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Biomedical subjects

K K Lau

Publications and source records attributed to K K Lau.

At least 19 recordsLinked to original sources
PubMed2003

Kennedy's disease.

Kennedy's disease is an X-linked, neurodegenerative disorder, characterised by lower motor neuron syndrome. This report gives the clinical details of six male patients with Kennedy's disease diagnosed at Princess Margaret Hospital. Three were initially diagnosed with other neurological diseases, with the diagnosis of Kennedy's disease made after genetic testing. This hereditary disease should be considered in male patients with muscle weakness, particularly those with a presentation suggesting atypical motor neuron disease.

Adult↗
PubMed2002

Epidemiological study of multiple sclerosis in Hong Kong Chinese: questionnaire survey.

OBJECTIVE: To study the epidemiology of multiple sclerosis in Hong Kong Chinese. DESIGN: Cross-sectional questionnaire survey. SETTING: Neurology and paediatric neurology departments in Hong Kong from January through June 1999. PARTICIPANTS: All confirmed multiple sclerosis patients. MAIN OUTCOME MEASURES: Demographic data, investigation results, Kurtzke's Expanded Disability Status Scale during the last follow-up visit, number of relapses between 1997 and 1998, and treatments used/currently in use. RESULTS: Fifty-three Chinese multiple sclerosis patients were identified. The prevalence was thus estimated to be 0.77 per 100,000 population. This low prevalence was also noted in other multiple sclerosis studies from South-East Asia (range, 0.8-4 per 100,000 population). The female to male ratio among the Chinese multiple sclerosis sufferers was 9.6:1, a figure somewhat higher than that reported in the other studies from South-East Asia (range, 3.2-6.6:1). The Chinese multiple sclerosis patients in this study also had a high spinal cord involvement (66%) and a low presence of cerebrospinal fluid oligoclonal banding (40%). These findings were different from those in Caucasian multiple sclerosis patients. CONCLUSION: Multiple sclerosis in Hong Kong Chinese has a low prevalence, a high female to male ratio, and a low cerebrospinal fluid oligoclonal banding presence.

Adult↗
PubMed2002

Respiratory insufficiency in a Chinese adult with mitochondrial myopathy.

Mitochondrial myopathy is an important but uncommon cause of respiratory insufficiency in adults. We report the first case of respiratory insufficiency associated with adult-onset mitochondrial myopathy seen in a Chinese adult in Hong Kong. The patient presented with peripheral oedema and shortness of breath over 2 to 3 days. There was a history of gradual progressive limb weakness over approximately 2 years, hypertrophic cardiomyopathy, intermittent diarrhoea, and weight loss. The diagnosis was made by skeletal muscle biopsy and molecular study, which revealed the A3243G point mutation.

Adult↗
PubMed2000

Phenytoin poisoning after using Chinese proprietary medicines.

We report a case of poisoning resulting from the use of Chinese proprietary medicines (CPM) containing anticonvulsants phenytoin, carbamazepine and valproate. The manufacturer's information leaflets did not mention any of these prescription drugs. As a consequence, the patient was admitted comatose due to severe phenytoin poisoning. We are not aware of any reported case of severe poisoning due to CPM adulterated with anticonvulsants and this is possibly the first case.

Adult↗
PubMed2000

Interferon treatment for multiple sclerosis patients in Hong Kong.

We report on nine patients with multiple sclerosis who had received interferon beta-1a treatment for 6 months or more. Seven patients were Chinese and two were Caucasian. Seven patients had the relapsing-remitting type of multiple sclerosis, one had the primary-progressive type, and one had the progressive-relapsing type. Among the six compliant patients with the relapsing-remitting type of disease, four had less frequent relapses after treatment. This study could not show whether or not the use of interferon beta-1a was beneficial to non-compliant patients, or patients with other types of multiple sclerosis.

Adolescent↗
PubMed1999

GLLS for optimally sampled continuous dynamic system modeling: theory and algorithm.

The original generalized linear least squares (GLLS) algorithm was developed for non-uniformly sampled biomedical system parameter estimation using finely sampled instantaneous measurements (D. Feng, S.C. Huang, Z. Wang, D. Ho, An unbiased parametric imaging algorithm for non-uniformly sampled biomedical system parameter estimation, IEEE Trans. Med. Imag. 15 (1996) 512-518). This algorithm is particularly useful for image-wide generation of parametric images with positron emission tomography (PET), as it is computationally efficient and statistically reliable (D. Feng, D. Ho, Chen, K., L.C. Wu, J.K. Wang, R.S. Liu, S.H. Yeh, An evaluation of the algorithms for determining local cerebral metabolic rates of glucose using positron emission tomography dynamic data, IEEE Trans. Med. Imag. 14 (1995) 697-710). However, when dynamic PET image data are sampled according to the optimal image sampling schedule (OISS) to reduce memory and storage space (X. Li, D. Feng, K. Chen, Optimal image sampling schedule: A new effective way to reduce dynamic image storage space and functional image processing time, IEEE Trans. Med. Imag. 15 (1996) 710-718), only a few temporal image frames are recorded (e.g. only four images are recorded for the four parameter fluoro-deoxy-glucose (FDG) model). These image frames are recorded in terms of accumulated radio-activity counts and as a result, the direct application of GLLS is not reliable as instantaneous measurement samples can no longer be approximated by averaging of accumulated measurements over the sampling intervals. In this paper, we extend GLLS to OISS-GLLS which deals with the fewer accumulated measurement samples obtained from OISS dynamic systems. The theory and algorithm of this new technique are formulated and studied extensively. To investigate statistical reliability and computational efficiency of OISS-GLLS, a simulation study using dynamic PET data was performed. OISS-GLLS using 4-measurement samples was compared to the non-linear least squares (NLS) method using 22-measurement samples, GLLS using 22-measurement samples and OISS-NLS using 4-measurement samples. Results demonstrated that OISS-GLLS was able to achieve parameter estimates of equivalent accuracy and reliability in comparison to NLS or GLLS using finely sampled measurements (22-measurement samples), or OISS-NLS using optimally sampled measurements (4-measurement samples). Further more, as fewer measurement samples are used in OISS-GLLS, this algorithm is computationally faster than NLS or GLLS. Therefore, OISS-GLLS is well-suited for image-wide parameter estimation when PET image data are recorded according to the optimal image sampling schedule.

Algorithms↗
PubMed1999

Use of intravenous immunoglobulin in a patient with refractory myasthenia gravis associated with malignant thymoma.

We report on a case of refractory myasthenia gravis that was managed by using intravenous immunoglobulin. A 35-year-old Chinese woman with malignant thymoma-associated myasthenia gravis was treated by total thymectomy, followed by chemotherapy. Thirty months later, she developed respiratory failure and required mechanical ventilation for 2 months. A course of intravenous immunoglobulin was given and her condition improved significantly. Two weeks later, the patient became ambulatory, was prescribed oral pyridostigmine, and was discharged home.

Journal Article↗
PubMed1998

Isolation of two chymotrypsins from grass carp.

Two chymotrypsins were purified from the hepatopancreas of grass carp (Ctenopharyngodon idellus) by chromatographies on phenyl-Sepharose and Q-Sepharose. The molecular weights of chymotrypsins I and II were 28 and 27 kDa, respectively. The two chymotrypsins showed similar susceptibility to inhibitions by phenylmethylsulfonyl fluoride and soybean trypsin inhibitor, but differed in their response to tosyl-L-phenylalanine chloromethyl ketone and aprotinin in which chymotrypsin I was more resistant. Chymotrypsin I was a less typical chymotrypsin and exhibited lower catalytic efficiency with the chymotrypsin-specific ester and amide substrates, when compared with chymotrypsin II. For both chymotrypsins, optimal activity was detected in the pH range 7.0-8.5.

Animals↗
PubMed1998

pha-4 is Ce-fkh-1, a fork head/HNF-3alpha,beta,gamma homolog that functions in organogenesis of the C. elegans pharynx.

The C. elegans Ce-fkh-1 gene has been cloned on the basis of its sequence similarity to the winged-helix DNA binding domain of the Drosophila fork head and mammalian HNF-3alpha,beta,gamma genes, and mutations in the zygotically active pha-4 gene have been shown to block formation of the pharynx (and rectum) at an early stage in embryogenesis. In the present paper, we show that Ce-fkh-1 and pha-4 are the same gene. We show that PHA-4 protein is present in nuclei of essentially all pharyngeal cells, of all five cell types. PHA-4 protein first appears close to the point at which a cell lineage will produce only pharyngeal cells, independently of cell type. We show that PHA-4 binds directly to a 'pan-pharyngeal enhancer element' previously identified in the promoter of the pharyngeal myosin myo-2 gene; in transgenic embryos, ectopic PHA-4 activates ectopic myo-2 expression. We also show that ectopic PHA-4 can activate ectopic expression of the ceh-22 gene, a pharyngeal-specific NK-2-type homeodomain protein previously shown to bind a muscle-specific enhancer near the PHA-4 binding site in the myo-2 promoter. We propose that it is the combination of pha-4 and regulatory molecules such as ceh-22 that produces the specific gene expression patterns during pharynx development. Overall, pha-4 can be described as an 'organ identity factor', completely necessary for organ formation, present in all cells of the organ from the earliest stages, capable of integrating upstream developmental pathways (in this case, the two distinct pathways that produce the anterior and posterior pharynx) and participating directly in the transcriptional regulation of organ specific genes. Finally, we note that the distribution of PHA-4 protein in C. elegans embryos is remarkably similar to the distribution of the fork head protein in Drosophila embryos: high levels in the foregut/pharynx and hindgut/rectum; low levels in the gut proper. Moreover, we show that pha-4 expression in the C. elegans gut is regulated by elt-2, a C. elegans gut-specific GATA-factor and possible homolog of the Drosophila gene serpent, which influences fork head expression in the fly gut. Overall, our results provide evidence for a highly conserved pathway regulating formation of the digestive tract in all (triploblastic) metazoa.

Animals↗
PubMed1998

Acute encephalitis complicating rubella.

During an epidemic of rubella in Hong Kong between October 1996 and June 1997, four male patients presented with rubella complicated by encephalitis, the symptoms of which started 1 to 5 days after the appearance of the rash characteristic of rubella. Two patients recovered completely within 1 week and one complained of a slight impairment of short-term memory. Severe cerebral oedema, and herniation across the brainstem and cerebellum developed in the fourth patient, who died 15 days later. The presence of serum immunoglobulin M antibody against rubella virus was demonstrated in all four patients; one patient also had immunoglobulin M antibody against rubella virus in his cerebrospinal fluid. No virus could be isolated during post-mortem examination of the fourth patient.

Journal Article↗
PubMed1997

Identification of an "alcohol dehydrogenase-activating" protease in grass carp hepatopancreas as a chymotrypsin.

Previous investigation [Tsui et al. (1996) Biochim. Biophys. Acta 1269: 41-46] showed that two active forms of alcohol dehydrogenase can be purified from grass carp. The use of a protease inhibitor and the results of SDS-PAGE analysis of the enzymes suggest that one form (ADH-C) is a proteolytic product of the other (ADH-I). In this study, the protease responsible for the cleavage was purified. The cleavage enzyme had a subunit molecular weight of 28 kDa. An inhibitor study identified it as a serine protease. It exhibited a strong chymotrypsin activity in both esterase and amidase assays with a pH optimum in the range 7.5-8.5. The purified chymotrypsin also cleaved the intact grass carp ADH-I into the two-fragment ADH-C, with an accompanying increase in enzyme activity. A similar effect was not found using horse liver alcohol dehydrogenase.

Alcohol Dehydrogenase↗
PubMed1996

Proteolytic activation of grass carp (Ctenopharygodon idellus) liver alcohol dehydrogenase.

Two different forms of alcohol dehydrogenase (ADH) were prepared from the liver of grass carp, using ion-exchange chromatography on DEAE-cellulose and affinity chromatography on Affi-gel Blue agarose. In the presence of dithiothreitol and benzamidine. ADH-l, a dimeric protein with native molecular weight of 80 kDa, was obtained. However, in their absence, another form of the enzyme, ADH-C, consisting of two 27 kDa and two 13 kDa subunits tightly but non-covalently associated with each other, can be isolated. ADH-C represented a cleaved form of the enzyme and was shown to be derived from the original, intact form, ADH-l through limited and specific proteolytic cleavage. Surprisingly, such a cleavage caused an activation of the enzyme toward the oxidation of ethanol at pH 10.5. The Vmax value of ADH-C was 5.16-fold greater than that of ADH-l. However, ADH-C had much weaker binding affinity for the alcohol. Its Km value toward ethanol was 163-fold higher than that of ADH-l.

Alcohol Dehydrogenase↗
PubMed1996

Activation of grass carp liver alcohol dehydrogenase by limited proteolysis.

Limited proteolysis of grass carp alcohol dehydrogenase by alkaline protease or subtilisin BPN' at 30 degrees C for 6 hr generated a nicked species that was catalytically active. Electrophoresis on a denaturing SDS-PAGE showed that the 40 kDa subunit of the intact enzyme was cleaved to produce subunits of 27 and 13 kDa, which remained tightly associated with each other under native condition. Such a proteolytically nicked form was catalytically more active than the original intact form of the enzyme. The Vmax value toward the oxidation of ethanol at pH 10 increased by 7.8 fold whereas the K(m) value also exhibited a 140 fold increase. On the other hand, when the same protease treatment was applied to horse liver alcohol dehydrogenase, no activation nor any specific cleavage can be observed.

Alcohol Dehydrogenase↗
PubMed1992

Pseudotumoral paraesophageal varices.

We report a case of paraesophageal varices presenting as a posterior mediastinal mass in a patient with long-standing portal hypertension. These collaterals were present, despite multiple previous sclerotherapies for submucosal esophageal varices and no endoscopic evidence of their recurrence.

Adult↗
PubMed1992

A case of hepatic hydrothorax due to a large diaphragmatic defect.

Hepatic hydrothorax is an infrequent complication of cirrhosis. The source of pleural fluid has been the subject of considerable speculation. A case of hepatic hydrothorax is discussed which illustrates a large diaphragmatic defect as the cause of ascitic fluid passing into the pleural cavity.

Adult↗