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Biomedical subjects

K Cheung

Publications and source records attributed to K Cheung.

At least 37 records · Page 2Linked to original sources
PubMed1996

An optimized model for rat liver perfusion studies.

Conditions which influence the viability, integrity, and extraction efficiency of the isolated perfused rat liver were examined to establish optimal conditions for subsequent work in reperfusion injury studies including the choice of buffer, use of oncotic agents, hematocrit, perfusion flow rate, and pressure. Rat livers were perfused with MOPS-buffered Ringer solution with or without erythrocytes. Perfusates were collected and analyzed for blood gases, electrolytes, enzymes, radioactivity in MID studies, and lignocaine in extraction studies. Liver tissue was sampled for histological examinations, and wet:dry weight of the liver was also determined. MOPS-buffered Ringer solution was found to be superior to Krebs bicarbonate buffer, in terms of pH control and buffering capacity, especially during any prolonged period of liver perfusion. A pH of 7. 2 is chosen for perfusion since this is the physiological pH of the portal blood. The presence of albumin was important as an oncotic agent, particularly when erythrocytes were used in the perfusate. Perfusion pressure, resistance, and vascular volume are flow-dependent and the inclusion of erythrocytes in the perfusate substantially altered the flow characteristics for perfusion pressure and resistance but not vascular volume. Lignocaine extraction was relatively flow-independent. Perfusion injury as defined by enzyme release and tissue fine structure was closely related to the supply of O2. The optimal conditions for liver perfusion depend upon an adequate supply of oxygen. This can be achieved by using either erythrocyte-free perfusate at a flow rate greater than 6 ml/min/g liver or a 20% erythrocyte-containing perfusate at 2 ml/min/g.

Animals↗
PubMed1995

Three distinct loci on human chromosome 21 contribute to interferon-alpha/beta responsiveness.

The species specificity of interferons (IFNs) depends on restricted recognition of these ligands by multisubunit cell surface receptors. Expression of the human receptor subunit IFNAR in mouse cells conferred sensitivity only to one subtype of human IFN, IFN-alpha B. Other genes on human chromosome 21 were required for responses to other subtypes of type I IFN. In contrast, IFNAR expression in hamster cells did not confer sensitivity to any human IFN tested, including IFN-alpha B. Using human-hamster somatic cell hybrids, we mapped the Ifnabr gene, encoding a ligand-binding subunit of the IFN-alpha/beta (type I) receptor, to human chromosome 21. Ifnabr colocalized with Ifnar to the distal region of q22.1. The presence of a chromosomal fragment encoding IFNABR and IFNAR was also not sufficient to confer sensitivity to human IFN. In contrast, hybrids carrying in addition the region 21q22.2 showed a full response to human IFN-alpha B, suggesting that a gene located in this region encodes a third factor required for type I IFN receptor activity.

Animals↗
PubMed1995

Glutaraldehyde concentration in the sterilization of endoscopes.

Controversy over appropriate disinfection of endoscopes continues with the most commonly utilized solution in Australian hospitals, despite concern over its efficacy, being 1% glutaraldehyde (AIDAL). Review of the in-use concentrations of glutaraldehyde at Princess Alexandra Hospital has documented a significant dilutional effect in 1% glutaraldehyde by gastrointestinal endoscopes. Each hospital should determine the minimum in-use concentration acceptable for any given disinfecting solution and any given range of endoscopes. Once this level is reached, a solution change should routinely occur. Such decisions can only be made by regularly monitoring in-use concentrations of disinfectants.

Disinfectants↗
PubMed1995

A comparison of the needle biopsy post mortem with the conventional autopsy.

Tru-cut biopsy post mortems were compared with the standard full autopsy at a large city mortuary. Subjects consisted of coronial cases excluding suspicious deaths, obvious trauma cases and children under the age of 14 yrs. The following comparisons were made: the ability to collect tissue from each of the organs; any abnormalities detected on histology; correlation of the Tru-cut biopsy results with the results of the conventional post mortem; and determination of cause of death with both techniques. Twenty-one cases were examined by both techniques. Tissue collection by biopsy varied from 100% for liver to 9.5% for kidney with heart, lung and brain giving intermediate results. The cause of death was determined in 9 cases (43%) by biopsy and in 20 cases (95%) by conventional post mortem; the cause of death was not ascertainable in 1 case. In 8 of the 9 cases (89%) where death could be determined by biopsy the cause of death was consistent with the findings of the full autopsy. The cause of death at needle biopsy examination was incorrect in 1 case (11%) compared to the findings of the standard post mortem. Clearly the needle post mortem is inferior to the conventional autopsy in determining the cause of death.

Adult↗