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Biomedical subjects

C W Chan

Publications and source records attributed to C W Chan.

At least 109 records · Page 6Linked to original sources
PubMed1982

Contrasts between the reflex responses to tibialis anterior and triceps surae to sudden ankle rotation in normal human subjects.

A detailed comparative study was made of the reflex responses of human ankle flexors (tibialis anterior, TA) and extensors (triceps surae, TS) to sudden ankle rotation. Subjects were instructed to maintain a tonic contraction of either TS or TA and subjected to sudden displacements of the ankle from its midposition in either the dorsiflexing or plantarflexing directions. Joint position, torque and smoothed rectified EMGs were recorded. The results revealed 5 principal differences in the behavior of the two muscles. (1) The TS response was typically a short, synchronous burst of activity starting at about 40 msec and lasting no more than 50 msec, termed the MSR. in contrast, the TA responses started at about the same latency but lasted much longer and frequently a second component (termed the PSR) could be distinguished. (2) The threshold of the TA reflex was much higher than that of TS. (3) Increasing displacement velocity increased the magnitude of the TS MSR as well as that of the TA MSR, but decreased the magnitude of the TA PSR. (4) Increasing the level of tonic activity augmented the magnitude of the TS activity initially but saturation soon occurred. In contrast, both components fo the TA response increased with increasing tonic TA activity. (5) Finally, shortening of the tonically active TS evoked no consistent response, where as shortening of TA evoked a significant pause in its activity. The contrasting behavior of the ankle flexors and extensors suggest that there are significant differences in their reflex organizations.

Ankle↗
PubMed1981

Interlimb reflexes evoked in human arm muscles by ankle displacement.

Interlimb reflexes evoked by ankle displacements were studied in arm muscles of 6 normal subjects. EMGs from grastrocnemius (G), tibialis anterior (TA), biceps brachii (BB), and triceps brachii (TB) were amplified, rectified and low-pass filtered before recording. Averaging and Wiener filtering were used to detect changes in tonic EMG activity evoked by dorsiflexing or plantarflexing displacements of the ankle. A consistent pattern of response was observed in all subjects. In the leg muscles, the responses to stretch were consistent with previous reports. In the arm muscles, the response of TB was dominant. Dorsiflexing displacements of the ankle evoked a small excitation followed by a more marked decrease in TB activity but had no effect on BB. In contrast, plantarflexing displacements of the ankle resulted in a large, early period of excitation followed by a decreased level of activity in TB. A similar but smaller pattern of activity was observed in BB. It is notable that the TB responses to displacement were sizable, often modulating the tonic EMG activity by as much as 80%. Interlimb reflexes evoked by ankle displacement were larger and of shorter latency than those evoked by cutaneous electrical stimulation of the foot reported previously. This suggests that proprioceptive afferents may have stronger and more direct interlimb reflex connections than cutaneous afferents and may therefore play an important role in the coordination of movement.

Adult↗
PubMed1981

Intraosseous glomus tumor--case report.

This case of an intraosseous glomus tumor reported in a 42-year-old Chinese housewife is believed to be the tenth case in medical literature. It was discovered on review of bone biopsy material examined at the Department of Pathology, Queen Mary Hospital, Hong Kong.

Adult↗
PubMed1981

Non-endocrine carcinoid tumour of the uterine cervix: aspects of diagnosis and treatment. Case report.

A case of primary well-differentiated carcinoid tumour of the uterine cervix in a Chinese woman of 62 years without endocrine symptoms is reported and its clinico-pathological features, ultrastructure and response to radiotherapy discussed. To our knowledge, it is the first of such cases seen in Hong Kong. Clinically, it presented as a polypoid lesion. The initial diagnosis was squamous carcinoma of cervix stage Ib and the patient was treated with radiotherapy. The tumour disappeared after application of first intracavitary irradiation of 4500 mg h. After completion of 9000 mg h, Wertheim hysterectomy followed and no residual tumour was found. Retrospective staining of the pre-irradiation cervical tumour by Grimelius method was positive for argyrophil granules and electron microscopic study demonstrated neurosecretory granules in the cytoplasm and established the diagnosis.

Carcinoid Tumor↗
PubMed1981

The pathology of primary IgA glomerulonephritis--a renal biopsy study.

Renal biopsies of 44 Chinese patients with primary IgA glomerulonephritis (IgA Gn) were examined by light (LM), electron (EM) and immunofluorescent microscopy (IF). The diagnosis of IgA Gn was based on IF staining showing predominant mesangial IgA deposition in the absence of systemic diseases. With LM, IgA Gn was not essentially different from other idiopathic forms of glomerulonephritis. The glomerular lesions showed features of focal proliferative glomerulonephritis (45.4%), focal sclerosing glomerulonephritis (25%), minimal glomerular lesions (18.2%) and diffuse mesangial proliferative glomerulonephritis (11.4%). Membranous and membrano-proliferative forms were not encountered. The variable LM findings contrasted markedly with the constancy of IF staining. EM revealed lumpy electron dense deposits in the mesangium in all cases which, in the relative absence of subendothelial and subepithelial deposits, might also be helpful in diagnosis.

Adult↗
PubMed1980

In vitro reaction of cancer patients and others to Bacillus Calmette-Gueérin.

We examined the in vitro reaction of leukocytes from 71 cancer patients and 121 control donors (disease-free individuals or patients with non-malignant non-debilitating conditions) against Bacillus Calmette-Guérin using a one-stage capillary leukocyte migration assay. The proportion of reactive cancer patients and control donors increased with increasing BCG concentration, but the proportion of patients who reacted was less than that of control donors at all concentrations of BCG. As cancer stage advanced and the volume of clinically detectable tumor increased, the proportion of reactive patients decreased. There was a small age-related decline in reactivity in the control population. The results of simultaneous in vitro tests and Mantoux reactions were concurrent in a majority of normal individuals so tested.

Adolescent↗
PubMed1980

Recurrent pyogenic cholangitis: a necropsy study.

Forty-six necropsy cases of recurrent pyogenic cholangitis (RPC) among Chinese in Hong Kong were reviewed. Intrahepatic biliary pigment stones or bile sludge were present in all cases and liver abscesses were common (80%). Histologically the early lesion was marked by acute inflammation in portal tracts with frequent pylethrombophlebitis and the advanced chronic lesion by periductal fibrosis. Most patients died from chronic persistent hepatic suppuration or disseminated infection. The pathogenesis is not fully understood; the present study favours the view that a protein-deficient diet initiates intrahepatic stone or sludge formation with biliary obstruction; subsequent bacterial infection probably originates from the portal system.

Adult↗
PubMed1980

Oligomeganephronic renal hypoplasia.

A case of oligomeganephronic renal hypoplasia is described. The patient presented in infancy with vomiting and diarrhoea and eventually developed progressive renal failure. Glomerular morphometry allowed definitive diagnosis and demonstrated a decrease in number and an increase in size of the glomeruli. Electron dense deposits seen on electron microscopy correlated with positive fluorescence for IgG and simulated overload glomerulitis.

Child, Preschool↗
PubMed1979

Tibialis anterior response to sudden ankle displacements in normal and Parkinsonian subjects.

It is well known that in Parkinsonian subjects with akinesia, reaction times are increased but reflex latencies remain normal. We have attempted to use this knowledge to distinguish between 'reflex' and 'voluntary' components of the electromyographic (EMG) response to ankle displacement. The EMG and torque responses of tibialis anterior (TA) to randomly applied servo-controlled plantar-flexing displacements of the ankle with and without the subject's intentional opposition were examined in 9 Parkinsonian and 9 age-matched normal humans. To obtain a measure of akinesia, the response latency to a visual stimulus was subsequently measured in the same subjects. Three principal findings emerged. (1) The intermediate latency EMG component (PSR) of the response evoked by ankle displacement with the subject instructed to relax was more regularly evoked and of lower threshold in Parkinsonians than in normals. This finding corresponds to the enlarged M2 component in upper limb muscles. However, the facilitation of PSR was not found to be associated with an increase in torque. In fact, the patients did not exhibit more stiffness than normals under our experimental conditions. (2) Mean latency estimate of the PSR was indistinguishable between Parkinsonians and normals. This finding puts the PSR in the nature of a reflex. Indeed, in accordance with reflex behaviour which is proportional to input characteristics, its area increased linearly with increase in the magnitude of displacement velocity. (3) In contrast, the 'late' EMG response (FSR) evoked by opposing sudden ankle displacement exhibited a significantly longer latency in 6 out of 8 Parkinsonians than normals. In the same patients, the EMG response latency to a visual signal was similarly increased. The delay of FSR in akinesia patients thus argued against its being a stereotyped reflex. The result is discussed with reference to the recent finding that preprogrammed responses are delayed in Parkinsonians.

Adult↗
PubMed1979

Fluorometric determination of chlorzoxazone in tablets and biological fluids.

A fluorometric determination for chlorzoxazone was developed based on the intrinsic drug fluorescence in chloroform using excitation and emission wavelengths of 286 and 310 nm, respectively. A calibration curve for chlorzoxazone in chloroform gave a linear working range of 0.027-2.3 microgram/ml (r = 0.9999) with the minimum detectability at 27 ng/ml. The procedure was applied to chlorzoxazone analysis in spiked plasma and urine samples. Minimum detectable drug levels in these samples were 60 and 130 ng/ml, respectively. Data revealed that chlorzoxazone could be determined in plasma and urine even in the presence of 20-fold molar excesses of its major metabolite, 6-hydroxychlorzoxaxone, and acetaminophen. The method also was applicable to chlorzoxazone analysis in a commercial dosage form containing acetaminophen.

Adult↗
PubMed1979

Dublin-Johnson syndrome with some unusual features in a Chinese family.

Three cases of chronic nonhaemolytic jaundice with conjugated bilirubin in the serum are described in a Chinese family. Bromsulphthalein excretion tests gave results typical of the Dubin-Johnson syndrome. Liver histology in the proband showed cytoplasmic pigment of the lipofuscinmelanin variety, and intravenous cholecystography failed to show visualisation of the gallbladder. Unusual findings included onset during the neonatal period in the proband and the presence of some iron pigment in the hepatic cells with a little canalicular cholestasis. It is suggested that the infant may have had a concomitant nonspecific hepatitis. These cases are regarded as belonging to a disease group in which the Dubin-Johnson syndrome is at one end of a spectrum. The mode of inheritance is discussed.

Adult↗