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Biomedical subjects

S Cheng

Publications and source records attributed to S Cheng.

At least 235 records · Page 13Linked to original sources
PubMed1994

A study using working DRGs to examine variations in length of stay.

The results of a working DRG utilisation review study conducted at St Vincent's Hospital, Sydney in 1992 are described. The project aimed to allocate a working DRG to Cardiology and Orthopaedic patients. Working DRGs are defined as DRGs allocated on admission based on the presenting problem or provisional diagnosis. Patients were then concurrently reviewed until discharge. Actual length of stay (LOS) of patients was compared to the LOS predicted by the working DRG. Results indicated that a utilisation review program using a working DRG can predict a LOS reasonably well for large groups of patients but not for individual patients and that St Vincent's is a comparatively efficient provider of Cardiology and Orthopaedic Services. The paper describes the study design, methods and results. Medical Record Managers played an integral role in the preparation phase, design of the study, day to day coordination and analysis of results. Medical Record Managers' participation in the study is highlighted in this paper.

Cardiology Service, Hospital↗
PubMed1994

[The protective effects of metallothionein on membrane proteins against endothelin--electron paramagnetic resonance spin labelling study].

Using EPR spin labelling 5 NS, 16 NS (for fatty acids) and MSL (for proteins), the changes in lipid fluidity and protein conformation in the ghost erythrocyte membrane of rat treated by endothelin have been studied. The results showed that the lipid fluidity in both of the polar region and the hydrophobic core in the membranes was not altered by endothelin at the concentration of 1 x 10(-9), 1 x 10(-8) and 1 x 10(-7) mol/L, but the ratio of S/W of membrane proteins was significantly changed by endothelin at 5 x 10(-9) and 1 x 10(-7) mol/L. This means that endothelin at the dosages used did not affect the membrane lipids but did alter protein conformation. Metallothionein (1 x 10(-5) mol/L) could attenuate this change and protect membrane proteins from endothelin. However, there is no effect of metallothionein on membrane proteins.

Animals↗
PubMed1993

Charged residues render pro-OmpA potential dependent for initiation of membrane translocation.

We have examined the effects of positively and negatively charged residues on the translocation of outer membrane protein A precursor (pro-OmpA) across the bacterial inner membrane. Pro-OmpA does not translocate across the membrane when 2 positively charged residues are inserted immediately after the leader peptide, whereas it does insert when 2 neutral or negatively charged residues are introduced. Using a cell-free translocation system, we show that the membrane potential stimulated the rate of initial insertion of pro-OmpA with negatively charged residues, inhibited pro-OmpA with positively charged residues, and had no effect on neutral pro-OmpA. Thus, acidic residues render pro-OmpA potential-dependent for loop formation, which then initiates the translocation process.

Amino Acid Sequence↗
PubMed1993

Micromanipulation of chromosomes in PTK2 cells using laser microsurgery (optical scalpel) in combination with laser-induced optical force (optical tweezers).

An optical scalpel and optical tweezer have been combined to perform intracellular microsurgery and micromanipulation in vivo. When only laser microsurgery was performed on metaphase chromosomes, the dissected sister chromatid fragments drifted off to either the side of the spindle or completely off the spindle. At anaphase the fragments separated and the two arms generally moved to their respective daughter cells. When the chromosome arm was cut during anaphase A and B, the distal chromosome fragment separated from the rest of the chromosome and moved toward the pole, following the proximal chromosome fragment. Distal chromosome fragments laser-dissected during metaphase were held together throughout anaphase using the optical trap. Optical trapping of dissected chromosome fragments during anaphase A and B inhibited movement of the chromosome fragment to its pole. As a result, the trapped chromosome fragments were (1) incorporated into the opposite daughter cell, (2) lost in the cleavage furrow during cytokinesis, or (3) eventually incorporated into the correct daughter cell. These results indicate that optical traps are effective in holding laser-dissected chromosome fragments throughout mitosis. This new tool should be useful for studies on chromosome movement and cell genetics.

Animals↗
PubMed1993

Bone mineral density in relation to anthropometric properties, physical activity and smoking in 75-year-old men and women.

Bone mineral content (BMC, g.cm-2) and density (BMD, g.cm-3) were studied in 75-year-old men and women in relation to anthropometric and certain life-style factors. This study covered all the men and women born in 1914 who were residents in the city of Jyväskylä in 1989 (N = 388). A hundred and three men and 188 women participated in bone measurements performed at the calcaneus using a 125I-photon absorption method. BMC was on average 36% and BMD 17% higher in the men than in the women. BMC and BMD associated with body mass in both sexes, and with body fat and use of estrogen in the women. There was a negative correlation between the BMD values and the number of cigarettes smoked over the entire life course in both sexes. Moderate physical activity was related to higher BMC in men. Men and women who had been physically active earlier in their life tended to show higher BMD values than those who had been more sedentary.

Aged↗
PubMed1993

A COOH-terminal peptide confers regiospecific orientation and facilitates atomic force microscopy of an IgG1.

An antibody (IgG1) was designed for oriented adherence to a metal-containing surface. This was achieved by adding a metal-chelating peptide, (CP = His-Trp-His-His-His-Pro), to the COOH-terminus of the heavy chain through genetic engineering. Electroporation of the engineered heavy chain gene into cells expressing the complimentary light chain yielded colonies secreting an intact antibody containing the metal-chelating peptide (IgG1-CP) which had high affinity for a nickel-loaded iminodiacetate column. Purified IgG1-CP was bound to nickel-treated mica and imaged by atomic force microscopy (AFM). Antibody lacking the COOH-terminal metal binding peptide failed to produce discernible AFM images. The AFM images of individual IgG1-CP molecules and their calculated dimensions demonstrated that regiospecific binding and uniform orientation of the antibody was imparted by the peptide. The ability to stably orient macromolecules in their native state to a surface may be used advantageously to visualize them.

Amino Acid Sequence↗
PubMed1993

A comparison of transhiatal and transthoracic resection for oesophageal carcinoma.

We compared the results of 327 transthoracic (TT) resections and 82 transhiatal (TH) resections for carcinoma of the oesophagus operated on between July 1982 and June 1991. Significantly more patients with carcinoma of the lower third of the oesophagus (54% versus 28%) and with increased pulmonary risks for surgery (61% versus 22%) were selected for the TH approach as compared with the TT approach. Results showed comparable intraoperative complications between the two groups. 5% of patients in the TH group required a thoracotomy for control of haemorrhage (3 patients) and repair of bronchial tear (1 patient) which occurred during the transmediastinal dissection. Postoperatively, mechanical ventilation requirement and complications involving the cardio-pulmonary systems were similar between the two groups. Anastomotic leakage occurred in 3% and 4%, respectively for the TH and TT patients (p = NS), whereas hoarseness occurred in 16% and 5%, respectively (p = 0.001). The 30-day mortality rates and hospital mortality rates were comparable between the two groups as were the overall survival rates. Our results suggested that while TH resection did not diminish the operative morbidity and mortality rates overall, it is appropriate for patients with increased pulmonary risks to be preferentially selected for this approach, and for tumours located in the upper and lower portion of the thoracic oesophagus where dissection of the tumour can be carried out mostly under vision.

Aged↗
PubMed1993

Pyridoxine-5'-beta-D-glucoside: metabolic utilization in rats during pregnancy and availability to the fetus.

Pyridoxine-5'-beta-D-glucoside (PNG), which is abundant in various plant-derived food products, has been shown to be poorly utilized in male rats and adult men. To assess the metabolic utilization of PNG during pregnancy and the availability to the fetus, [3H]PNG and [14C]pyridoxine (PN) were orally administered to 15-d pregnant rats for direct assessment of the intestinal absorption, tissue distribution, and urinary excretion of the radioisotopes. The level of 3H was significantly greater in the liver, and urinary excretion of 3H tended to be lower than that of 14C. The relative distribution of 3H among the groups of B-6 vitamers within the liver was similar to that for 14C. There was greater uptake by the fetus of 3H than of 14C. There was no difference in the relative concentrations of 3H and 14C among the groups of B-6 vitamers within the fetus. Results of this study suggest that the metabolic utilization of PNG is similar to that of PN during pregnancy. Therefore, the availability of vitamin B-6 derived from maternal PNG seems to be similar to that of vitamin B-6 derived from maternal PN.

Administration, Oral↗
PubMed1992

Demonstration of synergistic effects of hyperthermia and photodynamic therapy using the chick chorioallantoic membrane model.

The chick chorioallantoic membrane (CAM) model was used to study vascular effects of photodynamic therapy (PDT) and hyperthermia (HPT) and the synergism of these modalities. The CAM is a convenient medium for monitoring the modifications of the vasculature. It is possible to view the CAM and to examine structural changes of individual blood vessels in real time. Moreover, the CAM is a closed system which lends itself to mathematical modeling of the temporal and spatial temperature profile and in which HPT can be performed quantitatively and to a selected depth, using different lasers. A porphyrin-type photosensitizer solution was applied to areas of the CAM, defined by teflon O-rings placed on the surface. Uptake dynamics of the sensitizer into the CAM was determined by analyzing its fluorescence in vivo. The CAM area was irradiated with a dual-wavelength laser system composed of a dye laser at 644 nm (to induce PDT) and a CO2 laser at 10.6 microns (to bring about HPT). Damage to the CAM vasculature, due to combined PDT+HPT, was compared to the outcome of the separate modalities, and a synergistic effect of about 40% was observed.

Allantois↗