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Biomedical subjects

C T Tan

Publications and source records attributed to C T Tan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Auditory abnormalities associated with unilateral renal agenesis.

OBJECTIVE: To evaluate the relationship between unilateral renal agenesis and auditory abnormality, and to determine the clinical spectrum of hearing impairment in such patients. METHODS: Seventy-five children with unilateral renal agenesis underwent auditory examinations. The subjects comprised 35 males and 40 females. Fourteen females had mullerian abnormalities. Another 75 schoolchildren with the same gender profile were selected for audiometric testing as a control group. Children with sonographically evident urogenital system abnormalities were excluded from the control group. RESULTS: The prevalence of auditory abnormalities in children with unilateral renal agenesis (4/75) (5.3%) was higher than in the control group (0%). The prevalence in children with urogenital anomalies was significantly higher in patients with renal agenesis than in the normal population (28.5%). Audiometric results showed that four of the 75 children manifested ipsilateral sensorineural hearing impairment, particularly in the high-frequency range. All were females with coexisting genital abnormalities. Two were diagnosed with mild sensorineural hearing impairment while the other two had moderate hearing loss. CONCLUSIONS: The results of our study suggest that neurosensory hearing loss was found to be associated with renal agenesis. Further audiometric follow-up of children with renal agenesis seems worthwhile.

Abnormalities, Multiple↗
PubMed2001

The Torg--Pavlov ratio in cervical spondylotic myelopathy: a comparative study between patients with cervical spondylotic myelopathy and a nonspondylotic, nonmyelopathic population.

STUDY DESIGN: A radiologic study to compare the Torg--Pavlov ratios between patients with cervical spondylotic myelopathy and a nonspondylotic, nonmyelopathic population. OBJECTIVES: To determine and compare the Torg--Pavlov ratios between the two groups of patients. SUMMARY OF BACKGROUND DATA: Patients with congenital cervical spinal canal stenosis are more likely to develop cervical spondylotic myelopathy. The Torg--Pavlov ratio eliminates errors related to magnification, a problem with determination of spinal canal stenosis from direct measurements of plain cervical spine radiographs. There has only been one other study that directly compares the Torg--Pavlov ratio between patients with cervical spondylotic myelopathy and a normal control population. METHODS: The preoperative plain lateral cervical spine radiographs of 28 patients with cervical spondylotic myelopathy requiring surgical decompression were compared with radiographs of 88 nonspondylotic, nonmyelopathic patients. The Torg--Pavlov ratio was computed for each level from C3 to C7. RESULTS: The study showed that the Torg--Pavlov ratio is significantly smaller (P < 0.001) in myelopathic patients (mean 0.72 +/- 0.08) compared with the control patients (mean 0.95 +/- 0.14). This was so when individual levels and the mean values were compared. Age was also found to be a significant factor (P = 0.002), although lesser in magnitude when compared with the Torg--Pavlov ratio (P = 0.0001). CONCLUSIONS: The Torg--Pavlov ratio is significantly lower in patients with cervical spondylotic myelopathy compared with a nonspondylotic, nonmyelopathic population. It could possibly be used to predict the likelihood of developing cervical spondylotic myelopathy.

Adolescent↗
PubMed2001

Delayed post-irradiation bulbar palsy in nasopharyngeal carcinoma.

In a hospital series of 70 patients on follow-up after radiotherapy for nasopharyngeal carcinoma, 14 patients (20%) developed delayed post-irradiation bulbar palsy 1 to 18 years after radiotherapy (mean 5.5 years). Functional disability was moderate to severe. Three patients had aspiration pneumonia with one mortality. Post-irradiation bulbar palsy was a common complication and probably resulted from direct neuronal damage.

Adult↗
PubMed2001

Treatment of acute Nipah encephalitis with ribavirin.

Nipah virus, a newly identified paramyxovirus caused a severe outbreak of encephalitis in Malaysia with high fatalities. We report an open-label trial of ribavirin in 140 patients, with 54 patients who were managed prior to the availability of ribavirin or refused treatment as control. There were 45 deaths (32%) in the ribavirin arm; 29 deaths (54%) occurred in the control arm. This represents a 36% reduction in mortality (p = 0.011). There was no associated serious side effect. This study suggests that ribavirin is able to reduce the mortality of acute Nipah encephalitis.

Adult↗
PubMed2001

Effects of gentamicin and pH on [Ca2+]i in apical and basal outer hair cells from guinea pigs.

Aminoglycosides are widely used antibiotics and frequently produce acute ototoxicity. In this study we attempted to comparatively investigate the effects of gentamicin on Ca2+ influx of apical and basal outer hair cells (OHCs) isolated from guinea-pig cochlea. Since the solution of gentamicin sulfate salt is acidic (pH 3.1-3.3), we also explored the effect of external acidification on Ca2+ influx. By means of fura-2 microspectrofluorimetry, we measured the intracellular calcium concentration ([Ca2+]i) of OHCs bathed in Hanks' balanced salt solution (pH 7.40) during either a resting state or high K+-induced depolarization. Our results show that at the resting state, the baseline [Ca2+]i in apical OHCs (94+/-2.0 nM) was slightly lower than that in basal OHCs (101.1+/-2.4 nM). By contrast, the increase in [Ca2+]i evoked by high K+ depolarization in apical OHCs was about two-fold greater than that in basal OHCs. Nifedipine (30 microM) abolished the increased [Ca2+]i in both types of OHCs, suggesting that Ca2+ influx was mainly through L-type Ca2+ channels of OHCs. While gentamicin and extracellular acidification (pH 7.14) can separately attenuate this increase in [Ca2+]i in both types of OHCs, their suppressive effects are additive in basal OHCs, but not in apical OHCs. The implications of these findings are that: (1) apical and basal OHCs behave differently in response to depolarization-increased [Ca2+]i, and (2) basal OHCs are more vulnerable to the impairment of Ca2+ entry during depolarization by a combination of gentamicin and extracellular acidification, which is correlated with the clinical observation that ototoxicity of aminoglycosides at the basal coil of OHCs is more severe than that at the apical coils. Moreover, the possibility that extracellular acidification may enhance the acute ototoxic effects of aminoglycosides should be considered especially in topical applications.

Animals↗
PubMed2001

Na+,K+-ATPase and Ca2+-ATPase activities in the cochlear lateral wall following surgical induction of hydrops.

Na+,K+-ATPase and Ca2+-ATPase activities have not been studied quantitatively in the cochlea affected by endolymphatic hydrops. The present study was designed to measure quantitatively the Na+,K+-ATPase and Ca2+-ATPase activities in the cochlear lateral wall and the threshold of auditory brainstem response (ABR) for guinea pigs in the early stages (=2 months) of experimentally induced endolymphatic hydrops. A significant negative association was demonstrated between Ca2+-ATPase activity and the change in ABR threshold for hydropic cochleae (P=0.014), but not for control cochleae (P=0.123), although no such significant association was revealed between Na+,K+-ATPase activity and any change in ABR threshold for both hydropic cochleae (P=0.751) and control cochleae (P=0.352). A significant increase in Ca2+-ATPase activity in the cochlear lateral wall was observed for the hydropic ear, in which normal ABR thresholds were maintained, as compared to the control ear. On the contrary, a mild decrease in Ca2+-ATPase activity in the cochlear lateral wall was observed for the hydropic ear, in which ABR thresholds increased significantly. The present findings suggest that alterations of Ca2+-ATPase activity in the cochlear lateral wall may implicate disturbed calcium-homeostasis in the inner ear, resulting in hearing dysfunction in the early stages of experimentally induced endolymphatic hydrops.

Animals↗
PubMed2001

Potentiation of noise-induced hearing loss by amikacin in guinea pigs.

Noise and aminoglycosides initially attack cochlear outer hair cells (OHCs). Distortion product otoacoustic emissions (DPOAEs) are used for the early diagnosis of damage to OHCs. The effects of sub-damaging doses of amikacin, an aminoglycoside antibiotic agent, on noise-induced hearing loss (NIHL) were examined in guinea pigs. Animals were grouped by gender and exposed to broadband noise at 105 dB SPL for 12 h and/or injected i.m. with either amikacin (100 mg/kg/day) or saline for 10 days. Auditory brainstem response (ABR) thresholds, along with DPOAE amplitudes, were measured serially before and after noise exposure. DPOAE amplitudes decreased and ABR thresholds elevated immediately after noise exposure and then gradually recovered. At all frequencies, the emission amplitudes recovered completely to pre-exposure baseline values by 4 days after noise exposure. There was no effect of amikacin on either the ABR threshold or DPOAE amplitudes, in animals treated with amikacin only. However, amikacin significantly prolonged the effect of noise exposure on DPOAE amplitude but not on the noise-induced temporary threshold shift (TTS) of the ABR. In animals treated with a combination of noise and amikacin, significant changes in DPOAE amplitudes were still observed at 4 weeks after cessation of noise exposure. No gender difference in the responses to noise and/or amikacin could be demonstrated. The present findings indicate that even sub-damaging dosages of amikacin might impair recovery from NIHL in guinea pigs.

Amikacin↗
PubMed2001

Plasmapheresis in the University of Malaya Medical Centre, Malaysia.

Over the past 3 decades, plasmapheresis has been used more extensively for a variety of neurological and hematological disorders. We undertook a retrospective review to ascertain its safety, efficacy, and factor(s) that predispose to poor outcome. We reviewed 117 plasma exchanges in 24 patients with a mean age of 43 +/- 15 years; half were male. A total of 79% of the patients had neurological diseases, and the most common were chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, and myasthenic crisis. Plasmapheresis was effective in 79% of the patients, especially for neurological indications. Complications occurred in 23% of the exchanges affecting 58% of the patients. Most complications were mild; sepsis was the most common (9.4% of exchanges), especially catheter related sepsis (6%), rash (4.3%), and hypotension (4.3%). Only 2 (8%) patients had severe complications that required mechanical ventilation. There were 5 mortalities (21%), 3 due to sepsis and 2 due to myocardial ischemia and arrhythmia, none of which occurred within 48 h of the last exchange. Patients with poor renal function had higher mortality. Overall, our figures agree with those from other institutions and indicate that plasma exchange is an effective and safe procedure, especially for a variety of neuroimmunological conditions.

Academic Medical Centers↗
PubMed2001

The presence of Nipah virus in respiratory secretions and urine of patients during an outbreak of Nipah virus encephalitis in Malaysia.

OBJECTIVES: To study the excretion of Nipah virus in the upper respiratory secretions and urine of infected patients in relation to other clinical features. METHODS: Isolation of Nipah virus from the respiratory secretions and urine was made in Vero cells and identified by indirect immunofluorescence assay using anti-Hendra specific hyperimmune mouse ascitic fluid and FITC-conjugated goat anti-mouse IgG. RESULTS: During the peak outbreak of Nipah virus encephalitis in Malaysia, Nipah virus was isolated from the upper respiratory secretions and urine in eight of 20 patients who were virologically and/or serologically confirmed to be infected with the virus. From these eight patients, Nipah virus was isolated from six throat swab specimens, three urine specimens and only one nasal swab specimen. The positive virus isolation rate was related to the collection of these specimens during the early phase of the illness (P = 0.068). The presence of serum anti-Nipah specific IgM appeared to reduce the chance of isolating the virus (P = 0.049). There was no significant difference in the isolation rate with respect to the age, gender, ethnic group and clinical features associated with grave prognosis and mortality outcome of the patients. CONCLUSION: This study shows that it is possible to be infected from secretions of infected patients, but epidemiological survey on close contacts so far did not suggest that human-to-human transmission is common.

Adolescent↗
PubMed2001

Awake respiratory function in patients with the obstructive sleep apnoea syndrome.

INTRODUCTION: The flow-volume curves of patients with obstructive sleep apnoea (OSA) obtained during the awake state are frequently abnormal. OBJECTIVE: To determine 1) the relationship between the awake respiratory function and the severity of sleep-disordered breathing in a group of Malaysian patients with the OSA syndrome and 2) the frequency of flow-volume curve abnormality in these patients. MATERIALS AND METHODS: A retrospective analysis of the data from respiratory function tests during wakefulness and nocturnal polysomnography was performed on 48 patients with OSA. The severity of OSA was defined by the apnoea-hypopnoea index (AHI) and the lowest oxygen saturation during sleep (SpO2nadir). RESULTS: AHI had a significant relationship with alveolar-arterial oxygen gradient (r = 0.34, p = 0.046) and SpO2nadir (r = -0.49, p < 0.001) but not with any anthropometric parameter or the other awake respiratory function variables measured. SpO2nadir had a significant relationship with body mass index (r = -0.54, p < 0.001), neck circumference (r = -0.39, p = 0.013), awake room air PaO2 (r = 0.61, p < 0.001), alveolar-arterial oxygen gradient (r = -0.41, p = 0.015) and baseline supine SpO2 (r = 0.53, p < 0.001). There was no correlation between SpO2nadir and any spirometric or static lung volume parameters. The maximum inspiratory and maximum expiratory flow-volume curves of 26 patients (54%) showed a ratio of forced expiratory flow to forced inspiratory flow at mid-vital capacity (FEF50/FIF50) greater than one. In addition, flow oscillations (the "sawtooth" sign) were noted in the inspiratory and/or expiratory flow-volume curves of 21 patients (44%), 9 of whom did not have an FEF50/FIF50 > 1. Altogether, the maximum flow-volume curves during wakefulness of 35 (73%) of the 48 patients showed variable upper airway obstruction and/or flow oscillations. However, the presence of these two upper airway abnormalities, either occurring alone or together did not have an effect on the severity of OSA as measured by the AHI or SpO2nadir. CONCLUSIONS: Abnormalities of the flow-volume loop consistent with inspiratory flow limitation and/or upper airway instability during wakefulness are common in patients with the OSA syndrome. The degree of oxygen desaturation during sleep in these patients is related to their awake oxygenation status.

Adult↗
PubMed2000

Suramin protects the murine motor nerves from the toxic effects of presynaptic Ca(2+) channel inhibitors.

The purpose of this study is to investigate whether suramin is capable of preventing the neurotoxic effects of Ca(2+) channel inhibitors at the presynaptic sites. Mouse diaphragm and triangularis sterni preparations were used for this study in order to measure the muscle tension and nerve terminal Ca(2+) current, respectively. Both omega-conotoxin MVIIC and omega-agatoxin IVA markedly inhibit the nerve-evoked muscle contractions as well as the nerve terminal Ca(2+) current respectively. Pretreatment with suramin (0.3 mM) significantly reduced the inhibitory effect of nerve-evoked muscle contractions and Ca(2+) current induced by either omega-conotoxin MVIIC or omega-agatoxin IVA but not that induced by the non-selective Ca(2+) channel blocker, Cd(2+). Neither suramin nor Ca(2+)-channel toxins significantly affect Na(+)- and K(+) currents of the nerve terminals. These findings indicate that suramin selectively interferes the action of presynaptic Ca(2+) channel neurotoxins and thus reduces their depressant effects on the muscle contractions. The implication of these findings is that suramin and its derivatives may potentially become useful agents in management of intoxication of Ca(2+) channel neurotoxins.

Animals↗
PubMed2000

Clinical features of Nipah virus encephalitis among pig farmers in Malaysia.

BACKGROUND: Between September 1998 and June 1999, there was an outbreak of severe viral encephalitis due to Nipah virus, a newly discovered paramyxovirus, in Malaysia. METHODS: We studied the clinical features of the patients with Nipah virus encephalitis who were admitted to a medical center in Kuala Lumpur. The case definition was based on epidemiologic, clinical, cerebrospinal fluid, and neuroimaging findings. RESULTS: Ninety-four patients with Nipah virus infection were seen from February to June 1999 (mean age, 37 years; ratio of male patients to female patients, 4.5 to 1). Ninety-three percent had had direct contact with pigs, usually in the two weeks before the onset of illness, suggesting that there was direct viral transmission from pigs to humans and a short incubation period. The main presenting features were fever, headache, dizziness, and vomiting. Fifty-two patients (55 percent) had a reduced level of consciousness and prominent brain-stem dysfunction. Distinctive clinical signs included segmental myoclonus, areflexia and hypotonia, hypertension, and tachycardia and thus suggest the involvement of the brain stem and the upper cervical spinal cord. The initial cerebrospinal fluid findings were abnormal in 75 percent of patients. Antibodies against Hendra virus were detected in serum or cerebrospinal fluid in 76 percent of 83 patients tested. Thirty patients (32 percent) died after rapid deterioration in their condition. An abnormal doll's-eye reflex and tachycardia were factors associated with a poor prognosis. Death was probably due to severe brain-stem involvement. Neurologic relapse occurred after initially mild disease in three patients. Fifty patients (53 percent) recovered fully, and 14 (15 percent) had persistent neurologic deficits. CONCLUSIONS: Nipah virus causes a severe, rapidly progressive encephalitis with a high mortality rate and features that suggest involvement of the brain stem. The infection is associated with recent contact with pigs.

Adult↗
PubMed2000

Myopathic dropped head syndrome: a syndrome of mixed aetiology.

We report two patients with myopathic dropped head syndrome, a rare and interesting neuromuscular syndrome characterised by a predominant weakness of the neck extensor muscles. The first patient, a middle aged Chinese man, presented with progressive weakness of neck extension but his clinical course later stabilised despite a lack of response to corticosteroids. Muscle biopsy revealed a necrotising myopathy with no evidence of inflammation. This patient supports the existence of an idiopathic restricted non-inflammatory myopathy, a so called isolated neck extensor myopathy syndrome which is recognised to pursue a less progressive, more benign course. Our second patient had histopathological evidence for polymyositis; there was a favourable response to steroids. Our cases underscore the fact that there may be a spectrum of pathological processes associated with the myopathic dropped head syndrome ranging from non-inflammatory muscle necrosis to a full blown inflammatory myositis.

Adult↗
PubMed2000

Results of cervical laminoplasty and a comparison between single and double trap-door techniques.

Thirty-seven patients were studied for an average of 32.1 months after canal-expansive laminoplasty for the treatment of multiple-level cervical stenosis caused by spondylosis, ossification of posterior longitudinal ligament, prolapsed intervertebral disc, and other conditions. Short-term and medium-term results were recorded clinically, using the scoring system proposed by the Japanese Orthopedic Association. The canal expansion was also recorded with radiological studies. The improvement rate was good to excellent in 58.3% of the patients. Postoperative neurological deterioration occurred in only four patients. Poorer results were observed in female patients and in those in whom surgery was delayed. Surgery within 12 months of onset of symptoms gave good results. Serious complications occurred in only two patients. There were 12 patients who were treated with the single trap-door (unilateral) laminoplasty and 25 patients treated with the double trap-door (sagittal splitting of the spinous processes) laminoplasty; their results were compared. There was no significant difference in neurological outcome between the two methods.

Adult↗
PubMed2000

Mucociliary transport pathway on laryngotracheal tract and stented glottis in guinea pigs.

We investigated the laryngotracheal mucociliary transport pathway of guinea pigs in vivo and immediately postmortem. Only intraperitoneal anesthesia was used during the procedure to avoid the disturbance of mucociliary function. Resin particles were used as the marking substance. A microcolpohysteroscope was placed at different levels in the laryngotracheal region for observing the marking particles and recording the transport pattern. The tracheal mucociliary transport flow primarily moved along the posterior wall and both lateral walls in a zigzag trace. Upon reaching the subglottis, the resin particles stayed underneath the vocal cords, and a whirlpool phenomenon developed. The majority of the particles were shifted and directed onto the posterior glottic area. With a short delay, some resin particles crossed over the free edge of the vocal cords and turned posteriorly along the medial upper cordal margin. No mucociliary transport could be observed on the entire upper surface of the true vocal cords, which is covered by squamous epithelium. Occasionally, a few resin particles in the vicinity of the epiglottic root traveled along the aryepiglottic folds toward the posterior commissure. All streams of mucociliary transport finally joined together in the interarytenoid area. After leaving the glottis, the resin particles traveled to the hypopharynx and entered the esophagus through the motion of deglutition. The pattern of mucociliary clearance in the laryngotracheal region was not delayed by stenting.

Animals↗
PubMed2000

The spectrum of ocular involvement in patients with systemic lupus erythematosus without ocular symptoms.

The aim of the study was to determine the spectrum of clinical ocular involvement in patients with inactive systemic lupus erythematosus (SLE) who have no ocular symptoms. Patients with a diagnosis of SLE based on the 1982 revised American College of Rheumatology criteria and with no ocular complaints were recruited from the SLE clinic. Clinical data regarding their systemic disease and disease activity were recorded and a full ophthalmic examination carried out. 52 patients of mixed ethnicity comprising of 75% Chinese, 19% Malays and 6% Indian patients were recruited. Of these, 51 (98%) were female with a mean age of 34+/-11 (range 16-74 y). 16 (31%) patients had dry eyes while corticosteroid induced glaucoma and cataract was detected in 1 (2%) and 7 (14%) patients, respectively. No patients were found to have sight-threatening ocular conditions such as cotton wool spots, vasculitis, optic neuropathy or uveitis. Patients with clinically inactive disease were found not to have sight-threatening ocular diseases that are known to be associated with SLE. Although they have no ocular complaints, nearly one-third of these patients have dry eyes. Ocular examination may be unnecessary when the disease is clinically inactive and in the absence of ocular symptoms.

Adolescent↗
PubMed2000

MR imaging features of Nipah encephalitis.

OBJECTIVE: The newly discovered Nipah virus causes an acute febrile encephalitic illness in humans that is associated with a high mortality. The purpose of this study is to describe the MR imaging findings of Nipah encephalitis. MATERIALS AND METHODS: MR imaging of the brain was performed in 31 patients with Nipah encephalitis divided into three groups. The first group (14 patients) underwent MR imaging during the acute phase of the illness and the second group (10 patients) during the later phase of the acute illness. The third group consisted of six patients who underwent MR imaging because they experienced neurologic relapse and one patient who had late-onset encephalitis. Spin-echo T1- and T2-weighted sequences and T2-weighted fluid attenuated inversion recovery (FLAIR) sequences were performed. Contrast-enhanced MR imaging was performed in four patients. RESULTS: The FLAIR sequences revealed abnormalities in all patients studied. MR imaging findings in both the acute and later phases of encephalitis were similar; the main feature of both phases was the presence of discrete high-signal-intensity lesions, measuring 2-7 mm, disseminated throughout the brain, mainly in the subcortical and deep white matter of the cerebral hemispheres. Neither mass effect nor cerebral edema was seen. There was no correlation with the focal neurologic signs, depth of coma, and outcome of the patients. The lesions were attributed to widespread microinfarctions from underlying vasculitis of cerebral small vessels. Features found on MR imaging in relapsed and late-onset encephalitis differed from the features in acute encephalitis in that confluent cortical involvement was the prominent finding in the former, as opposed to discrete focal lesions in the subcortical and deep white matter in the latter. CONCLUSION: MR imaging is a sensitive and specific diagnostic tool for evaluating Nipah encephalitis.

Adolescent↗