhou reading children outperformed their Hong Kong counterparts on onset and coda analyses. Whereas finding (3) reflects an effect of alphabeticity in the first learned script, finding (2) in combination with finding (1) indicates an effect of early spoken language experience independent of orthography. The fact that orthographic and spoken language experience both impact on the development of phonological skills implies a mediating function of phonological awareness in integrating sound information derived from reading and perceiving speech.

Age Factors↗
PubMed2000

Staging computed tomography of the thorax for nasopharyngeal carcinoma.

BACKGROUND: To assess the role of staging CT of the thorax in advanced nodal stage nasopharyngeal carcinoma and to examine the hypothesis that contiguous spread of nodal metastases from the supraclavicular region to the upper mediastinal region occurs in this cancer. METHODS: Forty-four patients with newly diagnosed nasopharyngeal carcinoma with neck node metastases to the supraclavicular region (ie, AJCC N3b stage) underwent contrast-enhanced CT (CECT) thorax for staging. CT findings and clinical outcome were analyzed. RESULTS: No patient was found to have intrathoracic metastasis, although 1 had hepatic metastases on CECT of the thorax, resulting in upstaging in 1 of 44 (2%) of patients. With a median follow-up time of 21 months, 3 patients had lung metastases and 2 had axillary nodal metastases develop without evidence of upper mediastinal nodal metastases. CONCLUSION: Staging CECT of the thorax has a very low yield in nasopharyngeal carcinoma, even in advanced nodal disease. The hypothesis that contiguous spread of nodal metastases from the supraclavicular region to the upper mediastinum is not substantiated, and no evidence suggests that radiation therapy for N3b-stage disease needs to encompass the upper mediastinum.

Adult↗
PubMed2000

Cartilage tissue engineering using thyroid chondrocytes on a type I collagen matrix.

OBJECTIVE/HYPOTHESIS: Reconstructive procedures of the head and neck often require materials that offer long-term structural support. A problem that many surgeons have encountered is identifying a material that offers this support without rejection of the implanted material This has led many surgeons to prefer autologous cartilage However, autologous cartilage is of limited supply. Cartilage tissue engineering has become a new modality that allows investigators to harvest a small piece of cartilage and extract its chondrocytes for expansion in culture. These chondrocytes are applied to a matrix that will act as a scaffold and allow for cartilage growth. Finding a compatible matrix seems to be the limiting step in the progress of this research. We describe a new approach of tissue creation using bovine collagen matrices as templates onto which cells are seeded. STUDY DESIGN: Laboratory research. METHODS: Chondrocytes obtained from thyroid cartilage of dogs were seeded onto bovine collagen type I matrices and grown in vitro. Chondrocyte seeded matrices were evaluated histologically. RESULTS: Thyroid chondrocytes expressed themselves phenotypically by producing type II collagen in the presence of this type I collagen matrix. CONCLUSIONS: This study offers the preliminary findings on an exciting new type of matrix worth exploring in the ability to successfully engineer cartilage.

Animals↗
PubMed2000

CT and DSA appearances of a ruptured congenital arteriovenous malformation of the posterior mediastinal aorta.

A case of symptomatic congenital arteriovenous malformation detected in an adult patient is presented. The diagnosis was not suspected clinically but was demonstrated by CT and digital subtraction angiography. Although very rare, a congenital arteriovenous malformation of the posterior mediastinal aorta could present as a catastrophic event if it ruptures. Serpiginous vascular channels in the retro-oesophageal posterior mediastinum on CT and angiography should raise the possibility of an arteriovenous malformation.

Angiography, Digital Subtraction↗
PubMed2000

Effects of antecedent order and semantic context on Chinese pronoun resolution.

Three reading time experiments were conducted in order to examine the relative contributions of order of antecedents and semantic context to the resolution of temporarily ambiguous Chinese pronouns. These pronouns were ambiguous because each of them was preceded by two antecedents, both of which were likely candidates for coreference. The identity of the pronoun was revealed by subsequent disambiguating information that constrained the pronoun to one particular interpretation. Experiment 1 showed that reading of the disambiguating phrase was slower when the phrase confined the pronoun to the second rather than to the first antecedent. Experiment 2 produced the same effect of antecedent order (first vs. second antecedent) regardless of whether the target antecedent was an action-performing or an action-receiving entity. In Experiment 3, the order effect was eliminated by a biasing modifier inserted immediately before the pronoun. These results indicate that in a semantically neutral environment, the first-appearing antecedent is the preferred candidate for coreferencing the ambiguous Chinese pronoun. The interaction between order of antecedents and semantic context (in the form of preposed biasing modifiers) suggests that the initial comprehension of Chinese pronouns depends as much on contextual as on structural factors.

Adult↗
PubMed1999

Improving phonological awareness and word reading in a later learned alphabetic script.

This study examines the effects of phonological skill training on consonantal phoneme deletion and word reading performance in two groups of adolescent Chinese readers who were also literate in English. The research questions were: (1) whether training would promote segmentation skills over and above years of contact with the alphabetic (English) writing system, given an initial logographic (Chinese) reading background; (2) whether improvements in segmentation skills due to training would enhance word reading in the alphabetic script. The participants were trained on phoneme counting, phoneme blending and rime judgement with English materials over a period of two months. Resultant changes in consonantal phoneme deletion and English word reading performance were examined. Significant improvements in both activities due to training were observed for the younger (mean age 12.7 years) but not the older (mean age 15.8 years) participants. Follow-up analyses showed that language proficiency might be the factor underlying this age effect. Individual differences in phoneme deletion uniquely predicted word reading for both age groups, although the relationship tended to be stronger for the less proficient than the more proficient members. These findings suggest that beyond years of normal reading instruction in the alphabetic system, specialized segmentation training could still contribute to promoting consonantal phonemic analysis that is not supported by the logographic first-learned script. Moreover, improved phonological skills do lead to better word reading in the later-learned writing system. Implications of the present findings for second script reading instruction are considered.

Adolescent↗
PubMed1998

Lexical and conceptual processing in Chinese-English bilinguals: further evidence for asymmetry.

According to the asymmetry model of bilingual representation (Kroll & Stewart, 1994), the first language (L1) lexicon is closely tied to an underlying conceptual memory, whereas second language (L2) items are mostly associated with their L1 equivalents. An outcome of this architecture is that L1-to-L2, or forward, translation must be mediated by the conceptual memory, whereas L2-to-L1 (backward) translation takes a direct lexical path. Some predictions derived from this hypothetical structure were tested in the present study, which took into account, through analysis of covariance, variations in response production time, concept retrieval time, and some other characteristics associated with the individual test items. Proficient Chinese-English bilinguals were tested on delayed production (Balota & Chumbley, 1985), picture naming, word translation, and category matching. The expected asymmetrical pattern of translation latencies (i.e., forward > backward) was demonstrated, although it could be statistically explained by the item characteristic of familiarity; matching an L1 item to a category name was faster than matching an L2 item, suggesting relatively strong L1 conceptual links. The present results are best accommodated by a form of asymmetry that allows for nondominant L2-concept linkage, the use of which is conditional upon the familiarity of the test item to the bilingual.

Analysis of Variance↗
PubMed1997

Examining and reexamining the structure of Chinese-English bilingual memory.

The asymmetry model of bilingual memory proposed by Kroll and Stewart assumes that translation from a first language (L1) into a second language (L2), or forward translation, is mediated by an underlying conceptual memory, whereas L2-to-L1, or backward, translation is lexical and direct. Lexical links from L2 to L1 are hypothesized to be stronger than those from L1 to L2, but conceptual links are stronger for L1 than L2. These assumptions were evaluated in this study, which used stimulus items with similar recognition thresholds. Proficient Chinese-English bilinguals were tested on picture naming, word naming, word translation and category matching. The translation asymmetry effect predicted by the model (i.e., backward being faster than forward translation) was demonstrated; matching an L1 item to a category name was also faster than matching an L2 item. This pattern of results, nevertheless, did not completely hold after an adjustment procedure which sought to control for variations in response production and concept retrieval times due to stimulus types. The present findings are consistent with previous ones which show increased L2 conceptual processing for the proficient bilingual. They also suggest that an extended version of the asymmetry model should take into account possible biasing effects associated with some conventionally used bilingual tasks.

Analysis of Variance↗
PubMed1997

Sonographic, magnetic resonance imaging, and mammographic assessments of preoperative size of breast cancer.

High resolution sonographic (39 cases), magnetic resonance imaging (32 cases), and mammographic (35 cases) measurements of preoperative size of breast cancer were correlated with the pathologic size in 39 patients with breast carcinoma to determine the most accurate imaging technique for breast cancer size. There were nine T1, 21 T2, four T3, and four T4 tumors. Sonographic and magnetic resonance imaging measurements of tumor size demonstrated correlation coefficients of 0.92 and 0.93, respectively, both of which were superior to that of mammography (0.84). Sonographic tumor size evaluation thus is shown to be equivalent to magnetic resonance imaging in this study. Three of nine (33%), four of seven (57%), and four of eight (50%) T1 tumors would have been overstaged by ultrasonography, magnetic resonance imaging, and mammography, respectively. Three of 21 (14.3%), one of 16 (6.3%), and two of 18 (11.1%) T2 tumors would have been understaged by ultrasonography, magnetic resonance imaging, and mammography, respectively. We therefore found ultrasonography to be of value in the diagnosis and staging of breast cancer.

Aged↗
PubMed1996

Remacemide HCl and its metabolite, FPL 12495AA, limit action potential firing frequency and block NMDA responses of mouse spinal cord neurons in cell culture.

The novel anticonvulsant, remacemide HCl [(+/-)-2-amino-N-(1-methyl-1,2-diphenylethyl)acetamide monohydrochloride; FPL12924AA], and a desglycinated metabolite [(+/-)-1-methyl-1,2-diphenylethylamine monohydrochloride; FPL 12495AA] reversibly limited sustained high-frequency repetitive firing (SRF) of sodium-dependent action potentials by mouse spinal cord neurons in monolayer dissociated cell culture. Limitation occurred with an IC50 of 7.9 X 10(-6) M for remacemide and 1.2 X 10(-6) M for FPL 12495AA (P < 0.05 vs. remacemide). Stereoisomers of the desglycinate limited SRF with IC50 values of 3.3 X 10(-6) M and 3.5 X 10(-6) M for the S(+) and R(-) compounds, respectively. The concentration of racemic desglycinate and of either stereoisomer that produced limitation in all neurons tested was 10(-4) M. Maximal rate of rise (Vmax) of action potentials decreased progressively until firing ceased during 400-ms depolarizing pulses. Efficacy of remacemide, but not of the desglycinate, increased with time (maximum at 16-36 h). The limitation was voltage dependent. In addition, reduction of Vmax and action potential failure occurred during stimulation with 400-ms pulses and trains of brief (1 ms) depolarizations at different frequencies. These findings suggest an effect on voltage-sensitive sodium current that generates the action potential upstroke. Remacemide and the desglycinate also significantly reduced the amplitude of neuronal responses to pressure application of NMDA in use-dependent manner at concentrations equal to the IC50 values for limitation of action potential firing. Resting potential and input resistance were not changed significantly by either drug. Limitation of high-frequency firing of action potentials by both remacemide HCl and FPL 12495AA may contribute to the anticonvulsant efficacy of these compounds at concentrations overlapping the range required to block glutamatergic hyperexcitability.

Acetamides↗
PubMed1996

The imaging diagnosis of hepatic schistosomiasis japonicum sequelae.

We reviewed the ultrasound (US) and computed tomography (CT) examinations of the liver in 21 patients with hepatic schistosomiasis japonicum (HSJ), to assess the role of imaging in its diagnosis. Thirteen patients had histopathological evidence of hepatic ova deposition. A 'network' pattern was present in 14 of 17 (82%) patients on US, and 'turtle-back' calcification in 11 of 13 (85%) patients on non-contrast CT (NCCT). The combination of US and NCCT was positive for HSJ in all nine patients subjected to both investigations. These findings are specific for HSJ and we discuss how they differ from the imaging findings reported in hepatic Schistosoma mansoni (HSM). We conclude that the sequelae of HSJ infection create an imaging diagnosis. Although an uncommon incidental finding at liver imaging, the combined US and CT appearances are so characteristic that in the majority of patients biopsy can potentially be avoided.

Aged↗
PubMed1993

Management evolution of pulmonary atresia and intact ventricular septum.

To examine the impact on survival and clinical course of incorporating the morphologic classification of the right ventricle into the evolving management strategy for babies with pulmonary atresia and intact ventricular septum, the surgical results and follow-up status of the first 62 consecutive patients managed in this hospital between 1979 and 1990 were reviewed. Before 1984, all 23 babies from group I underwent primary right ventricular outflow reconstruction irrespective of right ventricular morphology and size. Since 1984, depending on the morphology and size of the right ventricle, 39 babies from group II had either closed transventricular pulmonary valvotomy (n = 31) or a shunt operation (n = 8). There were 10 hospital (43%) and 2 late deaths (total mortality 52%) in our group I patients. Three of the 11 long-term survivors had cyanosis at rest but none had any residual pressure gradient across the pulmonary outflow. Group II had 6 hospital (15%) and 4 late deaths (total mortality = 26%). Of the 29 long-term survivors, 9 had a second-stage right ventricular outflow reconstruction, 8 had balloon valvuloplasty and 2 had successful Fontan operation. At the latest follow-up, 5 children from this group have cyanosis at rest, 1 has a residual gradient (55 mm Hg) across the infundibulum, and 3 have right ventricular dysfunction. The hospital and total mortality for babies in group II was significantly lower than that in group I (p < 0.01). These data suggest that tailoring the treatment to the right ventricular anatomy results in a lower overall mortality although long term postoperative hemodynamic abnormalities are observed in both groups.

Abnormalities, Multiple↗
PubMed1993

On the preservation of syntax in Alzheimer's disease. Evidence from written sentences.

We examined the syntactic complexity of single written sentences elicited from 368 adults undergoing examination for possible Alzheimer's disease. The clause length and composition of the sentences varied with the severity of dementia. The nondemented adults' sentences contained more propositions, main and secondary verbs, and conjunctions than those produced by the mildly and moderately demented adults. Sentence length in clauses, propositional content, and the use of conjunctions and main and secondary verbs discriminated among stages of the severity of the disease. The present results suggest that, while dementia severity affects written linguistic output, such output is, nonetheless, grammatic and coherent.

Aged↗
PubMed1993

Ultrasound in the diagnosis of gall-bladder carcinoma in Chinese patients.

A review of the ultrasound (US) findings with clinical and pathological correlation in 18 Chinese patients with gall-bladder carcinoma (GBCa) showed that the most frequent appearance was that of diffuse infiltration and thickening of the GB wall (8/18 patients, 44%). Polypoid protrusion into the GB lumen (5/18 patients, 28%) and massive replacement of the entire GB (5/18 patients, 28%) accounted for the remainder. The infiltrating type of tumour was poorly-detected by US (1/8) and was more frequently seen than has been reported in the Western population. Frequent associations with GB calculi (13/18) and synchronous presentation of biliary sepsis (6/18) also contributed to a modest overall US detection rate of 50% (9/18) in this series. Most tumours detected by US were hyperechoic in appearance (6/9). Biliary obstruction was detected by US in 5/6 patients, but only thought to be malignant in 3/6. It most often occurred due to spread of tumour to peripancreatic lymph nodes. Hepatic metastases were seen by US in 4/5 patients. Discontinuous GB wall calcification and non-dependent stones due to elevation by tumour (the 'elevated stone' sign) were infrequent but reliable signs of GBCa, seen in 5/18 and 3/18 respectively. This study suggests that GBCa is as difficult to detect sonographically in Chinese patients as in the Western population. GBCa must be included in the differential diagnosis of causes of both the acutely-presenting 'hot' gall-bladder and lymph node masses in the peripancreatic region if the US detection rate of this important biliary malignancy is to be improved.

Aged↗
PubMed1993

Liver hamartomas in tuberous sclerosis.

Three patients with tuberous sclerosis (TS) and hepatic hamartomas are presented. Liver lesions are uncommonly documented in TS, compared to renal angiomyolipomas. The imaging characteristics of liver hamartoma in TS may resemble those of renal angiomyolipoma, hepatic cavernous haemangiomas, metastasis or abscess.

Adult↗
PubMed1993

Changes in myocardial blood flow rates during hyperdynamic sepsis with induced changes in arterial perfusing pressures and metabolic need.

OBJECTIVE: To determine whether hyperdynamic sepsis is associated with dysregulation in the control of myocardial blood flow rates unrelated to hypotension or the use of anesthetic agents. DESIGN: Prospective, nonrandomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Fifteen mature male sheep (34 to 61 kg). INTERVENTIONS: Data were recorded in study subjects before and after the induction of sepsis following cecal ligation and perforation. Data were then recorded during: a) an infusion of prostaglandin E1 (PGE1), which decreased mean arterial perfusing pressure; and b) an infusion of zymosan-activated plasma, which increased mean pulmonary arterial pressures. MEASUREMENTS AND MAIN RESULTS: Myocardial blood flow rates were measured by the radiolabeled microsphere technique and cardiac index was measured by the thermodilution technique. Cardiac index (change delta) postcecal ligation and perforation minus baseline (+2.3 +/- 1.0 L/min/m2; p < .01) was increased in the septic study. Blood flow rate to the left ventricle was simultaneously increased, and was not further affected when the PGE1 infusion decreased the mean arterial perfusing pressures (-19 +/- 4%). During the infusion of zymosan-activated plasma, mean pulmonary arterial pressures increased (50 +/- 30%) and right ventricular blood flow was increased (zymosan minus postcecal ligation and perforation study: delta 17.8 +/- 50 mL/100 g/min; p < .01). CONCLUSIONS: In this model of hyperdynamic sepsis, increases in blood flow to both the left and right ventricles were positively coupled to changes in respective ventricular work. From the interventional PGE1 and zymosan-activated plasma infusion studies, we found no evidence to support previous suggestions that the regulation of myocardial blood flow rates according to changes in perfusing pressure and/or metabolic oxygen need is significantly altered during hyperdynamic sepsis.

Alprostadil↗