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Biomedical subjects

P H Lam

Publications and source records attributed to P H Lam.

10 recordsLinked to original sources
PubMed1999

Mandibular asymmetry and condylar position in children with unilateral posterior crossbite.

The purpose of this retrospective study was to determine if condylar position in children with functional unilateral crossbites was different from that found in children with Class I noncrossbite malocclusions and if there was a change in condylar position after correction of the crossbite by palatal expansion. Mandibular asymmetry in children with functional unilateral posterior crossbite was also compared to that of a Class I noncrossbite group. Thirty-one children aged 6 to 14 years (mean, 9.3 years; standard deviation, 2.2) with functional unilateral crossbites were compared to 31 children aged 9.5 to 14.1 years (mean, 11.9 years; standard deviation, 1.3) exhibiting Angle Class I noncrossbite malocclusions. Pretreatment submentovertex radiographs were used to study mandibular skeletal, dental, and positional asymmetries with reference to cranial floor and mandibular coordinate systems. In addition, the anterior, superior, and posterior joint spaces were measured to determine differences between the groups with the use of pretreatment and posttreatment horizontally corrected tomograms of the temporomandibular joints. Finally, the distances of the mesiobuccal cusp of the upper first molar relative to the buccal groove of the lower first molar were measured in both groups before treatment. Univariate analyses revealed that the mandibles of children in the functional unilateral posterior crossbite group exhibited asymmetry in both anteroposterior and transverse dimensions when compared with the Class I noncrossbite group (P <. 05). These asymmetries were the result of a functional deviation of the mandible that was present in all subjects in the crossbite group. This deviation was manifested occlusally by a Class II subdivision on the crossbite side as indicated from the study model analysis (P <.05). Examination of condylar position as evidenced by horizontally corrected tomograms demonstrated a large standard deviation, resulting in an inability to detect any significant differences within or between groups at both T1 and T2 (P >.05). This study raised the question of the appropriateness of measuring joint spaces for routine diagnostic purposes.

Adolescent↗
PubMed1999

Expression and purification of a secreted functional mouse/human chimaeric antibody against bacterial endotoxin in baculovirus-infected insect cells.

We have created a mouse/human chimaeric antibody by taking antigen-binding fragment (Fab) genes of a mouse antibody-producing hybridoma with specificity for bacterial endotoxin and joining them to human Ig crystallizing-fragment (Fc) genes using recombinant DNA techniques. This chimaeric antibody has been expressed in Sf21 and High Fivetrade mark (BTI-TN-5B1-4) insect cells using the baculovirus expression system, which may allow the mass production of secretory recombinant antibodies. This was achieved by using infection with a double-recombinant virus containing cDNAs of both the Ig heavy-chain (HC) and light-chain (LC) genes. Prior to recombination, each gene was cloned into the dual-expression baculovirus transfer vector pPLSP2, which permitted the insertion of the LC gene in-frame with the signal peptide of honey bee melittin downstream of the polyhedrin promoter, and of the HC gene in-frame with the signal peptide of Bombyx mori larval serum protein downstream of the p10 promoter. Our results showed that the polypeptide chains were secreted by insect cells and correctly assembled into H(2)L(2) heterodimers containing N-linked carbohydrate at the heavy chain. Furthermore, the recombinant chimaeric antibody exhibited a similar antigen specificity to that of the monoclonal antibody. More importantly, it provides a generic method for the high-level expression of antibodies.

Amino Acid Sequence↗
PubMed1987

Phosphorylation of brain muscarinic receptor: evidence of receptor regulation.

Muscarinic receptor, from porcine synaptic membrane, was purified by affinity chromatography. Molecular weight analysis by SDS-gel electrophoresis revealed one major peptide with an apparent Mr of 68 +/- 2 Kda. The purified receptor was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase resulting in a concomitant loss in specific binding, and this loss was reversed by calcineurin.

Adenosine Triphosphate↗
PubMed1985

Demonstration of different metal ion-induced calcineurin conformations using a monoclonal antibody.

It has been suggested that calcineurin, a calmodulin-stimulated phosphatase, may exist in different metal ion-dependent conformational states (Pallen, C.J., and Wang, J. H. (1984) J. Biol. Chem. 259, 6134-6141). Evidence in favor of this hypothesis comes from studies involving a monoclonal antibody, VA1, which is specific for the small (beta) subunit of calcineurin. This antibody inhibits Ni2+-stimulated but not Mn2+-stimulated phosphatase activity against p-nitrophenyl phosphate and phosphorylase kinase. Inhibition is not due to competition of the antibody with substrate or to interference with metal ion binding to the enzyme. Complex formation between the antibody and calcineurin can be demonstrated either in the presence of Mn2+ or Ni2+ or in the absence of metal ion activators. These results indicate that the active conformational states of calcineurin are metal ion dependent, that the monoclonal antibody VA1 affects the Ni2+-induced conformational change of the enzyme, and that the beta subunit of calcineurin plays a critical role in the expression of Ni2+-stimulated phosphatase activity.

Animals↗
PubMed1982

Immediate definitive surgery for perforated duodenal ulcers: a prospective controlled trial.

A prospective, randomized, double-blind trial was conducted in 101 patients to evaluate the safety and benefits of immediate definitive surgery for perforated duodenal ulcers. These patients, who were judged by predefined criteria to be medically fit and to have perforations in chronic ulcers, were randomized to undergo simple closure (35 patients), truncal vagotomy and drainage (VD) (32 patients), or proximal gastric vagotomy with closure (PGV) (34 patients). Patients were followed with endoscopic assessment for up to 39 months. There was no mortality and only a few minor postoperative complications. At 39 months follow-up, the cumulative rates of recurrence were 63.3%, 11.8% and 3.8% after closure, VD, and PGV, respectively (p less than 0.001). With the exception of the one recurrence after PGV, all relapses were symptomatic, and eight of these 18 required reoperation. Relapse rates and Visick scores between VD and PGV were significantly different. Both safe as well as effective, immediate, nonresective, definitive operation is indicated for good-risk patients who have perforations in chronic duodenal ulcers.

Adult↗
PubMed1980

The hepatic arterial blood flow response to portal vein occlusion in the dog: the effect of hepatic denervation.

The acute effect of portal vein occlusion on hepatic arterial blood flow was studied in a group of nine anaesthetised dogs. The influence of hepatic artery denervation and total liver denervation on the hepatic arterial flow response was determined subsequently. Blood flows in the hepatic artery and portal vein were measured with electromagnetic flowmeters, and hepatic tissue perfusion with 85Krypton clearance. A side-to-side mesocaval shunt was constructed to provide a drainage channel for the mesenteric venous blood during the periods of portal vein occlusion. Occlusion of the portal vein produced an immediate and significant increase in hepatic arterial flow which was sustained at approximately 80% above control for the 6 min period of observation. Total liver blood flow and hepatic tissue perfusion were both significantly reduced by about 40%. Denervation either of the hepatic artery alone or the entire liver produced no change in the response, and it is concluded that there is no neurogenic component either initiating or modifying the early changes in hepatic arterial flow.

Animals↗
PubMed1980

Operative cholangiography: evaluation of its routine use in 569 cholecystectomies.

From 1974 till 1979, 569 cholecystectomies with routine operative cholangiography were performed in the university surgical unit, Kwong Wah Hospital, Hong Kong, for non-malignant disease of the gallbladder. Gallstones were present in 522 cases. Acalculous cholecystitis occurred in 47 cases. At least one of the clinical or operative indications to explore the common bile duct was present in 312 of the patients. However, in this group of patients in whom routine operative cholangiography was done, exploration of the common bile duct was performed in only 147, thus avoiding unnecessary exploration of the duct in 165 cases (52.8%). In the remaining 257 patients in whom there was no indication to explore the common bile duct, operative cholangiography revealed unexpected stones in the common bile duct in 14 (5.5%). After choledochotomy, post exploratory operative T-tube cholangiography was performed to rule out overlooked stones, which were present in six cases (6/161, i.e., 3.7%). Postoperative T-tube cholangiography performed on the 12th to the 14th postoperative day showed retained stones in 17 cases, giving an incidence of known retained stones of 11% (17/161) of cholecystectomies with exploration of the common bile ducts, or 3% (17/569) in the whole series of cholecystectomies.

Adult↗
PubMed1979

A simple technique of measuring liver blood flow--intrasplenic injection of 133Xenon.

Intrasplenic injection of 133Xe was studied as an inert gas clearance technique for measuring liver blood flow in 13 dogs. This was done by comparing technique with intraportal injection of 133Xe (n = 41), and with electromagnetic flowmeter measurements of total liver blood flow. Very good correlation was obtained against the two latter techniques, the correlation coefficients being 0.99 and 0.90 respectively. The comparisons were made over a range of liver blood flow rates from 37 to 297 ml 100 g-1 min-1. The technique is potentially suitable for preoperative measurements, and may be particularly convenient when performed in conjunction with splenoportovenography.

Animals↗