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K K Lau

Publications and source records attributed to K K Lau.

28 records · Page 2Linked to original sources

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↗

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↗

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↗

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↗

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↗

[Intravenous propofol as a supplement in epidural anesthesia].

Under study were thirty patients of ASA class I-II scheduled for lower abdominal and lower extremities surgery. Premedication included intramuscular injection of pethidine, atropine and prochlorperazine. Epidural anesthesia was accomplished with 12-15 ml 2% lidocaine with epinephrine (1:80,000). Thirty minutes later, when blood pressure returned to control value, patients were put to sleep by 2 mg/kg propofol and the sleep was maintained with continuous infusion of propofol at a rate of 6 mg/kg/h. Infusion rate was adjusted when necessary. Patients breathed room air spontaneously through the whole course of anesthesia. The results showed that all patients fell to sleep within 28.3 +/- 2.7 s after intravenous injection of propofol 2 mg/kg. Sleeping dose was satisfactorily achieved using a mean infusion rate of 6.1 +/- 1.7 mg/kg/h. The mean time from the end of the infusion of propofol to opening of the eyes on command and telling the correct date of birth were 7.9 +/- 2.8 min and 9.9 +/- 3.8 min respectively. Two minutes after injection, there were significant decrease in systolic pressure, diastolic pressure, cardiac output, and stroke volume with a mean of 17.9 +/- 3.8%, 18.8 +/- 3.3%, 7.6 +/- 0.5% and 11.1 +/- 1.9% respectively. Two patients (7%) developed apnea after 2 mg/kg propofol which was considered to be the most serious side effect. Propofol infusion had to be stopped in 13% patients due to a 30% fall of arterial blood pressure during maintenance. In the recovery stage, no other complications were noted except one patient who felt dizziness. Propofol, used as the supplementary sedative, provides satisfactory result for surgery under epidural anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Necrotizing fasciitis in the lower extremity: a review and case presentation.

Necrotizing fasciitis is a rare but potentially fatal disease which is often confused with cellulitis. By examining the pathogenesis, clinical presentation, treatment, and a representative case study, this article proposes to lend a broader perspective to this infection. Emphasis is placed on the necessity of surgical debridement in combination with antibiotic therapy to minimize the possible morbidity associated with this condition.

Anti-Bacterial Agents↗