Biomedical subjects

K C Ong

Publications and source records attributed to K C Ong.

24 records · Page 2Linked to original sources

PubMed1996

Insulinomimetic effects of myricetin on lipogenesis and glucose transport in rat adipocytes but not glucose transport translocation.

Myricetin is a naturally occurring flavonol that is commonly found in tea, berries, fruits, and medicinal plants. It mimics insulin in stimulating lipogenesis and glucose transport in rat adipocytes in vitro. It was found to stimulate lipogenesis in rat adipocytes and enhance the stimulatory effect of insulin. The EC50 was estimated to be about 65 microM. Myricetin did not have any effect on insulin receptor autophosphorylation nor on the tyrosine kinase activity of the receptor. However, myricetin stimulated both D-glucose and D-3-O-methylglucose uptake in rat adipocytes. The Vmax of glucose transport was increased, but the Km did not change significantly. Immunoblot analysis of Glut4 in rat adipocyte plasma membrane showed that the stimulation of glucose transport was not a consequence of glucose transporter translocation. Instead, the stimulation in glucose uptake probably was due to a change in the intrinsic activity of the glucose transporter possibly caused by alterations in membrane fluidity or transporter-lipid interactions as a result of the insertion of myricetin into the membrane bilayer. Thus, myricetin may have therapeutic potential in the management of non-insulin-dependent diabetes mellitus by stimulating glucose uptake without the presence of fully functional insulin receptor.

3-O-Methylglucose↗

PubMed1996

Ideal endotracheal tube placement by referencing measurements on the tube.

The ideal position of the endotracheal tube (ETT) within the trachea is 5 +/- 2 cm from the carina with the head and neck in neutral position (Goodman's criteria). We assessed the possibility of achieving ideal placement of ETTs in our population by positioning them at reference marks of 23 cm in men and 21 cm in women. From January 1995 to April 1995, 105 intubated patients in the Medical Intensive Care Unit, Singapore General Hospital were studied. The mean distance of the ETT tip from the carina was 4.02 cm +/- 3.90. The ETT tip was < 3 cm from the carina in 30 cases (28.6%) with one case resulting in endobronchial intubation. These 30 patients were significantly shorter in height when compared to the rest of the study population (P = 0.01). Five cases (4.8%) had ETT tip > 7 cm from the carina. Adopting the above-mentioned reference marks did not result in ideal positioning of ETTs in a significant proportion of cases (33.4%). We postulate that this is because our Asian population is generally shorter than those in previous studies which had achieved ideal ETT positioning using similar reference marks.

Body Constitution↗

PubMed1996

Noninvasive positive-pressure ventilation for acute respiratory failure in a medical intensive care unit in Singapore.

The main advantage of noninvasive ventilation over conventional mechanical ventilation is in the avoidance of endotracheal intubation and its related complications. Currently, the role of noninvasive ventilation in the management of patients with acute respiratory failure is still not firmly established. We conducted a prospective study to evaluate the efficacy of nasal positive pressure ventilation in patients with acute respiratory failure. Thirty-three consecutive patients with acute failure in whom intubation and mechanical ventilation were strongly considered were included in the study. They received ventilatory support by means of BiPAP ventilatory support system and nasal mask. Physical findings and laboratory measurements were documented before and at specific intervals after initiation of support. Eighty per cent (24/30) of patients were successfully supported. Successfully supported patients tolerated the device with improved gas exchange, hence avoiding endotracheal intubation. The mean duration of support was 19.2 hours. There were major associated complications, e.g. gastric distention or aspiration.

Acute Disease↗

PubMed1995

Tannic acid inhibits insulin-stimulated lipogenesis in rat adipose tissue and insulin receptor function in vitro.

Tannins occur naturally in relatively abundant amounts in fruits, herbal medicines and common beverages. Thus an understanding of how these polyphenols affect peptide hormone action is of importance. We report here that tannic acid (a hydrolysable tannin) inhibits insulin-stimulated lipogenesis in rat adipose tissue in vitro, with an IC50 estimated to be about 350 microM. However, its monomer, gallic acid, did not show a similar inhibitory effect at concentrations up to 1 mM. The inhibition by tannic acid was less evident with higher concentrations of bovine serum albumin in the incubation buffer. This was attributed to the formation of a tannin-protein complex between bovine serum albumin and tannic acid. In a binding assay, it was observed that the specific binding of insulin to its receptor was not inhibited by tannic acid in the concentration range 0-200 microM. However, insulin-stimulated autophosphorylation of the insulin receptor, and receptor-associated tyrosine kinase phosphorylation of RR-SRC peptide, were inhibited by tannic acid at concentrations as low as 25 microM. Our data do not support the current speculation that tannins affect the activity of peptide hormones by binding to them. Therefore, our finding opens up a new perspective in the understanding of the mode of action of tannins on such hormones.

Adipocytes↗

PubMed1995

Community-acquired pneumonia.

Major changes have occurred in the epidemiology of community-acquired pneumonia recently. The emergence of new pathogens emphasises the need for continued vigilance in the diagnosis of pneumonia while changes in the microorganism or in the host have resulted in exciting new aspects of several old pathogens. Clinical and radiologic signs are unreliable in predicting the infecting organisms. Thus initial therapy is nearly always empiric. This approach often requires good clinical judgement and a knowledge of local epidemiological patterns in choosing an appropriate regimen. State-of-the-art invasive diagnostic procedures are usually reserved for pneumoniae that fail to resolve with initial treatment. Non-specific measures like stabilisation of underlying medical conditions, adequate nutrition and cessation of smoking or alcohol may help prevent the development of community-acquired pneumonia. On a larger scale, influenza and pneumococcal vaccinations are cost-effective preventive measures.

Adult↗

PubMedDate not supplied

Radiofrequency shielding of surface coils at 4.0 T.

Because radiation loss associated with a radiofrequency (RF) coil increases as roughly the fourth power of the frequency, this loss mechanism may become important in high-field studies above 2.0 T. In this study, the contribution of radiation losses at 4.0 T were determined in a rectangular surface coil using an RF shield to modify the radiation losses. The effect of this shield was determined on coil Q, B1 distribution, and signal to noise as a function of distance between the coil and the shield. Phantoms and human tissue were evaluated to characterize the loss mechanisms. The results demonstrate a large radiation loss in the unshielded surface coil. However, the radiation losses in vivo were not dominant owing to a large inductive loss occurring from dielectric currents in the body at 170 MHz.

Artifacts↗