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Biomedical subjects

R C Chan

Publications and source records attributed to R C Chan.

At least 73 records · Page 4Linked to original sources
PubMed1995

Conserved intron elements repress splicing of a neuron-specific c-src exon in vitro.

The neuron-specific N1 exon of the mouse c-src transcript is normally skipped in nonneuronal cells. In this study, we examined the sequence requirements for the exclusion of this exon in nonneuronal HeLa cell nuclear extracts. We found that the repression of the N1 exon is mediated by specific intron sequences that flank the N1 exon. Mutagenesis experiments identified conserved CUCUCU elements within these intron regions that are required for the repression of N1 splicing. The addition of an RNA competitor containing the upstream regulatory sequence to the HeLa extract induced splicing of the intron downstream of N1, indicating that the competitor sequence binds to splicing repressor proteins. The similarities between this mechanism for src splicing repression and the repression of other regulated exons point to a common role of exon-spanning interactions in splicing repression.

Alternative Splicing↗
PubMed1993

Adrenocortical function and involvement in high risk cases of pulmonary tuberculosis.

SETTING: A regional hospital in Hong Kong. OBJECTIVE: To evaluate adrenocortical function in older patients admitted to hospital with active pulmonary tuberculosis (TB) and to determine whether adrenal insufficiency contributes to mortality in this high risk group. DESIGN: Adrenocortical function was assessed in 39 consecutive patients aged over 50 admitted to hospital with active pulmonary TB. Short Synacthen stimulation tests were performed before treatment and repeated at 2 months. In patients who died during treatment, a post-mortem examination was performed. Particular attention was paid to TB involvement of the adrenal glands. RESULTS: None of the patients had a subnormal basal cortisol concentration before treatment. 7 (18%) had raised basal cortisol concentrations and 16 (41%) had suboptimal cortisol responses to Synacthen stimulation. 14 patients (36%) died during treatment. The basal cortisol concentrations were significantly higher in the non-survivors compared to the survivors (743.7 +/- 288.5 vs 460.5 +/- 123.2 nmol/L, P < 0.0001). Autopsies were performed in 9 patients who died during treatment. Tuberculous involvement of the adrenal glands was found in only 1 patient who had a high basal cortisol concentration. After 2 months of treatment, all patients had normal cortisol concentrations and only 4 had borderline suboptimal Synacthen responses. The basal cortisol concentrations were significantly higher at presentation compared to those at 2 months after treatment (570.4 +/- 243.8 vs 386.3 +/- 108.3 nmol/L, P = 0.0014). CONCLUSION: Adrenal insufficiency is uncommon in patients with pulmonary TB. Suboptimal cortisol responses to Synacthen usually reflect a hyperstimulated basal state secondary to stress. Treatment with anti-TB drugs causes reduction in basal cortisol with associated improvement in the Synacthen response.

Adrenal Cortex↗
PubMed1993

Changes in follicular fluid gas and pH during carbon dioxide pneumoperitoneum for laparoscopic aspiration and their effect on human oocyte fertilizability.

OBJECTIVE: To determine changes in follicular fluid (FF) gases and acidity (pH) during either ultrasound (US)-guided or laparoscopic aspiration under carbon dioxide (CO2) pneumoperitoneum and relate the findings to the outcome of oocyte fertilization in vitro. DESIGN: A prospective study carried out over a limited period of 1 month during which test FF samples were obtained without direct exposure to CO2 or air. SETTING: Within the assisted pregnancy program setting at the Human Reproductive Biology Unit at the Soliman Fakeeh Hospital. PATIENTS: Infertile women undergoing either laparoscopic or US guided follicular aspiration for the purpose of in vitro fertilization treatment. INTERVENTION: Laparoscopic follicular aspiration under 100% CO2 pneumoperitoneum or transurethral US-guided follicular aspiration. RESULTS: Mean FF carbon dioxide partial pressure (pCO2) and oxygen partial pressure (pO2) were significantly higher in those aspirated at laparoscopy compared with those obtained by US-directed aspiration. The mean FF pH in the laparoscopic group was as a consequence significantly lower than in the US group. Oocyte fertilizability was significantly reduced in the laparoscopic aspiration group compared with the US group. This was more pronounced when the fertilization rate of the last recovered oocytes from the groups were compared. No difference was observed in the post fertilization embryonic development between the two groups. CONCLUSION: One hundred percent pneumoperitoneum leads to changes in FF that adversely affect oocyte fertilizability in a time-dependent manner. The use of US-directed procedure is advocated for all patients undergoing follicular aspiration in assisted pregnancy program. Where this is not feasible, the duration of CO2 pneumoperitoneum should be minimized.

Bicarbonates↗
PubMed1993

Epidemiology and etiology of pneumonia in children in Hong Kong.

The epidemiologic and etiologic features of cases of pneumonia among 1,740 children admitted to a teaching hospital in Hong Kong over a 3-year period were studied. Of the patients, 23% were < 1 year old and 69% were < 5 years old. The incidence of pneumonia requiring admission to the hospital was 6.4 episodes per 1,000 children per year for those < 5 years of age. The overall case fatality rate was 0.15% among patients who did not have severe underlying disease before contracting pneumonia. A bacterial etiology was confirmed by blood culture for only 2% of patients. However, culture of sputum or nasopharyngeal aspirates yielded predominant or pure growth of one bacterial agent in 17% of cases. Haemophilus influenzae was the bacterial agent most frequently isolated from nasopharyngeal aspirates or sputum, followed by Streptococcus pneumoniae and Staphylococcus aureus. Of the H. influenzae isolates, 38% were resistant to ampicillin. A viral etiology was proven in 9.1% of cases, and evidence of mycoplasmal infection was found in 3.8% of cases. Respiratory syncytial virus was the most frequently identified viral agent, followed by adenovirus and influenza A virus.

Adolescent↗
PubMed1993

[The effect of surface area of active recording electrode to CMAP parameters].

The purpose of this study is to quantitatively evaluate the effect of surface area of active recording electrodes to CMAP. The APB muscles from 19 young healthy subjects were included. The evoked CMAPs from median nerve supramaximal stimulation at wrist were recorded with regular surface disc electrode. Then the active recording electrode were changed to 1/2 surface area of disc, 1/4 surface area of disc, monopolar needle and concentric needle at the same recording sites. Computer reading of the latency, duration, amplitude and surface area of the CMAP were done and compared to that of standard electrode. Results disclosed that decrease the surface area of active recording did not significantly influence the distal latency, duration, amplitude and surface area of the CMAP (p > 0.1), although tendency to increase the amplitude and area were noted. The recording abilities of the active recording and the surface area difference between active recording and reference were considered to be the contributing factors. In clinical application such as recording an area with skin defect, the surface area of active recordling electrode can be altered without significant distortion of CMAP parameters.

Action Potentials↗
PubMed1992

Epidemiology and aetiology of acute bronchiolitis in Hong Kong infants.

The epidemiological, clinical and virological features of 1220 children with acute bronchiolitis admitted to the Prince of Wales Hospital, Hong Kong, from 1985 to 1988 are reported. They accounted for 6.6% of total paediatric admissions and provided a case incidence of bronchiolitis requiring admission to hospital of approximately 21 per 1000 children 0-24 months of age. The clinical course and outcome was in general benign. The average hospital stay was 5 days and there were no deaths. Ten per cent of patients were repeatedly admitted to hospital with recurrent wheezing after discharge. Two infants developed bronchiolitis obliterans. Respiratory syncytial virus (RSV) was shown by direct immunofluorescence, virus culture and serology to be the commonest cause of acute bronchiolitis in Hong Kong. Other aetiological agents included parainfluenza and influenza viruses, adenoviruses, and Mycoplasma pneumoniae. In contrast to western countries, a seasonal variation of bronchiolitis was found with a peak incidence in the summer months. The significance of these observations is discussed.

Acute Disease↗
PubMed1992

Mycobacteria as a cause of infective exacerbation in bronchiectasis.

In 91 patients with bronchiectasis seen over 6 years, a positive mycobacterial culture was obtained in 12 cases (13%). The organisms isolated were Mycobacterium tuberculosis in nine cases, Mycobacterium avium in two cases and Mycobacterium tuberculosis and chelonei were obtained on separate occasions in one case. Computed tomography and/or bronchography showed that the bronchiectatic changes commonly involved the lower lobes and to a lesser extent, the middle and lingula lobes. In none of these 12 cases was tuberculosis strongly suspected on clinical or radiological grounds. We conclude that mycobacterial infections are common in patients with bronchiectasis and sputum should be cultured for mycobacteria periodically in these patients. In doubtful cases, bronchoscopy may be helpful to obtain a positive mycobacterial culture.

Adult↗
PubMed1992

Motor unit potential analysis under submaximal contraction: ADEMG study in normal and radiculopathy subjects.

The purpose of this study was to investigate the motor unit potential (MUP) morphology in different degrees of muscle contraction. Fourteen normal volunteers and 8 patients with C7 radiculopathy were included. The extensor digitorum communis muscle was kept in minimal contraction and 5%, 10%, 30% and 50% of maximal contraction under the guidance of strain gauge. Automatic motor unit potential analysis was done by automatic decomposition electromyography for each epoch of muscle contraction in both normal and radiculopathic groups. The results revealed that as muscle contraction increased, the observed MUPs had higher amplitude, rising ratio and firing rate, while the duration became shorter, but no regular change was found in turns reading. These tendencies were found in both normal and radiculopathic groups. This study enhanced the understanding of morphology of MUPs with higher threshold, and proved the usefulness of ADEMG in differentiating normal from cervical chronic radiculopathy condition. It is suggested that the examiner should observe both lower and higher threshold MUPs during clinical needle examination to make diagnosis more accurately.

Adult↗
PubMed1992

Bronchoscopy and tuberculostearic acid assay in the diagnosis of sputum smear-negative pulmonary tuberculosis: a prospective study with the addition of transbronchial biopsy.

A prospective study of the efficacy of bronchoscopy and tuberculostearic acid assay in the diagnosis of sputum smear-negative pulmonary tuberculosis (TB) was carried out in 39 patients with symptoms and radiographic changes suggestive of active pulmonary TB. The diagnosis of TB was confirmed in 15 patients, probable TB was diagnosed in eight and 16 patients did not have TB. An early diagnosis of TB was made by bronchoscopy in six patients (40 per cent). Culture of sputum obtained before bronchoscopy was positive in nine patients (60 per cent) while combined with bronchoscopy specimens, a positive mycobacterial culture was obtained in 12 patients (80 per cent). Mycobacteria were cultured from transbronchial biopsy specimens from five patients (33 per cent) but none of these was exclusively positive. Histological examination of transbronchial biopsy tissue was diagnostic of TB in four patients and it was the exclusive means of early diagnosis in two. Transbronchial biopsy also provided an alternative diagnosis in four other patients. Tuberculostearic acid assay had a sensitivity of 0.40 in bronchial aspirate, 0.80 in bronchoalveolar lavage fluid, and 0.27 in transbronchial biopsy specimens: the combined result was 0.87. In nine patients with pulmonary TB in whom an early diagnosis could not be made, the tuberculostearic acid assay was positive in seven (78 per cent). We conclude that bronchoscopy with bronchoalveolar lavage and transbronchial biopsy is helpful in providing early diagnosis and positive culture results. Assay of tuberculostearic acid in bronchoalveolar lavage fluid is a useful adjunct to early diagnosis. However, mycobacterial culture and assay of tuberculostearic acid in transbronchial biopsy specimens have little diagnostic value.

Adolescent↗
PubMed1992

Common bile duct stones: a cause of chronic salmonellosis.

A chronic carrier state of Salmonella spp is present in 0.15% of the population, and is believed to be related to the presence of a diseased gallbladder. We present a patient with common bile duct (CBD) stones, whose bile cultures repeatedly indicated Salmonella typhi, despite an adequate course of antibiotic treatment. The carrier state was abolished after removal of the CBD stones 4 months later. The chronic carrier state may be related to biofilm formation on the surface of the CBD stones. The removal of the biliary stones, which are the most likely reservoir for Salmonella spp, may be a crucial step in eradication of the carrier state.

Aged↗
PubMed1991

Quantitative comparison of motor unit potential parameters between monopolar and concentric needles.

This study quantitatively compared the simultaneous recording of the "same" motor unit potentials recorded by closely positioned concentric and monopolar needles. The motor unit potentials from the anterior tibialis of 12 young subjects were analyzed independently by both needles being connected to 2 sets of EMG-computer combinations. Recordings of the same motor unit potentials were confirmed by triggering and averaging of the 2 sets of motor unit potentials with identical firing patterns on both EMG screens. Automatic analysis disclosed the monopolar recordings had a significantly higher mean amplitude (2.05 times), larger surface area (2.64 times), and longer duration (1.86 times) than the concentric recordings, while the mean number of phases (1.58 times) and turns (1.35 times) revealed no statistical differences. Both active recording and reference electrodes contributed to these differences.

Action Potentials↗
PubMed1991

A new approach to the management of patients at risk of ovarian hyperstimulation in an in-vitro fertilization programme.

In this study, we report an alternative method of management of patients at a potential risk of ovarian hyperstimulation syndrome (OHSS) in an in-vitro fertilization (IVF) programme, by the use of gonadotrophin releasing hormone analogue (GnRHa). Thirty eight women considered at risk of this syndrome, having serum oestradiol greater than 4000 pg/ml following ovarian stimulation, received a GnRHa nasal spray for induction of the preovulatory endogenous luteinizing hormone surge for follicular maturation prior to oocyte recovery. Oocyte recovery (mean oocytes per cycle 18.60 +/- 4.79; range 15-35) and IVF were successfully completed in 27 cycles. Twenty six women had embryos replaced and 11 pregnancies occurred (28.9% per operation, 42.3% per replacement cycle). None of the patients developed OHSS. Where there is a risk of OHSS, the use of GnRHa to induce the preovulatory surge of endogenous luteinizing hormone for final follicular maturation provides a successful and more economical alternative to cancellation of cycles.

Adult↗
PubMed1991

[Median nerve lesions at wrist in cyclists].

The purpose of this study is to detect the median nerve lesions at wrist in professional cyclists. Totally 14 national representative cyclists were included. Each subject was questionnaired and asked to draw their site of hand discomfort, followed by hand grip power test with grasp, lateral pinch and palmar pinch. A control group of 30 medical students were also tested for grip power. Electrodiagnostic examination of bilateral median nerves was then done on every cyclist, including motor and sensory nerve conduction studies, and needle EMG on abductor pollicis brevis and other associated muscles. Of the 28 hands in 14 cyclists, 7 in 4 subjects had neurologic symptoms related to median nerve, and 5 in 4 subjects had abnormal electrodiagnostic examinations. The grip power was significantly better in cyclists than in control. The prevalence of median nerve lesions at wrist in cyclists, although usually mild, was substantially higher than expected. Electrodiagnosis can be used as a sensitive detector for neuropathy even at subclinical stage. It is suggested that cyclists and trainers should be aware of the median nerve lesion during cycling and training in order to take early preventive, diagnostic and therapeutic procedures.

Adolescent↗
PubMed1991

[Electrodiagnostic evaluation of conservative treatment in carpal tunnel syndrome].

The incidence of carpal tunnel syndrome ranks first by far among all entrapment neuropathies. Many foreign studies have been reported over the years concerning the diagnosis of carpal tunnel syndrome, but very few about its treatment effects. Moreover, data have been based on the patients' subjective reports of their symptoms. Our data, however, are wholly derived from objective electromyographic examination. Five treatment approaches were compared for patients suffering from carpal tunnel syndrome in this study. Ninety-nine hands of 61 patients were divided into five treatment groups vitamins B6 & B12, steroid injection, hand splint, splint combined with vitamins, and splint combined with injection. Each patient was evaluated with electrodiagnostic study before the treatment, and 1 and 2 months after the treatment. Treatment with hand splinting, local injection at wrist, and combined therapies were all superior in effect to vitamins B6 & B12 alone in sensory nerve conduction study. The effects of treatment appeared faster in the groups with local injection and local injection combined with hand splinting in the sensory and motor nerve conduction studies. The results of this study suggest that treatment with vitamins B6 & B12 alone does not suit carpal tunnel syndrome well and that hand splint combined with steroid injection is the better conservative treatment.

Adult↗
PubMed1990

The effect of obstruction on the biliary excretion of cefoperazone and ceftazidime.

The biliary excretion of cefoperazone and ceftazidime was studied by endoscopic cannulation of the common bile duct, in patients with complete biliary obstruction and in an unobstructed control group. Patients were given each drug prophylactically for 24 h before endoscopy and as a single dose at the time of cannulation. In unobstructed patients biliary excretion of ceftazidime was passive. At the time of cannulation bile contained 10% of the peak serum concentration, rising to 20% 90 min later. Cefoperazone excretion was active. At cannulation biliary concentrations were 200% of the serum peak, 900% at 60 min and 700% at 90 min. In obstructed patients, bile sampled immediately at decompression contained neither antibiotic. Passive excretion of both drugs occurred rapidly after relief of obstruction and biliary concentrations were 20% of maximum serum levels at 60 min. Twenty-four hours later passive excretion had further improved, but the active excretion mechanism of cefoperazone had still not recovered. We conclude that obstruction impairs active as well as passive biliary excretion of antibiotics, that drainage is essential for the control of sepsis in obstructed cholangitis, and that both cefoperazone and ceftazidime achieve similar and therapeutic concentrations in bile during the 24 h after decompression.

Adult↗
PubMed1989

RNA-electrophoresis as a typing method for nosocomial rotavirus infection in a special-care baby unit.

During January and February 1988 an outbreak of nosocomial rotavirus infection occurred in a special-care baby unit (SCBU). Seven infants were affected, of whom five had symptoms of diarrhoea. Typing by RNA electrophoresis (electropherotyping) demonstrated that a single rotavirus strain was responsible for the outbreak. The epidemic electropherotype was introduced by an infant with diarrhoea admitted directly into the SCBU from the community. Eight other electropherotypes were identified during January and February in patients with community-acquired rotavirus diarrhoea on other paediatric wards, but the outbreak strain occurred only on the SCBU. Electropherotyping is a useful and rapid method for tracing the epidemiology of hospital-acquired rotavirus infection.

Communicable Disease Control↗